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165
Clinical Evaluation of 860 Anterior and Posterior Lithium Disilicate Restorations: Retrospective Study with a Mean Follow-up of 3 Years and a Maximum Observational Period of 6 Years
Giacomo Fabbri, DDS1/ Fernando Zarone, MD, DDS2 Gianluca Dellificorelli, DDS3/Giorgio Cannistraro, DDS4 Marco De Lorenzi, DDS5/Alberto Mosca, DDS6 Roberto Sorrentino, DDS, MSc, PhD7 This study aimed to assess the clinical performance of lithium disilicate restorations supported by natural teeth or implants. Eight hundred sixty lithium disilicate adhesive restorations, including crowns on natural teeth and implant abutments, veneers, and onlays, were made in 312 patients. Parafunctional patients were included, but subjects with uncontrolled periodontitis and gingival inflammation were excluded. Veneers up to 0.5 mm thick were luted with flowable composite resin or light curing cements, while dual-curing composite systems were used with veneers up to 0.8 mm thick. Onlays up to 2 mm in thickness were luted with flowable composite resins or dual-curing composite cements. Crowns up to 1 mm in thickness were cemented with self-adhesive or dual-curing resin cements. The observational period ranged from 12 to 72 months, with a mean follow-up of 3 years. The mechanical and esthetic outcomes of the restorations were evaluated according to the modified California Dental Association (CDA) criteria. Data were analyzed with descriptive statistics. Twenty-six mechanical complications were observed: 17 porcelain chippings, 5 fractures, and 4 losses of retention. Structural drawbacks occurred mainly in posterior segments, and monolithic restorations showed the lowest number of mechanical complications. The clinical ratings of the successful restorations, both monolithic and layered, were satisfactory according to the modified CDA criteria for color match, porcelain surface, and marginal integrity. The cumulative survival rates of lithium disilicate restorations ranged from 95.46% to 100%, while cumulative success rates ranged from 95.39% to 100%. All restorations recorded very high survival and success rates. The use of lithium disilicate restorations in fixed prosthodontics proved to be effective and reliable in the short- and medium-term. (Int J Periodontics Restorative Dent 2014;34:165–177. doi: 10.11607/prd.1769)
Private Practice, Cattolica, Italy. Professor and Chair, University “Federico II” of Naples, Naples, Italy. 3Private Practice, Rome, Italy. 4Private Practice, Castagnola delle Lanze, Italy. 5Private Practice, Padova, Italy. 6Private Practice, Brescia, Italy. 1
2
In recent decades, several types of all-ceramic systems have been developed to satisfy patients’ esthetic demands. All-ceramic materials can be divided into two groups: silica based (feldspathic and glassceramics) and polycrystalline ceramics (alumina and zirconia).1 Silica-based materials are characterized by etchability and translucency and ensure optimal esthetics, a natural appearance, and reliable clinical performances.2 Conversely, polycrystalline ceramics are characterized by outstanding mechanical properties.3 Such materials are mostly indicated to produce fixed dental prostheses (FDPs) with four or more units in anterior and posterior areas. The low translucency of polycrystalline materials facilitates the treatment of discolored abutments.3 Data on strength, color stability, precision of fit, and clinical performance of alumina and zirconia are available in the literature.4–7
Teaching and Research Assistant, University “Federico II” of Naples, Naples, Italy.
7
Correspondence to: Dr Giacomo Fabbri, Cattolica, Italy, Via del Porto 17 Cattolica (Rimini), 47841 Italy; fax + 39 0541 833322; email: [email protected]. ©2014 by Quintessence Publishing Co Inc.
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166 Zirconia core fractures were not reported in three-unit FDPs.8,9 On the contrary, chipping of the veneering ceramics was described as the most frequent complication: chipping rates ranging from 8% to 25% after 24 to 38 months were observed for three-unit posterior FDPs.8,9 Limited clinical data on the reliability of all-ceramic single crowns are available.10 Clinical retrospective studies showed excellent performances of alumina crowns in anterior areas and good rates in posterior segments.5,11 In 2006, a pressable lithium disilicate glassceramic (IPS e.max Press, Ivoclar Vivadent) with improved physical properties and translucency was developed. Restorations can be produced either with a core subsequently veneered with dedicated glass-ceramic fluoroapatite or in fully anatomical restorations and then stained. More recently, a lithium disilicate glass-ceramic designed for computer-aided design/computerassisted manufacture (CAD/CAM) (IPS e.max Cad, Ivoclar Vivadent) was introduced, and preliminary investigations showed excellent biomechanic characteristics.7 Because of its high strength (∙400 MPa), etchability, translucency, and optimal esthetics, this material offers versatile applications and can be used in several types of restorations, ensuring a minimally invasive approach, excellent function, and esthetics. Lithium disilicate glassceramic represents a clinical option in the prosthetic treatment of single restorations such as veneers, inlays, onlays, and crowns. Monolithic restorations with a staining technique
can be used to restore posterior segments.7,12–15 The same approach is paramount in anterior areas to manage extremely reduced thicknesses, preserving as much dental tissue as possible and often avoiding preprosthetic endodontic treatments. Acid-etching techniques and resin luting procedures allow clinicians to produce restorations with excellent clinical performances.16,17 Due to its high flexural strength, IPS e.max can be used for three-unit FDPs, particularly in anterior segments where esthetics represent a fundamental parameter.15,18 CAD/CAM technologies producing zirconia and titanium frameworks have increasingly gained popularity in implant dentistry, combining optimal biologic and mechanical characteristics19,20 and showing values of fit comparable with those of conventional superstructures.20,21 Zirconia and titanium are generally used to produce customized abutments22; in such cases, lithium disilicate single crowns and three-unit FDPs can be used to finalize the restoration. Titanium frameworks are usually indicated for full-arch prostheses using veneering acrylic or composite resin materials; the most common complication is chipping of the veneering materials.23 Zirconia frameworks represent a promising restorative option for implant single crowns and FDPs.24–27 However, the clinical success of zirconia implant restorations appears to be limited by chipping of the veneering ceramic.25–27 The combination of lithium disilicate restorations with zirconia or titanium frameworks represents a
valid option to combine mechanical effectiveness with excellent esthetics, improving the long-term clinical outcomes of implant prostheses. The adhesion between lithium disilicate and zirconia or titanium can be performed using resin cements.28 The present retrospective study aimed at assessing the clinical performance of anterior and posterior lithium disilicate restorations supported by either natural teeth or implants. This observational analysis evaluated both the mechanics and esthetics of the prostheses over a maximum period of 6 years.
Method and materials Study population
Between June 2006 and December 2010, six expert prosthodontists made 860 lithium disilicate restorations in 312 patients (143 men, age range: 19 to 61 years; 169 women, age range: 19 to 71 years). Patients were in need of different prosthetic therapies and were selected from consecutive patients both at the authors’ offices and at the Department of Fixed Prosthodontics of the University “Federico II” of Naples, Italy. The Ethical Committee of the university provided institutional review board approval, and all patients signed a written consent form to participate in the study. The following inclusion criteria for abutment teeth were adopted9: good oral hygiene, periodontally healthy, vital or endodontically
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167
Table 1
Descriptive characteristics of the study groups
Group
Follow-up range (mo)
Mean follow-up (mo)
Cumulative survival rate (%)
Cumulative success rate (%)
Anterior crowns
Veneered (n = 209) Monolithic (n = 22)
24–72
37.3
98.57 95.46
97.61 95.46
Posterior crowns
Veneered (n = 65) Monolithic (n = 132)
12–61
33.4
96.92 96.21
95.39 96.21
Implant crowns
Veneered (n = 7) Monolithic (n = 45)
12–61
28.3
100 97.78
100 97.78
Anterior veneers
Veneered (n = 239) Monolithic (n = 40)
12–72
42.1
97.91 100
96.24 100
Posterior veneers
Veneered (n = 26) Monolithic (n = 13)
24–61
37.5
100 100
100 100
Onlays
Veneered (n = 16) Monolithic (n = 46)
12–57
32.5
100 97.83
100 97.83
treated to a clinically sound state, and opposing natural teeth or fixed prostheses. Patients not fulfilling the inclusion criteria were excluded from the study. All patients were in good general health, and 34% were smokers (more than 5 cigarettes per day). The gingival health was maintained during the study period. According to patients’ needs, single crowns on both teeth and implants and veneers and onlays were made in anterior and posterior areas as follows: 480 crowns (329 maxillary, 151 mandibular), 318 veneers (203 maxillary, 115 mandibular), and 62 onlays (21 maxillary and 41 mandibular) (Table 1); 261 prostheses were placed in patients with parafunctions (30.3%). The restorations were fabricated using pressed lithium disilicate using both monolithic and layered techniques.
Patients with at least a 1-year follow-up were recalled for clinical and radiologic assessments. The observational period ranged from 12 to 72 months, with a mean follow-up of 3 years.
Veneers
A total of 318 veneers were made (203 in the maxilla and 115 in the mandible) (Table 2). Tooth preparations were performed with a slight chamfer with a depth of 0.2 to 0.8 mm, an axial reduction of 0 to 0.8 mm, and an incisal reduction of 0 to 1.5 mm in relation to the wax-up and the presence of discoloration on teeth. Transparent silicone templates derived from the wax-up were used to optimize the preparation.29 The axial reduction was achieved using tapered
round-ended burs, preserving as much enamel as possible, to keep the finish lines within enamel and achieve the best long-term retention.30 The interproximal contact points between teeth were opened only in the presence of Class III composite restorations or in clinical situations such as diastema or interproximal black triangles. A palatal chamfer was made in 56 veneers, while a butt joint was made in 262 restorations. The buccal thickness ranged from 0.2 to 0.8 mm in the cervical third, 0.2 to 1.2 mm in the middle third, and 0.3 to 0.9 mm in the incisal third. Centric contacts at the interface were prevented through the localization of opposing contacts.29 The margins were preferably located supragingivally, thus resulting in simplified impression taking and evaluation of marginal adaptation while help-
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168
Table 2
Anatomical distribution of lithium disilicate restorations Distribution of restored teeth Layered veneers
Teeth
Monolithic veneers
Layered crowns
Monolithic crowns
Maxilla
Mandible
Maxilla
Mandible
Maxilla
Mandible
Maxilla
Mandible
Central incisors
64
27
13
2
43
3
12
4
Lateral incisors
49
27
9
2
47
3
11
4
Canines
41
24
10
4
28
9
8
11
First premolars
12
8
5
4
40
18
28
23
Second premolars
5
8
2
2
38
23
29
29
First molars
–
–
–
–
13
8
17
10
Second molars
–
–
–
–
4
4
9
4
171
94
39
14
213
68
114
85
Total
Fig 1 Rehabilitation of the maxillary anterior teeth with six lithium disilicate veneers. (a) Preoperative view. (b) Five-year follow-up.
ing to maintain periodontal health. When the contour of the restoration needed to be changed, the margins were located at the gingival crest or slightly into the crevice. Specifically, 53 restorations were monolithic and 265 were layered. All veneers were cemented adhesively (Fig 1). The ceramic restorations were etched for 20 seconds with 4.5% hydrofluoric acid (IPS ceramic gel, Ivoclar Vivadent; Porcelain Etch, Ultradent). The acid was then washed with water and dried.
A silane agent (Monobond S, Ivoclar Vivadent; Ceramic Primer, 3M ESPE) was applied and blown dry on the veneer. Rubber dam was used for 139 veneers. In the remaining 179 restorations, a gingival cord (N. 000 Ultrapak, Ultradent) was placed into the sulcus prior to luting. Concurrently, the tooth surface was etched for 30 seconds with 37% orthophosphoric acid gel (Ultra-Etch, Ultradent). After water rinsing of the tooth surface for 30 seconds, a bonding agent (Opti-
bond FL, Kerr) was applied to both the prepared tooth and the internal surface of the veneers; a dentin primer (Optibond FL, Kerr) was applied only in areas of exposed dentin. Finally, luting procedures were performed as follows: veneers up to 0.5 mm in thickness were luted using flowable composites (Gradia Direct Flow, GC; Tetric EvoFlow, Ivoclar Vivadent) or light-curing cement (Variolink Veneer, Ivoclar Vivadent), while restorations up to 0.8 mm in thickness were cemented
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169
Distribution of restored teeth Layered onlays
Monolithic onlays
Maxilla Mandible Maxilla Mandible –
–
–
–
–
–
–
–
–
–
–
–
2
2
8
3
3
1
8
8
2
2
3
7
2
2
2
7
9
7
21
25
with dual-curing composite systems (Variolink II, Ivoclar Vivadent). Excess cement was removed with a brush and dental floss interproximally. The margins of the veneers were covered with glycerin gel, and resin luting agents were light polymerized for 30 seconds from each side. The margins were then finished with a plastic scaler to remove excess resin. The occlusal contacts were carefully evaluated and balanced.
Tooth-supported single crowns
A total of 428 tooth-supported single crowns were made (299 in the maxilla and 129 in the mandible) (Table 2). Tooth preparation was performed following the diagnostic wax-up. A general 0.3- to 1.0-mm overall reduction was performed, with the exception of the incisal/occlusal areas, which were
reduced by 1.5 mm. As to the marginal design, a 0.4- to 1-mm slight circumferential chamfer preparation was performed, with rounded internal angles. The taper of the preparations ranged from 5 to 10 degrees, depending on the abutment length.31 In posterior areas, the margins were located supra- or equigingivally to preserve enamel, facilitate impression making, and aid evaluation of marginal adaptation. In anterior areas, the margin was located at the gingival crest or slightly into the sulcus, depending on esthetic demands. The thickness of the restorations ranged from 0.3 to 1.0 mm on interproximal and axial walls; the minimum thickness was 1.5 mm on the occlusal/incisal surfaces to achieve proper biomechanics. On a total of 428 single crowns (231 anterior and 197 posterior), 407 restorations were pressed (274 layered, 154 monolithic). Among these, 21 crowns were fabricated with CAD/CAM (8 layered and 13 monolithic). All restorations were cemented adhesively using selfadhesive (RelyX Unicem, 3M ESPE) or dual-curing resin cements (Multilink Automix, Ivoclar Vivadent; Variolink II, Ivoclar Vivadent) in accordance with manufacturers’ instructions. The prepared teeth were isolated with a gingival cord (N. 000 Ultrapak), and the adhesive cementation was performed as previously described. The clinical conditions allowed for the cementation of 68 crowns with rubber dam. The occlusion was refined, and any adjusted surface was polished (Fig 2).
Onlays
A total of 62 onlays were made (21 in the maxilla and 41 in the mandible) (Table 2). Cavities were prepared with a minimum occlusal thickness of 2 mm, and an interproximal buildup was performed to facilitate impression making and cementation (Fig 3). On a total of 62 prostheses, 16 onlays were layered while 64 restorations were produced fully anatomical with subsequent stain characterization. As to cementation, the prepared teeth were isolated with rubber dam and flowable composite resin (Gradia Direct Flow; Tetric EvoFlow) or dualcuring composite systems (Variolink II) used in accordance with the protocol previously described. The occlusion was refined as needed, and any adjusted surface was polished.
Implant-supported restorations
A total of 52 implant-supported restorations on 36 implants were made (30 in the maxilla and 22 in the mandible) (Table 2): 7 cemented crowns, 9 screwed crowns, 2 screwed zirconia full-arches (overall 26 restorations), 1 screwed zirconia four-unit FDP, and 2 screwed titanium three-unit FDPs. Lithium disilicate crowns were used in combination with zirconia or titanium frameworks and CAD/CAM abutments. Abutments and frameworks were designed with a minimum crown thickness of 1.5 mm circumferentially and at least 2 mm in occlusal/incisal aspects. In the case of titanium frameworks, a layer of
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170
Fig 2 Full-mouth rehabilitation by means of lithium disilicate single crowns. (a) Finished and polished restorations on the master casts. (b) Five-year follow-up of the full-mouth rehabilitation onto natural teeth and implant abutments. Fig 3 (left) Six-year follow-up of inlay and onlay monolithic restorations. Fig 4 (below) Maxillary implant-supported full-arch rehabilitation. (a) Zirconia framework with 14 lithium disilicate single crowns. (b) Three-year follow-up.
a
opaque mass was applied onto the structures to mask the grayish appearance of the metal. The lithium disilicate restorations were cemented onto zirconia and titanium using self-adhesive (RelyX Unicem) or dual-curing resin luting agent (Multilink Automix). The crowns were treated as in the case of natural abutment restorations, and no procedures were performed on framework materials. As for screwed restorations, in all cases in which the screw access hole did not take up the buccal wall of the
b
restoration, an extraoral cementation was carried out, avoiding the risk of subgingival residual cement. The screw access holes were then filled with composite resin (Fig 4).
Clinical evaluation
Standardized photographs and radiographs were taken at all recall appointments. Data forms recording the mechanical and esthetic characteristics of each restoration were used as documentation tools.
Patients were examined at clinical recalls at least 1 year after cementation and then annually; color match, porcelain surface, marginal discoloration, and integrity were evaluated following the modified California Dental Association (CDA) criteria.32 The patients’ satisfaction was assessed using nominal scores (nonacceptable, acceptable, good, and excellent). In the case of any mechanical complication, the restoration was considered a failure.
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171 Statistical analysis
Descriptive statistics were made with dedicated software (SPSS, version 17, IBM). The minimum, mean, and maximum follow-ups were calculated for all lithium disilicate prostheses. The cumulative survival and success rates were recorded in all groups using the Kaplan-Meier analysis; all groups were divided into veneered and monolithic prostheses. Each mechanical complication, both minor (loss of retention, minor chipping) and major (core fracture, support fracture, major chipping), was considered as a statistical event. The log-rank test was performed to compare the survival curves of veneered and monolithic restorations. The level of significance was set at P = .05.
Results All prostheses were fabricated by six expert dental technicians according to the manufacturers’ instructions. A total of 860 restorative units were evaluated from a minimum of 12 to a maximum of 72 months in 312 patients.
Veneers
Anterior layered veneers showed cumulative survival and success rates of 97.91% and 96.24%, respectively. Anterior monolithic veneers showed cumulative survival and success rates of 100% (Table 1). Both posterior layered and monolithic veneers showed cumu-
lative survival and success rates of 100% (Table 1). Chipping was observed on five veneers, all at the maxillary arch. None of the minor cohesive fractures impaired function; the restorations were smoothed and finished intraorally and remained in situ for further observation. Core fractures were noted on three veneers, one on a maxillary lateral incisor and two in the mandibular anterior segment; they all were layered. All fractured restorations had ceramic materials in the opposite dentition and required the replacement of the restorations. The failed veneers were prepared with an incisal butt joint and fractures were observed 8 and 11 months after cementation, respectively; the replacements were performed with a new preparation design that involved the lingual aspect as well as a mini-chamfer. Loss of retention was observed on one mandibular veneer; the restoration was immediately rebonded and was still in function at the final follow-up.
Tooth-supported single crowns
Anterior layered tooth-supported crowns showed cumulative survival and success rates of 98.57% and 97.61%, respectively. Anterior monolithic crowns showed cumulative survival and success rates of 95.46% (Table 1). Posterior layered crowns showed cumulative survival and success rates of 96.92% and 95.39%, respectively. Posterior monolithic crowns showed cumu-
lative survival and success rates of 96.21% (Table 1). Minor cohesive fractures of the veneering ceramic occurred on eight tooth-supported crowns, three in the maxilla and five in the mandible; two of these chipped crowns were monolithic, one per arch. Crown chippings occurred mostly in posterior segments (premolars and molars); only four of these needed a replacement, while the remaining chipped areas were simply smoothed and finished. Core failures occurred 7 months after cementation on two maxillary crowns on central and lateral incisors in a single patient and required the replacement of the restorations. Both of the fractured restorations had ceramic materials in the opposite dentition. Loss of retention was observed on two mandibular crowns; the restorations were immediately rebonded and were still in function at the final follow-up. One mandibular crown needed root canal therapy because of a pulpitis occurring 18 months after cementation. The endodontic treatment was performed through the crown, and the access hole was then filled with composite resin; the restoration was considered a failure although it was still in function. Furthermore, one nonvital maxillary premolar restored with a crown was extracted because of root fracture.
Onlays
Layered onlays showed cumulative survival and success rates of 100% (Table 1). Monolithic onlays
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172
Veneered anterior crowns
Veneered posterior crowns
Monolithic anterior crowns 0.995
0.9 0.990
0.8
0.975
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0
8 12
0.992
1.0
Cumulative survival (%)
Cumulative survival (%)
1.0
Monolithic posterior crowns
0.985
24 29 36 40 48 35
60
Time to complication (mo)
showed cumulative survival and success rates of 97.83% (Table 1). Chipping was noticed on three onlays, all at the mandibular arch. Two of these chipped onlays were monolithic; both restorations were positioned on mandibular second premolars, and opposite dentition were represented by a natural tooth in one case and by a ceramic restoration in the other. The damaged area was intraorally repaired by means of composite resin. Loss of retention was observed on one maxillary onlay; the restoration was immediately rebonded and was still in function at the final followup.
Implant-supported restorations
Layered implant crowns showed cumulative survival and success rates of 100% (Table 1). Implant-support-
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
72 70
Fig 5 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate anterior single crowns.
0.9
0.985 0.984 0.976 0.954 0.969 0.968 0.961
0
9 12
24 30 36 25 3438 33
48
60 61
72
Time to complication (mo) Fig 6 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate posterior single crowns.
ed monolithic crowns reported cumulative survival and success rates of 97.78% (Table 1). Minor cohesive fractures of the veneering ceramic occurred on one monolithic implant crown on a maxillary canine. The chipping did not impair function; consequently, the area was smoothed and finished and the crown remained in situ.
Statistical analysis
Considering any complication as an event, the cumulative survival rates of lithium disilicate restorations ranged from 95.46% to 100%, while the cumulative success rates ranged from 95.39% to 100%, according to Kaplan-Meier survival analysis (Figs 5 to 10, Table 1). The log-rank test that compared the survival curves of veneered and monolithic restorations was not sta-
tistically significant in any research group (P > .05) (Table 3).
Clinical evaluation
The clinical ratings of the successful restorations, both monolithic and layered, were satisfactory according to the modified CDA criteria (Table 4). The color match of the monolithic restorations recorded the lowest proportion of A ratings (90.9%) but was considered absolutely acceptable both by clinicians and patients. With the exception of the previously reported failed prostheses, no restoration was rated C or D for any of the evaluation criteria. The patient satisfaction scores were mainly excellent for all restorations; a few prostheses were rated as good and none were reported to be nonacceptable or acceptable (Table 5).
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173
Veneered implant crowns
Veneered anterior veneers
Monolithic implant crowns
Monolithic anterior veneers
1.0
0.978
0.9
Cumulative survival (%)
Cumulative survival (%)
1.0 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0
12
24
36
48
60 61
0.9
0.6 0.5 0.4 0.3 0.2 0.1 0 4 8 12 10
Monolithic onlays
0.9
Cumulative survival (%)
Cumulative survival (%)
Veneered onlays
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 48
60 61
72
Time to complication (mo) Fig 9 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate posterior veneers.
Monolithic restorations showed the lowest number of mechanical structural complications. No monolithic veneer failed. Conversely, three monolithic crowns located on
72 70
Monolithic posterior veneers
1.0
36
60 59
Veneered posterior veneers
0.9
24
36 42 48 3943
Fig 8 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate anterior veneers.
1.0
12
24
Time to complication (mo)
Fig 7 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate implant-supported crowns.
0
0.963
0.7
Time to complication (mo)
0
0.984 0.976 0.967
0.8
0
72
0.980
0.996 0.988 0.992
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0
12
24
36 43 48
60 57
72
Time to complication (mo) Fig 10 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate onlays.
one implant and two natural teeth were affected by chipping. All failed crowns had ceramic restorations on the opposite dentition; two of these were placed in patients with
parafunctional habits. Unrestorable fractures were observed only in layered restorations positioned in anterior segments in patients with uncontrolled parafunctions.
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174
Table 3
Results of the log-rank test comparing the survival curves
Groups
Log-rank
P
Veneered anterior crowns vs monolithic anterior crowns
0.381
> .05
Veneered posterior crowns vs monolithic posterior crowns
0.084
> .05
Veneered anterior veneers vs monolithic anterior veneers
1.062
> .05
Veneered posterior veneers vs monolithic posterior veneers
2.004
> .05
Veneered onlays vs monolithic onlays
0.345
> .05
Veneered implant crowns vs monolithic implant crowns
0.154
> .05
Table 4
Frequency distribution of clinical ratings in lithium disilicate restorations according to the modified CDA criteria Modified CDA rating A
B
C
D
Parameter
Layered (%)
Monolithic (%)
Layered (%)
Monolithic (%)
Layered (%)
Monolithic (%)
Layered (%)
Monolithic (%)
Color match
97.9
90.9
2.1
7.4
0
1.7
0
0
Porcelain surface
96.7
97.1
3.3
2.9
0
0
0
0
Marginal discoloration
96.7
95.9
3.3
4.1
0
0
0
0
Marginal integrity
98.2
98.7
1.8
1.3
0
0
0
0
Table 5
Patients’ satisfaction scores for lithium disilicate restorations Observational period (mo)
Satisfaction score
12 < x > 24
24 < x > 36
36 < x > 48
48 < x > 72
Veneers Crowns Onlays Veneers Crowns Onlays Veneers Crowns Onlays Veneers Crowns Onlays
Nonacceptable
0
0
0
0
0
0
0
0
0
0
0
0
Acceptable
0
0
0
0
0
0
0
0
0
0
0
0
Good
0
9
2
4
13
1
15
14
0
0
0
0
Excellent
31
99
10
95
159
25
90
116
22
83
70
2
x = observational period in months.
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175
Fig 11 Minimally invasive preparations for lithium disilicate crowns.
Recurrent caries was not detected in any restoration, contour quality was satisfactory, and proximal contacts were well maintained over time.
Discussion In this study, lithium disilicate restorations were associated with very high success rates (95.39% to 100% at 72 months), comparable with results reported in previous studies.2,11 Several variables contribute to the clinical effectiveness of such restorations; particularly, lithium disilicate prostheses have to be bonded with correct adhesive techniques to achieve the reported success rates. Moreover, the quantity and quality of tooth structure is paramount, especially the enamel at the finish lines: the more the enamel is preserved, the better the adhesion and the more limited aging of the bonding interfaces will be over time.2,17,30 An estimated survival probability of 93.5% after
10 years was reported for porcelain laminate veneers.33 Moreover, a recent systematic review reported that glass-ceramic veneers present an adequate clinical survival for at least 5 years of function with very low complication rates.34 Accordingly to the clinical situations, the authors transferred the concept of adhesion to enamel to improve restoration longevity from veneers to crowns (Fig 11), producing very thin restorations and preserving as much enamel as possible. All fractures and mechanical complications occurred in restorations with thicknesses in accordance or even superior to manufacturing instructions but applied on teeth where the majority of supporting substrate was dentin or composite. Conversely, no mechanical complications were observed in restorations cemented on teeth where enamel represented at least 50% of the bonding substrate. As regards technical drawbacks, 63% of mechanical complications (fractures and chipping) were ob-
served on restorations that had porcelain as opponent and 33% of these occurred in patients with parafunctions. The remaining 37% of the mechanical complications were noticed in patients that had natural teeth as antagonist dentition and were not affected by bruxism or clenching. Considering the high rate of parafunctional patients (30.3%) and the high success rate in this study, lithium disilicate may be considered a valid option to treat such patients, especially using monolithic restorations, as they did not show any structural complications. According to the CDA quality evaluation system, all of the restorations were classified as satisfactory for marginal integrity, color, and surface, with the only exception of monolithic crowns and onlays, which did not show an optimal result in color match in some cases (9.1%). Case selection is a crucial factor for achieving natural appearance with a monolithic approach, as several variables contribute to
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176 the successful esthetic of a restoration, such as color of the natural abutment, ceramic thickness, correct choice of ingots, and color and value of adjacent teeth. The combination of lithium disilicate restorations with zirconia and titanium frameworks or abutments showed excellent results in terms of esthetics, function, and loss of retention. Only one monolithic crown placed on a zirconia framework was affected by chipping 6 days after cementation. This restoration fractured in a patient treated with an implant-supported full-arch prosthesis, and the premature fracture was probably due to an uneven occlusal control in centric relation; the fractured fragment was immediately rebonded with an adhesive technique, occlusion was refined, and the crown was still in function after 3 years. Lithium disilicate technology demonstrates unique features to be used in different clinical situations; the possibility to choose between ingots with different opacity and translucency allows the clinician to select the ideal core, even in cases in which severe discolorations make it very difficult to obtain satisfactory esthetics.3 The etchability of lithium disilicate improves the clinical performance of adhesive cementation and eases the management of clinical complications. Especially in cases of chipping or fractures, the possibility of applying an effective adhesive by means of the etching technique allows the clinician to repair any mechanical complication with easy handling procedures and a favorable prognosis.
As to the study’s limitations, the present investigation is a retrospective, clinical, multipractice study; consequently, although the same rigorous approach was respected, different operators and several clinical variables (restoration type, intraoral distribution, multiunit prostheses in a single patient) could act as confounders in the clinical and statistical results. Considering these limitations, further in vivo investigations would be necessary to validate the clinical reliability of lithium disilicate restorations in the long-term, confirming the effectiveness of the proposed prosthetic approach.
Conclusion According to the results of this study and within its limitations, the use of lithium disilicate in fixed prosthodontics proved to be effective and reliable in the short- and medium-term. The choice of this material may represent a valid option in many clinical situations, offering biologic, technical, and esthetic advantages.
Acknowledgments The authors reported no conflicts of interest related to this study.
References 1. Dumfahrt H. Porcelain laminate veneers. A restospective evaluation after 1 to 10 years of service. Part 1: Clinical procedure. Int J Prosthodont 1999;12:505–513.
2. Fradeani M, Rademagni M, Corrado M. Porcelain laminate veneers: 6 to 12 year clinical evaluation. A retrospective study. Int J Periodontics Restorative Dent 2005;25:9–17. 3. Fabbri G, Mancini R, Marinelli V, Ban G. Anterior discolored teeth restored with Procera all-ceramic restorations: A clinical evaluation of the esthetic outcome based on the thickness of the core selected. Eur J Esthet Dent 2011;6:76–86. 4. Boening KW, Wolf BH, Schmidt AE, Kastner K, Walter MH. Clinical fit of Procera AllCeram crowns. J Prosthet Dent 2000;84:419–424. 5. Martinez-Rus F, Suarez MJ, Rivera B, Padrìes G. Evaluation of the absolute marginal discrepancy of zirconia-based ceramic copings. J Prosthet Dent 2011; 105:108–114 6. Kokubo Y, Tsumita M, Kano T, Sakurai S, Fukushima S. Clinical marginal and internal gaps of zirconia all-ceramic crowns. J Prosthodont Res 2011;55:40–43. 7. Guess P, Zavanelli R, Silva N, Bonfante E, Coelho P, Thompson V. Monolithic CAD/ CAM lithium disilicate versus veneered Y-TZP crowns: Comparison of failure modes and reliability after fatigue. Int J Prosthodont 2010;23:434–442. 8. Raigrodski AJ, Hillstead MB, Meng GK, Chung KH. Survival and complications of zirconia-based fixed dental prostheses: A systematic review. J Prosthet Dent 2012;107:170–177. 9. Sax C, Hammerle CH, Sailer I. 10-year clinical outcomes of fixed dental prostheses with zirconia frameworks. Int J Comput Dent 2011;14:183–202. 10. Ortop A, Kihl ML, Carlsson GE. A 3-year retrospective and clinical follow-up study of zirconia single crowns performed in a private practice. J Dent 2009;37: 731–736. 11. Sorrentino R, Galasso L, Teté S, De Simone G, Zarone F. Clinical evaluation of 209 all-ceramic single crowns cemented on natural and implant-supported abutments with different luting agents: A 6-year retrospective study. Clin Implant Dent Relat Res 2012;14:184–197. 12. Marquardt P, Strub JR. Survival rates of IPS empress 2 all-ceramic crowns and fixed partial dentures: Results of a 5-year prospective clinical study. Quintessence Int 2006;37:253–259. 13. Taskonak B, Sertgöz A. Two-year clinical evaluation of lithia-disilicate-based all-ceramic crowns and fixed partial dentures. Dent Mater 2006;22:1008–1013.
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14. Gehrt M, Wolfart S, Rafai N, Reich S, Edelhoff D. Clinical results of lithiumdisilicate crowns after up to 9 years of service. Clin Oral Investig 2013;17: 275–284. 15. Kern M, Sasse M, Wolfart S. Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium-disilicate ceramic. J Am Dent Assoc 2012; 143:234–240. 16. Simonsen RJ, Calamia JR. Tensile bond strength of etched porcelain [abstract 1154]. L Debt Res 1983;62:297. 17. Dumfahrt H. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service. Part 1: Clinical procedure. Int J Prosthodont 1999;12:505–513. 18. Stappert CF, Dai M, Chitmongkolsuk S, Gerds T, Strub JR. Marginal adaption of three-unit fixed partial dentures constructed from pressed ceramic systems. Brit Dent J 2004;196:766–770. 19. Van Brakel R, Cune MS, van Winkelhoff AJ, de Putter C, Verhoeven JW, van der Reijden W. Early bacterial colonization and soft tissue health around zirconia and titanium abutments: An in vivo study in man. Clin Oral Implants Res 2011; 22:571–577. 20. Karl M, Taylor TD. Effect of material selection on the passivity of fit of implantsupported restorations created with computer-aided design/computer-assisted manufacture. Int J Oral Maxillofac Implants 2011;26:739–745. 21. Denry I, Kelly JR. State of the art of zirconia for dental applications. Dent Mater 2008,24:299–307.
22. Sailer I, Zembic A, Jung RE, Siegenthaler D, Holdergger C, Hämmerle CH. Randomized controlled clinical trial of customized zirconia and titanium implant abutment for canine and posterior single-tooth implant reconstructions: Preliminary result at 1 year of function. Clin Oral Implants Res 2009;20:219–225. 23. Fischer K, Stenberg T. Prospective 10year cohort study based on randomized, controlled trial (RCT) on implant-supported full-arch maxillary prostheses. Part II. Prosthetic outcomes and maintenance. Clin Implant Dent Relat Res 2013; 15:498–508. 24. Bremer F, Grade S, Kohorst P, Stiesch M. In vivo biofilm formation on different dental ceramics. Quintessence Int 2011; 42:565–574. 25. Sailer I, Philipp A, Zembic A, Pjetursson BE, Hammerle CH, Zwahlen M. A systematic review of the performance of ceramic and metal implant abutments supporting fixed implant reconstructions. Clin Oral Implants Res 2009;20(suppl 4):4–31. 26. Nothdurft FP, Pospiech PR. Zirconium dioxide implant abutments for posterior single-tooth replacement: First results. J Periodontol 2009;80:2065–2072. 27. Larsson C, Vult von Steyern P, Sunzel B, Nilner K. All-ceramic two-to five-unit implant-supported reconstructions. A randomized, prospective clinical trial. Swed Dent J 2006;30:45–53.
28. Martinez-Rus F, Ferreiroa A, Ozcan M, Bartolomè JF, Pradies G. Fracture resistance of crowns cemented on titanium and zirconia implant abutments: A comparison of monolithic versus manually veneered all-ceramic systems. Int J Oral Maxillofac Implants 2012;27:1448–1455. 29. Magne P, Perroud R, Hodges JS, Belser U. Clinical performance of novel-design porcelain veneers for the recovery of coronal volume and length. Int J Periodontics Restorative Dent 2000;20:441–457. 30. Friedman MJ. Porcelain veneer restorations: A clinician’s opinion about a disturbing trend. J Esthet Restorative Dent 2001;13:318–327. 31. Doyle MG, Goodacre CJ, Munoz CA, Andres CJ. The effect of tooth preparation design on the breaking strength of Dicor crowns. Part 3. Int J Prosthodont 1990;3:327–340. 32. California Dental Association. Quality Evaluation for Dental Care. Guidelines for the Assessement of Clinical Quality and Performance, ed 3. Sacramento, CA: California Dental Association, 1995. 33. Beier US, Kapferer I, Burtscher D, Dumfahrt H. Clinical performance of porcelain laminate veneers for up to 20 years. Int J Prosthodont 2012;25:79–85. 34. Petridis HP, Zekeridou A, Malliari M, Tortopidis D, Koidis P. Survival of ceramic veneers made of different materials after a minimum follow-up period of five years: A systematic review and meta-analysis. Eur J Esthet Dent 2012;7: 138–152.
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Clinical Evaluation of 860 Anterior and Posterior Lithium Disilicate Restorations: Retrospective Study with a Mean Follow-up of 3 Years and a Maximum Observational Period of 6 Years
Giacomo Fabbri, DDS1/ Fernando Zarone, MD, DDS2 Gianluca Dellificorelli, DDS3/Giorgio Cannistraro, DDS4 Marco De Lorenzi, DDS5/Alberto Mosca, DDS6 Roberto Sorrentino, DDS, MSc, PhD7 This study aimed to assess the clinical performance of lithium disilicate restorations supported by natural teeth or implants. Eight hundred sixty lithium disilicate adhesive restorations, including crowns on natural teeth and implant abutments, veneers, and onlays, were made in 312 patients. Parafunctional patients were included, but subjects with uncontrolled periodontitis and gingival inflammation were excluded. Veneers up to 0.5 mm thick were luted with flowable composite resin or light curing cements, while dual-curing composite systems were used with veneers up to 0.8 mm thick. Onlays up to 2 mm in thickness were luted with flowable composite resins or dual-curing composite cements. Crowns up to 1 mm in thickness were cemented with self-adhesive or dual-curing resin cements. The observational period ranged from 12 to 72 months, with a mean follow-up of 3 years. The mechanical and esthetic outcomes of the restorations were evaluated according to the modified California Dental Association (CDA) criteria. Data were analyzed with descriptive statistics. Twenty-six mechanical complications were observed: 17 porcelain chippings, 5 fractures, and 4 losses of retention. Structural drawbacks occurred mainly in posterior segments, and monolithic restorations showed the lowest number of mechanical complications. The clinical ratings of the successful restorations, both monolithic and layered, were satisfactory according to the modified CDA criteria for color match, porcelain surface, and marginal integrity. The cumulative survival rates of lithium disilicate restorations ranged from 95.46% to 100%, while cumulative success rates ranged from 95.39% to 100%. All restorations recorded very high survival and success rates. The use of lithium disilicate restorations in fixed prosthodontics proved to be effective and reliable in the short- and medium-term. (Int J Periodontics Restorative Dent 2014;34:165–177. doi: 10.11607/prd.1769)
Private Practice, Cattolica, Italy. Professor and Chair, University “Federico II” of Naples, Naples, Italy. 3Private Practice, Rome, Italy. 4Private Practice, Castagnola delle Lanze, Italy. 5Private Practice, Padova, Italy. 6Private Practice, Brescia, Italy. 1
2
In recent decades, several types of all-ceramic systems have been developed to satisfy patients’ esthetic demands. All-ceramic materials can be divided into two groups: silica based (feldspathic and glassceramics) and polycrystalline ceramics (alumina and zirconia).1 Silica-based materials are characterized by etchability and translucency and ensure optimal esthetics, a natural appearance, and reliable clinical performances.2 Conversely, polycrystalline ceramics are characterized by outstanding mechanical properties.3 Such materials are mostly indicated to produce fixed dental prostheses (FDPs) with four or more units in anterior and posterior areas. The low translucency of polycrystalline materials facilitates the treatment of discolored abutments.3 Data on strength, color stability, precision of fit, and clinical performance of alumina and zirconia are available in the literature.4–7
Teaching and Research Assistant, University “Federico II” of Naples, Naples, Italy.
7
Correspondence to: Dr Giacomo Fabbri, Cattolica, Italy, Via del Porto 17 Cattolica (Rimini), 47841 Italy; fax + 39 0541 833322; email: [email protected]. ©2014 by Quintessence Publishing Co Inc.
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166 Zirconia core fractures were not reported in three-unit FDPs.8,9 On the contrary, chipping of the veneering ceramics was described as the most frequent complication: chipping rates ranging from 8% to 25% after 24 to 38 months were observed for three-unit posterior FDPs.8,9 Limited clinical data on the reliability of all-ceramic single crowns are available.10 Clinical retrospective studies showed excellent performances of alumina crowns in anterior areas and good rates in posterior segments.5,11 In 2006, a pressable lithium disilicate glassceramic (IPS e.max Press, Ivoclar Vivadent) with improved physical properties and translucency was developed. Restorations can be produced either with a core subsequently veneered with dedicated glass-ceramic fluoroapatite or in fully anatomical restorations and then stained. More recently, a lithium disilicate glass-ceramic designed for computer-aided design/computerassisted manufacture (CAD/CAM) (IPS e.max Cad, Ivoclar Vivadent) was introduced, and preliminary investigations showed excellent biomechanic characteristics.7 Because of its high strength (∙400 MPa), etchability, translucency, and optimal esthetics, this material offers versatile applications and can be used in several types of restorations, ensuring a minimally invasive approach, excellent function, and esthetics. Lithium disilicate glassceramic represents a clinical option in the prosthetic treatment of single restorations such as veneers, inlays, onlays, and crowns. Monolithic restorations with a staining technique
can be used to restore posterior segments.7,12–15 The same approach is paramount in anterior areas to manage extremely reduced thicknesses, preserving as much dental tissue as possible and often avoiding preprosthetic endodontic treatments. Acid-etching techniques and resin luting procedures allow clinicians to produce restorations with excellent clinical performances.16,17 Due to its high flexural strength, IPS e.max can be used for three-unit FDPs, particularly in anterior segments where esthetics represent a fundamental parameter.15,18 CAD/CAM technologies producing zirconia and titanium frameworks have increasingly gained popularity in implant dentistry, combining optimal biologic and mechanical characteristics19,20 and showing values of fit comparable with those of conventional superstructures.20,21 Zirconia and titanium are generally used to produce customized abutments22; in such cases, lithium disilicate single crowns and three-unit FDPs can be used to finalize the restoration. Titanium frameworks are usually indicated for full-arch prostheses using veneering acrylic or composite resin materials; the most common complication is chipping of the veneering materials.23 Zirconia frameworks represent a promising restorative option for implant single crowns and FDPs.24–27 However, the clinical success of zirconia implant restorations appears to be limited by chipping of the veneering ceramic.25–27 The combination of lithium disilicate restorations with zirconia or titanium frameworks represents a
valid option to combine mechanical effectiveness with excellent esthetics, improving the long-term clinical outcomes of implant prostheses. The adhesion between lithium disilicate and zirconia or titanium can be performed using resin cements.28 The present retrospective study aimed at assessing the clinical performance of anterior and posterior lithium disilicate restorations supported by either natural teeth or implants. This observational analysis evaluated both the mechanics and esthetics of the prostheses over a maximum period of 6 years.
Method and materials Study population
Between June 2006 and December 2010, six expert prosthodontists made 860 lithium disilicate restorations in 312 patients (143 men, age range: 19 to 61 years; 169 women, age range: 19 to 71 years). Patients were in need of different prosthetic therapies and were selected from consecutive patients both at the authors’ offices and at the Department of Fixed Prosthodontics of the University “Federico II” of Naples, Italy. The Ethical Committee of the university provided institutional review board approval, and all patients signed a written consent form to participate in the study. The following inclusion criteria for abutment teeth were adopted9: good oral hygiene, periodontally healthy, vital or endodontically
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167
Table 1
Descriptive characteristics of the study groups
Group
Follow-up range (mo)
Mean follow-up (mo)
Cumulative survival rate (%)
Cumulative success rate (%)
Anterior crowns
Veneered (n = 209) Monolithic (n = 22)
24–72
37.3
98.57 95.46
97.61 95.46
Posterior crowns
Veneered (n = 65) Monolithic (n = 132)
12–61
33.4
96.92 96.21
95.39 96.21
Implant crowns
Veneered (n = 7) Monolithic (n = 45)
12–61
28.3
100 97.78
100 97.78
Anterior veneers
Veneered (n = 239) Monolithic (n = 40)
12–72
42.1
97.91 100
96.24 100
Posterior veneers
Veneered (n = 26) Monolithic (n = 13)
24–61
37.5
100 100
100 100
Onlays
Veneered (n = 16) Monolithic (n = 46)
12–57
32.5
100 97.83
100 97.83
treated to a clinically sound state, and opposing natural teeth or fixed prostheses. Patients not fulfilling the inclusion criteria were excluded from the study. All patients were in good general health, and 34% were smokers (more than 5 cigarettes per day). The gingival health was maintained during the study period. According to patients’ needs, single crowns on both teeth and implants and veneers and onlays were made in anterior and posterior areas as follows: 480 crowns (329 maxillary, 151 mandibular), 318 veneers (203 maxillary, 115 mandibular), and 62 onlays (21 maxillary and 41 mandibular) (Table 1); 261 prostheses were placed in patients with parafunctions (30.3%). The restorations were fabricated using pressed lithium disilicate using both monolithic and layered techniques.
Patients with at least a 1-year follow-up were recalled for clinical and radiologic assessments. The observational period ranged from 12 to 72 months, with a mean follow-up of 3 years.
Veneers
A total of 318 veneers were made (203 in the maxilla and 115 in the mandible) (Table 2). Tooth preparations were performed with a slight chamfer with a depth of 0.2 to 0.8 mm, an axial reduction of 0 to 0.8 mm, and an incisal reduction of 0 to 1.5 mm in relation to the wax-up and the presence of discoloration on teeth. Transparent silicone templates derived from the wax-up were used to optimize the preparation.29 The axial reduction was achieved using tapered
round-ended burs, preserving as much enamel as possible, to keep the finish lines within enamel and achieve the best long-term retention.30 The interproximal contact points between teeth were opened only in the presence of Class III composite restorations or in clinical situations such as diastema or interproximal black triangles. A palatal chamfer was made in 56 veneers, while a butt joint was made in 262 restorations. The buccal thickness ranged from 0.2 to 0.8 mm in the cervical third, 0.2 to 1.2 mm in the middle third, and 0.3 to 0.9 mm in the incisal third. Centric contacts at the interface were prevented through the localization of opposing contacts.29 The margins were preferably located supragingivally, thus resulting in simplified impression taking and evaluation of marginal adaptation while help-
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Table 2
Anatomical distribution of lithium disilicate restorations Distribution of restored teeth Layered veneers
Teeth
Monolithic veneers
Layered crowns
Monolithic crowns
Maxilla
Mandible
Maxilla
Mandible
Maxilla
Mandible
Maxilla
Mandible
Central incisors
64
27
13
2
43
3
12
4
Lateral incisors
49
27
9
2
47
3
11
4
Canines
41
24
10
4
28
9
8
11
First premolars
12
8
5
4
40
18
28
23
Second premolars
5
8
2
2
38
23
29
29
First molars
–
–
–
–
13
8
17
10
Second molars
–
–
–
–
4
4
9
4
171
94
39
14
213
68
114
85
Total
Fig 1 Rehabilitation of the maxillary anterior teeth with six lithium disilicate veneers. (a) Preoperative view. (b) Five-year follow-up.
ing to maintain periodontal health. When the contour of the restoration needed to be changed, the margins were located at the gingival crest or slightly into the crevice. Specifically, 53 restorations were monolithic and 265 were layered. All veneers were cemented adhesively (Fig 1). The ceramic restorations were etched for 20 seconds with 4.5% hydrofluoric acid (IPS ceramic gel, Ivoclar Vivadent; Porcelain Etch, Ultradent). The acid was then washed with water and dried.
A silane agent (Monobond S, Ivoclar Vivadent; Ceramic Primer, 3M ESPE) was applied and blown dry on the veneer. Rubber dam was used for 139 veneers. In the remaining 179 restorations, a gingival cord (N. 000 Ultrapak, Ultradent) was placed into the sulcus prior to luting. Concurrently, the tooth surface was etched for 30 seconds with 37% orthophosphoric acid gel (Ultra-Etch, Ultradent). After water rinsing of the tooth surface for 30 seconds, a bonding agent (Opti-
bond FL, Kerr) was applied to both the prepared tooth and the internal surface of the veneers; a dentin primer (Optibond FL, Kerr) was applied only in areas of exposed dentin. Finally, luting procedures were performed as follows: veneers up to 0.5 mm in thickness were luted using flowable composites (Gradia Direct Flow, GC; Tetric EvoFlow, Ivoclar Vivadent) or light-curing cement (Variolink Veneer, Ivoclar Vivadent), while restorations up to 0.8 mm in thickness were cemented
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169
Distribution of restored teeth Layered onlays
Monolithic onlays
Maxilla Mandible Maxilla Mandible –
–
–
–
–
–
–
–
–
–
–
–
2
2
8
3
3
1
8
8
2
2
3
7
2
2
2
7
9
7
21
25
with dual-curing composite systems (Variolink II, Ivoclar Vivadent). Excess cement was removed with a brush and dental floss interproximally. The margins of the veneers were covered with glycerin gel, and resin luting agents were light polymerized for 30 seconds from each side. The margins were then finished with a plastic scaler to remove excess resin. The occlusal contacts were carefully evaluated and balanced.
Tooth-supported single crowns
A total of 428 tooth-supported single crowns were made (299 in the maxilla and 129 in the mandible) (Table 2). Tooth preparation was performed following the diagnostic wax-up. A general 0.3- to 1.0-mm overall reduction was performed, with the exception of the incisal/occlusal areas, which were
reduced by 1.5 mm. As to the marginal design, a 0.4- to 1-mm slight circumferential chamfer preparation was performed, with rounded internal angles. The taper of the preparations ranged from 5 to 10 degrees, depending on the abutment length.31 In posterior areas, the margins were located supra- or equigingivally to preserve enamel, facilitate impression making, and aid evaluation of marginal adaptation. In anterior areas, the margin was located at the gingival crest or slightly into the sulcus, depending on esthetic demands. The thickness of the restorations ranged from 0.3 to 1.0 mm on interproximal and axial walls; the minimum thickness was 1.5 mm on the occlusal/incisal surfaces to achieve proper biomechanics. On a total of 428 single crowns (231 anterior and 197 posterior), 407 restorations were pressed (274 layered, 154 monolithic). Among these, 21 crowns were fabricated with CAD/CAM (8 layered and 13 monolithic). All restorations were cemented adhesively using selfadhesive (RelyX Unicem, 3M ESPE) or dual-curing resin cements (Multilink Automix, Ivoclar Vivadent; Variolink II, Ivoclar Vivadent) in accordance with manufacturers’ instructions. The prepared teeth were isolated with a gingival cord (N. 000 Ultrapak), and the adhesive cementation was performed as previously described. The clinical conditions allowed for the cementation of 68 crowns with rubber dam. The occlusion was refined, and any adjusted surface was polished (Fig 2).
Onlays
A total of 62 onlays were made (21 in the maxilla and 41 in the mandible) (Table 2). Cavities were prepared with a minimum occlusal thickness of 2 mm, and an interproximal buildup was performed to facilitate impression making and cementation (Fig 3). On a total of 62 prostheses, 16 onlays were layered while 64 restorations were produced fully anatomical with subsequent stain characterization. As to cementation, the prepared teeth were isolated with rubber dam and flowable composite resin (Gradia Direct Flow; Tetric EvoFlow) or dualcuring composite systems (Variolink II) used in accordance with the protocol previously described. The occlusion was refined as needed, and any adjusted surface was polished.
Implant-supported restorations
A total of 52 implant-supported restorations on 36 implants were made (30 in the maxilla and 22 in the mandible) (Table 2): 7 cemented crowns, 9 screwed crowns, 2 screwed zirconia full-arches (overall 26 restorations), 1 screwed zirconia four-unit FDP, and 2 screwed titanium three-unit FDPs. Lithium disilicate crowns were used in combination with zirconia or titanium frameworks and CAD/CAM abutments. Abutments and frameworks were designed with a minimum crown thickness of 1.5 mm circumferentially and at least 2 mm in occlusal/incisal aspects. In the case of titanium frameworks, a layer of
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170
Fig 2 Full-mouth rehabilitation by means of lithium disilicate single crowns. (a) Finished and polished restorations on the master casts. (b) Five-year follow-up of the full-mouth rehabilitation onto natural teeth and implant abutments. Fig 3 (left) Six-year follow-up of inlay and onlay monolithic restorations. Fig 4 (below) Maxillary implant-supported full-arch rehabilitation. (a) Zirconia framework with 14 lithium disilicate single crowns. (b) Three-year follow-up.
a
opaque mass was applied onto the structures to mask the grayish appearance of the metal. The lithium disilicate restorations were cemented onto zirconia and titanium using self-adhesive (RelyX Unicem) or dual-curing resin luting agent (Multilink Automix). The crowns were treated as in the case of natural abutment restorations, and no procedures were performed on framework materials. As for screwed restorations, in all cases in which the screw access hole did not take up the buccal wall of the
b
restoration, an extraoral cementation was carried out, avoiding the risk of subgingival residual cement. The screw access holes were then filled with composite resin (Fig 4).
Clinical evaluation
Standardized photographs and radiographs were taken at all recall appointments. Data forms recording the mechanical and esthetic characteristics of each restoration were used as documentation tools.
Patients were examined at clinical recalls at least 1 year after cementation and then annually; color match, porcelain surface, marginal discoloration, and integrity were evaluated following the modified California Dental Association (CDA) criteria.32 The patients’ satisfaction was assessed using nominal scores (nonacceptable, acceptable, good, and excellent). In the case of any mechanical complication, the restoration was considered a failure.
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171 Statistical analysis
Descriptive statistics were made with dedicated software (SPSS, version 17, IBM). The minimum, mean, and maximum follow-ups were calculated for all lithium disilicate prostheses. The cumulative survival and success rates were recorded in all groups using the Kaplan-Meier analysis; all groups were divided into veneered and monolithic prostheses. Each mechanical complication, both minor (loss of retention, minor chipping) and major (core fracture, support fracture, major chipping), was considered as a statistical event. The log-rank test was performed to compare the survival curves of veneered and monolithic restorations. The level of significance was set at P = .05.
Results All prostheses were fabricated by six expert dental technicians according to the manufacturers’ instructions. A total of 860 restorative units were evaluated from a minimum of 12 to a maximum of 72 months in 312 patients.
Veneers
Anterior layered veneers showed cumulative survival and success rates of 97.91% and 96.24%, respectively. Anterior monolithic veneers showed cumulative survival and success rates of 100% (Table 1). Both posterior layered and monolithic veneers showed cumu-
lative survival and success rates of 100% (Table 1). Chipping was observed on five veneers, all at the maxillary arch. None of the minor cohesive fractures impaired function; the restorations were smoothed and finished intraorally and remained in situ for further observation. Core fractures were noted on three veneers, one on a maxillary lateral incisor and two in the mandibular anterior segment; they all were layered. All fractured restorations had ceramic materials in the opposite dentition and required the replacement of the restorations. The failed veneers were prepared with an incisal butt joint and fractures were observed 8 and 11 months after cementation, respectively; the replacements were performed with a new preparation design that involved the lingual aspect as well as a mini-chamfer. Loss of retention was observed on one mandibular veneer; the restoration was immediately rebonded and was still in function at the final follow-up.
Tooth-supported single crowns
Anterior layered tooth-supported crowns showed cumulative survival and success rates of 98.57% and 97.61%, respectively. Anterior monolithic crowns showed cumulative survival and success rates of 95.46% (Table 1). Posterior layered crowns showed cumulative survival and success rates of 96.92% and 95.39%, respectively. Posterior monolithic crowns showed cumu-
lative survival and success rates of 96.21% (Table 1). Minor cohesive fractures of the veneering ceramic occurred on eight tooth-supported crowns, three in the maxilla and five in the mandible; two of these chipped crowns were monolithic, one per arch. Crown chippings occurred mostly in posterior segments (premolars and molars); only four of these needed a replacement, while the remaining chipped areas were simply smoothed and finished. Core failures occurred 7 months after cementation on two maxillary crowns on central and lateral incisors in a single patient and required the replacement of the restorations. Both of the fractured restorations had ceramic materials in the opposite dentition. Loss of retention was observed on two mandibular crowns; the restorations were immediately rebonded and were still in function at the final follow-up. One mandibular crown needed root canal therapy because of a pulpitis occurring 18 months after cementation. The endodontic treatment was performed through the crown, and the access hole was then filled with composite resin; the restoration was considered a failure although it was still in function. Furthermore, one nonvital maxillary premolar restored with a crown was extracted because of root fracture.
Onlays
Layered onlays showed cumulative survival and success rates of 100% (Table 1). Monolithic onlays
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172
Veneered anterior crowns
Veneered posterior crowns
Monolithic anterior crowns 0.995
0.9 0.990
0.8
0.975
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0
8 12
0.992
1.0
Cumulative survival (%)
Cumulative survival (%)
1.0
Monolithic posterior crowns
0.985
24 29 36 40 48 35
60
Time to complication (mo)
showed cumulative survival and success rates of 97.83% (Table 1). Chipping was noticed on three onlays, all at the mandibular arch. Two of these chipped onlays were monolithic; both restorations were positioned on mandibular second premolars, and opposite dentition were represented by a natural tooth in one case and by a ceramic restoration in the other. The damaged area was intraorally repaired by means of composite resin. Loss of retention was observed on one maxillary onlay; the restoration was immediately rebonded and was still in function at the final followup.
Implant-supported restorations
Layered implant crowns showed cumulative survival and success rates of 100% (Table 1). Implant-support-
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
72 70
Fig 5 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate anterior single crowns.
0.9
0.985 0.984 0.976 0.954 0.969 0.968 0.961
0
9 12
24 30 36 25 3438 33
48
60 61
72
Time to complication (mo) Fig 6 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate posterior single crowns.
ed monolithic crowns reported cumulative survival and success rates of 97.78% (Table 1). Minor cohesive fractures of the veneering ceramic occurred on one monolithic implant crown on a maxillary canine. The chipping did not impair function; consequently, the area was smoothed and finished and the crown remained in situ.
Statistical analysis
Considering any complication as an event, the cumulative survival rates of lithium disilicate restorations ranged from 95.46% to 100%, while the cumulative success rates ranged from 95.39% to 100%, according to Kaplan-Meier survival analysis (Figs 5 to 10, Table 1). The log-rank test that compared the survival curves of veneered and monolithic restorations was not sta-
tistically significant in any research group (P > .05) (Table 3).
Clinical evaluation
The clinical ratings of the successful restorations, both monolithic and layered, were satisfactory according to the modified CDA criteria (Table 4). The color match of the monolithic restorations recorded the lowest proportion of A ratings (90.9%) but was considered absolutely acceptable both by clinicians and patients. With the exception of the previously reported failed prostheses, no restoration was rated C or D for any of the evaluation criteria. The patient satisfaction scores were mainly excellent for all restorations; a few prostheses were rated as good and none were reported to be nonacceptable or acceptable (Table 5).
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173
Veneered implant crowns
Veneered anterior veneers
Monolithic implant crowns
Monolithic anterior veneers
1.0
0.978
0.9
Cumulative survival (%)
Cumulative survival (%)
1.0 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0
12
24
36
48
60 61
0.9
0.6 0.5 0.4 0.3 0.2 0.1 0 4 8 12 10
Monolithic onlays
0.9
Cumulative survival (%)
Cumulative survival (%)
Veneered onlays
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 48
60 61
72
Time to complication (mo) Fig 9 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate posterior veneers.
Monolithic restorations showed the lowest number of mechanical structural complications. No monolithic veneer failed. Conversely, three monolithic crowns located on
72 70
Monolithic posterior veneers
1.0
36
60 59
Veneered posterior veneers
0.9
24
36 42 48 3943
Fig 8 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate anterior veneers.
1.0
12
24
Time to complication (mo)
Fig 7 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate implant-supported crowns.
0
0.963
0.7
Time to complication (mo)
0
0.984 0.976 0.967
0.8
0
72
0.980
0.996 0.988 0.992
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0
12
24
36 43 48
60 57
72
Time to complication (mo) Fig 10 Kaplan-Meier graph of complication onset in relation to time for lithium disilicate onlays.
one implant and two natural teeth were affected by chipping. All failed crowns had ceramic restorations on the opposite dentition; two of these were placed in patients with
parafunctional habits. Unrestorable fractures were observed only in layered restorations positioned in anterior segments in patients with uncontrolled parafunctions.
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Table 3
Results of the log-rank test comparing the survival curves
Groups
Log-rank
P
Veneered anterior crowns vs monolithic anterior crowns
0.381
> .05
Veneered posterior crowns vs monolithic posterior crowns
0.084
> .05
Veneered anterior veneers vs monolithic anterior veneers
1.062
> .05
Veneered posterior veneers vs monolithic posterior veneers
2.004
> .05
Veneered onlays vs monolithic onlays
0.345
> .05
Veneered implant crowns vs monolithic implant crowns
0.154
> .05
Table 4
Frequency distribution of clinical ratings in lithium disilicate restorations according to the modified CDA criteria Modified CDA rating A
B
C
D
Parameter
Layered (%)
Monolithic (%)
Layered (%)
Monolithic (%)
Layered (%)
Monolithic (%)
Layered (%)
Monolithic (%)
Color match
97.9
90.9
2.1
7.4
0
1.7
0
0
Porcelain surface
96.7
97.1
3.3
2.9
0
0
0
0
Marginal discoloration
96.7
95.9
3.3
4.1
0
0
0
0
Marginal integrity
98.2
98.7
1.8
1.3
0
0
0
0
Table 5
Patients’ satisfaction scores for lithium disilicate restorations Observational period (mo)
Satisfaction score
12 < x > 24
24 < x > 36
36 < x > 48
48 < x > 72
Veneers Crowns Onlays Veneers Crowns Onlays Veneers Crowns Onlays Veneers Crowns Onlays
Nonacceptable
0
0
0
0
0
0
0
0
0
0
0
0
Acceptable
0
0
0
0
0
0
0
0
0
0
0
0
Good
0
9
2
4
13
1
15
14
0
0
0
0
Excellent
31
99
10
95
159
25
90
116
22
83
70
2
x = observational period in months.
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175
Fig 11 Minimally invasive preparations for lithium disilicate crowns.
Recurrent caries was not detected in any restoration, contour quality was satisfactory, and proximal contacts were well maintained over time.
Discussion In this study, lithium disilicate restorations were associated with very high success rates (95.39% to 100% at 72 months), comparable with results reported in previous studies.2,11 Several variables contribute to the clinical effectiveness of such restorations; particularly, lithium disilicate prostheses have to be bonded with correct adhesive techniques to achieve the reported success rates. Moreover, the quantity and quality of tooth structure is paramount, especially the enamel at the finish lines: the more the enamel is preserved, the better the adhesion and the more limited aging of the bonding interfaces will be over time.2,17,30 An estimated survival probability of 93.5% after
10 years was reported for porcelain laminate veneers.33 Moreover, a recent systematic review reported that glass-ceramic veneers present an adequate clinical survival for at least 5 years of function with very low complication rates.34 Accordingly to the clinical situations, the authors transferred the concept of adhesion to enamel to improve restoration longevity from veneers to crowns (Fig 11), producing very thin restorations and preserving as much enamel as possible. All fractures and mechanical complications occurred in restorations with thicknesses in accordance or even superior to manufacturing instructions but applied on teeth where the majority of supporting substrate was dentin or composite. Conversely, no mechanical complications were observed in restorations cemented on teeth where enamel represented at least 50% of the bonding substrate. As regards technical drawbacks, 63% of mechanical complications (fractures and chipping) were ob-
served on restorations that had porcelain as opponent and 33% of these occurred in patients with parafunctions. The remaining 37% of the mechanical complications were noticed in patients that had natural teeth as antagonist dentition and were not affected by bruxism or clenching. Considering the high rate of parafunctional patients (30.3%) and the high success rate in this study, lithium disilicate may be considered a valid option to treat such patients, especially using monolithic restorations, as they did not show any structural complications. According to the CDA quality evaluation system, all of the restorations were classified as satisfactory for marginal integrity, color, and surface, with the only exception of monolithic crowns and onlays, which did not show an optimal result in color match in some cases (9.1%). Case selection is a crucial factor for achieving natural appearance with a monolithic approach, as several variables contribute to
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176 the successful esthetic of a restoration, such as color of the natural abutment, ceramic thickness, correct choice of ingots, and color and value of adjacent teeth. The combination of lithium disilicate restorations with zirconia and titanium frameworks or abutments showed excellent results in terms of esthetics, function, and loss of retention. Only one monolithic crown placed on a zirconia framework was affected by chipping 6 days after cementation. This restoration fractured in a patient treated with an implant-supported full-arch prosthesis, and the premature fracture was probably due to an uneven occlusal control in centric relation; the fractured fragment was immediately rebonded with an adhesive technique, occlusion was refined, and the crown was still in function after 3 years. Lithium disilicate technology demonstrates unique features to be used in different clinical situations; the possibility to choose between ingots with different opacity and translucency allows the clinician to select the ideal core, even in cases in which severe discolorations make it very difficult to obtain satisfactory esthetics.3 The etchability of lithium disilicate improves the clinical performance of adhesive cementation and eases the management of clinical complications. Especially in cases of chipping or fractures, the possibility of applying an effective adhesive by means of the etching technique allows the clinician to repair any mechanical complication with easy handling procedures and a favorable prognosis.
As to the study’s limitations, the present investigation is a retrospective, clinical, multipractice study; consequently, although the same rigorous approach was respected, different operators and several clinical variables (restoration type, intraoral distribution, multiunit prostheses in a single patient) could act as confounders in the clinical and statistical results. Considering these limitations, further in vivo investigations would be necessary to validate the clinical reliability of lithium disilicate restorations in the long-term, confirming the effectiveness of the proposed prosthetic approach.
Conclusion According to the results of this study and within its limitations, the use of lithium disilicate in fixed prosthodontics proved to be effective and reliable in the short- and medium-term. The choice of this material may represent a valid option in many clinical situations, offering biologic, technical, and esthetic advantages.
Acknowledgments The authors reported no conflicts of interest related to this study.
References 1. Dumfahrt H. Porcelain laminate veneers. A restospective evaluation after 1 to 10 years of service. Part 1: Clinical procedure. Int J Prosthodont 1999;12:505–513.
2. Fradeani M, Rademagni M, Corrado M. Porcelain laminate veneers: 6 to 12 year clinical evaluation. A retrospective study. Int J Periodontics Restorative Dent 2005;25:9–17. 3. Fabbri G, Mancini R, Marinelli V, Ban G. Anterior discolored teeth restored with Procera all-ceramic restorations: A clinical evaluation of the esthetic outcome based on the thickness of the core selected. Eur J Esthet Dent 2011;6:76–86. 4. Boening KW, Wolf BH, Schmidt AE, Kastner K, Walter MH. Clinical fit of Procera AllCeram crowns. J Prosthet Dent 2000;84:419–424. 5. Martinez-Rus F, Suarez MJ, Rivera B, Padrìes G. Evaluation of the absolute marginal discrepancy of zirconia-based ceramic copings. J Prosthet Dent 2011; 105:108–114 6. Kokubo Y, Tsumita M, Kano T, Sakurai S, Fukushima S. Clinical marginal and internal gaps of zirconia all-ceramic crowns. J Prosthodont Res 2011;55:40–43. 7. Guess P, Zavanelli R, Silva N, Bonfante E, Coelho P, Thompson V. Monolithic CAD/ CAM lithium disilicate versus veneered Y-TZP crowns: Comparison of failure modes and reliability after fatigue. Int J Prosthodont 2010;23:434–442. 8. Raigrodski AJ, Hillstead MB, Meng GK, Chung KH. Survival and complications of zirconia-based fixed dental prostheses: A systematic review. J Prosthet Dent 2012;107:170–177. 9. Sax C, Hammerle CH, Sailer I. 10-year clinical outcomes of fixed dental prostheses with zirconia frameworks. Int J Comput Dent 2011;14:183–202. 10. Ortop A, Kihl ML, Carlsson GE. A 3-year retrospective and clinical follow-up study of zirconia single crowns performed in a private practice. J Dent 2009;37: 731–736. 11. Sorrentino R, Galasso L, Teté S, De Simone G, Zarone F. Clinical evaluation of 209 all-ceramic single crowns cemented on natural and implant-supported abutments with different luting agents: A 6-year retrospective study. Clin Implant Dent Relat Res 2012;14:184–197. 12. Marquardt P, Strub JR. Survival rates of IPS empress 2 all-ceramic crowns and fixed partial dentures: Results of a 5-year prospective clinical study. Quintessence Int 2006;37:253–259. 13. Taskonak B, Sertgöz A. Two-year clinical evaluation of lithia-disilicate-based all-ceramic crowns and fixed partial dentures. Dent Mater 2006;22:1008–1013.
The International Journal of Periodontics & Restorative Dentistry © 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
177
14. Gehrt M, Wolfart S, Rafai N, Reich S, Edelhoff D. Clinical results of lithiumdisilicate crowns after up to 9 years of service. Clin Oral Investig 2013;17: 275–284. 15. Kern M, Sasse M, Wolfart S. Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium-disilicate ceramic. J Am Dent Assoc 2012; 143:234–240. 16. Simonsen RJ, Calamia JR. Tensile bond strength of etched porcelain [abstract 1154]. L Debt Res 1983;62:297. 17. Dumfahrt H. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service. Part 1: Clinical procedure. Int J Prosthodont 1999;12:505–513. 18. Stappert CF, Dai M, Chitmongkolsuk S, Gerds T, Strub JR. Marginal adaption of three-unit fixed partial dentures constructed from pressed ceramic systems. Brit Dent J 2004;196:766–770. 19. Van Brakel R, Cune MS, van Winkelhoff AJ, de Putter C, Verhoeven JW, van der Reijden W. Early bacterial colonization and soft tissue health around zirconia and titanium abutments: An in vivo study in man. Clin Oral Implants Res 2011; 22:571–577. 20. Karl M, Taylor TD. Effect of material selection on the passivity of fit of implantsupported restorations created with computer-aided design/computer-assisted manufacture. Int J Oral Maxillofac Implants 2011;26:739–745. 21. Denry I, Kelly JR. State of the art of zirconia for dental applications. Dent Mater 2008,24:299–307.
22. Sailer I, Zembic A, Jung RE, Siegenthaler D, Holdergger C, Hämmerle CH. Randomized controlled clinical trial of customized zirconia and titanium implant abutment for canine and posterior single-tooth implant reconstructions: Preliminary result at 1 year of function. Clin Oral Implants Res 2009;20:219–225. 23. Fischer K, Stenberg T. Prospective 10year cohort study based on randomized, controlled trial (RCT) on implant-supported full-arch maxillary prostheses. Part II. Prosthetic outcomes and maintenance. Clin Implant Dent Relat Res 2013; 15:498–508. 24. Bremer F, Grade S, Kohorst P, Stiesch M. In vivo biofilm formation on different dental ceramics. Quintessence Int 2011; 42:565–574. 25. Sailer I, Philipp A, Zembic A, Pjetursson BE, Hammerle CH, Zwahlen M. A systematic review of the performance of ceramic and metal implant abutments supporting fixed implant reconstructions. Clin Oral Implants Res 2009;20(suppl 4):4–31. 26. Nothdurft FP, Pospiech PR. Zirconium dioxide implant abutments for posterior single-tooth replacement: First results. J Periodontol 2009;80:2065–2072. 27. Larsson C, Vult von Steyern P, Sunzel B, Nilner K. All-ceramic two-to five-unit implant-supported reconstructions. A randomized, prospective clinical trial. Swed Dent J 2006;30:45–53.
28. Martinez-Rus F, Ferreiroa A, Ozcan M, Bartolomè JF, Pradies G. Fracture resistance of crowns cemented on titanium and zirconia implant abutments: A comparison of monolithic versus manually veneered all-ceramic systems. Int J Oral Maxillofac Implants 2012;27:1448–1455. 29. Magne P, Perroud R, Hodges JS, Belser U. Clinical performance of novel-design porcelain veneers for the recovery of coronal volume and length. Int J Periodontics Restorative Dent 2000;20:441–457. 30. Friedman MJ. Porcelain veneer restorations: A clinician’s opinion about a disturbing trend. J Esthet Restorative Dent 2001;13:318–327. 31. Doyle MG, Goodacre CJ, Munoz CA, Andres CJ. The effect of tooth preparation design on the breaking strength of Dicor crowns. Part 3. Int J Prosthodont 1990;3:327–340. 32. California Dental Association. Quality Evaluation for Dental Care. Guidelines for the Assessement of Clinical Quality and Performance, ed 3. Sacramento, CA: California Dental Association, 1995. 33. Beier US, Kapferer I, Burtscher D, Dumfahrt H. Clinical performance of porcelain laminate veneers for up to 20 years. Int J Prosthodont 2012;25:79–85. 34. Petridis HP, Zekeridou A, Malliari M, Tortopidis D, Koidis P. Survival of ceramic veneers made of different materials after a minimum follow-up period of five years: A systematic review and meta-analysis. Eur J Esthet Dent 2012;7: 138–152.
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