Survival of Porcelain Laminate Veneers with Different Degrees of Dentin Exposure: 2-year Clinical Results Elif Öztürka / Şükran Bolayb
Purpose: To evaluate the clinical performance of porcelain laminate veneers (PLVs) after 2 years. Materials and Methods: Twenty-eight patients were treated with 125 PLVs. The experimental variables were preparation design (incisal overlap [IO] and incisal bevel [IB]) and adhesion surface (enamel [E], enamel with minimal dentin exposure [MDE], and enamel with severe dentin exposure (SDE)]. Marginal adaptation, marginal discoloration, secondary caries, postoperative sensitivity, and patient satisfaction were assessed according to the modified United States Public Health Service criteria. Each restoration was examined for fractures and debonding. In addition, gingival tissue health by gingival plaque, bleeding, and recession was recorded. An experienced clinician evaluated the restorations at baseline and after 6, 12, and 24 months, and survival rates evaluating relative and absolute failures were calculated (p = 0.05). Results: Eleven (8.8%) veneers failed, and the overall cumulative survival rate was 91.2% after 2 years of followup. IB and IO preparation designs exhibited survival rates of 94% and 85.7%, respectively, but this difference was not statistically significant (p > 0.05). PLVs bonded to SDE were more likely to fail than those bonded to E and MDE (p < 0.05). There was no significant difference between the failure rate of PLVs bonded to E and those bonded to MDE (p > 0.05). Conclusions: PLVs have high survival rates when bonded to enamel only, as well as to enamel with minimal dentin exposure. However, extensive dentin exposure should be avoided during the preparation. Keywords: porcelain laminate veneers, dentin exposure, preparation design. J Adhes Dent 2014; 16: 481–489. doi: 10.3290/j.jad.a32828
T
he porcelain laminate veneer (PLV) technique, which is one of the most popular esthetic treatment alternatives for anterior teeth to restore slight discolorations, abrasions, fractures, malformations, and/or malpositions, bonds a thin porcelain laminate to the tooth surface using dental adhesives and resin cements.23,26 One of the major advantages of the porcelain laminate veneer technique is that it can be performed on a conservative preparation with a minimum of tooth reduction.39 However, there are some problems associated with PLVs, such as debonding, fracture, or microleakage from the margins of the restoration.29 Many factors can
a
Assistant Professor, Department of Restorative Dentistry, Faculty of Dentistry, Hacettepe University, Ankara, Turkey. Experimental design, clinical applications, wrote the manuscript.
b
Professor, Department of Restorative Dentistry, Faculty of Dentistry, Hacettepe University, Ankara, Turkey. Idea and hypothesis, follow-up examinations, proofread the manuscript.
Correspondence: Assistant Professor Elif Öztürk, Hacettepe University, Faculty of Dentistry, Department of Restorative Dentistry, Sihhiye-06100, Ankara, Turkey. Tel: +90-312-305-2270, Fax: +90-312-311-3438. e-mail: [email protected]
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Submitted for publication: 05.03.14; accepted for publication: 19.09.14
influence the long-term success of porcelain laminate veneers, such as structure of the adhesion surface, preparation type and depth, type and thickness of the porcelain, type of the resin cement and dental adhesive, tooth morphology, as well as functional and parafunctional activities.22,26 Tooth preparation for PLVs is crucial for optimal function and esthetics; therefore, care should be taken to completely perform this preparation in the enamel.16,22 In general, anterior tooth preparation requires a 0.3- to 0.7-mm facial reduction, depending on the location of the crown, to imitate the natural contours of the tooth.28 This anatomical preparation technique may enable tooth preparation within only enamel, because enamel thickness is different in different zones of the tooth. For PLV restorations, preparation design is classified according to the type of incisal edge. The following two preparation designs are frequently used: incisal bevel (IB) and incisal overlap (IO) ending with a palatal chamfer. Both techniques allow characterization of the incisal region and better seating of PLVs.5 However, controversy exists over which preparation design is the most suitable,5,35 and few clinical studies have compared their efficacy.20 481
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Preparation performed completely in the enamel is believed to maintain an optimal bond with PLV and decrease stress in the porcelain. Thus, preparation of PLVs should be meticulously performed.16 In addition, the preparation technique used impacts on the longevity of the restoration, eg, high failure rates of PLVs have been attributed to the exposure of dentin surfaces. However, exposure of a considerable amount of dentin is inevitable during preparation, particularly in cervical and proximal areas, to compensate for slight malposition and/or discoloration.21 Several medium-to-long-term clinical studies have evaluated the clinical performance of PLVs. One longitudinal clinical study8 reported a low failure rate (0%–7%) after 5 to 12 years, whereas others31,32,37 describe higher failure rates (14%–33%). However, few clinical studies have considered the performance of PLVs according to preparation depth7,14 or preparation design,2 when dentin is exposed on the tooth surface. Therefore, in this study, we assessed the medium-term clinical performance of PLVs, using two preparation designs and a range of preparation depths, causing different degrees of dentin exposure on the tooth surface. The null hypotheses were as follows: 1. dentin exposure on the tooth surface does not affect the clinical survival of PLVs, and 2. there is no difference between IO and IB preparation designs in terms of the clinical survival of PLVs.
MATERIALS AND METHODS Study Design The protocol of this clinical study was approved by the Ethics Committee of Hacettepe University, Ankara, Turkey (FON 07/27-42). Informed consent was obtained from each participant. Twenty-eight patients (5 men, 23 women) aged 18 to 51 years (average: 30 years) were referred to the Department of Restorative Dentistry at Hacettepe University with the main complaint of unesthetic anterior teeth. The patients received 125 PLVs (29 in men, 96 in women) between May 2008 and May 2011. The indications for treatment were as follows: severe intrinsic and/or extrinsic discoloration unrelieved by bleaching (46, 36.8%); minor to moderate noncarious structural defects, and wear or fracture (6, 4.8%); diastema (4, 3.2%); slight malalignment (6, 4.8%); morphological disorders, such as peg-shaped maxillary lateral incisors, as well as the presence of a canine tooth instead of a missing lateral tooth (23, 18.4%); existing unesthetic composite restorations of the anterior teeth (40, 32%). Nonvital teeth (12, 9.6%) were not excluded from the study. Inclusion criteria were as follows: all patients were required to be at least 18 years old, able to read and sign the informed consent document, physically and psychologically able to tolerate conventional restorative procedures, willing to return for follow-up examinations as outlined by the investigators, and to have all maxillary anterior teeth, no active periodontal or pulpal diseases, and no systemic disorders. Patients with severe parafunc482
tional habits were excluded from the study. Initially, dental calculus and extrinsic stains were cleaned from patients’ teeth. Patients were instructed on improving their gingival health and maintaining effective plaque control. However, if their gingival health did not improve, they were excluded from the study. Diagnosis and Treatment Planning Patients were treated with a minimum of one and a maximum of nine veneers according to an evaluation. Pre-operative photographs of each patient were taken to evaluate the clinical appearance of their teeth. Before preparation, impressions were taken from each patient using a polyvinyl siloxane impression material in heavy body (Virtual Putty, Ivoclar Vivadent; Schaan, Liechtenstein) to prepare diagnostic wax-up models. For each patient, the wax-up models were duplicated, and cast models were produced to prepare the vacuum sheets. Final volume of the restorations was made with temporary flowable composite (Systemp.link, Ivoclar Vivadent) using transparent, rigid, vacuum-shaped sheets (VacuFormerSystem, Cavex; Haarlem, The Netherlands). Patients were able to preview the finished restoration from the provisional restorations. Furthermore, the maximum conservative preparation was permitted. The same sheet was kept during the treatment of each patient to produce provisional restorations after preparation. This technique was performed in accordance with the esthetic pre-evaluative temporary technique described by Gürel12 and Gürel et al.13 Preparations were made after patient approval of a mock-up, consisting of temporary composite restorations. Before treatment with PLVs, gingival corrections (17 teeth in four patients, 13.6%) were performed where necessary using a DELight Er:YAG laser (HOYA ConBio Laser; Chicago, IL, USA) with low-fluence irradiation at 35 mJ with 10 Hz. Tooth Preparation All preparations were performed over the provisional composite restorations using a 2.5X binocular dental loupe (Orascoptic, Kerr; Middleton, WI, USA) for minimal preparations. The preparation surfaces were initially colored with colored articulation papers. Facial surfaces of the teeth were prepared by making depth-orientation grooves (0.3 mm in depth) with a depth preparation diamond bur (Diatech, Coltène Whaledent; Altstätten, Switzerland). Facial reduction was continued with a tapered, rounded-end diamond bur (Diatech) until the color was removed from the facial surface. Facial preparation was deepened further when necessary to overcome slight malalignment or discoloration. Facial surfaces were reduced by 0.3 to 0.7 mm. The incisal edge was included in each preparation to maximize esthetics. Two different preparation designs were used according to incisal finishing. IB preparations were performed on 83 teeth (66%), whereas 42 teeth (34%) were prepared with IO ending with a palatal chamfer. The reduction ranged from 1.5 to 2 mm on the incisal edge. The Journal of Adhesive Dentistry
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Table 1
Materials used in this study
Brand name
Type
Manufacturer
Composition
Lot No.
IPS e.max Press
Lithium disilicate glass-ceramic
Ivoclar Vivadent; Schaan, Liechtenstein
SiO2, Li2O, K2O, P2O5, ZrO2, ZnO, other oxides, color oxides
M13076
Variolink Veneer
Light-curing resin cement
Ivoclar Vivadent
Dimethacrylates, inorganic fillers, ytterbium trifluoride, catalysts and stabilizers, pigments
P38760
Total-Etch
Phosphoric acid
Ivoclar Vivadent
37% phosphoric acid
K27710
Porcelain etchant
Hydrofluoric acid
Bisco; Schaumburg, IL, USA
5% hydrofluoric acid
1000003009
Syntac Primer
Primer
Ivoclar Vivadent
Triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, maleic acid, acetone
K16326
Syntac Adhesive
Adhesive
Ivoclar Vivadent
Polyethylene glycol dimethacrylate, glutaraldehyde
K30345
Heliobond
Bonding agent
Ivoclar Vivadent
Bis-GMA, triethylene glycol dimethacrylate, catalysts and stabilizers
K30706
Monobond Plus
Silane coupling agent
Ivoclar Vivadent
Alcohol solution of silane methacrylate, phosphoric acid methacrylate, sulfide methacrylate
K30207
All cervical margins were placed equi- or supragingivally and were created with a shallow chamfer finish line 0.3 to 0.5 mm in preparation depth. Gingival finish lines were cervically extended to half the interproximal area to hide restoration margins up to the contact area. All sharp edges and corners were smoothened with an extra-coarse aluminum-oxide polishing disk (OptiDisc, Kerr; Orange, CA, USA) to reduce stress concentrations. Impressions were subsequently obtained using a polyvinyl siloxane impression material (Virtual; Putty and Light Body, Ivoclar Vivadent). Provisional veneers were made chairside using an autopolymerizing temporary composite resin (Systemp.link, Ivoclar Vivadent). For fixation of the provisional veneers, enamel was spot etched with 37% phosphoric acid (Total Etch, Ivoclar Vivadent) for 30 s before application of the temporary composite resin. After completing the preparations, the adhesion surfaces were gently air dried and meticulously evaluated by the two experienced clinicians under 2.5X magnification to categorize them as follows: intra-enamel only (E; 68 restorations, 54.4%), enamel with minimal dentin exposure (MDE; 39 restorations, 31.2%), and enamel with severe dentin exposure (SDE; 17 restorations, 13.6%). PLVs were fabricated from a lithium-disilicate glass ceramic (IPS e.max Press, Ivoclar Vivadent) with a lowfusing nano-fluorapatite glass-ceramic (IPS e.max Ceram, Ivoclar Vivadent) for veneering and characterization of the restorations using the layering technique according to the manufacturer’s instructions. Cementation Procedures Table 1 presents the brand names, types, manufacturers, chemical compositions, and batch numbers of the materials used in this study. Form, contour, marginal Vol 16, No 5, 2014
adaptation, proximal contacts, and shade matching of the restorations were clinically checked after removing the provisional restorations and cleaning the teeth. The color of the cement used was determined using try-in pastes (Variolink Veneer Try-in Paste, Ivoclar Vivadent). All the veneers were adhesively cemented under rubber-dam (Optra-Dam, Ivoclar Vivadent) isolation. The bonding surface procedures for the tooth and porcelain surfaces using light-cured resin cement (Variolink Veneer, Ivoclar Vivadent) are described in Table 2. After these procedures, the PLV restoration was positioned, and excess luting cement was removed with hand instruments and a brush. Before final curing, PLVs were cervically pre-cured for 5 s to completely remove excess resin cement from the cervical and interproximal areas using hand instruments and dental floss without pressure. Final curing was performed according to the manufacturer’s instructions for 40 s on each surface (upper- and mid-buccal, cervical, mesial, distal, and palatal) with a light-emitting diode polymerizing unit (Bluephase LED, Ivoclar Vivadent, 1200 mW/cm 2). Restoration margins were finished and further polished with extra-fine diamond finishing burs (Diatech), polishing cups (Kerr HiLuster Plus, Kerr; Orange, CA, USA), and interproximal polishing strips (Soft-Lex Finishing Strips, 3M ESPE; Seefeld, Germany). Finally, the occlusion was checked in protrusive and lateral movements of the mandible. Follow-up Patients were recalled after 1 week to recheck occlusion, proximal contacts, and gingival margins. This recall was used as the baseline. The restorations were evaluated at baseline and after 6, 12, and 24 months by an experienced clinician (not the clinician who performed 483
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Table 2 Surface conditioning protocols for the tooth and porcelain Surface Tooth surface treatment
Porcelain inner surface
Etching
Enamel: 37% H3PO4 for 30 s Dentin: 37% H3PO4 for 15 s
5% HF for 60 s
Adhesive
(1) Syntac Primer for 15 s (1) Monobond S for 60 s (2) Syntac Adhesive for 10 s (2) Heliobond for 10 s (3) Heliobond for 10 s
H3PO4: phosphoric acid; HF: hydrofluoric acid.
the restoration) blinded to the objective of this study according to the modified United States Public Health Service (USPHS) criteria.3,4 The restorations were rated according to the four USPHS scores of Alfa, Bravo, Charlie, and Delta. The restorations were visually inspected with a dental mirror and probe. Digital photos were taken before and after PLV placement and during followup sessions. Statistical Analysis A survival rate evaluating absolute failures according to in situ criteria and success rates describing both relative (Bravo) and absolute (Charlie and/or Delta) failures were determined. 11 Absolute failure was defined as clinically unacceptable failures, such as loss, fracture, and debonding of the PLV. A relative failure was defined as minimal failures which were clinically acceptable in that they allowed repair of the restoration or healing of gingival tissues. Survival was defined at three levels: survival of the original restoration (Sr, endpoints: absolute failures); functional survival (Sf, endpoints: relative failures); overall survival (So, endpoints: both absolute and relative failures).19 The effects of the study parameters “preparation design” and “tooth tissue type” on the different survival levels were also analyzed. Survival analyses were performed with the statistical software program IBM SPSS Statistics for Windows (version 20.0; Armonk, NY, USA) (p = 0.05), using KaplanMeier and log-rank (Mantel-Cox) tests to obtain the cumulative survival rate in relation to observation time. A restoration-related analysis using each restoration as a statistical unit was used for the analysis.6
RESULTS Twenty-eight patients were treated with 125 PLVs with a 2-year follow-up. All patients came for a follow-up evaluation after 1 week (baseline), 6, 12, and 24 months. No patient was lost during this 2-year follow-up. The number of restorations evaluated at each of the follow-up phases is summarized in Table 3. 484
Fig 1 Preoperative view of a patient with diastemata between the four maxillary anterior teeth and lacking the maxillary left lateral incisor.
One restoration (0.8%) in the IO-MDE group debonded from the tooth without the PLV having any crack or fracture, and therefore it was re-bonded at 6 months. In the same patient, gingivitis was detected on the gingival tissues of five other restorations. In total, eight restorations (6.7%) in two patients were rated Bravo for gingival tissue health at a 6-month recall. At a 12-month follow-up, one score of Bravo (minimal ceramic cohesive fracture on the incisal edge) and one of Delta (total tooth and ceramic fracture) were recorded (Table 3). Marginal adaptation and discoloration, as well as secondary caries and postoperative sensitivity, were rated Alfa during the 2-year follow-up (Figs 1 to 3). As a consequence of the two absolute and nine relative failures, the Sr, Sf, and So rates were 98.4%, 92.7%, and 91.2%, respectively (Fig 4). The So rates for IO (85.7%) and IB (94%) preparations were not significantly different (p > 0.05; Fig 5). However, there were statistically significant differences between the So rates of the restorations bonded to the three different tooth surfaces (E, MDE, and SDE; p < 0.05; Fig 6). The So-E, So-MDE, and So-SDE were 94.1%, 97.4%, and 66.7% respectively. There were no significant differences between So-E and So-MDE (p > 0.05), whereas So-SDE was significantly lower than the other groups (p < 0.05). The survival rates of PLVs after 2 years according to different parameters are presented in Table 4.
DISCUSSION In the present study, we evaluated the clinical success of PLVs of different preparation designs bonded to tooth tissues prepared at different levels after 2 years. Longitudinal studies have some disadvantages, such as the withdrawal of certain dental materials and loss of a proportion of patients over time. In this study, no patients were lost to follow-up, and the materials used remain available. Therefore, the results of this study were presented after a relatively short period. The results of the present study suggest that PLVs are favorable restorations, withstanding 2 years of clinical service and demonstrating promising survival rates. The survival rates determined in this study are comparable The Journal of Adhesive Dentistry
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Table 3 Summary of the modified United States Public Health Service criteria and evaluation of porcelain laminate veneers during follow-up USPHS criteria
Score
Characteristics
Baseline
6 months
Marginal adaptation
Alfa Bravo Charlie Delta
Marginal discoloration
12 months 24 months
Smooth margin Minor voids/defects at margin Obvious crevice at margin Debonded
125 -
124 -
124 -
124 -
Alfa Bravo Charlie/Delta
No discoloration Slight staining/acceptable Large staining/unacceptable
125 -
124 -
124 -
124 -
Secondary caries
Alfa Bravo Charlie Delta
No caries Caries at the margin N/A N/A
125 -
124 -
124 -
124 -
Postoperative sensitivity
Alfa Bravo Charlie Delta
No symptoms Slight sensitivity Moderate pain Severe pain
125 -
124 -
124 -
124 -
Patient satisfaction
Alfa Bravo Charlie/Delta
High Moderate Not satisfied
125 -
124 -
124 -
124 -
Fracture
Alfa Bravo Charlie Delta
None Small/acceptable Moderate/unacceptable Large/unacceptable
125 -
124 -
122 1 1
124 -
Retention
Alfa Bravo Charlie Delta
None N/A N/A De-bonded
125 -
124 1
124 -
124 -
Gingival response
Alfa Bravo Charlie Delta
Healthy Calculus or gingivitis Moderate pocketing and bleeding present Severe periodontitis
125 -
116 8 -
124 -
124 -
N/A: not applicable.
b
a
Fig 2 Baseline view of the porcelain laminate veneers on teeth 12, 11, 21, and 23 from the anterior (a) and the palatinal (b) region. The left maxillary canine tooth was reshaped like a lateral incisor.
b
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Fig 3 Two-year recall of the same patient as in Figs 1 and 2 with porcelain laminate veneers from the anterior (a) and the palatinal (b) region. All restorations were scored Alfa.
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Survival Function Survival Function 0
1.0
0.8
0.8
Cum Survival
Cum Survival
Survival Function 0
1.0
0.6
0.4
0.2
0.6
0.4
0.2
0.0
0.0 .00
5.00
a
10.00
15.00
20.00
25.00
.00
5.00
b
Time_So
20.00
25.00
Survival Function Survival Function 0
PREPARATION DESIGN
1.0
IO IB IO-censored IB-censored
0.8
Cum Survival
0.8
Cum Survival
15.00
Time_Sr
Survival Function 1.0
0.6
0.4
0.6
0.4
0.2
0.2
0.0
0.0
c
10.00
.00
5.00
10.00
15.00
20.00
25.00
Time_Sf
.00
5.00
10.00
15.00
20.00
25.00
Time_So
Fig 4 Kaplan-Meier cumulative survival curves for (a) overall survival (So), (b) original restoration (Sr), and (c) functional survival (Sf).
Fig 5 Kaplan-Meier overall survival curve for preparation design. IO: incisal overlap; IB and incisal bevel.
with those of other mid-term clinical studies, which report So rates of 94%19 and 93.5%10 after 2.5 and 3 years, respectively. Therefore, the number of failures (two absolute and nine relative) observed in this study can be considered relatively low. These low failure rates imply that the clinical protocol employed and materials used are reliable. However, long-term follow-up of an increased number of restorations is necessary. In this study, one debonded restoration and gingivitis on the gingival margins of five other restorations occurred in a patient who reported that she could not brush her teeth for fear of her other restorations failing, as the debonded PLV detached 1 week before recall. This failure may have been caused by a mistake during the adhesive protocol. After cleaning the inner surface of PLV and applying the adhesion protocols, it was rebonded and remained functional
until the end of the follow-up period. The other absolute failure occurred in the form of a tooth fracture at the cervical margin during preparation of the endodontic access cavity on the palatal surface because of the loss of vitality. Subsequently, this tooth was restored with a post-core and full crown. In one patient, a fracture was clinically acceptable; after finishing and polishing the small fracture in the incisal edge, the patient continued to use the restoration until the end of the observation period (Figs 7a and 7b). The most common failure was gingivitis, which scored Bravo. This type of failure was observed to relate to patient behavior; after periodontal treatment and patient education, the gingival tissues healed. Therefore, patients should be thoroughly evaluated before treatment to determine whether they practice good oral hygiene. Otherwise, failure may occur in the early post-treatment period.
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Öztürk and Bolay Survival Function TOOTH TISSUE E MDE SDE E-censored MDE-censored SDE-censored
1.0
Parameter
Original restoration (Sr)
Functional (Sf)
Overall (So)
0.6
All
98.4%
92.7%
91.2%
0.4
Tooth tissue
E MDE SDE
98.5%a 100%a 94.4%a
95.5%b 97.4%b 70.6%c
94.1%d 97.4%d 66.7%e
Preparation design
IB IO
98.8%f 97.6%f
95.1%g 87.8%g
94%h 85.7%h
0.8
Cum Survival
Table 4 Different survival levels according to the tested parameters
0.2
0.0 .00
5.00
10.00
15.00
20.00
25.00
Time_So
*Same superscript letters show statistically homogeneous subgroups within the same column and row (p > 0.05). Adhesion surface enamel: E; enamel with minimal dentin exposure: MDE; enamel with severe
Fig 6 Kaplan-Meier overall survival curve for tooth tissue type. Adhesion surface enamel: E; enamel with minimal dentin exposure: MDE; enamel with severe dentin exposure: SDE.
dentin exposure: SDE.
Fig 7a Porcelain veneer failure on the right maxillary lateral incisor at a 12-month recall.
Fig 7b After finishing and polishing procedures on the incisal edge of the lateral tooth, the patient continued to use the restoration.
Fractures are reportedly the most frequent cause of the clinical failure of PLVs.11,25 The frequency of clinically unacceptable fractures was variously reported to be 0% by Magne et al,18 2% by Peumans et al,25 and 2.3% by Guess and Stappert.22 In this study, two absolute failures occurred (1.6%), which is consistent with the results of other clinical follow-up studies. Although early protocols suggested minimal or no tooth preparation, current opinion supports enamel reduction to remove the aprismatic enamel surface, which reportedly has a reduced retention capacity, and to improve the strength of PLV bonding to the tooth surface.27 In addition, it was believed that preparation should be completely performed in the enamel to maintain optimal bonding with the PLV.28 However, dentin exposure is inevitable in some cases depending on the degree of discoloration or thickness of the enamel during preparation.21 Thus, the primary objective of this study was to evaluate the survival of PLVs after dentin exposure. However, the results support the rejection of the first null hypothesis that dentin exposure on the prepared tooth surface does not affect the clinical survival of PLVs.
Few clinical studies correlate dentin exposure with PLV survival,13 and none identify an acceptable level for dentin exposure. In this study, the degree of dentin exposure on prepared and dried tooth surfaces was clinically classified after preparation. When less than about 30% of the dentin was observed on the cervical third of clinical crown, this was classified as minimal dentin exposure. If the dentinenamel junction exceeded the cervical third of the crown on the prepared surface, it was classified as severe dentin exposure. However, quantitative methods are necessary to accurately evaluate the proportion of dentin exposure on the prepared surfaces. In the literature, several studies that evaluate PLVs both in vivo and in vitro report these restorations to be extremely successful.27 Andreasen et al1 and Stokes and Hood36 reported that extracted incisor teeth restored with PLVs exhibited their original strength in vitro. Other studies6,9 reported that PLVs presented clinical survival rates of approximately 96% to 98% over a longterm period. However, PLVs do not demonstrate 100% success. In this study, the overall failure rate was 8.8%. This failure rate was related to both substantial den-
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tin exposure on the tooth surface and inadequate oral hygiene. Consistent with our results, the predisposing factors for PLV failure reportedly include partial adhesion to surfaces with large regions of dentin exposure, unfavorable occlusion, and the use of inappropriate materials and techniques.13,27 Four different types of preparation design have been described for porcelain laminate veneers: window preparation, feathered incisal edge preparation, incisal bevel preparation (butt joint or shoulder finishing line), and incisal overlap with a palatal chamfer.15,17,24,30,34,38 Incisal bevel and incisal overlap with palatal chamfer preparation designs have been proposed because they increase the bonding surface area and provide better occlusal load distribution as well as allow characterization of the incisal region and better seating of the restoration.5,30 Therefore, two different preparation designs with or without a palatal chamfer were preferred for this study. However, there is still no consensus regarding the use of a palatal extention for the veneer preparation.38 In the present study, the preparation design was selected according to the occlusion of the patient. When there was sufficient space between the maxilla and mandible, incisal overlap with a palatal chamfer was preferred for better esthetic and better seating of the restoration. In order to avoid the contacts between the incisal edge of the lower anterior tooth and tooth-ceramic junction of the maxillary restored tooth, incisal bevel preparation without any palatal chamfer was selectively applied. Conflicting evidence exists in the literature regarding optimal incisal edge preparation. Some authors favor the IO preparation design,2 whereas others observed no difference between the different incisal preparations.33 In this study, there was no statistically significant difference between IB and IO groups (p > 0.05). Thus, the second null hypothesis can be accepted. The results of this study emphasize the importance of preparation depth for the clinical success of PLVs. Patients should be carefully examined, and the most accurate indication should be assessed for the success of a PLV restoration. Preparation should also be meticulously undertaken to reduce the risk of failure. Furthermore, the vitality of the prepared tooth may influence the success of the restoration. In this study, existing composite restorations were renewed when the necessary and carious teeth were treated with composite resin restorations before treatment with PLVs. However, existing composite restorations can affect the success of PLV restorations. These factors should be considered in future studies.
CONCLUSIONS
y Preparation depth is an important factor for the success of PLVs. Minimal dentin exposure on the cervical third of the prepared tooth surface may be insufficient to influence the clinical success of restorations. y Incisal preparation design does not affect PLV survival.
ACKNOWLEDGMENTS This investigation was supported in part by Hacettepe University Scientific Research Projects Coordination Unit (Project Number: 07 A 201 003). The authors would like to thank Dr. Altay Uludamar and Dr. Merih Baykara for their contribution. The authors also acknowledge Mr. Ali Yılmaz for his work in fabricating the porcelain laminate veneers.
REFERENCES 1.
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15. 16.
Within the limitations of this study, the following conclusions can be drawn: y The So, Sf and Sr rates of PLVs after 2 years were 91.2%, 92.7%, and 98.4%, respectively. y PLV restorations can continue to function successfully even after clinically acceptable relative failure with treatment according to failure type. 488
17.
18.
Andreasen FM, Flugge E, Daugaard-Jensen J, Munksgaard EC. Treatment of crown fractured incisors with laminate veneer restorations. An experimental study. Endod Dental Traumatol 1992;8:30-35. Cotert HS, Dundar M, Öztürk B. The effect of various preparation designs on the survival of porcelain laminate veneers. J Adhes Dent 2009;11:405-411. Cvar JF, Ryge G. Criteria for the clinical evaluation of dental restoration materials. Government Printing Office, San Francisco, USA: US Public Health Service Publication, 1971. Cvar JF, Ryge G. Reprint of criteria for the clinical evaluation of dental restorative materials. 1971. Clin Oral Investig 2005;9:215-232. da Costa DC, Coutinho M, de Sousa AS, Ennes JP. A meta-analysis of the most indicated preparation design for porcelain laminate veneers. J Adhes Dent 2013;15:215-220. D’Arcangelo C, De Angelis F, Vadini M, D’Amario M. Clinical evaluation on porcelain laminate veneers bonded with light-cured composite: results up to 7 years. Clin Oral Investig 2012;16:1071-1079. Dumfahrt H, Schaffer H. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service: Part II – Clinical results. Int J Prosthodont 2000;13:9-18. Fradeani M. Six-year follow-up with Empress veneers. Int J Periodontics Restorative Dent 1998;18:216-225. Fradeani M, Redemagni M, Corrado M. Porcelain laminate veneers: 6to 12-year clinical evaluation – a retrospective study. Int J Periodontics Restorative Dent 2005;25:9-17. Gresnigt MM, Kalk W, Ozcan M. Randomized clinical trial of indirect resin composite and ceramic veneers: up to 3-year follow-up. J Adhes Dent 2013;15:181-190. Guess PC, Stappert CF. Midterm results of a 5-year prospective clinical investigation of extended ceramic veneers. Dent Mater 2008;24: 804-813. Gürel G. The science and art of porcelain laminate veneers. Chicago: Quintessence, 2003. Gürel G, Morimoto S, Calamita MA, Coachman C, Sesma N. Clinical performance of porcelain laminate veneers: outcomes of the aesthetic pre-evaluative temporary (APT) technique. Int J Periodontics Restorative Dent 2012;32:625-635. Gürel G, Sesma N, Calamita MA, Coachman C, Morimoto S. Influence of enamel preservation on failure rates of porcelain laminate veneers. Int J Periodontics Restorative Dent 2013;33:31-39. Highton R, Caputo AA, Mátyás J. A photoelastic study of stresses on porcelain laminate preparations. J Prosthet Dent 1987;58:157-161. Lin TM, Liu PR, Ramp LC, Essig ME, Givan DA, Pan YH. Fracture resistance and marginal discrepancy of porcelain laminate veneers influenced by preparation design and restorative material in vitro. J Dent 2012;40:202-209. Magne P, Douglas WH. Design optimization and evalution of bonded ceramics for the anterior dentition: a finite-element analysis. Quintessence Int 1999;30:661-672. Magne P, Perroud R, Hodges JS, Belser UC. Clinical performance of novel-design porcelain veneers for the recovery of coronal volume and length. Int J Periodontics Restorative Dent 2000;20:440-457.
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Öztürk and Bolay 19. Meijering AC, Creugers NH, Roeters FJ, Mulder J. Survival of three types of veneer restorations in a clinical trial: a 2.5-year interim evaluation. J Dent 1998;26:563-568. 20. Meijering AC, Roeters FJ, Mulder J, Creugers NH. Patients’ satisfaction with different types of veneer restorations. J Dent 1997;25:493-497. 21. Nattress BR, Youngson CC, Patterson CJ, Martin DM, Ralph JP. An in vitro assessment of tooth preparation for porcelain veneer restorations. J Dent 1995;23:165-170. 22. Öztürk E, Bolay S, Hickel R, Ilie N. Shear bond strength of porcelain laminate veneers to enamel, dentine and enamel-dentine complex bonded with different adhesive luting systems. J Dent 2013;41:97-105. 23. Öztürk E, Hickel R, Bolay S, Ilie N. Micromechanical properties of veneer luting resins after curing through ceramics. Clin Oral Investig 2012;16:139-146. 24. Perillo L, Sorrentino R, Apicella D, Quaranta A, Gherlone E, Zarone F, Ferrari M, Aversa R, Apicella A. Nonlinear visco-elastic finite element analysis of porcelain veneers: a submodelling approach to strain and stress distributions in adhesive and resin cement. J Adhes Dent 2010;12:403-413. 25. Peumans M, De Munck J, Fieuws S, Lambrechts P, Vanherle G, Van Meerbeek B. A prospective ten-year clinical trial of porcelain veneers. J Adhes Dent 2004;6:65-76. 26. Peumans M, Van Meerbeek B, Lambrechts P, Vanherle G. Porcelain veneers: a review of the literature. J Dent 2000;28:163-177. 27. Pini NP, Aguiar FH, Lima DA, Lovadino JR, Terada RS, Pascotto RC. Advances in dental veneers: materials, applications, and techniques. Clin Cosmet Investig Dent 2012;4:9-16. 28. Rouse JS, Robbins JW. Porcelain veneers. In: Summitt JB, Robbins JW, Hilton TJ, Schwartz RS (eds). Fundamentals of operative dentistry: a contemporary approach. Chicago: Quintessence, 2006:463-487. 29. Sadowsky SJ. An overview of treatment considerations for esthetic restorations: a review of the literature. J Prosthet Dent 2006;96:433-442. 30. Schmidt KK, Chiayabutr Y, Phillips KM, Kois JC. Influence of preparation design and existing condition of tooth structure on load to failure of ceramic laminate veneers. J Prosthet Dent 2011;105:374-382. 31. Shaini FJ, Shortall AC, Marquis PM. Clinical performance of porcelain laminate veneers. A retrospective evaluation over a period of 6.5 years. J Oral Rehabil 1997;24:553-559.
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32. Sieweke M, Salomon-Sieweke U, Zofel P, Stachniss V. Longevity of oroincisal ceramic veneers on canines--a retrospective study. J Adhes Dent 2000;2:229-234. 33. Smales RJ, Etemadi S. Long-term survival of porcelain laminate veneers using two preparation designs: a retrospective study. Int J Prosthodont 2004;17:323-326. 34. Sorrentino R, Apicella D, Riccio C, Gherlone E, Zarone F, Aversa R, Garcia-Godoy F, Ferrari F, Apicella A. Nonlinear visco-elastic finite element analysis of different porcelain veneers configuration. J Biomed Mater Res B Appl Biomater 2009;91:727-736. 35. Stappert CF, Ozden U, Gerds T, Strub JR. Longevity and failure load of ceramic veneers with different preparation designs after exposure to masticatory simulation. J Prosthet Dent 2005;94:132-139. 36. Stokes AN, Hood JA. Impact fracture characteristics of intact and crowned human central incisors. J Oral Rehabil 1993;20:89-95. 37. Walls AW. The use of adhesively retained all-porcelain veneers during the management of fractured and worn anterior teeth: Part 2. Clinical results after 5 years of follow-up. Br Dent J 1995;178:337-340. 38. Zarone F, Epifania E, Leone G, Sorrentino R, Ferrari M. Dynamometric assessment of the mechanical resistance of porcelain veneers related to tooth preparation: a comparison between two techniques. J Prosthet Dent 2006;95:354-363. 39. Zhang F, Heydecke G, Razzoog ME. Double-layer porcelain veneers: effect of layering on resulting veneer color. J Prosthet Dent 2000;84: 425-431.
Clinical relevance: Avoiding extensive dentin exposure during preparation is the key factor for the long-term success of PLVs. With restricted indications and the careful application of clinical procedures, porcelain laminate veneers are extremely reliable restorations.
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Purpose: To evaluate the clinical performance of porcelain laminate veneers (PLVs) after 2 years. Materials and Methods: Twenty-eight patients were treated with 125 PLVs. The experimental variables were preparation design (incisal overlap [IO] and incisal bevel [IB]) and adhesion surface (enamel [E], enamel with minimal dentin exposure [MDE], and enamel with severe dentin exposure (SDE)]. Marginal adaptation, marginal discoloration, secondary caries, postoperative sensitivity, and patient satisfaction were assessed according to the modified United States Public Health Service criteria. Each restoration was examined for fractures and debonding. In addition, gingival tissue health by gingival plaque, bleeding, and recession was recorded. An experienced clinician evaluated the restorations at baseline and after 6, 12, and 24 months, and survival rates evaluating relative and absolute failures were calculated (p = 0.05). Results: Eleven (8.8%) veneers failed, and the overall cumulative survival rate was 91.2% after 2 years of followup. IB and IO preparation designs exhibited survival rates of 94% and 85.7%, respectively, but this difference was not statistically significant (p > 0.05). PLVs bonded to SDE were more likely to fail than those bonded to E and MDE (p < 0.05). There was no significant difference between the failure rate of PLVs bonded to E and those bonded to MDE (p > 0.05). Conclusions: PLVs have high survival rates when bonded to enamel only, as well as to enamel with minimal dentin exposure. However, extensive dentin exposure should be avoided during the preparation. Keywords: porcelain laminate veneers, dentin exposure, preparation design. J Adhes Dent 2014; 16: 481–489. doi: 10.3290/j.jad.a32828
T
he porcelain laminate veneer (PLV) technique, which is one of the most popular esthetic treatment alternatives for anterior teeth to restore slight discolorations, abrasions, fractures, malformations, and/or malpositions, bonds a thin porcelain laminate to the tooth surface using dental adhesives and resin cements.23,26 One of the major advantages of the porcelain laminate veneer technique is that it can be performed on a conservative preparation with a minimum of tooth reduction.39 However, there are some problems associated with PLVs, such as debonding, fracture, or microleakage from the margins of the restoration.29 Many factors can
a
Assistant Professor, Department of Restorative Dentistry, Faculty of Dentistry, Hacettepe University, Ankara, Turkey. Experimental design, clinical applications, wrote the manuscript.
b
Professor, Department of Restorative Dentistry, Faculty of Dentistry, Hacettepe University, Ankara, Turkey. Idea and hypothesis, follow-up examinations, proofread the manuscript.
Correspondence: Assistant Professor Elif Öztürk, Hacettepe University, Faculty of Dentistry, Department of Restorative Dentistry, Sihhiye-06100, Ankara, Turkey. Tel: +90-312-305-2270, Fax: +90-312-311-3438. e-mail: [email protected]
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Submitted for publication: 05.03.14; accepted for publication: 19.09.14
influence the long-term success of porcelain laminate veneers, such as structure of the adhesion surface, preparation type and depth, type and thickness of the porcelain, type of the resin cement and dental adhesive, tooth morphology, as well as functional and parafunctional activities.22,26 Tooth preparation for PLVs is crucial for optimal function and esthetics; therefore, care should be taken to completely perform this preparation in the enamel.16,22 In general, anterior tooth preparation requires a 0.3- to 0.7-mm facial reduction, depending on the location of the crown, to imitate the natural contours of the tooth.28 This anatomical preparation technique may enable tooth preparation within only enamel, because enamel thickness is different in different zones of the tooth. For PLV restorations, preparation design is classified according to the type of incisal edge. The following two preparation designs are frequently used: incisal bevel (IB) and incisal overlap (IO) ending with a palatal chamfer. Both techniques allow characterization of the incisal region and better seating of PLVs.5 However, controversy exists over which preparation design is the most suitable,5,35 and few clinical studies have compared their efficacy.20 481
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Preparation performed completely in the enamel is believed to maintain an optimal bond with PLV and decrease stress in the porcelain. Thus, preparation of PLVs should be meticulously performed.16 In addition, the preparation technique used impacts on the longevity of the restoration, eg, high failure rates of PLVs have been attributed to the exposure of dentin surfaces. However, exposure of a considerable amount of dentin is inevitable during preparation, particularly in cervical and proximal areas, to compensate for slight malposition and/or discoloration.21 Several medium-to-long-term clinical studies have evaluated the clinical performance of PLVs. One longitudinal clinical study8 reported a low failure rate (0%–7%) after 5 to 12 years, whereas others31,32,37 describe higher failure rates (14%–33%). However, few clinical studies have considered the performance of PLVs according to preparation depth7,14 or preparation design,2 when dentin is exposed on the tooth surface. Therefore, in this study, we assessed the medium-term clinical performance of PLVs, using two preparation designs and a range of preparation depths, causing different degrees of dentin exposure on the tooth surface. The null hypotheses were as follows: 1. dentin exposure on the tooth surface does not affect the clinical survival of PLVs, and 2. there is no difference between IO and IB preparation designs in terms of the clinical survival of PLVs.
MATERIALS AND METHODS Study Design The protocol of this clinical study was approved by the Ethics Committee of Hacettepe University, Ankara, Turkey (FON 07/27-42). Informed consent was obtained from each participant. Twenty-eight patients (5 men, 23 women) aged 18 to 51 years (average: 30 years) were referred to the Department of Restorative Dentistry at Hacettepe University with the main complaint of unesthetic anterior teeth. The patients received 125 PLVs (29 in men, 96 in women) between May 2008 and May 2011. The indications for treatment were as follows: severe intrinsic and/or extrinsic discoloration unrelieved by bleaching (46, 36.8%); minor to moderate noncarious structural defects, and wear or fracture (6, 4.8%); diastema (4, 3.2%); slight malalignment (6, 4.8%); morphological disorders, such as peg-shaped maxillary lateral incisors, as well as the presence of a canine tooth instead of a missing lateral tooth (23, 18.4%); existing unesthetic composite restorations of the anterior teeth (40, 32%). Nonvital teeth (12, 9.6%) were not excluded from the study. Inclusion criteria were as follows: all patients were required to be at least 18 years old, able to read and sign the informed consent document, physically and psychologically able to tolerate conventional restorative procedures, willing to return for follow-up examinations as outlined by the investigators, and to have all maxillary anterior teeth, no active periodontal or pulpal diseases, and no systemic disorders. Patients with severe parafunc482
tional habits were excluded from the study. Initially, dental calculus and extrinsic stains were cleaned from patients’ teeth. Patients were instructed on improving their gingival health and maintaining effective plaque control. However, if their gingival health did not improve, they were excluded from the study. Diagnosis and Treatment Planning Patients were treated with a minimum of one and a maximum of nine veneers according to an evaluation. Pre-operative photographs of each patient were taken to evaluate the clinical appearance of their teeth. Before preparation, impressions were taken from each patient using a polyvinyl siloxane impression material in heavy body (Virtual Putty, Ivoclar Vivadent; Schaan, Liechtenstein) to prepare diagnostic wax-up models. For each patient, the wax-up models were duplicated, and cast models were produced to prepare the vacuum sheets. Final volume of the restorations was made with temporary flowable composite (Systemp.link, Ivoclar Vivadent) using transparent, rigid, vacuum-shaped sheets (VacuFormerSystem, Cavex; Haarlem, The Netherlands). Patients were able to preview the finished restoration from the provisional restorations. Furthermore, the maximum conservative preparation was permitted. The same sheet was kept during the treatment of each patient to produce provisional restorations after preparation. This technique was performed in accordance with the esthetic pre-evaluative temporary technique described by Gürel12 and Gürel et al.13 Preparations were made after patient approval of a mock-up, consisting of temporary composite restorations. Before treatment with PLVs, gingival corrections (17 teeth in four patients, 13.6%) were performed where necessary using a DELight Er:YAG laser (HOYA ConBio Laser; Chicago, IL, USA) with low-fluence irradiation at 35 mJ with 10 Hz. Tooth Preparation All preparations were performed over the provisional composite restorations using a 2.5X binocular dental loupe (Orascoptic, Kerr; Middleton, WI, USA) for minimal preparations. The preparation surfaces were initially colored with colored articulation papers. Facial surfaces of the teeth were prepared by making depth-orientation grooves (0.3 mm in depth) with a depth preparation diamond bur (Diatech, Coltène Whaledent; Altstätten, Switzerland). Facial reduction was continued with a tapered, rounded-end diamond bur (Diatech) until the color was removed from the facial surface. Facial preparation was deepened further when necessary to overcome slight malalignment or discoloration. Facial surfaces were reduced by 0.3 to 0.7 mm. The incisal edge was included in each preparation to maximize esthetics. Two different preparation designs were used according to incisal finishing. IB preparations were performed on 83 teeth (66%), whereas 42 teeth (34%) were prepared with IO ending with a palatal chamfer. The reduction ranged from 1.5 to 2 mm on the incisal edge. The Journal of Adhesive Dentistry
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Table 1
Materials used in this study
Brand name
Type
Manufacturer
Composition
Lot No.
IPS e.max Press
Lithium disilicate glass-ceramic
Ivoclar Vivadent; Schaan, Liechtenstein
SiO2, Li2O, K2O, P2O5, ZrO2, ZnO, other oxides, color oxides
M13076
Variolink Veneer
Light-curing resin cement
Ivoclar Vivadent
Dimethacrylates, inorganic fillers, ytterbium trifluoride, catalysts and stabilizers, pigments
P38760
Total-Etch
Phosphoric acid
Ivoclar Vivadent
37% phosphoric acid
K27710
Porcelain etchant
Hydrofluoric acid
Bisco; Schaumburg, IL, USA
5% hydrofluoric acid
1000003009
Syntac Primer
Primer
Ivoclar Vivadent
Triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, maleic acid, acetone
K16326
Syntac Adhesive
Adhesive
Ivoclar Vivadent
Polyethylene glycol dimethacrylate, glutaraldehyde
K30345
Heliobond
Bonding agent
Ivoclar Vivadent
Bis-GMA, triethylene glycol dimethacrylate, catalysts and stabilizers
K30706
Monobond Plus
Silane coupling agent
Ivoclar Vivadent
Alcohol solution of silane methacrylate, phosphoric acid methacrylate, sulfide methacrylate
K30207
All cervical margins were placed equi- or supragingivally and were created with a shallow chamfer finish line 0.3 to 0.5 mm in preparation depth. Gingival finish lines were cervically extended to half the interproximal area to hide restoration margins up to the contact area. All sharp edges and corners were smoothened with an extra-coarse aluminum-oxide polishing disk (OptiDisc, Kerr; Orange, CA, USA) to reduce stress concentrations. Impressions were subsequently obtained using a polyvinyl siloxane impression material (Virtual; Putty and Light Body, Ivoclar Vivadent). Provisional veneers were made chairside using an autopolymerizing temporary composite resin (Systemp.link, Ivoclar Vivadent). For fixation of the provisional veneers, enamel was spot etched with 37% phosphoric acid (Total Etch, Ivoclar Vivadent) for 30 s before application of the temporary composite resin. After completing the preparations, the adhesion surfaces were gently air dried and meticulously evaluated by the two experienced clinicians under 2.5X magnification to categorize them as follows: intra-enamel only (E; 68 restorations, 54.4%), enamel with minimal dentin exposure (MDE; 39 restorations, 31.2%), and enamel with severe dentin exposure (SDE; 17 restorations, 13.6%). PLVs were fabricated from a lithium-disilicate glass ceramic (IPS e.max Press, Ivoclar Vivadent) with a lowfusing nano-fluorapatite glass-ceramic (IPS e.max Ceram, Ivoclar Vivadent) for veneering and characterization of the restorations using the layering technique according to the manufacturer’s instructions. Cementation Procedures Table 1 presents the brand names, types, manufacturers, chemical compositions, and batch numbers of the materials used in this study. Form, contour, marginal Vol 16, No 5, 2014
adaptation, proximal contacts, and shade matching of the restorations were clinically checked after removing the provisional restorations and cleaning the teeth. The color of the cement used was determined using try-in pastes (Variolink Veneer Try-in Paste, Ivoclar Vivadent). All the veneers were adhesively cemented under rubber-dam (Optra-Dam, Ivoclar Vivadent) isolation. The bonding surface procedures for the tooth and porcelain surfaces using light-cured resin cement (Variolink Veneer, Ivoclar Vivadent) are described in Table 2. After these procedures, the PLV restoration was positioned, and excess luting cement was removed with hand instruments and a brush. Before final curing, PLVs were cervically pre-cured for 5 s to completely remove excess resin cement from the cervical and interproximal areas using hand instruments and dental floss without pressure. Final curing was performed according to the manufacturer’s instructions for 40 s on each surface (upper- and mid-buccal, cervical, mesial, distal, and palatal) with a light-emitting diode polymerizing unit (Bluephase LED, Ivoclar Vivadent, 1200 mW/cm 2). Restoration margins were finished and further polished with extra-fine diamond finishing burs (Diatech), polishing cups (Kerr HiLuster Plus, Kerr; Orange, CA, USA), and interproximal polishing strips (Soft-Lex Finishing Strips, 3M ESPE; Seefeld, Germany). Finally, the occlusion was checked in protrusive and lateral movements of the mandible. Follow-up Patients were recalled after 1 week to recheck occlusion, proximal contacts, and gingival margins. This recall was used as the baseline. The restorations were evaluated at baseline and after 6, 12, and 24 months by an experienced clinician (not the clinician who performed 483
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Table 2 Surface conditioning protocols for the tooth and porcelain Surface Tooth surface treatment
Porcelain inner surface
Etching
Enamel: 37% H3PO4 for 30 s Dentin: 37% H3PO4 for 15 s
5% HF for 60 s
Adhesive
(1) Syntac Primer for 15 s (1) Monobond S for 60 s (2) Syntac Adhesive for 10 s (2) Heliobond for 10 s (3) Heliobond for 10 s
H3PO4: phosphoric acid; HF: hydrofluoric acid.
the restoration) blinded to the objective of this study according to the modified United States Public Health Service (USPHS) criteria.3,4 The restorations were rated according to the four USPHS scores of Alfa, Bravo, Charlie, and Delta. The restorations were visually inspected with a dental mirror and probe. Digital photos were taken before and after PLV placement and during followup sessions. Statistical Analysis A survival rate evaluating absolute failures according to in situ criteria and success rates describing both relative (Bravo) and absolute (Charlie and/or Delta) failures were determined. 11 Absolute failure was defined as clinically unacceptable failures, such as loss, fracture, and debonding of the PLV. A relative failure was defined as minimal failures which were clinically acceptable in that they allowed repair of the restoration or healing of gingival tissues. Survival was defined at three levels: survival of the original restoration (Sr, endpoints: absolute failures); functional survival (Sf, endpoints: relative failures); overall survival (So, endpoints: both absolute and relative failures).19 The effects of the study parameters “preparation design” and “tooth tissue type” on the different survival levels were also analyzed. Survival analyses were performed with the statistical software program IBM SPSS Statistics for Windows (version 20.0; Armonk, NY, USA) (p = 0.05), using KaplanMeier and log-rank (Mantel-Cox) tests to obtain the cumulative survival rate in relation to observation time. A restoration-related analysis using each restoration as a statistical unit was used for the analysis.6
RESULTS Twenty-eight patients were treated with 125 PLVs with a 2-year follow-up. All patients came for a follow-up evaluation after 1 week (baseline), 6, 12, and 24 months. No patient was lost during this 2-year follow-up. The number of restorations evaluated at each of the follow-up phases is summarized in Table 3. 484
Fig 1 Preoperative view of a patient with diastemata between the four maxillary anterior teeth and lacking the maxillary left lateral incisor.
One restoration (0.8%) in the IO-MDE group debonded from the tooth without the PLV having any crack or fracture, and therefore it was re-bonded at 6 months. In the same patient, gingivitis was detected on the gingival tissues of five other restorations. In total, eight restorations (6.7%) in two patients were rated Bravo for gingival tissue health at a 6-month recall. At a 12-month follow-up, one score of Bravo (minimal ceramic cohesive fracture on the incisal edge) and one of Delta (total tooth and ceramic fracture) were recorded (Table 3). Marginal adaptation and discoloration, as well as secondary caries and postoperative sensitivity, were rated Alfa during the 2-year follow-up (Figs 1 to 3). As a consequence of the two absolute and nine relative failures, the Sr, Sf, and So rates were 98.4%, 92.7%, and 91.2%, respectively (Fig 4). The So rates for IO (85.7%) and IB (94%) preparations were not significantly different (p > 0.05; Fig 5). However, there were statistically significant differences between the So rates of the restorations bonded to the three different tooth surfaces (E, MDE, and SDE; p < 0.05; Fig 6). The So-E, So-MDE, and So-SDE were 94.1%, 97.4%, and 66.7% respectively. There were no significant differences between So-E and So-MDE (p > 0.05), whereas So-SDE was significantly lower than the other groups (p < 0.05). The survival rates of PLVs after 2 years according to different parameters are presented in Table 4.
DISCUSSION In the present study, we evaluated the clinical success of PLVs of different preparation designs bonded to tooth tissues prepared at different levels after 2 years. Longitudinal studies have some disadvantages, such as the withdrawal of certain dental materials and loss of a proportion of patients over time. In this study, no patients were lost to follow-up, and the materials used remain available. Therefore, the results of this study were presented after a relatively short period. The results of the present study suggest that PLVs are favorable restorations, withstanding 2 years of clinical service and demonstrating promising survival rates. The survival rates determined in this study are comparable The Journal of Adhesive Dentistry
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Table 3 Summary of the modified United States Public Health Service criteria and evaluation of porcelain laminate veneers during follow-up USPHS criteria
Score
Characteristics
Baseline
6 months
Marginal adaptation
Alfa Bravo Charlie Delta
Marginal discoloration
12 months 24 months
Smooth margin Minor voids/defects at margin Obvious crevice at margin Debonded
125 -
124 -
124 -
124 -
Alfa Bravo Charlie/Delta
No discoloration Slight staining/acceptable Large staining/unacceptable
125 -
124 -
124 -
124 -
Secondary caries
Alfa Bravo Charlie Delta
No caries Caries at the margin N/A N/A
125 -
124 -
124 -
124 -
Postoperative sensitivity
Alfa Bravo Charlie Delta
No symptoms Slight sensitivity Moderate pain Severe pain
125 -
124 -
124 -
124 -
Patient satisfaction
Alfa Bravo Charlie/Delta
High Moderate Not satisfied
125 -
124 -
124 -
124 -
Fracture
Alfa Bravo Charlie Delta
None Small/acceptable Moderate/unacceptable Large/unacceptable
125 -
124 -
122 1 1
124 -
Retention
Alfa Bravo Charlie Delta
None N/A N/A De-bonded
125 -
124 1
124 -
124 -
Gingival response
Alfa Bravo Charlie Delta
Healthy Calculus or gingivitis Moderate pocketing and bleeding present Severe periodontitis
125 -
116 8 -
124 -
124 -
N/A: not applicable.
b
a
Fig 2 Baseline view of the porcelain laminate veneers on teeth 12, 11, 21, and 23 from the anterior (a) and the palatinal (b) region. The left maxillary canine tooth was reshaped like a lateral incisor.
b
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Fig 3 Two-year recall of the same patient as in Figs 1 and 2 with porcelain laminate veneers from the anterior (a) and the palatinal (b) region. All restorations were scored Alfa.
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Öztürk and Bolay Survival Function
Survival Function Survival Function 0
1.0
0.8
0.8
Cum Survival
Cum Survival
Survival Function 0
1.0
0.6
0.4
0.2
0.6
0.4
0.2
0.0
0.0 .00
5.00
a
10.00
15.00
20.00
25.00
.00
5.00
b
Time_So
20.00
25.00
Survival Function Survival Function 0
PREPARATION DESIGN
1.0
IO IB IO-censored IB-censored
0.8
Cum Survival
0.8
Cum Survival
15.00
Time_Sr
Survival Function 1.0
0.6
0.4
0.6
0.4
0.2
0.2
0.0
0.0
c
10.00
.00
5.00
10.00
15.00
20.00
25.00
Time_Sf
.00
5.00
10.00
15.00
20.00
25.00
Time_So
Fig 4 Kaplan-Meier cumulative survival curves for (a) overall survival (So), (b) original restoration (Sr), and (c) functional survival (Sf).
Fig 5 Kaplan-Meier overall survival curve for preparation design. IO: incisal overlap; IB and incisal bevel.
with those of other mid-term clinical studies, which report So rates of 94%19 and 93.5%10 after 2.5 and 3 years, respectively. Therefore, the number of failures (two absolute and nine relative) observed in this study can be considered relatively low. These low failure rates imply that the clinical protocol employed and materials used are reliable. However, long-term follow-up of an increased number of restorations is necessary. In this study, one debonded restoration and gingivitis on the gingival margins of five other restorations occurred in a patient who reported that she could not brush her teeth for fear of her other restorations failing, as the debonded PLV detached 1 week before recall. This failure may have been caused by a mistake during the adhesive protocol. After cleaning the inner surface of PLV and applying the adhesion protocols, it was rebonded and remained functional
until the end of the follow-up period. The other absolute failure occurred in the form of a tooth fracture at the cervical margin during preparation of the endodontic access cavity on the palatal surface because of the loss of vitality. Subsequently, this tooth was restored with a post-core and full crown. In one patient, a fracture was clinically acceptable; after finishing and polishing the small fracture in the incisal edge, the patient continued to use the restoration until the end of the observation period (Figs 7a and 7b). The most common failure was gingivitis, which scored Bravo. This type of failure was observed to relate to patient behavior; after periodontal treatment and patient education, the gingival tissues healed. Therefore, patients should be thoroughly evaluated before treatment to determine whether they practice good oral hygiene. Otherwise, failure may occur in the early post-treatment period.
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Öztürk and Bolay Survival Function TOOTH TISSUE E MDE SDE E-censored MDE-censored SDE-censored
1.0
Parameter
Original restoration (Sr)
Functional (Sf)
Overall (So)
0.6
All
98.4%
92.7%
91.2%
0.4
Tooth tissue
E MDE SDE
98.5%a 100%a 94.4%a
95.5%b 97.4%b 70.6%c
94.1%d 97.4%d 66.7%e
Preparation design
IB IO
98.8%f 97.6%f
95.1%g 87.8%g
94%h 85.7%h
0.8
Cum Survival
Table 4 Different survival levels according to the tested parameters
0.2
0.0 .00
5.00
10.00
15.00
20.00
25.00
Time_So
*Same superscript letters show statistically homogeneous subgroups within the same column and row (p > 0.05). Adhesion surface enamel: E; enamel with minimal dentin exposure: MDE; enamel with severe
Fig 6 Kaplan-Meier overall survival curve for tooth tissue type. Adhesion surface enamel: E; enamel with minimal dentin exposure: MDE; enamel with severe dentin exposure: SDE.
dentin exposure: SDE.
Fig 7a Porcelain veneer failure on the right maxillary lateral incisor at a 12-month recall.
Fig 7b After finishing and polishing procedures on the incisal edge of the lateral tooth, the patient continued to use the restoration.
Fractures are reportedly the most frequent cause of the clinical failure of PLVs.11,25 The frequency of clinically unacceptable fractures was variously reported to be 0% by Magne et al,18 2% by Peumans et al,25 and 2.3% by Guess and Stappert.22 In this study, two absolute failures occurred (1.6%), which is consistent with the results of other clinical follow-up studies. Although early protocols suggested minimal or no tooth preparation, current opinion supports enamel reduction to remove the aprismatic enamel surface, which reportedly has a reduced retention capacity, and to improve the strength of PLV bonding to the tooth surface.27 In addition, it was believed that preparation should be completely performed in the enamel to maintain optimal bonding with the PLV.28 However, dentin exposure is inevitable in some cases depending on the degree of discoloration or thickness of the enamel during preparation.21 Thus, the primary objective of this study was to evaluate the survival of PLVs after dentin exposure. However, the results support the rejection of the first null hypothesis that dentin exposure on the prepared tooth surface does not affect the clinical survival of PLVs.
Few clinical studies correlate dentin exposure with PLV survival,13 and none identify an acceptable level for dentin exposure. In this study, the degree of dentin exposure on prepared and dried tooth surfaces was clinically classified after preparation. When less than about 30% of the dentin was observed on the cervical third of clinical crown, this was classified as minimal dentin exposure. If the dentinenamel junction exceeded the cervical third of the crown on the prepared surface, it was classified as severe dentin exposure. However, quantitative methods are necessary to accurately evaluate the proportion of dentin exposure on the prepared surfaces. In the literature, several studies that evaluate PLVs both in vivo and in vitro report these restorations to be extremely successful.27 Andreasen et al1 and Stokes and Hood36 reported that extracted incisor teeth restored with PLVs exhibited their original strength in vitro. Other studies6,9 reported that PLVs presented clinical survival rates of approximately 96% to 98% over a longterm period. However, PLVs do not demonstrate 100% success. In this study, the overall failure rate was 8.8%. This failure rate was related to both substantial den-
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tin exposure on the tooth surface and inadequate oral hygiene. Consistent with our results, the predisposing factors for PLV failure reportedly include partial adhesion to surfaces with large regions of dentin exposure, unfavorable occlusion, and the use of inappropriate materials and techniques.13,27 Four different types of preparation design have been described for porcelain laminate veneers: window preparation, feathered incisal edge preparation, incisal bevel preparation (butt joint or shoulder finishing line), and incisal overlap with a palatal chamfer.15,17,24,30,34,38 Incisal bevel and incisal overlap with palatal chamfer preparation designs have been proposed because they increase the bonding surface area and provide better occlusal load distribution as well as allow characterization of the incisal region and better seating of the restoration.5,30 Therefore, two different preparation designs with or without a palatal chamfer were preferred for this study. However, there is still no consensus regarding the use of a palatal extention for the veneer preparation.38 In the present study, the preparation design was selected according to the occlusion of the patient. When there was sufficient space between the maxilla and mandible, incisal overlap with a palatal chamfer was preferred for better esthetic and better seating of the restoration. In order to avoid the contacts between the incisal edge of the lower anterior tooth and tooth-ceramic junction of the maxillary restored tooth, incisal bevel preparation without any palatal chamfer was selectively applied. Conflicting evidence exists in the literature regarding optimal incisal edge preparation. Some authors favor the IO preparation design,2 whereas others observed no difference between the different incisal preparations.33 In this study, there was no statistically significant difference between IB and IO groups (p > 0.05). Thus, the second null hypothesis can be accepted. The results of this study emphasize the importance of preparation depth for the clinical success of PLVs. Patients should be carefully examined, and the most accurate indication should be assessed for the success of a PLV restoration. Preparation should also be meticulously undertaken to reduce the risk of failure. Furthermore, the vitality of the prepared tooth may influence the success of the restoration. In this study, existing composite restorations were renewed when the necessary and carious teeth were treated with composite resin restorations before treatment with PLVs. However, existing composite restorations can affect the success of PLV restorations. These factors should be considered in future studies.
CONCLUSIONS
y Preparation depth is an important factor for the success of PLVs. Minimal dentin exposure on the cervical third of the prepared tooth surface may be insufficient to influence the clinical success of restorations. y Incisal preparation design does not affect PLV survival.
ACKNOWLEDGMENTS This investigation was supported in part by Hacettepe University Scientific Research Projects Coordination Unit (Project Number: 07 A 201 003). The authors would like to thank Dr. Altay Uludamar and Dr. Merih Baykara for their contribution. The authors also acknowledge Mr. Ali Yılmaz for his work in fabricating the porcelain laminate veneers.
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Within the limitations of this study, the following conclusions can be drawn: y The So, Sf and Sr rates of PLVs after 2 years were 91.2%, 92.7%, and 98.4%, respectively. y PLV restorations can continue to function successfully even after clinically acceptable relative failure with treatment according to failure type. 488
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32. Sieweke M, Salomon-Sieweke U, Zofel P, Stachniss V. Longevity of oroincisal ceramic veneers on canines--a retrospective study. J Adhes Dent 2000;2:229-234. 33. Smales RJ, Etemadi S. Long-term survival of porcelain laminate veneers using two preparation designs: a retrospective study. Int J Prosthodont 2004;17:323-326. 34. Sorrentino R, Apicella D, Riccio C, Gherlone E, Zarone F, Aversa R, Garcia-Godoy F, Ferrari F, Apicella A. Nonlinear visco-elastic finite element analysis of different porcelain veneers configuration. J Biomed Mater Res B Appl Biomater 2009;91:727-736. 35. Stappert CF, Ozden U, Gerds T, Strub JR. Longevity and failure load of ceramic veneers with different preparation designs after exposure to masticatory simulation. J Prosthet Dent 2005;94:132-139. 36. Stokes AN, Hood JA. Impact fracture characteristics of intact and crowned human central incisors. J Oral Rehabil 1993;20:89-95. 37. Walls AW. The use of adhesively retained all-porcelain veneers during the management of fractured and worn anterior teeth: Part 2. Clinical results after 5 years of follow-up. Br Dent J 1995;178:337-340. 38. Zarone F, Epifania E, Leone G, Sorrentino R, Ferrari M. Dynamometric assessment of the mechanical resistance of porcelain veneers related to tooth preparation: a comparison between two techniques. J Prosthet Dent 2006;95:354-363. 39. Zhang F, Heydecke G, Razzoog ME. Double-layer porcelain veneers: effect of layering on resulting veneer color. J Prosthet Dent 2000;84: 425-431.
Clinical relevance: Avoiding extensive dentin exposure during preparation is the key factor for the long-term success of PLVs. With restricted indications and the careful application of clinical procedures, porcelain laminate veneers are extremely reliable restorations.
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