Q U I N T E S S E N C E I N T E R N AT I O N A L
RESTORATIVE DENTISTRY
Aristidis A. Galiatsatos
Clinical evaluation of anterior all-ceramic resin-bonded fixed dental prostheses Aristidis A. Galiatsatos, DDS, Dr Dent1/Dimitra Bergou, DDS2 Objectives: All-ceramic resin-bonded fixed dental prostheses (RBFDPs) were introduced as a conservative treatment many years ago. The purpose of this study was to evaluate for 8 years the clinical survival of RBFDPs made with a conventional tworetainer design. Method and Materials: A total of 54 anterior RBFDPs were made from the glass-infiltrated alumina ceramic In-Ceram. The restorations were placed in 49 patients, aged 18 to 60 years, by a single operator using the same clinical procedure. The restorations were examined for debonding, fracture rate, caries, and patient acceptance. All restorations
were examined clinically at 1, 2, 4, 6, and 8 years after placement. Results: At 8 years, the success rate was 85.18%. Patient acceptance was very encouraging and dental caries were not detected with any abutment. Two restorations debonded during the evaluation period and fracture of porcelain occurred in six restorations (two total fractures and four partial fractures). Conclusion: All-ceramic RBFDPs made from high-strength oxide ceramics offer an effective conservative treatment for replacing anterior teeth. (Quintessence Int 2014;45:9–14; doi: 10.3290/j.qi.a30766)
Key words: clinical performance, esthetics, fracture, In-Ceram system, resin-bonded FDP
Conventional resin-bonded fixed dental prostheses (RBFDPs) with metal framework have been used in dental practice for many years as alternatives to conventional FDPs when abutments are intact or exhibit only minimal caries lesions.1-5 The longevity of the prostheses has been improved since the initial use as a result of preparation of the abutment teeth and a variety of new methods to increase mechanical and chemical resin-tometal retention.2,6-9 The most common type of failure with RBFDPs is the debonding of the cast metal framework from the luting cement, but debondings of the luting cement from the enamel surface have also been reported.10-13 These res1
Assistant Professor, Department of Dental Technology, Division of Fixed Prosthodontics, Technological Educational Institution of Athens, Athens, Greece.
2
Private practice, Athens, Greece.
Correspondence: Dr Aristidis A. Galiatsatos, 60 Str. Rogakou Str., 15125 Athens, Greece. Εmail: [email protected]
VOLUME 45 • NUMBER 1 • JANUARY 2014
torations may present disadvantages with regard to esthetics and biocompatibility.14-16 The esthetically unsatisfactory grayish “shine through” of metal is a common problem in the anterior region. The biocompatibility of certain nonprecious alloys has been questioned because of their corrosive, allergenic, and even mutagenic potentials.14-18 To overcome these problems, all-ceramic RBFDPs were introduced.19-21 It has been shown by several authors that the aluminum oxide ceramic In-Ceram (Vita Zahnfabrik) has much better physical properties than other ceramic or glass materials.22-27 For this reason, RBFDPs have been suggested as an alternative to traditional resin-bonded restorations, which use a metal framework.25 The recommended design of InCeram prostheses is similar to the design of the conventional metal-ceramic resin-bonded restorations.25 Several studies on all-ceramic RBFDPs have been
9
Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
Table 1
Age and gender of patients
Age (years)
Men
Women
Total
18–30
10
12
22
31–40
8
8
16
41–50
2
4
6
51–60
1
4
5
Total
21
28
49
Table 2
Distribution of the restorations
Arch location
No. of RBFDPs
Replaced central incisors
Replaced lateral incisors
Maxilla
30
20
Mandible
24
15
9
Total
54
35
19
10
reported and the observation periods and success rates in these reports vary considerably. The purpose of this study was to add to the knowledge of all-ceramic RBFDPs by evaluating the longterm clinical survival of such restorations.
METHOD AND MATERIALS The study population consisted of 49 patients. There were 28 women and 21 men, ranging in age from 18 to 60 years (Table 1). Patient selection was accomplished according to preestablished criteria. Abutments were intact and caries-free, or exhibiting only minimal lesions that did not interfere with bonding, and tooth alignment was acceptable. Patients who exhibited bruxism, deep bite situation, severe inflammation, poor oral hygiene, or a high caries rate were ineligible for this study. Only patients with one missing mandibular or maxillary anterior tooth (central or lateral incisor) were selected. Five of them had both one missing maxillary and one missing mandibular anterior tooth. None of the selected patients dropped out or were dismissed. In the majority of the cases, an implant-supported prosthesis was not advisable as available bone volume was minimal, or the adjacent root was in close proximity.28 Also, many patients declined the several surgical procedures required.
10
Fig 1 Preoperative view of a patient with congenitally missing lateral incisor.
The selected patients were provided with a total of 54 anterior RBFDPs with a conventional two-retainer design in a private practice. The glass-infiltrated aluminum ceramic In-Ceram technique was selected to fabricate the above restorations. The distribution of the restorations is presented in Table 2. The reasons for the loss of teeth in this study were congenitally missing teeth, trauma, dental caries, endodontic complications, and periodontal disease (Fig 1). All procedures were performed by a single investigator, and all materials were mixed and used according to the recommendations of the manufacturers. Shades were matched with the Vita-Lumin Vacuum shade guide (Vita Zahnfabrik). All abutments were prepared according to common principles for these kinds of restorations.25,29-31 The lingual surfaces were reduced by approximately 0.5 mm to provide space for a sufficient thickness of ceramic material. The margins of the preparations were approximately 1 mm from the gingival margin and 1 to 1.5 mm from the incisal edge with a supragingival chamfer finish line. The proximal surfaces of abutments adjacent to the edentulous space were prepared to reduce convexity and provide an increased tooth surface available for bonding. An additional shallow box preparation was made in each abutment proximally to the pontic side (dimensions approximately 2 × 2 × 0.5 mm).32,33 Proximal contact areas were not invaded. Full-arch impressions were made with a single impression/double mixing technique and polyether ma-
VOLUME 45 • NUMBER 1 • JANUARY 2014
Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
Fig 2 cast.
Palatal view of the In-Ceram framework on the master
Fig 3 Intraoral view of completed treatment immediately after insertion.
terial (Permadyne, 3M Espe). Provisional restorations were made by placing composite resin (Tetric Ceram, Ivoclar Vivadent) directly on prepared unetched surfaces, finished, and polished. At the second visit, the provisional restorations were easily removed with a scaler. The In-Ceram restorations were constructed by the same technician in accordance with the manufacturer’s recommendations within 1 week after the final impressions were made (Fig 2). The inner surfaces of the restorations were air abraded with aluminum oxide particles (Korax 250, Bego) and coated with silane (Monobond S, Ivoclar Vivadent). After isolation of the teeth, the prepared surfaces of the abutment teeth were thoroughly cleaned with pumice slurry and etched with 37% phosphoric acid gel (Ultra-Etch, Ultradent) for 60 seconds, rinsed with water spray, and dried with air pressure. The dentin adhesive system Syntac Classic (Ivoclar Vivadent) was then applied. The ceramic restorations were cemented with dual polymerizing composite resin cement (Variolink II, Ivoclar Vivadent). After cementation, the occlusion was carefully evaluated and necessary corrections were performed. Finally, the inserted restorations were finished with diamonds burs and polishing disks and strips (Sof-Lex, 3M Espe). Intraoral color photographs were taken (Fig 3). All patients received oral hygiene instructions with special emphasis on the proximal and lingual surfaces. The patients were examined clinically at 1, 2, 4, 6, and 8 years after placement of the restorations. Such
periodic tests were conducted by the authors with a mirror, a sharp probe, and intraoral photographs. To assess reliability, 10% of the restorations were reexamined after 1 month, in order to confirm the findings of the first examination. The following information was recorded during the examination: • Debonding. Each retainer was checked for debonding through finger pressure and a sharp probe. The units were classified as debonding when it was possible to force the sharp tip between the retainer and the abutment, and when pushing the abutment teeth in the opposite direction of the restoration there was a visible gap between the retainer wing and the abutment. • Fracture. The fractures were divided into total and partial fractures. The loss of the restoration due to fracture of the ceramic was defined as a total fracture. A fractured restoration which remained in clinical service as a cantilevered FDP was considered a partial fracture. • Caries. All abutment teeth were examined to detect presence of dental caries by clinical examinations and by intraoral radiographs. • Patient acceptance. The patients were asked about the esthetic appearance of the restorations, their chewing ability, problems with cleaning, and symptoms of masticatory parafunction or dysfunction. A questionnaire presented an opportunity for giving alternative answers and personal remarks.
VOLUME 45 • NUMBER 1 • JANUARY 2014
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Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
RESULTS The results after 8 years of service are shown in Table 3. The reliability test showed no disagreement. Dental caries was not detected with any abutment during the observation time. On the 49 patients reexamined, 48 were satisfied with the function and the esthetic appearance of their restorations. The unsatisfied patient had a broad maxillary anterior edentulous space and the pontic created an asymmetrical appearance. All patients stated that the prosthesis did not cause any subjective symptoms such as headache, and their chewing ability was very good and satisfactory. Five patients avoided using their prostheses during chewing or biting on hard food, because they had previous fractures of porcelain-fusedto-metal crowns in the posterior teeth and, therefore, feared a new failure. Two restorations debonded during the evaluation period. Both of them were in the mandibular arch. In the first case, 3 years after the insertion of the restoration, the patient complained about mobility of the pontic replacing the mandibular right central incisor. Clinical examination revealed the wing on the mandibular right lateral incisor to be loose. In an attempt to create space to recement, the connector on the mandibular left central incisor was fractured. In the second case, which was similar, the pontic of the restoration was replacing the mandibular left lateral incisor and the wing debonded after a period of 3.5 years of clinical use. The fractured RBFDPs were removed and two new restorations were inserted.
Table 3
Results of the clinical investigation
Category
1Y
2Y
4Y
6Y
8Y
Satisfied patient
48
48
48
48
48
Unsatisfied patient
1
1
1
1
1
Caries
0
0
0
0
0
Debonding
0
0
2
2
2
Total fractures
1
1
2
2
2
Partial fractures
0
0
2
3
4
12
During the observation time, six fractures in the ceramic material occurred. These can be divided into two total and four partial fractures. In all cases, restorations fractured at the connector between the retainer and the pontic, but all retainer wings remained bonded to the abutment teeth. In total fractures, the bridge framework fractured at the mesial and distal connector. The first total fracture occurred during the first year after placement of the restoration, and the second after a period of 4 years of clinical use. Both were replaced during the observation period with similar restorations. In partial fractures, only one of the two connectors fractured. All partial fractures occurred between the fourth and seventh years of clinical use. These fractured RBFDPs remained in function as cantilevered restorations during the observation time.
DISCUSSION All-ceramic RBFDPs are used as a minimally invasive, tooth-tissue loss preventing alternative for replacing anterior teeth.34 They have been performed for many years and have become a useful and recognized technique. Clinical indicators include intact abutment teeth, a short edentulous span such as one missing tooth, and minimal dynamic occlusal contacts on the abutment teeth. The advantages of these restorations are numerous and result from the combined advantages of composite resins (adhesion, conservation of tooth substrate), and ceramic (color stability, wear resistance, enamel-like thermal expansion, and refined esthetics).21-32 This clinical study evaluated 54 In-Ceram anterior RBFDPs with a conventional two-retainer design for 8 years. The results suggest that when the indications and patient are selected appropriately, the overall outcome and clinical behavior are satisfactory. In this study the success rate for In-Ceram RBFDPs was 85.18% after 8 years. Patient acceptance of the restorations at 8 years was very encouraging. Only one patient complained about a minor esthetic problem, because he had a broad maxillary edentulous space and the pontic created an asymmetrical appearance.
VOLUME 45 • NUMBER 1 • JANUARY 2014
Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
During the observation time, two of the restorations debonded. The explanation of this phenomenon perhaps was related to the adhesive method used in this study (silane application after air-abrasion only). Kern and Thompson35 clearly showed in a laboratory study on bonding methods to In-Ceram, that silane application after air-abrasion of In-Ceram is inferior to silica coating and silane application or to using phosphate monomer–containing resins after air-abrasion. Also, a critical factor is the composite resin cement. Degradation within the resin cement may be related to breakdown of the filler-resin interface bond, which could contribute to resin cement failure.36 Many factors contribute to this phenomenon, like the polymerization shrinkage of composite resin, the dissolution of the resin matrix of composite resins in oral fluids, and the loss of marginal integrity caused at baseline by polymerization shrinkage or by removal of cement flashes with blunt instruments.37,38 In our study, both of the debonded restorations were in the mandibular arch. This may be attributable to the reason that moisture control during cementation is more difficult to obtain in the mandibular arch than in the maxillary arch. This means that a substantial amount of extra chairtime may be needed following the incorporation of a RBFDP, and the use of rubber dam during cementation is highly recommended. These two failures occurred 3 and 3.5 years after the insertion of the restorations. Complications such as debonding are most likely to occur with RBFDPs within a period of 5 years, with a 3% mean annual debonding rate.39 Fractures of ceramic material occurred in six restorations: two total fractures and four partial fractures. On condition that the absence of any ceramic fracture is chosen as a criterion for success, the success rate was 88.88%. Nevertheless, if functioning of the restorations is considered a success (thus including the three-unit and two-unit cantilever restorations) the success rate was 96.29%. Other clinical studies have reported higher and lower failure rates resulting from fracture (Kern and Strub32 94.1% after 5 years of clinical service; Pjetursson et al39 87.7% after 5 years; Wassermann et al40 92.3% after 5 years). In all cases, restorations fractured at the
VOLUME 45 • NUMBER 1 • JANUARY 2014
connector between the retainer and the pontic, but all retainer wings remained bonded to the abutment teeth. One of the main causes for failure of all-ceramic RBFDPs is fracture of the connector area.29,31,32,41 To achieve improved fracture strength, different framework designs have been proposed. Pospiech at al42,43 suggested a design with two proximal grooves (0.8 to 1.0 mm × 4.0 mm) and a connector with increased dimensions (4.0 × 2.0 mm minimum). Also, rounded edges and little interdental separation were significant for stress reduction. Kern at al44 concluded that the fracture strength of all-ceramic RBFDPs fabricated with In-Ceram substructure was significantly improved by the addition of small proximal box preparations to the abutments, and veneer applied to the In-Ceram framework circumferentially instead of only labially. In our study, the connectors of the frameworks were designed to be as thick as possible, and a shallow box preparation was made in each abutment proximally to the pontic side (dimensions approximately 2 × 2 × 0.5 mm) The four partial fractures in this study occurred between the fourth and seventh years of clinical use, but these fractured RBFDPs remained in function as cantilevered restorations during the observation time. Clinical and in vitro studies have reported that high-strength oxide ceramics used as a cantilever restoration is a viable alternative for anterior tooth replacement.29,32,40,45-48 These results may not be surprising if one considers the mechanics of tooth movement. Differential movement of the abutment teeth in a two-retainer RBFDP during occlusal excursive movements causes shear and torque forces on the pontic and connectors, resulting in a fracture, bending, debonding, or stress at the resin-RBFDP interface.29,36,46
CONCLUSION This study evaluated 54 In-Ceram anterior RBFDPs with a conventional two-retainer design for 8 years. The success rate was 85.18 % after 8 years. The results suggest that when the indications and patient are selected appropriately, the overall outcome and clinical behavior are satisfactory. Further research should be directed
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Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
toward the potential indications, efficacy, and prognosis of this type of prosthesis.
REFERENCES 1. Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J Prosthet Dent 1973;30:418–423. 2. Livaditis GJ, Thompson VP. Etched castings: an improved retentive mechanism for resin-bonded retainers. J Prosthet Dent 1982;47:52–58. 3. Barrack G. Etched cast restorations. Quintessence Int 1985;1:27–34. 4. Simonsen R, Thompson V, Barrack G. Etched cast restorations: clinical and laboratory techniques. Chicago, Quintessence, 1983:60–74. 5. Boening KW. Clinical performance of resin-bonded fixed partial dentures. J Prosthet Dent 1986;76:39–44. 6. Wood M. Etched casting resin-bonded retainers: an improved technique for periodontal splinting. Int J Periodontics Restorative Dent 1982;2:8–25. 7. Isidor F, Stockholm R. Resin-bonded prostheses for posterior teeth. J Prosthet Dent 1992;68:239–243. 8. Simon JF, Gartrell RG, Grogono A. Improved retention of acid-etched fixed partial dentures. A longitudinal study. J Prosthet Dent 1992;68:611–615. 9. Rammelsberg P, Pospiech P, Gernet W. Clinical factors affecting adhesive fixed partial dentures: a six year study. J Prosthet Dent 1993;70:300–307. 10. Hussey DL, Pagni C, Linden GJ. Performance of 400 adhesive bridges fitted in a restorative dentistry department. J Dent 1991;19:221–225. 11. Eshleman JB, Moon PC, Barnes RF. Clinical evaluation of cast metal resinbonded anterior fixed partial dentures. J Prosthet Dent 1984;51:761–764. 12. Yanover L, Croft W, Pulver F. The acid-etched fixed prosthesis. J Am Dent Assoc 1982;104:325–328. 13. Ziada HM, Orr JF, Bennington IC. Photoelastic stress analysis in a pier retainer of an anterior resin-bonded fixed partial denture. J Prosthet Dent 1998;80:661– 665. 14. Wirz J, Schmidli F, Steinemann S, Wall R. Aufbrennlegierungen im Spaltkorrosionstest. Schweiz Monatsschr Zahnmed 1987;97:571–590. 15. Meiners H, Dentallegierungen. In: Voss R, Meiners H, eds. Fortschritte der Prothetik und werkstoffkunde vol 4. Munich: Hanser Verlag, 1989:325–339. 16. Williams HA, Caughman WF, Pollard BL. The esthetic hybrid resin-bonded bridge. Quintessence Int 1989;20:623–626. 17. Sato A, Kumei Y, Sato K, Yoshio E, Ueno Y. Mutagenicity of dental nickelchromium alloys. Dent Jpn 1991;28:129–135. 18. Nilner K, Glantz PO, Ryge G, Sundberg H. Oral galvanic action after treatment with extensive metallic restorations. Acta Odontol Scand 1982;40:381–388. 19. Ibsen RL, Strassler HE. An innovative method for fixed anterior tooth replacement utilizing porcelain veneers. Quintessence Int 1986;17:455–459. 20. Garber DA, Goldstein RE, Feinman RA. Porcelain Laminate Veneers. 1st ed. Chicago: Quintessence, 1988:115–125. 21. Schaffer JL. All porcelain anterior fixed partial denture: a preliminary report. J Prosthet Dent 1988;59:669–671. 22. Claus H. Vita In-Ceram, ein neues Verfahren zur Herstellung oxidkeramischer Gerüste für kronen und Brücken. Quintessenz Zahntech 1990;16:35–46. 23. Kappert HF, Knobe H. Metallfreie Brücken für den Seitenzahnbereich. Dent Labor 1990;38:177–183. 24. Kappert HF, Knobe H. In-Ceram auf dem Prüfstand. Quintessenz Zahntech 1990;16:980–1002. 25. Kern M, Knobe H, Strub JR. The all porcelain resin-bonded bridge. Quintessence Int 1991;22:257–262. 26. Kappert HF, Knobe H. In-Ceram: testing a new ceramic material. Quintessence Dent Technol 1993;16:87–97.
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27. Probster L, Diehl J. Slip-casting alumina ceramics for crown and bridge restorations. Quintessence Int 1992;23:25–31. 28. Chiche GJ, Pinault A. Esthetics of anterior fixed prosthodontics. Chicago, Quintessence, 1994:48–50. 29. Ries S, Wolz J, Richter EJ. Effect of design of all-ceramic resin-bonded fixed partial dentures on clinical survival rate. Int J Periodontics Restorative Dent 2006;26:143–149. 30. Chow TW, Chung RW, Chu FC, Newsome PR. Tooth preparations designed for posterior resin-bonded fixed partial dentures: a clinical report. J Prosthet Dent 2002;88:561–564. 31. Koutayas OS, Kern M, Ferraresso F, Strub JR. Influence of design and mode of loading on the fracture strength of all-ceramic resin-bonded fixed partial dentures: an in vitro study in a dual-axis chewing simulator. J Prosthet Dent 2000;83:540–547. 32. Kern M, Strub JR. Bonding to alumina ceramic in restorative dentistry: clinical results over up to 5 years. J Dent 1998;26:245–249. 33. Kern M, Schwarzbach W, Strub JR. Stability of all-porcelain resin-bonded fixed restorations with different designs: an in vitro study. Int J Prosthodont 1992;5:108–113. 34. Edelhoff D, Sorensen JA. Tooth removal associated with various preparation designs for anterior teeth. J Prosthet Dent 2002;87:503–509. 35. Kern M, Thompson VP. Bonding to a glass infiltrated alumina ceramic: adhesion methods and their durability. J Prosthet Dent 1995;73:240–249. 36. Walker MP, Spencer P, Eick JD. Effect of simulated resin-bonded fixed partial denture clinical conditions on resin cement mechanical properties. J Oral Rehabil 2003;30:837–846. 37. Galiatsatos AA, Bergou D. Six-year clinical evaluation of ceramic inlays and onlays. Quintessence Int 2008;39:407–412. 38. Meng X, Yoshida K, Atsuta M. Influence of ceramic thickness on mechanical properties and polymer structure of dual-cured resin luting agents. Dental Materials 2008;24:594–599. 39. Pjetursson BE, Tan WC, Tan K, Bragger U, Zwahlen M, Lang NP. A systematic review of the survival and complication rates of resin-bonded bridges after an observation period of at least 5 years. Clin Oral Implants Res 2008;19:131–141. 40. Wassermann A, Kaiser M, Strub JR. Clinical long-term results of Vita In-Ceram Classic crowns and fixed partial dentures: a systematic literature review. Int J Prosthodont 2006;19:355–363. 41. Duarte S, Phark JH, Tomikazu T, Sadan A. Resin-bonded fixed partial dentures with a new modified zirconia surface: a clinical report. J Prosthet Dent 2009;102:68–73. 42. Pospiech P, Rammelsberg P, Unsold F. A new design for all-ceramic resinbonded fixed partial dentures. Quintessence Int 1996;27:753–758. 43. Pospiech P, Rammelsberg P, Goldhofer G, Gernet W. All-ceramic resin-bonded bridges. A 3-dimensional finite-element analysis study. Eur J Oral Sci 1996;104:390–395. 44. Kern M, Fechting T, Strub JR. Influence of water storage and thermal cycling on the fracture strength of all-porcelain, resin-bonded fixed partial dentures. J Prosthet Dent 1994;71:251–256. 45. Koutayias O, Kern M, Ferraresso F, Strub JR. Influence of framework design on fracture strength of mandibular anterior all-ceramic resin-bonded fixed partial denture. Int J Prosthodont 2002;15:223–229. 46. Kern M. Clinical long-term survival of two-retainer and single-retainer allceramic resin-bonded fixed partial dentures. Quintessence Int 2005;36:141– 147. 47. Kern M, Sasse M. Ten-year survival of anterior all-ceramic resin-bonded fixed dental prostheses. J Adhes Dent 2011;13:407–410. 48. Sasse M, Eschbach S, Kern M. Randomized clinical trial on single retainer allceramic resin-bonded fixed partial dentures: influence of the bonding system after up to 55 months. J Dent 2012;40:783–786.
VOLUME 45 • NUMBER 1 • JANUARY 2014
RESTORATIVE DENTISTRY
Aristidis A. Galiatsatos
Clinical evaluation of anterior all-ceramic resin-bonded fixed dental prostheses Aristidis A. Galiatsatos, DDS, Dr Dent1/Dimitra Bergou, DDS2 Objectives: All-ceramic resin-bonded fixed dental prostheses (RBFDPs) were introduced as a conservative treatment many years ago. The purpose of this study was to evaluate for 8 years the clinical survival of RBFDPs made with a conventional tworetainer design. Method and Materials: A total of 54 anterior RBFDPs were made from the glass-infiltrated alumina ceramic In-Ceram. The restorations were placed in 49 patients, aged 18 to 60 years, by a single operator using the same clinical procedure. The restorations were examined for debonding, fracture rate, caries, and patient acceptance. All restorations
were examined clinically at 1, 2, 4, 6, and 8 years after placement. Results: At 8 years, the success rate was 85.18%. Patient acceptance was very encouraging and dental caries were not detected with any abutment. Two restorations debonded during the evaluation period and fracture of porcelain occurred in six restorations (two total fractures and four partial fractures). Conclusion: All-ceramic RBFDPs made from high-strength oxide ceramics offer an effective conservative treatment for replacing anterior teeth. (Quintessence Int 2014;45:9–14; doi: 10.3290/j.qi.a30766)
Key words: clinical performance, esthetics, fracture, In-Ceram system, resin-bonded FDP
Conventional resin-bonded fixed dental prostheses (RBFDPs) with metal framework have been used in dental practice for many years as alternatives to conventional FDPs when abutments are intact or exhibit only minimal caries lesions.1-5 The longevity of the prostheses has been improved since the initial use as a result of preparation of the abutment teeth and a variety of new methods to increase mechanical and chemical resin-tometal retention.2,6-9 The most common type of failure with RBFDPs is the debonding of the cast metal framework from the luting cement, but debondings of the luting cement from the enamel surface have also been reported.10-13 These res1
Assistant Professor, Department of Dental Technology, Division of Fixed Prosthodontics, Technological Educational Institution of Athens, Athens, Greece.
2
Private practice, Athens, Greece.
Correspondence: Dr Aristidis A. Galiatsatos, 60 Str. Rogakou Str., 15125 Athens, Greece. Εmail: [email protected]
VOLUME 45 • NUMBER 1 • JANUARY 2014
torations may present disadvantages with regard to esthetics and biocompatibility.14-16 The esthetically unsatisfactory grayish “shine through” of metal is a common problem in the anterior region. The biocompatibility of certain nonprecious alloys has been questioned because of their corrosive, allergenic, and even mutagenic potentials.14-18 To overcome these problems, all-ceramic RBFDPs were introduced.19-21 It has been shown by several authors that the aluminum oxide ceramic In-Ceram (Vita Zahnfabrik) has much better physical properties than other ceramic or glass materials.22-27 For this reason, RBFDPs have been suggested as an alternative to traditional resin-bonded restorations, which use a metal framework.25 The recommended design of InCeram prostheses is similar to the design of the conventional metal-ceramic resin-bonded restorations.25 Several studies on all-ceramic RBFDPs have been
9
Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
Table 1
Age and gender of patients
Age (years)
Men
Women
Total
18–30
10
12
22
31–40
8
8
16
41–50
2
4
6
51–60
1
4
5
Total
21
28
49
Table 2
Distribution of the restorations
Arch location
No. of RBFDPs
Replaced central incisors
Replaced lateral incisors
Maxilla
30
20
Mandible
24
15
9
Total
54
35
19
10
reported and the observation periods and success rates in these reports vary considerably. The purpose of this study was to add to the knowledge of all-ceramic RBFDPs by evaluating the longterm clinical survival of such restorations.
METHOD AND MATERIALS The study population consisted of 49 patients. There were 28 women and 21 men, ranging in age from 18 to 60 years (Table 1). Patient selection was accomplished according to preestablished criteria. Abutments were intact and caries-free, or exhibiting only minimal lesions that did not interfere with bonding, and tooth alignment was acceptable. Patients who exhibited bruxism, deep bite situation, severe inflammation, poor oral hygiene, or a high caries rate were ineligible for this study. Only patients with one missing mandibular or maxillary anterior tooth (central or lateral incisor) were selected. Five of them had both one missing maxillary and one missing mandibular anterior tooth. None of the selected patients dropped out or were dismissed. In the majority of the cases, an implant-supported prosthesis was not advisable as available bone volume was minimal, or the adjacent root was in close proximity.28 Also, many patients declined the several surgical procedures required.
10
Fig 1 Preoperative view of a patient with congenitally missing lateral incisor.
The selected patients were provided with a total of 54 anterior RBFDPs with a conventional two-retainer design in a private practice. The glass-infiltrated aluminum ceramic In-Ceram technique was selected to fabricate the above restorations. The distribution of the restorations is presented in Table 2. The reasons for the loss of teeth in this study were congenitally missing teeth, trauma, dental caries, endodontic complications, and periodontal disease (Fig 1). All procedures were performed by a single investigator, and all materials were mixed and used according to the recommendations of the manufacturers. Shades were matched with the Vita-Lumin Vacuum shade guide (Vita Zahnfabrik). All abutments were prepared according to common principles for these kinds of restorations.25,29-31 The lingual surfaces were reduced by approximately 0.5 mm to provide space for a sufficient thickness of ceramic material. The margins of the preparations were approximately 1 mm from the gingival margin and 1 to 1.5 mm from the incisal edge with a supragingival chamfer finish line. The proximal surfaces of abutments adjacent to the edentulous space were prepared to reduce convexity and provide an increased tooth surface available for bonding. An additional shallow box preparation was made in each abutment proximally to the pontic side (dimensions approximately 2 × 2 × 0.5 mm).32,33 Proximal contact areas were not invaded. Full-arch impressions were made with a single impression/double mixing technique and polyether ma-
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Q U I N T E S S E N C E I N T E R N AT I O N A L Galiatsatos / Bergou
Fig 2 cast.
Palatal view of the In-Ceram framework on the master
Fig 3 Intraoral view of completed treatment immediately after insertion.
terial (Permadyne, 3M Espe). Provisional restorations were made by placing composite resin (Tetric Ceram, Ivoclar Vivadent) directly on prepared unetched surfaces, finished, and polished. At the second visit, the provisional restorations were easily removed with a scaler. The In-Ceram restorations were constructed by the same technician in accordance with the manufacturer’s recommendations within 1 week after the final impressions were made (Fig 2). The inner surfaces of the restorations were air abraded with aluminum oxide particles (Korax 250, Bego) and coated with silane (Monobond S, Ivoclar Vivadent). After isolation of the teeth, the prepared surfaces of the abutment teeth were thoroughly cleaned with pumice slurry and etched with 37% phosphoric acid gel (Ultra-Etch, Ultradent) for 60 seconds, rinsed with water spray, and dried with air pressure. The dentin adhesive system Syntac Classic (Ivoclar Vivadent) was then applied. The ceramic restorations were cemented with dual polymerizing composite resin cement (Variolink II, Ivoclar Vivadent). After cementation, the occlusion was carefully evaluated and necessary corrections were performed. Finally, the inserted restorations were finished with diamonds burs and polishing disks and strips (Sof-Lex, 3M Espe). Intraoral color photographs were taken (Fig 3). All patients received oral hygiene instructions with special emphasis on the proximal and lingual surfaces. The patients were examined clinically at 1, 2, 4, 6, and 8 years after placement of the restorations. Such
periodic tests were conducted by the authors with a mirror, a sharp probe, and intraoral photographs. To assess reliability, 10% of the restorations were reexamined after 1 month, in order to confirm the findings of the first examination. The following information was recorded during the examination: • Debonding. Each retainer was checked for debonding through finger pressure and a sharp probe. The units were classified as debonding when it was possible to force the sharp tip between the retainer and the abutment, and when pushing the abutment teeth in the opposite direction of the restoration there was a visible gap between the retainer wing and the abutment. • Fracture. The fractures were divided into total and partial fractures. The loss of the restoration due to fracture of the ceramic was defined as a total fracture. A fractured restoration which remained in clinical service as a cantilevered FDP was considered a partial fracture. • Caries. All abutment teeth were examined to detect presence of dental caries by clinical examinations and by intraoral radiographs. • Patient acceptance. The patients were asked about the esthetic appearance of the restorations, their chewing ability, problems with cleaning, and symptoms of masticatory parafunction or dysfunction. A questionnaire presented an opportunity for giving alternative answers and personal remarks.
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RESULTS The results after 8 years of service are shown in Table 3. The reliability test showed no disagreement. Dental caries was not detected with any abutment during the observation time. On the 49 patients reexamined, 48 were satisfied with the function and the esthetic appearance of their restorations. The unsatisfied patient had a broad maxillary anterior edentulous space and the pontic created an asymmetrical appearance. All patients stated that the prosthesis did not cause any subjective symptoms such as headache, and their chewing ability was very good and satisfactory. Five patients avoided using their prostheses during chewing or biting on hard food, because they had previous fractures of porcelain-fusedto-metal crowns in the posterior teeth and, therefore, feared a new failure. Two restorations debonded during the evaluation period. Both of them were in the mandibular arch. In the first case, 3 years after the insertion of the restoration, the patient complained about mobility of the pontic replacing the mandibular right central incisor. Clinical examination revealed the wing on the mandibular right lateral incisor to be loose. In an attempt to create space to recement, the connector on the mandibular left central incisor was fractured. In the second case, which was similar, the pontic of the restoration was replacing the mandibular left lateral incisor and the wing debonded after a period of 3.5 years of clinical use. The fractured RBFDPs were removed and two new restorations were inserted.
Table 3
Results of the clinical investigation
Category
1Y
2Y
4Y
6Y
8Y
Satisfied patient
48
48
48
48
48
Unsatisfied patient
1
1
1
1
1
Caries
0
0
0
0
0
Debonding
0
0
2
2
2
Total fractures
1
1
2
2
2
Partial fractures
0
0
2
3
4
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During the observation time, six fractures in the ceramic material occurred. These can be divided into two total and four partial fractures. In all cases, restorations fractured at the connector between the retainer and the pontic, but all retainer wings remained bonded to the abutment teeth. In total fractures, the bridge framework fractured at the mesial and distal connector. The first total fracture occurred during the first year after placement of the restoration, and the second after a period of 4 years of clinical use. Both were replaced during the observation period with similar restorations. In partial fractures, only one of the two connectors fractured. All partial fractures occurred between the fourth and seventh years of clinical use. These fractured RBFDPs remained in function as cantilevered restorations during the observation time.
DISCUSSION All-ceramic RBFDPs are used as a minimally invasive, tooth-tissue loss preventing alternative for replacing anterior teeth.34 They have been performed for many years and have become a useful and recognized technique. Clinical indicators include intact abutment teeth, a short edentulous span such as one missing tooth, and minimal dynamic occlusal contacts on the abutment teeth. The advantages of these restorations are numerous and result from the combined advantages of composite resins (adhesion, conservation of tooth substrate), and ceramic (color stability, wear resistance, enamel-like thermal expansion, and refined esthetics).21-32 This clinical study evaluated 54 In-Ceram anterior RBFDPs with a conventional two-retainer design for 8 years. The results suggest that when the indications and patient are selected appropriately, the overall outcome and clinical behavior are satisfactory. In this study the success rate for In-Ceram RBFDPs was 85.18% after 8 years. Patient acceptance of the restorations at 8 years was very encouraging. Only one patient complained about a minor esthetic problem, because he had a broad maxillary edentulous space and the pontic created an asymmetrical appearance.
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During the observation time, two of the restorations debonded. The explanation of this phenomenon perhaps was related to the adhesive method used in this study (silane application after air-abrasion only). Kern and Thompson35 clearly showed in a laboratory study on bonding methods to In-Ceram, that silane application after air-abrasion of In-Ceram is inferior to silica coating and silane application or to using phosphate monomer–containing resins after air-abrasion. Also, a critical factor is the composite resin cement. Degradation within the resin cement may be related to breakdown of the filler-resin interface bond, which could contribute to resin cement failure.36 Many factors contribute to this phenomenon, like the polymerization shrinkage of composite resin, the dissolution of the resin matrix of composite resins in oral fluids, and the loss of marginal integrity caused at baseline by polymerization shrinkage or by removal of cement flashes with blunt instruments.37,38 In our study, both of the debonded restorations were in the mandibular arch. This may be attributable to the reason that moisture control during cementation is more difficult to obtain in the mandibular arch than in the maxillary arch. This means that a substantial amount of extra chairtime may be needed following the incorporation of a RBFDP, and the use of rubber dam during cementation is highly recommended. These two failures occurred 3 and 3.5 years after the insertion of the restorations. Complications such as debonding are most likely to occur with RBFDPs within a period of 5 years, with a 3% mean annual debonding rate.39 Fractures of ceramic material occurred in six restorations: two total fractures and four partial fractures. On condition that the absence of any ceramic fracture is chosen as a criterion for success, the success rate was 88.88%. Nevertheless, if functioning of the restorations is considered a success (thus including the three-unit and two-unit cantilever restorations) the success rate was 96.29%. Other clinical studies have reported higher and lower failure rates resulting from fracture (Kern and Strub32 94.1% after 5 years of clinical service; Pjetursson et al39 87.7% after 5 years; Wassermann et al40 92.3% after 5 years). In all cases, restorations fractured at the
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connector between the retainer and the pontic, but all retainer wings remained bonded to the abutment teeth. One of the main causes for failure of all-ceramic RBFDPs is fracture of the connector area.29,31,32,41 To achieve improved fracture strength, different framework designs have been proposed. Pospiech at al42,43 suggested a design with two proximal grooves (0.8 to 1.0 mm × 4.0 mm) and a connector with increased dimensions (4.0 × 2.0 mm minimum). Also, rounded edges and little interdental separation were significant for stress reduction. Kern at al44 concluded that the fracture strength of all-ceramic RBFDPs fabricated with In-Ceram substructure was significantly improved by the addition of small proximal box preparations to the abutments, and veneer applied to the In-Ceram framework circumferentially instead of only labially. In our study, the connectors of the frameworks were designed to be as thick as possible, and a shallow box preparation was made in each abutment proximally to the pontic side (dimensions approximately 2 × 2 × 0.5 mm) The four partial fractures in this study occurred between the fourth and seventh years of clinical use, but these fractured RBFDPs remained in function as cantilevered restorations during the observation time. Clinical and in vitro studies have reported that high-strength oxide ceramics used as a cantilever restoration is a viable alternative for anterior tooth replacement.29,32,40,45-48 These results may not be surprising if one considers the mechanics of tooth movement. Differential movement of the abutment teeth in a two-retainer RBFDP during occlusal excursive movements causes shear and torque forces on the pontic and connectors, resulting in a fracture, bending, debonding, or stress at the resin-RBFDP interface.29,36,46
CONCLUSION This study evaluated 54 In-Ceram anterior RBFDPs with a conventional two-retainer design for 8 years. The success rate was 85.18 % after 8 years. The results suggest that when the indications and patient are selected appropriately, the overall outcome and clinical behavior are satisfactory. Further research should be directed
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toward the potential indications, efficacy, and prognosis of this type of prosthesis.
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