- Email: [email protected]
Retrospective clinical evaluation of ceramic onlays placed by dental students
RESEARCH AND EDUCATION
Retrospective clinical evaluation of ceramic onlays placed by dental students Jennifer J. Archibald, DDS,a Gildo Coelho Santos, Jr, DDS, MSc, PhD,b and Maria Jacinta Moraes Coelho Santos, DDS, MSc, PhDc Indirect ceramic restorations ABSTRACT have been considered an Statement of problem. Indirect restorations with partial or complete occlusal surface coverage excellent treatment option for have been recommended to restore teeth with weakened walls in order to prevent cusp fracture. patients with high esthetic The success of these restorations when performed by dental students is unknown. demands, especially where the Purpose. The purpose of this retrospective study was to evaluate the clinical performance of size of the cavity preparation is adhesively bonded ceramic onlay restorations placed by third- and fourth-year dental students. too large for direct restoraMaterial and methods. Sixty-five ceramic onlays were placed in patients between 2009 and 2015. tions.1 The development of The onlays were laboratory or chairside fabricated with a computer-aided design and computerhigh flexural strength ceramics aided manufacturing (CAD-CAM) system, using either IPS e.max Press or IPS e.max CAD. An has allowed the use of ceramic adhesive technique and luting composite resin agent were used to cement the restorations. restorations on teeth with Thirty-seven onlays were evaluated clinically using the modified United States Public Health higher functional loading.1,2 Service (USPHS) criteria. Data were statistically analyzed using the Cox proportional hazards model to compare tooth type and failures and the Fisher exact and McNemar tests to compare Manufacturers have been able the USPHS criteria for significant differences (a=.05). Survival probability was calculated using the to strengthen ceramics by Kaplan-Meier algorithm. adding filler particles to the base glass composition, such Results. Five onlays were considered to be failures and needed replacement. According to the Kaplan-Meier analysis, the estimated survival rate was 96.3% after 2 years and 91.5% at 4 years. All 5 as leucite and lithium disilicate 2 of the failures occurred on molars (13.5%) and none on premolars (P=.025). A statistically significant crystals. IPS e.max Press and difference was found for marginal discoloration between onlays placed within 0 to 3 years and 3 to IPS e.max CAD (Ivoclar Viva6 years (P<.05) but no differences between any other criteria. dent AG) are examples of Conclusions. Ceramic onlays placed by dental students demonstrated acceptable long-term clinical particle-filled glass ceramics performance. (J Prosthet Dent 2017;-:---) that contain high concentrations of lithium disilicate crysCeramic materials are available for fabricating partial tals for enhanced mechanical properties.3 restorations by using different techniques.11-14 Among Partial or complete coverage of the occlusal surface them, the IPS Empress system introduced in the early has been recommended to restore teeth with weakened 1990s combines heat and pressure in an injection walls and to prevent cusp fracture.4 Ceramic onlay resmolding process by using presintered glass-ceramic torations are able to provide cuspal protection while blocks enriched with leucite crystals.2,15 The addition of minimizing the extensive removal of sound tooth struccrystals in the glass phase helps to counteract the buildup ture.5,6 Adhesive cementation is indicated for use with of tensile stresses, improving the flexural strength and glass ceramic systems to create a strong bond between mechanical performance of the ceramic material.12,16 tooth and ceramic material.7-10 a
Predoctoral student, Schulich Medicine and Dentistry, Western University, London, Ontario, Canada. Associate Professor, Department of Restorative Dentistry, Schulich Medicine and Dentistry, Western University, London, Ontario, Canada. c Associate Professor, Department of Restorative Dentistry, Schulich Medicine and Dentistry, Western University, London, Ontario, Canada. b
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Clinical Implications The results observed in this study showed that ceramic onlay restoration is a successful treatment option for patients. The advantages of these conservative ceramic restorations include less tooth removal and excellent esthetics.
More recently, IPS e.max Press has been introduced by using a similar processing technique but using ceramic blocks enriched with lithium disilicate crystals (SiO2Li2O) to improve mechanical properties and translucency.3,12,17 Furthermore, machinable ceramics such as IPS e.max CAD have been developed for use with computer-aided design and computer-aided manufacturing (CAD-CAM) applications, either chairside or in the laboratory.18 Ceramic blocks in a partially crystallized, soft, state allow milling without excessive diamond tool wear or damage to the ceramic material. The long-term survival rates of adhesively bonded ceramics restorations have been reported to range from 76% to over 90%,19-25 with bulk fracture and marginal discoloration as the most common causes of failures.26-28 Although ceramic materials have been extensively used for crowns, numerous studies have reported the successful clinical behavior of partial ceramic restorations.29-39 The longevity of CAD-CAM onlays has also been studied, with marginal fit having a strong influence on success rates.40-43 To assess the behavior of partial ceramic restorations in a dental school environment, the present study aimed to evaluate the clinical performance of adhesively bonded ceramic onlay restorations placed by dental students within the past 6 years. MATERIAL AND METHODS This study was carried out according to research guidelines involving human subjects and was independently reviewed and approved by the Research Ethics Board for Health Sciences Research Involving Human Subjects (HSREB) for Western University, Ontario, Canada. Sixty-five ceramic onlays were placed in 52 patients at the Schulich Dental Clinic at Western University in the past 6 years. These ceramic onlay restorations were prepared and cemented by fourth-year predoctoral students supervised by a faculty member in the Department of Restorative Dentistry. The following criteria have been adopted by the dental school to determine the suitability of a tooth to receive an onlay restoration using clinical and radiographic examination: amount and quality of the remaining tooth structure, occlusion, periodontal assessment, pulpal or endodontic treatment evaluation,
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amenability for rubber dam placement, and esthetic requirement. The tooth preparations followed the general principles for adhesive ceramic onlays, including isthmus width between 1.5 and 2.5 mm; minimum occlusal reduction of 1.5 (nonfunctional cusps) to 2.0 mm (functional cusps); 1.25-mm modified shoulder margin around the preparation; round internal line angles; and divergence of walls at approximately 10 to 15 degrees with no bevel. After cavity preparation, interim restorations were fabricated with an automixed methacrylate resin (Integrity; Dentsply Sirona) and cemented with interim cement (Temp Bond; Kerr Dental). The shade was selected with the Vita Shade guide (Vita North America). Impressions were made with light-body and heavy-body polyvinyl siloxane materials (Aquasil; Dentsply Sirona), and onlays were fabricated in the dental school’s laboratory using IPS e.max Press or IPS e.max CAD (Ivoclar Vivadent AG). Six onlays were produced chairside by using the CEREC system (software 4.0; Dentsply Sirona). The prepared teeth were sprayed with a thin layer of powder spray (IPS Contrast Spray Labside; Ivoclar Vivadent AG) for image capture with the BlueCam digital scanner (BlueCam; Dentsply Sirona). The restorations were milled in a CEREC MC XL machine by using presintered glass ceramic blocks (IPS e.max CAD; Ivoclar Vivadent AG) and were polished with porcelain polishing points (Dialite Intra-Oral Polishing System; Brasseler USA). During the cementation appointment, the teeth to be restored were isolated with either rubber dam, displacement cords, dry angles, or cotton rolls. Interim restorations were removed, and the tooth was cleaned with pumice slurry. The fit of the ceramic onlays was evaluated before cementation, and minor adjustments were performed if necessary. The ceramic onlays were placed using the following cementation protocols: ceramic onlay, etched with 10% hydrofluoric acid (Prosthetic Etchant Gel; Dentsply Sirona) for 20 seconds, washed, and dried; silane agent (Monobond S; Ivoclar Vivadent AG) applied for 1 minute; prepared tooth, acid etched with 35% phosphoric acid, rinsed with water, and gently air dried; dentin bonding agent (Multilink Primer or Excite DSC; Ivoclar Vivadent AG or Scotchbond Universal Adhesive; 3M ESPE) applied over dentin and enamel. If Scotchbond was used, the silane agent was omitted as Scotchbond Universal contains a silane agent. The onlays were cemented with a dual-polymerizing resin luting material (Variolink II; Ivoclar Vivadent AG or RelyX Ultimate; 3M ESPE) according to the manufacturer’s instructions. The restorations were briefly polymerized (5 to 10 seconds) with a light-emitting diode light-polymerizing unit so that excess cement could be easily removed with explorers, scalers, and dental floss interproximally. Each surface was then polymerized for Archibald et al
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Table 1. Clinical investigation results with modified USPHS criteria Criteria
Alfa (%)
Bravo (%)
Postoperative sensitivity
91.2
8.8
Secondary caries
91.2
8.8
Charlie (%)
Anatomic form
76.5
20.6
2.9
Color match
32.4
67.6
0.00
Surface roughness
44.1
53.0
2.9
Marginal discoloration
47.1
52.9
0.00
Marginal adaptation
32.4
58.8
5.9
Delta (%)
2.9
USPHS, United States Public Health Service.
20 seconds. Restorations were adjusted with diamond finishing rotary instruments under water cooling and polished with porcelain polishing points (Dialite IntraOral Polishing System; Brasseler USA). Each patient received a 48-hour follow-up appointment to re-evaluate interproximal contacts, margins, and occlusion. Patients of the Schulich Dental Clinic who had onlays placed between January 2009 and March 2015 were contacted by telephone, letter, or email and were invited for a follow-up examination. After receiving information about the research methodology, risks, and benefits of their participation, a written informed consent was obtained. Restorations were assessed with the modified United States Public Health Service (USPHS) criteria (Supplementary Table 1) by 2 independent investigators (M.J.S., J.A.) calibrated in the use of the system.44 The investigators worked as a team but evaluated the onlays independently with mouth mirrors and dental explorers. A joint examination was performed to resolve any disagreements. The participants were also asked about their satisfaction with the restoration and whether they had experienced any sensitivity or discomfort after placement. Clinical photographs were made of select participants. Interexaminer reliability was determined to be above 0.85 for all criteria, demonstrating a high rate of agreement between examiners. The date of placement and the date of the last observation of the restoration were recorded for statistical analysis. Time of failure was fixed at the end of a 4-month time period because the exact time of failure could not be accurately determined for each participant. Failures were established as being restorations that were lost or had fractured prior to the evaluation or those that required replacement because of poor marginal quality (Charlie, Delta), secondary caries (Bravo), or endodontic complications. The ratings Alfa (A) and Bravo (B) are considered successful for most criteria. Statistical graphing software (Prism 6; GraphPad Software, Inc) was used to calculate survival probability using the Kaplan-Meier algorithm. The Cox proportional hazards model was used to compare tooth type (molar or premolar) and failures. The Fisher exact and McNemar statistical tests were used to compare the USPHS criteria for significant differences (a=.05). Archibald et al
Figure 1. Representative restoration scored Bravo for marginal discoloration (clinically acceptable).
RESULTS Among the 52 participants who received onlay restorations, 22 could not attend an appointment at the school because of work commitments, sickness, vacation, or relocation to another city. Of the participants who could not come into the clinic and were reached by telephone or email, 18 reported no postoperative sensitivity or other issues and overall patient satisfaction. One participant reported that the onlay had been rebonded in the past. However, information gathered from participants that could not be clinically evaluated was not added to the statistical analysis. Thirty participants, 19 women and 11 men with a median age of 52 years, (ranging from 24 to 80 years) were evaluated in the clinic for a total of 37 onlays. Fifteen onlays (40.5%) were placed on premolar teeth and 22 onlays (59.5%) were placed on molars. Of the 37 onlays evaluated clinically, 6 were fabricated with IPS e.max Press, and 31 with IPS e.max CAD. Six of the IPS e.max CAD onlays were produced chairside with the CAD-CAM machine. At the time of clinical observation, 34 (91.9%) of these restorations were considered clinically acceptable. The mean observation period for the ceramic restorations was 3.5 years, with an observation interval of up to 6 years. Table 1 summarizes the results of the modified USPHS criteria obtained at the recall appointments. Some Alfa and Bravo findings are illustrated in Figures 1 to 3. Five restorations were considered failures (Table 2). Two restorations received C/D scores for marginal adaptation and/or B scores for secondary caries and needed to be replaced. Three restorations could not be evaluated as they had been replaced. The Kaplan-Meier methodology was used to calculate the survival probabilities (Fig. 4). The estimated survival rate was 96.3% after 2 years and 91.5% at 4 years (n=37). The sample size after 5 to 6 years was much smaller,
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Figure 2. Representative restoration scored Bravo for marginal integrity (clinically acceptable).
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Figure 3. Representative restoration scored Bravo for recurrent caries (not clinically acceptable).
Table 2. Data of failed restorations Number
Time in Service (mo)
Material Used
Sex
1
Maxillary 1st molar
Location
Fracture
Rating
24
IPS e.max CAD
Male
2
Mandibular 1st molar
Fracture
48
IPS e.max CAD
Male
3
Mandibular 1st molar
Fracture
60
IPS e.max CAD*
Female
4
Maxillary 1st molar
Secondary caries
60
IPS e.max CAD*
Female
5
Maxillary 1st molar
Secondary caries
72
IPS e.max CAD*
Female
*Chairside CEREC CAD-CAM.
DISCUSSION The longevity and clinical performance of adhesively bonded ceramic onlays placed by dental students were evaluated. Few studies12,19,25,29,30,32 have retrospectively assessed ceramic onlays over more than 3 years, especially with the IPS e.max CAD and IPS e.max Press systems. Another particularity of the present study is related to the population analyzed, where the participants were from the community and represented to a certain extent a cross section of the population. Hickel et al45 have provided a practical approach for conducting clinical trials, which considers that the results of a clinical evaluation obtained from participants recruited from the
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Survival Probability (%)
reducing the survival rate. The mean survival rate after 6 years was 67.4% (95% confidence interval=62.3% to 72.5%). All 5 of the failures occurred on molars (13.5%) and none on premolars (P=.025). Three of the 6 onlays (50%) fabricated chairside with the CEREC machine failed, compared with 2 of the 31 (6.5%) fabricated with IPS e.max CAD in the laboratory. No IPS e.max Press onlays failed. The McNemar statistical test (n=34) revealed a statistically significant difference for marginal discoloration between onlays placed within 0 to 3 years and 3 to 6 years ago (P<.05). No significant differences were found for other criteria when time since placement (<3 years and >3 years) and tooth location (molar or premolar) were compared.
90 80 70 60 50 40 30
0
20
40
60
80
Time (mo) Figure 4. Kaplan-Meier survival analysis of all onlays examined clinically.
community may be more realistic than results obtained from a select group with more awareness of dental hygiene and preventive measures. Furthermore, several operators (fourth-year dental students) carried out the clinical procedures following guidelines adopted by the dental school for the preparation and cementation of ceramic onlays. A 4-year study20 reported success rates above 90%, similar to the 91.5% survival rate calculated with KaplanMeier statistics in the present study. Survival rate was higher at 2 years (96.3%), similar to previous findings.6,26,31 As expected, higher success rates were recorded for recently placed restorations. In the present study, Archibald et al
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the sample size after 5 years of service was smaller, causing the survival rate to decline. Due to the retrospective nature of this study in a dental school clinic setting, the recall rate was lower than that of similar studies. Success rates need to be verified by continual follow-up investigations over a 5-year period with a higher recall percentage. The survival rate of posterior ceramic crowns ranges between 84.4% and 95.5%. Recent studies on lithium disilicate crowns generally report survival rates of 95% over 5 years.22 Ceramic onlays have comparable survival rates with crowns yet are able to preserve healthy tooth structure. All the failures observed in the present study occurred on molars, as heavy occlusal loads tend to occur on molar teeth.26,32,33 Although a similar number of premolar and molar onlays were evaluated, 15 onlays (40.5%) on premolar teeth and 22 onlays (59.5%) on molars, no failures were observed on premolars. Occlusal forces are one of the main reasons for ceramic fracture.1,19 This finding is consistent with previous studies reporting great risk of failures on molars.26,32 Smales and Etemadi33 found a higher percentage of failures in molar onlays due to bulk fracture. Other studies, however, found no differences in the survival rates of ceramic inlays or onlays between the premolar and molar areas.12 Three of the onlays failed because of fracture, which is considered a common problem reported in clinical studies.6,12,27,32,34 Fracture may have been caused by excessive occlusal loads or insufficient ceramic thickness.45 Cracks produced by finishing and polishing procedures can lead to fracture of the material by crack propagation under excessive tensile stress.35 The treatment records revealed that all 3 of these onlays were adjusted with diamond rotary instruments and rubber points during the delivery appointment. This finding highlights the importance of careful finishing and polishing procedures in adjusting the restoration. Two onlays were replaced before evaluation. These failed onlays were from the same participant and had been placed on opposing first molars. The first fracture occurred at 2 years after placement, much earlier than the other failures in this study. This participant was found to be a bruxer with extensive wear facets on his dentition. This finding is supported by another retrospective study, which reported an early failure due to the patient’s bruxism.28 Because of their brittle nature, ceramic restorations should not be used in patients with excessive occlusal loads.23,36 Two restorations received Charlie or Delta scores for marginal adaptation, and one of them presented secondary caries. Both restorations failed after 56 months of service. Although several studies have reported decreased marginal adaptation over time,12,37 no significant statistical differences for marginal adaptation were observed for those onlays placed between 0 to 3 years of service Archibald et al
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compared with 3 to 6 years. However, few restorations received an Alfa score for marginal adaptation (32.4%). Previous studies have observed the deterioration of marginal quality because occlusal fatigue caused degradation of the resin-based luting agent.37 Deterioration at the margins may lead to recurrent caries and restoration fracture.28 The low modulus of elasticity of the resin-based luting agent compared with the high modulus of elasticity of the ceramic materials, combined with the fatigue of the adhesive luting agent under occlusal loading, are considered contributing factors for decreased marginal adaptation of partial ceramic restorations.6,25 Marginal adaptation is closely related to marginal discoloration. As such, statistically significant increased marginal discoloration (P=.013) was observed in this study as the restoration aged. Previous studies have shown that discoloration increases over time as a result of the wear of the luting resin cement.6,24,38 This finding is also consistent with the study of Tagtekin et al,39 which showed statistically significant marginal discoloration at 12- and 24-month recalls with IPS Empress ceramics. Coelho Santos et al6 illustrated cement wear with consequent marginal discoloration of the margins of ceramic onlays with scanning electron micrographs. Three of the 5 failures observed in the present study occurred on the onlays fabricated using the CAD-CAM CEREC machine in 2009, representing the oldest onlays in the sample. One onlay fractured before evaluation, and the other 2 received poor scores on marginal adaptation, leading to replacement because of secondary caries and endodontic treatment. These results may be attributed to the difficulty of digitally capturing subgingival margins40 or to the limitations of the previous software versions and milling machine.41 Posselt and Kerschbaum42 reported a large percentage of CEREC restorations with underfilled margins. Contrary to these findings, several studies have reported survival rates for CEREC manufactured onlays to be similar to those fabricated using the hot pressed technique, with rates over 90% for 10 years.42,43 The limited participant recall is a weakness of the present study and is an inherent problem with clinical studies.46 Follow-up by 32 of the 52 original participants might have been biased because those more motivated to receive an evaluation might have responded to the study recruitment. Additionally, the use of an older chairside CAD-CAM system to fabricate onlays in 2009 has some disadvantages compared with newer versions developed to eliminate previous limitations of the system and enhance marginal adaptation.47 Half of the chairside CEREC ceramic onlays evaluated in this study failed (3 of 6). Further long-term clinical studies should be conducted to evaluate the performance of IPS e.max CAD onlays fabricated chairside with newer software versions.
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CONCLUSIONS Based on the findings of this clinical study, the following conclusions were drawn: 1. Ceramic onlays placed by dental students demonstrated acceptable clinical performance over a 4-year period and are a successful treatment option for selected patients in a dental school. 2. These results are relevant to daily practice as highquality indirect partial restorations can protect compromised tooth structure without extensive removal of sound dental tissue and with increased patient satisfaction. REFERENCES 1. Griggs JA. Recent advances in materials for ceramic restorations. Dent Clin North Am 2007;51:713-27. 2. Dong JK, Luthy H, Wohlwend A. Heat-pressed ceramics: technology and strength. Int J Prosthodont 1992;5:9-16. 3. Guess PC, Schultheis S, Bonfante EA, Coelho PG, Ferencz JL, Silva NR. Ceramic systems: laboratory and clinical performance. Dent Clin North Am 2011;55:333-52. 4. Fennis WM, Kuijs RH, Kreulen CM, Verdonschot N, Creugers NH. Fatigue resistance of teeth restored with cuspal-coverage composite restorations. Int J Prosthodont 2004;17:313-7. 5. Edelhoff D, Sorensen JA. Tooth structure removed associated with various preparation designs for posterior teeth. Int J Periodont Restor Dent 2002;22:241-9. 6. Coelho Santos MJ, Mondelli RF, Lauris JR, Navarro MF. Clinical evaluation of ceramic inlays and onlays fabricated with two systems: two-year clinical follow up. Oper Dent 2004;29:123-30. 7. Burke FJT, Fleming GJP, Nathanson D, Marquis PM. Are adhesive technologies needed to support ceramics? An assessment of the current evidence. J Adhes Dent 2002;4:7-22. 8. Rekow D, Thompson VP. Engineering long term clinical success of advanced ceramic prostheses. J Mater Sci Mater Med 2007;18:47-56. 9. Kelly JR, Benetti P. Ceramic materials in dentistry: historical evolution and current practice. Aust Dent J 2011;56:84-96. 10. Hopp CD, Land MF. Considerations for ceramic inlays in posterior teeth: a review. Clin Cosmet Investig Dent 2013;5:21-32. 11. Shenoy A, Shenoy N. Dental ceramics: an update. J Conserv Dent 2010;13: 195-203. 12. Santos MJ, Freitas MC, Azevedo LM, Santos GC Jr, Navarro MF, Francischone CE, et al. Clinical evaluation of ceramic inlays and onlays fabricated with two systems: 12-year follow-up. Clin Oral Investig 2016;20: 1683-90. 13. Conrad HJ, Seong WJ, Pesun IJ. Current ceramic materials and systems with clinical recommendations: a systematic review. J Prosthet Dent 2007;98: 389-404. 14. Giordano R, McLaren EA. Ceramics overview: classification by microstructure and processing methods. Compend Contin Educ Dent 2010;31:682-700. 15. Brochu JF, El-Mowafy O. Longevity and clinical performance of IPSEmpress ceramic restorationsda literature review. J Can Dent Assoc 2002;68:233-7. 16. Ohyama T, Yoshinari M, Oda Y. Effects of cyclic loading on the strength of ceramic materials. Int J Prosthodont 1999;12:28-37. 17. Holand W, Rheinberger V, Apel E, van ’t Hoen C, Höland M, Dommann A, et al. Clinical applications of glass-ceramics in dentistry. J Mater Sci Mater Med 2006;17:1037-42. 18. Fasbinder DJ, Dennison JB, Heys D, Neiva G. A clinical evaluation of chairside lithium disilicate CAD-CAM crowns: a two-year report. J Am Dent Assoc 2010;141. 10S-4S. 19. van Dijken JWV, Hasselrotb L. A prospective 15-year evaluation of extensive dentin-enamel-bonded pressed ceramic coverages. Dent Mater 2010;26:929-39. 20. Krämer N, Frankenberger R, Pelka M, Petschelt A. IPS Empress inlays and onlays after four years: a clinical study. J Dent 1999;27:325-31. 21. Fradeani M, Barducci G. Versatility of IPS Empress restorations. Part II: Veneers, inlays, and onlays. J Esthet Dent 1996;8:170-6. 22. Pieger S, Salman A, Bidra AS. Clinical outcomes of lithium disilicate single crowns and partial fixed dental prostheses: a systematic review. J Prosthet Dent 2014;112:22-30.
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23. Sjögren G, Lantto R, Granberg A, Sundström BO, Tillberg A. A clinical examination of leucite reinforced glass-ceramic crowns (Empress) in general practice: a retrospective study. Int J Prosthodont 1999;12:122-8. 24. Zuellig-Singer R, Bryant RW. Three-year evaluation of computermachined ceramic inlays: influence of luting agent. Quintessence Int 1998;29:573-82. 25. Kramer N, Frankenberger R. Leucite-reinforced glass ceramic inlays after six years: wear of luting composites. Oper Dent 2000;25:466-72. 26. Beier US, Kapferer I, Burtscher D, Giesinger JM, Dumfahrt H. Clinical performance of ceramic inlay and onlay restorations in posterior teeth. Int J Prosthodont 2012;25:395-402. 27. Hickel R, Manhart J. Longevity of restorations in posterior teeth and reasons for failure. J Adhes Dent 2001;3:45-64. 28. Silva RHBT, Ribeiro APD, Catirze ABCE, Pinelli LAP, Fais LMG. Clinical performance of indirect esthetic inlays and onlays for posterior teeth after 40 months. Braz J Oral Sci 2009;8:154-8. 29. Felden A, Schmalz G, Hiller KA. Retrospective clinical study and survival analysis on partial ceramic crowns: results up to 7 years. Clin Oral Investig 2000;4:199-205. 30. Guess PC, Strub JR, Steinhart N, Wolkewitz M, Stappert CF. Ceramic partial coverage restorationsdmidterm results of a 5-year prospective clinical splitmouth study. J Dent 2009;3:627-37. 31. Studer S, Lehrer C, Brodbeck U, Schärer P. Short-term results of IPSEmpress inlays and onlays. J Prosthodont 1996;5:277-87. 32. Naeselius K. Clinical evaluation of ceramic onlays: a 4-year retrospective study. Int J Prosthodont 2008;21:40-4. 33. Smales RJ, Etemadi S. Survival of ceramic onlays placed with and without metal reinforcement. J Prosthet Dent 2004;91:548-53. 34. Arnelund CF, Johansson A, Ericson M, Häger P, Fyrberg KA. Five-year evaluation of two resin- retained ceramic systems: a retrospective study in a general practice setting. Int J Prosthodont 2004;17:302-6. 35. Della Bona A, Mecholsky JJ Jr, Anusavice KJ. Fracture behavior of lithia disilicate- and leucite-based ceramics. Dent Mater 2004;20:956-62. 36. Murgueitio R, Bernal G. Three-year clinical follow-up of posterior teeth restored with leucite-reinforced IPS empress onlays and partial veneer crowns. J Prosthodont 2012;21:340-5. 37. Krämer N, Frankenberger R. Clinical performance of bonded leucitereinforced glass ceramic inlays and onlays after eight years. Dent Mater 2005;21:262-71. 38. Federlin M, Sipos C, Hiller KA, Thonemann B, Schmalz G. Partial ceramic crowns. Influence of preparation design and luting material on margin integrity: a scanning electron microscopic study. Clin Oral Investig 2005;9: 8-17. 39. Tagtekin DA, Özyöney G, Yanikoglu F. Two-year clinical evaluation of IPS Empress II ceramic onlays/inlays. Oper Dent 2009;34:369-78. 40. Santos GC, Santos MJ, Rizkalla AS, Madani DA, El-Mowafy O. Overview of CEREC CAD-CAM chairside system. Gen Dent 2013;61:36-40. 41. Renne W, McGill ST, Forshee KV, DeFee MR, Mennito AS. Predicting marginal fit of CAD-CAM crowns based on the presence or absence of common preparation errors. J Prosthet Dent 2012;108:310-5. 42. Posselt A, Kerschbaum T. Longevity of 2328 chairside CEREC inlays and onlays. Int J Comput Dent 2003;6:231-48. 43. Reiss B, Walther W. Clinical long-term results and 10-year Kaplan-Meier analysis of Cerec restorations. Int J Comput Dent 2000;3:9-23. 44. Ryge G. Clinical criteria. Int Dent J 1990;30:347-58. 45. Ona M, Watanabe C, Igarashi Y, Wakabayashi N. Influence of preparation design on failure risks of ceramic inlays: a finite element analysis. J Adhes Dent 2011;13:367-73. 46. Hickel R, Roulet JF, Bayne S, Heintze SD, Mjör IA, Peters M, et al. Recommendations for conducting controlled clinical studies of dental restorative materials. Clin Oral Investig 2007;11:5-33. 47. Patel N. Contemporary dental CAD/CAM: modern chairside/lab applications and the future of computerized dentistry. Compend Contin Educ Dent 2014;35:36-40. Corresponding author: Dr Maria Jacinta Moraes Coelho Santos Department of Restorative Dentistry Schulich School of Medicine & Dentistry Western University DSB Rm 0149, London, ON CANADA Email: [email protected] Acknowledgments The authors thank Lisa Lyons for assistance in editing the manuscript. Copyright © 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
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Supplementary Table 1. Modified USPHS criteria for clinical evaluation of ceramic onlays Characteristic
Rating
Postoperative sensitivity
Alfa Bravo
No postoperative sensitivity. Postoperative sensitivity.
Criteria
Secondary caries
Alfa Bravo
No evidence of caries contiguous with margin of restoration. Caries evident contiguous with margin of restoration.
Marginal discoloration
Alfa Bravo Charlie
No discoloration on margin between restoration and tooth structure. Discoloration on margin between restoration and tooth structure. Discoloration has penetrated along margin of restorative material in pulpal direction.
Surface roughness
Alfa Bravo Charlie
Smooth surface. Slightly rough or pitted, can be refinished. Rough, cannot be refinished.
Marginal Integrity
Alfa Bravo Charlie Delta
No visible evidence of ditching along margin. Visible evidence of ditching along margin not extending to DE junction. Dentin or base is exposed along margin. Restoration is mobile, fractured or missing.
Color match
Alfa Bravo Charlie
No mismatch in color, shade, and translucency between restoration and adjacent tooth structure. Mismatch between restoration and tooth structure within normal range of color, shade, and translucency. Mismatch between restoration and tooth structure outside normal range of color, shade, and translucency.
Anatomic form
Alfa Bravo Charlie
Restorations continuous with existing anatomic form. Restorations continuous with existing anatomic form, but not exposing cement material or dentin. Sufficient material lost to expose cement material or dentin.
USPHS, United States Public Health Service.
Archibald et al
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Retrospective clinical evaluation of ceramic onlays placed by dental students Jennifer J. Archibald, DDS,a Gildo Coelho Santos, Jr, DDS, MSc, PhD,b and Maria Jacinta Moraes Coelho Santos, DDS, MSc, PhDc Indirect ceramic restorations ABSTRACT have been considered an Statement of problem. Indirect restorations with partial or complete occlusal surface coverage excellent treatment option for have been recommended to restore teeth with weakened walls in order to prevent cusp fracture. patients with high esthetic The success of these restorations when performed by dental students is unknown. demands, especially where the Purpose. The purpose of this retrospective study was to evaluate the clinical performance of size of the cavity preparation is adhesively bonded ceramic onlay restorations placed by third- and fourth-year dental students. too large for direct restoraMaterial and methods. Sixty-five ceramic onlays were placed in patients between 2009 and 2015. tions.1 The development of The onlays were laboratory or chairside fabricated with a computer-aided design and computerhigh flexural strength ceramics aided manufacturing (CAD-CAM) system, using either IPS e.max Press or IPS e.max CAD. An has allowed the use of ceramic adhesive technique and luting composite resin agent were used to cement the restorations. restorations on teeth with Thirty-seven onlays were evaluated clinically using the modified United States Public Health higher functional loading.1,2 Service (USPHS) criteria. Data were statistically analyzed using the Cox proportional hazards model to compare tooth type and failures and the Fisher exact and McNemar tests to compare Manufacturers have been able the USPHS criteria for significant differences (a=.05). Survival probability was calculated using the to strengthen ceramics by Kaplan-Meier algorithm. adding filler particles to the base glass composition, such Results. Five onlays were considered to be failures and needed replacement. According to the Kaplan-Meier analysis, the estimated survival rate was 96.3% after 2 years and 91.5% at 4 years. All 5 as leucite and lithium disilicate 2 of the failures occurred on molars (13.5%) and none on premolars (P=.025). A statistically significant crystals. IPS e.max Press and difference was found for marginal discoloration between onlays placed within 0 to 3 years and 3 to IPS e.max CAD (Ivoclar Viva6 years (P<.05) but no differences between any other criteria. dent AG) are examples of Conclusions. Ceramic onlays placed by dental students demonstrated acceptable long-term clinical particle-filled glass ceramics performance. (J Prosthet Dent 2017;-:---) that contain high concentrations of lithium disilicate crysCeramic materials are available for fabricating partial tals for enhanced mechanical properties.3 restorations by using different techniques.11-14 Among Partial or complete coverage of the occlusal surface them, the IPS Empress system introduced in the early has been recommended to restore teeth with weakened 1990s combines heat and pressure in an injection walls and to prevent cusp fracture.4 Ceramic onlay resmolding process by using presintered glass-ceramic torations are able to provide cuspal protection while blocks enriched with leucite crystals.2,15 The addition of minimizing the extensive removal of sound tooth struccrystals in the glass phase helps to counteract the buildup ture.5,6 Adhesive cementation is indicated for use with of tensile stresses, improving the flexural strength and glass ceramic systems to create a strong bond between mechanical performance of the ceramic material.12,16 tooth and ceramic material.7-10 a
Predoctoral student, Schulich Medicine and Dentistry, Western University, London, Ontario, Canada. Associate Professor, Department of Restorative Dentistry, Schulich Medicine and Dentistry, Western University, London, Ontario, Canada. c Associate Professor, Department of Restorative Dentistry, Schulich Medicine and Dentistry, Western University, London, Ontario, Canada. b
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Clinical Implications The results observed in this study showed that ceramic onlay restoration is a successful treatment option for patients. The advantages of these conservative ceramic restorations include less tooth removal and excellent esthetics.
More recently, IPS e.max Press has been introduced by using a similar processing technique but using ceramic blocks enriched with lithium disilicate crystals (SiO2Li2O) to improve mechanical properties and translucency.3,12,17 Furthermore, machinable ceramics such as IPS e.max CAD have been developed for use with computer-aided design and computer-aided manufacturing (CAD-CAM) applications, either chairside or in the laboratory.18 Ceramic blocks in a partially crystallized, soft, state allow milling without excessive diamond tool wear or damage to the ceramic material. The long-term survival rates of adhesively bonded ceramics restorations have been reported to range from 76% to over 90%,19-25 with bulk fracture and marginal discoloration as the most common causes of failures.26-28 Although ceramic materials have been extensively used for crowns, numerous studies have reported the successful clinical behavior of partial ceramic restorations.29-39 The longevity of CAD-CAM onlays has also been studied, with marginal fit having a strong influence on success rates.40-43 To assess the behavior of partial ceramic restorations in a dental school environment, the present study aimed to evaluate the clinical performance of adhesively bonded ceramic onlay restorations placed by dental students within the past 6 years. MATERIAL AND METHODS This study was carried out according to research guidelines involving human subjects and was independently reviewed and approved by the Research Ethics Board for Health Sciences Research Involving Human Subjects (HSREB) for Western University, Ontario, Canada. Sixty-five ceramic onlays were placed in 52 patients at the Schulich Dental Clinic at Western University in the past 6 years. These ceramic onlay restorations were prepared and cemented by fourth-year predoctoral students supervised by a faculty member in the Department of Restorative Dentistry. The following criteria have been adopted by the dental school to determine the suitability of a tooth to receive an onlay restoration using clinical and radiographic examination: amount and quality of the remaining tooth structure, occlusion, periodontal assessment, pulpal or endodontic treatment evaluation,
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amenability for rubber dam placement, and esthetic requirement. The tooth preparations followed the general principles for adhesive ceramic onlays, including isthmus width between 1.5 and 2.5 mm; minimum occlusal reduction of 1.5 (nonfunctional cusps) to 2.0 mm (functional cusps); 1.25-mm modified shoulder margin around the preparation; round internal line angles; and divergence of walls at approximately 10 to 15 degrees with no bevel. After cavity preparation, interim restorations were fabricated with an automixed methacrylate resin (Integrity; Dentsply Sirona) and cemented with interim cement (Temp Bond; Kerr Dental). The shade was selected with the Vita Shade guide (Vita North America). Impressions were made with light-body and heavy-body polyvinyl siloxane materials (Aquasil; Dentsply Sirona), and onlays were fabricated in the dental school’s laboratory using IPS e.max Press or IPS e.max CAD (Ivoclar Vivadent AG). Six onlays were produced chairside by using the CEREC system (software 4.0; Dentsply Sirona). The prepared teeth were sprayed with a thin layer of powder spray (IPS Contrast Spray Labside; Ivoclar Vivadent AG) for image capture with the BlueCam digital scanner (BlueCam; Dentsply Sirona). The restorations were milled in a CEREC MC XL machine by using presintered glass ceramic blocks (IPS e.max CAD; Ivoclar Vivadent AG) and were polished with porcelain polishing points (Dialite Intra-Oral Polishing System; Brasseler USA). During the cementation appointment, the teeth to be restored were isolated with either rubber dam, displacement cords, dry angles, or cotton rolls. Interim restorations were removed, and the tooth was cleaned with pumice slurry. The fit of the ceramic onlays was evaluated before cementation, and minor adjustments were performed if necessary. The ceramic onlays were placed using the following cementation protocols: ceramic onlay, etched with 10% hydrofluoric acid (Prosthetic Etchant Gel; Dentsply Sirona) for 20 seconds, washed, and dried; silane agent (Monobond S; Ivoclar Vivadent AG) applied for 1 minute; prepared tooth, acid etched with 35% phosphoric acid, rinsed with water, and gently air dried; dentin bonding agent (Multilink Primer or Excite DSC; Ivoclar Vivadent AG or Scotchbond Universal Adhesive; 3M ESPE) applied over dentin and enamel. If Scotchbond was used, the silane agent was omitted as Scotchbond Universal contains a silane agent. The onlays were cemented with a dual-polymerizing resin luting material (Variolink II; Ivoclar Vivadent AG or RelyX Ultimate; 3M ESPE) according to the manufacturer’s instructions. The restorations were briefly polymerized (5 to 10 seconds) with a light-emitting diode light-polymerizing unit so that excess cement could be easily removed with explorers, scalers, and dental floss interproximally. Each surface was then polymerized for Archibald et al
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Table 1. Clinical investigation results with modified USPHS criteria Criteria
Alfa (%)
Bravo (%)
Postoperative sensitivity
91.2
8.8
Secondary caries
91.2
8.8
Charlie (%)
Anatomic form
76.5
20.6
2.9
Color match
32.4
67.6
0.00
Surface roughness
44.1
53.0
2.9
Marginal discoloration
47.1
52.9
0.00
Marginal adaptation
32.4
58.8
5.9
Delta (%)
2.9
USPHS, United States Public Health Service.
20 seconds. Restorations were adjusted with diamond finishing rotary instruments under water cooling and polished with porcelain polishing points (Dialite IntraOral Polishing System; Brasseler USA). Each patient received a 48-hour follow-up appointment to re-evaluate interproximal contacts, margins, and occlusion. Patients of the Schulich Dental Clinic who had onlays placed between January 2009 and March 2015 were contacted by telephone, letter, or email and were invited for a follow-up examination. After receiving information about the research methodology, risks, and benefits of their participation, a written informed consent was obtained. Restorations were assessed with the modified United States Public Health Service (USPHS) criteria (Supplementary Table 1) by 2 independent investigators (M.J.S., J.A.) calibrated in the use of the system.44 The investigators worked as a team but evaluated the onlays independently with mouth mirrors and dental explorers. A joint examination was performed to resolve any disagreements. The participants were also asked about their satisfaction with the restoration and whether they had experienced any sensitivity or discomfort after placement. Clinical photographs were made of select participants. Interexaminer reliability was determined to be above 0.85 for all criteria, demonstrating a high rate of agreement between examiners. The date of placement and the date of the last observation of the restoration were recorded for statistical analysis. Time of failure was fixed at the end of a 4-month time period because the exact time of failure could not be accurately determined for each participant. Failures were established as being restorations that were lost or had fractured prior to the evaluation or those that required replacement because of poor marginal quality (Charlie, Delta), secondary caries (Bravo), or endodontic complications. The ratings Alfa (A) and Bravo (B) are considered successful for most criteria. Statistical graphing software (Prism 6; GraphPad Software, Inc) was used to calculate survival probability using the Kaplan-Meier algorithm. The Cox proportional hazards model was used to compare tooth type (molar or premolar) and failures. The Fisher exact and McNemar statistical tests were used to compare the USPHS criteria for significant differences (a=.05). Archibald et al
Figure 1. Representative restoration scored Bravo for marginal discoloration (clinically acceptable).
RESULTS Among the 52 participants who received onlay restorations, 22 could not attend an appointment at the school because of work commitments, sickness, vacation, or relocation to another city. Of the participants who could not come into the clinic and were reached by telephone or email, 18 reported no postoperative sensitivity or other issues and overall patient satisfaction. One participant reported that the onlay had been rebonded in the past. However, information gathered from participants that could not be clinically evaluated was not added to the statistical analysis. Thirty participants, 19 women and 11 men with a median age of 52 years, (ranging from 24 to 80 years) were evaluated in the clinic for a total of 37 onlays. Fifteen onlays (40.5%) were placed on premolar teeth and 22 onlays (59.5%) were placed on molars. Of the 37 onlays evaluated clinically, 6 were fabricated with IPS e.max Press, and 31 with IPS e.max CAD. Six of the IPS e.max CAD onlays were produced chairside with the CAD-CAM machine. At the time of clinical observation, 34 (91.9%) of these restorations were considered clinically acceptable. The mean observation period for the ceramic restorations was 3.5 years, with an observation interval of up to 6 years. Table 1 summarizes the results of the modified USPHS criteria obtained at the recall appointments. Some Alfa and Bravo findings are illustrated in Figures 1 to 3. Five restorations were considered failures (Table 2). Two restorations received C/D scores for marginal adaptation and/or B scores for secondary caries and needed to be replaced. Three restorations could not be evaluated as they had been replaced. The Kaplan-Meier methodology was used to calculate the survival probabilities (Fig. 4). The estimated survival rate was 96.3% after 2 years and 91.5% at 4 years (n=37). The sample size after 5 to 6 years was much smaller,
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Figure 2. Representative restoration scored Bravo for marginal integrity (clinically acceptable).
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Figure 3. Representative restoration scored Bravo for recurrent caries (not clinically acceptable).
Table 2. Data of failed restorations Number
Time in Service (mo)
Material Used
Sex
1
Maxillary 1st molar
Location
Fracture
Rating
24
IPS e.max CAD
Male
2
Mandibular 1st molar
Fracture
48
IPS e.max CAD
Male
3
Mandibular 1st molar
Fracture
60
IPS e.max CAD*
Female
4
Maxillary 1st molar
Secondary caries
60
IPS e.max CAD*
Female
5
Maxillary 1st molar
Secondary caries
72
IPS e.max CAD*
Female
*Chairside CEREC CAD-CAM.
DISCUSSION The longevity and clinical performance of adhesively bonded ceramic onlays placed by dental students were evaluated. Few studies12,19,25,29,30,32 have retrospectively assessed ceramic onlays over more than 3 years, especially with the IPS e.max CAD and IPS e.max Press systems. Another particularity of the present study is related to the population analyzed, where the participants were from the community and represented to a certain extent a cross section of the population. Hickel et al45 have provided a practical approach for conducting clinical trials, which considers that the results of a clinical evaluation obtained from participants recruited from the
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Survival Probability (%)
reducing the survival rate. The mean survival rate after 6 years was 67.4% (95% confidence interval=62.3% to 72.5%). All 5 of the failures occurred on molars (13.5%) and none on premolars (P=.025). Three of the 6 onlays (50%) fabricated chairside with the CEREC machine failed, compared with 2 of the 31 (6.5%) fabricated with IPS e.max CAD in the laboratory. No IPS e.max Press onlays failed. The McNemar statistical test (n=34) revealed a statistically significant difference for marginal discoloration between onlays placed within 0 to 3 years and 3 to 6 years ago (P<.05). No significant differences were found for other criteria when time since placement (<3 years and >3 years) and tooth location (molar or premolar) were compared.
90 80 70 60 50 40 30
0
20
40
60
80
Time (mo) Figure 4. Kaplan-Meier survival analysis of all onlays examined clinically.
community may be more realistic than results obtained from a select group with more awareness of dental hygiene and preventive measures. Furthermore, several operators (fourth-year dental students) carried out the clinical procedures following guidelines adopted by the dental school for the preparation and cementation of ceramic onlays. A 4-year study20 reported success rates above 90%, similar to the 91.5% survival rate calculated with KaplanMeier statistics in the present study. Survival rate was higher at 2 years (96.3%), similar to previous findings.6,26,31 As expected, higher success rates were recorded for recently placed restorations. In the present study, Archibald et al
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the sample size after 5 years of service was smaller, causing the survival rate to decline. Due to the retrospective nature of this study in a dental school clinic setting, the recall rate was lower than that of similar studies. Success rates need to be verified by continual follow-up investigations over a 5-year period with a higher recall percentage. The survival rate of posterior ceramic crowns ranges between 84.4% and 95.5%. Recent studies on lithium disilicate crowns generally report survival rates of 95% over 5 years.22 Ceramic onlays have comparable survival rates with crowns yet are able to preserve healthy tooth structure. All the failures observed in the present study occurred on molars, as heavy occlusal loads tend to occur on molar teeth.26,32,33 Although a similar number of premolar and molar onlays were evaluated, 15 onlays (40.5%) on premolar teeth and 22 onlays (59.5%) on molars, no failures were observed on premolars. Occlusal forces are one of the main reasons for ceramic fracture.1,19 This finding is consistent with previous studies reporting great risk of failures on molars.26,32 Smales and Etemadi33 found a higher percentage of failures in molar onlays due to bulk fracture. Other studies, however, found no differences in the survival rates of ceramic inlays or onlays between the premolar and molar areas.12 Three of the onlays failed because of fracture, which is considered a common problem reported in clinical studies.6,12,27,32,34 Fracture may have been caused by excessive occlusal loads or insufficient ceramic thickness.45 Cracks produced by finishing and polishing procedures can lead to fracture of the material by crack propagation under excessive tensile stress.35 The treatment records revealed that all 3 of these onlays were adjusted with diamond rotary instruments and rubber points during the delivery appointment. This finding highlights the importance of careful finishing and polishing procedures in adjusting the restoration. Two onlays were replaced before evaluation. These failed onlays were from the same participant and had been placed on opposing first molars. The first fracture occurred at 2 years after placement, much earlier than the other failures in this study. This participant was found to be a bruxer with extensive wear facets on his dentition. This finding is supported by another retrospective study, which reported an early failure due to the patient’s bruxism.28 Because of their brittle nature, ceramic restorations should not be used in patients with excessive occlusal loads.23,36 Two restorations received Charlie or Delta scores for marginal adaptation, and one of them presented secondary caries. Both restorations failed after 56 months of service. Although several studies have reported decreased marginal adaptation over time,12,37 no significant statistical differences for marginal adaptation were observed for those onlays placed between 0 to 3 years of service Archibald et al
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compared with 3 to 6 years. However, few restorations received an Alfa score for marginal adaptation (32.4%). Previous studies have observed the deterioration of marginal quality because occlusal fatigue caused degradation of the resin-based luting agent.37 Deterioration at the margins may lead to recurrent caries and restoration fracture.28 The low modulus of elasticity of the resin-based luting agent compared with the high modulus of elasticity of the ceramic materials, combined with the fatigue of the adhesive luting agent under occlusal loading, are considered contributing factors for decreased marginal adaptation of partial ceramic restorations.6,25 Marginal adaptation is closely related to marginal discoloration. As such, statistically significant increased marginal discoloration (P=.013) was observed in this study as the restoration aged. Previous studies have shown that discoloration increases over time as a result of the wear of the luting resin cement.6,24,38 This finding is also consistent with the study of Tagtekin et al,39 which showed statistically significant marginal discoloration at 12- and 24-month recalls with IPS Empress ceramics. Coelho Santos et al6 illustrated cement wear with consequent marginal discoloration of the margins of ceramic onlays with scanning electron micrographs. Three of the 5 failures observed in the present study occurred on the onlays fabricated using the CAD-CAM CEREC machine in 2009, representing the oldest onlays in the sample. One onlay fractured before evaluation, and the other 2 received poor scores on marginal adaptation, leading to replacement because of secondary caries and endodontic treatment. These results may be attributed to the difficulty of digitally capturing subgingival margins40 or to the limitations of the previous software versions and milling machine.41 Posselt and Kerschbaum42 reported a large percentage of CEREC restorations with underfilled margins. Contrary to these findings, several studies have reported survival rates for CEREC manufactured onlays to be similar to those fabricated using the hot pressed technique, with rates over 90% for 10 years.42,43 The limited participant recall is a weakness of the present study and is an inherent problem with clinical studies.46 Follow-up by 32 of the 52 original participants might have been biased because those more motivated to receive an evaluation might have responded to the study recruitment. Additionally, the use of an older chairside CAD-CAM system to fabricate onlays in 2009 has some disadvantages compared with newer versions developed to eliminate previous limitations of the system and enhance marginal adaptation.47 Half of the chairside CEREC ceramic onlays evaluated in this study failed (3 of 6). Further long-term clinical studies should be conducted to evaluate the performance of IPS e.max CAD onlays fabricated chairside with newer software versions.
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CONCLUSIONS Based on the findings of this clinical study, the following conclusions were drawn: 1. Ceramic onlays placed by dental students demonstrated acceptable clinical performance over a 4-year period and are a successful treatment option for selected patients in a dental school. 2. These results are relevant to daily practice as highquality indirect partial restorations can protect compromised tooth structure without extensive removal of sound dental tissue and with increased patient satisfaction. REFERENCES 1. Griggs JA. Recent advances in materials for ceramic restorations. Dent Clin North Am 2007;51:713-27. 2. Dong JK, Luthy H, Wohlwend A. Heat-pressed ceramics: technology and strength. Int J Prosthodont 1992;5:9-16. 3. Guess PC, Schultheis S, Bonfante EA, Coelho PG, Ferencz JL, Silva NR. Ceramic systems: laboratory and clinical performance. Dent Clin North Am 2011;55:333-52. 4. Fennis WM, Kuijs RH, Kreulen CM, Verdonschot N, Creugers NH. Fatigue resistance of teeth restored with cuspal-coverage composite restorations. Int J Prosthodont 2004;17:313-7. 5. Edelhoff D, Sorensen JA. Tooth structure removed associated with various preparation designs for posterior teeth. Int J Periodont Restor Dent 2002;22:241-9. 6. Coelho Santos MJ, Mondelli RF, Lauris JR, Navarro MF. Clinical evaluation of ceramic inlays and onlays fabricated with two systems: two-year clinical follow up. Oper Dent 2004;29:123-30. 7. Burke FJT, Fleming GJP, Nathanson D, Marquis PM. Are adhesive technologies needed to support ceramics? An assessment of the current evidence. J Adhes Dent 2002;4:7-22. 8. Rekow D, Thompson VP. Engineering long term clinical success of advanced ceramic prostheses. J Mater Sci Mater Med 2007;18:47-56. 9. Kelly JR, Benetti P. Ceramic materials in dentistry: historical evolution and current practice. Aust Dent J 2011;56:84-96. 10. Hopp CD, Land MF. Considerations for ceramic inlays in posterior teeth: a review. Clin Cosmet Investig Dent 2013;5:21-32. 11. Shenoy A, Shenoy N. Dental ceramics: an update. J Conserv Dent 2010;13: 195-203. 12. Santos MJ, Freitas MC, Azevedo LM, Santos GC Jr, Navarro MF, Francischone CE, et al. Clinical evaluation of ceramic inlays and onlays fabricated with two systems: 12-year follow-up. Clin Oral Investig 2016;20: 1683-90. 13. Conrad HJ, Seong WJ, Pesun IJ. Current ceramic materials and systems with clinical recommendations: a systematic review. J Prosthet Dent 2007;98: 389-404. 14. Giordano R, McLaren EA. Ceramics overview: classification by microstructure and processing methods. Compend Contin Educ Dent 2010;31:682-700. 15. Brochu JF, El-Mowafy O. Longevity and clinical performance of IPSEmpress ceramic restorationsda literature review. J Can Dent Assoc 2002;68:233-7. 16. Ohyama T, Yoshinari M, Oda Y. Effects of cyclic loading on the strength of ceramic materials. Int J Prosthodont 1999;12:28-37. 17. Holand W, Rheinberger V, Apel E, van ’t Hoen C, Höland M, Dommann A, et al. Clinical applications of glass-ceramics in dentistry. J Mater Sci Mater Med 2006;17:1037-42. 18. Fasbinder DJ, Dennison JB, Heys D, Neiva G. A clinical evaluation of chairside lithium disilicate CAD-CAM crowns: a two-year report. J Am Dent Assoc 2010;141. 10S-4S. 19. van Dijken JWV, Hasselrotb L. A prospective 15-year evaluation of extensive dentin-enamel-bonded pressed ceramic coverages. Dent Mater 2010;26:929-39. 20. Krämer N, Frankenberger R, Pelka M, Petschelt A. IPS Empress inlays and onlays after four years: a clinical study. J Dent 1999;27:325-31. 21. Fradeani M, Barducci G. Versatility of IPS Empress restorations. Part II: Veneers, inlays, and onlays. J Esthet Dent 1996;8:170-6. 22. Pieger S, Salman A, Bidra AS. Clinical outcomes of lithium disilicate single crowns and partial fixed dental prostheses: a systematic review. J Prosthet Dent 2014;112:22-30.
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23. Sjögren G, Lantto R, Granberg A, Sundström BO, Tillberg A. A clinical examination of leucite reinforced glass-ceramic crowns (Empress) in general practice: a retrospective study. Int J Prosthodont 1999;12:122-8. 24. Zuellig-Singer R, Bryant RW. Three-year evaluation of computermachined ceramic inlays: influence of luting agent. Quintessence Int 1998;29:573-82. 25. Kramer N, Frankenberger R. Leucite-reinforced glass ceramic inlays after six years: wear of luting composites. Oper Dent 2000;25:466-72. 26. Beier US, Kapferer I, Burtscher D, Giesinger JM, Dumfahrt H. Clinical performance of ceramic inlay and onlay restorations in posterior teeth. Int J Prosthodont 2012;25:395-402. 27. Hickel R, Manhart J. Longevity of restorations in posterior teeth and reasons for failure. J Adhes Dent 2001;3:45-64. 28. Silva RHBT, Ribeiro APD, Catirze ABCE, Pinelli LAP, Fais LMG. Clinical performance of indirect esthetic inlays and onlays for posterior teeth after 40 months. Braz J Oral Sci 2009;8:154-8. 29. Felden A, Schmalz G, Hiller KA. Retrospective clinical study and survival analysis on partial ceramic crowns: results up to 7 years. Clin Oral Investig 2000;4:199-205. 30. Guess PC, Strub JR, Steinhart N, Wolkewitz M, Stappert CF. Ceramic partial coverage restorationsdmidterm results of a 5-year prospective clinical splitmouth study. J Dent 2009;3:627-37. 31. Studer S, Lehrer C, Brodbeck U, Schärer P. Short-term results of IPSEmpress inlays and onlays. J Prosthodont 1996;5:277-87. 32. Naeselius K. Clinical evaluation of ceramic onlays: a 4-year retrospective study. Int J Prosthodont 2008;21:40-4. 33. Smales RJ, Etemadi S. Survival of ceramic onlays placed with and without metal reinforcement. J Prosthet Dent 2004;91:548-53. 34. Arnelund CF, Johansson A, Ericson M, Häger P, Fyrberg KA. Five-year evaluation of two resin- retained ceramic systems: a retrospective study in a general practice setting. Int J Prosthodont 2004;17:302-6. 35. Della Bona A, Mecholsky JJ Jr, Anusavice KJ. Fracture behavior of lithia disilicate- and leucite-based ceramics. Dent Mater 2004;20:956-62. 36. Murgueitio R, Bernal G. Three-year clinical follow-up of posterior teeth restored with leucite-reinforced IPS empress onlays and partial veneer crowns. J Prosthodont 2012;21:340-5. 37. Krämer N, Frankenberger R. Clinical performance of bonded leucitereinforced glass ceramic inlays and onlays after eight years. Dent Mater 2005;21:262-71. 38. Federlin M, Sipos C, Hiller KA, Thonemann B, Schmalz G. Partial ceramic crowns. Influence of preparation design and luting material on margin integrity: a scanning electron microscopic study. Clin Oral Investig 2005;9: 8-17. 39. Tagtekin DA, Özyöney G, Yanikoglu F. Two-year clinical evaluation of IPS Empress II ceramic onlays/inlays. Oper Dent 2009;34:369-78. 40. Santos GC, Santos MJ, Rizkalla AS, Madani DA, El-Mowafy O. Overview of CEREC CAD-CAM chairside system. Gen Dent 2013;61:36-40. 41. Renne W, McGill ST, Forshee KV, DeFee MR, Mennito AS. Predicting marginal fit of CAD-CAM crowns based on the presence or absence of common preparation errors. J Prosthet Dent 2012;108:310-5. 42. Posselt A, Kerschbaum T. Longevity of 2328 chairside CEREC inlays and onlays. Int J Comput Dent 2003;6:231-48. 43. Reiss B, Walther W. Clinical long-term results and 10-year Kaplan-Meier analysis of Cerec restorations. Int J Comput Dent 2000;3:9-23. 44. Ryge G. Clinical criteria. Int Dent J 1990;30:347-58. 45. Ona M, Watanabe C, Igarashi Y, Wakabayashi N. Influence of preparation design on failure risks of ceramic inlays: a finite element analysis. J Adhes Dent 2011;13:367-73. 46. Hickel R, Roulet JF, Bayne S, Heintze SD, Mjör IA, Peters M, et al. Recommendations for conducting controlled clinical studies of dental restorative materials. Clin Oral Investig 2007;11:5-33. 47. Patel N. Contemporary dental CAD/CAM: modern chairside/lab applications and the future of computerized dentistry. Compend Contin Educ Dent 2014;35:36-40. Corresponding author: Dr Maria Jacinta Moraes Coelho Santos Department of Restorative Dentistry Schulich School of Medicine & Dentistry Western University DSB Rm 0149, London, ON CANADA Email: [email protected] Acknowledgments The authors thank Lisa Lyons for assistance in editing the manuscript. Copyright © 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
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Supplementary Table 1. Modified USPHS criteria for clinical evaluation of ceramic onlays Characteristic
Rating
Postoperative sensitivity
Alfa Bravo
No postoperative sensitivity. Postoperative sensitivity.
Criteria
Secondary caries
Alfa Bravo
No evidence of caries contiguous with margin of restoration. Caries evident contiguous with margin of restoration.
Marginal discoloration
Alfa Bravo Charlie
No discoloration on margin between restoration and tooth structure. Discoloration on margin between restoration and tooth structure. Discoloration has penetrated along margin of restorative material in pulpal direction.
Surface roughness
Alfa Bravo Charlie
Smooth surface. Slightly rough or pitted, can be refinished. Rough, cannot be refinished.
Marginal Integrity
Alfa Bravo Charlie Delta
No visible evidence of ditching along margin. Visible evidence of ditching along margin not extending to DE junction. Dentin or base is exposed along margin. Restoration is mobile, fractured or missing.
Color match
Alfa Bravo Charlie
No mismatch in color, shade, and translucency between restoration and adjacent tooth structure. Mismatch between restoration and tooth structure within normal range of color, shade, and translucency. Mismatch between restoration and tooth structure outside normal range of color, shade, and translucency.
Anatomic form
Alfa Bravo Charlie
Restorations continuous with existing anatomic form. Restorations continuous with existing anatomic form, but not exposing cement material or dentin. Sufficient material lost to expose cement material or dentin.
USPHS, United States Public Health Service.
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