|Year : 2014 | Volume
| Issue : 2 | Page : 70-77
Clinical evaluation of direct composite restorations and inlays: Results at 12 months
Emine Sirin Karaarslan1, Ertan Ertas2, Bilinc Bulucu2
1 Department of Restorative Dentistry, Faculty of Dentistry, Gaziosmanpa?a University, Tokat, Turkey
2 Department of Restorative Dentistry, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey
|Date of Web Publication||11-Jul-2014|
Emine Sirin Karaarslan
Department of Restorative Dentistry, Faculty of Dentistry, Gaziosmanpa?a University, Tokat
Source of Support: None, Conflict of Interest: None
Background: The purpose of this study was to compare the clinical performance of Class II direct and indirect composite restorations according to the United States Public Health Service criteria (USPHS). Materials and Methods: Seventy patients were included and four different composite resins, P60 (FP), SureFil Posterior (SP), Gradia Posterior (GP), and Bisco Aelite LS Packable (BAP) were used as direct restorative material. All of the composite resins except BAP were used as indirect restorative material. Instead of BAP, Tescera Laboratory composites were polymerized in Tescera inlay oven. All restorations were evaluated according to USPHS criteria during a one-year period. Results: There were no statistically significant differences between direct and indirect composite restorations according to the retention, marginal discoloration, surface staining, proximal contact continuity, and secondary caries. Indirect restorations have less surface roughness, postoperative sensitivity (P < 0.05), and soft tissue irritation (P < 0.1) than direct ones. Conclusion: The clinical performances of the indirect restorations were more satisfactory than the direct restorations.
Keywords: Clinical evaluation, indirect polymerization, inlays, posterior teeth
|How to cite this article:|
Karaarslan ES, Ertas E, Bulucu B. Clinical evaluation of direct composite restorations and inlays: Results at 12 months. J Res Dent 2014;2:70-7
|How to cite this URL:|
Karaarslan ES, Ertas E, Bulucu B. Clinical evaluation of direct composite restorations and inlays: Results at 12 months. J Res Dent [serial online] 2014 [cited 2019 Apr 19];2:70-7. Available from: http://www.jresdent.org/text.asp?2014/2/2/70/136632
| Introduction|| |
Amalgam restorative material has been widely used in dental filling material worldwide for the restoration of posterior teeth because of its easy handling procedures, well-tested material properties, and clinical success.  Patients' esthetic preferences in the restoration of posterior teeth have stimulated the development of new, tooth-colored, non-metallic restorative materials. Esthetic alternatives to amalgam restorations and cast-gold inlays include direct composite resins, composite inlays, and ceramic inlays.  Lately, resin-based adhesives and restorative materials have stimulated an increase in the use of resin-based composites in posterior teeth. 
In direct composite resin restorations, the most important problems were various fractures, wear and loss of the marginal seal leading to pulpal irritation, postoperative sensitivity, marginal staining, and secondary caries. Also, other problems related to composite resins were insufficient interproximal and occlusal morphology due to difficult clinical handling procedures. ,, Several restorative techniques have been used to minimize the development of polymerization shrinkage and stress, such as multiple increment techniques, the use of ceramic inserts, and replacement of the dentin with a glass ionomer cement in the sandwich technique.  The composite resin inlay/onlay technique has been used to reduce the polymerization shrinkage.  The most noticeable advantage of the indirect restorative technique relates to its better potential for generating the appropriate anatomic form, as well as proximal contact and contour. The greater the size of the restoration, the more apparent this fact becomes. 
Indirect laboratory-processed composite systems present an esthetic alternative for intracoronal posterior restorations and provide esthetic results that may also reinforce tooth structure. Additional clinical benefits include exact marginal integrity, wear resistance similar to enamel, wear compatibility with opposing natural dentition, optimal esthetics, ideal proximal contacts, and excellent anatomic morphology. 
Many in vitro tests have been published ,, that were designed to predict the durability of resin-based composite restorations in clinical applications. Unfortunately, it seems impossible to properly simulate the intraoral environment and patient habits with current test designs and laboratory conditions. For these reasons, clinical studies have great importance and require objective, reliable, and relevant criteria to assess the performance of restorations.  The USPHS evaluation system is the most widely-used direct method for quality control of restorations.  Composite inlays have been followed in several short-term , and long-term clinical studies. ,
The aim of this study was to compare the clinical performance of Class II direct composite restorations with indirect composite restorations according to the modified USPHS criteria. The null hypothesis we were testing was that indirect composite restorations show better results than direct composite restorations according to the modified USPHS criteria.
| Subjects, Materials, and Methods|| |
Patient selection and operative procedures
The research protocol was initially submitted for the appreciation of the Ethics Committee of Ondokuz Mayis University. Each volunteer subject signed an informed-consent form before participating in the study. We recruited 70 healthy, adult subjects, 32 male and 38 female (18 to 55 years of age), from among university patients. Each patient required at least one Class II direct and one indirect composite restoration.
All patients received oral-hygiene instructions before operative treatment was performed. Patients with extreme poor oral hygiene, heavy bruxing habits, periodontal problems, and de-vital teeth were excluded. An operator (S. K. E) prepared, restored, and finished 140 cavities, following standard procedures and manufacturers' directions. The operator recorded the teeth's vitality test scores before any preparations were made. In total, 140 restorations (70 class II direct, 70 indirect composite restorations) in 70 patients under local anesthesia were conducted by one operator.
Five light-cured composite resins were used to restore the teeth. Their properties are shown in [Table 1] and [Table 2]. Gradia Posterior (GP), Filtek P60 (FP), and Surefil Posterior (SP) were used in both direct and indirect composite restorations. However, Bisco Aelite LS Packable (BAP) was used only for direct composite restorations, and Tescera Body and Dentin were used only for indirect composite restorations.
|Table 2: Indirect restorative materials belonged to indirect inlay system|
Click here to view
The decision to restore the teeth with an inlay or a filling was primarily influenced by the size of the defect of the hard tissue after caries excavation. Small and medium-sized defects were treated with an incremental direct filling technique; in larger cavities, composite inlays were inserted to reduce the effects of abrasion and polymerization shrinkage. All cavity preparations were conducted according to common principles for composite inlays or fillings. 
Clinical procedure for composite inlays
All cavities were prepared according to common principles for adhesive inlays. To achieve estimated convergence angles between opposing walls of 10 to 12 degrees, cavities were prepared with 80 μm and finished with 25 μm grit diamond burs with a slight taper (Intensiv, Viganello-Lugano, Switzerland). Internal line and point angles were rounded, and enamel margins were prepared as butt-joints. A calcium-hydroxide liner (Life, Kerr Italia S.p.A., Salerno, Italy) was applied to deep dentinal surfaces.
Complete arch impressions were taken with a polyether material (Impregum F, ESPE). Provisional restorations were placed with eugenol-free temporary cement (Provicol, VOCO, Cuxhaven, Germany). The inlays with GP, FP, and SP composite resins were polymerized with a light-emitting diode (LED, Hilux Ledmax 550, Benlioglu, Turkey). Light output was measured (600 mW/cm 2 ) using a curing radiometer (Demetron, Danbury, CT, USA). The inlay cavity was filled incrementally, and each increment was light-cured for 20s. The composite inlays were then post cured with the LED for 5 minutes to improve their physical properties.
The Tescera Aqua Thermal Light (ATL) inlays were polymerized in a polymerization unit (Tescera ATL Processing Unit, Bisco, USA), which was composed of two specialized cups (one gray cup for pressure/light and one black heat cup for in-water pressure/light/heat). Tescera ATL inlays were incrementally polymerized in the gray pressure/light cup for 2 minutes, and the final cure was accomplished in a black heat cup with the restoration submerged in water. The inlays were cured using an initial full cycle of pressure (60 psi) with light and heat (peak heat of 130°C with the temperature decreasing to approximately 90°C before the pressure is released) for approximately 10 to 13 minutes.
The inlay restorations were finished with fine-grit diamond instruments (Diatech, Coltene, Switzerland), and polished with polishing disks (Sof-lex, Pop On, 3M Dental Products, USA), and brushes (Astrobrush-Ivoclar-Vivadent). All finishing procedures were performed under water cooling. The provisional restorations were removed. The inlays were cemented with dual-cured resin cement made of every composite resin recommended by the manufacturer.
Clinical procedure for direct composite restorations
In Class II direct composite restorations, an adhesive cavity design was used previously. Preparation was limited to the removal of decay, thus preserving the sound tooth-structure. All cavities were restored using an ivory-metal matrix (Hahnenkratt, Germany) and wooden wedges (Kerr, Switzerland) that were inserted with firm pressure. After etching and application of the bonding, the direct composite cavities were filled incrementally with facially and lingually inclined layers of maximally 1.5-2.0 mm. Between each increment, polymerization was performed with an LED unit and each increment was light-cured for 20s. Light output was measured using a curing radiometer. After removing the matrix holder and wedges, the gingival areas were cured for 20s from the facial and lingual directions. The occlusion and articulation were checked and adjusted, and then the direct composite restorations were finished with fine-grit diamond instruments (Diatech, Coltene, Switzerland) and polished with polishing disks (Sof-lex, Pop On, 3M Dental Products, USA) and brushes (Astrobrush-Ivoclar-Vivadent). All finishing procedures were performed under water cooling.
Clinical evaluation of direct and indirect composite restorations
The restorations were rated independently with a mirror and probe by two other experienced dentists who were not involved with the insertion of the direct and indirect composite restorations.  The restorations were assessed after insertion (baseline evaluation), at 3, 6, 9, and 12 months using the modified USPHS criteria. , For each of the criteria, a score of Alfa was used to indicate the highest degree of clinical acceptability, and scores of Bravo, Charlie, and Delta were used to indicate progressively lessening degrees of clinical acceptability [Table 3].
Statistical analysis was carried out with Statistical Package for the Social Sciences (SPSS) 13.0 for Windows statistical program software. Since the assessment of the direct restorations and inlays yielded clearly ordinal structured data, only non-parametric statistical procedures were used. The Mann-Whitney U test and the Kruskal-Wallis H test were used to explore significant differences between direct composite restorations and composite inlays for the criteria listed in [Table 3].
| Results|| |
Seventy patients with 70 inlays and 70 direct composite restorations were evaluated in one year. All patients were evaluated for 12-month recalls. Results of the clinical evaluation at the 12-month follow-ups are presented in [Table 4].
Rating of the restoration parameters and factors
The restorations were evaluated for retention, surface staining, and secondary caries with 100% Alpha-ratings for both restorative systems at 12 months. Moreover, in both polymerization methods, there were no statistically significant differences between independent, experienced dentists for all criteria.
The GP composite resin was the best color-match material. Molar teeth exhibited more color matching than premolar teeth (P < 0.01). In indirect composite restorations, inlays with polymerized LED curing units exhibited more color matching than inlays with the polymerized Tescera system (P < 0.1).
Marginal integrity and discoloration
There were no statistically significant differences between direct and indirect polymerization methods. There were statistically significant differences between the baseline and 12-month periods, and the Tescera indirect system exhibited more marginal integrity than LED curing units (P < 0.05).
The direct polymerization methods exhibited more roughness than indirect polymerization methods (P < 0.05). There were statistically significant differences between the baseline and 12-month periods (P < 0.05).
The direct polymerization methods resulted in more postoperative sensitivity than the indirect polymerization methods, and at baseline, postoperative sensitivity was seen more frequently than at 12 months. Indirect composite restorations with the polymerized Tescera indirect system exhibited less postoperative sensitivity than indirect composite restorations with LED- curing units (P < 0.05).
Direct composite restorations exhibited more gingival bleeding than indirect composite restorations (P < 0.1). The FP composite resin exhibited the least gingival bleeding. In premolar teeth, gingival bleeding was seen more than molar teeth. At baseline, gingival bleeding was seen less than at 12 months (P < 0.05).
| Discussion|| |
This in vivo study compared the clinical performance of Class II direct composite restorations with indirect composite restorations according to the modified USPHS criteria. The results of this study partially supported the hypothesis that indirect composite restorations show better results than direct composite restorations. Indirect composite restorations have less surface roughness, postoperative sensitivity, and soft tissue irritation than direct composite restorations.
There are a number of problems associated with the use of direct composite resin restorations. Some in vivo studies have reported lack of contact, poor wear resistance in contact areas,  postoperative sensitivity, inadequate marginal integrity, and the development of secondary caries that begin with marginal gaps developing marginal staining, and progress to micro leakage along the cavity wall. 
The indirect composite resin restoration is an attempt to overcome the main disadvantage of polymerization shrinkage of the direct composite resin restorations. The secondary polymerization of the composite inlay, at a high temperature, improved the degree of conversion and allowed the initial polymerization shrinkage and the following post-cure stress to occur before insertion.  In addition, postoperative sensitivity is decreased in composite inlays compared to direct composite fillings. 
Most of the studies evaluated the clinical success of direct and indirect composite restorations. ,, Clinical evaluations of direct and indirect composite resin restorations are needed to substantiate and corroborate the data obtained from the in vitro studies of these materials. The USPHS evaluation system is the most commonly used direct method for quality control of restorations.  Many clinical trials have used the USPHS criteria to evaluate direct and indirect composite restorations. ,,
At all evaluation periods in the current study, the recall rate was 100% because patients were selected among the volunteers from faculty staff, students, and their families. The restorations were evaluated for retention, surface-staining, and secondary-caries criteria with 100% Alpha-ratings for both Class II direct and indirect restorative systems at 12 months. Loguercio et al. and Dresch et al. stated that 100% Alpha ratings were obtained for the retention criteria according to the modified USPHS system in a 12-month evaluation of different composite restorations. , In another one-year clinical evaluation by Yip et al., all the direct posterior composite restorations were also rated as excellent for surface-staining criteria. 
According to the results of this study, the GP composite resin demonstrated the best color-match material in both direct and indirect restorative systems. Gradia direct composite resin has color reflectance, absorption, shine, translucency, and color temperature features similar to tooth structure, according to the manufacturer. Gradia direct is a composite with a unique particle structure and a clever yet simple shade system. Available in anterior and posterior versions, Gradia direct sets a new standard for esthetic 'invisibility' and ease of use, giving a superb, natural-looking restoration with only one shade. Moreover, if further esthetic enrichment is required, extra shades can be added quite simply. Available in both the anterior and posterior versions, each is a delicate balance between hue, chroma, value, and translucency.  Micro-filled hybrid GP composite has 0.85 μm filler size for these small filler particles.  It was thought that small filler particles would provide an advantage in terms of color match.  The GP has a urethane dimethacrylate (UDMA) polymer matrix, which provides better resistance to color change. 
In the present one-year clinical study, SureFil composite resin was the worst color match material. This was due to the limited choice of color shades (only A, B, C) for SureFil. The restorations were predominantly lighter than the adjacent tooth structure. According to the manufacturer, the shades were deliberately selected to be lighter than the corresponding Vita (Vita Zahnfabrik H. Rauter GmbH KG, Bad Säckingen, Germany) shades so that marginal areas could be visualized during placement. 
Marginal discoloration usually results from defects present between tooth-colored restorations and cavity margins.  According to the results of this study, in both direct and indirect composite restorations, Bisco posterior composite resins exhibited 100% Alpha scores. In addition, Bisco posterior composite resins exhibited the best marginal integrity. At baseline, all restorations showed 100% Alpha scores. Similar to our results, Turkun et al. found that in a 2-year clinical evaluation for marginal discoloration, all restorations showed 100% Alpha scores during the six-month evaluation.  At the two-year recall evaluation, there were 5 bravos for marginal discoloration, and at the end of the study, 6% of the restorations had a slight crevice along the marginal interface.
Cetin and Unlu stated that better clinical performance might be obtained using Estenia and Tescera ATL indirect inlay systems since they are indirect composite resins specifically designed for restoring posterior teeth.  Furthermore, it is claimed that indirect composites, when tempered with heat and light, could have an enhanced degree of cure, thereby leading to improved physical properties.
In the present study, direct polymerization methods exhibited more roughness than indirect polymerization methods. Bisco posterior composite resins exhibited the most roughness and GP exhibited the least roughness. In a three-year clinical evaluation by Manhart et al. and a one-year clinical evaluation of direct and indirect composite restorations in posterior teeth by Cetin and Unlu, more Alpha ratings for composite inlays in comparison with direct restorations were shown for the criteria surface texture. ,
In the present one-year clinical study, direct polymerization methods exhibited more postoperative sensitivity than indirect polymerization methods. Manhart et al. found 97% Alpha scores in indirect composite restorations and 93% Alpha scores in direct composite restorations for postoperative sensitivity.  In the current study, postoperative sensitivity was seen more in molar teeth than premolar teeth, and at baseline, postoperative sensitivity was seen more than it was at 12 months. Premolar teeth usually offer a more favorable condition for composite restorations than molar teeth; cavities are usually smaller, the effect of the chewing forces is less intensive, and the access for dental treatment is easier. 
The results of the current study indicate that indirect composite restorations exhibited less gingival bleeding than direct composite restorations. The FP composite resin exhibited the least gingival bleeding of the composite resins. The most obvious advantage of the indirect technique relates to its higher potential for generating the appropriate anatomic form, as well as proximal contact and contour.  In their one-year clinical evaluation of direct nanofilled and indirect composite restorations in posterior teeth, Cetin and Unlu stated that 100% Alpha ratings were obtained for gingival adaptation in both restorative systems. 
| Conclusions|| |
Given the limitations of this study, the following conclusions were drawn:
- During the 12-month follow-up period, the lack of retention, surface staining, and secondary caries were observed in neither direct nor indirect composite restorations
- GP composite resin exhibited the best color match at the 12-month clinical evaluation
- For surface texture and gingival bleeding, indirect composite restorations exhibited higher Alpha scores than direct composite restorations
- During the 12-month follow-up period, direct polymerization methods exhibited more postoperative sensitivity and gingival bleeding than indirect polymerization methods. In time, postoperative sensitivity decreased, but gingival bleeding increased
- Longer-term observations are required to monitor the performance of the direct and indirect composite restorations
| Acknowledgments|| |
This article is a doctorate thesis submitted by Dr. Emine SİRİN KARAARSLAN in Restorative Dentistry at the Ondokuz Mayis University Faculty of Dentistry and was presented at 88. General Session and Exhibition of the IADR, Barcelona, Spain, July 14-17, 2010.
This research was supported by a grant from the "Ondokuz Mayıs Üniversitesi Bilimsel Araştırma Projeleri Müdürlüğü, project no: DHF 047.
| References|| |
|1.||Brunthaler A, Konig F, Lucas T, Sperr W, Schedle A. Longevity of direct resin composite restorations in posterior teeth. Clin Oral Investig 2003;7:63-70. |
|2.||Manhart J, Scheibenbogen-Fuchsbrunner A, Chen HY, Hickel R. A 2-year clinical study of composite and ceramic inlays. Clin Oral Investig 2000;4:192-8. |
|3.||Cobb DS, MacGregor KM, Vargas MA, Denehy GE. The physical properties of packable and conventional posterior resin-based composites: A comparison. J Am Dent Assoc 2000;131:1610-5. |
|4.||Dietschi D, Scampa U, Campanile G, Holz J. Marginal adaptation and seal of direct and indirect Class II composite resin restorations: An in vitro evaluation. Quintessence Int 1995;26:127-38. |
|5.||Leinfelder KF. Indirect posterior composite resins. Compend Contin Educ Dent 2005;26:495-503. |
|6.||Burke FJ, Watts DC, Wilson NH, Wilson MA. Current status and rationale for composite inlays and onlays. Br Dent J 1991;170:269-73. |
|7.||van Dijken JW, Kieri C, Carlen M. Longevity of extensive class II open-sandwich restorations with a resin-modified glass-ionomer cement. J Dent Res 1999;78:1319-25. |
|8.||James DF, Yarovesky U. An esthetic inlay technique for posterior teeth. Quintessence Int Dent Dig 1983;14:725-31. |
|9.||Howard NY. Advanced use of an esthetic indirect posterior resin system. Compend Contin Educ Dent 1997;18:1044-6. |
|10.||Burgoyne AR, Nicholls JI, Brudvik JS. In vitro two-body wear of inlay-onlay composite resin restoratives. J Prosthet Dent 1991;65:206-14. |
|11.||Gohring TN, Besek MJ, Schmidlin PR. Attritional wear and abrasive surface alterations of composite resin materials in vitro. J Dent 2002;30:119-27. |
|12.||Braga RR, Condon JR, Ferracane JL. In vitro wear simulation measurements of composite versus resin-modified glass ionomer luting cements for all-ceramic restorations. J Esthet Restor Dent 2002;14:368-76. |
|13.||Freilich MA, Goldberg AJ, Gilpatrick RO, Simonsen RJ. Direct and indirect evaluation of posterior composite restorations at three years. Dent Mater 1992;8:60-4. |
|14.||Cvar JF, Ryge G. Reprint of criteria for the clinical evaluation of dental restorative materials. Clin Oral Investig 2005;9:215-32. |
|15.||Scheibenbogen-Fuchsbrunner A, Manhart J, Kremers L, Kunzelmann KH, Hickel R. Two-year clinical evaluation of direct and indirect composite restorations in posterior teeth. J Prosthet Dent 1999;82:391-7. |
|16.||Wendt SL Jr, Leinfelder KF. Clinical evaluation of a heat-treated resin composite inlay: 3-year results. Am J Dent 1992;5:258-62. |
|17.||Donly KJ, Jensen ME, Triolo P, Chan D. A clinical comparison of resin composite inlay and onlay posterior restorations and cast-gold restorations at 7 years. Quintessence Int 1999;30:163-8. |
|18.||van Dijken JW. A 6-year evaluation of a direct composite resin inlay/onlay system and glass ionomer cement-composite resin sandwich restorations. Acta Odontol Scand 1994;52:368-76. |
|19.||Manhart J, Neuerer P, Scheibenbogen-Fuchsbrunner A, Hickel R. Three-year clinical evaluation of direct and indirect composite restorations in posterior teeth. J Prosthet Dent 2000;84:289-96. |
|20.||Ryge G, Snyder M. Evaluating the clinical quality of restorations. J Am Dent Assoc 1973;87:369-77. |
|21.||Ryge G. Clinical criteria. Int Dent J 1980;30:347-58. |
|22.||Shinkai K, Suzuki S, Leinfelder KF, Katoh Y. Effect of gap dimension on wear resistance of luting agents. Am J Dent 1995;8:149-51. |
|23.||Sarrett DC. Clinical challenges and the relevance of materials testing for posterior composite restorations. Dent Mater 2005;21:9-20. |
|24.||Kildal KK, Ruyter IE. How different curing methods affect the degree of conversion of resin-based inlay/onlay materials. Acta Odontol Scand 1994;52:315-22. |
|25.||van Dijken JW. Direct resin composite inlays/onlays: An 11 year follow-up. J Dent 2000;28:299-306. |
|26.||Wassell RW, Walls AW, McCabe JF. Direct composite inlays versus conventional composite restorations: 5-year follow-up. J Dent 2000;28:375-82. |
|27.||Cetin AR, Unlu N. One-year clinical evaluation of direct nanofilled and indirect composite restorations in posterior teeth. Dent Mater J 2009;28:620-6. |
|28.||Loguercio AD, Reis A, Rodrigues Filho LE, Busato AL. One-year clinical evaluation of posterior packable resin composite restorations. Oper Dent 2001;26:427-34. |
|29.||Dresch W, Volpato S, Gomes JC, Ribeiro NR, Reis A, Loguercio AD. Clinical evaluation of a nanofilled composite in posterior teeth: 12-month results. Oper Dent 2006;31:409-17. |
|30.||Yip KH, Poon BK, Chu FC, Poon EC, Kong FY, Smales RJ. Clinical evaluation of packable and conventional hybrid resin-based composites for posterior restorations in permanent teeth: Results at 12 months. J Am Dent Assoc 2003;134:1581-9. |
|31.||GC Gradia Direct, 2011. Available from: http://www.gceurope.com/pid/26/leaflet/en_Leaflet_Short_Version.pdf. [Last accessed on 2011 May 10]. |
|32.||Palaniappan S, Elsen L, Lijnen I, Peumans M, Van Meerbeek B, Lambrechts P. Three-year randomised clinical trial to evaluate the clinical performance, quantitative and qualitative wear patterns of hybrid composite restorations. Clin Oral Investig 2010;14:441-58. |
|33.||Leinfelder KF. Composite resins. Dent Clin North Am 1985;29:359-71. |
|34.||Bayne SC, Thompson JA. Biomaterials. In: Roberson TM, Heymann HO, Swift EJ, ed. Sturdevant's Art and Science of Operative Dentistry. 5 th ed. Missouri: Mosby Inc; 2006. p. 137-242. |
|35.||Turkun SL. Clinical evaluation of a self-etching and a one-bottle adhesive system at two years. J Dent 2003;31:527-34. |
|36.||Feilzer AJ, De Gee AJ, Davidson CL. Setting stress in composite resin in relation to configuration of the restoration. J Dent Res 1987;66:1636-9. |
[Table 1], [Table 2], [Table 3], [Table 4]