Composite restorations for primary molars: two-year results.

Two experimental composite resins were placed in the primary molars of 50 children aged 4 to 8 years. Three cavity preparations were used and 357 restorations were placed. The restoratiot~s were evaluated by 2 investigators at 0, 6, 12, and 24 months using the USPH evaluation criteria. At 24 months, 297 (83.1%) restorations were available for recall (48 patients). Discounting restorations lost natural exfoliation (39) the recall rate was 93.4%. There were no statistically significant changes between 0 and 24 months in the 3 preparations or the 2 materials except for the color ma’tch category. Color match deteriorated (p<O.05) significantly in all cavity preparations and for both materials. At 24 months there were no statistically significant differences (p<O.05) between the 2 materials or among the 3 cavity preparations. At 24 months 23 failures had occurred. The overall failure rate was 6.4% (23/357). The failure rate for conventional preparations was 4.5% (5/110); for conventional bevel, 2.5% (3/119); and for modified preparations, 11.7% (15/128). Posterior composite resins have been advocated in recent years as a substitute for dental amalgam in certain clinical situations. One factor that has intensified the search for such a substitute is the bleak forecasts about the future cost and availability of materials necessary to produce amalgam.1 Another factor adding importance to the search for an amalgam substitute centers on recent concerns relative to the potential for systemic absorption of mercury from dental amalgam restorations. 2 While these concerns remain somewhat speculative, the quest for an amalgam substitute is a reasonable research goal. It has been noted that the use of composites in posterior teeth drastically could change pediatric dentistry because amalgam is used widely as the restorative material of choice for posterior primary teeth. 3 This study extends research efforts on this topic. Literature Review Nelson’s report 4 of a 3-year clinical trial comparing posterior composites and amalgams in primary teeth stimulated the need for additional posterior composite studies in children. In comparing 2 composites a with amalgamb in 50 sets of Class II preparations over 3 years, Nelson et al. concluded that composite was a reasonable substitute for amalgam when a primary tooth is expected to be functional for 3 years or less. As a result of this study, many investigators have initiated clinical studies in primary molars, examining posterior composites with no amalgam controls. The specific cavity design for composites in primary molars is a subject of much interest and recently has been addressed in a study by Paquette et al. 3 They used a modified preparation wherein only carious enamel and infected dentin were removed. Cavity walls were extended only for visual and mechanical access and acid-etch techniques were employed for restoration retention and resistance. While they reported excellent success for this preparation in Class I restorations, the Class II restorations had a failure rate of 16.7-25%. Vliestra et al. s reported a similar failure rate after 1 year in a similar cavity preparation in which they used glass ionomer cement as a restorative material. Leifler and Varpio6 reported a 34% failure rate of composites in Class II modified preparations in primary Adaptic, Radio-Opaque Adaptic -Johnson & Johnson; East Windsor, NJ. Dispersalloy -Lee Pharmaceuticals Corp.; South Elmonte, CA. 96 COMPOSITE RESTOI~ATIONS: Oldenburg et al. teeth after 2 years. While the modified cavity preparation offers the potential to save tooth structure, clinical trials investigating this design modification for primary teeth have been disappointing. Another cavity design modification is the use of the enamel bevel. Beveling prior to acid etching has been credited with decreasing the incidence of enamel fractures at cavity margins, 7,8 decreasing marginal leakage, 9 and increasing retention. 1° However, these studies have been limited to investigations on permanent teeth, and most studies have examined only anterior teeth in vitro. Thus, although the use of the enamel bevel offers theoretical advantages, the scientific basis for the use of such a modification for primary molars is unexplored. At present, there appears to be no standard approach to the conventional cavity preparation for the posterior composite restoration. For example, the clinical trials conducted by Paquette3 and Nelson4 are the largest reported for composites in primary molars, and these studies employed different approaches to the cavosurface bevel. Nelson used no bevel in his study and Paquette beveled the cavosurface margins of his conventional preparations. Because this cavity design feature may have implications for retention and marginal leakage and the ultimate success of the restoration, determination of its value is timely and relevant. A primary objective of this study was to compare the clinical advantages of beveling conventional preparations for primary molar resin restorations. A beveled modified restoration also was included in this study. Another objective was to examine 2 new visible light-cured composite resin materials. Both materials were manufactured for use in posterior restorations, and their physical properties suggested that the materials might have excellent potential as amalgam substitutes. Methods and Materials General Procedures Children from the Chapel Hill, North Carolina, community participated in this study.. In order to be eligible, it was necessary that each child: (1) be 4-8 years of age, (2) not be presently under the care of dentist, (3) be available for recall appointments every 6 months for a minimum of 3 years, (4) have at least two Class II and/or Class I dental lesions present in primary molars, and (5) be mentally and physically healthy so that no unusual treatment procedures would be necessary. Approximately 225 children were screened and 50 were invited to participate in the study. At the initial visit a complete health history questionnaire and parental consent form were completed. Hard and soft tissues were examined. A preventive program was initiated including oral hygiene instructions, a toothbrush prophylaxis, and a topical fluoride treatment. Bite-wing radiographs were obtained (as well as a panorex radiograph when appropriate). A treatment plan, including a list of all necessary restorations, was developed at this appointment. Using a table of random numbers, each posterior restoration was assigned 1 of 6 possible combinations of resin/ cavity design. Two different resins and 3 different cavity designs were used in the study. The 2 experimental resins were condensable, visible light cured, and contained .04-10 t~ filler particles. The resins were filled approximately 75-80%. The only difference in the composites was that F-70 contained barium glass particles c and X-55 used barium-lithium glass particles (Table 1). The 3 cavity designs were: (1) a conventional conservative preparation, (2) a conventional preparation with a 45° 1 mm occlusal cavosurface bevel, and (3) a modified preparation in which enamel was removed only for access to decay. The modified preparation also was beveled. The cavity designs are illustrated in Figures 1, 2, and 3. A total of 357 composite restorations were placed in primary molars by 3 experienced operators including 137 Class I, 188 Class II, and 32 Class V restorations. Clinical Technique All restorations were placed using local anesthesia and a rubber dam. In most instances the child was treated by the same operator throughout the study to maintain consistent patient behavior. Traditional Class I and II cavity preparations were prepared utilizing a #245 bur. For the beveled preparations, a D4P round diamond bur was used to create a 1.0 mm TABLE 1. Physical Properties and Composition f F-70 and X55 Product Description F-70 X-55 Manufacturer L.D. Caulk Co. L.D. Caulk Co. Particle Size 0.04 10U 0.04 10U (Microns) Filler % 77.3 76.0 (Weight) Filler composition Ba Glass SiO2 Ba/Li Glass SiO2 Method of polymerization Visible light Visible light Coefficient of thermal expansion 28.1 (ppm/degree C) Water sorption 0.7 0.6 (Mg/cm 2) Condensable Yes Yes Fulfill -L.D. Caulk Co.; Milford, DE. PEDIATRIC DENTISTRY: June 1985A/ol. 7 No. 2 97 i:,G 1. Conventional Preparation. F,G 2. Conventional preparation with bevel. F,G g. Modified preparation with bevel. bevel in accessible enamel at approximately 45° to the cavosurface margin. The modified preparations were prepared using a #2 round bur. An attempt was made to remove only carious enamel and dentin and no attempt was made to develop cavity resistance and retention form. For the modified preparation, all accessible enamel margins were beveled with the D4P round diamond bur. Prior to tooth preparation an interproximal wooden wedge was placed for maximum separation of the teeth; this displacecl adjacent teeth and provided a guide for establishing the proper height of the gingival floor. Stainless steel matrix bands (0.002 in) were adapted for all Class II cavity preparations and interproximal wedges were placed to seal the gingival margins. A calcium hydroxide based was placed over all exposed dentin. Enamel margins and bevels were etched for 90 sec with a solution of free phosphoric acid (50% by weight). The acid was removed by applying an air-water spray and the tooth was air dried, A bonding agent was placed over the exposed enamel margins and a gentle blast of air assisted in distributing the bonding agent over the etched surfaces, preventing pooling of the bonding agent in the proximal box area. The experimental composite resins were placed on a paper pad and transferred to the preparation with a plastic instrumenl. Amalgam condensers were used to condense the composite into the preparations. The resin was polymerized utilizing a light, e Polymerization times varied from 20 to 60 sec according to the depth of cure required. Following removal of the wedge and matrix bands, the interproximal areas again d Dycal -L.D. Caulk Co.; Milford, DE. e Prisma Lite -L.D. Caulk Co.; Milford, DE. were exposed to the visible light for 20 sec. All composite restorations were finished with fluted carbide finishing burs, and cups~ and discs with petroleum jelly were used to smooth and polish the surfaces. Composite finishing strips improved interproximal contours. After removal of the rubber dam, occlusal contact was adjusted. Evaluation Procedures Following completion of all restorative treatment, patients returned for a baseline evaluation of the restorations. Direct clinical evaluation of each restoration was completed independently by 2 evaluators using the criteria of the United States Public Health Service (USPHS) system as described by Cvar and Ryge. ~ However, the USPHS system was modified to include a category for clinical evaluation of axial contour (Table 2). At baseline, 6, 12, and 24 months each restoration was evaluated in the following categories: color match, marginal integrity, wear, interfacial staining, axial contour, secondary caries, and postoperative sensitivity. Disagreements between evaluators were resolved immediately by consensus. In addition, clinical photographs taken at a magnification of 1.5x were obtained at the recall intervals (Figs 4, 5, 6). All evaluation data were recorded on evaluation forms and stored in a computer for tabulation and analysis. For purposes of this study, only the baseline and 24-month data will be presented and discussed. A McNemar’s test was used to analyze changes over time from baseline to 24 months.~2 For all other analyses, the Mantel-Haenszel chi-square test was used as the test statistic. ~3 An alpha of 0.05 was used as the level of significance for all tests. ~ Quasite -Shofu Dental Co.; Menlo Park, CA. 98 COMPOSITE RESTORATIONS: Oldenburg et al. TABLE 2. Criteria for Rating Composite Resin Restorations*