Marginal leakage of visible light-cured composite resin restorations

In vitro analysis of the effects of acid or laser etching on microleakage around composite resin restorations

OBJECTIVES

The aim of the present study was to determine the effect of two conditioning methods, phosphoric acid and XeCl laser application on microleakage at composite resin restorations.

METHODS

Class II MOD (mesio-occluso-distal) cavities were prepared on 90 extracted human wisdom teeth with one proximogingival margin on enamel and the other on dentin. Phosphoric acid (37%) and a XeCl excimer laser system were used for the etching procedure. The prepared teeth were randomly assigned to six groups: In group 1, acid-etching of the enamel margins was followed by application of enamel bonding, in group 2 additionally a dentin bonding system was used. In group 3, acid-etching of the enamel and dentin (total etch) was followed by the application of dentin bonding. In group 4, laser-etching of enamel margins was followed by the application of enamel bonding, in group 5 dentin bonding was used additionally. In group 6, laser-etching of enamel and dentin margins was followed by the application of dentin bonding. All restorations were placed incrementally and polymerized with a halogen light source. After restoration, all samples were thermocycled and stained in 0.5% basic fuchsin and sectioned longitudinally in a mesio-distal plane. Microleakage was scored by means of a stereomicroscope. The margins of the restorations at tooth-resin interface were examined with a scanning electron microscope.

RESULTS

In all groups, marginal leakage was more extensive at the gingival margin that was in dentin than at the gingival margin in enamel. Microleakage scores and the gap at the tooth-resin interface were significantly lower in all acid-etched groups than in laser-etched groups.

CONCLUSION

Acid-etch technique is more effective than the investigated laser-etch technique at 308nm concerning the reduction of marginal leakage in composite restorations.

Margin quality of Class III and IV composites in vitro

Polymerization shrinkage and thermal expansion/contraction of composites counteract marginal bonding. The purpose of this study was to determine the margin quality of Class III and IV microfilled and hybrid composite restorations placed with adhesive techniques. Two experiments were conducted. In experiment 1, small, beveled Class III cavities were prepared in 24 incisors. Twelve cavities were filled with an experimental microfilled composite (COMPAFILL) and 12 with a control microfilled material (DURAFILL). In experiment 2, standardized large, beveled Class IV cavities were prepared in 24 incisors. Twelve of these incisors were filled with DURAFILL and 12 with the hybrid composite HERCULITE XR. The teeth were stored in water for 21 days. Before and after the restorations were thermocycled (5 degrees C-55 degrees C), replicas were obtained for quantitative analysis in the SEM. Statistical analysis (non-parametric tests, p less than 0.05) revealed that the two microfilled materials behaved very well (greater than 95% excellent margins) in Class III restorations before being thermocycled. After the restorations were thermocycled, the margin quality of DURAFILL decreased to 90% excellence, due to the increase in restoration fractures. Thermocycling did not affect the margin quality in the Class IV cavities, and the hybrid composite showed superior margin qualities (89% excellent). Better margin qualities were obtained in Class III cavities. Class IV restorations showed more overhangs (12%) and submargination (6%) which were technique-related. In no cases were greater than 1% marginal openings found.

Reducing marginal leakage of posterior composite resin restorations: a review of clinical techniques

It has been well established that composite resin restorations have leakage at the margins. The polymerization shrinkage of the material and its inadequate adhesion to the cavity walls are the primary causes. Unlike silver amalgam restorations, which are self-sealing with age, the gap at the composite-to-tooth interface tends to persist and invite postoperative sensitivity, adverse pulp reactions, and the development of recurrent caries. Many techniques or materials have been advocated to improve the clinical adaptation of this material and to reduce marginal leakage. They limit the effect of polymerization shrinkage and/or enhance the bonding of the composite material to the tooth structure. This article reviews the clinical techniques and materials that have been suggested and are presently available to improve the marginal quality of composite resins, with special reference to posterior restorations.

Marginal fracture of posterior composite resins

This study assesses the early cavomarginal breakdown of the newer posterior composite resin restorations compared with that of amalgam restorations. A total of 432 posterior composite restorations and 73 amalgam restorations were examined: 121 composite restorations (28%) and 44 amalgam restorations (60%) clinically showed a marginal crevice at some point on the cavosurface margin of the restoration at 6-month, 1-year, and 2-year recalls. The largest single reason for poor marginal adaptation was marginal fracture. Up to 2 years, the marginal integrity of the studied posterior composites was superior to that of an amalgam alloy. It was determined that smaller cavities, greater bulk of resin at the margin (especially at functional cusp areas), and well-finished margins without overfiling seem to reduce the occurrence of marginal fracture on composite resin restorations.

Microleakage: the effect of storage and cycling duration

This investigation revealed that the limited storage time or cycling durations used had no significant impact on the microleakage patterns of a resin-bonded composite in Class V preparations. Short-term cycling appears as effective in demonstrating marginal leakage as protracted cycling regimens. These findings may be helpful in interpreting and comparing various microleakage studies.