The Effect Of Two Polishing Systems On The Leakage Of Composite Resin Restorations

Objective:The purpose of this in vitro study was to investigate the effect of two polishing systems on the leakage of composite resin restorations.Method:Class V cavities (mesio-distal width of 4 mm, occlusogingival length of 4 mm and a depth of 2 mm) were prepared on the bucco-palatal/lingual surfaces of 60 freshly extracted premolars at 1mm above the cementoenamel junction. The teeth were stored in isotonic saline at all times and were not permitted to dehydrate under any circumstances.The prepared teeth were randomly divided into six groups of ten teeth(P0,P1,P2,S0,S1,S2). Teeth in Group P0, PI and P2 were restored with conventional composite resin P60 while teeth in Group S0, S1 and S2 with Spectrum TPH. Immediately after light polymerization, the teeth were restored in distilled water for 24 hours. Gross finishing was done using diamond finishing burs with water spray. Group P0 and Group SO were used as negative control groups. Teeth in Groups P1 and S1 were polished using Sof-Lex discs, while teeth in group P2 and S2 using Composite polishing kit CA0310.The roughness of the restorations was measured after the above treatment.In preparation for dye penetration testing, the apical foramen of each tooth was covered with self-curing rising. Two layers of nail varnish were applied to all surfaces of the teeth leaving the finished restorations and 1mm beyond the margins exposed to dye.All the teeth were immersed in 500g/L ammoniacal silver nitrate (pH=9.5) solution for 24 hours at 37℃then washed with distilled water for 10 seconds. After this, all samples were immersed in the developer solution for 8 hours and exposured by the fluorescent lamp at the same time. Subsequently, all the teeth were cleaned by distilled water for 20 seconds and sectioned longitudinally through the restorations in a bucco-palatal/lingual plane with a low speed diamond disk with water coolant, producing approximately 2mm wide samples.The marginal sealing ability, as indicated by the depth of dye penetration around the occlusal and gingival margins, was evaluated under a VM stereomicroscope at×40 magnification. For each restoration, the section with greater leakage was selected for scoring.In the last, all the samples were evaluated under the Scanning electron microscopy (SEM) for the leakage of silver.Results:1. In groups restored with the same composite(Spectrum TPH or P60), the roughness of the restoration was significantly reduced by use of Sof-Lex discs or Composite polishing kit CA0310, however, there is no difference between the two polishing systems. Under the same polishing circumstances, teeth restored with Spectrum TPH received a smoother surface than that of P60.2. No significant difference in microleakage scores between the occlusal and gingival margins was found. In groups restored with the same composite(Spectrum TPH or P60), the microleakage scores were not statisticly different between different polishing systems. When polished with the same polishing system, teeth restored with different composite resin had no significant difference in microleakage scores.3. There is nanoleakage in both occlusal and gingival margins of different composite restorations under different polishing teeatments.Conclusion:1. Sof-Lex discs and Composite polishing kit CA0310 are efficient polishing systems; there is no significant difference in polishing effect between them.2. Spectrum TPH is better than P60 referring to surface roughness.3. The leakage resistance of Spectrum TPH and P60, at both occlusal and gingival margins, are not significantly affected by different polishing systems.