Topography and presence of a smear layer in deciduous molars prepared with high-speed cutting and ultrasonic abrasion: an in-vitro study.

OBJECTIVE: The aim of this in-vitro study was to compare the effect of high-speed cutting (HS) with ultrasonic abrasion (US) concerning the internal topography and the presence of a smear layer in a cavity preparation performed in healthy deciduous molars. MATERIAL AND METHODS: Seven first deciduous molars were used. Two occlusal cavity preparation were done, one in the medial fossula and another in the distal fossula, which were chosen randomly. One preparation was carried out with a diamond point adapted to the HS system (GI), while a chemical vapor deposition (CVD) point adapted to a US device (GII) was used for the other preparation. Subsequently, all samples (n = 14) were cleaved to observe the inside and then prepared for evaluation using scanning electron photomicroscopy. The internal topography of the prepared cavities was descriptively analyzed. In order to assess the presence of a smear layer, scores were tabulated using the 2000 GMC program and analyzed using the Mann-Whitney test. RESULTS: Concerning the internal topography, the presence of striae was verified in both groups. In the GI group they were finer, found in a greater number, and with narrower spaces between them. In the GII group, the striae were undulating, similar to the effect of wheels on sand, and with wider spaces between them. As regards the presence of a smear layer, there was no statistically significant difference between the groups (P > 0.05). CONCLUSIONS: In view of the methodology employed, it may be concluded that cavity preparation with a CVD point in a US abrasion system led to the formation of fewer striae and both devices promoted the marked presence of a smear layer, obstructing dentinal tubuli.

Randomised trial of resin-based restorations in Class I and Class II beveled preparations in primary molars: 48-month results.

OBJECTIVE: This randomised clinical trial evaluated the survival rate of resin-based restorations in Class I and Class II beveled preparations in primary molars, over 48 months. METHODS: Forty-eight children received 141 restorations in beveled cavosurface margin preparations in primary molars randomly assigned by a lottery method: 46 received treatment with Vitremer Tri-Cure Glass Ionomer System (33 Class I and 13 Class II restorations); 51 received treatment with Freedom (36 Class I and 15 Class II restorations); 44 received treatment with TPH Spectrum (30 Class I and 14 Class II restorations). Two calibrated examiners (weight kappa> or =0.85) evaluated the restorations using the modified USPHS criteria and visible plaque index score at baseline and after 12, 24, 36 and 48 months. Cox regression with survival analysis and logistic regression evaluated the clinical performance of restorations. RESULTS: After 48 months, 11 teeth had exfoliated, 16 restorations were dropouts, 83 restorations were clinically successful of which 26 had used Vitremer, 32 had used Freedom and 25 had used TPH Spectrum. Thirty-one restorations failed because of secondary caries, fractures and loss of retention. The cumulative survival was 73.9%, 83.4% and 79.6%, respectively for Vitremer, Freedom and THP Spectrum with no differences among materials (Log Rank Mantel-Cox, p>0.05). However, the Class II cavity preparation reduced the survival of the restorations (OR=5.1) for all materials evaluated (p>0.05). CONCLUSIONS: The life expectancy of Vitremer, Freedom and THP Spectrum in Class I and Class II restorations could be comparable after 48 months.

Influence of kinetic cavity preparation devices on dental topography: an in vitro study.

AIM: The objectives of this study were to assess the influence of four different kinetic cavity preparation devices on cavity preparation taking into account tip angulation, internal tip diameter, and distance to the dental substrate. The dental topography itself was also evaluated after the use of these devices. METHODS AND MATERIALS: Quantitative parameters using pertinent statistical tests as well as qualitative parameters were used to assess the topography in terms of the dispersion halo effect (DHE), size, and depth of the preparation. RESULTS: The DHE did not present differences among the groups. In relation to the preparation size, the internal diameter influenced 120 masculine point angles, whereas distance influenced the 90 masculine ones. Considering the preparation depth, the 90 degrees point angle yielded the deepest. In the qualitative analysis, both angles provided cavity preparations with rounded cavosurface angles. The 120 masculine point angles yielded inclined, shallow V-shaped preparations, whereas the 90 masculine angles presented U-shaped preparations reaching the dentin. The enamel had an irregular aspect and exposed prisms; dentin had a loose smear layer with aluminum oxide residues. CONCLUSION: The kind of device may influence the kinetic cavity design. CLINICAL SIGNIFICANCE: It is the clinician that knows how to select the appropriate devices to adopt in order to achieve the desired cut, depth, and shape of cavity preparations.