Surface roughness and enamel loss with two microabrasion techniques.

AIM: The aim of this study was to evaluate and compare the surface roughness and enamel loss produced by two microabrasion techniques. METHODS AND MATERIALS: Bovine teeth were selected and an area was delimited for microabrasion techniques. Surface roughness was determined before and after treatment using a digital profilometer. Specimens were randomized to one of two acid treatments (n = 10): 18% hydrochloric acid (HCl) and pumice or 37% phosphoric acid (H3PO4) and pumice. Acid treatments were applied using a wooden spatula for 5 seconds for a total of ten applications. Then, specimens were sectioned through the center of the demineralization area to obtain 80 microm thick slices. The wear produced by the microabrasion techniques was evaluated using stereomicroscopy (40 x). The greatest depth (microm) and the total surface area (microm(2)) of demineralization were measured using the Image Tool software (University of Texas Health Science, San Antonio, TX, USA). In addition, three specimens of each group were subjected to SEM analysis at different magnifications. RESULTS: The mean surface roughness was statistically lower for HCl than for H3PO4 (p < 0.001). Deeper demineralization (p < 0.003) and a larger total demineralization area was observed for HCl (p < 0.005). Under SEM analysis H3PO4 showed a selective conditioning etching, while HCl exhibited a non-selective pattern. CONCLUSIONS: Microabrasion using H3PO4 produced greater surface roughness but less demineralization than the microabrasion technique using HCl. CLINICAL SIGNIFICANCE: Both microabrasion techniques effectively remove the superficial enamel layer. However, the technique using H3PO4 was less aggressive, safer, and easier to perform.

Stem cells: therapeutic potential in dentistry.

AIM: The aim of this paper is to present a review and discussion of the current status of stem cell research with regard to tooth generation. BACKGROUND: Stem cells have been isolated from the pulp tissue of both deciduous and permanent teeth as well as from the periodontal ligament. Dental pulp stem cells demonstrate the capacity to form a dentin pulp-like complex in immunocompromised mice. A tooth-like structure was successfully formed, using a heterogeneous mixture of dental enamel epithelium, pulp mesenchymal cells, and scaffolds. CONCLUSION: The scientific community understands the need for more investigations to completely understand the conditions that would best favor the creation of a tooth substitute. Recent gains in the understanding of the molecular regulation of tooth morphogenesis, stem cell biology, and biotechnology offers the opportunity to realize this goal. CLINICAL SIGNIFICANCE: These findings, combined with the recent progress in stem cell research and tissue engineering, might allow the development of alternatives for current materials and therapies used to treat tooth tissue loss (e.g., enamel, dentin, pulp), reconstruct dentoalveolar and craniofacial bone defects, and eventually replace an entire tooth.

Class II composite restorations with metallic and translucent matrices: 2-year follow-up findings.

OBJECTIVE: The aim of this randomized, clinical study was to evaluate the performance of composite restorations placed with two matrix and wedge systems after a 2-year follow-up. METHODS: Twenty-three patients were selected, and received at least two Class II restorations, one with metallic matrix and wooden wedge and other with polyester matrix and reflective wedge. One dentist placed all the 109 restorations. All cavities were restored using Single Bond and P-60 (3M ESPE), according to manufacturer's instructions. In the metal matrix group, polymerization was performed from occlusal, and in the polyester group, through the reflective wedge. Restorations were evaluated at baseline and after 12 and 24 months by the modified USPHS criteria, and data were analyzed with Mann-Whitney and Wilcoxon Signed Rank tests (alpha=0.05). RESULTS: Fifteen subjects and 78 restorations were re-evaluated after 24 months. A significant decrease in the quality of cervical adaptation and proximal contacts by radiographic evaluation was evidenced (p<0.05), but no differences between the two matrix systems were detected (p>0.05). In the clinical evaluation there were no significant differences between matrices after 2 years (p>0.05). A compromising of marginal adaptation, marginal staining and proximal contacts aspects for both matrix systems was evidenced, and restorations placed with translucent matrices showed loss of color stability (p<0.05). CONCLUSIONS: Whereas restorations presented some clinical aspects somewhat compromised after 2 years, the matrix and wedge systems evaluated showed similar clinical performance.

Influence of cavity configuration on the microleakage of resin composite root-end fillings

The purpose of the present study was to evaluate, in vitro, the effect of three different cavity configurations on the microleakage of resin composite root-end fillings. Conventional root therapy was peformed in 60 anterior human teeth. Apicectomies were made, teeth were randomly divided in three groups and the apical cavities were prepared as following: Group 1 - classic Class I cavities; group 2 - saucer-shaped cavities; group 3 - adhesive cavities (round angles). The cavities were prepared with high speed pieces under air-water cooling and burs were replaced after four preparations. All cavities were restored with a self-etching adhesive system (Clearfil SE Bond, Kurakay) and a hybrid resin composite (Filtek Z-250, 3M Espe®). Teeth were isolated with two coats of nail varnish, except for the apical region, and immersed in methylene blue for 14 days, at 37ºC. Specimens were washed, sectioned and evaluated for absence or presence of dye penetration, in a stereomicroscope (40 X). Data were subjected to statistical analysis using Kruskal-Wallis test, with p<0.05. The degree of dye leakage was low in all groups (75-90% leakage-free specimens). No statistically significant difference was found between the three groups (p>0.05). Within the limitations of this study, cavity configuration did not have influence on microleakage of composite restorations used in root-end cavities.