Alterations in human enamel surface morphology following the use of an office bleaching agent and consecutive application of 37% phosphoric acid in vivo.

OBJECTIVE: The aim of this in vivo study was to evaluate the effects of a visible light-activated in-office bleaching agent, Opalescence Xtra (35% hydrogen peroxide) on the external enamel surface of human teeth by using scanning electron microscopy (SEM). METHODS: The labial surfaces of nine upper incisors from nine different patients were divided into four parts, and a bleaching agent was applied to the mesial halves of the teeth. Three weeks following this treatment, the teeth were extracted and divided into four quadrants. Each quadrant was treated with a different procedure and the samples were examined under SEM. The SEM photographs were blindly evaluated by a jury of four experts. RESULTS: Although there were no statistical differences in the rating of surface morphology of bleached and control groups, the 37% phosphoric acid etched and acid etched + bleached enamel samples demonstrated a statistically significant dissimilar surface morphology (p < 0.05). CONCLUSION: The bleached + etched enamel treatment showed an uneven etched surface compared to the acid etched control.

Comparison of the electromyographic activity of individuals with canine guidance and group function occlusion.

The purpose of this study was to investigate occlusal schemes (canine guidance and group function) in relation to masticatory muscle activity. It was performed on 30 subjects, 15 with canine guidance and 15 with group function. Bilateral electromyographic recordings of masseter and anterior temporal muscles were obtained by surface electrodes during gum chewing and sliding laterally from centric relation while the teeth were in contact. The obtained data for both groups were compared statistically. Electromyograms were also evaluated visually. There was no significant difference in results between the occlusal schemes. However, canine guidance showed a narrower chewing model than group function and reduced anterior temporal muscle activity during sliding. This suggests that in the presence of healthy and good supportive canine teeth, canine guidance occlusion will be preferable.

Microleakage of indirect inlays placed on different kinds of glass ionomer cement linings.

The objective of this study is to compare the marginal seal of Class II cavities restored with indirect inlays constructed on glass ionomer cement linings having different curing properties. Also the effect of acid-etching of these liners on microleakage was investigated. Mesio-occlusal and disto-occlusal cavities in 80 extracted human molars having the cervical floor below the cementoenamel junction were prepared (n:160). Half of the preparations were restored with Ceramco II porcelain and the rest with SR-Isosit resin inlay material. Liners as light curing Ionoseal light+chemically curing LCL 8 and Zionomer and chemically curing Ketac-Bond glass ionomer cements (GICs) were used. On mesial preparations GICs were acid-etched but were not on distal preparations. All inlays were cemented with Ultrabond composite material. After thermocycling the teeth were placed in a basic fuchsin dye solution for 24 h, then each tooth was sectioned. By using a stereomicroscope the extent of marginal leakage was scored and statistically evaluated. Microleakage was observed beneath all GIC linings and was more extensive between light curing GIC/dentine interface. By acid-etching of GICs the microleakage between GIC/dentine interface was increased significantly. Whether acid-etching was applied or not a significantly increased microleakage was recorded between chemically curing GIC/composite interfaces. Although the marginal microleakage was witnessed in both inlays, it appeared that porcelain inlays provided a better marginal seal, in comparison to SR-Isosit inlays.