Wear characteristics of trimethylolpropane trimethacrylate filler-containing resins for the full crown restoration of primary molars.

Although the demand for aesthetic restoration of primary molars has increased, the full-crown restorations using resin and the details of the wear characteristics of trimethylolpropane trimethacrylate (TMPT) filler containing resins for primary molars are not well understood. This study was conducted to determine whether new light-cured composite resin (Fantasista) and 4-META/MMATBB resin (Bondfill SB) are appropriate for full crown restoration of primary molars by evaluating their wear characteristics. Both resins products contain TMPT filler. The properties of the resins were evaluated through in vitro impacting-sliding wear tests; the wear properties of the opposing enamel specimens used in the tests were also studied. The properties of the resins were compared with those of Litefill, MetafilC, and Clearfil FII, which had been evaluated previously. Fantasista exhibited simple shape of wear that was suggestive of a higher wear resistance than that of Litefill. Fantasista caused the least damage to the antagonistic primary enamel.

Investigation of distortions around the cervical area of teeth restored with two kinds of crown materials.

The purpose of this study was to identify crown materials to decrease the stress concentrated at the cervical area of endodontically treated teeth. To this end, 14 extracted human mandibular premolars were divided into two groups for this study: complete cast crowns versus polymer-based crown and bridge material crowns. Both complete cast crowns (MC) and polymer-based crown and bridge material crowns (HC) were cemented with a glycidyl methacrylate-based resin cement (RC) to composite resin cores with glass fiber posts. Static loading was applied and distortion was measured with four pieces of strain gages attached to the marginal area. Findings showed that there was a large difference in distortion between crown and root in MC. On the other hand, distortions at the cervical area of crown and root were similar in HC.

[Influence of different spacer thickness and spacer coverage area on the adaptation of Cercon CAD/CAM copings].

OBJECTIVE: To evaluate the accuracy of Cercon CAD/CAM system and the influence of different spacer thickness and spacer coverage area on the internal and marginal fit of the copings. METHODS: A stainless steel master model of first molar was replicated. After scanning, designs of copings were made with different spacer thickness and spacer coverage area. There were six groups: S10C70, S10C90, S30C70, S30C90, S60C70, S60C90. Measurements of the adaptation were performed with silicone impression material and an image analysis system. RESULTS: Univariate ANOVA showed that variation in the internal fit of copings was related to measuring location, spacer thickness and spacer coverage area. There was significant difference between different spacer coverage area groups, and significant difference between spacer thickness 10 microm and 30 microm groups, 10 microm and 60 microm groups, no significant difference between spacer thickness 30 microm and 60 microm groups. Mean marginal fit was (27.7+/-7.6) microm. There was statistically significant difference between both mesial, distal marginal gaps and both buccal, lingual marginal gaps. No difference between mesial and distal marginal gaps, and between buccal and lingual marginal gaps. CONCLUSION: The accuracy by Cercon CAD/CAM system for the marginal and internal fit of zirconium dioxide copings is well within the range of clinical acceptability. Spacer thickness and spacer coverage area have statistically significant influence on the internal fit.

The effects of various finishing materials on the gloss and the color change of indirect prosthetic resin composites.

The effect of different polishing materials on the surface texture and the color change of indirect prosthetic resin composite materials exposed to a staining agent was studied. Six different resin composites were polished using the same procedures and were measured for the gloss. After exposed to a coffee solution, the changes were measured on the color properties. The six different types of resin composites were further divided into four groups of eight specimens each for the different surface polishing procedure. The gloss was measured by a gloss meter (TC-108D, Tokyo-Densyoku, Tokyo, Japan) with an angle of 45 degrees and expressed in gloss units (GU). Before and after exposure to the staining agent, the color measurements of all specimens were recorded with a colorimeter (TC-1800MKII, Tokyo-Densyoku, Tokyo, Japan) using CIE L* a* b*. All specimens were stored in the coffee solution for 5 weeks at 37 degrees C. Most of the resin composites showed the highest gloss and staining resistances when the fine silicone diamond polishing point was used. The results of this study suggested that there are differences in the gloss and the color changes depending on the filler type and the composition of the polishing materials.