Evaluation of Marginal Fits of Crown Substructure Designs in Implant-Supported Abutments.

BACKGROUND The purpose of this clinical study was to compare the marginal adaptation of infrastructure design with 4 different techniques. MATERIAL AND METHODS Forty tissue-level implant abutments (NTA, Shorter) were inserted on implant analogs. The samples were placed randomly in the wax blocks in the arch form of the upper jaw so that there would be 10 in each group. Test samples were obtained using the conventional casting method (CC), milling from metal blocks method (MB), direct metal laser sintering method (LS), and Noritake Alliance (NA) system. Data were analyzed by ANOVA with t tests. RESULTS After porcelain oven-drying, marginal gaps of metal substructures obtained by using conventional casting and milling methods were observed to decrease. The smallest value of the marginal gaps was found in the Noritake (NA) system, and the largest value in the milling (MB) method before and after oven-drying. The marginal gap of the direct metal laser sintering method was not significantly different from the change in the marginal gap of other metal substructures (p>0.05). CONCLUSIONS The marginal gap of the substructures obtained using the direct metal laser sintering method was not significantly different from the change in marginal gap of other metal substructures (p>0.05).

Laser Application to the Root Surface Increases the Bonding Strength of Surface-Treated Prefabricated Glass-Fiber Posts in Teeth with Excessive Substance Loss.

BACKGROUND This study examined the effect of roughening of the root surface using an erbium-doped yttrium aluminum garnet (Er: YAG) laser on the binding strength of teeth undergoing root canal treatment. MATERIAL AND METHODS Ninety single-rooted teeth were used and assigned randomly to 9 groups (n=10 each). Root canals were prepared using the FlexMaster rotary system. An Er: YAG laser was applied to the root canals in Group 1, with no surface treatment of the glass-fiber post. In Group 2, aluminum oxide particles were applied. In Group 3, the laser was applied to the root canals, with Cojet treatment. Group 4 received laser treatment and Clearfil Ceramic Primer. In Group 5, Clearfil Ceramic Primer silane coupling was performed on post surfaces without laser treatment. In Group 6, hydrofluoric acid (HF) application was followed by Clearfil Ceramic Primer cementing of the glass post surfaces with laser application. In Group 7, HF acid treatment was performed without laser. In Group 8, the laser was applied, followed by sanding of post surfaces using Korox 50, and silane coupling with Clearfil Ceramic Primer. In Group 9, the post surfaces were sanded using Korox 50 with laser application to the root canals. The samples were subjected to a push-out experiment. The data were analyzed using Friedman's test and the Wilcoxon signed-rank test. RESULTS A significant difference in bonding strength was found among the groups (p<0.005). CONCLUSIONS Use of an Er: YAG laser in the root canal may be beneficial prior to bonding of glass posts.