Retention of bonded titanium copings fixed to implant abutments.

STATEMENT OF PROBLEM: Conical abutments can be laser welded to the abutment base to compensate for differing implant axes. As laser welding requires expensive equipment, alternative methods for bonding the conical abutment part with the abutment base should be considered. PURPOSE: The purpose of this in vitro study was to evaluate the retention of Ti-6Al-7Nb copings bonded adhesively to Ti-6Al-7Nb abutments and to compare it with the stability achieved by laser welding. MATERIAL AND METHODS: A total of 104 two-part Ti-6Al-7Nb specimens were prepared and divided into 13 groups with 8 specimens each. In this 2-part study, 3 luting resins (Panavia F 2.0 [PF]; Multilink Automix [MA]; Superbond C&B [SB]) were used with or without metal priming (PR). The laser welding group (LW) served as the control. After storage for 1 or 150 days (150 days with thermal cycling [TC]), push-out retention and welded joint stability were tested. The data were analyzed with ANOVA and the Tukey HSD multiple comparison tests. RESULTS: The choice of resin, thermal cycling, and metal priming had a significant effect on resin push-out retention. LW provided the strongest retention, followed by PF, MA, and SB. For PF and SB, TC decreased retention. PR did not lead to higher retention but provided better bonding stability when TC was applied. CONCLUSIONS: The retention values suggest that considering the maximum mastication forces, resin bonding is an appropriate substitute for the laser welding method.

Electromyographic evaluation of masticatory function in denture wearers in related to existing occlusal support.

The aim of this study was to clarify the relationship between partially edentulous pattern and the masticatory function in removable partial denture wearers. Eighty eight removable partial denture wearers and 7 subjects with intact dentition volunteered for this study. Using the Eichner's index, all subjects were divided into 6 groups. Electromyographic (EMG) activities of the masticatory muscle were recorded during chewing a piece of raw carrot. The masticatory function was analyzed by using the variation coefficient (VC) of the time parameter of EMG interval recorded during mastication. The association of the VC with group classification based on Eichner's index was analyzed using analysis of covariance with gender and age as the covariates. The result of the analysis revealed that the VC was significantly associated with group classification and the patients in groups without posterior occlusal supports exhibited significantly higher VC values than those in groups with posterior occlusal supports. These findings suggested that the reduced function in patients without the posterior occlusal contacts was difficult to attain improved and satisfactory outcome with removable partial dentures and that there is a significant need for posterior occlusal support for the preservation of masticatory function.