Journal of Dental Medicine

Background and Aims: For the clinical success of implant-retained prostheses, fitness of matching components and stability of the applied torque to the implant-abutment assembly under dynamic occlusal loading is essential. The aim of this study was to evaluate the torque loss in Co-Cr castable abutments after cyclic loading.
Materials and Methods: 10 castable abutments were cast in Co-Cr alloy with similar size and height. Each specimen was mounted vertically on a separated implant using a 30 Ncm tightening torque. The detorque values of the abutments were evaluated after 10 min. The same tightening torque was applied to the abutments on their corresponding implants and cyclic loading was applied for 500,000 cycles to the implant-abutment assembly. The torque values after cyclic loading were recorded for each specimen. T-test analysis was conducted on scores from the groups.
Resultes: The results of this study showed that the percentage of torque loss in castable abutments was significantly increased after cyclic loading (P<0.001).
Conclusion: Misfit between the castable implant components can cause torque loss before and after cyclic loading. However, it is more appropriate to relate the results of this study to the screw loosening of the above mentioned abutments than judging their clinical performance.

Background and Aims: Removable partial denture (RPDs) is a common therapy for rehabilitation of partialy edentulous patients while RPD causes a lot of periodontal problems. The purpose of this study was to investigate the effect of RPDs made in Babol dental school on the periodontal health of abutment and non-abutment teeth.
Materials and Methods: In this cross sectional study, 70 patients who were candidates for RPDs divided into four groups according to Kennedy classification. The following periodontal parameters were evaluated for abutment and non-abutment teeth, plaque index (PI), calculus index (CI), width of keratinized gingiva, bleeding on probing (BOP), periodontal pocket depth (PPD), tooth mobility (TM) and gingival recession. This clinical measurement was taken immediately before insertion of the RPD, then one, three, and six months later. These parameters were then analyzed using Mann-Whitney, Independent sample t-test, Covariance, Chi-square statistical tests.
Results: In Class I; the mean score for the width of keratnized gingiva (P<0.001), PPD (P=0.002), and BOP (P<0.001) of the abutment and non-abutment teeth were significantly different after 1 month. After 3 months there were significant differences with regard to the PI (P=0.01), width of keratnized gingiva (P<0.001), BOP (P<0.001) and PPD (P<0.001). After 6 months, only the PI, CI, and TM parameters were not statistically significant. In Class II; the mean score for width of keratnized gingiva (P<0.001) and PI (P=0.002) after 1 month, width of keratnized gingiva (P<0.001), BOP (P=0.02), PPD (P=0.05) and TM (P=0.03) after 3 months and width of keratnized gingiva (P<0.001), PI (P=0.04), BOP (P<0.001) and TM (P=0.03) after six months were statistically significant. In Class III; only gingival recession did not show any significant difference at 1 and 3 months later. The width of keratnized gingiva (P<0.001), PI (P=0.001), BOP (P<0.001) and TM (P=0.03) after 6 months were statistically significant.
Conclusion: This study showed that RPDs affect the periodontal condition of both abutment and non-abutment teeth, which can be reduced by more precise design of the prosthesis, periodontal follow ups and good oral hygiene.