Primary Stability of Convencional and Extrashort Implants in Edentulous Mandibles

Objectives:
The aim of this study was to evaluate the primary stability of conventional and extra-short (4-mm) implants in mandibular edentulous patients using different methods of measurement.
Methods: Patients were selected according to eligibility criteria. Afterwards, they underwent implant surgery and randomly assigned to 2 groups: Test, with 2 conventional implants in the anterior region and 2 extra-short implants in the posterior region; and Control: 2 conventional implants in the anterior region only. The primary stability of the implants was evaluated by three methods: insertion torque, Implant Stability Quotient (ISQ; Osstell®) and, finally, damping capacity (PTV; Periotest®). The Chi-square test and the Mann-Whitney U-test were used to compare extra-short and conventional implants for the insertion torque variables, and ISQ and PTV, respectively (p <0.05). The methods were correlated using the Pearson's Correlation Test (p <0.05).
Results: Sixty implants (40 conventional, 20 extra-short) were installed in 20 patients. There was no difference between conventional and extra-short implants in the torque (p = 0.617) and PTV (p = 0.236). The ISQ values presented a statistically significant difference (p = 0.017) between the groups, and the conventional implant presented higher ISQ values (mean: 74.25; standard deviation: 4.92) than the extra-short (mean: 70.00; standard deviation: 4.02). The correlation between torque and PTV (r = -0.212; p = 0.104), as well as between torque and ISQ (r = 0.248; p = 0.056) was poor, whereas between PTV and ISQ there was a moderate correlation (r = -0.358; p = 0.005).
Conclusions: Within the limitations of the study, it can be concluded that the primary stability values of conventional and extra-short implants are comparable, and there was a weak to moderate correlation between the evaluation tools.