The Effect of Implant Thread Design on Implant Stability in the Early Post-operative Period
Available literature suggests that there is a transient drop in implant stability from approximately week 0 to week 3-4 as a result of bone remodeling around the implant as it transitions from a primary, mechanical stability to a secondary, biologic stability. Minimal research has been conducted investigating the potential influence of macrothread design on this process.
Objective: to determine the role of macrothread design on implant stability in the early post-operative healing period through the use resonance frequency analysis (RFA).
Methods: 7 patients, each missing at least two posterior teeth in the same arch, were included in the study, resulting in 10 matched pairs available for analysis. All sites were healed sites (> 6 months post-extraction) with sufficient bone volume for implant placement and no history of prior augmentation. Each site in a matched pair was randomly selected to receive either the control implant (Megagen EZPlus Internal) or the test implant (Megagen AnyRidge). The test implant incorporates a novel thread design which includes rounded, non-cutting edges, wide thread depth, and increased thread pitch compared to a conventional thread design. Implants were placed using a standardized drilling protocol. RFA was used to determine implant stability quotient (ISQ) values for each implant at the time of placement and weekly for the first 8 weeks.
Results: Surgical placement of implants and subsequent healing was uneventful in all cases. At insertion, implants consistently achieved a relatively high insertion torque (30-45 Ncm-1) and high initial ISQ value (79.8 +/- 1.49). Similar baseline ISQ values were found for the test (AR; 79.55 +/- 1.61) and control (EZ; 80.05 +/- 1.37) implants. A general pattern of mean stability in mean ISQ values from baseline across all eight follow-up evaluations was seen for the test implant. A pattern of decreasing ISQ values was seen across the follow-up evaluations for the EZ implant up to week four, where the value plateaued. There was a statistically significant main effect due to implant type (p<0.01). The main effect for time was not statistically significant (p=0.21). However, there was a statistically significant interaction between implant type and time (p<0.01), indicating that the test and control implants performed differently at certain time points.
Conclusions: Within the limitations of this study, macrothread design does appear to play a role in implant stability in the early post-operative healing period as assessed by RFA. These findings may have important implications related to immediate or early loading protocols.