An evaluation of resonance frequency analysis for the determination of the primary stability of orthodontic palatal implants. A study in human cadavers

Background: The primary stability of short orthodontic implants is important for anchorage. Methods: For this study 14 cadaveric human heads were used. The stability of orthodontic implants (Straumann) with lengths of 4 and 6 mm and different localization (palatal suture or paramedially) were evaluated. The implants with length of 6 mm were only placed in the suture and primary stability was non-invasively determined with the resonance frequency (Osstell((R))). The invasive method for the analysis of the morphometric parameters of the implant/bone contact was carried out by means of histological and radiological examinations. Results: The 6 mm implants have significant better primary stability in the palatal suture as 4 mm implants paramedially (P < 0.05). No differences were found between 6 and 4 mm implants in the palatal suture and between 4 mm implants in palatal suture to paramedially. The histological and radiological results demonstrate the ability to measure the implant stability by investigation of the bone offer and density around the implant. Bone structure, especially the pore size in the trabecular bone and the precision of placement may influence the stability. Conclusion: This study shows that the short implant gives sufficient bone fixation, independently of placement. The quality of implantation and bone structure are more important than the length of the orthodontic implant.