Implant Bio-mechanics for Successful Implant Therapy: A Systematic Review

BACKGROUND: Dental implants are considered the best treatment option for replacement of missing teeth due to high survival rates and diverse applications. However, not all dental implant therapies are successful and some fail due to various biological and or/mechanical factors. The objective of this study was to systematically review primary studies that focus on the biomechanical properties of dental implants in order to determine which biomechanical properties are most important for success of dental implant therapy. MATERIALS AND METHODS: An electronic database search was performed using MEDLINE (PubMed), EMBASE, Google Scholar, and CAB Abstracts. Six principal biomechanical properties were considered to prepare the search strategy for each database using key words and Boolean operators. Human and animal studies (observational studies, trials, and in vitro studies) were included in this review. Human studies that were considered eligible needed to have subjects above 18 years who received permanent restorations after implant surgery and followed up for at least 6 months after receiving permanent restorations. Studies with subjects who had absolute contraindications at the time of dental implant surgery were excluded. RESULTS: In total, 28 studies were included in the review after application of the eligibility criteria; 18 in vitro studies, 5 cohort clinical studies, 3 animal studies, and 2 nonrandomized trials. Six in vitro studies assessed loss of preload, five in vitro studies assessed fatigue strength, four assessed implant abutment connection design, and one assessed implant diameter. Two nonrandomized trials assessed torque and six observational studies assessed the effect of cantilevers. Gold alloy coating of abutment screws resulted in higher preload values followed by titanium alloy coating and gold coating; there was a difference in preload values between coated and uncoated screws when tightened repeatedly. Preload values decreased as a function of time with majority of preload loss occurred within 10s of tightening. The 8-degree internal conical implant performed better than the internal hex design. Higher rate of complications (porcelain chipping, de-cementation) was observed in the cantilever groups in studies. CONCLUSION: Biomechanical properties of implants like preload, torque, cantilever design, implant abutment design have profound effects on the survival rates of dental implants. With limiations, this review provides some important parameters to consider for successful implant therapy.