Page 166 - Peri-implant health: the effect of implant design and surgical procedure on bone and soft tissue stability

CHAPTER 7
and strain transmission around the implant; (3) the conical implant–abutment connection seems to be more resistant to abutment movement and microgap enlargement and has higher torque loss resistance in addition to high resistance to fatigue loading and maximum bending; (4) the conical implant–abutment connection seems to have lower abutment screw stresses than with external hexagon connection are detected but it is comparable to internal hexagon connections. The same review concluded from in vivo studies that (1) conical and non-conical systems are comparable in terms of implant success and survival and (2) in most cases conical connection systems seem to produce a lower marginal bone loss.5
Besides the implant–abutment connection type, also thread design at the coronal part of the implant is claimed to influence crestal bone loss. Several in vitro studies, using finite element analysis, showed better stress distribution on the surrounding crestal bone for microthreaded compared to non-microthreaded implants.6,7 Multiple in vivo clinical studies showed less crestal bone loss for microthreaded implants compared to non-microthreaded implants.8– 11 However, most of the aforementioned studies did not control other implant design factors and often the compared implants differed in more than one confounding factor thereby possible biasing the outcome of the study.
No connection has a 100% bacterial seal. However, evidence showed that conical connection systems seem to be superior in terms of bacterial seal. Conical implant- abutment connection systems seem to be more resistant to abutment movement and microgap enlargement under loading. Internal and external hexagonal connection systems seem to be inferior in terms of abutment movement and microgap formation. Conical connection systems have higher torque loss resistance than other systems. Conical connection systems have high resistance to fatigue loading and maximum bending. Conical connection systems seem to have lower abutment screw stresses than external hexagonal connection systems and are comparable to internal hexagonal systems. The cone compensates high stresses and protects the screw from overloading. The implant-abutment interface geometry seems to be an influencing factor for stress and strain transmission around the implant. Hence, this prospective clinical study assessed the 4–5 years effect of implant neck (microthreaded vs non-microthreaded) as well as the type of connection (internal conical vs external flat to flat) on peri-implant bone stability and peri-implant health.
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