Investigations into fracture thresholds of implants with internal tri-channel connections

Objectives: Implant fracture during placement is a rare occurrence, the consequence of which can have a significant impact on the placement of additional or replacement implants. With the development of narrow implants the type of connection used can leave the fixture susceptible to fracture during placement. These investigations aimed to assess the fracture thresholds of implants with an internal tri-channel connection. Furthermore, the study hoped to determine if the manufacturers recommended surgical protocols would help to avoid these failures.

Methods: Nine 13 mm NobelReplace Tapered Groovy implants were used in these investigations – six narrow platform (NP), two regular platform (RP) and one wide platform (WP) implants were mounted into Perspex blocks with 5 mm of the fixture head exposed above the surface of the block. They were then secured in place with an epoxy resin adhesive. Using the appropriate fixture mount the fracture threshold of the connection interface was then recorded using a torque gauge (Bestool, Kanon, USA). A maximum torque of 150 Ncm was applied as this was considered enough to significantly exceed the manufacturers recommended insertion protocol.

Results: All 6 narrow platform implants fractured at torque values between 119 – 139 Ncm (median - 132 Ncm). None of the RP or WP implants fractured at the maximum torque measured – 150 Ncm. However, subjective assessment of fracture thresholds of the RP and WP implants (>150 Ncm) demonstrated that the implants dislodged from the Perspex block before fracture. These values far exceeded the manufacturers recommended insertion torque of 45 Ncm.

Conclusion: NP implants with internal tri-channel connections are more susceptible to fracturing during placement than either RP or WP implants. However, the torque required to fracture these NP fixtures is significantly higher than that stated in the manufacturers recommended surgical protocols.