Self-drilling and self-tapping miniscrews for osteosynthesis fixture after LeFort I osteotomy: An ex vivo trial for primary stability and a randomized clinical study

Abstract

Background: Self-drilling osteosynthesis screws (SDS) have a potential higher primary stability together with clinical advantages such as less time effort compared to self-tapping screws (STS). The aims of the study were to compare the primary stability of SDS and STS ex vivo and to analyze of the time-saving effect in vivo.

Materials and methods: Ex vivo, both screws were placed in porcine bone. Torque was measured for insertion and removal. Four specimens were kept in bone for histologic bone-to-implant-contact examination. In vivo, 49 patients who received orthognathic surgery in the maxilla were included in 2 centers. In a split-mouth design, the time for osteosynthesis fixation and perioperative events were recorded.

Results: Ex vivo, insertion and removal torque measurements were higher for SDS, especially in dense bone. Histologic imaging on the exemplary-stained specimens showed higher bone contact and compressed bone matrix for SDS in all bone densities. In vivo, the mean osteosynthesis time in both centers was 5.5 min (±3.03) for SDS and 5.5 min (±2.37) for STS. Separate analysis showed that center I was faster with STS and center II with SDS. Although, in center I a higher rate of failed primary stability of SDS compared to STS was documented.

Conclusions: SDS showed a partially higher primary stability ex vivo, especially in dense bone. The timesaving effect of SDS is less pronounced than expected, but technically SDS might be favorable where drilling is difficult or even impossible.

Keywords: LeFort I osteotomy; Orthognathic surgery; Osteosynthesis; Primary stability; Self-drilling; Self-tapping.