Abstract
The purpose of this systematic review was to evaluate the clinical and laboratory
outcomes of angled screw channel (ASC) restorations and to summarize the influencing
factors. An electronic search of the English language literature was performed in
four databases and enriched by manual searches. Retrieved studies were screened against
the predefined exclusion and inclusion criteria. Eight clinical and seven laboratory
studies were eligible for the analysis. The risk of bias for included observational
studies was performed using the Newcastle–Ottawa quality assessment scale. Laboratory
studies quality assessment method was adapted from previous published systematic reviews.
Two clinical studies focused on technical outcomes and the rest reported the biological
outcomes of the ASC restorations. Out of the seven laboratory studies, two studies
investigated the fracture resistance of ASC restorations, four studies evaluated the
reverse torque value of the nonaxially tightened screws, and one study evaluated both
variables. The present review revealed that while the performance of ASC restorations
is promising in short-term clinical studies, the evidence of their long-term reliability
is still lacking. The laboratory studies indicated comparable fracture resistance
results of the ASC restorations with the straight screw channel restorations. In addition,
factors, such as initial torque value, configuration of the screw driver, screw design,
abutment system, and the angulation of screw channel, were shown to influence the
screw resistance to loosening.
Keywords
angulated screw channel - screw-retained prosthesis - computer aided design- computer
aided manufacturing - implant
