In-Vitro Heat Generation During Removal of a Fractured Screw Segment From a Dental Implant

Abstract

Objective: To compare in-vitro, peak temperature rise during removal of a fractured abutment screw segment from implants placed in a porcine mandible when using two commonly used drilling speeds: 600 or 2,000 RPM. Material and Methods: Twenty 4.3 x 13 mm implants (Nobel Replace Tapered, Nobel Biocare, Yorba Linda, CA) were placed m ten dissected porcine mandibles (two implants per mandible), one on each s1de. Localized defects were created in twenty surface-treated abutment screws (Nobel Biocare, Yorba Linda, CA), which were then torqued into each implant until a reproducible fracture occurred in each screw. Three Type-K thermocouples (Omega Engineering, Stamford, CT) were inserted through the buccal bone to contact the implant surface at 3 mm (crestal), 6 mm (mid-body) and 9 mm (apical) depths from the implant platform. The fractured screws were removed utilizing a handpiece removal kit (Broken Screw Extractor Kit, Rhein83, New Rochelle, NY) and room temperature water irrigation using either 600 or 2,000 RPM. Real-time temperature data were obtained at the three locations, and local peak temperature values were recorded. A 2-way ANOVA was performed, using Tukey's post-hoc test at a preset alpha of 0.05. Results: Mean peak temperatures were significantly higher using 2,000 RPM than at 600 RPM at the mid-body (p < 0.001) and crestal (p = 0.003) regions, but not at the apical (p = 0.225) locations. No statistical differences in mean peak temperatures were found among the three locations using 600 RPM (p = 0.179). In the 2,000 RPM group, mean peak temperature at the mid-body was consistently h1gher than that at the apical (p < 0.001) area, and more instances of temperature rise above 56" and 60" were observed. In one implant from this group, estimated peak temperature exceeded the bone-damage threshold value (50°C for 30 sec). Conclusion: Removal of fractured abutment screw segments should be performed using low speed (600 RPM) rather than at 2,000 RPM, to minimize temperature rise in adjacent bone.