Comparison of different dental implant thread shapes in terms of fracture strength and failure mode under static load

Aim: This research aimed to analyze the effect of variable dental implant thread shapes upon the fracture resistance and failure mode under static load. Material and Methods: According to the shape of thread, a total of 60 custom made titanium dental implant grade-4 were divided into four groups, namely V-Shape (Group 1), Square Shape (Group 2), Buttress Shape (Group 3), and Reverse Buttress Shape (Group 4), were subjected to laboratory analysis set-up recommended by ISO 14801. Implant specimens were mounted in an acrylic block and subjected to a 30° off-axis compression load. Universal Test Machine UTM was used to determine the fracture strength and the data were analyzed by one-way ANOVA and Tukey's test. Scanning Electron Microscope (SEM) fractographic analysis was used to determine the failure mode. Result: The mean ± standard deviation (SD) of Maximum Loads (N) was measured as 482,38±45,98 in Group 1, 422,08±41,73 in Group 2, 407,95±46,97 in Group 3, and 484,53±57,94 N in Group 4. The fracture resistance of the V-shape Thread was significantly higher than square and buttress thread (p<0.05). The fracture resistance of reverse buttress thread was significantly higher than square and buttress thread (p<0.05). There was no statistically significant difference between square and buttress thread (p>0.05). There was no statistically significant difference between V-shape and reverse buttress shape (p>0.05). Four distinct failure modes were identified: Fixture and Screw fracture, Abutment and Screw fracture, Screw fracture, and hole implant component deformations. SEM fractography analysis showed a ductile fracture mode with plastic deformation of the implants fixture and abutment screws. Conclusions: The result of this study indicates that different thread forms significantly affects the fracture strength of implants under 30° static load. Implants with Reverse buttress and V-shape threads designs are more resistance to fracture than implant with Square and Buttress thread designs. Failure mode was almost identical in all thread design. Keywords: Dental Implants; Thread Shapes; Fracture Strength; Failure Mode; SEM