Does Change in Thread Shape Influence the Pull Out Strength of Mini Implants? An In vitro Study

Area of Science:

• Orthodontics
• Biomaterials Engineering
• Dental Implantology

Background:

• Mini implants provide absolute anchorage for improved orthodontic treatment outcomes.
• Mini implant stability is a critical factor influencing treatment success.
• Thread shape significantly impacts the primary stability of mini implants.

Purpose of the Study:

• To investigate the influence of various thread shapes on the pull-out strength of mini implants.
• To identify optimal mini implant thread designs for enhanced stability.

Main Methods:

• Five distinct mini implant thread designs were evaluated: reverse buttress, buttress, 75° joint profile with flutes, trapezoidal, and trapezoidal fluted.
• Pull-out strength was measured using an Instron testing machine on mini implants inserted into polyurethane foam blocks.
• Statistical analysis included one-way ANOVA and Tukey post-hoc tests to compare pull-out strength across groups.

Main Results:

• Mini implants with a trapezoidal fluted design exhibited the highest mean pull-out strength (61 N).
• A statistically significant difference of 34.5 N was observed between the control (reverse buttress) and trapezoidal fluted groups (p<0.05).
• The trapezoidal thread design showed the lowest pull-out strength (13.45 N).

Conclusions:

• The trapezoidal fluted thread design offers superior pull-out strength compared to other tested designs.
• This finding suggests potential for improved stability and clinical efficacy of trapezoidal fluted mini implants.
• Further research using Finite Element Method (FEM) and denser foam blocks is recommended to validate this novel thread design.