Stability comparison between commercially available mini-implants and a novel design: Part 1

Abstract

Objective: To compare mechanical stability among five mini-implant designs-a newly invented design and four commercially available designs that vary by shape and threading; to calculate external surface area of each design using high-resolution micro-computed tomography; and to evaluate the relationship between surface area and stability results. Materials and Methods: The four commercially available mini-implants-single-threaded and cylindrical (SC), single-threaded and tapered (ST), double-threaded and cylindrical (DC), doublethreaded and tapered (DT)-and a new implant that is designed to engage mostly in cortical bone with shorter and wider dimensions (N1) were inserted in simulated bone with cortical and trabecular bone layers. The mechanical study consisted of torque measurements and lateral displacement tests. External surface area was computed using a 25-mm micro-CT. Results: Maximum insertion torque, maximum removal torque, and force levels for displacements were the highest in N1, followed by DT, ST, DC, and SC (a 5 .05). The surface area was largest in DT, followed by N1, ST, DC, and SC. Surface area engaged in cortical bone, however, was the greatest in N1. The surface area of mini-implants had positive correlation with stability. Conclusion: Among commercial designs, both added tapering and double threading improved stability. N1 was the most stable design within this research design. The new design has the potential to be clinically superior; it has enhanced stability and there is diminished risk of endangering nearby anatomic structures during placement and orthodontic treatment, but the design requires refinements to reduce insertion torque to avoid clinical difficulty and patient discomfort. (Angle

Microdamage generation by tapered and cylindrical mini-screw implants after pilot drilling

“…For example, some studies demonstrate that tapered MSIs generate higher insertion torque with higher primary stability than cylindrical MSIs, 3,7,[19][20][21] but they can produce excessive insertion torques, potentially damaging the bone. 13,17,[22][23][24] The latter findings correspond to finite element analyses, which suggest that tapered MSIs induce high stresses in the cortical bone 25 around the implant neck. 26 Another way to reduce insertion torque is with pilot holes.…”

Mechanical stability assessment of novel orthodontic mini-implant designs: Part 2

“…As in Part 1, 18 each design of mini-implants (n 5 20) was inserted and removed using a surgical engine and contra-angle handpiece (ElcomedSA200C, W&H, Burmoos, Austria). The unit was calibrated at each time, and rotation speed was set for 30 rpm.…”

“…18,29 In contrast, N2 required the greatest force to displace all three distances of 0.01, 0.02, and 0.03 mm in the lateral displacement test. This discrepancy in stability hierarchy may contribute to the microcracks introduced during the placement of N1 with high MIT.…”

“…19,20 Part 1 reported N1's improved stability compared with commercially-available designs and potential clinical strengths from short length to avoid biologic damages. 18 However, it was concluded that N1's high insertion torque can introduce clinical difficulty and compromised stability from damage to surrounding bone, 5,21 requiring further design improvements.…”

“…The lateral displacement test measures the force applied in transverse direction consistent with how mini-implants are utilized during orthodontic treatment. 18 The lateral displacement test may be a more accurate method of assessing mechanical stability than torque testing as it better corresponds to clinical orthodontics. Clinicians experience that initial micromovement or mobility is crucial to the success of miniimplants.…”