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

Abstract

Objective: To investigate the relationship between mini-screw implant (MSI) diameter (1.6 vs 2.0 mm) and shape (tapered vs cylindrical) and the amount of microdamage generated during insertion. Materials and Methods: Thirty-six cylindrical and 36 tapered MSIs, 6 mm long, were used in this study. Half of each shape was 1.6 mm in diameter, while the other half was 2.0 mm. After pilot drilling, four and five MSIs were inserted, respectively, into fresh cadaveric maxillae and mandibles of dogs. Bone blocks containing the MSIs were sectioned and ground parallel to the MSI axis. Epifluorescent microscopy was used to measure overall cortical thickness, crack length, and crack number adjacent to the MSI. Crack density and total microdamage burden per surface length were calculated. Three-way analysis of variance (ANOVA) was used to test the effects of jaw, and MSI shape and diameter. Pairwise comparisons were made to control the overall significance level at 5%. Results: The larger (2.0 vs 1.6 mm) cylindrical MSIs increased the numbers, lengths, and densities of microcracks, and the total microdamage burden. The same diameter cylindrical and tapered MSIs generated a similar number of cracks and crack lengths. More total microdamage burden was created by the 2.0-mm cylindrical than the 2.0-mm tapered MSIs. Although higher crack densities were produced by the insertion of 1.6-mm tapered MSIs, there was no difference in total microdamage burden induced by 1.6-mm tapered and 1.6-mm cylindrical MSIs. Conclusions: Pilot drilling is effective in reducing microdamage during insertion of tapered MSIs. To prevent excessive microdamage, large diameter and cylindrical MSIs should be avoided. (Angle Orthod. 2015;85:859-867.)

Histomorphometric analysis of microcrack healing after the installation of mini-implants

“…The gross pattern of microcracks showed both concentric and radial alignment, unlike what has been reported in previous studies [ 19 , 29 ]. This discrepancy occurred primarily because the sections were viewed differently.…”

“…Furthermore, little is known about the repair or healing of microdamage induced by cortical bone screws, dental implants, and MIs. A limited number of studies have performed histomorphometric analysis on the microdamage around MIs; however, most of these studies analyzed microdamage immediately after the installation, evaluated the effects of MI design or different pre-drilling procedures, and mainly dealt with bone-to implant contact [ 7 , 10 , 19 , 27 , 28 ]. In one of these studies, the researches took direct histomorphometric measurements of the microdamage as the healing period progressed and found that four weeks of healing were necessary for the microdamage to be repaired [ 29 ].…”

“…A relationship between the diameter of an MI and the emergence of microcracks after installation has been reported in previous studies, although no consensus has been reached. Other studies have demonstrated different dynamics of microcrack generation in a range of installation methods including self-drilling, self-tapping, and pilot drilling installation [ 19 , 20 ].…”

The effect of mini-implant design on peri-implantitis and pain level after insertion in orthodontic treatment: A prospective clinical study

“…11 Inflammation of soft tissues around the head of miniimplant is common and may lead to loss of clinical stability. [5][6][7][8][9][10][11] The main action to prevent periimplantitis is mini-implant insertion through firm attached gingiva. 2,15 Other factors related to inflammation are root contact during insertion, orthodontic auxiliaries attachment and oral hygiene.…”

“…However, no clear evidence is available in this respect. [6][7][8][9][10] Although clinical features and adverse effects of dental implants (e.g. peri-implantitis and pain) have been investigated extensively, lack of sufficient evidence still exists for orthodontic mini-implants.…”