Primary Stability Of Miniscrews Research Articles

Diode Laser Irradiation Effects on Miniscrew Stability and IL-1β and TGF-β1 Levels: A Split-Mouth Randomized Controlled Clinical Trial

Introduction: This study aimed to assess the effect of low-level laser therapy (LLLT) on miniscrew stability and concentrations of interleukin-1β (IL-1β) and transforming growth factor-beta (TGF-β1) in peri-miniscrew crevicular fluid in the course of orthodontic treatment. Methods: This randomized split-mouth double-blind clinical trial evaluated 18 patients requiring anterior retraction along with maximum anchorage. Miniscrews were placed between the maxillary second premolar and first molar. A diode laser was irradiated with a 980-nm wavelength and 100-mW output power in continuous-wave mode at four time points: T0 (1 hour after miniscrew placement), T1 (1 week later), T2 (at 1 month) and T3 (at 3 months) in one quadrant of the maxilla (laser group). The other quadrant of the maxilla underwent the pseudo-application of the laser (control group). The primary stability of miniscrews was measured by Periotest M and reported as Periotest value (PTV). Also, at each time point, samples were collected from the peri-miniscrew crevicular fluid one hour after laser irradiation to assess the concentration of IL-1β and TGF-β1. Results: The mean PTV (inverse of the stability) was smaller in the laser group compared with the control group at all time points; this difference was significant at T2 and T3. The mean concentration of IL-1β in the laser group was lower than that in the control group at all time points, and this difference was significantly remarkable at T0 and T3. The mean concentration of TGF-β1 in the laser group was lower than that in the control group at T0, T1 and T3; however, the difference was not statistically significant. Conclusion: The current results supported the efficacy of LLLT in increasing the miniscrew stability and decreasing the level of IL-1β pro-inflammatory cytokine.

Evaluation of Cortical Bone Microdamage and Primary Stability of Orthodontic Miniscrew Using a Human Bone Analogue.

Orthodontic miniscrews have gained popularity; however, they have some drawbacks, including screw loosening that results from bone resorption caused by excess microdamage created during screw insertion. Pilot hole preparation through the cortical bone is considered beneficial to avoid such microdamage, while an overly large pilot hole impairs primary stability. Hence, we used a human bone analogue to evaluate the microdamage and primary stability to estimate the optimal pilot hole size that would minimize the screw loosening risk. Ti6Al4V orthodontic miniscrews and 1.0-mm-thick synthetic cortical bone pieces were prepared. Various compressive loads were applied in indentation tests to test pieces’ surfaces, and the microdamaged areas were confirmed as stress-whitening zones. Screw insertion tests were performed in which a miniscrew was inserted into the test pieces’ pilot hole with a diameter of 0.7–1.2 mm in 0.1-mm intervals, and the stress-whitening area was measured. The insertion and removal torque were also measured to evaluate primary stability. The stress-whitening areas of the 1.0–1.2 mm pilot hole diameter groups were significantly smaller than those of the other groups (p < 0.05), whereas the 0.9 and 1.0 mm pilot hole diameter groups showed higher primary stability than other groups. In conclusion, the bone analogue could be utilized to evaluate microdamage in cortical bones and the primary stability of miniscrews.

The effect of cortical bone thickness on the primary stability of miniscrews, using CBCT (Cross-sectional clinical trial)

Objectives: The aim of the present study was to determine the correlation between the thickness of both cortical bone thickness, total bone thickness and the primary stability of mini-implants. Methods: Twenty-six mini-screws (Absoanchor) were inserted into the buccal alveolar bone between the roots of the second premolar and first molar on the right and left side of the patient. The mobility of the mini-screws was clinically assessed using the periotest device and the buccal cortical bone thickness of the maxilla was measured on the right and left side in the inter-radicular area between the second premolar and first molar at the site of the miniscrew insertion. The patient’s head was oriented in all 3 spatial planes by adjusting the Frankfort plane horizontal and the orbital plane parallel to the floor. Results: There was a statistical significant differences between mean measurements of the cortical bone thickness penetrated by the mini-screw and the negative stability scores. (P=0.03) Conclusions: There was a weak correlation between the primary stability of the mini-screw and the cortical bone thickness. However, a minimum thickness of 1.0 mm cortical bone thickness is necessary for adequate stability.

In-vitro impact of insertion angle on primary stability of miniscrews.

The use of miniscrews as anchorage has become increasingly popular, but there is no consensus on the best insertion angle. The purpose of this study was to determine the impact of insertion angle on implant primary stability. Sixty-four miniscrews, 6×1.6mm, were placed in 64 fresh bone segments from 32 sheep mandibles. The miniscrews were inserted into the bone surface at 4 angles: 30°, 45°, 60°, and 90°. The maximum resistance forces of miniscrews in pullout and shear tests were determined as primary stability using a universal testing machine. In the pullout tests, the 90° insertion angle had the highest primary stability. Oblique angulations of the miniscrews resulted in lower resistance. In the shear tests, angulations of the miniscrews from 90° to 45° led to increased primary stability. A more oblique insertion (30°) resulted in reduced primary stability. The direction of the applied force had a significant impact on the primary stability of miniscrews at various insertion angles. The highest primary stability values were achieved at 45° when the miniscrews were loaded by shear force and at 90° when pullout force was applied.

Buccal cortical bone thickness at miniscrew placement sites in patients with different vertical skeletal patterns

Cortical bone thickness plays an important role in the primary stability of miniscrews. The purpose of this study was to evaluate the buccal cortical bone thickness in adolescent subjects with different vertical skeletal patterns using cone-beam computed tomography (CBCT). We examined the CBCT images of 75patients (30males, 45females; mean age 16.5years; range 15.3-17.7years) in the present study. High-, average- and low-angle subgroups were generated according to SN-GoMe angle. On volumetric images, we measured the buccal cortical bone thickness from canine to the second molar teeth at heights of 5, 7 and 9mm from cemento-enamel junction (CEJ). For statistical evaluation, the Wilcoxon signed rank, Kruskal-Wallis and Tukey HSD tests were applied at the p < 0.05 level. Buccal cortical bone was thickest in the low-angle group. We observed statistically significant differences in the maxilla between the high- and low-angle groups at all levels. In the mandible, we noted statistically significant differences between high-angle and low-angle groups in the canine-first premolar regions at heights of 5 and 7mm, and in the second premolar-first molar region at 7mm height from CEJ. Significant differences were also present between the first and second premolars at heights of 7 and 9mm. Average cortical bone thickness ranged from 1.10-1.37mm in the maxilla and 1.20-3.28mm in the mandible for all groups. Buccal cortical bone thickness in adolescents varied in different vertical skeletal patterns and was greater in the mandible than in the maxilla, with the distance increasing from the CEJ to the apex. As the buccal cortical bone is thinner in high-angle patients, patient-specific measures should be taken when performing miniscrew treatment.