Can Initial Torque Value Predict the Success of Orthodontic Mini-Screws?

Objective:To investigate the correlation between initial torque and removal torque of orthodontic mini-screws.Materials and Method:Sixty-four orthodontic mini-screws (measuring 1.5 × 4.4 mm, 1.6 × 4.7 mm, 1.7 × 5.5 mm, and 1.8 × 5.6 mm) were used. All mini-screws were inserted into the fibulas of 8 male rabbits. The initial torque values were immediately recorded using a digital torque gauge. For 2 months, 115 g force was applied to mini-screws inserted into the right fibula of the rabbits. The same procedure was followed for inserting the mini-screws into the left fibula of the rabbits but without applying any force. After 2 months, the removal torque values were recorded for all mini-screws. All statistical analyses were performed using SPSS version 14.0 for Windows. Spearman's correlation coefficient was used to analyze the relationships between initial and removal torque values.Results:Intragroup comparison of all brands of mini-screws showed similar features. There were no statistically significant differences between the initial torque values of all mini-screws (p > 0.05). The Spearman correlation coefficient showed that correlations between the initial and removal torque values were insignificant (p>0.05).Conclusion:The results of this study suggest that the initial torque value is not a reliable method for predicting the success of a mini-screw

Relationship between CBCT and panoramic images of the morphology and angulation of the posterior mandibular jaw bone

WOS: 000373692100007PubMed: 26370261We determined actual bucco-lingual angulation values and morphological variations of residual bone in the mandibular posterior edentulous region using cone-beam computed tomography (CBCT) and panoramic radiography. A second aim was to investigate whether it was possible to predict bone morphology from panoramic radiographs. Data were collected from 77 consecutive patients referred for both CBCT and panoramic radiography in our department. Two-dimensional and three-dimensional images of the probable implant placement region were investigated. The bucco-lingual angulation values and crest type were determined directly from the cross-sectional images of the posterior edentulous region. The edentulous region was divided into three groups: second premolar, first molar, or second molar region. The observations were evaluated by the computer software, SPSS 22.0 (SPSS Inc. Chicago, USA). The crest type was classified into three groups: type U, type C, or type P. Kappa statistics, Kolmogorov-Smirnov tests, ANOVA, and Kruskal-Wallis tests were used in statistical analyses. The significance level was set at p < 0.05. Type C was more frequent in the second premolar region and the crest type had changed to type U in the second molar region. The predictability of the type U was highest in the second molar region. Moderate agreement was found in the predictability of type U in the molars (kappa = 0.602). The mean value of bucco-lingual angulation was highest in the second molar region, followed by the first molar region. There were statistically significant differences between the bucco-lingual angulation of the crest types in the second premolar and first molar regions (p < 0.05). Bucco-lingual angulation values and morphology change through the posterior mandible. Type U was predicted at a higher rate in the second molar region from panoramic radiographs. These results demonstrate predicting high-risk areas in the posterior mandible for implant therapy from panoramic radiography

Histomorphometric Evaluation of the Effects of Various Diode Lasers and Force Levels on Orthodontic Mini Screw Stability

Objective: The purpose of this study was to evaluate the effects of different laser dose and force levels on the stability of orthodontic mini screws used for anchorage, by histomorphometric analyses. Background data: Low-level laser therapy speeds up blood flow, improves the mechanism of the revitalization processes, reduces the risk of infection, boosts metabolic activities, and accelerates the healing of the damaged tissue. Although there are many research studies about low-level laser therapy applications in a variety of areas, no investigations were found concerning mini screw stability using various laser dose levels with different force level applications. Methods: Seventeen New Zealand white rabbits were used. A total of 68 cylindrical, self-drilling orthodontic mini screws were threaded at the fibula. Experimental subjects were divided into six groups; force application was not performed in the first three groups, whereas 150g of force was applied via nickel-titanium closed-coil springs placed between two mini screws in the other three groups. Measurements of the initial torque values (10 Ncm) were manipulated by a digital portable torque gauge. Various low-level laser doses were applied to the groups during the postoperative 10 days. After 4 weeks, bone-to-implant contact and cortical bone thickness were histomorphometrically analyzed. Results: In the 150g force plus 20 J/cm(2) dosage group, the highest bone-to-implant contact values were observed. (p<0.05) There were no statistically significant correlations between cortical bone thickness and bone-to-implant contact values; on the other hand, no significant difference was found among the same groups in terms of cortical bone thickness values (p>0.05). Conclusions: Low-level laser therapy was noticed to induce the mini screw-bone contact area. Low-level laser therapy may be a supplementary treatment method to increase the stability of the orthodontic mini screw