Is it possible to re-use mini-implants for orthodontic anchorage? Results of an in vitro study

The aim of this study was to compare the surface morphology and fracture torque resistance of as-received, sterilized and retrieved mini-implants in order to evaluate the fracture risks of re-using orthodontic mini-implants after sterilization. Thirty mini-implants retrieved from 19 patients, twenty as-received and twenty autoclaved mini-implants from the same manufacturer were used in this study. Ten samples from each group were analyzed by scanning electron microscopy and the remaining specimens were tested for their fracture torque resistance. Results were statistically analyzed using one-way ANOVA. No defects or corrosion could be identified in autoclaved and retrieved mini-implants, but a worn surface and scratch marks could be observed on the retrieved ones. A statistical significant difference in the fracture torque was observed between the as-received and the retrieved groups. Re-use of retrieved mini-implants should not be recommended because their torque resistance is reduced. As-received mini-implants submitted to autoclave sterilization can be recommended to be used clinically

Facial profile esthetic preferences: perception in two Brazilian states

OBJECTIVE: The aim of this study was to assess the regional influence on the perception of facial profile esthetics in Rio de Janeiro state (RJ) and Rio Grande do Sul state (RS), Brazil. METHODS: Two Caucasian models, a man and a woman, with balanced facial profiles, had their photographs digitally manipulated so as to produce seven different profiles. First year dental students (laypeople) assessed the images and classified them according to their esthetic preference. RESULTS: The result of the t test for independent samples showed differences among states for certain facial profiles. The female photograph identified with the letter 'G' (mandibular retrusion) received higher scores in RS state (p = 0.006). No differences were found for male photographs (p > 0.007). The evaluators' sex seemed not to influence their esthetic perception (p > 0.007). Considering all evaluators together, ANOVA/Tukey's test showed differences among the profiles (p ≤ 0.05) for both male and female photographs. The female photograph that received the highest score was the one identified with the letter 'F' (dentoalveolar bimaxillary retrusion/ straight profile). For the male profiles, photograph identified with the letter 'E' (dentoalveolar bimaxillary protrusion/ straight profile) received the best score. CONCLUSION: Regional differences were observed regarding preferences of facial profile esthetics. In Rio de Janeiro state, more prominent lips were preferred while in Rio Grande do Sul state, profiles with straight lips were favored. Class III profiles were considered less attractive

Maxillary dentoalveolar assessment following retraction of maxillary incisors: a preliminary study

ABSTRACT Objective: The aim of this preliminary study was to assess changes in tooth length and alveolar thickness following retraction of maxillary incisors. Methods: A total of 11 patients presenting severe maxillary dentoalveolar protrusion revealed by initial (T1) cone-beam computed tomography (CBCT), and whose treatment plan included extraction of maxillary first premolars and retraction of maxillary incisors, were selected and submitted to CBCT examination one month after the end of incisors retraction (T2). The premaxilla was assessed through seven axial slices by means of Dolphin ImagingTM software. In each of these slices, five measurements of the distance from the buccal cortical bone to the palatal cortical bone were performed. Tooth length of maxillary incisors (n = 44) was also measured in sagittal slices. Measurements were repeated after a two-week interval, and intraclass correlation coefficient (ICC) was used to test examiner calibration. Wilcoxon test was used to detect differences in measurements performed at the two time intervals. Results: The ICC was satisfactory for tooth length (0.890) and for premaxilla alveolar thickness measurements (0.980). Analysis of data showed no statistically significant differences (p > 0.05) in tooth length or alveolar thickness between the two-time intervals assessed. Conclusion: The force used in retraction of maxillary incisors in this research did not promote significant changes in tooth length of maxillary incisors or in premaxilla alveolar thickness

Stability of smooth and rough mini-implants: clinical and biomechanical evaluation - an in vivostudy

Objective: To compare in vivo orthodontic mini-implants (MI) of smooth (machined) and rough (acid etched) surfaces, assessing primary and secondary stability.Methods:Thirty-six (36) MI were inserted in the mandibles of six (6) dogs. Each animal received six (6) MI. In the right hemiarch, three (3) MI without surface treatment (smooth) were inserted, whereas in the left hemiarch, another three (3) MI with acid etched surfaces (rough) were inserted. The two distal MI in each hemiarch received an immediate load of 1.0 N for 16 weeks, whereas the MI in the mesial extremity was not subject to loading. Stability was measured by insertion and removal torque, initial and final mobility and by inter mini-implant distance.Results:There was no statistical behavioral difference between smooth and rough MI. High insertion torque and reduced initial mobility were observed in all groups, as well as a reduction in removal torques in comparison with insertion torque. Rough MI presented higher removal torque and lower final mobility in comparison to smooth MI. MI did not remain static, with displacement of rough MI being smaller in comparison with smooth MI, but with no statistical difference.Conclusions:MI primary stability was greater than stability measured at removal. There was no difference in stability between smooth and rough MI when assessing mobility, displacement and insertion as well as removal torques

Influence of cortical thickness on the stability of mini-implants with microthreads

The objective of this study was to assess the influence of cortical thickness and bone density on the insertion torque of a mini-implant (MI) with microthreads. Mini-implants with lengths of 6 and 8 mm in the active part were inserted into synthetic bone blocks (polyurethane resin). The density of these blocks was 20 pounds per cubic foot (pcf), simulating bone marrow, and that of blocks 1, 2, and 3-mm-thick blocks was 40 pcf, simulating cortical bone. Blocks with uniform density of 40 pcf were also used to simulate bone areas of greater density. Insertion torque was quantified with a universal testing machine (EMIC). For both MIs, increasing insertion torque was associated with increasing cortical bone thickness. For the same MI length, significant differences were observed among all assessed groups. The insertion torque of the 6-mm-long MI inserted in a 3-mm-thick cortical bone was equivalent to that of the 8-mm-long MI inserted in a 1-mm-thick cortical bone. MIs inserted in bone blocks of greater density presented insertion torque values almost twice as high as those in other groups. The shorter MI, the lower the insertion torque, and the greater the cortical bone thickness, the greater the insertion torque. To minimize fracture risk, the size of MI should be selected according to the insertion site