The aim of this study was to examine peri-implant stresses around orthodontic micro implants upon torque-tightening and static load application by quasi-three-dimensional photoelastic stress analysis. Self-tapping orthodontic micro implants were progressively inserted into photoelastic models at 30, 45, 70, and 90 degrees and insertion torques were measured. Stress patterns (isochromatic fringe orders) were recorded by the quasi-three-dimensional photoelastic method using a circular polariscope after insertion and 250 g static force application. Torque-tightening of implants generated peri-implant stresses. Upon insertion, 90 degree placed implants displayed the lowest and homogeneous stress distribution followed by 30, 70, and 45 degree tilted implants. Static loading did not dramatically alter stress fields around the implants tested. The highest alteration in stress distribution was observed for the 90 degree placed implant, while 70 degree tilted implant had the lowest stresses among tilted implants. Torque-tightening of orthodontic micro implants creates a stress field that is not dramatically altered after application of static lateral moderate orthodontic loads, particularly at the cervical region of tilted implants.
This study evaluates the skeletal and dental effects of a mini-implant supported maxillary expansion (MISME) appliance that applied forces directly to the maxilla. Materials and Method: Records of 9 patients (5 female and 4 male patients; mean age = 12 years 8 months) with indications of maxillary expansion were included in this study. After insertion of four miniscrews (1.6 mm in diameter, 7 mm in length), an acrylic expansion device was bonded on the screws. Two miniscrews were placed in the anterior palate bilaterally, 3-4 mm lateral to the suture and 3-4 mm posterior to the incisive foramen. Two miniscrews were placed bilaterally between the second premolar and first molar roots in the palatal alveolus. The MISME appliance was activated with a semi-rapid protocol until the desired expansion was achieved. The average treatment duration was 97.1 6 62.2 days. Measurements from cephalometric, posteroanterior radiographs and dental casts taken before and after expansion were evaluated statistically. The nonparametric Wilcoxon test was used for not normally distributed parameters (i.e., Nperp-A), and the parametric paired t test was performed for normally distributed parameters. A finding of p , 0.05 was considered to be statistically significant. Results: Forward movement of the maxilla (p,0.05) as well as an increase in nasal and maxillary skeletal and dental widths (p,0.001) were observed in the sample group. Maxillary intermolar, intercanine, and palatal widths also increased (p,0.001) without buccal tipping of molars. A slight posterior rotation of the mandible was seen. Dentoalveolar measurements did not show any significant changes. Conclusion: The MISME appliance showed successful expansion of the maxilla without such side effects as buccal tipping of molars and bite opening. This appliance, which provides parallel expansion, can be a simple and economic alternative to transpalatal distraction.
The effect of metallic fixation on growth is a major concern in children and is not yet clear. The aim of this study was to evaluate the effect of metallic fixation of mandibular symphyseal fracture on mandibular growth.Eighteen 90-day-old growing white New Zealand rabbits weighing 1.6 to 2.5 kg were included in this study and divided into 2 groups of 9 subjects. In the experimental group, animals underwent mandibular osteotomy, simulating a symphyseal fracture on the midline of mandibular symphysis. The bone segments were fixed with microplates and microscrews (1.6 mm).In the control group, the same surgical incision without performing symphyseal osteotomy was conducted, and 2 screws were inserted on each side of the symphyseal midline.Digital cephalometric and submentovertex radiographs were taken before the operation and at postoperative 6 months for each animal in 2 groups, and cephalometric measurements were performed. The distance between the centers of the head of 2 screws measured at the end of surgery in the control group was compared with measurements at 6 months after surgery. Obtained data were statistically analyzed.There is no statistically significant difference between the 2 groups for growth amount of both sides of the mandible. Difference of ANS-Id (the most anterior points of nasal bone, the most anterior point on the alveolar bone between the lower incisors) and Cd-Id (the uppermost and most distal point of the mandibular condyle, the most anterior point on the alveolar bone between the lower incisors) values of the 2 groups is not statistically significant (P > 0.05).The distance between the 2 screws at the first application significantly increased at the postoperative sixth month (P < 0.05). Metallic fixation of mandibular symphyseal fracture does not affect the vertical and sagittal mandibular growth in growing rabbits.
Vertically aligned and 30- to 40-degree angulated immediate orthodontic microimplants are associated with low amplitude strains upon torque tightening and orthodontic loading.
Objective: To determine the nasal soft-tissue profile changes in skeletal Class III patients who underwent maxillary or bimaxillary orthognathic surgery. Materials and Method: This clinical retrospective study consists of 40 patients (19 male and 21 female) who had undergone orthognathic surgery. All patients received single jaw maxillary (9 patients) or bimaxillary surgery (31 patients). Standardized lateral cephalograms obtained before operation and at least 6 months after the operation were used. Twelve measurements (4 skeletal and 8 soft-tissue measurements) were made. The distributions of the variables were checked by Shapiro-Wilk test. Paired-samples t test was used for parametric data and Wilcoxon sign rank test for nonparametric data, to analyze the differences between pre-and postoperative measurements. Results: After orthognathic surgery, SNA and ANB increased; SNB decreased significantly. A significant reduction in nasofrontal angle, TH-Prn, and nasal tip projection and a significant increase in nasofacial angle were found. In addition, superior movement of the nasal tip was found, and as a result, the nasal hump decreased. The N-Sn/Pr ratio, nasal tip angle, and nasolabial angle did not show any significant changes. Conclusion: It can be concluded that more vertical nasal changes rather than sagittal nasal changes are observed after maxillary surgery.
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