The rate and the type of orthodontic tooth movement is influenced by bone turnover in a rat model.
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The influence of bone metabolism on both the rate and the type of orthodontic tooth movement was investigated. A rat model in which high (n = 16) and low (n = 17) bone turnover was pharmacologically induced was used. A non-pharmacologically treated group (n = 19) served as the control. A mesially directed constant single force of 25 cN was applied to the upper left first molar for a period of 3 weeks. The study was performed as a split-mouth design, the contralateral side of each animal serving as its control. The displacement of the molar crown was measured with an electronic calliper, while changes in inclination of the teeth were measured from micro-CT scans of the excised maxillae. The bone turnover significantly affected the rate of tooth movement. In the case of high turnover, the rate of tooth movement was increased while it was reduced in the case of low turnover. A controlled mesial tipping in all three groups was observed, but the actual location of the centre of rotation seemed to be influenced by the metabolic state of the bone. Based on the results it can be concluded that deviations in bone turnover influence the response to orthodontic forces, and should be taken into consideration when planning orthodontic treatment in patients with metabolic bone disease or those on chronic medication influencing bone metabolism. (+info)
Three-dimensional changes in the position of unopposed molars in adults.
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The aim of this study was to longitudinally examine, in adults, changes of position in the three dimensions of maxillary molars unopposed for more than 10 years. Twelve healthy mature adults (six males, six females; mean age 45 years 11 months) with unopposed molars were followed-up for a mean period of 10 years 7 months. Plaster casts were made at the first and last examination. The patients presented 22 unopposed maxillary molars at both recordings and 14 posterior teeth with antagonists, at least one in each subject, without significant modifications during the study period. On three-dimensional scanned plaster casts, changes in the centroid of the occlusal surface were measured in the three dimensions. The changes observed on both occasions were compared with a t-test. Vertical displacement of unopposed molars [0.8 mm, standard deviation (SD) 0.65 mm] and controls (0.4 mm, SD 0.2 mm) was noted. The unopposed teeth overerupted more than the controls (P +info)
Evaluation of changes in the vertical facial dimension with different anchorage systems in extraction and non-extraction subjects treated by Begg fixed appliances: a retrospective study.
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The aim of the study was to evaluate and compare the effects of mesial movement of the maxillary and mandibular molars on the facial vertical dimensions following orthodontic treatment. Patients with an Angle Class I malocclusion were treated by four first premolar extractions and Begg fixed appliances (moderate and maximum anchorage groups), while those with an Angle Class II malocclusion were treated by Begg intraoral distalization mechanics without extractions (distalization group). Following treatment, the patients were grouped according to the mesial movement of the mandibular first molars and compared with an Angle Class I control group. All groups comprised 15 patients, their mean pre-treatment ages were 14.95 years for the moderate (13 females, 2 males), 14.88 years for the maximum (13 females, 2 males), 14.41 years for the distalization (10 females, 5 males), and 14.38 years for the control (13 females, 2 males) groups. Lateral cephalometric measurements were performed at two time points (T(1): pre-treatment/control, T(2): post-treatment/control). A paired t-test was used for within-group comparisons and non-parametric Kruskal-Wallis and Dunn's multiple-comparison tests to determine any differences. The increases in anterior and posterior face heights were similar between groups. The mandibular plane angle (SN/GoGn) was increased in all treatment groups, while it decreased in the control group. Although SN/GoGn increased more in the distalization and less in the moderate anchorage groups, these differences were not statistically significant. The change in SN/GoGn was significantly different only between the distalization and control groups. Facial vertical dimensions were not significantly affected by the amount of mesial movement of the molar teeth. (+info)
A randomized clinical trial to compare the Goshgarian and Nance palatal arch.
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Treatment changes in Class I and mild Class II malocclusions using the en masse removable appliance.
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The aim of this retrospective study was to examine the dental changes which occurred during buccal segment retraction in 39 subjects considered suitable for treatment with headgear to the maxillary dentition. Initially, a removable en masse appliance was fitted to distalize the buccal segments. Once the molar relationship was corrected, fixed appliances were placed for upper arch consolidation and/or alignment. Only five subjects required lower appliance therapy. Twenty-nine individuals had upper second molars extracted as an adjunct to treatment: in the remaining 10 patients these teeth were left in situ. Corresponding lower second molars were extracted in 19 children, whilst 20 pairs of teeth were not removed. Measurements were made at the start of treatment, the completion of buccal segment retraction, and when active treatment was complete. After the first stage, molars and premolars had been retracted nearly 4 mm, whilst the canines showed 2 mm spontaneous distal drift. The inter-molar width had increased by 4 mm and arch perimeter by 5 mm. There was a 5 per cent reduction in crowding. Spontaneous changes were also seen in the lower arch, despite the absence of any therapy. Crowding was slightly improved and inter-molar width increased, apparently as a response to the expansion in the opposing jaw. At the end of treatment, upper arch retraction and expansion were reduced as the teeth were integrated with the lower dentition: the canines required less than 1 mm further retraction. In the lower arch, the expansion of the molars was essentially stable. The extraction of upper second molars did not appear to influence the outcome of treatment. Although slightly more movement appeared to occur in the extraction group, few measurements showed statistical significance. (+info)
Third molar impaction in extraction cases treated with the Begg technique.
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The aim of this study was to investigate the differences between two groups of patients with either erupted or impacted mandibular third molars before and after orthodontic treatment. All patients were treated with Begg appliances following extraction of the four first premolars. The erupted group consisted of 14 subjects and the impacted group 13 subjects. Lateral cephalometric films, peri-apical radiographs, orthopantomographs and orthodontic casts of each subject were taken before and after treatment. Thirteen measurements were carried out on the lateral cephalometric radiographs. The results revealed slightly more vertical growth and a smaller mandibular arc angle in the erupted group at pre-treatment, and also a more upright lower third molar position and slightly greater distance between the distal point of the lower second molars and the centre of ramus (Xi) in the same group. In the course of treatment, mandibular third molars seemed less likely to erupt when the condyle grew vertically. The lesser resorption on the anterior border of the ramus might have played a part in this finding. In addition, a greater mesial inclination of the mandibular third molars might be an indication of the tendency for these teeth to be impacted in the present study. (+info)