En-masse retraction of maxillary anterior teeth with clear aligner: A finite element analysis / 实用口腔医学杂志

Objective:To investigate the stress distribution and the initial displacement of maxillary anterior teeth during en-masse retraction with clear aligner.Methods:The initial 3D finite element model of the maxillary teeth,PDL and alveolar bone was constructed by CBCT image reconstruction technique.Laser scanned image of crowns was merged with initial 3D model.The stress distribution and the initial displacement were analyzed by ANSYS Workbench when aligner was loaded.Results:The high simulation maxillary complex was constructed.Distal and lingual crown tipping of central incisors and lateral incisors were observed.The tendency of extrusion of the central and lateral incisors was consistant.The same tendency of stress distribution in PDL and initial displacement was appeared on incisors.The distal tipping movement was occurred on canine.Conclusion:Tipping movement along with extrusion can be produced by maxillary anterior teeth during en-rnasse retraction in extraction treatment with clear aligner.

Histologic assessment of the biological effects after speedy surgical orthodontics in a beagle animal model: a preliminary study / 대한치과교정학회지

OBJECTIVE: Speedy surgical orthodontics (SSO), an innovative orthodontic treatment, involves the application of orthopedic forces against temporary skeletal anchorage devices following perisegmental corticotomy to induce movement of specific dental segments. Herein, we report the biological effects of SSO on the teeth and periodontal structures. METHODS: Five beagle dogs were divided into 2 groups and their 6 maxillary incisors were retracted en masse by applying 500 g orthopedic force against a single palatal mini-plate. Retraction was performed without and with perisegmental corticotomy in groups I and II, respectively. All animals were killed on the 70th day, and their periodontal structures were processed for histologic analyses and scanning electronic microscopy (SEM). The linear distance between the third maxillary incisor and canine was used as a benchmark to quantify the retraction amount. RESULTS: Retraction was markedly faster and retraction amount greater in group II than in Group I. Surprisingly, Group II did not show any root resorption despite extensive retraction, while Group I showed prominent root surface irregularities. Similarly, SEM showed multiple resorption lacunae in Group I, but not in Group II. CONCLUSIONS: SSO is an effective and favorable orthodontic approach for major en masse retraction of the maxillary anterior teeth.

Severe bidentoalveolar protrusion treated with lingual Biocreative therapy using palatal miniplate / 대한치과교정학회지

This case report describes the treatment of a 23-year, 8-month-old female patient with a Class II malocclusion who showed severe bidentoalveolar protrusion and anterior crowding. The treatment plan consisted of extracting all the first premolars, decrowding and en masse retraction of the upper six anterior teeth and lower anteriors. The upper C-plate placed in the midpalatal area combined with lingual sheath fixtures were used as substitutes for posterior anchorage teeth during upper anterior retraction. Preadjusted brackets (0.022-inch) were used for upper anterior decrowding. A 0.9 mm diameter stainless steel lever-arm soldered to the main arch wire facilitated controlled retraction of upper anteriors. The upper and lower dentition was detailed using a tooth positioner during the finishing stage. Correct overbite and overjet were obtained by decrowding and retraction of the upper six anterior teeth into their proper positions. Use of the C-plate and lingual appliances provided ideal anchorage to enhance the improvement in facial balance. The active treatment period was 19 months. The treatment result was stable 13 months after debonding.

Factors influencing the axes of anterior teeth during SWA en masse sliding retraction with orthodontic mini-implant anchorage: a finite element study / 대한치과교정학회지

OBJECTIVE: With development of the skeletal anchorage system, orthodontic mini-implant (OMI) assisted en masse sliding retraction has become part of general orthodontic treatment. But compared to the emphasis on successful anchorage preparation, the control of anterior teeth axis has not been emphasized enough. METHODS: A 3-D finite element Base model of maxillary dental arch and a Lingual tipping model with lingually inclined anterior teeth were constructed. To evaluate factors influencing the axis of anterior teeth when OMI was used as anchorage, models were simulated with 2 mm or 5 mm retraction hooks and/or by the addition of 4 mm of compensating curve (CC) on the main archwire. The stress distribution on the roots and a 25000 times enlarged axis graph were evaluated. RESULTS: Intrusive component of retraction force directed postero-superiorly from the 2 mm height hook did not reduce the lingual tipping of anterior teeth. When hook height was increased to 5 mm, lateral incisor showed crown-labial and root-lingual torque and uncontrolled tipping of the canine was increased. 4 mm of CC added to the main archwire also induced crown-labial and root-lingual torque of the lateral incisor but uncontrolled tipping of the canine was decreased. Lingual tipping model showed very similar results compared with the Base model. CONCLUSION: The results of this study showed that height of the hook and compensating curve on the main archwire can influence the axis of anterior teeth. These data can be used as guidelines for clinical application.

A comparison of en masse retraction of six anterior teeth with separate canine retraction / 대한치과교정학회지

The purpose of this study was to compare en masse retraction of six anterior teeth with separate canine retraction in the amount of the anchorage loss and the retraction of the anterior teeth. The subjects consisted of 30 adult female patients with Angle Class I malocclusions who were treated by .022" straight wire appliance with 4 first premolar extraction. They were composed of two groups. Group 1 consisted of 15 subjects, whose six anterior teeth were retracted by en masse retraction. Group 2 consisted of 15 subjects, whose canines were retracted separately. Pre-treatment and post-treatment lateral cephalometric radiographs were analyzed. All data were processed statistically with independent samples t-test, and the conclusions were as follows. 1. There was no significant difference in the amount of the anchorage loss between two groups(p>0.05). 2. There was no significant difference in the amount of the retraction of the anterior teeth between two groups(p>0.05). 3. There was a significant difference in the amount of the inclinational change of the upper incisors between two groups. It was greater in Group 2. 4. There was a significant difference in the vertical positional change of the upper incisal edges between two groups. The upper incisal edges in Group 2 were more extruded than Group 1 by about 1 mm. 5. There was no significant difference in the vertical positional change of the root apex of the upper incisors between two groups(p>0.05). And there was no significant difference in the vertical positional change of the upper molar(p>0.05).

A Cephalometric study on tooth movement pattern of maxillary 6 anteriors with double keyhole loops / 대한치과교정학회지

The present study hypothesized that the double keyhole looped archwire plays a positive role for the sake of translatory movement and/or controlled tipping of upper 6 anteriors, and secures anchorage control as well. The purposes of the study were to evaluate the changes in lateral cephalograms during orthodontic treatment with DKHLs and to compare the skeletal & dental changes before- & after-treatment. The materials of this study were lateral cephalograms of 20 adult patients with upper dentoalveolar protrusion both in class I and in class II Division 1 malocclusion. Lateral cephalograms were taken before and after orthodontic treatment with upper 1st bicuspid extraction and DKHLs. The results were obtained as follows: 1. There were no statistically significant differences in skeletal measurement except SNB and PTFH between before- & after-treatment. The major changes were in dentoalveolar region. 2. After treatment, there were statistically significant decrease in dental measurement except interincisal angle. 3. Both upper & lower lip protrusion was decreased. 4. There were statistically differences in upper anterior crown horizontal & root vertical dimension(7.08+/-2.14 mm, 2.38+/-1.15 mm, p<0.01). 5. There were statistically differences in upper posterior dental(both crown & root) horizontal dimension(2.48+/-0.99 mm, 2.05+/-0.91 mm, p<0.01).