A prospective clinical trial of the effects produced by the extrusion arch in the treatment of anterior open bite

Effect of occlusal hypofunction on centre of resistance in maxillary central incisor using the finite element method

OBJECTIVES

To determine differences in the location of centre of resistance (Cres) between functional and hypofunctional teeth and to evaluate the relationship between the pulp cavity volume and locations of the Cres, using the finite element (FE) method.

DESIGN

Retrospective cohort study.

PARTICIPANTS

FE models of right maxillary central incisor, derived from cone-beam computed tomography (CBCT) images of 46 participants, were divided into normal function (n = 23) and hypofunction (n = 23) groups using anterior overbite and cephalometric measurements.

METHODS

Measurements of the tooth and pulp cavity volume were made from the CBCT. Cres levels were presented as percentages of the root length from the root's apex. All data were analysed and compared using the independent t-test (P < 0.05). The relationship between the location of Cres and volume ratios were evaluated statistically.

RESULTS

The means of the pulp cavity/tooth volume and root canal/ root volume ratio of the maxillary central incisor in the anterior open bite group were significantly greater than those in the normal group. The average location of Cres in the anterior open bite group was 0.6 mm (3.7%) apically from the normal group, measured from root apex. The difference was statistically significant (P < 0.01). There was a significant correlation between root canal/root volume ratio and locations of Cres (r = -0.780, P < 0.001).

CONCLUSIONS

The Cres in the hypofunctional group was located more apical than the functional group. As the pulp cavity volume increased, the level of Cres shifted apically.

Dentoalveolar effects of skeletally anchored extrusion arch in anterior open bite patients: A prospective clinical trial

OBJECTIVE

The purpose of this prospective clinical trial was to explore the dental and soft tissue changes accompanying the use of skeletally anchored nickel-titanium (NiTi) extrusion arch in the correction of anterior open bite (AOB).

MATERIAL AND METHODS

Twenty female patients with a mean age of 16.5 ± 1.5 years and a mean dentoalveolar AOB of 2.38±0.7 mm participated in this study. All patients were treated with an maxillary 0.017×0.025-in NiTi extrusion arch, with the aid of miniscrews inserted between the maxillary second premolars and first molars bilaterally, to act as indirect anchorage. Three-dimensional digital models and lateral cephalometric radiographs were taken just before the insertion of the extrusion arch (T0) and after 10 months (T1). Paired-sample t-tests were used in analyzing the data, to evaluate the changes after treatment (T1-T0). A significance level of p < 0.05 was used.

RESULTS

AOB was successfully closed in all patients, with a 4.35 ± 0.61 mm increase in the overbite. Maxillary incisors significantly extruded (2.52 ± 1.02 mm) and significantly reclined (5.78 ± 0.77°), with a resultant decrease in the overjet of 1.58 ± 0.5mm. A significant intrusion of maxillary first molars with no change in their inclination was observed. The upper lip showed a significant retraction tendency to the E-plane, and a significant increase in the nasolabial angle was observed.

CONCLUSION

The skeletally anchored NiTi extrusion arch was an effective technique in treating AOB, with no adverse effects on the molars.

Stability of anterior open bite cases treated with upper and lower extrusion arches in adults: a follow-up study

OBJECTIVES

To investigate the post-treatment stability of anterior open bite (AOB) cases treated with upper and lower extrusion arches in adults.

MATERIALS AND METHODS

23 patients with AOB were treated with extrusion arches and evaluated for dentoskeletal changes using lateral cephalometric radiographs before treatment (T0), after treatment (T1), and 12 months post-treatment (T2). Patients received bondable tongue spurs and vacuum-formed retainers as post-treatment retention/stability measures for 12 months. Post-treatment stability was further assessed qualitatively by the Photographic Openbite Severity Index.

RESULTS

All the cases showed positive overlap between the anterior teeth at the end of orthodontic treatment, and 20 of 23 treated patients attended the recall visit after 12 months. A total of 85% of the cases maintained positive overlap at least 1 year post-treatment, 10% showed edge-to-edge bite, and only 5% showed no overbite.

CONCLUSIONS

Treatment of AOB in adults with extrusion arches proved to be stable 1 year post-treatment. Changes in the overbite after 1 year of follow-up were not significant.

Effect of maxillary and mandibular extrusion arches on dentoskeletal changes in adults with anterior open bite: a quantitative analysis

OBJECTIVE

To quantify dentoskeletal changes accompanying the use of extrusion arches during the treatment of anterior open bite (AOB) in adults.

MATERIALS AND METHODS

A total of 23 adult patients with an AOB of -3.05 mm ± 1.27 mm were treated with upper and lower extrusion arches after the alignment phase. Lateral cephalograms were taken before placement of the extrusion arch, immediately after closure of the open bite (T2), and at the end of orthodontic treatment (T3). Data were statistically analyzed using repeated-measures analysis of variance and the Bonferroni post hoc test for pairwise comparisons (α = 0.05).

RESULTS

Successful closure of AOB, with an overall change in overbite of 4.73 ± 1.93 mm, was achieved in an average of 3.8 months and remained stable at T3. Upper and lower incisors were significantly extruded by 2.05 mm ± 0.72 mm and 2.54 mm ± 1.63 mm, respectively, and significantly retroclined by 6.36° ± 1.63° and 8.45° ± 3.83°, respectively, with a resultant increase in the interincisal angle of 12.80° ± 2.09°. Statistically significant intrusion and mesial tipping (P < .001) of the maxillary and mandibular first molars were observed at T2. Dentoskeletal changes remained stable at T3, except for a significant reduction of the mesial tipping of the maxillary and mandibular first molars.

CONCLUSIONS

The combined use of maxillary and mandibular extrusion arches resulted in significant favorable dentoskeletal changes that led to the successful closure of AOB during a short duration of treatment.