Comparison of WALA ridge and dental arch dimensions changes after orthodontic treatment using a passive self-ligating system or conventional fixed appliance

Effect of time between archwire changes on intended dentoalveolar expansion in orthodontic patients treated with fixed appliances : A prospective controlled clinical trial

OBJECTIVE

To analyze the effects of the time span between archwire changes on the amount of transverse dental arch expansion. The design was a prospective, controlled clinical trial. Randomization was performed by computer-generated allocation tables.

METHODS

In all, 35 patients were evaluated in three groups treated with fixed appliances and the same four sequential leveling archwires, however, with different replacement periods: 28 days (4-week [4W] group), 56 days (8-week [8W] group), and 84 days (12-week [12W] group). Digital models were measured before the treatment (T0) and at the end of the evaluation period (T1) by a blinded operator with OrthoAnalyzer® software (3-Shape, Copenhagen, Denmark) and compared using MANOVA. A multiple linear regression was also used to evaluate the influences of age, initial dental crowding, incisor inclination, and facial pattern on the amount of expansion.

RESULTS

Mean expansion was 2.77 ± 0.84 mm (upper arch) and 3.12 ± 0.88 mm (lower arch) in the 12W group; 1.96 ± 0.82 mm and 2.27 ± 0.96 mm in the 8W group, and 1.11 ± 0.93 mm and 1.32 ± 0.91 mm in the 4W group, respectively for the upper and lower arches. The amount of expansion varied significantly between the groups in the area of the canines, first premolars, and second premolars for both arches. Expansion was less in older patients. Initial dental crowding, incisor inclination and facial pattern had no influence on dental expansion.

CONCLUSION

Longer time spans between archwire changes provided greater amounts of expansion, while age is inversely related, with younger patients expressing greater amounts of expansion. The results also suggest that the expansion provided by the fixed appliances is expressed mainly in the canine and premolar areas.

Wilson curve modification in permanent dentition: a retrospective comparison between clear aligners and continuous archwire treatment

OBJECTIVES

To evaluate leveling of the Curve of Wilson (COW) by two different treatment appliances (clear aligners [CA] and continuous archwire fixed appliances [FA]) in a permanent dentition sample of patients.

MATERIALS AND METHODS

Digital casts of 40 patients (CA group = 20 patients; FA group = 20 patients) were collected. Angular values for COW, right and left vertical height difference of lower first molars, and linear distance between lower teeth and the WALA ridge were analyzed for pre- (T1), posttreatment (T2) and on final virtual (ClinCheck) models (T2-CC) of the CA group. An unpaired t-test was used to evaluate significant intergroup differences (P < .05), while a paired t-test was used for posttreatment CA intragroup comparison.

RESULTS

FA group showed better control of second molar crown positions compared to CA group (47-WALA = -0.2 ± 0.1 mm, 37-WALA = -0.6 ± 0.3 mm). No significant difference was detected for linear distance of lower first molars and the WALA ridge or for vertical height difference. CA group showed a greater reduction of distance between lower premolars and the WALA ridge (mean difference: -0.5 mm for both 45-WALA and 35-WALA; mean difference: -0.5 mm for 44-WALA, -0.6 mm for 34-WALA). Predictability for the CA group was high for every measurement (87% Right COW, 89% Left COW, 88% 46 Vertical Diff, 87% 36 Vertical Diff).

CONCLUSIONS

Clear aligner and continuous archwire mechanics were effective in leveling COW. FA was more effective in changing crown position of lower second molars with respect to the WALA ridge, while CA provided a greater distance reduction between lower premolars and WALA ridges compared to FA.

Orthodontic treatment and biological limits: a retrospective clinical trial

BACKGROUND

The fundamental part of every successful orthodontic treatment is the detailed treatment planning including a precise determination of the virtual treatment objective (VTO) while considering the biological and anatomical limits. The aim of this study is to investigate and to compare the feasibility of the established reference values before and after orthodontic treatment and to determine the usefulness of this parameters as guidance for the sagittal anterior, sagittal posterior and transverse biological boundaries.

MATERIALS AND METHODS

Thirty-two patients aged 9 to 18 years (12 male and 20 female) with all permanent teeth present were randomly selected for orthodontic treatment with fixed multibracket appliance regardless of the potential malocclusion. The parameters 6-PTV, 1-NB [mm] and the WALA ridge were set for the identification of the transverse, sagittal anterior and sagittal posterior tooth position. The measurements were carried out at the beginning (T0) and at the end (T1) of the orthodontic treatment. They were set in relation with their individual threshold values (G). After the results of the measurements were conducted using the software OnyxCeph3TM (version 3.2.185 (505), Image Instruments GmbH, Chemnitz, DE), they were statistically calculated in the software RStudio (2022.12.0 Build 353 © 2009-2022 Posit Software PBC).

RESULTS

Among the 32 patients, the mean pre- and post-treatment changes measured through the three parameters in relation to the individual reference values were statistically significant (p < 0.01). The mean values for 6-PTV, 1-NB and the WALA ridge amounted 15.37 mm, 2.56 mm and 4.23 mm at the beginning of the treatment, while after the treatment the measured values amounted 20.31 mm, 2.4 mm and 5.55 mm. These measurements combined with the statistical analysis of the changes of WALA ridge (T0, T1) confirmed that the teeth have been successfully uprighted and aligned. Furthermore, the maxillary first molars have been moved slightly mesially, as proven by the changes in 6-PTV, without certainty as to whether bodily movement or mesial tipping took place. Additionally, the lower incisors have been protruded, slightly exceeding the individual threshold values.

CONCLUSION

The parameters investigated provide a suitable assessment tool for recording the limits of the sagittal posterior, the sagittal anterior and the transverse dimension.