Effect of Conventional Versus Passive Self-Ligating Vestibular Appliances on Torque, Tip and Transverse Dental Changes in Patients Affected by Class I Malocclusion: A Retrospective Study

ABSTRACT Objective: To evaluate the effects of passive self-ligating appliances (PSLAs) and conventional ligating appliances (CLAs) during orthodontic treatment regarding torque, tip, and transversal dental changes. Material and Methods: Dental parameters were digitally acquired from pre- and post-treatment models of each subject belonging to two groups of patients treated with PSLAs (23 patients; 11 females and 12 males with a mean age of 14.2 ± 1.6 years) and CLAs (18 patients; 10 females and 8 males with a mean age of 14.3 ± 1.9 years), respectively. All subjects had Class I or slight Class II malocclusion (= 2mm), permanent dentition and no previous orthodontic treatment. After normality of data was assumed, a paired sample t-test rejected any side differences at T0 and, therefore, the data were grouped by tooth group. Statistical analyses were performed using a linear mixed-effect framework, assuming the appliance, time, and interactions as fixed effects and the tooth type as random effects. Finally, post-hoc effect analysis was used to contrast modeled marginal effects (p<0.05). Results: For both appliances, there is a general increase of both torque and transverse values at T1, especially for PSLAs. Tip shows a general reduction in the lateral sectors for both appliances is registered. The only significant statistical difference referred to appliances' efficacy is located to mandibular intermolar width. Conclusion: Both appliances have an expansive potential for both torque and transverse dental changes. No evident differences are detectable between appliances except for the rate of the mandibular intermolar width increase.

Correlation Between Mesio-Distal Teeth Diameters and Arch Width

ABSTRACT Objective: To verify the existence of a correlation between the mesio-distal size of teeth and the arch width by analyzing the data separately for maxillary and mandibular arch in patients with ideal occlusion Material and Methods: 58 patients with ideal occlusion were studied, for a total of 276 files analyzed. Dental casts were then scanned using a professional scanner (Epson Perfection v 330) and images were obtained in TIFF format at 600 dpi. All single teeth measurements were carried out for all teeth of both arches using the VAM software (Vectra, Canfield Scientific, Fairfield, NJ, USA). The repeatability and reproducibility of the measurement method were evaluated using the Gauge R&R method. In case a correlation between tooth size and arch size is found to be significant, a linear regression analysis can be applied through the following statistical relationship: y=a+b*x, where y is the result (inter-molar distance "AvgB66" or inter-canine distance "Cusp 33"), and x the specific tooth. The a and b respectively represent the intercept (point of intersection between the line and the y axis) and the slope of the line that describes the regression ratio. Results: The statistical analysis highlights a significant correlation (p<1%) between the results of the mesio-distal measurements of each tooth and the two variables considered to define the size of each arch ("AvgB66" and "Cusp 33"). Based on these results, a numerical relationship "y=a+b*x" has been extrapolated. Thus, it is possible to calculate the estimated inter-molar or inter canine distance necessary to have the teeth aligned. Conclusion: The inter-canine and inter-molar distances can be estimated starting from measuring the mesio-distal diameter of a single tooth.

Spontaneous Transversal Changes of Lower Arch Following Palatal Skeletal Expansion

ABSTRACT Objective: To evaluate how the lower arch spontaneously change after upper rapid palatal expansion in a group of patients with transversal skeletal deficit. Material and Methods: Twenty-four patients treated by the same orthodontist with a rapid palatal expander (RPE) bounded on a deciduous molar have been selected. The sample was divided into two groups: no treatment was provided for group one, while group two was treated using a lip bumper or Schwarz appliance. For each patient, dental casts were collected when the RPE was bounded (T0) and at the end of treatment, 9 months ± 3 months later (T1). Each outcome was analyzed, providing descriptive statistics, main effects significance tests and post-hoc analyses with the objective to evaluate the variations between pre-treatment (TO) and post-treatment (T1) of each of them. Results: If the linear measurements are considered, a significant beneficial effect on both arches is observed. However, the upper arch always shows a major increase of all values at T1 with respect to the lower arch. Even though the post-hoc tables indicate that time differences are all statistically significant across considered partitions, the lower arch's increase is more pronounced in group two, where patients were treated in both arches. If the angular measurements are concerned, the increase of lingual crown inclination was found in all patients, independently from the type of treatment in lower arch. Conclusion: All patients show normalization of upper diameters, regardless of whether the lower arch was treated or not.