Evaluation of tip and torque on virtual study models: a validation study

Background: The objectives of this study were to develop and validate a novel analysis protocol to measure linear and angular measurements of tip and torque of each tooth in the dental arches of virtual study models. Methods: Maxillary and mandibular dental casts of 25 subjects with a full permanent dentition were scanned using a three-dimensional model scanner. Sixty points per arch were digitized on each model, five points on each tooth. A custom analysis to measure linear distances and angles of tip and torque was developed using a new reference plane passing as a best-fit among all of the lingual gingival points, with the intermolar lingual distance set as the reference X-axis. The linear distances measured included buccal, lingual, and centroid transverse widths at the level of canines, premolars, and molars as well as arch depth and arch perimeter. Results: There was no systematic error associated with the methodology used. Intraclass correlation coefficient values were higher than 0.70 on every measure. The average random error in the maxilla was 1.5\ub0 \ub1 0.4\ub0 for torque, 1.8\ub0 \ub1 0.5\ub0 for tip, and 0.4 \ub1 0.2 mm for linear measurements. The average random error in the mandible was 1.2\ub0 \ub1 0.3\ub0 for torque, 2.0\ub0 \ub1 0.8\ub0 for tip, and 0.1 \ub1 0.1 mm for the linear measurements. Conclusions: A custom digital analysis protocol to measure traditional linear measurements as well as tip and torque angulation on virtual dental casts was presented. This validation study demonstrated that the digital analysis used in this study has adequate reproducibility, providing additional information and more accurate intra-arch measurements for clinical diagnosis and dentofacial research

Clinical effects of different prescriptions on the inclination of maxillary and mandibular incisors by using passive self-ligating brackets

Controlling the incisal inclination is fundamental in orthodontics. However, the relationship between the inclination prescription and its clinical outcome is not obvious, and the incisal inclination changes generated by different bracket prescriptions were investigated

MRI of the TMJ and sEMG of masticatory muscles in patients with arthrogenous temporomandibular disorders: a correlation analysis

The aim of this study was to verify if patients with arthrogenous temporomandibular disorders (TMD) with different Magnetic Resonance Imaging (MRI) diagnoses had some objective differences in the surface electromyography (sEMG) characteristics of their masticatory muscles. Twenty-four TMD patients were categorized according to the RDC/TMD [1]; MRI classified patients with disk displacement (DD, mean age 22 years, SD 5; M/F: 3/6), and osteoarthrosis and/or disk displacement (OA, mean age 37 years, SD 10; M/F: 4/11). sEMG of the right and left masseter and anterior temporalis muscles was performed according to a standardized protocol, recording teeth clenching on either cotton rolls or occlusal surfaces [2]. EMG data were compared to those collected in control subjects of similar age and sex, and EMG z-scores were computed. The comparison of EMG z-scores and MRI scores between the 2 patient groups using the Mann-Whitney test was statistically significant (P < 0.05): the patients with OA had larger scores than the patients with only DD. The linear correlation analysis run between the EMG and the MRI scores found significant correlations in both patient groups. The EMG characteristics allowed to well differentiate patients with MRI diagnosis of DD or OA. The objective recording of the masticatory muscle function and dysfunction through sEMG can be a first simple and low cost diagnostic approach to TMD patients

A 3D non invasive assessment of the position of the occlusal plane

Introduction. The occlusal plane has a key-role in various dental and medical fields. Several methods have analyzed and measured the relative positions of the occlusal and facial planes; most of these investigations used 2D radiographic exams. Currently, 3D assessments may be performed overlapping CT reconstructions and digitized dental casts, but the method requires ionizing radiations, and it is not applicable in reference studies performed with healthy subjects. The efficacy of these measurements could be improved by a 3D, non invasive approach to the problem. Methods. 20 healthy subjects were selected to have their maxillary dental casts digitized by laser scanning, and their 3D facial soft tissue stereophotogrammetry acquisition merged in a single file. The digital 3D coordinates of three facial (right and left Tragus, Subnasale) and three dental landmarks (inter-incisor, tips of the mesio-vestibular cuspids of right and left first permanent molars), were obtained and exported in a 3D CAD (computed aided design) software for a geometrical analysis. The 3D orientation of the planes, referred to a Cartesian orthogonal reference system, was estimated calculating angular values between the sagittal midlines of the two planes. To evaluate the repeatability of the measurements the protocol was performed independently by two different operators. In total 120 measurements were obtained; descriptive statistics were calculated for each variable. To evaluate the method repeatability mean absolute difference between repeated measurements (MAD), technical error of measurement (REM) and Paired Student’s T tests (P<0.05) were computed. Results. In the frontal and horizontal projections, the occlusal plane resulted nearly parallel to Camper’s plane, with average inclinations of 1.5 (frontal) and 1.9 (horizontal) degrees. In the sagittal projection, the two planes had an average angle of 4.9 degrees, with the occlusal plane more anteriorly inclined than Camper’s plane. For all three projections, a fair inter-operator repeatability was found, with all MADs and TEMs slightly lower than 2 degrees. No systematic errors between repeated measurements were found (T test > 0.05). Conclusions. The current non-invasive method resulted appropriate to the aims. Camper’s and occlusal planes resulted almost parallel in the frontal and horizontal projections, while in the sagittal projection the occlusal plane was 5 degrees more anteriorly inclined than Camper’s plane

Predictability of orthodontic movement with orthodontic aligners: a retrospective study

The aim of this study was to evaluate the predictability of F22 aligners (Sweden & Martina, Due Carrare, Italy) in guiding teeth into the positions planned using digital orthodontic setup

Accuracy of lingual straight-wire orthodontic treatment with passive self-ligating brackets and square slot: a retrospective study

Abstract Objectives To investigate the accuracy of torque, tip and rotation and linear intra-arch movements yielded by passive self-ligating lingual straight-wire appliances with brackets featuring square slots. Materials and methods Twenty-five adult Caucasian patients (16 females and 9 males; mean age 26.5 ± 4.3 years) with Class I or mild Class II head-to-head malocclusion were orthodontically treated via passive lingual self-ligating straight-wire appliances (ALIAS, Ormco, Orange, CA) with no extraction. Records were retrospectively analysed, and digital models of pre-treatment (T0), planned (T1) and achieved (T2) phase were acquired for both arches in each patient via an intraoral scanner (Medit I500 (iScan Medit, Seoul, Korea). VAM software (Vectra, Canfield Scientific, Fairfield, NJ, USA) was used to measure both angular values (torque, tip and rotation) and linear intra-arch widths (between canines, first and second premolars and first and second molars). Measurements were obtained for all the movements investigated for each tooth group (incisors, canines, premolars and molars), by arch (maxillary and mandibular) and for both arches at T0, T1 and T2. The accuracy of angular values was compared using Student's t-test against a hypothetical 100%, and among the various tooth groups by post-hoc tests. Transverse linear measurements were investigated by means of the non-parametric Friedman test. The significance threshold was set at 0.05. Results The mean accuracy of angular values was 77.25 ± 7.71% for torque, 78.41 ± 6.17% for tip and 77.99 ± 6.58% for rotation. In all cases, however, there was a significant difference between planned and achieved movements, and accuracy was significantly lower than the hypothetical 100% for all tooth groups, individual arches and dentition (p < 0.001). For intra-arch diameters, the greatest accuracy values were found for the anterior sectors (83.54 ± 5.19% for the maxillary inter-canine distance) and the lowest for the posterior sectors (67.28% for the maxillary inter-second molar distance). Conclusion Straight-wire lingual treatment with passive self-ligating appliances featuring with square slot displayed excellent clinical accuracy, albeit with statistical accuracy decreasing antero-posteriorly

Rapid palatal expansion effects on mandibular transverse dimensions in unilateral posterior crossbite patients: a three-dimensional digital imaging study.

Background The purpose of this controlled study was to investigate indirect effects on mandibular arch dimensions, 1 year after rapid palatal expansion (RPE) therapy. Methods Thirty-three patients in mixed dentition (mean age 8.8 years) showing unilateral posterior crossbite and maxillary deficiency were treated with a RPE (Haas type) cemented on the first permanent molars. Treatment protocol consisted of two turns per day until slight overcorrection of the molar transverse relationship occurred. The Haas expander was kept on the teeth as a passive retainer for an average of 6 months. Study models were taken prior (T1) and 15 months on average (T2) after expansion. A control group of 15 untreated subjects with maxillary deficiency (mean age 8.3 years) was also recorded with a 12-month interval. Stone casts were digitized with a 3D scanner (3Shape, DK). Results In the treated group, both mandibular intermolar distance (+1.9 mm) and mandibular molar angulation (+9°) increased. Mandibular incisor angulation showed an increase of 1.9°. There was little effect on intercanine distance and canine angulation. Controls showed a reduction in transverse arch dimension and a decrease in molar and canine angulation values. Conclusions RPE protocol has indirect widening effects on the mandibular incisors and first molars