Alberto Rossetti

Digital dental cast placement in 3-dimensional, full-face reconstruction: A technical evaluation

INTRODUCTION Several noninvasive methods are used for 3-dimensional (3D) morphologic facial and dental analysis to aid practitioners during diagnosis and treatment planning. Integrating dental and facial noninvasive 3D reproduction could improve the efficacy of treatment management. METHODS Dental virtual model and soft-tissue facial morphology were digitally integrated from 11 adults with a 3D stereophotogrammetric imaging system (Vectra, Canfield Scientific, Fairfield, NJ). The digital 3D coordinates of 3 facial landmarks (N, nasion; Ftr, frontotemporale right; Ftl, frontotemporale left) and 3 dental landmarks (I, interincisor; Pr, PI, tips of the mesiovestibular cusps of the right and left first permanent premolars) were then obtained by using Vectras software. Additionally, the coordinates of the same 6 landmarks were digitized directly on each subject by using a 3D computerized electromagnetic digitizer (in vivo). Seven linear measurements were made between the occlusal plane (Pr-I-Pl) and the facial landmarks (Ftr-N-Ftl). The accuracy and reliability of the reconstruction were tested by in-vivo measurements and repeated acquisitions. RESULTS The greatest mean relative error of measurements was smaller than 1.2%. No significant differences in repeatable reproductions were found. CONCLUSIONS Integration of facial stereophotogrammetry acquisition and dental laser scan reproduction is possible with marginal error.

The occlusal plane in the facial context: inter-operator repeatability of a new three-dimensional method

The repeatability of a non-invasive digital protocol proposed to evaluate the three-dimensional (3D) position of the occlusal plane in the face is assessed. Dental virtual models and soft tissue facial morphology of 20 adult subjects were digitally integrated using a 3D stereophotogrammetric imaging system. The digital 3D coordinates of facial and dental landmarks were obtained by two different operators. Campers (facial) and occlusal (dental) planes were individuated, and their 3D relationships were measured. The repeatability of the protocol was investigated and showed no significant differences in repeated digitizations. The angle between occlusal and Campers planes was smaller than 2° in the frontal and horizontal projections. In the sagittal projection, the angle was observed to be, on average, 4.9°. The determined occlusal plane pitch, roll and yaw values show good agreement with previously published data obtained by different protocols. The current non-invasive method was repeatable, without inter-operator differences and can facilitate assessment of healthy subjects.

Three-dimensional analysis of dentolabial relationships: effect of age and sex in healthy dentition.

Morphological changes in three-dimensional (3D) dentolabial relationships during ageing were assessed in healthy individuals. 38 subjects with healthy dentition were analysed. They were divided into a youthful group (21-34 years, mean 26 years, SD 4) and an older group (45-65 years, mean 53 years, SD 5). Stone labial and dental models were made, digitized and 3D virtual reproductions of dentolabial morphology were obtained. From the digital reconstructions, the relative positions of the labial commissure and of the maxillary dental clinical crowns in the vertical direction were obtained. Sex and age effects were compared using two-way analysis of variance. Lip position relative to the teeth was significantly different in youthful and older subjects (P<0.01). No statistically significant effects of sex in dentolabial relationship were demonstrated, but a sex×age effect was found in the anterior labial segments (P<0.05). The perioral soft tissues drop down in older subjects and the soft tissue descends on the entire labial arch. These differences may help the clinician when estimating, planning and evaluating surgical, orthodontic and prosthetic treatments.

Three-dimensional facial morphometry in patients rehabilitated with implant-supported prostheses

The aim of the present study was to assess a low-cost, non-invasive facial morphometric digitizer to assist the practitioner in three-dimensional soft-tissue changes before and after oral rehabilitation. The method should provide quantitative data to support an objective assessment of the facial esthetic outcome [1]. Twenty-two patients aged 45-82 years, all with edentulous maxilla and mandible, were assessed both before and after receiving their definitive complete implant-supported prostheses (each received 4-11 implants in each dental arch; full-arch fixed prostheses were made). The three-dimensional coordinates of 50 soft-tissue facial landmarks were collected with a non-invasive digitizer; labial and facial areas, volumes, angles and distances were compared without/ with the prostheses [2]. Dental prostheses induced significant reductions in the nasolabial, mentolabial and interlabial angles, with increased labial prominence (p<0.05, Wilcoxon test). Lip vermilion area and volume significantly increased; significant increments were found in the vertical and anteroposterior labial dimensions. The presence of the dental prostheses significantly (p<0.001) modified the three-dimensional positions of several soft-tissue facial landmarks. The current approach enabled quantitative evaluation of the final soft-tissue results of oral rehabilitation with implant-supported prostheses, without submitting the patients to invasive procedures. The method could assess the three-dimensional appearance of the facial soft tissues of the patient while planning the provisional prosthetic restoration, providing quantitative information to prepare the best definitive prosthesis. Dote ricerca: FSE, Regione Lombardia

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). 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.

Simulation of the effect of dental modifications on facial soft tissues: a 3D stereophotogrammetric study

Several dental treatments can change dental position, and modify lip support in the space. Current methods do not allow a non-invasive quantitative assessment of 3D lip dimensions and position, and no simulations of treatment effects can be made. In the current study we devised a method for the detection of the 3D dentolabial positions during simulated orthodontic and prosthetic dental treatments. The dental arches of 10 adult healthy subjects were reproduced with stone models, and 1and 2-mm thick resin blocks were modeled on the maxillary frontal teeth (from canine to canine) to simulate a prosthetic or orthodontic treatment. The facial soft tissues of the subjects with closed mouth were obtained using a 3D stereophotogrammetric imaging system (Vectra-3D, Canfield Scientific, Inc., Fairfield, NJ, USA), without/ with the two resin thicknesses. The relevant faces were superimposed, and the spatial displacements of selected facial landmarks without/ with the thicknesses were calculated. Additionally, upper and lower labial areas were individualized, and the relevant global distances without/ with the thickness were obtained. Average displacements ranged from 0.39 (sn landmark with the 1-mm thickness) to 1.62 mm (left side ch landmark with the 2-mm thickness). On average, ch and cph landmarks had the largest displacements. In all occasions, the larger movements were obtained with the 2-mm thickness, but the difference was significant only for the ls and cph landmarks (p<.05). The upper lip area had average anterior displacements of 0.28 (1-mm thickness) and 0.5 mm (2-mm thickness; p=.007), while the lower lip area had posterior displacements in 6 (1-mm thickness) and 4 subjects (2-mm thickness). In conclusion, the method devised in the current study allowed a 3D quantitative assessment of the effect of a simulated dental treatment without submitting the subjects to invasive or dangerous examinations. The method could be usefully employed for orthodontic treatment planning in children and adolescents, as well as for simulations of prosthetic oral rehabilitation in adults.