Comparison between 2D cephalometric and 3D digital model superimpositions in patients with lateral incisor agenesis treated by canine substitution.

INTRODUCTION: This study aimed to assess the reliability of measurements obtained after superimposing 3-dimensional (3D) digital models by comparing them with those obtained from lateral cephalometric radiographs in patients with lateral agenesis space closure by mesialization. METHODS: Data were collected from premaxillary and postmaxillary dental casts and lateral cephalometric radiographs of 26 patients presenting lateral incisor agenesis and treated with rapid maxillary expanders and space closure by mesialization of the lateral sectors. Sagittal and vertical movements of the incisors and the maxillary molars were evaluated with lateral cephalometric radiographs and digitized 3D models superimposed on the palatal area. Paired sample t tests were used to determine if any significant difference existed between the 2 measuring techniques and between 2 different localizations of superimpositions. RESULTS: Cephalograms and 3D digital model measurements were statistically similar in molars and incisor movements according to anteroposterior and vertical planes. Regarding incisor movements in the anteroposterior plane, measurements derived from second ruga 3D models were significantly greater than those derived from third ruga 3D digital models. CONCLUSIONS: The 3D model superimposition method using the palate as a reference area is clinically reliable for assessing anteroposterior and vertical tooth movement as cephalometric superimposition in patients treated with rapid maxillary expanders and space closure by mesialization.

Comparison of the accuracy of bracket positioning between direct and digital indirect bonding techniques in the maxillary arch: a three-dimensional study.

BACKGROUND/OBJECTIVES: When the indirect bonding technique was developed in 1972 by Silverman and Cohen, many authors wondered whether this technique would improve bracket positioning accuracy compared to the direct bonding technique. Studies have found little to no difference between them regarding positioning accuracy. Recently, technological advances have improved the indirect method by allowing the user to position the brackets virtually using software applications such as OrthoAnalyzer™. To the best of our knowledge, no studies have compared direct positioning to this new digital indirect technique. Thus, the aim of this study was to compare the accuracy of placement between the two techniques in the maxillary arch using two different bracket types: conventional twin brackets and self-ligating brackets. A secondary objective was to evaluate whether bracket type affected positioning accuracy. METHODS: A maxillary arch of a patient was scanned by digital impression. Forty resin duplicates of this model were printed and then mounted on a mannequin head, on which 20 practitioners performed direct bonding using the aforementioned brackets. Later on, they performed a virtual indirect bonding of the same case virtually, with the digital impression superimposed to the patient's CBCT (cone-beam computed tomography). Afterwards, the direct bonded models were unmounted, scanned, and then superimposed to the indirect models. Differences in height, angulation and mesio-distal position of the brackets were evaluated. RESULTS: Regarding height, the differences between direct and indirect methods were not significant. Height difference was significantly greater for self-ligating brackets compared to conventional brackets. Regarding mesio-distal positioning, significant differences were noted for teeth 13 and 15 with self-ligating brackets (p-value = 0.019 and p-value = 0.043, respectively). The deviation was also greater for these brackets. Regarding angulation, the difference was significant on tooth 12 when using conventional brackets (p-value = 0.04) and on 12 and 22 when using self-ligating brackets (p-value = 0.09). CONCLUSION/IMPLICATIONS: There were no major significant differences between direct and indirect bonding. Differences were significant only on the laterals for of angulation, and on teeth 13 and 15 for mesio-distal centering. The bracket type seems to influence positioning accuracy, since self-ligating brackets had a larger deviation range than conventional brackets.

Evaluation of the distance between the root apices of the upper first molars and the hard palate in an Eastern Mediterranean population: A retrospective study.

OBJECTIVE: The aims of this retrospective study were, first to evaluate the distance between the root apices of the upper first molars and the palatal plane (PP), and second to determine the validity (accuracy) of the use of cephalometric radiographs or panoramic X-rays compared to cone beam computed tomography (CBCT) in determining this distance. MATERIAL AND METHODS: The distance was calculated from the root apices of the first molars to PP, on the cephalometric radiographs of 204 subjects and then 57 measurements were compared to those obtained on panoramic X-rays and CBCT images, in order to find a statistically significant difference according to age, sex, side, vertical and sagittal skeletal patterns, and to determine if 2D radiographs are suitable for this task. RESULTS: The distance increased significantly in subjects after 20 years of age and in hyperdivergent patients, but was not influenced by sex, side or anteroposterior position of the mandible. No statistical significance was found between the calculated measurements on cephalometric and CBCT radiographs, but both were different from those taken on panoramic X-rays. CONCLUSIONS: Cephalometric radiographs are reliable in the assessment of the distance between the roots of the upper molars and the PP. In hyperdivergent and adult patients, posterior teeth have enough space between their roots and the upper limit of the hard palate to undergo intrusion mechanics using miniscrews, but care must be taken while planning and managing these movements in order to minimize the unwanted side effects.

Effect of sandblasting and enamel deproteinization on shear bond strength of resin-modified glass ionomer.

INTRODUCTION: The purpose of this study was to compare, in vitro, the shear bond strength of resin-modified glass ionomer (RMGI) bonded to an enamel surface prepared by either sandblasting with 50µm of aluminium oxide particles, deproteinization with 5.25% NaOCl, or by combining both techniques. MATERIAL AND METHODS: One hundred and fifty human premolars were cleaned and randomly divided into five groups. In group 1, the teeth were etched using 37% phosphoric acid and bonded with Transbond XT. In group 2, the teeth were etched using 37% phosphoric acid and bonded with Fuji Ortho LC. In group 3, the teeth were deproteinized with 5.25% NaOCl for one minute then etched with 37% phosphoric acid and bonded with Fuji Ortho LC. In group 4, the enamel was sandblasted with 50µm of aluminium oxide particles for 5seconds prior to etching and bonding with Fuji Ortho LC. In group 5, the teeth were both sandblasted with 50µm of aluminium oxide particles for 5seconds and deproteinized with 5.25% NaOCl for one minute prior to etching using 37% phosphoric acid and bonding with Fuji Ortho LC. The shear bond strength was tested using a universal testing machine with a crosshead speed of 1.0mm/min. The adhesive remnant index (ARI) index was also determined for each group. RESULTS: The mean shear bond strengths were as follows: group 1: 11.33±2.60MPa, group 2: 8.14±2.09, group 3: 9.57±3.25MPa, group 4: 9.49±1.99MPa and group 5: 9.76±2.29MPa (P=0.0001). CONCLUSION: The results show that pre-treating the enamel with either sandblasting, NaOCl, or both, could give a significantly higher shear bond strength than using RMGI with acid etch alone.

[The orthodontic surgical approach revisited]. / L'approche orthodontico-chirurgicale revisitée.

An adequate orthodontic preparation is a key to success of every orthognatic surgery. Therefore, the detection and the correction of the existing dentoalveolar compensation tend to favor the correction of the skeletal defects. The pre-surgical orthodontic goals have to be defined at the beginning of the treatment, thus, not always achieving a complete leveling of the arches, nor a final space closure and ideal intercuspation. The orthodontic preparation aims to guide the surgical skeletal displacements. Many dentoalveolar compensations can be identified as specific to different types of malocclusion. Accordingly, an adequate individualized planning and a good coordination between both orthodontist and surgeon, are of a major importance, in order to avoid unexpected traps during orthodontic pre-surgical preparation.