Influence of second premolar extractions on the volume of the oral cavity proper: a control comparative cone-beam computed tomography volumetric analysis study.

OBJECTIVES: To compare the pre- and postorthodontic treatment volumetric changes of the oral cavity proper (OCP) in extraction and nonextraction patients and to identify influencing variables. MATERIALS AND METHODS: Pre- and posttreatment cone-beam computed tomography (CBCT) scans of patients undergoing orthodontic treatment with fixed labial appliances and who satisfied the inclusion criteria were individually landmarked. Linear, angular, and volumetric measurements were determined. Descriptive statistics, repeated measure analyses of variance, correlations, and stepwise regression statistical analyses were applied. RESULTS: The CBCT scans of 54 patients who underwent the extraction of second premolars and/or extraction of second primary molars associated with agenic second premolars, and 59 nonextraction patients matched for crowding, were assessed. The mean age for both groups was 15 years. There was a statistically significant increase in the volume of the OCP for both the extraction and nonextraction groups, with the nonextraction group demonstrating a larger increase in the volume of the OCP. Gender, age, changes in mandibular and maxillary arch length, and changes in mandibular and maxillary intermolar width all influenced the change in the OCP volume. CONCLUSIONS: The volume of the OCP increased in growing patients with and without the extraction of the second premolars and/or extraction of second primary molars associated with agenic second premolars. Patients who did not have extractions as part of their orthodontic treatment demonstrated a greater overall increase in OCP volume.

Accuracy of an automated method of 3D soft tissue landmark detection.

INTRODUCTION: Due to technological advances, the quantification of facial form can now be done via three-dimensional (3D) photographic systems such as stereophotogrammetry. To enable comparison with traditional cephalometry, soft-tissue anatomical landmark definitions have been modified to incorporate the third dimension. Annotating these landmarks manually, however, is still a time-consuming and arduous process. OBJECTIVE: To develop an automated algorithm to accurately identify anatomical landmarks on three-dimensional soft tissue images. METHODS: Thirty 3dMD images were selected from a private orthodontic practice consisting of 15 males and 15 females between 9 and 17 years of age. The soft-tissue 3D images were aligned along a reference plane to setup a Cartesian coordinate system. Screened by 2 observers, 21 landmarks were manually annotated and their coordinates defined. An automated landmark identification algorithm, based on their anatomical definitions, was developed to compare the landmark validity against the manually identified counterpart. RESULTS: Twenty-one landmarks were analysed in detail. Inter-observer and intra-observer reliability using ICC was >0.9. The average difference and standard deviation between manual and automated methods for all landmarks was 3.2 and 1.64 mm, respectively. Sixteen out of twenty-one landmarks had a mean difference less than 4 mm. The landmarks of greatest agreement (≤2 mm) were mainly in the midline: pronasale, subnasale, subspinale, labiale superius, stomion, with the exception of chelion right. Five linear facial measurements were found to have moderate to good agreement between the manual and automated identification methods. CONCLUSIONS: The developed algorithm was determined to be clinically relevant in the detection of midsagittal landmarks and associated measurements within the studied sample of adolescent Caucasian subjects.

3D facial and dento-alveolar imaging.

This article reviews three-dimensional (1D) surface scanning contrasted with 3D imaging. Precise techniques are now available for capture of the face and craniofacial structures as well as improved introoral scanning for the production of virtual 3D casts of the dentition. Facial and intraoral scanners have established an accuracy that makes them viable for use in the clinical and research arenas. Three-dimensional imaging is a field of rapid change and currently-available scanners will doubtlessly be surpassed in the near future. Although there is much overlap between the capabilities of different proprietary systems, there are subtle, yet significant, differences between manufacturers. The differences have the potential to make a purchased scanner not fulfil expectations as much for reasons of software compatibility and integration, as for clinical usability and accuracy.