Dental casts of 160 Greek subjects (80 males, 80 females) were scanned by a structured-light scanner. The upper and lower right first molar occlusal surface 3D meshes were processed using geometric morphometric methods. A total of 265 and 274 curve and surface sliding semilandmarks were placed on the upper and lower molar surfaces, respectively. Principal component analysis and partial least square analysis were performed to assess shape parameters. Molars tended to vary between an elongated and a more square form. The first two principal components (PCs), comprising almost 1/3 of molar shape variation, were related to mesiodistal-buccolingual ratios and relative cusp position. Distal cusps displayed the greatest shape variability. Molars of males were larger than those of females (2.8 and 3.2% for upper and lower molars respectively), but no shape dimorphism was observed. Upper and lower molar sizes were significantly correlated (r(2) = 0.689). Allometry was observed for both teeth. Larger lower molars were associated with shorter cusps, expansion of the distal cusp, and constriction of the mesial cusps (predicted variance 3.25%). Upper molars displayed weaker allometry (predicted variance 1.59%). Upper and lower molar shape covariation proved significant (RV = 17.26%, P < 0.0001). The main parameter of molar covariation in partial least square axis 1, contributing to 30% of total covariation, was cusp height, in contrast to the primary variability traits exhibited by PC1 and PC2. The aim of this study was to evaluate shape variation and covariation, including allometry and sexual dimorphism, of maxillary and mandibular first permanent molar occlusal surfaces.

INTRODUCTION: Our objective was to investigate potential associations between maxillary sinus floor extension and inclination of maxillary second premolars and second molars in patients with Class II Division 1 malocclusion whose orthodontic treatment included maxillary first molar extractions. METHODS: The records of 37 patients (18 boys, 19 girls; mean age, 13.2 years; SD, 1.62 years) treated between 1998 and 2004 by 1 orthodontist with full Begg appliances were used in this study. Inclusion criteria were white patients with Class II Division 1 malocclusion, sagittal overjet of ≥4 mm, treatment plan including extraction of the maxillary first permanent molars, no missing teeth, and no agenesis. Maxillary posterior tooth inclination and lower maxillary sinus area in relation to the palatal plane were measured on lateral cephalograms at 3 time points: at the start and end of treatment, and on average 2.5 years posttreatment. Data were analyzed for the second premolar and second molar inclinations by using mixed linear models. RESULTS: The analysis showed that the second molar inclination angle decreased by 7° after orthodontic treatment, compared with pretreatment values, and by 11.5° at the latest follow-up, compared with pretreatment. There was evidence that maxillary sinus volume was negatively correlated with second molar inclination angle; the greater the volume, the smaller the inclination angle. For premolars, inclination increased by 15.4° after orthodontic treatment compared with pretreatment, and by 8.1° at the latest follow-up compared with baseline. The volume of the maxillary sinus was not associated with premolar inclination. CONCLUSIONS: We found evidence of an association between maxillary second molar inclination and surface area of the lower sinus in patients treated with maxillary first molar extractions. Clinicians who undertake such an extraction scheme in Class II patients should be aware of this potential association and consider appropriate biomechanics to control root uprighting.

Blending of chewing gums of different colours is used in the clinical setting, as a simple and reliable means for the assessment of chewing efficiency. However, the available software is difficult to use in an everyday clinical setting, and there is no possibility of automated classification of the patient's chewing ability in a graph, to facilitate visualisation of the results and to evaluate potential chewing difficulties. The aims of this study were to test the validity of ViewGum - a novel image analysis software for the evaluation of boli derived from a two-colour mixing ability test - and to establish a baseline graph for the representation of the masticatory efficiency in a healthy population. Image analysis demonstrated significant hue variation decrease as the number of chewing cycles increased, indicating a higher degree of colour mixture. Standard deviation of hue (SDHue) was significantly different between all chewing cycles. Regression of the log-transformed values of the medians of SDHue on the number of chewing cycles showed a high statistically significant correlation (r² = 0.94, P < 0.01). ViewGum eliminates drawbacks of previous two-colour chewing gum test methods by the simplicity of its application. The newly developed ViewGum software provides speed, ease of use and immediate extraction of clinically useful conclusions to the already established method of chewing efficiency evaluation and is a valid adjunct for the evaluation of masticatory efficiency with two-colour chewing gum.

This investigation aimed to quantify craniofacial variation in a sample of modern humans. In all, 187 consecutive orthodontic patients were collected, of which 79 were male (mean age 13.3, SD 3.7, range 7.5-40.8) and 99 were female (mean age 12.3, SD 1.9, range 8.7-19.1). The male and female subgroups were tested for differences in mean shapes and ontogenetic trajectories, and shape variability was characterized using principal component analysis. The hypothesis of modularity was tested for six different modularity scenarios. The results showed that there were subtle but significant differences in the male and female Procrustes mean shapes. Males were significantly larger. Mild sexual ontogenetic allometric divergence was noted. Principal component analysis indicated that, of the four retained biologically interpretable components, the two most important sources of variability were (i) vertical shape variation (i.e. dolichofacial vs. brachyfacial growth patterns) and (ii) sagittal relationships (maxillary prognatism vs. mandibular retrognathism, and vice versa). The mandible and maxilla were found to constitute one module, independent of the skull base. Additionally, we were able to confirm the presence of an anterior and posterior craniofacial columnar module, separated by the pterygomaxillary plane, as proposed by Enlow. These modules can be further subdivided into four sub-modules, involving the posterior skull base, the ethmomaxillary complex, a pharyngeal module, and the anterior part of the jaws.