Stereo-assisted landmark detection for the analysis of changes in 3-D facial shape.

In this paper, a semi-automated approach to 3-D landmark digitization of the face is described which uses a combination of active shape model-driven feature detection and stereophotogrammetric analysis. The study aims to assess whether the proposed method is capable of detecting statistically significant changes in facial soft tissue shape due to mandibular repositioning in a cross-sectional patient sample. A hybrid stereophotogrammetric and structured-light imaging system is used for acquiring 3-D face models in the first instance. A landmark-based statistical analysis of facial shape change is then carried out using procrustes registration, principal component analysis and thin plate spline warping on the 2-D facial midline profiles and automatically digitized 3-D landmarks. The proposed method is validated both statistically and visually by characterizing shape changes induced by mandibular repositioning in a heterogeneous cross-sample of 20 orthodontic patients. It is shown that the method is capable of distinguishing between changes in facial morphology due to simulated surgical correction and changes due to other factors such as growth and normal variation within the patient sample. The study shows that the proposed method may be useful for auditing outcomes of clinical treatment or surgical intervention which result in changes to facial soft tissue morphology.

Proportional changes in cephalometric distances during Twin Block appliance therapy.

The aim of the study was to evaluate the cephalometric changes produced by the Twin Block appliance. Lateral cephalometric radiographs were taken before and after Twin Block appliance treatment on 30 consecutive patients (14 male, 16 female, mean age 12 years 6 months). Published normative data tables were used to produce control data, which were individually matched to the test group for age, sex, and treatment time. Alteration in shape was assessed by measuring percentage change in linear dimensions as opposed to change in cephalometric angles used in previous investigations. The differential average percentage change was calculated by subtracting the control value from the Twin Block value. Clinically significant changes (2 per cent and greater) were found in lower anterior (6.6 per cent) and posterior (4.6 per cent) face heights, upper incisor to maxillary plane (4.9 per cent), i.e. upper incisor retraction, and increase in mandibular length (Co-B 3.3 per cent, Co-Po 2.6 per cent, Ar-B 3.5 per cent, Ar-Po 2.2 per cent).

A cephalometric evaluation of the Biobloc technique using matched normative data.

PATIENTS AND METHOD: The outcome of Biobloc treatment was evaluated on 35 patients, 13 male, 22 female, with Class II, Division 1 malocclusions. Cephalometric radiographs were taken before and after treatment. A control group was generated from published normative data in such a way that each treated case was matched individually for age, sex and treatment time. The cephalometric change during treatment was compared to the natural growth change in the matched control group using a Mann-Whitney U-test. The treatment effect was calculated by subtracting the natural growth change from the treatment change. This was then compared to twice the method error to see if the treatment change was clinically significant. RESULTS: There was both a statistically and a clinically significant reduction in overjet (p < 0.001), overbite (p < 0.001) and angle ANB (p < 0.001) with an increase in angle SNB (p < 0.001). None of the other cephalometric parameters measured showed a significant change except for upper incisor proclination (p < 0.05) and ArGoMe angle (p < 0.05) but these were not clinically significant.

Cephalometric evaluation of the Twin-block appliance in the treatment of Class II Division 1 malocclusion with matched normative growth data.

Cephalometric radiographs were taken before and after treatment with the Twin-block appliance on 30 consecutive patients with Class II Division 1 malocclusions. A control group was generated from published normative data such that each treated case was matched individually for age, sex, and treatment time. The cephalometric change during treatment was compared to the natural growth change in the matched control group using a Mann-Whitney U-test for statistical significance. The treatment effect was also calculated by subtracting the natural growth change from the treatment change. This was then compared to twice the method error to see if the treatment change was clinically significant. There was both a statistically and clinically significant reduction in overjet, angle ANB, increase in angle SNB, and mandibular length together with a reduction in upper incisor angle. None of the other cephalometric parameters measured showed a significant change.

Relationship of the functional oropharynx to craniofacial morphology.

The association between the functional oropharyngeal airway (defined as the minimal sagittal dimension at right angles to the airstream) and craniofacial morphology was investigated using 16 craniofacial variables taken from lateral cephalometric radiographs. The sample consisted of 70 subjects (31 males and 39 females) 10 to 13 years of age. There was no difference in ages between males and females, and no correlation with age except upper face height. Oropharyngeal airway was positively correlated with length of the mandible (Gon-Men), the distance between the third cervical vertebra and the hyoid bone (C3-Hy), and cranial base angle (NSBa). Although short mandibular length is a characteristic finding in patients with obstructive sleep apnea, none of the subjects in this study had this diagnosis.

Differences in cephalometric reference values between five centres: relevance to the Eurocleft Study.

Cephalometric data from five different geographical areas (Oslo, Manchester, London, Nijmegen, and Michigan) were compared. The angles SNA, SNB, and ANB were taken from published tables in the form of mean, standard deviation (SD) and number in the sample, divided up by age and sex. Angles SNA and SNB were significantly different among centres on univariate analysis. The Oslo data showed 23 instances in which they differed significantly from the other data, London 16, Manchester 11, Nijmegen 11, and Michigan 7. Multivariate analysis using Penrose distances were Oslo (2.04), Manchester (1.39), London (0.93), Nijmegen (0.80), and Michigan (0.66). The sums of the Mahalanobis distances were Nijmegen (3.60), Oslo (3.10), London (2.80), Manchester (2.25), and Michigan (1.49). As these results probably reflect racial and genetic differences, these must be taken into account when international comparisons are being made, as in the Eurocleft study.

Questionnaire evaluation of feeding methods for cleft lip and palate neonates.

A questionnaire evaluation was undertaken of feeding methods used by the mothers of 25 neonates with cleft lip and/or palate. Most parents had problems feeding their babies, both with the quantity of food taken and especially with the time taken to feed; even after a period of 2 months over a quarter were still having problems with the quantity of feed and a third had not established a regular feeding pattern. Just over a half needed to change the feeding method from the one with which they started. Twelve of the 25 mothers tried to breast-feed but none of them was successful. The Haberman feeder was the most popular, being used by 18 mothers. An acrylic feeding plate was considered to be helpful by 6 of 11 mothers of babies with complete clefts but by only 1 of 9 mothers of babies with secondary palate clefts. Almost all the mothers were dissatisfied with the information they had received while in hospital and with the back-up when they went home.

Alteration in facial shape in the anencephalic human foetus.

Tracings were produced from frontal radiographs of 11 anencephalic foetuses. These were compared analytically with standards derived from 60 normal foetuses. The anencephalics showed a marked reduction in the relative size of the cranium with considerable flattening of the calvarium, which is characteristic of the condition. The orbits were more medially placed, being closer together and somewhat higher in position that the normal foetal outline. The right and left mandible were more elongated with an increase in the intermaxillary space. The condyles were more medially positioned and were closer to the orbits than in the normal outlines. In normal growth, expansion of the brain flattens the cranial base, displacing the nasomaxillary segment forwards. In anencephally this does not happen so that the nasomaxillary segment rotates in an antero-inferior postero-superior direction along with the intermaxillary space and mandible. This produces a significant lengthening of the face accompanied by narrowing in the region of the cranial base relative to the normal outline.