The application of computers to the study of maxillary arch dimensions

Precision of Landmark Positioning on Digitized Models from Patients with Cleft Lip and Palate

Objective

To quantify the precision of landmark positioning on digitized casts of patients with unilateral cleft lip and palate.

Patients

Forty plaster models of newborns up to 8 months of age were selected from the archive of the Department of Orthodontics of the University of Heidelberg.

Material and Method

The plaster-cast models were digitized with a Micromeasure 70 three-dimensional laser scanner (Micromeasure, Bischoffen, Germany). The laser scanner used in this study operates with a precision of 0.15 mm on the x- and y-axes and 0.06 mm on the z-axis. In the intraobserver study, a single observer placed anatomical landmarks in four rounds, with at least 4 weeks between each round. In the interobserver study, four different observers each placed the same landmarks once. For the two different studies, an ideal location for each landmark was calculated by averaging the landmark positions of the four rounds or observers. The distance between each of the four landmark positions and the ideal landmark was measured.

Results

A 95% confidence interval for the landmark positioning error was calculated. For the intraobserver investigation, this error was 0.34 to 1.30 mm, and for the interobserver investigation it was 0.7 to 2.00 mm.

Conclusion

Because both investigations displayed comparable error intervals, it was concluded that different observers could perform landmark positioning for the same studies.

Palatal development of preterm and low birthweight infants compared to term infants - What do we know? Part 1: The palate of the term newborn

Background

The evidence on prematurity as 'a priori' a risk for palatal disturbances that increase the need for orthodontic or orthognathic treatment is still weak. Further well-designed clinical studies are needed. The objective of this review is to provide a fundamental analysis of methodologies, confounding factors, and outcomes of studies on palatal development. One focus of this review is the analysis of studies on the palate of the term newborn, since knowing what is 'normal' is a precondition of being able to assess abnormalities.

Methods

A search profile based on Cochrane search strategies applied to 10 medical databases was used to identify existing studies. Articles, mainly those published before 1960, were identified from hand searches in textbooks, encyclopedias, reference lists and bibliographies. Sources in English, German, and French of more than a century were included. Data for term infants were recalculated if particular information about weight, length, or maturity was given. The extracted values, especially those from non-English paper sources, were provided unfiltered for comparison.

Results

The search strategy yielded 182 articles, of which 155 articles remained for final analysis. Morphology of the term newborn's palate was of great interest in the first half of the last century. Two general methodologies were used to assess palatal morphology: visual and metrical descriptions. Most of the studies on term infants suffer from lack of reliability tests. The groove system was recognized as the distinctive feature of the infant palate. The shape of the palate of the term infant may vary considerably, both visually and metrically. Gender, race, mode of delivery, and nasal deformities were identified as causes contributing to altered palatal morphology. Until today, anatomical features of the newborn's palate are subject to a non-uniform nomenclature.

Conclusion

Today's knowledge of a newborn's 'normal' palatal morphology is based on non-standardized and limited methodologies for measuring a three-dimensional shape. This shortcoming increases bias and is the reason for contradictory research results, especially if pathologic conditions like syndromes or prematurity are involved. Adequate measurement techniques are needed and the 'normal palatal morphology' should be defined prior to new clinical studies on palatal development.

Quantitative 3D maxillary arch evaluation of two different infant managements for unilateral cleft lip and palate

OBJECTIVE

A two-institution retrospective study was undertaken to determine whether two different prepalatoplasty protocols quantitatively affect maxillary arch morphology in infants with complete unilateral cleft lip and palate (UCLP).

DESIGN

Serial maxillary dental casts, obtained at regular intervals through the first 18 months of life from preintervention until palatoplasty were evaluated quantitatively using computer-assisted three-dimensional digitization and analysis for three populations: institution 1 (protocol 1), institution 2 (protocol 2), and unaffected individuals (neither cleft nor treatment). Sequential UCLP patients from institution 1 were matched for age and initial alveolar cleft width, sex and cleft side having been demonstrated to be nonsignificant, with UCLP patients from institution 2 and to unaffected individuals for age for the analysis.

SETTING

Both treatment institutions are well-established regional interdisciplinary cleft centers. Institution 1 is located in a tertiary, academic children's hospital in a metropolis within a primarily agrarian region of the Midwest; institution 2 is a freestanding private clinic located in a small city within a primarily agrarian region of an eastern state; the unaffected population is a historic archive acquired in the 1930s. Data acquisition (model digitization) and computer processing were performed at institution 1.

PATIENTS

Eighty-five casts of 28 infants from institution 1, 106 casts of 31 infants from institution 2, and 68 casts of 29 unaffected infants were analyzed. All infants had alginate impressions taken prior to intervention and at several additional 6-month intervals after that, consistent with each institution's treatment protocol.

INTERVENTIONS

At institution 1, patients with UCLP underwent lip adhesion and placement of a passive alveolar molding plate at 7 weeks of age, definitive cheiloplasty at 7 months of age, and one-stage palatoplasty at 14 months of age. At institution 2, patients with UCLP underwent definitive cheiloplasty at 3 months of age, had no maxillary orthopedics, and had vomer flap hard palate repair at 12 months of age and soft palate repair at 18 months of age.

MAIN OUTCOME MEASURES

The outcome measures included directly digitized (cleft segment and hemialveolar ridge lengths) and derived (alveolar base width, alveolar cleft gap, maxillary frenum-alveolar base perpendicular angle, and rates of change over time of digitized cleft segment and hemialveolar ridge lengths) features. The data were assessed by comparing simple linear regression lines and an unpaired, two-tailed t test.

RESULTS

Prior to initiating therapy, there were no statistically significant differences between the two populations with clefts. However, both populations with clefts differed significantly from unaffected individuals (p < .001), with increased maxillary base widths and larger perpendicular/frenum angles. At the time of palatoplasty, the two populations with clefts had statistically significant differences between them in the maxillary base width (p < .01) and the cleft gap distance (p < .05). The base width of institution 1 did not differ significantly from that of widths of unaffected children, and that of institution 2 was significantly less, although the latter had already received first-stage palate repair. Alveolar segment growth rates were similar for the greater and lesser segments, respectively, and the left side hemialveolus of both groups. The growth rate for the noncleft side hemialveolus of institution 2 exceeded (p < .05) that of both institution 1 and unaffected patients.

CONCLUSION

Two different regimens for the initial management of UCLP can significantly affect maxillary alveolar arch growth with respect to the treatment used and in comparison with unaffected controls.

The development of a new method of cephalometric and study cast mensuration with a computer controlled, video image capture system. Part II: Study cast mensuration

A computerized system for mensuration of dental casts, developed at the Royal Berkshire Hospital in Reading was tested against a conventional manual method and a computer controlled reflex microscope. Systematic errors, calibration, and handling aspects are discussed. Results showed that the computerized system provided data which while statistically different, were clinically comparable with the same measurements carried out using conventional manual or digitizing techniques. The results indicated that future research is required with respect to object illumination for all indirect techniques.

Dimensions and form of dental arches in subjects with normal occlusions

To determine the main mandibular dental arch forms, 278 dental casts of untreated French adults with normal occlusions were examined. Six measurements of the mandibular dental arches were performed, and five independent ratios were determined. By following the k-means clustering method on the basis of these ratios and the use of polynomial functions of the sixth degree, five mandibular dental arch forms were defined, and an arch guide was developed. The proposed forms are relatively narrow in comparison with previous studies. No significant differences in their distributions were seen between male and female subjects. However, the dental arches of the women have smaller dimensions.

Palatal measurements of prematurely born, very low birth weight infants: comparison of three methods

To enable investigation of palatal changes in infants who are prematurely born, it is necessary to first establish a reliable method of measurement of these tiny edentulous palates. This study compared the Olivetti-Inspector machine, Vernier calipers, and stereophotogrammetry for this purpose. Measurements were taken of 12 palatal casts of four infants at prescribed time intervals during the neonatal period. In each of the three methods, measurements were recorded as variables generated in the X and Z axes of the Cartesian scale in relation to three specified points along the Y axis. The results revealed that all methods were comparable, but the Vernier calipers differed significantly from the other two methods in height measurements, (p < 0.001). It was also found that both the Olivetti-Inspector machine and the Vernier calipers consistently underestimated the width, compared with Olivetti-Inspector machine, (p < 0.05). Stereophotogrammetry was found to be the most consistent method of measuring the configuration of preterm infant palates.

A comparison of orthodontic treatment changes as measured from study casts and cephalometric radiographs

Orthodontic treatment change was examined for 106 consecutively referred patients using serial lateral cephalometric radiographs and study cast records. The 2-D and 3-D measurement systems used to assess the changes were compared for five variables common to both sets of records. No statistical differences were found between the study cast and radiographic records for these variables. The 3-D measurement with the Reflex Metrograph showed marginally better precision in the measurement of the treatment changes examined. However, the main advantage was that it allowed a more thorough and accurate assessment of both individual incisor position and measurement error.

The effect of form and dimension on the management of the maxillary arch in unilateral cleft lip and palate conditions

Over the past 28 years, a series of studies at the West Midlands Regional Plastic Unit has compared the maxillary arches at birth and 4 months of 30 normal children and two groups of children with unilateral cleft lip and palate, one of which had presurgical maxillary orthopaedic treatment and the other which did not. Other studies have compared the area of palatal mucosa at birth with the overall size of the arch at 5 years of age and have also assessed the long term effect of simultaneous lip and palate repair and presurgical treatment on the profile, occlusion and speech of the older patient. The paper summarises the findings of the investigations and considers how they have contributed to an understanding of the unilateral cleft lip and palate problem particularly with regard to the long term management of such cases and the provision of a suitable treatment protocol.

Morphological jaw differences in mentally subnormal and normal adult males

The shape of the mandibular symphysis was studied in four groups of adult male Caucasians, aged 18–49. The composition of the groups and their numbers were as follows: (1) Down's syndrome (20), (2) familial idiopathic subnormality (20), (3) healthy individuals, IQ range 94−120 (22), and (4) healthy individuals, IQ 130+ (22). From lateral skull radiographs, the outline of the mandibular symphysis was digitized with a D-mac pencil follower. Selected distances and angles were computed and used as variables in a canonical analysis. Plots of the canonical variates discriminated appreciably between each group. Generalized distance measurements between group means were significant for all pairs of groups except 2/3 and 3/4. The results suggest a genetic link between intelligence and symphysis shape. This hypothesis will be tested by introducing a brain-damaged group, matched in intelligence, and for length of stay in hospital, with Group 2. The finding could influence developments in human genetics and psychology.