Biomedical subjects
Publications and source records attributed to B Prahl-Andersen.
The authors investigated the necessity for preoperative orthodontic treatment in cases of unilateral complete clefts. For these groups of patients, they propose a pure surgical therapy instead of the preoperative orthodontic treatment.
Basic problems of the need and demand for orthodontic treatment have been discussed and new areas of research have been identified. Discrepancies have been described between the views of the dental profession and the potential patients on malocclusion and the need for treatment. For malocclusions with or without impairment of the function the self perception of the patient may be different from and of more relevance than the professional judgment of the orthodontist. Before going into orthodontic treatment, the social sufficiency of the patient should be evaluated.
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A battery of thirty dentofacial measurements was studied in an attempt to identify those measurements most closely related to a clinical assessment of the need for orthodontic treatment in the Dutch population. This was done by inspecting the mean values of these measurements computed within several treatment priority groups, a stepwise regression analysis relating treatment priority scores to these dentofacial measurements, and a quadratic discriminant function analysis between the group of children requiring orthodontic treatment and the group for which treatment was deemed unnecessary. The variables identified by inspection were 1) overjet, 2) overbite, 3) upper molar arch width, 4) the angle defined by articulare-gonion-menton, 5) lower arch length and 6) the ANB angle; the first four of these proved to be the most important when the contributions of all thirty of the variables to the TPI were assessed by means of the stepwise regression analysis. Overjet was also found to be an important predictor variable by Freer in relating Grainger's orthodontic TPI to dentofacial measurements in a group of patients with distoclusion; the ANB angle was found to be the most effective discriminator between normal and Class II American children. The results of the present study then, to this extent at least, agree with those found in other populations. It would appear that any "universal" TPI would have to involve those aspects of dentofacial morphology measured by overjet and the ANB angle. Within the context of the Dutch population the variables identified proved to be effective discriminators in the decision of "to treat or not to treat," correctly classifying 100% of the children in the sample who were judged by two experienced orthodontists as requiring treatment. While this decision rule did suggest treatment for 17% of the children judged to not require treatment, these cases were in the "doubtful" category (Table I) and might therefore warrant continued monitoring before any final decision is reached.
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The prevalence of dental caries was determined clinically in 2.5-year-old Dutch cleft lip and/or palate children (n = 76) and in children without congenital malformation (n = 75). The parents were given a structured questionnaire regarding the child's dietary habits, oral hygiene, fluoride exposure and social economic background. The prevalence of dental caries was higher in children with oral cleft than in children without oral cleft. Initial caries (white spots) was diagnosed in 17.1% of the subjects with oral cleft compared with 4.0% of the control subjects. Manifest caries (cavities) was found in 26.3% of the children with oral cleft compared with 5.3% of the controls. The dft score (manifest caries) was significantly higher for the oral cleft group (0.59 +/- 1.35) than for the control group (0.11 +/- 0.54). 52% of the total number of initial and manifest lesions were localized to the maxillary incisors. A multivariate analysis yielded initial caries, oral hygiene and treatment with preoperative infant orthopaedics as the variables significantly associated with manifest caries.
Caries prevalence on the buccal surfaces of teeth in orthodontic patients was determined with QLF and visual examination immediately after removal of fixed appliances. The number of lesions found by QLF far outnumbered that found by visual examination, but the distribution pattern was similar. 97% of all subjects and on average 30% of the buccal surfaces in a person were affected. On average, in males 40% of surfaces and in females 22% showed white spots (p < 0.01). Caries prevalence was lower (p < 0.01) in incisors and cuspids than in molars and premolars. A positive correlation with caries prevalence was found for the bleeding scores 6 weeks after debonding and lactobacillus counts before debonding. Mutans streptococci counts, age, treatment duration, socioeconomic status and dietary habits showed no correlation with caries prevalence.
In studying growth and developmental processes in dental research, variables other than simple chronological age must often be taken into account if we are to adequately characterize differences in the developmental patterns of the groups under consideration. As demonstrated in this article, cohort, time-of-measurement, and learning (testing) effects may significantly interfere with our ability to directly study development if the traditional cross-sectional and longitudinal designs are used. Mixed-longitudinal studies, with well-scheduled control groups, may better serve the dental research community in the design of studies dealing with the measurement of change.
Tooth size and morphology have been studied in 35 participants with trisomy G. The control material was obtained from 33 dental students. Special attention has been paid to the mean cusp pattern of the upper first and second molars. The classification matrix for the linear discriminant function analysis between participants with trisomy G and controls, based on five selected variables that determine the cusp pattern, showed three misclassifications.
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In this (semi) quantitative animal study the reaction of the periodontal ligament (PDL) to experimental tooth movement is described. To this end, rabbit first incisors were moved sideways with helical torsion springs for periods varying from 3-24 hours. The initial force of the springs was 50 gf. The histomorphology of the PDL was studied in 5 microns thick plastic sections. Comparison with control animals and animals wearing passive springs showed that tooth movement leads to an increased trauma in the PDL within only a few hours. This trauma is characterized by hyalinization, tears and ruptures in the fibres and blood vessels, and by the presence of extravascular erythrocytes and pyknosis. Tissue damage significantly increased with time. After 24 hours of tooth movement, the PDL fibers are compressed or stretched in 68% of the sections and the blood vessels in the PDL are compressed or stretched in 62% of the sections. Even in the controls, more than 15% of the sections displayed slightly stretched or compressed fibers, and about 10% showed slightly compressed or stretched blood vessels. This indicates that some damage is regularly present in a normally functioning PDL. Increases in the percentage of sections with blood vessel compression are found in all groups wearing passive springs, especially after 6 hours. A high concordancy in compression and tension patterns of blood vessels and fibers is present in 83% of the sections. Pyknotic cells are practically confined to areas with compressed PDL fibers in rabbits wearing active springs. Extravascular erythrocytes were found in sections with all types of fiber patterns. A significant majority of extravascular erythrocytes, however, was found in areas with compressed fibers.