Larry J. Green

A dental-facial attractiveness scale

Since the decision to seek orthodontic treatment is frequently the result of concerns about appearance, assessment of need for treatment should include an impartial evaluation of dental-facial appearance. While some of the standardized techniques for assessing malocclusion have included a consideration of esthetic impairment, they tend to confound this with functional impairment. The purpose of this study was to develop a valid and reliable index that provides relatively objective judgments of dental-facial attractiveness. The subjects in this study were eighth- and ninth-grade children seeking orthodontic treatment and their siblings, and eighth- and ninth-grade children not seeking treatment and their siblings. Photographs of the children were rated for dental-facial attractiveness by lay and dental judges. Children were also assessed for severity of malocclusion by means of the Treatment Priority index. Children seeking treatment were perceived as significantly less attractive than children not seeking treatment. Dental judges rated children seeking treatment as more attractive than did nondental judges. Intraclass reliability coefficients were moderate to high.

Root resorption in maxillary central incisors following active orthodontic treatment

The purpose of this study was to determine if apical root resorption associated with orthodontic treatment continues after the termination of active treatment (that is, the removal of fixed appliances). A sample of 45 subjects who had experienced root resorption during treatment was selected from the orthodontic clinic at the State University of New York at Buffalo. The length of the maxillary central incisors was measured from lateral cephalometric radiograms taken before treatment, after active treatment, and after retention. From these data, the resorption occurring during and after active treatment was calculated. The mean amount of root resorption during active treatment was 2.93 mm. The mean amount of root resorption during the posttreatment period was 0.1 mm. There was a statistical difference between these two means using the Students t test at the 0.05 level of significance. The reliability coefficient comparing the first tracings and measurements in the 19 cases that were retraced and remeasured was r = 0.993. The data from this radiographic study support the hypothesis that root resorption associated with orthodontic treatment ceases with the termination of active treatment. There was also evidence to suggest that when posttreatment root resorption does occur, it is not necessarily associated with large amounts of root resorption during the active treatment period. It is more likely associated with other factors, such as traumatic occlusion and active force-delivering retainers.

Physical and mechanical properties of elastomers in orthodontic positioners

Elastomers for conventional Kesling-type tooth positioners are relatively inelastic and are primarily indicated as finishing devices. However, new materials, first described in the Japanese literature, with claims of a greater range of tooth movement warrant a comparison with conventional materials. Physical and mechanical property testing of positioner elastomers has not been reported in the orthodontic literature. This investigation compared properties of a high temperature vulcanizing (HTV) Japanese silicone (Orthocon) to three traditional polyurethane and vinyl-based polymers and five experimental silicone elastomers. Fourier transform infrared spectroscopy established the definitive chemical composition of the urethane and vinyl materials obtained from a commercial positioner laboratory. Tear strength, tensile strength, tensile stress at selected elongations, and ultimate elongation of all materials were evaluated at 37 degrees C in an aqueous environment. Hardness and water sorption values also were determined and an in vitro force measurement apparatus was fabricated to determine force levels exerted by positioner materials at low displacements. Orthocon was statistically different (Duncans multiple range test, p less than 0.05) from the traditional commercial urethane and vinyl materials. Orthocon had lower tear strength than the traditional materials. It also demonstrated lower stress values below 100% elongation. The parameters of tensile stress at 50% elongation and ultimate elongation were statistically identical for Orthocon and one experimental silicone material.

Relationships between variation of mandibular morphology and variation of nasopharyngeal airway size in monozygotic twins.

Abstract No Abstract Available. Based on a thesis submitted to the Faculty of the Graduate School of State University of New York at Buffalo in partial fulfillment of the requirements for the degre...

Hypodontia in human twins and families.

Abstract The incidence of hypodontia was studied in 369 pairs of twins ranging in age from 5 years to 18 years. The condition was present in forty-two (5.7 per cent) of the 738 persons investigated. The incidence was 6.1 per cent for females and 5.3 per cent for males. The tooth most frequently missing was the mandibular second premolor (55.7 per cent). The mandibular central incisor (15.2 per cent) was the second most frequently absent tooth, and the maxillary lateral incisor (13.9 per cent) ranked third. A comparison of the frequencies of concordance and discordance for missing teeth between monozygotic and dizygotic twin pairs resulted in a chi-square value of 0.82 (df = 1), indicating no significant difference between concordance for hypodontia in the two types of twins. The families of forty-four children known to have hypodontia were studied. The forty-four propositi had a total of 109 siblings 5 years of age or older. Fourteen of these 109 children (12.8 per cent) were found to be missing teeth. This percentage of siblings missing teeth was not significantly higher than would be expected to occur by chance in a random sample of 109 children (chi-square = 1.52, df = 1). The incidence of hypodontia was found to be equally frequent in siblings, regardless of birth order. No association was found between maternal health during pregnancy, maternal age at birth of the child, or early childhood diseases and the incidence of hypodontia. There was a tendency for those children with a very low birth weight (5 pounds 8 ounces or less, or premature children) to show a greater incidence of hypodontia. Also, children with hypodontia, especially those missing two or more teeth, showed a higher incidence of premature births when compared with children without hypodontia.

Frequency of Dental Trait Anomalies in Cleft, Sibling, and Noncleft Groups

The incidence and types of dental trait anomalies found in individuals with cleft lip or cleft palate or both (cleft group), in siblings of the cleft group, and in a group of individuals without cleft lip or cleft palate (noncleft group) were compared. The cleft group had 1.02 anomalies per individual, the sibling group, 0.38; and the noncleft group, 0.17. The frequency of occurrence of thick-curved maxillary central incisors, incisal fissures, and missing teeth were significantly different among the three groups.

Second Premolar Morphologic Trait Similarities in Twins

Seven morphologic traits of the mandibular second premolars were compared in 32 pairs of like-sexed twins to determine their value in diagnosing twin zygosity. Homolateral comparisons of the mandibular second premolars were accurate enough to be used as an aid in the diagnosis of monozygosity.

Bilateral Asymmetry in Tooth Cusp Occurrence in Human Monozygotic Twins, Dizygotic Twins, and Nontwins

Bilateral asymmetry in cusp occurrence of the hypoconulid and seventh cusps on the permanent mandibular first molar and the number of cusps on the mandibular premolars was examined in specimens from monozygotic twins, dizygotic twins, and nontwins. Bilateral asymmetry was similar in frequency and displayed no sex or side differences in the three samples.

Intra-Alveolar Dental Development in Twins

Intra-alveolar dental development of several permanent mandibular teeth was compared in 69 sets of twins. Bilateral symmetry of dental development was found in monozygotic and dizygotic twins. Comparisons of intrapair variances between monozygotic and dizygotic twins indicated that a strong genetic component exists in the mechanisms that influence intraalveolar dental development.

Validity of an orthodontic treatment priority index to measure need for treatment.

In establishing the validity of an index for identifying individuals needing orthodontic treatment, we must concern ourselves with the construct validity of the measure. Since it is clear that the relevant theory concerning need for treatment must include esthetics and the accompanying social and psychological characteristics, the construct validation of an index to measure need for treatment must include tests of hypotheses with these dimensions. If we consider a childs self-perception of occlusion as a psychological variable and another persons perception of a childs occlusion as a social variable, theory relevant to an index of need for treatment would hypothesize that each should correlate positively with need for treatment. Subjects were eighth and ninth grade students from a metropolitan area in western New York State. Fifty-two of the children were planning to obtain orthodontic treatment, and 102 were not. Data were also obtained, whenever possible, from both parents and from a sibling (if any) nearest in age to the child. Data were collected in one session by a trained interviewer who used a structured interview and also photographed the childs teeth and jaws. In addition, the child was given an orthodontic Treatment Priority Index (TPI) examination by a dentist enrolled in a graduate program in orthodontics, who had previously been trained and standardized in the use of the TPI. In addition, to the TPI, scores obtained included three psychological measures and eight social measures. Each of the psychological and social variables correlated significantly with TPI at the 0.05 level, with values ranging from 0.21 to 0.54 and a median value of 0.42. On the basis of these correlations, evidence is presented for the construct validity of the TPI when measuring need for treatment.