PubMed Health⌕ Search

Biomedical subjects

Sheldon Peck

Publications and source records attributed to Sheldon Peck.

14 recordsLinked to original sources
PubMed2006

Extreme variations in the shape of mandibular premolars.

INTRODUCTION: Human mandibular premolars (MnP) are highly variable in shape. An extreme variation, called here MnP tooth-shape deviation (MnP-TSD), is characterized by a squeezed faciolingual (FL) dimension and an enlarged mesiodistal (MD) dimension, reversing the typical premolar proportions. This is the first in-depth study of the MnP-TSD anomaly. METHODS: Eighteen subjects with 29 MnP-TSD teeth were selected for odontometric analysis by using dental casts. For each affected MnP, an MD/FL proportional index and a representation of crown area (MD x FL) were calculated from maximum MD and FL crown diameters. Data were compared with reference values for MnP. RESULTS: MnP-TSD was observed over 8 times more frequently in second premolars than in first premolars. Male expression was slightly greater (ratio, 1.4:1), and bilateral occurrence was observed in 59% of the subjects. Occurrence was noted among all ethno-racial groupings in the sample (16 whites, 1 black, 1 Asian). The MD/FL index of premolars with the MnP-TSD anomaly always exceeded 100 (103 to 148); this is significantly higher than normal values. In contrast, the crown areas of the affected teeth were remarkably similar to normal reference values. In addition to the squeezed tooth shape, subjects with pronounced MnP-TSD also had mesiolingual/distofacial twisting in MnP occlusal features. CONCLUSIONS: Extremely abnormal MD/FL proportions coupled with normal crown-area values provide reliable factors for differential diagnosis of the MnP-TSD anomaly. This uncommon MnP dysmorphology can be a challenge to orthodontic movement and achievement of ideal occlusal intercuspation.

Bicuspid↗
PubMed2003

Palatally displaced canine anomaly in monozygotic twins.

The palatally displaced canine (PDC) anomaly is a tooth malposition occurring in 1% to 3% of most populations. From the results of family studies, the PDC phenotype appears to be under strong genetic influence. In this study we report monozygotic (MZ) twin girls with bilateral PDC expression. The finding of PDC anomaly in MZ twins--to our knowledge, the first such published case--lends further support to evidence of genetic control of the PDC anomaly.

Child↗
PubMed2002

Malposition of unerupted mandibular second premolar associated with agenesis of its antimere.

Aberrant tooth positions--such as infraocclusion, mesially ectopic maxillary first molar, palatally displaced canine, tooth transposition, and tooth rotation--are gaining attention as variables in a putative, genetically related pattern of dental anomalies. This study, using panoramic roentgenograms, was undertaken to measure the angular position of the unerupted mandibular second premolar (MnP2) in children. The experimental subjects were 17 children with an unerupted MnP2 and agenesis of the other MnP2, a likely indicator of site-specific genetic disturbance. An age/sex-matched control-reference group was similarly measured for comparison. The hypothesis tested was that the unerupted, developing MnP2 teeth in the experimental subjects would show measurably greater malpositions than those of the control sample. The results indicated a 10 degrees increase in distoangular inclination for the unerupted MnP2 in the agenesis sample; this was a highly significant difference statistically (P = .003), compared with the MnP2 inclinations in the control sample. These findings, associating exaggerated distoangular malposition of the unerupted MnP2 in children with agenesis of the contralateral MnP2, identify a new phenotype of dental developmental disturbance to add to the accumulated evidence supporting shared genetic mechanisms for dental anomaly patterns.

Adolescent↗
PubMed2002

Dental arch width in Class II Division 2 deep-bite malocclusion.

A severe phenotype of Angle's Class II Division 2 (II/2) malocclusion with extremely deep overbite has been called cover-bite, or "Deckbiss" in its early German descriptions. This distinctive occlusal variation is characterized by skeletofacial hypodivergence, mandibular dentoalveolar retrusion, excessive bony chin projection, reduced mesiodistal tooth size, maxillary incisor retroclination, and at least 100% overbite, covering at least 1 mandibular incisor in occlusion. In this study, maxillary and mandibular dental arch widths measured at the first molars and the canines were recorded from dental casts of 23 subjects with II/2 cover-bite malocclusions. The data were compared with a control-reference sample of 46 orthodontic patients matched for age and gender. In the cover-bite group, the intermolar widths in both arches and the intercanine width in the maxilla were comparable with those in the control sample. However, mandibular intercanine width in the II/2 cover-bite group was significantly less than that of the controls (P =.01). These findings suggest that II/2 deep overbite malocclusion is characterized by normalized and relatively compatible transverse dimensions in the maxilla and in the mandibular posterior segments. The transverse underdevelopment that this study identified in the mandible from canine to canine is probably responsible for mandibular incisor compression and crowding--natural sequelae of the deep overbite in II/2 cover-bite. Thus, a reasonable orthodontic treatment plan for the mandibular dentoalveolar compensation often seen in II/2 deep-bite patients would be anterior expansion of the mandibular arch width, usually reducing the need for orthodontic tooth extractions and increasing the desirability of fixed retention.

Adolescent↗
PubMed2002

Concomitant occurrence of canine malposition and tooth agenesis: evidence of orofacial genetic fields.

Certain discrete malpositions of the human canine tooth and agenesis of at least 1 tooth (hypodontia) are abnormalities known to occur together frequently. This study examines the specificity of tooth-agenesis sites associated with the occurrence of 3 unambiguous canine malpositions: palatally displaced canine (PDC; n = 58), mandibular lateral incisor-canine transposition (Mn.I2.C; n = 60), and maxillary canine-first premolar transposition (Mx.C.P1; n = 43). A fourth sample was formed from 4 cases of combined occurrence of PDC and Mn.I2.C, the only combination-phenotype noted among the 161 subjects. Oral panoramic radiographs were used to identify agenesis of at least 1 third molar (M3), mandibular second premolar (MnP2), and maxillary lateral incisor (MxI2)-the 3 most frequently absent tooth types among people of European descent. PDC and Mn.I2.C transposition appear to be associated with significantly increased M3 agenesis (P <.01), representing the posterior orofacial field, and Mx.C.P1 transposition appears to be associated with conspicuously elevated MxI2 agenesis (P <.001), representing the anterior orofacial field. MnP2 agenesis appears to represent an intermediate field, found in significantly elevated frequencies with all 3 canine positional anomalies. Coupling these new clinical findings with results from recent molecular studies, we suggest that transcription factors such as MSX1 and PAX9, which have been associated with agenesis of molars, might be involved in the genetic control of Mn.I2.C transposition and PDC, tooth malpositions connected here with the specific expression of posterior-field (M3) hypodontia.

Adolescent↗
PubMedDate not supplied

The students of Edward Hartley Angle, the first specialist in orthodontics: a definitive compilation.

Edward Hartley Angle, MD, DDS, (1855-1930) was ardent in making orthodontics a distinct specialty. In 1900, he founded the first school in the world devoted to specialty training in orthodontics, the Angle School of Orthodontia in St. Louis, Missouri. Over the next 30 years, the Angle School moved from St. Louis to New York City to New London, Connecticut, and finally to Pasadena, California. There was always some uncertainty regarding the accuracy of lists of graduates of the Angle School, since the associated prestige was often a lure for false representation by some practitioners. The purpose of this article is to delineate an authoritative list of Angle's students. Recent additions to primary source material help in reconstructing Edward Angle's seminal educational contributions. From 1900 to 1930, Angle taught orthodontics to 198 students of which 185 received certificates of course completion. The remaining 13 received some training from Angle, but did not complete his formal course for a variety of reasons. He was highly selective in choosing the best dentist-students. Among his students were 8 women, 6 Canadians and 27 from 15 countries outside North America. Angle's graduates invariably became worldwide leaders and contributors in orthodontics in the first half of the 20th century.

Education, Dental↗