Clinical, radiographic, and genetic evaluation of a novel form of autosomal-dominant oligodontia.

A frameshift mutation recently identified within the paired domain of the transcription factor, PAX9, has been linked to a unique form of oligodontia in a single, multigenerational family (Stockton et al., 2000). We now describe the phenotypic and segregation analyses of this remarkable kindred, the initial approach taken to identify a candidate gene involved in this form of oligodontia, and the power of this single-family pedigree to generate significant linkage in a genome search. Of the 43 family members enrolled in this study, 21 individuals were affected with several congenitally missing permanent teeth. The pattern of inheritance of the oligodontia trait suggested the involvement of a single gene bearing a dominant mutation. To various degrees, affected members lacked permanent first, second, and third molars in all four quadrants. Several individuals with missing molars also lacked second premolars- most commonly, maxillary second premolars and mandibular central incisors. To the best of our knowledge, this pattern of non-syndromic, familial tooth agenesis has not been previously described in the literature. Since a missense mutation in the homeobox gene, MSX1, was previously linked to tooth agenesis in a single family lacking second premolars and third molars, we performed a mutational analysis of MSX1 by PCR. The absence of a mutation in exons 1 and 2 of MSX1 suggested that allelic mutations in the coding region of MSX1 are not associated with this phenotypically distinct form of oligodontia. Computer simulation of linkage analysis further proved that this pedigree alone was sufficient to generate a significant result for a total genome scan.

An in vitro study of the accuracy of a new protocol for planning distraction osteogenesis of the mandible.

PURPOSE: The purpose of this study was to determine the in vitro accuracy of a new protocol for distraction osteogenesis of the mandible that involves a planning process and a surgical technique. MATERIALS AND METHODS: An experimental design was developed to simulate distraction osteogenesis on stereolithographic models of patients with craniofacial deformities. All patients had previously undergone 3-dimensional computerized scans of the craniofacial skeleton. The data from these scans were used to generate stereolithographic models. Before the fabrication of the models, the computed tomography (CT) data were manipulated to add a series of rulers and markers to the models. The 3-dimensional computerized scans were also used as the basis of the planning process. They were imported into an animation software (3D-Studio Max; Discreet, Montreal, Canada), and a virtual distractor was built and installed on the model, and the osteotomies and distraction processes were simulated. Finally, a recipe for sequencing the linear and angular changes of the distractor were calculated. A surgical technique was developed to facilitate the precise installation of the distractor as indicated in the presurgical plan. The transfer of information regarding pin position and orientation from the computer model to the patient was accomplished by creating a surgical template. This template was designed in the computer and fabricated by use of stereolithography. Mock surgery was performed on the stereolithographic models, and the results were compared with those predicted by the computer. The difference between the actual position and the predicted position was recorded. RESULTS: On the X-axis, the difference between the predicted position for the condylar marker and the actual position of the marker on the stereolithographic models was 0.6 +/- 1.1 mm. On the Y-axis, the difference between the predicted position for the condylar marker and the actual position of the marker on the stereolithographic models was -0.9 +/- 2.6. On the Z-axis, the difference between the predicted position for the condylar marker and the actual position of the marker on the stereolithographic models was 0.04 +/- 0.8 mm. There was excellent correlation between the predicted and the actual measurements for the X, Y, and Z axes: 0.98, 0.93, and 0.98, respectively. CONCLUSIONS: The results indicate that the combination of this planning process and surgical technique was very accurate. This in vitro study is the first step in determining the clinical usefulness of this protocol. If the results of this study are validated in clinical practice, this protocol will allow clinicians to improve the clinical outcomes of patients treated with distraction osteogenesis.

Cephalometric values for adult Mexican-Americans.

Cephalometric studies of adult Mexican-Americans are incomplete. The purpose of this study was to evaluate whether significant cephalometric differences exist between adult Mexican-American, black American, and white patients. Lateral cephalometric radiographs were taken of 48 Mexican-American adults (23 men, 25 women). All subjects met the following criteria: parents, grandparents, or great-grandparents were born in Mexico; 18 to 50 years of age; Class I occlusion with minor or no crowding; good facial balance; no significant medical history or history of facial trauma; no previous orthodontic treatment or maxillofacial surgery. Twenty-five cephalometric measurements were analyzed. Significant racial and sexual differences were found in the following areas: skeletal measurement (SNA, ANB, PO-N perpendicular, Co-A, Co-Gn, ANS-Me, MP-FH, MP-SN); dental measurement (U1-A perpendicular, L1-APo, U1-L1, IMPA); soft tissue measurement (NLA, FCA, UFH (pu), ULL). Orthodontists and oral surgeons will find the cephalometric values of help in the diagnosis and treatment planning of potential orthognathic surgery patients.

Culicoides spp. (Diptera: Ceratopogonidae) associated with cattle in St. Croix, Virgin Islands, and their relevance to bluetongue virus.

Potential biting midge vectors were collected at two sites on St. Croix as part of an ongoing study on the epidemiology of bluetongue viruses in the Caribbean region. Six species of Culicoides were trapped in a New Jersey light trap (mean = 173 biting midges/trap night) near cattle on a dairy farm. C. furens (Poey) and C. insignis Lutz were the predominant phototactic species, and C. pusillus Lutz, C. trilineatus Fox, C. jamaicensis Edwards, and C. phlebotomus (Williston) were collected less frequently. Four species of Culicoides were aspirated from bovine bait during the morning and evening crepuscular periods with a modified car vacuum. C. furens was aspirated primarily from the ventral portions of the bovine host, whereas C. insignis and C. pusillus were collected principally from the dorsum, and C. trilineatus was collected equally from all aspects. At least one individual of each of these aspirated species was blood engorged. Because C. furens, C. insignis, C. pusillus, and C. trilineatus were most abundant and feed on cattle, they deserve further consideration as vectors of bluetongue virus on St. Croix.

Structural responses of orthodontic wires in flexure from a proposed alternative to the existing specification test.

To be reaffirmed in 1987 for lack of a ready replacement, the flexural (elastic-bending) test protocol of ADA Specification No. 32 is judged inadequate. The protocol is problematic because of potentials for erroneous use of the theoretical component, incompatible with the flexible titanium alloy and multistrand stainless steel wires marketed subsequent to the preparation of the specification, and obscure to the clinician because it dictates quantifications of mechanical (pertaining to material only) rather than structural properties (including wire shape and size influences). A five-point elastic-bending test is proposed that stimulates wire activation toward engagement of a single, malaligned tooth crown. An experimental study was undertaken to determine values of transverse stiffness and corresponding elastic range for a broad sample of orthodontic wires and in the process to evaluate the proposed alternative test. Reduced test results are presented; comparisons of rankings and ratios from available theoretical developments and other experimental outcomes, including findings from the existing standard test, were completed. The difficulties with the existing protocol are largely eliminated with the alternative test; a test fixture and procedures are relatively straightforward to fabricate and follow, and the structural characteristics quantified are more meaningful to the practitioner.