Guided and unguided mandibular reference positions in asymptomatic individuals.

OBJECTIVES: To determine the difference between guided and unguided mandibular reference positions assessed by articulator simulation. SETTING AND SAMPLE POPULATION: This study was carried out at the Division of Orthodontics at Vienna Medical University. The sample population consisted of 19 men and 18 women aged 23-32 years and without temporomandibular disorder. MATERIALS AND METHODS: Three examiners used bimanual operator guidance and unguided mandibular stationary hinging at final jaw closure before occlusal contact and made occlusal wax recordings. The examiners repeated both techniques after 8 and 17 days on the same subjects. Condylar positions were assessed using articulator-mounted casts and a three-dimensional electronic condylar position indicator. RESULTS: Bimanual guidance positioned the condylar spheres, on average, 0.1 mm more right and 0.6 mm more posterior and superior to unguided hinging (p < 0.04). The repeatability of bimanual guidance by three operators and on 3 days resulted in inter-repetition standard deviations ranging from 0.19 to 0.4 mm and from 0.41 to 0.76 mm for unguided hinging. The highest fraction of the total variance came from the individuals, followed by days, then intra-operator and interoperator variability. Both methods showed considerable overlap of condylar sphere positions at the 95% confidence level. CONCLUSION: Within the limits of an articulator study, the spatial variability of condylar sphere positions suggested a statistically but not clinically relevant methodological difference between bimanual guidance and unguided stationary hinging.

An improved transpalatal bar design. Part I. Comparison of moments and forces delivered by two bar designs for symmetrical molar derotation.

Moments and forces delivered during symmetrical derotation of upper molars by 10 Goshgarian-type (GTPB) and 10 Zachrisson-type transpalatal bars (ZTPB) were measured in laboratory experiments using a computer-based strain gauge. The bar passivity in sagittal, transverse, and vertical planes was first assessed at the measurement apparatus. Then each end of the 20 passive bars was symmetrically activated by 10 mm in the sagittal plane using a template. The activated bars were placed into lingual attachments of the measuring apparatus, and three consecutive measurement steps were done for each bar. Measurements were made when the attachments were at 0 degrees, 5 degrees, and 10 degrees of deactivation. The mesiodistal (sagittal) forces, the horizontal forces, and the moments of rotation at the right and left attachments were measured at each step. The horizontal forces and the moments of rotation of the two designs had statistically significant differences. Greater moments of rotation were produced by the GTPB. The ZTPB produced significantly lower contractive horizontal forces than did the GTPB at 5 degrees and 10 degrees of deactivation.

An improved transpalatal bar design. Part II. Clinical upper molar derotation--case report.

Bilaterally rotated upper first molars (mesial in, distal out) were derotated in two different cases by using a custom-made transpalatal bar. The bars were reactivated, if necessary, at four-week controls. The derotations were fully corrected after about three months.

A distraction abutment system for 3-dimensional distraction osteogenesis of the alveolar process: technical note.

To date, distraction osteogenesis has been carried out exclusively with devices that allow distraction in one given direction only. However, the new distraction abutment system described in this article allows distraction in any functionally or esthetically desired direction following osseointegration of 1 or several implants, provided that there are adjacent teeth or other osseointegrated implants. With this abutment system, an implant fixed in a position dictated by available bone volume can be moved into a prosthetically desirable position following segmental osteotomy. Accordingly, it also allows correction of the position of implants that were placed at an early age but whose position has changed as the result of jaw growth. Compared with conventional augmentation techniques carried out before or after implant placement, this method should lead not only to a shorter overall treatment time, but also to reduced strain on the patient and better long-term prognosis for success of implants.