A method for integrating facial cephalometry and corrected lateral tomography of the temporomandibular joint.

OBJECTIVES: To test the validity of an indirect method for obtaining the Frankfort horizontal (FH) plane and transferring it from the originating cephalogram to a tomogram. METHODS: One hundred and fifty-two corrected lateral tomograms from 38 individuals, taken before and after treatment, were used for this study. The tomograms were scanned and digitized. The angle between the FH plane and the long axis of the pterygopalatine fossa was measured on the reciprocal cephalograms. In addition, a tangent was drawn at the uppermost point of the glenoid fossa and parallel to the upper border of the film. Common variables regarding these two planes were measured and compared. RESULTS: It was found that the tangent to the fossa roof, parallel to the superior border of the film, did not coincide with the transferred cephalometric FH plane. Statistically significant differences were found between all variables for the two groups. CONCLUSIONS: In cases where integration of cephalometric and tomographic measurements are needed, the drawing of a tangent on the roof of the fossa is not a reliable method.

The growth of articular eminence height during craniofacial growth period.

This study was done to study the growth of the articular eminence height during the postnatal craniofacial growth period. Ninety (90) skulls were divided into three equal groups, named A, B, and C. The A group belonged to individuals showing deciduous dentition, the B group showed mixed dentition, and the C group permanent dentition. The skulls were stabilized so that the FH plane was really horizontal. This was assured using a common facial bow, inserted into the acoustic meatuses and the infraorbital foramen, and a common water-level device. Using a silicone type impression material, impressions were taken of all temporal fossae. Special care was taken in order that the base of the materials was parallel to the FH plane. After setting, the impression was removed and a common eggslicer was used to cut the material into sections of 2.5 mm each. The three middle sections were removed, photocopied with a common photocopy machine, enlarged to a 200% scale and the height of the eminentia were measured by using an electronic caliper. The mean of the three calculations was reduced to its normal value, and was tabulated for each eminence. The study concluded that the articular eminence height grows at a very high rate until the age of seven (the period of deciduous dentition, development, and function), almost stops until the age of eleven (the period of mixed dentition), and acquires the rest of its height by the age of 20. This growth plan more nearly approximates the somatic or the general growth curve.

Intermaxillary forces during activator treatment.

The mode of action of the activator appliance is still unclear. Apart from a possible mandibular growth enhancing effect, some investigators believe that orthopedic forces may be applied to the maxilla, contributing to Class II correction by inhibition of maxillary growth. In addition, orthodontic forces may arise that produce dentoalveolar changes. The purpose of this study was to measure the magnitude of anteroposterior intermaxillary forces during wear of the activator appliance. Ten consecutive patients with Class II dental and skeletal relationships were treated with a modified activator appliance. The appliance had maxillary and mandibular segments that could be detached from each other during the measuring session. A force transducer was placed at the anterior part of the maxillary segment, and the anteroposterior force exerted by the mandibular segment was measured. Measurements were taken in the upright and reclined position at every patient visit for a period of 6 months. Results indicated that intermaxillary forces were generally in the orthodontic range (median values of 100 gf at the upright position and 123 gf at the reclined position). A wide variation in force levels was noted, both between patients and for the same patient during the experimental period. No statistically significant change in force levels was observed during the 6 month period and no difference was noted between upright and reclined posture.