316 Keviews and abstracts Am. J. Orthod. September 1913

5. Soft-tissue response showed no significant differences between Class I and Class II subjects.

increasing Vertical imension in the Growing Face: An Experimental Study

James A. McNamara, Jr. Department of Anatomy and Center for Human Growth and Development,

The University of Michigan, Ann Arbor, Mich.

Six young Jl’~cac, mulattu monkeys were used in an experiment designed to study craniofacial adaptation to increased vertical dimension. Through the use of fixed gold castings on the maxillary arch, the bite was opened 3, 5, 7, 10, and 15 mm. in the incisal region. All animals adapted quickly to the new occlusal position without observable discomfort or loss of weight. Adaptive changes were studied cephalometrically (with metallic implants), electromyo- graphically, and histologically.

Neuromuscular adaptation was complete within 1 month for a 3 mm. opening, and only slight changes in tooth position were observed when the appliance was removed and the dnimal was killed after 5 months.

The animals wearing 10 and 15 mm. appliances demonstrated hyperactivity of muscle function throughout the experimental period. When the appliances were removed after 5 months, the animals continued to demonstrate muscular hyperactivity during the ensuing 5 month period. Marked occlusal changes were noted in these animals, including differential eruption of teeth and change in molar relationship. All experimental changes were compared to a control group of fifteen animals of the same dentitional age.

Computerized Mesh iagram Analysis of Lateral Head Radiographs

Robert 6. Reed, Ralph L. Kent, Jr., Carlton 5. Glatky, and Laure M. L. Lebret Forsyth Dental Center-Harvard School of Public Health, Boston, Mass.

This cephalometric analysis permits graphic illustration of sagittal and vertical dysplasias as a guide in treatment planning.

The difference between the proportionate location of each landmark within its mesh rectangle and the proportionate location of the corresponding land- mark in the standard mesh defines a displacement vector for that landmark.

The mesh distorations, drawn by a computer-monitored Calcomp plotter, were based on twenty separate determinations, both horizontal and vertical, in each small mesh rectangle or a total of 1,160 determinations.

Each of these grid point vectors was calculated as an average of all facial landmark vectors, weighted inversely by the distances between the specific grid point and the facial landmarks normalized as in the reference standard.

Thereby, landmarks in close proximity to a specific grid point exerted the greatest influence on the vector of that grid point. Moreover, landmarks in the mandible and upper face were considered independent of each other to repre- sent an existing dysplasia in mandibular and maxillary development of a patient.