210 Revzews and abstracts Am. J. Orthod. August 1973

and vertical imbalances by means of three vertical and four horizontal equivalent dimensions of facial parts. The proposed geometric construction for this analysis was oriented on a line determined as a tangent to the maxillary tuberosities through the intersection of the great wings of the sphenoid with the planurn sphenoidale or cranial floor. This posterior nasomaxillary vertical line was the key reference line to which all other lines were drawn, either perpendicular or parallel. A study was conducted of 50 young women radio- graphed in the upright or natural head position (Moorrees and Kean: Am. J. Phys. Anthropol : 16 :213-234, 1958)) to assess the effect of biologic variation on the position of landmarks defining the reference line and cant of the entire geometric configuration on the clinical applicability of this analysis by Enlow and his co-workers. The posterior nasomaxillary reference “line was found to form an angle of 9.0 degrees caudad to the extracranial vertical, with a standard deviation of 4.4 degrees and a range of 18.7 degrees.

Three radiographs, selected at random from the sample, revealed bimaxillary prognathism according to the Enlow analysis while, clinically, two subjects were orthognathic and one subject was mesognathic. More realistic and meaningful determination of facial form and more precise definition of horizontal and vertical growth trends can be made by obtaining the radiographs in the natural head position. Thereby, the coordinate system proposed by Enlow and colleagues can be oriented on the extracranial vertical, that is, the posterior nasomaxillary line parallel to the vertical. This correction is necessary because variations in the spatial location of the middle cranial fossa and the dorsal limit of the maxilla are not interrelated.

Topical Application of Thyrocalcitonin in the Jaws of laboratory Dogs

Samuel Foster Tufts University Sohool of Dental Medicine, Boston, Mass.

This experiment was designed to confirm past experimental evidence and to determine if thyrocalcitonin applied topically to the extraction sites of dogs promoted increased bone formation and faster healing. Prior studies indicated that thyrocalcitonin, topically applied, causes bony changes. Topically ap- plied thyrocalcitonin was employed on the extraction sites in the jaws of four dogs. Prior to sacrifice at 30 and 60 days, oxytetracyclinel was injected intramuscularly into the animals. After sacrifice both the control and experimental sockets were examined under ultraviolet light. These sections were then decalcified and hematoxylin and eosin and trichrome stains were em- ployed for histologic evaluation.

The following conclusions were drawn from the study: 1. Thyrocalcitonin causes a more rapid proliferation of bone-forming

constituents. 2. Oxytetracycline used as a bone marker showed more increased

Volume 64 Numbel- 2 Reviews and abstracts 211

bone formation in the experimental sockets than in respective control sockets.

3. Physiologic bone healing was evident in both the control and ex- perimental groups.

4. There is no significant clinical difference between the experimental and control sites. In conclusion, the experimentally treated sockets had an increased rate of

bone formation with a resultant decrease in the maturity and density of the bone. The control sites contained more osteoid and less trabeculation and collagen, indicating a slower growth rate of new bone.