Louis A. Norton

Linguopalatal pressure in children

I t. is clear that tongue function plays some role in the devc~lopment of the dental arches. The distortions of the arches which accompany microor macroglossia, as well as the less dramatic but clinically significa.nt effects of such oral habits as tongue-thrusting, illustrate the possible effects. Theories of normal and abnormal oral development, particularly those concerning the functional matrix concepts of van der Klaauw and MOSS,~ have emphasized muscle function in recent years. This may reflect a return toward a middle ground after overemphasis on function in the 1920’s and relative neglect in the 1940’s. Several investigators have now presented data concerning lingual, labial, and buccal pressures against the dentition of youn g adults, using electronic pressure-recording techniyues.‘-4 Lear’s” recent work has confirmed the belief of most workers that it is not possible to demonstrate a true balance of cstcrnal forces on stable adult dentitions. In ordrr to study more closely the relationship between lingual function and dental arch development in growing chiltlrcn, mc began a longitudinal study of a group of 5 to 8-year-old children 2 years ago. This article presents the first data concerning linguopalatal pressures in this age group and discusses the implications of these initial findings with regard to dental arch development..

Effects of a pulsed electromagnetic field on a mixed chondroblastic tissue culture.

A mixed tissue culture predominantly composed of chondroblastic tissue was perturbed by a pulsed electromagnetic field (PEMF). Some cultures were nonconfluent, and purposely retarded in growth to resemble an atrophic nonunion, while others were grown to confluence in about one-half the time as a model for a hypertrophic nonunion. These two groups tested the effect of growth rate upon the products of cell proliferation and differentiation. The slowly growing cultures were stimulated to synthesize hydroxyproline. The rapidly growing cultures showed a large increase in lysozyme activity, and increase in hyaluronate and DNA, and a decrease in glycosaminoglycan. Exogenous lysozyme further decreased the glycosaminoglycan synthesis in the presence of PEMF. Chitotriose, a specific lysozyme inhibitor abolished this effect. Cycloheximide, a protein synthesis inhibitor, did not abolish the activation of lysozyme found in the matrix. Thus lysozyme appears to be activated by PEMF. These observations of the rapidly growing confluent cultures are consistent with events described in the normal healing of a bone fracture or endochrondral growth. Thus, PEMF appears to promote normal healing, probably by altering cartilaginous lysozyme activity in the matrix, and possibly the sequence of events leading to calcification.

Bone Growth in Organ Culture Modified by an Electric Field

Unidirectional pulsating electric fields caused changes in the patterns of growth in rat calvaria grown in organ culture. Morphologic pattern variations were studied by radioautographic techniques. The changes occurred at the negatively charged bone surface. In a strong field, the growth pattern became disoriented.

Inhibition of Bone Growth in vitro by Endotoxin: Histamine Effect

BECAUSE bacteria are found in close proximity to soft tissue and bone in the oral cavity, it seems logical that bacterial endotoxin could affect the metabolism of bone and contribute to the bone loss seen in periodontal disease. We investigated the effects of bacterial endotoxins on rapidly growing bone in an organ culture system. Also, because there is evidence that histamine affects the activity of endotoxin1–3, we cultured bones in an environment containing both endotoxin and histamine, and found that synthesis of structural protein was inhibited without affecting cell turnover.

Electrical stimulation of osteogenesis in periodontal defects.

Although the literature on bioelectrical phenomena is extensive, there is a paucity of research on its application in the field of dentistry. This study was designed to evaluate the effect of bioelectric phenomena on pathological osseous defects in the periodontium of Beagle dogs. Galvanic and thermocouple generators were designed to deliver a current in the nanoampere range. The galvanic unit implanted in the area of periodontal osseous defects in five dogs. These sites were randomly designated as experimental, active controls, and passive controls. The experimental and control units were implanted submucoperiosteally with the negative electrodes extending into the osseous defects. The bone was labeled with Procion Red H-8Bs at one week. Clinical and radiographic evaluation revealed no significant changes in the depth of the defects. The animals were sacrificed at 45 days and block sections were prepared. Histological measurement suggested that endosteal apposition was enhanced in all experimental sites as compared to controls. The results were discussed in relation to magnitude of current used, the influence of pathological bone, the potential of each type of experimental unit for clinical use, and the direction of further research in the area.

Method to Investigate Bioelectric Regeneration of Bone in Periodontal Defects

A piezoelectric potential may be generated when bone is stressed artificially or by function (FuKADA and YASUDA, J Physiol Soc Jap 12: 11581168, 1957; BASSETT, Sci Am 213: 18-25, 1965). Minute electric currents applied during bone repair and growth produce physical change (LAVINE ET AL, Science 175: 1118-1120, 1972; NORTON and MOORE, J Dent Res 51: 1492-1499, 1972). In view of these findings, it was hypothesized that new bone growth may be directed into a pathologically occurring defect by the application of current. To test this hypothesis, it was necessary to design a tissue-compatible miniature power source with low current values and long life, find a suitable experimental animal, and perfect a surgical implantation technique. A power source was designed which consisted of a 1.35 v hearing aid battery, a 1/ w 12 megolhm resistor and two dissimilar electrode wires. A direct current of 1.1 x 10-4 amperes was generated (SMITH, Ann NY Acad Sci 238: 500-507, 1974). Wire connections were made with a silver-filled epoxy compound., The power source was encapsulated with an epoxy resinb and reencapsulated in silastic elastomere (Fig 1). Adult beagle dogs with chronic periodontal disease were selected as the experimental animals. Beagles are a suitable size for surgical implantation and manifest a periodontal bone loss sim-

Prediction of orthodontic band sizes from selected teeth

Abstract An attempt was made to predict orthodontic band sizes from the band sizes of certain key teeth. In order to accomplish this, a study was designed to relate individual teeth to each other from a tooth size measurement. Various studies which had looked at tooth size from a mesiodistal standpoint were discussed. Some of these studies had observed a correlation between one tooth and another within the same individual. We decided to examine tooth circumference as a prediction. Fifty-three patients about to undergo active orthodontic treatment were selected for this study. Band sizes, which are really circumferential measurements, were recorded on prepared forms by the orthodontists involved in the study. A statistical correlation was made between the band sizes of certain key teeth in the dental arch and the remainder of the teeth in an attempt to simplify the selection of the preformed bands for a given patient. These data were subjected to additional analysis to determine whether an appropriate tooth could be used as the independent variable in predicting the band sizes for the remaining teeth. It was concluded from this study that the band size for the second premolar was sometimes significantly related to the band size for the canine and lateral incisor and only generally related to the band size for the central incisors. There appears to be a strong relationship between right and left counterparts. Finally, band size correlations were higher in the maxillary arch than in the mandibular arch. Other analyses were made from our data. Band size figures were examined for sex differences in case of predictability, with no significant differences being found. When the data were compared for intra-arch relationships, a very high correlation was observed between left and right band sizes. An experienced orthodontist could probably do as well as these prediction models. Still, these models may be useful in training dental auxiliary personnel in band selection.