OF REVIEWS AND ABSTRACTS

Edited by Alex Jacobson, DMD, MS, MDS, PhD Birminghnm, Ala.

All inquiries regarding information on reviews and abstracts should be directed to the respective authors. Articles or books for review in this department should be addressed to Dr. Alex Jacobson, University of Alabama School of Dentistry, University Station/Birmingham, Alabama 35294.

Nondental Study of the “Functional atrix” Hypothesis

Danielle I. Mollenhauer Aust. Qrthod. J. 1988;10:240-6

An exploratory study was undertaken to obtain data on arm measurements of competitive female tennis players at three age levels-prepubertal (10 to 12 years): postpubertal (16 to 18 years), and mature (45 to 70 years). They were matched with persons who did not play with racquets but who had generally taken part in sports (nonracquet sports persons). Comparisons were to be made between the arms they preferred for playing tennis with their other (nonpreferred) arms, and with the arms of nonracquet sports persons. The results suggest that competitive female tennis players differ from nonracquet sports persons in that these tennis play- ers have significantly shorter preferred forearm bone length and greater preferred forearm girth measure- ments than the nomacquet persons, because their pre- ferred forearm length was longer. These findings were most prominent in the postpubertal group, which in- dicates that a study to explore the epigenetic hypothesis using arms is justified. The fact that it was less prom- inent in the older age group could be explained by the observation that the older players did not stroke the ball as aggressively. The results of this study also indicated that there were no significant differences between tennis players and nontennis players in ponderal indices, pre- ferred grip strength, or preferred elbow and wrist widths. Therefore the results suggest that the phenom- enon should be studied in, rather than extrapolated to, tlle maxillofacial region.

Alex Jacobson

Head Position, Posture, and rognathism: The Chapman Prize ssay, 1966

Br. J. Orrhod. 1988;15:227-39

To reduce the confusion between natural head po- sition and natural head posture, the author describes natural head position as the relationship of the head to

true vertical, and he refers to natural head posture as the relationship of the head to the cervical column.

To investigate the two relationships of the head, the sample of 110 lateral head films were divided into five groups-three representing horizontal discrepancies selected on ANB differences (Classes I, II: and III dental base relationships) and two representing vertical discrepancies selected on Bjork’s posterior angles (“high angle” and “low angle” groups). marked differences in “skeletal” pattern shown between the five groups, the values obtained for the saddle angles (N-S-Ar) showed no significant difference. However, the natural head positions and natural head postures were significantly different (p < 0.01). Natural head position affected cranial base orientation, and this alone produced Class II or III effects. Natural head position was also associated with maxillary prognathism, while natural head posture appeared more closed in relation to mandibular prognathism. These phenomena may help to explain an apparent Class II or III tendency in cases in which the saddle angle is normal.

Alex Jacobson

Reaktionsf&higkeit des tierischen un menschlichen Kondyienknorpels auf Zell- und Molekularebene kybernetischen Auffassun fazialen Wachstums A. G. Petrovic and J. J. Stutzmann Fortschr. Kieferorthop. 1988;49:405-25

When investigated at tissue, cell, and molecular levels, condylar cartilage growth and responsiveness modalities are highly similar, no matter which animai species are tested: rat, mouse, guinea pig, rabbit, mon- key, or human. Consequently, any further statement claiming that the responsiveness of the condylar car- tilage to functional appliances is different in human beings and in laboratory animals appears to be biolog- ically unsupported and unjustified.

Interindividual heterogeneity in human condylar cartilage responsiveness to functional appliances orig- inates from distinct quantitative differences at the tis-

Reviews and abstracts

sue, cell, and molecular levels. These differences ac- count, indeed, for the level of mandibular “growth po- tential” and “responsiveness” (i.e., for the degree of effectiveness of functional appliances .)

The cybernetic approach to facial growth contrib- uted to the elaboration of a biologically and cephalo- metrically based procedure in orthodontic decision making. This procedure, using a new classification of facial growth rotations, leads to the indirect identifi- cation of the level of mandibular “growth potential” and “responsiveness .” The fact is that these biologic features of mandibular tissues are essential for the selection of the most appropriate treatment of skeletal malrelations and dental malocclusions.

Alex Jacobson

~ol~gical Evaluation of the Effects of ognathic Surgery for Male and Female nts With Mandibular Prognathism

corner Itok, Shoko Yamakage, Yasuko Endo, and Hideo Mitani J. Jpn. &hod. Sot. 1988;47:601-11

This study evaluated sex differences in psycholog- ical effects between male and female patients who un- derwent orthognathic surgery for correction of mandib- ular prognathism.

Materials consisted of 14 male and 16 female pa- tients, ail with diagnoses of severe mandibular prog- nathism before surgery. Evaluation was made at pre- operative and postoperative stages by means of the ~atabe-Guilford Personality Inventory Test and a ques- tionnaire especially designed for this study. The ques- tionnaire was composed of 20 items concerning facial esthetics and oral functions and was statistically ana- lyzed by factor analysis.

The foolowing results were obtained: 1. In both sexes, the mean profile of the scale and

factor values of the Y-G test indicated that the patients obtained higher emotional stability and extraversion af- ter operation. However, the changes occurred more sig- ~ifica~tly in females than in males.

2. The questionnaire test showed that, at the pre- operative stage, males had a greater inferiority complex to oral functional factors and that females had it to esthetic factors. The test also showed that this was improved after surgery.

The study concluded that orthognathic surgery for mandibular prognathism caused psychological effects in patients, but the effects were different between male and female patients. Males related more to the effects

for social problems; females related to those for self- internal emotional problems.

Alex Jacobson

Thesis abstracts

Enamel Demineralization: pH and Molarity Changes G. Kirkland and N. Soni Washington, D.C.: Howard University, CoElege qf Deniistry, Orthodorztic Department, 1988

Forty-four extracted first premolar teeth received bondable orthodontic brackets and were submerged in one of the prepared acidic buffers. The buffers were citrate and acetate at 4.5 and 5 .O pH witb concentrations of 0.1, 0.01, and 0.001 M. The teeth remained in so- lution until there was clinical evidence of white spot formation, at which time the teeth were removed from the solution. Twelve of the teeth in the most concen- trated solutions remained in solution until the teeth in the least concentrated solutions had white spot formation.

Five milliliter aliquots of the used buffer solution were removed so that calcium and phosphate quanti- tation could be performed using the Automated Astra Instrumentation. The demineralized tooth was sec- tioned leaving only the buccal surface, which was an- alyzed under the scanning electron microscope. The bracket was removed from some of the teeth to compare the exposed to the unexposed tooth surfaces. Nonpara- metric statistical analyses were used to assess the data because of the small sample size.

The initial day of demineralization for all 0.1 samples was at 2 days, at 5 days for all 0.0 1 M samples, and at 6 days for all 0.001 M samples. By means of the Mann-Whitney U test, it was determined that neither differing pH nor differing buffer when other variables were constant was statistically significant at or less than the 0.05 probability level. Comparison of the mineral loss between the most concentrated and the least con- centrated solutions after 6 days was statistically sig- nificant at and less than the 0.05 probability level. Cal- cium loss with citrate buffer after 6 days at 0.1 M ranged from 10 to 15 times more than the loss at 0.001 M. The Kruskal-Wallis II test did not find the values for the three differing molarities to be statisti- cally significant at or less than the 0.05 probability level, but it was significant for calcium at the 0.08 probability level.