Orhan C. Tuncay

The effect of indomethacin (an aspirin-like drug) on the rate of orthodontic tooth movement

Prostaglandins (PGs) have been suggested as mediators of bone resorption. In addition, their presence in the periodontal tissues has also been demonstrated. To characterize the involvement of PGs in orthodontic tooth movement, indomethacin, an aspirin-like drug and a potent inhibitor of PG synthesis, was administered orally to six mongrel cats; another group of six animals served as controls. These animals were fitted with orthodontic appliances that consisted of coil springs stretching between the right side maxillary and mandibular canines and third premolars. The data for tooth-movement measurements were analyzed by repeated measures factorial analysis of variance. At the end of the 21-day experimental period, the rate of tooth movement in experimental animals was approximately one half of controls (P less than 0.01). Findings of this study imply a significant role for PGs in bone resorption during orthodontic therapy. It is recommended that aspirin-like drugs not be administered to patients undergoing orthodontic tooth movement as it may extend the treatment time.

Oxygen tension regulates osteoblast function

Abrupt changes in oxygen availability within the periodontium have been suggested to have a regulatory role in alveolar bone remodeling during tooth movement; arguably, similar to that seen in bone growth or fracture healing. The purpose of this investigation was therefore to study the effects of ambient hypoxia and hyperoxia on osteoblast function in vitro. Osteoblast-enriched cultures from fetal rat calvariae were exposed to atmospheres of hyperoxia (90% O2) and hypoxia (10% O2) and assayed for media pH, pO2, pCO2, cellular proliferation, alkaline phosphatase (AP) activity, and collagen synthesis. Results of this study show that in low ambient oxygen tension cellular proliferation increases, whereas the AP activity, collagen synthesis, media pO2, PCO2 decreases. In contrast, in hyperoxic conditions cellular proliferation is suppressed with concomitant increases in: AP activity, collagen synthesis, and partial pressures for oxygen and carbon dioxide. Media pH remained unaffected. In crossover experiments, where cells were initially grown in hypoxic conditions and were switched to hyperoxic conditions, their metabolic activities were abruptly reversed. These findings in conjunction with earlier reports, suggest a triggering role for oxygen tension (an environmental factor) in bone remodeling.

Cephalometric evaluation of the changes in patients wearing complete dentures. A ten-year longitudinal study

This study analyzed the longitudinal cephalometric head films of 37 edentulous patients over a 10-year period. The purpose of the investigation was to document changes within the craniofacial complex, residual ridge resorption, and position of the dentures. The changes were correlated with the following variables: age, sex, skeletal pattern, number of years edentulous, technique of denture fabrication, and nighttime wear of the dentures. Findings in this study suggest the following. The maxillae and the mandible showed sagittal spatial counterclockwise displacement. Complete dentures exhibit a counterclockwise rotation and forward movement. Soft tissue seating is more important than alveolar ridge resorption in the positional changes of complete dentures. Variation in denture techniques had no influence on the observed changes. Artificial porcelain teeth did not show a measurable amount of attrition during the 10-year observation period. Observed changes were not significantly affected by variables such as sex, years edentulous, nighttime wear, or skeletal pattern. Two exceptions were that the skeletal pattern affects prognathism and number of years edentulous affects mandibular ridge resorption.

Cytotoxicity of orthodontic elastics

The neon-colored orthodontic rubber bands have recently become remarkably popular to wear among the young patients. In this study we examined if the dyes used in the manufacture of these elastics might exhibit any toxic effects. Gingival fibroblasts were exposed to extracts of colored and plain elastics in vitro. Cytotoxicity was examined by cellular proliferation rate and viability. Results showed that both the plain and the colored elastics display identical toxic effects. This ex vivo cytotoxicity, however, could not be observed in orthodontic patients: gingival fibroblast viability is no different in patients with and without rubber band wear. We conclude that in in vitro conditions, all orthodontic rubber bands are cytotoxic. Clinically, however, this effect is not demonstrable.

The effect of gingival fiberotomy on the rate of tooth movement

This study was designed to assess the gingival tissue resistance to remodeling in determining the rate of orthodontic tooth movement. Closed coil spring orthodontic appliances were stretched bilaterally between the first molars and incisors in the maxillary arches of 18 adult rats. The resistance of gingival tissues was eliminated around the randomly chosen first molars by a circumferential fiberotomy procedure. Movements of teeth were measured on submental vertex radiographs against the metallic implants that were placed in zygomatic processes. The data were analyzed by randomized block design analysis of variance. During the 30-day experimental period, the teeth that underwent the fiberotomy procedure moved faster (0.63 mm versus 0.51 mm, P less than 0.05), indicating that the resistance of gingival tissues may be a rate-limiting factor in orthodontic tooth movement.

A vertical cephalometric analysis of the human craniofacial complex

A vertical analysis involving ten linear measurements was developed to localize skeletal and dentoalveolar dysplasias. The measurements are of biologic relevance, reflecting the amount of growth harmony or disharmony to the examination and record-taking time. The vertical dimensional analysis uses the age- and sex-related University of Michigan mean values for comparative data for each measurement. Ratios were computed for a five-unit proportional analysis. Both analyses were applied to assess the vertical problems of three female patients. The analyses detected specific areas of dysplasia for each patient.

Effects of diazepam on orthodontic tooth movement and alveolar bone cAMP levels in cats.

Cyclic AMP has been suggested as a possible intracellular mediator in bone remodeling during tooth movement. Accordingly, an increase in the level of this nucleotide should result in faster tooth movement. Breakdown of cAMP was inhibited by administration of diazepam in eight cats undergoing orthodontic tooth movement; another matched group of eight animals served as controls. Orthodontic appliances consisted of coil springs stretching between the right side maxillary and mandibular canines and third premolars. The data for tooth movement and cAMP concentrations were analyzed by repeated measures factorial analyses of variance. The results indicated that administration of diazepam increased the rate of tooth movement at P less than 0.0005 and, interestingly, although diazepam had no effect on undisturbed tissues, it lowered the cAMP levels in the periodontal tissues of orthodontically moved teeth at P less than 0.01. On the basis of these results, it was concluded that the concentration of cAMP did not correlate with bone remodeling in this model and perhaps should not be used as an index of periodontal-tissue response during orthodontic tooth movement.

Unorthodox approaches to health care

Orthodontists are serenely content with their lot in life. ~ Perhaps, this quiet satisfaction is why many gifted persons are attracted to orthodontic graduate programs, and why some others wish they had such a station in life. Differences between these two groups are significant: As providers of accepted, orthodox orthodontic care, orthodontists employ varying approaches to treatment based on the collective research, education, and skills of a learned specialty. But the same cannot be said for the practitoners of alternative, unorthodox orthodontics. They entertain beliefs and engage in practices that vary considerably from traditional and accepted approaches without any comparative basis in either theory or practice. As a result, the orthodox health care practitioners see unorthodox practices as quackery. The term quack is a derivative from the Dutch word quacksalver, one who quacks like a duck or boasts about the virtues of his methods. Hence, to a quack, methods of promotion are more important than the usefulness of treatment. As early as 1858, King 2 in his book Quackery Unmasked wrote:

Orthodontic classifications: Mystique or reality?

F or years those who have attempted to create systems for orthodontic classifications have been shackled by the bonds of the E. H. Angle paradigm.’ The two-dimensional constraints of the most widely used and accepted orthodontic classification preclude advancement in this field. Therefore, orthodontics may be called a “science art” and/or a “transscience.“’ These terms are interpreted broadly in this article in an attempt to focus on the problem of classification and to create an awareness of the necessity to link the etiology of malocclusion accurately with a rational plan of therapy. The future of orthodontics becomes dimensionless if past biases are eliminated and today’s problems are resolved under an evolved or synthetic philosophy. Orthodontics has borrowed heavily from other disciplines, such as physical anthropology, anatomy, and metallurgical sciences. By doing so, it has utilized considerable data and adapted it, rightly or wrongly, to orthodontics. “We have acquired notions and compiled precious materials which will later have their place and be of importance.“3 However, the compiled data cannot properly explain biologic phenomena if they are acquired erroneously or if the interpretations are directed to other seemingly related or unrelated processes. In this sense, orthodontics must function under the nineteenth century philosophy that a discipline deserves its name only when it establishes quantitative relations between phenomena. However, biologic entities have not been reduced to an exact science. They often appear identical but are the results of different determinants. Further, biologic observations may be asymmetric, comprised of numerous components, each with its unique potential for growth. Pasteur stated: “The universe is a big dissymmetrical whole. I am inclined to believe that lift such as it is manifested to us must be a function of the dissymmetry of the universe and of the consequences which it entails. Life is dominated by dissym-