Meta analysis of the treatment-related factors of external apical root resorption

OBJECTIVE

To elucidate possible treatment-related etiological factors--such as, duration of treatment and apical displacement--for external root resorption.

DESIGN

Meta-analysis of the available English-language literature.

INCLUSION & EXCLUSION CRITERIA

Papers with a sample size > 10, fixed appliances, pre- and post-operative radiographs, and apical displacement recorded were included. History of trauma, prior root resorption and endodontic treatment were excluded. Appropriateness of these selections was tested with a 'funnel plot' analysis.

OUTCOME MEASURE

Correlations between root resorption, apical displacement, and treatment duration.

RESULTS

Mean apical root resorption was strongly correlated with total apical displacement (r = 0.822) and treatment duration (r = 0.852).

CONCLUSION

The treatment-related causes of root resorption appear to be the total distance the apex had moved and the time it took.

Perceived long-term prognosis of teeth with orthodontically resorbed roots

OBJECTIVES

To investigate the perceived significance of root resorption in the dental community. STUDY DESIGN AND SAMPLE: Mail out survey questionnaire accompanied by morphed images of 10-50% root resorption. General practitioners, periodontists, prosthodontists and orthodontists were the participants.

OUTCOME MEASURES

Correlations between 'significant' and 'detrimental to the longevity of the tooth'. These assessments were conducted within specialty groups and among. Also measured was the source of knowledge upon which practitioner assessments were based.

RESULTS AND CONCLUSIONS

General practitioners were the most concerned about root resorption. Although most practitioners feel 50% root resorption is significant and detrimental to the longevity of the tooth, extraction followed by prosthetic replacement was not an option. No agreement among practitioners when orthodontic treatment should be terminated; the general practitioners were conservative suggesting termination after 35% root loss. History of trauma, genetic disposition and root morphology are the most cited predisposing factors. Lengthy treatment time concerns general practitioners more than the orthodontists. With the exception of orthodontists, dentists believe excessive force is detrimental to the root, but no one is able to define what excessive force is. Overall, dental school curricula overstate the causes of root resorption. Generally, dental professionals seem to base their opinions on myths and are largely inconsistent in their assessments.

A stochastic evaluation of the decision to specialize in orthodontics

OBJECTIVE

The objective of this paper is to identify under different scenarios, and from a financial point of view, the conditions required to successfully switch from the general dentistry practice to orthodontics.

STUDY DESIGN

A mail survey was used to collect the data from the practicing orthodontists. They estimated the income, at certain points, in the working life of an orthodontist. The general practitioner data were taken from the American Dental Association figures. Subsequently, a stochastic model was constructed.

RESULTS AND CONCLUSION

Those who decide to buy an existing practice expect higher profits in the near future, and therefore the required minimum number of remaining years of practice is lower than for those deciding to start a new practice. For both scenarios, the 3-year residency will delay the profits compared with a 2-year residency. Thus, an increased number of remaining years of practice is required. There must be more than 10 working years left in the practitioner's life to make the switch profitable.

Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets

Efficiency of treatment mechanics has been a major focus throughout the history of orthodontics. Self-ligating brackets were developed on the premise that elimination of ligature ties creates a friction-free environment and allows for better sliding mechanics. It is expected that the self-ligating bracket will reduce the treatment time. This study was designed to compare the effectiveness and efficiency of Damon self-ligating (SL) brackets to those brackets ligated with either steel ligatures or elastomeric 'O' rings. Not only treatment time and the number of appointments needed were addressed, but the quality of the treatment outcome was also assessed. American Board of Orthodontics (ABO) grading criteria for models and panoramic radiographs were employed. Additionally, a nine-question survey was sent to the 215-patients in this study (108 Damon, 107 conventionally-ligated) to elicit their perceptions of how their orthodontic treatment progressed and finished. The results showed that patients treated with Damon SL brackets had significantly lower treatment times, required significantly fewer appointments, and had significantly higher ABO scores than those treated with conventionally-ligated edgewise brackets. There were no significant differences in Damon or non-Damon ABO scores with respect to gender. Damon patients over the age of 21 had significantly higher ABO scores. Conversely, the non-Damon patients under the age of 21 had significantly higher ABO scores. For pre-treatment Angle classification, no significant differences were noted. Patient responses showed that Damon patients perceived their treatment time as being shorter than expected. It appears that faster orthodontic treatment can be better as measured by the ABO criteria.

Maxillary expansion: a meta analysis

The utility of maxillary expansion has been equivocal for more than 100 years. The advent of meta-analysis and evidence-based learning has provided an opportunity to look objectively at this treatment modality. Medline was searched from 1978 to 1999 for all studies examining the stability of transverse expansion of the human maxilla using initial search terms of maxillary expansion and palatal expansion which were limited to those English language and human subjects. The more than 5000 articles were reduced to 12 based on the defined inclusion and exclusion criteria. The two investigators participating in the study were blinded, the studies' authors and origins blacked out and the evaluation coded and scored. A cumulative 'Meta evaluation score' was computed for each study. Six studies remained for the final analysis. The mean expansion after adjustment according to the principles of meta analysis was 6.00 mm with a standard deviation of 1.29 mm. Of the 6-mm average, 4.89 mm was retained while wearing retainers. Five of the papers provided retention data and post-retention data, but only three studies provided both retention and post-retention data. The average age of patients in these reports was 10.8 years. The 6-mm average expansion with retention in the short-term (<1 year) yielded a 4.71-mm residual expansion. Subsequently, this expansion during the short-term post-retention period was reduced to 3.88 mm. Finally, in the long-term post-retention study period only 2.4 mm of the residual expansion was reported to have remained. This 2.4 mm of expansion remaining after more than a year or more of post-retention period was no greater than what has been documented as normal growth. There is insufficient data to conclude that any useful expansion beyond that can be expected through normal growth was retained.

Regulation of IL-1-induced gingival collagenase gene expression by activator protein-1 (c-Fos/c-Jun)

Matrix metalloproteinase-1 is probably involved in the progression of periodontal disease. The aim of this study was to investigate whether IL-1beta stimulates the expression of the activator protein 1 (AP-1) transcription factor and, consequently, if the AP-1 transcription factor participates in the regulation of collagenase gene expression in human gingival fibroblast cells. In this study, we demonstrate that the concentration of the protein components of AP-1 transcription factor, c-Fos and c-Jun, is enhanced by IL-1beta both at mRNA and protein levels, utilizing Northern blot analysis, electrophoretic mobility gel shift assay and Western blot analysis. The IL-1beta stimulated the collagenase-CAT and AP-1-CAT activities in a dose dependent manner with respect to the amount of DNA used in transfections. Further, overexpression of c-Fos and c-Jun proteins revealed a dose-dependent transcriptional activation of the collagenase promoter. These findings, coupled with the existence of AP-1 consensus DNA binding sites on the collagenase gene promoter, show that regulation of collagenase gene expression by IL-1beta involves the transcription factor AP-1 in gingival fibroblasts.

Defining characteristics of financially successful orthodontists

Financially successful personality profiles in most of the business world have been reported to be the choleric (powerful) and the melancholy (perfect) types. In 1996, Hughes proposed that the same relationship possibly exists in the profession of orthodontics. The purpose of this study was to explore whether a dominant personality profile exists for the most financially successful orthodontists. A questionnaire was used to gather information regarding the financial sophistication and the dominant personality profile of each participating orthodontist. One hundred twenty-six of the 300 surveys distributed to orthodontists were returned for a response rate of 42%. For every question, the null hypothesis of independence was tested with the chi-square test. The null hypothesis of independence was rejected for a P value of less than.05. The results revealed that no correlation exists between the financial sophistication of orthodontists and their personality profiles. However, over two thirds of the orthodontists had the choleric (powerful) and the melancholy (perfect) as dominant personality types. Interestingly, the questionnaire shed much light on factors that do contribute to financial success in orthodontics. Although statistical differences are lacking in these data, certain traits about successful practitioners could be identified. These orthodontists (1) allow their practices to grow if it will increase the net income, (2) view control of overhead as a key principle, (3) emphasize the competence of staff in determining the success of practice, and (4) believe in marketing. Implementation of these simple and common sense principles in some orthodontic practices might affect the business significantly.

Patient and parent preferences for orthodontic practices

This study was designed to identify who chooses an orthodontic office and what factors might induce the attraction. Patients and parents from the lists provided by suburban orthodontic offices were contacted. A mail-out survey instrument was used to gather the data. Results revealed that the reputation of the practitioner was most important along with the level of caring attitude the office projected. It was also important that the office is located near home, interestingly, the mother is the most significant decision-maker in the family in choosing an orthodontic office. Moreover, not the cost of treatment but the payment plan was the critical element in the decision process. The higher income families with three or less children were attracted to office characteristics such as excellence of the orthodontist, attention, and convenience. A marketing strategy based on these elements might provide the best return on the investment.

Antizyme prevents ornithine decarboxylase-mediated cell death in human fibroblasts

Ornithine decarboxylase (ODC) is a key enzyme of polyamine biosynthesis essential for growth-related cellular functions. Apart from its physiological role in cell proliferation, ODC also contributes to the induction of apoptosis under certain conditions, e.g. following growth factor withdrawal. The rate of cell death is a function of its enzyme activity, ODC activity is inhibited by a regulatory protein antizyme, also known to suppress polyamine uptake. We report that forced expression of antizyme prevents ODC-mediated cell death in human gingival fibroblasts under very low serum conditions. These data suggest an important antiapoptotic role for antizyme in cell survival.

Prediction of mandibular third molar impaction in the orthodontic patient from a panoramic radiograph

In this study we explored the predictability of mandibular third molar impactions. Serial panoramic radiographs from 50 non-extraction and 15 extraction patients were traced for various angular and linear measurements. A linear discriminant function analysis was performed for each stage of third molar development. The results indicate that the earliest stages of development have very little predictive value. Accordingly, a justification for the oft-practiced enucleation procedure cannot be made. Although the more the tooth is developed, the higher is the accuracy of prediction, two earlier stages where the crown is fully formed or the roots 1/3 formed possess high predictive values. Based on our data, impaction of third molars in the mandible is a predictable event both in extraction and non-extraction patients.

Composite hooks enhance rotational control

We find hooks placed in positions of convenience useful in correcting rotations, especially with lingual appliances. The steps involved in building them are straightforward. Following acid etching of the spot where the hook is to be placed, a small amount of bonding material is carried onto the enamel surface and a base established by a series of circular motions with the tip of an explorer. The bonding material is then extruded with the tip of the explorer. As soon as the material is extruded to the desired length and curvature, the UV light is applied. Of course, if needed, bigger hooks can be constructed and then trimmed to shape with a bur. A short-beak band remover works best (in a scraping motion) for the removal of these hooks. The following figures illustrate the point (Figs. 1-7).

Inhibition of gingival collagenase gene expression by dexamethasone

Glucocorticoids are potent immunosuppressants shown to be effective in the treatment of inflammatory diseases. Reportedly, they work, in part, by inhibiting cytokines and other transcription factors including AP-1. In this study we investigated the mechanisms of efficient repression of collagenase gene expression by dexamethasone in the human gingival fibroblast. Northern analyses showed that IL-1-dependent collagenase mRNA production was significantly decreased in the presence of dexamethasone. The influence of dexamethasone on the transcription factor NF-kappaB, STAT3, and AP-1 was investigated by using the gel mobility shift assay with nuclear extracts prepared from the cells grown in the presence of dexamethasone. We observed that in addition to AP-1, binding of NF-kappaB and STAT3 to DNA was also decreased significantly. Additionally, dexamethasone induced the transcription of the I kappaB-alpha gene suggesting that in the presence of dexamethasone, NF-kappaB quickly reassociates with newly synthesized I kappaB-alpha and markedly reduces the amount of NF-kappaB. CAT transfection studies utilizing collagenase promoter demonstrated a dose-dependent transcriptional inhibition of IL-1-induced gingival collagenase gene expression by dexamethasone. These data reveal that collagenase gene expression can be regulated by the impairment of IL-1-stimulated NF-kappaB, STAT3, and AP-1 activities, and can highlight a possible molecular mechanism for the anti-inflammatory effects of glucocorticoids.

Gingival blood flow

In the oral cavity extensive vascular changes accompany progression of gingival inflammation or healing and remodeling of periodontal tissues. This study was designed to explore how the gingival capillary circulation might be influenced by mechanical stimuli; specifically, tooth brushing. Changes in blood flow subsequent to mechanical stimulus of brushing were measured by laser Doppler flowmetry at the midline, canine and premolar regions of maxillary and mandibular arches. Results showed that tooth brushing increased the blood flow in these regions by approximately 60 percent relative to the resting state. These changes, however, were shortlived. Fifteen minutes following this mechanical stimulus the capillary circulation returned back to within ten percent of baseline readings. We conjecture that frequently applied mechanical stimuli might aid in gingival remodeling, high tissue turnover and metabolic rate.

Association of interleukin-1-induced, NF kappa B DNA-binding activity with collagenase gene expression in human gingival fibroblasts

During earlier examination of interleukin-1 (IL-1)-induced matrix metalloproteinase gene expression in human gingival fibroblasts a highly induced immediate early gene, I kappa B-alpha, a NF kappa B DNA-binding inhibitor, was identified. The aim now was to investigate whether recombinant (r)IL-1 beta induces the stimulation of NF kappa B and its inhibitor proteins in human gingival fibroblasts and to understand if inhibition of its activity affects collagenase gene expression. Primary gingival fibroblasts (human) were treated with rIL-1 beta to determine the effect on NF kappa B-like DNA-binding activity. IL-1 induced the production of steady-state mRNA levels of I kappa B-alpha in the cultured fibroblasts. Nuclear run-on transcription studies demonstrated that rIL-1 induction of I kappa B-alpha may be transcriptionally regulated. Using electrophoretic mobility gel-shift assays it was shown that rIL-1 activates NF kappa B-like, DNA-binding activity in these fibroblasts. NF kappa B-like DNA-binding activity was rapidly induced and turned over in gingival fibroblasts with peak activity at 30 min after rIL-1 treatment. Further, treatment with chymotrypsin protease inhibitor and antioxidant inhibitor prevented IL-1-induced, NF kappa B-like, DNA-binding activity and collagenase mRNA production. When coupled with the existence of NF kappa B consensus DNA-binding sites on the collagenase gene promoter, these findings suggest that the stimulation of NF kappa B in gingival fibroblasts by rIL-1 could play an important part in the regulation of their collagenase gene expression. The ability of IL-1 to stimulate this expression may define a pivotal role for this cytokine in the pathogenesis of periodontitis.

Validity of computerized predictions of dentoskeletal and soft tissue profile changes after mandibular setback and maxillary impaction osteotomies

The aim of the present investigation was to evaluate the validity of the predictions of a computerized cephalometric system (Dentofacial Planner) regarding dentoskeletal and soft tissue profile changes after mandibular setback and maxillary impaction osteotomies. Tracings of lateral cephalograms taken at the end of preoperative orthodontics (within 1 week before surgery) and approximately 1 year after the operation were digitized and entered into the Dentofacial Planner. For the mandibular setback group, the computerized predictions tended to place the mandible less posteriorly than the actual situation and to significantly underestimate the mandibular plane angle, the total anterior skeletal and soft tissue facial heights, the lower anterior skeletal facial height, and the upper lip height. In the maxillary impaction group, the prediction printouts significantly overestimated the total anterior soft tissue facial height, the upper lip height and the inclination and curvature of the lower lip and underestimated the soft tissue thickness in the regions of pogonion and point B.

How dentists perceive the effects of orthodontic extraction on facial appearance

In recent years, orthodontic treatment, particularly that involving premolar extractions, has been alleged to cause flat facial profiles. Those who make such assertions also claim to be able to instantly identify from a distance faces of patients who have received orthodontic treatment. These are strong claims that could profoundly affect the public's perception of dentistry and its specialties. This study examined whether dentists could distinguish between profiles of treated and untreated patients as well as between patients who had undergone extraction and those who had not.

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.

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.

Methods used to evaluate growth modification in Class II malocclusion

The methods used to study growth modification in orthodontic patients can have considerable impact on the conclusions that may be drawn. Because of the large "between-patient" variation and small mean changes usually observed, apparent differences in response may sometimes be more attributable to study design than to treatment effectiveness. A systematic review of four major orthodontic journals (1980 to 1987) identified 50 studies reporting treatment of young patients with Class II malocclusion. Variables defined to classify the studies included appliance systems, patient selection, comparison groups, research design, data collection, analysis, and reporting. The appliance systems most frequently investigated were the function regulator and the activator, used with and without headgear. Only 11 (22%) studies were prospective, and random assignment to alternative treatments was never used in this sample. Comparison groups used in 76% of the studies were untreated Class II patients (n = 18) and/or patients with alternate appliance systems (n = 17). In only 24% of the reports were groups tested for pretreatment equivalence. Few studies reported fully how patients had been selected, how decisions had been made to discontinue or change treatment, or whether patients had been lost to study. While most studies reported "p values," in only four were alpha levels adjusted for the number of tests (type I error), and no study included a post beta estimate (type II error). Age, sex, maturation, and duration of treatment were usually reported but seldom adjusted for in the analyses. Given the multiple indices of treatment effect, the generally small sample sizes, weak research designs, and incomplete reporting of important data, we cannot yet conclude whether orthodontic treatment influences the growth of Class II patients.

[Why not try to move on ankylosed tooth orthodontically?]

Due to presence of rigid inorganic matrix, mechanical perturbations cannot affect the bone blood supply or deform osteocytes. Because convincing evidence that bone can directly perceive mechanical forces in lacking, we hypothesize that mechanical perturbations can only elicit remodeling by acting through a soft tissue envelope. These soft tissue envelopes are the periodontal ligament, periosteum, fibrous tissues that can form around implants, sutures and the like. Fibroblast, preosteoblast, and mesenchymal cells are composing the envelopes. It is possible that these cells are indeed responsible for bone remodeling subsequent to forces application.

Scanning microfluorimetric measurements of redox status in the rat dento-alveolar tissues

The oxidative state of periodontal tissues in situ is not known. Scanning microfluorimetry uses NADH fluorescence readings to provide a measure of a tissue's oxidative metabolic activity. Digitally recorded fluorescence signals were compiled to create a distribution map for this reduced pyridine nucleotide in the periodontal structures, which was then related to the morphology as seen by SEM. To distinguish between NADH fluorescence and intrinsic fluorescence of collagen, as well as to study the effect of oxygen deprivation, mitochondrial oxidative activity was inhibited by CO in some animals. Oxidative status and sensitivity to changes in cellular energy metabolism in the dento-alveolar complex were tissue specific; differences between tissues may play a part in the differential remodelling of the periodontium.

A review of clinical research in orthodontics

The orthodontic journals should provide valid and reliable information that helps clinicians make appropriate decisions about patient care. The nature of the published literature has not been categorized. The American Journal of Orthodontics and Dentofacial Orthopedics (formerly the American Journal of Orthodontics) was reviewed for the years 1976, 1981, and 1986, to determine the frequency of clinical articles, the topics reported, the study designs used to obtain information, the senior author affiliation, and the major funding sources. This review demonstrates that more than half the articles in this Journal report data on patients, with the majority focusing on the evaluation or description of therapeutic interventions. Academic institutions contribute the majority of the clinical research, although only a few student theses are published. The major support for this work continues to be from departmental resources with little external funding. Despite the introduction of powerful research designs such as randomized clinical trials, these methods have not been widely adopted for orthodontic clinical research. The case report (study containing fewer than 10 patients with no control nor comparison group) continues to be the most frequently published format. Clinicians should become aware of the inherent weakness in the research designs generally used and recognize the limited information that can be obtained from such methods. Support for this research needs to be greatly expanded if the more powerful type of study required to provide valid and reliable clinical information is to be continued.

Linkage between energy status of perivascular cells and mineralization of the chick growth cartilage

The objective of this investigation was to investigate the relationship between the energy status of epiphyseal chondrocytes of the chick growth cartilage and the development of mineralization. A microfluorimetric scanning technique was used to measure the reduced pyridine nucleotide content of transverse sections of freeze-trapped cartilage; these measurements were related to tissue structure by scanning electron microscopy. The results of this study show that the energy status of cells in the hypertrophic region of the growth cartilage is more complex than was previously believed. In hypertrophic cartilage, most chondrocytes are in a reduced state. However, in the early hypertrophic region, the vascular channels that penetrate the cartilage from the metaphysis exert a profound local effect on the energy metabolism of perivascular chondrocytes. Thus, around each of the channels, there exists a zone of chondrocytes about 40-60 micron wide which exhibits a low fluorescence yield. The fluorescence level suggests that these perivascular cells have a higher level of oxidative metabolism than hypertrophic chondrocytes that are a distance (greater than 150 micron) from the vascular channels. This finding, in conjunction with our earlier observation that mineralization is first seen in the perivascular region, leads us to the conclusion that mineralization is associated with cellular oxidative activity. We now reject the long-held concept that in cartilage the development of mineralization is entirely due to tissue hypoxia.

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.

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.

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.

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.

Molar uprighting with T-loop springs

Uprighting of molars is indicated as an adjunct to restorative and periodontal procedures. Limiting conditions exist in which previously reported helical and box-loop springs cannot be used effectively. In those instances, segmental arch wires with T-loops upright the molars efficiently while maintaining control in three planes of space. Furthermore, these loop designs permit immediate engagement of these appliances. Clinical experiences with these springs by students in the professional and graduate dental clinics at the University of Kentucky College of Dentistry lead to the conclusion that: segmental uprighting arch wires with T-loops are easy to fabricate and use; T-looped uprighting springs can be engaged immediately and used efficiently in instances in which helical spring or box-loop uprighting appliances are contraindicated; T-looped uprighting springs offer excellent controlled movements of teeth in three planes of space; acceptance by the patient is favorable; and treatment time, depending on the amount of tooth movement required, is rapid and varies between 8 to 16 weeks.

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.