Hypoxia triggers a HIF-mediated differentiation of peripheral blood mononuclear cells into osteoclasts.

BACKGROUND: The source and mechanisms leading to osteoclast (OC) generation during tooth movement are not clearly understood. We hypothesized that during tooth movement, OC differentiate from peripheral blood mononuclear cells (PBMNC) downstream of the global hypoxia-inducible transcription factor hypoxia-inducible factor (HIF)-1α. OBJECTIVE: The objective of this study was to demonstrate up-regulation of OC growth factors from osteoblasts (OB) and subsequent conversion of PBMNC into functional OC under hypoxic stress. MATERIAL AND METHODS: Human primary PBMNC were cocultured with/without OB and subjected to either hypoxia (2.5% O2) or normoxia (21% O2) over 14 days. Levels of HIF, vascular endothelial growth factor (VEGF) and receptor activator for nuclear factor kappa-ß ligand (RANKL) were measured. Conversion of PBMNC into OC was measured using resorption and TRAP assays. RESULTS: Functional OC were only observed in response to hypoxia during coculture of PBMNC and OB and only after up-regulation of HIF, VEGF and RANKL in the hypoxic conditions. YC-1, a HIF inhibitor, reduced OC formation in response to hypoxia. CONCLUSION: Hypoxia triggers the differentiation of PBMNC into functional OC in the presence of OB in a HIF-dependent manner as would occur during orthodontic loading of the periodontal ligament space.

The child and the adolescent: new rights for an "old" minority.

The use of the learning model is a necessary prerequisite for rendering dental care to the child or adolescent. The awareness of the emotional needs of the child and adolescent and the ability of the doctor to handle them is a requirement for an individual to treat these persons. The treatment plan and methods of treatment are essential factors in the behavioral management of the child or adolescent. There is a normal range for grwoth, development, and maturation in which sequences, timing, and rates of changes are critical. A cross-sectional approach in rendering care is not appropriate in learning to work with children and adolescents. The doctor who renders the care for this age group should be well versed in certain aspects of behavior, as this will affect the treatment plan and methodology, but that doctor must also have the technical abilities to do the spectrum of services to which the patient is entitled. One without the other is a definite compromise for the patient. If the doctor does not further pursue additional assistance from his colleagues, the rights of the child or adolescent have been violated.

A cephalometric evaluation of nonextraction cervical headgear treatment in Class II malocclusions.

The effects of orthodontic treatment with the use of the cervical pull facebow headgear in patients with Class II malocclusions were evaluated with special reference to the dentition, the maxillary complex, the mandible, and the facial profile. The records of 85 patients, with a mean age of 11.3 +/- 1.7 years, were selected from a sample of 125 patient records requested from the office of John S. Kloehn in Appleton, Wisconsin. Dr. Kloehn has used traditional cervical pull facebow therapy in his practice. Over 100 linear and angular cephalometric measurements were made from the pretreatment and posttreatment records. These measurements were used to evaluate growth and/or treatment changes. The treatment sample was divided by size of the pretreatment FMA, sex, and the age range in which treatment was started, i.e., prepubertal, circumpubertal, and postpubertal. Overall, the results showed that the changes were very close to what would occur as a result of normal growth in Class I individuals. The maxillary permanent first molars continued to progress forward, the maxilla continued to grow forward, and the cranial base showed very little change, if any. The mandibular plane angle did not increase appreciably with treatment, regardless of the size of the pretreatment mandibular plane angle. Very few significant differences were found between sexes, pretreatment age groups, or between groups based on pretreatment Frankfort mandibular plane angle.

Stiffness-deflection behavior of selected orthodontic wires.

Treatment of horizontal and vertical tooth discrepancies requires wires of low stiffness to produce forces as the teeth are leveled and aligned. In this investigation, the stiffness characteristics of several solid and multistrand nickel-titanium and stainless steel orthodontic wires were determined at selected clinically relevant deflections. Twenty specimens of 24 different wires were tested in both three-point and three-bracket bending modes. The unloading force deflection plot of each wire was described by a polynomial regression from which wire stiffnesses were obtained by mathematical differentiation. Graphs of the functional relationship between stiffness and deflection are presented. The results of this investigation show that wire stiffness can be altered not only by changing the size, but also by varying the number of strands and the alloy composition. An equally important finding was the dependence of stiffness on deflection for most of the wires measured. Comparisons were also made between the stiffness values obtained in three-point bending and the three-bracket bending systems.

Fracture strengths of ceramic brackets subjected to mesial-distal archwire tipping forces.

This study tested the strength of ceramic orthodontic brackets subjected to mesial-distal tipping forces on five types of preadjusted, maxillary right central incisor ceramic twin brackets for both 0.018" and 0.022" slot sizes. Description of each bracket was by manufacturer's abbreviation-crystallinity-slot bracket, eg., AL-P-18, meaning Allure-polycrystalline-0.018" slot bracket. Thirty brackets of each type were used for a total of 300 brackets, each bonded to a porcelain denture tooth. A special apparatus was designed to hold the denture tooth, the wire, and the bracket in a standard position while an Instron machine applied a tipping force to the full size rectangular archwire at a distance of 7.0 mm lateral to the center of the bracket. The tipping force was applied until the bracket fractured. The fracture force, fracture angle, and fracture location were recorded. High fracture force values tended to accompany large fracture angles while low fracture force values tended to be associated with small fracture angles. The clinical significance was that the stronger ceramic brackets can be expected to withstand larger amounts of archwire tipping adjustments prior to bracket fracture. With the literature indicating the optimum force for tipping of maxillary incisors to be from 50 to 125 g, all the brackets are sufficiently strong to consistently withstand the suggested magnitude of archwire tipping forces. However, if excessive tipping forces were required by the clinician, ceramic brackets would be prone to fracture.

Tomographic assessment of temporomandibular joints in patients with malocclusion.

There is a paucity of information on the morphological assessment of the temporomandibular joint in relation to varying skeletal and dental relationships. The purpose of this study was to evaluate the morphologic relationship of the condyle and fossa in patients with different malocclusions and skeletal relationships. Pretreatment records of 232 orthodontic patients, 95 males and 137 females, of Caucasian descent and ranging in age from 9 years 4 months to 42 years 6 months, were examined. Records included dental casts, lateral cephalometric radiographs, hand-wrist radiographs, and corrected tomograms of right and left TM joints. Nonconcentricity and mild asymmetry of the condyle-fossa relationship were commonly observed. The left condyle was found to be more anteriorly positioned than the right, with the mean percentage of joint space being 6.93% on the left side and -1.24% on the right. Skeletal and dental Class III patients demonstrated significantly more anteriorly positioned condyles (P < 0.05). There were no significant differences in condylar position between Class I and Class II groups based on ANB or Angle's classification. Further, no significant difference in condylar position was observed between groups based on overbite or crossbite.

Effect of behavior modification on patient compliance in orthodontics.

The purpose of this study was to evaluate the effects of a reward system for improving patient compliance in orthodontic treatment. The sample consisted of 144 orthodontic patients (63 male, 81 female, average age 12.8 years), 6 to 12 months into their treatment. The sample was divided into above-average and below-average compliers, based on the orthodontic patient cooperation scale (OPCS). Each group was further divided into three subgroups: (a) a control group, which received only standard instructions; (b) an award group, which received compliance instructions and a written evaluation of compliance; and (c) a reward group, which received compliance instructions, a report card, and eligibility to receive rewards for adherent behavior. Two measurements of patient compliance were used: (1) the OPCS, which divided the sample into high and low compliers and was used to compare compliance before and after the 6-month experimental period; and (2) a clinical evaluation of compliance that was based on oral hygiene, appointment punctuality, appliance wear, and appliance maintenance. Evaluations were completed at each monthly appointment. Average compliance scores of above-average compliers showed no significant improvement with rewards. The average scores of patients with below-average compliance did not improve significantly. Only oral hygiene scores in the low compliance reward group were better than in the low compliance control group. Academic performance in school was found to be correlated (p < 0.001) with compliance. Above-average compliers remained above average in their compliance. The award/reward system may help motivate below-average compliers to comply with prescribed instructions.

Load-deflection rate measurements of activated open and closed coil springs.

The purpose of this investigation was to provide load-deflection rate data for a variety of open and closed coil springs. Ten millimeter lengths of open and closed coil stainless steel and Cobalt-Chromium-Nickel (Co-Cr-Ni) alloys in combinations of 0.008, 0.009 and 0.010 inch wire sizes, and 0.030 and 0.032 inch lumen sizes were tested. Other groups included heat treated Co-Cr-Ni springs and springs of 15 and 20 millimeter lengths. Forces and activations were measured by a tension load cell with an Instron universal testing instrument. Stiffness increased dramatically with wire size and pitch angle of the coils. Stiffness decreased slightly with increased lumen size. Co-Cr-Ni closed coil springs were slightly stiffer than stainless steel, whereas stainless steel open coil springs were much stiffer than Co-Cr-Ni. Heat treatment increased the stiffness of Co-Cr-Ni coil springs. The length of the spring had a great effect on the load-deflection rate. A shorter spring is stiffer than a longer spring by an amount directly proportional to the ratio of the length of the longer spring to that of the shorter spring.

Motives to enter the dental profession: students, practitioners, faculty.

1. The dental student, the private practitioner, and the dental educator have similar self-motives related to an educational process which includes learning to develop to full potential and having the freedom to carry out one's ideas. 2. The motives perceived by dental students as important for the private practitioner are not the same as those the private practitioner perceives for himself. The student perceives good salary and a community reputation, while the practitioner perceives a continual educational process with freedom to carry out his ideas as the primary motive for entering the profession. The student and the practitioner are aligned on most of their self-motives. 3. The motives of the dental educator parallel those of the practitioner more than they parallel those of the student.

Pediatric orthodontics: where have we been? Where are we going?

Pediatric treatment planning is difficult for those doctors who observe their patients throughout the long period of childhood. Which changes are normal? Which will self-correct? How long should the therapy be? Which is the best, current modality of treatment? An understanding of cyclic patterns, a dentofacial orientation on an individual basis, problem-oriented treatment plans, and certain reasonably based protocols make this journey through the time of childhood and the current age of dentistry rather rewarding.

Nonsurgical and interactive orthodontics.

Cephalometric radiographic evaluation needs to be supplemented with soft tissue analyses that assist in the proper mechanics. Radiographs remain prescriptive to alter therapy. Patient cooperation is directly related to understanding and applying learning principles that are essential for quality orthodontic care. Prescriptions and new wires continue to make treatment more efficient and exacting. The anomalies of the teeth profoundly affect tooth placement in the occlusion. The transverse plane is the first and most important plane of occlusion that needs early intervention. This plane is directly related to correction of the sagittal through vertical development. The scope of airway and function needs to supplement specific modalities of therapy. Functional appliances usually have significant dentoalveolar effects within the growth process. Individual variation remains the hallmark of human growth and development, with or without therapeutic intervention.

Arch perimeter changes on rapid palatal expansion.

Relationships between changes in arch perimeter and arch width resulting from rapid palatal expansion with the Hyrax appliance were analyzed with the use of dental study casts of 21 adolescent patients. Photographs and measurements from the dental casts obtained before treatment and approximately 3 months after stabilization were used. Regression analysis indicated that changes in premolar width were highly predictive of changes in arch perimeter (r2 = 0.69) at approximately 0.7 times the premolar expansion. Without any orthodontic appliances attached to the mandibular teeth in 16 of the 21 patients, buccal uprighting of the posterior teeth was observed because of the redirection of occlusal forces. In addition, posterior movement of the maxillary incisors and buccal tipping of the anchor teeth were quantified. The prediction of arch perimeter change for a given amount of expansion is helpful in the treatment planning of rapid palatal expansion cases and may facilitate nonextraction orthodontic treatment.

A longitudinal cephalometric study of transverse and vertical craniofacial growth.

Longitudinal growth changes were studied from posteroanterior cephalometric radiographs of 25 male subjects from 4 to 25 years of age and 25 female subjects from 4 to 20 years of age who had Class I skeletal and dental patterns. Growth for males continued past age 18 years for all skeletal measurements, except for maxillary width. Growth for females was completed by 17 years for all skeletal measurements. At 6 years of age the transverse measurements had a greater percentage of the adult size completed than vertical measurements for both males and females. Gender differences at age 6 years were in the mean widths for the cranium, face, and maxilla. At age 12 years the differences were in cranial width, maxillary width, and maxillary and mandibular intermolar width (6-6). There were gender differences at age 18 years for all the variables, except for nasal width and mandibular intermolar width (6-6). Regression lines provided strong-to-moderate predictive equations to determine the size of most of the measurements at age 18 years, if the value at age 6 years is known.

A 3-year evaluation of skeletal stability of mandibular advancement with rigid fixation.

The postsurgical changes associated with mandibular advancements using the sagittal ramus osteotomy and rigid fixation were evaluated. This retrospective study was based on examination of lateral cephalometric radiographs of 19 individuals (16 females and 3 males) with a mean age of 26.6 years. These radiographs were evaluated presurgically, immediately postsurgery, and 3 years postsurgically (2 years, 9 months to 4 years, 5 months). The mean amount of sagittal surgical advancement was 6.7 +/- 2.3 mm, and the mean amount of postsurgical relapse was 1.3 +/- 2.0 mm, representing a 14% relapse of the original surgical advancement. However, individual variation in the amount and direction of movement of the mandible was found during the follow-up period. Postsurgical relapse was found to be related to the amount of surgical advancement. Linear-regression analysis between these two variables resulted in an R2 value of 0.448. Fourteen of the subjects relapsed in the posterior direction, with 2 relapsing more than 50% of the surgical advancement. Five of the subjects moved further anteriorly, with 1 advancing as much as 50% more than the original advancement. The findings of this study suggest that mandibular advancement with the sagittal ramus osteotomy and rigid fixation does not provide consistently stable postsurgical results. However, when compared with previously reported relapse studies using nonrigid fixation techniques, rigid fixation yielded superior results.

Mandibular arch perimeter changes with lip bumper treatment.

The effects of lip bumper treatment on the mandibular arch were observed in 32 patients with late transitional and early permanent dentitions. Dental cast measurements were made for arch perimeter, arch length, and arch width. Cephalometric radiographs were used to determine labial tipping of the incisors and distal movement of the molars. Arch circumference increased in all patients, ranging from 0.7 mm to 8.8 mm, with an average of 4.1 mm. The mean increase in arch length was 1.2 mm and was largely attributed to anterior tipping of the mandibular incisors. Change in arch length was the most predictive variable for the increase in arch circumference. Passive changes in arch width were recorded, with a mean increase of 2.0 mm in the intercanine distance and 2.5 mm in the first premolar distance. Arch width increments contributed to the increase in arch circumference, but the increases in arch width were not found to be predictive of the change in arch circumference. Changes in either arch circumference or arch length were not related to the duration of treatment, age and sex of the patient, or the eruption status of the permanent second molars.

An evaluation of the nasolabial angle and the relative inclinations of the nose and upper lip.

The purpose of this study was to develop a consistent and reproducible method of constructing a nasolabial angle that would also permit an evaluation of the relative inclination of the lower border of the nose and the upper lip, as well as their relationship to each other. Comparison of repeated individual measurements of soft tissue profile landmarks on 15 subjects, as completed by four orthodontists, revealed that the proposed method of constructing the nasolabial angle was consistent and reproducible by the same orthodontist and among different orthodontists. Normative data for the three nasolabial parameters were produced from a sample of 104 young white adults determined by the authors to have well-balanced faces. Mean and standard deviation values from this pooled sample demonstrated a lower border of the nose to Frankfort horizontal plane angle at 18 degrees +/- 7 degrees, upper lip to Frankfort horizontal plane angle 98 degrees +/- 5 degrees, and nasolabial angle 114 degrees +/- 10 degrees. No statistically significant difference was demonstrated between the values for men and women in this study, but the women did have a slightly larger nasolabial angle. A linear comparison of the three nasolabial parameters with six skeletal measurements revealed no significant relationship between the soft tissue profile of the nasolabial region and the underlying skeletal relationships.