Medicaid and privately financed orthodontic patients have similar occlusal and psychosocial outcomes.

OBJECTIVE: This study compares occlusal and psychosocial outcomes from comprehensive orthodontic treatment in Medicaid (MC) and privately financed (private pay, PP) patients. METHODS: Two cohorts received comprehensive orthodontics: MC (n = 66); PP (n = 60). A calibrated, blinded examiner scored dental casts at baseline (pretreatment, T1) and after completing 2 years of treatment (posttreatment, T2) using the Peer Assessment Rating (PAR) and the Index of Complexity, Outcome, and Need (ICON). The prevalence of patients in the validated ICON categories for treatment need, complexity, and improvement were calculated. Questionnaires to assess body image (BI) and expectations/experiences were administered. Occlusal measures at T2 were compared after adjustment for baseline characteristics. Psychosocial measures were compared between and within groups. Occlusal and psychosocial associations were evaluated. RESULTS: MC was 1.3 years younger (P < 0.001) and had worse malocclusions at baseline (PAR 32 versus 25; P < 0.001); (ICON 64 versus 56; P = 0.06). After adjustment for age and initial severity, estimated average differences between groups at T2 (MC-PP) were slight: 1.5 [95 percent confidence interval (CI) -2.9, 5.9] and 2.4 (95 percent CI -4.4, 8.9) for PAR and ICON, respectively. More PP completed treatment under 2 years (85 percent versus 62 percent; P = 0.03). At baseline, both groups needed treatment, but MC malocclusions were more complex (P = 0.05). At T2, both groups were acceptable and there were no differences in ICON improvement categories. Group differences in psychosocial measures and associations between psychosocial and occlusal measures were evident in the "teeth" domain but weak or lacking elsewhere. CONCLUSIONS: Occlusal and psychosocial outcomes from orthodontics in MC and PP were comparable, despite worse MC malocclusions at baseline.

Dental effects of interceptive orthodontic treatment in a Medicaid population: interim results from a randomized clinical trial.

INTRODUCTION: There are disparities in access to orthodontic treatment for children from low-income families. Systematic programs of limited-care interceptive and preventive orthodontics have been proposed as a solution. The purpose of this randomized clinical trial was to compare dental outcomes and funding eligibility from a group of Medicaid patients randomized to receive interceptive orthodontics (IO) in the mixed dentition or observation (OBS). METHODS: One hundred seventy Medicaid-eligible children were randomized to receive IO or OBS and followed for 2 years, when complete data were available on 72 and 74 children, respectively. The 2-year changes in the peer assessment rating (PAR) were compared using the Student t test. The proportions of children no longer eligible for Medicaid funding as defined by handicapping labiolingual deviation (HLD) scores less than 25 at the 2-year follow-up were compared with the chi-square test. RESULTS: The IO patients had significantly greater decreases in the PAR scores--50%-compared with the OBS subjects, -6% (P <0.001). Negative and positive overjet and maxillary alignment were the components most affected by IO; they decreased by 11.0, 7.2, and 3.7 PAR points, respectively (P <0.001). Overbite showed little change. At the 2-year follow-up, 80% of the IO patients' malocclusions that qualified initially were no longer deemed medically necessary by the HLD index, compared with 6% in the OBS group (P <0.001). CONCLUSIONS: IO significantly reduces the severity of malocclusions and moves most from the "medically necessary" category to elective but does not produce finished results for most patients. Overjet and alignment were most readily corrected by interceptive treatment. Deep overbites were the least susceptible to IO correction.

Effectiveness of interceptive orthodontic treatment in reducing malocclusions.

INTRODUCTION: In this retrospective cohort study of the effectiveness of interceptive orthodontic treatment, we compared patients receiving interceptive orthodontic treatment with untreated control subjects. METHODS: Models were scored by using the index of complexity, outcome and need (ICON). Control models (n = 113) were archival and were selected based on malocclusion in the early mixed dentition and no orthodontic treatment during the subsequent 2 years. The patients (n = 133) were in the mixed dentition and consecutively treated in the University of Bergen orthodontic clinic. Initial ages were 9.4 years (+ or - 1.4) for the treated group and 9.3 years (+ or - 0.8) for the control group. The treatment took a mean of 27.2 months (+ or - 16.3) for the patients; the control group was observed for a mean of 24.4 months (+ or - 3.6). Subject Groups were matched for age, need, complexity, duration, and all ICON components except spacing (P <0.006) and crossbite (P <0.000). RESULTS: ICON scores decreased after treatment by 38.8% (P <0.0001) from 54.9 (+ or - 16.6) to 33.6 (+ or - 16.1). The controls were unchanged, with ICON scores of 54.0 (+ or - 14.8) and 54.2 (+ or - 16.9). Improvement grades were different (P <0.0001), with most controls categorized as "not improved or worse" (89.4%), whereas only 36.1% of the treated group were in that category. However, there were increases in the "minimal," "moderate," and "substantial" improvement categories for the treated subjects (22.6%, 21.1%, and 17.3%, respectively). The controls did not change in any ICON component and worsened in crowding (P <0.007), whereas the patients improved in esthetics, crowding, crossbite, and overbite (P <0.007). CONCLUSIONS: These results indicate that interceptive orthodontic treatment is effective for improving malocclusion but does not produce finished-quality results.

Cephalometric and electromyographic study of patients of East African ethnicity with and without anterior open bite.

INTRODUCTION: A review of the literature showed that there are disturbances of muscle activity and tongue function in patients with anterior open bite (AOB). However, most studies have had white subjects, even though open bite is more prevalent in black populations. In this pilot study, we examined jaw muscle activity and tongue pressure in East African black subjects. METHODS: Ten subjects (4 boys, 6 girls; ages, 10.1-13.2 years) were recruited. A cephalometric comparison of subjects with and without AOB was performed. Surface electrodes were placed on the bilateral anterior temporalis, superficial masseter, superior orbicularis oris, and anterior digastric muscles. Electromyograms were recorded at rest, maximal voluntary clenching, chewing, and swallowing. Tongue pressure during rest and swallowing, and maximal bite force were also measured. RESULTS: There was no statistically significant difference between the 2 groups in cephalometric measures (except in amount of open bite and overbite) and maximum bite force. During chewing, both groups showed similar coordinated activity patterns in the muscles, but the AOB subjects tended to show more electromyographic activity in the muscles of the balancing side. During clenching, the AOB subjects exhibited lower electromyographic activity compared with the controls. AOB subjects also had greater anterior tongue pressure during swallowing. Data from tongue pressure at rest were inconclusive. CONCLUSIONS: East African blacks appear to have neuromuscular and skeletal predispositions to AOB, but their vertical incisor relationships are variable. Factors in addition to those investigated might be involved.

Effects of malocclusion and its treatment on the quality of life of adolescents.

INTRODUCTION: The relationship between malocclusion and quality of life (QoL) is complex and not well understood. The objective of this study was to determine whether malocclusion and its treatment influence an adolescent's general and oral health-related QoL. METHODS: An observational, cross-sectional design with a longitudinal component was used. Clinical and self-reported data were collected from 293 participants aged 11 to 14. The children were recruited from orthodontic and pediatric dental clinics at the University of Washington and a community health clinic in Seattle. The participants were classified into precomprehensive orthodontic (n = 93), postinterceptive orthodontic (n = 44), and nonorthodontic comparison (n = 156) groups. Assessments of dental esthetics and occlusion were evaluated with the Index of Complexity, Outcome, and Need. Three QoL questionnaires were completed: Youth Quality of Life to assess general QoL, Children's Oral Health-Related Quality of Life to assess oral health QoL, and Treatment Expectations and Experiences to evaluate participants' expectations for changes in specific aspects of their lives. Nonparametric tests were used for all analyses. RESULTS: In general, overall and oral health QoL were high in this population. The instruments were correlated so that when oral health QoL improved, so did general QoL. No differences were found in these measurements between the university and community health clinics. Nor were there differences between the 3 study groups on general QoL and oral health QoL. There was little effect of malocclusion complexity on any QoL measure. Both preorthodontic and postorthodontic participants expected improvements in their health, oral function, appearance, and social well-being after orthodontic treatment; the postinterceptive sample's posttreatment experiences were consistent with their pretreatment expectations in all domains. CONCLUSIONS: Malocclusion and orthodontic treatment do not appear to affect general or oral health QoL to a measurable degree, despite subjective and objective evidence for improved appearance, oral function, health, and social well-being.

Comparison of arch dimension changes in 1-phase vs 2-phase treatment of Class II malocclusion.

INTRODUCTION: We compared arch dimension changes in 1-phase and 2-phase treatment of Class II malocclusion. This was a prospective randomized clinical trial conducted in the Department of Orthodontics at the University of Florida between 1990 and 2003. METHODS: During phase 1 treatment, 86 subjects were treated with a bionator, 93 were treated with headgear/biteplane, and 81 served as the observation group. For phase 2, all subjects were then treated with full orthodontic appliances. Arch dimensions were followed; maxillary and mandibular alginate impressions were taken at baseline, end of early Class II treatment or observation, beginning of fixed appliance treatment, end of orthodontic treatment, and approximately 3 years posttreatment. Alginate impressions were taken of each dental arch at each data collection point. These were poured in orthodontic stone, trimmed, and photocopied from the occlusal aspect. These images were then scanned and measured. RESULTS: Although differences between the treatment groups were found in both the maxillary and mandibular arches after phase 1, these differences were no longer evident by the end of full orthodontic treatment or after posttreatment retention. CONCLUSIONS: There were no differences in arch dimensions after 1-phase or 2-phase treatment of Class II malocclusion.

Effect of early treatment on stability of occlusion in patients with Class II malocclusion.

INTRODUCTION: The purpose of this study was to evaluate the effect of early treatment on the stability of occlusion in patients with Class II malocclusions. The peer assessment rating (PAR) index was used to evaluate changes in occlusion after treatment of subjects treated in 1 phase or 2 phases. This study was a prospective, randomized, controlled clinical trial. METHODS: Dental casts were obtained from the participants, who were randomized into 3 phase-1 early treatment groups: bionator, headgear/bite plane, or observation. Phase 2 consisted of continued treatment of the bionator and the headgear/biteplane subjects and comprehensive treatment of the observation subjects. PAR scores were obtained for 208 subjects at end of treatment; 173 (83%) had at least 1 follow-up visit, with a median follow-up time of 5.0 years. PAR scores were calculated for each subject at key treatment and posttreatment time points. Linear mixed-effect models were used to evaluate the impact of phase-1 treatment group, years posttreatment, end of treatment PAR score, and other covariates that could affect stability on the posttreatment PAR score. RESULTS: Factors significantly affecting posttreatment PAR scores were PAR score at end of treatment (P <.0001), years posttreatment (P =.0064), and PAR score at the start of phase 2. Although phase-1 treatment was not statistically significant, those with early treatment had lower PAR scores at the start of phase 2 than the observation subjects (means [SD]: bionator 17.5 [7.4], headgear/biteplane 15.3 [7.0], observation 22.2 [8.6], P <.0001). Thus, early treatment had an indirect effect. CONCLUSIONS: Factors that affect posttreatment PAR score stability include PAR score at the end of treatment, years posttreatment, and PAR score at the start of phase-2 treatment. The early treatment modalities have limited positive impact on posttreatment stability PAR scores in Class II malocclusion patients due to their effect on PAR scores at the start of phase-2 treatment.

Timing of Class II treatment: skeletal changes comparing 1-phase and 2-phase treatment.

INTRODUCTION: Previous studies reported small but significant skeletal changes as a result of early treatment of Class II malocclusion with headgear and functional appliances. In this study, we report on the skeletal changes for 1-phase and 2-phase treatment of Class II malocclusion. METHODS: This was a prospective randomized clinical trial conducted sy the Department of Orthodontics at the University of Florida between 1990 and 2000. A total of 261 subjects demonstrating at least a one half-cusp Class II molar relationship and meeting the inclusion criteria were enrolled in the study and had at least 1 follow-up visit. During phase 1, 86 subjects were treated with a bionator, 95 were treated with a headgear/biteplane, and 80 served as the observation group. For phase 2, all subjects were then treated with full orthodontics appliances. Skeletal changes were monitored with cephalograms taken at baseline, at the end of early Class II treatment or observation baseline, at the beginning of fixed appliances, and at end of orthodontic treatment. RESULTS: Overall skeletal changes at the end of phase 1 treatment were as follows: (1) SNA angle increased in the bionator (0.51) and the observation groups (0.67), whereas it decreased (-0.50) in the headgear/biteplane group; (2) SNB angle increased in the bionator (1.36) and the observation groups (0.84), whereas it remained unchanged (0.19) in the headgear/biteplane group; (3) ANB angle decreased in the bionator (-0.85) and the headgear/biteplane groups (-0.72), and was unchanged in the observation group; and (4) the mandibular plane angle increased (1.30) only in the headgear/biteplane group. By the end of full orthodontic treatment, the skeletal differences in all measurements for all 3 groups were within 1 degrees . Linear regression models showed that, during phase 1, baseline value and treatment group were significant. However, when the entire treatment period was considered, treatment group had no effect. CONCLUSIONS: There is temporary skeletal change as a result of phase I treatment with both appliances but no detectible skeletal difference between 1-phase and 2-phase treatment of Class II malocclusion by the end of full orthodontic treatment.

Effects of human relaxin on orthodontic tooth movement and periodontal ligaments in rats.

INTRODUCTION: The rate-limiting step in orthodontic treatment is often the rapidity with which teeth move. Using biological agents to modify the rate of tooth movement has been shown to be effective in animals. Relaxin is a hormone present in both males and females. Its main action is to increase the turnover of fibrous connective tissues. Thus, relaxin might increase the amount and rate of tooth movement through its effect on the periodontal ligament (PDL). The purpose of this study was to measure the effect of relaxin on orthodontic tooth movement and PDL structures. METHODS: Bilateral orthodontic appliances designed to tip maxillary molars mesially with a force of 40 cN were placed in 96 rats. At day 0, the animals were randomized to either relaxin or vehicle treatment. Twelve rats in each group were killed at 2, 4, 7, and 9 days after appliance activation. Cephalograms were taken at appliance placement and when the rats were killed. Tooth movement was measured cephalometrically in relation to palatal implants. Fractal analysis and visual analog scale assessments were used to evaluate the effect of relaxin on PDL fiber organization at the tension sites in histologic sections. The in-vitro testing for PDL mechanical strength and tooth mobility was performed by using tissue from an additional 20 rats that had previously received the same relaxin or vehicle treatments for 1 or 3 days (n = 5). RESULTS: Both groups had statistically significant tooth movement as functions of time. However, relaxin did not stimulate significantly greater or more rapid tooth movement. Fractal and visual analog scale analyses implied that relaxin reduced PDL fiber organization. In-vitro mechanical testing and tooth mobility assessments indicated that the PDL of the mandibular incisors in the relaxin-treated rats had reduced yield load, strain, and stiffness. Moreover, the range of tooth mobility of the maxillary first molars increased to 130% to 170%, over vehicle-treated rats at day 1. CONCLUSIONS: Human relaxin does not accelerate orthodontic tooth movement in rats; it can reduce the level of PDL organization, reduce PDL mechanical strength, and increase tooth mobility at early time points.

Assessment of cell proliferation during mandibular distraction osteogenesis in the maturing rat.

INTRODUCTION: The cellular mechanisms controlling distraction osteogenesis are not well understood. The purpose of this study was to examine the role of cell proliferation in the regulation of mandibular distraction osteogenesis. METHODS: Unilateral mandibular ramus osteotomies were performed on 125 3-month-old Sprague-Dawley rats. The rats were randomized into 4 distraction rate groups and distracted for 5 days after 3-day latency. Rats (7 or 8 from each rate group) were killed at 4 time points. The rats received 5-bromo-2-deoxyuridine (BrdU) injections (40 mg per kilogram, i.p.) at day 3 (end of latency). RESULTS: Both intramembranous and endochondral ossification was seen in the osteogenesis area. BrdU+ mesenchymal progenitor cells were significantly higher at day 10 (P <.05) and were found most numerously around the sagittal middle portion of the gap (P <.01). The greatest numbers of BrdU+ osteocytes were seen at day 38 (P <.05). Both BrdU+ osteoclasts and chondrocytes peaked at day 24. CONCLUSIONS: Mesenchymal progenitor cells are mostly recruited in the early consolidation period, but they decrease in the middle and late consolidation periods during mandibular distraction osteogenesis. The rapid rate might suppress or sustain the proliferation and differentiation of mesenchymal progenitor cells during mandibular distraction osteogenesis. BrdU+ cells can survive throughout the entire experimental period of 5 weeks.

Early orthodontic treatment as a means to increase access for children enrolled in Medicaid in Washington state.

BACKGROUND: The authors assessed the likelihood that interceptive orthodontic Medicaid programs would increase access to care for Washington children. METHODS: The authors surveyed 210 Washington state orthodontists, including questions on demographics, attitudes toward early treatment, use of innovations and perceptions of Medicaid. Respondents were either Medicaid participants or nonparticipants. RESULTS: Fifty of 159 respondents were Medicaid participants. Most respondents perceived early orthodontic treatment as beneficial. Medicaid participants were more willing to participate in Medicaid early-treatment programs, had slightly fewer patients in the "other insurance" category, provided more discounted fees, received more Medicaid inquiries, practiced in rural areas with lower household incomes, reported feeling overworked and experienced fewer Medicaid problems. The principal problem reported with the Medicaid system was low fee reimbursement. CONCLUSIONS: Programs offering early orthodontic treatment could increase access. Important barriers would be low fees and unfamiliarity with Medicaid. PRACTICE IMPLICATIONS: Medicaid should design programs aimed at early treatment with reasonable reimbursement and an educational component.

Eligibility for publicly funded orthodontic treatment determined by the handicapping labiolingual deviation index.

INTRODUCTION: Access to orthodontic care for Medicaid patients has been limited, in part because of orthodontists' reluctance to treat severe malocclusions for low reimbursements. Limited orthodontic treatment in the mixed dentition (phase 1 treatment) has been proposed to address this issue, because the intent of phase 1 treatment is to improve or prevent severe malocclusions. Orthodontists might be more willing to provide shorter, simpler treatment. The purpose of this study was to determine whether phase 1 treatment would reduce malocclusion severity to the extent that eligibility for subsequent Medicaid-funded treatment was significantly reduced. METHODS: Eligibility was determined by the handicapping labiolingual deviation (HLD) index, which is used by several states for this purpose. Eligibility was also determined with the index of complexity, outcome, and need (ICON). This allowed us to compare these 2 indexes. Pre-phase 1 and post-phase 1 index scores were calculated by using study casts from 193 patients treated at the University of Washington orthodontic clinic and the Odessa Brown Children's Dental Clinic, both in Seattle. RESULTS: Using the HLD index, we found that eligibility for orthodontic treatment decreased by 62% after phase 1 treatment. This change was statistically significant at P < .0001. The ICON found significantly more treatment need before phase 1 (90%) than did the HLD index (35%) (P < .0001). CONCLUSIONS: Early interceptive treatment significantly reduces eligibility for comprehensive Medicaid-funded orthodontic treatment. The HLD index is a useful tool for determining Medicaid eligibility.

Occlusal perceptions of children seeking orthodontic treatment: impact of ethnicity and socioeconomic status.

INTRODUCTION: With the growth of orthodontic intervention at younger ages and increased interest in improving dentofacial appearance among the general public, it is important to assess whether demand for treatment is uniform across ethnic and socioeconomic groups. METHODS: This study compared 3 groups of children who varied by location, payment source, and ethnicity. The sample consisted of 150 children in the Bronx, NY, and 100 in Seattle, Wash, who were undergoing or anticipating orthodontic treatment in publicly funded dental clinics. Ethnic minorities comprised 69% and 92%, respectively, of these groups. The third group consisted of 84 children in Seattle, Anchorage (Alaska), and Chicago who had sought treatment by private practitioners; ethnic minorities comprised 22% of this group. Data were collected from children and parents or guardians by questionnaires. RESULTS: Desire for treatment was higher among children in the publicly funded clinics and among black children than whites or Asian Americans. Children in publicly funded clinics rated themselves as having worse occlusions as determined by anterior crowding, overbite, overjet, diastema, and open bite. Children in the Bronx clinic accepted a wider range of occlusion as attractive. Stage of treatment affected judgments of attractiveness. Vicarious experience with orthodontics through parents or siblings made children more tolerant of dentofacial disharmony, with more favorable ratings of malocclusion in this group than among children who had no family experience with orthodontics. Hispanic and mixed-ethnicity children rated themselves more negatively on all dimensions. CONCLUSIONS: These results suggest that both socioeconomic status and ethnicity play roles in children's desire for treatment, self-assessed need, and judgments of esthetics. A clinician's sensitivity to such differences can improve patient cooperation with treatment.

Does human relaxin accelerate orthodontic tooth movement in rats?

Human relaxin was administered to young rats through either minipumps (group P) or subcutaneous injections (group I). Control rats received pump implants containing placebo (group C). Day 0 was the day of orthodontic appliance placement and activation to pull bilateral upper first molars forward, and day 14 was the end time point. Cephalometric radiographs (three repeated exposures) were taken at 0, 3, 5, 7, 10, and 14 days. The total length of three maxillary molar segments and the space between the first and second molars were measured under a dissecting microscope postmortem. Both groups P and I showed rapid tooth movement at day 3. Movement slowed, but it still increased gradually in group P while decreasing in group I after that. Concurrent tooth lateral drifts to the buccal side were smaller in both groups P and I. The length and space were larger in both groups P and I. Thus, administration of human relaxin may accelerate the early stages of orthodontic tooth movement in rats.

The effectiveness of phase I orthodontic treatment in a Medicaid population.

BACKGROUND: The effectiveness of early orthodontic treatment for Medicaid-enrolled children in the mixed dentition was assessed and compared with results in a population of private-pay patients. MATERIAL: Pre- and posttreatment casts from 196 subjects treated with interceptive orthodontics in the mixed dentition were evaluated by using the peer assessment rating (PAR) index and the index of complexity, outcome, and need (ICON). Ninety-six of the patients were treated at Odessa Brown Community Clinic in Seattle; their treatment was paid by Medicaid. One hundred private-pay patients were treated at the University of Washington graduate orthodontic clinic. The Medicaid and private-pay populations were comparable with respect to initial severity of malocclusion, as assessed by both indexes. RESULTS: PAR and ICON scores fell by similar amounts in the Medicaid (44.1% and 37.5%, respectively) and private-pay (46.8% and 37.3%, respectively) populations. Thus, the groups exhibited similar degrees of improvement with interceptive orthodontic treatment. According to the PAR and ICON, midline discrepancy, overjet, and esthetics exhibited the greatest improvement. The Medicaid population missed significantly more appointments and had poorer oral hygiene than the private-pay group, but these factors did not appear to worsen the outcomes, as measured by the 2 indexes. An appliance with 2 bands and 4 brackets was the most commonly used, and it produced the most significant treatment effect. CONCLUSIONS: Phase I orthodontic treatment significantly reduces malocclusion severity in Medicaid and private-pay populations. There was no difference in initial severity or final outcome, as assessed by the PAR and ICON, between Medicaid and private-pay populations. The degree of improvement in PAR scores did not appear to be associated with compliance.

Alterations of morphology and microdensity in the condyle after mandibular osteodistraction in the rat.

PURPOSE: In this study, we examined the effects of mandibular distraction osteogenesis on the morphology and the microdensity of the rat condyle. MATERIALS AND METHODS: One hundred twenty-nine rats were allocated to 4 experimental groups (n = 32 or 33). Each received unilateral mandibular ramus osteotomy and distraction device placement. After a 3-day latency, these were distracted once a day for 5 days. The slow distraction group was distracted a total of 1 mm (0.2 mm/d); the moderate group, 2 mm (0.4 mm/d); the rapid group, 3 mm (0.6 mm/d); and the sham group, no distraction (0.0 mm/d). Eight to 9 rats in each group were sacrificed at each of 4 time points after device placement (6, 10, 24, and 38 days). Baseline data were obtained 3 days after osteotomy and device placement without distraction from an additional 10 rats. Radiographs of the hemimandibles were scanned and measured to evaluate changes in condylar size (height, width, and area), angulation, and bone microdensity converted to equivalent bone thickness using a stepwedge. The wet weights of masseter muscle were measured at the time of harvest. RESULTS: 1) Muscle weight gains over time were significantly lower in the treated than the untreated sides throughout the consolidation period (P <.001). 2) Condylar size and angulation on the untreated side increased postoperatively, whereas there was a significant reduction of these parameters (P <.01 to.001) on the treated side at 24 and/or 38 days. 3) Condylar microdensity significantly increased on the untreated side at 24 and 38 days (P <.05 to.01) but not on the treated side. 4) Faster or larger distraction caused more severe size reduction and more upright condylar angulation, prevented an increase in bone microdensity on the treated side, especially during the consolidation periods (P <.05 to.01), and retarded increase in muscle weight, whereas a slower distraction rate showed few negative, and even some positive effects. 5) Correlations in size, angulation, and microdensity between right and left condyles became less significant over time. 6) There were positive correlations between muscle weight and condylar size, angulation, and microdensity. CONCLUSION: An increased rate of mandibular distraction has significant negative effects on condylar morphology and microdensity.

Vascular leak syndrome of Sprague-Dawley rats in a mandibular distraction osteogenesis study.

Vascular leak syndrome (VLS) is a common and often fatal sequela of multiple bone traumas, and of infectious, toxic, and allergic insults in human patients. Although an animal model for VLS has not been fully established, rats have shown sensitivity to the syndrome that approximates that of the human population. We describe cases of VLS in three-month-old adult and one-month-old Sprague-Dawley rats in an osteogenesis study aimed at optimizing correction of bone hypoplasias and other craniofacial deformities in children, using a mandibular distraction device. In the study reported here, VLS was diagnosed in 40% of the rats that were necropsied after dying or being euthanized early, subsequent to mandibular osteotomy, a procedure that involves minimal bone trauma. The gross and histologic findings, as well as the clinical course of VLS in the rats of the osteogenesis study, were similar to those of documented human cases. Hence, the rat may be a useful animal model to h elp characterize the physiologic and molecular events that accompany this syndrome.