Microdamage in the alveolar process of rat maxillae after orthodontic tooth movement.

OBJECTIVE: Playing a decisive role in bone remodeling, microdamage was recently associated with orthodontic tooth movement in pigs. The present study was conducted to evaluate microdamage and its potential association with orthodontic tooth movement in the alveolar process of rat maxillae. MATERIAL AND METHODS: The upper right molars of 24 male Wistar rats (10 weeks old) were splinted and loaded against the (likewise splinted) upper incisors with 25 cN using a Nitinol coil spring. Four groups of 6 animals were treated in this fashion for 1, 2, 4, or 7 days. The upper left quadrants served as controls. The maxillae were halved, gently prepared, and stained en bloc with basic fuchsin. After embedding in resin, 80-µm-thick parasagittal sections were ground parallel to the mesial root of the first molar. These were used to assess microdamage under transmitted and epifluorescent light, also counting and measuring the length of microcracks. Differences between the loaded and unloaded side and between mesial and distal were checked using a Wilcoxon test and were considered significant at ≤ 0.05. RESULTS: Microdamage (in the form of diffuse damage and microcracks) was observed in both the loaded and control jaw halves, as well as on the mesial and distal sides in all four groups. Microcracks averaged 30-100 µm in length and 0.3-1.7/mm(2) in density. While they were more prevalent in the loaded than the control jaw halves, this difference was not statistically significant. CONCLUSION: The alveolar process of rat maxillae is characterized by microdamage (in the form of microcracks and diffuse damage) regardless of whether and for how long orthodontic loading has taken place. Within the limitations of this experimental study, our results do not confirm previous findings of significantly higher prevalence on the pressure side on the first day after initiating orthodontic tooth movement.

Bone condition of the maxillary zygomatic process prior to orthodontic anchorage plate fixation.

OBJECTIVES: The clinical success of orthodontic miniplates depends on the stability of the miniscrews used for fixation. For good stability, it is essential that the application site provides enough bone of good quality. This study was performed to analyze the amount of bone available for orthodontic miniplates in the zygomatic process of the maxilla. METHODS: We examined 51 dental CT scans (Somatom Plus 4; Siemens, Erlangen, Germany) obtained from 51 fully dentate adult patients (mean age 24.0 ± 8.1 years; 27 male and 24 female) prior to third molar surgery. The amount of bone in the zygomatic process region at the level of the first molar root tips and at several other cranial levels as far as 15 mm from the root tips was measured RESULTS: Bone thickness at the root tip level averaged 4.1 ± 1.0 mm; the lowest value measured at this level in any of the patients was 2.7 mm. Bone thickness averaged 8.3 ± 1.0 mm at 15 mm cranial to the root tips; 6.9 mm was the lowest value. CONCLUSION: The zygomatic process appears to provide sufficient bone to accommodate screws for miniplate fixation. While some patients may possess a borderline amount of bone at more caudal levels, lack of volume is not a problem near the zygomatic bone.

Histomorphometry in antigen-induced arthritis of the rabbit temporomandibular joint.

BACKGROUND: Juvenile idiopathic arthritis (JIA) of the temporomandibular joint (TMJ) can cause severe growth disturbances of the craniomandibular system. Antigen-induced arthritis (AIA) of the rabbit TMJ is simulating the inflammatory process of the TMJ in JIA. The aim of this study was to investigate the effect of a systemic administration of the tumor necrosis factor-alpha (TNF-α) antagonist etanercept on AIA in rabbits by means of three different histological staining methods. METHODS: After sensitization, a bilateral arthritis of the TMJ was induced and maintained by repeated intra-articular administrations of ovalbumin in 12 New Zealand white rabbits aged 10 weeks. From the 13th week of age, 6 of the 12 rabbits received weekly subcutaneous injections of etanercept, and the other 6 animals remained without therapy. Another 6 animals served as controls, receiving no treatment or intra-articular injections at all. After euthanasia at the age of 22 weeks, all TMJs were retrieved en bloc. Sagittal sections were cut and stained with hematoxylin-eosin (H-E), Safranin-O for the evaluation of the Mankin score, and tartrate-resistant acid phosphatase (TRAP). RESULTS: In the arthritis group, a chronic inflammation with degeneration of the articular cartilage was visible. In the etanercept group, the signs of cartilage degeneration were significantly reduced but present. In contrast, the joints in the control group were inconspicuous. A strong correlation between the Mankin score and TRAP-positive cells could be found. CONCLUSIONS: Antigen-induced arthritis causes severe damage in the TMJ of young rabbits. An improvement seems to be achievable by a systemic administration of etanercept.

Demineralization adjacent to orthodontic brackets after application of conventional and self-etching primer systems.

OBJECTIVES: The goal of this work was to compare the demineralization of enamel associated with two different self-etching primers and traditional acid etching. MATERIALS AND METHODS: A total of 15 volunteers (23-32 years, 8 male and 7 female) were provided with a removable archwire/resin appliance to be worn 20 h/day for 28 days. The device was attached to the mandibular posterior teeth and included samples of human enamel (from extracted third molars) located in both posterior vestibules. Both sides featured the same distribution of samples, including one untreated control sample (group A) and three samples with brackets (Victory™ APC II) bonded to their surface after conditioning with a self-etching non-fluoride primer (iBond™ Gluma® Inside; group B), a self-etching fluoride-releasing primer (Transbond™ Plus; group C), or traditional acid-etching with 35% phosphoric acid and Transbond™ XT (group D). Mineral loss was assessed extraorally under standardized conditions using quantitative light-induced fluorescence (QLF) with a specialized camera system (Inspektor Pro). Results were expressed as relative fluorescence loss (ΔF in %). A baseline measurement (T0) was taken before the appliance was first inserted but with the brackets already bonded. Fluorescence loss was analyzed after 3 (T1), 7 (T2), 14 (T3), and 28 days (T4) and compared to the baseline loss (T0) for each of the four study groups (A to D). Kruskal-Wallis and Mann-Whitney U tests were used to compare the results for statistical significance. RESULTS: The lowest percentages of fluorescence loss both at baseline and during the follow-up assessments was found in group C. While all three experimental groups (B, C, D) presented total decreases in fluorescence loss after 28 days, indicating remineralization, the decrease in group C was the largest. The Kruskal-Wallis test yielded no significant differences between the three groups other than a significantly lower percentage of fluorescence loss in group C than in group D during the last assessment (T4). The untreated samples of control enamel (group A) revealed increasing percentages of fluorescence loss over the entire study period. CONCLUSION: Use of the self-etching primers (groups B and C) was not associated with patterns of enamel demineralization different from those noted after traditional etching with phosphoric acid (group D). The only significant difference we observed was between the self-etching fluoride-releasing primer (group C) and traditional etching (group D) at the final assessment (T4). Thus, the fluoride-releasing system Transbond™ Plus was advantageous.

Assessing bone volume for orthodontic miniplate fixation below the maxillary frontal process.

OBJECTIVES: The maxillary bone below the frontal process is used for orthodontic anchorage; indications have included skeletally anchored protraction of the maxilla for treating Class III malocclusions or the intrusion of teeth in patients with a deep bite. This study was conducted to assess the condition of bone before cortically implanting miniplates in that area of the maxilla. PATIENTS AND METHODS: A total of 51 thin-sliced computed tomography scans of 51 fully-dentate adult patients (mean age 24.0 ± 8.1 years; 27 men and 24 women) obtained prior to third-molar osteotomy were evaluated. Study parameters included total bone thickness, thickness of the facial cortical plate, and width of the nasal maxillary buttress. All these parameters were measured at different vertical levels. RESULTS: The bone volume adjacent to the piriform aperture was most pronounced at the basal level and decreased progressively toward more cranial levels. The basal bone structure had a mean total thickness of 7.8 mm, facial cortical plate thickness of 1.9 mm, and nasal maxillary buttress width of 9.2 mm. At 16 mm cranial to the aperture base, these values fell to 5.6 mm, 1.3 mm, and 5.8 mm, respectively. CONCLUSION: These bone measurements suggest that screws 7 mm in length can be inserted at the base level of the piriform aperture and screws 5 mm long at the cranial end of the bone.

Application of a computer navigation system for the placement of orthodontic anchorage screws.

The computer navigation system Robodent, which was developed for dental implants, was used for the placement of orthodontic anchorage screws in a phantom head. The deviation between the planned and finally achieved position of the screws did not exceed that reported for dental implants. In conclusion, the system seem to be suitable and precise enough for orthodontic screws.

Non-Markovian approach to globally coupled excitable systems.

We consider stochastic excitable units with three discrete states. Each state is characterized by a waiting time density function. This approach allows for a non-Markovian description of the dynamics of separate excitable units and of ensembles of such units. We discuss the emergence of oscillations in a globally coupled ensemble with excitatory coupling. In the limit of a large ensemble we derive the non-Markovian mean-field equations: nonlinear integral equations for the populations of the three states. We analyze the stability of their steady solutions. Collective oscillations are shown to persist in a large parameter region beyond supercritical and subcritical Hopf bifurcations. We compare the results with simulations of discrete units as well as of coupled FitzHugh-Nagumo systems.

SureSmile--CAD/CAM system for orthodontic treatment planning, simulation and fabrication of customized archwires.

SureSmile is an all-digital system which uses new 3-D imaging and computer techniques for diagnostics and treatment planning and uses robotics to customize fixed orthodontic appliances. Treatment can be simulated in advance and different treatment strategies can be visualized; this allows detailed treatment planning. The application of CAD/CAM aims at improving reproducibility, efficiency, and quality of orthodontic treatment.

Phase velocity and phase diffusion in periodically driven discrete-state systems.

We develop a theory to calculate the effective phase diffusion coefficient and the mean phase velocity in periodically driven stochastic models with two discrete states. This theory is applied to a dichotomically driven Markovian two-state system. Explicit expressions for the mean phase velocity, the effective phase diffusion coefficient, and the Pe clet number are analytically calculated. The latter indicates as a measure of phase-coherence forced synchronization of the stochastic system with respect to the periodic driving and exhibits a "bona fide" resonance. In a second step, the theory is applied to a non-Markovian two-state system modeling excitable systems. The results prove again stochastic synchronization to the periodic driving and are in good agreement with simulations of a stochastic FitzHugh-Nagumo system.

Periodic driving controls random motion of Brownian steppers.

We study the motion of Brownian steppers, which are objects moving unidirectionally by discrete steps. A single step is composed of two processes. An activation process describing the random attachment of a fuel molecule is followed by a conformational change of the stepper, leading to the forward motion. Whereas activation is given by a Markovian rate process, the forward motion is defined by a gamma distribution. In this paper we propose a periodic modulation of the fuel concentration in order to control the random motion of the stepper. We show that the driving may reduce the fluctuations of the stepper. Corresponding minima of the diffusion coefficient and maxima of the Péclet number prove the regularity of the motion.

Stochastic resonance in a non-markovian discrete state model for excitable systems.

We study a non-Markovian three state model, subjected to an external periodic signal. This model is intended to describe an excitable system with periodical driving. In the limit of a small amplitude of the external signal we derive expressions for the spectral power amplification and the signal to noise ratio as well as for the interspike interval distribution.

The Houston Vision Assessment Test (HVAT): an assessment of validity. The Cataract Outcome Study Group.

PURPOSE: Cataract surgery is one of the most successful procedures in medicine, and outcome is typically measured by a single factor - improvement in visual acuity. Health-related functional outcome testing, which quantifies the patient's self-reported perception of impairment, can be integrated with objective clinical findings. Based on the patient's self-assessed lifestyle impairment, the physician and patient together can make an informed decision on the treatment that is most likely to benefit the patient. METHOD: A functional outcome test (the Houston Vision Assessment Test - HVAT, copyrighted 1990, 1992) was evaluated in a cataract population of 149 patients from seven study centers. Test results were correlated with objective ophthalmic endpoints. The HVAT divides an estimated total impairment into subcomponents of Visual Impairment (correctable by cataract surgery) and non-visual Physical Impairments (co-morbidities not affected by cataract surgery). RESULTS: In this prospective study, the average Visual Impairment score improved by 19 points (65%) following cataract extraction (the mean HVAT Visual Impairment score was 29 points before surgery and 10 points at 5 months post-surgery, a change of 65%). Physical Impairment remained unchanged by surgery. Visual acuity was a poor predictor of Visual Impairment. CONCLUSIONS: The HVAT has 11 simple questions. It may be self-administered and is available on the Internet: http://www.DHAC.com. The physician may err if his decision in favor of cataract surgery is based only on visual acuity. The HVAT has the potential to guide the decision-making process between patient and physician.

TMJ morphology and function in a patient with Klippel-Trenaunay syndrome. Case report.

Klippel-Trenaunay syndrome is a rare congenital mesodermal disturbance of uncertain etiology in variable expression. The classic manifestation is the triad of congenital mesodermal abnormalities. Clinically a diversity of phenotypes with subjacent malformations may be encountered. The deviations of the mesioblastic germ layer affecting angioblastic, lymphoblastic and osteoblastic structures, may give rise to malformations either alone or in an unlimited diversity of associations. While this syndrome may be diagnosed by chance in the course of ultrasonic scanning during pregnancy, it is normally diagnosed during infancy or early childhood. Evaluation and carefully coordinated medical treatment are important in minimizing morbidity and relieving multiple complaints. The aim of our investigation was to evaluate and correlate the clinical, functional, radiographic and MRI findings in a patient suffering from this syndrome. We present a 13-year-old male patient suffering from extreme facial asymmetry in association with hypertrophy of the complete right side of the body. In spite of pronounced functional and morphologic asymmetry, no signs of degenerative joint disease were identified by radiography or MRI. Since temporomandibular joint dysfunction and facial asymmetry can result in irreversible degenerative joint disease, close follow-up monitoring is indispensable if joint damage is to be prevented.

1999 Costenbader Lecture. Outcome study in amblyopia: treatment and practice pattern variations.

This study retrospectively evaluates the results of amblyopia therapy and suggests hypotheses for future study. We address the various methods of treatment and evaluate the results from the most common therapy techniques. Practice pattern variations were analyzed in addition to the analysis of overall results. For ophthalmologists, there is a need to determine whether actual medical practice approaches the established standard of care, if it exists at all. How often are medical procedures, thought to be appropriate, based on anecdotal observation (case reports) rather than hard data (clinical trials)? The 3 types of vision loss evaluated were strabismic, anisometropic, and deprivation amblyopia. The methods of treatment studied were full-time patching part-time occlusion, penalization, and occlusion of the contact lens. Nine centers, thought to have private as well as indigent patients, were recruited to participate in this study. The centers responded by filling out an extensive questionnaire and sending the information through the World Wide Web for inclusion in a spreadsheet. This information was then collated, and various statistical programs tabulated the results. Although trends, as a consequence of therapy, are suggested from our retrospective analysis, concrete results can only arise from a randomized prospective study. The study included 279 patients. There were a similar number of male and female patients. Only 77% of the patients without fusion before treatment had either single binocular vision or peripheral fusion at the conclusion of therapy. The log improvement of vision was significant in each group. Factors that potentially influenced the results were severity of distance acuity in the amblyopic eye before treatment, duration of treatment, and length of daily patching. The paper suggests that worse vision, not better vision, at the beginning, predicts better outcome in terms of improvement of visual acuity. For example, visual acuity less than 20/70 at the initiation of treatment led to better visual results of geometric log improvement. Surprisingly, among the 9 centers studied, there was a statistically significant difference in many of the areas related to practice patterns. Patient compliance, which directly affects outcome, was highly variable and is a factor that may be readily influenced by the treating physician.

An imaging guide to the evaluation of third cranial nerve palsies.

PURPOSE: To devise a cost-effective imaging guide for the evaluation of third nerve palsies (TNP), based on an extensive review of the literature. METHODS: A review of the pertinent English language literature was performed to devise a guideline for the evaluation and neuroimaging of TNP. The authors also report a retrospective review of the cost of imaging studies performed on 91 patients with TNP. RESULTS: On the basis of the available literature, an imaging guide was developed and applied to a retrospective chart review of 91 patients from a single tertiary care center (Baylor College of Medicine). The cost effectiveness as well as the efficacy of the imaging guide was analyzed. CONCLUSIONS: The evaluation of TNP can be difficult; however, using such guides may allow for more appropriate and cost-effective evaluation of these patients.

Evaluation of methods for assessing visual function of infants.

PURPOSE: Commonly used behavioral and electrical testing methods for estimation of visual acuity and visual function in infants yield different estimates and may not accurately predict visual acuity and visual function in later life. Moreover, neither test-retest variability nor side-by-side comparisons of the various methods have been thoroughly evaluated in the same infant population. The purpose of this study was to provide such an evaluation. METHOD: The test-retest variability of visual acuity and visual function was evaluated for the Teller Acuity Card (TAC) procedure, sweep visual evoked potential (VEP), as well as latency and amplitude measured by transient pattern VEP. Groups of approximately 20 infants contributed test-retest data. Visual function estimated by the various methods in a larger group of infants (n = 118) was compared. Correlations between methods and the validity of the various methods to detect maturational changes between 4 and 8 months of age were also assessed. Administration of these tests was according to standard and usual procedures. RESULTS: The average percent difference between test and retest estimates of acuity as well as the SD was lowest for transient VEP latency (3%, 7% SD). The other methods were markedly more variable: sweep VEP (2%, 22% SD), TAC procedure (8%, 20% SD), and transient VEP amplitude (7.5%, 39% SD). Average coefficients of variation showed a similar trend: transient VEP latency, 8%; sweep VEP, 15%; TACs, 30%; and transient amplitude, 53%. Correlations among estimates by the methods were poor, but expected changes in visual maturation from 4 to 8 months of age were detected with all methods. CONCLUSIONS: All methods evaluated provide valid and reliable test-retest data for a group, but are less valid for estimating visual acuity and visual function of an individual subject. The poor correlations between any 2 of the testing methods suggest that each test assesses a different aspect of vision. Nonetheless, expected maturational changes between 4 and 8 months of age were readily detectable by all methods evaluated.

A practice pathway for the initial diagnostic evaluation of isolated sixth cranial nerve palsies.

PURPOSE: To define a practice pathway for the evaluation of sixth-nerve palsies (SNPs) and to determine its cost-effectiveness and validity in a retrospective chart review. METHODS: A Medline search of the English-language literature from 1966 to 1995 was performed to define the available clinical evidence and develop the practice pathway. The authors retrospectively reviewed 407 charts with the diagnosis of SNP seen at three centers. Information obtained included: etiologic diagnosis if known; development of new neurologic or ophthalmologic findings; and results and costs of neuroimaging studies, if performed. RESULTS: Of the 407 patients, 98 underwent computed tomography scans and 212 underwent magnetic resonance imaging of the head. Eighty cases were non-isolated, 317 were isolated SNP, and ten could not be classified from chart information. Of the 317 cases of isolated SNP, 49 were classified as traumatic; 5, congenital; 158, vasculopathic; 63, nonvasculopathic; and 42, progressive or unresolved. Following the recommendations of the practice pathway, the 158 patients classified as having vasculopathic SNP would not have undergone neuroimaging studies, realizing a savings of $100,000 in this study population of 407 patients. CONCLUSION: The recommendations of the practice pathway are supported by review of the literature and the retrospective review of these cases. However, a prospective study with a matched control group is needed to demonstrate regional and specialty-specific variations in care and to strengthen the clinical certainty of the pathway recommendations.