Accuracy of orthodontic force and tooth movement measurements

The cytokine Eta-1/osteopontin is secreted by activated macrophages and may constitute the most abundant molecule secreted by activated T-lymphocytes. It causes macrophages to migrate and suppress production of reactive oxygen species. It enhances generation of immunoglobulins or proliferation of B-lymphocytes. Its biochemical characteristics suggest that Eta-1/osteopontin may be the T-lymphocyte suppressor factor. The apparently conflicting effects on individual immune functions may reflect homeostatic mechanisms.     

Immunocompetent cells in rat periodontal ligament and their recruitment incident to experimental orthodontic tooth movement

Individuals with HIV disease face ongoing and phasic challenges that may generate psychological stress or clinically significant distress. Such distress may in part be understood as a response to challenges to fundamental personal conceptions of self and world. The authors describe models generated from social cognition research and the stress response literature and then apply them to common psychological themes that are salient for persons with HIV disease. Implications for psychotherapeutic assessment and intervention are discussed, and a case report is presented to illustrate the use of this approach with HIV and AIDS patients.     

Esthetics and vertical tooth position: orthodontic possibilities

Throughout the 1990s, esthetic dentistry has become a prominent part of the treatment protocol of most dentists. Patients have become more conscious of the benefits of a beautiful smile and are willing to invest time and money to improve the appearance of their teeth. Many of these patients can be treated with routine restorative procedures (crowns, composites, laminates) to achieve the desired results. However, some patients have problems with tooth position that create significant discrepancies in gingival levels which can compromise the esthetic result of restorative dentistry. Prerestorative orthodontic therapy can often resolve these tooth position problems and enhance the esthetic restoration. This article describes the indication, methods, and results achieved when orthodontics preceded restorative dentistry in the treatment of various esthetic challenges.     

A review of orthodontic appliance problems in general dental practice

Data from the literature, as well as our previous work, indicate a protective effect of superoxide dismutase (SOD) in topical application against UV-induced cutaneous damage. In the present article we show that pre-treatment of the skin with SOD protects against PUVA-induced inflammatory reactions not only in murine, but also in human skin. Using fluorescently labelled Cu,Zn SOD, epifluorescence microscopy and digital image processing, we demonstrate that the FITC fluorescence localizes in the stratum corneum and upper granulosa, as well as in the epidermal cell layer surrounding the lumina of the hair follicles. These findings were similar for murine and human skin. Since autofluorescence was eliminated by a special filter, it can be ascertained that the fluorescence observed in the tissues was due to FITC-labelled SOD.     

Lay attitudes to dental appearance and need for orthodontic treatment

BACKGROUND AND PURPOSE: To compare dose values specified at the reference point, as recommended by the International Commission on Radiation Units and Measurements, ICRU, and the mean dose to the planning target volume, PTV. MATERIAL AND METHODS: CT-based dose calculations were performed with a 3-D treatment planning system for 6 series of patients treated for bladder, brain, breast, lung, oropharynx and parotid gland tumour. All patients were arbitrarily chosen from a set of previously treated patients irradiated with a two- or three-field technique using customised blocks. Appropriate wedge angles and beam weights were chosen to make the dose distribution as homogeneous as possible. RESULTS: The dose at the ICRU reference point was generally higher than the mean dose to the PTV. The difference between the ICRU reference dose and the mean dose to the PTV for an individual patient was less than 3% in 88% of cases and less than 2% in 72% of the cases. The differences were larger in those patients where the dose distribution is significantly influenced by the presence of lungs or air gaps. For each series of patients the mean difference between the ICRU reference dose and the mean dose to the PTV was calculated. The difference between these two values never exceeded 2%. Because not all planning systems are able to calculate the mean dose to the PTV, the concept of the mean central dose, the mean of the dose values at the centre of the PTV in each CT slice, has been introduced. The mean central dose was also calculated for the same patients and was closer to the mean dose to the PTV than the ICRU reference dose. CONCLUSION: The mean dose to the PTV is well estimated by either the ICRU reference dose or the mean central dose for a variety of treatment techniques for common types of cancer.     

The validation of an orthodontic expert system rule-base for fixed appliance treatment planning

A peer review clinical trial was undertaken to assess the appropriateness of the advice produced by an expert system designed to plan orthodontic treatment in which the pre-adjusted bracket appliance was to be used. The results showed that the expert system's treatment plans were as reliable as those produced by a group of orthodontists. Two members of the panel actually ranked the expert system's plans more highly than their own.     

Profile changes following orthodontic correction of bimaxillary protrusion with a preadjusted edgewise appliance

This study aimed to determine the changes in soft tissue and skeletal profiles following orthodontic correction of bimaxillary protrusion in 50 Chinese adult patients. Treatment involved extractions of four premolars and use of the preadjusted edgewise appliance. The average treatment time was 2.2 years. Cephalometric analysis was carried out on pretreatment and posttreatment cephalograms. The result of treatment was a more harmonious soft tissue profile; with a less acute nasolabial angle (following a 10.55-degree change), 2.75- and 2.09-mm reductions in upper and lower lip protrusions, respectively, and a 3.41-mm decrease in interlabial gap. Effects on dental relationships included a 0.90-mm reduction in incisal show, a reduction of overbite, and an improvement in the inclination of maxillary and mandibular incisors. Therefore, orthodontic correction of bimaxillary protrusion achieved favorable soft tissue changes without causing undesirable effects on the underlying hard tissues.     

Long-term development in the mandible and incisor crowding with and without an orthodontic stabilising appliance

Dimensional alteration of hepatic microvessels was demonstrated during reperfusion after normothermic hepatic ischemia. Using a specially designed cover glass, it was possible to relocate selected sites of observation and microvessels repeatedly throughout the whole reperfusion time. Twenty minutes of hepatic ischemia resulted in a decrease of sinusoidal diameter (mean +/- SEM; 10.0 +/- 0.3 microns at baseline, 8.2 +/- 0.2 microns after ischemia) and diameter of postsinusoidal venules (26.4 +/- 1.2 at baseline, 23.0 +/- 1.0 after ischemia). In the control group (no ischemia induced) no changes of these parameters were observed. Thus, the reduction of hepatic microvascular cross section was present during the early phase of reperfusion. Hepatic dysfunction was characterized by increased serum activity of liver enzymes and reduction of bile flow in the ischemia-exposed animals. It has been suggested that postischemic dimensional microvascular changes are involved in postischemic liver dysfunction.     

Stability of occlusion after orthodontic treatment with tooth extraction in adult cases

The purpose of this study was to evaluate stability of occlusion in adult cases at least 4 years after orthodontic treatment and to clarify parameters influencing this stability. The subjects were 25 cases (mean age: 19 y 8 m) who had been treated with Edgewise technique involving first-premolar extraction. During orthodontic treatment, decreases in the maxillary and mandibular incisors' irregularity index (Max.I.I. and Mand.I.I.), posterior movement of the upper and lower incisors, increases in upper incisal height, decreases in lower incisal height, and increases in upper and lower canine width were noted. In the posttreatment period, increases in Max.I.I. and Mand.I.I., anterior movement of incisors, increases in incisal height, and decreases in canine width were observed. The amounts of overjet and overbite decreased during the treatment period and increased during the post-treatment period. Multiple regression analysis was useful to deduce which parameters influenced stability of occlusion after orthodontic treatment.     

Expression of Fos in the rat forebrain following experimental tooth movement

Orthodontic tooth movement is known to cause pain and discomfort to patients. Mechanically induced inflammatory responses in the periodontium are assumed to be related to the mechanism of pain sensation. An immediate-early gene, c-fos, that is expressed within some neurons following synaptic activation, is widely used as a marker for neuronal activity following noxious or innocuous stimulation. We have recently demonstrated that experimental tooth movement produced Fos induction in the ipsilateral trigeminal subnucleus caudalis and in the bilateral lateral parabrachial nucleus, which is known to be involved in the transmission of nociceptive information. As a further step, we investigated the distribution of Fos-like immunoreactive neurons in the upper brain regions. Twenty-four hours after the commencement of the experimental tooth movement, the Fos-like immunoreactive neurons appeared in the central nucleus of the amygdala (Ce), paraventricular nucleus of the hypothalamus (PVH), and paraventricular nucleus of the thalamus (PV) of the experimental rats. The numbers of the labeled neurons were significantly increased by 639% (P < 0.001) and 644% (P < 0.001) in the ipsilateral and contralateral sides of the Ce, respectively, by 292% (P < 0.001) and 307% (P < 0.001) in the ipsilateral and contralateral sides of the PVH, and by 264% (P < 0.0001) in the PV with respect to sham control rats. These results suggest that nociceptive information caused by experimental tooth movement might be transmitted and modulated in several regions of the forebrain.     

A disclusion appliance to eliminate occlusally generated TMD symptoms prior to, and during, fixed orthodontic therapy

Temporomandibular disorders are of multifactorial origin. If it is determined that the patient's occlusal scheme is a contributing factor to his/her TMD symptoms, it is accepted that reversible, noninvasive procedures be instituted at the outset of treatment. Splint therapy conforms to this guideline and serves to provide temporary, reversible alteration of the occlusal scheme in order to provide this relief. In a mutually protected occlusion, the posterior teeth accept the occlusal force of closure, while the anterior teeth serve to separate the dentition during excursive movements. The purpose of the disclusion splint described in this article is to eliminate muscle hypertonicity, along with its ensuing problems, by establishing a mutually protected occlusion via the guide planes created by the acrylic portions of the splint. Simultaneously, it does not compromise the patient's freeway space but acts as a preorthodontic, adjunctive-orthodontic, or post-TMD "stabilization-retentive" appliance because of its inherent ability to promote disarticulation of occluding dental surfaces during function.     

Comparison of Roth appliance and standard edgewise appliance treatment results

The effect of the betamethasone sodium phosphate (BSP) enema on the colonic mucosal lesions in the carrageenan induced colitis (rabbit) was examined laboratory and histologically. The effect of drugs were evaluated by the changes of body weight, fecal occult blood, blood analysis, and histological examinations. Fecal occult blood were highly positive in the physiological saline treated but less positive in the BSP groups. In the blood analysis, anemia was not detected in both groups. Histological findings such as the defect of superficial epithelium, crypt abscess, inflammatory cell infiltration, atrophic changes, defect of muscularis mucosae, goblet cell depletion, goblet cell depletion, ulcer formation, and edematous change were scored to evaluate the colonic mucosal lesions. These scores (Mean +/- S.D.) were 4.4 +/- 1.96, 7.7 +/- 3.67 for BSP, physiological saline groups respectively. From these results, BSP enema showed an antiulcerative effect on the entire colonic lesions in the carrageenan induced colitis in the rabbit.     

Localization of uncalcified cementum in adult rat molar roots and its relation to physiological tooth movement

The study was designed to elucidate the effect of physiological tooth movement on cellular cementum, using the upper molar roots of 10-week-old rats. Paraffin sections stained with haematoxylin and eosin displayed two types of cellular cementum, lightly and darkly staining. The lightly stained was present on the distal half of all molar roots except the mesial root of the first molar. The alveolar bone facing the lightly stained cementum showed resorption lacunae and multinucleated osteoclasts, while the opposite bone surface was lined with osteoblasts. In contact microradiographs of undemineralized ground sections, the X-ray density of the lightly stained cementum was similar to that of the periodontal ligament and pulp, while the X-ray density of the darkly stained cementum was similar to that of alveolar bone. Tetracycline labelling lines were seen at the interface between the two types of cellular cementum as well as on surfaces of bone and cementum located mesially to the root dentine. The results suggest that the mechanical stress of tooth movement differently affects the alveolar bone and cellular cementum; the bone is resorbed whereas the cementum resists resorption and its calcification is inhibited under the compressive force of tooth movement.     

线位移测量装置在埋弧炉电极控制中的应用

详细介绍线位移测量装置的设计思想和实现方法,分析了在埋弧炉冶炼过程中线位移测量与电量测量同的时序关系,并讨论了该装置在生产过程中的指导作用,最后,强调指出电信号测量与工艺参数在埋弧炉控制中互相结合的重要性与必要性。     

Human vestibuloocular reflex and its interactions with vision and fixation distance during linear and angular head movement

Human vestibuloocular reflex and its interactions with vision and fixation distance during linear and angular head movement. J. Neurophysiol. 80: 2391-2404, 1998. The vestibuloocular reflex (VOR) maintains visual image stability by generating eye movements that compensate for both angular (AVOR) and linear (LVOR) head movements, typically in concert with visual following mechanisms. The VORs are generally modulated by the "context" in which head movements are made. Three contextual influences on VOR performance were studied during passive head translations and rotations over a range of frequencies (0.5-4 Hz) that emphasized shifting dynamics in the VORs and visual following, primarily smooth pursuit. First, the dynamic characteristics of head movements themselves ("stimulus context") influence the VORs. Both the AVOR and LVOR operate with high-pass characteristics relative to a head velocity input, although the cutoff frequency of the AVOR (<0.1 Hz) is far below that of the LVOR ( approximately 1 Hz), and both perform well at high frequencies that exceed, but complement, the capabilities of smooth pursuit. Second, the LVOR and AVOR are modulated by fixation distance, implemented with a signal related to binocular vergence angle ("fixation context"). The effect was quantified by analyzing the response during each trial as a linear relationship between LVOR sensitivity (in deg/cm), or AVOR gain, and vergence (in m-1) to yield a slope (vergence influence) and an intercept (response at 0 vergence). Fixation distance (vergence) was modulated by presenting targets at different distances. The response slope rises with increasing frequency, but much more so for the LVOR than the AVOR, and reflects a positive relationship for all but the lowest stimulus frequencies in the AVOR. A third influence is the context of real and imagined targets on the VORs ("visual context"). This was studied in two ways-when targets were either earth-fixed to allow visual enhancement of the VOR or head-fixed to permit visual suppression. The VORs were assessed by extinguishing targets for brief periods while subjects continued to "fixate" them in darkness. The influences of real and imagined targets were most robust at lower frequencies, declining as stimulus frequency increased. The effects were nearly gone at 4 Hz. These properties were equivalent for the LVOR and AVOR and imply that the influences of real and imagined targets on the VORs generally follow low-pass and pursuit-like dynamics. The influence of imagined targets accounts for roughly one-third of the influence of real targets on the VORs at 0.5 Hz.