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At least 793 records · Page 44Linked to original sources
PubMed1989

[Biomechanical aspect of closing median diastema with a segmental arch].

Before orthodontic movement of the tooth it is necessary to analyze the anticipated system of forces. On an example of closing diastema between the upper central incisors with a segmental arch an analysis of the force and the moment which are manifested in the course of disactivation of apparatuses has been done. Prior to that biomechanical analysis enables planning and construction of a fixed orthodontic apparatuses so that the possibility of the unwanted movement of the teeth is avoided.

Dental Arch↗
PubMed2005

Expression of osteocalcin and Jun D in the early period during reactionary dentin formation after tooth preparation in rat molars.

We examined, in rats, the expression of osteocalcin and Jun D in the early stage of reactionary dentin formation after tooth preparation and the accompanying morphological changes. Reverse transcription/polymerase chain reaction analysis revealed strong expression of osteocalcin mRNA in pulp tissue at 2 and 3 days post-preparation compared with that in control teeth. Light microscopy demonstrated that, at the dentin-pulp interface, damaged odontoblasts were detached from the dentin matrix immediately after preparation, with neutrophils lining the dental surface after 1 day. After 2-3 days, differentiated odontoblasts appeared at the interface. Reactionary dentin with tubular structures was formed under the cavity after 10 days. Immunoelectron microscopy showed that trace amounts of osteocalcin were expressed in odontoblasts at 2 days post-preparation, and abundant osteocalcin was found in the highly developed Golgi apparatus and granules at 3 days post-preparation. Osteocalcin was also found on type I collagen fibrils in newly formed predentin. The existing dentinal tubules were filled with osteocalcin-coated type I collagen fibrils. We observed, by immunohistochemistry, that Jun D was temporally expressed in the nuclei of the odontoblasts at 1 and 2 days post-preparation. However, no Jun D was found in the dental pulp cells at any other time or in control teeth. Thus, osteocalcin expression is correlated with reactionary dentin formation, and Jun D is associated with osteocalcin expression in odontoblasts. Osteocalcin may also serve as an obturator of the dentinal tubules to protect dental pulp vitality against external irritants after preparation.

Animals↗
PubMed1993

[Evaluation of amalgam separators].

There is an increased awareness about environmental protection and reduction of toxic waste. This applies also to the dental profession. One of the main concerns in dentistry is the reduction of amalgam slurry, which contains mercury, being drained by dental plants. The largest pieces of amalgam are stopped by the coarse filter. For eliminating the amalgam silt out of the sewage, amalgam separators have been developed. This paper presents an evaluation of seven separators, mounted in a preclinic set-up. The average particle size of the amalgam waste was determined. The flow-velocity of the separators differed very much between the different separators. One apparatus produced an inferior separation capacity compared to the others. Apparently not one was capable to purify the effluent to 0.05 mg/l during peak supplies of amalgam slurry. Other measures such as the reduction of the need for restoring, the use of alternative materials and modified preparation techniques, will further reduce the drain of amalgam silt by dental installations.

Dental Alloys↗
PubMed1998

[The new-generation laser surgical apparatus Doktor in the combined treatment of stomatological disease in an outpatient setting].

Presents the design, technological characteristics (wavelength 10.6 mu cm, power up to 7 W, permanent mode) of a new-generation surgical laser Doktor and its use in the treatment of dental and maxillofacial diseases (diseases of the periodontium and buccal mucosa, pericoronitis, trophic ulcers, retention cysts, furuncles and carbuncles of the skin of the neck and face, odontogenic inflammatory processes, injuries, tumors) and in reconstructive, plastic, and cosmetologic surgery.

Combined Modality Therapy↗
PubMedDate not supplied

[Electromyography recording of the silent period in masseter muscles in persons with total dental prostheses with various vertical occlusal dimensions].

Silent period is reflex pause or period suppressed activity after some kind of simulation during or after muscular contraction. In dentistry electromyographically registered silent period has important place as method of functional diagnosis. The aim of this investigation was to establish duration of silent period in both masseter muscles of persons with complete dentures in normal increased and decreased occlusal vertical dimensions. Subjects of investigation were 4 men and 4 women, average of 65 years. Occlusal vertical dimensions were established electromyographically. For every subject tree sets of complete dentures were made: with normal, increased and decreased occlusal vertical dimension for 4 mm. Silent period was registered by "Medlec" Mystro-MS 20 apparatus with intramuscular leads. The differences of silent period duration were registered among all three vertical dimensions, especially between and increased occlusal vertical dimensions.

Aged↗
PubMed2001

Study of occlusal-articulation relationships with the help of T-SCAN apparatus.

UNLABELLED: Normal occlusal-articulation relationship between the two jaws ensure the even distribution of the occlusal forces during mastication. Data from the literature and the absence of serious studies evaluating the T-Scan apparatus give reasons for the present study. AIM: To evaluate T-SCAN apparatus for registration and analysis of occlusal contacts in dynamic articulation. MATERIALS AND METHODS: The study was carried out with the medical diagnostic apparatus T-SCAN. Out of 180 students (19-24 years old) examined, we selected 15 with intact dentitions without or with some small obturations and Angle class I relationship between the two jaws. Using T-SCAN we made 7 to 10 records in each of the studied students. RESULTS: The occlusal contacts are presented as two-dimensional and three-dimensional images of the contour with different size and colour depending on the force of the pressure. A model of the dental arch is superimposed over the registered occlusal contacts. The place of the centre of the force in central occlusion is determined. The trajectory of the centre of the force during movements of the mandible is recorded which allows determination of the direction and amplitude of movement of the mandible. CONCLUSION: The results from the study reveal that the correct use and analysis of the data from the apparatus T-SCAN provide valuable and reliable information for the localization and distribution of occlusal contacts in dynamic articulation.

Adult↗
PubMed1991

Odontoblast-like cytodifferentiation of human dental pulp cells in vitro in the presence of a calcium hydroxide-containing cement.

The cement produced microcrystals of calcite by reaction with culture medium supplemented with calf serum. Human dental pulp cells seeded on such a substrate preferentially adhered and aggregated around the microcrystals. Immunofluorescence and immunogold labelling revealed a high affinity of serum fibronectin molecules for the calcite crystals. At 4 weeks in culture, the cells had various features of differentiated odontoblasts, notably nuclear polarization, typical appearance of the Golgi apparatus, synthesis of type I collagen and absence of type III, and apical accumulation of actin and vimentin. These cells also elaborated a collagenous extracellular matrix which did not mineralize.

Adolescent↗
PubMed1988

Forced eruption combined with gingival fiberotomy. A technique for clinical crown lengthening.

A new approach to clinical crown lengthening has been developed and described. The technique combines controlled eruptive tooth movement and incision of the supracrestal gingival attachment. The procedure was performed in patients with severe destruction of a tooth crown and in whom clinical crown lengthening procedures were essential before the teeth could be properly restored. Controlled eruptive forces were activated by simple orthodontic appliances. During the active phase of forced eruption, repeated intrasulcular incisions through the junctional epithelium and the supracrestal connective tissue attachment were performed. The technique prevented coronal displacement of the gingiva and the attachment apparatus during the orthodontic extrusion, thus overcoming the need for corrective osseous surgery.

Adolescent↗
PubMed2004

Susceptibility of GTR-regenerated periodontal attachment to ligature-induced periodontitis.

AIM: This study aimed to compare the susceptibility of guided tissue regeneration (GTR)-regenerated periodontal attachment to ligature-induced periodontitis with that of the pristine periodontium. METHODS: Periodontal breakdown was produced in four monkeys by the placement of orthodontic elastics around experimental teeth (test teeth). During a flap operation, the root surfaces were scaled and planed, and a notch indicating the apical termination of scaling and root planing was made in the root surface. Following resection of the crowns and endodontic treatment, an e-PTFE membrane was adapted over the roots. Subsequently, the flaps were sutured to complete closure of the wound (submerged). At membrane removal after 5 weeks, the crowns of the contralateral teeth serving as controls were resected, and the roots treated endodontically during a flap operation. Artificial composite crowns were then placed on both test and control roots. After 3 months of tooth cleaning, cotton floss ligatures were placed passively around both test and control teeth for a period of 6 months. Two weeks later the animals were sacrificed. RESULTS: Histological analysis demonstrated that the instrumented root surfaces of the test teeth were covered by newly formed cementum of the reparative, cellular, extrinsic and intrinsic fiber type, while the cementum on the controls was mainly acellular extrinsic fiber cementum. Histometric assessments demonstrated that similar attachment loss had occurred on test (1.0+/-0.5 mm) and control roots (1.0+/-0.4 mm) during the 6 months of ligature-induced plaque accumulation. CONCLUSION: The results indicate that teeth with a periodontal attachment apparatus formed by GTR is not more susceptible to periodontitis than those with a pristine periodontium.

Animals↗
PubMed1989

Porous hydroxyapatite grafts in chronic subcrestal periodontal defects in rhesus monkeys: a histological investigation.

The purpose of this investigation was to evaluate the histologic response to replamineform (porous) hydroxyapatite grafts in chronically inflamed, surgically created, periodontal pockets in Rhesus monkeys. Forty-eight subcrestal defects were surgically created in 8 Rhesus monkeys. Orthodontic wires were adapted to the base of the defects and left in place for 8 weeks. The defects were randomly assigned a treatment modality so that 8 granular porous and 8 block porous hydroxyapatite grafts were done. Eight sites were left as unoperated controls. Twenty-four contralateral sham-operated sites were treated by open curettage. Histometric measurements of the length of regenerated connective tissue attachment were recorded. Block hydroxyapatite, granular hydroxyapatite, and sham-operated sites exhibited similar amounts of regenerated connective tissue attachment, which was significantly greater than that which occurred in unoperated controls. Newly formed bone was observed within the porous channels of the hydroxyapatite grafts as well as in direct apposition on the surface of implant particles. New bone, cementum, and periodontal ligament was observed in grafted sites and in defects treated by open curettage. In some instances healing occurred by means of a long junctional epithelium. Histology confirmed that unoperated defects remained as unhealed, inflamed periodontal pockets. The results of this study suggest that porous hydroxyapatite grafts have the potential to regenerate the attachment apparatus in primates.

Alveolar Process↗
PubMed1989

Keller method of TMJ orthodontics.

This article explains a specific orthodontic method which has been designed to treat TMJ dysfunction patients. The desired mandibular/maxillary relationship is established and maintained throughout treatment. The resultant occlusion will then support a functional condyle-disc-fossa relationship. Cases are presented which illustrate the patented method and apparatus. Both patients have remained pain and dysfunction free for three years and five years respectfully.

Adolescent↗
PubMed1998

Handpiece degradation associated with performance testing of diamond rotary cutting instruments.

Reliable standardized testing of dental rotary cutting instruments remains a problem because of the many significant parameters that require identifying and quantifying. In a previous study, handpiece wear or degradation was identified as a potentially significant confounding variable leading to the suggestion that the use of industrial handpieces might be necessary. Therefore, the objective of this investigation was to measure and compare industrial and dental air rotor degradation during a simulated diamond rotary cutting instrument test. Two dental and two industrial products were tested in a random sequence using three replicate samples of each air rotor. The simulated test consisted of 10 diamond instruments each making 90 passes through a float glass substrate. The testing apparatus comprised a computer-interfaced device that controlled the contact force between the cutting diamond and the substrate. Air rotor performance was based on the time required to cut a standardized path through the substrate. The performance change that occurred from diamond instrument to instrument during the simulated test was attributed to air rotor degradation. Multiple regression analyses showed significant differences between replicate samples of the same type and between regression intercepts for different air rotor types. Surprisingly, four air rotors exhibited improving performance during the simulated test. Changing air rotor performance must be considered to achieve reliability for the testing of diamond rotary cutting instruments.

Air↗
PubMed2003

Caries diagnosis using a laser fluorescence system--observation of autofluorescence of dental caries--.

The purpose of this study was to evaluate the usefulness of autofluorescence of carious lesions on caries diagnosis. The observation of the micromorophology of caries lesions was conducted using a confocal laser scanning microscope, a fluorescence microscope and a WDX type electron probe X-ray microanalyzer. Observation of autofluorescence under Cy5 and UV fields showed clearly specific images of autofluorescence in the carious lesion. However, observation of autofluorescence under FITC field showed images of autofluorescence with unclear boundaries in the carious lesion. EPMA images showed decreases in Ca and P in the carious areas. As a result of the observation of autofluorescence and the EPMA images in the carious lesion, a correlation was noted between autofluorescence under the Cy5 field as the laser fluorescence apparatus for caries diagnosis and demineralized areas. The usefulness of autofluorescence of carious lesion on caries diagnosis was suggested.

Dental Caries↗
PubMed1990

Shear bond strengths to dentin and fluoride release from fluoride-containing liners.

The purpose of this study was to determine the shear bond strengths of five commercially available fluoride-containing restorative systems to dentin and to evaluate the fluoride release from them. The five systems evaluated were: (A) Vitrabond/Silux; (B) Zionomer Powder Liquid/Perfection; (C) Zionomer Paste Paste/Perfection; (D) TimeLine/Prisma-Fil; and (E) GC Dental Cement/Fuji II. Eighteen test specimens were prepared on the dentin surfaces of extracted human permanent first and second molars ground on 600 grit SiC paper with each system. The bonded cylinders were removed from the assembly apparatus 15 minutes after cure, stored in physiological saline at 37 degrees C for 24 hours and subjected to a shear load at 0.5 mm/min. Five cylindrical specimens were prepared for each system, the discs were suspended in 25 microL glass distilled water and the fluoride release (microgram F/mm2) determined at daily intervals for 15 days and then after 30 and 90 days. The data were analyzed by a one-way analysis of variance and Duncan's multiple range test. The following shear bond strengths (Mean +/- SD) were recorded (MPa): A: 8.86 +/- 1.49; B: 4.24 +/- 1.23; C: 4.41 +/- 1.39; D: 3.85 +/- 1.60; E: 4.81 +/- 1.21. With all the systems, the fluoride release dropped sharply during the first 7 days and then remained constant. The shear bond strength and the fluoride release from Vitrabond/Silux were significantly greater than that of the other systems.

Acrylic Resins↗