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Results for “DENTAL APPARATUS”

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At least 541 records · Page 30Linked to original sources
PubMed1990

Formation of a periodontal ligament around titanium implants.

The aim of this study was to examine wound healing events around titanium implants in the presence of retained root tips whose periodontium could serve as a source for cells which could participate in the healing process. Hollow cylinder implants with a titanium plasma-sprayed surface were placed in the mandible of monkeys where the apical portions of previously removed teeth were retained. After a healing period of 12 months, free of functional loading, the implants with surrounding tissues were removed and specimens analyzed in undecalcified sections. This report describes histologic findings of six such implants. Microscopic analysis revealed that in regions where implants were close to retained roots, a periodontal ligament had formed around large portions of the implant. Furthermore, there was a distinct layer of cementum on the implant surface and a periodontal ligament with collagen fibers perpendicularly oriented to the implant surface, implanted into the cementum on the implant surface as well as to the opposing bone. This initial observation suggests that it may be possible to achieve an anchorage of certain dental implants with a periodontium simulating that found surrounding the normal tooth. Furthermore, these findings provide the basis for further studies on regeneration of all components of the periodontal attachment apparatus including cementum, periodontal ligament, and bone.

Animals↗
PubMed2001

Abortive secretion of an enamel matrix in the inner enamel epithelial cells during an enameloid formation in the gar-pike, Lepisosteus oculatus (Holostei, Actinopterygii).

The tooth in the gar-pike, Lepisosteus oculatus, an actinopterygian fish, is characterized by the occurrence of both enamel and enameloid, the former covering the tooth shaft and the latter, the tooth cap. Our previous research demonstrated that the enamel in this species was, as in the lungfish, immunoreactive for amelogenin, indicating its homologous nature with the mammalian tooth enamel, whereas the enameloid was completely immunonegative. The present study demonstrates that, during the early maturation stage of the enameloid formation, the inner enamel epithelial cells (IEECs) synthesize through a well-developed Golgi apparatus a fine-granular substance which is intensely immunoreactive for amelogenin. This substance was accumulated in a large saccule extended in a suprabasal zone of the cell; we were unable to find any morphological sign indicating a connection of the substance with the enameloid matrix. The abortive secretion of the enamel matrix-like substance in the IEEC during an enameloid formation was considered to be an instance of rudimental enamel formation. In the gar-pike, the synthesis of amelogenin in the IEEC has been demonstrated to occur independently from that of the enameloid matrix. The present findings demonstrate a prominent difference between the tooth enamel and enameloid.

Amelogenin↗
PubMed2004

A comprehensive system for washing, pre-disinfecting and sterilizing of dental and surgical instruments.

PURPOSE: The purpose of this study was to test and describe in detail a newly developed comprehensive system for washing, pre-disinfecting and sterilizing of dental and surgical instruments. MATERIALS AND METHODS: The system consists of a combined washing and steam-operated pre-disinfection apparatus and newly developed trays, in which assorted instruments can be washed and disinfected without handling individual instruments. The system was subjected to a large number of tests. RESULTS: The cleaning efficiency of blood-soiled instruments was found to be excellent. The disinfection of dental instruments contaminated with bacteria, yeast and non-enveloped virus showed decimal reduction factors that were equivalent to sterilization. The trays had optimal sealing qualities. Their steam permeability was perfect even after prolonged use in N-, S- and B-type autoclaves. However, long-term tests in a clinic revealed shortcomings with regard to insufficient drying of instruments in the wash/disinfection apparatus. Furthermore, the mechanical stability of the polysulfonate tray covers needs to be improved. Occasionally, after extended use, the fit of the filters in metal trays became inadequate, in particular when trays were sterilized for 18 min at 134 degrees C for a prolonged period of time. CONCLUSION: In spite of the above-mentioned shortcomings, the system shows great labor and cost-saving potential, allowing a new approach to instrument recirculation and workflow in the dental office.

Dental Instruments↗
PubMed1975

Continuous monitoring of pH and Eh in bacterial plaque grown on a tooth in an artificial mouth.

Apparatus which enables the simultaneous continuous monitoring of pH and Eh of bacterial dental plaque as it develops on a tooth surface in an artificial mouth is described. Details of the electrodes used, monitoring equipment, and culture conditions are given. Preliminary results are given showing the Eh and pH values of plaque produced in vitro to be in close agreement with readings reported for plaque in vivo. The effect of the incorporation of 1 per cent sucrose in the medium on these parameters is reported and a distinct inverse relationship between pH and Eh recorded.

Corynebacterium↗
PubMed2002

Mineralization patterns in elasmobranch fish.

This article reviews current findings on the organic matrix and the mineralization patterns in elasmobranchs, including an analysis of the role of the dental epithelial cells and the odontoblasts during odontogenesis. Our electron micrographs demonstrated that tubular vesicles limited by a unit membrane occupied the bulk of the elasmobranch enameloid matrix during the stage of enameloid matrix formation. It is likely that the tubular vesicles originated from the odontoblast processes. Two types of electron-dense fibrils, with cross-striations at intervals of approximately either 17 nm or 55 nm, respectively, were detected in the enameloid matrix. These data suggest that odontoblasts were strongly involved in enameloid matrix formation and in initial enameloid mineralization. Two types of odontoblasts, dark and light cells, were recognized during the stage of dentinogenesis. The light cells contained numerous mitochondria, intermediate filaments, and microtubules that extended their processes into the dentin. The dark cells possessed a well-developed Golgi apparatus and many cisternae in the rough endoplasmic reticulum, which suggests that the dark cells are involved in the formation of dentin. The inner dental epithelial (IDE) cells exhibited a well-developed Golgi apparatus, many mitochondria, cisternae of smooth endoplasmic reticulum, vesicles, vacuoles, and granules during the mineralization and maturation stages. During the stages of mineralization and early maturation, ACPase-positive granules were visible in the IDE cells and ALPase and Ca-ATPase activities were found at the lateral and proximal cell membrane of the IDE cells, suggesting that the IDE cells are involved in the removal of enameloid organic matrix and in the process of mineralization during later stages of enameloid formation. Our data indicate that elasmobranch enameloid is distinct from teleost enameloid, based on its organic content, on the mechanisms of its mineralization, and on the role of IDE cells concerning enameloid formation.

Animals↗
PubMed1984

Creep of conventional and microfilled dental composites.

The creep of microspecimens of two conventional and two microfilled composites was studied using a torsional creep apparatus. Small stresses below the materials' proportional limits were maintained for 3 h and recovery was monitored for 30 h. Creep curves were obtained at 21.5, 37, and 50 degrees C, and three torque levels. The composites exhibited linear viscoelastic behavior at low deformations. The magnitude of creep depended on the amount and type of resin in the composites. The materials did not recover their original shape after 30 h after the stress was removed. No transitions were observed in the temperature range employed. The shear moduli decreased with temperature and are in reasonable agreement with literature values obtained with other tests.

Acrylic Resins↗
PubMed2000

The oblique radiographic technique for bone height measurements on edentulous mandibles: a preclinical study and an introduction to the clinical use.

OBJECTIVE: The aim of this study was to quantify the effect of mandibular angulation, position, and shape of the edentulous mandible on the distortion of its image on lateral oblique radiographs in a preclinical study. Suggestions for the clinical use of this technique are made. STUDY DESIGN: Five edentulous dry mandibles were used, varying in size from small to wide and equipped with metal bars in and on top of the mandible. The mandibles were radiographed at 9 different positions by tilting the mandible around the intercondylar axis and by using the oblique projection technique in a cephalostat. RESULTS: The length of the images of the metal bars varied significantly when we tilted the mandibles from 20 degrees to -20 degrees. As a result of the effects of magnification and distortion, the image size varied from between 0.96% and 1.06% of the real size. Neither the size of the mandible nor the position of the bars was related to the degree of magnification. CONCLUSION: The oblique projection technique has limited geometric errors in depicting the edentulous mandible. For evaluative bone height measurements in patients with extremely resorbed mandibles treated with dental implants, it is a promising technique if the patient (specifically the mandible) can be positioned reproducibly in the apparatus.

Analysis of Variance↗
PubMed1977

Aspects of functional improvement after treatment of a pain dysfunction patient.

First results of an investigation of several aspects of the function of the chewing apparatus by means of optical-electric movement scanning, EMG and occlusal sound registration on one time base, are presented. Observations made on a patient with pain-dysfunction syndrome before and after treatment has been compared with observations made on a healthy subject. It has been suggested that the method used, may be of value for objective evaluation of functional improvement and analyses of several aspects of the physiology of the chewing apparatus.

Adult↗
PubMed1990

Effects on the periodontium following corticotomy-facilitated orthodontics. Case reports.

This report describes the corticotomy surgical technique used in conjunction with orthodontic therapy and its effect on the periodontal status of the involved teeth. The surgical procedure included intracrevicular incisions and elevation of buccal and lingual mucoperiosteal flaps. Buccal and lingual vertical grooves penetrating the cortical bone were then made between the roots. These grooves were extended from just below the interproximal alveolar bone margin to beyond the apex levels of the teeth. Buccal and lingual horizontal grooves joined the apical extensions of the vertical grooves. The orthodontic appliance was activated immediately upon wound closure. Plaque scores, probing depths, and probing attachment levels were recorded before the surgical procedure and after the completion of the orthodontic treatment in 5 patients. The results showed that the corticotomy procedure caused minimal changes in the periodontal attachment apparatus.

Adult↗