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At least 343 records · Page 19Linked to original sources
PubMed1979

Porous titanium endosseous dental implants in Rhesus monkeys: microradiography and histological evaluation.

Artificial tooth roots with porous surface coatings were fabricated by sintering spherical powder of titanium alloy to solid cylindrical cores. The tooth roots were implanted subgingivally in healed mandibular premolar extraction sites of fifteen Rhesus monkeys. Supracrestal abutments were screwed into pretapped holes in the superior aspect of the primary subgingival stage four to eight weeks after implantation of the root. Clinical evaluations were performed monthly. Ten animals were sacrificed for histological evaluation of the functioning free standing implants. Of twenty-nine implants placed, three were lost and four were rated failures on the basis of histological evaluation. Postmortem evaluations revealed bone growth into the porous surface coating of the primary stage of all the implants. The most characteristic features which could be used to describe differences in the implant histology were the buccal and lingual crestal bone heights measured in relation to the root porosity. Twelve of sixteen implants had crestal bone heights within one millimeter of the superior aspect of the root. Four other implants displayed excessive bone recession, revealing as much as one half of the root porosity supracrestally. The four implant failures could be related to unfavorable features of recipient bone sites. The results demonstrate that the bone growth into the porous surface coatings of artificial tooth roots is an efficacious method of dental implant fixation.

Alloys↗
PubMed1990

Humoral immune response to active root resorption with a murine model.

A depression in autoantibody titers to tooth root antigens has been shown to coincide with active root resorption in the dog. Since a murine model would facilitate immunologic studies of root resorption because of the availability of syngeneic and immunodeficient strains, the objectives of this study were to develop a quantitative mouse model for root resorption and to determine if a similar drop in tooth root autoantibodies coincides with active root resorption in this species. Uniform areas of necrosis were created in the periodontal ligaments of lower incisors of 36 male Swiss albino mice by inserting a cryoprobe through a skin incision (-80 degrees C; 5 minutes). Contralateral incisors served as controls. At 0, 3, 5, 7, 10, 14, and 21 days; six mice were killed, and blood and incisors were collected. Relative surface areas of root resorption were quantified with micrographs taken at a standardized position, tilt, and magnification with a scanning electron microscope. Serum autoantibody titers were determined with an enzyme-linked immune sorbent assay with antigen prepared from a 5 mol/L guanidine-HCl-EDTA (pH 5.0) extract of incisor roots that were harvested from syngeneic mice. ANOVA and the paired Student t test were used to compare data at the various time points. No root resorption was evident on control teeth. Localized lesions on treated teeth were found to be of significant size between 7 and 14 days (p less than 0.05), but most of these erupted into the mouth by 21 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Actinomycosis associated with a root-treated tooth: report of a case.

An unusual case of a persistent infection related to a root-filled tooth is reported. Microscopical evaluation revealed the cause to be a large mass of Actinomyces-like filaments, and microbiological culture yielded a low level of Actinomyces israelii. The significance of such a presentation is discussed.

Actinomycosis↗
PubMed2002

[Analysis the stress variations of the root canal wall of pulpless tooth by different root canal preparation with finite-element method].

OBJECTIVE: To analyze the stress variations of the root canal wall of pulpless tooth by different root canal preparations. METHODS: On the basis of the set up model of the mandibular first molar, modified model was established by simulation of the routine or step-back root canal preparation and filling in. Then the maximum mises stress of each part of teeth and wall of root canal were calculated by special finite-element software. RESULTS: The stress-changing tendency is similar between two modified models but the maximum mises stress of the model by step-back technique is a little greater than one by routine. The stress of wall of mesial-buccal root canal was the greatest and one of mesial-lingual root canal was the least at three root canals. The stress-changing tendency of modified models was similar to original model. The maximum mises stress of modified models was near or less than one of original model except that of amalgam layer because of material property alteration. CONCLUSION: Not only routine but step-back technique is an effective and safe method. Dentist can choose them in practice.

English Abstract↗
PubMed1994

[Morphological and functional properties of odontoclasts on dentine resorption].

Tooth root resorption in tooth movement is the principal unsolved problem in orthodontics. In order to study this mechanism, odontoclasts in bovine deciduous tooth root-resorbing tissues (RRT) were cultured and characterized for their biological properties in comparison with those of osteoclasts. Multinucleated cells isolated from the RRT had tartrate-resistant acid phosphatase activity and responded to calcitonin and also formed the resorption lacunae on the dentine. These results are consistent with the notion that odontoclasts resemble osteoclasts with respect to enzyme-cytochemical and morphological properties. However, odontoclasts cultured on dentine in the presence of 1 alpha,25-dihydroxyvitamin D3 demonstrated a higher activity in forming resorption lacunae than did osteoclasts. Immunohistochemical examinations revealed that interleukin-1 (IL-1) was detected in mononuclear cells and occasionally in odontoclasts that were present adjacent to the site where active root resorption occurred. The IL-1 stimulated the formation of resorption lacunae on dentine to a higher extent in odontoclasts than in osteoclasts, suggesting functional differences between odontoclasts and osteoclasts. In conclusion, the present study demonstrates that 1) odontoclasts present in the RRT possess similar biological properties to those of osteoclasts. However, under certain circumstances odontoclasts may behave differently from osteoclasts; 2) IL-1 produced in the RRT might play a role in controlling the function of odontoclasts in a paracrine and autocrine fashion.

Animals↗
PubMed1981

Does an impacted tooth cause root resorption of the adjacent one?

External root resorption caused by an adjacent impacted tooth was studied radiographically in 199 cases. Resorption of the root had occurred in fifteen instances (7.5 per cent), the cervical region being least affected. The incidence was highest in the 21 to 30-year-old group and mainly involved male patients. Resorption of the periodontium alone was found in sixteen additional patients; of these, five were followed for 1 year after extraction of the impacted tooth. During this period, the damaged periodontium was completely re-established.

Adolescent↗
PubMed1991

Preventive implantations.

Preventive implantology is concerned with the preservation of the alveolar ridge of the (edentulous) jaw. Maintaining the volume of the alveolar ridge is a major problem in the prevention of oral disease. Loss of teeth and tooth roots leads to resorption of residual ridges. This being so, it is a logical approach to substitute artificial analogues for lost tooth roots. Hydroxyapatite implants have been studied as submerged tooth root substitutes and shown to maintain the bulk of the alveolar ridge. A drawback of the implants is that the ridge maintenance depends solely on the physical presence of the hydroxyapatite implants. No physiological influence on bone preservation can be attributed to the implants. However, long term research indicates that 75 per cent of the implants survive under full lower dentures and 100 per cent of the implants under fixed partial dentures.

Alveolar Process↗
PubMed1977

[Animal model for the etiopathogenesis of sialadenitis].

A longitudinal study with patient-specific jaw models and simultaneous X-Rays was undertaken to examine the eruption behaviour of the mandibular premolars following physiological and pathological resorption of the roots of primary teeth. 1. The molars of the first dentition fall out earlier after pathological resorption of the roots of primary teeth. In the presence of an occlusal bony bridge the appearance of a new tooth may take years. The eruption of the replacing tooth is delayed or it may be retained. 2. The eruption times of premolars after physiological resorption of primary tooth roots given in the literature and those obtained by the author converge. After pathological resorption of primary tooth roots and rarefying osteitis with interruption of the lamina dura, vertical development occurs significantly sooner (p less than 0,01). 3. The sequence of eruption of the premolars can be altered after pathological resorption of primary tooth roots.

Animals↗
PubMed2005

Restoration of the root-filled tooth: pre-operative assessment.

This is the first in a series of four papers related to the management of root canal treated teeth. When teeth compromised by extensive restorations become non-vital, suggestions have been given as to how root canal treatment can be carried out with the greatest chance of success. Once root canal treated, either by a previous dentist or by the current dentist, a review of the assessment process that should be carried out prior to placing costly indirect definitive restorations is given. It will be clear that post-retained restorations are mainly reserved for anterior or single-rooted teeth, posterior teeth rarely requiring a post for core retention. The second paper in this series describes the basic tooth preparation that should be carried out prior to placing a post. Depending on the type of post system used, further modifications to tooth preparation may be required and the cementation techniques may also have to be modified. The third paper therefore discusses the various post types, when and how they should be used for optimum results. The final paper addresses reinforcement and restoration of compromised root canals, such as those with immature, open apices, or those that have been over-prepared for previous post-retained restorations.

Dental Restoration, Permanent↗
PubMed1999

Surgical extrusion of a cervically root-fractured tooth after apexification treatment.

A case is reported in which an incisor fractured below the alveolar crest 6 months after completion of apexification treatment was surgically extruded for prosthetic coronal restoration. After the surgical procedure, a dowel post was placed in the root canal, a core was built using glass-ionomer cement, and a porcelain veneer crown restoration was completed. The 24-month follow-up examination after surgical, endodontic, and prosthetic treatments showed that the tooth was clinically and radiographically healthy and functioned well.

Child↗
PubMed1995

[The radiological-histological interpretation of artificial bone defects of the basal maxillary sinus cortical bone].

Twenty-one lateral maxilla specimens were taken from human autopsy specimens and after removing soft tissue 40 differing tooth roots of 23 molars and premolars were ground to create large artificial bone defects in the supporting cortical bone of the basal maxillary sinus. Conventional dental radiographs and axial CT scans were then compared with the macroscopic findings in relation to the identification of the artificial bone defects. Next the jaw segments were dissected analogous to the axial CT scan and corresponding histological microsections were prepared for a radiological-histological comparison. None of the artificial bone defects were identifiable on the dental radiographs. In comparison to this, however, cortical bone defects were identifiable on 25 tooth roots (62.5%) on the CT scans. The lateral demarcation of the antral defects on the CT scans depends on the setting of the tooth root, on the adjacent bone morphology, and on the visualization of the periodontal ligament space. If the periodontal space shows up on the CT images, it becomes possible to demarcate of a thin, 0.2 to 0.5 mm, cortical bone layer of the basal maxillary sinus.

Bicuspid↗
PubMed1997

Effects of collagenase on root demineralization.

The role of proteolytic enzymes in the root caries process remains unclear. The aim of this study was to investigate collagenase activity during tooth root demineralization and remineralization in an in vitro demineralization/remineralization pH-cycling model, Human tooth roots were subjected to pH cycling (alternating demineralization and remineralization) in one of two different time cycles for five days. Collagenase at 90, 180, or 360 micrograms per root was placed into either the demineralizing solution or the remineralizing solution in the pH-cycling system. The effects of additional exposure to collagenase before or after pH cycling were also studied. After the exposure, thin sections of the roots were examined histologically by polarized light microscopy. Changes of calcium and phosphate in the solutions were analyzed chemically. Surface erosion occurred only in the groups where collagenase was contained in the remineralizing solution and in which the root samples were exposed to severe demineralization. However, no differences among the control and experimental groups were found in calcium and phosphate changes in the pH-cycling solutions. These findings suggest that collagenase works during the remineralizing phase and predominantly attacks the organic matrix of the root after demineralization. Additional exposure to collagenase before or after pH cycling did not increase surface erosion except for exposure to collagenase in the absence of phosphate following pH cycling.

Calcium↗
PubMed1989

Distribution of mesencephalic nucleus and trigeminal ganglion mechanoreceptors in the periodontal ligament of the cat.

1. In anaesthetized cats recordings have been made in the mesencephalic nucleus of the fifth cranial nerve and the trigeminal ganglion from neurones that respond when forces are applied to the mandibular canine tooth. The site of the mechanoreceptors in the periodontal ligament and their distribution around the tooth root have been determined. 2. Receptors with their cell bodies in the mesencephalic nucleus were found to be situated in the periodontal ligament in a discrete area intermediate between the fulcrum and apex of the tooth, while those in the trigeminal ganglion were situated in the whole area of the periodontal ligament between the fulcrum and apex of the tooth. 3. All of the located mechanoreceptors responded maximally when that part of the ligament in which they lay was put under tension. 4. The directional sensitivities of the mechanoreceptors suggested that there was an uneven distribution around the tooth root of receptors with cell bodies in the mesencephalic nucleus. In contrast mechanoreceptors with cell bodies in the trigeminal ganglion were distributed more equally around the tooth root. The rationale for the differences requires further investigation.

Action Potentials↗
PubMed1994

Tooth and root conditions in the middle-aged and the elderly in Hong Kong.

In an oral health survey of Hong Kong Chinese conducted in 1991, a sample of 372 35-44-yr-olds and 537 noninstitutionalized 65-74-yr-olds were interviewed and clinically examined. The examination procedures, instruments, and diagnostic criteria used to detect coronal caries followed those recommended by the World Health Organization (1987). The diagnostic criteria used to assess root-surface caries were based on those used in a national oral health survey of US employed adults (National Institute of Dental Research, 1987). Calibration of examiners was conducted before the survey and the interexaminer reliability was found to be very high; the kappa statistics were 0.93 and 0.91 for the younger and older age groups, respectively. None of the 35-44-yr-olds were edentulous and 96% had 21 teeth or more. The prevalence of edentulousness among the elderly was 12%. The DMFT indices of the younger and older age groups were 8.7 and 18.9, respectively. In both age groups, MT was the major component of the DMFT index, and female subjects had a slightly higher score. The prevalences of decayed/filled roots were 7% and 26% for the 35-44- and 65-74-yr-olds, respectively. As compared with previous surveys conducted in Hong Kong, there has been a 40% reduction in the DMFT index of the 35-44-yr-olds since 1968, but little change in the tooth and root conditions was noted between 1984 and 1991.

Adult↗