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Stress analysis of endodontically treated anterior teeth restored with different types of post material.

Finite element analysis was performed to evaluate stress distribution in maxillary central incisors treated endodontically and restored with a post and an all-ceramic crown. Tensile stress at tooth root was analyzed using two-dimensional finite element models with different post diameters and lengths. One post length was 1/3 of the root (short), while the other was 2/3 of the root (long); one post diameter was 1/3 of the root (narrow), while the other was 2/3 of the root (wide). The following combinations were used for posts and cores: gold alloy cast post and core, commercial stainless steel post and resin core, and fiber post and resin core. Results showed that the fiber post produced less stress on the root dentin around the post tip than did the metal posts. This finding thus suggested that to reduce the stresses that cause root fracture, a long, thin fiber post should be used.

Dental Stress Analysis↗

Immunohistochemical localization of receptor activator of nuclear factor kappaB (RANK) and its ligand (RANKL) in human deciduous teeth.

Osteoblasts and osteoclasts are involved in bone formation and resorption. RANK and RANKL [receptor activator of nuclear factor kappaB (ligand)], two cytokine-like proteins of the tumor necrosis factor superfamily, are localized on these bone cells and are crucial for the regulation of osteoclastic cell differentiation from hematopoietic precursors and also for the upregulation of mature osteoclasts mediated by cell-to-cell contact and a subsequent cascade of diverse intracellular signaling processes in the osteoclasts. It was the aim of this study to examine the sites of expression of RANKL and RANK in the corresponding cells of human dental hard and periodontal tissues using immunohistochemical light microscopical methods on tissue sections of 15 paraffin-embedded human deciduous teeth undergoing root resorption. We detected granular cytoplasmic RANKL-immunoreactivity in odontoblasts, pulp fibroblasts, periodontal ligament fibroblasts, and in single odontoclasts, the latter finding suggesting an autocrine/paracrine role. RANK-positive cells were identified as multinucleated odontoclasts localized near the dentine surface in resorption lacunae or as mononucleated precursors. These findings indicate that human dental cells express key mediators of hard tissue resorption and, though the RANK/RANKL-system may not be the sole regulator of tooth root resorption, these factors could at least contribute to this complex process under both physiological and pathological conditions.

Adsorption↗

Clinical evaluation of two adhesive composite cements for the suppression of dentinal cold sensitivity.

STATEMENT OF PROBLEMS: Postoperative cold sensitivity after the cementation of indirect restorations with composite cements has been reported frequently but not scientifically documented. PURPOSE: This controlled clinical study was designed to simulate the dentin/composite cement interface immediately after cementation of a cast restoration. The desensitizing capabilities of a composite cement that contains a self-etching, dual-polymerizing resin adhesive system were compared with those of a composite cement that use phosphoric acid etching followed by a single-bottle, light-activated primer/resin-based adhesive. MATERIAL AND METHODS: The hypersensitive root surfaces of selected teeth were randomized to receive 1 of 3 treatments: coating with a self-etching adhesive (Linkmax) and its respective cement, coating with a conventionally etched adhesive (RelyX ARC) and its cement, or no treatment (negative control). The sample size was 22. Dentin sensitivity was ascertained with an accurate cold testing device that slowly decreased in temperature. Tooth sensitivity was measured both immediately and at 7 days after placement. Two-way analysis of variance and Fisher's least significant difference test (P<.05) were used to determine whether significant differences existed as a function of treatment type or time. RESULTS: Immediately after placement, the self-etching adhesive and its respective cement resulted in more suppression of cold sensitivity than no treatment (control); with Linkmax treatment, the temperature at which teeth responded was reduced by 8.4 degrees C. The conventionally etched adhesive and its cement reduced the temperature at which teeth responded by 9.4 degrees C. After 1 week, these temperature reductions were 7.0 degrees C and 4.3 degrees C, respectively. Untreated controls at the 2 intervals showed a mean decrease in sensitivity to cold of 3.6 degrees C and 4.1 degrees C. Statistical analysis showed type of composite cement to be a significant factor. CONCLUSION: Within the limitations of this study and in comparison to untreated control teeth, Linkmax treatment resulted in a significant reduction in tooth root sensitivity over 1 week (P=.02), whereas RelyX ARC did not (P=.066).

Acid Etching, Dental↗

Photoelastic stress analysis of natural teeth and three osseointegrated implant designs.

This study used photoelastic stress analysis to compare the location and magnitude of periradicular stresses created by load application directed through two anatomically different natural teeth and three different implant designs. Also studied was the contribution made by the periodontal ligament in the transfer of these stresses. Within the limits of this study, results suggest that the abutment structures with the greatest amount of periodontal support tend to distribute stresses in the most favorable manner. Also, the conical shape of the tooth root, with its large cervical area, has a distinctly positive effect on stress distribution.

Birefringence↗

Barriers to diffusion of Ledermix paste in radicular dentine.

Freshly extracted human single-rooted teeth with a single root canal were used to study the effects of 2 irrigation regimens and the effect of cementum on the diffusion of corticosteroid and antibiotic tracer molecules from Ledermix paste placed in the pulp space. An irrigation regime that combined the use of 15% EDTAC and 1% NaOCl resulted in a significant increase in the permeation of the trace molecules through dentine compared with teeth that were irrigated with Savlon solution. Mechanical removal of the cementum also resulted in a significant increase in the permeation of the trace molecules. This study demonstrated that neither the smear layer nor the cementum were complete barriers to diffusion. The data obtained appeared to be of clinical relevance and provided further understanding of the dynamics of drugs in tooth roots.

Adult↗

3D tooth shape from radiographs using thin-plate splines.

Current methods to produce 3-dimensional tooth root models involve conversion from radiographic means (computed tomography) or creation using computer-assisted design (CAD) software. The former lacks detail while the second is manually fabricated and can bear little resemblance to the original. Thin-plate splines have been used in morphometrics to define changes of shape between subjects of the same species. Herein, we use thin-plate splines to deform a 3D geometric prior model of a tooth to match 2D patient radiographs, producing a "best-fit" patient specific 3D geometric polygonal mesh of the tooth.

Humans↗

Incidence of inferior alveolar nerve injury in mandibular third molar surgery.

This paper documents the incidence of inferior alveolar nerve injury and resultant sensory disturbance encountered in the removal of 100 consecutive impacted mandibular third molars. Five cases of anesthesia and/or paresthesia resulted and all but one of these resolved within six months. The lack of direct correlation between surgical exposure of the neurovascular bundle intraoperatively and the proximity of radiographic images of tooth root and mandibular canal, with the occurrence of sensory deficit, is noted. Our findings support the 1979 Recommendations of NIHCDCRTM*, upon which the policy of informed consent regarding nerve injury was based.

Adolescent↗

The cracked tooth syndrome--crown root vertical fracture.

A case of an incomplete tooth fracture followed by a complete fracture was presented. The difficulty of diagnosing this condition was discussed as well as the possible histological explanation of the symptoms experienced by the patient. It once again points out to practising dentists, that whilst deep pockets can give rise to severe periodontal pain, intense and excruciating pain should be investigated with the cracked tooth in mind.

Cracked Tooth Syndrome↗

Radiological assessment of artificial bone defects in the floor of the maxillary sinus.

OBJECTIVE: To compare dental radiographs and axial high resolution (HR) CT scans for the identification of artificial bone defects between the maxillary sinus and the roots of the adjacent teeth and to evaluate the accuracy of HR-CT. METHODS: Artificial bone defects of different dimensions were produced in the antral floor adjacent to 40 roots of 23 premolars and molars in 21 human autopsy specimens of the posterior maxilla. Periapical radiographs were obtained together with 1 mm axial HR-CT scans. The macroscopic and radiological findings of both sets of images were compared. Histological sections were prepared corresponding to the CT scans and the accuracy of the scans evaluated by measurement of five parameters. RESULTS: None of the artificial bone defects could be identified on the dental radiographs. In contrast 62.5% of the antral bone defects could be identified in the axial HR-CT scans. Identification of their margins depended on the location on the tooth root, adjacent bone morphology and visualization of the periodontal ligament space. When the periodontal ligament space was visualised identification of an antral floor between 0.2 and 0.5 mm thick was feasible. CONCLUSION: In certain clinical situations HR-CT is appropriate for identifying antral bone detects between the maxillary sinus and the roots of the adjacent teeth.

Alveolar Process↗

Effects of sialoadenectomy and exogenous EGF on molar drift and orthodontic tooth movement in rats.

Effects on bone remodeling have been attributed to epidermal growth factor (EGF). Sialoadenectomy (SX) removes the major source of EGF in rodents and decreases both salivary and serum EGF levels. EGF effects on rat alveolar bone remodeling manifested by molar drift (MD) and orthodontic tooth movement (OTM) were examined using the following two approaches: 1) EGF depletion by SX and replacement by orally administered EGF (50 micrograms.animal-1.day-1); 2) sham rats supplemented with matching amounts of EGF. MD and OTM were measured using cephalometric radiographs; bone formation was measured histomorphometrically using tetracycline labeling. Normal MD was not detected after SX, and alveolar bone formation was significantly reduced both around the tooth and in nondental sites. Replacement EGF given to SX rats and supplemental EGF administered to sham rats changed the direction and enhanced the rate of MD. A mesially directed orthodontic force applied to the molars of SX animals increased bone formation on the distal aspect of the tooth roots. Supplemental EGF did not significantly affect OTM. EGF affects alveolar bone remodeling, as manifested clinically by alterations in normal maxillary MD.

Administration, Oral↗

Simple and surgical exodontia.

Preemptive and postoperative pain management is part of patient care when performing extractions. Simple extractions can become complicated when tooth roots are fractured. Adequate lighting,magnification, and surgical techniques are important when per-forming surgical (complicated) extractions. Radiographs should be taken before extractions and also during the procedure to assist with difficult extractions. Adequate flap design and bone removal are necessary when performing surgical extractions. Complications, including ocular trauma, jaw fracture, and soft tissue trauma, are avoided or minimized with proper patient selection and technique.

Analgesics↗

Tissue response to overdenture therapy.

Patients who had received overdenture treatment provided with uniform standards were recalled and studied. Two examiners simultaneously and independently evaluated the tissue response using a variety of indices. Data comparisons were made between overlaid teeth and control teeth and between overlaid teeth as a function of time to assess any effects of the treatment. Patients who did not apply fluoride to retained tooth roots had a high incidence of caries. No other significant differences were noted between the health of overlaid teeth compared to control teeth. Patients demonstrated large variations in their ability to maintain low plaque levels and healthy tissues. Despite this, on a longitudinal basis over 2 years, patients were able to maintain plaque levels and gingival response at clinically acceptable standards.

Consumer Behavior↗

Two- and three-dimensional orthodontic imaging using limited cone beam-computed tomography.

Considerable progress has been made in diagnostic, medical imaging devices such as computed tomography (CT). However, these devices are not used routinely in dentistry and orthodontics because of high cost, large space requirements and the high amount of radiation involved. A device using computed tomography technology has been developed for dental use called a limited cone beam dental compact-CT (3DX). The aim of this article is to demonstrate the usefulness of 3DX imaging for orthodontic diagnosis and treatment planning. We present three cases: (1) one case shows delayed eruption of the upper left second premolar, (2) the second case shows severe impaction of a maxillary second bicuspid; and (3) the third case shows temporomandibular joint disorder (TMD). In the tooth impaction cases, the CT images provided more precise information than conventional radiographic images such as improved observation of the long axis of the tooth, root condition, and overlap with bone. In the TMD case, clear and detailed temporomandibular joint images were observed and pre- and posttreatment condylar positions were easily compared. We conclude that 3DX images provide useful information for orthodontic diagnosis and treatment planning.

Adolescent↗

[Complications after ambulatory oral surgical interventions, their frequency and importance].

The rate of complications of the healing process observed during or after oral surgical intervention on an outpatient basis amounts to 9.75% of the cases. Most frequently occur tooth-root fractures, alveolitis/osteitis, osteomyelitis, soft-tissue infections, haematomas, postoperative bleedings, antral perforations, sinusitis and perception disorders. The great medical and economic importance of such complications is pointed to on the basis of personal results and relevant data from the literature. An improvement in treatment results can be aimed at by reducing the rate of complications as well as by shortening the duration of treatment. Some relevant suggestions are given.

Alveolar Process↗

Hereditary and environmental dental findings in identification of human remains.

The paper presents the results on hereditary and environmental dental findings in identification of human remains exhumed from mass graves in the Republic of Croatia. The total of 17,880 teeth from all the categories (incisors, canines, premolars and molars) was examined. Hereditary findings of the teeth such as shape, size, position, as well as age were used in all of the cases confirming and completing the identification. In only 15% of the cases they were the starting points for the identification that would be later confirmed with another 3-5 traditional identification procedures. Disturbances in tooth eruption were recorded in 22% of the cases, impaction of teeth in 10%, and retarded eruption of teeth in 12%. Disturbances of tooth position were recorded in 65% of the cases. Tooth rotation in 26% and diastema mediana in maxilla or mandible in 39%. Disorders of tooth number in the form of unilateral and bilateral missing of lateral maxillary incisors were recorded only in 2% of the monitored cases. Abnormalities of the tooth shape were found in 11% of the cases. The majority of them were found on the tooth crowns 6%, and less on the tooth roots 5%. Environmental dental findings that were the most significant for the identifications were prosthetic appliances in 30% of cases. Prostheses were helpful in the identification of 3% of the cases, while crowns and bridges were helpful in 27% of the cases. Ante mortem teeth extractions were helpful in 25% of the cases. Teeth restorations were recorded in 20% of the identified cases, amalgams in 19% and aesthetic filings in 1%. Dental caries was helpful in only 10% of the cases, superficial caries in 3% and caries of dentin in 7% of cases.

Croatia↗