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At least 829 records · Page 46Linked to original sources
PubMed2007

Concrescence of teeth: cemental union between the crown of an impacted tooth and the roots of an erupted tooth.

Concrescence of teeth is a condition showing a union of adjacent teeth by only cementum. In all the previously reported cases, the union has been observed between the roots of the affected teeth. Here, we describe the first case that showed a concrescence of the crown of an impacted tooth and the roots of the erupted tooth. In addition, we discuss how this condition, especially the deposition of acellular cementum on the crown, occurred.

Female↗
PubMed1997

Cell death during tooth eruption in the rat: surrounding tissues of the crown.

We investigated the occurrence of apoptosis and other types of cell death around the crown during tooth eruption of the rat upper molar. The TdT-mediated-dUTP-biotin nick end labeling (TUNEL) method and transmission electron microscopy (TEM) were employed. Apoptosis was detected by both TUNEL and TEM in part of the reduced enamel epithelium and connective tissue in the resorbing bony crypt of the pre-erupted tooth. In TEM, a large number of cells showed condensed chromatin and membrane-bound small bodies (apoptotic bodies). Macrophages that phagocytosed apoptotic bodies could be detected. Based upon the distance between bone surface and these apoptotic cells, and the characteristics of their organelles, we suggested that the apoptotic cells might be osteocytes, bone-lining cells (osteoblasts), and macrophages. We surmised that the osteoclasts had also died. Cells which contained autophagic vacuoles and autophagosomes, and others whose cytoplasm had dissolved, were also frequently observed. No progressive cell death was found in the oral epithelium or the fibrous connective tissue over the crown. These results suggest that apoptosis gives rise to some cell death during tooth eruption, but that other types of cell death also occur in various cells.

Age Factors↗
PubMed1989

[Effect of the 3/4 crown and porcelain-fused crown restorations on the tooth displacement and the loading force of the supporting tissues].

A mechanical simulation model of tooth and alveolar bone in the application of 3/4 crown and porcelain-fused crown restorations was made and analyzed using three-dimensional finite element technique. The results obtained were as follows. 1. When the physiological tooth mobility was less than 150 microns, the teeth were sufficiently fixed using the splint and the bridge connected with more than two teeth, in the case of 20 percent absorption of the alveolar bone, and more than three teeth in the case of 40 percent absorption. In the case of 60 percent absorption, the teeth were fixed with the splint of six teeth connections, and were fixed with the bridge of five teeth connections. 2. The periodontium supporting force decreased markedly according to the increase of the number of the abutment teeth. 3. The teeth accompanied with the absorption of the alveolar bone were connected, in order to inhibit the tooth mobility and the periodontium supporting force. In this application, it had the inhibitory action when the replacing ratio of metal and ceramics to a crown of the tooth was less than 35 percent. 4. According to the finite element analysis, the design bases of fixed restorations applied in the teeth accompanied with the absorption of the alveolar bone were preferred.

Alveolar Bone Loss↗
PubMed1990

Numerical simulation of the crown of an incisiform tooth by conformal and polynomial regression mapping of a simple model.

We present a simple bowl-shaped model in the complex plane for the enamel and dentin structure of a tooth. Isochronous mode lines, and path lines representing the paths followed by individual ameloblasts and odontoblasts, form a simple regular mesh in the model. After the conformal map W = Z2, the transformed model is remarkably tooth like. To further improve the simulation of the crown of an incisiform tooth in particular, we compare our results to our own data from actual teeth and data from the literature. This leads us (a) to adjust the initial model so that the mesh of mode and path lines intersects the boundary of the tooth in a realistic way, and (b) to refine the mapping using least-squares regression to fit polynomial functions of Z and W to the available data.

Computer Simulation↗
PubMed1990

[Therapy of fractured crown of juvenile permanent tooth].

Above all the treatment of fractured juvenile frontal teeth doesn't represent a restoration problem but a problem of conservation of the tooth. In cases of uncomplicated crown-fractures the covering of all opened dentin tubuli must be recommended. In complicated crown-fractures the method of partial pulpotomy is preferred instead of pulp amputation regarding special indication. A closed cooperation with the orthodontist should be in the treatment of juvenile frontal teeth with a vital pulp.

Adolescent↗
PubMedDate not supplied

Tolerance test of five different types of crowns on single-tooth implants.

PURPOSE: The main purpose of the present experimental study was to compare five different types of crowns, cemented on implant abutments, regarding their capability to withstand loads. MATERIALS AND METHODS: Three types of all-ceramic crowns, a gold-foil-reinforced porcelain crown, and, as a control, a conventional metal ceramic crown were tested. Each crown was cemented onto an Astra Tech Single-Tooth implant. The five types of crowns, three of each type, and the titanium implants were subjected to loading in Lloyd test equipment until part of them was damaged, at which point the compression value was recorded and the deflection and bending moment were calculated. Comparisons were made on the basis of these data. RESULTS: The results showed that the all-ceramic crowns fitted with a core should be able to withstand normally occurring biting forces without difficulty. The foil crown was also judged to be acceptable, while the bending moment of the cast call-ceramic crown without a core was considered unpredictable. The values for the metal ceramic design were as predicted, ie, they were clearly the highest in the study; the superior strength of metal ceramics should still be taken into account when deciding between all-ceramic solutions and the conventional metal ceramic crown. CONCLUSION: It was concluded that all-ceramic crowns are weaker than conventional metal ceramic crowns: however, based on estimated maximum clinical loading (370 N in the incisor and premolar regions), In-Cream and AllCeram crowns seem to function satisfactorily on implants.

Aluminum Oxide↗
PubMedDate not supplied

Finite element analysis of stress distribution of 2 different tooth preparation designs in porcelain-fused-to-metal crowns.

PURPOSE: The aim of this clinical simulation study was to investigate the effect of anatomic and nonanatomic occlusal preparation design on stress distribution in different metal-ceramic crowns and tooth and bone. MATERIALS AND METHODS: For the finite element analysis method, a 2-dimensional mathematical model of a mandibular second premolar tooth and its supporting tissues was used. The analysis was performed by using a structural analysis program. Four groups were designed: gold-palladium alloy/anatomic occlusal preparation (Au-Pd/A), Au-Pd alloy/nonanatomic (flat) occlusal preparation (Au-Pd/N), nickel-chromium alloy/anatomic occlusal preparation (Ni-Cr/A), and Ni-Cr alloy/nonanatomic occlusal preparation (Ni-Cr/N). A distributed type load of 400 N (total) was applied to the centric stop points on the tip of the buccal cusp and on the central developmental groove in centric occlusion to all types of restorations. RESULTS: The results demonstrated that shear stresses in the dentin tissues and restorations in Au-Pd/A and Ni-Cr/A were similar. The shear stresses within the restorations in Au-Pd/N and Ni-Cr/N were similar. CONCLUSION: Anatomic occlusal preparation designs were advantageous in stress distribution in the dentin tissue. Nonanatomic occlusal preparation designs were found to be advantageous in the stress amount and distribution in the porcelain structure. Occlusal preparation designs and restorative materials showed no differences in stress distribution and amount in the pulp tissue and bone tissues.

Alveolar Process↗
PubMed1990

[Clinical studies of the proper indication of inlay and crown therapy in lateral tooth areas].

187 students were examined an epidemiological study for their dental conditions and requirements with respect to preservation and prosthetics. The persons tested showed a DMF-T index of 11.6 and a DMF-S index of 24.2 in the lateral tooth area. In our opinion the clinical investigation revealed that the total number of caries cases will rise three-fold due to the above-average frequency of secondary caries cases as the filling size (or the number of filling surfaces) increases. The amount of single crown dentures found in the lateral tooth area with 0.1 crowns per person tested turned out to be fairly low. The actual need for a tooth-preserving therapy concept by crowning in preference to the concept of filling therapy amounts to the twelve-fold of the existing single crown dentures.

Adolescent↗
PubMed1975

Effects of artifical crown margin extension and tooth brushing frequency on gingival pocket depth.

The gingival tissues adjacent to the crowned and unrestored teeth were probed to determine individual pocket depths. The findings are listed here. (1) The average pocket depth adjacent to nonrestored teeth was 2.7 mm. The average pocket depth adjacent to teeth having crowns with subgingival margins was 3.4 mm. (2) Fifty-four nonrestored teeth had at least one pocket depth greater than 3 mm., while 84 crowned teeth had at least one or more measurements greater than 3 mm. (3) No positive relationship could be found between tooth brushing frequency and the pocket depth adjacent to teeth restored with complete cast crowns. (4) In nonrestored teeth, pocket depth increased with reduced frequency of tooth brushing. (5) Pocket depth increased with increased age of (a) the patient in both restored and nonrestored teeth and (b) the cast crown.

Adult↗