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At least 973 records · Page 54Linked to original sources

PubMed1992

Effect of cavity depth on stresses in a restored tooth.

Restorative procedures commonly replace lost tooth structure, but redistribution of functional stresses after treatment is not fully understood. Many restorative methods are dictated by the integrity of the remaining tooth structure, because sparse tooth structure can lead to fracture. It is essential to prevent fractures by having a clear concept of the designs for cavity preparations, and to anticipate the stresses of mastication on the remaining tooth structure. Knowledge of various internal parameters of cavity designs would facilitate selection of the appropriate cavity preparation for a specific clinical situation. Three cavity designs and restorations were examined in this study for stresses using the finite element technique. After placement of restorative materials, the dentin experienced a dramatic change in stress gradient immediately below the pulpal wall, and this response was magnified in deeper cavity preparations. Enamel also exhibited major alterations in the stress gradient in all three designs of cavity preparations. The combination of the changes can cause cracks in the remaining tooth structure, leading to cusp fracture immediately adjacent to the deepest portion of the cavity.

Alveolar Process↗

PubMed1989

Inhibition of tooth eruption through calcium-phosphate ceramic granules in the rat.

This experiment investigated the reason for disturbances of tooth eruption through hydroxylapatite (HA) granules. HA granules of compact and porous structure were implanted in the pathway of erupting teeth in 14 five-day-old rats. The results demonstrate that the use of this material can result in tooth retention and malformed tooth crowns. Tooth crown malformation can be traced to the formation of ceramo-dentinous complexes which promote bacterial invasion of the pulp cavity, resulting in arrest of the tooth eruption process.

Alveolar Process↗

PubMed1986

Analysis of moment/force ratios in the mechanics of tooth movement.

Orthodontic tooth movement is analyzed by means of the center of rotation model and the concept of moment/force ratios. Several equivalent force systems are considered at both the bracket and the center of resistance of the tooth. When moment/force ratios are evaluated at the bracket, the laws of physics appear to be suspended: inconsistencies occurring as single forces applied at different points claim equivalent results and pure translational movements purport to be nonzero moment/force ratios. These paradoxes can be reconciled only if the moment/force ratios are analyzed at the center of resistance of the tooth. Here, all of the moments applied to the tooth by the force system are included in the analysis. Only when the force system is evaluated around the center of resistance of the tooth is the concept of moment/force ratios consistently correct.

Biomechanical Phenomena↗

PubMed2005

Treatment of an ankylosed central incisor by single tooth dento-osseous osteotomy and a simple distraction device.

When teeth are replanted after being avulsed, the repair process sometimes results in ankylosis. In a growing child, the ankylosed tooth fails to move along with the remaining alveolar process during vertical growth, resulting in a tooth that gradually appears more and more impacted and requires several reconstructive procedures to correct. Ankylosed teeth can, however, serve as anchorage for orthodontic correction of a malocclusion and as a point of force application for a dentoalveolar segment during alveolar distraction osteogenesis. This case report describes the treatment of a 13-year-old girl whose maxillary left central incisor had been avulsed and replanted 5 years earlier. The tooth had become ankylosed, and it was used to provide "free anchorage" during distalization of the maxillary dentition. The underdeveloped alveolar process adjacent to the ankylosed tooth was reconstructed by dento-osseous segment distraction osteogenesis, by using the ankylosed tooth as the point of force application.

Adolescent↗

PubMed2006

ADAM28 participates in the regulation of tooth development.

Disintegrin and metalloprotease (ADAM) proteins are a family of membrane-anchored glycoproteins with diverse functions in fertilisation, development, neurogenesis and protein ectodomain shedding. ADAM28 is a newly discovered member of the ADAM family in humans and murine with autocatalytic activity. Recently, the authors screened ADAM28 genes from patients with congenital hypoplasia of tooth root, and studied the relationship between ADAM28 and tooth development. A polyclonal antibody (pAb) against ADAM28 was preparared, and the expression and localisation of ADAM28 were detected in tooth germ and dental mesenchymal cells. The results indicated that the prokaryotic expression vector pGEX-4T-ADAM28 was constructed successfully. Glutathione S-transferase-ADAM28 fusion protein was generated after inducement by isopropylthio-beta-d-galactoside and isolated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The purified fusion protein was used as an antigen for production of antibody. Western blot and enzyme-linked immunosorbent assay analyses verified that the antibody had a high specificity and titre. Immunohistochemistry and reverse transcriptase-polymerase chain reaction showed that ADAM28 was expressed at each stage of tooth germ development at different levels. Moreover, it was expressed in human dental follicle cells, human dental papilla cells, human dental pulp stem cells, human periodontal ligament cells and human dental cervical loop epithelial cells at transcription level. In conclusion, it is reasonable to suggest that ADAM28 may participate in tooth development and the regulation of odontogenic mesenchymal cells through progressive reciprocal inductive interactions between the epithelium and the mesenchyme.

ADAM Proteins↗

PubMed2006

CMT-3 inhibits orthodontic tooth displacement in the rat.

OBJECTIVE: Orthodontic tooth movement requires extensive remodeling of the periodontal ligament (PDL) and the alveolar bone. Osteoclasts resorb bone, allowing teeth to migrate in the direction of the force. Matrix metalloproteinases (MMPs) are able to degrade the extracellular matrix of the periodontal tissues. Chemically modified tetracyclines (CMTs) can inhibit MMPs, but lack antimicrobial activity. We hypothesize that CMT-3 will decrease the rate of orthodontic tooth movement in the rat. DESIGN: Eighteen Wistar rats received a standardized orthodontic appliance at one side of the maxilla. During 14 days, three groups of six rats received a daily dose of 0, 6 or 30mg/kg CMT-3, and tooth displacement was measured. Thereafter, osteoclasts were counted on histological sections using an ED-1 staining. Multi- and mononuclear ED-1-positive cells in the PDL were also counted. In addition, sections were stained for MMP-9. RESULTS: CMT-3 significantly inhibited tooth movement (p=0.03) and also decreased the number of osteoclasts at the compression sides in the 30mg/kg group (p<0.05). Significantly more mono- than multinuclear ED-1-positive cells were present in the PDL, but no significant differences were found between the dosage groups. Osteoclasts in the 30mg/kg group seemed to contain less MMP-9 than in the control. CONCLUSIONS: CMT-3 inhibits tooth movement in the rat, probably by reducing the number of osteoclasts at the compression side. This might be due to induction of apoptosis in activated osteoclasts or reduced osteoclast migration. Reduced MMP activity by CMT-3 might also directly inhibit degradation of the organic bone matrix.

Alveolar Process↗

PubMed2006

Pronamel and tooth mousse: an initial assessment of erosion prevention in vitro.

OBJECTIVES: The aim of this study was to examine whether a single topical application of proenamel or tooth mousse would prevent enamel erosion METHODS: Enamel samples were treated with either proenamel or tooth mousse applied for 15 min. The control group was placed in distilled water for 15 min. All specimens were then exposed to an erosive challenge of 0.2% citric acid for 1h. Enamel loss was determined using surfometry. RESULTS: The mean amount of enamel removed in the control group was 5.02 microm (S.D. 1.16). The mean enamel loss in the proenamel group was 2.60 microm (S.D. 0.90) and the mean enamel loss in the tooth mousse group was 3.28 microm (S.D. 1.22). The results for the proenamel group were statistically significantly different from the control group at the p<0.01 level and the results for the tooth mousse group were statistically significantly different from the control group at the p<0.05 level. CONCLUSIONS: Tooth mousse and proenamel may offer a degree of protection from erosion of permanent enamel.

Analysis of Variance↗

PubMed2004

Impacted tooth in mandibular fracture line: treatment with closed reduction.

PURPOSE: Most mandibular fractures occur because of blunt trauma. In some cases, the mandible can be weakened by the presence of an unerupted or impacted tooth. The fate of this tooth in the fracture line and its effects on bone healing remain an important outcome event. MATERIALS AND METHODS: In this study, we analyzed the records of 117 patients with a total of 121 fractures having an unerupted tooth remaining in the fracture line who were treated and followed by the Dental Faculty of Ankara University between 1986 and 1996. All were open fractures, and none of the patients had a history of an acute inflammatory episode related to the unerupted tooth before the injury. Intermaxillary fixation was used in all cases. RESULTS: Three of the patients subsequently required open reduction with internal fixation. The unerupted tooth was not extracted in any patient. The fixation was maintained for an average of 45 days and followed up for 3 months. No complications were encountered. CONCLUSION: According to these results, we suggest that asymptomatic impacted teeth in the fracture line of uncomplicated mandible fractures do not cause delayed healing when treated with closed reduction.

Adolescent↗

PubMed2004

Basic behavior of the finite helical axis in a simple tooth movement simulation.

A finite helical axis (FHA) analysis can provide precise three-dimensional information on orthodontic tooth movement compared to an analysis based on a rectangular coordinate system. The FHA has already been applied in an analysis of orthodontic tooth movement. Interestingly, the position of the FHA changes dramatically in different stages of treatment; however, no previous report has provided detailed information of its basic behavior for clinicians. The purpose of this study was to clarify the basic behavior of the FHA in simple tooth movement, which could promote a better understanding of the 3-D orientation of and rotation about the FHA during tooth movement. Parameters of the FHA were calculated from a simulation of canine retraction. As the tipping angle of the canine was increased from 5 degrees to 30 degrees , the orientation vector of the FHA approached the most affected axis of rotation (on a rectangular coordinate system) in a non-linear manner. The angle of rotation about the FHA also increased in a non-linear manner. This non-linear problem was solved analytically. The basic behavior of the orientation vector of the FHA and the non-linear characteristics of the FHA parameters clarified in this study should be important for the future analysis of actual tooth movement based on the FHA. However, we must be aware that the non-linearity of the FHA itself may affect the analysis of the mechanical properties of the periodontal tissue.

Computer Simulation↗

PubMed2004

Neurites from trigeminal ganglion explants grown in vitro are repelled or attracted by tooth-related tissues depending on developmental stage.

Although neurite attracting factors are present in the developing dental pulp and trigeminal ganglion (TG) axons can respond to such factors, nerve fibres do not enter the tooth pulp until a late developmental stage compared with surrounding tissues supplied by the TG. This suggests that the dental pulp secretes neurite growth inhibitory molecules. Semaphorins represent one group of substances, which can inhibit/repel growing neurites. The aims of the present study were to investigate if dental tissue explants inhibit/repel neurite growth from TGs at some developmental stages in vitro, and if so, to seek evidence for or against a participation of semaphorins in that interaction. By co-culturing mandibular or dental epithelial and mesenchymal tissue explants and TGs in collagen gels, we found that embryonic day 11 (E11) mandibular and E13 dental mesenchymal explants repel neurites from corresponding TGs. Repulsion was replaced by attraction if tissues from late embryonic or early postnatal mice (E17-postnatal day 5) were used. Using semi-quantitative reverse transcription/polymerase chain reaction we showed that a number of semaphorins were expressed by tooth-related mesenchyme collected from embryonic and postnatal mice. The expression of some semaphorins (3A, 3C, 3F, 4F, 5B, 6A, 6B and 6C) was high early in development and then decreased in a temporal pattern that correlated with neurite inhibitory/repulsive effects of dental mesenchyme observed in co-cultures. The expression of other semaphorins increased with development (3B, 4A and 7A), whilst others varied irregularly or remained at a fairly constant level (3E, 4B, 4C, 4D, 4G and 5A). Immunohistochemistry was used to determine if tooth-related nerve fibres possess neuropilins. This revealed that axons surrounding embryonic tooth buds express neuropilin-1, but not neuropilin-2. In postnatal teeth, nerve fibres located within the tooth pulp were immunonegative for neuropilin-1 and neuropilin-2. We conclude that developing mandibular/dental mesenchyme can inhibit/repel neurite growth in vitro. Our results support the hypothesis that semaphorins may be involved in this interaction.

Animals↗

PubMed2001

Calcium and vitamin D supplements reduce tooth loss in the elderly.

PURPOSE: Oral bone and tooth loss are correlated with bone loss at nonoral sites. Calcium and vitamin D supplementation slow the rate of bone loss from various skeletal sites, but it is not known if intake of these nutrients affects oral bone and, in turn, tooth retention. SUBJECTS AND METHODS: Tooth loss was examined in 145 healthy subjects aged 65 years and older who completed a 3-year, randomized, placebo-controlled trial of the effect of calcium and vitamin D supplementation on bone loss from the hip, as well as a 2-year follow-up study after discontinuation of study supplements. Teeth were counted at 18 months and 5 years. A comprehensive oral examination at 5 years included assessment of caries, oral hygiene, and periodontal disease. The odds ratio (OR) and 95% confidence interval (CI) of tooth loss were estimated by stepwise multivariate logistic regression. Initial age (mean +/- SD) of subjects was 71 +/- 5 years, and the number of teeth remaining was 22 +/- 7. RESULTS: During the randomized trial, 11 of the 82 subjects (13%) taking supplements and 17 of the 63 subjects (27%) taking placebo lost one or more teeth (OR = 0.4; 95% CI: 0.2 to 0.9). During the 2-year follow-up period, 31 of the 77 subjects (40%) with total calcium intake of at least 1000 mg per day lost one or more teeth compared with 40 of the 68 subjects (59%) who consumed less (OR = 0.5; 95% CI: 0.2 to 0.9). CONCLUSION: These findings suggest that intake levels of calcium and vitamin D aimed at preventing osteoporosis have a beneficial effect on tooth retention.

Aged↗

PubMed2001

A quantitative analysis of pharyngeal tooth shape in the zebrafish (Danio rerio, Teleostei, Cyprinidae).

To test whether successive replacement cycles in the pharyngeal dentition of the zebrafish, a polyphyodont vertebrate model organism, entail overall shape changes in the teeth, a qualitative and quantitative analysis was made of size and shape variables in the five ventral teeth. The following measurements were defined: tooth length, tooth height, neck-crown angle, cusp depth, and crown curvature. Ontogenetic changes in fish, ranging between 6 and 29 mm standard length (SL), were analysed by linear regressions on to SL. The teeth became significantly larger with growth of the fish, through successive replacements and cusp depth also increased over time. Neck--crown angle and crown curvature did not change over time. Position-dependent differences were analysed by Friedman ANOVA and Kendall concordance tests. Measurements differed significantly according to tooth position in the pharyngeal jaws. Tooth 1V was always the smallest, 3V the largest. The neck--crown angle and curvature of the crown increased from 1V to 5V. Cusp depth increased from 1V to 3V, and then decreased again. These results indicate that successive replacement cycles entail a size increase accompanied by shape changes apparently restricted to the crown. These quantitative data lay the basis for further descriptive and experimental studies of tooth shape in this model-species.

Analysis of Variance↗

PubMed1991

The effect of connector design on cement retention in an implant and natural tooth-supported fixed partial denture.

This study investigated the effect of connector design, rigid or nonrigid, on cement retention in a combined implant and natural tooth-supported fixed partial denture. A prepared natural tooth was placed in a Plexiglas block in a manner that it could move approximately the same as a healthy premolar. An endosseous implant was placed in the block so that it was immobile. Joining the prepared tooth and implant was a fixed partial denture that could be made rigid or nonrigid. The natural tooth retainer was cemented to the prepared tooth, and the implant retainer was affixed to the implant fixture with a gold screw. One year of stress was applied to the fixed partial denture by a force simulation machine. Twenty randomly ordered tests were completed, 10 of each connector design. Retentive values for the cemented retainers were recorded and statistically compared by use of Student's independent t test. No significant difference in cement retentive strength between designs was found (p less than 0.05).

Bicuspid↗

PubMed2001

Expression of cementum-derived attachment protein in bovine tooth germ during cementogenesis.

Cementum-derived attachment protein (CAP) is a 56 kDa collagenous protein that promotes attachment of mesenchymal cells. Previous studies have shown that the presence of CAP is restricted to cementum in adult human tissues. In this study, we report generation of a monoclonal antibody against CAP and its use for the investigation of CAP in developing bovine tooth germs. Mice were immunized with CAP purified from bovine cementum, and a monoclonal antibody, 3G9, was produced. Immunohistochemical staining of bovine tooth germ at root forming stage using 3G9 antibody showed that the tissue distribution of CAP expression was limited to cementum matrix and cementoblasts during cementogenesis. Alveolar bone did not stain with the 3G9 antibody, whereas anti-type I collagen stained positively. CAP was purified from bovine tooth germs with immunoaffinity purification using the 3G9 antibody. Examination of the immunoaffinity-purified fraction showed that CAP existed in tooth germ as a 65 kDa protein. The protein was susceptible to bacterial collagenase. To investigate the possible biological function of CAP during cementogenesis, we isolated dental follicle cells from the bovine tooth germ, and showed that they adhered to surfaces containing CAP. These data demonstrate that CAP is expressed by bovine cementoblasts as a 65 kDa protein and that the CAP may have a function in cementogenesis.

Animals↗

PubMed2002

Expression of matrix metalloproteinase-9 mRNA and protein during deciduous tooth resorption in bovine odontoclasts.

Matrix metalloproteinase-9 (MMP-9, or gelatinase B) is an extracellular proteinase that is highly expressed in osteoclasts and has been postulated to play an important role in their resorptive activity. Although MMP-9 has been reported to play a role in bone resorption, the association of this enzyme during deciduous tooth resorption has not yet been clarified. The purpose of the present study was to increase our understanding of the role of MMP-9 during deciduous tooth resorption. Reverse transcription-polymerase chain reaction (RT-PCR) and northern blot analysis of total RNAs extracted from bovine root-resorbing tissues, which lie between the root of a deciduous tooth and its permanent successor, revealed the expression of mRNA for MMP-9 in the tissue. These results indicate that MMP-9 may be involved in the process of deciduous tooth resorption. In addition, in situ hybridization and immunohistochemistry were also performed to identify the cells that produced MMP-9 in bovine root-resorbing tissue. MMP-9 mRNA was highly expressed in odontoclasts that were aligned along the surface of the tissue. Immunohistochemistry confirmed the predominant localization of MMP-9 in odontoclasts. The present data demonstrate that odontoclasts in deciduous root resorption express MMP-9, which may participate in proteolysis during root resorption of deciduous tooth.

Animals↗

PubMed2002

Bone morphogenetic protein 4 is involved in cusp formation in molar tooth germ of mice.

In order to clarify the role of BMP4 in the development of the tooth crown, we employed the antisense technique on molar tooth germs removed from the mandibles of embryonic 13.5-d-old mice. In the tooth germ explants incubated for 14 d with antisense oligodeoxynucleotide (AS-ODN) against Bmp4 (a) cusps were not formed, whereas dentin matrix was secreted in the whole region of the crown, (b) inner enamel epithelial (IEE) cells remained in the undifferentiated state in the occlusal region of the crown, though they differentiated in the proximal region (lateral surface region of tooth crown), and (c) insufficient growth of the dental papilla was observed. A 5-bromo-2'-deoxyuridine (BrdU) uptake experiment showed that, although a site-specific proliferation of IEE cells occurred in the occlusal region in the control explants, it was not found in the AS-ODN-treated explants. In the proximal region, however, the proliferation of IEE cells was detected evenly in all explants treated with or without AS-ODNs. These results suggest that AS-ODN against Bmp4 inhibited the differentiation and the site-specific proliferation of IEE cells in the occlusal region of molar tooth germs, resulting in the suppression of cusp formation. Our data thus suggest that BMP4 is involved in cusp formation and differentiation of ameloblasts in the occlusal region of molars.

Ameloblasts↗

PubMed2006

Surface and pulp chamber temperature rises during tooth bleaching using a diode laser: a study in vitro.

OBJECTIVE: To measure the surface and pulp chamber temperature increases in vitro on upper and lower anterior teeth during a tooth whitening procedure using a diode laser. METHOD: A thermocouple was used to measure the temperature increase on the surface of an extracted upper central incisor tooth. Pulp chamber temperature readings were made on upper and lower central incisors, lateral incisors and canines. A diode laser recommended for tooth bleaching was tested at three different power settings (1W, 2W, 3W). Temperature measurements were made with and without the bleaching agent present on the labial tooth surface. RESULTS: The increase in surface temperature readings ranged from 37 degrees C (1W) to 86.3 degrees C (3W) with no bleaching gel present. Pulp chamber temperature increases ranged from 4.3 degrees C (1W) to 16 degrees C (3W). The presence of the bleaching gel reduced temperature increases seen at the tooth surface and within the pulp. CONCLUSIONS: The increase in the pulp chamber temperature with the laser used at 1-2W was below the critical temperature increase of 5.5 degrees C thought to produce irreversible pulpal damage. However, a power setting of 3W produced a pulp chamber temperature increase above this threshold (16 degrees C) and caution is advised when using this setting.

Body Temperature↗

PubMed1992

Long-term orthodontic tooth movement response to short-term force in the rat.

Both the amount of force applied and the duration of the application affect tooth movement. To study the effect of duration, adult male Sprague-Dawley rats were fitted with orthodontic appliances delivering a 40-gm initial mesial tipping force to the maxillary molars. The animals were divided into two longitudinal groups (I: 1 hour and II: 24 hours; N = 15). Sham-treated control (III) and 14 day (IV) continuous cross-sectional force tooth movement data were also included for comparison (72 rats per group). Extraoral cephalometric radiographs were obtained at appliance placement and at 1, 3, 5, 7, 10, & 14 days. Tooth movement was determined with respect to palatal implants. ANOVA indicated significant differences existed over time in each group (p = 0.0001). Continuous force applied for 14 days generated a classic three-part tooth movement curve. Short-term forces were characterized by initial mesial movement, a distal relapse period (d3-d5), and a late mesial movement period (d7-d14). The results suggest short-term forces of 1 and 24 hours initiate remodeling events, which result in tooth movement 7 to 14 days later and that the minimum effective duration of a 40-gm activation is less than 1 hour in this animal model.

Activator Appliances↗