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At least 1,243 records · Page 69Linked to original sources

PubMed2005

[Influences of applying force during the different stages of estrous cycle on orthodontic tooth movement of rats].

OBJECTIVE: To explore the effects of applying force during the different stages of estrous cycle on orthodontic tooth movement of rats, so as to offer an experimental princinple for women's orthodontic treatment. METHODS: 80 female 3-month-old Wistar rats, which had a stable and five-day estrous cycle, were used. They were randomly divided into control groups and loading-force groups. Each group was divided again into 4 sub-groups according to the different stages of the estrous cycle. The loading-force groups received repeated intermittent orthodontic force for four times seperately during the same stage of the estrous cycle. The distance between upper incisor and the first molar on the left was measured. The data were analyzed by One-way ANOVA, S-N-K. RESULTS: There were significant variations in the amount of tooth movement among the groups which received the mechanical force during the different stages of the estrous cycle (P <0.01). There were significant variations in the amount of tooth movement between the groups received force during pre-estrus and estrus (P <0.05). There were not significant variations between the groups received force during metestrus and diestrus (P > 0.05). The largest amount of tooth movement was in estrus group and smallest in pre-estrus one. CONCLUSION: The effect of tooth movement depended on which stage of estrous cycle was chosen to be the time of applying orthodontic force.

Analysis of Variance↗

PubMed1991

Mechanical aspects of a Brånemark implant connected to a natural tooth: an in vitro study.

Mechanical in vitro tests of the Brånemark implant disclose that the screw joint which attaches the prosthetic gold cylinder and the transmucosal abutment to the fixture forms a flexible system. This inherent flexibility seems to match well the vertical mobility of a supporting tooth connected to the implant. Calculations of vertical load distribution based on measured flexibility data demonstrate that the forces are shared almost equally between tooth and implant even without taking the flexibility of the surrounding bone or the prosthesis into account. The therapy of a single Brånemark implant connected to a natural tooth should be considered without any additional element of a flexible nature. Mechanical tests and theoretical considerations, however, indicate that the transverse mobility of the connected tooth should be limited and that the attachment of the prosthesis to the tooth should be of a rigid design to avoid gold-screw loosening.

Dental Abutments↗

PubMed1991

[Somatosensory evoked potentials by mechanical stimulation of tooth in humans].

We examined topographical analysis of the PM-SEP (periodontal mechanoreceptor-sensory evoked potential) inducing by mechanical stimulation of the tooth in eight subjects. Sensory evoked potential were recorded from various regions of the scalp by the mechanical stimulation of the normal tooth. Eleven electrodes were placed according to the International 10-20 system (T3, T4, C3, C4, T5, T6, F7, F8, Fz, Cz, Oz). The mechanical stimulation was applied to the right upper first incisor tooth. PM-SEPs were averaged 100 times following the mechanical stimulation of the tooth produced six waves of SEP at the ipsilateral temporal area (T4), but did not evoked any potential from the other regions. PM-SEP included I, II, III, IV, V and VI. The earliest latency (I wave) was approximately 11ms and latest latency (VI wave) was approximately 40 ms. These PM-SEP observed by intensity with 3 times of the threshold. In addition, the all components were abolished after local anesthesia of the periodontal ligament. These data suggests that the six waves of the PM -SEP were evoked the ipsilateral temporal region following mechanical stimulation of the tooth, and these regions were projected by afferent impulse from the periodontal mechanoreceptor.

Adult↗

PubMed1990

[Growth factors in human tooth development].

Our research concerns the immunohistochemical localization of EGF and IGF-I receptors in the tooth germ, using monoclonal antibodies. The results show that in the early phases of human tooth development EGF and IGF-I receptors are present. At bud stage both receptors are localized at dental laminae level, in some epithelial cells of the tooth bud and in some mesenchymal cells. At cap stage the receptors are present in the outer and inner enamel epithelium, and in some cells of stellate reticulum. As far as concerns the mesenchymal cells, some cells of dental papilla in contact with enamel organ, are intensely positive. The immunopositivity is present also in some mesenchymal cells at follicular level. At late cap stage and at early bell stage receptors are not present at inner enamel epithelium level but they can be detectable in the mesenchyma of dental papilla and in some cells of the follicle. On the basis of these results it may be hypothesized that EGF and IGF-I can act as growth factors in the modulation of cellular proliferation and differentiation during the human tooth morphogenesis. Moreover, it is possible that these substances can play a role in the mesenchymal-epithelial interaction in the developing human tooth.

Cell Differentiation↗

PubMed1989

[Investigated reports of tooth fractures cases from November, 1986 to September, 1988].

Researching the actual condition of tooth fractures, clinical records and X-ray photographs of 2717 patients, visited P.D.I. Dental Clinic from November, 1986 to September, 1988 were investigated statistically. 174 cases were tooth fractures in 2717 patients. The frequency rate of tooth fractures at an early age was low, increased from the latter half of the 30s and was highest at the latter half of the 50s accounted for over 10%, and decreased from the 60s. In the upper anterior teeth, the crown fractures caused by traumatic factors, at an early age showed a high proportion, and in the lower anterior the tooth fractures were rare. In the posterior the root fractures of non-vital teeth attributed to dental treatment at the middle and advanced age indicated a high proportion. In the case of tooth restored with metalcore and bridge, the proportion of the root fractures were high, the metalcore, was used in 63%, and in the bridge in 27% of the root fractures.

Adult↗

PubMed1989

[Biodegradable ceramic as a bone graft substitute followed by orthodontic tooth movement].

This study was performed to evaluate the histological changes during remodelling of autogenous PMCB (particulate marrow and cancellous bone) and TCPC (beta-tricalcium phosphate ceramic) when transplanted into the jaw bone defects, and also to investigate the possibility of orthodontic tooth movement on them. Twenty dogs were used in this study. Following extraction of the upper 2nd and 3rd incisors, or only the 2nd incisor, maxillary alveolar bones were resected bilaterally. Autogenous PMCB obtained from the ilium and TCPC (Synthograft, Miter, Inc. U.S.A.) were grafted in each resected area. Nine dogs were sacrificed without applying the orthodontic force, whereas the rest of dogs were sacrificed after applying orthodontic force. Sectional arch wire with open coil spring was placed between the upper 1st incisors for tooth movement. Applications of orthodontic force were started anywhere from the 2nd to the 8th week following the grafting and continued for different experimental periods. Sections of maxillary bone including the grafted areas were prepared for light microscopy. It was observed that Synthograft area showed better organization than the bone graft area initially. However, later around the 8th week, both graft materials were well organized. The Synthograft was well accepted by the host tissue. The Synthograft filled area reconstructed the bony architecture more similar to the alveolar bone than the bone graft area. In addition, the radiological findings also showed orthodontic tooth movement through the PMCB and the Synthograft areas. Capability of orthodontic tooth movement at the Synthograft areas without any undue result is of significant clinical value. Thus in view of above points in conclusion it is suggested that, TCPC is a competent substitute for PMCB in filling up alveolar bone defects, even, in cases where orthodontic tooth movement is desirable.

Alveolar Process↗

PubMed1989

[Observation on calcification of necrotic tissue in pressure side of periodontal membrane incident to experimental tooth movement].

In an orthodontic point of view, it is said that necrotic tissues cause a standstill of tooth movement until they disappear and that term of the standstill is related to the size of the necrotic tissues. Although remodeling processes of a periodontal membrane in compressed area were reported as series of phenomena like degeneration, coagulative necrosis, calcification and histiolysis, there is no direct evidence that the necrotic tissue is really calcified. The purpose of this study is to clarify histologically whether the necrotic tissues in the periodontal membrane are calcified or not and to know when appearance and disappearance of the calcification occur during an experimental tooth movement. Twenty eight rats were used for this study. For the experimental tooth movement, the orthodontic elastics were inserted into the interproximal space between the maxillary right 1st and 2nd molars during 1, 2, 3, 5, 7 and 14 days respectively (Waldo's method). The periodontal tissues were observed on undecalcified sections by vital staining in which oxytetracycline (3 mg/kg), alizarin red (8 mg/kg) and calcein (0.8 mg/kg) were applied as well as by contact micro radiography (CMR). Findings were as follows: 1) After 2 days of tooth movement, a part of the periodontal membrane in compressed area showed fluorescence by vital staining and was radiopaque by CMR. This means that the necrotic tissues are really calcified at least after 2 days of experimental tooth movement. 2) After 7-14 days no calcified tissue could be found in the periodontal membrane. The calcified tissues may disappear under processes of resorption in this area.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1979

Tooth morphogenesis: the role of the innervation during induction and pattern formation.

The hypothesis is discussed that the innervation of the early mandibular and maxillary processes influences the initiation and patterning of tooth germs. Silver staining of embryonic mouse tissue supports the notion that the innervation is present before tooth buds appear. Data from other experimental studies is discussed in support of this hypothesis. The importance of the early events of tooth morphogenesis in initiating and patterning the dentition is discussed in the context of tooth morphogenesis as a whole. The processes involved in odontogenesis are categorized as Phase I: Initiating events; Phase II: Histogenetic events; and Phase III: Cytodifferentiative events. The complications of the interrelationship of these three seemingly discrete segments of tooth development are discussed in the context of inductive tissue interaction.

Ameloblasts↗

PubMed1987

Tooth eruption: the regulation of a localized, bilaterally symmetrical metabolic event in alveolar bone.

Tooth eruption is a complicated process by which developing teeth are moved within the jaws to their functional position. The usual model chosen to study this process, the erupted rodent incisor, differs both structurally and functionally from the human dentition and conclusions drawn from these studies are not directly applicable to tooth eruption in human beings. We have studied the eruption of developing permanent premolars in dogs and present evidence by scanning electron microscopy for regional differences in metabolic activities on bone surfaces of the crypt during eruption. We review evidence that these polarization of alveolar bone metabolism are cell-mediated, dependent upon the dental follicle, independent of root formation or the tooth itself and that tooth eruption depends on coordination of these activities by the dental follicle. We conclude that tooth eruption is a localized, bilaterally symmetrical event in alveolar bone and that this is an excellent model system in which to study the regulation of alveolar bone metabolism.

Animals↗

PubMed1979

Factors affecting adhesion of bacterial to a tooth in vitro.

The initial adhesion of oral bacteria to a tooth in vitro was examined. The organisms were grown in broth with and without sucrose, and suspensions made either in broth or a modified Ringer's solution. The tooth used was either dry or coated with natural or synthetic saliva. Adhesion was determined by counting organisms removed from the tooth surface by simple washing or by sonication. It was found that the firmest bonding occurred when a dry tooth was immersed in a suspension of bacteria in Ringer's solution; the prior growth of the organisms in the presence of sucrose did not affect adhesion. It was concluded that instantaneous irreversible adhesion of bacteria to a tooth occurs without the need for active metabolism, and that this process is inhibited by the presence of competing organic substances which probably produce a surface-conditioning film.

Corynebacterium↗

PubMed1983

Basal lamina persistence during epithelial-mesenchymal interactions in murine tooth development in vitro.

Numerous investigations have demonstrated the necessity of mesenchymal instruction for epithelial differentiation during epidermal organogenesis. In the specific case of tooth formation, cap-stage tooth organ mesenchyme instructs epithelial differentiation into ameloblasts with production of enamel extracellular matrix. The "instructive event" is presumed to be direct cell contact. Mesenchyme-mediated cell contact with adjacent epithelia is assumed to "instruct" epithelial differentiation into ameloblasts. If this were true, basal lamina removal and mesenchyme cell contact with epithelia would be prerequisites for epithelial cytodifferentiation and morphogenesis in the developing tooth system. To test this hypothesis, we designed experiments to evaluate basal lamina stability during epithelial differentiation into ameloblasts. Our studies utilized cap-stage murine molar tooth organs, a serumless and chemically defined medium (PYMS), metabolic isotopic labeling of basal lamina constituents, biochemical methods to analyze macromolecular stability throughout 10 days of organ culture in vitro, and immunological methods to localize the distribution of laminin and fibronectin. Our results indicate that (3H)glucosamine is incorporated into basement membranes present in Theiler stage 25 mandibular mouse molar tooth organ. At this stage, the isotope was incorporated into high molecular weight macromolecules. Specific enzyme methods coupled with electrophoresis and fluorography demonstrated that (3H)glucosamine was incorporated into proteoglycans containing chondroitin sulfates, dermatan sulfate, and hyaluronate. After 10 days in vitro the radiolabeled material remained localized in these same molecules, indicating stability of these constituents within basement membranes. Ultrastructural observations indicated that the basal lamina was not removed during ameloblast differentiation in vitro using PYMS medium. Laminin and fibronectin were localized in the basement membranes during cap stages and did not disappear during subsequent morphogenesis and differentiation. Mesenchymal cells appear to mediate epithelial differentiation in vitro using PYMS medium without a removal of the basal lamina.

Animals↗

PubMed1984

Identification of inner and outer cell proliferation centers during fetal tooth morphogenesis.

Patterns of cell division have been examined in the proliferative cervical loop tissues of fetal rabbit incisor tooth organs. Evaluation of the distribution patterns of silver grains, resulting from the incorporation of [3H]-thymidine into newly synthesized DNA within tooth organs in vitro, resulted in identification of two proliferation centers: (1) an inner center consisting of inner enamel epithelial cells (i.e., preameloblasts) and predontoblasts ; and (2) an outer center consisting of outer enamel epithelium and adjacent mesenchyme. In contrast to the classically held description of epithelial cell differentiation during tooth morphogenesis, our data suggest that outer enamel epithelial cells do not migrate around the cervical loop and do not provide progenitor cells for subsequent ameloblast cytodifferentiation. During tooth development, epithelial and mesenchymal cells, which arise from either an inner or outer proliferative center, migrate in distal directions relative to the proliferative sites. Therefore, the progenitor cells for ameloblasts and odontoblasts were found to be localized in the inner proliferation zone. The implications of these findings regarding the development of continuously erupting rabbit and rodent incisor tooth organs are discussed in the context of a model.

Animals↗

PubMed1982

A comparison of 15 year old children with excellent occlusion and with crowding of the teeth, Angle Class I malocclusion, in respect of face size and shape and tooth size.

The biological conflict that manifests itself in crowding of the teeth in man has fascinated orthodontists for generations. Correlations between tooth size and tooth arrangement can be shown, but such correlations tend to leave much unexplained in practical terms. The present report presents data from a preliminary examination of face size and shape and tooth size in boys and girls of 15-16 years, of which 47 had excellently arranged teeth and 91 showed crowding. Measurements were taken from lateral and posteroanterior cephalometric X-ray films and from dental casts. The statistical test used was the standard student t-test. Girls' faces were found to be on average significantly smaller than boys' whether the teeth were well arranged or were crowded. The comparisons of face size and shape of boys and girls with well arranged teeth with the faces of those with crowded teeth was less definite in its outcome. Girls' total tooth substance was on average significantly smaller than boys' whether the teeth were well arranged or crowded. Boys and girls with crowded teeth had a larger mean total tooth size than boys and girls with well arranged teeth.

Adolescent↗

PubMed1995

The mechanisms and mediators of tooth eruption--models for developmental biologists.

Tooth eruption is a localized process in the jaws which exhibits precise timing and bilateral symmetry. It involves resorption and formation of bone on opposite sides of the erupting tooth and these activities depend on the dental follicle, a thin connective tissue investment of the developing and erupting tooth. Biochemical studies have shown that during eruption cells, proteins and enzymes change in the dental follicle and several growth factors and proteins known to accelerate or retard eruption have been identified. This review discusses these aspects of tooth eruption and proposes testable hypotheses and strategies that can make studies of tooth eruption new experimental opportunities for developmental biologists.

Animals↗

PubMed1975

Selection of retainers in lower overlay denture-in relation to the abutment tooth mobility--(a laboratory study).

This study was done to evaluate the art of retaining the lower sub/complete, overlay denture, in relation to the abutment tooth mobility while the force was applied to the denture. The lower overlay denture was placed on a simulated model which was constructed of methylmethacrylate and silicone rubber. The author developed and used the special devices for measuring the tooth mobility. Results obtained were as follows: 1. When a force is applied directly to the abutment, the tooth mobility, i.e. the lateral excursion of the tooth, is markedly reduced according to the favorable ratio of the clinical crown to the root length. Splinting by the bar is effective to reduce the lateral excursion. 2. When a force is applied to the denture indirectly to the abutment tooth, the lateral excursion changes greatly according to the retainer selected. 3. The clasp retainer shows the greatest change in the lateral excursion against every loading on the denture. 4. All three types of bar attachment show the least value of lateral excursion.

Dental Abutments↗

PubMed1976

[Mechanical studies on the dental bridges by the finite element method. (1)--An abutment tooth model-- (author's transl)].

Biomechanical considerations are very important to design a prosthetic appliance; however, there have been no satisfactory quantitative studies of such problems, mainly because theoretical and experimental models are unable to represent exactly the natural conditions in the mouth. The finite element method has been successfully applied in each field of applied mechanics and found to be effective for the structural analysis of the biological systems, for it has the advantage of greater versatility for modelling. Accordingly, this analytical, computer-aided method was applied to the dental bridges to evaluate the loads transmitted to the abutment tooth and the stress distributions in the supporting tissues. As the preliminary study a two-dimensional model was constructed to simulate the tooth subject to a vertical and a horizontal load and a moment at the coronal portion. The stress distributions in the tooth and the periodontal membrane and the force distributions on the socket wall were calculated for three load conditions. The tooth mobility and the center-of-rotation position were compared with actual data available in some literatures and the characteristics of tooth support were discussed in terms of three spring constants.

Dental Abutments↗

PubMed1993

Changes in bone formation during experimental tooth movement after denervation of the rabbit inferior alveolar nerve.

The effects of nerve fibers on bone formation during tooth movement were examined using eight rabbits with denervation of inferior alveolar nerve (IAN). IAN on one side for all the animals was denervated and and sham operation was performed on the other side of denervation. The distance of tooth movement on the denervated and sham operated sides was very similar and 1.20 +/- 0.17 and 1.24 +/- 0.12 (mean +/- S.D. mm), respectively. From the fluorescent observations, the denervated and sham operated sides in the animals without tooth movement i.e. control group showed similar morphology. The animals with tooth movement i.e. experimental group showed significant new bone formation than the control group. However, the amount of new bone formation on the denervated side was less than the sham operated side. It was suggested that the nerve fibers might play some roles on bone formation during the tooth movement.

Alveolar Process↗

PubMedDate not supplied

[Guided impression in tooth preparation for the application of full veneer crowns].

In this study the authors emphasize the importance of the guiding impression for checking the depth of the tooth preparation for full veer crowns. For this purpose they took two impressions in heavy-body silicone before any tooth preparation was made. One of these impressions was cut from the buccal to the lingual aspect across the middle of the imprint of the tooth to be prepared. The other one was cut horizontally in a cervical and an occlusal half. We kept and repositioned from time to time over the preparation in order the distal half of the first impression and the cervical half of the second one to check for the adequate tooth reduction. This method of checking the tooth reduction is useful especially for undergraduates and young practitioners and has better results than the articulation paper.

Crowns↗