PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Tooth”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1989

A morphometric study of bone and tooth volumes in the pipid frog Xenopus laevis (Daudin), with comments on the importance of tooth resorption during normal tooth replacement.

Volumetric estimations of teeth and bone on serial sections using a semiautomatic image analyzer indicate that, in the polyphyodont dentition of the pipid anuran Xenopus laevis (Daudin), the mean volume of the dentine composing the teeth is about 23.5% of the volume of the supporting maxillae and premaxillae. During tooth replacement, osteoclasts resorb up to 98% of the dentine. Teeth may be resorbed rather than shed in order to conserve tooth constituents because, if shedding of complete teeth did occur, a quantity of calcified tissue equal to perhaps 45 times the volume of the bone of the upper jaw might be lost over an animal's projected life span of about 13-15 years.

Animals↗
PubMed1989

[Biomechanical study on orthodontic tooth movement: changes in biomechanical property of the periodontal tissue in terms of tooth mobility].

The magnitude of tooth mobility has been frequently used for evaluating biomechanical response of the periodontal tissue to applied forces. However, tooth mobility during orthodontic tooth movement has not been measured. The purpose of this study was to investigate changes in biomechanical property of the periodontal tissue during canine retraction, in terms of tooth mobility. The upper canines on both sides of ten orthodontic patients were moved in the distal direction for about four weeks with an initial force of 200 gf. An amount of tooth movement and a magnitude of tooth mobility were measured every 3 or 4 days during retraction. A distally directed force up to 500 gf was continuously applied to each canine and tooth mobility was measured with a noncontact type of eddy current displacement sensor. A two-dimensional finite element model was constructed and displacements of the finite element model were calculated with various Young's moduli in loading with a 100 gf force in the distal direction. In comparison with the magnitudes of the tooth mobility, Young's modulus of the periodontal membrane before retraction and the influence of the biomechanical factors on changes in tooth mobility were investigated. The tooth movement curve was divided into three phases; an initial phase, a lag phase and a post-lag phase. The magnitudes of tooth mobility at the initial phase were significantly larger than those before retraction within the range of 250 gf to 500 gf and these magnitudes decreased during the lag phase. The magnitudes of tooth mobility at the post-lag phase significantly increased, within the range of 50 gf to 500 gf, than those before retraction. As a result of curveliniar regression analysis, the tooth mobility curves approximated to delta = AFB, where delta and F denote tooth mobility and force respectively. The coefficients A and B changed according to the phases of tooth movement. An inclination of the tooth mobility curve expressed by a tangent at the 400 gf force was the largest at the initial phase, and this inclination at the 100 gf force was the largest at the post-lag phase. Young's modulus of the periodontal membrane before retraction was determined to be approximately 35 gf/mm2 and Young's modulus of the periodontal membrane was the most important factor on the increase of tooth mobility. Tooth mobility significantly varied associated with tooth movement. It was indicated that biomechanical property of the periodontal tissue changes in response to each phase of tooth movement. In particular, Young's modulus of the periodontal membrane decreased at the post-lag phase of the orthodontic tooth movement.

Cuspid↗
PubMed1990

[Process of the tooth brushing habit formation in children. 2. Factors forming the behavior of tooth brushing in children].

The purpose of this study was to find in the factors forming the habit of tooth brushing in children. Questionnaires about the habit of tooth brushing were collected in Nagoya and the suburbs from mothers of kindergarten pupils aged from one to six. These data were analysed by the second class of Hayashi's quantifying theory. The results of this study were summarised as follows: 1. Habit of tooth brushing: 1) A high correlation ratio was obtained in the discriminatory efficiency of the habit of tooth brushing, at ages one to three this was 0.44 and for ages four to six it was 0.47. 2) The following six items were chosen in relation to the habit formation of tooth brushing at ages one to three, "motive for starting tooth brushing", "frequency of tooth brushing per day on the average", "co-operative of the child towards its mother's help", "positive attitude towards tooth brushing", "experienced guidance in tooth brushing from its mother", "experienced guidance in tooth brushing from a dentist or dental hygienist". 3) Similarly for ages four to six, the following four items were chosen, "frequency of tooth brushing per day on the average", "persons who actually brush the children's teeth at night", "attitude of the child towards tooth brushing", "experienced guidance in tooth brushing from a dentist or dental hygienist". 2. Ability of tooth brushing: 1) A comparative high correlation ratio was obtained in the discriminatory efficiency of the ability of tooth brushing, at ages one to three this was 0.37 and for ages four to six it was 0.20. 2) The following five items were chosen in relation to the ability of tooth brushing at ages one to three, "age", "motive for the start of tooth brushing", "mother's attitude to child not brushing its teeth", "frequency of using tooth paste", "experienced guidance in tooth brushing from a dentist or dental hygienist". 3) Similarly for ages four to six, the following five items were chosen, "age", "persons who actually brush the children's teeth at night", "co-operative attitude of the child towards its mother's help", "attitude of the child towards tooth brushing", "frequency of using tooth paste".

Age Factors↗
PubMed1991

Tooth dislocation: the relationship with tooth wear and dental abscesses.

Tooth dislocation (tilting) was recorded in 1,200 skulls from 34 museum collections. The findings of dislocation by tooth type, tooth wear, and abscess location are presented. A model for dislocation based upon the progressive loss of tooth support provides a rational explanation for the phenomenon. Physiological continuous tooth eruption was considered to account for a component of the progressive loss of tooth attachment. The process of attrition, pulp perforation, and dental abscess cavity formation resulted in further, more severe loss of tooth support. Heavy functional forces, in association with greatly reduced bone support, tilted the crown lingually and root buccally. When the tooth had tilted to such an extent that the root apices protruded from the bone and, presumably (in life) through the gingival/mucosal tissues, the infected root canals were effectively isolated from the internal environment. The tooth continued to function. The more typical consequence of severe attrition and dental abscess formation was tooth loss; it also isolated an infected tooth from living tissue, but without the benefit of retaining function.

Bicuspid↗
PubMed1991

Tooth crown heights, tooth wear, sexual dimorphism and jaw growth in hominoids.

The aim of this review is to bring together data that link tooth morphology with tooth function and tooth growth: We aim to show how the microanatomy of hominoid teeth is providing evidence about rates of tooth growth that are likely to be a consequence of both masticatory strategy and social behaviour. First, we present data about incisor and molar tooth wear in wild short chimpanzees that demonstrate how crown heights are likely to be related to relative tooth use in a broad sense. Following this we review recent studies that describe the microanatomy of hominoid tooth enamel and show how these studies are providing evidence about tooth crown formation times in hominoids, as well as improving estimates for the age at death of certain juvenile fossil hominids. Next, we outline what is known about the mechanisms of tooth growth in the sexually dimorphic canine teeth of chimpanzees and compare these patterns of growth with tooth growth patterns in the canines of three fossil hominids from Laetoli, Tanzania. Finally, we discuss how selection pressures that operate to increase or reduce the size of anterior teeth interact with jaw size. We argue that the space available to grow developing teeth in the mandibles of juvenile hominoids is determined by the growth patterns of the mandibles, which in turn reflect masticatory strategy. The consequences of selection pressure to grow large or small anterior teeth are likely to be reflected in the times at which these teeth are able to emerge into occlusion.

Animals↗
PubMed1989

[A study on tooth marks--morphological differences between dentitions and tooth marks thereof and selection of measurement items effective in identification].

Tooth marks in human skin assume so various aspects depending upon such factors as the forms and properties of the bitten regions that they do not necessarily represent the dentition of a suspect as it is. In the present study a cylindrical dummy with skin-like elasticity was used as a recording medium on which to make experimental tooth marks. Morphological comparisons were made of the tooth marks with the oral models by the use of measurements of 28 items. Furthermore, the selection of the effective items for identification was also considered by applying the discriminant analysis to the rate of morphological change on the base of the measurements. The results obtained were as follows: 1) In respect of the tooth marks and the oral models derived from the same subject, the values of their difference (i.e., the measured value of the former minus that of the latter) were calculated for each item so that the directional changes of the tooth marks should be investigated. It was found that the values for the lengths of the dental arch showed a tendency to be positive and that those for the widths negative, and that the values for the angles of lateral incisors and canines tended to be positive. 2) Among the mean values of the rates of morphological change for each item on the same subject, those for the lengths of the dental arch were larger, whereas those for the widths were smaller. Regarding the widths of tooth edge, large were those values for the mandibular canines in particular. 3) The identifying indices were calculated from the rate of morphological change on the basis of the measured values for 28 items in 400 combinations of the oral models with the tooth marks. They indicated that, out of the combinations derived from different subjects, 11.3% for maxillary overlapped those from the same subject and so did 8.7% for mandible in the distribution of their indices. 4) A discriminant analysis was carried out for identification. The range of coefficients thereby obtained rendered it possible to consider how much each item contributed to identification. As a result, the range of the inter-canine distance was largest. It could be considered that these items are effective in identification for tooth marks by using measurements.

Bites, Human↗
PubMed1990

[Experimental study of bone resorption after tooth extraction with implanted hydroxyapatite tooth root substitute].

Hydroxyapatite (HAP) tooth root substitute implantation have been applied to extraction sockets in many studies for purpose of preservating alveolar bone. Dimensional changes were measured with sectioned study cast of cephalometric X-ray photo. In this study, dimensional changes were determined by newly developed evaluation system which utilizing image analyzer (Immunomedica Co., Ltd.), in a view of conserving alveolar ridges beneath the denture base. Cone shaped HAP tooth roots (5 or 6 mm in length) were implanted to one subject and disk-like shaped HAP tooth roots (2 mm in length) were also implanted to the other subject. Preservation of alveolar bone was observed in both shaped HAP tooth roots implanted site compared to control site. Bony ankylosis between HAP tooth root and alveolar bone, observed on 1 month after histological specimens, may contribute to this result. Smaller changes of blood flow compared to controls were obtained on implanted site, which were measured with Laser Doppler blood flow meter (Perimed KB; Sweden) on buccal mucosa. We consider that HAP shows good biocompatibility and HAP tooth roots implantation decrease the wound volume consequently.

Alveolar Bone Loss↗
PubMed1978

[Scanning electromicroscopic studies of the surface of teeth. I. After manual treatment with tooth cleansers. II. Tooth cleaning with power-driven instruments].

Scanning electron microscopic examination of tooth surfaces after using manually operated instruments to remove calculus showed distinct lesions on the hard substances of the tooth. The extent of damage depends considerably on the area of the tooth treated (the border between the enamel and the cementum is particularly endangered), the amount of force used, and the length of time required for treatment. Examination of tooth surfaces following application of various types of power-driven scaling instruments revealed that lesions of the hard substances on the tooth are possible. The extent of the damage depends on several different factors, particularly the pressure applied and the area of the tooth treated. The border between the enamel and the cementum is particulary endangered.

Dental Cementum↗
PubMed1990

[A study on tooth preparation by means of the newly developed parallelometer and its educational effect, with primary regard to convergence angles of abutment tooth].

Proper tooth preparation is one of the fundamental requirements in crown & bridge prosthodontics. However, it is difficult for students in particular to prepare adequate convergence angles of abutment tooth in the limited environment of patient's mouth. Therefore, the parallelometer was developed to improve the preparations as a supplementary device which informs the person by a signal of alarming simultaneously when a bur is not properly installed to convergence angles of abutment tooth. Sixty subjects were selected from students of Kanagawa Dental College and they were divided into two groups (A and B) to prepare abutment tooth of lower right 1st molar for full cast crown on typodont mounted into the manikin. A preliminary training was performed for once without the parallelometer for group A and with it for group B prior to a comparative experiment. The following results were obtained with primary regard to convergence angles of abutment tooth. 1. Related to each of four convergence angles, group B is superior to group A in all mean values with a statistical significance (P less than 0.01). 2. Related to a total of four convergence angles by the maximum number of subjects, group B is also superior to group A in a mean value by about ten degrees. 3. A newly developed parallelometer proved to be an efficient supplementary device for training of students to master a technique of preparation for adequate abutment tooth.

Crowns↗
PubMed1989

[Anatomical studies on a supernumerary tooth considered to be a successional tooth of the lower first molar].

The purpose of this study is to investigate features of the successional tooth of the lower first molar. Materials investigated in this study deal with a supernumerary tooth formed at the distolingual deep part to the lower right first molar of a male patient aged twenty-four. It was observed with binocular microscopy and under X-ray. The occlusal surface of it was observed with scanning electron microscopy. Horizontal ground sections of it were prepared and observed with polarizing microscopy, fluorescent microscopy, and scanning electron microscopy. It is thought that this supernumerary tooth is a true successional tooth of the lower first molar because it was formed at the distolingual deep part to the lower first molar and the fissure of it is Y-shaped and it has five cusps. It is considered that two impressions at buccal and distal surfaces of it isn't original hereditary features but was accidentally formed by pressures of mesial and distal roots of the lower first molar. The rough form of it has most resemblance to the lower second premolar and distal and lingual parts of it are smaller than that of the lower first molar. But fundamental features of the lower first molar are preserved in it. It is thought that the center of the molarization field of human lower successional teeth lies at the successional tooth of the lower first molar because the form of the occlusal surface of it is more complex and functional than those of the lower first and second premolars.

Adult↗
PubMed1986

Influence of changes of tooth temperature on reflex and central activity evoked by stimulation of tooth pulp afferents.

The importance of the temperature of the dentine was studied in teeth prepared for electrical stimulation. During experiments with the mouth open, the temperature of teeth covered by cement was normal. The digastric EMG and the brainstem--evoked response following electrical stimulation of the tooth pulp as well as the threshold for eliciting a jaw-opening response remained constant throughout prolonged experiments. However, heat produced by the cement used to fixate the tooth electrodes could have damaged the tooth if the dentine temperature had exceeded 45 degrees C. A careful preparation of the tooth pulp by repeated application of thin layers of cement allowed an adequate preparation without damage to tooth pulp afferents.

Animals↗
PubMed1975

The use of laser beams for measuring tooth mobility and tooth movements.

The laser reflexion method, a direct contactless measuring technique with a high accuracy, has been applied for clinical purposes. A prototype has been tested using a laser beam to illuminate a patient's tooth fixed to the equipment by an impression plate. The reflected patterns were thrown onto a screen with a coordinate system and photographically recorded, and the movement of the tooth has been geometrically calculated. The relapse tendency after orthodontic treatment of a patient with periodontal disease and parafunctions was studied by repeated measurements of the left medial upper incisor. By use of the method, it was possible to observe that the velocity of the studied tooth was highest during the 1st day and, besides the horizontal movement, a rotation of the tooth began at the end of the measuring period.

Adult↗