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At least 721 records · Page 40Linked to original sources

PubMed1998

Association of occlusal, periodontal, and dietary factors with the presence of non-carious cervical dental lesions.

PURPOSE: To investigate in vivo the relationship of occlusal stress factors, periodontal health status, and acidic dietary patterns to the presence of non-carious cervical lesions (NCCL) in a convenience sample of undergraduate clinic, adult dental patients. MATERIALS AND METHODS: Forty three subjects who met the entry criteria were admitted into the study; 178 teeth exhibiting NCCL were evaluated. A dietary assessment focusing on acidic food/beverage intake was used to evaluate nutritional intake over the most recent 24-hour period. Periodontal evaluation included intraoral measurement of gingival attachment loss, assessment of tooth mobility, and radiographic interpretation of percent bone loss using the Schei ruler method. Among the occlusal factors evaluated were shape and orientation of NCCL, presence and location of wear facets, and symptoms and characteristics of centric and eccentric occlusal function. RESULTS: 95% of teeth examined exhibited functional wear facets, indicating a systematic relationship with presence of NCCL (Chi Square = 16.9, P < 0.0001); 48% displayed buccal or incisal facets; 64% were accompanied by balancing interferences in lateral excursion; 98.3% had mobility scores < or = 1; there was no significant association between mobility and facets present (Chi Square = 3.04, P = 0.21); and, no relationship with dietary patterns was found. Group function, that may evolve with age, and/or traumatic occlusion factors may be related to etiology of NCCL. Longitudinal controlled clinical trials are needed to confirm suspected etiologies and establish treatment guidelines for non-carious cervical lesions.

Adult↗

PubMedDate not supplied

Clinical evaluation of a resin-modified glass-ionomer adhesive system.

One hundred cervical caries-free, nonundercut lesions were restored in 13 patients of mean age 60.5 years, using Silux Plus or Estio LC resin composite bonded with Fuji Bond LC. Patients were recalled at 6 months and 1 year. A 1-year cumulative retention rate of 98% was recorded, while marginal staining was absent.

Adult↗

PubMed2005

Alternative dental measurements: proposals and relationships with other measurements.

Most archaeological and fossil teeth are heavily worn, and this greatly limits the usefulness of tooth crown diameter measurements, as they are usually defined at the widest points of the crown. There are alternatives, particularly measurements at the cervix of the tooth, where the crown joints the root, and measurements along a diagonal axis in molars, that are much less affected by wear. These would allow a wider range of specimens to be included, e.g., in the study of dental reduction in Upper Palaeolithic and Mesolithic Homo sapiens. In addition, they would allow the little-worn teeth of children to be compared directly with well-worn teeth in adults. These alternatives, however, have been little used, and as yet there have not been any studies of the repeatability with which they can be measured, or of the extent to which they are related to the more usual crown diameters. The present study is based on a group of unworn teeth, where direct comparisons could be made between the alternative measurements, which are not much affected by wear, with the usual crown diameters, which are very much affected. In an interobserver-error study of this material, cervical and diagonal measurements could be recorded as reliably as the usual crown diameters. The buccolingual cervical measurement was strongly correlated with the normal bucclingual crown diameter in all teeth, whereas the mesiodistal cervical measurement was highly correlated with the normal mesiodistal crown diameter in incisors and canines, but less so in premolars and molars. The molar diagonal measurements showed high correlations with all other measurements. Crown areas (robustness index) calculated from the usual diameters were strongly correlated with crown areas calculated from cervical measurements, and crown areas calculated from molar diagonals were strongly correlated with both other areas. Despite the long usage of the more usual maximum crown diameters, the alternative dental measurements could be measured just as reliably, could record similar information about tooth crown size, and would be better measures for the worn dentitions seen in archaeological and fossil material.

Fossils↗

PubMed1991

Tooth bleaching: its effect on oral tissues.

After investigating the literature, we suggest these guidelines for tooth bleaching: If bleaching solutions of high concentration are used, prevent accidental exposure of gingival tissues to the solutions by use of a rubber dam. If using lower concentrations of bleaching solutions, avoid long-term exposures to gingival tissues. To maintain pulp vitality, keep bleaching time and temperatures to a minimum. Check teeth for exposed dentin and enamel fractures. Advise patients that thermal sensitivity may occur after the bleaching procedure and may persist for several days. Prescribe premedication with an anti-inflammatory drug, when necessary. Avoid bleaching the cervical area of the tooth by covering the area with a base to avoid cervical resorption. Avoid dentin exposure by noting that abrasive bleaching techniques can remove significant amounts of enamel. Take special care when bleaching enamel--especially near the cervix of the tooth, where the enamel is thin.

Dental Enamel↗

PubMed2004

Enamel hypoplasias and physiological stress in the Sima de los Huesos Middle Pleistocene hominins.

This study presents an analysis of linear enamel hypoplasias (LEH) and plane-form defects (PFD) in the hominine dental sample from the Sima de los Huesos (SH) Middle Pleistocene site in Atapuerca (Spain). The SH sample comprises 475 teeth, 467 permanent and 8 deciduous, belonging to a minimum of 28 individuals. The method for recording PFD and LEH is discussed, as well as the definition of LEH. The prevalence of LEH and PFD in SH permanent dentition (unilateral total count) is 4.6% (13/280). Only one deciduous tooth (lower dc) showed an enamel disruption. Prevalence by individual ranges from 18.7-30%. The most likely explanation for the relatively low LEH and PFD prevalence in the SH sample suggests that the SH population exhibited a low level of developmental stress. The age at occurrence of LEH and PFD was determined by counting the number of perikymata between each lesion and the cervix of the tooth. Assuming a periodicity of nine days for the incremental lines, the majority of LEH in the SH sample occurred during the third year of life and may be related to the metabolic stress associated with weaning.

Aging↗

PubMed1998

Histotomography of the odontoblast processes at the dentine-enamel junction of permanent healthy human teeth in the confocal laser scanning microscope.

The translucency of teeth allows the non-destructive subsurface visualisation of their microstructure by confocal laser scanning microscopy (CLSM) at a level of about 150 microns below the surface. The dentine-enamel junction (DEJ) is accessible only directly adjacent to the cervix of the tooth. Therefore teeth have to be sectioned for studying marginal areas of the dental hard tissue. The potential of the technique for (pseudo) three-dimensional visualisation allows the study of an array of individual confocal images, the interpretation of which is similar to that of macroscopic tomographs (CT-scan, MRI). Additionally, the extended focus mode yields the overlay of individual confocal images in the form of a two-dimensional projection. This mode of operation proved to be particularly suited for the visualisation of odontoblast processes in their whole extension. The three-dimensional junction between enamel and dentine, the branches of the odontoblast processes and their interactions with the DEJ is demonstrable by CLSM without staining or other procedures of sample preparation. The direct microscopic comparison between samples, either fresh or kept in a humid chamber, and Technovit-embedded sample blocks gives evidence that the risk of artefacts by sample storage or by the embedding procedure is minimal. The tomographs limited to subsurface areas of the tissue also exclude mechanical surface artefacts due to grinding or cutting.

Dental Enamel↗

PubMed1989

[Distortion of working models using different silicone impression techniques].

The influences of differing strains levels of impression materials in compression and impression techniques on the distortion of working models were examined. The working models, which differed in the size of cervical spillway (2mm and 9mm) and the impression techniques applied (the two-phase technique and the wash technique), were produced by using putty-type impression materials with three different strain levels (Reprosil, Express and Exaflex) following the metal master model of mandibular denture in an abutment form. Distortion of the working models was then measured by a three-dimensional measuring system. The results were as follows. 1) The models produced through the impression technique using hard impression materials with low strain levels displayed decreases both in the degree of inclination to the X axis of the abutment tooth variations distance between the left and right abutment teeth. This procedure was found to yield a model which was proximate to the master model. 2) The impression technique incorporating a small cervical spillway resulted in decreases in variations in the distance between the right and left abutment teeth and the diameter of the molar part of the abutment tooth, and the horizontal distortion of the alveolar ridge; the model thus produced was found to be proximate to the master model. 3) Application of the two-phase technique reduced variations in height of the abutment tooth, and the use of the wash technique led to decreased variations in the distance between the right and left abutment teeth and diameter of the molar cervix of the abutment tooth. 4) Differences in strain levels of putty-type impression materials, the size of cervical spillway and the impression technique used did not influence deviation of the model toward the Y axis (vertical direction). 5) The models with least distortion of the abutment tooth were obtained by the two-phase technique using hard impression materials with lower strain levels or by the wash technique using soft materials with higher strain levels.

Dental Impression Materials↗

PubMed2004

The bitewing radiograph as an assessment tool in fixed prosthodontics.

Molar crown preparations, as described in the literature, have standard forms dictated by the demands of retention, resistance and the physical properties of materials. Standard designs may not be appropriate for all patients because of ethnic variations in tooth shape, pulp size and dentine thickness. Accurate data on these features could assist clinicians to minimize the risk of accidental pulpal injury. The aim of this study was to compare the first molar crown and pulp dimensions between Asian (Chinese, Korean, Malay) and other ethnic groups, using measurements from the bitewing radiographs of 121 subjects. Comparisons revealed the following significantly different features of Asian first molars: larger total pulp areas in uppers (P < 0.0005); shorter crowns (P < 0.0005); narrower upper teeth at the cervix (P < 0.0005); wider pulps at the cervix of lowers (P < 0.02); more bulbous crowns (P < 0.0005 for uppers; P < 0.01 for lowers), and finally significantly thinner dentine interproximally at the cervix (P=0.001 for uppers; P=0.011 for lowers). Preparations with wide shoulders could pose hazards to the pulps in Asian subjects. This study emphasizes the value of bitewing films in assessing crown and pulp size and shape before making crown preparations. The experienced practitioner may intuitively include tooth and pulp morphology in treatment planning, but this appears not to be taught or documented in textbooks.

Adult↗

PubMed1990

[Effect of coronal gingival contour on contact between food bolus and cervical tooth surface during mastication].

At the coronal cervix, the so-called uncleaned area, the path of the food bolus and its rubbing effect are said to be regulated by the coronal and gingival contours. However, it has not been ascertained whether such regulation really exists. So, the force which was generated by a food bolus rubbing on the buccal surface was measured at the height of the cervical third of the lower first molar with a load cell inserted into the denture. The results obtained were as follows: 1. Cervixward forces were observed in the closing phase and cuspward forces, in the opening phase during mastication. The intensity of cervixward forces was stronger than that of the cuspward ones. And the occurrence of the former was more frequent than that of the latter. 2. The intensity and frequency of cervixward forces differed according to the kind of food. 3. Cervixward force under the degree of convexity of 0 mm was stronger in intensity and more frequent than that under the degree of convexity of 0.5 mm. 4. Cervixward force under the marginal gingiva thickness of 1 mm was stronger in intensity and more frequent than that under the marginal gingiva thickness of 2 mm.

Bite Force↗

PubMed2003

[Two-dimensional finite element stress analysis of simulating restored teeth with wedge-shaped defects under loads].

OBJECTIVE: To study the concentration of stresses at the cervix with simulating restoration of tooth defects. METHODS: A two-dimensional finite element model of a mandible first premolar with defect from longitudinal section was developed. The model was simulatedly restored, respectively by composite resin and glass ionomer cement, and then investigated stress variation in the cervical area. RESULTS: In the restored models, both of materials improved the concentration of stresses at the cervical area. The composite resin and the glass ionomer cement restorations made the maximum principal stresses declined respectively to 36.2 MPa and 42.5 MPa, which were close to the value of normal tooth in the deepest area of defects. CONCLUSION: The concentration of stresses are improved in the cervical area with teeth defects restored.

Composite Resins↗

PubMed2001

Clinical application of computer-aided rapid prototyping for tooth transplantation.

The maintenance of healthy periodontal ligament cells in the donor tooth is one of the most important factors for successful tooth transplantation. This is achieved by minimizing the extraoral time during the surgical procedure. If a duplicate form of donor tooth could be obtained before extraction, it would be possible to precontour the recipient alveolar bone compatible with the donor tooth, and thereby reduce the extra-oral time of the donor tooth. We obtained a three-dimensional image with the real dimensions of the donor tooth from a CT Highspeed Advantage, allowing a life-sized resin model of the tooth to be fabricated. From 22 clinical cases, we achieved an average total transplantation time of 7.7 min. The average distance between the transplanted root surface and the alveolar bone from 12 available cases was 0.87 mm at the mesial cervix, 0.91 mm at the mesial apex, 0.98 mm at the distal cervix and 1.16 mm at the distal apex on the postoperative radiographs. Clinical data indicate that computer-aided rapid prototyping may be of value in minimizing the extra-oral time and possible injury to transplanted tooth during the process of autotransplantation.

Adult↗

PubMed1980

Sensory differences between crown and root dentin in human teeth.

Earlier ultrastructural investigations of human teeth have revealed differences in the innervation between crown and root dentin. In the present investigation, an intradental comparison of human teeth was made to estimate the sensitivity to different stimuli applied to two cavities, one in the buccal cusp and the other half-way between the cervix and the apex of the tooth. It was found that the pain produced by the different stimuli in the cuspal cavity was described as "sharp" or shooting, while the same stimuli applied to the root cavity provoked "dull" pain, often of a longer duration. Gentle stimuli, such as dry absorbent paper, only produced pain in the cuspal cavities. Ultrastructural examination revealed no nervous elements in the vicinity of the ground surface of the tested cavities in the crown or in the root. Odontoblastic cells including nuclei, were a common finding in the dentinal tubules of both the roots and the cusps, indicating aspiration of these cells. In some cases, in the cuspal areas, accompanying nerve-fibres had also been aspirated. The conclusion of the present investigation is that there are differences in sensibility between crown and root dentin. These differences are observed in both intensity and modality, supporting earlier findings of morphological discrepancies in the innervation of the coronal and root dentin.

Adolescent↗

PubMed1989

[Experimental study on the effect of replantation of immature permanent teeth on the periapical and periodontal tissues].

Replantation and semi-rigid fixation were performed on canine immature permanent teeth, and one week after replantation the teeth were treated by root filling with calcium hydroxide. The root apex and periodontium of the teeth with replantation were examined for changes regularly during the experiment by microradiographic, fluorescence microscopic, polarizing microscopic and X-ray observation of undecalcified horizontal continual ground sections. The results obtained were as follows: 1) Immediately after replantation, root formation was observed, but its formation was found to cease at a relatively early time. No site of the root showed any inflammatory resorption. 2) The dentine of the teeth with replantation was narrow, and the whole tooth substance showed discoloration due to penetration of calcium hydroxide. 3) the periodontal space surrounding the teeth with replantation was decreased daily by new bone actively formed from the alveolar bone proper and by a thin cementum layer added on the periodontal surface. This change occurred from one week after replantation. 4) The width of the periodontal space of the teeth with replantation, which had been wider than that of a control tooth, was increased and decreased daily at the cervix and root apex and the central part of the root, respectively. 5) Collagen fibers of the periodontal membrane were present in the periodontal space of the teeth with replantation, together with regeneration of the periodontal membrane that had been cut by extraction. 6) There were no changes due to replantation in the two teeth adjacent to the tooth with replantation or the lateral jaw.

Cuspid↗

PubMedDate not supplied

A histological reconstruction of dental development in the common chimpanzee, Pan troglodytes.

Much is known about the dental development of Pan compared with that for other extant great apes. The majority of information available has concentrated either on the emergence times of teeth or on the sequence of mineralization stages of the teeth as revealed from radiographs. However, the problems of defining stages of tooth formation sufficiently accurately on radiographs are only now becoming recognized. All of the data available to date suggest the presence of a more variable picture for the timing of mineralization stages in chimpanzees than for the timing of tooth emergence. In particular, arguments persist in the literature over the time of initial mineralization and the time it takes to form each anterior tooth crown in chimpanzees. Therefore we attempt to provide a more precise chronological time scale for dental development in our closest living relative. Furthermore, we examine the sequence of molar cusp formation relative to enamel formation times related specifically to those cusps and to try to tie these data in with information from functional studies of molar crowns. Histological sections of 14 maxillary and 28 mandibular teeth from four chimpanzee (Pan troglodytes) individuals and three molar teeth from three chimpanzees of unknown origin were prepared in accordance with a well-established protocol. By combining data on short-period and long-period incremental lines (including daily secretion rates, periodicity, prism lengths and enamel thickness) in both enamel and dentine, we reconstruct times for the onset and duration of crown formation as well as construct a schedule for the pattern and timing of dental development in this one hominoid species. Interestingly, our histologically-derived data confirms that the data from radiographic studies underestimate crown formation times by the following amounts for each tooth type: I1 2.5 years, I2 3.1 years, C 1.6 years, P3 1.9 years, P4 0.1 years, M1 0.8 years, M2 1.1 years and M3 0.3 years. When combined with data on gingival emergence, it seems that chimpanzee teeth have a greatly reduced time for root growth before emergence occurs and that the major differences between Homo sapiens and Pan lie in the first part of the root formation rather than in the total period of crown formation. Maxillary and mandibular molar functional cusps take longer to complete enamel formation to the cervix than any other cusp in that same tooth, which makes sense as these cusps are thick enamelled. These results suggest that new links can be made between developmental aspects, occlusal morphology and tooth function.

Aging↗

PubMed1989

[Clinical and histopathological observation of CaO-P2O5-MgO-SiO2-CaF system glass ceramic tooth implants in monkeys].

The present study was undertaken to determine the biocompatibility of a newly-developed CaO-P2O5-MgO-SiO2-CaF system glass ceramic tooth implant. Two adult male monkeys were selected and 12 weeks after extraction of M1 and P1, 8 glass ceramic teeth were implanted into alveolar bone. At 1 week after implantation, 6 teeth were allowed occlusal function, and 2 teeth were left free from occlusion as control teeth. The implants were observed for 4-12 weeks and examined histopathologically. The results were as follows: 1. Seven implanted teeth were well maintained clinically, and only one tooth was lost after 5 weeks. 2. In histopathological observation, implanted teeth were surrounded by bone, and connected by bonyankylosis. At cervix of dental implant, connective tissue as also attached firmly to implanted tooth surfaces and epithelial attachment was observed. 3. Although these implants were allowed occlusal function at an early stage (1 week after implantation), osteogenesis around implants was not disturbed. These results suggest that the new glass ceramic implant has good biocompatibility and is useful as an implant tooth.

Acrylic Resins↗

PubMed2005

Cementum on Smilodon sabers.

The maxillary canines of Smilodon californicus Bovard, 1907 have a deeply curved cementoenamel junction. The gingiva of modern cats is attached to the tooth at the cementoenamel junction and provides tactile and other dental information to the animal. The presence of cementum at the cervix of the maxillary canines, also called sabers, would indicate that the gingiva in Smilodon was attached in this region. Such an attachment would be advantageous, providing stability and sensory input for the large tooth. Also, gingiva at the cervix would impact the manner in which the teeth were used. Previous study using scanning electron microscopy of dental casts was indirect. The purpose of this study was to confirm by direct methods the presence of cementum at the cervix of Smilodon californicus sabers. Parts of three Smilodon californicus sabers were sectioned and examined with light and scanning electron microscopy (EDS). In addition, percent weight of calcium and phosphorus was measured in enamel, dentin, and cementum using electron dispersive spectroscopy. Cementum was identified in the cervical region of each saber. Spectroscopy confirmed that the tissue is calcified and the mineral is hydroxyapatite. Percent calcium and percent phosphorus of individual tissues were highly variable between specimens. However, the ratios of calcium to phosphorus were not significantly different from the hydroxyapatite standard. In the future, bite models will have to take the presence of soft tissues into account.

Animals↗

PubMed2006

Eradication of intra-amniotic Streptococcus mutans in a woman with a short cervix.

BACKGROUND: Microbial invasion of the amniotic cavity (MIAC) remains an important pathogenetic factor in preterm births. Although most MIACs seem to originate in vaginal microflora, other reservoirs such as the oral microflora have been suggested. CASE: We report a case of successful eradication of Streptococcus mutans (a bacterium generally found in dental plaque) from the amniotic cavity, using ampicillin, gentamycin, and azythromycin in a woman who presented with threatened preterm labour and a short cervix at 25 weeks' gestation. She delivered at 34 weeks' gestation and was treated for tooth decay 12 weeks after delivery. CONCLUSION: Intra-amniotic infection should be suspected in the presence of a short cervix during the second trimester. Appropriate parenteral antibiotics can eradicate intra-amniotic infection and potentially prolong pregnancy.

Adult↗

PubMed1991

Material parameters and stress profiles within the periodontal ligament.

Levels and profiles of initial stress in the periodontal ligament after application of various force systems were studied. Two finite-element models, based on sections of human autopsy material, were developed to simulate one full and one partial mandible. The validity of the finite-element model was improved by identification of material parameters; the mechanical properties of the tissue were described by means of strain-gauge measurements of initial tooth movements in human autopsy material. The multiple modeling technique, in which data from a coarse global model are transferred to a more detailed one, was used to identify bone structure and boundary conditions. Parameters known to influence the results were varied to establish the validity of the finite-element model. Iterative calculation methods were used to gain stable results. However, optimizing features of the bone structure and boundary conditions did not influence the results significantly. The elastic stiffness of the periodontal ligament was determined to 0.07 MPa and tau = 0.49 (tau being the Poisson's ratio). Stress profiles were obtained for various force systems--as in tipping, translation, and root movement. As we expected, there was a marked variation in the stress distribution from cervix to apex when tipping forces were applied. Bodily movement of the tooth produced an almost uniform stress distribution; root movement produced stress patterns opposite to those observed during tipping; and masticatory forces alone produced stress patterns almost identical to those achieved by masticatory force in combination with orthodontic forces.

Adolescent↗