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This article explains what is needed for successful extraction of diseased cheek teeth and how to realign the occlusal surface. Incisor teeth procedures and correcting abnormalities of cheek tooth crown wear are also discussed along with wolf and floating teeth.
AIM: To compare the bleaching efficacy of three different types of sodium perborate (SP) commonly used for intracoronal bleaching of discoloured non-vital teeth. METHODOLOGY: Sixty-five extracted human maxillary central incisors with intact crowns were used. Following obturation with gutta-percha and a root canal sealer using a lateral condensation technique, the coronal aspects of the root canal fillings were covered with a 1-mm thick protective base placed to a level 1 mm apical to the labial cemento-enamel junction (CEJ). The teeth were than stained artificially with fresh blood over a period of 18 days. One or other of the bleaching materials (group 1: SP monohydrate + water, group 2: SP trihydrate + water, group 3: SP tetrahydrate + water, group 4: SP monohydrate + hydrogen peroxide (HP), group 5: SP trihydrate + HP, group 6: SP tetrahydrate + HP) were placed in the pulp chamber of the discoloured teeth and sealed with Cavit for 21 days. They were replaced with fresh preparations after 3, 7 and 14 days. The shades of the tooth crowns were evaluated at baseline and at 7, 14 and 21 days. Comparison of tooth shades was completed at each interval and analysed statistically using the chi-squared test. RESULTS: There was no statistically significant difference between the groups at 7, 14, 21 days. Period of bleaching significantly affected the outcome (P < 0.01). No colour changes were noted in the control teeth. CONCLUSION: The data obtained from this study demonstrate that sodium perborate can be used mixed with water rather than with hydrogen peroxide for bleaching discoloured teeth.
Studies on tooth crown size and structure of individuals with various sex chromosome anomalies and their normal male and female relatives have demonstrated differential direct effects on growth of genes on the human X and Y chromosomes. The Y chromosome promotes growth of both tooth enamel and dentin, whereas the effect of the X chromosome on tooth growth seems to be restricted to enamel formation. Enamel growth is decisively influenced by cell secretory function and dentin growth by cell proliferation. It is suggested that these differential effects of the X and Y chromosomes on growth explain the expression of sexual dimorphism in various somatic features, such as the size, shape and number of teeth, and, under the assumption of genetic pleiotropy, torus mandibularis, statural growth, and sex ratio. Future questions concern, among other topics, the Y chromosome and the mineralization process, concentric control of enamel and dentin growth, and gene expression.
UNLABELLED: Odontogenic lesions are rare, but can be associated with significant morbidity. While their molecular determinants are unknown, they likely express many genes common to normal odontogenesis. This study evaluated the histology and mRNA expression of an unusual odontogenic lesion in a patient with a confirmed history of tricho-dento-osseous syndrome. METHODS: Decalcified, frozen 8 micro m sections of the lesion were cut and mounted on glass slides and stained with hematoxylin/eosin for analysis. The expression of multiple genes associated with normal odontogenesis and related pathologies were evaluated by RT-PCR, where possible in samples of the hard and soft tissue components of the lesion. RESULTS: Histological examination showed the lesion had large areas of irregular, dentine-like material, enamel matrix, areas of woven immature bone and multiple fully mineralised tooth crowns. Although most of the gene transcripts were amplified from both samples, some, including DLX3/7 and Collagen I demonstrated differential expression. CONCLUSIONS: This study shows the gene expression profile of aberrant odontogenesis with associated odontoma formation is similar to that of normal tooth and the genes expressed in other odontogenic lesions. While the role of altered gene expression in the development of such lesions has previously been postulated from transgenic models, this is the only report of an odontogenic lesion in a patient with TDO, and begins to elucidate possible gene interactions key to its development.
Morphometric variables of second primary molar crowns from birth to completion were examined and measured. An image analysing technique comprising a photographic camera, a monitor, a computer with appropriate software and a digital caliper was used. Strong correlations were found between the 'external' aspect of the crown (mesiobuccal cusp height, mesiodistal and buccolingual dimensions and perimeter), and between all the 'occlusal' measurements of the crown, i.e. all the intercusp distances. However, poor correlations were found between the external and internal measurements of the crown such as the mesiobuccal cusp height and mesiobuccal-mesiolingual cusp-tip distance. It was also found that the mesiobuccal cusp serves as the apex of two triangles, the one formed by mesial cusps, and one formed by the distal cusps. The cusps on the mesial portion of the crown (ML, DB) are on a similar radius from the MB cusp, and the cusps on the distal portion are on a similar radius from the MB cusp. The small sample is a limitation but the results suggest a separate and independent pattern and rate of development of the external and the occlusal morphological variables of the tooth crown. Further research is needed on larger samples.
We measured the mesio-distal and bucco-lingual crown diameters of 13 males with the fra(X) or Martin-Bell syndrome. Fluctuating crown-size asymmetry was calculated and compared with values obtained in normal Caucasian children and also with a sample of 19 males with Down syndrome. A statistically significant increased asymmetry was found in the fra(X) males when compared to normal control individuals. In the maxilla, Down syndrome males showed a significantly higher tooth crown asymmetry than fra(X) males. (less than 0.02); in the mandible, no significant differences were found between the 2 groups. It is suggested that crown size asymmetry be included in the evaluation of fra(X) males.
An effective method for sealing pulp canals after partial removal of canine tooth crowns from adult rhesus monkeys is described.
The effects of injury to the inferior alveolar nerve on the distribution of neuropeptides and neurogenic blood-flow reactions were studied in rat mandibular dental pulp. In normal incisor pulps, calcitonin gene-related peptide (CGRP)-like immunoreactivity was common, while substance P- and neurokinin (NKA)-positive nerve fibres were much less abundant. There were no signs of vasoactive intestinal peptide-like, neuropeptide Y-like or 5-hydroxytryptamine-like immunoreactivity. In normal pulps, electrical stimulation (100 microA, 5 ms, 15 Hz for 30 s) of the tooth crown resulted in transient vasoconstriction followed by vasodilation, which was enhanced after alpha-adrenoceptor blockade. At 3 days-4 weeks after unilateral nerve section there were no signs of CGRP-, substance P- and NKA-immunoreactivity, and there was no vasodilation in response to tooth stimulation. The vasoconstrictor response was also absent during this period but at 4 weeks postoperatively a weak response was obtained and after 7 weeks the vasoconstrictor response had regained normal amplitude. At 7 weeks postoperatively, a large number of CGRP-positive fibres had reappeared and at 11 weeks the pattern of CGRP-immunoreactivity was normal. However, substance P- and NKA-immunoreactivity were not found at 7 or 11 weeks after surgery. Vasodilator responses appeared at 7 weeks, and showed normal amplitude at 11 weeks after the creation of the nerve lesion. The results show that during nerve regeneration, sympathetic vasoconstriction was regained earlier than neurogenic vasodilation in rat incisor teeth. The reappearance of neurogenic vasodilation after nerve injury was temporarily associated with the presence of CGRP-immunoreactivity in regenerating trigeminal afferent nerves.
Tooth crown and root fragments from a crime scene in which the remains were purposefully cremated, crushed and scattered were analyzed using a scanning electron microscope (SEM) in order to aid the identification process. The SEM was used to confirm the presence of parallel striations in tooth enamel and dentine as a means of determining past dental restoration. In the case presented, incinerated tooth fragments of determined type and position were subjected to SEM analysis, and ascertained to have had previous dental work that matched antemortem dental records of a missing person.
The tooth crowns of most mammals do not change in size except by attrition. Therefore, by comparing age groups within a population and finding differences in size or variation, the effects of such agencies as directional or stabilizing selection can be demonstrated. Mesiodistal and buccolingual measurements were taken on the maxillary and mandibular permanent dentition of a protohistoric Arikara Indian population from South Dakota. The tooth sizes of juveniles ages 6 through 15 were compared to those of adults ages 16 through 20. The two age groups were also compared by the cross-sectional areas of the posterior teeth. When a difference between age groups was demonstrated in either size or variation, a selection intensity was estimated using published graphs. Results from the comparisons show that adults, in general, have larger and less variable teeth than juveniles. The data suggest the possibility that both directional and stabilizing selection were operating on the Arikara dentition. Furthermore, the selection intensities suggest that selection was operating not on the individual teeth but on functional complexes such as the posterior teeth. It appears that in populations like the Arikara where crown attrition is severe, selection will be in the direction of large teeth.
A major complicating factor in using dental data in analyses of taxonomic and evolutionary problems is the existence of morphogenetic fields. Efforts are made to abstract tooth crown size morphogenetic fields of the orangutan. The utility of coefficients of variability and factor analysis, to this end, is presented. Resulting morphogenetic dental crown size fields are described and related to hominoid dental evolution.
Sub-Saharan African (and derived) populations typically exhibit larger mean tooth crown diameters than whites in spite of considerable population variability. We report on a 19th century series of American black slaves from a single cemetery near Charleston, South Carolina, that possessed notably smaller crown sizes. Analysis identifies a characteristic set of differences compared to caucasians, including retention of large maxillary lateral incisors and disproportionately large premolars and molars. Regression of principal components scores (derived from the mesiodistal diameters) on the sum of all diameters (used here as a measure of overall tooth mass) confirms a basic ethnic difference between black and white odontometrics: significantly more of the tooth mass is apportioned to the cheek teeth (premolars, molars) in blacks than whites. The difference (expressed as residuals from linear regression on tooth mass) holds for the several groups assessed here despite considerable intergroup variability in tooth sizes. Potential explanations for the notably small diameters of this plantation series are speculative, but may involve kin-based divergences and/or reflect the natural intergroup differences extant in the African slave sources.
Endodontic considerations is the fourth in the series on crowns and other extra-coronal restorations. This article focuses strongly on contemporary biological principles, and is not intended to provide a comprehensive review of commercially available materials and techniques. Principles are illustrated in a variety of clinical case scenarios.
Periodontal mechanosensitive (PM) primary afferent neurones were recorded from the rat trigeminal ganglion and their response to mechanical tooth stimulation studied. The majority (95%) of PM afferents were single-tooth units and most were sensitive to mechanical stimulation of the incisor. They had a sustained response to pressure applied to the tooth, and showed a directional selectivity to the stimulation. Only a small number (5%) of units were multi-tooth sensitive; their receptive fields were restricted to the molars. When the incisor was stimulated mechanically in 12 directions in a plane perpendicular to the axis of the tooth crown, the predominant response fields of the PM units were of the medium type (90-180 degree response angle) or the broad type (180-360 degrees). Each unit had single optimal stimulus direction oriented predominantly in the rostrocaudal or caudorostral direction. About 60% of the PM units responded to tooth stimulation at irregular spike intervals, whereas the remaining 40% fired at relatively regular intervals. When the tooth was stimulated at a force of 0.05 N, the mean spike interval and rate of spike-interval fluctuation [percentage of the standard deviation (SD) of the interval distribution to the mean interval (mean); SD/mean x 100] were 29.2 ms and 38.1% for the regular-interval units, and 15.1 ms and 8.8% for the irregular-interval ones. The mean spike interval of the regular units was significantly longer than that of the irregular ones.
The speed that a tooth bud or growing tooth attains on its way to the level of occlusion merits biological and clinical interest. In this work, all data available in the literature related to the eruptive movement of the various permanent teeth in man, both prior and after their clinical emergence in the oral cavity, have been gathered and recalculated in rates of movement per day. For comparative purposes, the rates of migration of nonerupted teeth, of bone resorption and bone apposition, as well as the rate of elongation of growing tooth roots were also collected from the literature. The standardized data (rates in micron/day) revealed the intraosseous movements of tooth buds and growing teeth are dependent and limited in speed by the rates of bone resorption and bone apposition. The extra-alveolar movement of clinically visible tooth crowns on their course of prefunctional eruption occurs at a much higher speed which probably results from a combination of the rate of bone apposition in the apical region and the rate of root elongation. These findings are discussed in connection with our present knowledge on the mechanisms of tooth eruption.
In 79 of 124 children with bilaterally located widened follicles around non-erupted canines one of the maxillary canines was chosen by lot for surgical exposure of the tooth crown. In seven cases both maxillary canines were exposed. The remaining 38 children were radiographically controlled at certain time intervals as were the 86 cases where surgery was performed. The follicles removed from 52 cases were histologically examined. The result showed that surgical exposure did not enhance the eruption of the tooth. The histological examination showed that the histologic appearance of the extirpated follicle did not correspond to the radiographically verified width of the pericoronal space. The specimens were composed of a loosely arranged fibrous connective tissue with an epithelial lining occurring in 77% of the cases. The epithelial lining consisted of reduced enamel epithelium and showed in none of the cases squamous metaplasia or keratinization. Nor was there any clinical or histologic sign of a neoplastic or cystic change of the follicle.
This article has aimed at providing information on how to improve clinical orthodontic results in cases in which maxillary central and lateral incisors are missing. Different sections deal with (1) treatment approach and mechanics, (2) details in finishing, (3) modifications of clinical tooth crowns by special procedures (grinding, composite "corners," gingivectomy), (4) functional considerations and root resorption, and (5) retention.
The aim of this study was to investigate the enamel microhardness and the histological features of eight enamel pearls of various size. The microhardness of the pearl enamel ranged from 272.4 to 407.2 Vickers microhardness values (VMV) and resembled that of the enamel of the carrier teeth (277.1-424.3). A histological resemblance between the tissues of the enamel pearls and those of the carrier teeth was also found. The resemblance was more pronounced in larger pearls, which showed a variability of the enamel microhardness and structure in the occlusal-cervical direction typical of the tooth crown. Large pearls also exhibited a root and a pulp. Some histological features of the enamel pearls were probably caused by pressures exerted on the developing pearl by its surroundings. It is suggested that the histogenesis of small and large pearls is based on the ability of the developing root of the carrier tooth to behave in part as a new tooth germ.