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At least 253 records · Page 14Linked to original sources
PubMed2000

Detection of a transitional ion concentration zone during electronic measurement of root canal length: a study in vitro.

AIM: The aim of this study was to examine the importance of a transitional ion concentration zone at the apical foramen during electronic root canal length measurement (ERCLM). METHODOLOGY: The model comprised 21 extracted single-rooted human teeth, divided into two experimental groups and one control group, each of seven teeth. The anatomical tooth length was determined from the site of reference on the tooth crown to the canal orifice and was measured using an endodontic file and a vernier caliper. Two aqueous solutions of various NaCl, KCl and CaCl2 concentrations were mixed with agar. The Na+, K+ and Ca++ concentrations corresponded to the average value of each group as determined by atomic spectrophotometry evaluation of the extirpated human pulps. The agar containing cations was injected into the root canals after their preparation to a foramen diameter of 0.70 mm. The control teeth were then completely immersed in agar having the same concentration of cations as the agar inside the canal. In the first experimental group (group 1), the teeth were immersed in agar so that the ion concentration was higher inside the canal; in the second experimental group (group 2), the concentrations were reversed. In all three groups, ERCLM was performed by an EED 11--resistance type device. Length d1 was defined as the length of the root when measured to a value one degree less than the test value. Length d2 was defined as the length of the root inducted by the test value, which corresponded to the resistance of the periapical agar. RESULTS: In group 1 the average d1 length was 0.44 +/- 1.05 shorter than the anatomical foramen (AF), and in group 2, 1.11 +/- 0.43 mm longer than AF. In the control group the d1 length was on average--3.02 +/- 3.72 mm from the AF. The d1 values of all groups were not statistically significantly different from the anatomical length (AL). In all three experimental groups the d2 length was statistically significantly different from the AL (P < 0.05, t-test); group 1 d2 = AL + 6.32 +/- 1.38 mm; group 2 d2 = AL + 6.27 +/- 1.47; control group d2 = AL + 9.15 +/- 1.00 mm. CONCLUSIONS: The results of this study indicated that when the electroconductive medium in the canal had a different ion concentration than the periapex, and the canal orifice had a wide diameter (0.70 mm), the transitional concentration zone influenced the accuracy of measurement during ERCLM with a resistance type device. When ion concentrations inside and outside the canal were identical, in teeth with a wide foramen diameter (0.70 mm or more) the lack of a transitional ion concentration zone meant that the length of the root canal could not be determined by ERCLM.

Agar↗
PubMedDate not supplied

Crown dimensions of deciduous and permanent teeth of Jats from Haryana (India).

Tooth crown dimensions of deciduous and permanent dentition have been measured in 356 male and 292 female Jats from Haryana, an important agriculturally-based community in North India. While the second molar is the biggest tooth of the deciduous dentition, the first molar showed greater mesiodistal and buccolingual diameters in the permanent dentition. Sex differences in the two dentitions were significant, the differences being more marked in the permanent teeth.

Demography↗
PubMed1998

Prevalence of dental anomalies in orthodontic patients.

The prevalence of dental anomalies including agenesis, crown shape, tooth position, root shape, and invagination were examined in 111 orthodontic patients; 74.77 per cent of the patients exhibited at least one dental anomaly. Invagination was found to be the most prevalent anomaly, whereas supernumerary teeth and root dilaceration were the least frequent anomalies. Dental invagination and short or blunt roots were significantly more prevalent in females than in males. Implications for orthodontic treatment planning are discussed.

Adolescent↗
PubMed1995

Treatment and prognosis of a vertically fractured maxillary molar with widely separated segments: a case report.

This is a report of the treatment and prognosis of a maxillary second molar exhibiting a complete vertical crown-root fracture. The buccal and palatal segments were widely separated by as much as 2 mm and were immobile. To restore this tooth, it was essential to bring the segments into close apposition. This was accomplished by application of orthodontic elastics to the tooth crown in combination with a wire splint. After approximately 1 month of continuous use of the orthodontic elastics, the dislodged segments were suitably repositioned close to their original positions. The tooth was then endodontically treated and restored with a cast complete crown. The restored tooth has been functioning well, with periodic periodontal maintenance, for more than 3.5 years, indicating a promising prognosis.

Adult↗
PubMed1971

Prediction models for 90Sr in shed deciduous teeth and infant bone.

Shed deciduous teeth were collected in 1966-69 in Denmark, the Faroes and Greenland from children born in the period 1953-63. 235 samples of crowns were analysed for 90Sr. The 90Sr levels in deciduous tooth crowns were related to the fall-out rate and the accumulated fall-out. The tooth levels in children born in 1950-62 could be described with the same equation as the 90Sr bone levels in 1-yr-old infants born in 1962-68. The prediction models for 90Sr in teeth and bones showed that for given amount of fall-out the Faroese levels became nearly twice as high as the Danish. The maximum teeth and bone levels were found in children born in 1963, where the Faroese level was estimated from the prediction model to be 24 pCi 90Sr/g Ca.

Bone and Bones↗
PubMed2004

Nonindependence of mammalian dental characters.

Studies of mammalian evolution frequently use data derived from the dentition. Dental characters are particularly central for inferring phylogenetic relationships of fossil taxa, of which teeth are often the only recovered part. The use of different aspects of dental morphology as phylogenetic signals implies the independence of dental characters from each other. Here we report, however, that, at least developmentally, most dental characters may be nonindependent. We investigated how three different levels of the cell signalling protein ectodysplasin (Eda) changed dental characters in mouse. We found that with increasing expression levels of this one gene, the number of cusps increases, cusp shapes and positions change, longitudinal crests form, and number of teeth increases. The consistent modification of characters related to lateral placement of cusps can be traced to a small difference in the formation of an early signalling centre at the onset of tooth crown formation. Our results suggest that most aspects of tooth shape have the developmental potential for correlated changes during evolution which may, if not taken into account, obscure phylogenetic history.

Animals↗
PubMed1989

Follicular cysts of mandibular third molar teeth: radiological evaluation of enlargement.

To test the hypothesis that follicular (dentigerous) cyst enlargement arises from impeded tooth eruption, data from standardized Orthopantomographs of 30 uninfected, wholly intracortical cysts associated with mandibular third molar teeth were analysed. Cyst areas were measured with a computer-aided image analyser (Magiscan 2, Joyce Loebl, Gateshead, UK). Two size categories, small and large, each comprising 15 cases, were distinguished. These were correlated with the radiographic variables of cyst relationships to tooth crown, and angulation and nature of impaction of associated tooth. Cyst enlargement is most active in the third and fourth decades of life. Smaller cysts were associated with teeth impacted against adjacent tooth or bone, whereas larger cysts developed predominantly from horizontally angulated teeth intruded endosteally. These findings lend support to the haemodynamic concept of follicular cyst enlargement linked with dysfunctional eruptive forces.

Adult↗
PubMed1999

[Human tooth tissue as dental restorative material].

With the recent development of copy-milling systems for porcelain, it has now become possible to construct fitting restorations from natural human tooth substance. This preliminary study aimed to find out whether it is possible to produce a well fitting Class II inlay from an extracted tooth using a copy-milling machine, so that the inlay produced will have enamel over its whole outer surface and dentine on its inner surface. Two pairs of matching sound extracted permanent molars were used. The molars were matched for mesio-distal size of the tooth crown and the convexity of the approximal surfaces. One tooth of each pair was assigned to be the 'donor' tooth, the other tooth being the 'host'. MO inlay preparations were made in the 'host' teeth. These were restored with the milled 'natural inlays' produced from the 'donor' teeth using the CELAY system. The restored 'host' teeth were sliced and examined using light-microscopy. All specimens showed a good fit and the desired location of enamel and dentine. The milling accuracy was assessed in a second experiment. This experiment showed similar marginal gaps for 'natural inlays' as for ceramic inlays. This study has shown that by using the CELAY milling machine it is possible to 'recycle' extracted teeth for the production of accurate restorations.

Dental Cavity Preparation↗
PubMedDate not supplied

Utilization of periodic markings in enamel to obtain information on tooth growth.

Enamel retains two fundamental periodic markings: the prism cross-striations, marking a diurnal rhythm of prism elongation, and the striae of Retzius, a longer-term marker of formation of the enamel surface. It is argued that, while artefacts superficially resembling prism cross-striations can be observed, these should not mislead an experienced histologist and that true cross-striations are reliable markers of the daily incremental apposition of enamel. The incremental markings can be used to elucidate several aspects of tooth crown growth. (1) Rate of enamel apposition. In some teeth, e. g., hominoid permanent teeth, the enamel apposition rate increases progressively between the inner and outer enamel, while in others the apposition rate appears to be uniform. (2) Crown formation time. This can be estimated on intact teeth, using counts of perikymata (surface traces of the striae), together with information on the time interval between successive striae. Much better estimates can be obtained from sections, using counts of cross-striations. (3) Pattern of crown formation. The rate at which new enamel formation extends over the presumptive enamel-dentine junction (extension rate) can be estimated from knowledge of the cross-striation interval together with angular measurements of prisms and striae. Multiple measurements of the extension rate within a tooth can be used to provide an estimate of crown formation time. The main application of extension rate measurements is to give quantitative information on the pattern of crown formation. In large primate teeth, the extension rate is high early in crown formation and slower later in crown formation. In smaller, more rapidly-formed teeth, a gradient in extension rate appears to be absent. Enamel thickness is negatively correlated with extension rate among primates. This seems to be a mechanism ensuring that there is sufficient time for enamel maturation to be completed before eruption takes place. Among primates it appears that variation in the prism pattern (i.e., the extent to which the outline of the pattern 3 prisms is closed or open) is correlated with the extension rate. It is postulated that the extension rate controls prism shape by influencing the morphology of the Tomes process pits during their initial formation.

Age Determination by Teeth↗
PubMed2002

Statistical genetic comparison of two techniques for assessing molar crown size in pedigreed baboons.

Dental anthropologists and paleoanthropologists commonly use an estimated molar crown area (mesiodistal length multiplied by buccolingual width) to describe and compare individuals, populations, and species. Advances in digital imaging now allow researchers to measure the actual crown area of a molar in an occlusal two-dimensional plane. Because error is reduced by this more accurate measurement, actual crown area is thought to be a better representation of the mechanisms that determine tooth crown size, meriting the additional time required to collect it. We tested this assumption by estimating the heritability of both these measurements for the second left mandibular molar from a sample of individuals (n = 332) from a captive breeding colony of baboons. Heritability estimates of both the actual and estimated crown areas of molars are approximately 0.83. Therefore, both measurements are informative as population descriptors, with no significant difference between the accuracy of either to reflect additive genetic contributions to molar crown size. This is fortunate, because genetic studies and inference can be based on estimated areas rather than actual crown area. The heritability estimates for mesiodistal length and buccolingual width are both substantial but lower: approximately 0.67 and approximately 0.73, respectively. The best fitting models in these analyses show that sex, body size, and subspecific affinity differentially affect molar length and width. We interpret these results to suggest that potentially some of the genetics underlying these covariates also underlie tooth size. As such, measurements designed to describe molar crown size are useful for general descriptive purposes, but do not conform to the assumption of independence inherent in phylogenetic analyses, such as cladistics (Hennig [1966] Phylogenetic Systematics. Urbana: University of Illinois Press). Therefore, if variables like actual crown area and estimated crown area are to be used in phylogenetic parsimony analyses, we suggest that researchers account for the effects of covariates such as sex and body size in their analyses.

Animals↗
PubMed1977

Dental condition of two tribes of Taiwan aborigines--Ami and Atayal.

This is a study of dental and oral conditions of Taiwan aborigines from the epidemiological and anthropological points of view. A total of 166 Ami and 128 Atayal adolescents were included from their original living area, the Hwa-Lien Hsin and Wa-Lai District, Taiwan, Republic of China. Oral examination was done carefully and caries incidence, periodontal index, and Angle's Classification combined with OFI were included. After that, hydrocolloid impressions were taken, and dental casts were immediately made. The mesiodistal and buccloingual crown diameters and also the arch depth and width were measured using a sliding caliper. Dental morphological traits, such as shovel-shaped incisors, Carabelli's cusp, protostylid, and upper and lower molar groove patterns were observed and classified, and the results are given with statistical analysis. The aborigines have a quite low incidence of dental caries and periodontal disease which may be related to their dietary habits, good oral hygiene, and good dental occlusion. With regard to the differences between the Ami and Atayal, most of the date show no statistical significance except in the dental occlusion. The Atayal's occlusion is better than that of the differences of genetics or other factors. There are no sex differences in all the date in the dental survey, but there are sex differences in both the misiodistal and buccolingual crown diameters of both the Ami and Atayal tribes (the tooth crown of the male subjects is invariably broader and larger than that of females). In the dental arch dimensions, most of the data show no sex diffreence, except in the breadth of the upper and lower dental arch of the Atayal. Anthropologically, there are no statistical differences, in mesiodistal and buccolingual crown diameters and most of the data of dental arch dimesions, but there is a difference in arch depth in Ami and Atayal adolescents. The Atayal have a deeper dental arch than do the Ami. As for dental morphologi, the Taiwan aborigines have a high frequency of shovel-shaped incisors and Carabelli's trait but a relatively low frequency of protostylid. There are no definite differences between races in the occlusal pattern of maxillary first molars, but there are differences in the maxillary second molars. The usual pattern is 4-- for the upper first and second molars of the Taiwan aborigines as well as for thedibular occlusal pattern, the first molar tends to follow the primitive "dryopithecus" pattern of 5 cusps and Y configuration, but in the second molar there are varying degrees of departure from Y5 to the more advanced +4 pattern with +5 and Y4 as intermediates.

Adolescent↗
PubMed1991

Anterior crown dimensions and relationship in an ethnic Chinese population with normal occlusions.

Odontometric measurements of anterior tooth crown sizes in a Chinese sample of 85 Class I occlusions were similar to those published in the white population except for larger upper lateral incisors and smaller upper central incisors in Chinese. Sex differences in tooth sizes were seen only in the maxillary and mandibular canines while differences between antimeres were not significant. The Bolton ratios of our Chinese sample revealed a Bolton ratio of 77.89 +/- 1.62 for the combined mesio-distal widths of the six mandibular anterior teeth as compared to the combined mesio-distal widths of the six maxillary anterior teeth. Surprisingly, the Bolton ratio in our sample compared favourably with those originally published by Bolton although the interfacial angles, overbite and overjet relationships were statistically different.

Adolescent↗
PubMed1988

Forced eruption combined with gingival fiberotomy. A technique for clinical crown lengthening.

A new approach to clinical crown lengthening has been developed and described. The technique combines controlled eruptive tooth movement and incision of the supracrestal gingival attachment. The procedure was performed in patients with severe destruction of a tooth crown and in whom clinical crown lengthening procedures were essential before the teeth could be properly restored. Controlled eruptive forces were activated by simple orthodontic appliances. During the active phase of forced eruption, repeated intrasulcular incisions through the junctional epithelium and the supracrestal connective tissue attachment were performed. The technique prevented coronal displacement of the gingiva and the attachment apparatus during the orthodontic extrusion, thus overcoming the need for corrective osseous surgery.

Adolescent↗
PubMed1977

[Studies on the problem of a composite anchoring post and core].

The authors conclude from the results of preliminary model experiments that the composite resins Noracryl 100 and Evicrol are suited as materials for stump restoration after the loss of the natural tooth crown in case of primarily shortened root.

Composite Resins↗
PubMed1977

Regeneration of tooth development in vitro following sodium fluoride treatment.

Mandibular incisors were dissected from the jaw of 15- and 16-day C57BL/10 mouse embryos and cultured on agar-solidified Eagle's basal medium supplemented with fetal calf serum, an antibiotic, and glutamine, The experimental medium was the same as the control except that fluoride was added such that the final concentrations ranged from 2.0-8.0 mM NaF. Control and experimental explants were recovered after two, four and six days of incubation and studied histologically. After two days of fluoride treatment (3.0 mM NaF), cellular degeneration was observed in the dental papilla mesenchyme while the enamel organ epithelium appeared more resistant. Prolonged treatment or treatment at higher concentrations resulted in destruction of the dental papilla. The enamel organ was still present but was abnormal and reduced. Older tooth germs were less affected overal when incubated at the same fluoride dosage and time of treatment. When explants subjected to limited exposure (2 days) to fluoride were placed on control medium, the suppressed tooth germs recovered. The recovery was enhanced by grafting untreated mesenchyme to the treated explants followed by incubation on control medium. The observations indicate that NaF can suppress the development of tooth germs in vitro and that recovery from the suppresion does occur. The more severe inhibition observed in the mesenchymal component when compared to the response of the epithelial component of the treated explants suggests that fluoride may alter the ultimate morphology of the tooth crown by disrupting the normal epithelial-mesenchymal interaction which occurs during early tooth development.

Animals↗
PubMed1994

Etiology and treatment of root hypersensitivity.

Class V cervical lesions are often observed in older patients during their treatment planning phase, resulting from root caries, toothbrush abrasion, chemical erosion, or to absraction due to unusual tooth flexure. Besides providing a nuisance space as a food trap or plaque buildup, patients also complain of hypersensitivity to air blasts, mechanical stimulation, thermal extremes, or to osmotic fluid shifts. The location of the root lesion in relation to the cemento-enamel junction is of extreme importance. For that reason root lesions limited to the coronal portion of the tooth and completely surrounded by enamel lend themselves to traditional restorative treatment procedures. However, as the root lesion moves apically and its cavosurface circumference is increasingly bound by cementum, clinical treatment becomes much more difficult and in most cases virtually impossible with conventional retentive restorations, and they tend to threaten the root structure and the dental pulp. If these root lesions are left untreated, progressive destruction of root structure occurs and if the causative agents are not removed, the depth of the lesion will threaten the periodontium, dental pulp, and the occlusal integrity of the tooth crown. In addition, cemental lesions are often associated with increased levels of hypersensitivity. Historically, dentistry treated root lesions with direct gold, gold or porcelain inlays, amalgam alloys and crowns, all relying on resistance and retention form. When unrestorable, modification of tooth-brushing techniques along with desensitizing agents were the only desirable treatment due to problems involved with the insertion of a proper restoration. Clinical studies have reported these procedures are often transient, offering no durable restoration of the tooth or elimination of the hypersensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Restoration, Permanent↗
PubMed2006

Dental features in patients with Turner syndrome.

AIM: This was to investigate the dental characteristics (caries sensitivity and tooth crown size of permanent elements) in subjects affected by Turner Syndrome (TS). PATIENTS AND METHODS: A group of 25 patients affected by TS, aged from 4 to 18 years, was selected and the data were compared to those of an age matched control healthy group. The caries index values in TS patients are higher in the permanent (6.4 vs. 3.9), mixed (0.5 vs. 0.75) and primary dentition (0 vs. 1). The mesio-distal diameter in TS patients was significantly reduced for every tooth measured (in particular for the lower first permanent molar). RESULTS AND CONCLUSION: This investigation confirms that numeric aberration of the X chromosome most likely affects the quantitative and qualitative excretion of amelogenin so that teeth often present enamel defects (reduced crown size and enamel hypoplasia). High caries index values (DMFT) highlight the demand of early preventive measures mostly focused on special care patients.

Adolescent↗