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PubMed1998

Comparison of exposed dentinal surfaces resulting from abrasion and erosion.

The aim of this study was to compare the shape of exposed dentinal surfaces caused by abrasion and erosion with a view to developing a diagnostic clinical test. The study material consisted of 80 natural teeth and 129 dental models obtained from Australian Aborigines known to display considerable dental abrasion due to their diet, and dental models of 37 Caucasians diagnosed with dental erosion through detailed history and dietary analysis. Polyvinyl siloxane impressions were obtained of all occlusal surfaces with dentinal scooping in both the 'abrasion' and 'erosion' groups. All impressions were sectioned buccolingually through the deepest point of the scooped dentine, and then the profiles were photocopied at x2 magnification. The breadth and depth of dentinal profiles were measured to an accuracy of 0.1 mm, enabling ratios of depth:breadth to be determined, and the position of the deepest part of each scooped surface was recorded. The mean depth:breadth ratio of scooped dentine was significantly greater in the Aboriginal natural teeth (0.19 +/- 0.06, mean +/- SE) than in the Aboriginal dental models (0.15 +/- 0.04). Both Aboriginal natural teeth and models with abrasion showed significantly smaller ratios (p < 0.05) than the Caucasian models showing erosion (0.33 +/- 0.07). Furthermore, in the abrasion samples, the deepest region of the scooped dentine tended to be lingually placed more often in maxillary teeth but buccally placed more often in mandibular teeth (p < 0.05). These results indicate that scooped dentine on abraded occlusal surfaces of teeth displays significant differences in shape compared with that caused mainly by erosion.

Adolescent↗
PubMed1999

Ethnic dental analysis of shovel and Carabelli's traits in a Chinese population.

Chinese populations differ from Caucasoids by having a high prevalence of shovel trait and a low prevalence of Carabelli's trait. This study was conducted to investigate the association between the shovel and the Carabelli's traits in a Chinese population. The research design investigated a Chinese population that resides in southern Taiwan. The ancestors of this Chinese population migrated to Taiwan from mainland China, mainly from Fukien and Kwangtung. The effects of sex and age on Carabelli's trait were controlled in this investigation, as was the association between tooth size and Carabelli's trait. Results show that males were more likely to have Carabelli's trait expressed on teeth than females. The buccolingual diameter of Carabelli's trait teeth was larger than that of teeth without the trait. After controlling for sex, age, and tooth size, the existence of the shovel trait increased the likelihood of having Carabelli's trait by a factor of five and a half, which is a significant effect.

Adolescent↗
PubMed2006

The effects of file size, sodium hypochlorite and blood on the accuracy of Root ZX apex locator in enlarged root canals: an in vitro study.

BACKGROUND: The initial electronic apex locator (EAL) length measurement is generally established with a small-sized file. It is not known whether file size would be interfering with the reading accuracy of the EAL. This study aimed to evaluate the effect of file size on the accuracy of Root ZX apex locator using an agar model when sodium hypochlorite solution or blood was present during electronic measurements in enlarged root canals. METHODS: A total of 36 extracted lower premolars were used. In stage 1, the canals were instrumented using size 10-40 K-files with a size 40 K-file as the master apical file (MAF). The teeth were then divided randomly into two groups of 18 teeth each. In group A, the teeth were mounted in one per cent agar and irrigated with six per cent sodium hypochlorite solution (NaOCl), while in group B the teeth were mounted in agar and irrigated with human blood. In stage 2, the canals were enlarged using a size 60 K-file as the MAF. In stages 1 and 2, the apical portions of the canals were instrumented using the step-back sequence (up to a size 80 K-file). In stage 3, the canals were enlarged using a size 80 K-file as the MAF. In each stage, the length was measured with a Root ZX until the meter value reached 'APEX' using small and large size files. RESULTS: Three-way ANOVA and Bonferroni test showed that file size, stage of preparation and type of irrigant all had a significant influence on the measurement error (P < 0.0001), with all the interactions between these three factors being significant (P < 0.0001). CONCLUSIONS: As the diameter of the root canal increased, the measured length with the smaller size files became shorter. A file of a size close to the prepared canal diameter should be used for root length measurement in the presence of blood. In the presence of NaOCl, the Root ZX was highly accurate even when the file was much smaller than the diameter of the canal. The agar model was effective and suitable for testing EALs in vitro.

Analysis of Variance↗
PubMed2006

Ex vivo evaluation of the ability of four different electronic apex locators to determine the working length in teeth with various foramen diameters.

BACKGROUND: The aim of this ex vivo study was to evaluate the accuracy of four electronic apex locators (EALs) to determine the working length in teeth with various foramen diameters. Our previous study revealed that electronically measured canal length was influenced by the root canal diameter. It is not known whether foramen size would interfere with the reading accuracy of an EAL. METHODS: A total of 36 extracted human lower single rooted premolar teeth were divided into four groups of nine teeth each. In groups A, B and C, the root canals were instrumented using #10-80, #10-100 and #10-120 K-files, and the tip of size #80, #100 and #120 K-files were permitted to pass through the apical foramen to a length of 1mm, respectively. In group D, the teeth were instrumented using #10-140 K-files and the tip of #140 K-file was permitted to pass through the apical foramen to a length of 5 mm. Thus, the average apical foramen diameters in groups A, B, C and D were approximately 0.82 mm, 1.02 mm, 1.22mm and 1.5 mm, respectively. The teeth were then mounted in 1% agar and four EALs were used: Root ZX, Foramatron D10, Apex NRG and Apit 7. For electronic measurement, sizes #10 and #80, #10 and #100, #10 and #120, and #10 and #140 K-files were used for groups A, B, C and D, respectively. During electronic measurement the canals were flushed with 6% sodium hypochlorite solution. RESULTS: Three-way ANOVA and Bonferroni test showed that EAL, file size and foramen size all had a significant influence on the measurement error (P<0.0001), with all the interactions between these three factors being significant (P<0.0001). CONCLUSIONS: The four EALs were unreliable to determine the working length of teeth with a wide apical foramen, when using a small size file. The Root ZX and Foramatron D10 showed significantly better scores than the other two EALs and may be more reliable to determine the working length of teeth with a wide apical foramen, if a tight-fit file is used.

Bicuspid↗
PubMed2006

Accuracy of dental digitizers.

UNLABELLED: The need for proper validation and verification methodology for CAD/CAM systems is imminent. CAD/CAM systems consisting of an optical impression system, design software and a fabrication machine have to perform to a certain level, whereby manufacturers need to prove the effectiveness of the system as a whole. However, especially when dental surface digitization devices are used as open, stand-alone applications in dental outsourcing, a reliable standard test for comparison is necessary. PURPOSE: This study evaluates a proposed test method to be used to quantify "digitizing quality" with respect to accuracy and reproducibility of two dental surface digitization devices. Comparability of the characteristics should be ensured. METHOD: Two laser light section scanners: DentaScope II and D200 were evaluated by means of the 'Sphere Test', that involves repeated measurements of a precision ball (radius: 6mm) according to a pre-defined protocol. The surface information was received as unmatched, overlapping point clouds and statistically processed with a newly developed software package. The standard deviation of all points as well as a measure for undercutting the equator were determined. RESULTS: The standard deviation for the radius for D and S were 7.7 (+/-0.8) and 13.9 (+/-1.0) microm respectively. The equator undercut elevations were -2.0 degrees and -0.25 degrees for scanner D and S respectively. CONCLUSION: Scanner D had a significantly higher accuracy than S (p<0.05), corresponding with the smaller pixel distance of the sensor. Both devices show adequate accuracy and reproducibility and have an adequate ability to detect the equator. The test is also suitable for calibration purposes.

Computer-Aided Design↗
PubMed1996

Molar tooth diversity, disparity, and ecology in Cenozoic ungulate radiations.

A classic example of adaptive radiation is the diversification of Cenozoic ungulates into herbivore adaptive zones. Their taxonomic diversification has been associated with changes in molar tooth morphology. Analysis of molar crown types of the Artiodactyla, Perissodactyla, and archaic ungulates ("Condylarthra") shows that the diversity of genera and crown types was high in the Eocene. Post-Eocene molars of intermediate crown types are rare, and thus the ungulate fauna contained more taxa having fewer but more disparate crown types. Taxonomic diversity trends alone give incomplete descriptions of adaptive radiations.

Animals↗
PubMed1975

Incisor size and diet in anthropoids with special reference to Cercopithecidae.

In 57 species of anthropoids relative size of incisors in highly correlated with diet. Anthropoids that feed primarily on large food objects (large fruits) have larger incisors than those that feed on smaller food objects (berries or leaves). This difference reflects a need for more extensive incisal preparation of larger food objects before mastication. Extensive incisal preparation causes increased tooth wear, therefore, enlarged incisors are probably an adaptive response to increase their wear potential.

Animals↗
PubMed1995

An evaluation of the accuracy of ageing horses by their dentition: a matter of experience?

There is a widely held belief that a horse can be accurately aged by an examination of its teeth but this belief has recently been questioned. In this study photographs were taken of the dentition of 434 thoroughbreds of known age. Four experienced equine clinicians provided estimates of the ages of the horses from the photographs. A comparison of the estimated and true ages showed large discrepancies in many cases and the discrepancies increased as the horse's true age increased. The results show that the ageing of horses from their dentition is an imprecise science. It is suggested that written records of the dental features are made on each occasion when a dental examination is made and that veterinary surgeons advise clients that estimating a horse's age from dental criteria can provide no more than an 'informed guess'.

Age Determination by Teeth↗
PubMed1995

An evaluation of the accuracy of ageing horses by their dentition: changes of dental morphology with age.

Dental features are commonly expected to provide an accurate estimate of a horse's age. In this study the dentition of 434 thoroughbreds was photographed and the individual dental features documented, the true age of all the horses was known. For each dental feature the correlation with true age was determined. The eruption of the incisor teeth was the most consistent feature but it was not totally reliable. The presence of a hook on the upper corner incisor and Galvayne's groove proved to be of no value when estimating age and, of the attritional features studied, the dental star showed the highest correlation with age. The results show that specific ages cannot be assigned to these dental criteria owing to the wide variation between horses, and that as a result the estimation of age from dentition can never be precise.

Age Determination by Teeth↗
PubMedDate not supplied

Thickness measurement of worn molar cusps by ultrasound.

This study aimed to evaluate the effectiveness of an ultrasonic system for in vitro measurement of cusp tips of human teeth. Each worn cusp of 12 molar teeth was measured with an industrial ultrasonic system. The teeth were sectioned and measured by polarized light microscopy. The ultrasonic measurements and histological readings were moderately correlated (r = 0.601, p < 0.01). The ultrasonic system used in this study seemed a promising method for measuring thickness of worn cusp tips of extracted human molar teeth.

Dental Enamel↗
PubMedDate not supplied

New fossil platyrrhine from Argentina.

A new fossil primate was found in the Pinturas Formation, south-western Patagonia, at the type locality of the rare Soriacebus ameghinorum. It is a mandibular fragment with two molars that strongly resemble those of S. ameghinorum in their high and closed trigonid, distal expansion of the talonid, small hypoconulid, buccal expansion of the enamel and similar cusp development. But the type of S. ameghinorum differs by having mesiodistally longer trigonids, long premetacristids and more oblique distal trigonid walls, with the metaconid more lingually placed and the postmetacristid distolingually oriented and with the talonid being buccolingually smaller than the trigonid with a more restricted basin. M2 is slightly smaller than in the new specimen, and the buccal enamel is less flared. Although it is difficult to determine if this new specimen represents an individual variation of S. ameghinorum or a new species of Soriacebus, its morphology appears to be less derived than that of the type mandible, and it is, therefore, of systematic significance.

Animals↗
PubMedDate not supplied

Artificial neural networks and three-dimensional digital morphology: a pilot study.

In this pilot study, we used an unsupervised learning algorithm for self-organization and pattern matching to create feature maps that can be applied to morphological problems. We designed a network to analyze 83 first and/or second upper and lower molar sets representing 13 anthropoid primate species, based on three-dimensional measures obtained from laser-digitized, virtual specimens. As shown in a comparison with a principal-component analysis of the virtual specimens, the artificial neural network approach provided more biologically meaningful information than the conventional multivariate analysis approach. The methodology discovered partitions and hierarchical clusters consistent with anthropoid systematics, from the species (or subspecies) level to the highest categories, by sorting and allocating upper and lower molar teeth. As one might expect, measures of upper molars were richer in phenetic information than those of lower molars, even among the anatomically diverse platyrrhines. We also show that reducing taxonomic noise (i.e. biological variation) by limiting the analysis to a monophyletic subset improves discrimination.

Algorithms↗
PubMedDate not supplied

Dental microwear variability on buccal tooth enamel surfaces of extant Catarrhini and the Miocene fossil Dryopithecus laietanus (Hominoidea).

Analyses of buccal tooth microwear have been used to trace dietary habits of modern hunter-gatherer populations. In these populations, the average density and length of striations on the buccal surfaces of teeth are significantly cor-related with the abrasive potential of food items consumed. In non-human pri-mates, tooth microwear patterns on both occlusal and buccal wear facets have been thoroughly studied and the results applied to the characterization of dietary habits of fossil species. In this paper, we present inter- and intra-specific buccal microwear variability analyses in extant Cercopithecoidea (Cercopithecus mitis, C. neglectus, Chlorocebus aethiops, Colobus spp., Papio anubis) and Hominoidea (Gorilla gorilla, Pan troglodytes, Pongo pygmaeus). The results are tentatively compared to buccal microwear patterns of the Miocene fossils Dryopithecus and Oreopithecus. Significant differences in striation density and length are found among the fossil taxa studied and the extant primates, suggesting that buccal microwear can be used to identify dietary differences among taxa. The Dryopithecus buccal microwear pattern most closely resembles that of abrasive, tough plant foods consumers, such as the gorilla, in contrast to stud-ies of dental morphology that suggest a softer, frugivorous diet. Results for Oreopithecus were equivocal, but suggest a more abrasive diet than that previously thought.

Analysis of Variance↗
PubMed1976

Odontometric study of African monkey teeth.

Univariate analysis of the mesiodistal and buccolingual crown diameters of Cercocebus albigena, Cercopithecus aethiops and Cercopithecus ascanius revealed a complex pattern of contrasts depending upon which tooth dimension was compared. By contrast, multivariate analysis discriminated between the dentitions of Cercocebus albigena on the one hand and Cercopithecus aethiops and Cercopithecus ascanius on the other hand, but whether these differences reflected genetic or environmental factors requires further data.

Anatomy, Comparative↗
PubMed1978

An analysis of molar tooth form.

The maxillary first permanent molars of different human population samples were compared by multivariate analysis of two-dimensional coordinates of datum points defining the occlusal surface and periphery of the crown. This technique proved that discrimination was possible between teeth which could not be discriminated visually or by analysis of the mesiodistal or buccolingual diameters.

Analysis of Variance↗
PubMed1980

The cheek teeth of the rabbit: morphology, histology and development.

A detailed anatomic and histologic description of the cheek teeth of the rabbit, both deciduous and permanent, is presented, together with the chronology of their pre- and postnatal development. The deciduous teeth are of limited growth, while the permanent ones grow continuously. Certain aspects of cementogenesis in these teeth are discussed.

Animals↗
PubMed1978

Correlations between tooth dimensions of man and apes.

Computation of simple, multiple and canonical correlation coefficents between the mesiodistal and buccolingual crown diameters showed a high degree of association between the overall crown dimensions of man and chimpanzee. Information regarding the partitioning of genetic and environmental influences on crown form must therefore await further data regarding the degree of correlation between detailed intra-crown dimensions. Nevertheless, the data from this study suggested that dentitions should be regarded as whole biological entities rather than a series of discrete teeth.

Analysis of Variance↗