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PubMedDate not supplied

The origin of Europeans is not rooted in the Middle East but in southern east Asia.

The study of tooth crown variables has proven useful in the assessment of human origin and dispersal. I show that multivariate analysis of quantified total tooth structure from dental X-rays is a powerful phylogenetic methodology. From an analysis of the complex global dental phenotype ("GDP," composed of approximately 30 root, pulp, crown, and enamel variables per tooth), a representative Western European population was found to associate with Southeast Asians, while Mongolians formed a tight cluster with all Native Americans. The results suggest that either an emigrant wave, or waves, of modern humans emerged from Africa and with time segregated into at least three groups: Australian aborigines, Europeans, and Southeast Asians, or less likely due to genetic and archaeologic observations, a southern Asia origin of all modern humans from an emigrant African hominid. Both hypotheses portend an early evolution of the European genotype and support the argument that Europeans are principally derived from Upper Paleolithic hunter-gatherers, and thus Middle East Neolithic people did not have a major genetic impact on Europeans.

Asia, Southeastern↗
PubMed1997

Possible application of transmitted laser light for the assessment of human pulpal vitality.

The purpose of this study was to determine whether use of transmitted laser light would enable a better assessment of human pulpal vitality than back-scattered light does (LDF: laser Doppler flowmetry). The experiments were carried out on ten upper central incisors in six subjects aged 23-28 years; five of the teeth were vital with no restoration, and five were non-vital. For use with transmitted laser light, the fibers within the probe of a conventional LDF apparatus were used, one for transmitting light onto the buccal surface, the other for receiving it at the palatal surface of the same tooth. For LDF, the probe was fixed at the buccal surface. Blood flow was measured at three different locations on each experimental tooth: the incisal third, the center and the cervical third of the tooth crown. In non-vital teeth, 1) output signals with transmitted laser light all registered zero, and no oscillation could be seen in recordings from any location on the tooth, but 2) LDF signals were above zero, there were regular oscillations related to heart rate, and passive increases in blood flow (corresponding to blood pressure increases) were recorded from both the center and the cervical third of the tooth, indicating that LDF registered blood flow of non-pulpal origin. In vital teeth, LDF signals were significantly higher than in non-vital teeth at each location on the tooth. At the central site on vital teeth, the output signals for transmitted laser light were about twice those seen with LDF, and passive blood flow changes corresponding to blood pressure increases were more clearly observed. These results indicated that transmitted laser light would be useful for the assessment of tooth pulp vitality both because the blood flow signals did not include flow of non-pulpal origin, and because its output signals and response to blood flow changes were clear and could easily be monitored.

Dental Pulp↗
PubMed2001

[Classification of a 300,000-year-old dental crown of the upper loamy deposit of the Bad Canstatter travertine zone].

Hominid dental remains were recovered in association with fossil bones and artifacts during systematic excavations in a loamy deposit located between the two travertine zones T4 and T5 at Stuttgart-Bad Cannstatt, Southwest Germany. Direct dating of a hominid tooth crown with thermoluminescence resulted in a date of 300 kya, which is in agreement with the Holstein Interglacial floral and faunal composition of this layer. The specimen is a lower left canine with hypoplastic morphology. This interpretation is supported by thorough assessment of its overall morphology, comparative metric evaluation, and by scanning electron microscopy analyses of the enamel prisms. Additional microstructural comparison of these dental remains with a tooth from the same site, but derived from a Cervidae specimen supported the distinct differences between both teeth. Here we discuss both the classification and significance of the specimen's evolutionary position as well as compare this specimen with stomatologic results from previous palaeopathological research.

Animals↗
PubMed2000

[Dental crowns made from a titanium alloy prepared by a superplastic molding method].

The possibility of making titanium tooth crowns by superplastic molding has been investigated. Optimal materials and technological parameters have been selected: Siolit molding mass, fixing composition for facing with plastic (Targit link + opaquer), method for tooth preparation under such crowns (step 135, stump height to diameter ratio 1.5:1, smooth transfer from occlusion surface to others, and disposition of stamps in the press form.

Crowns↗
PubMed2006

In vitro computer analysis of crown discolouration from commonly used endodontic sealers.

The aim of this study was to assess the degree of staining of tooth crowns by commonly used endodontic sealers using a computer analysis method. Crown discolouration by root canal sealers AH26, Endofill, Tubliseal, Zinc oxide eugenol (ZnOE), Apatite root canal sealer III as well as gutta-percha and Cavizol (a filling material containing ZnOE) were tested on extracted human premolar teeth. The roots of the teeth were resected 3 mm below the cemento-enamel junction. The pulp chambers were then cleaned and irrigated. The samples were divided into nine groups of five samples each and filled with test materials. Ten teeth were used as control groups: five positive (amalgam) and five negative (distilled water). The degree of tooth discolouration was analysed at 3, 6 and 9 months. The crown discolouration was assessed by computer analysis of digital images taken from the samples using the CIE Lab colour system. Statistical analysis was carried out using anova, repeated measure anova and Tukey's HSD tests. All sealers caused a degree of tooth discolouration, which increased with time. Endofill and ZnOE caused the greatest discolouration and Apatite root canal sealer III caused the least discolouration after 9 months. The most discolouration during the test periods occurred in the cervical third of the crown.

Analysis of Variance↗
PubMed1998

Odontometric microevolution in the Valley of Oaxaca, Mexico.

Tooth crown lengths, breadths, and areas were compared from five sequential human skeletal samples from the Valley of Oaxaca, Mexico, spanning the period from 1600 BC to AD 1521. Almost all of the measurements considered exhibited dramatic reduction over that period. Total crown area declined from 1320 mm2 to 1262 mm2, a change of 4.4% or 9.4 darwins, which is noticeably larger than any previously reported rate of dental reduction in a recent human population. This reduction was greatest in posterior tooth breadths, especially in the mandible. The patterning of the reduction, and of the variance of the measurements, indicates that natural selection was primarily responsible for the change. Of all the measurements, anterior breadths appear to have been the least subject to selection, and posterior lengths the next least. The degree of reduction suggests that selective pressures towards smaller teeth were greater in Mesoamerica than elsewhere. This case provides an example of the value of recent human skeletal series for the study of microevolutionary processes.

Animals↗
PubMed1998

Discrimination of hardness by human teeth apparently not involving periodontal receptors.

Periodontal receptors are generally thought to provide the input used to detect the hardness of food. Whether hardness can be sensed by teeth without periodontal assistance was tested here. A bite-force transducer was sandwiched between a hard acrylic strip on one side and rubber on the other side, both sides being covered with masking tape to prevent participants from sensing a difference in touch. Participants were asked to increase the bite force on the sandwich until, and if, they could detect which material, hard acrylic or rubber, was on the upper side. The positions of acrylic and rubber were randomly chosen. Fifteen participants each undertook three separate experiments each involving 10 tests using (1) bare incisors, (2) incisors capped with acrylic and (3) bare molars. The accuracy of responses and the direction and magnitude of bite forces were recorded. Participants most correctly detected the surfaces with bare incisors (91% correct, SD = 11%). Performance was significantly worse with capped incisors (79%, SD = 19%) (p < 0.01) and worse still with molars (57%, SD = 24%) (p < 0.001). The detection threshold using bare incisors was increased in 14 out of the 15 participants when the incisors were capped, but the increase was statistically significant (0.002 < p < 0.01) in only six of them. The molar threshold was significantly increased (0.002 < p < 0.01) in comparison with the bare incisor threshold in 12 of 15 participants. There was no correlation between bite direction and the position of the rubber. Because in each trial the upper and lower periodontal input was the same whether the rubber was on the top or on the bottom, it was concluded that the periodontal ligament was not involved. The observed discrimination was probably based on a difference in the pressure on the upper and lower teeth. Incisal edges sank more deeply into the rubber and reduced the pressure (force/unit area) on a tooth crown.

Acrylic Resins↗
PubMed2006

Associations between Carabelli trait and cusp areas in human permanent maxillary first molars.

Few dental anthropological studies have investigated the associations between tooth crown size and crown traits in humans using quantitative methods. We tested several hypotheses about overall crown size, individual cusp areas, and expression of Carabelli cusps in human permanent first molars by obtaining data from standardized occlusal photographs of 308 Australians of European descent (171 males and 137 females). Specifically, we aimed to calculate the areas of the four main molar cusps, and also Carabelli cusp, and to compare the relative variability of cusp areas in relation to timing of development. We also aimed to compare cusp areas between males and females and to describe how Carabelli cusp interacted with other molar cusps. Measurements included maximum crown diameters (mesiodistal and buccolingual crown diameters), the areas of the four main cusps, and the area of Carabelli cusp. The pattern of relative variability in absolute areas of molar cusps corresponded with their order of formation, the first-forming paracone displaying the least variation, and the last-forming Carabelli cusp showing the greatest. Overall crown size and areas of individual cusps all showed sexual dimorphism, with values in males exceeding those in females. Sexual dimorphism was smallest for paracone area and greatest for Carabelli cusp area. Overall crown size and cusp areas were larger in individuals displaying a Carabelli cusp, especially the hypocone area. Although the combined area of the protocone and a Carabelli cusp was greater in cuspal forms than noncuspal forms, protocone area alone was significantly smaller in the former. Our findings lead us to propose that, in individuals with the genotype for Carabelli trait expression, larger molar crowns are more likely to display Carabelli cusps, whereas molars with smaller crowns are more likely to display reduced forms of expression of the trait. We suggest that the pattern of folding of the internal enamel epithelium in developing molar crowns, particularly in the protocone region, can be modified by a developing Carabelli cusp.

Analysis of Variance↗
PubMed2004

A possible interdependency between the wavy path of enamel rods, distances of Retzius lines, and mitotic activity at the cervical loop in human teeth: a hypothesis.

In human enamel, the enamel rods do not run straight in most regions. Instead, they obtain an undulated path. The diameter of the enamel rods remains constant all the way, and a wavy pattern is necessary to produce the volume of the enamel mantle. It is not understood, how this undulated migration of ameloblasts is created. Considerations are presented to explain causal interdependencies between the wavy path of the enamel rods, unequal growth of the cervical loop cells and unequal distances of the striae of Retzius. To test these considerations, further research must record mitotic activity at the cervical loop during the stages of dental development. The distances of Retzius lines must be measured at different spots all over the whole enamel mantle, preferably in 3D. As a result, knowledge of the interdependency between the inner structure and the outer form of each tooth crown will lead to an understanding of tooth form and occlusion.

Ameloblasts↗
PubMed2006

A comparison of the visual and technical assessment of preparations made by dental students.

The preparation of acrylic teeth in a simulated clinical environment (phantom head) plays an essential role in pre-clinical dental education where evaluation is performed visually by instructors. The aim of this investigation was to verify the quality criteria of a tooth preparation for a metal-ceramic crown (tooth No. 21) with the help of digital measurement. Thirty-six acrylic teeth were prepared by students and one tooth was prepared ideally by a trained dentist: These were examined and compared. Five experienced instructors independently assessed the quality criteria with the use of a criterion list. Afterwards, the teeth were scanned with the 3D-laser scanner 'es1' (Etkon Company, Munich, Germany). The calculation of the correlation coefficient demonstrated a satisfactory correlation between visual and digital rating concerning convergence angle, shoulder width and occlusal reduction. Greater differences between experimental groups were observed with regards to other criteria on the applied criterion list. A directed calibration of the evaluators and a re-evaluation of some measurements would be necessary to gain more precise results.

Computer-Assisted Instruction↗
PubMed2004

[Restoring ceramo-metal tooth by using self-made crown post-core in order to re-utilize the broken crown of the base tooth].

OBJECTIVE: To explore a new method and its clinical significance of restorative ceramo-metal by using a self-made crown post-core to reutilize the broken crown. METHODS: 18 teeth were restored with ceramo-metal tooth by using self-made crown post-core in order to preserve the old broken base tooth. The patients' own feelings and clinical effect were observed. RESULTS: Followed up for 1-3 years, 83.3% (15 teeth) of the patients were successful. Among the group one was failed because of bad condition of post and caused split of tooth root. The second failure was caused by uneven force by coherent paste uneven. The third failure was caused by tight biting force and caused the tooth broken. CONCLUSION: Restoring ceramo-metal tooth by using self-made crown post-core in order to re-utilize the broken crown of the base tooth is convenient and low cost and is suitable for basic hospitals.

Crowns↗
PubMed1997

Long-term success rate of resin-bonded metal crowns on the canine teeth of working dogs.

In this clinical study, 19 full metal crown restorations of canine teeth were placed in seven working dogs. Thirteen canine teeth were severely abraded with no involvement of the pulp cavities; six fractured canine teeth were endodontically treated. At least 1/3 of the coronal part of the canine tooth was available for a supragingivally performed, minimal tooth crown preparation. An adhesive technique to bond the electrolytically etched crown (an alloy of cobalt-chrome-molybdenum) to the tooth was used. The metal crowns, slightly shorter and with a rounder tip than the original tooth, were bounded to the enamel and dentine by using a resin luting cement. Posts or post-and-core techniques were not used. Mean follow-up period was 32 months (range 24-52 months), at which stage 17 crowns were found to be intact and functional. Two crowns were lost as a result of trauma resulting in a fracture of the tooth below the crown.

Acrylic Resins↗
PubMed2002

Microscope observations of ART excavated cavities and restorations.

This in vitro light and scanning electron microscope study examined 39 extracted tooth specimens, hand excavated and restored according to atraumatic restorative treatment (ART), using 'press finger', by 'skilled' and 'novice' operators. Surface features of five excavated cavities, 12 restoration surfaces and the tooth restoration relationships of 22 bisected restored tooth crowns were examined to better understand the clinical effect of the technique. Hand-excavated cavity surfaces were rough with a complex surface arrangement of grooves, crevices, ridges, furrows and overhangs. Enamel and dentine were covered with debris except where surface fractures exposed enamel prisms and occluded dentinal tubules. Ten of the 22 bisected restored specimens had large voids (1-3 mm in length) within the glass-ionomer cement (GIC) restoration or at the tooth-restoration interface. Smaller bubbles (< 50 microns) and irregular shaped inclusions were common in all restorations. Adaptation of the GIC to the cavity margin was extremely variable and easily distinguished from the effects of dehydration shrinkage. It is thought that cavity surface irregularities could cause placement problems making it difficult to adapt the GIC to cavity peripheries. While 'press finger' enabled excellent penetration of GIC into fissures, the technique left restoration surfaces rough. At low magnification, surfaces were irregular; at magnifications higher than X500 scratches, pits, porosities, chipping and voids were evident. However, the 'press finger' technique was able to merge the GIC to a fine edge on the occlusal surface so that the restoration margin was not obvious. No apparent difference was found between the restorations placed by the 'skilled' and 'novice' operators. Tooth-restoration relationships in the ART approach are entirely different to those of traditional restorative techniques. The ART approach requires skill, diligence and comprehension to be undertaken correctly.

Clinical Competence↗
PubMed2003

Three-dimensional visualization of the craniofacial patient: volume segmentation, data integration and animation.

The research goal at the Craniofacial Virtual Reality Laboratory of the School of Dentistry in conjunction with the Integrated Media Systems Center, School of Engineering, University of Southern California, is to develop computer methods to accurately visualize patients in three dimensions using advanced imaging and data acquisition devices such as cone-beam computerized tomography (CT) and mandibular motion capture. Data from these devices were integrated for three-dimensional (3D) patient-specific visualization, modeling and animation. Generic methods are in development that can be used with common CT image format (DICOM), mesh format (STL) and motion data (3D position over time). This paper presents preliminary descriptive studies on: 1) segmentation of the lower and upper jaws with two types of CT data--(a) traditional whole head CT data and (b) the new dental Newtom CT; 2) manual integration of accurate 3D tooth crowns with the segmented lower jaw 3D model; 3) realistic patient-specific 3D animation of the lower jaw.

Cineradiography↗
PubMed1997

The craniofacial complex in 47,XYY males.

Eight adult, Finnish 47,XYY males were compared with population male and female controls and, in addition, three of them were compared with first-degree male relatives. Linear and angular measurements were made from standardized lateral cephalograms of patients and normal population controls from the "Kvantti" study series. In both comparisons the craniofacial dimensions in 47,XYY males were larger than those in population male and female controls. Their craniofacial proportions and plane angles were similar to those of normal men except for a larger lower facial height with posterior rotation of the mandible and a tendency to bimaxillary protrusion, a longer cranial base and a lesser cranial-base angle. Thus the supernumerary Y chromosomal gene(s) in 47,XYY males may result in larger craniofacial dimensions than in normal males, without substantial effects on dimensional ratios and plane angles. This general metric pattern is similar to that observed in relation to many adult body and head dimensions, and the dental arches and tooth crowns, of 47,XYY males. The foramen magnum in 47,XYY males was smaller in the sagittal plane than that of normal males and females.

Adolescent↗
PubMed1997

Smooth coronal surface, resin restoration and microleakage.

The space between the resin and the cavity walls has always become interesting to search. The aim of this study was to evaluate any differences on leakage values of Class 5 type resin restorations prepared on surrounding surfaces of the tooth crown. Ninety human teeth were prepared as Class 5 cavities on buccal, lingual, mesial and distal surfaces and were randomly divided into groups for bevelling, groove preparation and as control. The subgroups were arranged as fluoride gel and/or sealant applications. Fluoride gel was applied following the cavity preparations. Sealant was applied over composite resin restorations. Treated teeth were thermocycled and immersed into dye solution for 96 hours. The restorations were evaluated in a stereo-microscope following the sectioning. Bevelling of the cavosurfaces and/or preparation of a groove addition to cavity procedures did not make any difference on the microleakage scores of the restorations done on either surfaces statistically.

Composite Resins↗
PubMed2005

Regulation of mammalian tooth cusp patterning by ectodin.

Mammalian tooth crowns have precise functional requirements but cannot be substantially remodeled after eruption. In developing teeth, epithelial signaling centers, the enamel knots, form at future cusp positions and are the first signs of cusp patterns that distinguish species. We report that ectodin, a secreted bone morphogenetic protein (BMP) inhibitor, is expressed as a "negative" image of mouse enamel knots. Furthermore, we show that ectodin-deficient mice have enlarged enamel knots, highly altered cusp patterns, and extra teeth. Unlike in normal teeth, excess BMP accelerates patterning in ectodin-deficient teeth. We propose that ectodin is critical for robust spatial delineation of enamel knots and cusps.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The relationship of handedness to asymmetry in the occlusal morphology of first permanent molars.

Handedness has been shown to be related to a number of systematic asymmetries in body dimensions, dermatoglyphic patterns and cerebral morphology. The aim here was to compare linear and angular tooth crown asymmetries of the permanent molars in healthy right-handed and left-handed subjects. The material comprised 27 children with recorded concordant left-side dominance of hand, eye and foot. The controls were an age- and sex-matched group with right side dominance. The material is based on the Collaborative Perinatal Project where detailed medical records and the dentitions, including accurate dental impressions, of over two thousand American children were examined in the USA in the sixties. Machine vision technique was used to obtain accurate three-dimensional information from the occlusal surfaces of the first permanent upper and lower molars. The directional asymmetry values of angular measurements of mandibular first molars showed evidence of asymmetry of opposite direction between the two examined groups. The results indicate that occlusal morphology of first permanent molars may be affected by handedness, and this tendency is most evident in the angular measurements of the mandibular molars. Fluctuating asymmetry did not differ significantly between the examined groups.

Child↗