The influence of age on tooth root colour changes

The purpose of this study was to examine the relationship between tooth root colour and age, and its possible application in age assessment. In this research altogether 100 tooth roots have been analysed. All teeth, that is their roots, were digitally recorded and the colorimetric treatment was made using Adobe Photoshop 7.0 computer program. Studies have shown no significant difference between RGB values analysed on the whole root surface or only on its central part, with certainty p >0.99. It is also established that there is no statistically significant difference in colouration on four anatomical surfaces (buccal, mesial, lingual, distal) of tooth roots with certaintyp>0.99 for red, p>0.99 for green and p>0.50 for blue colouration component. Statistical data interpretation showed that there is a linear correlation between obtained RGB values and age, with r=-0.994, p>0.99 for red component, r=-0.972, p>0.99 for green and r=-0.982, p>0.95 for blue colouration component. From the obtained results it is possible to conclude that analysing the above mentioned parameter we can easily establish dental age and this technique can be the basis of practical application in establishing chronological age of man.     

Physical dimensions influence the functional property of the semicircular canal

The functional dependence of the semicircular canal upon its physical dimensions was evaluated by measuring the internal radius (r), the radius of curvature (R) and the cupula radius (rC) of the posterior canal in 10 freshly dissected frog labyrinths. These values have been compared to the same parameters of the cat labyrinth. The coefficients I, B, K in the Steinhausen equation were determined for both animals. The A ratio between cupula deflection and endolymph displacement was also calculated by utilizing the Bernard equation. The A ratio is three times larger in the frog than in the cat. It follows that if the same acceleration produces similar endolymph displacements in the posterior canal of both animals, the cupula deflection will be larger in the frog. The solution of the Steinhausen equation in the presence of a constant acceleration, however, reveals that the same stimulus intensity will result in a larger endolymph displacement in the cat posterior canal; similarly, the endolymph displacement directly depends on the duration of the stimulating period in both animals. Contrary to the Bernard assumption, these effects generate a G ratio (psi frog/psi cat) which is less than the Q ratio (A frog/A cat). Moreover, G decreases on increasing the duration of the stimulating period. For stimuli of short duration the semicircular canal of a small animal is expected to exhibit a higher sensitivity than that of a larger one. However, the definitive primary afferent discharge will be largely controlled by the receptor/generator potential properties.     

Microbiota in the apical root canal system of tooth with apical periodontitis

Background

Apical periodontitis (AP) is essentially an inflammatory disease of microbial etiology primarily caused by infection of the pulp and root canal system. Variation of the bacterial communities caused by AP, as well as their changes responding to dental therapy, are of utmost importance to understand the pathogensis of the apical periodontitis and establishing effective antimicrobial therapeutic strategies. This study aims to uncover the composition and diversity of microbiota associated to the root apex to identify the relevant bacteria highly involved in AP, with the consideration of root apex samples from the infected teeth (with/without root canal treatment), healthy teeth as well as the healthy oral.

Methods

Four groups of specimens are considered, the apical part of root from diseased teeth with and without root canal treatment, and wisdom teeth extracted to avoid being impacted (tooth healthy control), as well as an additional healthy oral control from biofilm of the buccal mucosa. DNA was extracted from these specimens and the microbiome was examined through focusing on the V3-V4 hypervariable region of the 16S rRNA gene using sequencing on Illumina MiSeq platform. Composition and diversity of the bacterial community were tested for individual samples, and between-group comparisons were done through differential analysis to identify the significant changes.

Results

We observed reduced community richness and diversity in microbiota samples from diseased teeth compared to healthy controls. Through differential analysis between AP teeth and healthy teeth, we identified 49 OTUs significantly down-regulated as well as 40 up-regulated OTUs for AP.

Conclusion

This study provides a global view of the microbial community of the AP associated cohorts, and revealed that AP involved not only bacteria accumulated with a high abundance, but also those significantly reduced ones due to microbial infection.

     

Human tooth wear, tooth function and cultural variability

Among primitive peoples dental attrition appears to be a natural phenomenon. Often the degrees and kinds of tooth wear vary from population to population. This variability is possibly related to certain material aspects of culture such as diet, food preparation techniques and tool usage. In order to learn more about these relationships, extensive cross cultural comparisons must be made. This paper reports on a study of dental attrition among skeletal remains of North American Indians from three areas: California, the Southwest and the Valley of Mexico. A method of comparing worn teeth of these populations was devised so several characteristics of the teeth and supporting bone could be examined by population. This study showed significant differences in type and degree of wear among the three groups as well as differences between sexes within each population. A positive correlation between tooth wear and cultural factors was found. Dietary specialization and division of labor appear to be responsible for the degree and type of wear found in this sample. Further studies of this type are planned to expand the sample size and, if the new data support these correlations, valuable information about human–environmental relationships can be gained.     

奥硝唑用于感染根管消毒的细菌学研究

目的　观察和探讨新型抗厌氧菌药物奥硝唑消毒感染根管的抗菌效果。方法　选择感染根管患牙98颗,常规根管预备后,随机分为试验组(奥硝唑组)和对照组(甲醛甲酚组)各4 9颗。分别在根管预备前、预备后及封药后进行根管内细菌标本采样、培养、分离与鉴定,测定根管内细菌变化及检出情况,并观察封药后临床症状和体征的变化。结果　2组封药后,根管内细菌数量及检出率均较封药前明显降低( P<0 .0 5 ) ,根管内细菌数量及检出率比较,差异无显著性( P>0 .0 5 ) ,奥硝唑的近期临床疗效优于甲醛甲酚。结论　奥硝唑是一种较安全、有效的根管消毒药物     

Field age determination of leopards by tooth wear

Age determination is an important tool in wildlife studies. Estimating the age of animals in the field using tooth wear criteria may be subject to error as a result of variations between individuals, habitats and populations. Data on age estimation of leopards and tooth wear characteristics are lacking. Nineteen leopards in Namibia were assessed for tooth eruption and wear. Between 1991 and 1995 leopards (including 13 individuals of known age) were monitored at one year intervals ('28 leopard years') to record age and tooth wear. At the age of two years leopards had fully developed dentition. Wear started with the incisors and canines, and spread to the premolars and molars. A chronology of tooth eruption and wear in relation to age is presented. Above the age of three years, male leopards showed higher frequencies of enamel flaking and canine fractures than females.     

The influence of oligohydramnios on thoracic dimensions of fetal sheep.

Oligohydramnios frequently leads to lung hypoplasia in the fetus, but the underlying mechanisms are incompletely understood. Our aim was to determine the effects of oligohydramnios on the dimensions of the fetal thorax. Using pairs of implanted ultrasound transducers in 6 fetal sheep, we measured 4 thoracic dimensions (transverse, anterior-posterior, manubrium to left and right hand sides of the diaphragmatic dome) for 2 control days, 3 days of amniotic and allantoic fluid drainage (oligohydramnios), and 2 days after the return of drained fluids. The effect of oligohydramnios, which began at 121-2 days of gestation (term being c.145 days), on each dimension was quantified daily as the difference between the measured value and the value predicted from the growth of that dimension over the study period. Oligohydramnios led, within 48 hours, to significant reductions in the transverse dimension (5.9-6.1%) and in the distance between the manubrium and the dome of the diaphragm (1.7-2.2%). There was no change in the anterior-posterior dimension. We conclude that oligohydramnios causes alterations, within 48 hours, in the dimensions of the fetal thorax which can be reversed, at least partially, by re-expansion of the fluid sacs. These changes, which are expected to produce reductions in thoracic volume, may, if prolonged, lead to lung hypoplasia.     

The ecology and evolution of tooth wear in red deer and moose

Differences in body size and diet type (browser–grazer continuum) have formed functional traits of ruminants, including tooth design. Grazers and mixed-feeders eat a more fibrous diet than browsers, which arguably increase tooth wear. Tooth wear has also been suggested to increase with body size. Moreover, for species with large distribution ranges, different populations may be exposed to very different ecological factors affecting diet and thus tooth wear rates. Therefore, evolutionary history and contemporary ecological conditions, both operating through diet, may be important for patterns of tooth wear. Here, we compare inter- and intraspecific rates of tooth wear in multiple populations of one large browser (moose Alces alces ) and one mixed-feeder (red deer Cervus elaphus ) covering the main distribution range of each species in Norway. We found that the mixed-feeding red deer wore teeth faster than the larger and browsing moose, suggesting that feeding-type was more important than body size for patterns of wear. There was substantial spatial variation in tooth wear rates, but the inter-specific difference in wear was consistent. Molar wear rates, but not incisors wear rates, in the browser were less variable between populations than in the mixed-feeder. There was no close link between incisor and molar wear rates at the population level. Our findings are consistent with the view that both evolution related to diet type and current ecological conditions (being proxies for within-species variation in diet quality) are important for patterns of tooth wear.     

Experimental studies in human tooth wear: I

The construction of a machine called CANIBAL which is capable of simulating the actions of the human mandible during chewing is reported. Powered by an electric motor, a cam activated rocker arm assembly transmits force by means of wires to each point on the mandible where muscles would be attached. A separately adjustable cam, rocker arm, directional pulley and wire represents each muscle. Models of dental arches cast in dental stone or other materials can be mounted and subjected to extended wear. With different cam settings, wear patterns can be produced which resemble those seen on various fossil and living human dental arches.     

Experimental studies in human tooth wear. II

Studies of human tooth wear have been carried on for the past two years using a machine designed to approximate human chewing motions. During this time wear patterns that resemble those frequently found on the teeth of various American Indian skulls have been produced on casts of the definition. Noticeably among these patterns produced are examples of wear on the front end of the dental arches that result in an edge to edge bite. This type of wear was produced by wearing down casts of a modern dentition with a “normal” overbite. The forces applied to the casts mounted on the machine are variable over a wide range and numerous force combinations are possible. By noting these forces and the resulting vectors, the motions necessary to produce different wear patterns can be determined. This has especially aided in understanding the ways in which the oblique molar wear is produced.     

Fate of HERS during tooth root development

Tooth root development begins after the completion of crown formation in mammals. Previous studies have shown that Hertwig's epithelial root sheath (HERS) plays an important role in root development, but the fate of HERS has remained unknown. In order to investigate the morphological fate and analyze the dynamic movement of HERS cells in vivo, we generated K14-Cre;R26R mice. HERS cells are detectable on the surface of the root throughout root formation and do not disappear. Most of the HERS cells are attached to the surface of the cementum, and others separate to become the epithelial rest of Malassez. HERS cells secrete extracellular matrix components onto the surface of the dentin before dental follicle cells penetrate the HERS network to contact dentin. HERS cells also participate in the cementum development and may differentiate into cementocytes. During root development, the HERS is not interrupted, and instead the HERS cells continue to communicate with each other through the network structure. Furthermore, HERS cells interact with cranial neural crest derived mesenchyme to guide root development. Taken together, the network of HERS cells is crucial for tooth root development.     

Comparative observations on the tooth root morphology of Gigantopithecus blacki

The extinct great ape Gigantopithecus blacki from the middle Pleistocene of China and Vietnam is known only from dental and mandibular remains, and its dietary specializations remain contentious. Here, for the first time, we describe the root morphology in G. blacki using computed tomography and three-dimensional image processing. We quantify the tooth root lengths and surface areas of the female G. blacki mandible No. 1 from the Liucheng Cave and compare it to a sample of extant great apes and humans, as well as the giant panda (Ailuropoda melanoleuca) and the American black bear (Ursus americanus). The results show that, in G. blacki, the pattern of mandibular root numbers-particularly that of the premolars-corresponds with that of Gorilla gorilla, Pan troglodytes, and Pongo pygmaeus. However, G. blacki can be distinguished from the extant hominids by having relatively higher values for postcanine root length and surface area, both absolutely and relative to mandibular size (except for premolar root lengths of humans). The relatively large postcanine root surface areas, which are most similar to A. melanoleuca, suggest that the dentition of G. blacki was adapted to sustaining relatively large occlusal forces needed to fracture mechanically resistant foods such as bamboo.     

Effect of root canal sealers on mouse peritoneal macrophage functions

Three root canal filling materials, viz. calcium hydroxide-based cement (Apexit, resin-based cement (AH-plus) and glass-ionomer based material (Ketac Endo) were tested for their influence on several functions of peritoneal macrophages from Balb/c mice. Macrophage functions were evaluated by the adherence, phagocytic, candidacidal and Nitro blue tetrazolium-dye assays. Ketac-Endo enhanced all macrophage functions in the first 2 d (p < or = 0.05), when compared to the positive control, but this effect had changed after 7 and 14 d, causing inhibition of these functions. Other materials suppressed substrate adherence capacity and phagocytosis, while significantly stimulating macrophage microbicidal activity (p < or = 0.05) in a time-dependent manner.     

The influence of age and denture wear on the size of edentulous structures

Objectives : This study was designed to evaluate the influence of age and denture use on the size of arches and residual ridges in edentulous patients. Design : At two nursing homes, maxillary and mandibular stone casts of 302 fully edentulous patients were utilized to measure the size of the arches and residual ridges, according to age and use of complete dentures. Age cohorts were divided into three groups; 60–69, 70–79, and 80–89 years old. Two hundred and forty‐nine denture wearers used complete dentures for at least 2 years before examinations. Fifty‐three non‐denture users had never worn removable prostheses. Chi‐square analysis (p<0.05) was used to establish the possible relations between the linear values and the size indexes of the ridges and arches and the two examined parameters: age and denture wear. Results : Young old patients possessed edentulous structures that were not significantly larger than elderly old patients in both the maxilla and the mandible. Non‐denture users had significantly bigger arches and ridges in both edentulous jaws than denture users. Conclusions : Young old, non‐denture users tended to have bigger residual edentulous tissues compared to elderly old patients who used complete dentures.     

Decelerating and sex-dependent tooth wear in Norwegian red deer

In ungulates, tooth wear is often suggested as a proximate cause of senescence. Tooth wear is expected to be sex-dependent since energetic requirements and food selection varies largely between sexes in sexually dimorphic ungulates. Furthermore, tooth wear may lower mastication efficiency, and we predict a negative correlation between tooth wear and body weight or condition. We tested these predictions on data on tooth wear (estimated as height of first molar) of 1,311 male and 1,348 female red deer ( Cervus elaphus) aged 3-25 years and harvested along the west coast of Norway. The rate of tooth wear decreased with age. Males wear teeth at a higher rate (from 0.61 mm/year in 4-year olds to 0.45 mm/year in 11-year olds) than females (from 0.52 mm/year in 4-year olds to 0.39 mm/year in 11-year olds). Molar height correlated positively with body weight in both sexes, but not after adjusting for body size. Molar height was strongly dependent on body size in 3-year-old individuals (when tooth wear is minimal). Earlier reports in the literature of a positive correlation between tooth height and body weight may therefore be due to initial size differences rather than differences in condition due to tooth wear.     

后磨牙模拟根管模型制备与研究

目的：制备后磨牙模拟根管模型。方法：依照预实验中测试的牙本质和树脂根管模型材料的布氏硬度值（牙本质HB72,树脂块HB54）选取纯铜质铜管为材料（纯铜HB58）同时利用预实验中确认的后磨牙模拟根管模型弯曲角度的范围（70°-60°）并参照树脂根管模型相关数据,设计不同弯曲角度（70°,64°,60°）的纯铜质根管模型,将20套镍钛根管锉随机分为4组,其中3组根管锉分别预备相应角度的10个纯铜质后磨牙根管模型,另一组在临床预备10个后磨牙根管作为对照组。所有镍钛根管锉均在疲劳寿命测试装置中测试疲劳寿命。结果：选用根管长度为16mm±1mm,弯曲半径为5mm,内径为0.70mm的纯铜质铜管制作后磨牙根管模型。其中在弯曲角度为70°的后磨牙根管模型中有33%（2/6）近似临床;在弯曲角度为64°的后磨牙根管模型中有67%（4/6）近似临床;在弯曲角度为60°的后磨牙根管模型中有33%（2/6）近似临床。结论：弯曲角度为64°的纯铜制后磨牙模拟根管模型更接近于临床实际,可为体外研究镍钛根管锉各项指标提供一个较为理想的模型。     

Single visit versus multiple visit root canal

Single visit endodontics offers many advantages over multi visit treatment. Therefore, it is of interest to assess the preference of single visit over multiple visit root canals. We used 86,000 patient records and selected 9017 records matching the inclusion criteria for the analysis using statistical tools (Chi square test at p value <0.05). Data shows that people between 26 to 45 years are often affected with dental caries. Available data is biased towards multi visits rather than single visit regardless number of canals.