Economic impact on tooth emergence

As shown in nearly 10,000 Negro and White boys and girls between 4.5 and 16.5 years of age, poverty-level children (with an income-to-needs ratio of 1.0) tend to be delayed in permanent tooth emergence as compared with those approximating median per-capita income. For boys, a per-capita income difference of $2200 was associated with a 0.15 standard deviation difference in emergence timiing of 28 permanent teeth.     

Some observations on the dentition of an isolated group in northeast Poland.

Clinical examination of the teeth and the mouth was carried out on a group of 133 "Old Believers," 54 males and 79 females, and a control group of 138 Poles living in the same area of Augostova in northeast Poland, 63 males and 75 females. Studying the frequency of Carabelli's cusp, shovel-shaped incisors, missing teeth, microdonita, supernumerary teeth, and torus palatinus in both groups, it was found that Carabelli's cusp and torus palatinus are more frequent among Poles. Such differences could be attributed to differences in ethnic origin of the two groups.     

Dental Ontogeny in Macroscelides proboscideus (Afrotheria) and Erinaceus europaeus (Lipotyphla)

We investigated the state of dental eruption in specimens of Macroscelides proboscideus and Erinaceus europaeus of known age. When M. proboscideus reaches adult size and sexual maturity, few or none of its replaced permanent cheek teeth have erupted. The approximate sequence of upper tooth eruption is P1, [I3, C, M1], [I1–2], M2, P4, [P2, P3]. Chronologically, E. europaeus erupts its molars and most premolars prior to M. proboscideus; but its first two upper incisors erupt after those of M. proboscideus, and its canines erupt around the same time. The approximate sequence of upper tooth eruption in E. europaeus is [M1, M2, P2, I3], C, M3, P4, P3, I2, I1. Unlike M. proboscideus, E. europaeus does not reach adult size until all permanent teeth except for the anterior incisors have erupted. While not unique among mammals, the attainment of adult body size prior to complete eruption of the permanent cheek teeth is particularly common among macroscelidids and other afrotherians.     

Mandibular precedence in the prenatal development of four permanent teeth.

As shown in 62 pairs of dental opponents from 32 grossly normal human fetuses in the 75-378 mm crown-rump range, mandibular precedence is the rule for 11, 12, C and M1, a trend in agreement with mandibular precedence for deciduous teeth through dm1 and in the gingival emergence of the same permanent teeth during postnatal development.     

Genetic and epidemiologic studies of oral characteristics in Hawaii's school children: dental anomalies

Racial comparisons of prevalences of dental anomalies were made on 13,473 Hawaiian-born children aged 12 to 18 years. Dental anomalies studied included supernumerary teeth, peg-shaped lateral incisors, dens in dente (invaginated tooth), hypoplasia, fusion (or gemination), and high cingulum of upper lateral incisors (barrel-shaped teeth) in the permanent dentition. The highest frequency of peg-shaped laterals was observed among Filipinos and part-Filipinos with no evidence of heterogeneity among other racial groups. Dens in dente was more common among Hawaiian descendents. Fusion or gemination was observed more commonly among children with Chinese parentage. High cingulum of laterals was fairly common in Orientals particularly in Filipinos and nil among Caucasians and Hawaiians. There was neither significant maternal effect nor effect (non-additive) of hybridity.     

铸造支架式弹性义齿联合正畸治疗在修复牙列缺损伴牙颌畸形中的效果观察

摘要 目的：探讨铸造支架式弹性义齿联合正畸治疗在修复牙列缺损伴牙颌畸形中的效果。方法：于2022.7-2023.6选取100例牙列缺损伴牙颌畸形患者,分为对照组（n=51）、观察组（n=49）。对照组接受铸造支架式弹性义齿修复治疗,观察组在正畸治疗6个月后行铸造支架式弹性义齿修复治疗。比较两组相关指标。结果：观察组治疗6个月后临床总有效率比对照组高（P<0.05）;观察组患者治疗后各项生活质量评分比对照组更高（P<0.05）;观察组患者治疗6个月后各项牙菌斑附着指数、软垢指数、牙周袋深度比对照组低（P<0.05）;观察组患者治疗6个月后各项龈沟液炎性因子水平比对照组低（P<0.05）;观察组治疗期间不良反应总发生率比对照组更低（P<0.05）。结论：铸造支架式弹性义齿联合正畸治疗可促进牙列缺损伴牙颌畸形患者牙齿功能恢复,修复牙列,积极纠正牙齿畸形,改善口腔卫生状况,抑制炎症反应,减少不良反应发生,疗效显著,整体方案可行。     

Aberrant growth of maxillary canine teeth in male babirusa (genus Babyrousa)

A worldwide survey of babirusa skulls curated in museum and private collections located 431 that were from adult males and had retained at least one maxillary canine tooth. Eighty-three of these skulls were identified as exhibiting aberrant maxillary canine tooth growth. Twenty-four of the skulls represented babirusa from Buru and the Sula Islands, and forty-five skulls represented babirusa from Sulawesi and the Togian Islands. The remaining series of fourteen babirusa skulls originally came from zoo animals. Fifteen skulls showed anomalous alveolar and tooth rotation in a median plane. Twenty-nine skulls had maxillary canine teeth that did not grow symmetrically towards the median plane of the cranium. Fourteen skulls showed evidence that the tips of one or both maxillary canine teeth had eroded the nasal bones. Twenty-one skulls had maxillary canine teeth that had eroded the frontal bones. The teeth of two skulls had eroded a parietal bone. One skull had two maxillary canines arising from an adjacent pair of alveoli on the left side of the cranium. Three skulls exhibited alveoli with no formed maxillary canine teeth in them. Analysis suggested that approximately 12% of the adult male babirusa in the wild experience erosion of the cranial bony tissues as a result of maxillary canine tooth growth. There was no skeletal evidence that maxillary canine teeth penetrate the eye.     

Dietary boron does not affect tooth strength,micro-hardness,and density,but affects tooth mineral composition and alveolar bone mineral density in rabbits fed a high-energy diet

The objective of this study was to determine whether dietary boron (B) affects the strength, density and mineral composition of teeth and mineral density of alveolar bone in rabbits with apparent obesity induced by a high-energy diet. Sixty female, 8-month-old, New Zealand rabbits were randomly assigned for 7 months into five groups as follows: (1) control 1, fed alfalfa hay only (5.91 MJ/kg and 57.5 mg B/kg); (2) control 2, high energy diet (11.76 MJ and 3.88 mg B/kg); (3) B10, high energy diet + 10 mg B gavage/kg body weight/96 h; (4) B30, high energy diet + 30 mg B gavage/kg body weight/96 h; (5) B50, high energy diet + 50 mg B gavage/kg body weight/96 h. Maxillary incisor teeth of the rabbits were evaluated for compression strength, mineral composition, and micro-hardness. Enamel, dentin, cementum and pulp tissue were examined histologically. Mineral densities of the incisor teeth and surrounding alveolar bone were determined by using micro-CT. When compared to controls, the different boron treatments did not significantly affect compression strength, and micro-hardness of the teeth, although the B content of teeth increased in a dose-dependent manner. Compared to control 1, B50 teeth had decreased phosphorus (P) concentrations. Histological examination revealed that teeth structure (shape and thickness of the enamel, dentin, cementum and pulp) was similar in the B-treated and control rabbits. Micro CT evaluation revealed greater alveolar bone mineral density in B10 and B30 groups than in controls. Alveolar bone density of the B50 group was not different than the controls. Although the B treatments did not affect teeth structure, strength, mineral density and micro-hardness, increasing B intake altered the mineral composition of teeth, and, in moderate amounts, had beneficial effects on surrounding alveolar bone.     

The eruption pattern of the permanent incisors and first permanent molars in Australopithecus (Paranthropus) robustus

This study aims to reassess the claim that the eruption sequence of the permanent incisor and first permanent molar teeth of Australopithecus (Paranthropus) robustus is identical with that in modern Homo sapiens. Eight fossil hominid mandibles of equivalent dental developmental age were chosen for comparative study. Emphasis has been placed upon the comparative timing of events within the growth period rather than eruption sequence alone. The results of this study indicate that Homo sapiens and Australopithecus (Paranthropus) robustus share the same pattern of permanent molar and incisor eruption and that this is significantly different from the pattern of eruption shared by the great apes, Australopithecus africanus and Australopithecus afarensis.     

Changes in the structure of the baboon hybrid zone in the Awash National Park,Ethiopia

The zone of hybridization between anubis and hamadryas baboons in the Awash National Park, Ethiopia, evidently changed significantly in the early 1970s. When first studied, by Nagel in 1968, the distribution of adult male phenotypes suggested that the hybrid zone was a narrow, static, genetic sink. In contrast, studies during the 1970s found evidence for a broad hybrid zone intergrading with parental populations and probably expanding. A more detailed investigation of data collected in 1973, presented here, shows that between 1968 and 1973 the distribution of phenotypes changed to a more clinal pattern because of the maturation and successful integration of an extensive cohort of hybrid males. We present a provisional model that accounts for the changes in terms of climatic oscillations, with the hybrid zone tending to expand during periods of climatic instability.     

Evolution de la capacité morphogénétique de la région stomodéale chez l'embryon dePleurodeles waltlii Michah (amphibien urodéle). etude par transplantation intrablastocélienne et par culture in vitro

Summary Transplantations into the blastocoel of gastrulae and cultures in vitro of the stomodeal region ofPleurodeles waltlii Michah embryos have been carried out. These experiments gave the following results:Neural crest cells reach the stomodeal region at the young tail-bud stage (stage 22), and are able to take part in formation of teeth and cartilage, it is possible to dissociate the phenomena of mouth opening, complete mouth formation and complete head formation, differentiation of a digestive tube from the pharyngeal endoderm and the formation of a mouth opening both depend on the presence of mesentoderm and mesectoderm in the explant or in the environment, during the tail-bud stage a symmetry factor plays a part in mouth formation, bone formation likewise coincides with the presence of neural crest cells.

     

Japanese tooth size: past and present

Mesial-distal and buccal-lingual crown measurements were made on male and female samples of recent Japanese teeth from three locations, Fukuoka, Kyoto, and Tokyo, and for Hokkaido Ainu and Koreans. Similar data were collected for prehistoric Middle-to-Late Jomon Japanese and from Yayoi specimens representing the first agriculturalists to appear in Japan. From a tooth-by-tooth comparison of cross-sectional areas, it was shown that the modern Japanese samples did not differ from one part of Japan to another. Korean tooth size also is not significantly different from Japanese, while Ainu have the smallest teeth recorded in Asia. The Yayoi who brought rice to Japan about 300 B.C. came in with teeth that were the same size as Chinese Neolithic teeth. They encountered a resident Jomon population whose teeth were 10% smaller. From tooth size measures alone, it is most economical to suggest that, if the rates of reduction observed elsewhere in the world applied in Japan, the recent Ainu would best be regarded as the direct descendants of the Jomon, while the modern Japanese are the results of in situ reduction from the incoming Yayoi. Other aspects of craniofacial morphology suggest that some Jomon was incorporated by the Yayoi. The modern Japanese, then, while predominantly derived from the Yayoi, would include a Jomon component.     

Developmental biology meets materials science: Morphogenesis of biomineralized structures

Biomineralization is the process by which metazoa form hard minerals for support, defense, and feeding. The minerals so formed, e.g., teeth, bones, shells, carapaces, and spicules, are of considerable interest to chemists and materials scientists. The cell biology underlying biomineralization is not well understood. The study of the formation of mineralized structures in developing organisms offers opportunities for understanding some intriguing aspects of cell and developmental biology. Five examples of biomineralization are presented: (1) the formation of siliceous spicules and frustules in sponges and diatoms, respectively; (2) the structure of skeletal spicules composed of amorphous calcium carbonate in some tunicates; (3) the secretion of the prism and nacre of some molluscan shells; (4) the development of skeletal spicules of sea urchin embryos; and (5) the formation of enamel of vertebrate teeth. Some speculations on the cellular and molecular mechanisms that support biomineralization, and their evolutionary origins, are discussed.     

Incidence and patterning of dental enamel hypoplasia among the Neandertals

Dental enamel hypoplasia (DEH), as an indicator of nonspecific stress during development, provides an assessment of the relative morbidity of past human populations. An investigation of 669 Neandertal dental crowns yielded an overall DEH frequency of 36.0% by tooth (41.9% for permanent teeth; 3.9% for deciduous teeth) and about 75% by individual. These incidences place the Neandertals at the top of recent human ranges of variation in DEH frequencies, indicating high levels of stress during development. The paucity of deciduous tooth DEH and M1 DEH, combined with generally increasing levels of DEH through later calcifying teeth, suggests that the stress was primarily nutritional, beginning at weaning and continuing through adolescence. This supports paleontological and archeological interpretations implying significantly lower effectiveness for Neandertal foraging compared to that of modern humans.     

早期哺乳动物三尖齿兽类牙齿的超微结构

本文用扫描电镜研究了中国云南禄丰盆地下禄丰组发现的以及英国威尔士晚三迭世的三尖齿兽类牙齿的超微结构.其釉质具有准釉柱结构,它们呈并行排列从釉牙质界延伸到釉质外表面.这种准釉柱结构由很多羽支状排列的磷灰石微晶组成.微晶的C轴与准釉柱的长轴形成交叉的角度大约为10-20度.早期哺乳动物牙齿釉质的准釉柱结构,很可能是从爬行动物无釉柱结构向哺乳动物真釉柱结构进化过程中的标志.     

A factor analysis of morphogenetic fields in the human dentition

The traditional morphogenetic fields of the human dentition were evaluated by means of factor analysis of dental dimensions taken from a series of human crania. When crown length, crown width and crown index were considered separately, factors emerged which could be identified with the tooth group fields. But a combined crown length-crown width analysis generated factors which extended beyond the regional tooth groups. Crown width itself was revealed to be an important axis of morphologic intergration. It was concluded that univariate methods are not adequate for identifying morphogenetic fields; the teeth must be treated as multidimensional units where the correlation among dimensions is accounted for.