Influence of root maturity or periodontal involvement on dentinal collagen changes following NaOCL irrigation: an ex-vivo study

Abstract Aims: To refine FTIR protocol for detection of NaOCl-induced dentinal collagen changes using an ex- vivo irrigation model, and to apply it to determine the collagen change within 0.5mm of canal or root surfaces, with or without mature roots or periodontal involvement. Methodology: Extracted human roots were irrigated with control saline (n=3) or 5% NaOCl (n=3) and sectioned into transverse discs for FTIR analyses, 0.5mm from both the canal lumen and root surface, before and after surface-treatment with 17% EDTA. Amide I/phosphate and amide II/phosphate absorbance ratios were compared using the Wilcoxon sign rank test. Mature roots without periodontal involvement were irrigated with: saline (n=7), 5% NaOCl (n=7), or 5% NaOCl+17% EDTA (n=7); those with periodontal involvement (n=7) or immature roots (n=7) were irrigated with 5% NaOCl. Dentine discs were then prepared for FTIR analyses. The effects of irrigant/root-maturity/periodontal involvement were analysed using linear mixed models. Results: FTIR analyses of the irrigated samples revealed significant (P < 0.05) reduction in collagen bands near the canal lumen after NaOCl irrigation using surface-EDTA treated samples. Irrigation with test solutions resulted in significant (P < 0.0001) dentinal collagen changes in the mature roots, whilst those in the immature roots were significantly (P < 0.05) greater compared with the mature roots with or without periodontal involvement; but there were no difference between the latter groups. Conclusion: EDTA surface-treatment of polished dentine surfaces enhanced FTIR detection of NaOCl-induced collagen changes. Both root maturity and irrigation protocol influenced the ability of NaOCl to alter dentinal collagen up to 0.5mm from the canal lumen

Association of Environmental Cadmium Exposure with Pediatric Dental Caries

Background: Although animal experiments have shown that cadmium exposure results in severe dental caries, limited epidemiologic data are available on this issue. Objectives: We aimed to examine the relationship between environmental cadmium exposure and dental caries in children 6–12 years of age. Methods: We analyzed cross-sectional data, including urine cadmium concentrations and counts of decayed or filled tooth surfaces, from the Third National Health and Nutrition Examination Survey. We used logistic and zero-inflated negative binomial (ZINB) regression to estimate the association between urine cadmium concentrations and caries experience, adjusting these analyses for potential confounders including environmental tobacco smoke (ETS). Results: Urine cadmium concentrations ranged from 0.01 to 3.38 ng/mL. Approximately 56% of children had experienced caries in their deciduous teeth, and almost 30% had been affected by caries in their permanent dentition. An interquartile range (IQR) increase in creatinine-corrected cadmium concentrations (0.21 μg/g creatinine) corresponded to a 16% increase in the odds of having experienced caries in deciduous teeth [prevalence odds ratio (OR) = 1.16; 95% confidence interval (CI), 0.96–1.40]. This association was statistically significant in children with low ETS exposure (prevalence OR = 1.30; 95% CI, 1.01–1.67). The results from the ZINB regression indicated that, among children with any caries history in their deciduous teeth, an IQR increase in cadmium was associated with 17% increase in the number of decayed or filled surfaces. We observed no association between cadmium and caries experience in permanent teeth. Conclusions: Environmental cadmium exposure may be associated with increased risk of dental caries in deciduous teeth of children

New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism

BACKGROUND: Protocetidae are middle Eocene (49-37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning to land to rest. METHODOLOGY/PRINCIPAL FINDINGS: Two adult skeletons of a new 2.6 meter long protocetid, Maiacetus inuus, are described from the early middle Eocene Habib Rahi Formation of Pakistan. M. inuus differs from contemporary archaic whales in having a fused mandibular symphysis, distinctive astragalus bones in the ankle, and a less hind-limb dominated postcranial skeleton. One adult skeleton is female and bears the skull and partial skeleton of a single large near-term fetus. The fetal skeleton is positioned for head-first delivery, which typifies land mammals but not extant whales, evidence that birth took place on land. The fetal skeleton has permanent first molars well mineralized, which indicates precocial development at birth. Precocial development, with attendant size and mobility, were as critical for survival of a neonate at the land-sea interface in the Eocene as they are today. The second adult skeleton is the most complete known for a protocetid. The vertebral column, preserved in articulation, has 7 cervicals, 13 thoracics, 6 lumbars, 4 sacrals, and 21 caudals. All four limbs are preserved with hands and feet. This adult is 12% larger in linear dimensions than the female skeleton, on average, has canine teeth that are 20% larger, and is interpreted as male. Moderate sexual dimorphism indicates limited male-male competition during breeding, which in turn suggests little aggregation of food or shelter in the environment inhabited by protocetids. CONCLUSIONS/SIGNIFICANCE: Discovery of a near-term fetus positioned for head-first delivery provides important evidence that early protocetid whales gave birth on land. This is consistent with skeletal morphology enabling Maiacetus to support its weight on land and corroborates previous ideas that protocetids were amphibious. Specimens this complete are virtual 'Rosetta stones' providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way

A new family of bizarre durophagous carnivorous marsupials from Miocene deposits in the Riversleigh World Heritage Area, northwestern Queensland

A new specimen of the bizarrely specialised Malleodectes mirabilis from middle Miocene deposits in the Riversleigh World Heritage Area provides the first and only information about the molar dentition of this strange group of extinct marsupials. Apart from striking autapomorphies such as the enormous P3, other dental features such as stylar cusp D being larger than B suggest it belongs in the Order Dasyuromorphia. Phylogenetic analysis of 62 craniodental characters places Malleodectes within Dasyuromorphia albeit with weak support and without indication of specific relationships to any of the three established families (Dasyuridae, Myrmecobiidae and Thylacinidae). Accordingly we have allocated Malleodectes to the new family, Malleodectidae. Some features suggest potential links to previously named dasyuromorphians from Riversleigh (e.g., Ganbulanyi) but these are too poorly known to test this possibility. Although the original interpretation of a steeply declining molar row in Malleodectes can be rejected, it continues to seem likely that malleodectids specialised on snails but probably also consumed a wider range of prey items including small vertebrates. Whatever their actual diet, malleodectids appear to have filled a niche in Australia’s rainforests that has not been occupied by any other mammal group anywhere in the world from the Miocene onwards

Cytokeratin intermediate filaments in oral and odontogenic epithelia

With the development of monoclonal antibodies, the intermediate filaments of the cytoskeleton have attracted a great deal of interest in the last twenty years. Because they are highly antigenic, they could be easily identified using immunohistochemical methods and their specificity for one type of cell offered possibilities in the field of diagnostic pathology. The intermediate filaments most specific for epithelial cells are the cytokeratins (CK). After CK were classified, and certain "rules" regarding CK defined, research proceeded apace to investigate epithelia in a vast array of anatomical and pathological situations. However, much of the immunohistochemical data that was generated during the 1980's was difficult to digest and sorne difficult to interpret. Reasons for this include identification of CK by molecular weight rather than CK number, or confusion as to which CK were being labelled by a particular antibody clone known to detect more than one CK. The aim of this article is therefore to present a digest of current knowledge of the CK present within the epithelium of the oral cavity (including the odontogenic epithelium) and its glandular component, and to highlight the significance of the CK phenotype in our understanding of pathological change