Effect of guided bone regeneration on bone quality surrounding dental implants

Bone quality as well as its quantity at the implant interface is responsible for determining stability of the implant system. The objective of this study is to examine the nanoindentation based elastic modulus (E) at different bone regions adjacent to titanium dental implants with guided bone regeneration (GBR) treated with DBM and BMP-2 during different post-implantation periods. Six adult male beagle dogs were used to create circumferential defects with buccal bone removal at each implantation site of mandibles. The implant systems were randomly assigned to only GBR (control), GBR with demineralized bone matrix (DBM), and GBR with DBM + recombinant human bone morphogenetic protein-2 (rhBMP-2) (BMP) groups. Three animals were sacrificed at each 4 and 8 weeks of post-implantation healing periods. Following buccolingual dissection, the E values were assessed at the defects (Defect), interfacial bone tissue adjacent to the implant (Interface), and pre-existing bone tissue away from the implant (Pre-existing). The E values of BMP group had significantly higher than control and DBM groups for interface and defect regions at 4 weeks of post-implantation period and for the defect region at 8 weeks (p < 0.043). DBM group had higher E values than control group only for the defect region at 4 weeks (p < 0.001). The current results indicate that treatment of rhBMP-2 with GBR accelerates bone tissue mineralization for longer healing period because the GBR likely facilitates a microenvironment to provide more metabolites with open space of the defect region surrounding the implant.     

Dental Microwear Texture Analysis of Varswater Bovids and Early Pliocene Paleoenvironments of Langebaanweg,Western Cape Province,South Africa

The extensive early Pliocene mammalian assemblages at Langebaanweg hold the potential to provide important information about paleoenvironments of the southwestern tip of Africa, an area that today consititutes the Fynbos Biome. We here add to a growing body of literature on the paleoenviornments of the site with an examination of dental microwear textures of bovids from the Varswater Formation. Microwear texture analysis is a new, automated and repeatable approach that measures whole surfaces in three dimensions without observer error. A study of extant ruminants indicates that grazers have more anisotropic microwear surface textures, whereas browsers have more complex microwear surface textures. Fossil bovids recovered from the Muishond Fontein Pelletal Phosphorite Member vary in their microwear textures, with some taxa falling within the extant browser range, some closer to extant grazers, and others in between. These results are consistent with scenarios suggesting mosaic habitats including fynbos vegetation, some (probably C₃) grasses, and woodland elements when these fossils were accumulated.     

Twins and the paradox of dental-age estimations: A caution for researchers and clinicians

The biological age difference among twins is frequently an issue in studies of genetic influence on various dental features, particularly dental development. The timing of dental development is a crucial issue also for many clinicians and researchers. The aim of this study was therefore to verify within groups of twins how dental development differs, by applying Demirjian's method, Mincer's charts of development of third molars and two of Cameriere's methods for dental age estimation, which are among the most popular methods both in the clinical and the forensic scenario. The sample consisted of 64 twin pairs: 21 monozygotic, 30 dizygotic same-sex and 13 dizygotic opposite-sex with an age range between 5.8 and 22.6 years. Dental age was determined from radiographs using the mentioned methods. Results showed that dental age of monozygotic twins is not identical even if they share all their genes. The mean intra-pair difference of monozygotic pairs was low and similar to the difference in dizygotic same-sex twins; the maximum difference between monozygotic twins, however, was surprisingly large (nearly two years). This should lead to some circumspection in the interpretation of systematic estimations of dental age both in the clinical and forensic scenario.     

Apparent density of the primate calcaneo‐cuboid joint and its association with locomotor mode,foot posture,and the “midtarsal break”

Primates use a range of locomotor modes during which they incorporate various foot postures. Humans are unique compared with other primates in that humans lack a mobile fore‐ and midfoot. Rigidity in the human foot is often attributed to increased propulsive and stability requirements during bipedalism. Conversely, fore‐ and midfoot mobility in nonhuman primates facilitates locomotion in arboreal settings. Here, we evaluated apparent density (AD) in the subchondral bone of human, ape, and monkey calcanei exhibiting different types of foot loading. We used computed tomography osteoabsorptiometry and maximum intensity projection (MIP) maps to visualize AD in subchondral bone at the cuboid articular surface of calcanei. MIPs represent 3D volumes (of subchondral bone) condensed into 2D images by extracting AD maxima from columns of voxels comprising the volumes. False‐color maps are assigned to MIPs by binning pixels in the 2D images according to brightness values. We compared quantities and distributions of AD pixels in the highest bin to test predictions relating AD patterns to habitual locomotor modes and foot posture categories of humans and several nonhuman primates. Nonhuman primates exhibit dorsally positioned high AD concentrations, where maximum compressive loading between the calcaneus and cuboid likely occurs during “midtarsal break” of support. Humans exhibit less widespread areas of high AD, which could reflect reduced fore‐ and midfoot mobility. Analysis of the internal morphology of the tarsus, such as subchondral bone AD, potentially offers new insights for evaluating primate foot function during locomotion. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Dental screening of medical patients for oral infections and inflammation: consideration of risk and benefit

The primary purpose of preoperative dental screening of medical patients is to detect acute or chronic oral conditions that may require management prior to planned medical interventions. The aim of this communication is to discuss the background of preoperative dental screening and the link between dental pathologies and systemic diseases.     

Direct evidence that KLK4 is a hydroxyapatite-binding protein

The protease kallikrein 4 (KLK4) plays a pivotal role during dental enamel formation by degrading the major enamel protein, amelogenin, prior to the final steps of enamel hardening. KLK4 dysfunction is known to cause some types of developmental defect in enamel but the mechanisms responsible for transient retention of KLK4 in semi-hardened enamel matrix remain unclear. To address contradictory reports about the affinity of KLK4 for enamel hydroxyapatite-like mineral, we used pure components in quasi-physiological conditions and found that KLK4 binds hydroxyapatite directly. Hypothesising KLK4 self-destructs once amelogenin is degraded, biochemical analyses revealed that KLK4 progressively lost activity, became aggregated, and autofragmented when incubated without substrate in both the presence and absence of reducer. However, with non-ionic detergent present as proxy substrate, KLK4 remained active and intact throughout. These findings prompt a new mechanistic model and line of enquiry into the role of KLK4 in enamel hardening and malformation.     

Secretor status and dental caries in Iceland

Abstract The proportion of non-secretors of ABH blood-group substances among Icelanders is one of the highest recorded for European countries. Dental caries prevalence is also very high. In this study of dental caries in young adults mean number of decayed, missing and filled teeth for secretors were 17.4 and for non-secretors 19.9 ( P < 0.05). A majority of patients seeking free dental treatment in the Dental School were non-secretors (62.7%) significantly more than the proportion of non-secretors in the general population (36%; P < 0.01). It is postulated that blood group substances may interfere with the adherence of Streptococcus mutants to teeth.     

Allometric scaling in palaeontology: A critical survey

Allometric scaling models, used to describe morphological and functional relationships between two sets of observations, are examined both in concept and in application. This paper focuses on the underlying assumptions and statistics of the methods most frequently used: linear regression, principal axis and standard major axis analysis. It is shown that the standard major axis (SMA) is the most appropriate bivariate linear model in palaeonotological research. Differences among the models discussed are illustrated by a morphometric analysis of dental dimensions in australopithecines.     

Dandy�CWalker malformation: An incidental finding

Dandy–Walker malformation (DWM) is a rare intracranial congenital abnormality that affects the cerebellum and some of its components; particularly cerebellar vermis, fourth ventricle and is characterized by an enlarged posterior fossa. Although there is an extensive list of signs attributed to DWM, final diagnosis is solely dependent on imaging techniques as there are no signs that are characteristic of DWM. This article reports a case with DWM who was diagnosed by magnetic resonance imaging.