Extended CT scale overcomes restoration caused streak artifacts for dental identification in CT--3D color encoded automatic discrimination of dental restorations

OBJECTIVE: Besides DNA, dental radiographs play a major role in the identification of victims in mass casualties or in corpses with major postmortem alterations. Computed tomography (CT) is increasingly applied in forensic investigations and is used to scan the dentition of deceased persons within minutes. We investigated different restoration materials concerning their radiopacity in CT for dental identification purposes. METHODS: Extracted teeth with different filling materials (composite, amalgam, ceramic, temporary fillings) were CT scanned. Radiopacities of the filling materials were analyzed in extended CT scale images. RESULTS: Radiopacity values ranged from 6000-8500HU (temporary fillings), 4500-17000HU (composite fillings) and >30710HU (Amalgam and Gold). The values were used to define presets for a 3D colored volume rendering software. CONCLUSIONS: The effects of filling material caused streak artifacts could be distinctively reduced for the assessment of the dental status and a postprocessing algorithm was introduced that allows for 3D color encoded visualization and discrimination of different dental restorations based on postmortem CT data.

Specialisation and specialist education in prosthetic dentistry in Europe

This presentation reports on the results of a meeting of prosthodontists from selected European countries. The aim of the meeting was to analyse and promote specialisation and specialist education in Prosthetic Dentistry in Europe. Representatives for Europe were selected from the European Prosthodontic Association (EPA) board, the Education and Research Committee of International College of Prosthodontists (ICP), countries with a legally recognised speciality, countries without a recognised speciality but organised training programmes and countries with neither of these situations. Data about specialisation and specialist training in Prosthodontics in Europe was scrutinised and discussed. The programmes for countries with specialist training had relatively similar content, mostly of three years duration. There was strong agreement that a recognised speciality raises the level of care within the discipline for both specialists and non-specialists. In several of the countries where a speciality had been introduced it had been initiated by pressure from public health planning authorities. The conclusions are that from a professional viewpoint an advancement of the speciality over Europe would develop the discipline, improve oral health planning and quality of patient care. A working group for harmonisation was recommended.

A noncoding melanophilin gene (MLPH) SNP at the splice donor of exon 1 represents a candidate causal mutation for coat color dilution in dogs

Coat color dilution in several breeds of dog is characterized by a specific pigmentation phenotype and sometimes accompanied by hair loss and recurrent skin inflammation, the so-called color dilution alopecia or black hair follicular dysplasia. Coat color dilution (d) is inherited as a Mendelian autosomal recessive trait. In a previous study, MLPH polymorphisms showed perfect cosegregation with the dilute phenotype within breeds. However, different dilute haplotypes were found in different breeds, and no single polymorphism was identified in the coding sequence that was likely to be causative for the dilute phenotype. We resequenced the 5'-region of the canine MLPH gene and identified a strong candidate single nucleotide polymorphism within the nontranslated exon 1, which showed perfect association to the dilute phenotype in 65 dilute dogs from 7 different breeds. The A/G polymorphism is located at the last nucleotide of exon 1 and the mutant A-allele is predicted to reduce splicing efficiency 8-fold. An MLPH mRNA expression study using quantitative reverse transcriptase-polymerase chain reaction confirmed that dd animals had only about approximately 25% of the MLPH transcript compared with DD animals. These results provide preliminary evidence that the reported regulatory MLPH mutation might represent a causal mutation for coat color dilution in dogs.

Computer technology applications in surgical implant dentistry: a systematic review

PURPOSE: To assess the literature on accuracy and clinical performance of computer technology applications in surgical implant dentistry. MATERIALS AND METHODS: Electronic and manual literature searches were conducted to collect information about (1) the accuracy and (2) clinical performance of computer-assisted implant systems. Meta-regression analysis was performed for summarizing the accuracy studies. Failure/complication rates were analyzed using random-effects Poisson regression models to obtain summary estimates of 12-month proportions. RESULTS: Twenty-nine different image guidance systems were included. From 2,827 articles, 13 clinical and 19 accuracy studies were included in this systematic review. The meta-analysis of the accuracy (19 clinical and preclinical studies) revealed a total mean error of 0.74 mm (maximum of 4.5 mm) at the entry point in the bone and 0.85 mm at the apex (maximum of 7.1 mm). For the 5 included clinical studies (total of 506 implants) using computer-assisted implant dentistry, the mean failure rate was 3.36% (0% to 8.45%) after an observation period of at least 12 months. In 4.6% of the treated cases, intraoperative complications were reported; these included limited interocclusal distances to perform guided implant placement, limited primary implant stability, or need for additional grafting procedures. CONCLUSION: Differing levels and quantity of evidence were available for computer-assisted implant placement, revealing high implant survival rates after only 12 months of observation in different indications and a reasonable level of accuracy. However, future long-term clinical data are necessary to identify clinical indications and to justify additional radiation doses, effort, and costs associated with computer-assisted implant surgery.

An outline of competencies and the appropriate postgraduate educational pathways in implant dentistry

The use of dental implants has become a widely accepted and well-documented treatment option offering to both patients and dentists an alternative to traditional treatment modalities and at the same time opening a brand new area in dental postgraduate education. As such, it is necessary to define the competencies that the graduate student/dentist will need at the different levels of clinical practice in Implant Dentistry and the educational pathways that are required to convey those competencies in a structured manner. The present position paper provides an initial suggestion for the knowledge, skills and behaviour necessary for a graduate student to practice implant dentistry at the different levels of clinical complexity. An outline of the necessary competencies and structure of various levels of postgraduate university courses is provided together with different educational approaches to support them. The present paper should be evaluated as a platform for discussion for future development of postgraduate curricula in implant dentistry rather than a manual on how to design and operate such curricula.

Teaching and assessment of implant dentistry in undergraduate and postgraduate education: a European consensus

This paper constitutes a summary of the consensus documents agreed at the First European Workshop on Implant Dentistry University Education held in Prague on 19-22 June 2008. Implant dentistry is becoming increasingly important treatment alternative for the restoration of missing teeth, as patients expectations and demands increase. Furthermore, implant related complications such as peri-implantitis are presenting more frequently in the dental surgery. This consensus paper recommends that implant dentistry should be an integral part of the undergraduate curriculum. Whilst few schools will achieve student competence in the surgical placement of implants this should not preclude the inclusion of the fundamental principles of implant dentistry in the undergraduate curriculum such as the evidence base for their use, indications and contraindications and treatment of the complications that may arise. The consensus paper sets out the rationale for the introduction of implant dentistry in the dental curriculum and the knowledge base for an undergraduate programme in the subject. It lists the competencies that might be sought without expectations of surgical placement of implants at this stage and the assessment methods that might be employed. The paper also addresses the competencies and educational pathways for postgraduate education in implant dentistry.

Color polymorphism and intrasexual competition in assemblages of cichlid fish

The origin and maintenance of phenotypic polymorphisms is a classical problem in evolutionary ecology. Aggressive male-male competition can be a source of negative frequency-dependent selection stabilizing phenotypic polymorphisms when aggression is biased toward the own morph. We studied experimental assemblages of red and blue color morphs of the Lake Victoria cichlid fish Pundamilia. Aggression was investigated in mixed-color and single-color assemblages. We found that aggression was indeed biased toward males of the same color, which could in theory reduce aggression levels in mixed-color assemblages and promote coexistence. However, previous studies showed high aggression levels in red and dominance of red over blue males in dyadic interactions, which could hinder coexistence. We found that coexistence in mixed-color assemblages reduced the level of aggression in red males but not in blue males. Red and blue males were equally dominant in mixed-color assemblages, suggesting that predictions derived from dyadic interactions may not be valid for an assemblage situation. The results are consistent with field data: the geographic range of red is nested within that of blue, suggesting that red cannot displace blue. Our study suggests that male-male competition may be a significant force for maintaining phenotypic diversity.

Mapping Individual Variation in Male Mating Preference Space: Multiple Choice in a Color Polymorphic Cichlid Fish

Sexual selection theory largely rests on the assumption that populations contain individual variation in mating preferences and that individuals are consistent in their preferences. However, there are few empirical studies of within-population variation and even fewer have examined individual male mating preferences. Here, we studied a color polymorphic population of the Lake Victoria cichlid fish Neochromis omnicaeruleus, a species in which color morphs are associated with different sex-determining factors. Wild-caught males were tested in three-way choice trials with multiple combinations of different females belonging to the three color morphs. Compositional log-ratio techniques were applied to analyze individual male mating preferences. Large individual variation in consistency, strength, and direction of male mating preferences for female color morphs was found and hierarchical clustering of the compositional data revealed the presence of four distinct preference groups corresponding to the three color morphs in addition to a no-preference class. Consistency of individual male mating preferences was higher in males with strongest preferences. We discuss the implications of these findings for our understanding of the mechanisms underlying polymorphism in mating preferences.

Female preference for male color is necessary and sufficient for assortative mating in 2 cichlid sister species

A critical step for speciation in the face of gene flow is the origination of reproductive isolation. The evolution of assortative mating greatly facilitates this process. Assortative mating can be mediated by one or multiple cues across an array of sensory modalities. We here explore possible cues that may underlie female mate choice in a sympatric species pair of cichlid fish from Lake Victoria, Pundamilia pundamilia and Pundamilia nyererei. Previous studies identified species-specific female preferences for male coloration, but effects of other cues could not be ruled out. Therefore, we assessed female choice in a series of experiments in which we manipulated visual (color) and chemical cues. We show that the visibility of differences in nuptial hue (i.e., either blue or red) between males of the 2 species is necessary and sufficient for assortative mating by female mate choice. Such assortment mediated by a single cue may evolve relatively quickly, but could make reproductive isolation vulnerable to environmental changes. These findings confirm the important role of female mate choice for male nuptial hue in promoting the explosive speciation of African haplochromine cichlids.

In vitro staining effects of stannous fluoride and sodium fluoride on ceramic material.

STATEMENT OF PROBLEM: Long-term fluoride application on the teeth of patients receiving radiation therapy for head and neck tumors results in excessive staining and roughening of ceramic restorations. PURPOSE: The purpose of this in vitro study was to compare the staining effects of 2 fluoride treatments on ceramic disks by simulating 1 year of clinical exposure at 10 minutes per day. In addition, 2 different surface preparations were tested. MATERIAL AND METHODS: Eighty ceramic disks (IPS Empress), 20 x 2 mm, were fabricated. Half of the disks were glazed, and the remaining disks were polished. All disks were brushed for 3 minutes with a soft-bristle power toothbrush and mild dentifrice (baseline) and were immersed in 1 of the 2 fluoride products (0.4% SnF(2), Gel-Kam Gel, or 1.1% NaF, Prevident 5000) for 10 days (n=20). Means and standard deviations of color change (Delta E), surface roughness (Ra, um), and surface gloss (GU) of the ceramic material were measured with a reflection spectrophotometer, a profilometer, and a gloss meter, respectively, at baseline and after fluoride treatment. Two- and 3-way ANOVA (alpha=.05), with surface preparation (polished vs. glazed) and fluoride treatment (0.4% SnF(2) or 1.1% NaF) as independent variables and condition (baseline vs. after fluoride treatment) as a repeated measure, was used to analyze the data. Fisher's PLSD intervals (alpha=.05) were calculated for comparisons among the means. RESULTS: The polished specimens had significantly higher Delta E values, significantly higher surface gloss values, and significantly lower surface roughness values than the glazed specimens before fluoride treatment (P<.001). After both fluoride treatments, ceramic disks exhibited significantly higher surface roughness values when polished and significantly lower surface gloss values when glazed or polished (P<.001). The glazed specimens presented significantly higher surface roughness (P<.001) and lower surface gloss values (P<.001) when treated with 0.4% SnF(2) as compared to NaF. For the polished specimens, there was no significant difference in surface roughness and surface gloss values between the 2 fluoride treatments. CONCLUSIONS: Use of 0.4% SnF(2) and 1.1% NaF gels, in vitro, caused significant color change in the polished IPS Empress ceramic disks. Polishing of the ceramic surface before immersion in either fluoride agent caused the ceramic tested to be more resistant to etching by the 2 solutions tested. The NaF caused less deterioration of the porcelain surface and was less stain inducing than SnF(2).

Different dark conformations function in color-sensitive photosignaling by the sensory rhodopsin I-HtrI complex.

The haloarchaeal phototaxis receptor sensory rhodopsin I (SRI) in complex with its transducer HtrI delivers an attractant signal from excitation with an orange photon and a repellent signal from a second near-UV photon excitation. Using a proteoliposome system with purified SRI in complex with its transducer HtrI, we identified by site-directed fluorescence labeling a site (Ser(155)) on SRI that is conformationally active in signal relay to HtrI. Using site-directed spin labeling of Ser(155)Cys with a nitroxide side chain, we detected a change in conformation following one-photon excitation such that the spin probe exhibits a splitting of the outer hyperfine extrema (2A'(zz)) significantly smaller than that of the electron paramagnetic resonance spectrum in the dark state. The dark conformations of five mutant complexes that do not discriminate between orange and near-UV excitation show shifts to lower or higher 2A'(zz) values correlated with the alterations in their motility behavior to one- and two-photon stimuli. These data are interpreted in terms of a model in which the dark complex is populated by two conformers in the wild type, one that inhibits the CheA kinase (A) and the other that activates it (R), shifted in the dark by mutations and shifted in the wild-type SRI-HtrI complex in opposite directions by one-photon and two-photon reactions.