Cervical wear pathobiology by robot-simulated 3-year toothbrushing - New methodological approach.

OBJECTIVES: An ex-vivo study was aimed at (i) programming clinically validated robot three-year random toothbrushing, (ii) evaluating cervical macro- and microwear patterns on all tooth groups of different functional age, (iii) documenting and codificating wear related morphological features at the cemento-enamel junction in young teeth and on roots in older teeth. DESIGN: Following ethical approval random toothbrushing (44 strokes per tooth horizontally, rotating, vertically; 2x/d) with manual toothbrushes and low-abrasive dentifrice was performed in an artificial oral cavity with brushing-force 3.5 N on 14 extracted human teeth. Morphological features were examined by SEM at baseline and after simulated 3 years using the replication technique. 3D-SEM analyses were carried out with a four-quadrant back scattered electron detector. Wilcoxon-Mann-Whitney-test was used for statistical analyses. RESULTS: 3-year random toothbrushing with horizontal, rotating and vertical brushing movements revealed morphological features classified as four enamel patterns, one dentin pattern and three cervical patterns. Negative impacts were enamel, cementum and dentin loss. Positive impact on oral health was removing dental calculus and straightening cervical traumatic and iatrogenic damages. The volume loss varied from x̅=34.25nl to x̅=87.75nl. Wear extended apically from 100 to 1500 micrometres. CONCLUSION: Robot simulated toothbrushing in an artificial oral cavity, with subsequent SEM and 3D-SEM assessment, elucidated both negative and oral health-contributing micromorphology patterns of cervical wear after simulated 3-year random toothbrushing. Cervical macro- and microwear of cementum revealed, for the first time, what we describe as overhanging enamel peninsulas and enamel islands on roots in young teeth, but no enamel islands on roots from older teeth after root cementum loss. In contrast, many older teeth exhibited enamel peninsulas.

Clinical and Micromorphologic 29-year Results of Posterior Composite Restorations.

Prospective clinical studies of composite restorations revealed their safety and longevity; however, studies did not elucidate the dynamic mechanisms of deterioration caused by fractures and secondary caries. Therefore, the aims of this 29-y controlled study were 1) to follow up on the clinical behavior of posterior composite restorations annually and 2) to compare clinical outcomes with micromorphologic scanning electron microscopy features. After ethical approval, the single-arm study commenced in 1987 with 194 class I or II primary posterior composite restorations with glass ionomer cement providing pulp protection. Each restoration was evaluated annually for 15 y and then again at 29 y per the US Public Health Service-compatible Clinical, Photographic and Micromorphologic coding index, with clinical and photographic criteria for anatomic form, color matching, surface quality, wear, marginal integrity, secondary caries, and clinical acceptability. Parallel micromorphologic criteria were applied at baseline and after 1, 3, 5, 7, 10, 15, and 29 y to assess surface roughness, texture, marginal integrity, fractures, ledges, and marginal gaps with semiquantitative coding and with quantitative 3-dimensional scanning electron microscopy profilometric measurements of marginal grooves next to the enamel, grooves within the bonding zone, and ledges. Statistical analysis included the calculation of the annual failure rate and the use of Kaplan-Meier methodology and nonparametric tests. The cumulative survival rates were 91.7% (6 y), 81.6% (12 y), and 71.4% (29 y). The mean annual failure rate was 1.92%. Significant changes in the restoration-tooth interface from baseline to 5 y resulted in functional masticatory equilibrium. Clinical deterioration year by year, including micromorphologic microfractures and wear, reflected unique dynamic changes in long-term surviving restorations with very low secondary caries and fracture risks (German Network for Health Care Research VfD 29 99 003924).

First-time isolation of Candida dubliniensis from plaque and carious dentine of primary teeth.

AIM: To determine those organisms of the genus Candida associated with dental caries by investigating samples from active carious lesions. Within the genus Candida, the species Candida albicans and Candida dubliniensis are capable of forming chlamydospores and germ tubes. Until it became possible in 1995 to differentiate between the two species taxonomically, C. dubliniensis was falsely identified as C. albicans. Whilst the importance of C. albicans for rapidly progressing early childhood caries (ECC) has been recognised, so far there have been only reports about C. dubliniensis in connection with children/mothers who have been infected with HIV or already developed AIDS. In the present study, C. dubliniensis was for the first time isolated from plaque and carious dentine of a healthy five-year-old boy. METHODS: As part of the investigation, a number of samples were collected from individual children affected by active dental caries. Amongst the samples, one in particular indicated that Candida species might be involved. The patient was a five-year-old boy with ECC of the primary dentition, scheduled for restorative treatment under general anaesthesia. Before treatment, a salivary, plaque (region of 54/55) and soft carious dentine sample from the tooth 51 was taken before extraction. The counts of yeasts, lactobacilli (LB) and mutans streptococci were determined in the samples. RESULTS: The boy's dmft was 11, which was dominated by the d component. In the saliva of the boy, LB and mutans streptococci (MS) were detected. In plaque and carious dentine, MS and most interestingly C. dubliniensis were present. The yeasts were visualised in carious dentine by means of scanning electron micrographs. CONCLUSIONS: Plaque and carious dentine may be a further habitat of C. dubliniensis.

The innervation of synovium of human osteoarthritic joints in comparison with normal rat and sheep synovium.

OBJECTIVE: To study whether osteoarthritis (OA) in the knee is associated with a change of the innervation pattern in the synovial layer. DESIGN: In synovial tissue from the normal knee joint of rat and sheep we studied the presence of vessels and of nerve fibres using transmission electron microscopy and immunohistochemistry. Synovial material was also obtained from patients who underwent total knee replacement surgery. This material was examined for inflammatory changes, and the presence of vessels and nerve fibres was assessed. RESULTS: The synovium in the parapatellar region of the normal knee joint of rat and sheep exhibited a dense capillary and neuronal network. It was entered by calcitonin gene-related peptide containing sensory fibres and tyrosine hydroxylase-positive sympathetic nerve fibres. Synovial material from patients with knee OA exhibited different degrees of inflammation. Synovial material without inflammation exhibited a similar vascular and neuronal network as the normal knee joint from rat and sheep. However, in synovium with inflammatory changes we found a significant decrease of nerve fibres in depth ranges close to the synovial lining layer depending on the degree of inflammation whereas deeper regions were less affected. CONCLUSIONS: Inflammatory changes in the synovium of OA joints are associated with a massive destruction of the capillary and neuronal network which is present in normal synovium. Due to the disappearance of the sensory fibres it is unlikely that OA pain is initiated directly in the synovium. The loss of normally innervated vascularisation may have multiple consequences for the physiological functions of the synovium.

The urinary antibiotic 5-nitro-8-hydroxyquinoline (Nitroxoline) reduces the formation and induces the dispersal of Pseudomonas aeruginosa biofilms by chelation of iron and zinc.

Since cations have been reported as essential regulators of biofilm, we investigated the potential of the broad-spectrum antimicrobial and cation-chelator nitroxoline as an antibiofilm agent. Biofilm mass synthesis was reduced by up to 80% at sub-MIC nitroxoline concentrations in Pseudomonas aeruginosa, and structures formed were reticulate rather than compact. In preformed biofilms, viable cell counts were reduced by 4 logs at therapeutic concentrations. Complexation of iron and zinc was demonstrated to underlie nitroxoline's potent antibiofilm activity.

Demineralization of enamel in primary second molars related to properties of the enamel.

Enamel structure is of importance in demineralization. Differences in porosity in enamel effect the rate of demineralization, seen between permanent and deciduous teeth. Individual differences have been shown in the mean mineral concentration values in enamel, the role of this in demineralization is not thoroughly investigated. The aim of this study was to study variations of depths of artificial lesions of demineralization and to analyze the depth in relation to variations in the chemical and mineral composition of the enamel. A demineralized lesion was created in second primary molars from 18 individuals. Depths of lesions were then related to individual chemical content of the enamel. Enamel responded to demineralization with different lesion depths and this was correlated to the chemical composition. The carbon content in sound enamel was shown to be higher where lesions developed deeper. The lesion was deeper when the degree of porosity of the enamel was higher.

Intracellular ion monitoring using a gold-core polymer-shell nanosensor architecture.

In this study, we describe the design of new ratiometric fluorescent nanosensors, whose architecture is based on a gold core surrounded by a poly(vinyl alcohol)-polyacetal shell. To the gold core, indicator dyes and reference dyes are attached via a cysteine linker. This nanosensor architecture is flexible with regards to the number and types of fluorophore linkages possible. The robust poly(vinyl alcohol)-polyacetal shell protects the fluorophores linked to the core from non-specific interactions with intracellular proteins. The nanosensors developed in this way are biocompatible and can be easily incorporated into mammalian cells without the use of transfection agents. Here, we show the application of these nanosensors for intracellular pH and sodium ion measurements.

Morphological and chemical characterization of tooth enamel exposed to alkaline agents.

OBJECTIVES: In this study, morphological and chemical changes in teeth enamel exposed to alkaline agents, with or without surfactants, have been investigated. In addition, chemical effects of the organic surface layer, i.e. plaque and pellicle, were also investigated. METHODS: The present study was conducted using several techniques: Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). RESULTS: From XPS-measurements, it was found that exposure to alkaline solutions resulted in a massive removal of carbon from the tooth surface, and that the addition of surfactants increased the rate under present conditions. Based on the results from the FTIR-analysis, no substitution reactions between phosphate, carbonate and hydroxide ions in the enamel apatite could be detected. From a minor SEM-analysis, degradation and loss of substance of the enamel surface was found for the exposed samples. From XRD-analysis, no changes in crystallinity of the enamel apatite could be found between the samples. CONCLUSIONS: The findings in this study show that exposure to alkaline solutions results in a degradation of enamel surfaces very dissimilar from acidic erosion. No significant erosion or chemical substitution of the apatite crystals themselves could be discerned. However, significant loss of organic carbon at the enamel surface was found in all exposed samples. The degradation of the protective organic layer at the enamel surface may profoundly increase the risk for caries and dental erosion from acidic foods and beverages.