Gray value differences to dentin of root posts radiographed with digital intraoral systems and conventional X-ray films.

This study compared the gray value differences to dentin of titanium and FRC root posts in anterior and posterior teeth radiographed with digital intraoral systems and conventional x-ray film. Radiographic images (n=5) of titanium or fiber-reinforced composite (FRC) root posts placed in extracted teeth were taken with six digital intraoral radiographic devices and conventional x-ray film (control group). Gray value differences were evaluated between the root posts and root dentin. Statistical analyses of the results were performed with three-way and one-way ANOVA with Bonferroni-Dunn's multiple comparisons post-hoc analyses (α=0.05). Significantly higher gray value differences of titanium and FRC posts were found in anterior teeth but not in molars for XIOS, Sidexis and Visualix digital intraoral systems, but not for RVG, DenOptix and VistaScan (FRC posts). Except for DenOptix with incisors and molars and VistaScan with molars, conventional x-ray films showed significantly lower gray value differences of titanium posts in incisors and molars compared to the corresponding digital radiographs.

Melanoma progression exhibits a significant impact on connexin expression patterns in the epidermal tumor microenvironment.

Melanoma depends on, interacts with and reacts to the stroma in which it is embedded, including fibroblasts, extracellular matrix, endothelial cells and immune cells. However, the impact of melanoma on the epidermal tumor microenvironment-the multilayered epithelium of the skin-is poorly understood. Gap junctions are essential for intercellular communication and involved in proliferation, differentiation and homeostasis of keratinocytes. We have shown previously that the gap junction proteins connexin 26 and 30 (Cx26 and Cx30) are induced in the epidermal tumor microenvironment of skin cancers including melanoma. This study compares the extent of Cx26, Cx30 and Cx43 expression in the epidermal microenvironment of melanocytic nevi and melanomas and its association with melanoma thickness, proliferative index of the tumor and its microenvironment, and with 5-year metastasis and survival. We found that induction of Cx26 and Cx30 cell-cell border expression in the epidermal tumor microenvironment correlates to malignancy. Importantly, there was a significant correlation of tumor thickness with the vertical epidermal Cx26 and Cx30 expression pattern and the horizontal Cx26 dissemination. Furthermore, horizontal Cx26 expression correlated with metastasis. Vertical epidermal expression patterns of Cx26 and Cx30 significantly correlated with the proliferative index in the epidermal tumor microenvironment but not with the proliferative index in the tumor. In contrast, Cx43 did not correlate with malignancy, thickness or proliferative index. In summary, here we show for the first time a significant association between the progression of melanoma and alterations in its epithelial tumor microenvironment.

An ex-vivo oral mucosa infection model for the evaluation of the topical activity of antifungal agents.

Although Nystatin has been used since 1950s as a non-absorbable antifungal agent, there is still no reliable in-vivo data available stating a dose-effect relationship of Nystatin-suspension in the treatment of oropharyngeal infection with Candida albicans. Here, we studied the efficacy of a commercially available topical Nystatin suspension in a new ex-vivo model of candidiasis using porcine oral mucosa. After 48 and 96 h of C. albicans infection, 230 IU Nystatin (standard dosage), 100 IU and 20 IU proved to be equally efficacious. Multiple applications of Nystatin were not superior compared with single application. In dosages of 10 and 0.1 IU the activity of Nystatin suspension against C. albicans was no longer confirmed. In an agar diffusion model, the minimal biocidal concentration of Nystatin proved to be 0.25 IU. Our results suggest that the proposed porcine ex-vivo model is much closer to the in-vivo situation compared with other established in-vitro models of the treatment of muco-cutaneous candidiasis and may provide a substitute for animal models in the investigation of antifungal agents. Additionally, it seems to be a valuable tool for further investigations of the pathogenesis of C. albicans infections.

Bending resistance of unit cast posts-and-cores compared with noble posts following molten cast core attachment.

The aim of this in vitro study was to evaluate the bending resistance of unit cast posts-and-cores (UPC) and prefabricated high noble posts with cast-on cores. Tapered posts (ER post-restoring system) of three sizes in diameter (ISO 50, 90, 110) were investigated: UPC were cast of three different alloys (Au-Pt-Pd, Au-Ag-Pt, Co-Cr-Mo). Also, prefabricated tapered noble posts (Heraplat and Pt-Ir) were cast over with metal cores of the different alloys. Prefabricated titanium posts of each size were precision fit into the central core channels of the Co-Cr-Mo cores to serve as control specimens. The 0.2% yield strengths (R(0.2)) of all specimens were tested on a universal testing machine. One-way and three-way anova and Bonferroni-Dunn's multiple comparison tests were performed for the statistical analysis. The mean bending resistance R(0.2) of the unit cast posts-and-cores was 45 +/- 4-46 +/- 5 N for ISO 50 (control group: 54 +/- 3 N), 91 +/- 9-93 +/- 7 N for ISO 90 (control group: 117 +/- 11 N) and 115 +/- 13-130 +/- 12 N for ISO 110 (control group: 141 +/- 12 N). Except for the Au-Pt-Pd UPC of ISO 110, the yield strengths of the control groups were significantly superior to all unit cast alloy combinations (P < 0.05). Significantly lower bending resistance was found for Co-Cr-Mo cores cast over Heraplat and Pt-Ir posts compared with the corresponding Heraplat/Au-Ag-Pt, Heraplat/Au-Pt-Pd and Pt-Ir/Au-Ag-Pt posts-and-cores.

Yield strength of zirconia and glass fibre-reinforced posts.

The aim of this in vitro study was to evaluate the yield strengths of glass fibre-reinforced composite (FRC) posts and zirconia dioxide ceramic (ZDC) posts. Tapered glass FRC posts (DentinPost) and ZDC posts (Cerapost) of three sizes in diameter (ISO 50, 90, 110) were used for bending tests. Conventional prefabricated titanium posts of the same sizes served as control groups. The 0.2% yield strengths (R(0.2)) were tested on a universal testing machine. As zirconia posts fractured before they were yielded 0.2%, the fracture strength instead of the yield strength was recorded for these posts. One-way and two-way anova and Bonferroni-Dunn's multiple comparison tests were performed for the statistical analysis. The mean 0.2% yield strengths of the posts were 27 +/- 1 N for glass fibre-reinforced posts and 58 +/- 4 N for zirconia posts of ISO 50 (control group: 54 +/- 3 N). For ISO 90 yield strengths of 52 +/- 4 N for glass fibre-reinforced posts, 117 +/- 20 N for zirconia posts and 117 +/- 11 N for the control group were obtained. For ISO 110 mean yield strengths amounted to 73 +/- 5 N for glass fibre-reinforced posts, 166 +/- 23 N for zirconia posts and 141 +/- 12 N for the control group. Significantly higher yield strength was recorded for the zirconia and the titanium posts compared with the glass fibre-reinforced posts for the tested ISO sizes.

Effect of luting agents and reconstruction techniques on the fracture resistance of pre-fabricated post systems.

Fracture resistance and fracture modes of endodontically treated maxillary central incisors restored with different post-and-core systems covered with all-ceramic copings were evaluated. Ten samples were prepared for each group. Groups 1, 2 and 3 consisted of tooth-coloured post-and-core, zirconia post (Cosmopost) with a composite core (Tetric Ceram), zirconia post (Cosmopost) with a custom made ceramic core (Cosmo Ingot), glass fibre-reinforced post (FRC Postec) with a composite core (Tetric Ceram), respectively. Group 4 consisted of a titanium post (ERpost) with a composite core (Tetric Ceram). The control group (group 5) consisted of root-filled incisors without posts. Tooth-coloured posts were cemented in the roots using Variolink-2, while titanium posts were cemented in the roots using Harvard cement. The all-ceramic copings were cemented using Variolink-2. Static load was applied to 2 mm below the incisal edge on the palatinal surface of each sample until they were fractured. Fracture data were obtained and statistically analysed with One-way anova and a Tukey's test. The results of the means and standard deviations of the fracture resistance during static loading were: 497.5 +/- 61.94 (1), 474.61 +/- 96.84 (2), 494.61 +/- 104.67 (3), 581.34 +/- 105.36 (4), 420.42 +/- 127.48 (5). There were statistically significant differences between groups 4 and 5. Glass fibre-reinforced posts and composite cores (group 3) showed the most catastrophic failure. Consequently, zirconia ceramic posts can be used in clinical practice.

Various conditioning methods for root canals influencing the tensile strength of titanium posts.

Conditioning the root canal is frequently advised to achieve high post-retention when resin composite luting cements are used. However, manufacturers' instructions for this purpose differ widely from one another. The aim of this study was to compare the tensile bond strengths of passive, tapered, titanium root posts that were luted with four different resin composite cements (Compolute Aplicap, Flexi-Flow cem, Panavia 21 EX, Twinlook) in the root canals at three conditions, namely (i) no conditioning, (ii) etching with 37% phosphoric acid, and (iii) etching + bonding agent application. Panavia 21 EX was further tested after using the primer for the post-surface according to the manufacturer's recommendations. The posts luted with zinc phosphate cement (Tenet) acted as the control group. Following endodontic preparation of 140 intact anterior teeth with hand instruments, the post-spaces were prepared using the opening drills of the corresponding size of the posts. The samples were first stored in water at 37 degrees C for 24 h and then thermocycled (5000 cycles, 5-55 degrees C, 30 s). The tensile strength values were measured with the universal testing machine at a crosshead speed of 0.5 mm min(-1). The data were analysed statistically using anova and corrected with Scheffé test due to the significance levels (P < 0.05). The tensile bond strengths of the titanium posts after luting with various cements and thermocycling were affected by the conditioning systems used for the root canals. Tensile bond strengths were the highest with Flexi-Flow (475 +/- 78 N) followed in descending order by Panavia 21 EX (442 +/- 97 N), Twinlook (430 +/- 78 N) and Compolute Aplicap (352 +/- 76 N) after conditioning the root canal. The use of primer on the post improved the tensile bond strength compared with the non-conditioned group for the Panavia 21 EX group (375 +/- 77 N) (P < 0.001). Tensile bond strengths obtained after luting the posts with zinc phosphate cement (414 +/- 102 N) were not significantly different (P < 0.05) than those of resin composite cements. Although the importance of conditioning the root canal was evident for Panavia 21 EX, it was not the case for the other luting cements tested.

Bond strengths of five tapered root posts regarding the post surface.

The advantage of tapered passive root posts is their homogenous force transmission without creating stress peaks on the root surface because of their anatomical root form. However, their expected retentive strengths are low compared with the other post systems. The objective of this in vitro study was to determine the retentive strengths of five tapered post systems from different manufacturers using tensile tests. For this purpose, all posts were cemented with zinc phosphate cement (Tenet) into the roots of 50 intact anterior teeth according to the manufacturer's instructions for each system. The contact surface area between the root canal wall and the post was taken into account in the calculations in order to obtain comparable results for different post configurations. The highest bond strength values were achieved for the Erlangen post system (10.8 N mm(-2)) and MP Pirec post system (10 N mm(-2)). These values were more than three times those of the Velva-Post (3.2 N mm(-2)) and the Cylindro-Conical system (3.5 N mm(-2)) and five times more than those of the Dr Mooser post system (1.7 N mm(-2)). The bond strength values of the Erlangen post system, Cylindro-Conical system and Dr Mooser post system showed statistically significant differences compared with the other groups. The results of this study indicated that the bond strengths of tapered posts were not only affected by the contact surface but also by the taper angle, shape of the post system, the width of the cement joint, surface roughness of the posts as well as the form of the canal wall. In clinical practice, in case of choosing tapered posts with similar shapes, retention may still vary because of other factors.

Effect of length and diameter of tapered posts on the retention.

The force transmission of tapered unthreaded posts along the root has been reported to be homogenous but their retentive strength was found to be lower compared with those of parallel unthreaded or other kinds of threaded posts. The purpose of this in vitro study was to investigate the effect of length and diameter on the retentive strength of sandblasted tapered prefabricated titanium posts (Erlangen post system). Posts with constant taper angle but with three different lengths (9, 12, 15 mm) and apical diameters (0.5, 0.9, 1.1 mm) were cemented using zinc phosphate cement into the prepared and roughened post spaces of 90 intact anterior teeth. The post retention concerning length and diameter, being independent from each other, was measured by a tensile force test. The retentive strength was found to be proportional to the length as well as to the diameter of the posts. The mean minimum strength (181 +/- 14 N) recorded for the thinnest and shortest post was significantly lower than that of mean maximum strength (612 +/- 85 N) obtained from those of the thickest and longest post. Proportional bond strengths of the posts comprising their surface areas ranged between 6.8 and 7.9 N mm(-2) which were not significantly different between any group. The retention was effected strongly with the increase in the length (approximately 100%) than with the increase in the diameter (approximately 60%). Concerning the posts tested in this study, it is concluded that some caution should be exercised in the choice of post with appropriate length rather than diameter for the tooth concerned.

Effects of different exposure values on diagnostic accuracy of digital images.

OBJECTIVE: The aim of this in vitro study was to compare the effects of different exposure values on the image clarity of 3 digital radiographic systems and 1 conventional direct-exposure emulsion x-ray film. METHOD AND MATERIALS: Three digital radiographic systems, Digora, RVG, and Sidexis, were compared with the conventional dental x-ray film, Ektaspeed Plus. A medullary bone fragment and human teeth were radiographed with varying voltage, exposure time, and focus-receptor distance. Clinical criteria to evaluate image clarity were detail resolution, sharpness, contrast resolution, and artifacts of the different tooth and jaw structures. RESULTS: The optimal exposure times for digital imaging varied between 0.02 and 0.13 seconds and depended on the objects and the imaging systems. Optimal resolution was obtained when a voltage of 60 kV was used. The focus-receptor distance of 33 to 40 cm resulted in the best contrast and sharpness. Digital images did not always provide the detail resolution or sharpness achieved by conventional radiographs. CONCLUSION: The recommended exposure time for digital images amounted to approximately half the time needed for conventional film. Digital images had to be modified by adjusting the contrast and brightness to optimize the visibility of the areas to be diagnosed.

Comparison between manual and mechanical methods of interproximal hygiene.

OBJECTIVE: The aim of this study was to compare the effectiveness of the automated Interclean Interdental Plaque Remover with that of interdental brushes and Ultrafloss. METHOD AND MATERIALS: The interdental hygiene effectiveness of 35 healthy patients suffering from gingivitis was studied by an examiner daily over a period of 1 week. The sizes of the interdental spaces were classified and corresponding-sized interdental brushes or floss was selected. In a random, split-mouth design both interdental cleaning methods, mechanical and manual, were applied while the patients continued to use standard brushing techniques. Disclosed proximal plaque, the papillary bleeding index, and interdental bleeding tendency on stimulation were evaluated. RESULTS: The papillary bleeding index was reduced from an average value of 40% to 25%. Only 5% of interproximal plaque remained after manual interdental cleaning, whereas 40% of plaque was still present after use of the Interclean device. Cleaning efficiency of manual and mechanical methods was comparable in only 1 interproximal space size. At the end of the study, the interdental bleeding on stimulation was significantly higher in the automatically cleaned interspaces than in the manually cleaned spaces. CONCLUSION: Manual interproximal cleaning was more effective than the automated device.

Effect of different surface textures on retentive strength of tapered posts.

STATEMENT OF PROBLEM: Tapered posts allow for the preservation of tooth substance in the fragile apical area and are advantageous in clinical situations where they conform to the root and canal configuration of endodontically treated teeth. However, their lower retention compared with passive parallel-sided or active threaded posts is a disadvantage. PURPOSE: This study determined the retentive strength of tapered titanium posts with different surface textures and examined the effect of roughening dentinal walls of the prepared post space. MATERIAL AND METHODS: Posts with four surface configurations (smooth, with and without grooves, and sandblasted, with and without grooves) were examined when cemented in extracted anterior teeth. RESULTS: The smooth post showed the lowest retentive strength. Sandblasting the smooth post more than doubled its retentive strength. The retentive strength of both smooth and sandblasted posts could be further increased by the addition of circumferential grooves. Roughening the dentinal walls of the prepared post space increased the retentive strength of sandblasted posts with and without grooves even more. CONCLUSIONS: These findings indicated that, when a tapered post is used, roughening the dentin canal wall, as well as sandblasting and grooving the post, can provide statistically significant additional resistance to dislodgment.

Interdisciplinary concepts in treating adult patients.

Pre-prosthetics, as a part of orthodontic treatment in adults has gained increasing importance during recent years. Through coordinated orthodontic, prosthetic and periodontal treatment plans, patients with partial dentition can be offered further treatment possibilities. Such planning would allow for fixed prosthetic treatment possibilities and the survival of critical teeth. They would provide for better aesthetics and avoid functional disturbances. The aim of the present study was to present reports of patients treated by coordinated work at the Dental School of Hamburg University. In patients with partial dentition, premolars were uprighted and distally moved and molars were extruded to be used as abutments for fixed prosthetic reconstructions. Following trauma, the position of the remaining anterior teeth was improved to provide for optimal aesthetics after prosthetic treatment. Extraction of a subalveolarly fractured tooth is avoided through root extrusion and post-core reconstruction. The results demonstrate the advantages of pre-prosthetic treatment as regards stability, aesthetics and function. With the help of pre-prosthetic orthodontic treatment, complicated treatment situations could be handled more successfully than would have been the case without such treatment.