Bovine Bone Screws: Metrology and Effects of Chemical Processing and Ethylene Oxide Sterilization on Bone Surface and Mechanical Properties

We assess the effects of chemical processing, ethylene oxide sterilization, and threading on bone surface and mechanical properties of bovine undecalcified bone screws. In addition, we evaluate the possibility of manufacturing bone screws with predefined dimensions. Scanning electronic microscopic images show that chemical processing and ethylene oxide treatment causes collagen fiber amalgamation on the bone surface. Processed screws hold higher ultimate loads under bending and torsion than the in natura bone group, with no change in pull-out strength between groups. Threading significantly reduces deformation and bone strength under torsion. Metrological data demonstrate the possibility of manufacturing bone screws with standardized dimensions.

Organophosphate-related ototoxicity: Description of the vestibulocochlear system ultrastructural aspects of guinea pigs

Organophosphate toxic agents are used in agriculture and are currently part of the group of toxic agents which can lead to hearing loss, in which we have solvents, metals and asphyxiation agents. Aim: to analyze the acute ototoxic action of a group of organophosphate agents in the vestibulocochlear system. This is a prospective experimental study. Materials and Methods: we used male albino guinea pigs, broken down into three groups, to which we provided distilled water (group 1 - control), agrotoxic agent - 0.3mg/Kg/day (group 2), agrotoxic - 3 mg/Kg/day (group 3), during 7 seven consecutive days. The most used agrotoxic agent was Tamaron BR (metamidophos). The anatomical evaluation of the cochlea, saccule and utricle was carried out by means of electronic scanning microscopy after the use of the agrotoxic agent. Results: the guinea pigs submitted to the organophosphate presented cochlear morphological alterations with lesions on the three turns analyzed, as well as cilia alterations in the saccule and utricle, intensified according to the agent dosage. Conclusion: the morphological alterations seen in the hair cells exposed to daily doses of organophosphate promote evidences of an acute deleterious effect of agrotoxic agents on the vestibulocochlear system.

Tactile threshold detection in leprosy patients with an electronic algometer

Objective: To propose an electronic method for sensitivity evaluation in leprosy and to compare it to the Semmes-Weinstein monofilaments. Methods:Thirty patients attending the Dermatology outpatient clinic of HCFMRP-USP were consecutively evaluated by both the electronic aesthesiometer and Semmes-Weinstein monofilaments on hand and foot test points. The intraclass correlation coefficient (ICC) was calculated to determine the variability of the electronic measures and the Kappa coefficient was calculated to determine the agreement between methods according to their categories (altered and non-altered tactile sensitivity). Results: The ICC was approximately 1, demonstrating repeatability. The Kappa coefficient showed more than 75 and 63% agreement on the hand and foot points, respectively. The mean agreement between the 2 methods for the 7 points of the right and left hand was 77.14 and 75.71%, respectively. The mean agreement for all 10 points was 74.33 and 63.66% on the right and left foot, respectively. In cases of disagreement the detection of altered tactile sensitivity by the electronic esthesiometer on the right and left foot was 90.91 and 84.25%, respectively, with no detection by the monofilaments. Conclusion: The results suggest that the electronic esthesiometer is a reliable and easy application, capable of evaluating alterations of tactile sensitivity in leprosy patients. (C) 2009 Elsevier B.V. All rights reserved.

Accuracy of working length determination using 3 electronic apex locators and direct digital radiography

Objectives. The objectives of this study were to assess the accuracy of working length determination using 3 electronic apex locators and direct digital radiography and to compare the results with those obtained using the visual method (control measurement). Study design. Twenty extracted human maxillary premolars were selected: 17 two-rooted and 3 single-rooted (total of 37 canals). Working length was measured using electronic apex locators Elements Diagnostic, Root ZX, and Just II. Subsequently, teeth were positioned in the alveolar bone of a dry skull and submitted to direct digital radiography. A variation of +/- 1 mm was considered as acceptable. Results were analyzed using the Wilcoxon and the chi(2) tests. Results. Results presented an accuracy of 94.6% for Elements Diagnostic, 91.9% for Root ZX, 73.0% for Just II, and 64.9% for direct digital radiography when considering the margin of +/- 1 mm in relation to the control measurement. Comparisons with the actual control measurements resulted in accuracy results of 13.51%, 13.51%, 10.10%, and 2.70%, respectively. Conclusions. Root ZX and Elements Diagnostic are more accurate in determining working length when compared with Just II and Schick direct digital radiography. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:e44-e49)

Analysis in vitro of the cytotoxicity of potential implant materials. I: Zirconia-titania sintered ceramics

Zirconia (ZrO(2)) is a bioinert, strong, and tough ceramic, while titania (TiO(2)) is bioactive but has poor mechanical properties. It is expected that ZrO(2)-TiO(2) mixed ceramics incorporate the individual properties of both ceramics, so that this material would exhibit better biological properties. Thus, the objective of this study was to compare the biocompatibility properties of ZrO(2)-TiO(2) mixed ceramics. Sintered ceramics pellets, obtained from powders of TiO(2), ZrO(2), and three different ZrO(2)-TiO(2) mixed oxides were used. Roughnesses, X-ray diffraction, microstructure through SEM, hardness, and DRIFT characterizations were performed. For biocompatibility analysis cultured FMM1 fibroblasts were plated on the top of disks and counted in SEM micrographs 1 and 2 days later. Data were compared by ANOVA complemented by Tukey`s test. All samples presented high densities and similar microstructure. The H(2)O content in the mixed ceramics was more evident than in pure ceramics. The number of fibroblasts attached to the disks increased significantly independently of the experimental group. The cell growth on the top of the ZrO(2)-TiO(2) samples was similar and significantly higher than those of TiO(2) and ZrO(2) samples. Our in vitro experiments showed that the ZrO(2)-TiO(2) sintered ceramics are biocompatible allowing faster cell growth than pure oxides ceramics. The improvement of hardness is proportional to the ZrO(2) content. Thus, the ZrO(2)-TiO(2) sintered ceramics could be considered as potential implant material. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 94B: 305-311, 2010.

Esthetic restorative materials and opposing enamel wear

This in vitro study compared the effects of a gold alloy (Degulor M), four dental ceramics (IPS Empress, IPS Empress 2, Duceram Plus, Duceram. LFC) and a laboratory-processed composite (Targis) on the wear of human enamel. The amount of wear of the enamel (dental cusps) and restorative materials (disks) were tested in water at 37 degrees C under standard load (20 N), with a chewing rate of 1.3 Hz and was determined after 150,000 and 300,000 cycles. Before the test, the average surface roughness of the restorative materials was analyzed using the Ra parameter. The results of this study indicate that Targis caused enamel wear similar to Degulor M and resulted in significantly less wear than all the ceramics tested. IPS Empress provoked the greatest amount of enamel wear and Degulor M caused less vertical dimension loss. Targis could be an appropriate alternative material to ceramic, because it is esthetic and produces opposing enamel wear comparable to gold alloy.

Effect of prolonged erosive pH cycling on different restorative materials

This in vitro study evaluated the effect of a prolonged erosive pH cycling on the superficial microhardness change (SMHC) and the erosive wear of different restorative materials. Eighty enamel specimens with prepared cavities of 1.5 x 1.5 mm were randomly divided into eight groups according to the restorative materials used for the fillings (RMGI - resin-modified glass-ionomer, CGI - conventional glass-ionomer, CR- composite resin, A - amalgam) and immersion media used (ERO - erosive medium or SAL - artificial saliva). During 35 days, half of the specimens were immersed in a cola drink (ERO), for 5 min, three times a day, and they remained in SAL between the erosive cycles. The other half of the specimens was immersed in SAL only, for the entire experimental period (control). Data were tested for significant differences by anova and Tukey`s tests (P < 0.05). Scanning electron microscopy images were made to illustrate the enamel erosive wear and restorative materials alterations. The mean SMHC (%) and mean erosive wear (mu m) of the materials were: RMGI-ERO (30/0.5); CGI-ERO (37/0.5); CR-ERO (-0.3/0.3); A-ERO (-4/0.3); RMGI-SAL (4/0.4); CGI-SAL (-6/0.4); CR-SAL (-3/0.2) and A-SAL (2/0.4). Scanning electron microscopy images showed pronounced enamel erosive wear on groups submitted to erosive pH cycling when compared with groups maintained in saliva. In conclusion, the prolonged pH cycling promoted significantly higher alterations (SMHC and erosive wear) on the glass-ionomer cements than the CR and amalgam.

Effect of erosive pH cycling on different restorative materials and on enamel restored with these materials

This in vitro study evaluated the effect of erosive pH cycling on the percentage of surface micro-hardness change (%SMHC) and wear of different restorative materials and bovine enamel restored with these materials. Eighty enamel specimens were randomly divided into eight groups according to the restorative materials and immersion media used: GI/GV-resin-modifled glass-ionomer, GII/GVI-conventional glass-ionomer, GIII/GVII-resin composite and GIV/GVIII-amalgam. Over a period of seven days, groups GI to GIV were immersed in a cola drink (ERO) for 5 minutes, 3x/day and kept in artificial saliva between erosive cycles. Groups GV to GVIII were immersed in artificial saliva (SAL) throughout the entire experimental period (control). Data were tested for significant differences using ANOVA and Tukey`s tests (p < 0.05). For %SMHC, considering the restorative materials, no significant differences were detected among the materials and immersion media. Mean wear was higher for the resin modified glass ionomer cement when compared to conventional cement, but those materials did not significantly differ from the others. For enamel analyses, erosive pH cycling promoted higher wear and %SMHC compared to saliva. There were no significant differences in wear and %SMHC of enamel around the different restorative materials, regardless of the distance from the restorative material (50, 150 or 300 mu m). In conclusion, there were only subtle differences among the materials, and these differences were not able to protect the surrounding enamel from erosion.

Comparison of GPX with or without solvent and hand files in removing filling materials from root canals-An ex vivo study

Objective. The aim of this study was to compare GPX instruments and hand files for gutta-percha removal. Study design. Fifty maxillary central incisors with a single straight canal were instrumented and filled. The teeth were divided into 5 groups of 10 specimens each, according to the gutta-percha removal techniques: group 1: GPX (21-mm-long teeth); group 2: GPX and xylol as solvent (21-mm-long teeth); group 3: GPX (25-mm-long teeth); group 4: GPX and xylol as solvent (25-mm-long teeth); and group 5: hand files and xylol as solvent. The amount of time for gutta-percha removal and the number of fractured instruments were evaluated. Radiographs were taken, and the teeth were grooved longitudinally and split. The area of residual debris was measured using Sigma Scan software. Results. The time for filling material removal was significantly shorter when GPX was used (P < .05). Overall, hand files and solvent produced fewer remnants of filling materials (P < .05). In the GPX 25 mm-long teeth group, the filling material was not removed in the apical third. Conclusions. Under the experimental conditions, the GPX instruments proved to be faster than hand instruments in removing root filling materials; however, hand instruments left a smaller amount of residual filling materials on the canal walls. The GPX instruments did not pull the gutta-percha beyond its tip. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110: 675-680)

Evaluation of the physical and chemical properties of two commercial and three experimental root-end filling materials

Objective. The aim of this study was to evaluate the pH, calcium release, setting time, and solubility of two commercially available mineral trioxide aggregate (MTA) cements (white MTA Angelus and MTA Bio), and of three experimental cements (light-cured MTA, Portland cement with 20% bismuth oxide and 5% calcium sulfate, and an epoxy resin-based cement). Study design. For evaluation of pH and calcium ion release, polyethylene tubes with 1.0 mm internal diameter and 10.0 mm length were filled with the cements and immediately immersed in flasks containing 10 mL deionized water. After 3, 24, 72, and 168 hours, the tubes were removed and the water from the previous container was measured for its pH and calcium content with a pH meter and an atomic absorption spectrophotometer. For analysis of the setting time, Gilmore needles weighing 100 g and 456.5 g were used, in accordance with the American Society for Testing and Materials specification no. C266-03. Solubility of each cement was also tested. Results. All the cements were alkaline and released calcium ions, with a declining trend over time. After 3 hours, Portland cement + bismuth oxide and MTA Bio had the highest pH and light-cured MTA the lowest. After 1 week, MTA Bio had the highest pH and light-cured MTA and epoxy resin-based cement the lowest. Regarding calcium ion release, after 3 hours, Portland cement + bismuth oxide showed the highest release. After 1 week, MTA Bio had the highest. Epoxy resin-based cement and light-cured MTA had the lowest calcium release in all evaluation periods. Regarding setting times, white MTA Angelus and MTA Bio had the shortest, Portland cement + bismuth oxide had an intermediate setting time, and the epoxy resin-based cement had the longest. The materials that showed the lowest solubility values were the epoxy resin-based cement, Portland cement + bismuth oxide, and light-cured MTA. The highest solubility values were presented in white MTA Angelus and MTA Bio. Conclusions. The white MTA Angelus and MTA Bio had the shortest setting times, higher pH and calcium ion release, and the highest solubility. In contrast, the epoxy resin-based cement and light-cured MTA showed lower values of solubility, pH, and calcium ion release. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110: 250-256)