Gentamicin attenuates gentamicin-induced ototoxicity - Self-protection

Aminoglycoside antibiotics cause considerable toxicity to the inner ear. A progressive hearing loss at high frequencies resulted from the loss of hair cells in the base of the cochlea and a constant preoccupation with finding a treatment that protects against their toxic effects. A self-protection phenomenon to high ototoxic doses of gentamicin is proposed in this paper. Thirty-eight adult guinea pigs with normal hearing were tested using Preyer`s reflex and the distortion product otoacoustic emission (DPOAE) test, and their cochleae were analyzed by scanning electron microscopy. To the four groups investigated, group I (control) and group II (low dose, 10 mg/kg/day for 30 days) showed a normal DPOEA and normal outer hair cells; group III (high dose, 160 mg/kg/day for 10 days) showed the absence of DPOEA and damage to the outer hair cells; and group IV (low dose, 10 mg/kg/day for 30 days followed by a high dose of 160 mg/kg/day for 10 days) showed a normal DPOEA and normal outer hair cells. These results demonstrate that there was a considerable self-protection phenomenon by gentamicin.

Multiplex semi-nested RT-PCR with exogenous internal control for simultaneous detection of bovine coronavirus and group A rotavirus

Neonatal calf diarrhea is a multi-etiology syndrome of cattle and direct detection of the two major agents of the syndrome, group A rotavirus and Bovine coronavirus (BCoV) is hampered by their fastidious growth in cell culture. This study aimed at developing a multiplex semi-nested RT-PCR for simultaneous detection of BCoV (N gene) and group A rotavirus (VP1 gene) with the addition of an internal control (mRNA ND5). The assay was tested in 75 bovine feces samples tested previously for rotavirus using PAGE and for BCoV using nested RT-PCR targeted to RdRp gene. Agreement with reference tests was optimal for BCoV (kappa = 0.833) and substantial for rotavirus detection (kappa = 0.648). the internal control, ND5 mRNA, was detected successfully in all reactions. Results demonstrated that this multiplex semi-nested RT-PCR was effective in the detection of BCoV and rotavirus, with high sensitivity and specificity for simultaneous detection of both viruses at a lower cost, providing an important tool for studies on the etiology of diarrhea in cattle. (C) 2010 Elsevier B.V. All rights reserved.

Experimental infection of pregnant queens with two major Brazilian clonal lineages of Toxoplasma gondii

Toxoplasma gondii isolates from Brazil are biologically and genetically different from European and North America isolates. Recently, four genotypes were considered the common clonal lineages in Brazil and were designated as types BrI, BrII, BrIII, and BrIV. The pathogenicity of two major Brazilian lineages was investigated after oral inoculation of queens in the middle third of their pregnancies with T. gondii cysts. Twelve pregnant queens without T. gondii antibodies were distributed in group A (infected with a type BrI isolate); group 2 (infected with type BrIII isolate), and group 3 (non-infected control). Infection with type BrI isolate caused toxoplasmosis manifestations and abortion from one litter. Toxoplasmosis manifestations besides premature stillbirth of one litter were observed in queens infected with type BrIII isolate. Indirect fluorescence antibody test showed T. gondii antibodies in all eight infected queens at 30 days after inoculation. In two 10-day-old kittens of the same litter (group 1), titers of 16 and 64 were detected. At the same time, titers of 16, 32, and 32 were detected in three kittens from the same litter (group 2). Experimental infection with tissue cysts from a type BrI and type BrIII isolates of T. gondii developed similar reproductive disturbance in primary infected pregnant queens.

In Vitro Microleakage of Composite Restorations Prepared by Er:YAG/Er,Cr:YSGG Lasers and Conventional Drills Associated with Two Adhesive Systems

Purpose: The objective of this in vitro study was to compare the degree of microleakage of composite restorations performed by lasers and conventional drills associated with two adhesive systems. Materials and Methods: Sixty bovine teeth were divided into 6 groups (n = 10). The preparations were performed in groups 1 and 2 with a high-speed drill (HID), in groups 3 and 5 with Er:YAG laser, and in groups 4 and 6 with Er,Cr:YSGG laser. The specimens were restored with resin composite associated with an etch-and-rinse two-step adhesive system (Single Bond 2 [SB]) (groups 1, 3, 4) and a self-etching adhesive (One-Up Bond F [OB]) (groups 2, 5, 6). After storage, the specimens were polished, thermocycled, immersed in 50% silver nitrate tracer solution, and then sectioned longitudinally. The specimens were placed under a stereomicroscope (25X) and digital images were obtained. These were evaluated by three blinded evaluators who assigned a microleakage score (0 to 3). The original data were submitted to Kruskal-Wallis and Mann-Whitney statistical tests. Results: The occlusal/enamel margins demonstrated no differences in microleakage for all treatments (p > 0.05). The gingival/dentin margins presented similar microleakage in cavities prepared with Er:YAG, Er,Cr:YSGG, and HD using the etch-and-rinse two-step adhesive system (SB) (p > 0.05); otherwise, both Er:YAG and Er,Cr:YSGG lasers demonstrated lower microleakage scores with OB than SB adhesive (p < 0.05). Conclusion: The microleakage score at gingival margins is dependent on the interaction of the hard tissue removal tool and the adhesive system used. The self-etching adhesive system had a lower microleakage score at dentin margins for cavities prepared with Er:YAG and Er,Cr:YSGG than the etch-and-rinse two-step adhesive system.

Erbium, chromium : yttrium scandium gallium garnet laser for caries removal: influence on bonding of a self-etching adhesive system

This study evaluated the influence of the dental substrates obtained after the use of different caries removal techniques on bonding of a self-etching system. Forty, extracted, carious, human molars were ground to expose flat surfaces containing caries-infected dentine surrounded by sound dentine. The caries lesions of the specimens were removed or not (control-G1) either by round steel burs and water-cooled, low speed, handpiece (G2), or by irradiation with an erbium, chromium:yttrium scandium gallium garnet (Er,Cr:YSGG) laser (2W, 20 Hz, 35.38 J/cm(2), fiber G4 handpiece with 0.2826 mm(2), non-contact mode at a 2 mm distance, 70% air/20% water-G3) or using a chemo-mechanical method (Carisolv-G4). Caries-infected, caries-affected and sound dentines were submitted to a bonding system followed by construction of a resin-based composite crown. Hour-glass shaped samples were obtained and submitted to a micro-tensile bond test. The bond strength data were compared by analysis of variance (ANOVA), complemented by Tukey`s test (P <= 0.05). The samples of sound dentine presented higher bond strengths than did samples of caries-affected dentine, except for the groups treated with the Er,Cr:YSGG laser. The highest bond strengths were observed with the sound dentine treated with burs and Carisolv. The bond strengths to caries-affected dentine were similar in all groups. Additionally, bonding to caries-affected dentine of the Er,Cr:YSGG laser and Carisolv groups was similar to bonding to caries-infected dentine. Thus, caries-affected dentine is not an adequate substrate for adhesion. Moreover, amongst the caries removal methods tested, the Er,Cr:YSGG laser irradiation was the poorest in providing a substrate for bonding with the tested self-etching system.

Micro-shear bond strength of Er : YAG-laser-treated dentin

This study tested if dentin adhesion is affected by Er:YAG laser. Ninety dentin disks were divided in groups (n=10): G1, control; G2, Er:YAG laser 150 mJ, 90 degrees contact, 38.8 J/cm(2); G3, Er:YAG laser 70 mJ, 90 degrees contact, 18.1 J/cm(2); G4, Er:YAG laser 150 mJ, 90 degrees non-contact, 1.44 J/cm(2); G5, Er:YAG laser 70 mJ, 90 degrees non-contact, 0.67 J/cm(2); G6, Er:YAG laser 150 mJ, 45 degrees contact, 37.5 J/cm(2); G7, Er:YAG laser 70 mJ, 45 degrees contact, 17.5 J/cm(2); G8, Er:YAG laser 150 mJ, 45 degrees non-contact, 1.55 J/cm(2); and G9, Er:YAG laser 70 mJ, 45 degrees non-contact, 0.72 J/cm(2). Bonding procedures were carried out and the micro-shear-bond strength (MSBS) test was performed. The adhesive surfaces were analyzed under SEM. Two-way ANOVA and multiple comparison tests revealed that MSBS was significantly influenced by the laser irradiation (p < 0.05). Mean values (MPa) of the MSBS test were: G1 (44.97 +/- 6.36), G2 (23.83 +/- 2.46), G3 (30.26 +/- 2.57), G4 (35.29 +/- 3.74), G5 (41.90 +/- 4.95), G6 (27.48 +/- 2.11), G7 (34.61 +/- 2.91), G8 (37.16 +/- 1.96), and G9 (41.74 +/- 1.60). It was concluded that the Er:YAG laser can constitute an alternative tool for dentin treatment before bonding procedures.

Can the durability of one-step self-etch adhesives be improved by double application or by an extra layer of hydrophobic resin?

Objectives: This study evaluated the immediate and 6-month resin-dentin mu-bond strength (mu TBS) of one-step self-etch systems (Adper Prompt L-Pop [AD] 3M ESPE; Xeno III [XE] Dentsply De Trey; iBond [iB] Heraeus Kulzer) under different application modes. Materials and methods: Dentin oclusal surfaces were exposed by grinding with 600-grit SiC paper. The adhesives were applied according to the manufacturer`s directions [MD], or with double application of the adhesive layer [DA] or following the manufacturer`s directions plus a hydrophobic resin layer coating [HL]. After applying the adhesive resins, composite crowns were built up incrementally. After 24-h water storage, the specimens were serially sectioned in ""x"" and ""y"" directions to obtain bonded sticks of about 0.8 mm 2 to be tested immediately [IM] or after 6 months of water storage [6M] at a crosshead speed of 0.5 mm/min. The data from each adhesive was analyzed by a two-way repeated measures ANOVA (mode of application vs. storage time) and Tukey`s test (alpha = 0.05). Results: The adhesives performed differently according to the application mode. The DA and HL either improved the immediate performance of the adhesive or did not differ from the MD. The resin-dentin bond strength values observed after 6 months were higher when a hydrophobic resin coat was used than compared to those values observed under the manufacturer`s directions. Conclusions: The double application of one-step self-etch system can be safety performed however the application of an additional hydrophobic resin layer can improve the immediate resin-dentin bonds and reduce the degradation of resin bonds over time. (c) 2008 Elsevier Ltd. All rights reserved.

Microshear Bond Strength of Self-etching Systems Associated with a Hydrophobic Resin Layer

Purpose: To evaluate in vitro the microshear bond strength of adhesive systems applied to dentin according to manufacturers` instructions, associated or not with a hydrophobic layer of unfilled resin. Materials and Methods: Six self-etching adhesives (Clearfil SE Bond, Kuraray Medical; AdheSE, lvoclar Vivadent; Xeno III, Dentsply; I Bond, Heraeus-Kulzer; Bond Force, Tokuyama; Futurabond DC, Voco) were tested. The labial dentin of sixty bovine incisors was exposed, and the teeth were divided into two groups according to the application or not of an extra hydrophobic resin layer (Scotchbond Multi Purpose Plus, bottle 3). Six composite cylinders (Filtek Z250, 3M ESPE) were built up on each treated surface. Specimens were stored in distilled water at 37 C for 24 h and then subjected to the microshear bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. Microshear bond strength values were analyzed by 2-way ANOVA and Tukey`s post-hoc test. Failure mode was determined using a stereomicroscope under 20X magnification. Results: The application of the hydrophobic resin layer did not affect bond strength, except for AdheSE. However, the bond strengths with the hydrophobic layer were similar among the six tested systems (Clearfil: 17.1 +/- 7.9; AdheSE: 14.5 +/- 7.1; Xeno III: 12.8 +/- 7.7; I Bond: 9.5 +/- 5.8; Bond Force: 17.5 +/- 4.1; Futurabond: 7.7 +/- 2.3). When used as recommended by the manufacturers, Bond Force presented statistically higher bond strength than AdheSE and I Bond (p < 0.05) (Clearfil 10.4 +/- 4.9; AdheSE 1.6 +/- 1.6; Xeno III: 9.0 +/- 3.8; I Bond: 3.0 +/- 1.5; Bond Force: 14 +/- 3.9; Futurabond: 8.8 +/- 3.8). Failure mode was predominantly adhesive. Conclusion: The bond strength of the self-etching systems tested was not significantly affected by the application of a hydrophobic layer, but a significant improvement was observed in AdheSE.

Adhesives bonded to erbium:yttrium-aluminum-garnet laser-irradiated dentin: transmission electron microscopy, scanning electron microscopy and tensile bond strength analyses

The aim of this in vitro study was to investigate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation on dentinal collagen by transmission electron microscopy and to analyze the resin-dentin interface by scanning electron microscopy. A tensile bond strength test was also applied. Specimens from 69 sound human third molars were randomly divided into three groups: control (no laser), and two irradiated groups, laser 250 (250 mJ/2 Hz) and laser 400 (400 mJ/4 Hz). Then, specimens were restored with two adhesive systems, an etch-and-rinse or a self-etch system. Although ultrastructural examination showed a modified surface in the irradiated dentin, there was no statistical difference in bond strength values between the laser groups and controls (P < 0.05). In conclusion, the use of Er:YAG laser for ablating human dentin did not alter the main adhesion parameters when compared with those obtained by conventional methods, thus reinforcing its use in restorative dentistry.

Effect of the C-factor and Dentin Preparation Method in the Bond Strength of a Mild Self-etch Adhesive

This study evaluated the effect of the C-factor and dentin preparation method (DPM) in the bond strength (BS) of a mild self-etch adhesive; the study also observed the SEM superficial aspects of the corresponding smear layer. For purposes of this study, 25 molars (n=5) were used in a bond strength test. The molars were divided into two parts (buccal and lingual): one part received a Class V cavity (C-factor=3) and the other received a flat surface (C-factor=0) with the same bur type (coarse diamond or carbide bur and fine diamond or carbide bur), both within the same dentin depth. Five teeth were prepared with wet 60-grit and 600-grit SiC papers. After restoration with Clearfil SE Bond, microtensile beans (0.8 mm(2)) were prepared and tested after 24 hours in a universal testing machine (0.5 mm/minute). An additional two teeth for each DPM were prepared for SEM evaluation of the smear layer superficial aspects. The BS values were submitted to one-way ANOVA, considering only the DPM (flat surfaces) and two-way ANOVA (C-Factor x DPM, considering only burs) with p=0.05. Although the DPM in the flat surfaces was not significant, the standard deviations of carbide bur-prepared specimens were markedly lower. The BS was significantly lower in cavities. The fine carbide bur presented the most favorable smear layer aspect. It was concluded that different dentin preparation methods could not prevent the adverse effect in bond strength of a high C-factor. A coarse cut carbide bur should be avoided prior to a mild self-etch adhesive, because it adversely affected bond strength. In contrast, a fine cut carbide bur provided the best combination: high bond strength with low variability, which suggests a more reliable bond strength performance.

Durability of Enamel Bonding Using One-step Self-etch Systems on Ground and Unground Enamel

Objective: To examine the morphological, early and long-term microtensile bond strengths (mu TBS) of one-step self-etch systems to unground and ground enamel. Materials and Methods: Resin composite (Filtek Z250) buildups were bonded to the buccal and lingual enamel surfaces (unground, bur-cut or SiC-roughened enamel) of third molars after adhesive application using the following adhesives: Clearfil S(3) Bond (CS3); Adper Prompt L-Pop (ADP); iBond (iB) and, as the control, Clearfil SE Bond (CSE). Six tooth halves were assigned for each condition. After storage in water (24 hours/37 degrees C), the bonded specimens were sectioned into beams (0.8 mm(2)) and subjected to pTBS (0.5 mm/min) either immediately (IM) or after six (6M) or 12 months (12M) of water storage. The data were analyzed by three-way repeated measures ANOVA and Tukey`s test (alpha=0.05). Surface conditioning was observed under scanning electron microscopy (SEM). Results: The mu TBS in the Si-C paper and diamond bur groups were similar and higher than the unground group. No significant difference was observed among the different storage periods, except for CS3, which showed an increase in the pTBS after 12M. The etching pattern was more retentive on ground enamel. Conclusions: One-step self-etch adhesives showed higher bond strengths on ground enamel and no reductions in resin-enamel bonds were observed after 12M of water storage.

Early and 24-hour bond strength and degree of conversion of etch-and-rinse and self-etch adhesives

Purpose: To evaluate early and 24-hour microtensile bond strength (mu TBS) and the degree of conversion (DC) of one representative adhesive system from each of the four current bonding approaches. Methods: 40 human molars were sectioned occluso-gingivally into two halves. Resin composite was bonded incrementally to flat, mid-coronal dentin, using the adhesives Adper Scotchbond MP (MP); Adper Scotchbond 2 (SB); Clearfil SE Bond (SE); and Adper Prompt L-Pop (LP) according to the respective manufacturer`s instructions (n= 10). One half was immediately sectioned into sticks and subjected to mu TBS test. As the sectioning process took approximately 1 hour, the results were designated as 1-hour bond strengths. The other half was stored in distilled water at 37 degrees C for 24 hours before being sectioned and tested. The DC of these systems was measured using Fourier Transform-Raman spectroscopy in three periods: immediately, 1 and 24 hours after polymerization. Data were analyzed with ANOVA and Tukey`s tests. Results: There were no significant differences between the 1-hour and 24-hour bond strengths (P> 0.05), or among the DC measured immediately, 1 hour and 24 hours after polymerization (P> 0.05). However, significant differences were observed among adhesives (P< 0.05). mu TBS values obtained, in MPa (1 hour/24 hour), were: SB (48.6 + 1.3/48.4 + 3.5) = SE (51.9 + 4.7/53.3 +/- 2.9) > MP (35.3 +/- 10.9/38.6 + 6.7) > LP (25.5 + 1.1/26.0 + 1.5). The DC, in percentage (immediately/1 hour/24 hour), were: SE (81/82/87) > MP (79/77/81) > SB (60/63/65) > LP (39/37/42).

Differential bonds degradation of two resin-modified glass-ionomer cements in primary and permanent teeth

Objectives: To evaluate the effect of chemical degradation on bond strength of resin-modified glass-ionomer cements bonded to primary and permanent dentin. Methods: Class I cavities of permanent and primary extracted human molars were restored with two resin-modified glass-ionomer cements: Fuji 11 LC and Vitremer, and stored in water for 24 h. Half samples were immersed in 10% NaOCl aqueous solution for 5 h. Teeth were sectioned into beams and tested for microtensile bond strengths. Results were analyzed with multiple ANOVA and Tukey`s tests (p < 0.05). Analysis of debonded surfaces was performed by SEM. Results: 24 h bond strengths for Vitremer and Fuji 11 LC were similar. For Fuji 11, bond strength values were higher for primary than for permanent dentin. Vitremer bond strength was similar for both. Chemical degradation did not affect Fuji I] LC bond strength to dentin. However, decreases in bond strength were found for Vitremer groups after NaOCl immersion. Signs of glass ionomer-dentin interaction were evident by SEM analysis for Fuji 11 LC specimens. Conclusions: Vitremer and Fuji II presented similar bond strength at 24. Vitremer dentin bonds were prone to chemical degradation. Fuji II LC-dentin bonds showed typical features of glass-ionomer dentin interaction at the bonded interfaces, and were resistant to in vitro degradation. (C) 2009 Elsevier Ltd. All rights reserved.

The Drop Technique: a Method to Control the Amount of Fluoride Dentifrice Used by Young Children

Purpose: The purpose of this study was to evaluate the amount of dentifrice applied to the toothbrush by school children using a liquid dentifrice (drop technique), when compared to toothpaste. Materials and Methods: A total of 178 school children (4-8 years old) from two cities in Brazil (Bauru and Bariri) participated in the present two-part crossover study. Children from Bauru received training regarding tooth-brushing techniques and use of dentifrice before data collection. In each phase, the amount of toothpaste or liquid dentifrice applied by the children to the toothbrush was measured, using a portable analytical balance (+/- 0.01 g). Data were tested by analysis of covariance (Ancova) and linear regression (p < 0.05). Results: The mean (+/- standard deviation) amounts of toothpaste and liquid dentifrice applied to the toothbrushes for children from Bauru were 0.41 +/- 0.20 g and 0.15 +/- 0.06 g, respectively. For children from Bariri, the amounts applied were and 0.48 +/- 0.24 g and 0.14 +/- 0.05 g, respectively. The amount of toothpaste applied was significantly larger than the amount of liquid dentifrice for both cities. Children from Bariri applied a significantly larger amount of toothpaste, when compared to those from Bauru. However, for the liquid dentifrice, there was no statistically significant difference between the cities. A significant correlation between the amount of toothpaste applied and the age of the children was verified, but the same was not found for the liquid dentifrice. Conclusion: The use of the drop technique reduced and standardised the amount of dentifrice applied to the toothbrush, which could reduce the risk of dental fluorosis for young children.

Effect of 2% Chlorhexidine Digluconate on the Bond Strength to Normal Versus Caries-affected Dentin

This study evaluated the effect of 2% chlorhexidine digluconate (CHX) used as a therapeutic primer on the long-term bond strengths of two etch-and-rinse adhesives to normal (ND) and caries-affected (CAD) dentin. Forty extracted human molars with coronal carious lesions, surrounded by normal dentin, were selected for this study. The flat surfaces of two types of dentin (ND and CAD) were prepared with a water-cooled high-speed diamond disc, then acidetched, rinsed and air-dried. In the control groups, the dentin was re-hydrated with distilled water, blot-dried and bonded with a three-step (Scotchbond Multi-Purpose-MP) or two-step (Single Bond 2-SB) etch-and-rinse adhesive. In the experimental groups, the dentin was rehydrated with 2% CHX (60 seconds), blot-dried and bonded with the same adhesives. Resin composite build-ups were made. The specimens were prepared for microtensile bond testing in accordance with the non-trimming technique, then tested either immediately or after six-months storage in artificial saliva. The data were analyzed by ANOVA/Bonferroni tests (alpha=0.05). CHX did not affect the immediate bond strength to ND or CAD (p>0.05). CHX treatment significantly lowered the loss of bond strength after six months as seen in the control bonds for ND (p<0.05), but it did not alter the bond strength of CAD (p>0.05). The application of NIP on CHX-treated ND or CAD produced bonds that did not change over six months of storage.