Effects of citric acid modified with fluoride, nano-hydroxyapatite and casein on eroded enamel.

OBJECTIVES: The aim of this in vitro study was to evaluate the effects of citric acid containing fluoride, nano-hydroxyapatite, and casein on eroded enamel. DESIGN: The crowns of 120 extracted bovine incisors were embedded in acrylic resin. An enamel window (2 × 3 mm) was created on the surface. Before in vitro pellicle formation samples were eroded in 1% citric acid (pH = 3.2) for 1 h at 36 °C and were randomly classified to eight groups (n = 15) as follows: Positive control: 1% citric acid, Negative control: Distilled water, F1: 0.047 mmol/L sodium fluoride, F2: 0.071 mmol/L sodium fluoride, NHA1: %0.05 Nano-Hydroxyapatite, NHA2: %0.1 Nano-Hydroxyapatite, C1: %0.02 Casein, C2: %0.2 Casein. Erosion cycling was performed three times daily for 3 days. In each cycle, the samples were immersed in 10 mL of control or modified solutions (10 min) and in 10 mL of artificial saliva (60 min). The surface roughness and enamel loss were analyzed by using profilometer, scanning electron microscopy (SEM) and atomic force microscopy techniques (AFM). RESULTS: Among the groups, the positive control group was found to be having the highest erosive wear. Erosive wear in the F2, NHA2, C1, and C2 groups was not significantly different from the negative control group (p > 0.05). The C1 and C2 groups showed that erosion terminated and minimal tissue recovery occurred on the enamel surface. CONCLUSION: Although all modifications reduced further demineralization, the citric acid modification with casein was found to be having a greater impact on dental erosion than the others.

Cytotoxicity evaluation of luting resin cements on bovine dental pulp-derived cells (bDPCs) by real-time cell analysis.

To evaluate the cytotoxicity of resin cements on dental pulp-derived cells (bDPCs), Bifix QM (BQM), Choice 2(C2), RelyX U200(RU200), Maxcem Elite(ME), and Multilink Automix(MA) were tested. The materials were incubated in DMEM for 72 h. A real-time cell analyzer was used to evaluate cell survival. The statistical analyses used were one-way ANOVA and Tukey-Kramer tests. BQM, RU200, and ME demonstrated a significant decrease in the bDPCs' index at 24 and 72 h (p≤0.001). These materials were found to be the most toxic resin cements, as compared to the control and other tested materials (C2 and MA). However, C2 and MA showed a better survival rate, compared to BQM, RU200, and ME, and had lower cell index than the control group. The cytotoxic effects of resin cements on pulpa should be evaluated during the selection of proper cements.

Cytotoxicity of temporary cements on bovine dental pulp-derived cells (bDPCs) using realtime cell analysis.

PURPOSE: To evaluate the cytotoxicity of temporary luting cements on bovine dental pulp-derived cells (bDPCs). MATERIALS AND METHODS: Four different temporary cements were tested: Rely X Temp E (3M ESPE), Ultratemp (Ultradent), GC Fuji Temp (GC), and Rely X Temp NE (3M ESPE). The materials were prepared as discs and incubated in Dulbecco's modified eagle's culture medium (DMEM) for 72 hours according to ISO 10993-5. A real-time cell analyzer was used to determine cell vitality. After seeding 200 µL of the cell suspensions into the wells of a 96-well plate, the bDPCs were cured with bioactive components released by the test materials and observed every 15 minutes for 98 hours. One-way ANOVA and Tukey-Kramer tests were used to analyze the results of the proliferation experiments. RESULTS: All tested temporary cements showed significant decreases in the bDPCs index. Rely X Temp E, GC Fuji Temp, and Rely X Temp NE were severely toxic at both time points (24 and 72 hours) (P<.001). When the cells were exposed to media by Ultratemp, the cell viability was similar to that of the control at 24 hours (P>.05); however, the cell viability was significantly reduced at 72 hours (P<.001). Light and scanning electron microscopy examination confirmed these results. CONCLUSION: The cytotoxic effects of temporary cements on pulpal tissue should be evaluated when choosing cement for luting provisional restorations.

Dental approach to erosive tooth wear in gastroesophageal reflux disease.

BACKGROUND: The duration of gastro-esophageal reflux disease (GERD), the frequency of reflux, the pH and type of acid, and the quality and quantity of saliva affect the severity of dental erosion due to GERD. OBJECTIVE: To summarize the diagnostic protocol and treatment of dental erosion due to GERD. METHODS: A Medline literature search was performed to identify articles associated with a dental approach to GERD. RESULTS: The dental professional must carry out a diagnostic protocol, which includes collecting data on the patient's medical and dietary history, occupational/recreational history, dental history, and oral hygiene methods. Intraoral, head and neck, and salivary function examinations should be performed to expose the dental implications of GERD symptoms. CONCLUSION: Diagnosing the cause of erosive tooth wear can help prevent further damage. Patients must be informed about how to prevent GERD.

Effect of accelerated aging on the bonding performance of fluoridated adhesive resins.

The purpose of this study was to investigate the dentin bond durability of a one-step, fluoride-containing, glass ionomer-based adhesive system, Reactmer Bond (RB), and that of a two-step, fluoride-containing, self-etch adhesive system, Clearfil Protect Bond (CPB). Enamel was removed from the occlusal surfaces of teeth, and flat dentin surfaces were entirely covered with a composite resin following the application of an adhesive material (n=10). After specimens were sectioned into rectangular sticks of 0.87 ± 0.03 mm(2), the sticks were randomly assigned into two accelerated aging time period groups: 1 week or 1 year. Microtensile bond strengths were determined. Bond strength of RB increased significantly after 1 year (1 week=27.80 ± 10.57 MPa versus 1 year=36.93 ± 14.38 MPa) (p<0.05). In contrast, there was no significant difference in bond strength between the two time periods for CPB (1 week=51.74 ± 17.8 MPa versus 1 year=56.03 ± 18.85 MPa) (p>0.05). Both fluoride-containing adhesives seemed to demonstrate reliable bonding performance after 1 year of accelerated aging in water.

Cytotoxicity testing of temporary luting cements with two- and three-dimensional cultures of bovine dental pulp-derived cells.

This study evaluated the cytotoxicity of eugenol-containing and eugenol-free temporary luting cements. For cytotoxicity testing, bovine pulp-derived cells transfected with Simian virus 40 Large T antigen were exposed to extracts of eugenol-containing (Rely X Temp E) and eugenol-free (Provicol, PreVISION CEM, and Rely X Temp NE) temporary luting cements for 24 h. The cytotoxicity of the same materials was also evaluated in a dentin barrier test device using three-dimensional cell cultures of bovine pulp-derived cells. The results of the cytotoxicity studies with two-dimensional cultures of bovine dental pulp-derived cells revealed that cell survival with the extracts of Rely X Temp E, Provicol, PreVISION CEM, and Rely X Temp NE was 89.1%, 84.9%, 92.3%, and 66.8%, respectively. Rely X Temp NE and Provicol showed cytotoxic effects on bovine dental pulp-derived cells (P < 0.05). The results of the dentin barrier test revealed that cell survival with the above-mentioned temporary cement was 101.5%, 91.9%, 93.5%, and 90.6%, respectively. None of the temporary luting cements significantly reduced cell survival compared with the negative control in the dentin barrier test (P > 0.05). Biologically active materials released from temporary luting cements may not influence the dentine-pulp complex if the residual dentine layer is at least 0.5 mm thick.

Human and bovine pulp-derived cell reactions to dental resin cements.

OBJECTIVES: The objective of this study was to evaluate the cytotoxic reaction of transfected human pulp derived cells (tHPDC) and transfected bovine pulp derived cells (tBPDC) after exposure to resin cements [RelyX UnicemClicker (RX), MaxCem (MC), Panavia F 2.0 (PF), BisCem (BC), and Bistite II DC (BII)] and to compare it to the generation of reactive oxygen species (ROS). MATERIALS AND METHODS: Set materials were extracted in culture medium, cell survival as a measure of cytotoxicity was determined photometrically using crystal violet after cells were exposed to the extracts for 24 h. The generation of ROS was detected by flow cytometry after cells were exposed to extract dilutions for 1 h. RESULTS: The ranking of the least to the most cytotoxic material was: RX < BII < PF < BC < MC for both cell lines, but for tHPDC, only MC and PF eluates were different from untreated controls. Generally, tBPDC were more susceptible to materials than tHPDC, but only for RX and BC was this difference statistically significant. All undiluted extracts increased ROS production in both cell lines but to a higher amount in tHPDC than in tBPDC. CONCLUSIONS: tHPDC reacted less sensitive than tBPDC in the cytotoxicity test but with the same rank order of materials. In contrast, the cellular oxidative stress reaction was more pronounced in tHPDC than in tBPDC. CLINICAL RELEVANCE: Depending on the residual dentine layer in deep cavities, biologically active resin monomers or additives released from resin cements may influence the dentine­pulp complex, for instance, its regenerative and reparative capacities.

Cytotoxicity evaluation of dentin bonding agents by dentin barrier test on 3-dimensional pulp cells.

OBJECTIVE: The aim of this study was to evaluate the effects of 4 dentin-bonding agents on the cell viability of bovine derived cells. STUDY DESIGN: Cytotoxicity of dentin-bonding agents (G-Bond [GB], Adper Prompt Self-Etch [APSE], Clearfil DC Bond System [CDCB], and Quadrant University-1-Bond [UB]) was analyzed with a dentin barrier test device using 3-dimensional (3D) pulp cell cultures. A commercially available cell culture perfusion chamber was separated into 2 compartments using a 500 µm dentin disk. The 3D cultures were placed on a dentin disk and held in place with a special biocompatible stainless steel holder. Test materials were introduced into the upper compartment in direct contact with the cavity side of the dentin disks according to the manufacturer's instructions. Subsequently, the pulpal part of the perfusion chamber containing the cell cultures was perfused with a medium (2 mL/h). After an exposure period of 24 hours, cell survival was determined by using the MTT assay. Statistical analyses were performed using the Mann-Whitney U test. RESULTS: In the dentin barrier test, cell survival rates of UB and CDCB were similar to the control group (P > .05). However, all other tested materials were cytotoxic for the 3D pulp-derived cell cultures (P < .05). CONCLUSIONS: Dentin-bonding agents include biologically active ingredients and may modify pulp cell metabolism when the materials are used in deep cavities in spite of a dentin barrier. If these adhesive agents are used in deep cavities, a biocompatible cavity liner should be used.

Cytotoxic effects of resin-modified orthodontic band adhesives. Are they safe?

OBJECTIVE: To evaluate the cytotoxic effects of three different resin-modified orthodontic band adhesives. MATERIALS AND METHODS: Three resin-modified orthodontic band adhesives (Bisco Ortho Band Paste LC, Multi-Cure Glass Ionomer Band Cement, and Transbond Plus Light Cure Band Adhesive) were prepared and the samples were extracted in 3 mL of Basal Medium Eagle with 10% newborn calf serum for 24 hours. The L929 cells were plated (25,000 cells/mL) in wells of 96-well dishes and maintained in a humidified incubator for 24 hours at 37 degrees C, 5% CO(2), and 95% air. After 24-hour incubation of the cells, the incubation medium was replaced by the immersed medium in which the samples were stored. Then L929 cells were incubated in contact with eluates for 24 hours. The cell mitochondrial activity was evaluated by the methyltetrazolium test. Twelve wells were used for each specimen, and methyltetrazolium tests were applied two times. The data were statistically analyzed using one-way analysis of variance and Tukey Honestly Significantly Different tests. RESULTS: Results with L929 fibroblasts demonstrated that all freshly prepared resin-modified orthodontic band adhesive materials reduced vital cell numbers (P > .05), in comparison to the control group. Our data demonstrate that all materials showed significant cytotoxicity compared to the control group. CONCLUSIONS: The results indicate that all materials showed significant cytotoxicity compared to the control group, and further studies using different test methods are needed for all resin-modified orthodontic band adhesives.

Cytotoxic effects of orthodontic composites.

OBJECTIVES: To evaluate the cytotoxic effects of five different light-cured orthodontic bonding composites. MATERIALS AND METHODS: The orthodontic composites Heliosit Orthodontic (Ivoclar), Transbond XT (3M Unitek), Bisco ORTHO (Bisco), Light Bond (Reliance), and Quick Cure (Reliance) were prepared, and the samples were extracted in 3 mL of BME (Basal Medium Eagle) with 10% newborn calf serum for 24 hours. The L929 cells were plated (25,000 cells/mL) in a 96-well dish and maintained in a humidified incubator for 24 hours at 37 degrees C, 5% CO(2), and 95% air. After 24 hours of incubation of the cells, the incubation medium was replaced by the immersed medium in which the samples were stored. Then, L929 cells were incubated in contact with eluates for 24 hours. The cell mitochondrial activity was evaluated by the methyl tetrazolium (MTT) test. Twelve wells were used for each specimen, and the MTT tests were applied two times. The data were statistically analyzed by one-way analysis of variance (ANOVA) and Tukey HSD tests. RESULTS: Results with L929 fibroblasts demonstrated that except for Transbond XT, freshly prepared composite materials did not reduce vital cell numbers (P > .05) compared with the control group. Our data demonstrate that Transbond XT showed significant cytotoxicity compared with the control group. CONCLUSION: Results indicate that tested orthodontic bonding composites are suitable for clinical application, but that further studies using different test methods are needed for Transbond XT.

Effect of artificial aging regimens on the performance of self-etching adhesives.

This in vitro study was performed to compare the microtensile bond strengths (MTBS) of current self-etching adhesives to dentin and to evaluate the effects of artificial aging [(thermocycling (TC) and/or mechanic loading (ML)] on MTBS and on nanoleakage of self-etching adhesives. Two-step (AdheSE Bond, Clearfil Protect Bond, Clearfil SE Bond, Optibond Self-Etch) and one-step (Hybrid Bond, G-bond, Clearfil Tri-S Bond, and Adper Prompt L-Pop) self-etching adhesives were tested. Resin composite build-ups were created, and the specimens were subjected to 10(4) TC, 10(5) ML, and 10(4)/10(5) TC/ML. Non-aged specimens served as controls. In the control group, no significant differences were found among the MTBS of the one-step self-etching adhesives and among those of three two-step self-etching adhesives (AdheSE Bond, Clearfil Protect Bond, and Clearfil SE Bond) (p > 0.05). The MTBS of AdheSE Bond and Clearfil Protect Bond were higher than were those of all one-step self-etching adhesives and than those of Optibond Self-Etch. The MTBS of Clearfil SE Bond was higher than were those of two one-step self-etching adhesives (Adper Prompt L-Pop, G-bond) (p < 0.05). Compared with the non-aged controls, TC did not decrease (p > 0.05), but ML and TC/ML significantly decreased the MTBS of the adhesives tested (p < 0.05). Two-step self-etching adhesives tended to fail more cohesively in dentin. Transmission electron microscopy revealed different nanoleakage patterns in the adhesive and hybrid layers of all adhesives examined, and signs of additional silver-filled water channels were more readily detectable after TC/ML.

Cytotoxicity Evaluation of Self Adhesive Composite Resin Cements by Dentin Barrier Test on 3D Pulp Cells.

OBJECTIVES: The aim of this study was to evaluate the effects of five self-etch dental composite resin cements on the cell viability of bovine dental papilla-derived cells. METHODS: The cytotoxicity of composite resin cements (Rely X Unicem Clicker, 3M ESPE; MaxCem; KERR, Panavia F 2.0; Kuraray, BisCem; Bisco and Bistite II DC; Tokuyama) was analyzed in a dentin barrier test device using three-dimensional (3D) pulp cell cultures. A commercially available cell culture perfusion chamber was separated into two compartments by 500 mum dentin disc. The three dimensional cultures placed on a dentin disk held in place by a special biocompatible stainless-steel holder. Test materials were introduced into the upper compartment in direct contact with the cavity side of the dentin disks according to the manufacturer's instructions. Subsequently, the pulpal part of the perfusion chamber containing the cell cultures was perfused with medium (2 ml/h). After an exposure period of 24 h, the cell survival was determined by the MTT assay. Statistical analyses were performed using the Mann-Whitney U-test. RESULTS: In dentin barrier test, cell survival was similar with Maxcem and negative control group (P>.05), and all other tested materials were cytotoxic for the three dimensional cell cultures (P>.05). CONCLUSIONS: The significance of composite resin cements is being more important in dentistry. The cytotoxic potencies demonstrated by these materials might be of clinical relevance. Some composite resin cements include biologically active ingredients and may modify pulp cell metabolism when the materials are used in deep cavities or directly contact pulp tissue.

Effect of a new restoration technique on fracture resistance of endodontically treated teeth.

The aim of the study was to investigate the effect of a new fiber-reinforced composite restoration technique on fracture resistance in endodontically treated premolars. Eighty sound extracted human mandibular premolars were assigned to four groups (n = 20). Group 1 did not receive any treatment. In groups 2, 3 and 4, the teeth received root canal treatment and a mesio-occluso-distal cavity preparation. Group 2 was kept unrestored. Group 3 was restored with a dentin bonding system and composite resin. In group 4, a piece of polyethylene ribbon fiber was inserted into the groove in a buccal to lingual direction during the restoration of teeth with dentin bonding system and composite resin. After finishing and polishing, the specimens were stored in 100% humidity at 37 degrees C for 24 h and placed at an angle of 45 degrees to the long axis of the tooth and subjected to compressive loading in a universal testing machine at a crosshead speed of 0.5 mm min(-1). The load necessary to fracture the samples was recorded in Newton (N) and submitted to Kruskal-Wallis anova and Mann-Whitney U-test. The fracture strength of the teeth reinforced with a combination of polyethylene fiber and composite resin were not significantly different than those that were restored with only composite resin (P > 0.05). However, most of the failure modes of the reinforced teeth were limited to the level of the enamel, while the other three groups showed fractures generally at the level of the dentin, cemento-enamel junction or more below (P < 0.05). Therefore, polyethylene ribbon fiber-reinforced composite resin restorations seemed a more reliable restorative technique than traditional composite restorations for extensive cavities.

Bond strength of two total-etching bonding systems on caries-affected and sound primary teeth dentin.

AIM: As bond strength of currently available adhesive systems in caries-affected teeth dentin on primary tooth dentin was not well known, the bond strength of two bonding systems (PQI and OptiBond Solo Plus) was evaluated on caries-affected and sound primary molar tooth dentin and observed the micromorphology of the adhesive-dentin interfaces. METHODS: By grinding both the sound (n = 30) and caries-affected (n = 30) approximal surfaces of teeth, flat dentin surfaces were obtained. The prepared surfaces were bonded with one of the each adhesive systems and a composite resin. After storing the bonded specimens in water at 37 degrees C for 24 h, the samples were sectioned and the bond strength of the adhesive systems was tested by the microshear test method. The data were statistically analysed. RESULTS: Microshear bond strengths of PQI group for caries-affected and sound primary tooth dentin were 9.43 +/- 2.44 (MPa) and 9.32 +/- 2.95 (MPa) (P > 0.05), respectively, and the bond strengths of OptiBond Solo Plus group for caries-affected and sound primary tooth dentin were 15.33 +/- 3.59 (MPa) and 11.96 +/- 2.30 (MPa) (P < 0.05), respectively. Micromorphological features between sound and caries-affected dentin were similar in both PQI and OptiBond Solo Plus groups. CONCLUSION: Both the adhesives showed significantly different bond strengths in caries-affected dentin but showed similar bond strengths in sound dentin.

Microtensile and microshear bond strength of an antibacterial self-etching system to primary tooth dentin.

OBJECTIVES: The aim of this study was to test the hypothesis that the bonding ability of antibacterial bonding system to primary dentin was not different from the parental material which did not contain any antibacterial component. METHODS: Extracted human non-carious primary molars were ground to expose the coronal dentin, and then randomly divided into two experimental groups: treatment with Clearfil Protect Bond or with Clearfil SE Bond (Kuraray Medical Inc.). Composite-dentin sticks with a cross-sectional area of approximately 0.90 mm(2) were prepared and subsequently subjected to microtensile bond strength (muTBS) and microshear bond strength (muSBS) tests. For the muTBS tests, specimens were attached to an Instron testing machine with a cyanoacrylate adhesive. For muSBS testing, the sticks were mechanically fixed to the muSBS testing apparatus. The bonds were stressed in shear or tension at a crosshead speed of 1mm/min until failure occurred. Resin-dentin interfaces produced by each system were examined using SEM. The data were analyzed with Mann-Whitney's U test. RESULTS: The muTBS and muSBS of Clearfil Protect Bond were 30.69+/-9.71 and 9.94+/-3.78 MPa, respectively. Clearfil SE Bond showed significantly greater values of 37.31+/-9.57 and 12.83+/-3.15 MPa, respectively. SEM analysis demonstrated similar micro-morphological features including the thickness of the hybrid layer for both materials. CONCLUSIONS: It was showed that antibacterial self-etching system Clearfil Protect Bond showed lower bond strength values compared to primary dentin than that of to Clearfil SE Bond on primary dentin. (Eur J Dent 2008;2:11-17).

Evaluation of Antibacterial Effectiveness of Desensitizers against Oral Bacteria.

OBJECTIVES: Desensitizers contribute to better clinical results by reducing the rate of cervical dentin sensitivity. However, information on their antibacterial effect is limited. This study examined the antibacterial activities of a triclosan containing (Seal & Protect), a benzalconium containing desensitizer (Micro Prime), a fluoride containing prophilaxy paste (Sultan Desensitizer), two fluoride containing varnishes (Cavity Shealth and Ultra EZ), and a dentin bonding primer (All Bond). METHODS: The test materials were inserted in the wells of Muller Hinton agar plates inoculated with Streptococcus mutans, Streptococcus salivarious, Staphylococcus aureus, Streptococcus faecalis and Pseudomonas aeruginosa. The diameters of the inhibition zones produced around the materials were measured after 24 h of incubation. The results were analyzed by the Kruskal Wallis one way ANOVA and the Mann-Whitney tests at a significance level of P<.05. RESULTS: Micro Prime Desensitizer containing benzalkonium chloride had the highest antibacterial effectiveness compared to other desensitizers used in this study. In addition, triclosan containing Seal & Protect and acidic components containing All Bond showed very high antibacterial efficacy. On the other hand, fluoride within both varnishes had little antibacterial effectiveness. However a fluoride component in a paste (Sultan Desensitizer) showed very high bactericidal effect. CONCLUSIONS: All desensitizers except fluoride varnishes showed various degrees of antibacterial effect against the bacteria tested in this study. If antibacterial effect is also required from the desensitizers' clinicians should avoid use of varnishes.

Adhesion of two bonding systems to air-abraded or bur-abraded human enamel surfaces.

OBJECTIVES: The purpose of this in vitro study was to evaluate whether mechanical alteration of the enamel surfaces with air abrasion and bur abrasion techniques could enhance the bonding performance of a three step and a self etching adhesive resin systems to enamel. METHODS: 126 extracted lower human incisor teeth were used. The teeth were divided into three groups including 40 teeth each. First group; teeth were used as control and no preparation was made on enamel surfaces, 2(nd) group; outer enamel surfaces were air abraded, 3(rd) group; outer enamel surfaces were abraded mechanically with a diamond fissure bur. Cylinder composite resin blocks were bonded to the buccal enamel surfaces with two bonding systems (20 specimens in each group). Bond strengths to enamel surfaces were measured at a cross-head speed of 1 mm/min. The data were analyzed by ANOVA and Duncan Tests. To examine interface composite resin/enamel surfaces at scanning electron microscopy, remaining 6 teeth were used. Fracture analysis was performed using an optical stereomicroscope. RESULTS: Bond strengths values of Solid Bond were significantly higher than bond strengths of Clearfil SE Bond for all types of enamel (P<.05). Shear bond strength values obtained with Solid Bond (three step system) to three types of enamel surfaces [air-abraded (30.25+/-7.00 MPa), bur-abraded (29.07+/-3.53 MPa), control (31.74+/-7.35 MPa)] were close to each other (P>.05). The macroscopic mode of failures for bonding systems, SB and SE Bond appeared to be adhesive and cohesive in nature. CONCLUSIONS: In order to get better bond strength values with self etching systems, it is advisable to prepare enamel surfaces with bur or air abrasion, but it enamel preparation is not necessary for three step systems.

Effect of storage duration/solution on microshear bond strength of composite to enamel.

The aim of this study was to determine the effect of three storage solutions and two storage durations on microshear bond strength (microSBS) of a resin composite. Sixty non-carious human permanent molars were stored in three storage solutions (0.1% thymol, 10% formalin, and distilled water). Each tooth was separated mesio-distally into two parts. Specimens of the first part were stored for 24 hours, while specimens of the second part were stored for two months in the solutions. After each storage period, the enamel surface was covered with a composite resin in combination with an etch-rinse adhesive system. Specimens were then serially sectioned into sticks of 1 mm' bond area and subjected to microSBS test. There were no statistically significant differences between the two storage periods for each solution (p>0.05). The thymol solution group showed lower microSBS values than those of distilled water for both storage periods (p<0.05). As for the formalin group, its microSBS values were not statistically different from those of distilled water and thymol groups at each storage period (p>0.05). In conclusion, the thymol solution caused the microSBS of the resin composite to decrease when compared to both formalin and distilled water after 24 hours and two months. However, the microSBS of the resin composite was not affected by storage duration.

Cytotoxicity of mouthrinses on epithelial cells by micronucleus test.

OBJECTIVES: To determine the cytotoxicity of three commercial mouthrinses Klorhex, Andorex and Tanflex on buccal epithelial cells using micronucleus (MN) test. MATERIALS AND METHODS: 28 patients with aged 16-24 undergone three mouthrinses' application were analyzed before and after one week exposure. Physiologic saline was used for the control group. The MN incidence was scored in the buccal epithelial of each participants. The difference in pre- and post-treatment after one week incidence of MN and plaque (PI) and gingival indices (GI) was compared by non-parametric statistical tests. RESULTS: The micronuclei incidence increased in Klorhex, Tanflex and Andorex groups after exposure to mouth rinses (P<.05). But when compared with the control group, there was not any difference between Andorex and control group (P>.05). In the other study groups, MN incidence was significantly increased after 7 days treatment (P<.05). GI scores of all groups were decreased significantly (P<.05). PI scores were decreased only in the Klorhex group (P<.05). CONCLUSIONS: Our primary findings support the presence of possible cytotoxic effects of the mouthrinses on gingival epithelial cells.

Shear bond strengths of self-etching adhesives to caries-affected dentin on the gingival wall.

The purpose of this study was to evaluate the bonding ability of five current self-etching adhesives to caries-affected dentin on the gingival wall. Seventy extracted human molars with approximal dentin caries were employed in this study. In order to obtain caries-affected dentin on the gingival wall, grinding was performed under running water. Following which, specimens mounted in acrylic blocks and composite resins of the bonding systems were bonded to dentin with plastic rings and then debonded by shear bond strength. With Clearfil SE Bond, bonding to caries-affected dentin showed the highest bond strength. With Optibond Solo Plus Self-Etch, bonding to caries-affected dentin showed higher shear bond strength than AQ Bond, Tyrian SPE & One-Step Plus, and Prompt-L-Pop (p<0.05). Further, the bond strengths of Clearfil SE Bond and Optibond Solo Plus Self-Etch to sound dentin were higher than those of Prompt-L-Pop, AQ Bond, and Tyrian SPE & One-Step Plus (p<0.05). In conclusion, besides micromechanical interlocking through hybrid layer formation, bond strength of self-etch adhesives to dentin may be increased from additional chemical interaction between the functional monomer and residual hydroxyapatite. The results of this study confirmed that differences in bond strength among self-etching adhesives to both caries-affected and sound dentin were due to chemical composition rather than acidity.