The effect of varying head tilt on the perceived color from composite resin and porcelain restorations: Simulating the effect of altering torque.

INTRODUCTION: This study aimed to assess the effect of changes in tooth torque on the perceived color of composite and porcelain restorations. METHODS: A total of 30 patients with previous composite restorations and 30 patients with porcelain restorations on lateral and central incisors were selected. To simulate the effect of dental torque change, we asked the patients to tilt their heads upwards and downwards to represent buccal and palatal crown torque, respectively. Photographs were taken in 3 different positions (natural head position, 15° upward tilt, and 15° downward tilt). A laser alignment tool was used to help with head positioning. Color was measured on the 3 principal axes of the Commission Internationale de L'Eclairage, L∗, a∗, and b∗ color space using Photoshop software (Adobe, San Jose, Calif), and color differences were calculated. The midpoint of the clinical crown, both mesiodistally and incisogingival, was selected as the point of measurement. A general linear model was used to analyze the significance of changes in each value of different tooth torques. A t test was used to compare color changes of 2 different incisors (central and lateral) and overall color differences in the 2 types of restoration. RESULTS: Significant changes of the L∗ and a∗ values were found as a result of the change in head inclination, whereas b∗ values remained unchanged. It was found that buccal crown torque resulted in lighter and greener porcelain restorations. Composite restorations behaved similarly with the only difference being that the central incisors appeared bluer. Palatal crown torque resulted in a darker and redder porcelain restoration and a darker, redder, and yellower composite restoration. No significant differences were found between color changes in the central and lateral incisors. Furthermore, porcelain and composite restorations had similar color changes with alteration of head inclination. CONCLUSIONS: Orthodontic changes of tooth torque alter the color perceived from composite and porcelain restorations.

Effect of Simulated Pulpal Pressure on Knoop Hardness of Two Self-etch Adhesives with Different Aggressiveness.

AIM: Simulated pulpal pressure (PP) has been shown to affect the bond strength and nanoleakage of different adhesives at dentin interfaces but the effect of simulated PP on polymerization of adhesives has not been studied yet. Furthermore, it has been proposed that strong and mild self-etch adhesives have different polymerization behaviors. This study aimed to evaluate the effect of simulated PP on polymerization of two self-etch adhesives, Adper Prompt L-Pop (APLP) and Adper Easy Bond (AEB), by means of the Knoop hardness test. MATERIALS AND METHODS: Sixty caries-free human molars were used to prepare deep dentin specimens with a mean remaining dentin thickness of 0.9 mm. The specimens were bonded in the absence or presence of PP. The specimens were assigned to four equal groups (n = 15) as follows: AEB/-PP, APLP/-PP, AEB/+PP, and APLP/+PP. Bonding procedures were completed; then the specimens' hardness was measured with the Knoop test. Data were analyzed with two-way ANOVA and the t test. RESULTS: In the absence of PP, the hardness of AEB was significantly higher than that of APLP (p < 0.001). In contrast, when PP was simulated, the hardness of APLP was higher than that of AEB (p = 0.002). The hardness of AEB was not influenced by the presence of PP (p = 0.153). Simulation of PP resulted in a significant improvement in the hardness of APLP (p < 0.001). CONCLUSION: The polymerization degree of strong self-etch adhesive was lower compared to mild self-etch adhesive. In the presence of hydrostatic PP, the polymerization degree of strong self-etch adhesive was higher than mild self-etch adhesive. CLINICAL SIGNIFICANCE: Dentin moisture caused by positive PP might improve polymerization of strong self-etch adhesives.

The Simultaneous Effect of Extended Etching Time and Casein Phosphopeptide-Amorphous Calcium Phosphate containing Paste Application on Shear Bond Strength of Etch-and-rinse Adhesive to Caries-affected Dentin.

AIM: This study evaluated the simultaneous effect of extended etching time and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) containing paste application on shear bond strength (SBS) of etch-and-rinse adhesive to caries-affected-dentin (CAD). MATERIALS AND METHODS: Fifty human third molars were used; 10 normal in group 1 and 40 caries-affected teeth in groups 2 to 5. In the CAD groups, teeth were randomly assigned into four groups (n = 10). In groups 2 and 4, phosphoric acid etching for 15 and 45 seconds was used and in groups 3 and 5, after 15 or 45 seconds etching respectively, CPP-ACP containing paste (MI paste) was applied for 3 minutes. After rinsing, single bond adhesive system and Z250 composite were used for resin composite build-up in all groups. After storage, SBS test was measured at cross head speed of 0.5 mm/min. Data were analyzed using one/two-way ANOVA and Tukey HSD test (α = 0.05). RESULTS: Normal dentin groups showed the highest SBS among different groups. There was a statistically significant difference between different etching times in CAD groups (p < 0.05), but there were no significant differences between SBS of SB adhesive to CAD with or without CPP-ACP pretreated in both etching times. Most of the failure modes were adhesive except in groups 1 and 5 which cohesive failure in composite was also observed. CONCLUSION: The results of our study indicated that extended etching time up to 45 seconds could enhance the SBS of CAD and approach nearly to SBS of normal dentin. Moreover, MI paste pretreatment had not significant effect on SBS of etch-and-rinse adhesive in CAD. CLINICAL SIGNIFICANCE: Simultaneous application of extended etching time and CPP-ACP containing paste may be a suggested method in increasing the SBS of adhesive to CAD.

Finite Element Analysis of the Endodontically-treated Maxillary Premolars restored with Composite Resin along with Glass Fiber Insertion in Various Positions.

AIM: This study evaluated the effect of three methods of glass fiber insertion on stress distribution pattern and cusp movement of the root-filled maxillary premolars using finite element method (FEM) analysis. MATERIALS AND METHODS: A three-dimensional (3 D) FEM model of a sound upper premolar tooth and four models of root-filled upper premolars with mesiocclusodistal (MOD) cavities were molded and restored with: (1) Composite resin only (NF); (2) Composite resin along with a ribbon of glass fiber placed in the occlusal third (OF); (3) Composite resin along with a ribbon of glass fiber placed circumferentially in the cervical third (CF), and (4) Composite resin along with occlusal and circumferential fibers (OCF). A static vertical load was applied to calculate the stress distributions. Structural analysis program by Solidworks were used for FEM analysis. Von-Mises stress values and cusp movements induced by occlusal loading were evaluated. RESULTS: Maximum Von-Mises stress of enamel occurred in sound tooth, followed by NF, CF, OF and OCF. Maximum Von-Mises stress of dentin occurred in sound tooth, followed by OF, OCF, CF and NF. Stress distribution patterns of OF and OCF were similar. Maximum overall stress values were concentrated in NF. Although stress distribution patterns of NF and CF were found as similar, CF showed lower stress values. Palatal cusp movement was more than buccal cusp in all of the models. CONCLUSION: The results of our study indicated that while the circumferential fiber had little effect on overall stress concentration, it provided a more favorable stress distribution pattern in cervical region. The occlusal fiber reduced the average stress in the entire structure but did not reduce cuspal movement. CLINICAL SIGNIFICANCE: Incorporating glass fiber in composite restorations may alter the stress state within the structure depending on fiber position.

Effect of three different contamination removal methods on bond strength of a self-etching adhesive to dentin contaminated with an aluminum chloride hemostatic agent.

AIM: This study evaluated the effect of three different contamination removal methods on bond strength of one-step self-etching adhesive to dentin contaminated with an aluminum chloride hemostatic agent. MATERIALS AND METHODS: One hundred noncarious adult molars were used in this study; 2-mm-thick dentin disks were prepared and randomly assigned to 5 groups (n = 20). Group I: control; group II: hemostatic agent-contaminated; group III: hemostatic agent-contaminated and rinsing with water; group IV: hemostatic agent-contaminated and ethylene diamine tetraacetic acid (EDTA) application; and group V: hemostatic agent-contaminated and phosphoric acid application. Clearfil S3 Bond was used to bond composite to dentin surfaces. Subsequent to adding composite cylinders the shear bond strength test was performed. Data were analyzed by one-way ANOVA and Tukey test. Two additional specimens from each group were prepared and evaluated under scanning electron microscope (SEM). RESULTS: There were statistically significant differences in bond strength among the groups (p < 0.001). In two-by-two comparisons statistically significant differences were observed in bond strength values between all the groups (p < 0.001) except for groups I and IV (p = 0.933). CONCLUSION: Aluminum chloride hemostatic agent adversely affected the bond strength of self-etch adhesive to dentin. However, application of EDTA increased the bond strength to the level of normal dentin. CLINICAL SIGNIFICANCE: EDTA and phosphoric acid removed aluminum chloride hemostatic agent contamination of dentin surfaces. However, unlike EDTA phosphoric acid failed to increase the bond strength of self-etch adhesive to dentin to the level of the control group.

Shear bond strength of self-etching adhesive systems with different pH values to bleached and/or CPP-ACP-treated enamel.

PURPOSE: To compare shear bond strengths of three different self-etching adhesive systems of different pH values to enamel bleached with carbamide peroxide, treated with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), or treated with CPP-ACP subsequent to bleaching with carbamide peroxide. MATERIALS AND METHODS: Thirty-six human third molars were cut into 4 sections and randomly assigned to 4 groups (n = 36): group I: no treatment; group II: bleaching; group III: CPP-ACP; group IV: bleaching and CPP-ACP. After surface treatments, the samples of each group were further divided into three subgroups (n = 12) based on the adhesive used. The adhesives Clearfil SE Bond (CSE), AdhesE (ADE), and Adper SE Plus (ADP) were applied, and resin composite cylinders with a diameter of 2 mm and a height of 4 mm were bonded to the enamel. Then the specimens were subjected to shear bond strength testing. Two-way ANOVA and a post-hoc Tukey's test were used for statistical analysis (α = 0.05). RESULTS: There were significant differences between the adhesive systems (p < 0.001) and surface treatments (p < 0.001), but no significant interactions were observed between these variables (p = 0.78). The CSE adhesive system showed the highest bond strength, and the bleaching procedure reduced bond strengths (p = 0.001). Furthermore, there were no significant differences in shear bond strength values between the control and CPP groups. However, the differences between other groups were statistically significant (p < 0.05). CONCLUSION: Bleaching reduced shear bond strength to enamel, but CPP-ACP application did not affect the bond strength to intact and previously bleached enamel. The bond strength of adhesives with different pH values to enamel was material dependent.

Influence of different concentrations of titanium dioxide and copper oxide nanoparticles on water sorption and solubility of heat-cured PMMA denture base resin.

OBJECTIVES: This study aimed to evaluate the effect of different concentrations of titanium dioxide (TiO2 ) and copper oxide (CuO) nanoparticles on the water sorption and solubility of heat-cured polymethyl methacrylate (PMMA). MATERIALS AND METHODS: Fifty disc-shaped specimens (10 × 2 mm) of heat-cured PMMA were prepared and divided into five groups (n = 10) to be modified with 2.5 wt.% or 7.5 wt.% of either TiO2 or CuO nanoparticles. One group was left unmodified, serving as the control group. Water sorption and solubility were measured by weighing the specimens before and after immersion in distilled water and desiccation. The data were analyzed by using one-way ANOVA and Tukey's post hoc test (α = .05). RESULTS: The 2.5 wt.% CuO nanoparticles significantly decreased the water sorption (p = .016), but did not change the water solubility (p = .222) compared with the control group. The 7.5 wt.% CuO and both concentration of TiO2 nanoparticles did not change the water sorption, but significantly increased the solubility of heat-cured PMMA (p ≤ .05). CONCLUSION: Adding 2.5 wt.% CuO nanoparticles to heat-cured PMMA decreases the water sorption; although, it has no significant effect on the solubility. Likewise, 2.5 and 7.5 wt.% TiO2 and 7.5 wt.% CuO do not affect the water sorption, but increase the water solubility of heat-cured PMMA. CLINICAL SIGNIFICANCE: Reinforcing the heat-cured PMMA denture base resin materials with the right concentration and type of nanoparticles can decrease the water sorption of resin base materials, and consequently can influence the durability of dentures.

Evaluating the Effect of Pretreatment with Matrix Metalloproteinase Inhibitors on the Shear Bond Strength of Composite Resin to Primary Teeth Dentin: A 6-Month In vitro Study.

OBJECTIVE: The purpose of this study was to evaluate the effect of pretreatment with of matrix metalloproteinase inhibitors on the shear bond strength (SBS) of Adper Single Bond 2 total etch adhesive to the primary teeth dentin following 6 months of storage in artificial saliva. MATERIALS AND METHODS: One hundred and twenty primary anterior teeth extracted for orthodontic reasons were selected. After etching, dentin blocks from each tooth were pretreated for 60 s with: (i) phosphate-buffered saline (0.01 M, pH 7.2) as the control group, (ii) 17% ethylenediaminetetraacetic acid (EDTA), (iii) 2% doxycycline (DO) solution, and (iv) 2% chlorhexidine (CHX) solution, with subsequent application of an etch-and-rinse adhesive system (Adper Single Bond 2). The composite was placed in clear Teflon cylinders. The SBS values were determined immediately and following 6 months of aging with a universal testing machine. Failure mode was evaluated using the stereomicroscope and scanning electron microscope. Data were analyzed by the SPSS software using the one-way analysis of variance and post hoc tests (P = 0.05). RESULTS: At baseline, no significant difference was observed between control, EDTA, CHX, and DO groups (P = 0.554). Following 6 months of aging, the SBS of the CHX group was significantly higher than the control group (P = 0.013). However, the SBS of the control, EDTA, and DO groups was not statistically different (P < 0.05). CONCLUSIONS: Following 6 months of aging, among different groups of the study, only CHX significantly preserved the SBS of composite resin to primary teeth dentin using Adper Single Bond 2 adhesive.

The effect of proanthocyanidin and casein phosphopeptide-amorphous calcium phosphate on the bond strength durability to caries-affected dentin.

OBJECTIVES: The aim of this study was to evaluate the effect of proanthocyanidin (PA) and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste on the micro-shear bond strength (µSBS) durability of an etch-and-rinse adhesive to caries-affected dentin (CAD). MATERIALS AND METHODS: The occlusal surfaces of 80 human molars with occlusal caries were ground to expose flat dentin surfaces with CAD. Then, they were randomly divided into four groups (n = 20) according to the CAD pretreatment. The study groups included no pretreatment, pretreatment with CPP-ACP for 3 min, pretreatment with PA for 1 min, and pretreatment with PA for 1 min followed by CPP-ACP for 3 min before adhesive application. After restoring the specimens with composite resin, µSBS testing was performed for half of the bonded surfaces in each group after 24 h and the other half was tested after 6 months of water storage and failure mode analysis was performed. RESULTS: The PA group was associated with a higher µSBS than the control and CPP-ACP groups after 24 hours (p < 0.05). No significant difference was observed regarding the µSBS of the control and the other groups after 24 h (p > 0.05). No significant difference was observed regarding the µSBS of the PA and PA + CPP-ACP groups (p > 0.05). The µSBS of the 6-month specimens was significantly lower than those of the 24-h specimens for all the groups (p < 0.05) except for the PA group which did not exhibit a significant difference between the two times (p > 0.05). The most common type of failure was mixed failure. CONCLUSION: PA pretreatment could stabilize the CAD-resin interface and protect degradation over time. The same effect was not observed for CPP-ACP or PA + CPP-ACP.

Fracture Strength and Marginal Adaptation of Conservative and Extended MOD Cavities Restored with Cention N.

The aim of the present study was to compare the fracture strength and marginal adaptation of MOD cavities restored with Cention N, bonded Cention N, and resin composite, as well as to investigate the effect of cavity preparation volume on those properties. In this experimental study, 120 human maxillary premolars were randomly divided into six groups according to the type of restoration and cavity volume (n = 20): (I) conservative MOD restored with Cention N, (II) conservative MOD restored with bonded Cention N, (III) conservative MOD restored with Z250 resin composite, (IV) extended MOD restored with Cention N, (V) extended MOD restored with bonded Cention N, and (VI) extended MOD restored with Z250 resin composite. Fracture strength (MPa) was tested using a universal testing machine. To investigate marginal adaptation, polyvinyl-siloxane impressions were taken and poured with epoxy resin. Resin replicas were examined by SEM (×400) for marginal adaptation. ANOVA tests, Tukey's test, and independent t-test were used to analyze data (P ≤ 0.05). Among conservative restorations, the fracture strength of bonded Cention N was significantly greater than that of Cention N (P = 0.001), while in the extended preparations, there was no significant difference between fracture strengths of different types of restorations (P = 0.579). In terms of marginal adaptation, there was no significant difference between different types of conservative restorations (P = 0.232). However, in extended preparations, composite showed significantly lower marginal adaptation than Cention N and bonded Cention N (P = 0.004 and P = 0.045, respectively). Conservative preparations showed significantly greater fracture strength and marginal adaptation compared to extended ones in groups restored with composite. The volume of cavity preparation was shown to be effective in the materials fracture strength and marginal adaptation. Cention N showed promising results in terms of fracture strength and marginal adaptation.

Antimicrobial Activity of Thermocycled Polymethyl Methacrylate Resin Reinforced with Titanium Dioxide and Copper Oxide Nanoparticles.

AIMS: This study aimed to evaluate the effect of 2.5% and 7.5% copper oxide (CuO) and titanium dioxide (TiO2) nanoparticles on the antimicrobial activity of thermocycled polymethyl methacrylate (PMMA) denture base material against standard strains of yeast and bacteria species. Material and Methods. In this in vitro study, 150 disk-shaped (10 × 2 mm) specimens of heat-cured PMMA were prepared and divided into five groups (n = 30) to be reinforced with 2.5% CuO, 7.5% CuO, 2.5% TiO2, or 7.5% TiO2 nanoparticles and a control group (without nanoparticle). The specimens were thermocycled, and their antimicrobial activity was assessed against standard strains of yeast including Candida albicans and C. dubliniensis and oral bacteria species including Streptococcus mutans, S. sobrinus, S. salivarius, and S. sanguis. Data were analyzed with ANOVA and Tukey's post hoc tests (α = 0.05). RESULTS: Both concentrations of CuO and TiO2 nanoparticles had significant antimicrobial activity against S. salivarius, S. sanguis, and C. dubliniensis compared with the control group (P < 0.05). Significant differences existed between both 2.5% (P = 0.006) and 7.5% CuO (P = 0.005) and the control group against S. mutans. However, TiO2 groups were not significantly different from the control group against S. mutans. Concerning C. albicans, 7.5% TiO2 was the only nanoparticle with significantly higher antimicrobial activity compared with the control group (P = 0.043). CONCLUSIONS: Both concentrations of CuO and TiO2 were effective antimicrobial agents against S. salivarius, S. sanguis, and C. dubliniensis, and the concentration of CuO was effective against S. mutans. Yet, TiO2 was not much effective. Regarding C. albicans, only 7.5% TiO2 showed efficient antimicrobial activity.

Knoop Hardness of Self-Etch Adhesives Applied on Superficial and Deep Dentin.

STATEMENT OF THE PROBLEM: Low pH of self-etch adhesives might cause suboptimal polymerization. PURPOSE: This study aimed to evaluate the effect of dentin depth (deep and superficial) on polymerization efficacy of two self-etch adhesives, with different pH by means of Knoop hardness test. MATERIALS AND METHOD: In this in vitro study, sixty sound molars were used to prepare 30 superficial dentin and 30 deep dentin specimens. Dentin specimens of each depth were randomly distributed into two equal subgroups (N=15) and bonded by either Adper Prompt L-Pop (strong self-etch adhesive) or Adper Easy Bond (mild self-etch adhesive). Knoop hardness test was employed to evaluate degree of cross-linking of the adhesives. Data were analyzed with SPSS 16, using two-way ANOVA to compare mean hardness values of the study groups (p< 0.05). RESULTS: There was no interaction effect between dentin depth and the type of adhesive (p= 0.36). Regardless of dentin depth, hardness of Adper Easy Bond was significantly higher than that of Adper Prompt L-pop (p< 0.001). Moreover, both the adhesives showed higher hardness when bonded to superficial dentin compared to deep dentin (p< 0.001). CONCLUSION: Degree of cross-linking of the self-etch adhesive with mild acidity was more than that of the strong self-etch adhesive after light-curing. Surface hardness of both adhesives was higher on superficial dentin compared to deep dentin.

Marginal Fit of Full Contour Monolithic Zirconia in Different Thicknesses and Layered Zirconia Crowns.

AIM: Use of monolithic zirconia for fabrication of all-ceramic crowns eliminates several shortcomings of layered zirconia crowns. Long-term success of restorations highly depends on the marginal fit. The crown thickness is among the factors that affect the marginal integrity. Meanwhile, reduced thickness of crowns has several advantages such as preservation of tooth structure. The aim of this study was to evaluate the marginal fit of monolithic zirconia crowns in reduced thickness and to compare the marginal fit of full-contour monolithic zirconia in different thicknesses with layered zirconia crowns. MATERIALS AND METHODS: In this in vitro study, two standard brass dies (7 mm × 5 mm length diameter) were prepared with a heavy chamfer finish line with 0.5 and 1 mm depth. By using a CAD-CAM system, 30 crowns were made in three groups (n = 10) of 1-mm thick layered zirconia, 1-mm thick monolithic zirconia, and 0.5-mm thick monolithic zirconia. Crowns were placed on master dies and randomly numbered. The marginal gap was measured on 18 points by using a digital microscope (×230). The mean ± standard deviation (SD) values were calculated and analyzed by Statistical Package for the Social Sciences (SPSS) software program through Kruskal-Wallis and Mann-Whitney tests (α = 0.05). RESULTS: The marginal gap of 1-mm layered zirconia was significantly different from that of 1-mm monolithic zirconia (P = 0.001) and 0.5-mm monolithic zirconia (P = 0.004). Analysis of variance (ANOVA) revealed no significant difference between 0.5 and 1 mm thicknesses of monolithic zirconia (P = 0.141). CONCLUSION: Marginal gap in all the three groups was clinically acceptable. The two different thicknesses of monolithic zirconia crowns had no significant effect on the restoration marginal fit; however, layered zirconia crowns showed a significantly higher marginal gap than monolithic zirconia crowns.

Effect of silver diamine fluoride and proanthocyanidin on resistance of carious dentin to acid challenges.

The aim of this study was to evaluate the effect of silver diamine fluoride and grape seed extract on the microstructure and mechanical properties of carious dentin following exposure to acidic challenge. Ninety-eight molars with occlusal caries were used. In the control group the specimens were kept in distilled water. In the GSE group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes. In the SDF group, the specimens were immersed in 30% SDF solution for 4 minutes. In the GSE+SDF group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes and then exposed to 30% SDF solution for 4 minutes. All the groups underwent pH cycling model for 8 days. Microhardness measurements were taken at the baseline before surface treatments and after pH cycling. Elastic modulus was measured, after pH cycling. In the control group, the final hardness was significantly lower than the initial hardness (P = 0.001). In the SDF group, the final hardness was significantly higher than the initial hardness (P < 0.001). There was no significant difference between the initial and final hardness values in the GSE and GSE + SDF groups (p = 0.92, p = 0.07). The H1-H0 in the SDF group was significantly higher than the other groups (P<0.05). Moreover, elastic modulus of the experimental groups except GSE+SDF group was significantly higher than control. The highest mean elastic modulus was detected in the SDF group (P<0.001). The use of SDF and GSE prior to the acid challenge improved mechanical properties. Microstructural investigation, using scanning electron microscope showed dentin structure protection against acid challenges with SDF treatment and collagen matrix stabilization with GSE treatment. However combined use of these agents was not beneficious.

Effect of silver diamine fluoride on the bond durability of normal and carious dentin.

BACKGROUND: Silver diamine fluoride (SDF) has attracted attention because of its clinical success in arresting dentin caries. It has been shown that it can inhibit matrix metalloproteinases and cysteine cathepsins. These two properties might be beneficial in bonding to caries-affected dentin (CAD). Therefore, the present study aimed to investigate the effect of SDF on the durability and bond strength to the CAD. MATERIAL AND METHODS: Forty-eight third molars with occlusal caries were used. The roots were cut, and the occlusal enamel was removed. The CAD area surrounded by the normal dentin (ND) was exposed. All the specimens were bonded with an etch-and-rinse adhesive, but half of them were treated with SDF after acid etching (NT or SDF). Two cylinders of composite (0.9 mm in diameter and 0.7 mm in height) were built-up on each specimen, one on the CAD and the other on the ND area. The specimens in each group (NT-ND, NT, CAD, SDF-ND, SDF-CAD) (n=24) were equally divided into two subgroups. One subgroup was tested for microshear bond strength 24 hours after bonding (T0), and the other subgroup was tested after six months of water storage (T6). The bond strength data were analyzed using three-way ANOVA. Subgroup analysis was performed using independent samples t-test. Fracture patterns were also evaluated. RESULTS: At T0, the bond strength of NT-ND was higher than that of NT-CAD (p<0.00), but the bond strength of SDF-ND and SDF-CAD were not different (p=0.77). Comparison of the bond strength of the groups between the two time intervals yielded the following results: NT-ND-T0> NT-ND-T6 (p=0.04), SDF-ND-T0=SDF-ND-T6 (p=0.39), NT-CAD-T0=NT-CAD-T6 (p=0.51) and SDF-CAD-T0>SDF-CAD-T6 (p<0.00). CONCLUSIONS: The SDF treatment increased the bond strength to CAD but did not affect the bond strength to the ND. SDF hindered the decrease in the bond strength to the ND caused by aging. However, the effect of SDF on increasing the bond strength to CAD disappeared after aging. Key words:Silver diamine fluoride, caries-affected dentin, bond strength.

Effect of Casein Phosphopeptide-Amorphous Calcium Phosphate on Fracture Resistance of Reattached Tooth Fragments Using Conventional and Self-Adhesive Bioactive Flowable Composite.

OBJECTIVES: The present study aimed to investigate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) complex and the type of flowable composite (conventional or self-adhesive bioactive) on the fracture resistance of fractured incisors restored through reattachment technique. MATERIALS AND METHODS: In this experimental in vitro study, 60 extracted bovine central mandibular incisors were randomly divided into six groups (n = 10) according to the reattachment technique. Their incisal edges were cut off to represent an enamel-dentin fracture. The fragment edges were reattached as follows: Group 1-selective etching and bonding followed by conventional flowable composite; Group 2-selective etching and bonding followed by bioactive flowable composite; Group 3 was like Group 2 but without applying bonding; Groups 4, 5, and 6 were similar to Groups 1, 2, and 3, respectively, but both tooth fragments were pretreated with CPP-ACP-containing paste for 3 minutes. Fracture resistance was assessed by a universal testing machine. STATISTICAL ANALYSIS: Data were analyzed by SPSS-Statistical Package for the Social Sciences-software using one-way analysis of variance and Tukey post-hoc tests (α= 0.05). RESULTS: The highest and lowest fracture resistance was recorded in Groups 5 (15.96 MPa) and Group 6 (1.95 MPa), respectively, being significantly different from the other groups. The mean fracture resistance of Groups 3 and 6 was significantly lower than the other groups (p < 0.05). However, Groups 1, 2, and 4 showed no difference in fracture resistance. CONCLUSION: Bioactive composite was not superior to conventional composite for fragment reattachment, but using it in self-adhesive mode reduced the fracture strength significantly. Yet, pretreatment with CPP-ACP, followed by application of adhesive, improved the fracture resistance of bioactive composite.

Effect of Silver Diamine Fluoride and Proanthocyanidin on Mechanical Properties of Caries-Affected Dentin.

OBJECTIVES: Inner carious dentin is specified with decreased minerals and collagen cross-links but without protein denaturation. Current minimally invasive dentistry concepts recommend removal of only the outer layer of carious dentin and biomodification of repairable inner carious dentin. The present study aims to investigate the possibility of functional repair of this layer using silver diamine fluoride (SDF) and grape seed extract (GSE). MATERIALS AND METHODS: Molar teeth with occlusal caries were used to prepare caries-affected dentin specimens for hardness and elastic modulus measurements. The specimens of each test were divided randomly into four equal groups. In the GSE group, the specimens were immersed in 6.5% GSE solution for 10 minutes. In the SDF group, the specimens underwent a topical application of a 30% SDF. In the GSE+SDF group, first the specimens were immersed in GSE and then exposed to SDF. In the SDF+GSE group, first SDF was applied and then the specimens were immersed in GSE. Microhardness measurements were taken at baseline and after treatment. A control group with distilled water treatment was also prepared for elastic modulus measurements. STATISTICAL ANALYSIS: One-way analysis of variance and post-hoc tests were used for statistical analysis. RESULTS: There were significant differences in H1-H0 (final hardness-baseline hardness) among the groups. Baseline and final hardness of each group was also significantly different (SDF>SDF+GSE>GSE>GSE+SDF). Elastic modulus of SDF and SDF+GSE increased compared to the control group. CONCLUSIONS: SDF and SDF+GSE treatment can be recommended to increase hardness and elastic modulus of caries-affected dentin.

Detection of Hepatitis C Virus RNA in Blood and Saliva of Transfusion-Dependent Thalassemia Patients Diagnosed with Hepatitis C.

BACKGROUND: The aim of the current study was to detect hepatitis C virus (HCV) RNA in blood and saliva of a population of patients with thalassemia who have HCV antibody in their serum. MATERIALS AND METHODS: In this cross-sectional study, blood and saliva samples were collected and were analyzed with quantitative reverse transcription polymerase chain reaction (RT-PCR) for the detection of HCV RNA. In addition, liver-related blood tests were performed, and patients' medical history was recorded. Data were analyzed by independent samples t-test and Chi-square with a significant level of 0.05. RESULTS: Overall, 62 adult patients (29 males and 33 females) were included. Most (87%) of the patients had major thalassemia and genotype 1a was the most common (42%) type. HCV RNA was detected in 71 and 16% of blood and saliva samples, respectively. HCV RNA was detected more in female patients (31%) (P = 0.003) and in intermediate thalassemia (50%) (P < 0.005). The mean age of the patients with positive saliva was almost 10 years older (P < 0.001), and the mean number of blood transfusion was fewer in positive saliva group (P = 0.037). The sensitivity, specificity, and positive and negative predictive values of saliva PCR was calculated to be 18%, 88%, 80%, and 69%, respectively. CONCLUSION: Saliva contained HCV RNA in 16% of the assessed population. The probability of detection of HCV RNA in saliva increased in older patients, less number of blood transfusions, females and intermediate thalassemia. Saliva RT-PCR demonstrated low sensitivity and high specificity with high positive predictive value in the assessed population.

The effect of two cross-linking agents on dentin bond strength of resin-modified glass ionomer.

OBJECTIVES: The hybrid layer at the interface of resin-modified glass ionomer cements and dentin is prone to degradation by endogenous matrix metalloproteinases. We aimed to investigate the effect of two types of collagen crosslinkers, carbodiimide and proanthocyanidin (PA), on immediate and medium-term bond strength of a resin-modified glass ionomer to dentin. MATERIALS AND METHODS: Seventy-two molars were flattened on the occlusal surface to expose dentin. The specimens were divided into control, 1-ethyl-3-(3-dimethylaminopropy) carbodiimide hydrochloride (EDC), and PA groups (n = 24). In the EDC and PA groups, carbodiimide and PA solutions were applied for 1 min, respectively. Resin-modified glass ionomer was bonded. Half of the specimens in each group were tested for shear bond strength after 24 h and the other half were tested after 6 months. STATISTICAL ANALYSIS: Data were analyzed with SPSS version 16 (SPSS Inc, Chicago, IL, USA), using two-way ANOVA, and subgroup analysis was performed using one-way ANOVA, Tukey's test, and t-test. RESULTS: Two-way ANOVA showed that treatment and time affected the bond strength. Carbodiimide and PA did not affect the immediate bond strength (P = 0.51). After 6 months, the bond strength of the EDC group was significantly lower than that of the control and PA groups. Bond strength of the control and PA groups increased after 6 months (P ≤ 0.002). CONCLUSION: PA did not interfere with maturation of RMGIC unlike carbodiimide. Therefore, it can be suggested as an matrix metalloproteinase inhibitor before bonding of resin-modified glass ionomer to dentin.