Comparative Study of the Shear Bond Strength of Flowable Composite in Permanent Teeth Treated with Conventional Bur and Contact or Non-Contact Er:YAG Laser

Introduction:The aim of this study was to evaluate and compare the in vitro effect of the Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser with different radiation distances and high-speed rotary treatment on the shear bond strength of flowable composite to enamel of human permanent posterior teeth .Methods : freshly extracted human molar teeth with no caries or other surface defects were used in this study (n=45). The teeth were randomly divided into 3 groups. Group 1: treated with non-contact Er:YAG Laser and etched with Er:YAG laser, Group 2: treated with contact Er:YAG Laser and etched with Er:YAG laser, Group 3 (control): treated with diamond fissure bur and etched with acid phosphoric 37 % . Then the adhesive was applied on the surafces of the teeth and polymerized using a curing light appliance. Resin cylinders were fabricated from flowable composite. Shear bond strength was tested at a crosshead speed of 0.5 mm/min.Results: The amount of Shear Bond Strength (SBS) in the 3 treatment groups was not the same (P<0.05).The group in which enamel surfaces were treated with diamond fissure bur and etched with acid (conrtol group) had the highest mean shear bond strength (19.92±4.76) and the group in which the enamel surfaces were treated with contact Er:YAG laser and etched with Er:YAG laser had the lowest mean shear bond strength (10.89±2.89). Mann-whitney test with adjusted P-value detected significant difference in shear bond strength between the control group and the other 2 groups (P < 0.05).Conclusion: It was concluded that both contact and non-contact Er:YAG laser treatment reduced shear bond strength of flowable resin composite to enamel in comparison with conventional treatment with high speed rotary. Different Er:YAG laser distance irradiations did not influence the shear bond strength of flowable composite to enamel

The effect of bleaching on microhardness of silorane-based composite resins

Introduction: Bleaching treatments may negatively affect the surface quality of composite restorations existing in the mouth. This study sought to assess the effect of 16% and 35% carbamide peroxide on microhardness of silorane-based versus two methacrylate-based composite resins. Methods: A total of 54 discs were fabricated from FiltekP90 (P90), FiltekZ350XT(Z350) Enamel and Filtek Z250(Z250) (n=18). Each group of composite specimens was randomly divided into 3 subgroups (n=6). The control subgroup was stored in distilled water for 2 weeks. Subgroup 2 specimens were bleached 4hours a day with 16% carbamide peroxide (Home bleaching) for 14 days. The 3rd subgroup specimens were subjected to 35% carbamide peroxide (Office bleaching) applied once for 40 minutes. Microhardness of specimens was measured before and after bleaching by using Vickers hardness testing machine. Data were analyzed by using Repeated Measures ANOVA. Results: Baseline microhardness of P90 was lower than that of the other two composite resins (p=0.001). Bleaching decreased the microhardness of Z250 and Z350 compared to the control group (p<0.001). However, in P90, only the office bleaching material caused a reduction in microhardness (p=0.009). The effect of home and office bleaching on microhardness of P90 was different (p=0.015). Conclusion: Bleaching treatments significantly decreased the microhardness of Z250 and Z350 composite resins but this reduction in P90 was not statistically significant after home bleaching

Oral health and school performance in elementary students: A cross-sectional study in a group of Iranian students, Tehran, Iran

BACKGROUND AND AIM: Dental health plays a key role in the overall health status and quality of life in children. Consequences of dental diseases in children may result in impairments of daily life activities. The aim of this study was to assess the relationships between dental health and educational performances in elementary students. METHODS: A total of 300 elementary students from the second to fifth grades in ninth district of Tehran, Iran, were included in this study according to inclusion criteria. Questionnaire gathering information about the students’ demographic background, medical and dental histories was sent to their parents. The students’ academic performances were assessed based on the school absence in relation to dental problems, their school grades and doing homework. Oral health status was assessed based on the World Health Organization (WHO) standards using caries and oral hygiene indices. Data were analyzed by the Pearson’s correlation and linear regression analysis. All statistical levels were made at 0.05 for the Pearson’s correlation and 0.1 for linear regression analysis. RESULTS: School test grades and school absences due to dental problems were statistically associated with oral hygiene index (OHI) of the students (P = 0.010 and P = 0.040, respectively). The indices of dental caries in primary or permanent teeth were not significantly associated with school performances (P ≥ 0.140). The analysis revealed that the factors i.e., housing status and living with the parents are statistically associated with the oral health indices (P = 0.050 and P =0.080; respectively) and on the other hand with school performances (P = 0.020 and P = 0.010; respectively). CONCLUSION: Children with poorer oral health status were more likely to perform poorly in school. Socio-economic status of the students affects negatively both school performances and oral health care. Also, oral health status and dental problems may cause deterioration in educational conditions. KEYWORDS: Students, Oral Health, Dental Caries, School, Performanc

Diagnostic Accuracy of Inverted and Unprocessed Digitized Periapical Radiographs for Detection of Peri-Implant Defects

Objectives: This study aimed to compare the diagnostic accuracy of inverted and unprocessed digitized periapical radiographs for detection of peri-implant defects. Materials and Methods: A total of 30 osteotomy sites were prepared in three groups of control, study group 1 with 0.425 mm defects and study group 2 with 0.725 mm defects using the SIC and Astra Tech drill systems with 4.25mm and 4.85mm diameters. Small and large defects were randomly created in the coronal 8mm of 20 implant sites; implants (3.4mm diameter, 14.5mm length) were then placed. Thirty periapical (PA) radiographs were obtained using Digora imaging system (Soredex Corporation, Helsinki, Finland), size 2 photostimulable storage phosphor (PSP) plate sensors (40.0mm×30.0mm) and Scanora software. Unprocessed images were inverted using Scanora software by applying image inversion and a total of 60 images were obtained and randomly evaluated by four oral and maxillofacial radiologists. Data were analyzed using the t-test. Results: Significant differences were observed in absolute and complete sensitivity and specificity of the two imaging modalities for detection of small and large defects (P<0.05). Unprocessed digital images had a higher mean in terms of absolute sensitivity for detection of small defects, complete sensitivity for detection of large peri-implant defects and definite rule out of defects compared with inverted images. Conclusion: Unprocessed digital images have a higher diagnostic value for detection of small and large peri-implant defects and also for definite rule out of defects compared with inverted images

Effect of organic acids in dental biofilm on microhardness of a silorane-based composite

Objectives This study evaluated the effect of lactic acid and acetic acid on the microhardness of a silorane-based composite compared to two methacrylate-based composite resins. Materials and Methods Thirty disc-shaped specimens each were fabricated of Filtek P90, Filtek Z250 and Filtek Z350XT. After measuring of Vickers microhardness, they were randomly divided into 3 subgroups (n = 10) and immersed in lactic acid, acetic acid or distilled water. Microhardness was measured after 48 hr and 7 day of immersion. Data were analyzed using repeated measures ANOVA (p < 0.05). The surfaces of two additional specimens were evaluated using a scanning electron microscope (SEM) before and after immersion. Results All groups showed a reduction in microhardness after 7 day of immersion (p < 0.001). At baseline and 7 day, the microhardness of Z250 was the greatest, followed by Z350 and P90 (p < 0.001). At 48 hr, the microhardness values of Z250 and Z350 were greater than P90 (p < 0.001 for both), but those of Z250 and Z350 were not significantly different (p = 0.095). Also, the effect of storage media on microhardness was not significant at baseline, but significant at 48 hr and after 7 day (p = 0.001 and p < 0.001, respectively). Lactic acid had the greatest effect. Conclusions The microhardness of composites decreased after 7 day of immersion. The microhardness of P90 was lower than that of other composites. Lactic acid caused a greater reduction in microhardness compared to other solutions

Effect of Lactic Acid on Microleakage of Class V Low-Shrinkage Composite Restorations

Objectives: To assess the effect of lactic acid (LA) on microleakage of silorane-based composite restorations and methacrylate-based composites with self-etch and etch-and-rinse bonding systems. Materials and Methods: Class V cavities were prepared in 120 extracted human teeth, divided into four groups and restored as follows: 1. Silorane-based composite+P90 adhesive system (P90); 2. Filtek Z250+SE Bond (Z250SE); 3. Filtek Z350+SE Bond (Z350SE) and 4. Filtek Z250+Single Bond (Z250SB). Half of the samples in each group were immersed in LA and the other half in distilled water (DW) for seven days. Degree of microleakage was determined by dye penetration. Data were analyzed using Kruskal Wallis and Mann Whitney-U tests (type 1 error was considered 0.05 for primary and 0.017 for post-hoc tests). Results: No significant difference was found in microleakage between LA and DW groups. The difference among groups in gingival margin microleakage was significant (P<0.05). The highest degree of microleakage was seen in Z250SB; which was significantly higher than Z250SE (DW: P=0.012 and LA: P=0.002) and Z350SE (DW: P=0.002 and LA: P=0.014). Microleakage was not significantly different between Z250SE and Z350SE (DW: P=0.683 and LA: P=0.533). The degree of microleakage of P90 in both media was lower than Z250SB and higher than that of Z250SE and Z350SE; but these differences were not significant. Conclusions: Immersion in LA has no effect on microleakage of class V composite restorations regardless of the type of composite and adhesive system. At gingival margins, the highest microleakage occurred in Z250SB followed by P90 and self-etch groups.