Comparison Of The Adaptability Of Two Fissure Sealants In Various Tooth Fissure Morphology Patterns: An In Vitro Experimental Study.

BACKGROUND: This study was conducted to compare the adaptation of resin-based sealants with that of Resin modified glass ionome-based sealants in various tooth fissure morphologies. METHODS: It was an in vitro experimental study done at the Dow University and NED University, Karachi, Pakistan. Ten extracted human molars were randomly assigned to two groups, (n=5) each. Fissure sealant material (Resin based sealant or resin modified glass ionomer-based sealant) was applied on the occlusal surface of the tooth according to manufacturer's recommendations. Specimens were thermocycled and then sectioned into three longitudinal parts in the bucco- lingual direction. Specimens were examined using scanning electron microscope for the adaptation of the sealant in the occlusal fissure. Mann-Whitney -U test and Kruskall-Wallis test were applied to compare the adaptability scores of sealant materials in the tooth fissure. Level of significance was kept at 0.05. RESULTS: There were no significant differences in the adaptability scores among U-shaped (p-value=0.35), V-shaped (p-value=0.89), IK-shaped (p-value=0.52), I-shaped (p-value- =0.41) and Y-shaped (p-value=1.00) fissure patterns. Similarly, there were no significant differences observed between the resin-based sealant (p-value=0.95) versus RMGIC based sealant (p-value=0.63) for the adaptability scores in various tooth fissure morphologies. CONCLUSIONS: No significant difference was found between resin-based sealants and resin modified glass ionomerbased sealants for the adaptation in various tooth fissure patterns.

In Vitro Comparative Study of Two Different Bleaching Agents on Micro-hardness Dental Enamel.

OBJECTIVE: To evaluate the effect of home-use bleaching agent containing 16% Carbamide Peroxide (CP) and in-office bleaching agent containing 38% Hydrogen Peroxide (HP) on enamel micro-hardness. STUDY DESIGN: An in vitroexperimental study. PLACE AND DURATION OF STUDY: Department of Operative Dentistry and Science of Dental Materials at Dr. Ishrat-ul-Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences and Material Engineering Department of NED University of Engineering and Technology, Karachi, from July to December 2014. METHODOLOGY: Atotal of 90 enamel slabs from 45 sound human 3rd molar were randomly divided into 3 groups. Each group contained 30 specimens (n=30). Group 1 was kept in artificial saliva at 37°C in incubator during the whole experiment. However, Groups 2 and 3 were treated with power whitening gel and tooth whitening pen respectively. After bleaching session, specimens were thoroughly rinsed with deionized water again for 10 seconds and then stored in artificial saliva at 37°C in incubator. Artificial saliva was changed after every 2 days. The Vickers hardness tester (Wolpert 402 MVD, Germany) was adjusted to a load of 0.1 kg (100 gm) and dwell time of 5 seconds. Three Vickers were performed on each specimen using a hardness tester according to the ISO 6507-3:1998 specification. Micro-hardness measurements were performed before and after bleaching at day 1, 7 and 14. RESULTS: In the control group, the baseline micro-hardness was 181.1 ±9.3 which was reduced after the storage on day 1, 7 and 14 (p = 0.104). In Group 2, baseline micro-hardness was 180.4 ±10.1 which was reduced to 179.79 ±10.0 units after day 1. Whereas, on day 7 and 14, the values of micro-hardness were 179.8 ±10 and 179.7 ±10.29, respectively (p=0.091). Furthermore, the baseline micro-hardness in Group 3 was 174.0 ±22.9 units which was reduced to 173 ±23 on day 1, 170 ±30 on day 7 and 173 ±23 on day 14 (p = 0.256). The statistically insignificant difference was found among micro-hardness values of different bleaching agents (p = 0.118). CONCLUSION: Bleaching with 38% Hydrogen Peroxide (HP) and 16% Carbamide Peroxide (CP) resulted in insignificant effect on surface micro-hardness of enamel.

Micromechanical Intervention in Sandwich Restoration.

OBJECTIVE: To evaluate the sealing ability of two different types of Glass Ionomer Cements (GICs) used for sandwich restorations and assess the effect of acid etching of GIC on microleakage at GIC-resin composite interface. STUDY DESIGN: Experimental study. PLACE AND DURATION OF STUDY: Department of Operative, DIEKIOHS (DUHS) and NED University, Karachi, from February to June 2011. METHODOLOGY: Eighty cavities were prepared on the proximal surfaces of 40 permanent human premolars (2 cavities per tooth), assigned to 4 groups (n=20) and restored as follows: Group CIE - Conventional GIC (CI) was applied onto the axial and cervical cavity walls, allowed setting for 5 minutes and acid etched (E) along the cavity margins with 37% phosphoric acid for 15 seconds, washed for 30 seconds and dried; the adhesive system was applied and light cured for 10 seconds, completing the restoration with composite resin light cured for 40 seconds; Group CIN - same as Group CIE, except for acid etching of the CI surface; Group RME - same as CIE, but using a resin modified GIC (RMGIC); Group RMN - same as Group RME, except for acid etching of the RMGIC surface. Specimens were soaked in 1% methylene blue dye solution at 37ºC for 24 hours, rinsed under running water for 15 minutes, bisected mesiodistally and dye penetration was measured following the ISO/TS 11405-2003 standard. Kruskal Wallis and post Hoc tests significant differences in the microleakage among all the four groups. RESULTS: There was a significant difference between the two groups of GICs (RMGIC and CI, p=0.001). There was no significant difference in between the two sub-groups that is between CIN and CIE (p=0.656), and between Groups RME and RMN (p=0.995). CONCLUSION: Phosphoric acid etching of GIC, prior to the placement of composite resin, does not improve the sealing ability of sandwich restorations. RMGIC was more effective in preventing dye penetration at the GIC-resin composite dentine interfaces than CI.

Effectiveness of commonly available surface protecting agents in maintaining microhardness of two cements.

OBJECTIVE: To estimate the microhardness of glass ionomer cement (vitrofil) and resin modified glass ionomer cement (vitremere) in the presence and absence of different surface protections. STUDY DESIGN: An in-vitro experimental study. PLACE AND DURATION OF STUDY: The Department of Operative Dentistry, Dr. Ishrat-ul-Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences and the Department of Material Sciences, NED University, Karachi, from August 2011 to January 2012. METHODOLOGY: Seventy-two discs of each material were made in polytetrafluoroethylene mold which was 10 mm in diameter and 2 mm in thickness. Four groups were made for each material containing 18 discs; G1/G5 (control group), G2/G6 (solid petroleum jelly), G3/G7 vernal (resin varnish), G4/G8 (nail varnish). After initial setting reaction surface protection was applied to discs. Once the surface protection was dried, discs were stored in deionized water at 37°C for 24 hours. After 24 hours, the discs were polished. Microhardness test were performed in digital microhardness tester. The results were statistically analyzed with the help of two-way ANOVA. RESULTS: For glass ionomer cement the only G4 (nail varnish) differed from the G1 (control group) [p < 0.05], No significant difference was seen with other surface protection agents. For resin modified glass ionomer cement, the G7 (resin varnish) and G8 (nail varnish) gave better result from the G5 (control group). CONCLUSION: Nail varnish and resin varnish showed better surface protection for GIC and RMGIC. The presence of toluene in nail varnish have harmful effects so should not be preferred if resin varnish is available.

Effect of different irradiation times on microhardness and depth of cure of a nanocomposite resin.

OBJECTIVE: To determine the microhardness and depth of cure of nanocomposite using different irradiation times on both upper and lower surfaces of composite material. STUDY DESIGN: In-vitro experimental study design. PLACE AND DURATION OF STUDY: Dr. Ishrat-ul-Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences and NED University of Engineering and Technology, Karachi, from March to May 2010. METHODOLOGY: Total 120 cylinder shaped specimens; 60 specimens for depth of cure test and 60 specimens for micro hardness test were fabricated using A3 shade of nanocomposite (Filtek Z350 XT, 3M ESPE). For each irradiation time four groups were made (Group 1 = 20s), (Group 2 = 30s), (Group 3 = 40s) and (Group 4 = 60s). For each group fifteen specimens were used. The resin was placed and polymerized into a cylindrical plastic mold. Depth of cure was measured by using micrometer. Micro Vickers hardness was measured on both top and bottom surfaces. SPSS-16.0 was used for statistical analysis. RESULTS: There was statistically significant difference in the depth of cure between all groups showing the highest value in group 4 (p < 0.001). For hardness on top surface, there was a statistically significant difference in between groups 1 and 2 (p=0.001), groups 1 and 3 (p < 0.001), groups 1 and 4 (p < 0.001). There was no statistically significant difference between groups 2 and 3, groups 2 and 4 and in between groups 3 and 4. For hardness on bottom surface, there was statistically significant difference in between all groups showing the highest value in group 4 (p < 0.001). CONCLUSION: Depth of cure and hardness was increased by increasing irradiation time. Hardness on the top surface was higher than bottom surface values.