Poonam Bogra

The effect of occlusal restoration and loading on the development of abfraction lesions: A finite element study.

Background: Abfraction, a type of non-carious cervical tooth loss, is a poorly understood condition. One factor thought to contribute to the development of these lesions is the effect of occlusal loading and the presence of occlusal restoration. Aim and Objectives: The aim of this paper is to study the stress profile in the cervical region of mandibular first premolar with variation of occlusal loads, and to compare the stress profile between sound and occlusally restored tooth under variation of occlusal load, using two-dimensional plane strain finite element model. Materials and Methods: A mandibular first premolar was sectioned and modeled in the finite element software, along with its peridontium. Varying occlusal loads were applied along the cuspal inclines, with and without an occlusal restoration. The software used was NISA II EMRC. Result: It was found that higher occlusal loads caused more cuspal flexure and that the maximum shear stress was much higher and closer to the cervical area. It was also observed that there was a slight increase in shear stress when occlusal restoration was present. Conclusion: It was suggested that high occlusal loading and the presence of an occlusal amalgam restoration increased the stress concentration at the cervical area, which may lead to the breakdown of enamel at the cervical region.

Effect of occlusal restoration on stresses around class V restoration interface: a finite-element study.

BACKGROUND Causes of failures in class V restorations have always been controversial until now, since the biomechanical aspects of these restorations have been understood. AIMS AND OBJECTIVE This study was aimed to verify the hypothesis that eccentric forces are the cause of cuspal flexure, which lead to excessive stresses at the periphery of a class V restoration, further it identifies the amount of the stress and the flexure increase in the presence of an occlusal restoration using different restorative materials to restore (both cervical and occlusal) along with their comparison with respect to amount of stresses around the cervical restorations. MATERIALS AND METHODS The study was done by modeling a mandibular first premolar which was sectioned bucco-lingually, in the NISA, EMRC II finite element software. A 100N eccentric load was applied on the tooth structure and stresses were observed at the peripheries of the class V restoration when it was restored with composite and with glass ionomer cement. The stresses were further analyzed in the presence of occlusal restorations with different materials and configurations. RESULTS It was seen that the stresses at the gingival wall interface in case of class V glass ionomer cement was more than that for composite. In the presence of an occlusal amalgam restoration, the cuspal flexure was more than that of occlusal composite and the stresses at the class V peripheries were also statistically significant. CONCLUSION It was suggested that lower modulus composites can flex with the tooth structure decreasing the bond failure and that the stresses are much lesser when there is absence of an occlusal restoration. Occlusal composite restorations reinforce the tooth structure and reduce the cuspal flexure as compared to silver amalgam.

Comparative evaluation of intracanal sealing ability of mineral trioxide aggregate and glass ionomer cement: An in vitro study.

Aims: The purpose of this study was to compare the sealing ability of Mineral Trioxide Aggregate (MTA) and Glass Ionomer Cement (GIC) when used over gutta-percha as intracanal sealing materials. The study also evaluated the sealing ability of Zinc oxide eugenol (ZOE) cement and Acroseal sealer. Materials and Methods: Teeth were obturated with gutta-percha using sealer ZOE (group A, C, D) and Acroseal (group B). The groups were further divided into 2 subgroups (15 premolars each) on the basis of intracanal sealing material used: GIC subgroups (A1, B1) and MTA in subgroups (A2, B2). The clearing technique was used in this study for leakage evaluation. Seventy mandibular premolars were prepared using step-back technique and divided into experimental groups A and B (30 premolars each) and the positive and negative control groups C and D (5 premolars each). Statistical analysis used: Coronal microleakage was determined under stereomicroscope using 15X magnification. Data was statistically analyzed using one-way ANOVA followed by Post-Hoc Multiple comparison (Bonferroni). Results: MTA group leaked significantly less than GIC group (P < 0.05). Acroseal exhibited better sealing ability than ZOE sealer. Teeth with no intracanal barrier showed almost complete leakage. Conclusions: MTA may be preferred over GIC as an intracanal barrier.

Comparative evaluation of traditional and self- priming hydrophilic resin

Background: The purpose of this study was to compare the microleakage of traditional composite (Charisma/Gluma Comfort Bond) and self-priming resin (Embrace Wetbond). Materials and Methods: Standardized Class V cavities partly in enamel and cementum were prepared in 20 extracted human premolars. Teeth were divided into two groups. Group 1 was restored with Charisma/Gluma Comfort Bond and Group 2 with Embrace Wetbond. The specimens were stored in distilled water at room temperature for 24 h and then subjected to 200 thermocycles at 5°C and 55°C with a 1 min dwell time. After thermocycling teeth were immersed in a 0.2% solution of methylene blue dye for 24 h. Teeth were sectioned vertically approximately midway through the facial and lingual surfaces using a diamond saw blade. Microleakage was evaluated at enamel and cementum surfaces using 10 × stereomicroscope. The statistical analysis was performed using Wilcoxon signed-rank test. Results: Wetbond showed less microleakage at occlusal and gingival margins as compared with Charisma/Gluma Comfort Bond and the results were statistically significant (P < 0.05). Conclusion: Class V cavities restored with Embrace Wetbond with fewer steps and fewer materials offers greater protection against microleakage at the tooth restorative interface.

The Effect of Different Post Materials and Cements on Fracture Resistance of Endodontically Treated Teeth - an in Vitro Study

Objective: To evaluate the effect of various post materials and cements on fracture resistance of endodontically treated teeth. Material and Methods: Three post systems; custom made Ni-Cr post and core, prefabricated stainless steel and carbon fibre post with composite core and two different luting cements i.e glass ionomer and resin cements were used. Results and Conclusions: Carbon fibre post cemented with resin cements showed higher failure load than Ni-Cr and stainless steel post and resin cement performed better than glass ionomer cement, the mode of fracture was more favourable with carbon fibre post than in metallic post.

Comparative evaluation of sealing ability of mineral tri-oxide aggregate with intact, removed and modified smear layer: An in vitro study

Objective: The aim was to evaluate the sealing ability of mineral tri-oxide aggregate (MTA) with intact, removed, and modified smear layer. 5.2% sodium hypochlorite was used for irrigation to keep smear layer intact, 17% ethylenediamine tetraacetic acid (EDTA) followed by 5.2% sodium hypochlorite was used to remove the smear layer and 30% potassium oxalate was used for its modification. Materials and Methods: A total of 112 intact single canaled mandibular premolar teeth were selected for the study. Roots were separated from the crown portion. All 112 roots were then randomly placed into one of five groups: Three experimental groups of 28 roots each, one group of 14 roots (negative control), and one group of 14 roots (positive control). All specimens were immersed in 1% methylene blue dye for 72 h and viewed microscopically. The results obtained were subjected to statistical analysis using one-way ANOVA test and unpaired Students t-test. Results: When group 1a was compared with 2a and 3a, there was a statistically significant difference (P 0.05) when 1a and 3a were compared. When groups 1, 2, 3, 4 and 5 were compared irrespective of the subgroups, the results were statistically significant (P < 0.05) between 1 and 2, 1 and 4, 1 and 5, 2 and 3, 2 and 4, 2 and 5, 3 and 4, 3 and 5, and 4 and 5. Conclusion: About 5.2% sodium hypochlorite and MTA produced less leakage than 17% EDTA, followed by 5.2% sodium hypochlorite but more than 30% potassium oxalate.