Effect of different dentin thicknesses between floor of pulp chamber and furcation area, alone or with addition of MTA, on fracture resistance in mandibular molars (An in-vitro study)

Abstract

Aim: This study aimed to compare the effect of different remaining dentin thicknesses RDT (1mm, 2mm and 3mm), between floor of pulp chamber and furcation area, alone or after addition of MTA layers (1 mm and 2 mm), on fracture resistance of mandibular molars. Subjects and methods: Access cavities were performed on fifty human extracted mandibular molars using a round diamond and tapered stone. Pulp debridement of all samples was done. Teeth were randomly assigned into 3 main groups according to dentin thickness. Group 1: remaining dentin thickness 2 mm between the floor of pulp chamber and bifurcation area (n=20). Group 2: remaining dentin thickness 1 mm between the floor of pulp chamber and bifurcation area (n=20). Group 3: average dentin thickness 3 mm between the floor of pulp chamber and bifurcation area (n=10). Group 1 and 2 were sub-divided into two equal subgroups (n=10) according to the thickness of MTA added. For group 1: Subgroup (1a): no MTA was added and subgroup (1b): 1 mm of MTA was added. For group 2: Subgroup (2a): no MTA was added and subgroup (2b): 2 mm of MTA was added. Then, a compressive force was applied toward the floor of the prepared cavity causing vertical fracture by using Instron testing machine to determine the remaining dentin thickness behaviour in all groups and their subgroups. Results: There was no statistically significant difference between the three groups (G: 1a, 2a and 3) with pvalues 0.54, 0.67 and 0.99 respectively. As well as no statistically significant difference between Group 2b and Group 1b (RDT 2 mm with 1 mm MTA) with p-value 0.12. In contrast to Group 2b and other groups (Group 3, 1a and 2a) where there were statistically significant differences with P-values= 0.05, 0.04 and 0.006, respectively. Conclusion: Addition of a layer of 2 mm thickness of MTA to the floor of pulp chamber significantly increases the fracture resistance at bifurcation area.