Effect of rotary cutting instruments on the resin-tooth interfacial ultra structure: An in vivo study

Abstract

Objectives: To evaluate the effect of cutting teeth with different types of burs at various speeds on surface topography of tooth surface and interfacial gap formation at resin-tooth interface.

Material and methods: The human molars were divided into seven groups: Diamond bur in airrotor (DA) & micromotor (DM), crosscut carbide bur in airrotor (CCA) & micromotor (CCM), plain carbide bur in airrotor (CA) & micromotor (CM) and #600-grit silicon carbide paper (SiC). In five samples from each group Class II box-only cavities were restored. The occlusal surface of four teeth per group was flattened. Two out of four teeth were acid etched. Teeth were subjected for scanning electron microscopy (SEM).

Results: Interfacial gap was observed in all groups with no significant difference. SEM observations revealed CA, CCA & DA were coarser than CM, CCM, DM and SiC. SEM of etched tooth surfaces revealed complete removal of amorphous smear layer in CA & CM, partial removal in CCA, CCM, DA & DM and no removal in SiC.

Conclusions: Selecting an appropriate bur and its speed may not play an important role in bonding in terms of interfacial gap formation. Variable changes were observed in surface topography with different burs before and after acid etching. Key words:Surface topography, resin-tooth interface, interfacial gap, bonding.

Figure 1

A) SEM view of the interfacial gap at resin-dentin interface at 500x, B) SEM view of tooth surface prepared with fine grit straight fissure diamond bur in air rotor at 500x, C) SEM view of tooth surface prepared with fine grit straight fissure diamond bur in micro motor at 500x, D) SEM view of tooth surface prepared with crosscut fissure carbide bur in air rotor at 500x, E) SEM view of tooth surface prepared with crosscut fissure carbide bur in micro motor at 500x.

Figure 2

A) SEM view of tooth surface prepared with plain fissure carbide bur in air rotor at 500x, B) SEM view of tooth surface prepared with plain fissure carbide bur in micro motor at 500x, C) SEM view of tooth surface prepared with #600-grit silicon carbide abrasive paper at 500x, D) SEM view of tooth surface prepared with fine grit straight fissure diamond bur in air rotor and conditioned with 38% H3Po4 at 500x, E) SEM view of tooth surface prepared with fine grit straight fissure diamond bur in micro motor and conditioned with 38% H3Po4 at 500x.

Figure 3

A) SEM view of tooth surface prepared with crosscut fissure carbide bur in air rotor and conditioned with 38% H3Po4 at 500x, B) Scanning electron microscopic view of tooth surface prepared with crosscut fissure carbide bur in micro motor and conditioned with 38% H3Po4 at 500x, C) SEM view of tooth surface prepared with plain fissure carbide bur in air rotor and conditioned with 38% H3Po4 at 500x, D) SEM view of tooth surface prepared with plain fissure carbide bur in micro motor and conditioned with 38% H3Po4 at 500x, E) SEM view of tooth surface prepared with #600-grit silicon carbide abrasive paper and conditioned with 38% H3Po4 at 500x.