Bonding Capacity of a Universal Adhesive in Different Etching Modes to Caries Affected Dentin Prepared by Two Caries Excavation Techniques

Objectives: The aim of the present study was to evaluate and compare the microtensile bond
strength (μTBS) and resin penetration into caries affected dentin (CAD), of a universal adhesives
applied into two different etching modes (i.e. self-etch or etch-and-rinse), after caries excavation
with two methods, Round tungsten carbid bur CB or Carisolv chemomecanical caries removal
(CMCR). Materials and Methods: Fourty human third molar teeth with moderate occlusal carious
lesions were collected. The selected teeth were cut parallel to the occlusal surface of the tooth to
expose the carious lesion. Teeth were divided into two groups (n=20) relative to the caries excavation
methods i.e. Group1: Carisolv CMCR and group 2: round (CB). Each group was subdivided into
two subgroups (n=10) relative to the applied adhesive mode i.e. subgroup a: the adhesive system
was applied in a self-etch mode (SE), while in subgroup b: the adhesive system was used in the
etch & rinse mode (E & R). Following the application of the adhesive, Filtek Z350 XT resin
composite was applied incrementally onto the CAD. The bonded specimens were thermocycled
for 5000 cycles. The restored teeth were sectioned longitudinally to obtain bonded beams for
μTBS. Beams were mounted into the universal testing machine. Bond strength, for each subgroup,
was calculated and statistically analyzed. After debonding the beams, the fracture surfaces were
examined under stereomicroscope to detect the failure modes. One beam, from the area of CAD,
from each subgroup was selected for SEM examination. Results: Two-way ANOVA indicated high
significances for caries excavation and adhesive modes factors (p <.0001). The highest mean value
of μTBS was recorded with CMCR , bonded with E & R mode , followed by CB method, bonded
with E & R mode, CMCR bonded with SE and CB and bonded with SE adhesive; respectively.
Tukey’s test displayed that there is no significant difference in the μTBS between the groups bonded
with E & R adhesives, while CB method bonded with SE mode showed significant decrease in the
μTBS value (p < 0.05), with all test groups. All the tested groups showed cohesive failure mode in
dentin rather than adhesive. In contrast, CB excavation method with SE mode displayed increased
adhesive mode of failure rather than the cohesive and mixed modes. Removal of the caries with
both methods and bonding with E & R adhesive resulted in relatively thin hybrid layer, but thicker
with CMCR, with moderate distribution of resin tags. SE mode of adhesion showed a relatively
thick hybrid layer with short conical shaped resin tags. The dentinal tubules were at most occluded
with smear blugs and calcfic precipitates. Conclusions: Based on the limitation of this study, the
results showed that the use of Carisolv CMCR does improve the μTBS of universal adhesives to
CAD, either in SE or E & R modes.