**2.3 Influence of copaiba oil emulsions as dentin surface biomodifiers**

Bandeira et al. [5] used scanning electron microscopy (SEM) to investigate the morphology of the dentin surface, cut and treated with CO and ethanolic extract of propolis, with the aim of using them as bioactive agents for cleaning teeth. For the formulations of 10% CO, 10% CO + PB, 30% CO, and 30% CO + PA emulsions, the same cleaning pattern was obtained as that obtained with 2% chlorhexidine, which is considered the gold standard, because it had substantivity and showed bacteriostatic and bactericidal activities (**Figure 3**).

 The bond of polymer-based materials to dentin is still considered a significant challenge because the latter is a complex substrate, predominantly tubular, and intrinsically moist. The use of disinfectant and anti-proteolytic solutions may be an alternative for reducing these effects. In a histological evaluation, 10% CO was used on the exposed collagen of the dentin matrix, with the purpose of verifying whether there was interference in the adhesive system. Thus, 80 specimens (CPs) were prepared from healthy third molars, and after the induction of caries lesions, the specimens were treated with test materials for 3 months of aging. The CPs treated with the copaiba emulsions presented higher exposed and hybridized collagen thickness values than the groups treated with CLX 2% and AD. Relative to caries-affected dentin, the group treated with CLX 2% showed a higher proportion of CPs with hybridized collagen. The emulsion presented 100% specimens with hybridized collagen and improved hybrid layer homogeneity (**Figure 4**).

#### **Figure 3.**

*Photomicrograph of the group (A) without dentin surface treatment, (B) air/water spray treatment, (C) chlorhexidine, and (D) copaiba oil emulsion treatments.* 

*Biopharmaceutical Products and Biomaterials of the Amazon Region Used in Dentistry DOI: http://dx.doi.org/10.5772/intechopen.82056* 

**Figure 4.** 

*Hybrid dentin specimen stained with Goldner's Trichrome. (A) Chlorhexidine treatment and (B) copaiba oil emulsion treatment; (a) hybridized collagen, (b) mineralized dentin, (c) adhesive.* 

 Given the biological properties of *C. multijuga* Hayne, a copaiba oil emulsion was formulated for use before applying the adhesive to improve the quality of dentin bonding. The morphological characteristics of the dentin surface and the hybrid layer formed with etch-and-rinse and self-etching adhesive systems in healthy and caries-affected dentin after using the 10% copaiba oil emulsion were analyzed. A total of 96 third molars from Biobank of the School of Dentistry, Federal University of Amazonas (FAO-UFAM), were used. Half of the teeth underwent artificial induction of dental caries and the other half formed the group of healthy teeth. The roots of all the teeth were removed, yielding dentine disks that were divided into groups according to test substances (CLX 2%, copaiba oil emulsion, calcium hydroxide solution, and distilled water), the dentin (sound or caries-affected), and the adhesive system (Adper Single Bond 2® and Clearfil SE Bond®)*.* 

 SEM was used to analyze the dentin surface and hybrid layer of the specimens obtained, according to the experimental groups. The dentin surface treatment with copaiba oil emulsion showed no physical barrier to adhesive penetration. The dentin surface treated with 2% chlorhexidine showed phosphate salts in two types of dentin. Dentin surface treatment with calcium hydroxide solution resulted in the deposition of mineral precipitate obstructing the lumen of the tubules in sound dentin. The result of calcium hydroxide solution applied on the conditioned sound dentin differed from those of the other substances (p < 0.05). On the smear layer surface, the result of distilled water on sound dentin showed a significant difference from the results of all experimental groups (p < 0.05). There was no statistical difference between the hybrid layer formed with the Single Bond® adhesive in otherwise healthy dentin specimens and those of caries-affected dentin treated with the test substances.

In the dentin-rich and caries-affected dentin treated with CLX 2%, the hybrid layer formed with Adper Single Bond® was thick, regular, and homogeneous, with long resin tags, but in smaller quantity than those in the distilled water group. The hybrid layer formed with Clearfil SE Bond® on the dentin treated with CLX showed few irregular resin tags with little adhesive infiltration into the dentin (**Figure 5**).

The hybrid layer formed with the Clearfil SE Bond® adhesive on the cariesaffected dentin and caries-affected dentin treated with the copaiba oil-based emulsion presented regular and homogeneous hybrid layer with a large number of resin tags (**Figure 6**).

The CO application showed no morphological change in sound and cariesaffected dentin, irrespective of phosphoric acid etching, and presented a uniform hybrid layer, regular, and extensive monomer infiltration into sound and cariesaffected dentin, irrespective of the adhesive system.

#### **Figure 5.**

*Hybrid layer formed with Single Bond in the dentin treated with chlorhexidine: (A) Healthy dentin and (B) cariesaffected dentin. Hybrid layer formed with Clearfil on the dentin treated with chlorhexidine: (C) Healthy dentin and (D) caries-affected dentin. (a) Adhesive, (d) Dentin, (CH) Hybrid layer. The arrows point to the resin tags.* 

#### **Figure 6.**

*Hybrid layer formed with Single Bond in dentin treated with copaiba oil: (A) healthy dentin and (B) cariesaffected dentin. Hybrid layer formed with Clearfil in dentin treated with copaiba oil: (C) healthy dentin and (B) caries-affected dentin. (a) adhesive, (d) dentin, and (CH) hybrid layer. The arrows point to the resin tags.* 

*Biopharmaceutical Products and Biomaterials of the Amazon Region Used in Dentistry DOI: http://dx.doi.org/10.5772/intechopen.82056* 

The hybrid layer formed with Adper Single Bond® in the carious-affected and caries-affected dentin treated with copaiba oil-based emulsion was thick, regular, and homogeneous, with long resin tags, but in smaller quantity than those in the distilled water group (**Figure 6**).

 Thus, the copaiba oil emulsion as dentin biomodifiers with their antibacterial activity and property of inhibiting MMPs may contribute to stability of the hybrid layer, perhaps because they prevent the enzymatic hydrolysis of collagen due to their oily nature similar to that of mineral oil. Further studies must be conducted to show the mechanism of action of the oil on the MMPs and the formation of the hybrid layer. In the present work, it was shown that the MMPs were resistant to the time-dependent destruction of the hybrid layer and that the use of inhibitors could improve the durability of the composite resin-dentin bond [35].
