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ORIGINAL RESEARCH
Year : 2023 | Volume
: 14
| Issue : 1 | Page : 10-12
Assessment of Shear Bond Strength to Sound and Artificial Caries Affected Dentin Using Different Adhesive Systems: An In Vitro Study
Zahraa Salman Al-Obaidi1, Haider Hasan Jasim2
1 Ministry of Health, Baghdad, Iraq
2 Department of Conservative Dentistry, College of Dentistry, Mustansiriyah University, Baghdad, Iraq
Correspondence Address:
Zahraa Salman Al-Obaidi
Ministry of Health, Baghdad
Iraq
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/denthyp.denthyp_126_22
Introduction: We aimed to determine how the various adhesive systems affect the shear bond strength (SBS) to normal and artificially create caries affected dentin (CAD) in permanent teeth. Methods: Forty eight sound premolars had their occlusal enamel ground to create flattened midcoronal dentin. According to the dentin substrate, specimens were allocated into sound and artificially created CAD induction using the pH-cycling technique. Each group was further subdivided according to the adhesive materials: Scotchbond Universal Plus, Scotchbond Universal, and Adper Single Bond 2 adhesives (applied in Etch and Rinse Adhesive Protocol). After that, a composite was put on and shear bond strength (SBS) tests were done. Data analyzed using two-way ANOVA and chi-squared tests. Results: Overall model test of the ANOVA statistics showed that both type of dentin and types of adhesive had a significant effect on the SBS values (P < 0.001). Tuckey post hoc comparisons showed a significant difference for type of dentin (P < 0.001) and types of adhesive (P ≤ 0.005). Mode of failure assessment is non-statistically significant difference (P = 0.41). Conclusion: All adhesives showed a decrease in SBS when used on artificial CAD.
Keywords: Adhesion, bonding system, caries-affected dentin, shear bond strength
Dental caries is still the most common problems in the dental clinic, affecting both enamel and dentin. Nowadays, the application of the conservative concept during the removal of the only irreversibly damaged tissue must be done with great care. The dentin caries consists of two layers: the exterior "caries infected dentin (CID)" and inner "caries affected dentin (CAD)" layers. The exterior layer is largely demineralized and contains cariogenic microorganisms. The collagen fibrils did experience some irreversible alterations, but the inner layer, CAD, has the capacity to remineralize. It has reversible collagen modifications, is completely sterile, and is slightly demineralized. Consequently, it must be maintained throughout clinical restorative process. Even though a large portion of the cavity floor is still caries-affected dentin following caries removal, due to the histological differences between CAD and sound dentin (SD), research on CAD is required.[1]
One of the most popular mechanical property tests was the shear bond strength (SBS) test, which measures the greatest shear force that can be applied to an adhesive joint before a fracture occurs.[2],[3] SBS to CAD was rarely reported in the literature and outputs were controversial. This study goal was to determine how various adhesive systems affected the SBS to normal and artificially created CAD in permanent teeth.
Materials and methodsStudy protocol was approved by the Research Ethics Committee, Mustansiriyah University, College of Dentistry (study number Muopr15). Forty-eight sound human upper premolars were extracted for orthodontic reasons were collected and stored in an aqueous solution of thymol (0.1% weight/volume) (CAROLINA, Burlington, USA). The occlusal surface of each sample was cut to obtain flat midcoronal dentin using a diamond disk (Dentaurum, Ispringen, Germany) under running water. The cut surface of the teeth was smoothed with sandpaper (600 grit) (Hubei Zhongtai Abrasive Tools Co., Ltd., Hubei, China) by moving the dentin surface four times against the sandpaper of 10 cm length and washed to remove debris.
The samples were separated into two main groups (24 each) which were following:
Group (A): sound dentin (SD): stored in periodically renewed deionized water.
Group (B): dentin specimens had artificially created caries affected dentin (CAD) by the pH cycling method.
Each group was further subdivided into three smaller groups (eight each) according to the type of adhesive system used: Scotchbond Universal Plus (3M, St. Paul, USA), Scotchbond Universal, and Adper single bond 2 (3M, St. Paul, USA) (all of them were used in etch and rinse protocol).
For group (B) samples were protected with two layers of an acid resistance nail polish (Essence, Port Charlotte, England), except for the dentin surface that was left exposed. Then, each sample lasted 8 hours in a 10 mL demineralizing solution (2.2 mM CaCl2, 2.2 mM NaH2PO4, 50 mM acetic acid adjusted pH of 4.5) and 16 hours in a 10 mL remineralizing solution (1.5 mM CaCl2, 0.9 mM NaH2PO4, 0.15 mM KCl adjusted pH of 7.0).[4] This process was run for 14 days at room temperature. With each cycle, the solutions were refreshed. All chemicals were from (Alpha Chemika, Andheri, India). For etching a 37% phosphoric acid gel (Scotchbond etchant, St. Paul, USA) was used following the manufacturer instructions. Then adhesive was applied following manufacturer instructions for all subgroups then light cured for 10 seconds (SDI, Bayswater, Australia).
After bonding, Filtek Z350 XT universal restorative composite (3M, St. Paul, USA) had been utilized for build-ups that were each 2-mm thick by using a specially constructed device fabricated from Teflon to standardize the manner of composite application to dentin surface, then cured with an LED light curing device for 40 seconds.
After that a universal testing machine (Laryee, Beijing, China) with a crosshead speed of 1 mm/min was used to test the shear bond strength of composite to dentin. The sample blocks were attached to the lower jaw of the testing machine so that the chisel rod was held at right angles to the composite tooth interface from the buccal side. The test continued till failure.
After testing the shear bond strength, the samples were looked at with the naked eye to see if any composite pieces were left behind.[8] Results were supported by using methylene blue dye (Alpha Chemika, Andheri, India) to color the samples and a digital microscope (Zumax, Hubei, China) to look at them using 5× magnification.
The two-way ANOVA with Tuckey post hoc tests and chi-squared test were employed to analyze the data using the R 4.1.3 (R Foundation for Statistical Computing, Vienna, Austria).
ResultsOverall model test of the ANOVA statistics showed that both type of dentin and types of adhesive had a significant effect on the SBS values (P < 0.001). Tuckey post hoc comparisons showed a significant difference for the type of dentin (P < 0.001) and types of adhesive (P ≤ 0.005) [Figure 1]. Mode of failure assessment via chi-squared test showed no-statistically significant difference among study groups (P = 0.41) [Table 1].
Figure 1 Violin plot showed shear bond strength values (MPa) among different study groups. Discussion From a clinical point of view, it is important to figure out how well the various adhesive systems bond to both healthy and caries-affected dentin. Most bonding sites are not in normal dentin, but in dentin that has been affected by caries.
The loss of minerals that occurs throughout the carious process results in the formation of porous zones inside the intertubular dentin. Water was used to fill the space which was created by the mineral that was removed from the CAD matrix. This rise in the water content as well as the condition of increased permeability was both thought to be potential causes that could affect the quality of the bond. Other chemical and structural changes in the demineralized CAD, like the loss of its organic content, collagen fibrils with fewer cross-links, increased porosity in the intertubular dentin, dissolving of apatite crystals, and collagen fibril breakdown, could also make it difficult to bond to the substrate. Furthermore, noncollagenous protein content (mucopolysaccharide or glycoprotein molecules) is present in the matrix of the peritubular dentin in CAD, which may prevent the adhesive from bonding to the dentin substrate.[5],[6]
However, results of this study showed SD had higher SBS than CAD.
Shadman et al.[7] reported non-significant differences between SD and CAD regarding SBS. They used Adper Single Bond 2, Scotchbond Universal without etch, and Scotchbond Universal with etch. Sami et al., reported significantly higher SBS for SD for Single Bond universal adhesive using both etch-and-rinse and self-etch protocol. Yet, they reported non-significant difference between SD and CAD for Prime & Bond universal adhesive using both etch-and-rinse and self-etch protocol.[8] Drobac et al., stated non-significant differences between SD and CAD on the subject of SBS. They employed Adper Single Bond 2, AdheSE One, and Prime&Bond NT.[9]
Nevertheless, more investigations are needed to find pros and cons of these controversial results. Meanwhile readers must note to limitations of in vitro studies. In vitro environment such as artificial caries affected dentin cannot exactly simulate complicated oral situation. Moreover, this must be taken into consideration that “One of the main reasons for statistically insignificant results could be a small sample size” [10]
Acknowledgement
The authors would like to thank the Mustansiriyah University (www.uomustasiryah.edu.iq), Baghdad-Iraq, for its support in the present work.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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