BACKGROUND:A number of in vitro experiments have confirmed that the tricalcium silicate not only can be closely integrated with the dentin through self-curing process, but also can induce dentin remineralization in the physiological environment, thereby effectively blocking the dentinal tubules.
OBJECTIVE:To further verify the effects of tricalcium silicate solution on the occlusion of dentinal tubules.
METHODS:Thirty-six dentinal discs were made of free first premolars from orthodontic patients, and divided into three pretreatment groups randomly. The teeth were soaked in pretreatment solution for 2 minutes, namely 0.29 mol/L ethylene diamine tetraacetie acid, 6%citric acid, and rinsed ultrasonical y with deionized water 20 minutes, respectively. Every above-mentioned group was randomly assigned into experimental group (tricalcium silicate), control group (sodium fluoride) and blank group, and corresponding materials in each group were used to coat the outer dentinal tubules (2 minutes/time). Then, the dentinal discs were saved in artificial saliva in a 37 observed using scanning electron microscope. Diameter and area of open dentinal tubules were calculated.
RESULTS AND CONCLUSION:After pretreatment, the dentinal tubules were at open state;except for the blank control group to maintain the original state, acid etching and ethylene diamine tetraacetie acid pretreatment solutions had a stronger capacity of demineralization, which led to the dentinal tubules open. After the dentinal tubules were treated with sodium fluoride and tricalcium silicate, there were varying degrees of sediments, and open dentinal tubule area and average diameter in the sodium fluoride and tricalcium silicate groups were lower than those in the control group (P<0.05). The dentinal tubule treated with tricalcium silicate was almost entirely closed homogeneously, and occasional y, a single open dentinal tubule was seen. Open dentinal tubule area and average diameter in the tricalcium silicate group were significantly lower than those in the sodium fluoride group (P<0.05). The findings verify that dentin occlusion using tricalcium silicate is superior to that using sodium fluoride;and dentin tubule pretreatment with acid etching or ethylene diamine tetraacetie acid is beneficial to desensitization effects.

The mixed methods research is the third research method following quantitative study and qualitative study which plays an unique role in nursing research. This paper reviewed the application of mixed methods research in nursing research and expounded the design flow of the mixed methods research based on explanatory sequential design as well as the key questions during combining quantitative study with qualitative study.