Effect of disinfection solutions on the adhesion force of root canal filling materials.

INTRODUCTION: Sodium hypochlorite (NaOCl) and chlorhexidine (CHX) are usually used to disinfect gutta-percha (GP) and Resilon (Res) cones. This study investigated the adhesion force (Fad) between root canal sealers and GP and Res cones following different disinfection protocols by using atomic force microscopy. METHODS: Nine flat surfaces of each material were obtained with medium points of GP and Res. The samples were divided into 6 groups (n = 3): control group GP, immersion in distilled water (DW); NaOCl group GP, immersion in 5.25% NaOCl and then washing with DW; CHX group GP, immersion in 2% CHX and then washing with DW; control group Res, immersion in DW; NaOCl group Res, immersion in 5.25% NaOCl and then washing with DW; and CHX group Res, immersion in 2% CHX and then washing with DW. Atomic force microscopy tips containing AH Plus sealer were used to obtain force versus distance curves regarding GP surfaces. Fad was calculated from the force curves. The same procedure was performed with Real Seal SE and Res surfaces. Data were statistically analyzed. RESULTS: A higher Fad between solid filling materials (GP and Res) and root canal sealers was found when CHX solution was used. Treatment with NaOCl solution did not show influence on the Fad values. CONCLUSIONS: The decontamination of GP and Res with 2% CHX resulted in higher Fad values. The use of CHX in the disinfection process of GP and Res cones might be a better option before root canal obturation.

Evaluation of the interaction between endodontic sealers and dentin treated with different irrigant solutions.

INTRODUCTION: Dentin surface treatment with different substances might cause alterations in chemical and structural compositions of the human dentin. The aim of this study was to investigate the wettability of endodontic sealers in contact with dentin treated with 5.25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX) in the presence or absence of smear layer. METHODS: Thirty-six dentin slices were used. They were irrigated with NaOCl and washed with distilled water (DW) to simulate irrigation during chemomechanical preparation. After this procedure, the samples were divided into 6 groups: group 1, DW (control); group 2, NaOCl + DW; group 3, CHX + DW; group 4, ethylenediaminetetraacetic acid (EDTA) + DW; group 5, EDTA + DW + NaOCl + DW; group 6, EDTA + DW + CHX + DW. The Ramé-Hart goniometer was used to measure the contact angle between the dentin surfaces and the AH Plus and Real Seal SE sealers. Data were statistically analyzed. RESULTS: With regard to the contact angle between AH Plus and treated surfaces, the values of contact angle were lower when CHX was used, regardless of the presence or absence of smear layer. When Real Seal SE was evaluated, in the absence of smear layer, CHX presented lower values of contact angle. In the presence of smear layer, the use of NaOCl and CHX did not favor the spread of the sealer. CONCLUSIONS: The present study has revealed that smear layer removal and final flush with CHX favor the wettability of AH Plus and Real Seal SE sealers.

Effect of disinfectant solutions on the surface free energy and wettability of filling material.

INTRODUCTION: Gutta-percha (GP) and Resilon (Res) cones are usually disinfected by the use of solutions such as sodium hypochlorite (NaOCl) and chlorhexidine (CHX). The aims of this study were to evaluate the surface free energy of GP and Res cones after disinfection procedures and to investigate the wettability of endodontic sealers in contact with these surfaces. METHODS: GP and Res flat smooth surfaces were prepared. Thirty-six samples of each material were used. The samples were divided into 6 groups as follows: Control group GP, immersed in Milli-Q water (MQW); CHX group GP, immersed in 2% CHX solution and then washed with MQW; NaOCl group GP, immersed in 5.25% NaOCl and then washed with MQW; Control group Res, immersed in MQW; CHX group Res, immersed in 2% CHX solution and then washed with MQW; and NaOCl group Res, immersed in 5.25% NaOCl and then washed with MQW. Samples were analyzed first with a goniometer to measure the contact angle between the test surfaces and 3 solutions (water, ethylene glycol, and diiodomethane) to determine the surface free energy. Then the contact angle between surfaces and each one of the sealers tested, AH Plus and Real Seal SE, was measured. Data were statistically analyzed. RESULTS: The results showed that when disinfectant solutions were used, the surface free energy was greater. When evaluating the interaction between materials and sealers, the use of CHX presented lower values of contact angle, followed by NaOCl. CONCLUSIONS: It was concluded that the solutions used in decontamination increase the surface free energy, promoting high interaction between GP/Res and sealers.