The effect of NaOCl gel activated by ultrasonic device on bovine dental pulp dissolution: an in vitro study

Introduction
The main objective of pulp therapy is to prevent and treat lesions. Sodium hypochlorite (NaOCl) became the primary and most preferred irrigation solution in the daily practice of dental clinics because of its ability to dissolve pulp tissues.

Objective
This study aimed to compare the ability to dissolve dental pulp tissue with or without ultrasonic activation between NaOCl solution and gel.

Material and methods
The study consisted of 50 pieces of dental pulp removed from bovine teeth, divided into five equal groups (n = 10). The pulps were removed from the upper molars after cleaning the teeth and were cut to obtain appropriate samples using a punch of 2 mm in diameter and 2 mm in length. The samples were placed in plastic containers and submerged in one of the following combinations – group 1: 2.2% NaOCl solution; group 2: 2.2% NaOCl gel; group 3: 2.2% NaOCl solution with ultrasonic activation; group 4: 2.2% NaOCl gel with ultrasonic activation, and group 5: saline as a negative control. The experiment was filmed with a digital camera to accurately determine the time of dissolution.

Results
All pulp tissue samples were completely dissolved within the one-hour test time, except for the negative control. One-way ANOVA analysis showed significant difference between the groups (p = 0.000). LSD test showed significantly higher dissolution for all NaOCl groups compared to the negative control. NaOCl solution had significantly lower dissolution time compared to the gel type regardless of the activation (p = 0.000). Ultrasonic activation significantly shortened the time of dissolution to its half in both NaOCl solution and gel.

Conclusions
NaOCl gel was inferior to the NaOCl solution in its ability to dissolve pulp tissue. Ultrasonic activation was able to shorten the time duration to approximately more than half the period for the samples to complete dissolution.