Efficacy of Smart Burs II ® in Selective Caries Removal in Permanent Molars: Randomized Controlled Trial

One of the prime goals of the evolution of minimally invasive dentistry is conserving healthy tooth structure by eliminating infected carious dentin while retaining impacted carious dentin intact and minimizing the needless destruction of teeth. Dentin carious lesions is formed of two distinct layers that differ from one another regarding their microscopic structure and physiological and bacteriological characteristics. The external superficial infected layer is soft, heavily contaminated by bacterial invasion, and incapable of being repaired owing to the collagen fibers' irreversible denaturation. While the affected dentin, which is a hard substance with few bacteria and can be remineralized due to limited collagen degradation, is located beneath the infected layer.

Conventional caries removal could possibly be traumatic as it tends to remove both infected and affected dentin, which may induce an unneeded weakening of the tooth structure and often leads to overextended cavities. Moreover, it has deleterious thermal influences on the pulp. Accordingly, the dental industry has recently witnessed the emergence of the polymer bur, which manufacturers claim is the best for selectively removing caries while minimizing the patient's discomfort. By introducing a polymer prototype bur in 2003, a potential substitute for traditional techniques of removing carious dentin has emerged. This self-limiting polymer bur is known as SmartBurTM, a variant of SmartPrepTM (SS White, Lakewood, NJ, USA). It is a single-use bur-like instrument constructed of a polymer with a lower hardness than healthy dentin. Different sizes are available; #4, #6, and #8 for right angle latch handpieces.

Polymer bur tools resemble conventional burs in appearance, but they are made of unique polymer material rather than metal. The cutting edges are not spiral, like those of a shovel. The polymer material was designed to be softer than healthy dentin (Knoop hardness 70-90) but harder than carious, softening dentin (Knoop hardness 50-70) (Knoop hardness 0-30). Therefore, it has a knoop hardness of 50 kg/mm2, and its cutting elements effectively remove soft dentin but cannot remove healthy dentin.

Materials and methods Sample size calculation The minimum required sample size will be 15 molars in each group. Thus, a total of thirty permanent first molars will be divided into two groups for this study. The sample size was computed as per G*Power software version 3.1.9.3.

Allocation of samples A 1:1 allocation ratio was used to allocate each of the 30 selected permanent first molars to either Group 1 (Carbide Bur group) or Group 2 (Smart Bur II group).