An In Vitro Evaluation of Fracture Resistance of Endodontically Treated Teeth Restored With New Contemporary Core Build-up Materials: A Randomized Control Trial

Total 80 recently extracted single rooted lower second premolars, extracted for orthodontic treatment, will be selected for this study. Because lower second premolars are commonly extracted for orthodontic purposes and during mastication, the anatomic shape ofpremolars create tendency for separation of cusps. Indenter contacts the tooth and acts as a wedge between buccal and lingual cusps and decrease mean fracture resistance values. So the application of force vertically on cusp inclines found to be appropriate to simulate intraoral clinical conditions.

Teeth will be washed under running water and any soft tissue attached to root surfaces will be scraped off with hand scaler. Teeth disinfected with 0.1% thymol solution and will be stored in 10% formalin solution for four days atleast, until they are used, teeth will be stored in 0.9% saline solution at room temperature.

With the help of computer generated software, Teeth will be randomly divided into two groups. Each group contains 40 teeth. Class 1 cavity preparation will be done in teeth of group 1 with straight fissure diamond bur (HiCare ISO. 109/010) in high speed handpiece (Nsk, Japan) along with water coolant and cavity will be prepared on occlusal fissures.

Intercuspal distance and mesio-distal dimension of teeth will be measured with digital caliper. The buccolingual width of class 1 cavity will be one-third of the distance between buccal and lingual cusps and mesiodistal width would be one-third of mesio-distal distance. Buccal and lingual walls will be parallel to one other and cavo-surface angle of approximately 90 degree will be prepared. Class 2 cavity will be prepared in teeth of group 2, in the same way as class 1 except that proximal box will also be prepared in class 2. The width of occlusal isthmus will be the one-third of intercuspal distance and the buccolingual dimension of approximal preparation will be the one-third of buccolingual dimension of overall crown. Gingival extent of this approximal preparation will be 1mm coronal to cemento-enamel junction and the gingival width would be of 2 +/- 0.2mm. Buccal and lingual walls of occlusal preparation will be parallel to each other.

Class 1 and class 2 cavities are prepared because occlusal and proximal surfaces of teeth are the main surfaces which are subjected to higher forces during mastication and these two surfaces are more susceptible to caries attack and standard method for access opening is from occlusal and proximal surface (if carious lesion involve proximal surface too).