Clinical Performance of the Indirect Resin Composite Restorations in Endodontically Treated Teeth With Different Cavity Preparation Designs: (A Randomized Clinical Trial)

Selection and examination of the all patients will be done according to inclusion and exclusion criteria( by Hoda omar fouda in the Faculty of Dentistry Cairo University, Egypt ) from the outpatient clinic of the conservative department of the faculty of oral and dental medicine , cairo university .Patients should have an endodontically treated molar with remaining three walls fulfilling the inclusion criteria of the selected teeth or patients who need root canal treatment to be done prior to restoration to be enrolled in the study. Root canal treatment for all patients will be done by step back technique using rotary files .Sodium hypochlorite and EDTA solution will be used as root canal irrigant solution. Root canals will be obturated with gutta percha cones using AH Plus (Dentsply, Konstanz Germany). Eugenol based sealers will avoided to avoid the contamination of the remaining walls with eugenol that can interfere with the polymerization of the adhesive.

Eugenol free temporary filling material (Coltosol F by Coltene, Switzerland) will be used to seal the cavity till the restorative visit A digital periapical radiograph will be done to check the quality of the root canal treatment. The selected tooth should be free from any periapical radiolucency, missed canals or poor obturation. The periodontal condition of the tooth will be also checked radiographically. The tooth should be free from any clinical symptoms as pain on biting or swelling. A period not more than a month should pass from the root canal treatment to avoid any coronal leakage that might affect the prognosis of the root canal treatment during the time of the study. Any defects in the temporary filling material should be restored again to assure proper coronal seal till the beginning of the treatment. Before the removal of the temporary filling, assessment of centric and eccentric occlusal contacts will be performed with an articulating paper. The tooth should be then checked for the contact points in the centric relation and eccentric movements It is important to determine the contact points during the centric and eccentric movements to maintain the tooth restoration interface at a stress free areas as much as possible for more durable bonding. The quadrant with the cavity will be isolated using rubber dam system with two suctions tips one below the rubber dam sheet and the other one near to the tooth to keep the working area always clean and keep the patient comfortable during the procedures. Using straight and round blue coded diamond stones attached to high speed handpiece with copious air and water coolant, the temporary filling will be removed from the cavity. The cavity should then be checked for any remaining carious lesions to be removed. All the undermined enamel walls should be removed so that all the remaining cavity walls have well supported sound enamel margins. Any soft carious lesions will be by a sharp spoon excavator. Any gutta-percha remnants in the pulp chamber should be removed till the gutta percha becomes at the level of the orifice and all the walls and floor are completely clean. All the procedures will be performed with magnifying loupes 3.5 x (Univet, Italy). The angulation of the cavity walls will be adjusted to be 6 degrees diverge of the axial inclination using blue coded diamond tapered with round end bur diameter 16, length 10.

Standardization of the prepared cavity dimensions should be done as follows:

1. For the inlay group thickness of remaining walls (in order to maintain them) has to be 1.5 mm.
2. The occlusal inter-cuspal distance ranges from 4-5 mm

4- Width of occlusal isthmus had to be 2-3 mm. 5- Buccal and lingual walls of the proximal parts of the cavity will be prepared using the same diamond bur (MIDWEST Dentsply) used for the occlusal part of the cavity to provide the same angle of divergence (6 degrees) as that of the occlusal walls. 6- The proximal boxes corresponds to one-third the distance between the buccal and lingual surfaces of the teeth 7- The gingival floor of the proximal part of the cavity has to be continuous with the pulpal floor of the occlusal part having the same depth. 8- Interproximal overjet has to be ≤ 2 mm. 9- The internal line angles should be rounded, the cavo-surface angles should be 90° For the Intervention Group: no cuspal reduction will be done as these will be the cavities prepared to receive the inlay restorations For the Comparator Group: cuspal reduction to buccal and lingual cusps will be done as these will be the cavities prepared to receive the onlay restorations