Crowns Fabricated Digitally by CAD-CAM Technology Versus Prefabricated Crowns on Primary Teeth

This is a 12-month randomized, controlled, two parallel arms clinical trial. Patients aging from 4 to 10 years with multi-surface decay will be selected. After caries removal and pulp exposure, pulpotomy or partial pulpectomy technique will be performed,then the teeth will be randomized to the interventional group of digital crowns or to the control group of prefabricated zirconia crowns. For preparation of digital crowns, the occlusal reduction was done by 1.5-2 mm. The proximal contacts will be broken and the entire clinical crown structure was reduced by 0.8-1.0 mm , followed by a a subgingival finish line . For the scanning procedure, the upper and lower arches will be scanned with intra oral scanner, and making sure every point is well detailed . A third scan of the occlusal bite is then performed in order to establish the patient's occlusion.

For the milling procedure, Brilliant Crios composite the blocks will be used and milled with the CEREC MC X milling unit . The inner surface of the crown will be sandblasted with Al2O3 .

For zirconia crown preparation, occlusal reduction of 1.5-2mm will be performed by a football diamond bur. The occlusal third of the buccal and lingual surfaces will be also reduced . The whole crown will be reduced by 0.8-1.0 mm by means of a tapered diamond stone .A shoulder finish line will be created. The try in crown will be tested, then the shoulder finish line will be removed and the preparation will be extended subgingivally to feather-edge.

The crowns will then be cemented with the self-adhesive resin cement (Solocem, Coltene, Whaledent, Altstatten, Switzerland) .Light curing was performed while applying pressure on the crown and then waiting for 5 minutes for complete cementing