The main problem introduced in this study is the aggressive reduction needed for ready-made zirconia crowns to be passively fitted. In addition, its relatively expensive cost and wear of the opposing tooth structure. In this study, different crown materials will be introduced, such as customized zirconia crowns and novel 3D printed resin crowns who may offer better adaptability and gingival health and are relatively cost effective. The proposed study will help in increasing studies of different crown materials for primary teeth

According to AAPD, pulpally treated or deep carious primary teeth should be restored with full coverage crowns for protection of the remaining tooth structure and integrity of occlusion. Different crown materials and compositions have been introduced; however, each with their own drawbacks. Stainless steel crowns have remained the gold standard for restoring primary molars, with the advantages of minimal preparation needed and better adaptability of margins due to their burnishing ability. On the other hand, stainless steel crowns suffer from poor aesthetics and gingival health. The aesthetics of pre-veneered stainless-steel crowns improved but were significantly reduced when the veneered surface was chipped, which was a major drawback in the crown; in addition to their decreased strength and durability in comparison to stainless steel crowns. Strip crowns and polycarbonate crowns were also introduced; however, because of their weak bonding capacity, they have poor strength and an uncertain position in the posterior primary teeth. Due to the increase of aesthetic demand in pediatric dentistry, zirconia crowns have been introduced. Zirconia crowns present the highest aesthetics compared to different pediatric crowns and highest strength compared to all ceramic restorations. However, they need very deep subgingival preparation, poor adaptability because it can't be crimped due to poor burnishing ability and relatively expensive.

Recently, new advances in pediatric crowns have been introduced including computerized 3D printed resin or milled zirconia crowns. Those recent advances have promising results in aesthetics and strength in comparison to ready-made zirconia crowns. Ready-made zirconia crowns have been an exceptionally good biocompatible material. One of the main benefits of those crowns is their durability alongside an outstanding aesthetic appearance. Furthermore, because of their extremely polished surface, ready-made zirconia crowns have proved to have less plaque buildup when compared to other materials. However, because they are costly, need extensive sub-gingival tooth reduction, and cause wear of opposing tooth structure, there are several clinical restrictions and drawbacks.

New computer-aided design digital models serve as the foundation for three-dimensional (3D) printing technologies, which are sophisticated manufacturing techniques that generate customized 3D objects automatically. With applications in almost all fields of dentistry, three-dimensional printing fabricates excellent fitted, accurate, and biocompatible crowns that may overcome ready-made zirconia crowns.

On the other hand, currently the zirconia-based CAD/CAM system has the strongest fracture strength of any all-ceramic material and has continuously produced the most accurate, aesthetically pleasing replication of natural dentition.

They've been acknowledged by patients and dentists alike. The zirconia-based CAD/CAM system is recommended for crowns and bridges in natural teeth, implants, and telescopic dentures. Customized zirconia crowns could be an alternative to the drawbacks presented in ready-made zirconia crowns

Inclusion Criteria:

• Healthy children within age range of 5-8 years old
• Upper and lower primary second molars
• Vital primary second molars
• Cooperative children Frankl scale 3 (positive) and 4 (definitely positive)

Exclusion Criteria:

• Radiographic radiolucency related to the furcation and periapical area or any evidence of root resorption
• Deep bite
• More than 2 walls lost due to caries
• Presence of parafunctional habits