The goal of this clinical trial is to evaluate the occlusal wear of Bioflx crowns compared to zirconia crowns in the restoration of primary molars.

The main question[s] it aims to answer : " Is there a difference in the occlusal wear of BioFlx crowns compared to zirconia crowns in the restoration of primary molars?" The study will also assess the clinical performance of both types of crowns in terms of retention,gingival health, preparation time, as well as child and parental satisfaction.

Occlusal wear is a critical factor in determining the longevity and functional efficiency of dental restorations, especially in pediatric patients. Primary molars undergo significant masticatory forces, which can lead to material wear and affect the restoration's durability. Bioflex (a relatively new material) and zirconia crowns are commonly used for full-coverage restorations in primary molars, yet there is limited research comparing their occlusal wear characteristics. Understanding how these materials perform under occlusal forces can guide clinicians in selecting the most suitable material for pediatric dental restorations Dental caries in primary molars represent a significant issue within pediatric dentistry. In cases where traditional fillings prove insufficient, full coronal coverage becomes necessary. Stainless steel crowns (SSCs) have long been the standard due to their durability and cost-effectiveness, but their metallic appearance has led to increased interest in aesthetic alternatives like zirconia and Bioflx crowns.

Zirconia offers improved aesthetics, biocompatibility, and mechanical strength, though its long-term clinical performance remains underexplored. While zirconia crowns provide durability and superior aesthetics, they require significant tooth preparation, which may compromise tooth structure. Bioflx crowns, a newer option, combine the benefits of stainless steel and zirconia with more flexibility and less tooth reduction. However, comparative studies on their clinical efficacy, occlusal wear, and patient satisfaction are still needed.

Zirconia offers improved biocompatibility, mechanical strength, and enhanced esthetics, but limited comparative data exists regarding its clinical performance.

The growing awareness among parents regarding the importance of maintaining primary teeth until their natural shedding necessitates a thorough evaluation of the durability, wear resistance, retention, gingival response, and overall clinical efficacy of these crown materials. Zirconia crowns have been the preferred choice for aesthetic restorations due to their natural appearance and durability. However, their requirement for excessive tooth preparation poses challenges in pediatric patients.

Bioflx crowns, made from a biocompatible hybrid resin polymer, offer a flexible fit with minimal tooth reduction while maintaining aesthetic appeal. A comprehensive comparison of occlusal wear between these two materials is crucial for assisting clinicians in selecting the most suitable restorative solution for primary molars. This research seeks to offer evidence-based guidance by evaluating the long-term clinical performance of Bioflx crowns in relation to zirconia crowns.

Inclusion Criteria:

1. Children aged between 4 and 8 years with primary molar that needs to be covered by crown.
2. Medically healthy children (ASA I or II according to the American Society of Anesthesiologists classification).
3. Children whose parent or guardian are willing to sign an informed consent.
4. Children whose parent or guardian are willing to comply with follow-up visits. -
5. Frankl's positive and definitely positive patient

Exclusion Criteria:

1. Molars with severe structural loss that may compromise crown retention.
2. Children with poor oral hygiene that may contribute to higher plaque levels and affect the clinical outcomes of the crown restorations.
3. Children with history of allergies; Known allergies to dental local anesthesia or to the materials used in Bioflx crowns.
4. Children with any systemic conditions or disabilities that may affect their ability to participate in the study.

statistician