The goal of this clinical trial is to learn if prefabricated zirconia crowns (PZCs) improve gingival health compared to stainless steel crowns (SSCs) in primary molars of young children. It will also learn about plaque accumulation and parental satisfaction with the crowns. The main questions it aims to answer are:

1. Do PZCs lead to better gingival health than SSCs over time?
2. Do PZCs reduce plaque accumulation compared to SSCs?
3. Do parents report higher satisfaction with PZCs versus SSCs?

Researchers will compare PZCs to SSCs in a split-mouth design (each child receives one of each crown type on contralateral molars) to see if PZCs provide superior gingival health, plaque control, and satisfaction.

Participants will:

1. Receive PZCs on one primary molar and SSCs on the contralateral molar after tooth preparation
2. Attend follow-up visits at 12, 24, and 36 months for gingival health and plaque assessments
3. Complete parental satisfaction surveys at each follow-up visit

This clinical trial is a prospective, randomized, split-mouth controlled study designed to compare the long-term effects of prefabricated zirconia crowns (PZCs) and stainless steel crowns (SSCs) on gingival health, plaque accumulation, and parental satisfaction in primary molars of young children. The study addresses the need for evidence on how these restorative materials influence periodontal outcomes, given the conflicting data in existing literature regarding their biocompatibility, esthetics, and impact on gingival tissues. SSCs have been the standard for durability and cost-effectiveness in pediatric dentistry, but their metallic appearance and potential for plaque retention due to marginal microgaps raise concerns for esthetics and gingival inflammation. PZCs, offering superior esthetics and a polished surface, may provide advantages in reducing plaque adherence and improving mucosal compatibility, though long-term comparative data are limited.

This trial will employ a split-mouth design at the Pediatric Dental Clinic of Qassim University, Buraydah, Al-Qassim Province, Saudi Arabia. This intra-subject approach minimizes inter-individual variability in factors such as salivary composition, microbial ecology, brushing habits, dietary sugar intake, and systemic health, enabling direct comparison of the two crown types within the same child. One hundred healthy children with bilateral primary molars requiring full-coverage restorations will be enrolled. Randomization using a computer-generated sequence with allocation concealment via opaque envelopes opened chairside post-preparation will be implemented. Contralateral molars will receive either a PZC or SSC (randomly assigned), ensuring balanced distribution.

Tooth preparation will be standardized under local anesthesia (2% lidocaine with 1:100,000 epinephrine): pulpotomy/pulpectomy as indicated, circumferential reduction (1-1.5 mm) with tapered diamond burs, occlusal clearance (1.5-2 mm), and proximal adjustments. PZCs will be fitted without crimping for optimal marginal adaptation (<50 μm target), while SSCs will undergo mechanical crimping for tight cervical fit (<30 μm discrepancy). Both will be luted with resin-modified glass ionomer cement (RelyX™ Luting Plus, 3M™) for fluoride release and reliable bonding. Assessments will be conducted by two independent, calibrated examiners (inter-rater kappa >0.80) blinded to crown type via opaque cheek retractors.

Inclusion Criteria:

1. Healthy children aged 3-7 years.
2. Bilateral primary molars requiring full-coverage restorations.
3. Adequate tooth structure (>50% remaining post-preparation).

Exclusion Criteria:

1. Children with moderate to severe baseline plaque accumulation (Silness & Löe Plaque Index ≥2) or parents/caregivers reporting inconsistent brushing (<2x/day).
2. Children with excessive sugar intake (>3 sugary snacks/beverages daily), assessed via the Beverage and Snack Questionnaire.
3. Systemic diseases affecting oral health (e.g., immunocompromised status, diabetes mellitus).
4. Active periodontal disease or severe malocclusion.
5. Allergy to crown materials.

Individual participant data will not be shared publicly to protect participant confidentiality. Summary data and results will be published in the peer-reviewed manuscript. Requests for additional aggregate data may be directed to the corresponding author.

Supporting information will be available upon reasonable request starting after publication of the primary results and indefinitely thereafter, or until no longer needed for scientific purposes.

Aggregate/summary data underlying published results and supporting documents such as the study protocol may be shared upon reasonable request to the corresponding author (Murad Alrashdi, email: MU.ALRASHIDI@qu.edu.sa). Requests should include the requester's affiliation, research purpose, and intended use. Access will be granted at the author's discretion for legitimate scientific purpose. No automated repository or public link is planned.