Custom-made Versus Prefabricated Zirconia Crowns for Primary Molars.

This study is a randomized, 12-month follow up clinical trial. According to sample size calculation, ten patients will be selected in conjunction with departments of Pedodontics and Crowns \& Bridges. The study will be conducted in accordance with the principles of the Research Ethics Committee, Faculty of Dental Medicine for Girls, Al-Azhar University, Egypt.

The purpose of the investigation and the clinical procedures of this study will be explained to the parents and children. A written informed consent form will be signed from patient guardians and obtained prior to study initiation. The inclusion and exclusion criteria are established as the following;

• Inclusion criteria

1. Children of 5-9 years old.
2. The children have at least 2 pulpotomized primary molars with no clinical signs \& symptoms or periapical pathosis.
3. Presence of an intact contralateral primary molar as a control.
4. Willingness to participate and to continue with the follow up appointments.
5. Clinical and radiographically confirmed dental caries extending to the middle third of dentin.
6. Presence of teeth in opposite arch with normal occlusion.

• Exclusion criteria

1. Children with systemic health problem.
2. Children with periodontal disease.
3. Children with unilateral chewing habit or allergic to local anesthesia.
4. Presence of parafunctional habit.

• Clinical procedure;

1. Patient selection and education; The participating children will continue with their routine dental appointments in the undergraduate training clinic. Before beginning, children, along with their parents will receive a standard oral hygiene education by an undergraduate student through brushing demonstration on a model. Parents will be warned when signs of gingival inflammation are present, or plaque control is inadequate.
2. Samples grouping and teeth preparation: Forty primary molars will be included in the study. Twenty decayed teeth will be restored with crowns (10 with custom-made ZrCs and 10 with prefabricated ZrCs), and the other twenty intact contralateral teeth will be evaluated as the controls (10 molars will be the controls for custom-made ZrCs and 10 molars will be the controls for prefabricated ZrCs). Preparation of the crowns will be performed under local anesthesia, according to manufacturers' instructions with the following guidelines; 1-2mm occlusal reduction, 0.5-1mm axial reduction, and a chamfer finish line will be established 0.5-1mm subgingivally.
3. Impression taking and temporization: After preparation, rubber-base impressions will be taken for the teeth specific for custom-made ZrCs. Then SSCs will be temporarily cemented over the prepared teeth till the next appointment.
4. Try-in and cementation of ZrCs: SSCs will be removed and the custom-made and prefabricated ZrCs will be tried in and permanently cemented.

• Follow-up visits:

The participants will be recalled for evaluation after a baseline and at 1, 3, 6 and 12 months.

• Evaluation methods:

1. The periodontal health will be assessed using the plaque index (PI) and the gingival index (GI).
2. The clinical success of the crowns will be assessed in terms of crown retention, marginal adaptation, crown contour, fracture, stain resistance, opposing tooth wear and tooth exfoliation.