Comparative Clinical Evaluation of Layered Zirconia and Zirconia-Reinforced Lithium Disilicate Crowns: A Randomized Controlled Trial

Aim

To compare the Clinical Evaluation of Layered Zirconia and Zirconia-Reinforced Lithium Disilicate crowns in posterior and anterior restorations over a period of two years.

OBJECTIVES

To compare the survival ratesinLayered Zirconia and Zirconia-Reinforced Lithium Disilicate crowns**.**

To compare the fracture resistancein Layered Zirconia and Zirconia-Reinforced Lithium Disilicate crowns.

To compare the aesthetic performancein Layered Zirconia and Zirconia-Reinforced Lithium Disilicate crowns and

To compare thepatient satisfaction of layered zirconia vs. zirconia-reinforced lithium disilicate Zr-LD crowns in posterior and anterior restorations over a 2 year period.

STUDY DESIGN

Type Prospective, triple-blind, randomized controlled trial RCT

Participants97 patients requiring single-unit posterior or anterior crowns will be allocated randomly and allocation concealment will be done.

Groups Group 1 Layered zirconia crowns zirconia core with veneering ceramic

Group 2 Zirconia-reinforced lithium disilicate monolithic crowns

Follow-up 6 months, 1 year, 2 years.

Inclusion Criteria

Adults (18–60 years) requiring single-unit posterior or anterior crowns with written consent (Annexure I)

Adequate occlusal clearance for material thickness

Good oral hygiene and periodontal health

No history of parafunctional habits (e.g., bruxism)

Exclusion Criteria

Severe bruxism or clenching

Patients withgingivitis and periodontitis

Heavy occlusal loads or malocclusion

Patients with systemic conditions affecting healing (e.g., uncontrolled diabetes, osteoporosis)

History of allergic reactions to ceramic materials

Outcome Measures

Primary Outcomes

Fracture/chipping rate of the crowns

Survival rate over the study period

Marginal adaptation and retention

Secondary Outcomes

Patient satisfaction measured using a Visual Analog Scale

Colour stability and translucency over time

Wear resistance and antagonist tooth wear

Periodontal health around restorations gingival index, plaque index

METHODOLOGY

Sample size calculationwill be done using Statulator,a sample calculator.

Sample size is 97based on with 0.95 level of confidence, 0.5 expected proportion and 0.1 absolute value of margin of error.

Calibration and training of the observerwill be done for reliability and validity of the questionnaires

Pilot studywillbe done on 10 percent of the total sample size

Patients will be randomly assigned to receive either a layered zirconia or a zirconia-reinforced lithium disilicate crown.

Patients, evaluators and statistician will be blinded to the material used. The prosthodontist performing the restorations will not be blinded due to procedural requirements.

Allocation concealment Patients will be allocated in two groups.

Clinical Procedures

Standardized tooth preparation (1.5–2.0 mm occlusal reduction, chamfer margin)

Conventional impressions recorded and compared

Crowns cemented using standardized adhesive protocols

Follow-Up Assessments:

At 6 months, 1 year, 2 years.

Evaluations will include radiographic analysis, clinical examination, and patient-reported outcomes