Clinical Evaluation of Additive and Subtractive Onlay Restorations

Inclusion Criteria: Participant-Level Criteria * Adults aged 18-84 years * No active periodontal disease (probing depth ≤ 3 mm, no clinical attachment loss) * No parafunctional habits such as bruxism, clenching, or foreign object chewing * Willingness to attend regular follow-up visits during the study period * Adequate oral hygiene status * No history of systemic disease or medically stable condition if present * No history of similar restorative procedures involving the target teeth Tooth-Level Criteria * Vital posterior teeth (premolars or molars) confirmed by thermal or electric pulp testing; teeth requiring endodontic treatment or with necrosis will be excluded * Permanent posterior teeth located in functional occlusion (premolar or molar region) * Teeth with moderate structural loss suitable for onlay restorations, including mesio-occlusal (MO), disto-occlusal (DO), or mesio-occluso-distal (MOD) cavities with partial crown loss but sufficient remaining tooth structure not requiring full coverage * Periodontally healthy teeth with no mobility, no clinical attachment loss, and probing depth ≤ 3 mm * Teeth that can be matched in contralateral quadrants to allow split-mouth design (structurally and clinically comparable teeth) * Teeth free from cracks, fractures, or internal resorption; supporting tissues without structural defects that may compromise restoration success * Teeth with clearly defined preparation margins located in enamel or sound dentin; subgingival margin…