Aim of the study: The aim of this RCT is to evaluate CAD/CAM onlays fabricated by subtractive technique (brilliant crios) versus additive technique (varseosmile crown plus material), in terms of clinical functional evaluation following the FDI criteria and three-dimensional digital evaluation of the marginal and internal fit by triple scan protocol.

Materials and methods: A total of 30 patients will be enrolled in the clinical trial following the eligibility criteria. Then, the patients will be randomly allocated to receive either 3D printed onlays or milled ones. A blinded operator will prepare a standardized cavity for the restoration and an impression will be performed. After designing the restoration on the Exocad software, A dentist not involved in the clinical part of the study will receive the STL file of the design and envelopes containing the information necessary only to manufacture the restorations (tooth numbers and restorative materials) to proceed with either the milling or printing procedures. Try in and cementation procedures will be similarly performed for both groups by a blinded operator. Finally, the marginal and internal fit will be evaluated by using the triple scan protocol for digital 3D assessment.

Also, a baseline, six months and 12 months assessments will be performed by a blinded examiner, not involved in the clinical part for assessing the functional clinical performance of the re3stprations using the FDI criteria. Finally, the data will be statistically analyzed.

Statement of the problem: Several randomized clinical trials (RCT) investigated the clinical performance of milled ceramic and composite posterior indirect adhesive restorations. However, none investigated that of 3D printed ones and the differences in their fabrication process and material properties of these restorations may impact their clinical performance. Therefore, clinical assessment of that novel additive technique is required.

Aim of the study: The aim of this RCT is to evaluate CAD/CAM onlays fabricated by subtractive technique (brilliant crios) versus additive technique (varseosmile crown plus material), in terms of clinical functional evaluation following the FDI criteria and three-dimensional digital evaluation of the marginal and internal fit by triple scan protocol.

Materials and methods: A total of 30 patients will be enrolled in the clinical trial following the eligibility criteria. Then, the patients will be randomly allocated to receive either 3D printed onlays or milled ones. A blinded operator will prepare a standardized cavity for the restoration and an impression will be performed. After designing the restoration on the Exocad software, A dentist not involved in the clinical part of the study will receive the STL file of the design and envelopes containing the information necessary only to manufacture the restorations (tooth numbers and restorative materials) to proceed with either the milling or printing procedures. Try in and cementation procedures will be similarly performed for both groups by a blinded operator. Finally, the marginal and internal fit will be evaluated by using the triple scan protocol for digital 3D assessment.

Also, a baseline, six months and 12 months assessments will be performed by a blinded examiner, not involved in the clinical part for assessing the functional clinical performance of the re3stprations using the FDI criteria. Finally, the data will be statistically analyzed.

Inclusion Criteria:

1. Presence of caries lesion, defective amalgam, or composite restorations in posterior dentition (molars), suitable for the restoration with ceramic onlays.
2. Presence of antagonist tooth.
3. Adult patients (age: 18-50 years) of both genders.
4. Good general and oral health; Able to tolerate necessary restorative procedures and willing to sign an informed consent.
5. Absence of orthodontic appliances.
6. Absence of malocclusion and tooth malformation.

Exclusion Criteria:

1. Presence of non-carious cervical lesions.
2. Pregnant women.
3. Allergy to any of the restorative materials.
4. Mobile teeth, indicating periodontal disease or trauma.
5. External or internal resorption.