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J Conserv Dent. 2019 Jul-Aug;22(4):336-339. doi: 10.4103/JCD.JCD_31_19.

The marginal discrepancy of lithium disilicate onlays: Computer-aided design versus press.

Author information

Department of Conservative Dentistry and Endodontics, Faculty of Dentistry, AMIST University, Kedah Malaysia.
Department of Conservative Dentistry and Endodontics, Drs. Sudha and Nageswara Rao Siddhartha Institute of Dental Sciences, Vijayawada, Andhra Pradesh, India.
Department of Oral Pathology, Faculty of Dentistry, AMIST University, Kedah Malaysia.
Department of Pedodontics, Faculty of Dentistry, AMIST University, Kedah Malaysia.
Department of Public Health Dentistry, Mallareddy Dental College for Women, Hyderabad, Telangana, India.
Department of Conservative Dentistry and Endodontics, Mamata Dental College, Khammam, Telangana, India.



The aim of the study was to evaluate and compare the vertical marginal discrepancy of computer-aided design (CAD)/computer-aided manufacturing (CAM) and pressable lithium disilicate onlays.

Materials and Methods:

A maxillary first premolar typodont tooth was prepared to receive lithium disilicate onlay. Mesio-occluso-distal cavity was prepared with palatal cusp reduction and collar preparation. In the proximal box, gingival seat was placed 1 mm coronal to the cementoenamel junction and mesiodistal width of the seat was kept to 1 mm. Thirty stone models were prepared from thirty rubber base impressions and divided into two groups, based on the technique of fabrication of onlays: (1) Group CL (CAD/CAM lithium disilicate) and (2) Group PL (Pressable lithium disilicate). Fifteen onlays per each group were fabricated by following the manufacturer instructions. Marginal fit of all the samples were analyzed by using stereomicroscope with Image Analysis software. Statistical analysis was done by t-test.


Statistical significant difference was found between both the groups. The lowest marginal discrepancy (41.46 μm) was measured for Group CL (CAD/CAM lithium disilicate) specimens, and the highest (55.95 μm) discrepancy was observed on the Group PL (Pressable lithium disilicate) specimens.


Although there was a statistically significant difference between the two groups, marginal gap of both the groups were in clinically acceptable levels.


All-ceramics; computer-aided design/computer-aided manufacturing; lithium disilicate; marginal gap; onlays

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