In the early days, popular treatments of large tooth defects were crowns or metal inlay/onlays. With the development of modern dental adhesives, ceramic inlay/onlays have become alternative treatment options. Ceramic inlay/onlays have the advantages of esthetic appearance and preserving more tooth structure. However, the design of ceramic inlay/onlays challenges traditional prosthodontic concepts. There are still no final conclusions when it comes to material selection, preparation principles, adhesion methods, etc. This case was a middle-aged woman who came to our out patient department for a full mouth caries check-up. After radiographic examination, secondary caries over the lower right secondary molar were founded. After evaluation and discussion, we chose lithium disilicate onlay as the treatment plan for the tooth. This article includes the clinical treatment steps, intraoral photos, x-ray films before and after treatment, final discussion and a summary.