Inclusion Criteria for the participants:  The individuals with the mandibular or maxillary single missing occlusal unit (2nd premolar, 1st molar) adjacent to a premolar and/or molar tooth Participants over 20 years old with no contradiction of dental treatment. Good oral hygiene habits, healthy periodontal status, no sign of bruxism (e.g. attrition score >2 according to Wigdorowicz-Makowerowa, and/or muscle pain), and no self-reported grinding and/or clenching.  Inclusion criteria for the abutment teeth included:  No visible periapical lesion Presence of minimum 1:1 crown/root ratio Class I mobility (Nyman & Lindhe 2003) No probing depth more than 4mm Presence of natural opposing teeth with no restorative treatment. Presence of a stable maximum intercuspation (MI) relationship  Exclusion Criteria:  Patients and teeth that are not fulfilling the inclusion criteria