BACKGROUND This study investigated different access cavity designs of mandibular anteriors in terms of their effect on the biomechanical behavior and longevity using finite element analysis (FEA). METHODS A 3-dimensional model of a mandibular incisor was created for FEA. After validating the intact tooth (IT) model, 4 experimental models were developed (traditional lingual access cavity [TLA], facial access cavity [FAC], incisal access cavity [ICA], and cervical access cavity [CVA]). Cyclic loading was simulated, and the number of cycles until failure (NCF) was compared to the IT model. Stress distribution patterns, maximum von Mises stresses (vMSs), and maximum principal stresses (MPSs) were analyzed mathematically. The safety factor was also calculated and demonstrated. RESULTS The maximum vMS registered on the IT model was 134.16 MPa. The FCA and the CVA provided the highest NCF (193.7% compared with the IT model) followed by ICA (58.2%) and TLA (21.4%). The vM and MPS analysis revealed that the lingual surface is a primary stress channel, and the presence of an access cavity significantly weakens the tooth structure. Although the maximum vMS registered for the IT model was 134.16 MPa, the maximum vMS was 73.97 MPa for both the FCA and the CVA, 152.27 MPa for the ICA, and 173.63 MPa for the TLA. CONCLUSIONS The facial and cervical access cavity designs provided considerable reinforcement to the endodontically treated mandibular incisors. With advancements in esthetic restorative materials and endodontic instruments, facial access design could emerge as the new standard for access cavity preparation in mandibular incisors.