Restoring extensively damaged endodontically treated teeth presents a challenging task due to the state of biomechanical deterioration affecting long-term prognosis. Therefore, the study aims to assess and compare the biomechanical performance of endocrowns and post core-crown restorations in anterior endodontically treated teeth with severe coronal structure loss. Following PRISMA guidelines, a systematic search was conducted using PubMed, Scopus, Web of Science, and Google Scholar for articles published from January 2014 to March 2024. Two independent reviewers screened and selected studies based on the predefined inclusion and exclusion criteria. The included studies were analyzed using the QUIN tool for risk of bias assessment in in-vitro studies. Additionally, the biomechanical outcomes were collected for qualitative comparative analysis. Twelve studies were included in this systematic review. In most studies, Endocrowns demonstrated comparable fatigue resistance under load to failure to post core-crown restorations. Endocrowns without ferrule exhibited a higher rate of debonding but had significantly more repairable failures. Conversely, post core-crown restorations demonstrated higher fracture resistance with the presence of ferrule, but were associated with more catastrophic failure patterns. Additionally, endocrowns generated lower stress levels in both the restorative material and the luting material compared to post core-crown restorations. Among the tested materials, lithium disilicate ceramics provided the best biomechanical properties. Overall, the studies included provided sufficient information for most evaluation criteria of the QUIN risk of bias assessment tool. Endocrowns are a viable and conservative approach for restoring endodontically treated anterior teeth, offering comparable biomechanical performance to traditional post core-crown restorations and less catastrophic failures. The findings of this systematic review suggest that endocrown restorations, especially with lithium disilicate ceramics and proper ferrule design, can improve fracture resistance and longevity of rehabilitated teeth, enhancing patient outcomes for severely damaged anterior endodontically treated teeth.

This study investigates the impact of tightening torque (preload) and the friction coefficient on stress generation and fatigue resistance of a Ti-6Al-4V abutment screw with an internal hexagonal connection under dynamic multi-axial masticatory loads in high-cycle fatigue (HCF) conditions. A three-dimensional model of the implant–abutment assembly was simulated using ANSYS Workbench 16.2 computer aided engineering software with chewing forces ranging from 300 N to 1000 N, evaluated over 1.35 × 10⁷ cycles, simulating 15 years of service. Results indicate that the healthy range of normal to maximal mastication forces (300–550 N) preserved the screw’s structural integrity, while higher loads (≥800 N) exceeded the Ti-6Al-4V alloy’s yield strength, indicating a risk of plastic deformation under extreme conditions. Stress peaked near the end of the occluding phase (206.5 ms), marking a critical temporal point for fatigue accumulation. Optimizing the friction coefficient (0.5 µ) and preload management improved stress distribution, minimized fatigue damage, and ensured joint stability. Masticatory forces up to 550 N were well within the abutment screw’s capacity to sustain extended service life and maintain its elastic behavior.

Background/Objectives: This study aimed to evaluate the mechanical properties, particularly the fracture load, modulus of elasticity, and fracture patterns, of four-unit posterior tooth-supported fixed dental prostheses (FDPs) fabricated from various computer-aided design/computer-aided manufacturing (CAD-CAM) materials. Understanding the mechanical behavior of these materials is crucial for optimizing prosthesis performance in high-load-bearing posterior regions. Methods: A total of 68 standardized FDP frameworks were fabricated, each consisting of two abutments (first premolar and second molar) and two pontics (second premolar and first molar). The specimens were divided into four groups (n = 17): polyetheretherketone (PEEK), polyetherketoneketone (PEKK), 3Y zirconia (control 1), and 4Y zirconia (control 2). All samples underwent three-point bending tests using a universal testing machine with a crosshead speed of 0.5 mm/min. Fracture patterns were assessed visually and documented. Fractured specimens were examined using scanning electron microscopy (SEM). Data were analyzed using the SPSS v20. Normality was assessed with the Shapiro–Wilk test. The fracture loads were compared using the Kruskal–Wallis test with Bonferroni correction, and the modulus of elasticity was analyzed via a one-way ANOVA with Dunnett’s T3 post hoc test. A significance level of α = 0.05 was applied. Results: Significant differences were observed among the groups. The 3Y zirconia demonstrated the highest fracture load (2275 ± 511.03 N), followed by the 4Y zirconia (1034.28 ± 221.55 N), PEEK (883.21 ± 172.24 N), and PEKK (402.01 ± 127.98 N). PEEK showed ductile fracture behavior, while PEKK exhibited brittle failure. Both zirconia groups demonstrated brittle fracture patterns. Conclusions: PEEK and 4Y zirconia presented comparable fracture loads, but with differing fracture behaviors—ductile in PEEK and brittle in 4Y zirconia. The 3Y zirconia offered the highest fracture load, but with limited flexibility. PEKK showed the lowest mechanical performance. These findings highlight the importance of material selection for FDPs in posterior load-bearing areas, considering both fracture load and failure mode.

Introduction: Hypodontia or Dental agenesis; is defined as a developmental missing of any teeth, excluding the last molars. It may befall as a genetic syndrome or as a non-syndromic isolated trait. However, there is no prevalence available in our city. Aim and Objectives: The tenacity of this research is to assess the frequency of hypodontia among the population who received dental care at King Abdul Aziz University Dental Hospital in the city of Jeddah. Study Design: Retrospective digital orthopantomographic: cross-sectional study. Place and Duration of Study: Oral & Maxillofacial Prosthodontic Department, King Abdulaziz University, between January 2019 and July 2020. Methodology: This research is a retrospective cross-sectional study based on the examination of an archival dental record and 2D panoramic radiographs of patients who are presented at King Abdulaziz University Dental Hospital, Jeddah. A total of 2045 records were reviewed and included in this study. Two general practitioners reviewed patient’s dental charts looking for congenital missing tooth/teeth in a dark room by the method that the practitioners use. Careful reviews of each patient’s record were done to ensure that the cause of the missing tooth/teeth were congenital and not surgical or traumatic. Data were gathered from dental records of patients’ age period 6-9 years since most of the dental follicle of the permanent teeth should be completed or the tooth just erupts, radiographic findings were always compared to the patients’ file and progress notes to ensure the causative factors of missing teeth. The data were recorded in an excel sheet which included gender, age, the type, area and counting of the missing teeth. Results: After collecting the data, the total number of patients after exclusion were 1984. The prevalence of hypodontia in our tested population was %5.39. Statistical analysis were done by using SPSS software to correlate between variables. Varices grades. Conclusion: Within the limitations of this study our data shows that the most common congenitally tooth agenesis is the second premolar %47.6 and the second most common congenitally missing tooth is lateral incisor %18.6.