Liangzhi Du1, Zhe Li2, Xiaofeng Chang3, Omar Rahhal2, Bowen Qin4, Xi Wen5, Dangxia Zhou6. 1. PhD Candidate, Department of Implant Dentistry, College of Stomatology, Xi'an Jiaotong University & Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University & Department of Pathology, College of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi, PR, China. 2. MD Candidate, Department of Implant Dentistry, College of Stomatology, Xi'an Jiaotong University & Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University, Xi'an, Shaanxi, PR, China. 3. Dean, Department of Implant Dentistry, College of Stomatology, Xi'an Jiaotong University & Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University, Xi'an, Shaanxi, PR, China. 4. Assistant Researcher, Biological Diagnosis and Treatment of National and Local Joint Engineering Research Center, the Second Affiliated Hospital of Xi`an Jiaotong University, Xi'an, Shaanxi, PR, China. 5. Associate professor, School of Sports and Health, Guangzhou University of Chinese Medicine, Guangzhou, PR, China. 6. Professor, Department of Pathology, College of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi, PR, China.
Abstract
PURPOSE: To investigate the effect(s) of screw-access hole (SAH) in different diameters on the cement-retained implant prosthodontic systems and surrounding cortical bones. MATERIALS AND METHODS: Twenty finite element models were divided into 4 groups: 2 types of full-contour (FC) crowns (Y-TZP, gold alloy) and 2 types of porcelain-fused-to-metal crowns (based on Co-Cr, Au-Pd alloy). For each group, 5 crowns were simulated by varying the diameter of SAH (0, 1, 2, 3, and 4 mm). A vertical load of 200 N and an oblique load of 100 N (45°s) were applied. All models were analyzed with finite element analysis software. RESULTS: The stress on the occlusal surface of crowns was almost unchanged when the SAH was within 0 to 3 mm, whereas it showed an obvious increase when it reached 4 mm. The stress concentration was also suddenly changed from the loading area to the hole margin under vertical loading. As for the screw, a lower stress level was observed in vertical loading when an FC crown with an SAH within 0 to 1 mm was applied. The stress concentration was constantly located at the beginning of the first thread. Stresses of other components remained almost unchanged. CONCLUSIONS: From the aspect of biomechanics, an FC crown with a 1-mm access hole is recommended when a combined cement- and screw-retained crown was used in the posterior region.
PURPOSE: To investigate the effect(s) of screw-access hole (SAH) in different diameters on the cement-retained implant prosthodontic systems and surrounding cortical bones. MATERIALS AND METHODS: Twenty finite element models were divided into 4 groups: 2 types of full-contour (FC) crowns (Y-TZP, gold alloy) and 2 types of porcelain-fused-to-metal crowns (based on Co-Cr, Au-Pd alloy). For each group, 5 crowns were simulated by varying the diameter of SAH (0, 1, 2, 3, and 4 mm). A vertical load of 200 N and an oblique load of 100 N (45°s) were applied. All models were analyzed with finite element analysis software. RESULTS: The stress on the occlusal surface of crowns was almost unchanged when the SAH was within 0 to 3 mm, whereas it showed an obvious increase when it reached 4 mm. The stress concentration was also suddenly changed from the loading area to the hole margin under vertical loading. As for the screw, a lower stress level was observed in vertical loading when an FC crown with an SAH within 0 to 1 mm was applied. The stress concentration was constantly located at the beginning of the first thread. Stresses of other components remained almost unchanged. CONCLUSIONS: From the aspect of biomechanics, an FC crown with a 1-mm access hole is recommended when a combined cement- and screw-retained crown was used in the posterior region.