Monolithic crowns fracture analysis: The effect of material properties,cusp angle and crown thickness

ObjectivesThis study aimed to investigate the collective influence of material properties and design parameters on the fracture behavior of monolithic dental crowns.MethodsThree-dimensional (3D) models (N = 90) with different combinations of design parameters (thickness, cusp angle and occlusal notch geometry) and material type (lithium disilicate, feldspar ceramic, zirconia, hybrid resin ceramic and hybrid polymer-infiltrated ceramic) were developed for the failure analysis using extended finite element method (XFEM) to identify the stress distribution, crack initiation load, fracture surface area and fracture pattern. Analytical formulation, in vitro fracture tests and fractographic analysis of dedicated models were also performed to validate the findings of the XFEM simulation.ResultsFor all material types considered, crowns with a sharp occlusal notch design had a significantly lower fracture resistance against occlusal loading. In most of the models, greater crown thickness and cusp angle resulted in a higher crack initiation load. However, the effect of cusp angle was dominant when the angle was in the low range of 50° for which increasing thickness did not enhance the crack initiation load.SignificanceComparing the critical load of crack initiation for different models with the maximum biting force revealed that for the studied monolithic materials excluding zirconia, a design with a rounded occlusal notch, 70° cusp angle and medium thickness (1.5 mm occlusal) is an optimum combination of design parameters in terms of tooth conservation and fracture resistance. Zirconia crowns exhibited sufficient strength for a more conservative design with less thickness (1.05 mm occlusal) and sharper cusp angle (60°).     

圆锥型套筒冠修复体修复治疗对牙周病患者牙龈指数、龈乳头探诊出血指数、牙周探诊深度的影响

目的 探讨圆锥型套筒冠修复体修复治疗对牙周病患者牙龈指数、龈乳头探诊出血指数、牙周探诊深度的影响。方法 选取2017年3月～2019年3月我院收治的牙周病患者60例,随机分为对照组和研究组两组。对照组进行常规治疗,研究组进行圆锥型套筒冠修复体修复治疗。比较两组患者疗效、牙齿松动度(TM)、牙龈指数(GI)、龈乳头探诊出血指数(PBI)、牙周探诊深度(PD)、改良菌斑指数(mPLI)、改良龈沟出血指数(MSBI)、牙龈乳头指数(PIS)、白细胞介素-8(IL-8)、白细胞介素-2(IL-2)水平、口腔健康影响程度评分(OHIP-14)、咀嚼功能、满意率。结果 研究组有效率高于对照组(P0.05);研究组TM、GI、PBI、PD低于对照组(P0.05);研究组mPLI、MSBI、PIS低于对照组(P0.05);研究组IL-8、IL-2水平低于对照组(P0.05);研究组OHIP-14评分低于对照组(P0.05);研究组咀嚼功能高于对照组(P0.05);研究组修复满意率高于对照组(P0.05)。结论 牙周病治疗中,圆锥型套筒冠修复体修复疗效显著,应在临床上广泛推广与应用。     

一次性根管与常规根管治疗后冠修复对隐裂性牙髓炎患者的影响

目的 探讨一次性根管与常规根管治疗后冠修复对隐裂性牙髓炎患者的治疗效果。方法 选取2014年5月至2017年5月诊治的187例隐裂性牙髓炎患者随机分为观察组和对照组,观察组给予一次性根管治疗后冠修复,对照组给予常规根管治疗后冠修复,比较两组术前及术后1周Mohd Sulong疼痛分级、术后3个月临床疗效、术后6个月X线改变、术后2年治疗成功率。结果 术前两组Mohd Sulong疼痛分级无统计学差异(P＞0.05),冠修复术后1周两组疼痛分级无统计学差异(P＞0.05),术后3个月观察组临床疗效总有效率为97.83%较对照组88.41%显著提高(P＜0.05),术后6个月观察X线改变率为3.26%较对照组14.74%显著降低(P＜0.05),术后2年观察组治疗成功率为94.57%较对照组82.11%显著提高(P＜0.05)。结论 一次性根管治疗后冠修复能够缓解隐裂性牙髓炎疼痛,提高临床疗效,提高患者咀嚼功能和生活质量,值得在临床上推广。     

Unemployment,employment precarity,and inflammation

Unemployment has been associated with poorer health, but few studies have examined the biological mechanisms that confer these health decrements. Further, no studies to date have examined differences across employment groups to consider whether employment (in whatever means) is preferential in terms of health. The present study utilised secondary data from Understanding Society: The Household Longitudinal Survey during the aftermath of the recent global recession. Two markers of peripheral inflammation: C-reactive protein (CRP) and fibrinogen were assessed across employment groups (unemployed; permanent, temporary, and self-employed), controlling for individual, socio-demographic and health variables to give greater context to our understanding of how employment status influences health. After controlling for relevant confounds, unemployment was associated with higher levels of fibrinogen but not CRP. Subsequent analyses of employment subgroup revealed the temporary employed have similar levels of fibrinogen to the unemployed, and may therefore be at a similar health disadvantage. The findings confirm that unemployment is associated with increases in one marker of peripheral inflammation, but that this health protection is not conferred to those in precarious employment.