Microleakage of Different Self-Adhesive Materials for Lithium Disilicate CAD/CAM Crowns

Objectives: To evaluate the microleakage and marginal gap of various luting materials after cementing ceramic crowns. Methods: Cervical margins of human molars were designed as circular chamfers. Cementation of full-contour ceramic crowns was conducted with zinc-phosphate cement (Harvard cement), resin cement (Panavia F 2.0) and self-adhesive resin cements (RelyX Unicem, BifixSE, MaxCem Elite, PermaCem2.0, G-Cem). Aging of specimens was performed in artificial saliva, at 37 °C for four weeks and thermocycling. The marginal gap was measured with a scanning electron microscope and silver precipitation within the microleakage. All data were compared statistically. Results: Independent of the margin preparation, the highest median value for microleakage was 320.2 μm (Harvard cement), and the lowest was 0 μm (Panavia F 2.0). The median value for enamel was 0 µm and for dentin 270.9 μm (p < 0.001), which was independent of the luting material. The marginal and absolute marginal gaps were not significantly different between the tested materials. There was no correlation between microleakage and the marginal gaps. Conclusion: Significant differences in microleakage were found between the tested luting materials (p < 0.05). Independent from the luting materials, the microleakage in dentin showed significantly higher values than in enamel.     

Clinical assessment of enamel wear caused by monolithic zirconia crowns

The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6‐, 12‐, and 24‐month follow‐up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser‐scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two‐sided paired Student's t‐tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19–26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75–115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia‐opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified.     

Complication and failure rates in patients treated for chronic periodontitis and restored with single crowns on teeth and/or implants

Objectives: To assess the biological and technical complication rates of single crowns on vital teeth (SC‐V), endodontically treated teeth without post and core (SC‐E), with a cast post and core (SC‐PC) and on implants (SC‐I). Material and methods: From 392 patients with chronic periodontitis treated and documented by graduate students during the period from 1978 to 2002, 199 were reexamined during 2005 for this retrospective cohort study, and 64 of these patients were treated with SCs. Statistical analysis included Kaplan–Meier survival functions and event rates per 100 years of object‐time. Poisson regression was used to compare the four groups of crowns with respect to the incidence rate ratio of failures, and failures and complications combined over 10 years and the entire observation period. Results: Forty‐one (64%) female and 23 (36%) male patients participated in the reexamination. At the time of seating the crowns, the mean patient age was 46.8 (range 24–66.3) years. One hundred and sixty‐eight single unit crowns were incorporated. Their mean follow‐up time was 11.8 (range 0.8–26.4) years. During the time of observation, 22 biological and 11 technical complications occurred; 19 SC were lost. The chance for SC‐V (56) to remain free of any failure or complication was 89.3% (95% confidence interval [CI] 76.1–95.4) after 10 years, 85.8% (95% CI 66–94.5) for SC‐E (34), 75.9% for SC‐PC (39), (95% CI 58.8–86.7) and 66.2% (95% CI 45.1–80.7) for SC‐I (39). Over 10 years, 95% of SC‐I remained free of failure and demonstrated a cumulative incidence of failure or complication of 34%. Compared with SC‐E, SC‐I were 3.5 times more likely to yield failures or complications and SC‐PC failed 1.7 times more frequently than did SC‐E. SC‐V had the lowest rate of failures or complications over the 10 years. Conclusions: While SCs on vital teeth have the best prognosis, those on endodontically treated teeth have a slightly poorer prognosis over 10 years. Crowns on teeth with post and cores and implant‐supported SCs displayed the highest incidence of failures and complications. To cite this article :
Schmidlin K, Schnell N, Steiner S, Salvi GE, Pjetursson B, Matuliene G, Zwahlen M, Brägger U, Lang NP. Complication and failure rates in patients treated for chronic periodontitis and restored with single crowns on teeth and/or implants
Clin. Oral Impl. Res. 21 , 2010; 550–557.
doi: 10.1111/j.1600‐0501.2009.01907.x     

Comparison of the tensile bond strengths of cast metal crowns luted with resin cements

The limitation of photoactivation of dual-polymerized resin cements along the margins of metal restorations may adversely affect the mechanical properties of these cements, thus impairing the retention of restorations. The aim of this study was to assess the bond strength of cast metal crowns cemented with three dual-polymerized resin cements, using a chemically-activated resin cement and zinc phosphate as controls. Fifty nickel-chromium alloy crowns were cast and randomly assigned to five groups of equal size. Castings were cemented on their corresponding metal dies with one of the tested luting agents: Scotchbond Resin Cement, Enforce and Panavia F (dual-polymerized resin cements), Cement-It (chemically-activated resin cement) and Zinc Phosphate Cement (zinc phosphate cement). Specimens were stored in distilled water at 37 degrees C for 24 h and then loaded in tension until failure. Panavia F and Zinc Phosphate Cement provided the highest and lowest bond strength means, respectively. Scotchbond Resin Cement, Enforce and Cement-It cements exhibited similar intermediate values, but with statistically significant difference compared to the other materials (P < 0.05). Even with the restriction or absence of light activation, all tested dual-polymerized resin cements produced significantly higher bond strength than did the zinc phosphate cement and yielded similar or better results than the chemically activated cement. It should be pointed out that the findings of this study relate to a test scenario which does not mimic clinical circumstances and that further work is required to identify the clinical significance of the reported tensile bond strength differences between the different luting materials.     

Fractographic features of glass‐ceramic and zirconia‐based dental restorations fractured during clinical function

Fractures during clinical function have been reported as the major concern associated with all‐ceramic dental restorations. The aim of this study was to analyze the fracture features of glass‐ceramic and zirconia‐based restorations fractured during clinical use. Twenty‐seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass‐ceramic restorations and 13 zirconia‐based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all‐ceramic single‐tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass‐ceramic, and alumina single‐tooth restorations. Design features seem to be of great importance for fracture initiation.     

不同材料暂时冠戴用后牙龈组织中Ki67、P53蛋白的表达

目的:研究4种常用暂时冠戴用后Ki67、P53蛋白在牙龈组织中的表达,探讨4种暂时冠材料的生物学效应。方法:给犬进行自凝塑料、热凝塑料、DMG-TEMP复合树脂和松风SWIFT-TEMP树脂暂时冠修复,建立实验动物模型。应用免疫组化Envision二步法检测戴冠前、戴冠后1周、2周及1月时Ki67、P53蛋白在牙龈组织中的表达,并观察HE切片。结果:自凝塑料暂时冠和热凝塑料暂时冠戴用后,牙龈组织中Ki67、P53蛋白的阳性表达率逐渐升高,戴冠1周后达到最高,随后逐渐降低;而DMG-TEMP树脂暂时冠和SWIFT-TEMP树脂暂时冠戴用后,Ki67、P53的阳性表达率与空白对照组无统计学差异,随时间延长亦无明显改变。结论:自凝塑料暂时冠和热凝塑料暂时冠戴用后,牙龈组织中Ki67、P53蛋白表达明显,而DMG-TEMP和SWIFT-TEMP树脂暂时冠戴用后表达不明显。4种材料暂时冠并未造成长时期的牙龈上皮细胞异常增殖。     

130个前牙桩冠修复体远期疗效分析

目的：通过病例复查，找出前牙桩冠修复工作中的问题及不足，使前牙桩冠修复技术更加完善。方法：收集临床病例进行有关项目复查。结果：成品桩钉和铸造桩核固位效果无差异，烤瓷冠满意度100％。塑料冠外观差，对龈组织刺激性大，远期效果不理想。结论：桩核的类型不影响桩冠的固位，金属烤瓷冠是前牙桩冠理想的修复材料。     

“速宁”制作临时冠桥的临床研究

目的:评价"速宁"制作临时冠桥的临床效果。方法:用松风Switf-Temp临时冠桥材料为145例患者制作临时冠桥,其中临时冠92个,临时桥53个:并且对每个临时冠桥评分,根据评分结果判断为三个等级:优良、合格、失败,计算合格率。结果:92个临时冠,合格89个,合格率96.74%;53个临时桥,合格47个,合格率为88.68%。结论:用"速宁"材料制作临时冠桥,具有成功率高,刺激性小,操作简单,节省时间的特点,是一种值得推广应用的方法。     

Survival analysis of crown margin repair: A retrospective study in a dental school setting

BackgroundRepairing crowns with defective margins is minimally invasive and cost-effective compared with replacement. The authors’ objectives were to examine the survival trajectory of crown margin repairs and to determine the factors associated with survival.MethodsRecords of adult patients from January 2008 through August 2019 were reviewed for crown margin repairs completed at University of Iowa College of Dentistry. A total of 1,002 crown margin repairs were found. Each repair was followed through the end of study in 2019 or until an event (for example, additional repair, endodontic treatment, crown replacement, or extraction). A Cox proportional hazards model was used to study the relationship between selected covariates and time to event.ResultsDuring the follow-up period, 32.8% of the repairs needed reintervention. In the final model, repair material was the only significant covariate. No difference was found between the survival of repairs done with resin-modified glass ionomer and amalgam. However, the repairs done with resin-based composite and conventional glass ionomer were more likely (1.5 times: 95% CI, 1.02 to 2.10 times; and 2 times: 95% CI, 1.40 to 2.73 times, respectively) to need reintervention than were those done with amalgam.ConclusionsMedian survival time of crown margin repairs was 5.1 years (95% CI, 4.48 to 5.72 years). Median survival times for amalgam, resin-modified glass ionomer, resin-based composite, and glass ionomer repair materials were 5.7 years (95% CI, 4.80 to 6.25 years), 5.3 years (95% CI, 4.73 to 6.34 years), 3.2 years (95% CI, 2.51 to 6.19 years), and 3.0 years (95% CI, 2.53 to 3.62 years), respectively.Practical ImplicationsWhen considering crown margin repairs, resin-modified glass ionomer or amalgam is preferable to resin-based composite or glass ionomer.