Radiopaque properties of polyetheretherketone crown at laboratory study

ObjectivesThere have been no reports on the radiopaque properties of new polyetheretherketone (PEEK) crowns for locating crowns during accidental ingestion or aspiration and detection of secondary caries, which is essential information for clinical application. This study aimed to investigate whether the radiopaque properties of PEEK crowns could be used to identify the site of accidental ingestion or aspiration and detect secondary caries.MethodsFour types of crowns were fabricated: three non-metal crowns (PEEK, hybrid resin, and zirconia) and one full metal cast crown (gold-silver-palladium alloy). Initially, the images for these crowns were compared using intraoral radiography, chest radiography, cone-beam computed tomography (CBCT), and multi-detector computed tomography (MDCT); computed tomography (CT) values were calculated. Subsequently, the images for the crowns placed on the secondary caries model with two artificial cavities were compared using intraoral radiography.ResultsThe PEEK crowns displayed the lowest radiopaque properties on radiography and very few artifacts were observed on CBCT and MDCT. On the other hand, the CT values of the PEEK crowns were a little lower than those of the hybrid resin crowns and considerably lower than the zirconia and full metal cast crowns. The cavity could be detected in the PEEK crown-placed secondary caries model through intraoral radiography.ConclusionsThis simulated study of radiopaque properties with four types of crowns suggested that a radiographic imaging system can be used to identify the site of accidental ingestion and aspiration of PEEK crowns and to detect secondary caries of the abutment tooth within a PEEK crown.     

铸瓷贴面与全瓷冠在前牙美学修复中的应用效果比较

探讨铸瓷贴面与全瓷冠在前牙美学修复中的应用效果。方法 选取2021年1月-2022年1月于固原市人民医院行前牙美学修复治疗的70例患者为研究对象,应用随机数字表法分为A组与B组,各35例。A组给予铸瓷贴面法治疗,B组给予全瓷冠修复术治疗,比较两组修复效果、VAS评分、修复满意度及不良反应发生情况。结果 A治疗后颜色评分、形态评分、半透明度评分、边缘美观评分均高于B组（P ＜0.05）;A组治疗后2、6、12个月VAS评分均低于B组（P ＜0.05）;A组修复满意度为97.14%,高于B组的80.00%（P ＜0.05）;A组不良反应发生率为5.71%,低于B组的28.57%（P＜0.05）。结论 前牙美学修复中,应用铸瓷贴面治疗,其整体效果优于全瓷冠修复,能减少不良反应的发生,降低患者的疼痛感和不适感,具有更优的美学效果。     

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     

265件钴铬烤瓷单冠返工的原因分析

目的：分析钴铬合金烤瓷全冠返工的原因,探讨钴铬合金烤瓷全冠制作中医技交流的方式方法。方法：技工中心质监小组根据临床医师反馈的信息,对265件返工件进行技术分析,确定返工的技术原因。结果：因技工制作失误共109件（41．13％）,其中模型处理30件（27．52％）、金属内冠制作35件（32．11％）、瓷塑形44件（40．37％）。因临床医生失误共156件（58．87％）,其中设计不当9件（5．77％）、模型变形21件（13．46％）、牙体预备质量差62件（39．74％）、试戴调磨不当19件（12．18％）、比色问题40件（25．64％）、其他5件（3．20％）。结论：医生失误所致返工的比例高于技工。应加强医技间的交流,共同提高钻铬合金烤瓷全冠的质量,真正体现临床修复技术的先进性,才能获得最佳的修复效果,满足忠者在美观、舒适、功能、快速等方面的要求,使患者满意。     

后牙烤瓷修复冠、桥疲劳寿命的测定

目的：测定后牙烤瓷修复冠、桥的疲劳寿命。方法：制作后牙烤瓷冠、桥试件各3个,进行疲劳寿命测定,分别在实验进行0、16、48、80、160h时,用体视显微镜下咬合部位瓷层表面状态,至320h后实验结束,在扫描电镜下观察。结果：各组烤瓷冠桥体均未出现明显的瓷崩裂现象,但在咬合部位及其附近均出现的微裂隙长达30～50μm。结论：烤瓷修复体具有相当优良的机械力学性能,可以作为后牙的永久性修复体。