烤瓷表面抛光和上釉对其表面粗糙度及细菌黏附的影响

目的比较不同抛光方法对烤瓷表面粗糙度的影响,以及不同粗糙度烤瓷表面对口腔变异链球菌黏附的影响。方法采用原子力显微镜测量不同抛光方法对瓷表面粗糙度的影响,并通过细菌实验观察不同粗糙度的瓷表面对细菌黏附的影响。结果用抛光膏抛光或者上釉后,瓷面平整且有光泽。无论是表面粗糙度还是表面黏附的细菌数,橡皮轮组都大于抛光膏组和上釉组（P<0.05）。结论建议调改过的瓷表面进行抛光膏抛光或上釉以恢复瓷表面的光滑度和减少口腔致龋菌的黏附。     

有无洞缘斜面对聚合瓷嵌体微渗漏影响的实验研究

目的评估洞缘斜面对聚合瓷嵌体直接修复的边缘微渗漏的影响。方法 60颗人磨牙随机分成2组,每组30颗,在每颗牙的近中HE面制备典型的Ⅱ类洞,一种制备短斜面,一种不制备短斜面,聚合瓷嵌体直接修复经硝酸银染色后,每颗牙沿近远中方向经修复体切为3部分,取中间部分为观察对象。结果聚合瓷嵌体直接修复在HE面的微渗漏有明显差异（P〉0.05）。结论斜面组的微渗漏现象要比不做斜面的少,但是在HE面无明显差异（P〉0.05）,在龈壁则有显著差异（P〈0.05）。     

Acceptance of dental care following early extractions under rectal sedation with diazepam in preschool children

The aim of the study was to evaluate the effect of amnesia in preschool children on their later acceptance of dental care. Forty-six 4-6-year-old children, who between 2 and 4 years previously had had primary incisors extracted because of trauma, were reexamined for dental health and acceptance of dental care. The extractions had been performed under rectal sedation with diazepam (0.7 mg/kg body weight). Information about dental treatment and degree of cooperation during the intervening period was obtained from records at the referring clinic. The parents were interviewed about their child's experience of amnesia concerning the extractions, background variables, and experiences of dental care before the follow-up examination. Amnesia concerning the extractions was reported in 85% of the children. Twenty-nine percent had on some occasion exhibited behavior management problems (BMP) during the intervening period. Lack of amnesia was significantly associated with BMP (P &lt; 0.002). Children without amnesia concerning the extractions tended to accept dental care less well at the reexamination. Parents were able to predict their child's acceptance of dental care at the follow-up with a significant degree of success (P = 0.02). In conclusion, amnesia in preschool children concerning extractions seems to be essential to facilitate positive acceptance of future dental care.     

Analysis of thermal distributions in veneered zirconia and metal restorations during firing

Objective

The present work evaluated the thermal behavior of porcelain–metal and porcelain–zirconia restorations during fast and slow firing and cooling.

Methods

All-ceramic (porcelain on zirconia) and porcelain-fused-to-metal (PFM) molar crowns were fabricated with 1 or 2 mm porcelain thickness. Thermocouples were attached to the cementation (T1) and occlusal (T4) surfaces of the restoration and embedded at the framework–porcelain interface (T2) and inside the porcelain (T3) to acquire temperature readings by time. Slow heating was set as 45 °C/min and fast heating as 140 °C/min. For fast cooling, the furnace was opened immediately after the holding time. Slow cooling was effected by opening the furnace when it reached 50 °C below the T_g. Porcelains T_g were calculated for each cooling rate.

Results

Slow heating rate was measured at T4 as being 30 °C/min while fast heating at T4 was 100 °C/min. The measured cooling rates within the porcelain (T2) around the T_g range were 20 °C/min and 900 °C/min for slow and fast cooling, respectively. During slow cooling, similar temperatures were found for both zirconia and metal crowns. Remarkable temperature gradients were observed for the fast cooled all-ceramic crown (T1–T4 = 100 °C) and, of lower magnitude for PFM (T1–T4 = 30 °C). T_g of porcelains increase with faster cooling rates.

Significance

Slow cooling appears to be especially important for all-ceramic crowns to prevent high magnitude thermal gradients, which could influence cracking and fracture of the porcelain.     

Plaster pipes and crystalized graphite: Open transventricular transcatheter aortic valve replacement for failed mechanical aortic valve prostheses in the porcelain aorta

Patients with a true porcelain aorta and a failed mechanical aortic valve prosthesis have limited treatment options. Using a hybrid of an open trans-ventricular approach with peripheral cardiopulmonary bypass and integration of transcatheter techniques this challenge can be overcome. Trans-ventricular mechanical valve extraction (with transcatheter endovascular occlusion and cardioplegia) followed by direct ante-grade transcatheter heart valve implantation offers a potential solution to this conundrum. The procedure described is a novel technique that allows for the effective treatment of patients with failed mechanical surgical aortic valve prostheses in the setting of an inoperable porcelain aorta. In addition, a collaborative integrated multi-disciplinary heart team environment is required for the management of these complex patients.     

Chipping fracture resistance of dental CAD/CAM restorative materials: Part I – Procedures and results

Objective

The edge chipping test was used to measure the fracture resistance of CAD/CAM dental restoration ceramics and resin composites.

Methods

An edge chipping machine was used to evaluate six materials including one feldspathic porcelain, two glass ceramics, a filled resin-composite, a yttria-stabilized zirconia, and a new ceramic-resin composite material. Force versus edge distance data were collected over a broad range of forces and distances. Data were analyzed by several approaches and several chipping resistance parameters were evaluated. The effects of using different indenter types were explored.

Results

The force versus distance trends were usually nonlinear with good fits to a power law equation with exponents usually ranging from 1.2 to 1.9. The order of chipping resistance (from least to greatest) was: feldspathic porcelain and a leucite glass ceramic (which were similar), followed by the lithium disilicate glass ceramic and the two resin composites (which were similar), and finally the zirconia which had the greatest resistance to chipping. Chipping with a Vickers indenter required 28–45% more force than with the sharp conical 120° indenter. The two indenters rank materials approximately the same way. The power law exponents were very similar for the two indenters for a particular material, but the exponents varied with material. The Rockwell C indenter gives different power law trends and rankings.

Significance

Despite the variations in the trends and indenters, simple comparisons between materials can be made by chipping with sharp conical 120° or Vickers indenters at 0.50 mm. Broad distance ranges are recommended for trend evaluation.     

可切削瓷贴面厚度及粘接剂对变色牙遮色效果的影响

目的研究CAD／CAM可切削陶瓷贴面厚度与粘接剂颜色双重因素对变色牙修复后颜色效果的影响。方法用C4色复合树脂制作基底板模拟重度变色牙,将5种不同厚度的A1色可切削陶瓷片标准件（厚度分别为0．50mm、0．75mm、1．00mm、1．25him及1．50ram）与6种不同颜色的试色糊剂（A4、opaquewhite、A1、A3、BleachXLOIO、Transparent）混合搭配,分别置于基底板上共30种组合作为实验组,测量其L、a、b值及A-D（VITA）色系结果。计算每种组合与基底板之间的色差值E,进行统计学分析。结果30种组合与基底板之间的色差值（E）均大于1．5NBS,有肉眼可辨的颜色差异。30种组合中,除1．25-op-及1．5-op-的色系为A色系外,其余各组的色系结果均为C或D色系。结论当瓷贴面达到一定厚度且所用糊剂含有遮色成分时,色系结果有明显变化。通过CAD／CAM瓷贴面厚度及试色糊剂颜色的不同组合,能对重度变色牙的遮色效果进行一定程度的调整。     

Prosthodontic Considerations in the Implant‐Supported All‐Ceramic Restoration of Congenitally Missing Maxillary Lateral Incisor: A Clinical Report

The congenitally missing maxillary lateral incisor is the most common agenesis in the anterior region. There are several treatment options for this anomaly, which causes severe deficiencies: orthodontic space closure, tooth‐supported restoration, or single‐tooth implant. Each of these solutions has a high degree of success if used in the correct situation. An implant‐supported restoration with an interdisciplinary approach provides a predictable outcome. This article describes the treatment of a patient with agenesis of the maxillary left lateral incisor. After orthodontic space management, it was decided to restore the tooth with an all‐ceramic crown cemented on a zirconia custom abutment, which fractured after only 6 weeks of service. Fractographic analysis revealed that the failure was due to over‐reduction of the buccal wall to correct the labial emergence of the implant. Zirconia abutments should be designed with even wall thicknesses of at least 0.8 mm to avoid areas that may compromise functional success.