Chemical Removal of Lead Corrosion Products

Restoration treatment, specimen preparation or mass loss measurements on coupons made of lead require a reliable process of dissolution of corrosion products. In this study, several types of model corrosion products with compositions representative of those found on real objects were prepared and characterized. Ten solutions were then thoroughly tested in interval cleaning experiments, regarding the efficiency of removal of the corrosion products, corrosivity towards bare lead, and remnants left on the surface. The solution recommended in the current version of the ISO 8470 standard was found to be improper for the cleaning of both historical artefacts and corrosion coupons due to its inability to remove sulfide corrosion products and the risk of surface contamination and staining. A solution of 20% hydrochloric acid is the best choice for the preparation of lead coupons before exposure or for evaluation of mass loss of exposed samples because its somewhat higher corrosivity towards metallic lead is tolerable for these applications. Rochelle salt solution was found to be optimal for the cleaning of historical artefacts free of sulfide corrosion products due to the lowest corrosivity. None of these alternative solutions leave remnants on the surface and they are efficient at laboratory temperature.     

改良美容缝合法对急诊面部皮肤软组织损伤切口愈合、瘢痕产生及美学效果影响

目的:评价改良美容缝合术在急诊面部皮肤软组织损伤患者中的应用效果,观察对术后切口愈合、瘢痕产生及美学满意度的影响.方法:选择我院2018年2月-2019年1月急诊科治疗的65例面部皮肤软组织损伤患者为本次研究对象,患者随机分为对照组32例,观察组33例.对照组开展传统缝合术,观察组开展改良美容缝合术,对比2组患者术后切口愈合、瘢痕产生及美学满意度情况.结果:观察组甲级愈合率63.64%,明显多于对照组31.25%,组间数据比较差异存在统计学意义(P<0.05);观察组患者Ⅰ级瘢痕率57.58%,明显多于对照组31.25%,组间数据比较差异存在统计学意义(P<0.05);观察组术后美学满意度93.94%,明显高于对照组的75.00%,组间数据比较差异存在统计学意义(P<0.05).结论:改良美容缝合法在急诊面部皮肤软组织损伤患者中应用可提升切口愈合效果,减少瘢痕产生,提高患者术后美学满意度,值得临床应用.     

不同基牙设计对CAD/CAM全瓷修复体抗折强度的影响

目的 研究不同CAD/CAM全瓷修复体修复根充后前磨牙的抗折强度。方法 收集21颗因正畸拔除的上颌第一前磨牙,制备近面及舌尖缺损洞型。样品分为3组,第1组为直接树脂充填组;第2组为保留缺损组;第3组为纤维桩核组,然后利用IPS e.max CAD全瓷修复体进行修复,采用Rely X U200树脂黏结剂进行黏固。对所有样品进行抗折强度测试,采用光学显微镜观察样品的断裂类型。采用SPSS 15.0软件包对数据进行统计学分析。结果 纤维桩核组全瓷修复体的抗折强度显著大于树脂充填组和保留缺损组。第1组和第2组以修复体破裂为主,第3组除修复体破裂外,还发生牙体组织破裂。结论 对于伴有功能牙尖缺损的前磨牙,建议采用纤维桩核+全瓷冠进行修复。     

Long-term clinical evaluation of direct resin composite restorations in vital vs. endodontically treated posterior teeth — Retrospective study up to 13 years

ObjectivesThis retrospective study evaluated and compared the survival rate of Class II posterior direct resin based composite (RBC) restorations made in vital teeth (VT) and endodontically treated teeth (ETT). The influence of risk factors on the long-term performance of restorations was also investigated.MethodsPatients (n = 245) receiving RBC posterior restorations between 2004 and 2012 were selected. A total of 597 restorations (485 in VT, 112 in ETT) with minimum 2.5–3 mm remaining cusp thickness, made with the same brand of RBC and adhesive, were evaluated using the USPHS criteria. Data were analyzed with Mann–Whitney, Chi-square and Fisher’s Exact Test, Extended Cox-regression and Kaplan–Meier analysis (p < 0.05). Relative risk ratio was estimated for each evaluated parameter.ResultsThe mean observation period was 8.6 ± 2.3 years. An annual failure rate in VT and ETT of 0.08% and 1.78%, respectively, was detected. The reasons of failures included restoration fracture, secondary caries in VT; vertical root fracture, cusp fracture, restoration fracture, secondary caries and loss of adhesion in ETT. Significantly better performance was observed in RBCs of VT for each evaluated parameter. Among the evaluated risk factors only occlusal stress affected negatively the survival of RBC in ETT (Hazard Ratio 37.1; CI_95% 8.4–163.7).SignificanceAlthough, there is significant difference in the success rate of RBCs in VT (98.97%) and ETT (76.8%), the long-term (6–13 years) durability of Class II RBCs with 2.5–3 mm cusp thickness in ETT is also clinically acceptable. The presence of occlusal stress decreases the survival of RBCs in ETT.     

Do bulk‐fill resins decrease the restorative time in posterior teeth? A systematic review and meta‐analysis of in vitro studies

The aim of the present study was to compare the restorative time for filling cavities in posterior teeth using bulk‐fill and conventional resin composites through a systematic review and meta‐analysis. A search for clinical trials and laboratory studies was performed in PubMed/MEDLINE, Scopus, the Latin American and Caribbean Health Sciences Literature database, the Brazilian Library in Dentistry, Cochrane Library, Clinical Trials, and ReBEC (Registro Brasileiro de Ensaios Clínicos) databases without publication year or language restriction. Two reviewers identified eligible studies according to the inclusion criteria: bulk‐fill compared to conventional resin in class I or II, and the restorative time as an outcome. A meta‐analysis of the restorative time mean difference between composites was performed (inverse variance method, random effects model; Z‐test, P ≤ .05). From the 662 eligible studies, 133 were selected for full‐text analysis; three were included in the systematic review and in the meta‐analysis. Overall, the restorative time was lower when bulk‐fill was used (P = .0007, Z = 3.37), as the subgroup full‐body bulk‐fill (P < .00001, Z = 21.00). There was no difference in restorative time between flowable bulk‐fill and conventional resins (P = .08, Z = 1.76). Moderate‐to‐substantial heterogeneity was detected. Full‐body bulk‐fill composites decrease the restorative time in posterior teeth compared to conventional resins. Full‐body bulk‐fill resins require a shorter restorative time to perform restorations in posterior teeth than conventional resins, but the same is not valid for flowable bulk‐fill resin composites.     

冠延长术在前牙桩核冠修复失败后的临床应用

纳入20例牙体缺损达龈下(≤3 mm)修复失败的前牙,经完善牙周基础治疗后行冠延长术,记录术前、术后2、4、6周牙周袋探诊深度(PD)、龈沟出血指数(SBI)。PD值术后2周减小(P<0.05),术后2、4、6周间差异无显著性(P>0.05);SBI值术后减小,2周与术前、术后4、6周差异存在显著性(P<0.05)。术后6周龈缘位置相对稳定,此时行桩核冠修复,成功率较高。牙冠延长术可提高残根的修复质量和效果。     

Color change of some aesthetic dental materials: Effect of immersion solutions and finishing of their surfaces

ObjectivesThe purpose of this research was to evaluate the color change of five aesthetic dental materials, before and after immersion in distilled water and blue food color solution for 7 and 21 days, and to study the effect of finishing the surfaces on any color change.MethodsDisc shaped samples of five types of light curing composite (A2) (n = 10 samples/composite) were prepared and all samples were light-cured with a Plasma Arc light cure unit for ten seconds. One side of each sample disc was finished and polished with a Super-Snap system all samples. After 24 h, color measurements of each sample were conducted using a digital spectrophotometer. Five sample discs from each composite group were immersed in 30 ml of food color solution for 7 and 21 days, while the remaining five sample discs were immersed in 30 ml of distilled water as a control. Color measurements were repeated for all samples at 7 and 21 days after immersion. The color changes were statistically analyzed using t-tests within the same group. A result was considered statistically significant at α = 0.05.ResultsThe color differences (ΔE) ranged from 0.4 to 4.66 and statistically significant differences on the finished and unfinished surfaces were observed after immersion in the food color solution for 7 days. No significant differences were found in any group after immersion in the food color solution for 21 days. The Tetric EvoCeram and Arabesk groups showed less color differences after 7 and 21 days than other composites.ConclusionFinished composite surfaces showed less coloration than unfinished surfaces after 7 days, but all surfaces (finished and unfinished) were highly colored for all composite types after 21 days.     

骨水平Xive种植体系统用于前牙美学修复的临床研究

目的:美学效果是种植修复追求的目标之一,相比功能方面的修复成功而言,实现美学方面的修复成功要更为困难,通常需要较为复杂的手术处理。本研究采用一种微创手术模式和简化的修复治疗程序,在前牙区植入骨水平种植体,评价其美学效果。方法:16例前牙缺失患者纳入本研究。所有患者经过全面检查,并做美学风险评估。采用不翻瓣加骨膨胀手术方法植入Xi ve骨水平种植体,术后连接基台,制作树脂牙冠即刻完成临时修复。四个月后更换为烤瓷牙冠完成恒久修复。观察种植体周硬软组织的变化,并对最终美学修复效果做临床评价。结果:16例患者所植入的22枚种植体在平均观察期8.3个月(5-24个月)无松动脱落。所有患者对修复结果都高度满意。种植修复的白色美学效果,受制于技工制作水平显得不太理想,而粉红色美学效果与患者组织条件有关,但与术前比较,种植体区硬软组织均有明显改善。结论:种植即刻暂时修复体,既可以满足患者美观需要,又对软组织实施了诱导成形。不翻瓣加骨膨胀手术方法,有利于增加种植体区硬软组织量,减少骨吸收,避免牙龈退缩,并避免牙龈组织的瘢痕形成,有利于获得较好的健康的软组织美学,其远期效果还有待继续观察。