A retrospective analysis of peri-implant tissue responses at immediate load/provisionalized microthreaded implants

PURPOSE: The aim of this retrospective study was to examine the peri-implant tissue status at immediately provisionalized anterior maxillary implants 12 to 30 months following tooth replacement. MATERIALS AND METHODS: This is a retrospective study of 43 microthreaded, TiO2 grit-blasted implants placed in healed ridges and immediate extraction sockets to restore maxillary anterior and premolar teeth in 28 patients. The cortical bone position relative to the implant reference point was evaluated at implant placement and 6 to 30 months following restoration. Radiographs were assessed using 7x magnification. The distance from the reference point to the cortical bone was measured to +/- 0.1 mm. The relationship of the peri-implant mucosa to the incisal edge of the definitive prosthesis was recorded. RESULTS: Four implants in 3 individuals failed during the first 6 weeks following placement and provisional loading. Cortical bone adaptation from the time of implant placement up to 30 months following restoration ranged from 0.0 mm to 1.5 mm (average, 0.33 +/- 0.40 mm mesially and 0.28 +/- 0.37 mm distally). The mean radiographic measurements from the interproximal crestal bone to the contact point were 4.53 +/- -0.91 mm (mesial) and 4.06 +/- 0.98. Maintenance and growth of papilla was observed in this group of immediate provisionalized single-tooth implants. Definitive abutment or abutment screw loosening was not observed. DISCUSSION: The linear clinical and radiographic measures of peri-implant tissue responses suggest that proper implant placement is followed by supracrestal biological width formation along the abutment and preservation of toothlike tissue contours. This may influence buccal peri-implant tissue dimensions. CONCLUSIONS: Generalized maintenance of crestal bone and the increased soft tissue dimension with maintenance of peri-implant papilla were identified as expected outcomes for immediate loading/provisionalization of microthreaded, TiO2 grit-blasted implants. Control of peri-implant tissues can be achieved to provide predictable and esthetic treatment for anterior tooth replacement using dental implants.     

Control of apatite crystal growth by the co-operative effect of a recombinant porcine amelogenin and fluoride

Recently, we used native amelogenins extracted from developing pig enamel to examine the combined effect of fluoride and amelogenins on the growth of octacalcium phosphate (OCP) and apatite crystals. The purpose of the present study was to investigate this combined effect using a highly purified recombinant amelogenin. We applied porcine amelogenin (rP172) and fluoride in a dual-membrane system as a model for tooth enamel formation. The combination of rP172 and fluoride in this system resulted in the formation of rod-like apatite crystals. On the other hand, without fluoride, rod-like OCP crystals of a comparable size were formed, and rather large hexagonal prisms of mixed crystals of OCP and apatite grew without amelogenins. Thus, highly purified and homogeneous recombinant amelogenin, in co-operation with F, regulated the mineral phase, habit, and size of crystals in the same manner as the extracted heterogeneous porcine amelogenins. We suggest that in both cases the control over the crystal phase and morphology was a direct effect of amelogenin protein serving as a scaffold for apatite mineralization.     

Stresses at the dentinoenamel junction of human teeth--a finite element investigation.

A three-dimensional, linear, elastic finite element model of a maxillary first premolar from longitudinal ground sections was developed to investigate stress variation in the enamel and dentin adjacent to the dentinoenamel junction (DEJ). The effect of regional variation in the contour of the DEJ on the stress patterns for enamel and dentin was also analyzed. The normal (compressive or tensile) and shear stresses in the dentin and enamel surfaces of the DEJ were computed for a vertical load of 170 N acting on the entire occlusal surface of the model. The normal stresses in dentin and enamel were maximum on the occlusal surface of the model and diminished along the buccal and lingual surfaces of the DEJ. However, the magnitude of the normal stresses increased at the cervical enamel, which also showed increased values for shear stress distribution. The normal and shear stresses were markedly affected by the contour of the DEJ and the thickness of enamel in the occlusal third on the buccal and lingual surfaces. The results suggested that because the mechanical interlocking between enamel and dentin in the cervical region is weaker than in other regions of the DEJ, enamel in this region may be susceptible to belated cracking that could eventually contribute to the development of cervical caries.     

Root contact during insertion of miniscrews for orthodontic anchorage increases the failure rate: an animal study

OBJECTIVES: Miniscrews and miniplates are increasingly being used for absolute anchorage during orthodontic treatment. However, potential problems of damaging adjacent roots and their consequences during mini-implant placement in the alveolar process have not been clearly described. MATERIALS AND METHODS: Animal experiments were used to evaluate the stability of miniscrews placed with intentional root contact. The root repair was evaluated after screw removal. Seventy-two miniscrews were surgically placed in the mandibular alveolar bone of six adult mongrel dogs with metabolic bone labeling at 3-week intervals. Miniscrews of the experimental group were placed so that they contacted the root of the adjacent teeth, were retained for different time durations, and were then removed. The insertion torque, clinical measurements, removal torque, and histological findings were analyzed. RESULTS: (1) miniscrews contacting the roots showed a significantly higher insertion torque than those without contact; (2) there was a significant difference in the removal torque measurements based on the mobility of miniscrews and the state of root contact; and (3) miniscrews contacting the root were at greater risk of failure. CONCLUSIONS: During placement of miniscrews in the aveolar process, increased failure rates were noticed among those contacting adjacent roots. Failed miniscrews appeared to be surrounded with a greater volume of soft tissue. When more inflammation was present, the adjacent roots seemed to experience more resorption. Nevertheless, the created lesion was repaired with a narrow zone of mineralized tissue deposited on the root surface, which was likely cellular cementum, and was mainly filled with alveolar bone, with the periodontal ligament space being maintained.     

Wnt/beta-catenin inhibits dental pulp stem cell differentiation

Dental pulp stem cells (DPSCs) are a unique precursor population isolated from postnatal human dental pulp and have the ability to regenerate a reparative dentin-like complex. Canonical Wnt signaling plays a critical role in tooth development and stem cell self-renewal through beta-catenin. In this study, the regulation of odontoblast-like differentiation of DPSCs by canonical Wnt signaling was examined. DPSCs were stably transduced with canonical Wnt-1 or the active form of beta-catenin, with retrovirus-mediated infection. Northern blot analysis found that Wnt-1 strongly induced the expression of matricellular protein osteopontin, and modestly enhanced the expression of type I collagen in DPSCs. Unexpectedly, Wnt-1 inhibited alkaline phosphatase (ALP) activity and the formation of mineralized nodules in DPSCs. Moreover, over-expression of beta-catenin was also sufficient to suppress the differentiation and mineralization of DPSCs. In conclusion, our results suggest that canonical Wnt signaling negatively regulates the odontoblast-like differentiation of DPSCs.     

不同铸造合金对铸造冠边缘适合性影响的实验研究

目的观察Dentaurum包埋材料与3种牙科合金匹配对铸造冠边缘适合性的影响。方法制作模拟后牙全冠外形的标准帽状试件及圆管,于试件上制作30个熔模,随机分为3组,每组按照Dentaurum包埋材料的使用说明进行有圈包埋,分别采用3种合金进行铸造。铸造冠在原标准帽状试件上试合,在扫描电镜下测量铸件的边缘浮出量。结果第1组铸造冠与其余2组的边缘浮出量差异有显著性(P<0.05)。其余2组间的边缘浮出量差异无显著性(P>0.05)。结论Dentaurum包埋材料与Dentaurum NiCrMo合金有良好的匹配性,与其余2种合金匹配其边缘浮出量也在临床允许范围内。     

中国第9次北极科学考察期间科考队员睡眠质量分析

目的 了解北极特殊环境对科考队员睡眠质量的影响.方法 应用匹兹堡睡眠质量指数(PSQI)量表对参加我国第9次北极科学考察的科考队员(131人)在出行前、北极考察期间、考察结束后的睡眠情况进行调查,并记录队员的入睡时间点、晨起时间点、入睡时间、睡眠时间.结果 共发放问卷131份,回收有效问卷88份.88名队员中男77名、女11名,年龄为22～50(48.1±17.9)岁,包括船员18人、科考队员70人.考察期间队员的中位晨起时间点比出行前早180 min,入睡时间长于出行前及考察结束3个月后[(45.23±25.84)min vs(18.45±14.34)min、(19.50±12.57)min,P均<0.01],夜晚睡眠时间短于出行前及考察结束3个月后[(6.83±2.24)h vs(8.36±1.45)h、(8.14±1.45)h,P均<0.01].根据PSQI量表评分,考察期间队员的睡眠质量下降、入睡时间延长、睡眠时间缩短、睡眠效率下降、催眠药物使用增加,与出行前相比差异均有统计学意义(P均<0.01).结论 极地极昼及低温环境显著影响北极科学考察时科考队员的睡眠节律,导致入睡时间延长、睡眠时间缩短、助眠药物使用增加,这可能影响到队员的工作状态.     

许芝银调治气阴亏虚型石瘿

石瘿,西医病名甲状腺恶性肿瘤,目前是临床上最常见的头颈部恶性肿瘤类型之一,甲状腺癌术后常出现各种并发症.许芝银教授认为,石瘿术后常表现出气阴亏虚的证型,治疗以益气养阴为根本治法,同时注重调和肺脾肾,维持脏腑功能正常运行,术后短期使用全蝎清除余邪,术后长期使用西洋参补气扶正,同时对抗左甲状腺素钠片的副作用.     

纤维肌痛运动干预患者实践指南(2021年)

纤维肌痛发病率仅次于腰痛和骨关节炎,是第三常见的肌肉骨骼相关疾患.运动干预是纤维肌痛的主要治疗方法之一,患者如何更好地进行自我运动是提高纤维肌痛康复效果的关键因素.我们成立多学科专家和患者共同参与的纤维肌痛运动干预患者实践指南工作组,依据《世界卫生组织指南制订手册》原则和程序,筛选纤维肌痛患者关注的运动干预相关问题,提出纤维肌痛运动干预患者实践11条意见.