Viscoelastic stability of pre-cured resin-composite CAD/CAM structures

ObjectivesTo study the effect of water storage (3 months) on the creep deformation and recovery of CAD/CAM composite materials to determine their viscoelastic stability.Materials and methodsFive CAD/CAM composite blocks, with increasing filler loading, and one polymer-infiltrated ceramic network (PICN) were studied. Six specimens of each material were separated into two groups (n=3) according to their storage conditions (24 h dry storage at 23°C versus 3 months storage in 37°C distilled water). A constant static compressive stress of 20 MPa was applied on each specimen via a loading pin for 2 h followed by unloading and monitoring strain recovery for a further period of 2 h. The maximum creep-strain (%) and permanent set (%) were recorded. Data were analysed via two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests (<0.05) for comparisons between the materials. Homogeneity of variance was calculated via Levene’s statistics.ResultsThe maximum creep strain after 24 h dry ranged from 0.45% to 1.09% and increased after 3-month storage in distilled water to between 0.71% and 1.85%. The permanent set after 24 h dry storage ranged from 0.033% to 0.15% and increased after 3-month water storage to between 0.087% and 0.18%. The maximum creep strain also reduced with increasing filler loading.SignificanceThe PICN material exhibited superior dimensional stability to all of the pre-cured resin composite blocks in both storage conditions with deformation being predominantly elastic rather than viscoelastic. Notwithstanding, two of the resin-matrix composite blocks approached the PICN performance, when dry, but less so after water storage.     

改良CAD/CAM全瓷嵌体对微渗漏影响的实验研究

目的:比较传统法和改良法制作CAD/CAM氧化锆基底全瓷嵌体发生微渗漏的差异。方法:离体磨牙30个随机分成对照组与实验组,均按Ⅱ类洞制备箱状洞型,实验组洞缘预备短斜面并于相应部位制作氧化锆边缘,对照组洞缘不预备短斜面,边缘用饰瓷封闭。两组样本进行疲劳循环和冷热循环试验,染色法检测微渗漏情况。结果:实验组嵌体边缘微渗漏小于对照组,有显著性差异。结论:采用改良法制作CAD/CAM全瓷嵌体能有效减少边缘微渗漏。     

计算机辅助个性化舌侧矫治器设计制作系统的开发

目的完成基于计算机三维技术的国产个性化舌侧矫治器设计制作系统的开发。方法该系统主要由三部分组成,通过数据采集部分将石膏模型转化为数字化三维数据,利用软件根据牙齿舌侧面形态设计个性化底板然后将虚拟三维托槽和底板进行数据融合,最后采用快速成型技术完成托槽制作。结果制作完成的个性化舌侧托槽与牙面结合紧密,对位关系准确。结论计算机辅助个性化舌侧矫治器设计制作系统能够简化矫治器制作程序,达到临床应用要求。     

Eruption of the central incisor,the intermaxillary suture,and maxillary growth in patients with a single median maxillary central incisor

The occurrence of a single median maxillary central incisor (SMMCI) is a very rare condition and might be a sign of a more severe midline defect, which could be a mild degree of holoprosencephaly. Absence of the internasal and partial absence of the intermaxillary suture has been observed in a fetus with holoprosencephaly. The purpose of this study was to evaluate the intermaxillary suture, the eruption pattern of the single central incisor in the SMMCI condition, and the growth of the maxilla in a group of patients with SMMCI. A similar study was not found in the scientific literature. The material included orthopantomographs, dental radiographs, and lateral cephalometric radiographs from 11 patients with an SMMCI. The orthopantomographs and dental radiographs showed that the intermaxillary suture was abnormal anterior to the incisive foramen; however, the SMMCI erupted within the expected time interval. Superimposition on stable structures on lateral cephalometric radiographs from two untreated patients, in which growth analysis was possible, showed that the horizontal and vertical growth of the maxilla was normal. Due to the sutural midline defect it is suggested that a transversal growth analysis is included in all treatment planning of SMMCI patients.     

CAD/CAM氧化锆及Empress全瓷冠修复三年临床效果比较

目的:比较CAD/CAM氧化锆及Empress全瓷冠修复3年的临床效果。方法:选择350例患者共838个全冠修复体(其中CAD/CAM氧化锆全冠428颗、Empress铸瓷全冠410颗),平均观察期36.2±5月,随访检查基牙和修复体情况,分别对两组全瓷冠的存留率和修复成功率进行统计学分析。结果:观察期内共有41颗全瓷冠(19颗为氧化锆,22颗为Empress铸瓷)完全失败,需重新制作。氧化锆全瓷冠和Empress铸瓷全冠的存留率分别为95.1%和95.8%,成功率分别为90.7%和91.2%,其差异均无统计学意义。结论:CAD/CAM氧化锆和Empres铸瓷全冠均能满足临床需要,有较好的修复效果。     

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本文主要介绍了无托槽隐形矫治器的生产工艺流程及现代无托槽隐形矫治技术的临床应用流程。无托槽隐形矫治器的生产工艺流程主要步骤为：扫描硅橡胶印模或石膏模型,从而获得数字化牙列模型,运用计算机辅助设计与制造（CAD／CAM）系统模拟治疗计划并生产加工母模,采用热压成型技术加工隐形矫治器。现代无托槽隐形矫治技术临床应用主要流程有：临床接诊、病例提交、确认模拟矫治方案、生产矫治器、临床配戴矫治器、精细调整,最终完成治疗并保持。     

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数字印模技术是随着计算机辅助设计与制作（CAD／CAM）技术逐渐发展起来的,与模型扫描相比存在更大的难度,对系统本身的要求更高。常见的口腔数字印模系统包括CEREC蓝光系统（德国Sirona公司）、CERECOmicam系统（德国Sirona公司）、LavaC．O．S．系统（美国3M公司）、iTero系统（美国Cadent／Straumann公司）和E4D系统（美国E4D公司）,这些系统获取印模的方式和软件不同,各有优势。数字印模在效率、精度和舒适性方面与传统印模技术相比具有很大的优势,但需要在牙体预备、干燥隔湿和喷粉取像方面注意操作技巧。