数字化口腔虚拟教学评估系统用于前牙全瓷冠牙体预备评分的初步评价

目的探讨数字化口腔虚拟教学评估系统在前牙全瓷冠牙体预备评分中的应用及可靠性。 方法2018年参加第二届"华南杯"口腔医学生临床技能邀请赛的21名选手和2019年参加第三届"光华杯"口腔医学生临床技能展示活动的24名选手，使用数字化口腔虚拟教学评估系统的考试模式进行左上中切牙全瓷冠牙体预备。分别采用评委评分和机器评分两种方式对牙体预备结果进行评分，记录评委所用评分时间，采用SPSS 26.0软件对评委评分与机器评分的结果进行相关性分析。 结果2018年和2019年两种评分方式评分结果均相关（r₂₀₁₈ = 0.567，P₂₀₁₈ = 0.007；r₂₀₁₉ = 0.546，P₂₀₁₉ = 0.006）；机器评分在牙体预备结束时即刻获得，评委用于每个学生的平均评分时间分别为2.31和1.88 min。 结论数字化口腔虚拟教学评估系统可应用于固定义齿修复牙体预备教学，可对牙体预备结果进行即刻评分，机器评分与评委评分成正相关性，两者各有优缺点，在牙体预备实验教学中应注意取长补短。     

A clinical evaluation of prefabricated CAD-CAM crowns for restoring anterior and posterior primary teeth

PurposeThe purpose of this study was to produce an esthetic and economical prefabricated crowns which can be used as a final restoration for primary teeth by using CAD-CAM system.Methods44 children, five to nine year olds with at least one decayed primary teeth were included. This study was designed as a randomized controlled clinical trial, with 63 primary teeth were divided into two groups: CAD-CAM crowns (CCZC)[16 Posterior, 15 Anterior] and NuSmile crowns (NZC)[16 Posterior, 16 Anterior]. Crowns were evaluated at one-month, three-month, and six-month recall appointments, examining the following criteria: proximal contact area, marginal adaptation and Restoration failure. Maan-Whitney U, Friedman test and Wilcoxon tests were used for statistical analysis.ResultsAnalysis of variance showed poor marginal adaptation in all crowns, loss of proximal contact area in one mesial surface and two distal surfaces in posterior teeth which restored with CCZC compared to the two distal surfaces in posterior teeth with NZC. fracture occurred on the surface of one NZC after one month. However, there was no significant difference between NuSmile Crowns and CAD-CAM crowns after six months follow up (P > 0.05).ConclusionsPrefabricated CAD-CAM crowns are acceptable option as final restorations for primary teeth.     

Associations between clinical parameters assessed around implants and teeth

The aim of the present study was to clinically assess the peri-implant and periodontal conditions 1 year after placement of oral implants (ITI® Dental Implant System) in partially edentulous patients. In all, 127 patients (median age 50 years, range 17 to 79) were examined. They were all treated according to a concept of comprehensive dental care and had received fixed partial dentures (FPD). Significant differences were observed between implants and contralateral control teeth with respect to mean pocket probing depth (PPD)(2.55 mm at implants/2.02 mm at teeth), mean probing attachment level (PAL)(2.97 mm/253 mm) and bleeding on probing (BOP)(24%/12%)(Wilcoxon matched pairs sign rank test, P≥0.0l), whereas mean modified plaque index (0.22/0.30), mean modified bleeding index (0.351 0.44) and mean recession (?0.42 mm/?0.51mm) did not significantly differ between implants and teeth. Compared to control teeth, the width of keratinized mucosa at implants was significantly smaller at lingual, but not at buccal aspects. Regression analyses showed no significant association between the amount of keratinized mucosa and degree of inflammation. Recession, PPD and PAL were slightly influenced by the amount of keratinized mucosa indicating greater resistance to probing. Grouping the implants according to various lengths, type of fixation of the FPD or combination with natural teeth did not result in statistically significant different clinical parameters, whereas grouping according to different localization within the oral cavity did. For example, the mean PAL in 83 anterior implants was 2.52mm, whereas 175 posterior implants had a mean PAL of 3.18mm (Mann-Whitney U-test, P≤0.01). Regression analyses between the mean PAL for all implants in each patient and the mean PAL of the corresponding dentition revealed an r² of 0.23 (P≤0.01). Using multiple regression analysis, the mean PAL of the implants showed to be significantly influenced by the combined factors “fullmouth” PII, “fullmouth” BOP and mean PAL of all teeth. The resuhs of this study suggest that in partially edentulous patients the overall periodontal condition may influence the clinical condition around implants and thus reinforces the importance of periodontal treatment prior to and supportive periodontal therapy after the incorporation of osseointegrated oral implants.     

The effect of cement thickness on the fracture strength of all-ceramic crowns

The effect of increasing cement thickness on the fracture strength of aluminous porcelain jacket crowns was investigated in this study. Thirty-three aluminous porcelain jacket crowns were divided into three groups. In Group 1, only platinum foil was used to provide cement space. In Group 2 two layers and Group 3 four layers of die spacer were painted onto the metal die before impression taking. Each crown was cemented onto a metal die with zinc phosphate cement and loaded until fracture. The maximum force to break each crown was recorded. The average fracture load was 408 N for Group 1,365 N for Group 2 and 324 N for Group 3. ANOVA (SPSS) found a significant difference (p < 0.05) between groups. A Scheffe Test revealed a significant difference between Groups 1 and 3. It was concluded that increasing the cement thickness above 70 μm reduced the fracture strength of porcelain jacket crowns.     

反复烧结对 In-Ceram全瓷冠适合性的影响

[目的]研究体瓷的反复烧结对In-Ceram全瓷冠适合性的影响.[方法]制作In-Ceram后牙全瓷冠试件50个.试件分为5组.对照组为氧化铝底层冠,实验组依体瓷烧结次数分为4组,即烧结3次、5次、7次和9次.采用片切法,用万能工具显微镜测量冠边缘,轴壁和面与代型之间的粘固剂厚度.[结果]对照组和实验各组(烧结3次、5次、7次和9次)冠边缘粘固剂厚度分别为69μm、74μm、64μm、68μm和65μm;各组的平均粘固剂厚度依次为61μm、63μm、58μm、63μm和59μm.实验各组与对照组各测量点之间的粘固剂厚度的差异无显著性;实验各组与对照组之间的平均粘固剂厚度的差异无显著性.[结论]在实验条件下,体瓷的反复烧结对In-Ceram全瓷冠的适合性无影响.In-Ceram全瓷冠在瓷烧结热循环中的尺寸稳定性较好.