Clinical fit of four‐unit zirconia posterior fixed dental prostheses

The objective of this clinical study was to assess the internal and marginal accuracy of computer‐aided design/computer‐aided manufacturing (CAD/CAM)‐generated four‐unit all‐ceramic posterior fixed dental prostheses (FDPs). The data were compared with the results of three‐unit metal‐ceramic and all‐ceramic FDPs that were obtained in a previous study. Twenty‐four patients were provided with all‐ceramic posterior four‐unit FDPs made from semisintered blank zirconia material. Prior to definitive insertion the accuracy was evaluated using a replica technique with a light body silicone that was stabilized with a heavy body material. The replica samples were examined using microscopy. The median marginal gap of the 24 four‐unit FDPs was 77 μm. The median gap widths were 87 μm at the midaxial wall, 167 μm at the axio‐occlusal transition of the abutments, and 170 μm at centro‐occlusal location. Although the marginal accuracy of the four‐unit FDPs differed significantly from that of the three‐unit metal‐ceramic FDPs (median 54 μm), the values obtained were clinically satisfactory and showed that semisintered zirconia blanks could be used for the fabrication of four‐unit FDPs.     

整体切削的聚醚醚酮可摘局部义齿即刻修复1例

聚醚醚酮(PEEK)是一种具有良好的力学性能和生物安全性的新型高分子化合物,近年来逐渐应用于口腔修复、种植、正畸等领域。目前,PEEK在可摘局部义齿中的应用已有临床报道,但整体切削的PEEK可摘局部义齿还未见相关临床报道。本病例应用全程数字化设计和PEEK材料,整体切削制作了集支架、人工牙和基托为一体的可摘局部义齿,对1例83岁上下颌牙列缺损的患者进行了即刻修复治疗,并进行了3~6个月的随访,患者对修复效果满意。     

Fit of zirconia fixed partial denture: a systematic review

Summary The aim of this study is to review all the published literature investigating the accuracy of fit of zirconia fixed partial dentures (FPD). A comprehensive electronic search was performed through PubMed (MEDLINE) using Boolean operators to combine the following key words: ‘zirconia,’‘margin,’‘FPD,’‘internal,’‘fit,’‘gap,’‘fitting surface,’‘bridge’ and ‘fixed prosthesis.’ The search was limited to articles written in English, published up to January 2010. In addition, a manual search was also conducted through articles and reference lists retrieved from the electronic search and peer‐reviewed journals. A total of 115 articles were retrieved and only 15 met the specified inclusion criteria for the review. Twelve of these articles were in vitro and three of them were in vivo. The selected articles had assessed marginal and/or internal fit of zirconia FPDs against the effect of various parameters that were computer‐aided design and computer‐aided manufacturing (CAD/CAM) and CAM systems, post‐sintered and pre‐sintered milling, framework configuration, span length, veneer application and ageing. Conclusions: CAD/CAM, post‐sintered milling, straight configuration and shorter span frameworks provided superior results than CAM, pre‐sintered milling, curved configuration and longer span frameworks. Veneering zirconia frameworks caused deterioration in fit, while ageing of zirconia had no implications on the fit. Further studies are needed to determine the clinical significance of the differences in the accuracy reported in this review.     

Effect of veneering technique on the fracture resistance of zirconia fixed dental prostheses

Summary To compare the fracture resistance of zirconia 3‐unit posterior fixed dental prostheses (FDPs) frameworks veneered with different veneering materials and techniques before and after artificial ageing. Forty‐eight zirconia 3‐unit FDPs, representing a missing first molar, were adhesively cemented on human teeth. The zirconia frameworks were randomly distributed according to the veneering materials and techniques into three groups, each containing 16 samples: group LV (layering technique/Vintage ZR), group LZ (layering technique/ZIROX) and group PP (CAD/CAM and press‐over techniques/PressXZr). Half of each group was artificially aged through dynamic loading and thermocycling to simulate 5 years of clinical service. Afterwards, all specimens were tested for fracture resistance using compressive load. An analysis of variance (anova ) was used to assess the effect of veneering ceramic and artificial ageing on fracture resistance (P < 0·05). Except for one minor cohesive chipping in group LV1, all specimens survived artificial ageing. The mean fracture resistance values (in Newton) of different non‐aged (± s.d.)/aged (± s.d.) groups were as follows: LV0 2034 (± 401)/LV1 1625 (± 291); LZ0 2373 (± 718)/LZ1 1769 (± 136); and PP0 1959 (± 453)/PP1 1897 (± 329). Artificial ageing significantly reduced the fracture resistance in groups veneered with the layering technique (P < 0·05), whereas no significant effect was found in specimens veneered with the CAD/CAM and press‐over techniques. All tested systems have the potential to withstand occlusal forces applied in the posterior region. The combination of the CAD/CAM and press‐over techniques for the veneering process improved the overall stability after artificial ageing, relative to the layering technique.     

Inlay‐retained cantilever fixed dental prostheses to substitute a single premolar: impact of zirconia framework design after dynamic loading

The purpose of this in‐vitro study was to evaluate the influence of the framework design on the durability of inlay‐retained cantilever fixed dental prostheses (IR‐FDPs), made from zirconia ceramic, after artificial ageing. Forty‐eight caries‐free human premolars were prepared as abutments for all‐ceramic cantilevered IR‐FDPs using six framework designs: occlusal–distal (OD) inlay, OD inlay with an oral retainer wing, OD inlay with two retainer wings, mesial–occlusal–distal (MOD) inlay, MOD inlay with an oral retainer ring, and veneer partial coping with a distal box (VB). Zirconia IR‐FDPs were fabricated via computer‐aided design/computer‐aided manufacturing (CAD/CAM) technology. The bonding surfaces were air‐abraded (50 μm alumina/0.1 MPa), and the frameworks were bonded with adhesive resin cement. Specimens were stored for 150 d in a 37°C water bath during which they were thermocycled between 5 and 55°C for 37,500 cycles; thereafter, they were exposed to 600,000 cycles of dynamic loading with a 5‐kg load in a chewing simulator. All surviving specimens were loaded onto the pontic and tested until failure using a universal testing machine. The mean failure load of the groups ranged from 260.8 to 746.7 N. Statistical analysis showed that both MOD groups exhibited significantly higher failure loads compared with the other groups (i.e. the three OD groups and the VB group) and that there was no significant difference in the failure load among the OD groups and the VB group. In conclusion, zirconia IR‐FDPs with a modified design exhibited promising failure modes.     

下颌牙列缺损患者可摘局部义齿铸造支架的计算机辅助设计

目的对20例临床下颌牙列缺损患者可摘局部义齿支架进行三维计算机辅助设计。方法光栅投影测量法获取20例下颌牙列缺损患者石膏模型的三维数据,按照临床设计原则,利用3DMax、Geomagic和RapidForm等软件分别构建卡环、支托、舌杆、舌板和加强网等可摘局部义齿支架各部件的三维数字化模型,组合完成可摘局部义齿支架的计算机辅助设计,并构建了支架及其部件数据库。结果成功构建了20例临床患者下颌可摘局部义齿的个性化计算机三维支架模型。结论通用三维设计软件可以实现个性化支架的计算机辅助设计。     

机器人辅助全口义齿排牙系统的初步研究

目的 研制机器人辅助制作全口义齿人工牙列的计算机系统。方法 利用CRS-450 6自由度机器人使被抓取的物体实现任意位置和姿态,研制可调式排牙器。用三维激光扫描测量系统获取无牙颌骨形态的几何参数。根据高级口腔修复专家排牙经验奸商的数学模型,用VC^ 和RAPL机器人语言编制了专家排牙、三维牙列模拟显示和机器人排牙控制程序。当排牙方案确定后,数据传给机器人,由机器人完成排牙器的定位工作,最终完成全口义齿人工牙列的制作。结果 建立了完整的机器人辅助全口义齿人工牙列制作系统。已用该系统为一例患者试作人工牙列。目前该牙列在咬合方面存在一些误差,尚需调整和完善。结论 首次实现了由机器人辅助制作人工牙列,具有科技进步意义。虽牙列在咬合方面还不十分理想,但实验结果已证明该系统的设计思想和技术路线是可行的。     

Accuracy of metal 3D printed frameworks for removable partial dentures evaluated by digital superimposition

ObjectivesTo evaluate the accuracy of metal 3D printed frameworks (MEP group) for removable partial dentures (RPDs) by digital superimposition, in comparison to that of frameworks produced by the conventional (CON group) and resin printing/casting (RPC group) workflows.MethodsA partially edentulous maxillary dentiform was prepared with rest seats and guiding planes on the right canine, left first premolar, and left second molar. Thirty master casts were prepared via repeated impressions of the dentiform. Frameworks were fabricated by three different workflows (n = 10 for each group). The internal discrepancies of the frameworks were assessed at 12 points by digital scanning with an optical triangulation principle-based tabletop scanner and superimposition using a reference best-fit alignment method. First, the master cast was scanned alone. Subsequently, a thin silicone material was applied to the framework and fitted onto the master cast, after which the framework was removed. Finally, the master cast with the silicone material attached was rescanned. The data from the two scans were matched, with the reference being the area not occupied by the silicone.ResultsFor the CON, MEP, and RPC groups, respectively, the mean overall internal discrepancies (279.72 µm, 241.02 µm, and 331.70 µm), and the mean internal discrepancies on palate areas (292.92 µm, 250.72 µm, and 355.84 µm) and rest seat areas (240.12 µm, 211.91 µm, and 259.26 µm) did not significantly differ among the three fabrication methods (p = 0.558, 0.542, and 0.774).SignificanceThe reference best-fit alignment of scan datasets is a useful approach to evaluate the internal discrepancy of frameworks. Metal 3D printing produces RPD frameworks that are comparable to conventional frameworks and meet clinical standards.     

Surface modification with alumina blasting and H2SO4–HCl etching for bonding two resin‐composite veneers to titanium

The purpose of this study was to investigate the effect of an experimental surface treatment with alumina blasting and acid etching on the bond strengths between each of two resin composites and commercially pure titanium. The titanium surface was blasted with alumina and then etched with 45wt% H₂SO₄ and 15wt% HCl (H₂SO₄–HCl). A light‐ and heat‐curing resin composite (Estenia) and a light‐curing resin composite (Ceramage) were used with adjunctive metal primers. Veneered specimens were subjected to thermal cycling between 4 and 60°C for 50,000 cycles, and the shear bond strengths were determined. The highest bond strengths were obtained for Blasting/H₂SO₄‐HCl/Estenia (30.2 ± 4.5 MPa) and Blasting/Etching/Ceramage (26.0 ± 4.5 MPa), the values of which were not statistically different, followed by Blasting/No etching/Estenia (20.4 ± 2.4 MPa) and Blasting/No etching/Ceramage (0.8 ± 0.3 MPa). Scanning electron microscopy observations revealed that alumina blasting and H₂SO₄–HCl etching creates a number of micro‐ and nanoscale cavities on the titanium surface, which contribute to adhesive bonding.