齿科用钴铬合金熔模铸造残余应力初探

目的 对可摘局部义齿支架变形问题进行分析,探索钴铬合金熔模铸造支架产生变形的原因。方法 设计专门试件模拟铸造支架对残余应力进行测定。结果 钴铬合金熔模铸造支架产生变形的直接原因系铸造时的残余应力。结论 残余应力是支架变形的直接原因并提出增加热处理工序以解决残余应力的方案。     

应用牙科X线机探测口腔金属修复体的内在缺陷

目的:探讨用牙科X线机探测钛、镍铬合金、钴铬合金铸件缺陷的可行性,同时分析金属铸件厚度对探测参数设置的影响。方法:按常规铸造方法制作3种厚度(1.0mm、0.6mm、0.3mm)的钛、镍铬合金、钴铬合金金属片,选用激光点焊机在金属表面打孔,模拟金属铸件铸造过程中产生的缺陷。调整牙科X线机各可调参数,在各参数下拍摄金属铸件照片,观察探伤结果。采用SPSS12统计软件包对数据进行组间t检验。结果:钛金属厚度对探伤参数设置的影响无统计学意义,P>0.05。镍铬合金和钴铬合金厚度对探伤参数设置的影响具有显著性差异,P<0.05。结论:钛金属铸件厚度对探伤参数设置的影响不大,可用牙科X线机代替专门的探伤机进行探测。     

新型牙科铸钛包埋材料铸造纯钛铸件的粗糙度研究

目的 探讨自行研发并已获得国家发明专利的新型牙科铸钛包埋材料和商品铸钛包埋材料铸造纯钛铸件的表面粗糙度差异,以期为临床应用提供依据.方法 制作20 mm×20 mm×0.5 mm的蜡型6片,分为A、B两组,每组3片,分别用新型牙科铸钛包埋材料和商品铸钛包埋材料( Rematitan Plus)包埋铸造纯钛铸件.表面粗糙度检查仪测试铸件表面粗糙度,每个铸件测试3个部位,表面描记长度为5.6 mm,比较两组铸件表面粗糙度Ra值的差异.结果 A组铸件表面粗糙度Ra值为(1.72±0.08) μm,小于B组[(1.91 ±0.15) μm],差异有统计学意义(P＜0.05).结论 新型牙科铸钛包埋材料所铸钝钛铸件的表面粗糙度比目前临床常用的商品铸钛包埋材料所铸钝钛铸件表面粗糙度小,可满足临床应用要求.     

贵金属烤瓷合金旧料再利用后金瓷结合性能测试研究

目的 :探讨废旧贵金属烤瓷合金的重复利用对金瓷结合性能的影响。方法 :对照组采用单纯反复重熔利用BioHeradorN金烤瓷合金至第 4代 ,实验组则采用 2 / 3上代废旧料加 1/ 3新合金循环利用至第四代 ,通过剪切试验测试各组各代试样金瓷结合力。结果 :对照组Ⅰ～Ⅳ代剪切强度依次为 ( 47.5 3±2 .0 2 )、( 33.2 3± 2 .0 3)、( 2 5 .0 8± 1.88)、( 14 .61± 1.5 6)MPa ,呈显著下降趋势 (P <0 .0 1) ;实验组Ⅰ～Ⅳ代剪切强度则为 ( 46.81± 1.5 4)、( 41.0 0± 4.5 6)、( 37.2 5± 2 .2 7)、( 33.37± 2 .17)MPa ,比对照组显著提高(P <0 .0 5 ) ,但各代之间仍存在显著性差异 (P <0 .0 1)。结论 :添加 1/ 3新合金循环重复利用废旧合金 ,可明显改善金瓷之间的结合 ,并能达到临床要求 ,是行之有效的途径     

A comparative study on the bond strength of porcelain to the millingable Pd-Ag alloy

PURPOSE

The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys.

MATERIALS AND METHODS

Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe''s tests (α=.05).

RESULTS

The 3-point bending test showed the strongest (40.42 ± 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 ± 2.46 MPa), precious metal alloy containing 83% of gold (35.89 ± 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 ± 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05).

CONCLUSION

The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa).     

Biocompatibility effects of indirect exposure of base-metal dental casting alloys to a human-derived three-dimensional oral mucosal model

Objectives

The study employed a three-dimensional (3D) human-derived oral mucosal model to assess the biocompatibility of base-metal dental casting alloys ubiquitous in fixed prosthodontic and orthodontic dentistry.

Methods

Oral mucosal models were generated using primary human oral keratinocyte and gingival fibroblast cells seeded onto human de-epidermidised dermal scaffolds. Nickel–chromium (Ni–Cr) and cobalt–chromium (Co–Cr) base-metal alloy immersion solutions were exposed to oral mucosal models for increasing time periods (2–72 h). Analysis methodologies (histology, viable cell counts, oxidative stress, cytokine expression and toxicity) were performed following exposure.

Results

Ni-based alloy immersion solutions elicited significantly decreased cell viability (P < 0.0004) with increased oxidative stress (P < 0.0053), inflammatory cytokine expression (P < 0.0077) and cellular toxicity levels (P < 0.0001) compared with the controls. However, the Ni-free Co–Cr-based alloy immersion solutions did not elicit adverse oxidative stress (P > 0.4755) or cellular toxicity (P < 0.2339) responses compared with controls.

Conclusions

Although the multiple analyses highlighted Ni–Cr base-metal alloy immersion solutions elicited significantly detrimental effects to the oral mucosal models, it was possible to distinguish between Ni–Cr alloys using the approach employed. The study employed a 3D human-derived full-thickness differentiated oral mucosal model suitable for biocompatibility assessment of base-metal dental casting alloys through discriminatory experimental parameters.

Clinical significance

Increasing incidences of Ni hypersensitivity in the general population warrants serious consideration from dental practitioners and patients alike where fixed prosthodontic/orthodontic dental treatments are the treatment modality involved. The novel and analytical oral mucosal model has the potential to significantly contribute to the advancement of reproducible dental medical device and dental material appraisals.