Discoloration of a titanium alloy removable partial denture: A clinical report

With recent advances in dental technology, titanium is currently used for fabrication of crowns, fixed partial dentures, implant frameworks, and removable partial denture frameworks. The use of titanium-aluminum-vanadium (Ti-6Al-4V) alloy assumes that it imparts similar anti-corrosion characteristics to the commercially pure titanium. This clinical report describes a patient who experienced discoloration of a Ti-6Al-4V alloy removable partial denture.     

Fabrication of a removable partial denture combining conventional and digital techniques

This article describes a combined conventional and digital workflow for fabricating removable partial dentures (RPDs). After scanning the dental cast and RPD framework assembly, artificial teeth and denture base regions were designed using computer-aided design software. The artificial teeth and denture base assembly was milled as a single structure by using a wax disk and then placed on the RPD framework. The artificial teeth were additionally milled from a polymethyl methacrylate disk. Conventional procedures were followed for denture investment until the wax elimination procedure, after which the assembly was replaced with the artificial teeth in the cope of the flasks, and the denture resin material was injected to process the RPD. This technique enabled the RPD to be fabricated in the same form as the design state.     

Wear of resin denture teeth in partial removable dental prostheses

PurposeTo investigate occlusal wear of resin denture teeth in partial removable dental prostheses worn by partially edentulous patients.MethodsThirty patients with partial removable dental prostheses were included in the study. Thirty-two patients with complete dentures served as a reference group. Occlusal wear after two years was evaluated indirectly using gypsum casts and a three-dimensional laser-scanner device. Overall wear of complete occlusal surfaces and maximum wear of occlusal contact areas were measured. Patient and prosthesis data were analyzed using univariate and multiple linear mixed models.ResultsOverall wear of denture teeth in partial removable dental prostheses was 91 (SD 85) μm, and maximum wear of occlusal contact areas was 329 (SD 204) μm (means and standard deviations). Average and maximum wear values for teeth in complete dentures were both lower than those for teeth in partial removable dental prostheses. However, differences between wear of different types of denture did not reach statistical significance after adjustment for gender, type of tooth, dental status of the opposing jaw, and antagonist material. Statistical analysis revealed that wear was greater for denture teeth occluding with ceramic crowns and/or fixed partial dentures as antagonists.ConclusionsResin denture teeth in partial removable and complete dental prostheses are subjected to clinically important occlusal wear that might destabilize occlusion and cause further problems. Patient-related factors and dental status affect wear behavior and should be taken into consideration when treating patients with removable dentures.     

北京口腔医院技工中心11年修复体加工情况的统计分析

目的客观评估不同种类修复体的应用情况,为临床应用、资源优化配置和科研课题选择等提供参考信息。方法收集首都医科大学附属北京口腔医院技工中心2002-2012年的工作月报和制作数据,以299953件修复体为研究对象,统计冠桥固定修复体、种植固定修复体、可摘局部义齿、全口义齿等主要修复体类别的数量,分析发展趋势。结果活动类修复体构成比呈逐年下降趋势,固定类修复体逐年成为主要修复类型。全口义齿与胶连活动义齿缓慢减少,4种铸造支架活动义齿均增长。贵金属烤瓷固定义齿的制作量增长速率较快,种植体固定修复体一直呈稳定增长趋势,全瓷固定修复体制作量自开展后加速增长。贵金属全冠修复体制作量呈整体增长,成为铸造全冠修复体主要材料类型,而普通钴铬全冠修复体制作量则持续缓慢降低。结论固定类修复体占主导地位,活动类修复体逐年降低,各种材料修复体均有不同程度的起伏,但都有各自的临床需求,其中贵金属、全瓷、种植类需求量增长最为明显,预示未来修复体发展的方向。     

Casting titanium partial denture frameworks: a radiographic evaluation

STATEMENT OF PROBLEM: Titanium is the most biocompatible metal available for dental castings. However, there is some concern about the castability of titanium used on a daily basis. PURPOSE: A radiographic evaluation of titanium partial denture frameworks was undertaken to ascertain whether these castings were technically acceptable for clinical use. MATERIAL AND METHODS: Three hundred Grade II titanium removable partial denture frameworks were cast in a Titec 205M casting machine. All materials were used as directed by the manufacturer, and all castings were made by an experienced titanium specialist. Each casting was evaluated by radiograph. Based on the number, location, and size of argon inclusions, the frameworks were rated as follows: technically acceptable for clinical use as cast; technically acceptable after laser welding modifications; or unacceptable as cast, with remake necessary. RESULTS: Of the 300 titanium frameworks cast, 97% were rated technically acceptable for clinical use in terms of castability. SUMMARY: Within the limitations of this radiographic evaluation, it was determined that the castability of titanium was such that technically acceptable castings could be made on a daily basis.     

Removable partial dentures applied by electric welding and soldering methods

The joining procedure for uniting metal structures is very important in the dental clinic, and various kinds of metal joining methods have been performed for clinical application. The conventional torch soldering method using a blow torch has been generally adopted. However, it has several clinical problems, especially in the construction of removable partial dentures. The base metal wires made of a chromium-cobalt alloy are subject to changes in their mechanical properties caused by heating, when wrought wire clasps are joined to rests or frameworks. In addition to the flexibility of wrought wire clasps, damage to acrylic resin denture bases and acrylic resin teeth occurs in the repair of removable partial dentures. In this paper, the electric resistance welding and soldering methods were applied to attach wrought wire components to a removable partial denture framework to resolve the problems of the torch soldering method. As a result, it is suggested that these electric resistance welding and soldering methods have the following advantages, as compared with the conventional torch soldering method. 1. When using this electric resistance welding method, it is possible to fix metals temporarily to each other more securely and strongly than the conventional temporary fixation methods using sticky wax or acrylic resin. 2. The electric resistance soldering method does not require any heat insulation or a partition as the torch soldering method does, because the soldered area is only heated partially. 3. In the case of soldering electrically wrought wire clasps to metal structures such as rests and connectors, there is no fear of of overheating a wide area of wires.(ABSTRACT TRUNCATED AT 250 WORDS)     

A survey of dentitions and removable partial dentures constructed for patients in North America

The prevalence of removable partial dentures in North America is not known. This study was designed to collect information about (1) the indications for, (2) the teeth to be replaced with, and (3) the type of major connectors used in removable partial dentures. Five commercial dental laboratories situated in different regions of North America were selected to give as wide as possible a view of the production of removable partial dentures. Each laboratory was asked to provide details of 300 consecutive removable partial dentures. Photographs (35 mm) of master casts and processed partial dentures were obtained for more than 1300 patients. The color slides were analyzed and the remaining teeth and types of dentures were recorded. The dentures were classified as follows: cast frame denture, acrylic resin denture with or without some wrought metal, and acrylic resin denture with some cast units. The major connectors were classified as one of seven alternatives in the maxillae, and as one of six alternatives in the mandible.     

Repair of a Removable Partial Denture Using Gold Occlusals

Limited interarch space causes maintenance problems with removable partial dentures. The problem of abrasion and breakage of acrylic resin teeth, the concomitant supraeruption of opposing natural teeth, and possible decrease of vertical dimension of occlusion can be prevented or minimized with cast-gold occlusals. Use of metal occlusals has been advocated on newly constructed removable partial dentures, but not on existing prostheses with severely worn or broken denture teeth. This article describes a repair procedure for a removable partial denture where minimal interarch distance resulted in wear and breakage of denture teeth. A thin, abraded denture tooth that had been repaired numerous times was prepared and covered with a cast gold restoration. The problem of abrasion and breakage of the acrylic resin tooth was solved and the service life of the prosthesis was extended.     

Radiographic detection of porosities in removable partial denture castings

The purpose of this study was to discern the existence of structural defects in removable partial denture frameworks by means of radiographs. A simple technique was described using a dental radiograph unit and routine periapical dental films. All components of removable partial denture castings were radiographed with different angulations. The visibility of defects was clear. Structural defects were located and classified in two brands of removable partial denture base metal alloys (Ticonium and Nobilium) commonly used in fabrication of removable partial denture castings. The technique described is simple, inexpensive, not time-consuming, and can be implemented with minimum instrumentation. Future studies with this radiographic method for investigation of internal defects in fixed prostheses or dental implants are recommended.     

模型置换印模技术修复下颌游离端牙列缺损的临床研究

目的：探讨模型置换印模技术对双侧下颌游离端缺牙患者的修复效果。方法：在解剖式印模上常规制作铸造支架,在铸造支架上制作自凝暂时基板,经口内肌功能修整并制取咬合记录后于口内取功能性印模。经模型置换后常规完成义齿。结果：90.2%的患者用模型置换印模技术制作的义齿疗效良好。结论：模型置换印模作为游离端可摘部分义齿的重要功能印模方法,可以有效改善义齿修复质量。     

Esthetic designs of removable partial dentures

The increased emphasis on physical appearance in contemporary society has increased the demand for esthetic dental restorations. Although the success of implant dentistry has expanded the scope of esthetic fixed prostheses, many patients demand a removable partial denture (RPD) for health, anatomic, psychological, or financial reasons. Fabricating an esthetically pleasing RPD while avoiding the unsightly display associated with conventional clasp assemblies often presents a challenge to dentists. This article examines using lingual clasps, proximal undercuts (also known as rotational path insertion), and acetal resin clasps as simple and effective means of improving RPD esthetics.     

Time to survival for the restoration of the shortened lower dental arch

Removable partial dentures may adversely affect remaining tissues and have a low prevalence of use. This randomized controlled trial was designed to compare the time to survival of cantilever resin-bonded fixed partial dentures and conventional removable partial dentures to restore shortened lower dental arches. We randomly allocated 25 male and 35 female patients (median age, 67 years) to fixed or removable partial denture groups of 30 persons, matched for age and sex. Survival of the prostheses was assessed, based on listed criteria, at each review or when problems arose. Although the removable partial denture group required rather more maintenance visits, the difference in survival rates was not statistically significant (hazard ratio = 0.59, with 95% CI 0.27, 1.29). In the absence of significant differences in five-year survival, the reported advantages of fixed partial dentures, including reduced maintenance frequency, offer positive support for the use of resin-bonded fixed partial dentures.     

An Evaluation of Microwave-Polymerized Resin Bases for Removable Partial Dentures

Purpose The hardness, porosity, and adaptation of removable partial dentures fabricated with one heat-polymerized denture base resin and two resins designed for microwave polymerization were evaluated. Materials and Methods Five prostheses were evaluated for each resin. Adaptation of the denture bases to the master cast was evaluated by spatial orientation and mean weight of residual impression material. The prostheses were then embedded in epoxy resin and sectioned for evaluation of resin hardness (Knoop hardness) and microporosity. Results There were no significant differences in the adaptation of the acrylic resin bases for Acron MC and Ch Lucitone. There was no significant difference in the mean Knoop hardness values for any of the resin bases near and away from the metal. None of the denture bases showed porosity greater than 100 μm. Conclusions Both resin bases formulated for microwave polymerization were effectively polymerized around metal frameworks without adverse effects on resin hardness or porosity. Justi Denture Base material had poorer base adaptation than the other two resins.     

A technique for fabrication of an extracoronal attachment-retained removable partial denture to fit an existing fixed partial denture

Precision attachments have been used for many years to retain removable partial dentures (RPDs). Common reasons for a failed attachment-retained RPD are fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention. When an RPD framework major connector has been fractured, it should be remade. This article describes a technique to remake a fractured mandibular RPD using cast round profile attachment analogs without the need for replacement of the fixed partial denture.     

可摘局部义齿卡环疲劳性能测试方法及研究现状

牙列缺损是老年人的常见口腔疾病,会给患者的生活造成诸多不便,不仅影响患者的咀嚼、发音和口颌系统健康,也会对患者的心理健康和生活质量产生不同程度的负面影响.牙列缺损常见的修复方式有种植义齿、固定义齿和可摘局部义齿.目前,虽然选择种植义齿的患者日趋增多,然而仍有很多患者由于身体原因、经济原因等无法选择种植义齿修复.可摘局部...     

A short-term clinical follow-up study of superplastic titanium alloy for major connectors of removable partial dentures

Statement of problem . Superplastic forming of Ti-6Al-4V alloy has been used in the fabrication of a removable denture framework. The method provides the titanium alloy denture framework with excellent physical properties not seen in cast titanium prostheses.Purpose . This study describes the technical procedure for fabricating removable dentures with this type of framework and evaluates clinical applications of the dentures in short-term follow-up periods from 6 months to 3 years.Results . Results of this study demonstrated that the dentures functioned well and did not cause any major clinical difficulties. The patients have expressed satisfaction with the dentures at regular recall appointments.Conclusion . The clinical observations suggest that this method is suitable for fabricating titanium alloy removable dentures. (J Prosthet Dent 1997;77:583-7.)     

Comparative study of two commercially pure titanium casting methods

The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior.

Objective

This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure.

Material and Methods

72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey''s to compare materials and cast methods (α=0.05).

Results

Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted.

Conclusion

Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.     

可摘局部义齿支架的计算机辅助设计与快速制造

目的 自主开发可摘局部义齿支架三维设计软件及选择性激光熔融制造(selective laser melting,SLM)设备,探讨应用其进行可摘局部义齿支架设计并直接成形金属支架的方法 .方法 使用层析扫描仪获得两个牙列缺损模型的三维点云数据.使用自主开发的可摘局部义齿支架三维设计软件进行模型观测及可摘局部义齿支架(牙合)支托、卡环、舌杆、金属加强网、上颌大连接体等组件的设计.组件设计路线:首先确定组织面轮廓,利用轮廓线内的点云数据生成组织面.根据各个组件的特点,设定抛光面截面形态,结合轮廓线生成抛光面.各组件完成后,用小连接体连成完整支架.将完成的支架数据导入SLM设备中,直接成形金属支架.结果 应用自主开发的可摘局部义齿支架三维设计软件及SLM设备,成功进行了两个可摘局部义齿金属支架的计算机辅助设计及快速制造,在模型上试戴后目测金属支架适合性良好.结论 自主开发的具有完全自主知识产权的可摘局部义齿支架计算机辅助设计与辅助制作系统,可为可摘局部义齿金属支架的制作提供一种新的方法.     

Cast connectors as cores for ceramometal pontics on removable partial dentures and for splinting anterior crowns

A cast connector is a solderless union between two metal components, an alternative to soldering. Cast connectors depend upon mechanical retention for their strength and integrity and are mostly used in repairing or adding to prostheses cast in base metal alloys. Two techniques using cast connectors are described. One is for a removable partial denture that requires the replacement of an anterior tooth or teeth incorporating diastemas or unusual surface anatomy and color variations. Stock denture teeth may not adequately replicate such teeth. A solution to the problem is to extend a porcelain-compatible base metal cast connector from the removable partial denture framework onto the pontic site. A ceramometal pontic reproducing the unusual characteristics of the natural teeth may then be placed by vacuum-firing porcelain directly onto the framework. A second technique is described whereby multiple ceramometal anterior crowns may be splinted together by creating interproximal retentive zones in the frameworks, casting connectors into the retentive zones, and proceeding with porcelain application.