Analysis of stress on a fixed partial denture with a blade-vent implant abutment.

Using a two-dimensional finite element method, a study was made that compared the behavior of a model mandibular posterior fixed partial denture constructed on the second premolar abutment and a blade-vent implant imbedded at the site of the second molar with the behavior of a fixed partial denture constructed on the second premolar and second molar abutments. The following were the results: 1. Deflections of the implant fixed partial denture were less than those of the natural tooth fixed partial denture in vertical and inclined loads. 2. Stress concentration was markedly found in the pontic and the mesial and distal parts of the premolar retainer in both restorations and the implant neck in the implant fixed partial denture. 3. In the implant fixed partial denture, stresses induced in the surrounding bone became higher around the posterior abutment and became lower around the premolar retainer than the stresses produced with the natural tooth fixed partial denture. 4. Therefore it was suggested that, to relieve stress to the surrounding bone around the implant abutment, occlusal forces loaded to the implant fixed partial denture have to be more concentrated on the premolar abutment than do forces loaded to the natural tooth fixed partial denture.     

The effect of connector design on cement retention in an implant and natural tooth-supported fixed partial denture

This study investigated the effect of connector design, rigid or nonrigid, on cement retention in a combined implant and natural tooth-supported fixed partial denture. A prepared natural tooth was placed in a Plexiglas block in a manner that it could move approximately the same as a healthy premolar. An endosseous implant was placed in the block so that it was immobile. Joining the prepared tooth and implant was a fixed partial denture that could be made rigid or nonrigid. The natural tooth retainer was cemented to the prepared tooth, and the implant retainer was affixed to the implant fixture with a gold screw. One year of stress was applied to the fixed partial denture by a force simulation machine. Twenty randomly ordered tests were completed, 10 of each connector design. Retentive values for the cemented retainers were recorded and statistically compared by use of Student's independent t test. No significant difference in cement retentive strength between designs was found (p less than 0.05).     

A technique for using endosteal blade implants

A technique for insertion of an endosteal blade implant and its use as a retainer for a fixed partial denture have been described. Careful planning for the location of the implant, good surgical procedures, and attention to proper detail in fixed partial denture construction are essential to success of blade implants.     

Transforming an existing fixed provisional prosthesis into an implant-supported fixed provisional prosthesis with the use of healing abutments

Maintaining a fixed provisional prosthesis through all phases of complex implant prosthodontic therapy for a soon-to-be completely edentulous arch is a difficult task. This article focuses on the treatment phase in which teeth and/or transitional implants supporting a provisional fixed partial denture are removed. The described technique makes use of healing abutments to support a modified provisional fixed partial denture. This protocol ensures patient comfort and allows proper soft tissue healing before definitive implant abutment selection. It also eliminates the placement of interim implant abutments.     

三种不同连接方式的天然牙—游离端种植体联合支持的 固定义齿集中载荷应力分析

目的 研究三种不同连接方式的天然牙——游离端种植体联合支持的固定义齿在集中载荷下的应力值和应力分布。方法 应用三维有限元应力分析法。结果 ①固定连接式固定义齿的种植体基牙应力峰值高于天然牙;②刚性栓道式固定义齿的种植体基牙应力峰值最高;③缓冲式固定义齿的种植体基牙应力峰值最低。结论 ①固定连接式固定义齿设计可能损伤种植体基牙,需采取适当措施;②刚性栓道式固定义齿设计对种植体基牙损伤最大;③缓冲式固定义齿设计有利于保护种植体基牙。     

Replacement of a mandibular implant-fixed prosthesis with an implant-supported overdenture to improve maintenance and care

PatientsA 69-year-old woman presented to the Osaka University Dental Hospital. She had two chief complaints, (a) food accumulation under the lower teeth and (b) poor maxillary denture retention while eating. On clinical examination the patient presented with a maxillary complete denture and fixed mandibular implant prosthesis. For preventing food accumulation under the fixed implant prosthesis and to keep the maxillary denture stable by providing posterior occlusal contact for bilaterally balanced occlusion, the use of a mandibular implant-supported overdenture with self-adjusting magnetic attachments provided a prosthetic solution for this patient. After provided the new dentures, the patient was pleased and was comfortable with the aesthetic, stability and retention of the dentures. There were no discernable clinical or radiographic changes after 1 year of use.DiscussionTo prevent food accumulation beneath the fixed implant prosthesis and maintain the stability of the maxillary denture by providing posterior occlusal contact for bilaterally balanced occlusion, a mandibular implant-retained overdenture with magnetic attachments was used to provide a prosthetic solution for this patient.ConclusionIn this clinical case, an implant-fixed prosthesis in the edentulous mandibular region was replaced into an implant-supported overdenture with considerations for (a) preventing the food accumulation beneath the lower prosthesis, (b) achieving the proper occlusion in the posterior part for maxillary denture stability and (c) ease of maintenance and care for the prostheses.     

Fabrication of a two-piece superstructure for a fixed detachable implant-supported mandibular complete denture

This article describes a procedure to fabricate a 2-piece superstructure for a fixed detachable implant-supported mandibular complete denture prosthesis. With this unique technique, unsuitable implant angulation can be corrected, and retention of the second superstructure is accomplished with 2 esthetically positioned screws and an antirotational attachment.     

Chairside prefabricated fiber-reinforced resin composite fixed partial dentures.

The introduction of pre-impregnated fiber-reinforced resin composites has provided the dental profession with the opportunity to fabricate and deliver adhesive, esthetic, and metal-free tooth replacements. Utilizing this technology, a prefabricated fiber-reinforced resin composite fixed partial denture prototype that allows rapid, cost-effective, and noninvasive fixed tooth replacement for single anterior teeth has been developed. Ideal situations for this type of service include: a fixed replacement following tooth loss from trauma; a fixed tooth replacement in medically compromised patients who cannot sit for extended periods of time or have local anesthesia; periodontally compromised abutments; a fixed space maintainer following orthodontic movement; and a fixed provisional during the post implant healing phase prior to loading. This article describes the framework construction and placement protocol for the prefabricated fiber-reinforced resin composite fixed partial denture.     

Hemorrhage related to implant placement in the anterior mandible

Implant placement in the edentulous anterior mandible is relatively considered a routine and safe procedure. The interforaminal area is the usual area in the mandible for implant placement for the support and retention of a fixed partial denture or removable overdenture. This region is also the usual donor site of bone grafts. However, implant placement, like any other surgical procedure, is not free of risks and complications. The purpose of this review article was to investigate the risk of a life threatening hemorrhage due to arterial injury at implant placement in the anterior mandible.     

Single-tooth replacement: bridge vs. implant-supported restoration

Options for restoring a single tooth include fixed partial denture, resin-bonded restoration and single-tooth implant. In this paper, we discuss the advantages and disadvantages of these methods and factors that must be considered when choosing between them for the replacement of a single tooth. Although in some cases a fixed partial denture is the most appropriate choice, implants have the advantage of allowing preservation of the integrity of sound teeth adjacent to the edentulous area.     

不同直径种植体与天然牙联合支持固定桥的应力分析

目的:通过三维有限元方法研究种植体直径对天然牙种植体联合固定桥周围骨组织应力的影响。方法:CT扫描获得志愿者DICOM数据,通过Mimics软件、Imageware逆向工程软件及ANSYS软件处理,先建立左侧下颌第二前磨牙和第二磨牙支持的天然牙固定桥三维有限元模型,用不同直径种植体替换下颌第二磨牙得到一系列种植体-天然牙联合支持式固定桥的三维有限元模型。分别在垂直向和斜向45°集中加载下,对比分析天然牙及种植体周围的应力分布情况。结果:相同加载条件下,不同模型的第二前磨牙(天然牙)颈部应力无明显区别。对联合支持式固定桥,当种植体直径由3.5 mm增加为4.3 mm时,种植体颈部和基台的应力明显降低(近1/2);随种植体直径增加,2处应力也继续降低,但降低的幅度明显放缓。结论:随着种植体直径的增大,种植体颈缘处骨组织及基台的von Mises应力逐渐减小,但对天然牙周围的应力影响较小。斜向载荷时,天然牙、种植体周围骨组织及基台受到的von Mises应力显著增大,更易导致固定桥修复的失败。     

Magnetic retention for complete and partial overdentures. Part I

Magnets have been used as aids to denture retention for many years with some success. The development of new cobalt and rare earth magnet alloys has greatly extended the potential application of magnetic retention in removable partial dentures, complete overdentures, fixed partial dentures, and sectional dentures.Effects of magnetic fields on tissues have been investigated extensively, with conflicting results, but reports describing dental applications for magnets claim no damaging tissue effects. The closed-field magnetic retention system described avoids any possibility of magnetic field effects on tissues by using paired magnets and a fixed and detachable keeper in a modified horseshoe arrangement. The detachable keeper is cemented or screwed to a decoronated, root-treated tooth. The denture-retention element, consisting of paired magnets and a fixed keeper, abuts the keeper in the tooth root and holds the denture in place by magnetic attraction. When in position, there is no external field surrounding the denture or tooth root. This arrangement also doubles the available retention.The shape, size, and configuration of the two magnets and fixed and removable keepers were chosen to provide maximum retention in a magnetic denture retention unit of a size convenient for most applications. The retention provided is approximately 300 gm per unit.The magnet alloy, Co₅Sm, is very hard but brittle, and it can corrode in the mouth. To prevent this from occurring in service, end plates protect the exposed magnet faces. The plates, of the same stainless steel alloy as the keepers, prevent magnet corrosion and reduce wear at the denture-retention keeper-element interface in service.     

Utilizzo implantare strategico del triangolo retrocanino con bypass del seno mascellare mediante espansori ossei e inserti piezoelettrici

Objectives

The study reports about two patients who received an implant rehabilitation device consisting in a three-unit fixed partial denture supported by two implants, one of which tilted. They were strategically placed in the retrocanine triangle after bypassing the maxillary sinus by the use of bone expanders and special piezoelectric inserts.

Materials and methods

Two patients were treated with this technique and received two implants each. The distal one was placed tilted in the retrocanine bone triangle through conic screw bone expanders and special piezoelectric inserts to avoid high demanding surgical skill sinus lift procedures. The mesial implant was axially placed with a piezoelectric preparation of the implant site. After a 6-month healing period, three unit, screw retained, fixed partial dentures were delivered. After one year of loading the rehabilitation implants were clinically and radiographically examined.

Results

After one year of loading all four implants were osseointegrated and the marginal bone reabsorption was in line with the traditional techniques. No biological or mechanical complications were found.

Conclusions

The synergy between these special piezoelectric inserts used for implant site preparation and conic screw bone expanders seems to offer a more gentle approach and a better bone compaction around the implants in comparison with the traditional technique. An implant-supported rehabilitation in the retrocanine triangle with delayed function on a three-unit fixed partial denture, avoiding sinus floor elevation procedures by using this modified technique, might be a less invasive technique, reducing costs and increasing benefits for the patients.     

Management of loading forces on mandibular distal-extension prostheses. Part I: Evaluation of concepts for design

The viscoelastic reaction of ridge mucosa and abutment teeth, by virtue of their periodontal ligaments, is a necessary dimension in the evaluation of design concepts for removable partial dentures for patients with distal-extension ridges. The possible modalities are (1) removable partial dentures with flexible denture bases (stressbreakers), (2) use of a floating denture base impression technique, (3) use of a mucofunctional impression technique to relate the denture base to the framework, and (4) use of an endosseous implant. An evaluation of each modality has been made.     

无牙颌种植义齿修复设计与病例分析

目的:通过病例分析讲解无牙颌种植义齿修复设计.方法:对3个典型无牙颌病例进行全面综合检查,提出设计方案,进行种植义齿修复,并分析修复效果,总结无牙颌种植修复的经验.结果:3个无牙颌病例经过种植义齿修复后,义齿固位稳定,功能良好,美观舒适,长期成功率高.结论:在无牙颌种植义齿修复设计中应注意①同位方式转变(可摘变固定);...     

Alternative complete-arch cement-retained implant-supported fixed partial denture.

Early implant prostheses designs, which used screw-retained metal and acrylic resin structures, frequently left a space between the prosthesis and the soft tissue. Common deficiencies of this design included phonetic and esthetic problems and screw loosening. Cement-retained implant prostheses are also used in partially and completely edentulous patients, and are thought to have optimal occlusion and esthetics. Moreover, cement-retained prostheses may induce less stress on the implant, thereby maximizing the possibility of a passive fit. Porcelain fused to metal prostheses have been used mostly in partially edentulous situations. Recently, complete-arch porcelain fused to metal prostheses that replace hard and soft tissue have been used and, although this restoration can have excellent esthetics, there are disadvantages such as high cost, potential framework distortion during fabrication, and difficulty in repairing fractures of in-service porcelain. This article describes an alternative technique for the fabrication of a complete-arch, cement-retained, metal-acrylic resin implant-supported fixed partial denture. When compared with porcelain fused to metal complete-arch restorations, this prostheses is esthetic, has excellent retention and stability, yet is relatively inexpensive to fabricate, and requires less laboratory skill.     

Cross-pin fixation for fixed partial dentures

A technique is described in which a standardized post system is used as a cross pin. The pin is partially embedded in the mesial or distal aspect of the abutment tooth and the remainder of the pin diameter is incorporated in the metallic substructure of the fixed partial denture. The cemented pin will add retention and resistance to the fixed partial denture. The differences between threaded and smooth cross pins are discussed.     

种植全口覆盖义齿应力分布的三维有限元分析

目前种植技术在无牙颌患者中应用广泛,但随之亦发现种植固定义齿的一些不足,所以种植覆盖义齿应运而生,并以其特有的优势得到了越来越多的关注,那么种植体支持的覆盖义齿在固位方式、种植体的数量和植入部位等方面该如何选择和把握呢?本文利用三维有限元的分析方法,研究受力状态下的无牙颌种植覆盖义齿应力分布状况,并对应力分布的影响因素进行探讨,拟为种植覆盖义齿应力分布均匀,优化种植覆盖义齿的临床修复设计提供理论依据,从而提高种植覆盖义齿的远期成功率.     

A double casting technique to minimize distortion when constructing fixed partial dentures on implants

The casting of extensive implant superstructures that have a good passive fit may be technically demanding. A simple, 2-stage casting technique is presented that avoids common problems associated with the casting of large superstructures. The fabrication of a 7-unit metal-ceramic screw-retained fixed partial denture supported by 5 implants is used to illustrate this technique.     

Influence of length and diameter of implants associated with distal extension removable partial dentures

PURPOSE: The aim of this study was to evaluate the influence of the length and diameter of the implant incorporated under the saddle of a distal-extension removable partial denture, acting as support. MATERIALS AND METHODS: Six hemi-mandibular models were made with the presence of left inferior cuspid and first bicuspid, with the following differences: model A, without removable partial denture; model B, removable partial denture only; model C, removable partial denture and implant of 3.75 x x mm; model D, removable partial denture and implant of 3.75 x x3 mm; model E, removable partial denture and implant of 5 x x mm; and model F, removable partial denture and implant of 5 x x3 mm. These models were designed with the aid of AutoCAD 2000 (Autodesk, Inc., San Rafael, CA) and processed for finite element analysis by ANSYS 5.4 (Swanson Analysis Systems, Houston, PA). The loads applied were 50 N vertical on each cuspid point. RESULTS: It was noted that the presence of the removable partial denture overloaded the supporting tooth and other structures. The introduction of the implant reduced tensions, mainly at the extremities of the edentulous edge. Both the length and diameter tended to reduce tensions as their dimensions increased. CONCLUSIONS: Increasing the length of the implant had a great influence on the decrease of displacement and von Mises tension values. Increasing the diameter of the implant had a great influence on the decrease of von Mises tension values, but did not influence the displacement values. According to the results of this study, it is a good choice to use the greater and larger implant possible in the association between implant and distal extension removable partial denture.