插销式附着体的临床应用

目的 探讨插销式附着体在双侧远中游离端局部活动义齿中的固位和稳定性。方法 制作带有插销式附着体底座的基底冠,并通过平行研磨仪确定附着体的工仙就位道。结果 以插销式附着体为固位体的双侧远中游离端局部活动义齿的固定和稳定性高于普通三臂卡环为固位体的义齿。结论 插销式附着体是一种结构简单,固位和稳定性较好的固位体。值得临床推广应用。     

Clinical evaluation of abutment teeth of removable partial denture by means of the Periotest method

Prosthodontics should be one of the means of establishing conditions for the maintenance of periodontal health. The forces applied to the abutment teeth and their effects are very important considerations in the design and construction of the removable partial dentures. This 6-month follow-up clinical study evaluated the degree of mobility of abutment teeth of distal extension and tooth supported removable partial dentures by using Periotest. Two types of clasp design were selected for evaluation. In cases with unilateral and bilateral distal-extension, a clasp design including a T clasp of Roach retentive arm, a rigid reciprocal arm and a mesial rest were used. For the abutments of tooth-supported removable partial dentures, a second clasp design with a cast circumferential buccal retentive arm, a rigid reciprocal clasp arm and a rest adjacent to the edentulous ridges was selected. A total of 68 abutment teeth was analysed. Periotest values were made at the time of denture placement (control) and at 1, 3 and 6 months after the denture placement. The statistical analysis was performed using Friedman test. All analysis was performed at a 0.05 level of significance. The results revelled that no significant changes in tooth mobility were observed during the 6-months follow-up (P > 0.05). In conclusion, our findings suggest that adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments play an important role in preventing changes in abutment tooth mobility caused by removable partial denture placement.     

An analysis of mesial rest-I-bar clasp designs

The mesial rest-I-bar concept is the most important contribution to clasp partial denture design in the last 30 to 40 years. When used with discernment in situations where it is not contraindicated, it constitutes an excellent design for extension-base removable partial dentures. It has become the design of choice for an increasing number of dentists.Use of the three elements that make up the clasp assembly does not necessarily insure that the clasp will function as intended. There are situations for which it should not be used. Unless adequately adjusted after framework construction as well as during the maintenance program, the beneficial effects may be more imaginary than actual.Strict adherence to the mesial position for the rest is not rational for tooth-supported dentures and may be questioned for some extension-base prostheses (Fig. 17).I-bars have several advantages as direct retainers. However, no single type of retainer is applicable for all retentive situations, and other types should be selected where conditions are unfavorable for I-bar use.A framework which permits a slight amount of movement toward the edentulous residual ridge is an important consideration in design of extension-base removable partial dentures, particularly for those of the mandibular arch. However, compromise of this principle is sometimes necessary to satisfy other design requirements.Design of the framework is only one of the factors that contribute to a successful removable partial denture. Of at least equal importance is the adequacy of support provided by the denture base and the nature of the occlusion. If meticulous attention is directed to these two factors, the forces transmitted to the teeth through the framework can be kept to a minimum and within physiologic tolerance. Conversely, neglect of these considerations may cause a framework of any design to become destructive.     

Finite element analysis on preferable I-bar clasp shape

An I-bar clasp is one of the most popular direct retainers for distal-extension removable partial dentures. However, no adequate information is available on preferable shape as determined by biomechanics. This study aimed (1) to investigate, by finite element analysis (FEA), the dimensions and stress of I-bar clasps having the same stiffness, and (2) to estimate a mechanically preferable clasp design. Three-dimensional FEA models of I-bar clasps were created with vertical and horizontal straight sections connected by a curved section characterized by six parameters: thickness of the clasp tip, width of the clasp tip, radius of the curvature, horizontal distance between the base and the vertical axis, vertical dimension between the tip and the horizontal axis, and taper (change of width per unit length along the axis). Stress was calculated with a concentrated load of 5 N applied 2 mm from the tip of the clasp in the buccal direction. A thinner and wider clasp having an taper of 0.020-0.023 and radius of curvature of 2.75-3.00 showed less stress. The results suggest that such a shape might be the preferable I-bar clasp shape as biomechanical viewpoint.     

A loading impression technique for semiprecision and precision removable partial dentures

The rationale of designing a semiprecision or precision distal-extension removable partial denture and the justification of ridge loading in distal-extension ridge impression techniques have been presented. The effectiveness of existing impression techniques in securing firm seats for abutment castings, accurate border extension of the denture base, and loading of the ridge mucosa has been evaluated.A technique has been described that overcomes the limitations of existing impression techniques for semiprecision and precision distal-extension removable partial dentures.     

The mandibular first premolar as an abutment for distal-extension removable partial dentures: a modified clasp assembly design

Sound mandibular first premolars can be used as sole abutments for bilateral distal-extension removable partial dentures, if the denture is designed to minimise the torque applied to the abutment teeth. A simplified modification of the conventional torque-releasing clasp-assembly designs is suggested for these teeth. This modification entails a mesial rest on each abutment tooth connected to the distal proximal plate via a lingual bracing arm. A circumferential clasp arm is optional for buccal retention of the removable partial denture. As with conventional designs, the metal framework is designed to permit some rotational tissueward movement of the distal extension bases, yet not compromise the retention and stability of the prosthesis.     

A modified direct retainer design for distal-extension removable partial dentures

The rationale for designing a direct retainer for a distal-extension removable partial denture is described. The advantages of an L-bar clasp arm over the I-bar clasp arm are discussed. The retentive surface of an abutment tooth is divided into three zones according to the clasp tip movement and the importance of placing the retentive tip in the zone of vertical movement is emphasized.     

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.     

Stress distribution and abutment tooth mobility of distal-extension removable partial dentures with different retainers: an in vivo study

Three types of retainers (wrought wire clasp, Aker's cast clasp, and conical crown telescopic retainer) designed for distal-extension removable partial dentures (RPDs) were assessed in two Kennedy class I patients' mouths. The assessment, included the ratio of denture base shearing load and mobility of the terminal abutments when loaded on a free-end RPD occlusal surface. The mean values of denture base shearing ratios of wrought wire clasp, Aker's clasp and conical crown telescope were 60, 42 and 20%, respectively. The abutment mobility of the three types of retainers were all within the 'mobile ability area' except the wrought wire clasp for patient A's right side. The greatest tooth mobility was observed with the wrought wire clasps, followed by Aker's clasp and the conical crown telescopic retainer. From the analysis the following was concluded: (i) different retainers do influence the occlusal load distribution; (ii) the occlusal load distributed to the free-end saddle is closely related to the connecting rigidity of the retainer; (iii) mucosal support has an indispensable role in sharing the occlusal load with various retainers, even the rigid telescopic retainer.     

Load transfer characteristics of unilateral distal extension removable partial dentures with polyacetal resin supporting components

Background:  To photoelastically examine load transfer by unilateral distal extension removable partial dentures with supporting and retentive components made of the lower stiffness polyacetal resins.
Methods:  A mandibular photoelastic model, with edentulous space distal to the right second premolar and missing the left first molar, was constructed to determine the load transmission characteristics of a unilateral distal extension base removable partial denture. Individual simulants were used for tooth structure, periodontal ligament, and alveolar bone. Three designs were fabricated: a major connector and clasps made from polyacetal resin, a metal framework as the major connector with polyacetal resin clasp and denture base, and a traditional metal framework I-bar removable partial denture. Simulated posterior bilateral and unilateral occlusal loads were applied to the removable partial dentures.
Results:  Under bilateral and left side unilateral loading, the highest stress was observed adjacent to the left side posterior teeth with the polyacetal removable partial denture. The lowest stress was seen with the traditional metal framework. Unilateral loads on the right edentulous region produced similar distributed stress under the denture base with all three designs but a somewhat higher intensity with the polyacetal framework.
Conclusions:  The polyacetal resin removable partial denture concentrated the highest stresses to the abutment and the bone. The traditional metal framework I-bar removable partial denture most equitably distributed force. The hybrid design that combined a metal framework and polyacetal clasp and denture base may be a viable alternative when aesthetics are of primary concern.     

Clasp design for extension-base removable partial dentures

A clasp design that can be employed for abutment teeth on extension-base removable partial dentures has been presented. The clasp, referred to as an R.P.I. clasp, minimizes tooth coverage and reduces stress on the abutment tooth.     

An intracoronal semiprecision retainer for removable partial dentures--the Thompson dowel

An intracoronal semiprecision retainer for removable partial dentures has been described. The advantages, disadvantages, and indications for use of the semiprecision retainer have been detailed and compared with those of other types of intracoronal retainers.The versatility of design, combined with retention, stressbreaking features, and an effective method of indirect retention, make this semiprecision retainer the one of choice for mesial- and distal-extension removable partial dentures.     

Design of removable partial dentures: a survey of dental laboratories in Greece

The aim of this study was to compare data on design and fabrication methods of removable partial dentures (RPDs) in two major cities in Greece. A questionnaire was sent to 150 randomly selected dental technicians. The participation rate was 79.3%. The anterior palatal strap, the lingual bar, and the Roach-type clasp arm designs were preferred. Half of the RPDs fabricated were retained using precision attachments. Differences between the two cities were observed in types of major maxillary connectors used, types of attachments and impression materials used, as well as the design of distal-extension RPDs. Postdoctoral education was found to have an impact on RPD fabrication. Despite the differences observed, design and fabrication of RPDs followed commonly used principles.     

Stress distribution of abutments and base displacement with precision attachment- and telescopic crown-retained removable partial dentures

Five types of removable partial dentures (two attachment dentures, two telescopic dentures and one clasp denture) were designed. The two attachment dentures were retained by the rigid-precision attachments with or without a stabilizing arm, and the two telescope dentures were retained with cone telescope crowns with or without cross-arch stabilization. The stresses acting on abutment teeth and denture bases and the movements of denture bases were investigated, and the influences of denture design were clarified. The stress acting on a terminal abutment tooth retained by a rigid-precision attachment or cone telescopic crown was larger than that acting on a terminal abutment tooth retained by a clasp. The attachment dentures tended to concentrate more stress at the terminal abutment tooth than did the telescopic dentures. The stress of denture base of an attachment denture and a telescopic denture was less than that of a clasp denture. There was no difference between the stresses of attachment and telescopic dentures. The displacement of the denture base tended to be less when the denture was designed with a rigid connection for the retainer and with cross-arch stabilization.     

RPI卡环的改良设计

描述了改良ＲＰＩ卡环的设计,并与传统的ＰＲＩ卡环相比较,改良ＲＰＩ卡固位尖端只需进入基牙颊面最远的较小倒凹则可获得听固位,而且更美观,同时也符合远中游离鞍基围绕近中Ｈｅ支托转下沉中,Ｉ杆固位尖端与基牙脱离接触原则。因此发言奶卡环可小或避免伟给基牙持力,量种适用远中淳离端可摘局部义齿的新型止环设计。     

Photoelastic analysis of pressure on teeth and bone supporting removable partial dentures

The direction and pattern of forces delivered to teeth, periodontal membrane, and bone supporting a removable partial denture can be demonstrated by reproducing the dental arch in a photoelastic plastic material. Occlusal forces delivered to tooth-supported and distal-extension removable partial dentures produced repeatable patterns in the supporting structures. Physiologic adjustment of the metal contacts against the teeth on distal-extension removable partial denture castings is necessary to minimize tipping and torquing movement.     

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...     

改良美学卡环可摘局部义齿修复远中游离缺失的临床疗效观察

目的 比较牙列末端游离缺失的RPI卡环组和改良美学卡环可摘局部义齿修复的临床效果.方法 选择84例远中游离缺失的患者,将其随机分为2组:第一组采用RPI卡环组修复,第二组采用改良美学卡环修复.分别于1、3、6个月后通过问卷调查的方式,比较2种修复方式的修复效果.结果 在咀嚼功能、固位稳定和食物嵌塞方面,二者差异无统计学意义,在美观和舒适方面,改良美学卡环明显优于RPI卡环组(P＜0.05).结论 改良美学卡环可摘局部义齿修复能提供更好的美学修复效果和舒适度,能更好地满足牙列末端游离缺失患者的需求.     

Comparison of vertical movement occurring during loading of distal-extension removable partial denture bases made by three impression techniques.

Although the altered-cast impression technique attains stability and controlled tissue support for distal-extension removable partial dentures, the procedure is time-consuming and technique-sensitive. This study clinically compared the vertical displacement of distal-extension removable partial dentures made from different impression techniques. The impressions studied were the altered-cast impression, an impression made from a border-molded custom tray, and a stock tray irreversible hydrocolloid impression that served as a control. A post hoc analysis, using a Tukey Q-test, exhibited significance (p less than 0.01) between the two impression techniques after intraoral loading was performed. Although statistically significant, the 0.19 mm difference between the impression techniques may or may not be clinically relevant. Additional research is required in this area.     

Impression procedures for semiprecision removable partial dentures

The concept for impressioning procedures for semiprecision removable partial dentures are reviewed. Techniques that are applicable to various situations are examined, and detailed coverage has been given to the advocated impression procedures for the distal-extension semiprecision removable partial denture.