Pressure distribution of implant-supported removable partial dentures with stress-breaking attachments

PurposeThis in vitro study investigated the pressure distribution of the implant-supported removable partial dentures (RPDs) with the stress-breaking attachments under the occlusal force.MethodsThe experimental model of bilateral missing premolars and molars was modified from a commercial simulation model. Five pressure sensors were embedded near the bilateral first molars, first premolars, and medio-lingual alveolar crest. Two implants were placed near the second molars, and they were connected to the denture base using the following conditions: complete separation between the denture base and implant with cover screws (CRPD), flexible connection with a stress-breaking ball (SBB) attachment, and rigid connection without stress breaking with healing caps (HC). The pressure at five different areas of the soft tissue and the displacement of the RPDs were simultaneously measured, loading up to 50 N. The coefficient of variation (CV) for each connection was calculated from all data of the pressure at five areas to evaluate the pressure distribution.ResultsThe pressure on medio-lingual alveolar crest and molars of the HC was less than SBB and CRPD. In contrast, the pressure on premolars of SBB was greater than for the HC and CRPD. The CV of SBB was less than that of HC and CRPD. Denture displacement of HC and SBB was less than for CRPD.ConclusionsWithin the in vitro limitations, precise denture settlements and pressure distribution under the denture base could be controlled using an SBB attachment. An SBB attachment might be able to protect the implant from harmful force.     

Effect of implant support on mandibular distal extension removable partial dentures: Relationship between denture supporting area and stress distribution

PurposeThis study explored the relationship between implant support and the denture-supporting area by comparing the stability of an implant-supported distal extension removable partial denture and a conventional distal extension removable partial denture.MethodsA model simulating a mandibular bilateral distal extension missing (#34–37 and #44–47) was fabricated using silicone impression material as soft tissue (2 mm thick) on an epoxy resin bone model. The denture base was reduced by 5 mm cutting part of both the retromolar pad and the lingual border. Loads of up to 5 kg were applied, and the pressure and displacement of the RPDs were simultaneously measured and analyzed using the Wilcoxon test (α < 0.05).ResultsThe pressure on the bilateral first molar and the middle areas of the implant-supported distal extension removable partial denture (ISRPD) was significantly less than on the conventional RPD (CRPD). As the supporting area of the denture base decreased, the pressure and the denture displacement of the CRPD were greater than for the ISRPD.ConclusionThis study indicated that implant placement at the distal edentulous ridge can prevent denture displacement of the distal extension bases, regardless of the supporting area of the denture base.     

Distal implants to modify the Kennedy classification of a removable partial denture: a clinical report

Dental implants or precision attachments can be used to resolve the bilateral distal extension removable partial denture (RPD) dilemma. This report describes the fabrication of a mandibular implant-supported chromium-cobalt RPD with a combination of bilateral single molar implants and metal ceramic crowns using the principles of the channel-shoulder-pin system. The maxillary arch was restored with splinted metal crowns and a conventional RPD retained by extracoronal precision attachments.     

Does the Presence of Anterior Mandibular Teeth Increase the Incidence of Denture Stomatitis?

Purpose : To compare the frequency of denture stomatitis (DS) under maxillary complete dentures (CDs) in patients with opposing mandibular distal extension removable partial dentures (RPDs) and CDs. Materials and Methods : Participants included 365 maxillary CD wearers (241 women, mean age 70.5 ± 13.2 years; 124 men, mean age 71.5 ± 10.4 years) from 7 rest homes in Istanbul. A total of 268 had mandibular CDs; 97 had mandibular distal extension RPDs. Two independent, calibrated examiners performed oral examinations. Presence of maxillary denture‐related stomatitis and the effect of risk factors on DS were evaluated and recorded. Results : The frequency of palatal DS (Newton I‐III) was 45.1% (n = 121) in the mandibular CD group and 49.5% (n = 48) in the mandibular distal extension RPD group, a statistically insignificant difference (p= 0.4). Factors significantly associated with palatal DS were maxillary denture age (p= 0.02), reduced occlusal vertical dimension (p= 0.04), and nocturnal denture wear (p= 0.03). Conclusion : In this study, DS beneath maxillary CDs did not differ between mandibular distal extension RPD and CD wearers. The presence of mandibular anterior teeth did not influence the occurrence of palatal DS.     

Clinical application of stress-breaking ball attachment for implant overdenture

PatientThe patient was a 62-year-old partially edentulous woman with missing bilateral premolars and molars in the mandibular jaw. The patient selected implant supported-removable partial denture rehabilitation. Implants were placed bilaterally at the distal extension of the denture base in order to minimize denture displacement. The stress-breaking ball (SBB) attachment consists of a flat-top ball head male and O-ring rubber female. The female was covered by a silicone housing with three amounts of space to allow three kinds of settlement (0.3 mm, 0.5 mm, and 0.7 mm); they were selected by thickness or pressure displacement of the mucosa and occlusal force. After the healing period, the SBB attachments (0.3 mm) were placed on the implants, and the implant-supported removable partial denture was then conventionally fabricated. The delivered denture had sufficient retention and appropriate stress breaking.DiscussionThe advantages of SBB attachments over conventional attachments are as follows: (1) they prevent the implant from excessive occlusal force, (2) they are ready-made, (3) they show appropriate retention, and (4) they can be easily mounted on the denture base. The disadvantages of these attachments are as follows: (1) they are approximately 1 mm higher than conventional ball attachments and (2) the retentive force cannot be adjusted.ConclusionThe use of a stress-breaking attachment for implant overdenture rehabilitation should be considered so that the occlusal force is equally distributed between the alveolar ridge and the implants.     

两种游离端半精密附着体可摘局部义齿的应力分析

目的:研究双侧游离缺失活动义齿使用两种不同类型的半精密附着体固位时周围支持骨的表面应力。方法:采用电阻应变测量法在人体下颌骨标本上测量以冠内栓道式及冠外垂直杆式半精密附着体固位的双侧游离缺失活动)固定联合修复体的表面应力值并做统计分析。结果:冠内附着体在基牙周围牙槽骨上产生的总体应力较大,而冠外附着体在缺牙区牙槽嵴和近缺隙侧基牙远中颈部牙槽嵴上产生的应力较大。结论:冠内附着体适用于远中基牙牙周条件良好的情况,而冠外附着体则适用于缺牙区牙槽嵴条件良好、远中基牙条件相对欠佳的情况。     

Three-dimensional finite element analysis of implant-assisted removable partial dentures

Statement of problem

Whether the implant abutment in implant-assisted removable partial dentures (IARPDs) functions as a natural removable partial denture (RPD) tooth abutment is unknown.

A survey of treatment outcomes with removable partial dentures

The patient's satisfaction with removable partial denture (RPD) therapy has become an increasingly important factor in prosthetic treatment. This study examined patients' satisfaction with RPDs in relation to some socio-economic variables, patients' habits of wearing and cleaning RPDs, comfort of wearing RPDs and different RPDs characteristics. A questionnaire was devised for the purpose. Two hundred and five patients were required to assess satisfaction with RPDs. They graded RPDs, depending on the level of satisfaction, on scale ranging from 1 to 5. A dentist determined Kennedy classification, material and denture support, denture base shape, number of missing teeth and evaluated denture construction. Majority of the patients were satisfied with the prosthesis. The patients of a higher education level gave lower grades (P < 0.05) to aesthetics of maxillary RPDs. Almost half of the patients were wearing RPDs during the day. Most of the patients cleaned RPDs three times a day. A significant difference was found between the patients' grades for comfort of wearing mandibular RPDs and number of missing teeth and between hygiene of mandibular RPDs and habits of cleaning them. Majority of the patients treated with RPDs were satisfied with the prosthesis. Dissatisfaction was related to mastication, esthetics, number of missing teeth and maintenance of oral hygiene.     

软衬材料对下颌全口义齿稳定性影响的三维有限元分析

目的分析下颌全口义齿软衬前后的义齿基托组织面位移情况,研究其对义齿稳定性的影响.方法采用三维有限元法,选择标准无牙下颌牙槽嵴模型为实验对象,分别建立有软衬和无软衬两个有限元模型.采用双侧后牙垂直加载,并对义齿基托组织面位移结果进行分析.结果有软衬基托组织面位移大于无软衬时义齿组织面位移(P＜0.01);无软衬时后牙区舌侧基托组织面与黏膜出现缝隙;软衬时义齿基托组织面位移波动变化大于无软衬时.结论软衬材料的应用有利于下颌全口义齿的稳定.     

Functional mobility measurement of removable partial dentures using newly-developed analyzing system in six degrees of freedom--effect of cusp inclination of molar artificial teeth on denture displacement in function]

A measuring system to record three-dimensional displacement of removable partial dentures (RPDs) in six degrees of freedom has been developed. The system employed three pairs of photodiode and LED that were set up in a triangle. This system was capable of recording the in vivo RPD displacement with a recording sensitivity of 0.1 mm. In vivo displacement of upper RPDs with unilateral distal extension saddle was investigated using this measuring system to determine the effect of artificial cusp inclination of molar teeth on denture mobility. Two groups of different artificial dentition were switched to be attached to each of three experimental RPDs. The artificial teeth with cusp inclinations were calibrated to contact with opposing natural dentition during lateral grinding of the mandible, while the other artificial teeth were prepared to disclude with the mandibular teeth (flat-cusp group). Displacement range and average position of a reference point at the first molar of the RPDs during mastication were measured and analyzed as a function of the cusp inclination and the test food. As a result, the average displacement of the RPDs toward the edentulous ridge was smaller in the cusp group than that in the flat-cusp group, while the range of horizontal displacement in the buccal-palatal direction was greater in the former group than the latter. The denture wearers demonstrated typical grinding strokes at the end of the closing phase of the mandiblar movements when they chewed a peanut, which was attributed to a wide range of horizontal displacement of the dentures.     

Influence of implant inclination associated with mandibular class I removable partial denture

The aim of this study was to use two-dimensional finite element method to evaluate the displacement and stress distribution transmitted by a distal extension removable partial denture (DERPD) associated with an implant placed at different inclinations (0, 5, 15, and 30 degrees) in the second molar region of the edentulous mandible ridge. Six hemimandibular models were created: model A, only with the presence of the natural tooth 33; model B, similar to model A, with the presence of a conventional DERPD replacing the missing teeth; model C, similar to the previous model, with a straight implant (0 degrees) in the distal region of the ridge, under the denture base; model D, similar to model C, with the implant angled at 5 degrees in the mesial direction; model E, similar to model C, with the implant angled at 15 degrees in the mesial direction; and model F, similar to ME, with the implant angled at 30 degrees in the mesial direction. The models were created with the use of the AutoCAD 2000 program (Autodesk, Inc, San Rafael, CA) and processed for finite element analysis by the ANSYS 8.0 program (Swanson Analysis Systems, Houston, PA). The force applied was vertical of 50 N on each cusp tip. The results showed that the introduction of the RPD overloaded the supporting structures of the RPD and that the introduction of the implant helped to relieve the stresses of the mucosa alveolar, cortical bone, and trabecular bone. The best stress distribution occurred in model D with the implant angled at 5 degrees. The use of an implant as a support decreased the displacement of alveolar mucosa for all inclinations simulated. The stress distribution transmitted by the DERPD to the supporting structures was improved by the use of straight or slightly inclined implants. According to the displacement analysis and von Mises stress, it could be expected that straight or slightly inclined implants do not represent biomechanical risks to use.     

The Effect of Removable Partial Dentures on Alveolar Bone Resorption: A Retrospective Study with Cone‐Beam Computed Tomography

Purpose: The aim of this study was to compare vertical and horizontal mandibular alveolar bone resorption by measuring bone morphological variation in Kennedy Class II removable partial denture (RPD) wearers and non‐wearers using cone‐beam computed tomography (CBCT). Materials and Methods: In total, 124 sites in the CBCT scans of 62 (29 RPD non‐wearers, 33 RPD wearers) Kennedy Class II patients were analyzed retrospectively. Three‐dimensional representations of the mandible with superimposed cross‐sectional slices were developed with the CBCT scans to evaluate the mandibular alveolar height and width by measuring distances between the mandibular canal, mylohyoid ridge, alveolar crest, and lower border of the mandible in four regions (eight sites) of Kennedy Class II non‐wearers and wearers of RPDs. Results: Mandibular alveolar bone height and width were significantly lower in edentulous sites when compared with dentate sites in both Kennedy Class II non‐wearers and wearers of RPDs (p < 0.05). Additionally, mean vertical and horizontal mandibular bone resorption was significantly higher in RPD wearers than in non‐wearers (p < 0.05). Conclusions: Vertical and horizontal alveolar bone resorption was found to be higher in the RPD wearing patients when comparing the dentate and edentulous sites.     

人工牙颊舌径对单侧游离端套筒冠义齿基牙位移的影响

目的：探讨不同的人工牙颊舌径对单侧游离端套筒冠义齿基牙位移的影响。方法：建立肯氏Ⅱ类塑料模型,制作套筒冠义齿,改变人工牙颊舌径,垂直加载29．4N、49N、68．6N力时,测量基牙位移值,通过计算求出各方向的位移、扭转量,最后进行统计分析。结果：与未减径时相比,人工牙颊舌向减径1／4后,2基牙水平扭转程度显著减小,差异有统计意义（P〈0．05）;减径1／3后,2基牙在各方向的位移、倾斜、扭转均显著减小,差异有统计意义伊〈0．05）。结论：单侧游离端套简冠义齿人工牙颊舌向减径1／3后,基牙的位移、倾斜,扭转程度明显减小,可增加义齿稳定性,有利于基牙牙周支持组织的健康。     

The management of a severely resorbed edentulous maxilla using a bone graft and a CAD/CAM-guided immediately loaded definitive implant prosthesis: a clinical report

Functional reconstruction of an occlusion with severe residual ridge resorption is a clinical challenge. Removable prostheses are unsuccessful in situations with severe bone resorption. A patient with an edentulous maxilla received bone grafts from the anterior iliac crest to augment the maxillary alveolar residual ridges. The maxilla underwent bilateral sinus lift in the posterior area and onlay bone graft on the anterior maxilla using platelet-rich plasma. Eight endosseous implants were placed using a CAD/CAM surgical template approximately 6 months after the bone augmentation procedure. A prefabricated definitive implant-supported fixed complete denture was connected immediately after implant placement using a CAD/CAM-guided surgical implant placement protocol.     

不同临床设计的ERA附着体义齿修复下颌牙列游离端缺损的三维有限元分析

目的:研究3种不同临床设计ERA附着体义齿修复下颌远中游离端缺损的应力及位移分布.方法:建立ERA附着体义齿修复下颌远中游离端缺损的三维有限元模型,根据临床设计分为基本组、支托组和跨弓组.应用有限元法研究在垂直及45°斜向2种载荷方向100 N的作用下,基牙及基托下黏膜的应力和位移以及基托的位移情况.结果:2种载荷下3组模型均在远中基牙远中邻面肩台出现应力集中,远中基牙预备体咬合面位移最大,支托组基牙位移最大,分别为14.91 μm和63.09μm,其次为基本组(9.38 μm和50.56μm),跨弓组最小(8.85 μm和47.31μnn).结论:在本研究条件下,为远中游离端牙列缺损设计基本的ERA附着体义齿更趋于合理.     

三维有限元法分析功能性印模全口义齿下颌牙槽黏膜的应力分布

目的:分析正中咬合接触时功能性印模法制取的下颌全口义齿基托下黏膜组织的应力分布和位移状况。方法:通过Mimics、Geomagic Studio和Unigraphics NX软件,将CT图像建立为下颌无牙颌骨、黏膜及解剖式和功能性印模全口义齿的三维有限元模型,用三维有限元法比较2种不同印模方法制作的全口义齿对基托下应力分布、黏膜位移的影响。结果:2种不同印模方法制作的下颌总义齿基托下黏膜等效应力由大至小排列为:后牙牙槽嵴顶区、前牙牙槽嵴顶区、外斜嵴区、内斜嵴区。在内斜嵴和牙槽嵴顶区,功能性印模全口义齿下黏膜承受的应力与Z向位移量小于解剖式印模全口义齿。结论:功能性印模全口义齿下颌基托下黏膜的应力分布较解剖印模全口义齿更均匀、广泛。     

Influence of the interimplant distance on crestal bone resorption and bone density: a histomorphometric study in dogs

BACKGROUND: The position of gingival soft tissues depends on the position and health of the underlying alveolar bone. The aim of this study was to evaluate the influence of different interimplant distances on crestal bone resorption after prosthetic restoration with a 5-mm distance between the contact point and the bone crest. METHODS: The mandibular bilateral premolars of six dogs were extracted and, after 12 weeks, each dog received eight implants, totaling 48 implants in the experiment. Two pairs, one in each hemiarch, were separated by 2 mm (group 1) and two by 3 mm (group 2). After 12 weeks, the implants received temporary acrylic prostheses. After 4 more weeks, metallic crowns substituted the temporary prostheses. After 4 more weeks, the animals were sacrificed, and their hemimandibles were removed, dissected, and processed. RESULTS: For groups 1 and 2, respectively, the mean of interimplant bone resorption (IIBR) analyzed histologically was 2.03 and 1.98 mm (P >or=0.05), and the mean of the distal extension bone resorption was 2.04 and 1.92 mm for groups 1 and 2, respectively (P >or=0.05). The crestal bone resorption between the implants was 0.13 mm (P >or=0.05) for both groups. The mean of IIBD for groups 1 and 2 was 79% and 80%, respectively. When the IIBD was compared to the distal extension bone density for group 1 (79% and 64%) and group 2 (80% and 62%), statistically significant differences were obtained for both groups (P 相似文献   

角度螺丝通道基台在上颌切牙种植修复的临床应用

目的:评估应用角度螺丝通道基台种植修复上颌切牙的临床效果。方法:临床选择2015年12月前使用角度螺丝通道基台行上颌切牙种植修复15例。随访6个月,观察方法为X线片、临床检查及患者满意度调查,分析其存留率、骨吸收情况、软组织及美学效果。结果:使用角度螺丝通道基台的上颌切牙种植义齿存留率为100%;种植体近远中牙槽骨吸收量为(0.447±0.121)、(0.355±0.127) mm,软组织状况良好; 93.3%患者对种植修复表示满意。结论:使用角度螺丝通道基台行上颌切牙种植修复是一种微创、简洁的种植治疗方案设计,有一定的临床推广价值。     

两侧非对称性下颌牙槽嵴形态对全口义齿稳定性影响的初步探讨

目的：初步探讨下颌两侧非对称性牙槽嵴形态对全口义齿稳定性的影响.方法：利用激光三维扫描仪取得下颌无牙颌标准模型牙槽嵴表面形态数据,通过计算机辅助工程（CAE）软件形成下颌全口义齿,标准形态牙槽嵴黏膜,以及4种左右形态非对称的牙槽嵴黏膜三维有限元模型：首先建立标准牙槽嵴（S）,其次按下颌牙槽骨不同部位吸收至S的1/4高度为条件,分别形成右侧磨牙区吸收（Rm）,右侧后牙区吸收（Rpm）,右侧牙槽骨吸收（Rapm）及左侧前牙区和右侧牙槽骨吸收（LaRapm）的黏膜模型.在S条件下义齿左右两侧咬合面的双尖牙区P,第一磨牙区M1及第二磨牙区M2等6个部位分别设定位于牙槽嵴顶及其颊侧的2个加载位置,共计12个加载点,单侧垂直加载9.8N的力,利用三维有限元分析各条件下义齿最大综合位移.结果：M1加载时各牙槽嵴条件下的义齿最大位移较P和M2加载时的小.各部位加载时LaRapm条件下义齿最大综合位移都较其他牙槽嵴条件下的大.左侧M2加载时的Rapm较Rm和Rpm的大,P加载及右侧M2加载时的Rm、Rpm、Rapm相近,且都大于S.结论：在单侧加载条件下,下颌两侧非对称性牙槽嵴前牙区高度影响全口义齿稳定性.     

Oral health status of patients 5-6 years after placement of cobalt-chromium removable partial dentures

This study is a clinical survey of cobalt-chromium (Co-Cr) removable partial denture (RPD) wearers that aimed to investigate the effects of denture wearing on oral tissues. A random sample of patients who had received their dentures 5-6 years previously from a dental teaching hospital in Hong Kong was selected. Those who had been constantly wearing the RPDs were examined by one calibrated examiner under an optimal clinical setting. The patients' dental, periodontal and mucosal status were assessed. A total of 87 patients were examined. Mucosal lesions under the Co-Cr RPDs were uncommon in this study sample. However, there was a high prevalence of plaque, gingivitis and gingival recession, especially in dento-gingival surfaces in close proximity (within 3 mm) to the dentures. Thus, there is a special need for regular oral hygiene reinforcement, scaling and prophylaxis among RPD wearers. Despite a low caries incidence in the study sample, root caries were found to be associated with contact with the RPDs (P < 0.05) but coronal caries were not. It is recommended that coverage of the exposed root surfaces by RPD components should be avoided. Also, topical fluorides should be regularly applied onto exposed root surfaces as a preventive measure.