Retrospective investigation of the remaining teeth status of patients with implant-supported fixed partial dentures in unilateral free-end edentulism

PurposeThis study aimed to compare the various complication-free rates and survival rates of remaining teeth among implant-supported fixed dentures (IFDs), removable partial dentures (RPDs) and no-restoration (NR) patients with unilateral free-end edentulism.Material and methodsThe study subjects were selected among those who received prosthodontic treatment at Okayama University Dental Hospital for their unilateral free-end edentulism (2 or 3 missing teeth). Thirty-three patients were included in the IFD group, 41 matched patients in the RPD group, and 10 patients who received RPDs but refused their use were regarded as NR group. The remaining dentition was classified into five subcategories in relation to the missing portion: adjacent teeth to the missing portion (AD), contralateral posterior dentition in the same jaw (CS) and in the opposite jaw (CO), ipsilateral opposing posterior dentition (IO), and anterior dentition (AN). Complications were defined as tooth extraction, periodontal lesions, periapical lesions or loss of retention of the prosthesis and were assessed by one examiner based on the hospital chart records.ResultsThe cumulative complication-free rates in the remaining teeth were significantly different among each of the three groups (p < 0.01), with a significantly lower incidence rate in the IFD group. Regarding the cumulative survival rate of the remaining teeth, there was a significant difference only between IFD and NR group (p = 0.01), especially in the CO region (p = 0.04).ConclusionsStable posterior occlusal support obtained with IFD treatment for unilateral free-end edentulism may reduce the incidence of complications in the remaining teeth, by decreasing the adverse mechanical stress.     

Multifactorial risk assessment for survival of abutments of removable partial dentures based on practice-based longitudinal study

Objectives

Predicting the tooth survival is such a great challenge for evidence-based dentistry. To prevent further tooth loss of partially edentulous patients, estimation of individualized risk and benefit for each residual tooth is important to the clinical decision-making. While there are several reports indicating a risk of losing the abutment teeth of RPDs, there are no existing reports exploring the cause of abutment loss by multifactorial analysis. The aim of this practice-based longitudinal study was to determine the prognostic factors affecting the survival period of RPD abutments using a multifactorial risk assessment.

Methods

One hundred and forty-seven patients had been previously provided with a total of 236 new RPDs at the Osaka University Dental Hospital; the 856 abutments for these RPDs were analyzed. Survival of abutment teeth was estimated using the Kaplan–Meier method. Multivariate analysis was conducted by Cox's proportional hazard modelling.

Results

The 5-year survival rates were 86.6% for direct abutments and 93.1% for indirect abutments, compared with 95.8% survival in non-abutment teeth. The multivariate analysis showed that abutment survival was significantly associated with crown-root ratio (hazard ratio (HR): 3.13), root canal treatment (HR: 2.93), pocket depth (HR: 2.51), type of abutments (HR: 2.19) and occlusal support (HR: 1.90).

Conclusion

From this practice-based longitudinal study, we concluded that RPD abutment teeth are more likely to be lost than other residual teeth. From the multifactorial risk factor assessment, several prognostic factors, such as occlusal support, crown-root ratio, root canal treatment, and pocket depth were suggested.

Clinical significance

These results could be used to estimate the individualized risk for the residual teeth, to predict the prognosis of RPD abutments and to facilitate an evidence-based clinical decision making.     

Microbiological risk for periodontitis of abutment teeth in patients with removable partial dentures

Summary  Tannerella forsythia , Porphyromonas gingivalis and Treponema denticola are identified as the red complex which exists in high proportions in periodontally diseased patients. The aim of this study was to assess the microbiological risk for periodontitis of abutment teeth in subjects wearing removable partial dentures (RPDs) by measuring the red complex using BANA-ZymeTM test. Thirty-eight subjects (mean age: 62·2 years) with Kennedy Class II partially edentulous arch participated in this study. The red complex and clinical parameters, such as plaque index, gingival index, probing depth and tooth mobility were recorded at abutment teeth in contact with the direct retainer of unilaterally designed RPDs and the corresponding non-abutment teeth on the opposite side. Mean scores for the red complex, plaque index, gingival index and tooth mobility of the abutment teeth were significantly greater than those of the non-abutment teeth ( P  < 0·01). No significant mean difference in pocket depth was found between the abutment and non-abutment teeth. Logistic regression analysis revealed that abutment teeth, high scores of plaque index and a maintenance interval longer than 6 months were significant predictors for positive red complex scores ( P  < 0·05). These results suggest that the microbiological risk for periodontitis of abutment teeth is greater than that for non-abutment teeth in RPD wearers.     

Comparisons of tactile thresholds between implant-supported fixed partial dentures and removable partial dentures.

This study compared the tactile sensitivity of splinted abutment and denture teeth of 16 fixed partial dentures (FPD) supported by blade implants and 16 removable partial dentures (RPD) in patients with Kennedy Class I and Class II edentulous conditions. No significant differences were noted between the tactile thresholds of the natural abutment teeth and artificial teeth in the FPD and RPD groups. The splinted abutment teeth required 45.4 g, or 5.4 to 5.8 times higher occlusal loads than did those needed for the comparable nonsplinted teeth, to detect the stimulus. A further increase of 54% in thresholds with the FPD and over 100% with the placement of the RPD indicated the superiority of the RPD in terms of load distribution as a result of the cross-arch splinting and mucosal support. Moderate positive correlations (r = 0.37 to 0.46; P < .05) between tactile thresholds and masticatory performance were found, signifying that reduced tactile perception was not responsible for the incomplete restoration of the masticatory function with RPDs or FPDs but might be contributing to increased masticatory performance within both treatment groups.     

Prevalence of temporomandibular disorder signs in patients with complete versus partial dentures

Objectives: To determine the prevalence of signs of a temporomandibular disorder (TMD) in completely edentulous patients wearing upper and lower complete dentures (CD) and to compare this to the prevalence of signs in partially edentulous patients wearing upper and lower clasp-retained acrylic removable partial dentures (RPD). Materials and methods: A questionnaire and a clinical examination were used to assess 200 patients. One hundred of these were complete denture wearers being treated for the provision of replacement CD. The other 100 patients were partially edentulous patients, who had RPD replacing upper and lower partially missing teeth and their supporting structures. Results: It was shown that there was a statistically significant difference between the two groups regarding the presence of temporomandibular signs. Partially edentulous patients wearing upper and lower RPD had a significantly higher prevalence of TMD signs than edentulous patients wearing CD (36% compared to 17%). They also exhibited significantly (P<0.04) more signs of joint tenderness (18%) on clinical examination compared to (5%) only in the CD-wearing patients. Tenderness upon palpation in the periauricular region was the most common site reported in both groups. Conclusions: The partially edentulous patients (wearing RPD) exhibited more TMD signs when compared with the CD-wearing patients. Significantly, more partially edentulous patients had joint tenderness (P<0.04) than did CD-wearing patients. The masseter muscle most commonly demonstrated muscle tenderness.     

Technical failure rates of double crown-retained removable partial dentures

Removable partial dentures (RPD) can be retained using conical crowns or parallel-sided telescopic double crowns. The purpose of this study was to evaluate and compare the technical failure rate of the two retainer systems. One hundred seventeen dentures made by dentists of the medical school were included. Seventy-four RPD were retained with parallel-sided crowns (n=251) and 43 with conical crowns (n=160). Following the medical report follow-ups from January 1992 to December 1998, technical RPD failures were noted and analyzed. Technical problems occurred during the observation time in 48.8% of the conical retained dentures and 34.2% of the parallel-sided retained dentures. In both cases, loss of cementation was most frequently noted, while loss of the facings occurred only with conical crowns. Other technical failures did not depend on the type of retainer system used. These were most frequently problems with the denture base, e.g., fracture of artificial teeth or the metal framework. We conclude that there were different technical failures of both double crown retainer systems. These problems were not insignificant in number but treatable. Received: 14 December 1999 / Accepted: 19 January 2000     

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.     

Effect of complete and partial removable dentures on chewing movements

Partial or complete edentulism impairs mastication. However, it is unclear how the chewing cycle is affected by prosthetics. We evaluated the chewing movements of patients fitted with complete (CD) or removable partial denture (RPD). A total of 29 subjects were kinesiographically evaluated during chewing of peanuts and Optocal portions in a random sequence. The subjects were divided into two groups according to prosthesis type. Group RPD was composed of 14 partially edentulous patients using a lower distal extension RPD (mean age 61 ± 8 years), and group CD contained 15 completely edentulous patients using CD (mean age 65·9 ± 7·9 years) in both jaws. Opening, closing, occlusal and masticatory cycle times, movement angle (opening and closing), maximum velocity (opening and closing), total area and chewing cycle amplitudes were evaluated. The results were subjected to anova and Tukey's HSD test at a significance level of 5%. The RPD group exhibited shorter opening and closing phases and masticatory cycle time (P < 0·05). Maximum velocities were also higher in the RPD group, irrespective of the test material (P < 0·05). The area and amplitude of the chewing envelope was smaller in the CD group (P < 0·0001). The test material did not influence chewing cycles in any of the parameters evaluated (P > 0·05). RPD wearers use a faster chewing sequence with greater vertical and lateral jaw excursions compared with CD wearers.     

Removable partial denture design and its effect on remaining teeth, based on Hungarian national survey

Removable partial dentures (RPD) are used to restore Class 2A, 2B, 2A/1, and Class 3 type partially edentulous arches. Calibrated dentists of the Department of Prosthodontics performed oral health survey first in 1985-1989 and a second survey in 2003-2004. The oral surveys were carried out at the lung cancer screening stations, after obtaining formal consent of those individuals who were originally referred to perform x-ray lung screening examination. Subjects were interviewed and clinically examined under artificial lighting conditions. In the "second" survey data collected on 765 RPDs were analysed. Examined aspects of RPD design were: the protection of the marginal periodontium, extension of major connectors, base plate materials, tooth and tissue support. The level of restoration related damage on the remaining teeth was estimated according to whether remaining teeth were used for retention or for support; had any other type of denture-contact or remaining teeth were free from contact with denture. Approximately 50% of dentures showed dento-mucosal or muco-dental support; metal base was present in 45-48% of dentures; 47% of major connectors were designed with reduced extension; freedom of gingival margin was assured in 43-45% of the dentures. 26.10% of reference teeth; 19.11% of the remaining teeth used for support; 31.53% of the teeth used for retention; 28.07% of the teeth free from contact with denture and 38.00% of those remaining teeth with any other type of denture contact showed a sign of damage. Findings of the authors' survey show a considerable improvement in all aspects of RPD design--but still further progression is required. Those principles of RPD design taught in dental schools can only gradually influence the routine daily dental practice. Assessment of remaining teeth damages confirm the standards we outlined for RPD design with the main priorities of dental support and the protection of the gingival margin.     

A 5-year longitudinal study of cantilevered fixed partial dentures compared with removable partial dentures in a geriatric population

Prosthesis function and dental conditions were observed for 5 years in 27 elderly patients treated with mandibular cantilevered fixed partial dentures (FPDs) and in 26 elderly patients treated with distal-extension removal partial dentures (RPDs). All patients were treated with a complete upper denture. The patients were assigned randomly into two treatment groups that had the same composition with regard to sex, age, and distribution of teeth. The patients were under supervised oral hygiene and prosthodontic care. Clinical examination of prostheses, masticatory system, periodontal status, and caries was carried out yearly. Oral hygiene was good, and the periodontal status was maintained in both groups. Caries was observed six times more frequently in the RPD group than in the group with fixed restorations, however. Occlusal and functional conditions deteriorated in the RPD group only. Eight of 42 fixed partial dentures (19%) failed; of these, six were recemented with composite resin. Generally the need for dental and prosthetic follow-up treatment was more pronounced in the RPD group than in the FPD group.     

Treatment with removable partial dentures: a longitudinal study. Part II

The aim of this study was to evaluate the effectiveness of an oral rehabilitation by removable partial denture (RPD). Between 1983 and 1994, 629 patients were provided with an RPD at the Dental School of the Université catholique de Louvain. All the RPDs were constructed with a cobalt-chromium framework. All the treatments were provided by dental students under the supervision of clinical instructors. At recall time (1998-2000), 269 patients could not be reached neither by telephone nor by mail and 27 had died. Consequently, 333 patients were called for clinical examination and 254 of these (76.3%) actually attended. For a total of 292 RPDs checked 1893 persistent teeth were listed, with 804 serving as abutments; more than half (57.6%) of these were crowned, for which 51 debondings were recorded. For the period of observation we listed 79 abutments lost (37 at the upper jaw and 42 at the lower jaw), i.e. 9.8% of the total number of abutments. No relation could be established between the type of the abutments (natural or crowned teeth) and the losses observed (Test of Mantel-Haenszel: P=0.9496). In the upper jaw, the percentage of abutments lost was significantly higher in the presence of free-end edentulous areas as compared with bounded edentulous areas (Test of Mantel-Haenszel: P=0.0002); this difference does not appear for the lower jaws (P=0.9558). If we deduct the 25 abutments related with the 11 non-worn RPDs and the 79 abutments lost, no change becomes apparent for 92.2% of the maxillary abutments and for 85.8% of the mandibular abutments. For the 1089 other teeth, we observed the loss of 40 teeth and the appearance of caries or new fillings for 95 teeth. The fractures of cast clasps represent 3.4%.     

Effect of implant support on distal extension removable partial dentures: in vitro assessment

The implants in implant-supported removable partial dentures (RPDs) are placed in the edentulous ridge to stabilize the RPD and minimize the resultant rotational movement. This study investigated the effect of implant placement on RPD stability. A model simulating a mandibular bilateral distal extension missing was fabricated using epoxy resin and silicone impression material as thin (1 mm) and thick (2 mm) soft tissues. Five pressure sensors (PS-10K, Kyowa, Tokyo, Japan) were attached near the left and right first molars (#36 and #46), first premolars (#34 and #44) and medio-lingual alveolar crest. Five bilateral distal extension RPDs with Co-Cr frameworks were conventionally fabricated. After the implants were placed at the bilateral second molar areas, healing caps (4.5 mm high) were connected to the denture base with autopolymerized resin to support the RPD. As in a conventional RPD, sealing screws were placed without connecting them. Loads up to 5 kg were applied, and the pressure and displacement of the RPDs (n = 5) were simultaneously measured and analysed using the Wilcoxen test (alpha = 0.05). There was less pressure on both thin and thick soft tissues, the #36, #46 and the medio-lingual alveolar crest from the implant-supported RPD than from the conventional RPD (P < 0.05). There were no significant differences in pressure on #34 and #44 between the two RPDs (P > 0.05). There was significantly less denture displacement of the implant-supported RPD than of the conventional denture (P < 0.05). Implant support helped prevent the displacement of distal extension RPDs and decreased the pressure on soft tissues.     

Fit of direct retainers in removable partial dentures after 8 years of use

summary In a cross-sectional study the fit of direct retainers was assessed after 8 years of use. A total of 101 metal frame removable partial dentures (RPD) were investigated, including 54 extension base prostheses without any tooth supported replacement and 47 tooth supported prostheses that replaced only premolars and molars. Of the frameworks studied, about 60% of the clasps showed a space between retainers and abutments. Logistic regression analyses demonstrated that the age of the RPD and the type of opposing dentition significantly influenced the fit of the clasps. The relative risks and a backward regression analysis revealed that the variable non-rigid extention base RPD had the greatest influence on clasp fit. It was concluded that in extension base RPDs a rigid design should be preferred.     

弹性义齿与传统可摘局部义齿对牙周情况影响的比较

目的比较弹性义齿与传统可摘局部义齿对牙周组织健康的影响。方法选择12例牙列缺损病人。每例受试者同时制作一件铸造卡环活动桥修复体和一件弹性义齿。先后戴用两种义齿，对基牙临床检查和龈下茵斑检查。结果戴用铸造卡环活动桥后PLI高于戴用弹性义齿后。戴用弹性义齿后BI及龈下菌宽螺旋体比例略高于戴用铸造卡环活动桥后。其他指标两者无差别。结论弹性义齿卡环设计时应尽量减少覆盖牙龈的面积，避免卡环边缘终止于龈缘处。     

Comparison of mandibular bone density and radiomorphometric indices in wearers of complete or removable partial dentures

Objectives To examine bone mineral density (BMD) and linear radiomorphometric parameters of the mandible in elderly patients with different types of dentures. Methods Patients had mandibular complete dentures (CDs) or Kennedy Class I removable partial dentures (RPDs) in the mandible; all patients had CDs in the maxilla. The age and sex distributions of patients with CDs and of those with RPDs were not significantly different. Three parameters were measured in dental panoramic radiographs (DPRs) from a total of 136 patients: thicknesses of the mandibular cortex below the mental foramen, the antegonion, and the gonion. Mandibular BMD was measured densitometrically using DPRs and a copper step wedge. All BMD values were expressed relative to the step wedge thickness. Results There was a significant difference between patients with CDs and those with RPDs for all the radiomorphometric indices measured (P < 0.001); specifically, radiomorphometric indices were higher in RPD wearers. Mandibular BMD values in RPD wearers were higher than those of patients with CDs, and BMD was significantly higher under the saddle in RPD wearers (P < 0.05). Conclusions These results support the hypothesis that occlusal forces that are transmitted directly to the mucosa beneath mucosa-borne dentures may cause overloading, which may cause bone resorption; by contrast, under tooth and mucosa-borne dentures, occlusal forces are transmitted not only to mucosa but also to the periodontal ligament of the abutment teeth, thereby reducing the transmission of force to the mucosa, which prevents overload. Greater chewing forces might thus be achieved with tooth and mucosa-borne dentures, which may stimulate bone growth at the mandibular cortex.     

Use of dental implants to improve unfavorable removable partial denture design

This study aimed to determine whether the use of a limited number of dental implants, with no rigid connection between implants and teeth and as few as possible prosthetic element requirements, is a viable solution for improving unfavorable removable partial dentures (RPD) design. Fifteen partially edentulous patients with an unfavorable number and distribution of abutment teeth were treated, each with a limited number of implants, from 1997 to 2004, resulting in an improved RPD design. Implant survival rate was 100%, and prosthetic complications were minor. All patients reported great satisfaction with the partial dentures and good chewing efficiency. The results indicate that the use of dental implants to improve unfavorable RPD design is a viable and cost-effective treatment modality.     

义齿大基板对口腔黏膜微循环的影响

目的:研究义齿大基板对口腔黏膜微循环的影响.方法:对22例牙缺失行义齿大基板修复的患者,分别在修复前、修复后7天及修复后4周,对义齿修复区的牙槽嵴的黏膜微循环血流量进行检测.结果:同义齿修复前相比,修复后短时间内大基板覆盖区牙槽嵴顶黏膜的微循环血流量明显下降,而唇侧黏膜的微循环血流量则明显升高.随着修复时间的延长,上述修复区域黏膜的微循环血流量都逐渐恢复,到修复后4周时已基本恢复正常.结论:义齿大基板修复对牙槽嵴黏膜微循环的影响是应激性的,并可以恢复.     

老年人可摘局部义齿折裂的设计因素

目的：分析老年人可摘局部义齿折裂的设计因素，旨在提高可摘局部义齿的设计水平和质量。方法：通过对临床上216例老年人可摘局部义齿折裂病例的观察，根据王征寿分类法归纳各类义齿折裂的常见类型，分析其中的薄弱环节和设计因素。结果：一类义齿咬合低时易发牛近远中向折裂；二类义齿咬合紧时常在游离端远中发生近远中向折裂，尤以上颌结节和磨牙后垫部位多见；三类和五类义齿的舌腭侧基托常在两个缺牙区之间尤其是靠近缺牙区的部位发牛与牙弓相交叉的折裂；四类义齿常发牛人工牙脱落或腭侧基托横折；人类义齿舌腭侧基托易发生纵折，折裂线常位于人工牙与基牙交界处。以上可摘局部义齿折裂的发生部有其设计与制作上的原冈，作者对此提出了相应的对策。结论：应特别注重义齿的抗折设计，这是提高可摘局部义齿修复质量的重要环节。     

The effect of removable partial dentures on the oral function in shortened dental arches*

In this study the effect of free-end removable partial dentures (RPD) on oral function was investigated by comparing subjects with shortened dental arches (SDA, n=55) and a group of subjects with SDA and RPD (n=25). In addition, a group of subjects were selected who had worn an RPD in the past (n=19). All subjects had a remaining natural dentition consisting of an intact front region and three to five occlusal units (OU) in the posterior area. On the whole, subjects with RPD had less natural OU compared with subjects without RPD. However, this is also true for those who had worn an RPD in the past. The oral functions of subjects with SDA did not differ significantly when compared with subjects with SDA and RPD. Significantly more subjects who had an RPD in the past reported a limited mobility of the mandible, an impaired chewing capacity and chewing with the front teeth. They also reported more aesthetic complaints due to missing posterior teeth. It is concluded that within the populations investigated in this study oral function is not evidently improved by the insertion of a free-end RPD.