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.     

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

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 fitted for these 254 patients, 218 (74.7%) were still being worn at the time of the check-up. Seventy-four dentures were considered to be 'failures', either because they were replaced by another RPD or by a complete denture, or because they had actually never been worn. The statistical analysis (Mantel-Haenszel and Kaplan-Meier) shows that the number of failures is significantly higher at the lower jaw compared with the upper jaw. Most of the failures are attributable to RPDs with free-end saddles and, in particular, to class I mandibular dentures. The patients are wearing their denture(s) mostly continuously (63.6%) and award a high degree of satisfaction to their denture. In general, the results recorded may be considered as very satisfactory, all the more so as we have no regular recall procedures established at our school and as check-up asked for spontaneously by the patients in the course of the period of observation are most of the time occasional or non-existent.     

Shortened dental arches and periodontal support.

The periodontal support of subjects with shortened dental arches (SDA, n = 74), and of subjects with SDA and free-end removable partial dentures in the lower jaw (SDA and RPD, n = 25) was compared with that of subjects with complete dental arches (CDA, n = 72). The periodontal support was determined by tooth mobility and alveolar bone height, measured on a radiograph, of the distal alveolar bone of the premolars. Significant differences in tooth mobility were found between the three groups of subjects. The relative bone height showed a trend towards lower values for the SDA group and the SDA and RPD group. For some teeth these differences were significant. Premolars that are the most posteriorly located occluding teeth in the dental arch tend to have a lower relative alveolar bone height than premolars in an intermediate location. This effect is more marked in the upper jaw than in the lower jaw. Premolars in the lower jaw, that serve as abutment teeth for free-end RPDs, tend to show lower values for the relative bone height. It is concluded that the differences between the three groups with regard to the periodontal support are small. The large amount of crowns and bridges in both the SDA and SDA and RPD groups, and the dental history of these subjects, resulting in SDA, should be taken into account. However, as indicated by the periodontal breakdown of premolars in some subjects with SDA, the combination of an existing severe periodontal involvement and a SDA is considered to be an unfavourable situation.     

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.     

A retrospective comparative ten-year study of cumulative survival rates of remaining teeth in large edentulism treated with implant-supported fixed partial dentures or removable partial dentures

PurposeThis study aimed to compare the survival rates of remaining teeth between implant-supported fixed dentures (IFDs) and removable partial dentures (RPDs) in patients with large edentulous cases. The second goal was to assess the risk factors for remaining tooth loss.Materials and methodsThe study subjects were selected among those who received prosthodontic treatment at Okayama University Dental Hospital for their edentulous space exceeding at least four continuous missing teeth. Twenty-one patients were included in the IFD group and 82 patients were included in the RPD group. Survival rates of remaining teeth were calculated in three subcategories: (1) whole remaining teeth, (2) adjacent teeth to intended edentulous space, and (3) opposing teeth to intended edentulous space.ResultsThe ten-year cumulative survival rate of the whole remaining teeth was significantly higher in the IFD group (40.0%) than in the RPD group (24.4%). On the other hand, there was no significant difference between two groups in the survival rate of teeth adjacent or opposing to intended edentulous space. A Cox proportional hazard analysis revealed that RPD restoration and gender (male) were the significant risk factors for remaining tooth loss (whole remaining teeth).ConclusionsThese results suggest that IFD treatment can reduce the incidence of remaining tooth loss in large edentulous cases.     

Dual Path: A Concept to Improve the Esthetic Replacement of Missing Anterior Teeth with a Removable Partial Denture

The dual path of insertion concept for removable partial denture (RPD) design may be used in esthetically demanding situations. When compared to conventional RPDs, the main advantage of this design is the minimal use of clasps. This clinical report describes the treatment of a patient with an anterior maxillary edentulous area using a dual path RPD. The diagnostic cast was surveyed to ensure the adequacy of the undercuts on the mesial surfaces of the anterior abutments, where rigid minor connectors were placed. Inverted V‐shaped canine cingulum rest seats were prepared to provide resistance to tooth movement during function. The dual path RPD concept allows excellent esthetic results, minimizes tooth preparation, and reduces the tendency toward plaque accumulation in a Kennedy class IV partially edentulous arch.     

Wearing of removable partial dentures in relation to dental caries

Using a representative sample of 5028 dentulous Finnish adults the occurrence of dental caries was studied among removable partial denture (RPD) wearers and non-wearers. Of the subjects wearing no RPD(s) 61.4% had one or more carious teeth, among those wearing a single RPD the figure was 60.5% and among those wearing RPDs in both jaws 62.7%, respectively. When sociodemographic background, other oral status measures than caries and oral health care habits were simultaneously controlled, subjects wearing RPDs in both jaws had slightly increased (P less than 0.05) probability of having one or more carious teeth compared to those with no RPD(s). Subjects with a single RPD did not have a statistically significantly increased probability of having carious teeth. Among those 3075 subjects who had one or more carious teeth the wearing of one or two RPDs did not significantly increase the number of carious teeth. Because the subjects wearing RPDs in both jaws were seen to have a slightly increased risk of having caries, this confirms the view that dentists should emphasize good oral hygiene habits and regular dental attendance among RPD wearers.     

弹性树脂与铸造支架在义齿修复中的应用(附28例报告)

目的设计一种联合义齿以解决传统可摘局部义齿易显露金属卡环影响美观的问题.方法用弹性树脂制作可摘局部义齿的基托及唇侧固位体,结合铸造支架,制作联合可摘局部义齿,修复28例因多数后牙缺失或前后牙均有缺失须在前牙区设计固位体的病例,行联合义齿修复.结果联合可摘局部义齿具有良好的美观效果及咀嚼功能.结论联合可摘局部义齿兼有弹性树脂和铸造支架的优点,可作为临床上选用的一种修复体.     

Survival rate of endodontically treated teeth with posts after prosthetic restoration

The purpose of this retrospective clinical study was to evaluate the survival rate of teeth that were endodontically treated and restored with endodontic posts and prosthodontic restorations. A total of 864 teeth in 360 patients were included in the study. Dental records and radiographs of the patients were evaluated and four parameters were documented. The parameters were type of post, type of prosthodontic restoration, observation time, and, in cases of failure, failure mode. Statistical survival analyses were performed according to Kaplan-Meier. The mean observation time was 22.5 +/- 14.9 months. The calculated survival rates of the abutments were statistically significant different for fixed partial dentures (FPDs) and for removable partial dentures (RPDs) with survival rates of 92.7% and 51.0% after 60 months, respectively. Most of the presumed factors influencing the survival rate of endodontically treated abutment teeth only affected the outcome in the RPD group. Teeth restored with post and cores present a high risk for failure when used as abutments for conical-double-crown-retained RPDs.     

不同固位形式可摘局部义齿对支持组织应力分布的研究

目的:探讨附着体义齿与常见可摘局部义齿修复单侧游离端缺失对支持组织应力分布的影响.方法:分别以磁性附着体、RPI卡环组、联合卡环组三种固位形式的可摘局部义齿修复下颌单侧游离端缺失,用三维光弹应力冻结切片技术测试义齿加载后对基牙和缺牙区牙槽骨应力分布,并与基牙不戴义齿时载荷下的应力比较.结果:磁性附着体对54|基牙和缺牙区的牙槽骨应力稍大于RPI,只占54|基牙应力的48%,且对基牙近、远中应力基本相等;联合卡环对基牙牙槽骨应力最小,对缺牙区牙槽骨应力最大.结论:磁性附着体义齿修复单侧游离端缺失能够达到RPI义齿功能效果,特别适合于对美观和舒适要求较高者,不主张使用仅靠单侧固位的联合卡环组义齿.     

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.     

Novel fully digital workflow for removable partial denture fabrication

PurposeThis technical procedure report introduces a newly developed method for removable partial denture (RPD) fabrication using computer-aided design and computer-aided manufacturing (CAD/CAM) and rapid prototyping (RP) technologies.MethodsFull-arch digital impressions of the partially edentulous jaw were made by an IOS or the conventional method. The denture framework, artificial teeth, and denture base were designed by commercially available CAD software. Each of the denture components including connectors, clasps, and artificial teeth and the denture bases were fabricated separately by the CAM machine or the three-dimensional (3D) printer, and then assembled using an adhesive material.ConclusionsRPDs were successfully fabricated using fully digital workflow and delivered to the patient, and no clinical complications were reported. Within the limitations of this report, the newly developed RPD fabrication techniques have the potential to change clinical and laboratory workflow from analog to digital.     

Rotational path removable partial denture (RPD): conservative esthetic treatment option for the edentulous mandibular anterior region: a case report

It can be esthetically and financially daunting for patients to lose teeth in an anterior region of the mouth. For these patients, traditional treatment options presented in the past have included fixed partial denture, implants, and conventional removable partial denture (RPD). For patients faced with financial, anatomical, and/or esthetic limitations, the edentulous region can be restored successfully with a rotational path RPD. Rotational path RPD designs have often been overlooked by the dental profession due to its complex concepts involving the prosthetic design and sensitive laboratory techniques. With better understanding of the concepts and design, the dental clinician can deliver the highest esthetic outcome in compromised areas in which other treatment options may often face limitations. This paper reviews the method used to esthetically design and plan a posterior-anterior rotational path RPD in an edentulous mandibular anterior region for a patient missing the mandibular incisors. CLINICAL SIGNIFICANCE: Due to inadequate understanding of the mechanics of rotational path RPDs, many clinicians have not adapted the application of this advantageous prosthesis. When correctly designed and fabricated, the rotational path RPD provides improved esthetics, cleanliness, and retention for patients who may not be suitable candidates for implants or fixed partial dentures in tooth-supported edentulous regions.     

Oral comfort in shortened dental arches

In this study, the oral comfort was compared between subjects with shortened dental arches (SDA, n = 74), subjects with SDA and free-end removable partial dentures (SDA + RPD, n = 25) and subjects with complete dental arches (CDA, n = 72). Oral comfort was measured by (i) absence of pain or distress; (ii) chewing ability; (iii) appreciation of the appearance of the dentition. Additionally, the history of free-end RPD over a period of nearly 7 years was taken into consideration. On the whole, the results did not reveal any significant differences between the three groups with respect to pain or distress. Only 8% of the subjects with SDA reported impairment of chewing ability, and 11% had aesthetic complaints, due to missing posterior teeth in the upper jaw. Of the subjects with SDA + RPD, 20% had complaints about the RPD. In addition, the repeated necessity for repair or replacement of free-end RPD and the fact that some subjects (20%) stopped wearing the RPD during the observation period, confirm the poor performance of this dental provision. It is concluded that the oral comfort of subjects with SDA in this study is compromised to a small extent but remains on an acceptable level. Free-end RPDs do not appear to help oral comfort in these cases.     

A telescopic crown concept for the restoration of the partially edentulous arch: the Marburg double crown system

PURPOSE: This article describes the concept of the Marburg double crown system (MDC system) in the treatment of partially edentulous patients. Long-term success is assessed by a review of patient records. MATERIALS AND METHODS: Double crowns with clearance fit are used to retain tooth-, mucosa-, and implant-supported removable partial dentures (RPD). To achieve retention, an additional attachment, the TC-SNAP system, is used. All metal components are fabricated in a single cobalt-chromium-molybdenum alloy; the framework (including outer crowns) is cast in one piece. Because of the framework's rigidity, the RPD can be constructed without major and minor connectors. The denture base adjacent to the abutments is fabricated using a perioprotective design that is similar to fixed partial dentures. One hundred eleven dentures, of which 49 (44%) were fabricated for patients with intraoral defects, were evaluated by reviewing patient records. RESULTS: The mean age of the patients at the time of insertion was 57.5 years (+/- 12.3). The mean number of double crowns per denture was 3.5 +/- 2.1 (range, 1 to 9). The probability that a patient will have lost all abutment teeth 10 years after insertion of the denture is 4%. The probability that a patient will have kept all teeth that abut the denture 5 years after insertion is 87%; 10 years after insertion the probability is 80%. CONCLUSION: The Marburg double crown system is a versatile and successful means of achieving the long-term restoration of the partially edentulous jaw. Insertion and removal of the denture and routine oral hygiene are easy to perform, even for patients with limited manual dexterity. As a full-arch reconstruction, the MDC system enables easy adjustment, modification, and relining with low follow-up costs.     

The effect of removable partial dentures on periodontal health of abutment and non-abutment teeth

BACKGROUND: A removable partial denture (RPD) is a common treatment available for restoration of partially edentulous ridges. Longitudinal studies indicate that RPDs have been associated with increased gingivitis, periodontitis, and abutment mobility. METHODS: A total of 205 patients with RPDs participated in this study. There were 80 males and 125 females aged 38 to 89, with 123 maxillary and 138 mandibular RPDs. Patients were wearing existing RPDs for different periods ranging from 1 to 10 years. A two-part questionnaire was devised for this study. In the first part, patients answered questions on gender; age; smoking habits; denture age; denture wearing habits; mouth odor; and problems with food accumulating under the denture base, on the outside surface of the denture, and on the outside surface of remaining teeth after eating. The Kennedy classification, material, denture support, denture base shape, and number of teeth in contact, number of existing clasps, and occlusal rests were categorized. The quality of denture construction was also evaluated. In the second part of the questionnaire, baseline recordings of plaque (PI), gingival (GI), and calculus (CI) indexes were made, and Tarbet index (TI), as well as probing depth (PD), gingival recession (GR), and tooth mobility (TM) were measured, both on abutment and non-abutment teeth. RESULTS: Significant differences (P <0.01) were noted for PI, Cl, GI, PD, TM, and GR between abutment and non-abutment teeth, with abutment teeth showing more disease. CONCLUSIONS: RPD design plays an important role in the state of the periodontium. Appropriate design and good oral hygiene may decrease the appearance of periodontal disease.     

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.     

Prevalence of apical periodontitis, crowned teeth and teeth with posts in a Swedish population

Abstract A longitudinal radiological study was carried out of 200 consecutive patients in a Swedish population. The aims of the investigation were to study the prevalences of crowned teeth, pontics and posts on two occasions with an interval of 5–7 years and, furthermore, to study apical periodontitis in connection with teeth with crowns and posts to see if such treatments affected this prevalence. 417 (mean 2.1) teeth were crowned at the first examination and 529 (mean 2.6) at the second. For pontics, the corresponding figures were 93 (mean 0.5) and 141 (mean 0.7). Crowns and pontics were more common in the upper jaw. 59.4% of the endodontically treated teeth had posts at the first examination and 64.4% at the second. 34.5% of the 255 teeth with apical periodontitis found at the first examination and 41.0% of the 268 at the second were in connection with posts. It was concluded that both crowns and pontics were common treatment procedures in the studied population. Crown therapy did not seem to impair the apical status while teeth with posts more often had apical periodontitis than other teeth and, furthermore, teeth with screw posts were lost more frequently than other teeth.     

Prevalence of apical periodontitis, crowned teeth and teeth with posts in a Swedish population.

A longitudinal radiological study was carried out of 200 consecutive patients in a Swedish population. The aims of the investigation were to study the prevalences of crowned teeth, pontics and posts on two occasions with an interval of 5-7 years and, furthermore, to study apical periodontitis in connection with teeth with crowns and posts to see if such treatments affected this prevalence. 417 (mean 2.1) teeth were crowned at the first examination and 529 (mean 2.6) at the second. For pontics, the corresponding figures were 93 (mean 0.5) and 141 (mean 0.7). Crowns and pontics were more common in the upper jaw. 59.4% of the endodontically treated teeth had posts at the first examination and 64.4% at the second. 34.5% of the 255 teeth with apical periodontitis found at the first examination and 41.0% of the 268 at the second were in connection with posts. It was concluded that both crowns and pontics were common treatment procedures in the studied population. Crown therapy did not seem to impair the apical status while teeth with posts more often had apical periodontitis than other teeth and, furthermore, teeth with screw posts were lost more frequently than other teeth.     

A 25 year longitudinal study of patients treated with removable partial dentures

summary A 25 year longitudinal study was carried out on a number of patients fitted with removable partial dentures (RPDs) in 1969. Before the prosthetic treatment all patients were given oral hygiene motivation and instructions in order to create a high level of co-operation. The RPDs, most of which were lower bilateral distal extension dentures, were carefully planned and designed. During the first 10 years the patients were examined in our clinic at yearly intervals at which time encouragement and reinstruction regarding oral hygiene were given and various treatment procedures were performed as required. After the initial 10 years the patients were advised, for practical reasons, to continue to have yearly controls on their own initiative. Of the initial 30 patients from 1969, 23 were still alive in 1994, all of whom were examined. In five of those 23 the original RPD situation had changed more or less due mainly to general illness contracted and/or change to other therapies. In the remaining 18 patients wearing in total 20 RPDs, 13 (65%) of the original RPDs were still functioning. Seven RPDs were new with principally the same design as the original ones. Among these 18 patients the number of lost teeth, the number of new DF surfaces and the increased number of endodontically treated teeth were few. No apparent changes took place regarding the periodontal condition during the follow-up period. These favourable biological conditions in the RPD jaws, in combination with the patients' satisfaction with the comfort and chewing ability, reinforce the conclusions drawn at our 10 year control – that an RPD is a valuable treatment procedure for patients with a markedly reduced number of teeth.