Number of implants for mandibular implant overdentures: a systematic review

Comparative Analysis of the Structural Weights of Fixed Prostheses of Zirconium Dioxide, Metal Ceramic, PMMA and 3DPP Printing Resin-Mechanical Implications

The aim of this study was to determine the mechanical implications of four-unit fixed dental prostheses (FDPs) made of (1) monolithic zirconium dioxide (ZR O2), (2) polymethylmethacrylate (PMMA), (3) metal ceramic (PFM) and (4) impression resin (3DPP).

METHODS

Four groups were studied with eight samples for each material (n: 32). Each structure was weighed, subjected to compressive tests and analyzed using 3D FEA.

RESULTS

PMMA presented the lowest structural weight (1.33 g), followed by 3DPP (1.98 g), ZR O2 (6.34 g) and PFM (6.44 g). In fracture tests, PMMA presented a compressive strength of 2104.73 N and a tension of 351.752 MPa; followed by PFM, with a strength of 1361.48 N and a tension of 227.521 MPa; ZR O2, with a strength of 1107.63 N and a tension of 185.098 MPa; and 3DPP, with a strength of 1000.88 N and a tension of 143.916 MPa. According to 3D FEA, 3DPP presented the lowest degree of deformation (0.001 mm), followed by PFM (0.011 mm), ZR O2 (0.168 mm) and PMMA (1.035 mm).

CONCLUSIONS

The weights of the materials did not have a direct influence on the mean values obtained for strength, stress or strain. Since the performance was related to the tension and forces supported by the structures in critical zones, the importance of considering design factors is clear. In vitro and 3D FEA assays allowed us to simulate different scenarios for the mechanical properties of certain materials before evaluating them clinically. Thus, they can generate predictions that would allow for the design of a better research methodology in future clinical trials.

'Differences in self-perceived OHRQoL between fully dentate subjects and edentulous patients depending on their prosthesis type, socio-demographic profile, and clinical features'

OBJECTIVES

This observational cross-sectional study aimed to evaluate and compare the oral health-related quality of life (OHRQoL) and clinical performance between dentate subjects and edentulous patients restored with conventional dentures or implant overdentures.

METHODS

85 edentulous patients were grouped as follows: Group-1 (CD): conventional denture wearers (n= 42), and Group-2 (IO): implant-retained overdenture wearers (n= 43). For the OHRQoL comparisons, a control group of subjects with a healthy natural dentition (Group-3, ND; n= 50) was included. Participants completed three validated questionnaires (OHIP-14sp, OHIP-20sp, and QoLIP-10). Socio-demographic data, prosthesis-related factors, clinical condition of the mouth, and patient subjective evaluations, were gathered. Descriptive and non-parametric probes were run (α= 0.05).

RESULTS

The ND group was the most unsatisfied (OHIP-14sp; p≤ 0.001). The OHIP-20sp attributed significantly worse Psychological disability (p= 0.029) and Handicap (p= 0.027) to CD wearers when compared to IO wearers. The CD group showed the significantly highest need for relining (p= 0.041), and the lowest retention (p= 0.011). The OHIP-14sp disclosed a significantly worse OHRQoL for those volunteers who had a job (p= 0.003), a basic education instead of a secondary one (p= 0.022), and no partner (p= 0.006).

CONCLUSIONS

The overall OHRQoL was comparable for both prosthodontic groups, being modulated by socio-demographic and prosthesis-related features. Nonetheless, CD wearers presented prosthetic complications more frequently.

Clinical and satisfaction outcomes of using one or two dental implants for mandibular overdentures: preliminary short-term follow-up of a randomized clinical trial

Objective

This randomized clinical trial aimed to evaluate the marginal bone loss and peri-implant aspects in patients with mandibular overdentures retained by one or two implants and assess patient satisfaction, prosthesis-related clinical outcomes, and masticatory efficiency.

Methods

Patients from the School of Dentistry of the University of Passo Fundo (UPF) with lower conventional complete dentures dissatisfied with prosthetic retention were selected. Eighteen patients were analyzed and divided into randomized treatment groups: GA, installation of one implant in the midline of the mandibular symphysis (8 patients), and GB, installation of two implants in the lower canine region (10 patients). Implant survival and prosthetic maintenance were assessed by clinical and radiographic examinations performed 6 months after implant placement and 3 months after loading. Finally, the masticatory efficiency of the prostheses was evaluated with the QoLIP-10 (Quality of Life with Implant-Prostheses) questionnaire, and the degree of patient satisfaction used the visual analog scale (VAS).

Results

Regarding the esthetic satisfaction of the patients, there was no statistical difference between the two groups studied (p = 0.680). Patients who received two implants presented easier chewing (p = 0.049) and a lower average number of prosthesis maintenance. There was no difference between the groups regarding peri-implant bone resorption 3 months after the use of prostheses.

Conclusions

The use of two dental implants showed higher masticatory ability and lower need for maintenance appointments when compared with one implant in mandibular overdentures but did not affect peri-implant aspects and patient satisfaction. The treatment using one implant was effective for the aspects evaluated, but further clinical studies are required on the subject.

Evaluation of the quality of life and satisfaction in patients using complete dentures versus mandibular overdentures. Systematic review and meta-analysis

Background

The World Health Organization (WHO) recognizes edentulism as a physical impairment that results in a negative impact in the daily activities.

Objective

The study aimed to compare the satisfaction and the quality of life, in patients treated with implant retained overdentures with two mandibular implants (IOD) against those with mandibular conventional complete dentures (CCD).

Methods

Different search strategies were used to screen for articles in Pubmed/Medline, Cochrane Library and Scielo of the last 17 years (2003–2020). The keywords used were: “quality of life OR satisfaction” AND “complete denture OR conventional denture” AND “overdenture OR implant retained.”

Results

Six articles and two more were added by manual search. The population was 400 in the CCD and 412 for IOD. The mean age was 64.3 ± 6.41 years. The group was comprised of 283 men and 427 women. The scores obtained in the visual analog scale (VAS) before and after the treatment were statistically significant in favor of the IOD for overall satisfaction, (WMD: 12.329; 95% CI: 4.873 to 19.784, p‐value = 0.001), comfort, speech and stability. For esthetics and chewing there was non‐significant improvement while hygiene worsened for the IOD. For the comparison after the treatment between both treatment modalities a statistically significant improvement was found in overall satisfaction (WMD: 14.408; 95% CI: 8.589 to 20.226, p‐value < 0.001), comfort, speech, chewing and stability in favor of the IOD but not in esthetics or hygiene.

Conclusions

This systematic review and meta‐analysis show the superiority of the IOD, despite is not achieved in all aspects.

Does the prosthesis weight matter? 3D finite element analysis of a fixed implant-supported prosthesis at different weights and implant numbers

PURPOSE

This study evaluated the influence of prosthesis weight and number of implants on the bone tissue microstrain.

MATERIALS AND METHODS

Fifteen (15) fixed full-arch implant-supported prosthesis designs were created using a modeling software with different numbers of implants (4, 6, or 8) and prosthesis weights (10, 15, 20, 40, or 60 g). Each solid was imported to the computer aided engineering software and tetrahedral elements formed the mesh. The material properties were assigned to each solid with isotropic and homogeneous behavior. The friction coefficient was set as 0.3 between all the metallic interfaces, 0.65 for the cortical bone-implant interface, and 0.77 for the cancellous bone-implant interface. The standard earth gravity was defined along the Z-axis and the bone was fixed. The resulting equivalent strain was assumed as failure criteria.

RESULTS

The prosthesis weight was related to the bone strain. The more implants installed, the less the amount of strain generated in the bone. The most critical situation was the use of a 60 g prosthesis supported by 4 implants with the largest calculated magnitude of 39.9 mm/mm, thereby suggesting that there was no group able to induce bone remodeling simply due to the prosthesis weight.

CONCLUSION

Heavier prostheses under the effect of gravity force are related to more strain being generated around the implants. Installing more implants to support the prosthesis enables attenuating the effects observed in the bone. The simulated prostheses were not able to generate harmful values of peri-implant bone strain.

Cost-effectiveness of implant-supported dental prosthesis compared to conventional dental prosthesis

OBJECTIVE

To conduct a cost-effectiveness analysis of alternatives for rehabilitation treatment of mandibular edentulism in the context of the Brazilian Unified Health System (implant-supported total dental prosthesis versus conventional total dental prosthesis).

METHODS

A Markov model was developed to capture long-term clinical and economic outcomes. The model’s population was comprised of a hypothetical cohort of 1,000,000 patients, aged 55 years, with total mandibular edentulism and without medical contraindications for performing surgical procedures. The adopted analysis perspective was that of the Brazilian Unified Health System. Based on the proposed model, we calculated cost – in BRL, and effectiveness – measured by quality-adjusted prosthesis year (QAPY). The time horizon of the analysis was 20 years.

RESULTS

Considering a 5% discount in costs and effects, the incremental cost-effectiveness ratio of implant-supported total dental prostheses compared to conventional total dental prosthesis (BRL 464.22/QAPY) was lower than the willingness to pay threshold adopted in the model (BRL 3,050.00/QAPY).

CONCLUSIONS

The results of this economic analysis showed that the rehabilitation of mandibular edentulous patients by implant-supported total prosthesis is very cost-effective when compared to conventional complete prosthesis, considering the cost-effectiveness limits employed.

Managing complications resulting from limited prosthetic space with a monolithic, multichromatic CAD-CAM implant-retained overdenture: A dental technique

This article proposes a 2-visit clinical protocol to manage prosthodontic complications resulting from limited prosthetic space, using a monolithic, multichromatic computer-aided design and computer-aided manufacturing (CAD-CAM) acrylic resin implant overdenture. The advantages and limitations of using this approach are outlined and discussed.

Prosthetic maintenance of different mandibular implant overdentures: A systematic review

STATEMENT OF PROBLEM

Different factors can affect prosthetic maintenance requirements for mandibular implant overdentures (IODs). However, the literature shows a high level of disagreement concerning the effect of each factor on maintenance needs.

PURPOSE

The purpose of this systematic review was to address the focus question: "In the clinical studies published since 2004 of adult patients with totally edentulous mandibles treated by IODs with a variable number of implants and different designs, what were the maintenance types, frequencies, and complications?"

MATERIAL AND METHODS

A search of MEDLINE and PubMed databases was performed targeting papers in English on prosthetic maintenance of mandibular IODs published between 2004 and June 2015, aiming at recognizing the needs for adjustment, repair, and renewal. The recorded data were divided into 6 categories, and a percentage value was attributed to each.

RESULTS

From a total of 130 articles, 33 studies met the specified inclusion criteria for the review (14 randomized controlled trials, 8 prospective clinical trials, 3 retrospective studies, and 4 systematic reviews). These articles provided evidence that a mean complication rate was impossible to determine because of the multiplicity of contributing factors. No clear identification of the causes of mechanical complications was found, nor was there any clear evidence of superiority of one implant and/or attachment design over another.

CONCLUSIONS

Prosthetic complications with IODs are unavoidable. However, they can be reduced to an expected level if a close follow-up protocol is implemented aiming at anticipating risks of unexpected complications. Further clinical studies are needed to achieve a constructive meta-analysis that accounts for different parameters such as opposite arch, attachment functional variety, connection method, and prosthesis quality.

An International Survey among Prosthodontists of the Use of Mandibular Implant-Supported Dental Prostheses

PURPOSE

To evaluate the use of implant-supported overdentures (IOD) and implant-supported fixed dental prostheses (IFDP) in patients with edentulous mandibles among international prosthodontists.

MATERIALS AND METHODS

A questionnaire was sent by e-mail to all clinically active prosthodontists in the International College of Prosthodontists with questions related to implant treatment of the edentulous mandible performed in 2015.

RESULTS

One hundred and sixteen prosthodontists from 33 countries responded to the questionnaire. The vast majority of the responding prosthodontists was faculty or worked in private practice, and the great majority had performed treatment with mandibular implant-supported dental prostheses; however, two thirds of the respondents reported that <20% of the implant patients in their clinic had received treatment related to edentulous mandibles. The majority reported using 2 implants (84%), while 13% used 4 for overdenture retention. There were great variations regarding retention systems used for mandibular IODs; the most common was individual Locator attachments. Cost was considered the most common reason to choose mandibular IOD, There was a wide variation of materials used for mandibular IFDPs. The most common combination included milled titanium frameworks and acrylic resin teeth.

CONCLUSIONS

This survey, completed by 116 prosthodontists from 33 countries, showed that implant treatment for edentulous mandibles is common, but there was great variation among the respondents regarding amount of treatments performed, design, and materials used for the implant prostheses.

Effects of Length and Inclination of Implants on Terminal Abutment Teeth and Implants in Mandibular CL1 Removable Partial Denture Assessed by Three-Dimensional Finite Element Analysis

OBJECTIVES

This study sought to assess the effects of length and inclination of implants on stress distribution in an implant and terminal abutment teeth in an implant assisted-removable partial denture (RPD) using three-dimensional (3D) finite element analysis (FEA).

MATERIALS AND METHODS

In this in vitro study, a 3D finite element model of a partially dentate mandible with a distal extension RPD (DERPD) and dental implants was designed to analyze stress distribution in bone around terminal abutment teeth (first premolar) and implants with different lengths (7 and 10 mm) and angles (0°, 10° and 15°).

RESULTS

Stress in the periodontal ligament (PDL) of the first premolar teeth ranged between 0.133 MPa in 10mm implants with 15° angle and 0.248 MPa in 7mm implants with 0° angle. The minimum stress was noted in implants with 10mm length with 0° angle (19.33 MPa) while maximum stress (25.78 MPa) was found in implants with 10mm length and 15° angle. In implants with 7 mm length, with an increase in implant angle, the stress on implants gradually increased. In implants with 10 mm length, increasing the implant angle gradually increased the stress on implants.

CONCLUSION

Not only the length of implant but also the angle of implantation are important to minimize stress on implants. The results showed that vertical implant placement results in lower stress on implants and by increasing the angle, distribution of stress gradually increases.