The mandibular complete overdenture

Tooth-Supported Overdentures Revisited

The goal of prosthodontics is to provide a functional prosthesis to restore aesthetics, functions, and masticatory efficiencies. Tooth-supported overdentures are one of the treatment options for removable dentures. This article aims to discuss the advantages and disadvantages of tooth-supported overdentures and the principles of using various overdenture attachments, including non-attachment overdentures. The common treatment options in preparing the overdenture abutment are either with or without abutment coping with or without attachment systems, which were discussed and illustrated. A range of tooth-supported overdenture systems were addressed, from low to high financial implications and treatment complexities. The clinician can choose a system that best fits the patient's condition and expectations. This allows clinicians to decide and consider tooth-supported overdentures as a treatment option before full edentulism. A well-executed tooth-supported overdenture ensures the preservation of alveolar bone, optimizes patient satisfaction in denture treatment, and eventually improves the patient's adaptation when transitioning to complete dentures.

The Effect of Mini Dental Implant Number on Mandibular Overdenture Retention and Attachment Wear

Purpose

Evaluate the effect of different mini-implant numbers on overdenture retention and evaluate attachment wear following one year of simulated placement/removal. Material and Methods. Nine models simulating atrophic mandibles held 27 mini dental implants in three groups of 2, 3, and 4 mini-implants. A total of 1080 simulated placement/removal cycles were carried out, and a digital force gauge was used to measure the overdenture dislodgment force. The means of the retention forces were analyzed using SPSS with one-way ANOVA and post hoc (p < 0.05). The inner diameter of attachment inserts was evaluated using a light microscope before and after testing. A paired t-test was used to compare the mean of inner ring diameters (p < 0.05).

Results

The retention was significantly reduced regardless of the mini dental implant number, but the number affected overdenture retention. The placement of 4 mini dental implants provided higher retention and less reduction in retentiveness. However, no significant difference was found when 3 mini dental implants were compared to 2 mini dental implants (p = 0.21). Microscopic examination showed abrasion wear in all inserts following testing. However, the inserts of the 4 mini dental implants showed less wear than those used for 2 or 3 mini dental implants with p ≤ 0.001 and p ≤ 0.001, respectively.

Conclusion

Mini dental implant overdenture retention force and attachment wear could improve by increasing the mini dental implants to 4. However, there was no difference in retention force or attachment wear when 2 or 3 mini dental implant overdentures were compared.

Comparison of stress induced in mandible around an implant-supported overdenture with locator attachment and telescopic crowns - a finite element analysis

Introduction

One of the principle factors for the success of implant supported/retained overdentures (IOs) is the manner in which the stresses are transferred to the surrounding bone. Hence, the aim of the present study is to compare the stress induced in the mandible around IOs, using two different attachment systems, locator and telescopic.

Methods

3D finite element models were prepared using Pro/ENGINEER or PTC Creo to simulate 4 clinical situations: IOs using two different attachment systems, locator and telescopic, with and without splinting. A vertical compressive load of 35N was directed toward the central fossa in the molar region of each overdenture. Non-linear static contact analysis was carried out to determine the stress distribution in various components of IOs. Then, the models were analyzed by a finite element program ABAQUS, and displayed using Von Mises stress patterns.

Results

The contact stress values developed on the implant and attachment components were lower with locator attachment, in both splinted and non-splinted models. On the other hand, the stress distribution to the cortical bone was more with non-splinted/splinted locator attachments (3.73/4.12 Mega Pascals) when compared to the non-splinted/splinted telescopic attachments (2.66/3.7 Mega Pascals). The stresses in all the components of overdenture were greater with the splinted model compared to non-splinted, in both the attachment systems.

Conclusion

The locator attachment might demonstrate superior clinical performance, as the stresses on implant and attachment components were less compared to telescopic. Non-splinted model showed better results in both the attachment types.

Stress distribution in fixed mandibular prostheses fabricated by CAD/CAM and conventional techniques: Photoelastic and strain gauge analyses

Background

The aim of this study was to evaluate the distribution of stress in complete fixed mandibular prostheses with infrastructures (IE) fabricated with different materials and techniques, under compressive force.

Material and Methods

A model of an edentulous mandible, which received five 4x11 mm external hexagon implants between the mental foramens, was fabricated. The groups were divided into: Group I - IE in nickel-chromium with an acrylic resin occlusal coating; Group II – IE in nickel-chromium with a ceramic occlusal coating; Group III – IE milled in zirconia with a ceramic coating. For the photoelastic methodology, 70 N axial loads were applied in three regions. Photographic images were taken and analyzed according to the number of high-intensity fringes. For the strain gauge methodology, the measurement of stresses was performed in two distinct regions. The same compression tests described earlier were then performed. The registered stress values were grouped in tables and submitted to two-factor variance analysis (ANOVA) and the Tukey test with 5% significance.

Results

The results of the two methodologies demonstrated smaller stress values for Group I, when compared to the other groups.

Conclusions

It was possible to conclude that the complete fixed prostheses, with infrastructures cast in metal and acrylic occlusal coating, demonstrated better biomechanical results.

Key words:Dental implants, mandibular prosthesis implantation, biomechanics.

Longitudinal Assessment of Denture Maintenance Needs in an Overdenture Population

PURPOSE

To evaluate the longitudinal denture maintenance needs of a tooth-supported overdenture population.

MATERIALS AND METHODS

This prospective cohort study was composed of patients who had received tooth-supported overdentures from 1974 to 1994 in the Department of Prosthodontics, University of Iowa. There were 272 persons with 662 abutments who fulfilled the inclusion criteria. To simplify analysis and reduce the number of confounding variables, only those participants wearing complete maxillary dentures and opposing complete mandibular overdentures supported by teeth #22 and #27 were included in this analysis. The denture maintenance needs of these participants were identified and related to age, gender, length of time wearing overdentures, number of medications, and denture-wearing habits. Descriptive statistics and bivariate analyses were used for the statistical analysis (α = 0.05).

RESULTS

Of the 91 participants (mean age = 59.5 ± 10.1 years; 63.7% male) who fulfilled the inclusion criteria at baseline, 48.4% took 1 to 3 medications daily, and 84.6% wore their dentures day and night. The percentages of participants who needed one or more of the following denture treatments were: 91.2% denture base adjustments, 76.9% laboratory processed relines, 61.5% denture remakes, 33% laboratory remount and occlusal adjustment, 22% repaired bases, and 19.8% needed denture teeth replaced. Bivariate analyses indicated that participants who were 65 years and older needed more denture adjustments than patients younger than 65 years (p = 0.0343). Participants who had worn overdentures for more than 5 years were more likely to require denture remakes (p = 0.0304). Participants who wore their dentures only during the day were less likely to require repairs (p = 0.0403). Participants who did not take any medications were significantly less likely to require denture base repairs (p = 0.0258). For the 35 participants who returned for recalls at all 4 time points, males were more likely to need denture teeth repaired or replaced (p = 0.0335) and those aged 50 to 64 were more likely to need 2 or more adjustments (p = 0.0311). No overdenture abutments were lost by the participants in this study.

CONCLUSIONS

According to the results of this study, age, medication usage, denture-wearing habits, and age of the overdentures were significant factors associated with denture maintenance needs. Persons wearing overdentures need regular recalls, because they have continuing maintenance needs.

Implant supported overdenture in the patients with history of radio and chemotherapy for the prostate malignancy

The success of dental implants in patients that have undergone chemo and radiotherapy for a region other than head and neck remain unclear, although some local and systemic factors could be contraindications to dental implant treatment. As there are very few absolute medical contraindications to dental implant treatment, but a number of conditions may increase the risk of treatment failure or complications. The case report describes the successful survival of dental implants placed in maxilla and mandible of a patient who had undergone radio and chemotherapy for prostate cancer.

Two-Year Success Rate of Implant-Retained Mandibular Overdentures by Novice General Dentistry Residents

The purpose of the present study was to evaluate the clinical success and patient satisfaction when dental implant–retained mandibular overdentures are placed and restored by novice general dentistry residents. A total of 50 subjects who were dissatisfied with their mandibular complete dentures were enrolled in the study. Two dental implants were placed in the anterior mandible between the mental foramina by novice general dentistry residents under the direct supervision of the principal investigator. The resident attached the denture to the implants 3 to 4 months later using locator attachments. The implant success rate was determined by measuring bone loss, mobility, pocket probing depth, and gingival and plaque indices. Subjects were asked to complete a satisfaction questionnaire with the prosthesis at 3 months, 1 year, and 2 years after overdenture delivery. A total of 100 implants were placed in the 50 study subjects. Of these, 2 implants were lost in 1 subject, and 1 subject died due to unrelated causes. Of the 48 remaining subjects, 45 have had their implants restored with overdentures. The subjects' overall satisfaction with fit and ability to chew hard foods with their mandibular overdentures improved significantly (P &lt; .05) following the denture attachment to the dental implants. We conclude that novice general dentistry residents can successfully place mandibular implants and restore them with overdentures under direct supervision, subsequently enhancing the subjects' satisfaction with their mandibular dentures.

Small-diameter titanium Grade IV and titanium-zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial

OBJECTIVE

The aim of this study was to compare crestal bone-level changes, soft tissue parameters and implant success and survival between small-diameter implants made of titanium/zirconium (TiZr) alloy or of Grade IV titanium (Ti) in edentulous mandibles restored with removable overdentures.

MATERIALS AND METHODS

This was a randomized, controlled, double-blind, split-mouth multicenter clinical trial. Patients with edentulous mandibles received two Straumann bone-level implants (diameter 3.3 mm), one of Ti Grade IV (control) and one of TiZr (test), in the interforaminal region. Implants were loaded after 6-8 weeks and removable Locator-retained overdentures were placed within 2 weeks of loading. Modified plaque and sulcus bleeding indices, radiographic bone level, and implant survival and success were evaluated up to 36 months.

RESULTS

Of 91 treated patients, 75 completed the three-year follow-up. Three implants were lost (two control and one test implant). The survival rates were 98.7% and 97.3%, and the mean marginal bone level change was -0.78 ± 0.75 and -0.60 ± 0.71 mm for TiZr and Ti Grade IV implants. Most patients had a plaque score of 0 or 1 (54% for test and 51.7% for control), and a sulcus bleeding score of 0 (46.1% for test and 44.9% for control). No significant differences were found between the two implant types for bone-level change, soft tissue parameters, survival and success.

CONCLUSIONS

After 36 months, similar outcomes were found between Ti Grade IV and TiZr implants. The results confirm that the results seen at 12 months continue over time.

Study of Biomechanics of Porous Coated Root Form Implant Using Overdenture Attachment: A 3D FEA

The purpose of this article is to do a three-dimensional finite element stress analysis, in relation to root form implant supported by overdenture attachment, during axial and non-axial loading. Two porous coated Titanium-aluminum-vanadium (Ti-6Al-4V) implants with overdenture abutment were embedded in both simple and 3D model of interforaminal region of mandible. The material properties of tissue ingrowth bonded interface were calculated considering Iso-Strain condition. The masticatory forces: axial load of 35 N, a horizontal load of 10 N, and an oblique load of 120 N, was applied for the two qualities of cancellous bone. It implied that porous topography of the implant led to optimal stress transfer at the tissue ingrowth bonded interface and insignificant punching stress at the apex than a smooth surface implant. The inferior bone quality was deformed even under physiologic loads and showed wider stress pattern. Simulated implant abutment to implant bone interface stress may be significantly affected by the quality of the bone and the surface topography of the implant. The interface is affected to a lesser extent by the prosthetic material properties. Threedimensional anatomical model was more close to reality than the geometry of much simpler altered models.

A comparison of retention characteristics in prefabricated and custom-cast dental attachments

PURPOSE

The aim of this in vitro study was to investigate the retention characteristics of attachments fabricated by machine milling or by custom casting. In addition, the retention of reduced dimension attachments was also evaluated.

MATERIALS AND METHODS

Three types of ERA matrices, one prefabricated and two cast, were used. Ten specimens were made for each type, and white nylon patrices were transferred to denture bases. Tests were performed at a crosshead speed of 0.2 in/min with an Instron machine. The dislodging force at baseline, 100, 200, 300, 400, 500, and subsequently after every 500 pulls up to 2500 pulls were measured. ANOVA and Student's t-test were used to analyze the measurements.

RESULTS

All three groups showed no difference at the baseline, but the cast groups showed greater variation within group. The prefabricated group showed higher retention after 200 pulls. Decreased-dimension attachments have no significant difference when compared to the cast regular dimension group after 400 pulls.

CONCLUSION

The prefabricated attachments had superior retention than the cast groups over time. Reduced dimension did not reduce the retention when compared to the cast group.

Can general dentists produce successful implant overdentures with minimal training?

OBJECTIVES

This study was carried out to determine whether inexperienced dentists can provide two-implant overdentures that are as satisfactory and of the same cost as those provided by experienced prosthodontists.

METHODS

Edentulous elders were enrolled in a randomized controlled clinical trial to compare the effects of mandibular conventional and two-implant overdentures on nutrition. They were randomly assigned to groups that were treated by either an experienced prosthodontist or by a newly-graduated dentist with minimal training in implant treatment. Data for this study were obtained during the treatment of the first 140 subjects enrolled. The change in patient ratings of satisfaction after treatment, laboratory costs and the number of unscheduled visits up to 6 months following prosthesis delivery were compared.

RESULTS

Satisfaction was significantly higher with implant overdentures than with conventional dentures, but there were no differences in scores for either prosthesis between the groups treated by experienced specialists or new dentists. Furthermore, six of the seven inexperienced dentists reported that they found the mandibular two-implant overdenture easier to provide than the conventional denture.

CONCLUSIONS

The results of this study suggest that general dentists can provide successful mandibular two-implant overdentures with minimal training.