Implant and root supported overdentures - a literature review and some data on bone loss in edentulous jaws

PURPOSE

To present a literature review on implant overdentures after a brief survey of bone loss after extraction of all teeth.

MATERIALS AND METHODS

Papers on alveolar bone loss and implant overdentures have been studied for a narrative review.

RESULTS

Bone loss of the alveolar process after tooth extraction occurs with great individual variation, impossible to predict at the time of extraction. The simplest way to prevent bone loss is to avoid extraction of all teeth. To keep a few teeth and use them or their roots for a tooth or root-supported overdenture substantially reduces bone loss. Jaws with implant-supported prostheses show less bone loss than jaws with conventional dentures. Mandibular 2-implant overdentures provide patients with better outcomes than do conventional dentures, regarding satisfaction, chewing ability and oral-health-related quality of life. There is no strong evidence for the superiority of one overdenture retention-system over the others regarding patient satisfaction, survival, peri-implant bone loss and relevant clinical factors. Mandibular single midline implant overdentures have shown promising results but long-term results are not yet available. For a maxillary overdenture 4 to 6 implants splinted with a bar provide high survival both for implants and overdenture.

CONCLUSION

In edentulous mandibles, 2-implant overdentures provide excellent long-term success and survival, including patient satisfaction and improved oral functions. To further reduce the costs a single midline implant overdenture can be a promising option. In the maxilla, overdentures supported on 4 to 6 implants splinted with a bar have demonstrated good functional results.     

Number of implants for mandibular implant overdentures: a systematic review

PURPOSE

The aim of this systematic review is to address treatment outcomes of Mandibular implant overdentures relative to implant survival rate, maintenance and complications, and patient satisfaction.

MATERIALS AND METHODS

A systematic literature search was conducted by a PubMed search strategy and hand-searching of relevant journals from included studies. Randomized Clinical Trials (RCT) and comparative clinical trial studies on mandibular implant overdentures until August, 2010 were selected. Eleven studies from 1098 studies were finally selected and data were analyzed relative to number of implants.

RESULTS

Six studies presented the data of the implant survival rate which ranged from 95% to 100% for 2 and 4 implant group and from 81.8% to 96.1% for 1 and 2 implant group. One study, which statistically compared implant survival rate showed no significant differences relative to the number of implants. The most common type of prosthetic maintenance and complications were replacement or reattaching of loose clips for 2 and 4 implant group, and denture repair due to the fracture around an implant for 1 and 2 implant groups. Most studies showed no significant differences in the rate of prosthetic maintenance and complication, and patient satisfaction regardless the number of implants.

CONCLUSION

The implant survival rate of mandibular overdentures is high regardless of the number of implants. Denture maintenance is likely not inflenced substantially by the number of implants and patient satisfaction is typically high again regardless os the number of implants.     

Attachment systems for mandibular implant overdentures: a systematic review

PURPOSE

The aim of this systematic review was to address treatment outcome according to attachment systems for mandibular implant overdentures in terms of implant survival rate, prosthetic maintenance and complications, and patient satisfaction.

MATERIALS AND METHODS

A systematic literature search was conducted using PubMed and hand searching of relevant journals considering inclusion and exclusion criteria. Clinical trial studies on mandibular implant overdentures until August, 2010 were selected if more than one type of overdenture attachment was reported. Twenty four studies from 1098 studies were finally included and the data on implant survival rate, prosthetic maintenance and complications, patient satisfaction were analyzed relative to attachment systems.

RESULTS

Four studies presented implant survival rates (95.8 - 97.5% for bar, 96.2 - 100% for ball, 91.7% for magnet) according to attachment system. Ten other studies presented an implant survival rate ranging from 93.3% to 100% without respect to the attachment groups. Common prosthetic maintenance and complications were replacement of an assay for magnet attachments, and activation of a matrix or clip for ball or bar attachments. Prosthetic maintenance and complications most commonly occurred in the magnet groups. Conflicting findings were found on the rate of prosthetic maintenance and complications comparing ball and bar attachments. Most studies showed no significant differences in patient satisfaction depending upon attachment systems.

CONCLUSION

The implant survival rate of mandibular overdentures seemed to be high regardless attachment systems. The prosthetic maintenance and complications may be influenced by attachment systems. However patient satisfaction may be independent of the attachment system.     

Standardizing the evaluation criteria on treatment outcomes of mandibular implant overdentures: a systematic review

PURPOSE

The aim of this review was to analyze the evaluation criteria on mandibular implant overdentures through a systematic review and suggest standardized evaluation criteria.

MATERIALS AND METHODS

A systematic literature search was conducted by PubMed search strategy and hand-searching of relevant journals from included studies considering inclusion and exclusion criteria. Randomized clinical trials (RCT) and clinical trial studies comparing attachment systems on mandibular implant overdentures until December, 2011 were selected. Twenty nine studies were finally selected and the data about evaluation methods were collected.

RESULTS

Evaluation criteria could be classified into 4 groups (implant survival, peri-implant tissue evaluation, prosthetic evaluation, and patient satisfaction). Among 29 studies, 21 studies presented implant survival rate, while any studies reporting implant failure did not present cumulative implant survival rate. Seventeen studies evaluating peri-implant tissue status presented following items as evaluation criteria; marginal bone level (14), plaque Index (13), probing depth (8), bleeding index (8), attachment gingiva level (8), gingival index (6), amount of keratinized gingiva (1). Eighteen studies evaluating prosthetic maintenance and complication also presented following items as evaluation criteria; loose matrix (17), female detachment (15), denture fracture (15), denture relining (14), abutment fracture (14), abutment screw loosening (11), and occlusal adjustment (9). Atypical questionnaire (9), Visual analog scales (VAS) (4), and Oral Health Impact Profile (OHIP) (1) were used as the format of criteria to evaluate patients satisfaction in 14 studies.

CONCLUSION

For evaluation of implant overdenture, it is necessary to include cumulative survival rate for implant evaluation. It is suggested that peri-implant tissue evaluation criteria include marginal bone level, plaque index, bleeding index, probing depth, and attached gingiva level. It is also suggested that prosthetic evaluation criteria include loose matrix, female detachment, denture fracture, denture relining, abutment fracture, abutment screw loosening, and occlusal adjustment. Finally standardized criteria like OHIP-EDENT or VAS are required for patient satisfaction.     

Does mandibular edentulous bone height affect prosthetic treatment success?

Objectives

The aim of this study is to determine whether mandibular bone height affects patients’ ratings of satisfaction and function with mandibular 2-implant overdentures (IODs) and conventional dentures (CDs).

Methods

214 edentulous elders were randomly allocated into 2 groups and treated with maxillary CDs and either mandibular CDs or IODs. Classifications of mandibular bone height were carried out on panoramic radiographs using 4 published methods. At baseline and 6 months after delivery, all participants rated their satisfaction with their prostheses using the McGill Denture Satisfaction Instrument. Independent t-tests and a linear multivariable regression model were used for statistical analyses.

Results

Mandibular bone height has no effect on patients’ ratings of general satisfaction, nor on ratings of ability to chew, stability, comfort, aesthetics and ability to speak at 6 months (p > 0.05, linear regression). There were significant between treatment differences in ratings of general satisfaction, comfort, stability and ability to chew from all mandibular bone height categories, with higher ratings assigned to IODs (p < 0.01, t-tests). Linear regression analyses confirmed that, for general satisfaction, as well as ability to chew, stability, comfort, aesthetics and ability to speak, treatment with IODs contributes to higher satisfaction ratings (p < 0.001), while mandibular bone height does not.

Conclusions

The evidence demonstrates that mandibular bone height has no effect on patients’ satisfaction with the function, chewing ability and comfort of their prostheses. Furthermore, no matter how much mandibular bone, these results suggest that edentulous elders will benefit more from mandibular IODs than from CDs.     

Numerical study of effect of elastomeric stress absorbers on stress reduction in bone-dental implant interface

Objective

This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and is devoted to the development of a modified Osteoplant^® implant type in order to minimize stress concentration in the bone-implant interface.

Material and Methods

This study investigated 0.4 mm thick layers of two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis.

Results

Overall, this proposed implant provoked lower load transfer in bone-implant interface due to the effect of the elastomers as stress absorbers. The stress level in the bone was reduced between 28% and 42% for three load cases: 75 N, 60 N and 27 N in corono-apical, linguo-buccal and disto-mesial direction, respectively.

Conclusion

The proposed model provided an acceptable solution for load transfer reduction to the mandible. This investigation also permitted to choose how to incorporate two elastomers into the Osteoplant^® implant system.     

Patient satisfaction with mandibular implant overdentures and conventional dentures 6 months after delivery

Purpose

This study examined patient satisfaction with conventional complete dentures and mandibular implant overdentures opposing conventional maxillary dentures 6 months after delivery.

Materials and Methods

Sixty edentulous subjects (aged 65 to 75 years) were randomly assigned to either a mandibular conventional denture or an overdenture supported by two implants with ball-shaped retentive anchors. Patients rated their general satisfaction and other features of their prostheses, together with their ability to eat certain food items, on 100-mm visual analogue scales before assignment, and after 2 and 6 months.

Results

Both treatment groups reported greater satisfaction with their new prostheses at 6 months. General satisfaction ratings were higher in the implant group than in the conventional denture group by approximately 36% (mean difference 22.3 mm). The implant group also rated comfort (mean difference 22.4 mm), stability (mean difference 28.5 mm), and ability to chew (mean difference 17.3 mm) significantly higher. Significantly higher scores were also given by the implant group for their ability to chew certain hard foods. A trend for an increase in the differences between the groups, in favor of the implant group, was observed between the 2- and 6-month recalls, although the increase was only significant for ease of cleaning. The primary influence on general satisfaction 6 months after the delivery of the prostheses was the provision of the two-implant overdenture.

Conclusion

Edentulous seniors who received mandibular implant overdentures opposing a conventional denture rated their general satisfaction approximately 36% higher than did a comparable group provided with new conventional dentures.     

Drilling dimension effects in early stages of osseointegration and implant stability in a canine model

Background

This study histologically evaluated two implant designs: a classic thread design versus another specifically designed for healing chamber formation placed with two drilling protocols.

Material and Methods

Forty dental implants (4.1 mm diameter) with two different macrogeometries were inserted in the tibia of 10 Beagle dogs, and maximum insertion torque was recorded. Drilling techniques were: until 3.75 mm (regular-group); and until 4.0 mm diameter (overdrilling-group) for both implant designs. At 2 and 4 weeks, samples were retrieved and processed for histomorphometric analysis. For torque and BIC (bone-to-implant contact) and BAFO (bone area fraction occupied), a general-linear model was employed including instrumentation technique and time in vivo as independent.

Results

The insertion torque recorded for each implant design and drilling group significantly decreased as a function of increasing drilling diameter for both implant designs (p<0.001). No significant differences were detected between implant designs for each drilling technique (p>0.18). A significant increase in BIC was observed from 2 to 4 weeks for both implants placed with the overdrilling technique (p<0.03) only, but not for those placed in the 3.75 mm drilling sites (p>0.32).

Conclusions

Despite the differences between implant designs and drilling technique an intramembranous-like healing mode with newly formed woven bone prevailed. Key words: Histomorphometry, biomechanical, in vivo, initial stability, insertion torque, osseointegration.     

Comparison Between Two Techniques for the Treatment of Mandibular Subcondylar Fractures: Closed Treatment Technique and Transoral Endoscopic-Assisted Open Reduction

Purpose

The endoscopic-assisted technique for the treatment of subcondylar fractures has been used successfully and its acceptance develops as more surgeons gain experience. We present the short term results of this technique in a randomized prospective clinical trial.

Methods and Materials

A total of 40 patients with mandibular subcondylar fracture were included in our study in two groups randomly. Patients of first group were treated by closed treatment technique and patients of second group by transoral endoscopic-assisted open reduction. All patients were followed for minimum of 12 weeks and occlusion, Mandibular Anterior Opening (MAO), mandibular deviation, and posterior ramal height were assessed.

Results

In the endoscopic group the MAO was significantly greater and mandibular deviation was lesser at 2nd and 4th week of follow up. Posterior ramal height showed significant increase in the endoscopic group rather than closed treatment group.

Conclusion

The transoral endoscopic-assisted technique is a reliable and successful technique to address subcondylar fractures. The patients who were treated by this technique showed better results in the fields of mandibular function and patient satisfaction and comfort, although it is time consuming and needs expensive instruments.     

A finite element study on stress distribution of two different attachment designs under implant supported overdenture

Objective

This study aimed to evaluate stress patterns generated within implant-supported mandibular overdentures retained by two different attachment types: ball and socket and locator attachments.

Materials and methods

Commercial CAD/CAM and finite element analysis software packages were utilized to construct two 3D finite element models for the two attachment types. Unilateral masticatory compressive loads of 50, 100, and 150 N were applied vertically to the overdentures, parallel to the longitudinal axes of the implants. Loads were directed toward the central fossa in the molar region of each overdenture, that linear static analysis was carried out to find the generated stresses and deformation on each part of the studied model.

Results

According to FEA results the ball attachment neck is highly stressed in comparison to the locator one. On the other hand mucosa and cortical bone received less stresses under ball and socket attachment.

Conclusions

Locator and ball and socket attachments induce equivalent stresses on bone surrounding implants. Locator attachment performance was superior to that of the ball and socket attachment in the implants, nylon caps, and overdenture. Locator attachments are highly recommended and can increase the interval between successive maintenance sessions.     

Effect of loading time on the survival rate of anodic oxidized implants: prospective multicenter study

PURPOSE

The purpose of this prospective study was to evaluate the effect of early loading on survival rate or clinical parameter of anodic oxidized implants during the 12-month postloading period.

MATERIALS AND METHODS

Total 69 implants were placed in 42 patients. Anodic oxidized implants (GS II, Osstem Cor., Busan, Korea) placed on the posterior mandibles were divided into two groups, according to their prosthetic loading times: test group (2 to 6 weeks), and control group (3 to 4 months). The implant survival rates were determined during one-year postloading period and analyzed by Kaplan-Meier method. The radiographic peri-implant bone loss and periodontal parameters were also evaluated and statistically analyzed by unpaired t-test.

RESULTS

Total 69 implants were placed in 42 patients. The cumulative postloading implant survival rates were 88.89% in test group, compared to 100% in control group (P<.05). Periimplant marginal bone loss (T: 0.27±0.54 mm, C: 0.40±0.55 mm) and periodontal parameters showed no significant difference between the groups (P>.05).

CONCLUSION

Within the limitation of the present study, implant survival was affected by early loading on the anodic oxidized implants placed on posterior mandibles during one-year follow-up. Early implant loading did not influence peri-implant marginal bone loss, and periodontal parameters.     

The Effect of Alloplastic Bone Graft and Absorbable Gelatin Sponge in Prevention of Periodontal Defects on the Distal Aspect of Mandibular Second Molars,After Surgical Removal of Impacted Mandibular Third Molar: A Comparative Prospective Study

Aim

Recent studies claim that haemostatic agents can be used as bone graft substitutes. The aim of this study was to compare the efficacy of alloplastic bone graft with absorbable gelatin sponge in prevention of periodontal defects distal to mandibular second molar after the surgical removal of impacted mandibular third molars.

Materials and methods

A prospective, randomized, single-blind split-mouth study was designed. The study consisted of 25 patients requiring surgical removal of bilateral impacted mandibular 3rd molars. The surgical sites were randomly divided into 2 groups: group I: G-graft (hydroxyapatite + collagen, study group) and group II: Abgel (absorbable gelatin sponge, control group). Patients were recalled on lst and 7th postoperative days and 3rd and 6th postoperative months. Probing depth, alveolar bone levels and soft tissue wound healing were evaluated. Paired t test was used to compare pre and post-operative alveolar bone levels and probing depth (PD). Wilcoxon signed ranks test was used to compare the wound healing.

Results

The soft tissue wound healing, PD and the distance between the cemento–enamel junction on the distal aspect of mandibular second molar (point A) and the alveolar crest on the distal aspect of the same tooth (point B) were significantly higher in group I as compared to group II.

Conclusion

This study reveals an increase in the alveolar bone level, improvement of PD and better wound healing in group I. Group II subjects required longer healing time than the normal. The authors disagree the claim that the haemostatic agents can be used as bone graft substitutes. However, long-term, multicenter, randomized controlled clinical trials are required.     

The effect of the thread depth on the mechanical properties of the dental implant

PURPOSE

This study aimed to evaluate the effect of implant thread depth on primary stability in low density bone.

MATERIALS AND METHODS

The insertion torque was measured by inserting Ti implants with different thread depths into solid rigid polyurethane blocks (Sawbones) with three different bone densities (0.16 g/cm³, 0.24 g/cm³, and 0.32 g/cm³). The insertion torque value was evaluated with a surgical engine. The static compressive strength was measured with a universal testing machine (UTM) and the Ti implants were aligned at 30° against the loading direction of the UTM. After the static compressive strength test, the Ti implants were analyzed with a Measurescope.

RESULTS

The Ti implants with deeper thread depth showed statistically higher mean insertion torque values (P<.001). Groups A and group B had similar maximum static compressive strengths, as did groups C and D (P>.05). After the static compressive strength, the thread shape of the Ti implants with deeper thread depth did not show any breakage but did show deformation of the implant body and abutment.

CONCLUSION

The implants with deeper thread depth had higher mean insertion torque values but not lower compressive strength. The deep threads had a mechanical stability. Implants with deeper thread depth may increase the primary stability in areas of poor quality bone without decreasing mechanical strength.     

Mandibular cephalometric characteristics of a Saudi sample of patients having impacted third molars

Objective

To evaluate the cephalometric characteristics of mandibles of Saudi patients having impacted third molars and to compare them to those of patients having normally erupted third molars.

Material and methods

One hundred and twenty-one Saudi adult subjects (59 females and 62 males; age: 20–40 years) were divided into two groups based on the status of the mandibular third molars: (1) impaction group and (2) normal group. Means and standard deviations of 21 cephalometric measurements related to mandibular geometry were measured and compared between the two groups using the unpaired t-test. Males and females in the impaction group were also compared with their equivalent subgroups in the normal group using the unpaired t-test.

Results

Anteroposteriorly, space distal to second molar, ramal width and mandibular body length were significantly less in the impaction group than in the control group. In addition, posterior teeth were more upright in the impaction group. Vertically, posterior alveolar height was significantly less in the impaction group. The Y-axis was significantly increased in the impaction group.The significance of these measurements was variable between males and females.

Conclusions

Third-molar impactions in the Saudis living in the Western region of Saudi Arabia were more likely to occur when inadequate retromolar space is present. This can be attributed to certain mandibular skeletal and dental features, among which the increased width of mandibular ramus and backward inclination of posterior teeth seem to be the most influencing factors in both sexes.     

In vitro evaluation of resonance frequency analysis values to different implant contact ratio and stiffness of surrounding material

PURPOSE

The present study was aimed to evaluate the influence of implant contact ratio and stiffness of implant-surrounding materials on the resonance frequency analysis (RFA) values.

MATERIALS AND METHODS

Seventy resin blocks that had the different amounts (100, 50, 30, 15%) of resin-implant contact (RIC) were fabricated. Ten silicone putty blocks with 100% silicone-implant contact were also made. The implants with Ø5.0 mm × 13.0 mm were placed on eighty specimen blocks. The RFA value was measured on the transducer that was connected to each implant by Osstell Mentor. Kruskal-Wallis and Scheffe''s tests (α=.05) were done for statistical analysis.

RESULTS

The control resin group with 100% RIC had the highest RFA value of 83.9, which was significantly different only from the resin group with 15% RIC among the resin groups. The silicone putty group with 100% contact had the lowest RFA value of 36.6 and showed statistically significant differences from the resin groups.

CONCLUSION

Within the limitations of this in vitro study, there was no significant difference in the RFA values among the resin groups with different RIC''s except when the RIC difference was more than 85%. A significant increase in the RFA value was observed related to the increase in stiffness of material around implant.     

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.     

Satisfaction and quality of life with palatal positioned implants in severely atrophic maxillae versus conventional implants supporting fixed full-arch prostheses

Background

To evaluate satisfaction and quality of life in patients with palatal positioned implants supporting fixed full-arch prostheses to rehabilitate edentulous maxillae with horizontal atrophy and compare them with conventional well-centered implants placed in non-atrophic supporting fixed full-arch prostheses.

Material and Methods

A clinical retrospective study was performed of patients that were rehabilitated with full-arch fixed implant-supported maxillary prostheses and had a minimum follow-up of 5 years after implant loading. Patients were divided into 2 groups: patients with class IV maxilla according to Cawood and Howell and treated with palatal positioned implants (test) and with class III maxilla and treated with implants well-centered in the alveolar ridge and completely surrounded by bone (control). Ten-cm visual analogue scales (VAS) (range 1-10) and the OHIP-14 (Oral Health Impact Profile) questionnaire were used respectively to estimate patient satisfaction and quality of life after implant therapy. Statistical analysis was performed applying Mann-Whitney Test using alpha set at 0.05.

Results

Mean global and specific satisfaction – except for self-esteem – were superior for the test group than the control group, although differences were not statistically significant. Regarding quality of life, the reported incidence of problems was lower in the test group for all the studied ítems except for ‘problems at work’. However, differences were not statistically significant in any case.

Conclusions

Despite the limitations of the study (retrospective and nonrandomized design) the results suggest that the prosthesis design needed to rehabilitate palatally positioned implants (more coverage of palate) does not lead to lower satisfaction and quality of life of patients, compared to patients treated with implants placed centered and conventional design prostheses that do not cover the palate. Key words:Atrophic maxilla, palatal implants, satisfaction, quality of life.     

A torque-measuring micromotor provides operator independent measurements marking four different density areas in maxillae

PURPOSE

Bone density at implant placement site is a key factor to obtain the primary stability of the fixture, which, in turn, is a prognostic factor for osseointegration and long-term success of an implant supported rehabilitation. Recently, an implant motor with a bone density measurement probe has been introduced. The aim of the present study was to test the objectiveness of the bone densities registered by the implant motor regardless of the operator performing them.

MATERIALS AND METHODS

A total of 3704 bone density measurements, performed by means of the implant motor, were registered by 39 operators at different implant sites during routine activity. Bone density measurements were grouped according to their distribution across the jaws. Specifically, four different areas were distinguished: a pre-antral (between teeth from first right maxillary premolar to first left maxillary premolar) and a sub-antral (more distally) zone in the maxilla, and an interforaminal (between and including teeth from first left mandibular premolar to first right mandibular premolar) and a retroforaminal (more distally) zone in the lower one. A statistical comparison was performed to check the inter-operators variability of the collected data.

RESULTS

The device produced consistent and operator-independent bone density values at each tooth position, showing a reliable bone-density measurement.

CONCLUSION

The implant motor demonstrated to be a helpful tool to properly plan implant placement and loading irrespective of the operator using it.