Treatment concept of the edentulous mandible with prefabricated telescopic abutments and immediate functional loading

PURPOSE

The present paper demonstrates a new technique and long-term results of a treatment concept that uses four implants placed in the anterior mandible that are connected to prefabricated telescopic abutments and immediately loaded with removable restorations.

MATERIALS AND METHODS

The present retrospective study included 488 implants (Ankylos, Dentsply) placed in 122 patients (mean age: 65.2 ± 9.8 years) with clinical and radiographic evaluation for a period of at least 1 year. Eighty-four implants were placed in fresh extraction sockets and combined in the restorations with implants placed in healed ridges. All implants were placed 2 mm subcrestally (based on chart documentation, measured from the midfacial bone level). The implants were connected immediately after surgery to conical prefabricated abutments (angle of 4 to 6 degrees) using a final torque of 15 Ncm. Secondary prefabricated copings that fit the abutments were placed over the abutments after abutment connection, and the complete denture of each patient was relined chairside with methyl methacrylate resin. The prosthetic restorations were to remain in place for 10 days to ensure that the implants remained immobile.

RESULTS

After a mean of 79 ± 29.8 months (range, 17 to 129 months) only eight implants failed (1.6%). Twenty-one implants (4.3%) showed crestal bone loss greater than 2 mm relative to the implant position at the time of implant insertion. Therefore, the failure rate was 5.94% for the entire observation period. The success rate for the evaluated implants was 94.06%. The patients were satisfied with the stability of their prostheses, and no prosthetic or peri-implant problems were observed.

CONCLUSIONS

These telescopic implant-supported restorations with immediate loading seem to be an alternative prosthetic solution for the edentulous patient, providing long-term implant stability.

Fit of screw-retained fixed implant frameworks fabricated by different methods: a systematic review

PURPOSE

The aim of this study was to review the published literature investigating the accuracy of fit of fixed implant frameworks fabricated using different materials and methods.

MATERIALS AND METHODS

A comprehensive electronic search was performed through PubMed (MEDLINE) using Boolean operators to combine key words. The search was limited to articles written in English and published through May 2010. In addition, a manual search through articles and reference lists retrieved from the electronic search and peer-reviewed journals was also conducted.

RESULTS

A total of 248 articles were retrieved, and 26 met the specified inclusion criteria for the review. The selected articles assessed the fit of fixed implant frameworks fabricated by different techniques. The investigated fabrication approaches were one-piece casting, sectioning and reconnection, spark erosion with an electric discharge machine, computer-aided design/computer-assisted manufacturing (CAD/CAM), and framework bonding to prefabricated abutment cylinders.

CONCLUSIONS

Cast noble metal frameworks have a predictable fit, and additional fit refinement treatment is not indicated in well-controlled conditions. Base metal castings do not provide a satisfactory level of fit unless additional refinement treatment is performed, such as sectioning and laser welding or spark erosion. Spark erosion, framework bonding to prefabricated abutment cylinders, and CAD/CAM have the potential to provide implant frameworks with an excellent fit; CAD/CAM is the most consistent and least technique-sensitive of these methods.

Rehabilitation of malpositioned implants with a CAD/CAM milled implant overdenture: a clinical report

Dentists may be faced with the challenge of restoring unfavorably placed implants. In some instances, previously integrated implants may be from different manufacturers. This clinical report describes the rehabilitation of a patient with a maxillary CAD/CAM implant bar-supported overdenture that presented with malpositioned implants, from different manufacturers, including one from a discontinued implant system.

Comparison of three-implant-supported fixed dentures and two-implant-retained overdentures in the edentulous mandible: a pilot study of treatment efficacy and patient satisfaction

PURPOSE

The mandibular two-implant overdenture has been shown to be a highly successful treatment. However, overdenture patients who desire a fixed prosthesis may not be satisfied with a removable overdenture. This prospective study sought to compare prosthetic outcomes, patient satisfaction, and survival rates of implants between two-implant-supported overdentures (IODs) and three-implant-supported fixed dentures (ISFDs).

MATERIALS AND METHODS

Twenty completely edentulous patients were randomly and equally assigned to two groups. New conventional complete dentures were made, and the mandibular denture was used as a surgical guide during implant placement. Implants were placed in one stage, followed by a mandibular denture soft reline (provisional loading). Ball attachments were inserted at 8 weeks, and ISFDs were delivered at 16 weeks. IODs were connected to the attachments at 8 weeks, using each patients's existing denture. The definitive ISFDs were fabricated using computer-aided design/computer-assisted manufacture milled titanium frameworks and acrylic resin base and teeth. Patient satisfaction and panoramic radiographs were investigated at 6 and 12 months.

RESULTS

Both treatments had significant and positive effects on patient satisfaction and quality of life. None of the 50 implants placed had failed at 12 months of follow-up; therefore, the implant survival rate was 100%. Prosthetic complications were generally rare and easily manageable.

CONCLUSIONS

Both the treatment modalities-the ISFD supported by three implants and the IOD supported by two implants-significantly and similarly improved patient satisfaction and oral health-related quality of life, and prosthetic complications were relatively rare for both treatments. Three implants can be used to support a mandibular fixed prosthesis; however, a longer observation period is needed to validate this treatment modality.

Early loading of fixture original implants with mandibular overdentures--a preliminary report on a prospective study

PURPOSE

The aim of this study was to report the short-term clinical- and patient-based results of an early loading protocol using two Fixture Original implants with a mandibular overdenture.

MATERIALS AND METHODS

Fifteen consecutively treated patients were enrolled in this study. Each patient received 2 implants; one patient received an additional implant during the observation period, yielding a total of 31 implants used in this study. All patients were treated with overdentures supported by a resilient ovoid bar mechanism. Clinically based outcomes were documented throughout the study, while patient-based outcomes were recorded at baseline and at the 1-year follow-up using the Denture Satisfaction and the Oral Health Impact Profile.

RESULTS

Patients were followed for an average of 28.87 ± 5.04 months. The overall success rate was 100% for the implants and 93% for the original prosthetic treatment plan, since an overdenture was converted to a fixed prosthesis for one patient throughout follow-up. The mean bone loss measured during the first year of loading was 0.11 mm (standard deviation: 0.14 mm). Prosthetic maintenance events were mainly related to the acrylic superstructure. Patient-based treatment outcomes showed a statistically significant improvement with the prosthetic treatment and in their quality of life (Wilcoxon signed rank rest, P < .05).

CONCLUSIONS

This short-term longitudinal study suggests that Fixture Original implants can be loaded early using mandibular overdentures. Additionally, modified prosthetic and surgical protocols led to minimal postinsertion prosthodontic maintenance. The results underscore the effectiveness of the overdenture technique in rectifying patients' complaints with conventional mandibular prostheses.

Effect of splinting mini-implants on marginal bone loss: a biomechanical model and clinical randomized study with mandibular overdentures

PURPOSE

This aim of this study was to evaluate the effect of splinting mini-implants on marginal bone loss when used to retain mandibular overdentures.

MATERIALS AND METHODS

With mathematical models, a finite element analysis was performed to compare the bone stress distribution around two mini-implants, either splinted with a bar superstructure or not splinted. In the clinical portion of this study, 90 mini-implants were placed in the anterior mandibles of 45 completely edentulous patients selected from a public health center. Patients were randomly allocated into two groups. Group-ball (22 patients, n = 44) received two single ball-type mini-implants, and group-bar (23 patients, n = 46) received two mini-implants splinted with a prefabricated bar. All implants were placed using a flapless technique and loaded immediately. Marginal bone loss was assessed through standardized retroalveolar radiographs of each mini-implant and compared 5, 10, 15, and 24 months after implant placement.

RESULTS

The finite element analysis showed the highest minimum principal stress (-118 MPa) in bone surrounding the unsplinted mini-implant, while around the splinted implants the principal stresses were -56.8 MPa. After 2 years of follow-up in the clinical study, group-ball showed a trend toward greater marginal bone loss than group-bar (1.43 ± 1.26 mm and 0.92 ± 0.75 mm, respectively). Group-ball showed a significantly higher prevalence of vertical bone loss than group-bar (chi-square test, two-tailed).

CONCLUSION

Splinted mini-implants with a rigid superstructure decrease the bone stress level in comparison with single mini-implants. The effects of bone stress magnitude may explain the clinical outcome, in which splinted mini-implants supporting a mandibular overdenture showed less marginal bone loss compared with nonsplinted mini-implants. Vertical bone resorption morphology was significantly more prevalent in the latter group.

[Restore two posterior teeth with modified resin-bonded-bridge]

OBJECTIVE

To restore two posterior teeth with resin-bond-bridge with attachments.

METHODS

Twenty patients were selected with two adjacent posterior teeth missing and the opposite teeth were natural teeth. The mean age was 45.6 years old, 9 male and 11 female. The maxillary cases were 12 and mandibules case were 8. The female part of attachment was attached with the retainer on the bicuspid teeth; the male part was attached with the pontic. After try-in, the two parts were adhered to the abutments separately and joined by the attachment.

RESULTS

The mean survival time of the 20 cases was 28.8 months, and the max was 42 months. In only one case the posterior part debonded, and it resumed being used after rebonding.

CONCLUSION

In recent years the successful rate of resin-bond-bridge has got close to that of the traditional bridge. Most RBB were used to restore the single missing tooth. Now RBB with non-rigid connector can restore two missing teeth. When the teeth get stress, the directions of stress are different. The longer span of RBB with rigid connector, the bigger interbutment stress on the adhere layer. With the non-rigid connector the stress between the retainer and the adhesive layer can be reduced. Our clinic treatment showed that this kind of method got good results and even the service time was not very long.

Immediate loading of implants and fixed complete dentures: a simplified prosthetic procedure

The immediate placement of fixed prostheses after the surgical phase is a challenge for prosthodontists using the All-on-four method. This article describes a simplified technique for constructing a conventional complete denture ahead of the surgery date and adapting it to the implants by using a laboratory reline procedure. This technique accommodates the immediate placement of the fixed prosthesis after surgery without compromising the quality of the prosthesis, requiring only a simple dental laboratory procedure.

Metal bases for implant overdentures

Reinforcement of implant overdenture bases with chromium alloys offers a number of advantages that offset the initial greater cost. These bases offer increased strength, the ability to detect thermal changes, and the option for use when space is at a minimum. Both acrylic resin and chromium alloy have long (approximately 80 years), successful histories as accepted dental materials. Low-heat (nickel) or high-heat (cobalt) chromium alloys can be used with equal success.

Mandibular overdentures retained by two implants: 10-year results from a crossover clinical trial comparing ball-socket and bar-clip attachments

PURPOSE

The aim of this study was to evaluate patient satisfaction and clinical and prosthetic outcomes of two-implant mandibular overdenture treatment with different attachment types after 10 years of function.

MATERIALS AND METHODS

In a crossover clinical trial, 18 edentulous subjects with complaints regarding their mandibular dentures received two implants and a new denture with magnet, ball-socket, or bar-clip attachments that were applied in a random order. At the end of the experiment, the attachment type of their choosing was fitted in the overdenture. After 10 years, 7 subjects with a ball-socket and 7 subjects with a bar-clip attachment were available for evaluation. The same questionnaire from 10 years before was completed, and subjects were asked to express their overall appreciation of their dentures on a visual analog scale (VAS). Six scales of denture complaints were constructed. Mean scale and VAS scores between initial evaluation and after 10 years were compared. In addition, marginal probing depths, Bleeding Index, and radiographic marginal bone loss were assessed.

RESULTS

There was no marked difference in satisfaction between subjects with ball-socket- and bar-clip-retained two-implant mandibular overdentures at initial evaluation and after 10 years of function.

CONCLUSION

Patients' appreciation of their implant-retained denture was and remained high over time. Clinical parameters revealed healthy mucosal conditions and stable marginal bone levels, determined radiographically. Probing depths around implants provided with ball-socket attachments were slightly shallower than those with bar-clip attachments after 10 years of function (P < .05).

Marginal bone loss with mandibular two-implant overdentures using different loading protocols and attachment systems: 10-year outcomes

PURPOSE

The aim of this study was to evaluate long-term marginal bone levels for two unsplinted implants supporting mandibular overdentures using conventional and early loading protocols with different implant surfaces and attachment systems.

MATERIALS AND METHODS

A cohort of 106 edentulous participants (mean age: 65 years) was treated with mandibular two-implant overdentures opposing complete maxillary dentures. Participants were randomly allocated into three loading protocol groups using four implant systems; single-stage surgery was performed for all participants, followed by an unsplinted prosthesis using six different attachment systems. Standardized intraoral radiographs taken at baseline (loading) and over 10 years appraised marginal bone levels mesially and distally from reference points under magnification. Three calibrated examiners repeated measurements, diminishing intra- and interobserver variability. Progressive attrition of participants occurred as a result of deaths, dropouts, and emigration. Seventy-nine participants (74.5%, mean age: 72 years) were available at the 10-year recall. Differences in bone loss among different loading protocols, implant surfaces, and attachment systems were tested using chi-square and one-way analysis of variance tests.

RESULTS

Minimal, time-dependent, long-term marginal bone loss occurred with all loading protocols. Annual marginal bone loss progressed at low levels after the first year with episodes of bone loss and gain. There was stability in marginal bone levels over the long term, with the majority of remodeling occurring during the first year of function. Roughened implant surfaces may be beneficial during the early remodeling period. The amount of marginal bone loss in the first year of loading differed significantly by loading protocol and implant surface, whereas attachment system had a minor influence. Differences were not reflected in the success rates calculated using standard criteria. The remaining participants at 10 years were classified as successful related to the criterion of marginal bone loss, irrespective of the determining criteria for success.

CONCLUSIONS

Either a 2- , 6-, or 12-week loading protocol for mandibular two-implant overdentures is possible in the long term, irrespective of the attachment system used. Minimal marginal bone loss may be attributed primarily to mandibular basal bone remaining from long-term edentulism. Revision of the current implant success criteria to offer a stricter limit is desirable.

A new treatment concept for immediate loading of implants inserted in the edentulous mandible

OBJECTIVES

Retention of mandibular complete dentures on two or four interforaminal implants is considered the most reliable procedure in implant therapy. There are different retention elements available for all implant systems. The aim of the present study was to clinically evaluate patients with a mandibular overdenture supported by the Ankylos SynCone system (Dentsply).

METHOD AND MATERIALS

Thirty-nine patients were treated with 156 implants. The treatment method was based on immediate loading of four interforaminal implants without the use of a bar retainer. The denture was placed on and retained by prefabricated conical crowns that were inserted into the existing denture base by direct intraoral polymerization immediately after surgery and supported by the corresponding conical primary implant abutments.

RESULTS

The cumulative implant survival rate was 98.7% (two failures), while the prosthesis survival rate was 100%. After a total observation of 30.3 months (range 12 to 60 months), all other implants presented healthy peri-implant soft tissue conditions showing low value of clinical parameters.

CONCLUSION

This method facilitates secondary splinting of the inserted complete denture. The conical crowns concept presented here resulted in stable complete denture retention, reduced the denture base, and improved oral hygiene.

Clinical evaluation of a fixed (retrievable) implant-supported prosthesis in the edentulous jaw: a 5-year report

OBJECTIVE

This retrospective study evaluated the success rate of a fixed retrievable prosthesis based on an electroforming technique combining the advantages of screw- and cement-retained principles.

METHOD AND MATERIALS

Forty patients (17 men and 23 women) with a mean age of 62.2 years were treated. A total of 353 implants were placed in the edentulous maxilla, mandible, or both jaws to allow prosthetic rehabilitations with 55 fixed prostheses. Clinical success of the implants was based on the criteria of Buser. Technical complications monitored throughout the wearing period are described. Retrievability of the restoration with a conventional crown remover was checked at 6, 12, and 36 months. The cumulative survival rate of the implants was measured.

RESULTS

After a mean observation period of 4.08 years (range 22 to 62 months), a cumulative survival rate of 99.15% was recorded for the 234 maxillary implants (234 Camlog RootLine, Camlog) and for the 119 mandibular implants (72 Camlog RootLine, 47 Camlog ScrewLine). Three implants failed before prosthetic loading. Monitored technical complications were seen in 10.91% of the restorations; they comprised ceramic chip-off and relining.

CONCLUSIONS

This fixed implant-retained prosthesis based on electroforming indicates a comparable clinical efficacy to other techniques and allows scheduled retrieval.

Mandibular implant overdentures followed for over 10 years: patient compliance and prosthetic maintenance

PURPOSE

The mandibular implant overdenture is a popular treatment modality and is well documented in the literature. Follow-up studies with a long observation period are difficult to perform due to the increasing age of patients. The present data summarize a long-term clinical observation of patients with implant overdentures.

MATERIALS AND METHODS

Between 1984 and 1997, edentulous patients were consecutively admitted for treatment with an implant overdenture. The dentures were connected to the implants by means of bars or ball anchors. Regular maintenance was provided with at least one or two scheduled visits per year. Recall attendance and reasons for dropout were analyzed based on the specific history of the patient. Denture maintenance service, relining, repair, and fabrication of new dentures were identified, and complications with the retention devices specified separately.

RESULTS

In the time period from 1984 to 2008, 147 patients with a total of 314 implants had completed a follow-up period of >10 years. One hundred one patients were still available in 2008, while 46 patients were not reexamined for various reasons. Compliance was high, with a regular recall attendance of >90%. More than 80% of dentures remained in continuous service. Although major prosthetic maintenance was rather low in relation to the long observation period, visits to a dental hygienist and dentist resulted in an annual visit rate of 1.5 and 2.4, respectively. If new dentures became necessary, these were made in student courses, which increased the treatment time and number of appointments needed. Complications with the retention devices consisted mostly of the mounting of new female retainers, the repair of bars, and the changing of ball anchors. The average number of events and the rate of prosthetic service with ball anchors were significantly higher than those with bars. Twenty-two patients changed from ball anchors to bars; 9 patients switched from a clip bar to a rigid U-shaped bar.

CONCLUSIONS

This long-term follow-up study demonstrates that implant overdentures are a favorable solution for edentulous patients with regular maintenance. In spite of specific circumstances in an aging population, it is possible to provide long-term care, resulting in a good prognosis and low risk for this treatment modality. For various reasons the dropout rate can be considerable in elderly patients and prosthetic service must be provided regularly.

A systematic review of marginal bone loss around implants retaining or supporting overdentures

PURPOSE

To evaluate, through a systematic review of the literature, the effects of implant design and attachment type on marginal bone loss in implant-retained/supported overdentures.

MATERIALS AND METHODS

With the combined search terms "implant and overdenture," "implant-supported overdenture," "implant-retained overdenture," and "implant-anchored overdenture," along with specific inclusion and exclusion criteria, eligible articles between 1997 and 2008 (up to April 1) were retrieved from PubMed, EMBASE, OVID, the Cochrane Library databases, and seven journals by hand searching. Marginal bone loss values with regard to time, attachment type, and implant system used were compared by Kruskal-Wallis tests. Means and standard deviations of data were combined using fixed- and random-effect models and evaluated using meta-analysis.

RESULTS

Forty-six articles were included in the analyses; data extraction and meta-analysis were able to be conducted on eight studies. Data regarding maxillary overdentures could not be analyzed statistically. Bone loss around mandibular implants did not seem to be influenced by implant system or attachment design (bar, ball, magnet, and other types) in the first year, from 1 to = or < 5 years, and even after 5 years (P > .05). Meta-analysis could not detect differences in implant systems or attachment types (P > .05).

CONCLUSIONS

Based upon a systematic review and meta-analysis of the literature that identified a total of 4,200 implants from 13 manufacturers, there was no difference in marginal bone loss around implants retaining/supporting mandibular overdentures relative to implant type or attachment designs.

Retrospective analysis of bar-retained dentures with cantilever extension: marginal bone level changes around dental implants over time

PURPOSE

The aim of this study was to retrospectively determine whether a relationship exists between the length of the distal bar extension and the amount of marginal bone loss around implants supporting cantilevered bar-retained dentures.

MATERIALS AND METHODS

This study was performed using data from patients who had been restored with implant-supported cantilevered bar-retained prostheses. Panoramic radiographs were obtained annually starting at the time of prosthetic loading of the implants; the protocol included a 4-year observation period. Vertical changes in the bone level were measured on the mesial and distal of implant sites with respect to a defined reference point per implant system, and radiographic distortions were compensated. Statistical analysis was performed with the Wilcoxon signed-rank test, the Spearman rank correlation test, and the two-factor nonparametric analysis for repeated measurements.

RESULTS

A total of 48 edentulous patients who were consecutively treated with 313 dental implants and rehabilitated with 66 bar-retained prostheses were included in the study. Implants were used to support 30 prostheses in the maxilla (172 implants) and 36 prostheses in the mandible (141 implants). These prostheses were supported by bars with distal cantilevers of up to 12 mm. Patients with bars without cantilevers served as the control group. After 4 years, mean mesial bone loss was 2.20 +/- 0.91 mm; for distal implant sites it was 2.31 +/- 1.05 mm. The number of implants inserted and implant length did not correlate with bone loss. Jaw (maxilla versus mandible) and implant system exerted a significant influence on the amount of bone lost within the first year. Cantilever length did not influence marginal bone loss.

CONCLUSION

In this clinical study, no influence of the length of cantilever extensions on crestal bone loss was found. Within the limitations of the study, the results indicate that restorations with distal bar extensions up to 12 mm are an adequate treatment option for edentulous patients.

A modified method for rebasing implant-retained overdentures

There is a constant need for rebasing implant-retained overdentures because of the inevitable continuous absorption of the underlying residual ridge, which results in a lack of proper occlusion and possible rotation of the denture around the retentive components. This step-by-step article describes all of the clinical and laboratory procedures needed for rebasing a mandibular implant overdenture retained with a bar on two implants, securing an accurate fit. This procedure can be applied successfully for rebasing overdentures with different superstructures (ball attachments or magnets), and for replacing worn or damaged retentive components and matrices.

Attachment systems for mandibular single-implant overdentures: an in vitro retention force investigation on different designs

PURPOSE

The aim of this study was to investigate the retentive force of six different attachment systems used for mandibular single-implant overdentures, including two prototype large ball attachment designs.

MATERIALS AND METHODS

Two prototype ball attachments of larger dimensions (7.9 and 5.9 mm) and four commercially available ball and stud attachments of standard dimensions (2.25 and 4.0 mm) were evaluated on three identical test casts resembling an edentulous mandible with severe residual ridge resorption. Five samples from each attachment system (n=30) were connected to three different implants (8.0-mm wide diameter, 3.75-mm regular diameter, and 4.0-mm regular diameter). An Instron testing machine with a computer software package was used to deliver a vertical dislodging force at a cross-head speed of 50 mm/min to each overdenture sample from the anterior direction. A total of 300 pull tests were conducted (50 per attachment system). The maximum load (retentive force) required to separate each overdenture from the supporting implant was then measured.

RESULTS

The highest retentive force (36.97+/-2.23 N) was achieved with the 7.9-mm prototype ball attachment design, followed in a decreasing order by the 5.9-mm prototype ball attachment design (32.06+/-2.59 N), the standard 2.25-mm ball attachment (17.32+/-3.68 N), Locator white (12.39+/-0.55 N), Locator pink (9.40 N+/-0.74 N), and Locator blue (3.83+/-0.64 N). A statistically significant difference (P<.0001) was found between all attachments.

CONCLUSIONS

Attachment systems of larger dimensions provided higher retentive forces for mandibular single-implant overdentures. Further in vitro and in vivo research is necessary to determine prosthodontic outcomes with these attachments in edentulous patients prior to their routine clinical use internationally.

The evaluation of selected attachment systems for implant-retained overdenture based on retention characteristics analysis

The results of mechanical characteristics of attachments used for retaining and stabilizing overdenture have been analysed. Two commercially used attachments (a ball attachment and a bar attachment) and elastic frictional attachments designed by the research team with Professor Chladek as the leader have been investigated. The diagrams of force-displacement characteristics have been registered. Retention forces (F(R)) have been determined and total work (W(T)) disconnecting the attachments has been calculated on the basis of these diagrams. The analysis of total work corresponding to different types of attachments made it possible to distinguish some characteristic areas which illustrate specific features of particular designs. It has been revealed that determining the retention force allows us to compare only the attachments which work on similar bases. In order to conduct a purely objective comparison of the efficiency of different designs, it is necessary to analyze complete force-displacement characteristics as well as to determine on this basis the subsequent phases of separating the parts of attachments and to find the value of the work which in fact determines their quality. The comparison of selected commercially used designs and the presented elastic frictional attachments (taking into account the criterion of work) gives clear evidence that the introduced design of attachment enables us to create very good conditions of retaining overdenture.

Marginal bone loss and prosthetic maintenance of bar-retained implant-supported overdentures: a prospective study

PURPOSE

To compare marginal bone loss, soft tissue conditions, and prosthetic outcomes of implants supporting mandibular and maxillary bar-retained overdentures.

MATERIALS AND METHODS

A total of 124 implants (80 in the mandible and 44 in the maxilla) were placed in 35 patients. Bar-retained overdentures were fabricated for each patient. Prosthetic complications were recorded throughout the study. Plaque, peri-implant inflammation, bleeding, and calculus indices were recorded, and standard periapical radiographs were obtained at each implant site for measurement of marginal bone loss.

RESULTS

One implant failed in the mandible prior to prosthesis fabrication and one failed in the maxilla 5 years after prosthesis delivery. Both were replaced after 12 weeks of bone healing. The mean marginal bone loss around maxillary implants was greater than that around mandibular implants. Comparative evaluations of subgroups followed for < 5 years and greater than or equal to 5 years showed that soft tissue parameters were similar for maxillary and mandibular implants. One- and 5-year survival probabilities of the mandibular and maxillary overdentures were comparable. Kaplan-Meier and log-rank tests revealed that the probabilities of retightening of retainer and requirements for occlusal adjustments were higher for mandibular overdentures, whereas other maintenance requirements were comparable. The retainers in mandibular overdentures needed retightening more frequently than the retainers in maxillary overdentures.

CONCLUSIONS

Dental implants supporting mandibular and maxillary bar-retained overdentures have similar peri-implant soft tissue outcomes and overall prosthetic survival probabilities.

Systematic review of prosthetic maintenance requirements for implant-supported overdentures

PURPOSE

To evaluate prosthetic maintenance requirements for implant-retained/supported overdentures via a review of the literature.

MATERIALS AND METHODS

Using the combined search terms "implant and overdenture," "implant-supported overdenture," "implant-retained overdenture," and "implant-anchored overdenture," along with specific inclusion and exclusion criteria, eligible articles between 1997 and 2008 (up to April 1) were retrieved from PubMed, EMBASE, OVID, the Cochrane Library databases, and seven journals by hand-searching. The initial search yielded 3,120 titles, and 287 articles were assigned to full-text analysis. Upon classification of the prosthetic complications with regard to the jaws treated and the attachment systems used, within- and between-group comparative frequency analyses were undertaken with the Kruskal-Wallis test or the Mann-Whitney U test at P < .05.

RESULTS

A total of 49 articles were included. Within- and between-group evaluations with regard to jaw treated as well as the attachment systems used showed that the frequency of complications did not change over time (P > .05). The differences detected were more matrix replacements after 5 years in the maxilla and mandible and more matrix replacements and patrix fractures after the first year in the mandible (P < .05). Among the attachment systems, a dislodged, worn, or loose matrix or its respective housing was more common in the ball-attachment group after the first year (P < .05). Prosthetic complications for all types of attachments were comparable (P > .05), except for the differences in peri-implant or interabutment mucosal enlargement rates after 1 year.

CONCLUSIONS

Prosthetic maintenance requirements for overdentures on both jaws seem to be comparable. The impact of attachment system on the prosthetic outcome is negligible.

Evaluation of the retentive force of a b-type Ti-6Mo-4Sn alloy wire clasp

The retentive force of a wire clasp composed of a b-type Ti-6Mo-4Sn alloy (b-Ti alloy) with a low Young modulus was evaluated using a piezoelectric transducer to determine the appropriate undercut for removable partial dentures. There were no significant differences in retentive force between a b-Ti alloy wire with a 0.50-mm undercut and a cobalt-chromium alloy (Co-Cr alloy) wire with a 0.25-mm undercut, or between a b-Ti alloy wire with a 0.75-mm undercut and a Co-Cr alloy wire with a 0.50-mm undercut. The b-Ti alloy wire may be applicable for abutment teeth with a large number of undercuts. Int J Prosthodont 2010;23:38-41.