|Year : 2019 | Volume
| Issue : 4 | Page : 189-196
Evaluation of bilateral mandibular distal extension implant supported overdenture retained by two clasp assemblies
Reda F. Radwan BSc , Attiah A. El Gendy, Azza A. El-Segai, Saied M. Abdalla
Department of Prosthodontics, Faculty of Dentistry, Tanta University, Tanta, Egypt
|Date of Submission||02-Feb-2019|
|Date of Acceptance||30-Nov-2019|
|Date of Web Publication||28-Feb-2020|
Reda F. Radwan
Department of Prosthodontics, Faculty of Dentistry, Tanta University, Tanta
Source of Support: None, Conflict of Interest: None
Clinically evaluate the effect of clasp design on tissue health around abutment teeth and implants assisting mandibular bilateral distal extension removable partial overdenture. M&M: 12 partially edentulous patients with mandibular bilateral free end saddle opposed by almost dentulous intact maxilla with the first premolars. Two dental implants were inserted at the first molar areas to support a bilateral distal extension partial overdenture with lingual bar as major connector. According to clasp design patients are divided in two groups. Group I: six patients for whom removable partial overdentures were retained with O-ring attachment to the implants and RPI clasp to the first premolar abutment teeth. Group II: six patients for whom removable partial overdentures were retained with O-ring attachment to the implants and conventional Aker clasp to the abutment teeth.
Gingival index, probing depth and teeth mobility together with radiographic evaluation for alveolar bone loss around both implants and abutments using Digora for Windows were carried out immediately at insertion, 3, 6, and 9 months after insertion.
After the first 3 months gingival index and probing depth increased significantly in both groups within the physiological limit while at the end of ninth month after insertion, no statistically significant difference between two groups. Differences between two groups regarding mobility and alveolar bone loss around abutment teeth through all the study periods, there is no statistically significance difference between the two groups. Regarding mobility and alveolar bone loss around implants through all the study periods, there is no statistically significant difference between results.
Presence of bilateral posterior implants reduce most problems of mandibular Kennedy class I such as preservation of abutment teeth, reduction of alveolar bone loss around the abutments and reduction the problems of rigid (Aker) clasp.
Keywords: aker clasp, bilateral mandibular distal extension, bilateral mandibular, clasp assemblies, implant, RPI clasp
|How to cite this article:|
Radwan RF, El Gendy AA, El-Segai AA, Abdalla SM. Evaluation of bilateral mandibular distal extension implant supported overdenture retained by two clasp assemblies. Tanta Dent J 2019;16:189-96
|How to cite this URL:|
Radwan RF, El Gendy AA, El-Segai AA, Abdalla SM. Evaluation of bilateral mandibular distal extension implant supported overdenture retained by two clasp assemblies. Tanta Dent J [serial online] 2019 [cited 2020 Jul 6];16:189-96. Available from: http://www.tmj.eg.net/text.asp?2019/16/4/189/279726
| Introduction|| |
The distal extension partial denture is supported and retained by natural teeth at one end of the denture base segment and on which a portion of the functional load is carried by the residual alveolar ridge. The bilateral distal extension removable partial denture has always been associated with number of problems such as retention, stability, support and discomfort upon loading, most of these problems could be attributed to absence of posterior abutment. Patient lacking mandibular posterior teeth as (Kennedy class I) is frequently present in the dental clinics and require more accurate prosthodontics rehabilitation for preserving the remaining teeth and residual ridge.
The difference in resiliency between the mucosa and the periodontal ligament present a considerable challenge, as support is needed from natural teeth, mucosa and residual alveolar ridges, many investigators suggested different approaches to balance the loads distributed among the teeth and ridge such as making functional impressions, periodic rebasing of the prosthetic seat, use of stress releasing clasps and splinting of the distal support abutments.
None of the management options appear to provide an ideal solution to Kennedy class I cases, possible solution to this clinical challenge were the use of single implants placed bilaterally at the molar areas beneath distal extension base which reduce lateral stress of the abutments minimize the resultant denture displacement and reduce ridge resorption.
Dental implants placed in the posterior site modify the Kennedy classification of partially edentulous arches by converting class I into class III to overcome the numerous problems associated with removable partial dentures in addition to achieving a higher level of patient satisfaction.
As the different retainers influenced the occlusal load distribution, the type of retainer is important for a long-term successful restoration. This study was aimed to clinically evaluate the effect of different clasp designs on the tissue health around the abutment teeth and distal implants supporting the mandibular bilateral distal extension removable partial overdenture.
| Materials and Methods|| |
Twelve healthy partially edentulous male patients their age ranged from 30 to 50 years were selected from the outpatient clinic of Prosthodontics Department.
The surgical guide stent was inserted in the patient's mouth and the probe was used to form bloody points to mark the proposed site for implant placement. Standardized surgical minimally invasive flapless approach according to Becker and Kaiser was followed for proper osteotomy. Postoperative panoramic radiograph was done to every case after fixture insertion. After 3 months of osseointegration removable partial overdenture was constructed [Figure 1].
The removable partial denture design on the surveyed study was identified to determinate rest positions, major connector and the extension base boarder. The design of the mandibular removable partial denture was the same for all groups; the only difference was in the type of direct retainer used. Preparation of abutment teeth (reshaping, occlusal rest seat and proximal plate preparation)
- In group I:the prosthesis is retained by RPI clasp.
- In group II:prosthesis is retained by conventional Aker clasp.
Final impression was made using rubber base condensation silicon type impression material (hydrogum extra fast setting alginate, Zhermack, Italy) then poured with type II dental stone. The metal framework was cheeked in the patient mouth. An altered cast procedure according to Leupold and Kratochvil to improve tissue support for removable partial denture. Chair-side pick-up procedure was done according to Banton and Henry.
Gingival index (GI), probing depth (PD), and mobility three clinical evaluations were assessed around natural abutments and implants immediately at insertion, 3, 6, and 9 months after removable partial overdenture loading.
The gingival index
The gingival tissues around the implants were isolated and gently dried by a piece of gauze. For each abutment, the buccal and lingual surfaces were individually scored. This was done according to the gingival scores described by Loe and Silness.
According to Ramfojord, PD measurements were taken at six-points measuring mesial, middle, and distal from the buccal and the lingual aspect.
According to Meredith et al.:
- The entire measuring procedure was took a round 4 s.
- The periotest was correctly positioned, perpendicular to the long axis of the ball abutment or the abutment tooth to be sure of obtaining valid and meaningful measurement.
An assessment of the bone quantity at the implant site was done with the help of intra-oral periapical radiographs obtained by the long cone paralleling technique to minimize the distortion and standardized results using the film holders (Rinn XCP, TPC; Advanced Technology Inc., USA). All patients will expose to periapical radiographs and digital panoramic radiographs for comparison at insertion, 3, 6, and at 9 months. By using film holder to standardize the results, Digora sensor was inserted into Digora scanner (Soredex Inc., Tuusula, Finland) for processing [Figure 2],[Figure 3],[Figure 4].
|Figure 2: Both side fixtures insertion and cover screw tightened in its place.|
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Reference lines for abutment and implants
All patients were registered into the program and tabulated to compare the results [Digora for Windows, version 2.7 (DFW)]. Following steps were done for abutments and implants for both groups [Figure 5].
|Figure 5: Digital periapical radiograph for group I present the alveolar bone loss around abutment and implant from insertion, 3, 6 and 9 months..|
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- Horizontal line was drown at the apex of abutment tooth and implant with 40 mm (software will calibrate the distance for standardization).
- Mesial and distal vertical line (B and C) was drowning around the mesial and distal aspect of implant and abutments from most superior point of alveolar bone height (point D) to the reference line (line A).
- A minimum of two readings were made for each implant and two reading were made for each abutment for both groups and the average values were used to calculate the amount of crystal bone loss. The results obtained were subjected to statistical analysis using Student's unpaired t test.
- Reference line.
- Line B to determine.
- The measurement from the most superior the bone–implant contact to the reference point from distal side.
- Line C to determine the measurement from the most superior the bone–implant contact to the reference point from mesial side.
- Point D, the most superior bone–implant contact. The point where we start the measuring.
| Results|| |
[Table 1] and [Table 2].
|Table 1: Gingival Index scores around abutments in both groups through all study period|
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|Table 2: Gingival index scores around implants in both groups through all study period|
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Propping depth was demonstrated in [Table 3] and [Table 4].
|Table 3: Comparison between two groups regarding probing depth around implants|
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|Table 4: Probing depth scores around implants in both groups through all study period|
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Mobility was recorded and mentioned in [Table 5] and [Table 6].
|Table 5: Mobility (PTVs) scores around abutments in both groups through all study period|
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|Table 6: Comparison between two groups regarding mobility (PTVs) around implants through all study period|
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Radiographic evaluation recorded Alveolar bone loss as shown in [Table 7] and [Table 8].
|Table 7: Alveolar bone loss around abutment teeth for both groups through all study period|
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|Table 8: Alveolar bone loss around implants for both groups through all study period|
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| Discussion|| |
The mandibular distal extension RPDs have many problems which can be overcome with the placement of implants at the first molar areas, the implant assisted removable partial denture serves as a cost-effective, prosthetic solution for partially edentulous patients who are not candidates for extensive fixed implant supported restorations.
This study was aimed to evaluate the effect of clasp designs clinically and radiographically on the abutment teeth and distal implants regarding GI, PD, mobility and alveolar bone loss. As different retainers influence the occlusal load distribution with long-term successful restoration.
Different retainers of RPDs will have different effects on abutments and residual ridges. Rigid retainers (Aker clasps) produced less damage to the residual ridges and much stresses to the abutments, while flexible retainers (RPI clasps) were found to create greater stress concentrations on the residual ridges and less stresses to the abutments. The use of dental implant to Kennedy class I cases control the excessive torque forces that may act on the abutment.
The RPI clasp fulfills the requirements or proper clasp design, and minimizes stress on the abutment tooth. The rest, located on the mesial occlusal surface of the abutment tooth, acts as the point of rotation and exerts a mesial force on the tooth rather than a distal displacing force. Pressure exerted on the extension base moves the proximal plate tissue ward without torque the tooth. The (I) bar also moves mesiogingivally away from the tooth under masticatory load.
Aker (circumferential clasp) would appear to be the most simple and versatile clasp suitable for the mandibular first premolars. Excellent bracing qualities and easy to design and construct. Presence of soft tissue undercuts buccally often precludes the use of RPI clasp, the Aker clasp was able to resist lateral forces.
The O-ring is perhaps the most popular attachment available to the dental implant to increase the retention of partial overdentures as well as conventional overdentures. Compressive loading of implant O-ring attachments assemblies must occur only in conjunction with tissue loading; otherwise, forces may develop can be destructive to the implant, the abutment, the tissue, and the prosthesis.
Clinical evaluation parameters include: GI according to Loe and Sinless, PD according to Ramfojord and mobility test together with radiographic evaluation for alveolar bone loss around both implants and abutments using Digora for Windows software were carried out immediately at insertion, 3, 6 and 9 months after insertion.
Digora system was consider one of the reliable and versatile technology due to good image quality and easy to use and reduce exposure time which expand the diagnostic and image referral possibilities of radiology in dentistry.
Regarding to GI the increase of GI after 3 months of insertion was statistically significant in both groups this may be correlated to increased plaque accumulation, this was in agreement with Karoussis et al. and Amaral et al..
While at the sixth month the increase was not statistically significant up to ninth months. This result was in agreement with Alam-Eldeen, he concluded that, regardless the type of the retainer used with natural abutments, GI and PD have no significant differences effect on implants and natural abutment teeth.
This result was in agreement with Saleh, who study the effect of two different clasps, Aker clasp and reverse Aker clasp on tissue health around abutment teeth and implants assisting mandibular bilateral removable partial overdenture, the results was no statistically significant differences between results in regard oral tissue health around the abutment teeth and implants located in the first molar area.
Another explanation for this result may be related to the first contact of the denture to the patient's soft tissue, which may be combined with some inflammation in the mucosa and periodontium supporting structure.
In this study, with time, in both groups, PD of the abutment teeth and implants there was no statistically significant differences after 9 months, this may be attributed to the sufficient oral hygiene instruction after insertion and continuous recall appointment, and this was in agreement with Mekkawy, Eugenio et al. and Gerber et al..
Also our results for pocket depth are in agreement with Abo Elnaga, she was compered between two groups group I retained with O-ring attachment and group II retained with dome shape abutment she found that, no statistically significance difference in PD around abutment teeth and implants regardless type of attachment used with implants.
Almost all the fixtures were successfully osseointegrated all over the follow-up period, that there is no mobility, no pain and the fixtures were surrounded by normal bone tissue in intimate contact with their surfaces this was in agreement with Zancopé et al..
I-bar and circumferential clasps did not differ significantly in terms of success rates after 60 month.
The differences between the mobility of the abutments and implants in both groups were not statistically significant differences throughout the observation period, these results are in agreement with Miller and Grasso, and Kapura et al., Naert et al. and Jorge et al. they measure the mobility to the abutment and implants after the insertion of the prosthesis and the result was a more stable prosthesis associated with a progressive osseointegration process.
Also the results were in agreement with Aparicio et al. they were study implant stability and evaluated that there were direct correlation between decreased negative periotest values and osseointegration.
The amount of peri-implant bone loss agrees with the findings obtained by Albrektsson et al. who proposed criteria for implant survival and success, in which marginal bone level changes in the first year should be less than 1 mm, and annual bone loss should be less than 0.2 mm.
In this study, crestal bone resorption related to implant and abutments in both groups after 9 months follow up did not exceed 1 mm, hence implants were considered successful this were in agreement with Piao and Koak and Mahrous.
The placement of a bilateral distal implants to assist and retain a RPD can prevent most of abutment teeth problems associated with conventional RPD and reduce marginal bone loss this were in agreement with Bortolini et al. and Chronopoulos et al..
Continuous recall for checkup the occlusion and partial denture fit is necessary. Also, the oral hygiene instruction is very important factors for long-term successful restoration.
| Conclusion|| |
Through ready established data, the use of rigid (Aker clasps) can cause significant changes regarding to GI, PD, mobility and alveolar bone loss to abutment teeth when used as a direct retainers in case of bilateral mandibular free end saddle cases when compared with gingival approaching resilient retainers (RPI clasps). Our results concluded that, the placement of a bilateral distal implants in case of mandibular bilateral free end saddle reduce most problems of direct retainers on the abutments when adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments were done. Despite these favorable clinical findings, it is important to mention that, future long-term investigations are needed before definite conclusions [Figure 6],[Figure 7],[Figure 8],[Figure 9],[Figure 10].
|Figure 6: Digital periapical radiograph for group II present the alveolar bone loss around abutment and implant from insertion, 3, 6 and 9 months.|
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|Figure 8: The mean values of gingival index in both groups around abutment and implants at the different intervals of the follow-up period.|
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|Figure 9: The mean values of probing depth in both groups around abutments and implants at the different intervals of the follow-up period.|
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|Figure 10: The mean values of mobility (PTVs) scores for both groups around abutments and implants at the different intervals of the follow-up period.|
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Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]