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Effect of implant-supported or retained dentures on masticatory performance: A systematic review
Effect of implant-supported or retained dentures on masticatory performance: A systematic review Kenji Fueki, DDS, PhD,a Katsuhiko Kimoto, DDS, PhD,b Takahiro Ogawa, DDS, PhD,c and Neal R. Garrett, PhDd Tokyo Medical and Dental University, Tokyo, Japan; Kanagawa Dental College, Yokosuka, Japan; The Jane and Jerry Weintraub Center of Reconstructive Biotechnology, University of California Los Angeles, School of Dentistry, Los Angeles, Calif; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, Calif Statement of problem. While subjective patient-based measures have been increasingly recognized as critical outcomes for prosthodontic treatment, there continues to be a need to validate for patients what changes in masticatory function can be expected with the provision of new implant-supported or retained dentures. Purpose. The purpose of this review was to evaluate the critical factors impacting change in masticatory performance following the provision of new implant-supported or retained dentures. Material and methods. Information retrieval followed a systematic approach using PubMed and the Cochrane Library. English articles published from 1966 to June 2007, in which the masticatory performance of subjects with implant-supported or retained dentures was assessed by objective methods and compared to performance with conventional dentures, were included. Ratings of the evidence provided in each article followed United States Agency for Healthcare Research and Quality recommendations. Results. From 281 articles identified, 18 peer-reviewed articles met prespecified criteria for inclusion. Specific outcomes of significance identified by these articles rated as level II are: (1) fixed implant-supported partial dentures do not provide significant improvement in masticatory performance compared to conventional removable partial dentures for Kennedy Class I and II partially edentulous mandibles; (2) the combination of a mandibular implant-supported or retained overdenture (IOD) and maxillary conventional complete denture (CD) provides significant improvement in masticatory performance compared to CDs in both the mandible and maxilla for a limited population having persistent functional problems with an existing mandibular CD due to severely resorbed mandible; and (3) the type of implant and attachment system for mandibular IODs has a limited impact. Specific outcomes of significance identified by articles rated as having a moderate level of evidence (level III) are: (1) mandibular fixed implant-supported complete dentures provide significant improvement in masticatory performance compared to mandibular CDs in subjects dissatisfied with their CDs; and (2) implant-supported mandibular resection dentures have an advantage over conventional dentures in masticatory performance on the defect side of the mouth. Supported by the Overseas Advanced Educational Research Practice Support Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology. This investigation used resources of a facility constructed with support from the Research Facilities Improvement Program Grant No. C06 RR-14529-01 from the National Center for Research Resources, National Institutes of Health, Bethesda, Maryland. Lecturer, Removable Partial Denture Prosthodontics, Tokyo Medical and Dental University. Professor, Division of Fixed Prosthodontics , Department of Oral and Maxillofacial Rehabilitation, Kanagawa Dental College. c Associate Professor, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, The Jane and Jerry Weintraub Center for Reconstructive Biotechnology and the UCLA School of Dentistry. d Professor, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, and Director, The Jane and Jerry Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry; Director, Dental Research Laboratory, Veterans Administration Greater Los Angeles Healthcare System. a
b
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December 2007 Conclusions. Objective benefits in masticatory performance of implant-supported or retained dentures compared to conventional dentures are limited to a mandibular IOD in edentulous patients with a resorbed mandible and/or difficulty adapting to CDs. (J Prosthet Dent 2007;98:470-477)
Clinical Implications
Clinicians should be aware of the limitations of the objective functional benefits of implant-supported and/or retained dentures and relate these benefits and limitations to patients in order to have a well-informed discussion related to treatment choices.
Implant-supported or retained dentures have been increasingly accepted as an alternative to conventional dentures for oral rehabilitation of edentulous patients.1,2 Patient desire for improved masticatory function is often given as a primary reason for treatment with implant-supported or retained dentures. While this restoration of masticatory function may be of critical value to the patient, there is some concern that this rationale for selection of implant-supported or retained dentures compared to conventional dentures may be based on a perception that implant-supported or retained dentures will routinely improve masticatory ability. This belief may be reinforced by studies comparing patient perceptions of functions related to mastication with conventional and implant-supported or retained dentures.3,4 Subjective patientbased outcomes, including ratings by patients of masticatory ability, food preferences, satisfaction with treatment, and oral health-related quality of life, have been increasingly recognized as critical outcomes for prosthodontic treatment.5,6 However, there continues to be a need to validate to patients the changes, or lack of, in masticatory function that can be expected with new implant-supported or retained dentures. In fact, it has been repeatedly shown that relationships between objective measures of masticatory performance and perceptional estimates of masticatory ability are weak in patients wearing conven-
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tional dentures7,8 and implant-supported or retained dentures.9-12 A variety of methods have been developed to assess masticatory performance and patients’ perceptions of masticatory ability.13,14 Characteristics of both subjective and objective methodologies for assessing masticatory performance have been reported previously.14 These tests have been used in numerous studies to clarify the effect of various factors such as age, tooth loss, and dental prosthodontic rehabilitation.7-18 It is possible that tests more sensitive than the current methodologies may show small differences in masticatory ability. However, the various studies used slightly different tests with similar findings. These standardized tests for masticatory performance can discriminate between patients with differing numbers of occlusal contacts, and normative data provides a point of reference for interpretation of the data. If differences are large enough to be clinically significant, it should be apparent with these standardized masticatory tests. The purpose of the current review was to clarify the objective impact of implant-supported or retained dentures on masticatory performance. The research questions evaluated were: (1) whether partial or complete implant-supported or retained dentures provide greater improvement in masticatory performance compared to conventional dentures; and (2) if the implant type or attachment sys-
tem supporting or retaining the mandibular overdenture impacts masticatory performance.
MATERIAL AND METHODS Search strategy Two electronic databases (PubMed: http://www.pubmed.com; Cochrane Library 2007 issue 2: http:// www.interscience.wiley.com) were accessed to search for all relevant articles published from 1966 to June 2007. Key elements for the search strategy were the following: (1) dental implants [MeSH]; (2) dental implantation [MeSH]; (3) dental prosthesis, implant-supported [MeSH]; (4) OR/1-3; (5) mastication [MeSH]; (6) humans [MeSH]; (7) English [la]; and (8) AND/4-7. The articles returned by the databases were then filtered for specific inclusion criteria: articles, (1) in which patients were rehabilitated with fixed or removable dentures supported or retained by implants in the mandible and/or maxilla; (2) in which masticatory performance was assessed objectively with standardized masticatory tests; and (3) in which statistical comparisons of masticatory performance were made between implant-supported or retained dentures and conventional dentures. Studies of single tooth replacement supported with an implant, review articles without meta-analysis, and theses were excluded.
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Volume 98 Issue 6 Article analysis Characteristics of subjects, type of dentures, and quantitative results were extracted from original articles. Study design was assessed using a clinical epidemiology-based classification.19 Level of evidence was rated by 2 authors following the United States Agency for Healthcare Research and Quality (AHRQ, http:// www.ahrq.gov/) recommendations (I, meta-analysis of multiple studies; II, experimental studies; III, well-designed; quasi-experimental studies; IV, well-designed, nonexperimental studies; and V, case reports and clinical examples). Estimation of effect size Effect size is a benchmark to evaluate within-subject change of measures between intervals.20 It can be used to compare effects of an intervention assessed on different scales. The standardized response mean (SRM) has been widely used to estimate effect size. SRM was computed with the following function: SRM = (mean score after intervention – mean score at base line) / standard deviation (SD) of change scores. Effect size of <0.2 is considered to be small, 0.4 is moderate, and >0.8 is large.21 In this review, for randomized controlled trials (RCT) and prospective studies, SRMs were computed with a change score from original denture to new denture. When masticatory performance was assessed with multiple tests, a summarized SRM was synthesized on the fixed effect model.22 Confidence intervals (CI, 95%) were estimated for each effect size based on assumption of normal distribution of effect size.
RESULTS Two hundred and twenty-five articles were identified by PubMed and 56 articles were identified by the Cochrane Library, 2007 issue 2. Eighteen articles met the inclusion criteria.
There were no studies on objective masticatory performance for single tooth replacement supported with an implant. The 18 articles10,11,23-38 meeting the inclusion criteria were peerreviewed and based on 14 studies. There were no level I meta-analyses, 7 articles (5 studies) were rated as level II, 9 articles (7 studies) were rated as level III, and 2 articles (2 studies) were rated as level IV, according to AHRQ recommendations. The age of participants treated with implant-supported dentures ranged from 38 to 83 years. All studies used an alpha level of .05 for statistical significance. Fixed implant-supported partial denture versus conventional removable partial denture There was only 1 prospective (RCT) study and there were no retrospective studies comparing a fixed implant-supported partial denture (FIPD) with a conventional removable partial denture (RPD) (Table I). In the single RCT, masticatory performance with an FIPD was compared with an RPD in Kennedy Class I and II partially edentulous mandibles.23 FIPDs were supported by 1 or 2 blade-vent implant(s). The results of the RCT indicated no significant differences in masticatory performance between the FIPD (n=105) and RPD (n=104). Effect size (ES) for the FIPD group (ES=0.7, 95% CI [0.5-0.8]) was similar to the RPD group (ES=0.8, 95% CI [0.7-1.0]). Fixed implant-supported complete denture versus conventional removable complete denture Masticatory performance with a fixed implant-supported complete denture (FICD) was compared with a conventional removable complete denture (CD) in 3 prospective studies (5 articles) (Table I).10,11,24-26 FICDs were supported by 4-6 implants10,11,26 or 4-7 implants.24,25 There were no RCTs or retrospective studies. A within-subject prospective study
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compared a mandibular FICD and an original mandibular CD (n=27) in edentulous subjects with a maxillary CD.10,11 The subjects participating in this study were selected from a group seeking treatment with FICDs in the mandible due to difficulties with their original CDs. The results after 3 years of treatment with mandibular FICDs indicated significant improvement in masticatory performance from original CDs (ES=1.3, 95% CI [0.8-1.9]).10 Nine subjects received additional treatment with maxillary FICDs after the 3-year evaluation. Ten years following initial treatment with mandibular FICDs, the improvement in masticatory performance relative to original CDs was maintained, but no significant differences in masticatory performance were found between the groups treated with FICDs for the mandible only (n=14) and with FICDs for the mandible and maxilla (n=9).11 The effect size could not be determined at the 10-year evaluation because the SD for each evaluation interval was not shown in the article. A within-subject prospective study compared a maxillary FICD and original maxillary CD (n=21).24,25 The mandibular conditions were FICD, natural dentitions with fixed partial denture, or natural dentitions with RPDs. The results showed significant improvement in masticatory performance with maxillary FICDs compared to original maxillary CDs at 3-6 months after treatment (n=21, ES=1.6, 95% CI [1.0-2.2])24 and at 3 years after treatment (n=17, ES=1.8, 95% CI [1.1-2.5]).25 A small prospective study compared a maxillary FICD and original maxillary CD (n=5).26 The mandibular conditions were FICD, fixed tooth-supported complete denture, natural dentitions with RPDs, or complete natural dentitions. The results indicated a large effect (ES=1.0, 95% CI [-0.7-2.7]), but statistically marginal improvement in masticatory performance with a maxillary FICD compared to the original maxillary CD (P=.06). Masticatory performance with the original CD was not assessed
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Table I. Comparisons of masticatory performance between fixed implant-supported dentures and conventional dentures
Result Study
Year Sample Evidence Study Published Size Level(*) Design(**)
Arch Treated
Denture Type(+)
Masticatory Performance Effect Size [95% CI](++)
Kapur et al23
1991
209
II
Pros (RCT)
mandible
FIPD / RPD
FIPD = RPD
FIPD: 0.7 [0.5 - 0.8] / RPD: 0.8 [0.7 - 1.0]
Lindquist and Carlsson10
1985
27
III
Pros (within-subject)
mandible
CD→FICD
FICD > CD
1.3 [0.8 - 1.9]
Carlsson and Lindquist11
1994
14 9
III
mandible mandible and maxilla
CD→FICD CD→FICD
FICD > CD FICD > CD
-
Lundqvist and Haraldson24
1990
21
III
Pros (within-subject) Pros (within-subject)
maxilla
CD→FICD
FICD > CD
1.6 [1.0 - 2.2]
Lundqvist and Haraldson25
1992
17
III
Pros (within-subject)
maxilla
CD→FICD
FICD > CD
1.8 [1.1 - 2.5]
Akeel et al26
1993
5
III
Pros (within-subject)
maxilla
CD→FICD
FICD = CD
1.0 [-0.7 - 2.7]
*I, meta-analysis of multiple studies; II, experimental studies; III, well-designed, quasi-experimental studies; IV, well-designed, nonexperimental studies; V; case reports and clinical examples **RCT: randomized controlled trial, Pros: prospective study, within-subject: within-subject trial +FIPD: fixed implant-supported partial denture, FICD: fixed implant-supported complete denture, RPD: conventional removable partial denture, CD: conventional removable complete denture. Original denture is indicated on left side of arrow and new denture is indicated on right side of arrow. ++CI: confidence interval, positive effect size indicates that masticatory performance with new dentures is greater than for original dentures
in 2 of the 5 subjects enrolled in the study. Implant-supported or retained overdenture versus conventional complete denture Masticatory performance with mandibular implant-supported or retained overdentures (IODs) and CDs was compared in 2 prospective (RCT) studies (4 articles ),27-30 3 within-subject prospective studies,31-33 and 2 retrospective studies (Table II).34,35 IODs were retained by 2 implants27-33 or supported by 4 or 6 implants.29,30,34 In all these studies, the subjects used CDs in the maxilla. In 1 RCT, subjects having average mandibular residual ridge height
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(mean height = 27 mm, ranged from 11 to 40 mm) achieved similar masticatory performance following treatment with a new mandibular CD (n=25, ES=0.2, 95% CI [-0.1-0.4]) or IOD (n=43, ES=0.5, 95% CI [0.30.7]).27 Subgroup analyses of this RCT found significantly greater improvement for the IOD group (n=11, ES=0.8, 95% CI [0.4-1.2]) compared to the new CD group (n=6, ES=-0.3, 95% CI [-0.9-0.2]) in patients having resorbed mandibular residual ridges (height <21 mm).28 In the other RCT, subjects with reduced mandibular residual ridge height (mean height = 14 mm) were evaluated. Masticatory performance with the IOD (n=56) was found to be significantly greater than with the new CD (n=28) at 1
year after treatment,29 but not 4 years after treatment.30 In this RCT, the effect size could not be determined due to a lack of assessment of the original CD at baseline. A within-subject prospective study failed to show significant improvement in masticatory performance with a mandibular IOD compared to the subject’s original mandibular CD (n=9).31 In this study, the effect size could not be determined due to a lack of standard deviation of measures. However, other within-subject prospective studies found significant improvements in masticatory performance with a mandibular IOD compared to a new mandibular CD fabricated prior to implant surgery (n=12, ES=2.4, 95% CI [1.5-3.2]32; n=12,
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Table II. Comparisons of masticatory performance between mandibular implant-supported or retained overdenture and conventional complete denture
Study
Mean Mandibular Year Sample Evidence Study Denture Attachment Support/ Residual Ridge Published Size Level(*) Design(**) Type(+) System(+) Retain(+) Height (mm)
Result Masticatory Performance
Effect Size [95% CI](++)
Garrett et al27
1998
68
II
Pros (RCT)
IOD/CD
1 bar
Retain
IOD: 27/CD: 27
IOD = CD
IOD: 0.5 [0.3 - 0.7]/ CD: 0.2 [-0.1 - 0.4]
Kimoto and Garrett28
2003
63
II
Pros (RCT)
IOD/CD
1 bar
Retain
low ridge group: IOD: 19/CD: 16 mid ridge group: IOD: 24/CD: 24 high ridge group: IOD: 33/CD: 31
low: IOD > CD
low: IOD: 0.8 [0.4 - 1.2]/ CD: -0.3 [-0.9 - 0.2] mid: IOD: 0.4 [0.0-0.8]/ CD: 0.6 [0.1 - 1.1] high: IOD: 0.6 [0.2 - 1.0]/ CD: 0.2 [-0.2 - 0.6]
mid: IOD = CD high: IOD = CD
Geertman et al29
1994
84
II
Pros (RCT)
IOD/CD
1 bar (IMZ)/ 3 bars (TR)
Retain/ Support
IOD (IMZ): 14/IOD (TR): 14/CD: 14
IOD (IMZ)= IOD (TR)>CD
–
FontijnTekamp et al30
2004
67
II
Pros (RCT)
IOD/CD
1 bar (IMZ)/ 3 bars (TR)
Retain/ IOD (IMZ): 14/IOD Support (TR): 14/CD: 14
IOD (IMZ)= IOD (TR)=CD
–
Stellingsma et al36
2005
58
II
Pros (RCT) IOD (TR / AG/SH)
van Kampen et al37
2004
18
II
Pros IOD (ball/ 2 balls/1 bar/ (crossover) bar/magnet) 2 magnets
Haraldson et al31
1988
9
III
Pros (within- CD→IOD subject)
Pera et al32
1998
12
III
Pros (within- CD→IOD subject)
Bakke et al33
2002
12
III
Pros (within- CD→IOD 1 bar/2 balls subject)
FontijnTekamp et al34
2000
143
IV
Retro
IOD/TOD/ 1 bar (IMZ)/ CD/ND 3 bars (TR)
Chen et al35
2002
42
IV
Retro
IOD/TOD/ CD
3 bars
Support
IOD (TR):10/IOD IOD (TR)=IOD (AG): 10/IOD (SH) 10 (AG)=IOD (SH)
–
Retain
≤ 15
IOD (ball)=IOD (bar)=IOD (magnet)
ball: 1.3 [0.6 - 2.0]/ bar: 1.2 [0.5 - 1.9]/ magnet: 0.7 [0.0 - 1.4]
1 bar
Retain
low ridge
IOD = CD
–
2 balls
Retain
severe resorption
IOD > CD
2.4 [1.5 - 3.2]
Retain
low ridge
IOD > CD
1.1 [0.3 - 2.0]
Retain/ Support
IOD: 14, TOD: 29, CD(low ridge group):14, CD(high ridge group): 23
ND> TOD= CD (high ridge height >IOD>CD (low ridge height)
–
–
–
IOD=TOD>CD
–
–
*I, meta-analysis of multiple studies; II, experimental studies; III, well-designed, quasi-experimental studies; IV, well-designed, nonexperimental studies; V; case reports and clinical examples **RCT: randomized controlled trial, Pros: prospective study, Retro: retrospective study, crossover: crossover trial, within-subject: within-subject trial +IOD: implant-supported overdenture, TOD: tooth-supported over denture, CD: conventional removable complete denture, ND: natural dentate, IMZ: IMZ implants, TR: transmandibular implant, AG: bone augmentation with 4 IMZ implants, SH: 4 short IMZ implants. Original denture is indicated on left side of arrow and new denture is indicated on right side of arrow. Support: IODs are supported by 4 or 6 implants, retain: IODs are retained by 2 implants. ++CI: confidence interval, positive effect size indicates that masticatory performance with new dentures is greater than for original dentures
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December 2007 ES=1.1, 95% CI [0.3-2.0]33 ). These study populations were primarily composed of subjects with low satisfaction with their original dentures, but no data was provided regarding the mandibular residual ridge height.31-33 A retrospective study found mean masticatory performance for a mandibular IOD group with reduced mandibular residual ridge height (n=40, mean height = 14 mm) was significantly greater than for a CD group with reduced mandibular residual ridge height (n=13, mean height = 14 mm), but significantly less than for a CD group with high mandibular residual ridge height (n=24, mean height = 23 mm).34 The other retrospective study found mean masticatory performance for subjects treated with a mandibular IOD (n=14) was significantly greater than for subjects treated with a CD (n=14).35 In this study, subjects were selected according to the following inclusion criteria: adequate retention and stability with the dentures; adequate denture-base extension; satisfactory occlusal relationships; no need for denture adhesives; and absence of inflammation of oral tissues. No information was provided regarding the number of implants and the mandibular residual ridge height.35 Effect of type of implant and attachment system for complete overdentures on masticatory performance Masticatory performances with mandibular IODs supported and retained by various types of implants and attachment types were found in 2 RCTs29,30,36 and 1 crossover trial.37 IODs were retained by 2 implants29,30,37 or supported by 4-6 implants.29,30,36 In these studies, subjects used CDs in the maxilla. An RCT in subjects with reduced mandibular residual ridge height (mean height = 14 mm) found no significant difference in masticatory performance with IODs supported and retained by 2 different combinations of types of implants and attachment systems (n=27, transmandibu-
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lar implant with a triple bar-5 clips; and n=29, 2 cylindrical IMZ (Friatec, Mannheim, Germany) implants with a single bar-1 metal clip).29,30 An RCT in subjects with severely reduced mandibular ridge height (mean height =10 mm) found no significant differences in mean masticatory performance between 3 different combinations of implant type and the attachment system (n=20: transmandibular implant with a triple extended bar-5 clips; n=19: 4 IMZ cylindrical implants with a triple bar-3 clips following augmentation; and n=19: 4 short IMZ cylindrical implants with a triple bar-3 clips).36 In this RCT, the effect size could not be determined, because the SD for each evaluation interval was not shown in the article. A crossover trial in subjects with reduced mandibular ridge height (≤15 mm) found no significant differences in masticatory performance between 3 attachment systems (n=18: ball-socket, bar-clips, and magnet) retaining mandibular IODs supported by 2 cylindrical implants.37 Implant-supported denture versus conventional denture after mandibular reconstruction Masticatory performance with dentures supported by 2-4 implants and conventional dentures after mandibular fibula free-flap reconstruction were compared in a within-subject prospective study.38 Masticatory performance was evaluated at entry; prior to the mandibular resection and reconstructive surgery; postsurgically following recovery; following at least a 4-month adaptation to conventional dentures; and following at least a 4-month adaptation to an implantsupported denture. Masticatory performance on the defect side of the mouth was improved significantly after treatments with both conventional dentures (n=15, ES=0.7, 95% CI [0.0-1.4]) and implant-supported dentures (n=15, ES=1.8, 95% CI [1.02.5]) compared to the interval prior to prosthetic rehabilitation. Similar, and not statistically significant, im-
provements were seen for both types of dentures on the nondefect sides. Masticatory performance on the defect side improved significantly with the implant-supported dentures compared to the conventional dentures (ES=0.7, 95% CI [0.0-1.5]), but not on the nondefect side (ES=0.1, 95% CI [-0.7-0.80]).
DISCUSSION The results of the current study support the hypothesis that IODs provide greater improvement in masticatory performance compared to CDs in edentulous patients with resorbed mandibles and/or difficulty adapting to CDs. However, the hypothesis that the implant type or attachment system supporting or retaining IODs impacts masticatory performance was not supported with the current studies. A single RCT has demonstrated that an FIPD offers no advantage in masticatory performance over RPDs for Kennedy Class I and II mandibles.23 This would be an unexpected result given the belief that fixed dentures result in better masticatory function than removable dentures. In this RCT, the buccal-lingual width of the occlusal platform for FIPDs was narrowed to reduce functional load on implants, and the occlusal platform for RPDs was larger than for FIPDs. A recent study has shown that increased width of the occlusal platform for an RPD is associated with greater masticatory function, as measured by the mixing ability test.39 As the authors discussed,23 a larger occlusal platform with the RPDs may have offset the advantages in retention and support offered by the FIPDs. Many within-subject prospective studies have demonstrated improvements in masticatory performance for a mandibular or maxillary FICD from the original CD.10,11,24,25 These results suggest that FICDs in the mandible or maxilla have advantages in masticatory performance compared to CDs. However, the participants in
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Volume 98 Issue 6 the study of mandibular FICDs sought treatment with mandibular FICDs due to difficulty wearing CDs.10,11 It is not clear that provision of mandibular FICDs offers greater masticatory performance compared to CDs for patients with well-adapted CDs or who are satisfied with their CDs. Furthermore, these studies did not include control groups treated with new CDs, and several include mixed dentition/denture categories in the opposing arch.10,11,24,25 Definitive evidence should be provided with RCTs comparing FICDs and new CDs. In addition, an intergroup comparison found no significant difference in masticatory performance between groups with FICDs for the mandible and for both the mandible and maxilla.11 This suggests the impact of an FICD for maxillary masticatory performance may be limited. Well-designed studies are necessary to confirm this hypothesis. A prospective study failed to show statistical significance (P=.06) even with the large effect (ES=1.0).26 This result is likely due to low statistical power with the small sample size (n=5). Subgroup analyses of 1 RCT 6 months after treatment28 and another RCT 1 year after treatment29 have demonstrated that a mandibular IOD has an advantage over a new CD in masticatory performance for patients having a resorbed mandibular residual ridge. Within–subject prospective studies comparing a new mandibular IOD and an original CD,32,33 and retrospective studies comparing IOD and CD groups,34,35 support this finding. However, when patients having average mandibular residual ridge height were enrolled, no advantages in masticatory performance with IODs compared to new CDs were found.27 This suggests mandibular residual ridge height in edentulous patients is a critical factor for providing greater improvement in masticatory performance with IODs. Although the advantage of an IOD for masticatory performance was validated by outcomes at short intervals after treat-
ment, it should be noted that evaluations of masticatory performance at 4 years after treatment failed to show significant difference between IODs and new CDs.30 Edentulous patients with resorbed mandibles may require longer adaptation periods with new CDs compared to IODs. The type of implant and attachment system for mandibular IODs were found to have no significant effects on masticatory performance.29,30,36,37 These results suggest that the degree of support by implants and level of retention with attachments for a mandibular overdenture have a limited impact on masticatory performance. However, the patients in all of these studies on mandibular implant-supported or retained overdentures used CDs in the maxillary arch. Additional studies are necessary to investigate the effect of improvements in retention and stability afforded by IODs for both the mandible and maxilla on masticatory performance. Following partial mandiblulectomy and free-flap reconstruction, treatments with implant-supported dentures may provide superior benefits in mastication on the defect side of the mouth compared to conventional dentures.38 However, this treatment should be considered after 1 year of surgical treatment due to a high rate of recurrence/metastasis (35%; 16/46).40 There were no articles identified evaluating masticatory performance in maxillectomy patients with conventional or implant-supported dentures. Evaluation of masticatory function and validation of implant-supported dentures are needed in this population. In this review, information retrieval followed a systematic approach. However, searches for primary data on broader sources, including abstracts and proceedings without language restriction, should be undertaken to minimize publishing bias. In general, abstracts and proceedings are not peer-reviewed. Thus, the primary data from these sources should be interpreted with caution. In ad-
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dition, meta-analyses to synthesize primary data obtained in high quality RCTs would be desirable to provide highest quality evidence.22 More well-designed studies are required to generalize the effect of implant-supported dentures on masticatory performance.
CONCLUSIONS While a number of studies on masticatory performance have been conducted in patients with various designs of implant-supported or retained dentures, high-level evidence supporting advantages in masticatory performance of implant-supported or retained dentures over conventional dentures is limited. Objective benefits in masticatory performance of implant-supported or retained dentures compared to conventional dentures have been substantiated for mandibular implant-supported or retained dentures in edentulous patients with resorbed mandibles and/or difficulty adapting to conventional removable complete dentures.
REFERENCES 1. Batenburg RH, Meijer HJ, Raghoebar GM, Vissink A. Treatment concept for mandibular overdentures supported by endosseous implants: a literature review. Int J Oral Maxillofac Implants 1998;13:539-45. 2. Stellingsma C, Vissink A, Meijer HJ, Kuiper C, Raghoebar GM. Implantology and the severely resorbed edentulous mandible. Crit Rev Oral Biol Med 2004;15:240-8. 3. Locker D. Patient-based assessment of the outcomes of implant therapy: a review of the literature. Int J Prosthodont 1998;11:453-61. 4. Feine JS, Dufresne E, Boudrias P, Lund JP. Outcome assessment of implant-supported prostheses. J Prosthet Dent 1998;79:575-9. 5. Guckes AD, Scurria MS, Shugars DA. A conceptual framework for understanding outcomes of oral implant therapy. J Prosthet Dent 1996;75:633-9. 6. Anderson JD. The need for criteria on reporting treatment outcomes. J Prosthet Dent 1998;79:49-55. 7. Garrett NR, Kapur KK, Perez P. Effects of improvements of poorly fitting dentures and new dentures on patient satisfaction. J Prosthet Dent 1996;76:403-13. 8. Wayler AH, Muench ME, Kapur KK, Chauncey HH. Masticatory performance and food acceptability in persons with removable partial dentures, full dentures
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December 2007 and intact natural dentition. J Gerontol 1984;39:284-9. 9. Kapur KK. Veterans Administration Cooperative Dental Implant Study--comparisons between fixed partial dentures supported by blade-vent implants and removable partial dentures. Part IV: Comparisons of patient satisfaction between two treatment modalities. J Prosthet Dent 1991;66:51730. 10.Lindquist LW, Carlsson GE. Long-term effects on chewing with mandibular fixed prostheses on osseointegrated implants. Acta Odontol Scand 1985;43:39-45. 11.Carlsson GE, Lindquist LW. Ten-year longitudinal study of masticatory function in edentulous patients treated with fixed complete dentures on osseointegrated implants. Int J Prosthodont 1994;7:448-53. 12.Geertman ME, Slagter AP, van't Hof MA, van Waas MA, Kalk W. Masticatory performance and chewing experience with implant-retained mandibular overdentures. J Oral Rehabil 1999;26:7-13. 13.Boretti G, Bickel M, Geering AH. A review of masticatory ability and efficiency. J Prosthet Dent 1995;74:400-3. 14.Kimoto K, Ogawa T, Garrett NR, Toyoda M. Assessment of masticatory performance: methodologies and their application. Prosthodont Res Pract 2004;3:33-45. 15.Yurkstas AA. The masticatory act. A review. J Prosthet Dent 1965;15:248-62. 16.Feldman RS, Kapur KK, Alman JE, Chauncey HH. Aging and mastication: changes in performance and in the swallowing threshold with natural dentition. J Am Geriatr Soc 1980;28:97-103. 17.van der Bilt A, Olthoff LW, Bosman F, Oosterhaven SP. Chewing performance before and after rehabilitation of postcanine teeth in man. J Dent Res 1994;73:1677-83. 18.Kapur KK, Garrett NR, Hamada MO, Roumanas ED, Freymiller E, Han T et al, Randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part III: comparisons of patient satisfaction. J Prosthet Dent 1999;82:416-27. 19.Hulley SB, Newman, TB, Browner WS, Cummings SR, Grady D. Designing clinical research: an epidemiologic approach. 3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2006. p. 97-182. 20.Husted JA, Cook RJ, Farewell VT Gladman DD. Methods for assessing responsiveness: a critical review and recommendations. J Clin Epidemiol 2000;53: 459-68.
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21.Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. Hillsdale: Lawrence Erlbaum Associates; 1988. p. 8-13. 22.Petitti DB. Meta-analysis, decision analysis, and cost-effectiveness analysis: methods for quantitative synthesis in medicine. 2nd ed. London: Oxford University Press; 2000. p. 43-139. 23.Kapur KK. Veterans administration cooperative dental implant study: comparisons between fixed partial dentures supported by blade-vent implants and removable partial dentures. Part III. Comparisons of masticatory scores between two treatment modalities. J Prosthet Dent 1991;65:27283. 24.Lundqvist S, Haraldson T. Oral function in patients wearing fixed prosthesis on osseointegrated implants in the maxilla. Scand J Dent Res 1990;98:544-9. 25.Lundqvist S, Haraldson T. Oral function in patients wearing fixed prosthesis on osseointegrated implants in the maxilla: 3-year follow-up study. Scand J Dent Res 1992;100:279-83. 26.Akeel R, Fernandes CP, Vassilakos N. Masticatory efficiency of patients treated with implant retained fixed bridges in the upper jaw over a 2-year period. Eur J Prosthodont Restor Dent 1993;1:131-3. 27.Garrett NR, Kapur KK, Hamada MO, Roumanas ED, Freymiller E, Han T et al. A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part II. Comparisons of masticatory performance. J Prosthet Dent 1998;79:632-40. 28.Kimoto K, Garrett NR. Effect of mandibular ridge height on masticatory performance with mandibular conventional and implant-assisted overdentures. Int J Oral Maxillofac Implants 2003;18:523-30. 29.Geertman ME, Slagter AP, van Waas MA, Kalk W. Comminution of food with mandibular implant-retained overdentures. J Dent Res 1994;73:1858-64. 30.Fontijn-Tekamp FA, Slagter AP, Van der Bilt A, Van't Hof MA, Kalk W, Jansen JA. Swallowing thresholds of mandibular implantretained overdentures with variable portion sizes. Clin Oral Impl Res 2004;15:375-80. 31.Haraldson T, Jemt T, Stalblad PA, Lekholm U. Oral function in subjects with overdentures supported by osseointegrated implants. Scand J Dent Res 1988;96:235-42. 32.Pera P, Bassi F, Schierano G, Appendino P, Preti G. Implant anchored complete mandibular denture: evaluation of mastica-
tory efficiency, oral function and degree of satisfaction. J Oral Rehabil 1998;25:462-7. 33.Bakke M, Holm B, Gotfredsen K. Masticatory function and patient satisfaction with implant-supported mandibular overdentures: a prospective 5-year study. Int J Prosthodont 2002;15:575-81. 34.Fontijn-Tekamp FA, Slagter AP, Van Der Bilt A, Van'T Hof MA, Witter DJ, Kalk W et al. Biting and chewing in overdentures, full dentures, and natural dentitions. J Dent Res 2000;79:1519-24. 35.Chen L, Xie Q, Feng H, Lin Y, Li J. The masticatory efficiency of mandibular implant-supported overdentures as compared with tooth-supported overdentures and complete dentures. J Oral Implantol 2002;28:238-43. 36.Stellingsma K, Slagter AP, Stegenga B, Raghoebar GM, Meijer HJA. Masticatory function in patients with an extremely resorbed mandible restored with mandibular implant-retained overdentures: comparison of three types of treatment protocols. J Oral Rehabil 2005;32:403-10. 37.van Kampen FM, van der Bilt A, Cune MS, Fontijn-Tekamp FA, Bosman F. Masticatory function with implant-supported overdentures. J Dent Res 2004;83:708-11. 38.Roumanas ED, Garrett N, Blackwell KE, Freymiller E, Abemayor E, Wong WK et al. Masticatory and swallowing threshold performances with conventional and implantsupported prostheses after mandibular fibula free-flap reconstruction. J Prosthet Dent 2006;96:289-97. 39.Yoshimura M, Fueki K, Garrett N, Ohyama T. Influence of food platform width of mandibular removable partial denture on food mixing ability. J Oral Rehabil 2006;33:33540. 40.Garrett N, Roumanas ED, Blackwell KE, Freymiller E, Abemayor E, Wong WK et al. Efficacy of conventional and implant-supported mandibular resection prostheses: study overview and treatment outcomes. J Prosthet Dent 2006;96:13-24. Corresponding author: Dr Kenji Fueki Removable Partial Denture Prosthodontics Tokyo Medical and Dental University 1-5-45 Yushima, Bunkyo-ku Tokyo, 113-8549 JAPAN Fax: 81-3-5803-5514 E-mail: [email protected] Copyright © 2007 by the Editorial Council for The Journal of Prosthetic Dentistry.
b
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December 2007 Conclusions. Objective benefits in masticatory performance of implant-supported or retained dentures compared to conventional dentures are limited to a mandibular IOD in edentulous patients with a resorbed mandible and/or difficulty adapting to CDs. (J Prosthet Dent 2007;98:470-477)
Clinical Implications
Clinicians should be aware of the limitations of the objective functional benefits of implant-supported and/or retained dentures and relate these benefits and limitations to patients in order to have a well-informed discussion related to treatment choices.
Implant-supported or retained dentures have been increasingly accepted as an alternative to conventional dentures for oral rehabilitation of edentulous patients.1,2 Patient desire for improved masticatory function is often given as a primary reason for treatment with implant-supported or retained dentures. While this restoration of masticatory function may be of critical value to the patient, there is some concern that this rationale for selection of implant-supported or retained dentures compared to conventional dentures may be based on a perception that implant-supported or retained dentures will routinely improve masticatory ability. This belief may be reinforced by studies comparing patient perceptions of functions related to mastication with conventional and implant-supported or retained dentures.3,4 Subjective patientbased outcomes, including ratings by patients of masticatory ability, food preferences, satisfaction with treatment, and oral health-related quality of life, have been increasingly recognized as critical outcomes for prosthodontic treatment.5,6 However, there continues to be a need to validate to patients the changes, or lack of, in masticatory function that can be expected with new implant-supported or retained dentures. In fact, it has been repeatedly shown that relationships between objective measures of masticatory performance and perceptional estimates of masticatory ability are weak in patients wearing conven-
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tional dentures7,8 and implant-supported or retained dentures.9-12 A variety of methods have been developed to assess masticatory performance and patients’ perceptions of masticatory ability.13,14 Characteristics of both subjective and objective methodologies for assessing masticatory performance have been reported previously.14 These tests have been used in numerous studies to clarify the effect of various factors such as age, tooth loss, and dental prosthodontic rehabilitation.7-18 It is possible that tests more sensitive than the current methodologies may show small differences in masticatory ability. However, the various studies used slightly different tests with similar findings. These standardized tests for masticatory performance can discriminate between patients with differing numbers of occlusal contacts, and normative data provides a point of reference for interpretation of the data. If differences are large enough to be clinically significant, it should be apparent with these standardized masticatory tests. The purpose of the current review was to clarify the objective impact of implant-supported or retained dentures on masticatory performance. The research questions evaluated were: (1) whether partial or complete implant-supported or retained dentures provide greater improvement in masticatory performance compared to conventional dentures; and (2) if the implant type or attachment sys-
tem supporting or retaining the mandibular overdenture impacts masticatory performance.
MATERIAL AND METHODS Search strategy Two electronic databases (PubMed: http://www.pubmed.com; Cochrane Library 2007 issue 2: http:// www.interscience.wiley.com) were accessed to search for all relevant articles published from 1966 to June 2007. Key elements for the search strategy were the following: (1) dental implants [MeSH]; (2) dental implantation [MeSH]; (3) dental prosthesis, implant-supported [MeSH]; (4) OR/1-3; (5) mastication [MeSH]; (6) humans [MeSH]; (7) English [la]; and (8) AND/4-7. The articles returned by the databases were then filtered for specific inclusion criteria: articles, (1) in which patients were rehabilitated with fixed or removable dentures supported or retained by implants in the mandible and/or maxilla; (2) in which masticatory performance was assessed objectively with standardized masticatory tests; and (3) in which statistical comparisons of masticatory performance were made between implant-supported or retained dentures and conventional dentures. Studies of single tooth replacement supported with an implant, review articles without meta-analysis, and theses were excluded.
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Volume 98 Issue 6 Article analysis Characteristics of subjects, type of dentures, and quantitative results were extracted from original articles. Study design was assessed using a clinical epidemiology-based classification.19 Level of evidence was rated by 2 authors following the United States Agency for Healthcare Research and Quality (AHRQ, http:// www.ahrq.gov/) recommendations (I, meta-analysis of multiple studies; II, experimental studies; III, well-designed; quasi-experimental studies; IV, well-designed, nonexperimental studies; and V, case reports and clinical examples). Estimation of effect size Effect size is a benchmark to evaluate within-subject change of measures between intervals.20 It can be used to compare effects of an intervention assessed on different scales. The standardized response mean (SRM) has been widely used to estimate effect size. SRM was computed with the following function: SRM = (mean score after intervention – mean score at base line) / standard deviation (SD) of change scores. Effect size of <0.2 is considered to be small, 0.4 is moderate, and >0.8 is large.21 In this review, for randomized controlled trials (RCT) and prospective studies, SRMs were computed with a change score from original denture to new denture. When masticatory performance was assessed with multiple tests, a summarized SRM was synthesized on the fixed effect model.22 Confidence intervals (CI, 95%) were estimated for each effect size based on assumption of normal distribution of effect size.
RESULTS Two hundred and twenty-five articles were identified by PubMed and 56 articles were identified by the Cochrane Library, 2007 issue 2. Eighteen articles met the inclusion criteria.
There were no studies on objective masticatory performance for single tooth replacement supported with an implant. The 18 articles10,11,23-38 meeting the inclusion criteria were peerreviewed and based on 14 studies. There were no level I meta-analyses, 7 articles (5 studies) were rated as level II, 9 articles (7 studies) were rated as level III, and 2 articles (2 studies) were rated as level IV, according to AHRQ recommendations. The age of participants treated with implant-supported dentures ranged from 38 to 83 years. All studies used an alpha level of .05 for statistical significance. Fixed implant-supported partial denture versus conventional removable partial denture There was only 1 prospective (RCT) study and there were no retrospective studies comparing a fixed implant-supported partial denture (FIPD) with a conventional removable partial denture (RPD) (Table I). In the single RCT, masticatory performance with an FIPD was compared with an RPD in Kennedy Class I and II partially edentulous mandibles.23 FIPDs were supported by 1 or 2 blade-vent implant(s). The results of the RCT indicated no significant differences in masticatory performance between the FIPD (n=105) and RPD (n=104). Effect size (ES) for the FIPD group (ES=0.7, 95% CI [0.5-0.8]) was similar to the RPD group (ES=0.8, 95% CI [0.7-1.0]). Fixed implant-supported complete denture versus conventional removable complete denture Masticatory performance with a fixed implant-supported complete denture (FICD) was compared with a conventional removable complete denture (CD) in 3 prospective studies (5 articles) (Table I).10,11,24-26 FICDs were supported by 4-6 implants10,11,26 or 4-7 implants.24,25 There were no RCTs or retrospective studies. A within-subject prospective study
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compared a mandibular FICD and an original mandibular CD (n=27) in edentulous subjects with a maxillary CD.10,11 The subjects participating in this study were selected from a group seeking treatment with FICDs in the mandible due to difficulties with their original CDs. The results after 3 years of treatment with mandibular FICDs indicated significant improvement in masticatory performance from original CDs (ES=1.3, 95% CI [0.8-1.9]).10 Nine subjects received additional treatment with maxillary FICDs after the 3-year evaluation. Ten years following initial treatment with mandibular FICDs, the improvement in masticatory performance relative to original CDs was maintained, but no significant differences in masticatory performance were found between the groups treated with FICDs for the mandible only (n=14) and with FICDs for the mandible and maxilla (n=9).11 The effect size could not be determined at the 10-year evaluation because the SD for each evaluation interval was not shown in the article. A within-subject prospective study compared a maxillary FICD and original maxillary CD (n=21).24,25 The mandibular conditions were FICD, natural dentitions with fixed partial denture, or natural dentitions with RPDs. The results showed significant improvement in masticatory performance with maxillary FICDs compared to original maxillary CDs at 3-6 months after treatment (n=21, ES=1.6, 95% CI [1.0-2.2])24 and at 3 years after treatment (n=17, ES=1.8, 95% CI [1.1-2.5]).25 A small prospective study compared a maxillary FICD and original maxillary CD (n=5).26 The mandibular conditions were FICD, fixed tooth-supported complete denture, natural dentitions with RPDs, or complete natural dentitions. The results indicated a large effect (ES=1.0, 95% CI [-0.7-2.7]), but statistically marginal improvement in masticatory performance with a maxillary FICD compared to the original maxillary CD (P=.06). Masticatory performance with the original CD was not assessed
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Table I. Comparisons of masticatory performance between fixed implant-supported dentures and conventional dentures
Result Study
Year Sample Evidence Study Published Size Level(*) Design(**)
Arch Treated
Denture Type(+)
Masticatory Performance Effect Size [95% CI](++)
Kapur et al23
1991
209
II
Pros (RCT)
mandible
FIPD / RPD
FIPD = RPD
FIPD: 0.7 [0.5 - 0.8] / RPD: 0.8 [0.7 - 1.0]
Lindquist and Carlsson10
1985
27
III
Pros (within-subject)
mandible
CD→FICD
FICD > CD
1.3 [0.8 - 1.9]
Carlsson and Lindquist11
1994
14 9
III
mandible mandible and maxilla
CD→FICD CD→FICD
FICD > CD FICD > CD
-
Lundqvist and Haraldson24
1990
21
III
Pros (within-subject) Pros (within-subject)
maxilla
CD→FICD
FICD > CD
1.6 [1.0 - 2.2]
Lundqvist and Haraldson25
1992
17
III
Pros (within-subject)
maxilla
CD→FICD
FICD > CD
1.8 [1.1 - 2.5]
Akeel et al26
1993
5
III
Pros (within-subject)
maxilla
CD→FICD
FICD = CD
1.0 [-0.7 - 2.7]
*I, meta-analysis of multiple studies; II, experimental studies; III, well-designed, quasi-experimental studies; IV, well-designed, nonexperimental studies; V; case reports and clinical examples **RCT: randomized controlled trial, Pros: prospective study, within-subject: within-subject trial +FIPD: fixed implant-supported partial denture, FICD: fixed implant-supported complete denture, RPD: conventional removable partial denture, CD: conventional removable complete denture. Original denture is indicated on left side of arrow and new denture is indicated on right side of arrow. ++CI: confidence interval, positive effect size indicates that masticatory performance with new dentures is greater than for original dentures
in 2 of the 5 subjects enrolled in the study. Implant-supported or retained overdenture versus conventional complete denture Masticatory performance with mandibular implant-supported or retained overdentures (IODs) and CDs was compared in 2 prospective (RCT) studies (4 articles ),27-30 3 within-subject prospective studies,31-33 and 2 retrospective studies (Table II).34,35 IODs were retained by 2 implants27-33 or supported by 4 or 6 implants.29,30,34 In all these studies, the subjects used CDs in the maxilla. In 1 RCT, subjects having average mandibular residual ridge height
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(mean height = 27 mm, ranged from 11 to 40 mm) achieved similar masticatory performance following treatment with a new mandibular CD (n=25, ES=0.2, 95% CI [-0.1-0.4]) or IOD (n=43, ES=0.5, 95% CI [0.30.7]).27 Subgroup analyses of this RCT found significantly greater improvement for the IOD group (n=11, ES=0.8, 95% CI [0.4-1.2]) compared to the new CD group (n=6, ES=-0.3, 95% CI [-0.9-0.2]) in patients having resorbed mandibular residual ridges (height <21 mm).28 In the other RCT, subjects with reduced mandibular residual ridge height (mean height = 14 mm) were evaluated. Masticatory performance with the IOD (n=56) was found to be significantly greater than with the new CD (n=28) at 1
year after treatment,29 but not 4 years after treatment.30 In this RCT, the effect size could not be determined due to a lack of assessment of the original CD at baseline. A within-subject prospective study failed to show significant improvement in masticatory performance with a mandibular IOD compared to the subject’s original mandibular CD (n=9).31 In this study, the effect size could not be determined due to a lack of standard deviation of measures. However, other within-subject prospective studies found significant improvements in masticatory performance with a mandibular IOD compared to a new mandibular CD fabricated prior to implant surgery (n=12, ES=2.4, 95% CI [1.5-3.2]32; n=12,
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Table II. Comparisons of masticatory performance between mandibular implant-supported or retained overdenture and conventional complete denture
Study
Mean Mandibular Year Sample Evidence Study Denture Attachment Support/ Residual Ridge Published Size Level(*) Design(**) Type(+) System(+) Retain(+) Height (mm)
Result Masticatory Performance
Effect Size [95% CI](++)
Garrett et al27
1998
68
II
Pros (RCT)
IOD/CD
1 bar
Retain
IOD: 27/CD: 27
IOD = CD
IOD: 0.5 [0.3 - 0.7]/ CD: 0.2 [-0.1 - 0.4]
Kimoto and Garrett28
2003
63
II
Pros (RCT)
IOD/CD
1 bar
Retain
low ridge group: IOD: 19/CD: 16 mid ridge group: IOD: 24/CD: 24 high ridge group: IOD: 33/CD: 31
low: IOD > CD
low: IOD: 0.8 [0.4 - 1.2]/ CD: -0.3 [-0.9 - 0.2] mid: IOD: 0.4 [0.0-0.8]/ CD: 0.6 [0.1 - 1.1] high: IOD: 0.6 [0.2 - 1.0]/ CD: 0.2 [-0.2 - 0.6]
mid: IOD = CD high: IOD = CD
Geertman et al29
1994
84
II
Pros (RCT)
IOD/CD
1 bar (IMZ)/ 3 bars (TR)
Retain/ Support
IOD (IMZ): 14/IOD (TR): 14/CD: 14
IOD (IMZ)= IOD (TR)>CD
–
FontijnTekamp et al30
2004
67
II
Pros (RCT)
IOD/CD
1 bar (IMZ)/ 3 bars (TR)
Retain/ IOD (IMZ): 14/IOD Support (TR): 14/CD: 14
IOD (IMZ)= IOD (TR)=CD
–
Stellingsma et al36
2005
58
II
Pros (RCT) IOD (TR / AG/SH)
van Kampen et al37
2004
18
II
Pros IOD (ball/ 2 balls/1 bar/ (crossover) bar/magnet) 2 magnets
Haraldson et al31
1988
9
III
Pros (within- CD→IOD subject)
Pera et al32
1998
12
III
Pros (within- CD→IOD subject)
Bakke et al33
2002
12
III
Pros (within- CD→IOD 1 bar/2 balls subject)
FontijnTekamp et al34
2000
143
IV
Retro
IOD/TOD/ 1 bar (IMZ)/ CD/ND 3 bars (TR)
Chen et al35
2002
42
IV
Retro
IOD/TOD/ CD
3 bars
Support
IOD (TR):10/IOD IOD (TR)=IOD (AG): 10/IOD (SH) 10 (AG)=IOD (SH)
–
Retain
≤ 15
IOD (ball)=IOD (bar)=IOD (magnet)
ball: 1.3 [0.6 - 2.0]/ bar: 1.2 [0.5 - 1.9]/ magnet: 0.7 [0.0 - 1.4]
1 bar
Retain
low ridge
IOD = CD
–
2 balls
Retain
severe resorption
IOD > CD
2.4 [1.5 - 3.2]
Retain
low ridge
IOD > CD
1.1 [0.3 - 2.0]
Retain/ Support
IOD: 14, TOD: 29, CD(low ridge group):14, CD(high ridge group): 23
ND> TOD= CD (high ridge height >IOD>CD (low ridge height)
–
–
–
IOD=TOD>CD
–
–
*I, meta-analysis of multiple studies; II, experimental studies; III, well-designed, quasi-experimental studies; IV, well-designed, nonexperimental studies; V; case reports and clinical examples **RCT: randomized controlled trial, Pros: prospective study, Retro: retrospective study, crossover: crossover trial, within-subject: within-subject trial +IOD: implant-supported overdenture, TOD: tooth-supported over denture, CD: conventional removable complete denture, ND: natural dentate, IMZ: IMZ implants, TR: transmandibular implant, AG: bone augmentation with 4 IMZ implants, SH: 4 short IMZ implants. Original denture is indicated on left side of arrow and new denture is indicated on right side of arrow. Support: IODs are supported by 4 or 6 implants, retain: IODs are retained by 2 implants. ++CI: confidence interval, positive effect size indicates that masticatory performance with new dentures is greater than for original dentures
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December 2007 ES=1.1, 95% CI [0.3-2.0]33 ). These study populations were primarily composed of subjects with low satisfaction with their original dentures, but no data was provided regarding the mandibular residual ridge height.31-33 A retrospective study found mean masticatory performance for a mandibular IOD group with reduced mandibular residual ridge height (n=40, mean height = 14 mm) was significantly greater than for a CD group with reduced mandibular residual ridge height (n=13, mean height = 14 mm), but significantly less than for a CD group with high mandibular residual ridge height (n=24, mean height = 23 mm).34 The other retrospective study found mean masticatory performance for subjects treated with a mandibular IOD (n=14) was significantly greater than for subjects treated with a CD (n=14).35 In this study, subjects were selected according to the following inclusion criteria: adequate retention and stability with the dentures; adequate denture-base extension; satisfactory occlusal relationships; no need for denture adhesives; and absence of inflammation of oral tissues. No information was provided regarding the number of implants and the mandibular residual ridge height.35 Effect of type of implant and attachment system for complete overdentures on masticatory performance Masticatory performances with mandibular IODs supported and retained by various types of implants and attachment types were found in 2 RCTs29,30,36 and 1 crossover trial.37 IODs were retained by 2 implants29,30,37 or supported by 4-6 implants.29,30,36 In these studies, subjects used CDs in the maxilla. An RCT in subjects with reduced mandibular residual ridge height (mean height = 14 mm) found no significant difference in masticatory performance with IODs supported and retained by 2 different combinations of types of implants and attachment systems (n=27, transmandibu-
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lar implant with a triple bar-5 clips; and n=29, 2 cylindrical IMZ (Friatec, Mannheim, Germany) implants with a single bar-1 metal clip).29,30 An RCT in subjects with severely reduced mandibular ridge height (mean height =10 mm) found no significant differences in mean masticatory performance between 3 different combinations of implant type and the attachment system (n=20: transmandibular implant with a triple extended bar-5 clips; n=19: 4 IMZ cylindrical implants with a triple bar-3 clips following augmentation; and n=19: 4 short IMZ cylindrical implants with a triple bar-3 clips).36 In this RCT, the effect size could not be determined, because the SD for each evaluation interval was not shown in the article. A crossover trial in subjects with reduced mandibular ridge height (≤15 mm) found no significant differences in masticatory performance between 3 attachment systems (n=18: ball-socket, bar-clips, and magnet) retaining mandibular IODs supported by 2 cylindrical implants.37 Implant-supported denture versus conventional denture after mandibular reconstruction Masticatory performance with dentures supported by 2-4 implants and conventional dentures after mandibular fibula free-flap reconstruction were compared in a within-subject prospective study.38 Masticatory performance was evaluated at entry; prior to the mandibular resection and reconstructive surgery; postsurgically following recovery; following at least a 4-month adaptation to conventional dentures; and following at least a 4-month adaptation to an implantsupported denture. Masticatory performance on the defect side of the mouth was improved significantly after treatments with both conventional dentures (n=15, ES=0.7, 95% CI [0.0-1.4]) and implant-supported dentures (n=15, ES=1.8, 95% CI [1.02.5]) compared to the interval prior to prosthetic rehabilitation. Similar, and not statistically significant, im-
provements were seen for both types of dentures on the nondefect sides. Masticatory performance on the defect side improved significantly with the implant-supported dentures compared to the conventional dentures (ES=0.7, 95% CI [0.0-1.5]), but not on the nondefect side (ES=0.1, 95% CI [-0.7-0.80]).
DISCUSSION The results of the current study support the hypothesis that IODs provide greater improvement in masticatory performance compared to CDs in edentulous patients with resorbed mandibles and/or difficulty adapting to CDs. However, the hypothesis that the implant type or attachment system supporting or retaining IODs impacts masticatory performance was not supported with the current studies. A single RCT has demonstrated that an FIPD offers no advantage in masticatory performance over RPDs for Kennedy Class I and II mandibles.23 This would be an unexpected result given the belief that fixed dentures result in better masticatory function than removable dentures. In this RCT, the buccal-lingual width of the occlusal platform for FIPDs was narrowed to reduce functional load on implants, and the occlusal platform for RPDs was larger than for FIPDs. A recent study has shown that increased width of the occlusal platform for an RPD is associated with greater masticatory function, as measured by the mixing ability test.39 As the authors discussed,23 a larger occlusal platform with the RPDs may have offset the advantages in retention and support offered by the FIPDs. Many within-subject prospective studies have demonstrated improvements in masticatory performance for a mandibular or maxillary FICD from the original CD.10,11,24,25 These results suggest that FICDs in the mandible or maxilla have advantages in masticatory performance compared to CDs. However, the participants in
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Volume 98 Issue 6 the study of mandibular FICDs sought treatment with mandibular FICDs due to difficulty wearing CDs.10,11 It is not clear that provision of mandibular FICDs offers greater masticatory performance compared to CDs for patients with well-adapted CDs or who are satisfied with their CDs. Furthermore, these studies did not include control groups treated with new CDs, and several include mixed dentition/denture categories in the opposing arch.10,11,24,25 Definitive evidence should be provided with RCTs comparing FICDs and new CDs. In addition, an intergroup comparison found no significant difference in masticatory performance between groups with FICDs for the mandible and for both the mandible and maxilla.11 This suggests the impact of an FICD for maxillary masticatory performance may be limited. Well-designed studies are necessary to confirm this hypothesis. A prospective study failed to show statistical significance (P=.06) even with the large effect (ES=1.0).26 This result is likely due to low statistical power with the small sample size (n=5). Subgroup analyses of 1 RCT 6 months after treatment28 and another RCT 1 year after treatment29 have demonstrated that a mandibular IOD has an advantage over a new CD in masticatory performance for patients having a resorbed mandibular residual ridge. Within–subject prospective studies comparing a new mandibular IOD and an original CD,32,33 and retrospective studies comparing IOD and CD groups,34,35 support this finding. However, when patients having average mandibular residual ridge height were enrolled, no advantages in masticatory performance with IODs compared to new CDs were found.27 This suggests mandibular residual ridge height in edentulous patients is a critical factor for providing greater improvement in masticatory performance with IODs. Although the advantage of an IOD for masticatory performance was validated by outcomes at short intervals after treat-
ment, it should be noted that evaluations of masticatory performance at 4 years after treatment failed to show significant difference between IODs and new CDs.30 Edentulous patients with resorbed mandibles may require longer adaptation periods with new CDs compared to IODs. The type of implant and attachment system for mandibular IODs were found to have no significant effects on masticatory performance.29,30,36,37 These results suggest that the degree of support by implants and level of retention with attachments for a mandibular overdenture have a limited impact on masticatory performance. However, the patients in all of these studies on mandibular implant-supported or retained overdentures used CDs in the maxillary arch. Additional studies are necessary to investigate the effect of improvements in retention and stability afforded by IODs for both the mandible and maxilla on masticatory performance. Following partial mandiblulectomy and free-flap reconstruction, treatments with implant-supported dentures may provide superior benefits in mastication on the defect side of the mouth compared to conventional dentures.38 However, this treatment should be considered after 1 year of surgical treatment due to a high rate of recurrence/metastasis (35%; 16/46).40 There were no articles identified evaluating masticatory performance in maxillectomy patients with conventional or implant-supported dentures. Evaluation of masticatory function and validation of implant-supported dentures are needed in this population. In this review, information retrieval followed a systematic approach. However, searches for primary data on broader sources, including abstracts and proceedings without language restriction, should be undertaken to minimize publishing bias. In general, abstracts and proceedings are not peer-reviewed. Thus, the primary data from these sources should be interpreted with caution. In ad-
The Journal of Prosthetic Dentistry
dition, meta-analyses to synthesize primary data obtained in high quality RCTs would be desirable to provide highest quality evidence.22 More well-designed studies are required to generalize the effect of implant-supported dentures on masticatory performance.
CONCLUSIONS While a number of studies on masticatory performance have been conducted in patients with various designs of implant-supported or retained dentures, high-level evidence supporting advantages in masticatory performance of implant-supported or retained dentures over conventional dentures is limited. Objective benefits in masticatory performance of implant-supported or retained dentures compared to conventional dentures have been substantiated for mandibular implant-supported or retained dentures in edentulous patients with resorbed mandibles and/or difficulty adapting to conventional removable complete dentures.
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