An Innovative Meta-Systematic Review into the Landscape of Literature and the Concluding Evidence on the Quality of Life of Patients Using Two Implant Supported Mandibular Complete Denture Prosthesis

Abstract

Aim:

The aim of this systematic review is to analyze the existing evidence on the quality of life of patients completely edentulous in the mandible.

Materials and Methods:

A search questionnaire was formulated using population intervention comparison outcome (PICO) analysis, and a comprehensive search was initiated in PubMed Central, Medline, Cochrane, and Google Scholar databases for the related topics. Manuscripts published till December 2019 were included in this review. Out of the 63 articles obtained from searching all databases, 27 studies were excluded based on the title and abstract. Out of the remaining 36 studies, 12 were excluded based on the inclusion and exclusion criteria of our interest and 24 were included on the basis of core data.

Results:

One review author identified randomized trials meeting inclusion criteria for this review. Two review authors extracted data and assessed study quality. The oral health-related quality of life in completely edentulous mandibular patients wearing implant-supported overdentures was better when compared to conventional tissue-supported complete denture, and a minimum two implant-supported mandibular complete denture has sufficient improvement in oral health-related quality of life.

Conclusion:

There are about more than 170 reviews and clinical trials that have been published in support of the same for the past two decades. Thus, the clinicians may not be tempted in placing additional implants in well-formed mandibular edentulous ridges. To enhance the understanding of mandibular implant overdenture treatment, clinicians must scrutinize the existing evidence and formulate a protocol by striking a balance between efficient and evidence based treatment.

Keywords

Edentulism Mandibular Implants Overdentures

List of Abbreviations

CD: Complete denture

DS-VAS: Denture satisfaction-visual analog scale

EDENT: Edentulous

GOHAI: Geriatric oral health assessment index

IOD: Implant retained over dentures

Iqr: Inter quartile range

MESH: Medical subject headings

OHIP: Oral health impact profile

OHIP-EDENT: Oral health impact profile—edentulous

OHIP-49: Oral health impact profile-49

OHIP-20: Oral health impact profile-20

OHIP-14: Oral health impact profile-14

OHRQoL: Oral health-related quality of life

PICO: Population–intervention–comparison–outcome

PRISMA: Preferred reporting items for systematic reviews and meta-analyses

QoL: Quality of life

SF-36: Short form health survey

VAS: Visual analog scale

Introduction

Edentulism rate is decreasing globally every decade because of wider and better oral health services.^1,2 Edentulism has a significant esthetic and functional concern in patients and leads to reduced quality of life (QoL) along with impact on general health. QoL is a multidimensional construct, which emphasizes thoroughly investigating the qualitative effects of diseases and therapies, as well as other relevant issues on health status.³ Evidence from the existing literature clearly shows the negative effect of edentulism on oral health-related QoL (OHRQoL) in the form of functional, psychological, and social impairment, thus affecting day-to-day life.^4,5

A significant paradigm shift in diagnosis, treatment planning, and definitive treatment for patients has been witnessed with the introduction of dental implants.^6,7 Until the 1980s, conventional tissue-supported complete dentures (CD) were the traditional method for the treatment of edentulism.^8–10 The advent of dental implants created multiple options to treat edentulism beyond traditional CD. They typically provide superior long-term results, particularly beneficial when treating patients with conventional CD. Substantial scientific data are available regarding the psychosocial, functional, and anatomic benefits that patients derive from implant overdentures.^11–14

In the mid-1980s, treatments with mandibular implant overdenture were introduced.^15,16 Being less expensive and less complicated, yet successful, mandibular implant overdenture soon became popular in many countries. Implant-retained overdentures are purported to decrease the negative outcomes the elderly patients have often experienced with CD, namely poor retention, poor stability, inability to chew, and inability to speak. Implant-retained dentures have the potential for increased retention as well as patient comfort when compared to CDs, offering better comfort, stability, and chewing functions and thereby improving the OHRQoL of geriatric edentulous patients.

The rehabilitation of edentulous mandible with conventional tissue-supported CD is no longer the most appropriate primary choice of prosthodontic treatment. There is now evidence that implant retained overdenture should become the first choice of treatment for edentulous mandibles.^17–20 Research data reporting the success, however, are not fully convincing to support all of the considerations necessary to predict effective clinical treatment outcome with respect to the total number of implants in overdenture treatment for completely edentulous mandibles.

According to the McGill consensus 2002, the rehabilitation of edentulous mandible with conventional tissue-supported CD is no longer the most appropriate first choice of prosthodontic treatment. The suggested first line of therapy for a lower edentulous arch is implant-supported overdenture. However, there are varied opinions regarding the number of implants to be placed to support the overdenture with several reports advocating a minimum of four to five implants and McGill consensus recommending a minimum of two implants. There are about more than 170 reviews and clinical trials that have been published in support of the same for the past two decades. Because most of this literature has been supported by private market players with an intention to promote one form of treatment over another, there is a need to analyze the literature for the significance of improvement and bias-adjusted outcome evaluation to determine the universal external validity of this clinical practice guideline. Previously our department has published extensive research on various aspects of prosthetic dentistry.^21–31 This vast research experience has inspired us to do a systematic review to objectively understand the validity of treatment protocol with differential number of implants with respect to absolute success in improving the OHRQoL.

Materials and Methods

Data Collection and Analysis

The studies considered were based on the data extraction and analysis of quality and publication bias. The data collection form was customized. The outcome measure was QoL of patients. In cases of no clear index specified, the most significant parameter was used.

Literature Search Protocol

For the identification of studies included or considered for this systematic review, detailed search strategies were developed for the database searched. The search methodology applied was a combination of MeSH terms and suitable keywords. The keywords employed in this search were broadly classified into four categories describing population, intervention, outcome, and the type of study. Keywords within each group were combined using Boolean operator (OR) and the searches of individual groups were combined using Boolean operator (AND) to retrieve articles electronically.

Searched Databases

The electronic databases included were National Library of Medicine (PubMed), Google Scholar, Medline, Ovid, and Cochrane database of systematic reviews. No limitation regarding publication type and publication date was set.

Search Strategy

P: completely edentulous, complete edentulism, completely edentulous patients.

I: implant-retained prosthesis, implant-retained denture(s), implant-supported denture(s), implant-supported prosthesis, implant denture(s), implant-retained removable prosthesis, implant-retained removable denture(s), implant-supported removable denture(s), implant-supported removable prosthesis, implant-supported overdentures.

C: conventional CD(s), conventional CD prosthesis, CD(s), CD prosthesis, tissue-supported CD, tissue-supported CD prosthesis.

O: quality of life, patient satisfaction, patient perception, patient-related outcome(s), patient-related outcome measure(s), OHRQoL.

The PICO search terms were loaded in the search engine by using Boolean operators (OR) for each cluster and integrating Boolean operator (AND) between the PICO clusters. The results obtained were further processed and the data were extracted (Figure 1).

Figure 1.

The PRISMA Chart Depicting the Article Selection Process for This Systematic Review

Search Algorithm

(Completely edentulous OR Completely edentulous [MeSH Terms] OR Completely edentulism OR Completely edentulism [MeSH Terms] OR Completely edentulous patients OR Completely edentulous [MeSH Terms]) AND (Implant-retained prosthesis OR Implant-retained prosthesis [MeSH Terms] OR Implant-retained dentures OR Implant-retained dentures [MeSH Terms] OR Implant-retained denture OR Implant-retained denture [MeSH Terms] OR Implant-supported dentures OR Implant-supported dentures [MeSH Terms] OR Implant-supported denture OR Implant-supported denture [MeSH Terms] OR Implant-supported prosthesis OR Implant-supported prosthesis [MeSH Terms] OR Implant denture OR Implant denture [MeSH Terms] OR Implant dentures OR Implant dentures [MeSH Terms] OR Implant-retained removable prosthesis OR Implant-retained removable prosthesis [MeSH Terms] OR Implant-retained removable denture OR Implant-retained removable denture [MeSH Terms] OR Implant-retained removable dentures OR Implant-retained removable dentures [MeSH Terms] OR Implant-supported removable denture OR Implant-supported removable denture [MeSH Terms) OR Implant-supported removable dentures OR Implant-supported removable dentures [MeSH Terms] OR Implant-supported removable prosthesis OR Implant-supported removable prosthesis [MeSH Terms] OR Implant-supported overdentures OR overdentures) AND (Conventional complete denture OR Conventional complete denture [MeSH Terms] OR Conventional complete dentures OR Conventional complete dentures [MeSH Terms] OR Complete denture OR Complete denture [MeSH Terms] OR Complete dentures OR Complete dentures [MeSH Terms] OR Complete denture prosthesis OR Complete denture prosthesis [MeSH Terms] OR Conventional complete denture prosthesis OR Conventional complete denture prosthesis [MeSH Terms] OR Tissue-supported complete denture OR Tissue-supported complete denture prostheses) AND (Quality of life OR Quality of life [MeSH Terms] OR Patient satisfaction OR Patient satisfaction [MeSH Terms] OR Patient perception OR Patient perception [MeSH Terms] OR Patient-related outcome OR Patient-related outcome [MeSH Terms] OR Patient-related outcome measure OR Patient-related outcome measure [MeSH Terms] OR Patient-related outcome measures OR Patient-related outcome measures [MeSH Terms] OR Oral health-related quality of life OR Oral health-related quality of life [MeSH Terms]).

Article Eligibility Criteria

Inclusion Criteria

Articles reporting QoL post implant-retained removable prosthesis with no restrictions on age or gender, ethnicity

Randomized control trial, clinical trial

Studies on mandibular implant-supported overdenture

Exclusion Criteria

Studies done using clinical parameters

Studies with review articles, case reports, or case series

Studies on fixed implant prosthesis, hybrid prosthesis

Studies comparing implant-supported fixed prosthesis

Studies comparing implant attachments

Studies on maxillary implant-supported overdenture

Results

One review author identified randomized trials meeting inclusion criteria for this review. Two review authors extracted data and assessed study quality. Agreement between observers for methodological quality was measured using kappa with quadratic weights. Disagreements were resolved by consensus. Out of the 62 articles obtained from searching all databases, 26 studies were excluded based on title and abstract. Out of the remaining 36 studies, 12 were excluded based on the inclusion and exclusion criteria of our interest and 24 were included on the basis of core data. The PRISMA chart depicts the article selection process for this systematic review (Figure 1). The general information of all the included articles in this systematic review, the statistics used, and the outcome measures of those studies were tabulated (Table 1). The types of outcome measures related to the QoL used in studies included in this systematic review were consolidated (Table 2). The data extracted from these studies were analyzed (Table 3). The level of evidence according to Oxford Centre for Evidence-Based Medicine 2011 was also tabulated (Table 4). The risk of bias of the included studies was analyzed and summarized (Table 5). Because the included studies exhibited wide heterogeneity, a meta-analysis was not possible and forest plot could not be generated.

Table 1.

General Information of all the Included Articles in This Systematic Review and the Outcome Measures Used in Those Studies

Author Year	Country	Sample Size	Intervention	Groups	Type of Statistics	Outcome Measures	Sponsorship
Pan et al. 2014	Taiwan	75	4-implant overdenture	Implant overdenture (N = 60) Complete denture (N = 15)	t-test and Kruskal–Wallis test	Comprehensive Self-estimated questionnaire • Masticating ability • Masticating type of food • Effect on mental and daily life • Overall denture satisfaction • Functional complaints of denture	Self-sponsored
Cardoso et al. 2016	Brazil	50	Implant overdenture	Implant overdenture (N = 25) Complete denture (N = 25)	One-sample Kolmogorov–Smirnov test and Mann–Whitney test	OHIP-EDENT	Self-sponsored
Awad et al. 2000	Canada	102	Implant overdenture	Implant overdenture (N = 54) Complete denture (N = 48)	Chi-square test Linear multiple regression analysis	OHIP-49	Nobel Biocare Canada Inc. Dentachrome Inc., DENTSPLY Canada Inc. Canadian MRC, Health And Welfare Canada (NHRDP)
Heydecke et al. 2003	Canada	60	Implant overdenture	Implant overdenture (N = 30) Complete denture (N = 30)	Linear regression model	OHIP-49	Not mentioned
Awad et al. 2003	Canada	60	Implant overdenture	Implant overdenture (N = 30) Complete denture (N = 30)	Student’s t-test	OHIP-49	Not mentioned
Harris et al. 2011	Ireland	122	Implant overdenture	Implant overdenture (N = 60) Complete denture (N = 62)	ANOVA for repeated measures	OHIP–49	Straumann Ltd
Heydecke et al. 2005	Canada	102	Implant overdenture	Implant overdenture (N = 54) Complete denture (N = 48)	Independent t test	OHIP-20	Straumann Canada and Canadian Institute of Heath Research
Farias Neto et al. 2012	Brazil	29	Implant overdenture	Implant overdenture (N = 14) Complete denture (N = 15)	Student’s t test	Questions with three-grade answers (well satisfied, satisfied and dissatisfied) 12 factors; chewing, tasting, speech, pain, aesthetics, fit, retention and comfort	Self-sponsored
Muller et al. 2013	Switzerland	34	Implant overdenture	Implant overdenture (N = 16) Complete denture (N = 18)	Student’s t test or Fisher’s exact test	DS-VAS (0–10) OHIP-EDENT	ITI Foundation
Allen et al. 2006	Canada	118	Implant overdenture	Implant overdenture (N = 62) Complete denture (N = 56)	Wilcoxon signed rank test	OHIP-49 Genera satisfaction (Likert Scale 1–5)	PPP Medical Health Care Trust
Gonclaves et al. 2007	Brazil	34	Implant overdenture	Implant overdenture (N = 17) Complete denture (N = 17)	–	Variation of OHIP	Not mentioned
Jofre et al. 2013	Chile	30	Implant overdenture	Implant overdenture (N = 15) Complete denture (N = 15)	–	OHIP-EDENT	National Commission of Scientific and Technological research of CHILE
Morias et al. 2003	Canada	60	Implant overdenture	Implant overdenture (N = 30) Complete denture (N = 30)	–	Patient satisfaction( Likert scale 1–5)	STRAUMANN CANADA TD and Canadian Institute of Health Research
Awad et al. 2013	UAE	203	Implant overdenture	203 edentulous patients	Mann–Whitney test	OHIP-20	ITI
Sun et al. 2014	China	50	Implant overdenture	15 edentulous patients	-	OHIP-49	National Natural Science Foundation, China
Batisse et al. 2016	France	11	Mini implants	44	-	GOHAI	Not mentioned
Enkling et al. 2016	Switzerland	20	Mini implants	80	Brunner–Langer models	OHRQoL	Self-sponsored
Elysad et al. 2016	Egypt	28	Mini implants	19	One-sample Kolmogorov–Smirnov test	VAS Patient satisfaction	Not mentioned
Catalan et al. 2015	Chile	7	Mini implants	14	Friedman test	Patient satisfaction	Not mentioned
Souza et al. 2015	Brazil	120	Mini implants	236 Mini 80 Standard	Generalized estimating equations (Gees)	OHRQoL Patient satisfaction	FAPESP
Griffitts et al. 2005	USA	30	Mini implants	116	Not mentioned	Patient satisfaction	Not mentioned
Tomasi et al. 2013	Sweden	21	Mini implants	80	Friedman test Mann–Whitney U test McNemara test	VAS	Dentatus AB, Sweden
Gjengedal et al. 2013	Norway	54	Implant overdenture	Implant overdenture (N = 26) Complete denture (N = 28)	–	OHIP- EDENT SF-36	Astratech and University Of Bergen
Cakir et al. 2014	Turkey	58	Implant overdenture	Implant overdenture (N = 29) Complete denture (N = 29)	One-way ANOVA Kruskal–Wallis	OHIP- EDENT SF-36	Self-sponsored

Discussion

This study included 24 randomized control trials, majority of which conclude that implant-supported overdenture provides improved QoL for edentulous patients. The studies showed high risk of bias and thus meta-analysis was not performed. The quality of the edentulous ridges was not mentioned clearly and randomization and allocation concealment were not done prudently in many of the studies included. Heydecke et al. published two studies and concluded that the majority of patients in this trial were significantly more satisfied with maxillary implant overdentures than with fixed prosthesis^32,33 Awad et al. conducted two studies before the McGill consensus statement in 2000 and 2003, and one study post the consensus in 2014. The conclusion of two out of three studies, post the consensus statement declaration seems to favor implant overdenture over conventional in the improvement of QoL of edentulous patients.

Table 2.

Types of Outcome Measures Review Related to the Quality of Life, Used in Studies Included in This Systematic Review

S. No.	Types of Outcome Measures
1	OHIP-49
2	OHIP-20
3	GOHAI
4	OHRQoL
5	DS-VAS or general satisfaction VAS
6	Patient satisfaction questionnaire
7	OHIP-EDENT

It is also essential to note that there is an enormous amount of publications on this topic, especially post the consensus statement, heavily focusing on the use of implant-supported overdenture.^{15,17,32–36} Of the 16,500 published articles, 80% were published after 2003, which is post the consensus (Figure 2). Financial aid for the studies included in this review was majorly from commercial entities, which could be a possible influence on positive reporting (Figure 3).^36–41 The risk of bias is high with the included studies in this review and the conclusions drawn from the studies should be interpreted with caution.

The most commonly used parameter to objectify the QoL is Oral Health Impact Profile (OHIP) questionnaire index (Figure 4).^42–44 Following are the three versions of this index available till date, which have been improved over the years: OHIP-49, OHIP-20, and OHIP-14. These deduce the same outcome and have 49, 20, 14 questions in the questionnaire, respectively.^32,45–49 The OHIP-49 has 407 citations in implant overdenture studies and is the most often used parameter in the articles included in this review. The other versions OHIP-20^33,36 and OHIP-14^43,50 have about 419 and 135 citations, respectively (Figure 5). Awad et al., used the index OHIP-49 in the studies conducted in 2000 and 2003, whereas they shifted to the modified version, OHIP-20, in the year 2014. Heydecke et al., used OHIP-49 in the year 2003 and OHIP-20 in the year 2005. This information focuses on the paradigm shift in the use of modified versions of OHIP in recent years.^41,46,51

Tissue-supported CD have rendered excellent service in rehabilitating edentulous patients. If patients adapted to these dentures express satisfaction with their QoL, the question of placing implants to further improve the QoL should be approached prudently after careful evaluation of the magnitude of the expected effect size. It was observed in this review that the difference in the QoL of edentulous patients with implant-supported overdenture was very fluctuant. This substantial variation for similar treatments shows that the data may not be used as absolute confirmatory evidence to formulate clinical practice guidelines and strong consensus reports based on research sponsored by private bodies. Although most implant manufacturing companies disclaim their influence on the research, one should acknowledge that there is an unspoken expectation placed on researchers to look for positive correlations in line with the expectations of the market.

One of the most emphasized philosophies in evidence-based dentistry is that correlation does not equal causation. Hence, the consensus statement based on nonobjective measurements may not be fully authenticated to recommend multiple implant-supported overdenture as the general protocol for patients all over the world. Future research with well-designed randomized, multicentric clinical trials sponsored by nonprofit organizations with stringent objective outcome measures should be the preferable form of evidence to scholars to select while making consensus statements to avoid the influence of major commercial entities in our medical decision-making process.

Conclusion

The OHRQoL in completely edentulous mandibular patients wearing implant-supported overdentures was better when compared to conventional tissue-supported CD. However, all the parameters for evaluating absolute clinical success of OHRQoL showed wider variability in success rates with two implant-supported overdentures. Hence, there is a definitive need for more clarity in the understanding of the success of mandibular implant overdenture treatment that was proposed by the McGill consensus. Clinicians must scrutinize the existing evidence and determine the external validity of the clinical practice guideline to formulate a protocol by striking a balance between efficient and evidence-based treatment. Independent studies funded by nonprofitable organizations are of paramount importance to derive a standard protocol to enhance more effective patient care.

Clinical Significance

There are about more than 170 reviews and clinical trials that have been published in support of the same for the past two decades. Because most of this literature has been supported by private market players with an intention to promote one form of treatment over another, there is a need to analyze the literature for the significance of improvement and bias-adjusted outcome evaluation to determine the universal external validity of this clinical practice guideline.

Table 3.

Details About the Outcome Variables, Their Statistical Significance, and Conclusion Data Extracted From the Studies Included in This Systematic Review

Author Year	Title	Outcome Parameters	Results		P-value	Conclusion
			Implant Overdenture Mean (SD)	Complete Denture/Edentulous Mean (SD)
Pan et al. 2014	Comparison of patient’s satisfaction with implant‑supported mandibular overdentures and complete dentures	Comprehensive self-estimated questionnaire: Masticating ability, Masticating type of food, Effect on mental and daily life, Overall denture satisfaction, Functional complaints of denture	1.06 (0.15) 1.09 (0.15) 1.08 (0.18) 8.89 (0.31) 1.09 (0.16)	1.64 (0.47) 1.92 (0.56) 1.42 (0.81) 6.99 (2.11) 1.66 (0.45)	<.001 <.001 .12 .004 <.001	This investigation showed that the mandibular implant‑retained overdenture is better than the traditional complete denture in every respect from a patient’s point of view.
Cardoso et al. 2016	Impact of mandibular conventional denture and overdenture on quality of life and masticatory efficiency	OHIP-EDENT Before treatment After treatment	Median scores 9.0 2.0	Median scores 5.0 2.0	P = .001	The results of this study suggest that treatment With immediately loaded 2-implant mandibular Overdenture associated with maxillary conventional Denture provides better masticatory efficiency and Oral health–related quality of life than upper and lower conventional dentures
Awad et al. 2000	Measuring the effect of intraoral implant rehabilitation on health-related quality of life in a randomized controlled clinical trial	OHIP -49 Pretreatment Posttreatment	100.6 (37.3) 66.1 (28.08)	98.7 (38.1) 89.3 (40.42)	Implant overdenture P < .05	These results suggest that implant treatment provides significant short-term improvement over conventional treatment in oral health-related quality of life.
Heydecke et al. 2003	Relationship between prosthodontic evaluation and patient ratings of mandibular conventional and implant prostheses.	OHIP-49	Not available	Not available	P = .001	The majority of patients in this trial were significantly more satisfied with maxillary implant overdentures than with fixed prostheses.
Awad et al. 2003	Comparing the efficacy of mandibular implant-retained overdentures and conventional dentures among middle-aged edentulous patients: satisfaction and functional assessment.	OHIP-49	Not available	Not available	P = .001	A mandibular two-implant overdenture opposed by a maxillary conventional denture is a more satisfactory treatment than conventional dentures for edentulous middle-aged adults.
Harris et al. 2013	A comparison of implant-retained mandibular overdentures and conventional dentures on quality of life in edentulous patients: a randomized, prospective, within-subject controlled clinical trial	OHIP–49 Baseline three months	35.57 (12.17) 8.29 (8.79)	32.67 (13.57) 20.39 (12.66)	P < .001	The findings show that, controlling for expectancy bias and variability in baseline levels, IODs significantly increase patient satisfaction, dental function and quality of life over and above those achieved with good quality CCDs.
Heydecke et al. 2005	Cost-effectiveness of mandibular two-implant overdentures and conventional dentures in the edentulous elderly	OHIP-20	31.3	47.0	P < .05	The values translate into a yearly additional cost for IOD treatment of $14.41 per OHIP-20 point. These results are the key to the implementation of programs to provide this form of therapy for edentulous adults.
Farias Neto et al. 2012	The influence of mandibular implant-retained overdentures in masticatory efficiency	questions with three-grade answers (well satisfied, satisfied and dissatisfied) 12 factors	92.4 ( 5.2)	81.9 (6.6)	P < .05	The results of this study suggest that mandibular overdenture significantly improves chewing Experience, although limited effect on masticatory efficiency has been observed.
Muller et al. 2013	Implant-supported mandibular overdentures in very old adults: a randomized controlled trial	DS-VAS (0-10) OHIP-EDENT Baseline three months	41.1 (20.31) 20.9 ( 16.74)	32.9(20.84) 25.9 ( 13.46)	P < .35	Stabilizing existing lower dentures by means of two short regular-diameter interforaminal implants in very old edentulous patients who are dependent for the activities of daily living provides significantly higher denture satisfaction than that of a conventional reline.
Allen et al. 2006	A randomized controlled trial of implant-retained mandibular overdentures	OHIP-49 Genera satisfaction (Likert scale 1–5) Pretreatment OHIP Posttreatment OHIP	112 (22-218) 30.5 (1-129)	57.5 (12-163) 54 ( 0-125)	P = .006 P = .51	Significant improvement in oral-health related quality of life and denture satisfaction was reported by both groups.
Gonclaves et al. 2007	Comparing the efficacy of mandibular implant-retained overdentures and conventional dentures among elderly edentulous patients: satisfaction and quality of life	Variation of OHIP S, satisfactory; T, tolerate; U, unsatisfactory.	Mandible 13 3 1	Mandible 12 3 2	P = 1.0000 P = 1.0000	Although the stability of the mandibular implant-retained overdenture was enhanced compared to a conventional denture, the quality of life and satisfaction levels were similar for both the groups.
Jofre et al. 2012	Influence of minimally invasive implant-retained overdenture on patients’ quality of life: a randomized clinical trial	OHIP-EDENT	25.4 (10.7)	9.5 ± 8.3	P ≤ .001	Patients wearing mandibular overdentures with two minimally invasive splinted SDI, experienced more improvements in perceived oral health-related quality of life, than patients having conventional treatment.
Morias et al. 2003	The effects of mandibular two-implant overdentures on nutrition in elderly edentulous individuals	Patient satisfaction (Likert scale 1 to 5) Minimum score = 1, maximum = 5. Lower scores represent improvement Pretreatment Posttreatment	3.0 2.0	4.0 2.0	–	These results suggest that low-cost IOD treatment may improve the nutritional state of edentulous people.
Awad et al. 2014	The effect of mandibular two-implant overdentures on oral health–related quality of life: an international multicenter study	OHIP-20	Median scores 42.8	Median scores 21.1		Mandibular two-implant overdentures are more likely than conventional dentures to improve OHRQL for edentulous patients. Cultural differences were also observed in the impact of implant overdentures on the different domains of the OHIP-20.
Sun et al. 2014	Masticatory efficiency and oral health-related quality of life with implant-retained mandibular overdentures	OHIP-49	59.6 (25.2) 39.3 (14.7)		P = .000	Implant-retained mandibular over dentures can significantly improve patients’ ME and OHRQoL. The improvement in OHRQoL is mainly because of the improved ME. An improved chewing experience, and pain relief also contributes to improvement of OHRQoL.
Batisse et al. 2016	Stabilization of mandibular complete dentures by four mini implants: Impact on masticatory function	GOHAI	55.4 (3.6)	36.7 (9.9)	P < .001	The placement of mini implants as retentive elements for mandibular full dentures had a positive impact on patients’ masticatory function and quality of life.
Enkling et al. 2016	Chewing efficiency, bite force and oral health-related quality of life with narrow diameter implants - a prospective clinical study: results after one year	OHRQoL Baseline At 12 weeks	31.0 [iqr 40.0] 9.0 [iqr 23.5]		P < .0001	The stabilization of a lower complete prosthesis with four NDIs is a feasible minimally invasive and economical approach to improve oral function and OHRQoL, especially in elderly patients with limited bone support.
Elysad et al. 2016	Patient satisfaction and prosthetic aspects with mini-implants retained mandibular overdentures. A 5-year prospective study	VAS Patient satisfaction			P < 0.05	Within the limitations of this clinical study, patient satisfaction with mini-implant retained mandibular overdentures increased significantly with time.
Catalan et al. 2015	Mandibular overdentures retained by two mini-implants: A seven-year retention and satisfaction study	Patient satisfaction Category score range Very poor 0 to 73 Poor 74 to 100 Good 101 to 127 Very good 128 to 148	122	72	P = .010	After connecting mandibular overdentures to two mini-implants, patient satisfaction significantly increased and retention significantly improved during the 7-year observation period.
Souza et al. 2015	Mini vs. standard implants for mandibular overdentures: a randomized trial	OHRQoL Patient satisfaction 4 mini implants 2 mini implants Standard implants	2.4 (1.5, 3.4) 3.0 (1.9, 4.0) 2 6.4 (3.9, 8.9)	15.2 (9.1) 13.9 (7.8) 17.6 (9.4)	P < .05 P > .05 P < .05	Mandibular mini-implant-retained overdentures can achieve results at least comparable with the standard of care for edentulism, according to the patient perspectives. The insertion of 4 mini-implants results in superior OHRQoL and patient satisfaction as compared with 2 mini- or standard implants.
Griffitts et al. 2005	Mini dental implants: an adjunct for retention, stability, and comfort for the edentulous patient	Patient satisfaction Comfort Retention Chewing ability Speaking ability	Before After 2.2 9.4 1.7 9.6 2.3 9.3 5.3 8.5			MDI’s are a highly successful implant option for patients with poor tolerance to maxillary and mandibular Prosthesis. The implants are relatively affordable and overall patient satisfaction is excellent.
Tomasi et al. 2013	Patient satisfaction with mini-implant stabilized full dentures. A 1-year prospective study	VAS Pretreatment 12 months	3_3 (1 _8–5_8) 9_0 (9 _0–10)		P < .05	placement of mini-implants as retentive elements for full dentures with poor functional stability has a marked positive impact on the patients’ perception of oral function and comfort as well as security in social life
Gjengedal et al. 2013	The influence of relining or implant retaining existing mandibular dentures on health-related quality of life: A 2-year randomized study of dissatisfied edentulous patients.	OHIP- EDENT SF-36	Not available	Not available	No significant improvement	The results of this study support the findings from other RCT studies that to implant-retain the mandibular denture significantly improves self-reported oral health and OHRQoL. This treatment modality should be a minimum standard of care in complete denture wearers dissatisfied with their mandibular denture.
Cakir et al. 2014	Evaluation of the efficacy of mandibular conventional and implant prostheses in a group of Turkish patients: A quality of life study	OHIP- EDENT SF-36 Pretreatment Posttreatment	18.07 (2.52) 3.03 (1.45)	21.24 (2.82) 12.24 (2.80)		Positive influence on oral health-related QoL was observed in all groups. The QoL values were the most improved in the implant-retained overdenture group.

Table 4.

CEBM Level of Evidence of Included Studies (According to Oxford Centre for Evidence-Based Medicine 2011, Levels of Evidence)

Author Year	Study Design	CEBM Level of Evidence
Pan et al. 2014	Case-control	Level 4
Cardoso et al. 2016	Nonrandomized control trial	Level 3
Awad et al. 2000	Randomized control trial	Level 2
Heydecke et al. 2003	Randomized control trial	Level 2
Awad et al. 2003	Randomized control trial	Level 2
Harris et al. 2013	Randomized control trial	Level 2
Heydecke et al. 2005	Randomized control trial	Level 2
Farias Neto et al. 2012	Randomized control trial	Level 2
Muller et al. 2013	Randomized control trial	Level 2
Allen et al. 2006	Randomized control trial	Level 2
Gonclaves et al. 2007	Prospective cohort	Level 3
Jofre et al. 2012	Randomized control trial	Level 2
Morias et al 2003	Randomized control trial	Level 2
Awad et al. 2014	Randomized control trial	Level 2
Sun et al. 2014	Randomized control trial	Level 2
Batisse et al. 2016	Cohort study	Level 3
Enkling et al. 2016	Prospective clinical study	Level 3
Elysad et al. 2016	Observational prospective clinical study	Level 3
Catalan et al. 2015	Prospective cohort	Level 3
Souza et al. 2015	Randomized control trial	Level 2
Griffitts et al. 2005	Prospective cohort	Level 3
Tomasi et al. 2013	Prospective, clinical study	Level 3
Gjengedal et al. 2013	Randomized control trial	Level 2
Cakir et al. 2014	Randomized control trial	Level 2

Figure 2.

Image Showing the Number of Studies Published on Mandibular Two Implant-Supported Overdenture

Table 5.

Risk of Bias of Included Studies

Author Year	Sample Size Estimation	Power Calculation	Blinding	Inclusion and Exclusion Criteria	Randomization	Allocation Concealment	Measuring Instrument	Dropouts	Risk
Pan et al. 2014	Not mentioned	Not mentioned	Not mentioned	Incomplete	Not mentioned	Not mentioned	Comprehensive self-estimated questionnaire	Not mentioned	High
Cardoso et al. 2016	Not mentioned	Not mentioned	Not mentioned	Not mentioned	Not mentioned	Not mentioned	OHIP-EDENT	Not mentioned	High
Awad et al. 2000	Yes	Yes	Not mentioned	Incomplete	Yes	Not mentioned	OHIP-49	Mentioned	Low
Heydecke et al. 2003	Yes	Yes	Not mentioned	Yes	Yes	Not mentioned	OHIP-49	Mentioned	Low
Awad et al. 2003	Not mentioned	Not mentioned	Not mentioned	Not mentioned	Not mentioned	Not mentioned	OHIP-49	Not mentioned	High
Harris et al. 2011	Yes	Yes	Not mentioned	Incomplete	Not mentioned	Not mentioned	OHIP49	Mentioned	Moderate
Heydecke et al. 2005	Yes	Yes	Not mentioned	Yes	Yes	Not mentioned	OHIP-20	Mentioned
Farias Neto et al. 2012	Yes	Yes	Yes	Yes	Yes	Not mentioned	Questions with three-grade answers (well satisfied, satisfied and dissatisfied)	Not mentioned	Moderate
Muller et al. 2013	Not mentioned	Yes	Not mentioned	Not mentioned	Yes	Yes	DS-VAS (0–10) OHIP-EDENT	Mentioned	Moderate
Allen et al. 2006	Not mentioned	Not mentioned	Not mentioned	Not mentioned	Yes	Not mentioned	OHIP-49 Genera Satisfaction (Likert Scale 1-5)	Mentioned	High
Gonclaves et al. 2007	Not mentioned	Not mentioned	Yes	Not mentioned	Yes	Not mentioned	OHIP	Not mentioned	High
Jofre et al. 2013	Not mentioned	Not mentioned	Yes	Yes	Yes	Not mentioned	OHIP-EDENT	Mentioned	Moderate
Morias et al. 2003	Yes	Not mentioned	Not mentioned	Yes	Yes	Not mentioned	Patient satisfaction(Likert scale 1–5)	Mentioned	Moderate
Awad et al. 2013	Yes	Yes	Not mentioned	Yes	Yes	Not mentioned	OHIP-20	Not mentioned	Moderate
Sun et al. 2014	Not mentioned	Not mentioned	Not mentioned	Yes	Not mentioned	Not mentioned	OHIP-49	Not mentioned	High
Batisse et al. 2016	Yes	Yes	Not mentioned	Yes	Not mentioned	Not mentioned	GOHAI	Not mentioned	Moderate
Enkling et al. 2016	Not mentioned	Yes	Not mentioned	Yes	Not mentioned	Not mentioned	OHIP-49	Mentioned	High
Elysad et al. 2016	Yes	Yes	Not mentioned	Yes	Not mentioned	Not mentioned	VAS Patient satisfaction	Not mentioned	High
Catalan et al. 2015	Not mentioned	Not mentioned	Not mentioned	Not Mentioned	Not mentioned	Not mentioned	Patient satisfaction survey	Mentioned	High
Souza et al. 2015	Yes	Yes	Not mentioned	Yes	Not mentioned	Not mentioned	OHIP-20	Not mentioned	High
Griffitts et al. 2005	Not mentioned	Not mentioned	Not mentioned	Not Mentioned	Not mentioned	Not mentioned	Patient satisfaction questionnaire	Not mentioned	High
Tomasi et al. 2013	Yes	Yes	Not mentioned	Yes	Not mentioned	Not mentioned	VAS	Not mentioned	High
Gjengedal et al. 2013	Yes	Yes	Not mentioned	Incomplete	Yes	Not mentioned	OHIP-EDENT SF-36	Mentioned	Moderate
Cakir et al. 2014	Yes	Yes	Yes	Yes	Yes	Yes	OHIP-EDENT SF-36 OHRQoL-Uk35 OHIP-14 SF-36	Not mentioned	Low

Figure 3.

Image Showing the Funding for the Studies on Mandibular Two Implant Supported Overdenture Included in This Systematic Review

Figure 4.

Image Showing the Frequency of Indexes Used for OHRQoL of Mandibular Two Implant-Supported Overdenture Included in This Systematic Review

Figure 5.

Image Showing the Number of Citations of Index With Respect to Mandibular Two Implant-Supported Overdenture Included in This Systematic Review

Future Scope

This review offers scope for further well-structured randomized control trials in different geographical locations studying different ethnic populations about implant-supported mandibular overdentures. This can be used as future evidence to assess the hard and soft tissue changes associated with the prosthesis.

Footnotes

Acknowledgements

The authors acknowledge Saveetha University for all the help and support.

Author Contributions

Vaishnavi Rajaraman carried out the systematic review by collecting data and drafted the manuscript after performing necessary statistical analysis. Deepak Nallaswamy aided in the conception of the topic, participated in the study design and statistical analysis, and supervised the preparation of manuscript. Dhanraj M Ganapathy helped in the study design and coordinated in developing the manuscript. Ashok Velayudhan helped in editing and revising the manuscript. All the authors have equally contributed in developing the manuscript.

Data Availability Statement

The authors confirm that the data supporting the findings of this study are available within the article (and/or) its supplementary materials.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

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