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Review
Mandibular complete denture versus single-implant
overdenture: a systematic review of patient-reported
outcomes
T.E.NOGUEIRA,D.R.DIAS&C.R.LELES Department of Prevention and Oral Rehabilitation, School
of Dentistry, Federal University of Goias, Goiania, Brazil
SUMMARY The single-implant mandibular overden-
ture (SIMO) has been proposed as an alternative
for edentulous patients who are poorly adapted to
their dentures due to low retention and stability
of the conventional mandibular complete denture
(CD). However, there is a lack of evidence
regarding the effectiveness of SIMO, which can be
measured by examining patient perception of
treatment effects. The aim of this systematic
review was to assess the comparative results of CD
and SIMO treatments using patient-reported
outcome measures. A literature search was carried
out in PubMed, Scopus and Cochrane Central
databases. The search included studies published
up to July 2017. The focus question was: ‘Do
single-implant mandibular overdentures improve
patient-reported outcomes compared to conven-
tional complete dentures in edentulous patients?’
Eligible studies were randomised clinical trials
(RCT) and prospective studies. After initial
screening for eligibility and full-text analysis, 11
studies were included for data extraction and
quality assessment (five parallel-group RCTs, two
crossover RCTs and four prospective studies). All
studies reported marked improvement in
satisfaction with the dentures and quality of life
measures after SIMO treatment, irrespective of
variations in implant treatment protocols and
retention systems. Methodological considerations
revealed a lack of evidence from RCTs on the
comparative effectiveness of the two treatment
strategies. Hence, although available evidence
suggests considerable improvement in patient-
reported outcomes following the insertion of a
single implant to retain a mandibular denture, fur-
ther well-designed comparative studies between
SIMO and CD are required to improve the level of
evidence and to support the indication of SIMO
treatment in routine practice.
KEYWORDS: patient satisfaction, quality of life,
overdenture, complete denture, patient-reported
outcomes, systematic review
Accepted for publication 10 August 2017
Background
Despite the significant decline in the prevalence and
incidence of total tooth loss in the last decades at the
global, regional and country levels (1), the continuing
rate of decline in edentulism is projected to slow,
compensated partially by population growth and age-
ing (2). Nevertheless, edentulism is still a relevant
health problem and there are significant barriers to
oral health care of older people. Poor socio-economic
conditions of older people also contribute to their
under-utilisation of oral health services even when
these are available (3), which reinforces the need for
accessible and cost-effective treatments that minimise
the financial barrier in oral health care.
Conventional complete dentures are the most com-
mon treatment for edentulous subjects worldwide
and, in general, edentulous patients treated with
©2017 John Wiley & Sons Ltd doi: 10.1111/joor.12550
Journal of Oral Rehabilitation 2017
Journal o f Oral Rehabilitation
conventional complete dentures (CD) are well
adapted to their dentures. Most of them, particularly
older individuals, have expectations limited to well-
functioning CDs and are less likely to be candidates
for implant therapy (4). However, reports of
impaired function, oral pain and discomfort are fre-
quent, especially about the mandibular denture.
Patient complaints and dissatisfaction with the den-
tures may be related to technical aspects of the treat-
ment but may also be due to prognostic factors that
are multifactorial and largely dependent on clinical,
psychological and behavioural aspects of the patients
(5). For these difficult clinical situations, especially
for patients with edentulous mandible, implant-sup-
ported or implant-retained dentures are recom-
mended to improve denture retention and stability
and increase overall oral comfort, function and psy-
chosocial well-being.
The mandibular overdenture retained by two
implants has been recommended as the minimum
standard of care for the edentulous mandible (6, 7).
However, in recent years, the single-implant
mandibular overdenture (SIMO) has been proposed
as an alternative to more complex overdenture
designs (8, 9). SIMO is assumed to be simpler and less
costly than both the fixed-implant treatment and the
overdenture retained by two implants. It is also con-
sidered a more feasible option for geriatric patients,
who are less likely to adhere to complex implant
interventions, because of its diminished functional
demands and because of the favourable local bone
condition in the symphyseal region, which ensures
satisfactory primary implant stability (8).
Previous clinical studies showed satisfactory results
of SIMO treatment using clinical outcomes such as
implant survival rate, marginal bone loss and implant
stability over time, as well as improved patient satis-
faction and quality of life (10). The post-loading
implant survival in 1- and 2-implant mandibular
overdentures was compared in a meta-analysis, and
no significant difference was observed between the
two treatment modalities (11). Another review, which
gathered evidence from clinical studies, suggested that
SIMO could be a reliable alternative for elderly
patients on the basis of implant survival, patient satis-
faction and prosthodontic maintenance (12). How-
ever, it is difficult to make reliable comparisons across
clinical studies because they differed greatly on the
experimental design, use of different implant and
retention systems, loading protocols and evaluation of
distinct clinical outcomes.
There is sound evidence available about the positive
impacts of the 2-implant mandibular overdenture on
patient-reported outcomes, such as oral health-related
quality of life and satisfaction, when compared to CD
(13–15). Similarly, preliminary reports showed that
there is no detrimental effect on denture mainte-
nance, patient satisfaction, implant survival and peri-
implant bone loss when the number of implants is
reduced from two to one (16, 17). However, the
incremental effect of SIMO is still poorly understood
when CD, which is still the standard of care in the
majority of health systems worldwide, is considered
the reference for comparison. In addition, the impact
of SIMO based on an assessment from the patient’s
perspective is critical to reveal whether this treatment
truly improves a patient’s health status and quality of
life. Those two outcomes are crucial aspects of a
patient-centred approach to oral health care.
The aim of this review was to assess the changes in
patient-reported outcome measures between CD and
SIMO treatment. The focus question was as follows:
‘Do single-implant mandibular overdentures improve
patient-reported outcomes compared to conventional
complete dentures in edentulous patients?’ The study
hypothesis is that SIMO provides significant improve-
ments for CD wearers when patient-reported out-
comes are considered.
Methods
Search strategy
The ‘Preferred Reported Items for Systematic Reviews
and Meta-Analysis’ (PRISMA) guidelines were used as a
reference for reporting this systematic review (18). A
broad systematic literature search was conducted in
PubMed, Scopus and Cochrane Central focusing on clin-
ical studies of edentulous subjects treated with SIMO.
The last literature search was performed in July 2017.
The question and the search strategy were struc-
tured based on the ‘PICOS’ method: ‘Population’ –
edentulous patients; ‘Intervention’ –single-implant
mandibular overdenture; ‘Comparator’ –conventional
mandibular denture; ‘Outcome’ –patient-reported
outcomes; ‘Study design’ –randomized controlled tri-
als (RCTs) and single-arm prospective studies. A
detailed description of the search strategy containing
©2017 John Wiley & Sons Ltd
T. E. NOGUEIRA et al.
2
MeSH terms, keywords, Boolean operators and their
combinations for PubMed and Scopus is detailed in
Table 1. No time frame was used to limit the number
of eligible studies, and no language restriction was
considered for this review.
Selection criteria
To be included in this systematic review, the study
had to be preferably classified as a randomised
controlled trial (RCT), but prospective studies with
before–after comparisons were also considered, and
all of them had to include at least 10 SIMO patients.
RCTs had to include conventional denture wearers as
an active comparator (control group), and single-arm
prospective studies had to have assessed patients
treated with conventional dentures as the baseline
treatment. Moreover, one or more patient-reported
outcomes had to be assessed in the study. The
patient-reported outcomes are important because
Table 1. Electronic databases and search strategies according to the PICO question components
Database Search strategy
PubMed (P) #1 (mouth, edentulous[MeSH Terms]) OR mouth, edentulous[Title/Abstract]) OR mouth, toothless[Title/
Abstract]) OR edentul*[Title/Abstract]) OR edentulous patients[Title/Abstract]) OR toothless patients[Title/
Abstract]) OR jaw, edentulous[MeSH Terms]) OR jaws, edentulous[Title/Abstract])
(I) #2 (denture, overlay[MeSH Terms]) OR denture, overlay[Title/Abstract]) OR overdenture*[Title/Abstract])
OR implant overdenture[Title/Abstract]) OR mandibular overdenture[Title/Abstract]) OR single implant[Title/
Abstract]) OR one implant[Title/Abstract]) OR midline implant[Title/Abstract]) OR median implant[Title/
Abstract]) OR single implant overdenture[Title/Abstract]) OR single-implant overdenture[Title/Abstract])
(C) #3 (denture, complete[MeSH Terms]) OR denture, complete[Title/Abstract]) OR denture[Title/Abstract])
(O) #4 (quality of life[MeSH Terms]) OR quality of life[Title/Abstract]) OR patient satisfaction[MeSH Terms]) OR
patient satisfaction[Title/Abstract]) OR satisfaction with the denture*[Title/Abstract]) OR patient outcome
assessment[MeSH Terms]) OR patient outcome assessment[Title/Abstract]) OR research, patient-centered
outcomes[Title/Abstract]) OR outcome assessment, patient[Title/Abstract]) OR patient*reported outcome*[Title/
Abstract]) OR patient*centered outcome*[Title/Abstract]) OR patient*related outcome*[Title/Abstract]) OR
patient*oriented outcome*[Title/Abstract]) OR treatment outcome[MeSH Terms] OR treatment outcome[Title/
Abstract]) OR effectiveness, clinical[Title/Abstract]) OR patient*relevant outcome*[Title/Abstract]) OR clinical
efficacy[Title/Abstract]) OR treatment effectiveness[Title/Abstract]) OR treatment efficacy[Title/Abstract]) OR
rehabilitation outcome[Title/Abstract])
#1 AND #2 AND #3 AND #4
Scopus (P) #1 ‘mouth, edentulous’ OR ‘mouth, toothless’ OR edentul*OR ‘edentulous patients’ OR ‘toothless patients’
OR ‘jaw, edentulous’ OR ‘jaws, edentulous’
(I) #2 ‘denture, overlay’ OR overdenture*OR ‘implant overdenture’ OR ‘mandibular overdenture’ OR ‘single
implant’ OR ‘one implant’ OR ‘midline implant’ OR ‘median implant’ OR ‘single implant overdenture’ OR
‘single-implant overdenture’
(C) #3 ‘denture, complete’ OR ‘denture’
(O) #4 ‘quality of life’ OR ‘patient satisfaction’ OR ‘patient outcome assessment’ OR ‘research, patient-centered
outcomes’ OR ‘outcome assessment, patient’ OR ‘patient-reported outcome*’ OR ‘patient-centered
outcome*’OR ‘patient-related outcome*’ OR ‘patient-oriented outcome*’ OR ‘treatment outcome’ OR
‘effectiveness, clinical’ OR ‘patient-relevant outcome*’ OR ‘clinical efficacy’ OR ‘treatment effectiveness’ OR
‘treatment efficacy’ OR ‘rehabilitation outcome’
#1 AND #2 AND #3 AND #4
Cochrane
Central
(P) #1 edentulous mouth OR toothless mouth OR edentulous OR edentulism OR edentulous patients OR
toothless patients OR edentulous jaw
(I) #2 overdenture OR implant overdenture OR mandibular overdenture OR single implant OR one implant OR
midline implant OR median implant OR single implant overdenture
(C) #3 complete denture OR denture
(O) #4 quality of life OR patient satisfaction OR patient outcome assessment R patient-centered outcomes OR
patient-reported outcome OR patient-centered outcome OR patient-related outcome OR patient-oriented
outcome OR treatment outcome OR clinical effectiveness OR patient-relevant outcome OR clinical efficacy OR
treatment effectiveness OR treatment efficacy OR rehabilitation outcome
#1 AND #2 AND #3 AND #4
©2017 John Wiley & Sons Ltd
SINGLE-IMPLANT MANDIBULAR OVERDENTURES 3
they are reports that come directly from patients
about how they feel or function in relation to a
health condition and its treatment without interpre-
tation by healthcare professionals or anyone else
(19). In vitro studies and reviews were excluded. In
the case of multiple studies from a single cohort and
with the same study design, we used the following
criteria to decide which data to use in this review: if
the publications from the same cohort reported dif-
ferent patient-reported outcomes (i.e. patient satisfac-
tion in one and oral health-related quality of life in
another), both of them were included; if the same
outcome was reported in the multiple papers, only
the publication with the longest follow-up was
included.
After completing the PubMed and Scopus searches,
two reviewers (DRD and TEN) independently read
all titles and abstracts (when available) to identify
eligible studies. The full-text versions were obtained
for studies appearing to meet the inclusion criteria or
when the titles and abstracts presented insufficient
data to make a clear decision. The reviewers (DRD
and TEN) then assessed the full-text version indepen-
dently to judge whether the studies met the inclu-
sion criteria. A specific protocol for full-text reading
was formulated and used to record the rationale for
making a decision. Disagreements between the
reviewers were decided by discussion and a third
review author (CRL) was consulted if necessary.
Additionally, a manual search was performed in the
reference lists of all selected articles, aiming to iden-
tify studies with titles that seemed relevant but that
may have been missed through the PubMed,
Cochrane CENTRAL and Scopus searches.
Data extraction and quality assessment
A data extraction form was designed and used by the
two review authors (DRD and TEN) independently.
The following information was extracted from the
studies: first author, year of publication, study design,
country, implant and retention system, surgical and
loading protocols, number of patients and details of
the outcomes reported, including method of assess-
ment and time intervals. When any clarification or
information was needed, the corresponding authors
were contacted by e-mail.
Moreover, an adapted version of the Cochrane
checklist for describing and assessing patient-reported
outcomes in clinical trials (20) was used as a guide to
assess the quality of the included studies.
Results
Eleven studies fulfilled the eligibility criteria and were
included in the final list. Figure 1 presents a flow dia-
gram, based on PRISMA guidelines, of the detailed data
search used for this review, the identification and selec-
tion processes, the number of excluded studies and the
reasons for exclusion. Three studies were excluded
because they reported previous results of the same
patient cohorts (21–23) from those already included.
Table 2 details the main characteristics of the
selected studies. Studies differed widely with regard to
the follow-up period (mean follow-up time of
218 months, range: 1–60 months), implant and
retention systems used and the surgical and implant
loading protocols. Three different methodological
designs were identified in the included studies: five
parallel-group trials (16, 17, 24–26), two crossover
clinical trials (27, 28) and four prospective studies
(single-group trials) (8, 29–31). In the selected stud-
ies, the sample size ranged from 10 to 158 partici-
pants, and patient-reported outcomes were assessed in
328 SIMO patients.
Tables 3 and 4 describe the assessment of the meth-
ods that were used for the evaluation of patient satis-
faction and quality of life outcomes in the studies
included in this review. The most common instru-
ments used to measure patient-reported outcomes
were rating scales to measure satisfaction with care
(8, 16, 24–27, 29–31) and oral health-related quality
of life instruments (17, 28, 30). Irrespective of the
outcomes measured and related instruments, all stud-
ies showed satisfactory ability to detect changes
between treatments and patient condition. However,
the great variation in measurements and methods did
not allow for the calculation of a common summary
statistic for each study to describe the observed inter-
vention effect.
In summary, all studies reported a positive effect on
satisfaction and quality of life measures after rehabili-
tation with SIMO compared with the conventional
denture treatment, which was the reference interven-
tion. This improvement was found irrespective of
variations in implant and prosthodontic procedures
and materials. However, due to the absence of a stan-
dard outcome measure, a simple descriptive analysis
©2017 John Wiley & Sons Ltd
T. E. NOGUEIRA et al.
4
was performed by calculating the difference between
initial and final measurements in order to identify the
magnitude of change after SIMO treatment (Table 5).
Discussion
This systematic review summarised evidence from clin-
ical studies regarding the effect of SIMO treatment on
patient-reported outcomes after the insertion of a single
implant to retain a mandibular overdenture in conven-
tional denture wearers. Overall results suggest a signifi-
cant improvement in patient satisfaction and a
reduction in oral health-related quality of life impacts.
Nevertheless, the heterogeneity among primary studies
and the absence of randomised clinical trials comparing
SIMO with CD may render meaningless any pooled
estimate in a meta-analysis. Hence, this review is lim-
ited to a descriptive summary of the selected studies
that described patient-reported outcomes, as well as an
analysis of the main weaknesses and strengths of the
methods used for outcome assessment in those studies.
Although the earliest reports identified in this topic
were dated nearly two decades ago (8, 32), there are
relatively few studies on SIMO, considering the high
and growing number of publications in the implantol-
ogy field. Furthermore, our literature search did not
identify any results of randomised clinical trials that
compared edentulous subjects receiving SIMO as the
intervention and CD as the control treatment. How-
ever, a study protocol of an ongoing randomised con-
trolled trial comparing SIMO and CD conducted by
our research group was retrieved by our search and
the results will possibly contribute to an answer for
the focus question of this systematic review (33).
Even though there were limitations of the studies
included in this review, a clear superiority of SIMO
compared to CD was observed when considering
patient-reported outcomes. Conversely, previous stud-
ies that used patient-reported outcome measures also
reported the non-inferiority characteristics of SIMO
compared to the two-implant overdenture, suggesting
that SIMO could also be a viable alternative for
patients with higher surgical risks or impaired health
conditions, such as very old patients, or in situations
when simplification of the intervention is desirable
due to financial restrictions (16, 17).
Fig. 1. Flow diagram of articles
screened through the review process.
©2017 John Wiley & Sons Ltd
SINGLE-IMPLANT MANDIBULAR OVERDENTURES 5
Table 2. Main characteristics of the studies included in the systematic review
Authors/Year Study design Country
Implant
system(s)
Retention
system(s)
Surgical
protocol
Loading
protocol
Number
of SIMO
wearers
Follow-up
period
Patient-reported
outcome(s) Instrument(s)
Cordioli
et al.,
1997 (8)
Single-group design
(CD?SIMO)
Italy 3i implant O’ring/Ball
attachment
2-stage CL 21 Up to 5
years
Satisfaction (stability,
retention, masticatory
function, migrating
pain, use of adhesive
pastes)
VAS
Liddelow &
Henry,
2010 (29)
Single-group design
(CD?SIMO)
Australia Branemark
machined/
TiUnite
implants
O’ring/Ball
attachment
1-stage IL 32 Up to 3
years
Satisfaction (pain,
comfort, appearance,
function, stability,
speech, hygiene,
overall satisfaction)
VAS
Harder
et al., 2011
(30)
Single-group design
(CD?SIMO)
Germany Camlog
implant
Gold matrix/
Ball
attachment
1/2-stages EL 11 1 month Chewing ability and
OHRQoL
VAS and
OHIP-49
Cheng et al.,
2012 (27)
Crossover design
(locator vs.
magnetic
attachment)
China Straumann
standard
implant
Magnetic and
Locator
attachments
1-stage CL 13 3 months Satisfaction (comfort
level, speech,
chewing ability,
stability and
retention, overall
satisfaction)
VAS
Kronstrom
et al., 2014
(17)
Parallel-group
design (SIMO vs.
2-implant
overdenture)
Canada Branemark
TiUnite
implant
O’ring/Ball
attachment
1-stage IL 11 1–3 years OHRQoL OHIP-Edent
Grover et al.,
2014 (28)
Crossover design
(shortened vs.
conventional
dental arch)
India Zimmer
tapered
implant
Magnetic
attachment
1-stage EL 10 Up to 3
months
OHRQoL OHIP-49
(continued)
©2017 John Wiley & Sons Ltd
T. E. NOGUEIRA et al.
6
Table 2. (continued)
Authors/Year Study design Country
Implant
system(s)
Retention
system(s)
Surgical
protocol
Loading
protocol
Number
of SIMO
wearers
Follow-up
period
Patient-reported
outcome(s) Instrument(s)
Bryant et al.,
2015 (16)
Parallel-group
design (SIMO vs.
2-implant
overdenture)
Canada Straumann
implant
O’ring/Ball
attachment
2-stage EL 42 Up to 5 years Overall satisfaction VAS
Tavakolizadeh
et al., 2015
(25)
Parallel-group
design (SIMO vs.
2-implant
overdenture)
Germany/
Iran
Implantium
implant
O’ring/Ball
attachment
1/2-stages IL 10 Up to 1 year Satisfaction (overall
satisfaction, social life,
chew hard foods,
comfort, fit)
VAS
Ismail et al.,
2015 (24)
Parallel-group
design (ball vs.
magnetic
attachment)
Egypt/
Saudi
Arabia
Dyna Dental
implant
Ball and
Magnetic
attachment
2-stage CL 10 Up to 2 years Satisfaction and
function complaints
5-point scale
Bhat et al.,
2016 (31)
Single-group design
(CD?SIMO?2-
IOD?3-IOD)
India Snap
Equinox
implant
Dalla Bona
attachment
2-stage CL 10 1 month Satisfaction
(appearance, speech,
chewing and self-
confidence for the
dentures; retention/
stability, comfort,
pain and handling for
the lower denture)
Grade scale
up to 10
Passia et al.,
2017 (26)
Parallel-group
design (IL-SIMO
vs. CL-SIMO)
Germany Camlog
implant
Ball
attachment
1/2-stages IL or CL 158 4 months Satisfaction (pain,
comfort, appearance,
function, cleaning,
stability/fit and
overall evaluation)
VAS
CD, conventional denture; IOD, implant overdenture; CL, conventional loading; IL, immediate loading; EL, early loading; OHRQoL, oral health-related quality of life; VAS,
visual analogue scale; OHIP, Oral Health Impact Profile; OHIP-Edent, Oral Health Impact Profile for Edentulous.
©2017 John Wiley & Sons Ltd
SINGLE-IMPLANT MANDIBULAR OVERDENTURES 7
Table 3. Quality assessment of the methods used for the evaluation of quality of life in the included studies
Authors/Year
What were the
patient-reported
outcome(s)
measured?
Who completed
the instruments?
How was the
measurement scale?
Was the
instrument
used as originally
proposed?
Was the
instrument
validated
previously
(reference
provided?)
Was evidence of
prior validation
for use in this
population
presented?
Does the instrument
have ability to
measure change?
Harder et al.,
2011 (30)
Oral health-
related quality
of life
Not reported Oral Health Impact Profile
(OHIP-49)
questionnaire [a 5-point
scale (0 =never,
1=hardly ever,
2=occasionally,
3=fairly
often and 4 =very
often)]
Not reported Yes Yes Yes
Kronstrom
et al., 2014 (17)
Oral health-
related quality
of life
Self-administered Oral Health Impact Profile
for Edentulous
(OHIP-EDENT)
questionnaire [five
response
alternatives ranging from
a negative opinion
(‘very often’) to a
positive (‘never’)]
Yes Yes Yes Yes
Grover et al.,
2014 (28)
Oral health-
related quality
of life
Self-administered OHIP-49 questionnaire
(no scale reported)
Unclear No reference
provided
No Yes
©2017 John Wiley & Sons Ltd
T. E. NOGUEIRA et al.
8
Table 4. Quality assessment of the methods used for the evaluation of patient satisfaction in the included studies
Authors/Year
What were the patient-
reported outcome(s)
measured?
Who completed
the instruments?
How was the
measurement scale?
Was the
instrument
used as
originally
proposed?
Was the instrument
validated previously
(reference provided?)
Was evidence of
prior validation
for use in this
opulation
presented?
Does the
instrument have
ability to measure
change?
Cordioli
et al., 1997 (8)
Patient satisfaction based
on oral comfort and
function (prosthesis
stability and retention,
masticatory function,
migrating pain and use
of adhesive pastes)
Self-administered VAS –unclear scaling Yes No (a reference was
provided but do not
describe a
validation process)
No Yes
Liddelow &
Henry,
2010 (29)
Patient satisfaction based
on oral comfort and
function (general
satisfaction, social life,
mastication of hard food,
comfort and fit)
Self-administered VAS –0–100 score Yes Yes Yes Yes
Harder et al.,
2011 (30)
Patient’s perception of
chewing ability of eight
different hard and soft
foods
Self-administered VAS –no markings
between the endpoints
(interpreted as 0 and
100%)
Not reported No No Yes
Cheng et al.,
2012 (27)
Patient satisfaction
(comfort, speech,
chewing ability,
retention and stability
and overall satisfaction)
Self-administered VAS –100-mm scale,
from left (0) as
completely unsatisfied
and right (100) as
completely satisfied
Not reported No No Yes
Bryant et al.,
2015 (16)
Patient satisfaction
(overall satisfaction with
the lower denture)
Self-administered VAS –10-cm
uninterrupted scale
representing a
continuum of feelings,
with ‘unsatisfied’ at one
end and ‘satisfied’ at the
other
Not reported No No Yes
(continued)
©2017 John Wiley & Sons Ltd
SINGLE-IMPLANT MANDIBULAR OVERDENTURES 9
Table 4. (continued)
Authors/Year
What were the patient-
reported outcome(s)
measured?
Who completed
the instruments?
How was the
measurement scale?
Was the
instrument
used as
originally
proposed?
Was the instrument
validated previously
(reference provided?)
Was evidence of
prior validation
for use in this
opulation
presented?
Does the
instrument have
ability to measure
change?
Tavakolizadeh
et al., 2015 (25)
Patient comfort and
function (general
satisfaction, social life,
mastication of hard and
soft foods and fit)
Self-administered VAS –100-mm line
anchored at the
beginning and end by
opposing statements
(‘not at all satisfied’ to
‘extremely satisfied’)
Yes Yes Yes Yes
Ismail et al.,
2015 (24)
Patient satisfaction and
complaints
Unclear Scale ranging from 1 to 5
–Level of satisfaction:
very good, good,
satisfactory, sufficient,
not satisfactory;
Complaints: no, mild,
moderate, severe, very
severe complaints
Yes No (a reference was
provided but do
not describe a
validation process)
No Yes
Bhat et al.,
2016 (31)
Patient satisfaction Unclear Questionnaire (eight
questions, without
figures or line designs,
maximum score of 10)
Not reported No No Yes
Passia et al.,
2017 (26)
Patient satisfaction (pain,
comfort, appearance,
function, cleaning,
stability/fit and overall
evaluation)
Self-administered VAS –no markings
between the endpoints
(interpreted as 0 and
100%)
Yes No (a reference was
provided but do
not describe a
validation process)
No Yes
VAS, visual analogue scale.
©2017 John Wiley & Sons Ltd
T. E. NOGUEIRA et al.
10
Four included studies were classified as prospective
studies, designed as single-group trials in which all
study participants received the same intervention and
then were followed over time to have their response
observed in a before–after comparison of measured
outcomes. Despite its simplicity, inferences from sin-
gle-arm trials are limited due to the inability to distin-
guish between the effect of the treatment and the
difficulty with interpreting the response without a
frame of reference for comparison (34). Conclusions
drawn from these studies may be considered prelimi-
nary evidence of the efficacy and safety of SIMO
treatment. Even though the selected studies reported
relatively small sample sizes, most of them were pow-
erful enough to detect differences, mainly for within-
group comparison of single-group studies. These dif-
ferences could be detected because of the marked
increase in patient satisfaction after SIMO treatment
when compared to CD. On the other hand, the small
sample sizes limit the ability to test the effect of speci-
fic patients’ conditions on clinical and radiographic
outcomes, and the detection of significant general and
local risk factors.
Besides the wide spectrum of outcome measures in
implant and prosthodontic interventions, this review
focused on outcomes directly reported by the patient.
Patient-reported outcomes include any evaluation
obtained directly from patients through interviews, self-
completed questionnaires, diaries or other data collec-
tion tools such as hand-held devices and web-based
forms (19). The measuring instrument must be stan-
dardised and show external validity to reduce bias and
provide comparable results among different studies.
Currently, there is an increasing focus in clinical studies
on placing patients at the centre of healthcare research
and on evaluating clinical care. The goal is to improve
the patient’s experience and ensure that research is both
robust and of maximum value for the use of health
interventions and products (35). Patient-reported out-
comes are also suggested to be of more importance in
the future compared to any other outcomes –for exam-
ple, clinical, physiological or caregiver-reported out-
comes –because patient feedback and change in patient
behaviour are essential to improve treatment adherence
and satisfaction with care (36).
In general, we observed a lack of information
regarding the use of data collection instruments
among studies, the absence of references related to the
respective validation process, how the instrument was
used (self-completed or interview) and how the result-
ing data were analysed. One study reported the Oral
Health Impact Profile (OHIP) as a questionnaire to
measure patient satisfaction (17); whilst it is known
that OHIP does not measure any positive aspects of
oral health and excludes perceptions of satisfaction
with oral health, changes in oral health, prognosis or
self-reported diagnoses and all impacts in the OHIP are
conceptualised as adverse outcomes (37).
This systematic review highlighted the need for
additional evidence derived from rigorously designed
and delivered randomised clinical trials, as well as
subsequent reports containing high-quality descrip-
tions of all aspects of the study methodology. Such
studies and reports would enable a systematic apprai-
sal and interpretation of results, which could provide
sound evidence about the effectiveness of SIMO com-
pared to other treatments and about the improvement
of patient-reported outcomes for poorly adapted CD
wearers.
Conclusions
The available evidence suggests a considerable
improvement in patient-reported outcomes following
Table 5. Estimates of the magnitude of change (before–after
difference) in patient-reported outcome between initial
(complete denture phase) and last measurements in the individ-
ual studies for patients treated with single-implant mandibular
overdentures
Patient satisfaction Baseline
Last
follow-up Difference*
Bhat et al. (31)
†
2439150
Bryant et al. (16)
†
381688307
Cheng et al. (27)
†
85097074
Ismail et al. (24)
†
1337480
Liddelow & Henry (29)
†
30 83 530
Tavakolizadeh et al. (25)
†
2771440
Cordioli et al. (8)
§§
—
Harder et al. (30)
त
—
Passia et al. (26)
§§
—
OHIP score Baseline Last
follow-up
Difference
(points)
Harder et al. (30) 490250240
Kronstrom et al. (17) 508832324
Grover et al. (28)
§§
—
*0–100 converted scale.
†
General satisfaction.
‡
Satisfaction with chewing ability.
§
No summary data available.
©2017 John Wiley & Sons Ltd
SINGLE-IMPLANT MANDIBULAR OVERDENTURES 11
the insertion of a single implant to retain a mandibular
denture. The results observed in the selected studies
also suggest that the instruments used to measure
patient-reported outcomes were able to detect the
changes between treatments; however, poor reporting
and lack of standardised instruments and scale mea-
sures make it difficult any attempt to combine data
from these studies in a meta-analysis. To add evidence
and support the indication of SIMO, further studies
specifically designed to compare SIMO and CD are
needed.
Acknowledgments
There was no source of funding for this systematic
review. There are no conflict of interests in connec-
tion with this article. No review protocol was
published before.
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Correspondence: Cl
audio Rodrigues Leles, Faculdade de Odontolo-
gia, Universidade Federal de Goi
as, Prac
ßa Universit
aria S/N. Setor
Universit
ario. CEP 74605-220, Goi^
ania, Goi
as, Brasil.
E-mail: claudio_leles@ufg.br
©2017 John Wiley & Sons Ltd
SINGLE-IMPLANT MANDIBULAR OVERDENTURES 13