Key words: Ball attachment - bar attachment - implant overdenture - systematic review - telescopic
attachment
INTRODUCTION
Usually, edentulous patients are complaining of difficulties during chewing and speaking
leading to a decline in their quality of life. Especially in the mandibular arch,
the space available to the prosthesis and its stability are reduced due to the presence
of the tongue. The placement of two or more dental implants in the anterior mandible
provides additional means of retention to stabilize mandibular overdentures and affords
a safe and long-term clinical success.[1 ]
[2 ]
[3 ]
Mandibular implant-retained overdentures (MIRO) present a reliable and simple solution
to enhance denture retention and stability. The retention and stability characteristics
are provided mainly by implants through attachments. Hence, various types of attachment
systems have been proposed for connecting implant-retained mandibular overdentures
to the underlying implants.[4 ]
Splinted attachments as bar attachments is a popular choice because of its load sharing
but requires sufficient interarch space;[4 ] it may cause mucosal hyperplasia underneath the bar if insufficient relief is present,
and contraindicated to be used with a V-shaped ridge to avoid encroaching on the tongue
space.[5 ]
Non-splinted attachments as telescopic and ball attachments.[6 ]
[7 ] Ball attachments are susceptible to wear and technique sensitive as they require
parallel implants placement.[8 ] Telescopic attachments have excellent retention due to frictional fit between primary
and secondary copings. The circumferential relation between telescopic attachment
and the abutment allows better distribution of forces, results in transferring the
occlusal load more axially leads to reducing the rotational torque on the abutment.[9 ]
[10 ] However, they require enough inter-arch space to be occupied. If there is no sufficient
inter-arch space, telescopic attachment is not recommended to be used.[11 ]
To assess a MIRO, the implant survival rate and the complication rate are the most
important factors.[12 ] To determine an implant prosthesis survival, it is better to mention “time to retreatment”[13 ] which is the time needed to perform any interference by the clinician to manage
any prosthetic complications during the maintenance period.[14 ]
Implant overdentures complications may be biologic and technical complications. Biologic
complications are any disturbances in implant function that affect the supporting
peri-implant tissues in terms of early or late implant failures, and adverse reactions
in the peri-implant hard and soft tissues. Technical complications are any mechanical
damage of the implant, implant components, and suprastructures.[15 ] Prosthetic complications are the need of the final prosthesis after the insertion
to be relined or repaired although it affects or not affects implant.[16 ]
In this review, the question is, Could the telescopic attachments in completely edentulous
patients needing dental implant rehabilitation better than other attachment systems
regarding implant survival, complications, and peri-implant tissue condition?
MATERIALS AND METHODS
Protocol registration
A prior protocol was made and registered at PROSPERO with registration NO: CRD42017054762.
The review structure
The “Preferred Reporting Items for Systematic Reviews and Meta-Analyses” was followed.[17 ]
Eligibility criteria
According to the PICOS format provided by the Center for Evidence-Based Medicine,
the focused question was formulated and served as a basis for the systematic literature
search.[18 ]
Population/problem: Completely edentulous patients with a MIRO
Interventions: Telescopic crown attachments retaining MIRO
Comparators: Other attachment systems (Ball, Bar, and Locator) retaining MIRO
Outcome: Any outcome not predetermined or included in the search strategy
Study design: Randomized-controlled trials (RCTs).
Exclusion criteria
Case report, case series studies, retrospective studies, cohort studies, animal studies,
in vitro studies, or non-RCTs were not included. And any observation period of leass than
3 years.
Search strategy
The search was performed by two reviewers independently. Combinations of controlled
terms (MeSH) and keywords were used whenever possible [Table 1 ]. A comprehensive electronic search was done in both PubMed and the Cochrane Central
Register of controlled trials databases with language restriction to English only
and without time restrictions. Furthermore, a manual search was done in the related
journals, including; the Journal of Prosthodontics, the International Journal of Prosthodontics,
Journal of Advanced Prosthodontics, the Journal of Prosthodontic Research, Journal
of oral rehabilitation, Journal of Dental Research, and Journal of Oral and Maxillofacial
surgery. Moreover, online databases providing information about clinical trials in
progress were checked such as www.clinicaltrials. gov, www.centerwatch.com/clinicaltrials,
and www. clinicalconnection.com. The last performed search was on December 5, 2016.
Table 1:
The search terms used for the search in electronic databases
(edentulous jaw) OR (edentulous mouth) OR (edentulous ridge) OR (edentulous arch)
OR (edentulous mandible) OR (completely edentulous patient) OR (totally edentulous
patient) OR (mandibular prosthesis) OR (mandibular prostheses) OR (mandibular overdenture)
OR (mandibular implant retained overdenture) OR (mandibular implant assisted overdenture)
OR (mandibular implant supported overdenture) OR (implant overlay) OR (implant prosthesis)
AND (telescopic attachment) (OR telescopic crown) OR (telescopic overdenture) OR (telescopic
prosthesis) OR (telescopic prostheses) OR (double crown) OR (double crowns) OR (double-crown)
OR (conus attachment) OR (conical crown) OR (conical attachment) AND (bar attachment)
OR (attachment bar) OR (bar overdenture) OR (bar overdentures) OR (bar retained implant
overdenture) OR (ball attachment) OR (ball overdenture) OR (ball retained implant
overdenture) OR (ball and socket) OR (locator attachment) OR (locator overdentures)
Study selection
Study selection and data extraction were performed independently by two reviewers
and any disagreement was solved by discussion. If not, a third reviewer was consulted.
Data extraction
Two reviewers performed the data extraction independently and were reciprocally blinded
to the extraction each other. The following information was extracted: author, country,
follow-up year, age of the patient, gender, implant system, number of participants,
the total number of implant placed, interventions, attachment system, participants
per group, participant analyzed, implant per participant, implant survival rate, prosthetic
maintenance, and peri-implant condition.
The quality assessment (risk of bias)
The risk of bias assessment of the included trials was done by two reviewers independently
using the Cochrane collaboration’s tool,[19 ] six specific domains titled sequence generation, allocation concealment, blinding,
incomplete outcome data, selective outcome reporting, and other bias. An RCT was assigned
(Low risk of bias) if all domains were at low risk of bias, (Unclear risk of bias)
if there was unclear risk of bias of at least one domain, and (High risk of bias)
if at least one domain was scored as being at a high risk of bias. In the case of
disagreement, discussion between the two reviewers reveals final decisions.
Statistical analyses
Measures of treatment effect
For dichotomous outcomes, the effect of an intervention was expressed as risk differences
(RDs) together with 95% confidence intervals (CIs). However, for continuous outcomes,
mean differences (MDs) and standard deviations were used to summarize the data for
each group with 95% CIs.
Unit of analysis issues
The statistical unit was the patient.
Missing data
If there is any relevant missing information in the included articles, the corresponding
authors of these articles were contacted by E-mail. In the situations of no responses,
reminder E-mails were sent.
Data synthesis
All statistical tests were performed using the Review Manager (RevMan) software release
version 5.3.[20 ] RevMan is The Cochrane Collaboration’s software for preparing and maintaining Cochrane
reviews. Meta-analyses were done for studies reported the same outcomes. Risk differences
(RDs) for prosthodontic maintenance and MDs for peri-implant tissue were calculated
and compared between the two studied interventions (telescopic crown versus ball attachment
retaining mandibular implant overdenture). CIs were set at 95%. Weighted means across
the studies were calculated using a fixed-effects model. A random-effects model was
used to assess the significance of treatment effects.
Heterogeneity assessment
Cochran’s test for heterogeneity was used to assess any variations significance in
the estimates of the treatment effects of the different trials, heterogeneity would
be considered significant if P < 0.1. Heterogeneity between the studies was assessed using the I 2-statistic, which describes the variation percentage due to heterogeneity rather
than chance.[21 ] I 2 over 50% was considered as moderate to high heterogeneity.
Reporting biases assessment
If there had been sufficient numbers of trials (>10) in any meta-analyses, publication
bias would have been assessed according to funnel plot asymmetry. If asymmetry was
identified, we would have examined possible causes.
RESULTS
The electronic search yielded a total of 54 articles (PubMed = 36 and The Cochrane
Library = 13). 5 records identified from other sources. 25 potentially relevant articles
were selected after screening with title and abstract and removing duplicates. After
the initial screening, nine potentially eligible RCTs,[12 ]
[22 ]
[23 ]
[24 ]
[25 ]
[26 ]
[27 ]
[28 ]
[29 ] four publications[22 ]
[27 ]
[28 ]
[29 ] were included and five publications[12 ]
[23 ]
[24 ]
[25 ]
[26 ] were excluded. Reasons for exclusion were as follows: Three were nonrandomized clinical
trials.[12 ]
[23 ]
[25 ] One was of unclear data.[26 ] One had a period of follow-up <1 year (3 months).[24 ]
Only two trials were subsequently analyzed in this systematic review [Figure 1 ]. Details of all included studies are summarized in [Tables 2 ] and [3 ].
Figure 1: Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow chart
Table 2:
Data extraction
Study ID
Country
Follow-up year
Age
Gender
Implant system and type
Number of participants
Total number of implant placed
Interventions
Attachment system
Participants per group
Participant analyzed
Implant per participant
Implant survival rate (%)
*NR: Not reported
Cepa et al . 2016
Germany
3
62.9±8.98
NR*
ANKYLOS, DENTSPLY implants, Manheim, Germany
25
50
Telescopic
ANKYLOS SynCone, DENTSPLY
13
5
2
38.5
65.2±7.02
NR
Ball
ANKYLOS ball heads, DENTSPLY
12
11
2
91.7
Krennmair et al ., 2011 Krennmair et al ., 2006
Austria
3 and 5
63.2±8.4
(8 female, 5 male)
Camlog, Altatec
25
50
Telescopic
Camlog, Altatec + TC-SNAP (Si-Tec)
12
10
2
100
58.1±9.2
(8 female, 5 male)
Ball
Camlog, Altatec
13
9
2
100
Krennmair et al ., 2012
Austria
3
61.1±7.6
(16 female, 9 male)
Camlog, root-line, screw line, Altec, Wurmberg, Germany
51
204
Telescopic
Gold alloy
25
23
4
100
58.6±9.1
(12 female, 14 male)
Bar
The milled bar (titanium laser welding/gold alloy casting)
26
22
4
100
Table 3:
Data extraction
Study ID
Interventions
Prosthetic maintenance
Peri-implant condition
Attachment system maintenance
Overdenture maintenance
Retention loss
Fractured
Matrix activated
Matrix replaced
Replacement of patrix
Fracture/remade
Relined/rebased
Bone loss
Probing depth
Bleeding index
Gingival index
Plaque index
Presence of calculus
Mesial
Distal
NR: Not reported
Cepa et al ., 2016
Telescopic
5
1
0
4
1
0
3
1.7±0.4
0.7±0.3
2.9±0.5
0.43±0.53
0.68±0.66
0.83±0.80
NR
Ball
9
0
6
7
6
0
7
1.6±0.3
1±0.2
1.8±0.4
0.35±0.34
0.43±0.18
0.99±0.65
NR
Krennmair et al ., 2011 Krennmair et al ., 2006
Telescopic
0
0
4
0
NR
2
4
1.5±0.8
3.4±2.2
0.6±0.5
0.5±04
0.6±0.9
NR
Ball
1
0
4
0
NR
2
3
1.8±0.6
3.5±2.1
0.8±0.5
0.3±0.3
0.8±0.6
NR
Krennmair et al ., 2012
Telescopic
NR
0
2
NR
0
9
1.85±0.8
3.4±2.1
NR
NR
NR
NR
Bar
NR
0
4
NR
0
8
1.5±0.6
3.2±1.9
NR
NR
NR
NR
Characteristics of included studies
The included publications were published within 10 years (2006–2016). All of them
were RCTs that examined edentulous mandibular arches. Their observation periods were
3 years, but one of them[27 ] has a follow-up period of 5 years.
One of the include trials is a 3-year follow-up study[29 ] which is a part of extended another trial of 5-year follow-up;[27 ] therefore, both studies are included in one study.
One trial[22 ] conducted in Germany, the other three trial[27 ]
[28 ]
[29 ] in Austria. All trials conducted in university dental clinics and their study protocols
were approved by the Local Ethics Committee of their universities.
Three of the included trials compared the effect of telescopic versus ball attachments[22 ]
[27 ]
[29 ] and one compared the effect of telescopic versus bar attachments[28 ] retaining mandibular implant overdentures.
The same participants’ number was (25 patients) in three trials that compare between
the telescopic and ball attachments retaining mandibular implant overdentures.[22 ]
[27 ]
[29 ] One trial had 51 participants which compared the effect of telescopic versus bar
attachments[28 ] retaining mandibular implant overdenture.
The inclusion or exclusion criteria of patients were reported clearly in one trial.[22 ] However, regarding the other 3 trials, they are not mentioned[27 ]
[28 ]
[29 ] in all included trials, each patient was given a detailed prescription of the planned
procedures and signed a written informed consent before participation.
One hundred and twenty-six patients received 354 implants. All implants were titanium
implants, had various types and surface modifications and with different lengths and
diameters. Implant numbers per patient varied between 2 implants in the mandible[22 ]
[27 ]
[29 ] and 4 implants in the mandible.[28 ] The mandibular interforaminal area was the implant positioning preferred area. A
two-stage surgical procedure and conventional loading protocol were followed.
The outcomes were reported as follows:
Implant survival rate (reported in all trials)
Prosthodontic maintenance, which subdivided into two categories: (1) attachment system
maintenance in terms of retention loss, fracture, matrix activated, matrix replaced,
and replacement of patrix. (2) The overdenture maintenance in terms of overdenture
fractured/remade and overdenture relining/ rebased
Peri-implant tissue condition evaluation in terms of plaque indices, bleeding indices,
gingival indices, and probing depth. A radiographic evaluation was done to measure
the marginal bone level around implants.
Quality assessment
The risk of bias assessment of the included trials is summarized in [Table 4 ]. Each trial was assessed to be at low, unclear, or high risk of bias. Two of three
included RCTs were assessed to be at high risk and one at unclear risk of bias.
Table 4:
The risk of bias assessment
Study ID
Random sequence
Allocation concealment
Blinding
Incomplete outcome data
Selective reporting
Others
Cepa et al .[22 ]
Low risk
Low risk
Unclear
Low risk
Low risk
Low risk
Krennmair et al .[27 ]
[29 ]
Unclear
High risk
Unclear
Low risk
Low risk
Low risk
Krennmair et al .[28 ]
Unclear
High risk
Unclear
Low risk
Low risk
Low risk
Effects of interventions
After 3-year follow-up, Cepa et al .[22 ] evaluated 25 patients with completely edentulous mandibular arches for implant survival,
peri-implant tissue parameters, and patient satisfaction regarding two different attachment
systems (ball and telescopic) retaining implant mandibular overdentures. Randomly,
twelve patients have received ball attachments, and other thirteen patients received
the prefabricated telescopic attachment. All follow-ups were done and documented annually
up to 3 years.
The results showed 100% implant survival rate. No significant differences in the peri-implant
tissue evaluation. About 64% of patients that received ball attachments were satisfied,
but 100% patients that received telescopic attachments were satisfied. The latter
only respecting five of initially 13 patients. In addition, Cepa et al .[22 ] concluded that the ball attachments group required intensive prosthetic maintenance.
Krennmair et al .[27 ]
[29 ] observed implant success, peri-implant conditions, prosthodontic maintenance, and
patient satisfaction annually during a 5-year follow-up period by comparing ball and
telescopic attachments retaining mandibular implant overdentures. Krennmair et al . published two articles, one during a 3-year period[29 ] and the other after a 5-year period.[27 ] Twenty-five patients were randomly distributed into; 13 patients received ball attachments
and 12 patients received telescopic crowns.
The results revealed that peri-implant tissue conditions, implant survival rate, and
subjective patient satisfaction scores did not show the difference between the ball
and telescopic attachments. After 5-year follow-up, the prosthodontic maintenance
was more significant in the ball group (87 interventions, 61.1%) than in the telescopic
attachments group (53 interventions, 37.9%; P < 0.01). In the second and third years, differences in prosthodontic maintenance
efforts were most significant (P < 0.05) but both were similar at the end of the study for both attachment systems.
Krennmair et al .[27 ] concluded that 100% implant survival rate, good peri-implant tissue conditions,
and general patient satisfaction were scored. Although the higher prosthetic maintenance
incidence of the ball attachments group than of the telescopic attachments, similar
frequencies of maintenance efforts may be anticipated for both retention systems over
a 5-year period.
During a 3-year follow-up period, Krennmair et al .[28 ] evaluated 45 patients (dropout rate: 45/51 = 11.8%) who received four mandibular
interforaminal implants in the edentulous mandible and complete maxillary dentures.
Randomly, 23 patients were received milled bars and 22 patients received telescopic
attachments.
The results showed high implant survival rate (100%). Peri-implant marginal bone resorption,
pocket depth as well as bleeding index and gingival index did not differ for both
retention systems. However, annually higher values for plaque index (NS) and calculus
index (P < 0.035) were noticed for the bar than for the telescopic attachments.
Prevalence of prosthodontic maintenance did not differ between both retention modalities.
However, prosthodontic adaption for handling mechanism showed benefits for the bar
retention.
Krennmair et al .[28 ] concluded drawbacks such as higher plaque/calculus for bar retention and less favorable
handling properties (output) for telescopic crown attachment leave the selection decision
on the clinician.
Meta-analysis
A meta-analysis was performed for the studies having same comparison groups and same
outcomes.
Prosthetic maintenance
The meta-analyses of two trials[22 ]
[29 ] regarding the need for prosthetic maintenance comparing telescopic and ball-retained
mandibular overdenture showed no differences between two interventions in regard to
matrix activation, matrix replacement, patrix replacement, overdenture relining, and
overdenture remake [Figure 2 ].
Figure 2: Forest plot telescopic versus ball implants-retained mandibular overdenture: prosthodontic
maintenance
Peri-implant conditions
The meta-analyses of two trials[22 ]
[29 ] regarding peri-implant conditions comparing telescopic and ball-retained mandibular
overdenture showed statistically significant more probing depth around implants records
in ball-retained overdenture when compared to telescopic group (I 2 = 47%, P = 0.00001; MD: 1.1, 95% CI: 0.52, 1.48). However, there are no statistically significant
differences between two interventions in regard to marginal bone loss, bleeding index,
gingival index, and plaque index [Figure 3 ].
Figure 3: Forest plot telescopic versus ball implants-retained mandibular overdenture: peri-implant
condition
DISCUSSION
The MIRO gave the best results compared to the conventional removable prostheses resulting
in improved quality of life, the masticatory efficiency, and therefore, the nutritional
condition and patient’s health.[30 ]
The MIRO represents a first choice option, especially when there is a need to anchor
the mandibular conventional denture. It is important to remember that dental implants,
although they afford the overdenture with enhanced retention and support, differ significantly
from the natural teeth. The most important difference from the biomechanical point
of view is the absence of the periodontal ligament (PDL), which performs the amortization
functions of occlusal loads, the proprioceptive sensitivity, and promotes bone regeneration
activities.[31 ]
Under loading forces over the natural teeth, the PDL involved first followed by the
alveolar bone. However, dental implant, due to the absence of the PDL, has a linear
model of the deflection force that depends on the elastic deformation of the alveolar
bone.[32 ]
This review delivers meta-analyses of the RCTs that is considered as the highest level
of confirmatory scientific evidence today.[33 ] In terms of internal validity, RCTs represent the most scientifically rigorous study
designs, as they are best able to control bias and serve as a gold standard of study
designs for evaluating treatment efficacy.[34 ]
The meta-analysis of the two included RCTs[22 ]
[29 ] reveals that when comparing telescopic and ball-retained mandibular overdenture,
there are no differences between two interventions regarding the need for prosthetic
maintenance. This is in agreement with MacEntee et al .[35 ] and Watson et al .[36 ] who record no differences regarding postinsertion maintenance between interventions
of the attachment systems that being compared.
Karabuda et al .[37 ] found similar results. They compared overdentures with bar and ball abutment on
two to four implants in 26 patients. The treatment success with both techniques was
also compared with our meta-analysis as they reported a total of 20 prosthetic complications
were recorded in both groups. No differences in prosthetic complications were observed
for two attachment systems.
Regarding peri-implant tissue conditions, when comparing the telescopic and ball retained
mandibular overdenture the results showed statistically significant more probing depth
around implants. This may be explained by bone remodeling and consolidation of biological
width after implant placement.[38 ]
[39 ]
However, the meta-analysis showed no statistically significant differences between
two interventions in regard to marginal bone loss, bleeding index, gingival index,
and plaque index. Naert et al .[40 ] studied the influence of splinted and unsplinted oral implants retaining mandibular
overdentures. Over 10 years, no implants failed. Mean plaque index, bleeding index,
change in attachment level, periotest values, and marginal bone level at the end of
the follow-up period were not significantly different among the groups. Periotest
values and marginal bone level at the end of the follow-up period were not significantly
different among the groups.
CONCLUSION
The meta-analysis revealed no significant difference regarding peri-implant tissue
condition and prosthodontic maintenance when comparing telescopic attachments with
ball attachments. However, this should be interpreted with caution because limited
number included studies. More well-designed RCTs are highly recommended to evaluate
the effectiveness of telescopic versus other attachment systems retaining mandibular
implant overdentures.
Financial support and sponsorship
Nil.
