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ORIGINAL ARTICLE
A comparative study on 7-year results of ‘‘All-on-Four
TM
’’
immediate-function concept for completely edentulous mandibles:
metal-ceramic vs. bar-retained superstructures
Mustafa Ayna
1
•Aydin Gu
¨lses
2
•Yahya Acil
3
Received: 28 September 2016 / Accepted: 21 February 2017
The Society of The Nippon Dental University 2017
Abstract The study aims to document the clinical out-
comes over a 7-year period of two techniques used for the
rehabilitation of edentulous mandibles according to the
‘‘All-on-Four
TM
’’ concept: (1) fixed complete-arch pros-
theses fabricated with metal-ceramic implant-supported
fixed prosthesis with a titanium framework and all-ce-
ramic crowns and (2) bar-retained implant-supported
removable prosthesis with acrylic resin prosthetic teeth.
The study was performed on 32 patients who received
immediately loaded ‘‘All-on-Four
TM
’’ fixed mandibular
prostheses. (Fixed prostheses with ceramic superstruc-
tures, n:16; bar-retained removable acrylic prostheses,
n:16). The patients were evaluated for up to 7 years after
prosthesis completion. The endpoints included the evalu-
ation of prosthodontic complications, bone resorption,
plaque accumulation, bleeding on probing, periodontal
probing depth and an oral health impact profile (OHIP).
Bone loss remained under 1.2 mm in all of the implants,
and no difference was observed between two groups.
Plaque accumulation increased gradually in both groups,
and the bar-retained acrylic-bearing implants showed
significantly higher values during the first 5 years.
Immediate improvement was assessed by the OHIP score
in both groups. The observed bone loss and the subjective
outcomes showed equivalent levels of clinical success for
bar-retained and ceramic superstructures over a 7-year
period. The higher level of plaque accumulation observed
around implants with bar-retained superstructures requires
that patients with acrylic superstructures be highly moti-
vated to maintain their personal oral hygiene. Further
studies are needed to clarify the occurrence of
prosthodontic complications and assess their economic
aspects.
Keywords Acrylic dentures Bleeding on probing Bone
loss Plaque accumulation Probing depth Immediate
loading All-on-Four
TM
Introduction
The ‘‘All-on-Four
TM
’’ concept, which exploits the load-
bearing capacity of the mandible allows basically for two
different types of superstructures [1–3]: 1. a metal-ceramic
implant-supported fixed prosthesis with a titanium frame-
work and all-ceramic crowns and 2. a metal-acrylic resin
implant-supported fixed prosthesis with a titanium frame-
work and acrylic resin prosthetic teeth. In addition, bar-
retained removable acrylic superstructures can be used as
an alternative to the metal-acrylic resin implant-supported
fixed prosthesis [4].
When selecting a superstructure type, the dental pro-
fessional primarily needs to consider the patients’ prefer-
ences and economic status. There is a considerable
difference in the cost of different types of superstructures
(laboratory costs in Germany are approximately 1700 USD
[acrylic]; 3400 USD [bar-retained]; 5500 USD [ceramic]);
thus, it would be useful to perform a comparative evalua-
tion of these methods [5]. Unfortunately, a limited number
of studies have been conducted on the clinical outcomes of
&Aydin Gu
¨lses
aydingulses@gmail.com
1
Center for Dental Implantology, 47051 Duisburg, Germany
2
Christian Albrechts University, Department of Oral and
Maxillofacial Surgery, 24105 Kiel, Germany
3
Christian Albrechts University, Department of Oral and
Maxillofacial Surgery, 24105 Kiel, Germany
123
Odontology
DOI 10.1007/s10266-017-0304-7
different types of superstructures and there is a need for
long-term comparative studies in this area.
In a recent study [5], patients who received ceramic were
compared with those who received acrylic superstructures
over a period of 5 years. However, clinical results for bar-
retained removable acrylic superstructures mounted on four
interforaminal implants according to the ‘‘All-on-Four
TM
’’
concept have not been investigated thus far.
The purpose of the present study was to document the
long-term clinical outcomes of the use of two techniques
for the rehabilitation of completely edentulous mandibles
according to the ‘‘All-on-Four
TM
’’ concept: 1. the use of
fixed complete-arch prostheses that are fabricated with
metal-ceramic implant-supported fixed prosthesis with a
titanium framework and all-ceramic crowns and 2. a bar-
retained implant-supported removable acrylic prosthesis
with acrylic resin prosthetic teeth.
Materials and methods
Between February 2006 and February 2007, patients with
edentulous mandibles were screened for participation in a
trial where they would receive implant-based fixed den-
tures. To participate, patients had to fulfill the following
criteria: Atrophy of the edentulous mandible (class C and D
according to Misch and Judy [6]) with the rehabilitation
option of ‘All-on-4
TM
’ concept. Opposing natural dentition
or implant-based prosthesis. An interforaminal bone width
C5 mm and bone height C8 mm. Completely healed, at
least 6 months postextraction socket(s). The exclusion
criteria were as follows: General systemic contraindica-
tions against implant surgery (psychiatric disorders, preg-
nancy, metabolic bone diseases, etc.). The presence of
systemic diseases which may jeopardize the success of
implant integration (uncontrolled diabetes, osteoporosis,
etc.). The use of drugs which may negatively affect the
osseointegration process (bisphosphonates, corticosteroids,
etc.). Active inflammation or neighboring pathologies in
the areas intended for implant placement. Radiation ther-
apy to the head and/or neck region in the preceding
12 months. Requirement of bone augmentation during
implant placement. Clinically significant parafunction.
Poor oral hygiene and/or compliance. Eligible patients,
which have to pay for their surgical and prosthetic treat-
ments, were informed orally and in writing about the goals
and the duration of the study (observation period of
7 years) and the pertinent risks and benefits of the proce-
dure and of the respective superstructures. Thirty-two
patients were assigned to different superstructure groups
(ceramics or bar-retained acrylic resin) of their own choice;
the primary decision criterion was the substantial differ-
ence in price between the techniques.
Surgical procedure
Standard dental records and radiographs were taken as if
the patient were to receive an immediate mandibular
denture after extractions. A finished complete mandibu-
lar denture was fabricated by the dental laboratory for
later modification as a provisional fixed restoration
according to the manufacturer’s guided-surgery protocol.
CBCT scans (iCat
, Imaging Sciences International,
LLC, http://www.i-cat.com) using the double-scan tech-
nique were taken with the patient wearing this appliance
and occlusal registration. The CBCT data were con-
verted into DICOM images and imported into the
NobelClinician software for guided-surgery treatment
planning. The completed plan was digitally sent to the
manufacturer for surgical guide fabrication. In addition,
preoperative pictures, capturing the patient’s smile, high
lip line, and resting line were recorded. The vertical
dimension was ensured.
All procedures were performed by the same dental
surgeon (M.A.) under local anesthesia [articaine chloro-
hydrate (72 mg/1.8 ml) with epinephrine (0.018 mg/
1.8 ml) 1:100,000]. All of the patients received four Nobel
Speedy
TM
implants according to the ‘‘All-on-Four
TM
’’
protocol in the edentulous mandibles [1–3] (Fig. 1). A
mucoperiosteal flap was raised at the ridge crest with
relieving incisions on the buccal aspect in the molar area.
The mental nerve was exposed to exactly identify the
neurovascular bundle. The implants and abutments were
placed in one position at a time, starting with the posterior
ones. A special guide (edentulous guide, Nobel Biocare
AB, Goteborg, Sweden) was used to assist implant and
abutment placement. This guide was placed into a 2 mm
osteotomy made at the midline of the jaw and the titanium
band is bent so that the occlusal centerline of the opposing
Fig. 1 Surgical phase—insertion of implants and placement of 30
multi-unit abutments
Odontology
123
jaw was followed. By doing this, it was possible to guide
the implants to be placed in the center of the opposing
prosthesis and at the same time find the optimal position
and inclination for best implant anchorage and prosthetic
support.
Two distal implants in the posterior region which are
tilted anterior to the mental foramen were inserted at an
angulation of 30
–45
. The use of the All-on-4
surgical
guide assists in ensuring that the distal screw access holes
were located at the occlusal face of the first molar, the
second premolar, or the first premolar.
The insertion of the implants followed standard proce-
dures, except that under preparation was used to achieve an
insertion torque of at least 35 Ncm before final seating of
the implant. After closing and suturing the flap with 3-0
nonresorbable suture, the abutments were accessed by
means of a punch if needed, and impression copings were
placed. The implant sizes were 4 913 mm mesial and
4915 mm distal, with the longer distal implants provid-
ing bicortical anchoring. All implants were immediately
loaded within 24 h.
Antibiotics (amoxicillin 875 mg ?clavulanic acid
125 mg) were given 1 h prior to surgery and two times a
day for 6 days thereafter. Antiinflammatory medication
(ibuprofen, 600 mg) was administered for 5 days.
Immediate prosthetic procedure
For both groups, a rounded titanium bar with two distal
extensions on both sides was welded on to the implant
abutments. A high-density acrylic resin prosthesis was then
manufactured at the dental laboratory and mounted within
24 h post-surgery (Fig. 2). All centric and lateral contacts
were evaluated with articulating paper 40 microns and
adjusted to obtain a correct occlusal contact. Cantilever
length was determined according to 1.5-2 x A-P-spread
rule [7], which allows a 10–12 mm posterior cantilever
extended to the first molar regions.
Final prosthetic procedure
Three months later, for the patients who were slated to
receive a bar-retained acrylic resin implant-supported
removable prosthesis, a chrome-molybdenum bar with a
quadrilateral shape and two distal extensions with ball
attachments was fabricated using CAD/CAM technology,
and an acrylic removable prosthesis with acrylic resin
prosthetic teeth was prepared (Fig. 3).
For the patients who were slated to receive ceramic
superstructures, 3 months later, a metal-ceramic implant-
supported fixed prosthesis with a titanium framework that
Fig. 2 a,bImmediately loaded
provisional acrylic prosthesis
with a rounded titanium bar
which was welded on the
abutments with two distal
extensions on both sides
Fig. 3 a,bThree months later,
a chrome-molybdenum bar with
a quadrilateral shape with two
distal extensions with ball
attachments and a rubber ring
retention was fabricated using
CAD/CAM technology
Odontology
123
was fabricated using CAD/CAM technology (Fig. 4) and
connected to the implants with abutment screws to 15N
(Fig. 5).
Outcome parameters
•Measurement of bone resorption Bone crest levels
around the implants were measured with a standard
right-angle parallel technique, based on single digital
X-rays. The radiographs were scanned at 600 dpi
(Trophy RVG UI USB Sensor, KODAK 5.0 software,
Carestream, Stuttgart, Germany), and image analysis
software was used to assess bone level (UTHSCSA
Image Tool version 3.00 for Windows, University of
Texas Health Science Center, San Antonio, Texas
USA). The linear distance between the implant neck
and the most coronal bone-to-implant contact at the
mesial and distal aspect was measured for each implant
[5,8,9] immediately after implant insertion and 1, 3, 5
and 7 years after, and the bone loss was calculated
using the bone level immediately after implantation as
a reference.
•PPD was measured in mm at six peri-implant sites at 1,
3, 5 and 7 years postoperatively. BOP was measured at
four sites every year. The deepest pocket was consid-
ered in the analysis, and any bleeding on probing was
recorded as affirmative.
•Plaque accumulation was evaluated using the plaque
Index according to Mombelli et al. [10]. The exami-
nation was performed every year during the follow-up
period.
•The impact of the reconstruction on the quality of life
was assessed using the German version of the OHIP
[11–16], which was applied before surgery, immedi-
ately after implantation and at 1, 5 and 7 years after
denture integration. OHIP considers 14 metrics in seven
domains using a five-point verbal rating scale ranging
from ‘‘never’’ (coded 0) to ‘‘very often’’ (coded 4).
Statistical analysis
The data were analyzed using the software package SPSS
20. The following non-parametric methods were used: the
Wilcoxon test for differences over time, Mann–Whitney
Utest for group differences and for discrete parameters.
The level of significance was set at p\0.05. The Spear-
man correlation coefficient was calculated to analyze the
relationship between scale variables.
Results
One patient in the ceramic superstructure group was lost to
follow-up during the observation period due to relocation
and was excluded from the study group.
A total of 32 patients between 66 and 83 years of age
(mean 71.00 ±4.07 years) were enrolled in the study.
The female/male ratio was 19:13. None of the patients
were smokers as a part of the study design. There were
no statistically significant differences in the demo-
graphics and the baseline data between the two groups.
(Table 1) Totally, 128 implants were placed and none of
the implants failed during the observation period. In
addition, no biological complications such as fistula
formation, pain, infection or soft-tissue inflammation
were found. The survival rate of the prosthesis was
100%.
An analysis of the difference in the insertion torque
between patients with bar-retained and ceramic super-
structures (Table 2) revealed significantly higher values in
region 45 for patients in the former group. Moreover, the
straight implants (regions 32 and 42) were inserted with
Fig. 4 Metal-ceramic implant-supported fixed prosthesis with a
titanium framework fabricated using CAD/CAM technology
Fig. 5 Metal-ceramic implant-supported fixed prosthesis was con-
nected to implants with abutment screws to 15N
Odontology
123
significantly less torque than the angulated implants in
regions 35 and 45 (p\0.0001, Table 2).
Outcome parameters
In both groups, a uniform, albeit slight, a progression of
bone loss was observed over the 7-year observation period
that remained well within the limits for ‘success’, as
defined by the 2007 Pisa consensus [17](\2 mm). In
addition, bone loss was significantly more pronounced
around the distal implants in regions 35 and 45
(p\0.0001). There were no significant differences
between the groups in terms of the bone loss between the
ceramic and bar-retained superstructures (Table 3).
The probing pocket depth (PPD) increased consistently
and significantly over time in both groups. There was a
Table 1 Demographics and
baseline data Total Bar-retained acrylic Ceramics
Number of patients (n, %) 32 16 (50.0%) 16 (50.0%)
Males/females (n, %) 13/19 (40.6/59.4%) 7/9 (43.8/56.3%) 6/10 (37.5/62.5%)
Age (years) 66–83 (71.00 ±4.070) 66–80 (71.50 ±3.86) 66–83 (72.06 ±4.35)
Table 2 Evaluation of insertion
torque values Insertion torque (N) Total Bar-retained acrylic Ceramics
Region 32 40–59 (47.7 ±5.2) 40–58 (45.5 ±6.0) 40–59 (48.4 ±4.3)
Region 42 42–63 (50.2 ±5.7) 43–63 (51.5 ±6.5) 45–55 (48.8 ±4.6)
Region 35
¥
51–80 (66.1 ±6.3) 51–80 (67.0 ±7.1) 64–69 (65.2 ±5.3)
Region 45
¥
56–79 (69.3 ±5.9) 56–79 (71.4 ±6.2)* 57–73 (67.1 ±5.1)
According to the guidelines of all on 4
TM
treatment protocol, an insertion torque of 35–45 Ncm should be
achieved. Greater torque values in region 35 and 45 could be attributed to the fact that the implants placed
at these sites were 15 mm in length and bicortical anchorage has been achieved, which resulted in higher
torque values
*p\0.05 and ** p\0.01, comparison of region 32 vs. 35 and 42 vs. 45 ¥ p\0.0001
Table 3 Peri-implant bone loss
(mm) throughout 7 years of
function
Total Bar-retained acrylic Ceramics
Bone loss in region 32
After 1 year 0.1–0.6 (0.30 ±0.31) 0.2–0.4 (0.29 ±0.06) 0.1–0.6 (0.32 ±0.13)
After 3 years 0.2–0.8 (0.47 ±0.15) 0.2–0.6 (0.46 ±0.09) 0.2–0.8 (0.48 ±0.17)
After 5 years 0.3–0.8 (0.60 ±0.15) 0.3–0.8 (0.59 ±0.16) 0.4–0.8 (0.60 ±0.14)
After 7 years 0.4–0.9 (0.66 ±0.14) 0.4–0.9 (0.66 ±0.14) 0.4–0.9 (0.66 ±0.15)
Bone loss in region 35*
After 1 year 0.2–0.8 (0.65 ±0.15) 0.2–0.7 (0.53 ±0.16) 0.3–0.8 (0.55 ±0.15)
After 3 years 0.3–0.9 (0.75 ±0.16) 0.3–0.9 (0.64 ±0.15) 0.3–0.9 (0.66 ±0.15)
After 5 years 0.4–1.0 (0.80 ±0.17) 0.4–1.0 (0.74 ±0.16) 0.4–1.0 (0.76 ±0.18)
After 7 years 0.5–1.2 (0.59 ±0.17) 0.5–1.2 (0.80 ±0.17) 0.5–1.1 (0.81 ±0.18)
Bone loss in region 42
After 1 year 0.2–0.6 (0.37 ±0.14) 0.2–0.6 (0.40 ±0.11) 0.2–0.6 (0.35 ±0.11)
After 3 years 0.3–0.8 (0.49 ±0.14) 0.3–0.8 (0.52 ±0.15) 0.3–0.7 (0.46 ±0.13)
After 5 years 0.3–0.9 (0.59 ±0.15) 0.4–0.9 (0.63 ±0.14) 0.3–0.8 (0.55 ±0.13)
After 7 years 0.3–0.9 (0.62 ±0.15) 0.4–0.9 (0.65 ±0.15) 0.3–0.9 (0.60 ±0.15)
Bone loss in region 45*
After 1 year 0.3–1.0 (0.59 ±0.19) 0.3–0.9 (0.59 ±0.18) 0.3–1.0 (0.58 ±0.21)
After 3 years 0.4–1.0 (0.70 ±0.16) 0.4–0.9 (0.73 ±0.13) 0.4–1.0 (0.67 ±0.19)
After 5 years 0.5–1.1 (0.84 ±0.16) 0.6–1.0 (0.86 ±0.13) 0.5–1.1 (0.82 ±0.19)
After 7 years 0.6–1.2 (0.91 ±0.16) 0.7–1.1 (0.93 ±0.14) 0.6–1.2 (0.89 ±0.20)
Comparison of region 32 vs. 35 and 42 vs. 45 after 1, 3, 5 and 7 years * p\0.0001
Odontology
123
tendency towards shallower pockets for the ceramic
superstructures, which was mostly not significant
(Table 4).
Bleeding on probing (BOP) measurements around the
implants in region 35 showed statistically significant higher
values in the group with bar-retained superstructures
throughout the observation period over the group with
ceramic superstructures. Higher BOP values were also found
for implants in regions 42 and 32, especially in the first year
for the group with bar-retained superstructures (Table 5).
The plaque index showed that the plaque accumulation
was higher in the group with the bar-retained superstruc-
tures (Table 6).
There was a dramatic subjective improvement, as
assessed by the Oral Health Impact Profile (OHIP) score in
both groups. There were no differences in the OHIP scores
between patients with bar-retained dentures and ceramic
dentures (Fig. 6).
Complications
Bar-retained group
The following mechanical complications were recorded:
fractures of the extensions of the provisional acrylic
removable prosthesis (n:1) and dislodgement of the acrylic
teeth the provisional acrylic removable prosthesis (n:3).
The complications were resolved by repairing the pros-
thesis and adjusting the occlusion in situ. No mechanical
problems were observed in patients with definitive acrylic
prostheses, except for the attrition of the acrylic teeth.
Ceramics group
An acrylic tooth dislodged for one patient during the use of
provisional acrylic bridges and was repaired in situ. Some
problems were observed for patients with definitive cera-
mic superstructures. In one patient, the prosthesis around
the right premolar area dislodged at the end of the 7-year
period. The denture had to be removed and repaired in the
laboratory. Loosening of the multi-unit abutment screw
was observed in one patient at the implant region 32 and
was resolved by re-tightening the abutment screw.
All prostheses were easily mended and served well after
revision. No further mechanical complications were reg-
istered during the follow-up of this study.
Discussion
There have been numerous reports [2,18–20] that bar-
retained acrylic superstructures function well if carefully
designed and manufactured and if good implant support is
provided; however, these superstructures are also some-
times associated with prosthetic problems. A literature
Table 4 The evaluation of the
probing pocket depth Total Bar-retained acrylic Ceramics
PPD in region 32 ¥ ¥ ¥
After 1 year 1.0–3.0 (2.00 ±0.50) 1.0–3.0 (2.03 ±0.53) 1.0–2.5 (1.96 ±0.49)
After 3 years 1.0–4.0 (2.50 ±0.60) 1.0–4.0 (2.62 ±0.69) 1.0–3.0 (2.37 ±0.50)
After 5 years 1.5–4.5 (3.01 ±0.61) 1.5–4.5 (3.12 ±0.69) 1.5–3.5 (2.90 ±0.52)
After 7 years 1.5–4.5 (3.23 ±0.62) 1.5–4.5 (3.31 ±0.68) 1.5–3.5 (3.15 ±0.56)
PPD in region 42 ¥ ¥ ¥
After 1 year 1.0–3.0 (2.26 ±0.59) 1.0–3.0 (2.43 ±0.60) 1.0–3.0 (2.09 ±0.55)
After 3 years 1.0–4.0 (2.54 ±0.65) 1.0–4.0 (2.65 ±0.72) 1.0–3.0 (2.43 ±0.57)
After 5 years 1.5–4.5 (3.06 ±0.63) 1.5–4.5 (3.21 ±0.70) 1.5–3.5 (2.90 ±0.52)
After 7 years 2.0–5.0 (3.23 ±0.60) 2.0–5.0 (3.40 ±0.68) 2.0–4.0 (3.06 ±0.47)
PPD in region 35 ¥ ¥ ¥
After 1 year 2.0–4.0 (2.87 ±0.50) 2.0–4.0 (2.93 ±0.54) 2.0–4.0 (2.81 ±0.47)
After 3 years 2.0–4.5 (3.10 ±0.57) 2.0–4.5 (3.18 ±0.65) 2.0–4.5 (3.03 ±0.49)
After 5 years 2.5–4.5 (3.56 ±0.56) 2.5–4.5 (3.56 ±0.57) 2.5–4.5 (3.56 ±0.57)
After 7 years 2.5–5.0 (3.70 ±0.59) 2.5–5.0 (3.68 ±0.57) 2.5–5.0 (3.68 ±0.57)
PPD in region 45 ¥ ¥ ¥
After 1 year 2.0–4.5 (2.96 ±0.59) 2.0–4.5 (2.96 ±0.64) 2.0–4.0 (2.96 ±0.56)
After 3 years 2.0–4.5 (3.34 ±0.54) 2.5–4.5 (3.40 ±0.55) 2.0–4.0 (3.28 ±0.54)
After 5 years 2.5–5.5 (3.81 ±0.60) 2.5–5.5 (3.87 ±0.69) 2.5–4.5 (3.75 ±0.51)
After 7 years 3.0–5.5 (4.07 ±0.55) 3.0–5.5 (4.15 ±0.59) 3.0–4.5 (4.00 ±0.51)
Increase over time: ¥ p\0.0001
Odontology
123
survey revealed several problems with bar-retained
implant-supported prostheses: bar fracture, retention clip
activation or O-ring replacement, abutment screw failure
and fracture of the retention clip [21–23]. In the current
study, no mechanical problems were observed for the
group with definitive bar-retained acrylic prostheses,
except for the fracture of the extension of the provisional
acrylic prosthesis, which could be repaired in situ. An
O-ring replacement was performed every year for all of the
patients who were treated with bar-retained superstruc-
tures, even if no loss was observed in the retention clips.
Prosthetic problems were rarely observed in both groups in
this study; however, in the literature, it has been suggested
that [23] a significant shortcoming of acrylic removable
superstructures was the substantial increase in susceptibil-
ity to various prosthodontic complications with long-term
use. In addition, it has been proclaimed that mechanical
problems related to the bar-retained acrylic superstructures
could be resolved more cheaply than those related to the
ceramic superstructures, considering that acrylic super-
structures could be mostly repaired in situ, whereas the
denture had to be removed and repaired in the laboratory in
the ceramic group. In the ceramic superstructure group, we
have observed a dislodgement of the prosthesis around the
right premolar area in one patient at the end of the 7-year
period, and the denture had to be removed and repaired in
the laboratory. Further studies with long-term results are
needed to compare the economic aspects of prosthetic
complications between acrylic and ceramic superstructures.
It is obvious that the success of a dental prosthesis is
highly dependent on fulfilling the cosmetic and functional
demands of the patients. Measurement of occlusal forces is
a useful tool in comparing the functional aspects of dif-
ferent superstructures. We have used OHIP instrument to
assess subjective treatment outcomes, and found no sta-
tistically significant differences between two groups.
However, objective parameters such as occlusal force
measurements and comparative evaluation of the cosmetic
results via analysis of the lip support, cephalometric anal-
ysis, etc. were not included in the ‘‘Material and method’’
of the present study.
There are reports in the literature of patients who were
treated with bar-retained implant-supported overdentures
and experienced difficulties in maintaining good oral
hygiene, even when they were highly motivated to do so
[21,24–27]. Similar to the aforementioned findings, in the
present study, the difference in plaque accumulation, as
evaluated by the plaque index of Mombelli et al. [10],
between ceramic and bar-retained acrylic-bearing implants
was significant throughout the observation period, and the
highest plaque indexes were found for patients with bar-
retained superstructures. Clinicians should be made aware
of this result, and patients with poor oral hygiene motiva-
tion should be informed of the risk of plaque accumulation
and instructed in oral hygiene maintenance. The observa-
tion of higher BOP values in the removable superstructure
group could also be attributed to higher plaque accumula-
tion, which depends on the maintenance of a patient’s
personal oral hygiene [28].
Conclusion
In the current article, equivalent results were obtained for
bar-retained and ceramic superstructures over a 7-year
period. The higher level of plaque accumulation observed
around implants with bar-retained superstructures requires
Table 5 Evaluation of the BOP values
Total Bar-retained acrylic Ceramics
BOP in region 32
After 1 year 37.5% 68.75%* 6.25%
After 2 years 43.75% 56.25% 31.25%
After 3 years 37.5% 62.5% 12.5%
After 4 years 40.63% 56.25% 25.0%
After 5 years 31.25% 43.75% 18.75%
After 6 years 21.88% 37.5% 6.25%
After 7 years 21.88% 37.5% 6.25%
BOP in region 42
After 1 year 43.75% 68.75%* 18.75%
After 2 years 34.38% 56.25% 12.50%
After 3 years 37.50% 75.00% 0.00%
After 4 years 31.25% 43.75% 18.75%
After 5 years 28.13% 50.00%* 6.25%
After 6 years 25.00% 37.50% 12.50%
After 7 years 25.00% 25.00% 25.00%
BOP in region 35
After 1 year 53.13% 75.00%* 31.25%
After 2 years 37.50% 75.00%* 0.00%
After 3 years 37.50% 50.00% 25.00%
After 4 years 43.75% 75.00%* 12.50%
After 5 years 28.13% 31.25% 25.00%
After 6 years 46.88% 68.75%* 25.00%
After 7 years 21.88% 43.75%* 0.00%
BOP in region 45
After 1 year 12.50% 25.00% 0.00%
After 2 years 34.88% 43.75% 25.00%
After 3 years 18.75% 37.50% 0.00%
After 4 years 28.13% 43.75% 12.50%
After 5 years 25.00% 37.50% 12.50%
After 6 years* 31.25% 43.75% 18.75%
After 7 years* 34.38% 25.00% 43.75%
Comparison of bar-retained acrylic resin and ceramic suprastructures
*p\0.05
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123
Fig. 6 OHIP scores for both
groups during the observation
period (preoperative and at the
end of 1st, 3rd 5th and 7th years
postoperatively) showing no
significant differences between
groups
Table 6 Evaluation of the
plaque accumulation (PA)
according to Mombelli and co-
workers
Total Bar-retained acrylic Ceramics
PA in region 32
After 1 year 0.0–3.0 (1.06 ±0.98) 0.0–3.0 (1.75 ±0.77)* 0.0–2.0 (0.37 ±0.61)
After 2 years 0.0–3.0 (1.37 ±1.00) 2.0–3.0 (2.18 ±0.40)* 0.0–2.0 (0.56 ±0.72)
After 3 years 0.0–3.0 (1.50 ±1.01) 1.0–3.0 (2.18 ±0.75)* 0.0–2.0 (0.81 ±0.75)
After 4 years 0.0–3.0 (1.46 ±1.01) 0.0–3.0 (1.87 ±0.95)* 0.0–3.0 (1.06 ±0.92)
After 5 years 0.0–3.0 (1.31 ±0.93) 1.0–3.0 (1.93 ±0.68)* 0.0–2.0 (0.68 ±0.70)
After 6 years 0.0–3.0 (1.34 ±0.90) 1.0–3.0 (1.93 ±0.77) 0.0–2.0 (0.75 ±0.57)
After 7 years 0.0–3.0 (1.25 ±0.95) 0.0–3.0 (1.87 ±0.88) 0.0–1.0 (0.62 ±0.50)
PA in region 42
After 1 year 0.0–3.0 (1.31 ±1.09) 0.0–3.0 (1.93 ±1.06)* 0.0–2.0 (0.68 ±0.70)
After 2 years 0.0–3.0 (1.21 ±0.94) 1.0–3.0 (1.93 ±0.57)* 0.0–2.0 (0.50 ±0.63)
After 3 years 0.0–3.0 (1.53 ±1.01) 0.0–3.0 (2.25 ±0.77)* 0.0–2.0 (0.81 ±0.65)
After 4 years 0.0–3.0 (1.40 ±0.94) 1.0–3.0 (2.06 ±0.68)* 0.0–2.0 (0.75 ±0.68)
After 5 years 0.0–3.0 (1.21 ±1.00) 1.0–3.0 (1.93 ±0.77)* 0.0–2.0 (0.50 ±0.63)
After 6 years 0.0–3.0 (1.28 ±0.99) 0.0–3.0 (1.75 ±1.06)* 0.0–2.0 (0.81 ±0.65)
After 7 years 0.0–3.0 (1.18 ±0.82) 1.0–3.0 (1.62 ±0.61)* 0.0–2.0 (0.75 ±0.77)
PA in region 35
After 1 year 0.0–3.0 (1.37 ±0.83) 1.0–3.0 (1.87 ±0.61)* 0.0–2.0 (0.87 ±0.71)
After 2 years 0.0–3.0 (1.18 ±0.89) 0.0–3.0 (1.75 ±0.85)* 0.0–1.0 (0.62 ±0.50)
After 3 years 0.0–3.0 (1.21 ±0.94) 0.0–3.0 (1.81 ±0.75)* 0.0–2.0 (0.62 ±0.71)
After 4 years 0.0–3.0 (1.34 ±0.97) 1.0–3.0 (2.00 ±0.63)* 0.0–2.0 (0.68 ±0.79)
After 5 years 0.0–3.0 (1.25 ±0.91) 0.0–3.0 (1.56 ±0.96) 0.0–2.0 (0.93 ±0.77)
After 6 years 0.0–3.0 (1.62 ±0.87) 1.0–3.0 (2.18 ±0.65)* 0.0–2.0 (1.06 ±0.68)
After 7 years 0.0–3.0 (1.25 ±0.91) 1.0–3.0 (1.87 ±0.71)* 0.0–2.0 (0.62 ±0.61)
PA in region 45
After 1 year 0.0–3.0 (0.84 ±0.91) 0.0–3.0 (1.31 ±1.01)* 0.0–1.0 (0.37 ±0.50)
After 2 years 0.0–3.0 (1.03 ±0.96) 0.0–3.0 (1.37 ±1.08) 0.0–2.0 (0.68 ±0.70)
After 3 years 0.0–3.0 (1.15 ±0.80) 0.0–3.0 (1.37 ±1.02) 0.0–2.0 (0.93 ±0.44)
After 4 years 0.0–3.0 (1.25 ±0.87) 0.0–3.0 (1.62 ±0.95)* 0.0–2.0 (0.87 ±0.61)
After 5 years 0.0–3.0 (1.31 ±1.02) 0.0–3.0 (1.81 ±1.16)* 0.0–2.0 (0.81 ±0.54)
After 6 years 0.0–3.0 (1.09 ±1.08) 0.0–3.0 (1.43 ±1.26) 0.0–2.0 (0.75 ±0.77)
After 7 years 0.0–3.0 (1.34 ±0.70) 0.0–3.0 (1.25 ±0.85) 0.0–2.0 (1.43 ±0.51)
Comparison of bar-retained acrylic resin and ceramic suprastructures, *p\0.05, were used to demonstrate
the values which were statistically significant
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123
that patients with acrylic superstructures be highly moti-
vated to maintain their personal oral hygiene. Further
studies are needed to clarify the occurrence of
prosthodontic complications and assess their economic
aspects.
Acknowledgements The authors would like to thank Dr. Cengiz Han
Acikel from the Gulhane Military Medical Academy, Department of
Biostatistics, for conducting the statistical analysis of the current
study.
Contributions MA has performed the surgical interventions. AG,
MA and YA have written and edited the paper.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Consent Written informed consent was obtained from the patient for
publication of this case report and any accompanying images.
Disclosure The authors claim to have no financial interest, either
directly or indirectly, in the products or information listed in the
paper.
Approval This study was approved by the Ethics Review Committee
(NEAH/12.15.2015#498).
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