The aim of this clinical study was to evaluate the prosthodontic maintenance requirements during the first year of service of mandibular overdentures supported by interforaminal implants and to assess the influence of attachment type, implant number, and bite force on these requirements. Fifty-nine patients treated with mandibular implant overdentures between the years 2004 and 2009 and appearing in the 12th-month recall were included in this study. The overdentures constituted 4 groups: 2 single interforaminal implants (1 group with locator and 1 group with ball attachments), 3 single interforaminal implants, 3 splinted interforaminal implants (bar), and 4 splinted interforaminal implants (bar). During the examination, prosthetic parameters such as occlusion, tissue adaptation, condition of the retentive mechanism (matrice and patrice), and the condition of the denture-bearing tissues were evaluated and recorded. No statistically significant relation was found between attachment type, bite force values, implant number, and the occurring complications except the need for relining, which was found significantly more in the ball attachments than in other attachment groups (P  =  .03). After 12 months following the overdenture insertion, there seems to be no relation between occurring complications and patient-related factors, such as maximum bite force, age, and gender, as well as factors related to the overdentures such as number and type of attachments.

Introduction

Mandibular implant overdentures (OVDs) offer an effective rehabilitative treatment for edentulous patients.13 Generally, the implants that are assumed to achieve a good retention and stability for the planned OVDs are placed interforaminally for anatomical and surgical reasons, thus offering the patient a higher satisfaction and quality of life.4,5 However, it is well known that implant-retained OVDs require routine maintenance and periodic repairs, since the denture-supporting implants are subject to biomechanical forces.613 Controversy exists about the force transmission of single or splinted attachments.1013 Although some studies suggest that when loaded, splinted implants act together as a group instead of single units and protect the implants14,15 and that bar retention is a solution with least complications and repairs,1618 there are authors pointing out the danger of mismatch of deformations between the mandible and a rigid single continuous bar, which could lead to bone loss around the supporting implants, material fracture, or screw loosening due to stress accumulation.19,20 

Even though little is known about the influence of the number of implants on generated stresses, retention and stability are believed to be better with more implants. Although there are a few clinical reports, the effect of the number and distribution of implants on the stresses is an even less investigated issue.21,22 

In fact, in the interforaminal region where the overdenture-supporting implants are positioned, the flexure could have a more significant effect than in the posterior mandible. A bar fixation, which is more rigid than the bony tissue, would not follow the flexure and thus generate stress. On the other hand, in several clinical follow-up studies evaluating edentulous patients with 2 interforaminal implants, the retention mechanism of mandibular implants supporting an OVD was found to have no influence on the marginal bone level maintenance and clinical parameters; thus, this assumption was not supported.1,3,23,24 

Although there are numerous studies1217 reporting several implant- and denture-related complications, obviously there is a lack of knowledge on the influence of implant number and attachment type on time-dependent need of OVD repairs.

This study was planned to evaluate the relation between implant number, attachment type, and maximum bite force on occurring complications in mandibular OVDs.

Materials and Methods

Patient recruitment and clinical procedures

Fifty-nine patients (20 male [33.9%] and 39 female [66.1%]) with an average age of 63.83 ± 10.10 (range, 42–90 years) with mandibular implant OVDs treated between the years 2004 and 2009 and appearing in the 12th-month recall were included in this study. Informed written consent with regard to treatment and measurement procedures was given by the patients involved, and approval from the ethics commission was duly obtained. The patients' OVDs constituted 4 groups: 2 single interforaminal implants (1 group with Zest Anchor locator and 1 group with ball attachments), 3 single interforaminal implants, 3 splinted interforaminal implants (bar), and 4 splinted interforaminal implants (bar). All patients included in the study had been maxillary edentulous full denture wearers.

At the recall session, a clinical examination was performed by the same 2 examiners. During the examination, prosthetic parameters such as occlusion, tissue adaptation, condition of the retentive mechanism (matrice and patrice), and the condition of the denture-bearing tissues were evaluated. While the condition of the denture-bearing tissues was inspected, the adaptation of the dentures was checked using a pressure indication paste, which was prepared chair-side with a mixture of 1 g zinc oxide ointment (White Impression Paste, S.S. White Manufacturing, Glouchester, England) and 1 g petroleum jelly. Pressure spots were eliminated by grinding from inside the denture base. If the denture base adaptation was not acceptable, a relining was performed. Occlusion was checked for premature contacts, which could have arisen due to wear and eliminated. In case of loosening of abutment or occlusal screws, these were tightened up. Loosened retentive mechanisms were either changed or tightened. In case of loss of retention, the matrices in the dentures were changed. The patrices were checked for the presence of an eventual wear and changed if necessary.

All required corrections and repairs were recorded. The maintenance required for each overdenture was recorded either as an adjustment or a repair. Adjustment indicated a modification that did not add new material to the existing overdenture or replace broken or missing components such as correction of occlusion, tightening of abutment screws, or correcting the underlying cause of traumatic ulcerations, whereas repair indicated the addition or replacement of material or teeth.

Statistical analyses

Statistical analyses were used in this study to assess the potential effect of various parameters on the maximum bite forces. For the statistical analysis of the results, the Number Cruncher Statistical System (NCSS, 2007) and PASS 2008 statistical software (Kaysville, Utah) were used. Demographic parameters (age and gender), prosthetic options (bar, locator, or ball attachment), and number of implants was evaluated. Beside descriptive statistics (means and standard deviations), the comparison of quantitative data was accomplished with the 1-way analysis of variance test for the comparison of groups with normal distribution, whereas the comparison of qualitative data was done with the χ2 test. The results were assessed at the 95% confidence interval, at a significance level of .05.

Results

Fifty-nine mandibular implant-supported OVD patients (20 male [33.9%] and 39 [66.1%] female) with an average age of 63.83 ± 10.10 years (range, 42–90 years) appearing in the 12th-month recall were included in the study.

The distribution of prosthetic complications is shown in Table 1.

Table 1

The distribution of prosthetic complications

The distribution of prosthetic complications
The distribution of prosthetic complications

While in more than one-third of all patients (n  =  20; 33.9%) no complications were detected, in nearly two-thirds of the patients (n  =  39; 66.1%) 1 or more complications could be recorded. Nineteen of 39 patients showed the need for only one type of adjustment or repair, whereas in 20 patients, the combination of several types of adjustments or repairs had been necessary. The most frequent observed single complications were the following:

  1. Loss of retention: n  =  6 (10.2%)

  2. Fracture of denture base: n  =  5 (8.5%)

  3. Pressure spots (ulceration): n  =  5 (8.5%)

  4. Dislodged attachment clip: n  =  4 (6.8%)

  5. Screw loosening: n  =  2 (3.4%)

  6. Need of occlusal adjustment: n  =  1 (1.7%)

The need for relining was observed in 10 patients but only in combination with other complications and significantly higher in ball attachments (P  =  .30).

There was no statistically significant relation between attachment type (Table 2), age (P  =  .890) or gender (P  =  .428) of patients, maximum bite force values (P  =  .837), or number of implants (Table 3) and the occurring complications and complication types (P > .05)

Table 2

The evaluation of prosthetic complications related to the attachment type†

 The evaluation of prosthetic complications related to the attachment type†
 The evaluation of prosthetic complications related to the attachment type†
Table 3

The evaluation of prosthetic complications related to the implant number†

The evaluation of prosthetic complications related to the implant number†
The evaluation of prosthetic complications related to the implant number†

When evaluated particularly, the bar clip retention showed significantly less complications, especially less need of relining of the mandibular OVD (P  =  .03; Table 2).

Discussion

It is of great importance for the clinician to know what complications may occur during the use of implant OVDs in order to choose the treatment that requires least maintenance.

Studies have shown that technical problems occur both during the first year after treatment and in the long term, whereas it was reported that the frequency of technical problems decreases over time.2528 Taking this opinion into consideration, the evaluation of the first-year complications of mandibular implant OVDs is demonstrative for overall maintenance requirements. The most frequent complications related to mandibular implant OVDs that have been reported in the literature are loss of retention or damage to the retention mechanism,22,2934 fractures of the restorative material,2932,3539 and need of rebasing or relining.3,22,29,3133,35,36,38 

There is an ongoing debate about the influence of attachment type on later technical complications in implant OVDs, although only a few studies have compared treatment outcomes with different attachment devices of OVDs. As an example, a comparative study on different connection systems (splinted vs unsplinted) found that single attachments provide lower retention than do bars for fixation of OVDs, but the long-term complication outcome was not mentioned.34 

It is well recognized that attachments of OVDs on implants lose retention after some time. Fatigue and wear of the material could be another factor causing complications with retention loss.40 Several clinical measurements proved that 3-dimensional loads occur regularly during function. A denture may rotate around an anterior bar, or it may rock slightly, when food is chewed on 1 free-end denture base. These movements can clinically lead to plastic deformation of the matrice, resulting in a reduction of retention or dislodgement of the clip.

In some publications in the past decade, there was an agreement about no observable effect of the attachment design on the incidence of maintenance requirements.41 Although there is no unanimous opinion, several authors have reported that prosthodontic maintenance requirements with ball attachments were higher,4244 particularly during the first year.30 The review by Cehreli et al45 pointed out that a dislodged, worn, or loose matrix or its respective housing was more common after the first year with ball retainers and the most common repair was retentive component replacement. The results of a study by Dudic and Mericske-Stern13 focused mainly on the comparison of the retention mechanism complications. Broken, loose, or lost bar clips and female retainers of ball anchors had been significantly more often detected with resilient attachments, whereas the rigid bar required significantly more retightening of the female part during the first 5 years.13 Considering the fact that activation of female parts is less time-consuming than is changing them, an advantage for the rigid attachment was pointed out.13 This fact had been confirmed by the slightly higher incidence of all types of complications for the ball attachment devices in the present study. Nevertheless, in contradiction, it was reported in a study that there was a higher number of technical complications per patient with bars than with ball attachments, and the mean frequency of complications per patient per year was 1.0 in the bar group and 0.6 in the ball group during the 5-year observation period.3 

An in vivo study has shown that during chewing, bars with distal cantilevers tend to increase the loads on the most distal implants by more than 3 times.46 For this reason, none of the bar designs in our study had cantilever extensions, which could be the reason for the slightly better results in favor of the bar attachments.

Alloy selection for the construction of the superstructure also seems to be important.47 If a soft gold alloy is used instead of a rigid nonprecious alloy, the resistance of the superstructure to bending decreases by two-thirds. As a result, the stress is about 50% larger compared with the values obtained by the rigid superstructure. Important parameters influencing the stress distribution include material properties, such as the modulus of elasticity. The bars in the present study have been constructed with rigid alloys such as CoCrMo alloy (DEGUSSA, Degussa-Hüls AG/Germany; 63% Co, 28% Cr, 5% Mo, 4% others) or gold-palladium alloy (Security, Jensen Dental, North Haven, Conn; 40% Au, 40% Pd, 9% Ag, 11% others). The rigidity could have been another reason explaining the success of the bar attachments in the present study.

When more than 2 implants and multiple bars are used between implants, as in our study, the attachment clips located on each bar are often not parallel to each other or perpendicular to the posterior ridges. In these situations, the clips can bind in function, thus limiting the movement of the prosthesis. Use of a rigid joint between bar and the denture usually places more load on the implants than on the denture-bearing mucosa surfaces.48 However, a clinical study that measured the force transmission onto implants supporting OVDs found that maximum forces measured in the vertical direction were higher with single telescopes than with bars and clips and that rigid bars contributed to load sharing between the implants.49 Although further investigation is necessary, it could be stated that if the prosthesis is well designed and under ideal conditions, there is no significant difference between ball attachments and bar-clip designs in terms of stress distribution to the implants.

Considering other kinds of maintenance requirements, it was emphasized by several authors that OVDs with rigid attachments show less need to be relined.50,51 

The need for reline for prosthetic maintenance, in a period of 0.5–1.5 years, is reported to range from 6.5% to 18%.26,52 Higher reline rates have also been reported.3133 Resilient attachments are claimed to conduct undesirable forces to the denture-bearing tissues, resulting in resorption, which makes relining necessary.53 It should be kept in mind that the denture-bearing tissues are subject to changes and atrophy over time, which is another reason revealing spaces under the denture base makes relining necessary. In the present study, the need for relining was predominately seen in ball attachments (Table 2), confirming the above-mentioned studies. However, it was observed that locator attachments did not cause the significant relining needs the ball attachments did. This may be due to the dissimilar resilience mechanisms of 2 attachment types.54 

The cause of mechanical complications might be expected to be overloading and insufficient number of implants, but no study has been able to prove that. On the contrary, in a review it was concluded that the success rate of implants and prostheses or patient satisfaction with the OVD treatment of the mandible is not dependent on the number of implants or abutment type.55 If cost-effectiveness is the preliminary goal, a 2-implant OVD is reported to provide an excellent alternative to a conventional complete denture, and there are clinical studies reporting successful rehabilitation with mandibular OVDs anchored to only a single implant in the midline of the mandible.56,57 The results of the present study failed to show a statistically significant correlation between implant number and occurring complications, although there was a numerical trend indicating fewer complications with more implants supporting the mandibular OVDs (Table 3). In addition, the evaluation of the maximum bite force of the patients showed no significant relation with complications. To draw more reliable conclusions, further studies with a larger patient population and a longer observation period should be conducted.

Conclusions

Within the limitations of this study, the following conclusions can be drawn:

  1. Twelve months following the denture insertion, there seems to be no statistically significant relation between occurring complications and factors related to patients, such as maximum bite force or age and gender of the patient, as well as factors related to the overdenture, such as number and type of attachments.

  2. Although the results show a trend toward fewer complications with the bar attachment, this finding is not statistically significant.

Abbreviation

     
  • OVD

    mandibular implant overdenture

References

References
1.
Oetterli
M
,
Kiener
P
,
Mericske-Stern
R
.
A longitudinal study on mandibular implants supporting an overdenture: the influence of retention mechanism and anatomic-prosthetic variables on peri-implant parameters
.
Int J Prosthodont
.
2001
;
14
:
536
542
.
2.
Tokuhisa
M
,
Matsushita
Y
,
Koyano
K
.
In vitro study of a mandibular implant overdenture retained with ball, magnet, or bar attachments: comparison of load transfer and denture stability
.
Int J Prosthodont
.
2003
;
16
:
128
134
.
3.
Gotfredsen
K
,
Holm
B
.
Implant-supported mandibular overdentures retained with ball or bar attachments: a randomized prospective 5-year study
.
Int J Prosthodont
.
2000
;
13
:
125
130
.
4.
Cune
M
,
van Kampen
F
,
van der Bilt
A
,
Bosman
F
.
Patient satisfaction and preference with magnet, bar-clip, and ball-socket retained mandibular implant overdentures: a cross-over clinical trial
.
Int J Prosthodont
.
2005
;
18
:
99
105
.
5.
Sadowsky
SJ
,
Caputo
AA
.
Effect of anchorage systems and extension base contact on load transfer with mandibular implant-retained overdentures
.
J Prosthet Dent
.
2000
;
84
:
327
334
.
6.
Meijer
HJ
,
Kuiper
JH
,
Starmans
FJ
,
Bosman
.
Stress distribution around dental implants: influence of superstructure, length of implants, and height of mandible
.
J Prosthet Dent
.
1992
;
68
:
96
102
.
7.
Meijer
HJ
,
Starmans
FJ
,
Steen
WH
,
Bosman
F
.
Location of implants in the interforaminal region of the mandible and the consequences for the design of the superstructure
.
J Oral Rehabil
.
1994
;
21
:
47
56
.
8.
Menicucci
G
,
Lorenzetti
M
,
Pera
P
,
Preti
G
.
Mandibular implant-retained overdenture: a clinical trial of two anchorage systems
.
Int J Oral Maxillofac Implants
.
1998
;
13
:
851
856
.
9.
Brunski
JB
.
Biomaterials and biomechanics in dental implant design
.
Int J Oral Maxillofac Implants
.
1988
;
3
:
85
97
.
10.
Kenney
R
,
Richards
MW
.
Photoelastic stress patterns produced by implant-retained overdentures
.
J Prosthet Dent
.
1998
;
80
:
559
564
.
11.
Chun
HJ
,
Park
DN
,
Han
CH
,
Heo
SJ
,
Heo
MS
,
Koak
JY
.
Stress distributions in maxillary bone surrounding overdenture implants with different overdenture attachments
.
J Oral Rehabil
.
2005
;
32
:
193
205
.
12.
Walton
JN
,
MacEntee
MI
.
Problems with prostheses on implants: a retrospective study
.
J Prosthet Dent
.
1994
;
71
:
283
288
.
13.
Dudic
A
,
Mericske-Stern
R
.
Retention mechanisms and prosthetic complications of implant-supported mandibular overdentures: long-term results
.
Clin Implant Dent Relat Res
.
2002
;
4
:
212
219
.
14.
Tanino
F
,
Hayakawa
I
,
Hirano
S
,
Minakuchi
S
.
Finite element analysis of stress-breaking attachments on maxillary implant-retained overdentures
.
Int J Prosthodont
.
2007
;
20
:
193
198
.
15.
Bergkvist
G
,
Simonsson
K
,
Rydberg
K
,
Johansson
F
,
Dérand
T
.
A finite element analysis of stress distribution in bone tissue surrounding uncoupled or splinted dental implants
.
Clin Implant Dent Relat Res
.
2008
;
10
:
40
46
.
16.
Timmerman
R
,
Stoker
GT
,
Wismeijer
D
,
Oosterveld
P
,
Vermeeren
JI
,
van Waas
MA
.
An eight-year follow-up to a randomized clinical trial of participant satisfaction with three types of mandibular implant-retained overdentures
.
J Dent Res
.
2004
;
83
:
630
633
.
17.
Stoker
GT
,
Wismeijer
D
,
van Waas
MA
.
An eight-year follow-up to a randomized clinical trial of aftercare and cost-analysis with three types of mandibular implant-retained overdentures
.
J Dent Res
.
2007
;
86
:
276
280
.
18.
Wismeijer
D
,
van Waas
MA
,
Mulder
J
,
Vermeeren
JI
,
Kalk
W
.
Clinical andradiological results of patients treated with three treatment modalities for overdentures on implants of the ITI Dental Implant System: a randomized controlled clinical trial
.
Clin Oral Implants Res
.
1999
;
10
:
297
306
.
19.
Hobkirk
JA
,
Havthoulas
TK
.
The influence of mandibular deformation, implant numbers, and loading position on detected forces in abutments supporting fixed implant superstructures
.
J Prosthet Dent
.
1998
;
80
:
169
174
.
20.
Zarone
F
,
Sorrentino
R
,
Traini
T
,
Di lorio
D
,
Caputi
S
.
Fracture resistance of implant-supported screw- versus cement-retained porcelain fused to metal single crowns: SEM fractographic analysis
.
Dent Mater
.
2007
;
23
:
296
301
.
21.
Närhi
TO
,
Hevinga
M
,
Voorsmit
RA
,
Kalk
W
.
Maxillary overdentures retained by splinted and unsplinted implants: a retrospective study
.
Int J Oral Maxillofac Implants
.
2001
;
16
:
259
266
.
22.
Kiener
P
,
Oetterli
M
,
Mericske
E
,
Mericske-Stern
R
.
Effectiveness of maxillary overdentures supported by implants: maintenance and prosthetic complications
.
Int J Prosthodont
.
2001
;
14
:
133
140
.
23.
Bergendal
T
,
Engquist
B
.
Implant-supported overdentures: a longitudinal prospective study
.
Int J Oral Maxillofac Implants
.
1998
;
13
:
253
262
.
24.
Wright
PS
.
Two implants for all edentulous mandibles
.
Br Dent J
.
2006
;
200
:
469
.
25.
Zarb
GA
,
Schniitt
A
.
The longitudinal clinical effectiveness of osseointegrated dental implants: the Toronto Study. Part 11: the prosthetic results
.
J Prosthet Dent
.
1990
;
1
:
53
61
.
26.
Naert
I
,
Quirynen
M
,
Theuniers
G
,
van Steenberghe
D
.
Prosthetic aspects of osseointegrated fixtures supporting overdentures: a 4-year report
.
J Prosthet Dent
.
1991
;
5
:
671
680
.
27.
Johansson
G
,
Palmqvist
S
.
Complications, supplementary treatment, and maintenance in edentulous arches with implant-supported fixed prostheses
.
Int J Prosthodont
.
1990
;
1
:
89
92
.
28.
Jemt
T
.
Failures and complications in 391 consecutively inserted fixed prostheses supported by Branemark implants in edentulous jaws: a study of treatment from the time of prosthesis placement to the first annual checkup
.
Int J Oral Maxillofac Implants
.
1991
;
3
:
270
276
.
29.
Johns
RB
,
Jemt
T
,
Heath
MR
,
et al.
A multicenter study of overdentures supported by Branemark implants
.
Int J Oral Maxillofac Implants
.
1992
;
7
:
513
522
.
30.
Allen
PF
,
McMillan
AS
,
Smith
DC
.
Complications and maintenance requirements of implant-supported prostheses provided in a UK dental hospital
.
Br Dent J
.
1997
;
182
:
298
302
.
31.
Hemmings
KW
,
Schmitt
A
,
Zarb
GA
.
Complications and maintenance requirements for fixed prostheses and overdentures in the edentulous mandible: a 5-year report
.
Int J Oral Maxillofac Implants
.
1994
;
9
:
191
196
.
32.
Jemt
T
,
Book
K
,
Lindén
B
,
Urde
G
.
Failures and complications in 92 consecutively inserted overdentures supported by Brånemark implants in severely resorbed edentulous maxillae: a study from prosthetic treatment to first annual check-up
.
Int J Oral Maxillofac Implants
.
1992
;
7
:
162
167
.
33.
Smedberg
JI
,
Lothigius
F
,
Bodin
I
,
Frykholm
A
,
Nilner
K
.
A clinical and radiological two-year follow-up study of maxillary overdentures on osseointegrated implants
.
Clin Oral Implants Res
.
1993
;
4
:
39
46
.
34.
Naert
I
,
Quirynen
M
,
Hooghe
M
,
van Steenberghe
D
.
A comparative prospective study of splinted and unsplinted Branemark implants in mandibular overdenture therapy: a preliminary report
.
J Prosthet Dent
.
1994
;
5
:
486
492
.
35.
Wismeyer
D
,
van Waas
MA
,
Vermeeren
JI
.
Overdentures supported by ITI implants: a 6.5-year evaluation of patient satisfaction and prosthetic aftercare
.
Int J Oral Maxillofac Implants
.
1995
;
10
:
744
749
.
36.
Mericske-Stern
R
.
Clinical evaluation of overdenture restorations supported by osseointegrated titanium implants: a retrospective study
.
Int J Oral Maxillofac Implants
.
1990
;
5
:
375
383
.
37.
Cooper
LF
,
Scurria
MS
,
Lang
LA
,
Guckes
AD
,
Moriarty
JD
,
Felton
DA
.
Treatment of edentulism using Astra Tech implants and ball abutments to retain mandibular overdentures
.
Int J Oral Maxillofac Implants
.
1999
;
14
:
646
653
.
38.
Meijer
HJ
,
Raghoebar
GM
,
Van't Hof
MA
,
Visser
A
,
Geertman
ME
,
Van Oort
RP
.
A controlled clinical trial of implant-retained mandibular overdentures: five-years' results of clinical aspects and aftercare of IMZ implants and Branemark implants
.
Clin Oral Implants Res
.
2000
;
11
:
441
447
.
39.
Davis
DM
,
Rogers
JO
,
Packer
ME
.
The extent of maintenance required by implant-retained mandibular overdentures: a 3-year report
.
Int J Oral Maxillofac Implants
.
1996
;
11
:
767
774
.
40.
Trakas
T
,
Michalakis
K
,
Kang
K
,
Hirayama
H
.
Attachment systems for implant retained overdentures: a literature review
.
Implant Dent
.
2006
;
15
:
24
34
.
41.
Karabuda
C
,
Yaltirik
M
,
Bayraktar
M
.
A clinical comparison of prosthetic complications of implant-supported overdentures with different attachment systems
.
Implant Dent
.
2008
;
17
:
74
81
.
42.
Naert
I
,
Alsaadi
G
,
van Steenberghe
D
,
Quirynen
M
.
A 10-year randomized clinical trial on the influence of splinted and unsplinted oral implants retaining mandibular overdentures: peri-implant outcome
.
Int J Oral Maxillofac Implants
.
2004
;
19
:
695
702
.
43.
van Kampen
F
,
Cune
M
,
van der Bilt
A
,
Bosman
F
.
Retention and postinsertion maintenance of bar-clip, ball and magnet attachments in mandibular implant overdenture treatment: an in vivo comparison after 3 months of function
.
Clin Oral Implants Res
.
2003
;
14
:
720
726
.
44.
Walton
JN
.
A randomized clinical trial comparing two mandibular implant overdenture designs: 3-year prosthetic outcomes using a six-field protocol
.
Int J Prosthodont
.
2003
;
16
:
255
260
.
45.
Cehreli
MC
,
Karasoy
D
,
Kokat
AM
,
Akca
K
,
Eckert
SE
.
Systematic review of prosthetic maintenance requirements for implant-supported overdentures
.
Int J Oral Maxillofac Implants
.
2010
;
25
:
163
180
.
46.
Kramer
A
,
Weber
H
,
Benzing
U
.
Implant and prosthetic treatment of the edentulous maxilla using a bar-supported prosthesis
.
Int J Oral Maxillofac Implants
.
1992
;
7
:
251
255
.
47.
Benzing
UR
,
Gall
H
,
Weber
H
.
Biomechanical aspects of 2 different implant prosthetic concepts for the edentulous maxilla
.
Int J Oral Maxillofac Implants
.
1995
;
10
:
188
198
.
48.
Setz
J
,
Krämer
A
,
Benzing
U
,
et al.
Complete dentures fixed on dental implants: chewing patterns and implant stress
.
J Oral Maxillofac Implants
.
1989
;
4
:
107
111
.
49.
Mericske-Stern
R
,
Piotti
M
,
Sirtes
G
.
3-D in vivo force measurements on mandibular implants supporting overdentures: a comparative study
.
Clin Oral Implants Res
.
1996
;
7
:
387
396
.
50.
Saito
M
,
Miura
Y
,
Notani
K
,
Kawasaki
T
.
Stress distribution of abutments and base displacement with precision attachment- and telescopic crown-retained removable partial dentures
.
J Oral Rehabil
.
2003
;
30
:
482
487
.
51.
Öwall
B
,
Bieniek
K. W
,
Spiekermann
H
.
Removable partial denture production in Western Germany
.
Quintessence Int
.
1995
;
26
:
621
627
.
52.
Cune
MS
,
de Putter
C
.
A comparative evaluation of some outcome measures of implant systems and suprastructures types in mandibular implant overdenture treatment
.
J Oral Maxillofac Implants
.
1994
;
9
:
548
555
.
53.
Langer
A
.
Telescope retainers for removable partial dentures
.
J Prosthet Dent
.
1981
;
45
:
37
43
.
54.
Geckili
O
,
Bilhan
H
,
Bilgin
T
.
Locator attachments as an alternative to ball attachments in 2-implant retained mandibular overdentures
.
J Can Dent Assoc
.
2007
;
73
:
691
694
.
55.
Klemetti
E
.
Is there a certain number of implants needed to retain an overdenture
?
J Oral Rehabil
.
2008
;
35
:
80
84
.
56.
Liddelow
G
,
Henry
P
.
The immediately loaded single implant-retained mandibular overdenture: a 36-month prospective study
.
Int J Prosthodont
.
2010
;
23
:
13
21
.
57.
Cordioli
G
,
Majzoub
Z
,
Castagna
S
.
Mandibular overdentures anchored to single implants: a five-year prospective study
.
J Prosthet Dent
.
1997
;
78
:
159
165
.