A key criterion of success following dental implants is the marginal bone level. Long-term clinical and radiographic evaluation is necessary to test the results of in vitro studies investigating how cantilevering of restorations or implant size affect bone level changes around implants. There is no consensus on the effect of several variables such as age, gender, implant size, and cantilever prostheses on marginal bone levels around fixed dentures supported by dental implants. Patients who received cemented, fixed restorations supported by implants and who were examined in routine recall sessions 6, 12, 24, and 36 months after loading were included in the study group. Comparative bone level measurements were obtained from images of radiographs at ×20 magnification using the CorelDraw 11.0 software program. Statistical analysis was performed using the Student t test and 1-way analysis of variance. In the 36-month observation period, there were no incidences of implant failure, excessive bone loss around implants, or peri-implant inflammation. One hundred twenty-six implants in 36 patients were evaluated, and the effect of several factors on marginal bone loss (MBL) during the 36 months after loading was analyzed statistically. There was no significant relationship between MBL and implant length or diameter, whereas age, gender, and cantilevers affected bone loss rates. MBL was elevated in older and female patients as well as in patients who received cantilevers. In cases of limiting anatomic conditions, short and/or narrow implants should be preferred over cantilever extensions.

Introduction

Long-term clinical evaluation of dental implants is crucial for gaining more information about causes of implant success and failure. One of the most important criteria is the marginal bone level around implants.1 Since bone-anchored prostheses are planned to be sustained in the oral environment for a lifetime,2 a pathologic decrease in bone level could lead to loss of bone anchorage of the implant, and it is important to know what factors contribute to bone resorption.

Controversy exists about several variables influencing implant success and especially marginal bone loss (MBL). The size of the implants,314 age and gender of patients,1519 and the presence of cantilevers2032 as influencing factors are subject of debate.

In this retrospective clinical study, the impact of these factors on MBL surrounding implants with fixed restorations was evaluated over a 36-month period following loading.

Materials and Methods

The study group included 36 patients with 126 implant-supported fixed restorations, who appeared for routine recall sessions 6, 12, 24, and 36 months after loading. Information was given to each patient regarding alternative treatment options. All subjects were required to be at least 18 years old, able to read and sign the informed consent document, physically and psychologically able to tolerate conventional surgical and restorative procedures, and willing to return for follow-up examinations as outlined by the investigators.

Four different brands of implants were used: 47 Astra Tech (Astra Tech AB, Mölndal, Sweden), 40 ITI Standard Plus (Institut Straumann AG, Basel, Switzerland), 10 SwissPlus (Zimmer Dental, Carlsbad, Calif), and 29 BioLok (Biohorizons, Birmingham, Ala).

The implants were all put in place by the same surgeon following the manufacturers' recommendations and were restored by various prosthodontists at a university clinic. All patients received fixed restorations ranging from single crowns to full-arch bridges (Figure 1).

The implant sites included all mandibular and maxillary positions. The implant loading period was 36 months. Data recorded for all implants included the patient's age and gender, the diameter and length of the implant, and the presence or absence of a cantilever.

Forty-six implants in 16 patients had been supporting a fixed prosthesis with a cantilever. In 10 patients, 2 implants were supporting the cantilever, whereas in 6 patients 3 or more implants have been the support. Recall sessions were routinely performed 6, 12, 24, and 36 months after loading. At each recall visit, a clinical examination was performed by the same examiner.

Panoramic radiographs (Planmeca, Proline XC, Helsinki, Finland) were taken preoperatively, immediately after surgery, immediately after loading, and at every recall session. Intraoral radiographs were taken if visual assessment of the marginal bone attached at the distal and mesial surfaces for all implants was not possible with magnified panoramic radiographs. Mesial and distal marginal bone levels of all implants were determined during baseline and recall evaluations. Currently, the best method of measuring marginal bone levels around implants is examination of scanned and digitized conventional radiographs,33,34 which were used in the present study. Measurements were obtained from images of successive radiographs that had been scanned and digitized (Epson 1680, Pro-Seiko Epson Corp, Nagano, Japan), and were analyzed at ×20 magnification using CorelDraw 11.0 software (Corel Corp and Coral Ltd, Ottawa, Canada). The implant diameter at the collar region, as specified by the manufacturer, was used as a reference point. The distance from the widest supracrestal part of the implant to the crestal bone level was measured on the magnified images. To account for variability, the implant width was measured and compared with the documented dimensions, and ratios were calculated to adjust for distortion. Bone levels were determined by applying a distortion coefficient (true bone height  =  [true implant width][measured bone height]/measured implant diameter). The actual bone level measurement was performed independently by 2 examiners, a prosthodontist and a specialist in oral and maxillofacial radiology. The average from both examiners' calculations was used as the marginal bone level value. The level at which the marginal bone appeared to be attached was assessed visually at the distal and mesial surfaces for all implants (Figure 2). The radiographs were reviewed by 2 examiners on 2 separate occasions, 1 week apart. The radiographs were available to none of the examiners between the first and second viewings. In addition, the examiners' measurements made at the first testing were not available during the second testing. During the first review, the observers did not know that they would be retested. Intraobserver reliability was determined via comparison of the measurements decided on by each individual observer for the first and second testing sessions. Interobserver reliability was assessed via comparison of the measurements decided on by the 2 different examiners. Statistical analyses were used to assess mean MBL changes at 6, 12, 24, and 36 months and to explore the potential effect of various parameters on bone loss. NCSS 2007 and PASS 2008 statistical software (NCSS, Kaysville, Utah) was used. The following clinical parameters were assessed relative to MBL: peri-implant parameters, demographic parameters (age and gender), implant brand, implant diameter and length, presence or absence of cantilever, and implant location. Descriptive statistics (means and standard deviations for continuous variables, frequencies for categorical variables) were used to analyze all implants as well as each type of implant. Quantitative data were compared using a one-way analysis of variance test, and comparisons between groups with normal distributions and outlier groups were detected with the Tukey honestly significant difference test. For comparison of the 2 groups with normal distributions, the Student t test was used. For analysis of repeated measures, variance analysis, and detection of the outliers, the paired sample t test was used. The results were assessed at 95% confidence interval, at a significance level of .05.

Results

During the 36-month observation period, there was no incidence of implant failure or excessive bone loss around implants and no recorded peri-implant inflammation. One hundred twenty-six implants in 36 patients (21 female patients with 73 implants and 15 male patients with 53 implants; mean age 54.97 ± 12.24 years, minimum 18 years and maximum 68 years) were evaluated, and the effect of several factors on MBL during the 36-month period after loading was analyzed statistically.

No statistically significant differences in MBL changes were observed between male and female patients in the first 24 months (P > .05). By month 36, however, female patients showed higher MBL than male patients (P < .05) (Table 1).

Table 1

Relation between marginal bone loss (mean values and SD in mm) and gender

Relation between marginal bone loss (mean values and SD in mm) and gender
Relation between marginal bone loss (mean values and SD in mm) and gender

There was a significant difference between age groups in the average distal and mesial bone loss at month 6, with patients 45 years of age and younger showing lower MBL than patients 60 years of age and older (P < .01) (Table 2). There were no differences in distal (P  =  .360) and mesial (P  =  .211) bone loss rates between 45- and 60-year-old patients and patients over 60 years of age at month 6. However, by month 12, the overall and mesial bone loss levels of patients 45 years of age and younger were significantly lower than those of the 46- to 60-year-old group (P  =  .033 and P  =  .005, respectively) and the over 60-year-old group (P  =  .044 and P  =  .004, respectively). There was no significant difference between the 46- to 60-year-old group and the over 60-year-old group, either in overall (P  =  .099) or mesial (P  =  .988) bone loss levels.

Table 2

The influence of patient age on marginal bone loss (mean values and SD in mm)

The influence of patient age on marginal bone loss (mean values and SD in mm)
The influence of patient age on marginal bone loss (mean values and SD in mm)

By month 24, mesial bone loss averages differed significantly between age groups (P < .05), with those of the 45 years of age and under group significantly lower those of the 46- to 60-year-old group (P  =  .029). There was no difference in mesial bone loss levels between the over 60-year-old group and either the under 45-year-old group (P  =  .137) or the 45- to 60-year-old group (P  =  .612).

There was no significant difference in mesial bone loss averages between month 24 and 36 month for any age group (P > .05). However, the mesial bone loss averages differed significantly between age groups at month 36 (P < .05). For instance, mesial bone loss rates of patients under 45 years of age were significantly lower than those of patients 46 to 60 years old (P  =  .036). There was no significant difference between the over 60-year-old group and either the under 45-year-old (P  =  .297) or the 46- to 60-year-old (P  =  .329) age groups.

The length and diameter of the implants were measured and their effects on MBL were analyzed statistically. There was no significant association between implant diameter (Table 3) or implant length (Table 4) and mesial and distal bone loss averages at month 6, 12, 24, and 36 (P > .05).

Table 3

The influence of implant diameter on marginal bone loss (mean values and SD in mm)

The influence of implant diameter on marginal bone loss (mean values and SD in mm)
The influence of implant diameter on marginal bone loss (mean values and SD in mm)
Table 4

The influence of implant length on marginal bone loss (mean values and SD in mm)

The influence of implant length on marginal bone loss (mean values and SD in mm)
The influence of implant length on marginal bone loss (mean values and SD in mm)

There was no significant association between the presence of cantilevers and mesial and distal bone loss averages at month 6 (P > .05). However, by month 12, the mesial (P < .05) and distal (P < .01) bone loss in the presence of cantilevers was significantly higher. Similarly, mesial and distal bone loss at month 24 was higher in the presence of cantilevers (P < .05). At month 36, the distal bone loss with cantilevers was higher (P < .05), whereas the mesial bone loss was not significantly affected by the presence of cantilevers (P > .05) (Table 5).

Table 5

The influence of cantilever on marginal bone loss (mean values and SD in mm)

The influence of cantilever on marginal bone loss (mean values and SD in mm)
The influence of cantilever on marginal bone loss (mean values and SD in mm)

There was no incidence of excessive bone loss at implants, and there was no recorded incident of peri-implant inflammation.

Discussion

The aim of this study was to examine the effect of several variables on MBL around dental implants supporting fixed restorations. In spite of lack of consensus on what factors affect MBL, the generally accepted guidelines for implant-induced bone loss since the late 1980s are less than 1.5 mm for the first year after implant loading and less than 0.2 mm for each additional year.35,36 However, other studies have suggested that these guidelines may be too lax, especially for young implant patients.15 Indeed, significant variability in MBL following dental implants has been reported. There are studies describing a mean crestal bone loss of 0.6 mm for the first year and 0.2 mm for the following years up to 36 months after implant loading.37,38 Mean annual losses of 0.03–0.05 mm have also been reported,38,39 and some studies have reported no change or even gains in bone level for individual implants.4042 Implant surface roughness has been shown to balance bone apposition and facilitate remodeling at the bone-implant interface, thereby minimizing crestal bone loss.4346 In our study, the bone loss rate was about half of that suggested by Albrektsson et al,35 possibly due to the use of rough surfaced implants.

No significant differences in marginal bone level changes were observed between male and female patients in the first 24 months (P > .05), consistent with results from a previous study.19 By month 36, however, female patients showed higher MBL than male patients (P < .05). Further studies observing a larger number of patients over a longer period of time are necessary to investigate this further.

According to a 4-year clinical follow-up study, elderly and young patients should expect similar levels of oral implant success.15 However, only implant survival was examined in this study, with no mention of the condition of the surrounding bone and soft tissues. While another study showed comparable bone level changes for younger and older patients,16 others report that bone and soft tissue healing after implant placement can be compromised by aging.17,18 In the present study, the MBL was found to proceed more slowly in patients under 45 years of age, possibly due to lower bone vascularity and healing potential in older individuals. Moreover, although clinicians generally expect more bone loss around dental implants in women of increased age due to hormonal changes, few clinical studies have examined the effect of gender on bone loss, and in one study, no gender differences were found.19 

Stress distribution in the surrounding bone has been reported to depend on the dimensions of the implant,37 as the implant directly affects the area of possible bone retention.8 It has been recommended that implants be as long and as wide as possible within the anatomic limitations of the patient.9 Although a number of investigators reported higher rates of loss in shorter implants,10,11 and the importance of implant length in sustaining the load of fixed restorations has been pointed out,21 there are also studies where implant length was reported to have little influence on the amount of stress in vertical loading6 and to have a smaller effect on stress distribution in the bone than the implant diameter.8,13 Indeed, finite element method (FEM) analysis of implants has shown stress reduction with increasing diameter,8 and radiographically measured bone loss for 4.0-mm diameter implants has been found to be less than for 3.5-mm implants.14 However, in the present study, neither the diameter (P > .05) nor the length (P > .05) of the implant caused a significant impact on MBL. Thus, once implant stability and successful osseointegration are established, MBL is not influenced by implant size. An important result of the present study was that in the presence of cantilevers, MBL after the first year had been significantly higher.

As well known, in partially dentate patients with bone deficits or limiting anatomic structures, such as expanded maxillary sinuses or a high mandibular canal, 2 options for treatment with fixed prostheses may be considered: bone augmentation or rehabilitation of the partially edentulous site with cantilever extensions (Figure 3). Mechanical studies have demonstrated that implant-supported cantilevers can induce stress concentration in the supporting alveolar bone,20,21 which might lead to excessive bone resorption under functional occlusal loads, especially around the implant shoulder, thus resulting in failure.2226 In a more recent FEM study,19 cantilevers longer than 9 mm were found to significantly contribute to bone stress. Another FEM study showed that the maximum von Mises stress occurred at the most distal bone/implant interface on the load side, and significantly increased with the length of the cantilever.28 Most studies using FEM analysis on cantilever extensions showed higher stress at implants adjacent to the cantilevers compared with implants distant to cantilevers. Highest stress values were found in the cortical bone at the surface of the implant facing the cantilever.20,29 On the other hand, several clinical studies have reported that cantilevers do not lead to a higher implant failure rate or to increased bone loss around supporting implants.3032 The outcomes of a recent systematic review showed that fixed partial dentures with cantilever extensions represented a predictable treatment modality.47 No major detrimental effects with respect to peri-implant tissues were observed at implants in the proximity of cantilever extensions. However, in another recent systematic review it was pointed out that the incorporation of cantilevers into implant-borne prostheses may be associated with a higher incidence of minor technical complications.48 

Figure 1.

Nonstandardized radiography used for bone level measurement.

Figure 1.

Nonstandardized radiography used for bone level measurement.

Figure 2.

Fixed restorations supported by implants.

Figure 2.

Fixed restorations supported by implants.

Figure 3.

Use of cantilever extensions due to anatomic limitations.

Figure 3.

Use of cantilever extensions due to anatomic limitations.

Radiography is important for routine clinical practice and in research projects evaluating dental implants. In particular, radiographic measurements of the marginal alveolar bone level change over time have been reported to be important parameters.49 Different methods have been used to assess bone height in the implant region, from simply counting the number of threads on screw-type implants to using a computer-based interactive image analysis system. Panoramic radiographs of the jaws and the teeth are widely used as a simple and fast method of evaluating the condition of the bone around implants.5055 A recent study showed that panoramic radiographs were as reliable as conventional intraoral radiographs when used to assess the point of bone attachment to implant threads.56 Thus, provided that the images are of high quality, the radiographic examination of choice for assessing the marginal bone level is the panoramic radiograph.55,57 Moreover, the interobserver agreement in marginal bone assessment from intraoral and panoramic radiographs was investigated in several studies.58,59 The authors concluded that reliability can be improved by one observer making multiple readings or by multiple observers making several independent readings. This approach limits the effects of single observers who may be outliers. In the present study, we have preferred to use 2 readings of 2 observers to increase the reliability.

The bone loss documented here measured the reduction of the bone levels at the mesial and distal sides of the implants and ignored the so-called saucerization of the crestal bone around the neck of the implants, since only 2-dimensional imaging was used. To obtain data on vestibular crestal bone changes, a 3-dimensional imaging technique such as volumetric tomography is necessary. Nevertheless, since panoramic radiographs have been reported to be a simple and reliable method of measuring bone level changes,5557 they were used in this study in the routine recall sessions of all patients and supplemented in cases of insufficient quality with intraoral radiographs. To ensure reliable bone loss measurements, a prosthodontist and a specialist in oral and maxillofacial radiology assessed the bone levels in the radiographs.

Although further studies observing a larger number of patients are necessary, our results prompt discussion about whether small diameter or short implants should be preferred over cantilevers when anatomic limitations make standard-sized implants impossible.

Conclusions

Within the limitations of this study the following conclusions were drawn:

  1. The size of the implants supporting fixed prostheses does not influence marginal bone levels after 36 months.

  2. MBL was higher in older patients at all recall sessions and in female patients after the second year.

  3. In the presence of cantilevers, MBL occurring after the first year in fixed restoration-supporting implants was higher.

Abbreviations

     
  • FEM

    finite element method

  •  
  • MBL

    marginal bone loss

References

References
1.
Esposito
M
,
Hirsh
JM
,
Lekholm
U
,
Thomsen
P
.
Biological factors contributing to failures of osseointegrated oral implants. (II). Success criteria and epidemiology
.
Eur J Oral Sci
.
1998
;
106
:
527
551
.
2.
Bryant
SR
,
Zarb
GA
.
Crestal bone loss proximal to oral implants in older and younger adults
.
J Prosthet Dent
.
2003
;
89
:
589
597
.
3.
Pilliar
RM
,
Deporter
DA
,
Watson
PA
,
Valiquette
N
.
Dental implant design: effect on bone remodeling
.
J Biomed Mater Res
.
1991
;
25
:
467
483
.
4.
Brunski
JB
.
Biomechanical considerations in dental implant design
.
Int J Oral Implantol
.
1988
;
5
:
31
34
.
5.
Holmgren
EP
,
Seckinger
RJ
,
Kilgren
LM
,
Mante
F
.
Evaluating parameters of osseointegrated dental implants using finite element analysis—a two-dimensional comparative study examining the effects of implant diameter, implant shape, and load direction
.
J Oral Implantol
.
1998
;
24
:
80
88
.
6.
Meijer
HJ
,
Kuiper
JH
,
Starmans
FJ
,
Bosman
F
.
Stress distribution around dental implants: influence of superstructure, length of implants, and height of mandible
.
J Prosthet Dent
.
1992
;
68
:
96
102
.
7.
Iplikcioglu
H
,
Akca
K
.
Comparative evaluation of the effect of diameter, length and number of implants supporting three-unit fixed partial prostheses on stress distribution in the bone
.
J Dent
.
2002
;
30
:
41
46
.
8.
Himmlova
L
,
Dostalova
T
,
Kacovsky
A
,
Konvickova
S
.
Influence of implant length and diameter on stress distribution: a finite element analysis
.
J Prosthet Dent
.
2004
;
91
:
20
25
.
9.
Winkler
S
,
Morris
HF
,
Ochi
S
,
Implant survival to 36 months as related to length and diameter
.
Ann Periodontol
.
2000
;
5
:
22
31
.
10.
Bahat
O
.
Treatment planning and placement of implants in the posterior maxillae: report of 732 consecutive Nobelpharma implants
.
Int J Oral Maxillofac Implants
.
1993
;
8
:
151
161
.
11.
van Steenberghe
D
,
Lekholm
U
,
Bolender
C
,
et al.
Applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: a prospective multicenter study on 558 fixtures
.
Int J Oral Maxillofac Implants
.
1990
;
5
:
272
281
.
12.
Block
MS
,
Kent
JN
,
Guerra
LR
.
Implants in Dentistry
.
Philadelphia, Pa
:
WB Saunders
;
1997
:
125
127
.
13.
Misch
CE
.
Divisions of available bone. Contemporary Implant Dentistry. 2nd ed
.
St Louis, Mo
:
Mosby
;
1999
:
91
94
.
14.
Ivanoff
CJ
,
Sennerby
L
,
Johansson
C
,
Rangert
B
,
Lekholm
U
.
Influence of implant diameters on the integration of screw implants. An experimental study in rabbits
.
Int J Oral Maxillofac Surg
.
1997
;
26
:
141
148
.
15.
Bryant
SR
,
Zarb
GA
.
Crestal bone loss proximal to oral implants in older and younger adults
.
J Prosthet Dent
.
2003
;
89
:
589
597
.
16.
Meijer
HJ
,
Batenburg
RH
,
Raghoebar
GM
.
Influence of patient age on the success rate of dental implants supporting an overdenture in an edentulous mandible: a 3-year prospective study
.
Int J Oral Maxillofac Implants
.
2001
;
16
:
522
526
.
17.
Cummings
SR
,
Kelsey
JL
,
Nevitt
MC
,
O'Dowd
KJ
.
Epidemiology of osteoporosis and osteoporotic fractures
.
Epidemiol Rev
.
1985
;
7
:
178
208
.
18.
Holm-Pedersen
P
,
Löe
H
.
Wound healing in the gingiva of young and old individuals
.
Scand J Dent Res
.
1991
;
79
:
40
53
.
19.
Norton
MR
.
Multiple single-tooth implant restorations in the posterior jaws: maintenance of marginal bone levels with reference to the implant-abutment microgap
.
Int J Oral Maxillofac Implants
.
2006
;
21
:
777
784
.
20.
Stegaroiu
R
,
Sato
T
,
Kusakari
H
,
Miyakawa
O
.
Influence of restoration type on stress distribution in bone around implants: a three-dimensional finite element analysis
.
Int J Oral Maxillofac Implants
.
1998
;
13
:
82
90
.
21.
Kunavisarut
C
,
Lang
LA
,
Stoner
BR
,
Felton
DA
.
Finite element analysis on dental implant-supported prostheses without passive fit
.
J Prosthodont
.
2002
;
11
:
30
40
.
22.
Adell
R
,
Lekholm
U
,
Rockler
B
,
Branemark
PI
.
A 15-year study of osseointegrated implants in the treatment of the edentulous jaw
.
Int J Oral Surg
.
1981
;
10
:
387
416
.
23.
Lozada
JL
,
Abbate
MF
,
Pizzarello
FA
,
James
RA
.
Comparative three dimensional analysis of two finite-element endosseous implant designs
.
J Oral Implantol
.
1994
;
20
:
315
321
.
24.
Branemark
PI
.
Osseointegration and its experimental background
.
J Prosthet Dent
.
1983
;
50
:
399
410
.
25.
Isidor
F
.
Loss of osseointegration caused by occlusal load of oral implants. A clinical and radiographic study in monkeys
.
Clin Oral Implants Res
.
1996
;
7
:
143
152
.
26.
Morgan
MJ
,
James
DF
,
Pilliar
RM
.
Fractures of the fixture component of an osseointegrated implant
.
Int J Oral Maxillofac Implants
.
1993
;
8
:
409
414
.
27.
Yokoyama
S
,
Wakabayashi
N
,
Shiota
M
,
Ohyama
T
.
The influence of implant location and length on stress distribution for three-unit implant-supported posterior cantilever fixed partial dentures
.
J Prosthet Dent
.
2004
;
9
:
234
240
.
28.
Sertgöz
A
,
Güvener
S
.
Finite element analysis of the effect of cantilever and implant length on stress distribution in an implant-supported fixed prosthesis
.
J Prosthet Dent
.
1996
;
76
:
165
169
.
29.
Akca
K
,
Iplikcioglu
H
.
Finite element stress analysis of the effect of short implant usage in place of cantilever extensions in mandibular posterior edentulism
.
J Oral Rehabil
.
2002
;
29
:
350
356
.
30.
Romeo
E
,
Lops
D
,
Margutti
E
,
Ghisolfi
M
,
Chiapasco
M
,
Vogel
G
.
Implant-supported fixed cantilever prostheses in partially edentulous arches. A seven-year prospective study
.
Clin Oral Implants Res
.
2003
;
14
:
303
311
.
31.
Wennstrom
J
,
Zurdo
J
,
Karlsson
S
,
Ekestubbe
A
,
Grondahl
K
,
Lindhe
J
.
Bone level change at implant-supported fixed partial dentures with and without cantilever extension after 5 years in function
.
J Clin Periodontol
.
2004
;
31
:
1077
1083
.
32.
Halg
GA
,
Schmid
J
,
Hammerle
CHF
.
Bone level changes at implants supporting crowns or fixed partial dentures with or without cantilevers
.
Clin Oral Implants Res
.
2008
;
19
:
983
990
.
33.
Batenburg
RH
,
Meijer
HJ
,
Geraets
WG
,
van der Stelt
PF
.
Radiographic assessment of changes in marginal bone around endosseous implants supporting mandibular overdentures
.
Dentomaxillofac Radiol
.
1998
;
27
:
221
224
.
34.
Bittar-Cortez
JA
,
Passeri
LA
,
de Almeida
SM
,
Haiter-Neto
F
.
Comparison of peri-implant bone level assessment in digitized conventional radiographs and digital subtraction images
.
Dentomaxillofac Radiol
.
2006
;
35
:
258
262
.
35.
Albrektsson
T
,
Zarb
G
,
Worthington
P
,
Eriksson
AR
.
The long-term efficacy of currently used dental implants: a review and proposed criteria for success
.
Int J Oral Maxillofac Implants
.
1986
;
1
:
11
25
.
36.
Smith
DE
,
Zarb
G
.
Criteria for success of osseointegrated endosseous implants
.
J Prosthet Dent
.
1989
;
62
:
567
572
.
37.
Weber
HP
,
Crohin
CC
,
Fiorellini
JP
.
A 5-year prospective clinical and radiographic study of non-submerged dental implants
.
Clin Oral Implants Res
.
2000
;
11
:
144
153
.
38.
Buser
D
,
Nydegger
T
,
Hirt
HP
,
Cochran
DL
,
Nolte
LP
.
Removal torque values of titanium implants in the maxilla of miniature pigs
.
Int J Oral Maxillofac Implants
.
1998
;
13
:
611
619
.
39.
Mericske-Stern
R
,
Steinlin Schaener
T
,
Marti
P
,
Geering
AH
.
Peri-implant mucosal aspects of ITI implants supporting overdentures. A five-year longitudinal study
.
Clin Oral Implants Res
.
1994
;
5
:
9
18
.
40.
Mericske-Stern
R
,
Aerni
D
,
Buser
D
,
Geering
AH
.
Long-term evaluation of non-submerged hollow cylinder implants
.
Clin Oral Implants Res
.
2001
;
12
:
252
259
.
41.
Goodacre
CJ
,
Kan
JYK
,
Rungcharassaeng
K
.
Clinical complications of osseointegrated implants
.
J Prosthet Dent
.
1999
;
81
:
537
552
.
42.
Mericske-Stern
R
,
Grütter
L
,
Rösch
R
,
Mericske
E
.
Clinical evaluation and prosthetic complications of single tooth replacements by non-submerged implants
.
Clin Oral Implants Res
.
2001
;
12
:
309
318
.
43.
Cochran
DL
,
Nummikoski
PV
,
Higginbottom
FL
,
Hermann
JS
,
Makins
SR
,
Buser
D
.
Evaluation of an endosseous titanium implant with a sandblasted and acid-etched surface in the canine mandible. Radiographic results
.
Clin Oral Implants Res
.
1996
;
7
:
240
252
.
44.
Norton
MR
.
Marginal bone levels at single tooth implants with a conical fixture design. The influence of surface macro and microstructure
.
Clin Oral Implants Res
.
1998
;
9
:
91
99
.
45.
Wiskott
HW
,
Belser
UC
.
Lack of integration of smooth titanium surfaces: a working hypothesis based on strains generated in the surrounding bone [review]
.
Clin Oral Implants Res
.
1999
;
10
:
429
444
.
46.
Warren
P
,
Chaffee
N
,
Felton
DA
,
Cooper
LF
.
A retrospective radiographic analysis of bone loss following placement of TiO2 grit-blasted implants in the posterior maxilla and mandible
.
Int J Oral Maxillofac Implants
.
2002
;
17
:
399
404
.
47.
Aglietta
M
,
Siciliano
VI
,
Zwahlen
M
,
et al.
A systematic review of the survival and complication rates of implant supported fixed dental prostheses with cantilever extensions after an observation period of at least 5 years
.
Clin Oral Implants Res
.
2009
;
20
:
441
451
.
48.
Zurdo
J
,
Romão
C
,
Wennström
JL
.
Survival and complication rates of implant-supported fixed partial dentures with cantilevers: a systematic review
.
Clin Oral Implants Res
.
2009
;
204
:
59
66
.
49.
Chaytor
DV
,
Zarb
GA
,
Schmitt
A
,
Lewis
DW
.
The longitudinal effectiveness of osseointegrated dental implants. The Toronto study: bone level changes
.
Int J Periodontics Restorative Dent
.
1991
;
11
:
113
125
.
50.
Donatsky
O
.
Osseointegrated dental implants with ball attachments supporting overdentures in patients with mandibular alveolar ridge atrophy
.
Int J Oral Maxillofac Implants
.
1993
;
8
:
162
166
.
51.
Boerrigter
EM
,
Van Oort
RP
,
Raghoebar
GM
,
Stegenga
B
,
Schoen
PJ
,
Boering
G
.
A controlled clinical trial of implant-retained mandibular overdentures. Clinical aspects
.
J Oral Rehabil
.
1997
;
24
:
182
190
.
52.
Versteegh
PM
,
Van Beek
GJ
,
Slagter
AP
,
Ottervanger
JP
.
Clinical evaluation of mandibular overdentures supported by multiple-bar fabrication: a follow-up study of two implant systems
.
Int J Oral Maxillofac Implants
.
1995
;
10
:
595
603
.
53.
Spiekermann
H
,
Jansen
VK
,
Richter
EJ
.
A 10-year follow-up study of IMZ and TPS implants in the edentulous mandible using bar-retained overdentures
.
Int J Oral Maxillofac Implants
.
1995
;
10
:
231
243
.
54.
Leimola-Virtanen
R
,
Peltola
J
,
Oksala
E
,
Helenius
H
,
Aponen
RP
.
ITI titanium plasma-sprayed screw implants in the treatment of edentulous mandibles: a follow-up study of 39 patients
.
Int J Oral Maxillofac Implants
.
1995
;
10
:
373
378
.
55.
Åkesson
L
,
Håkansson
J
,
Rohlin
M
,
Zöger
B
.
An evaluation of image quality for the assessment of the marginal bone level in panoramic radiography
.
Swed Dent J
.
1992
;
17
:
9
21
.
56.
Kullman
L
,
Al-Asfour
A
,
Zetterqvist
L
,
Andersson
L
.
Comparison of radiographic bone height assessments in panoramic and intraoral radiographs of implant patients
.
Int J Oral Maxillofac Implants
.
2007
;
22
:
96
100
.
57.
Persson
RE
,
Tzannetou
S
,
Feloutzis
AG
,
Brägger
U
,
Persson
GR
,
Lang
NP
.
Comparison between panoramic and intraoral radiographs for the assessment of alveolar bone levels in a periodontal maintenance population
.
J Clin Periodontol
.
2003
;
30
:
833
839
.
58.
Molander
B
,
Ahlqwist
M
,
Gröndahl
HG
,
Hollender
L
.
Agreement between panoramic and intra-oral radiography in the assessment of marginal bone height
.
Dentomaxillofac Radiol
.
1991
;
20
:
155
160
.
59.
Pikner
SS
.
Radiographic follow-up analysis of Branemark dental implants
.
Swed Dent J Suppl
.
2008
;
194
:
5
69, 2
.