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The effect of vertical level discrepancy of adjacent dental implants on crestal bone resorption: a retrospective radiographic analysis
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The effect of vertical level discrepancy of adjacent dental implants on crestal bone resorption: a retrospective radiographic analysis
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Content
The effect of vertical level discrepancy of
adjacent dental implants on crestal bone
resorption: A retrospective radiographic
analysis
Vahid Khoshkam DDS
Master of Science in Craniofacial Biology
candidate
Mentor: Homayoun H. Zadeh DDS, PhD
August 2017
2
Table of Contents
Figure legend 3
Abstract 4
Introduction 7
Materials and methods
Study population
Data collection
Radiographic analysis
Statistical Analysis
9
9
10
11
12
Results 13
Discussion 15
Conclusion 20
References 22
Figures
Tables
27
35
3
Figure legends
Figure 1. Schematic diagram demonstrating the evaluated
radiographic parameters
Figure 2. Pearson Correlation test for all inter-implant horizontal
distances from placement to the last follow-up
Figure 3. Pearson correlation test for inter-implant horizontal
distances of 2mm or less from placement to the last follow-up
Figure 4. Pearson correlation test for inter-implant horizontal
distances of 3 mm or less from placement to the last follow-up
Figure 5. Pearson correlation test for inter-implant horizontal
distances of 4 mm or less from placement to the last follow-up
Figure 6. Pearson correlation test for inter-implant horizontal
distances of 3 mm or more from placement to the last follow-up
Figure 7. Pearson correlation test for inter-implant horizontal
distances of 4 mm or less from placement to the last follow-up
Figure 8. Pearson correlation test for inter-implant horizontal
distances of 3 mm or less and vertical discrepancy of one mm or
more from placement to the last follow-up
4
Abstract
Introduction: The purpose of the present study was to investigate
the effect of relative vertical and horizontal position of adjacent
implants on peri-implant marginal bone alterations.
Materials & methods: Radiographic records of patients who had
received multiple adjacent dental implants at two centers were
examined. Inclusion criteria consisted of: 1) multiple adjacent dental
implants restored with splinted or non-splinted restorations, 2)
availability of diagnostic quality radiographs at time of implant
installation, prosthesis connection and a minimum of one year post-
loading follow-up. Parameters of interest included: horizontal
distance (HID) and vertical level discrepancy (VLD) between the
platform of adjacent implants, distance between the implant platform
and bone level at the first implant bone contact at the mesial and
distal surfaces of the implants designated as bone level. Pearson
correlation coefficient was calculated to determine the relationship
between implant proximity measurements and marginal bone loss
(MBL). In order to determine the effect of implant position on
marginal bone level, the data were stratified according to different
5
horizontal and vertical subgroups. The data were analyzed with
respect to coronal and apical implant units and their relative
horizontal distance. The results were presented as mean values ±
standard deviations. Two-tailed independent student t test with alpha
value of .05 was used to evaluate the difference in mean marginal
bone level between the compared groups. Pearson correlation test
was run to investigate the possible correlation between the vertical
discrepancy and MBL.
Results: 65 patients with the mean age of 59 ± 8.9 years having 153
implants with the mean follow up period of 57.2 ± 0.3 months
fulfilled the inclusion criteria. The mean VLD was 1.44 ± 0.86 mm
and the mean horizontal distance between the implants was 3.36 ±
1.49 mm. When horizontal inter-implant distance was less than 3
mm, from the placement time to prosthesis installation, the mean
MBL for the coronal and apical implants were 1.53 ± 1.04 mm and
0.99 ± 00.93 mm , respectively. The MBL of the coronal and apical
implants in this category were statistically significant (P=0.04).
Among implants with HID < 3mm, from implant installation to the
last follow up, the coronal (MBL=1.71 ± 1.14 mm) and apical
(MBL= 1.05 ± 0.87mm) implants exhibited statistical significant
6
different MBL (P=0.009).
Among implants with HID<3 mm and VLD> 1 mm, MBL for the
coronal (2.03 ± 1.25 mm) and apical implants (1.01 ± 0.84 mm) from
implant placement to the last follow-up were statistically
significantly different (P=0.004). When examining VLD and MBL
on a continuous scale, Pearson correlation test demonstrated a
positive correlation between these two parameters from implant
placement to the last follow-up (R
2
=0.29; P=0.009).
Conclusion: Vertical level discrepancy between the platforms of
adjacent implants was associated with significant MBL changes
around the coronal implant. This association was limited to implants
with horizontal inter-implant distance of less than 3 mm.
7
Introduction
Decades after the introduction of osseointegrated dental implants
(Branemark et al., 1969), researchers have been striving to promote
the longevity of implant supported restorations. The stability of peri-
implant hard and soft tissues is one of the most critical factors for
long-term implant maintenance, function and esthetics.
Pre-clinical studies have demonstrated that following implant
installation; a soft tissue seal of about 3-4mm will form around
implants (Abrahamsson et al., 1996; Berglundh and Lindhe, 1996).
Loss of crestal bone in the interproximal area often leads to esthetic
and eventually functional problems that include but are not limited to
pocket formation, reduction in the papillary height, poor embrasure
morphology and improper emergence profile (Cardaropoli et al.,
2003). Changes in the peri-implant bone level may jeopardize peri-
implant soft tissue seal, and consequently may have a negative
impact on the long-term outcomes of implant therapy.
Given the finding that the bone crest was more apically located at
sites with ≤3mm inter-implant distance, Tarnow and coworkers
(Tarnow et al., 2000) suggested that a horizontal inter-implant
distance of at least 3 mm should be observed. However; several
8
reports have shown conflicting results when investigating the impact
of inter-implant distance on peri-implant bone topography. (Scarano
et al., 2004) reported a negative effect of the reduced inter-implant
distance on mid-proximal crestal bone levels. On the other hand,
Koutouzis et al. (2015) did not find such a negative relationship.
A pre-clinical study (Hermann et al., 2000) demonstrated that the
vertical position of unloaded single implants relative to the alveolar
crest level predicts crestal bone changes in the early phases of healing
following implant placement. A recent retrospective study showed
that although placement of the implants in the subcrestal position will
minimize the odds of having exposed implant surface; the pattern of
remodeling is similar to supra- or equi-crestal placement (Ercoli et
al., 2017). To date, the information regarding such effects in multiple
unit implant restorations before and after loading is not available.
Additionally, the combined effect of horizontal and vertical inter-unit
distances on marginal bone loss has not been thoroughly investigated.
A retrospective analysis (Cardaropoli et al., 2003) demonstrated that
both vertical and horizontal distances in implant positions might
influence bone alterations in the inter-implant area during the first 3
years of loading. However, all the implants in that study were
9
Branemark machined surface implants that are no longer available in
the market and hence the results of that study cannot be directly
extrapolated to the implants with rough or moderately rough surface.
Furthermore, the abovementioned study (Cardaropoli et al., 2003)
only evaluated splinted three -unit implant fixed partial dentures.
The aim of the present retrospective study was to evaluate the
association between inter-implant spatial relationship and
interproximal MBL.
Materials and methods
Study Population
The institutional review board of the University of Southern
California approved the protocol of this study (HS-15-00427). A
query was run to identify patients who were treated at the University
of Southern California and a private periodontal practice with 2 or 3
adjacent dental implants. Radiographic records of the patients were
evaluated to ensure fulfillment of pre-determined inclusion and
exclusion criteria. Inclusion criteria were as follows:
1) Multiple adjacent dental implants restored with splinted or non-
splinted fixed restorations
2) Availability of diagnostic quality radiographs at the time of
10
implant placement, prosthesis installation and at least one-year post
loading
3) The implants had to be placed in the maxillary or mandibular
posterior segments
4) Screw type rough surface implants with an internal or external
connection placed equicrestally, supracrestally or subcrestally.
Exclusion criteria were as following:
1) Implants that were placed in fresh socket or immediately loaded
2) Adjacent implants placed at different times
3) Restorations with cantilever extension
4) Any grafting procedure at the time of implant placement
5) Radiographs with indiscernible implant threads
6) Heavy smoker patients (More than 10 cigarettes daily)
Data Collection
Available electronic records of the patients at the two centers were
completely reviewed to identify subjects that received 2 or 3 implants
at the same time. After identification of the possible eligible patients,
their charts and radiographs were reviewed for conformance to the
inclusion and exclusion criteria. Additional data collected included
type of the implants, type of the restoration (cemented or screw
11
retained), and splinted versus non-splinted.
Radiographic analysis
Radiographs were evaluated and analyzed with Adobe Photoshop CC
2015 (Adobe Systems Incorporated, San Jose, CA, USA) on a
MacBook Pro laptop with built in Intel Iris graphics card with a 13-
inch 2560 x 1600 retina display monitor. Known distances e.g.
implant lengths and thread pitch were used to calibrate the
radiographs for linear measurements. Landmarks of interest were as
follows:
a) The implant platform
b) First radiographic bone-implant contact
The following parameters were measured:
i) MLB was measured form the implant platform to the first
bone-implant contact. If the implant was placed subcrestally
the value was calculated as zero. This measurement was
performed in mesial and distal of the implants.
ii) Vertical implant discrepancy (VID) defined as the vertical
distance between the platforms of the adjacent implants. If
the implants were at the same level this measurement was
calculated as zero.
12
iii) Horizontal inter-implant distance (HID) defined as the
horizontal distance between the platforms of the adjacent
implants (Figure1).
Statistical analysis
The implants were divided into either coronal or apical implants
depending on the relationship between adjacent implants. The value
of vertical discrepancy for the coronal implants was defined as a
positive numeric value while for the apical implants, these numbers
had negative values. In order to determine the association between
implant position and MBL, the data were categorized into different
horizontal and vertical subgroups. Based on the horizontal inter-
implant distances, data were stratified into two groups: HID > 3 mm
and HID < 3mm. Two-tailed independent Student T-test with alpha
value of 0.05 was run to evaluate the difference in mean marginal
bone level changes between the two groups in three different time
periods as follows: from the implant insertion time to the time of
prosthesis installation, from the time of the prosthesis installation to
the last follow-up and from the time of implant placement to the last
follow-up. All statistical analyses were performed with SPSS
Statistics for Mac (Version 24, IBM Corp, New York, USA). The
13
results were presented as mean values ± standard deviations. Pearson
correlation test was run to investigate possible correlation between
the vertical and horizontal distances and marginal bone loss.
Results
Sixty-five patients, who had received 153 implants fulfilled the
inclusion and exclusion criteria (Table 1). Patient population
consisted of 39 women (60%) and 26 men with a mean age of 59 ±
8.9 years. Five patients (7.6%) were light smokers.
Analyzed implants consisted of seven different implant systems, of
which, 58.8% of the implants were placed in the mandible (Table 2).
Mean follow-up period was 57.2 ± 30 months, ranging from 18 to
144 months after implant installation.
The mean vertical discrepancy between the platforms of adjacent
implants was 1.44 ± 0.86 mm, ranging from 0 to 3.79 mm. The mean
horizontal inter- implant distance was 3.36 ±1.49 mm, ranging
between 1.06 to 7.32 mm. Mean marginal bone loss for the inter-unit
implant surfaces from the implant placement to the final follow-up
was 1.31 ± 1.07 mm (Table 3).
Regardless of the vertical discrepancy between the implants and
based on different horizontal inter-implant distance subgroups,
14
corresponding marginal bone loss from the placement to prosthesis
installation, from prosthesis installation to the last follow up and
from placement to the last follow up calculated (Table 4).
In separate analyses, the inter-unit surfaces were divided into
different sub-groups based on the horizontal inter-unit distances of
less- and more than 3 mm. Corresponding marginal bone loss for the
coronal and apical implants is shown in table 5. Likewise, in the
presence of horizontal inter-unit distance of less and more than 3
mm, in all three time periods, the corresponding MBL when the
vertical discrepancy was more than 1mm was calculated that in
shown in table 6.
When all the implants were divided based on horizontal inter-implant
distances of more or less than 2 and 3 mm, there was no significant
difference at any time period between the groups in terms of marginal
bone loss (Table 7). While comparison of marginal bone loss for
coronal and apical inter-unit surfaces in different time periods based
on horizontal inter-unit distances of less than 2 mm did not reveal
any significant differences (Table 8), the difference between the
marginal bone loss of coronal and apical implants when the
horizontal inter-unit distance was less than 3 mm was significant
15
from the placement to prosthesis installation and from the placement
to final follow-up (Table 9). Moreover, in the presence of horizontal
distance of less than 3 mm, the coronal implants with more than 1
mm vertical discrepancy had significant bone loss at all time periods
compared to the apical implants (Table 9).
The results of Pearson correlation tests are depicted in Figures 2-8.
Positive correlation (R2=0.29; P=0.009) was found between the
vertical discrepancy and MBL from implant placement to the last
follow-up (Figure 2). Significant correlation was observed between
vertical implant discrepancy and MBL from the placement to the last
follow-up when the horizontal distance was 3 mm or less (R2=0.49;
p=0.02) as depicted in figure 8.
When the horizontal inter implant distance was >4 mm, no
correlation between vertical discrepancy and MBL was found (Figure
7).
Discussion
The null hypothesis tested in the present study was that the placement
of the adjacent implants is not associated with peri-implant marginal
bone loss. This null hypothesis was rejected as the results of this
study clearly indicate that placing an implant in a coronal position
16
relative to the adjacent implant was associated with increased risk of
marginal bone loss. Although the correlation test overall
demonstrated a positive correlation between the vertical discrepancy
between adjacent implants and marginal bone loss from the
placement to the last follow up period on the side of the coronal
implant, this finding was found to be dependent to horizontal inter-
implant distance. To best of our knowledge, this is the first
demonstration of the relationship between both vertical and
horizontal spatial relationship of adjacent implants and MBL. A
previous study that analyzed 35 machine surfaced implant supported
restorations (Cardaropoli et al., 2003) showed that both vertical and
horizontal differences in implant positions might have an impact on
bone level changes in the inter-implant area during the first 3 years
however they did not specify which side is at risk.
All of the patients included had received implant at least 4 months
post- extractions to avoid post-extraction alveolar bone changes
(Schropp et al., 2003). All of the patients had received maintenance
therapy at the period between the implant placement and the last
follow-up with a maximum time of 6 months intervals (Monje et al.,
2016).
17
During the mean follow up period of the study (57.2 ± 30 months),
the mean marginal bone loss for the total inter-implant surfaces was
1.31±1.07 mm, a magnitude of bone loss that is not in agreement
with criteria defined for success (Albrektsson et al., 1986). Given the
amount of mean marginal bone loss recorded from the loading time
to the last follow-up (0.27±0.61mm), it could be realized that with
vertical implant discrepancy, most of he marginal bone loss occurred
before the prosthesis connection. This is accordance with previous
data showing that the largest amount of bone loss occurs during the
initial period following implant installation and before abutment
connection (Berglundh et al., 2005).
The findings of this retrospective analysis demonstrated that
regardless of the implant system, the horizontal inter-unit distance by
itself was not a predictor for marginal bone loss. This finding is in
agreement with previous reports (Chang and Wennstrom, 2010;
Koutouzis et al., 2015; Novaes et al., 2006; Papalexiou et al., 2006;
Scarano et al., 2004). The present data showed that among implants
with horizontal inter-implant distance < 3 mm, coronal implants
exhibited greater MBL from the placement to prosthesis installation
18
and from the placement to the last follow-up. The reason for this
phenomenon is not fully understood and will require further
investigation.
The reason why implants are typically are placed with discrepant
platform location is because of the alveolar bone topography, which
is often irregular in contour. In some cases, at the time of placement
the inter-proximal surface of the coronal implant is not totally placed
subcrestally. This in turn will result in exposure of the implant
surface to the oral cavity that could facilitate more plaque
accumulation. This might partially explain the reason for the
significant bone loss on the coronal implants compared to the apical
implants when the discrepancy was more than 1 mm the at all 3 time
periods. The implants with high vertical discrepancy and reduced
inter-implant distance showed significant bone loss even post implant
loading.
In order to prevent placement of the implants with increased vertical
discrepancy and decreased horizontal inter-implant distance some
treatment strategies could possibly minimize this risk. Based on the
results of our study, the negative effect of vertical implant
discrepancy on marginal bone loss is not significant when the
19
horizontal inter-implant distance is 4 mm or more.
According to our findings, it can be recommended that, in cases with
unavoidable vertical discrepancy, the adjacent implant should be
placed at least 4 mm apart. When there is severe resorption next to a
natural tooth, it is prudent to place the implant far from the tooth in
order to avoid high vertical distance from the implant platform to the
CEJ of the adjacent tooth (Mailoa et al., 2015). Furthermore, this will
prevent placement of the implant in the sloped area of the ridge,
reducing the possibility of vertical discrepancy with the adjacent
distal implant. The gap between the mesial implant and the natural
tooth could be filled with the cantilever extension of the restoration
(Romeo and Storelli, 2012). Performing vertical ridge augmentation
before implant placement is another option; however, it may increase
the patient morbidity and the cost of the treatment (Esposito et al.,
2014).
Some limitations of the present study must be addressed. First, the
analyzed radiographs were not standardized, potentially leading to
measurement errors. Calibrating the radiographs using known
implant dimensions minimized this limitation. Second, since this was
a retrospective study on patients who were treated routinely, the
20
protocol was not standardized. It was not possible to investigate all
the confounding factors including but not limited to initial ridge
width, tissue thickness, surgical technique etc. It is noteworthy that
conducting a prospective study to investigate the effect of vertical
discrepancy of the adjacent implants on marginal bone loss is not
ethical, since it will require placement of implants that may have
unfavorable outcome. Therefore, retrospective analysis is the only
method of investigating this hypothesis in a clinical study; hence,
further pre-clinical research is warranted to validate the findings of
the present retrospective study.
Conclusions
Within the limits of the present study, following conclusions could be
drawn:
• There was a positive correlation between the vertical
discrepancy of the adjacent implants and marginal bone loss
on the coronal implant.
• The negative effect of vertical discrepancy of the adjacent
implant demonstrated significant marginal bone loss on the
coronal implant when the horizontal inter-implant distance
was less than 3 mm.
21
• As a result of vertical discrepancy between the platforms of
the adjacent implants, most of the marginal bone loss of the
coronal implant took place before loading of the implants.
• In clinical situations with inevitable vertical discrepancy
between the adjacent implants, placement of the implants at
least 4mm apart may reduce the negative effects of such
vertical discrepancy.
22
References
Abrahamsson, I., Berglundh, T., Wennstrom, J., and Lindhe, J.
(1996). The peri-implant hard and soft tissues at different implant
systems. A comparative study in the dog. Clinical oral implants
research 7, 212-219.
Albrektsson, T., Zarb, G., Worthington, P., and Eriksson, A.R.
(1986). The long-term efficacy of currently used dental implants: a
review and proposed criteria of success. The International journal of
oral & maxillofacial implants 1, 11-25.
Berglundh, T., Abrahamsson, I., and Lindhe, J. (2005). Bone
reactions to longstanding functional load at implants: an experimental
study in dogs. Journal of clinical periodontology 32, 925-932.
Berglundh, T., and Lindhe, J. (1996). Dimension of the periimplant
mucosa. Biological width revisited. Journal of clinical
periodontology 23, 971-973.
Branemark, P.I., Adell, R., Breine, U., Hansson, B.O., Lindstrom, J.,
and Ohlsson, A. (1969). Intra-osseous anchorage of dental
prostheses. I. Experimental studies. Scandinavian journal of plastic
and reconstructive surgery 3, 81-100.
23
Cardaropoli, G., Wennstrom, J.L., and Lekholm, U. (2003). Peri-
implant bone alterations in relation to inter-unit distances. A 3-year
retrospective study. Clinical oral implants research 14, 430-436.
Chang, M., and Wennstrom, J.L. (2010). Bone alterations at implant-
supported FDPs in relation to inter-unit distances: a 5-year
radiographic study. Clinical oral implants research 21, 735-740.
Ercoli, C., Jammal, G., Buyers, M., Tsigarida, A.A., Chochlidakis,
K.M., Feng, C., and Caton, J. (2017). The Influence of Apico-
Coronal Implant Placement on Post-Surgical Crestal Bone Loss in
Humans. Journal of periodontology, 1-14.
Esposito, M., Pistilli, R., Barausse, C., and Felice, P. (2014). Three-
year results from a randomised controlled trial comparing prostheses
supported by 5-mm long implants or by longer implants in
augmented bone in posterior atrophic edentulous jaws. European
journal of oral implantology 7, 383-395.
Hermann, J.S., Buser, D., Schenk, R.K., and Cochran, D.L. (2000).
Crestal bone changes around titanium implants. A histometric
evaluation of unloaded non-submerged and submerged implants in
the canine mandible. Journal of periodontology 71, 1412-1424.
24
Koutouzis, T., Neiva, R., Lipton, D., and Lundgren, T. (2015). The
Effect of Interimplant Distance on Peri-implant Bone and Soft Tissue
Dimensional Changes: A Nonrandomized, Prospective, 2-Year
Follow-up Study. The International journal of oral & maxillofacial
implants 30, 900-908.
Mailoa, J., Fu, J.H., Chan, H.L., Khoshkam, V., Li, J., and Wang,
H.L. (2015). The Effect of Vertical Implant Position in Relation to
Adjacent Teeth on Marginal Bone Loss in Posterior Arches: A
Retrospective Study. The International journal of oral &
maxillofacial implants 30, 931-936.
Monje, A., Aranda, L., Diaz, K.T., Alarcon, M.A., Bagramian, R.A.,
Wang, H.L., and Catena, A. (2016). Impact of Maintenance Therapy
for the Prevention of Peri-implant Diseases: A Systematic Review
and Meta-analysis. Journal of dental research 95, 372-379.
Novaes, A.B., Jr., de Oliveira, R.R., Muglia, V.A., Papalexiou, V.,
and Taba, M. (2006). The effects of interimplant distances on papilla
formation and crestal resorption in implants with a morse cone
connection and a platform switch: a histomorphometric study in
dogs. Journal of periodontology 77, 1839-1849.
25
Papalexiou, V., Novaes, A.B., Jr., Ribeiro, R.F., Muglia, V., and
Oliveira, R.R. (2006). Influence of the interimplant distance on
crestal bone resorption and bone density: a histomorphometric study
in dogs. Journal of periodontology 77, 614-621.
Romeo, E., and Storelli, S. (2012). Systematic review of the survival
rate and the biological, technical, and aesthetic complications of fixed
dental prostheses with cantilevers on implants reported in
longitudinal studies with a mean of 5 years follow-up. Clinical oral
implants research 23 Suppl 6, 39-49.
Scarano, A., Assenza, B., Piattelli, M., Thams, U., San Roman, F.,
Favero, G.A., and Piattelli, A. (2004). Interimplant distance and
crestal bone resorption: a histologic study in the canine mandible.
Clin Implant Dent Relat Res 6, 150-156.
Schropp, L., Wenzel, A., Kostopoulos, L., and Karring, T. (2003).
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26
Tarnow, D.P., Cho, S.C., and Wallace, S.S. (2000). The effect of
inter-implant distance on the height of inter-implant bone crest.
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27
Figures
Figure 1.Schematic diagram demonstrating the evaluated
radiographic parameters
A: daIBC distance from the coronal implant platform to the fist bone to
implant contact in the distal B: VID vertical inter-implant distance C:HID
Horizontal inter-implant distance , D:mpIBC distance from the apical
implant platform to the first bone to implant contact in the mesial
28
Figure 2. Pearson Correlation test for all inter-implant distances
from placement to the last follow-up
29
Figure 3. Pearson correlation test for horizontal inter-implant
distances of 2mm or less from placement to the last follow-up
30
Figure 4. Pearson Correlation test for horizontal inter-implant
distances of 3mm or less from placement to the last follow-up
31
Figure 5. Pearson correlation test for the inter-implant distances
of less than 4 mm from placement to the last follow-up
32
Figure 6. Pearson correlation test for the inter-implant distances
of 3mm and more from placement to the last follow-up
33
Figure 7. Pearson correlation test for the inter-implant distances
of 4 mm and more from placement to the last follow-up
34
Figure 8. Correlation between the vertical implant discrepancy of
more than 1 mm and marginal bone loss less on the coronal
implant when the horizontal inter-implant distance was less than
3 mm
35
Tables
Description of the study sample
No. Of the patients 65
Mean age/range (years) 59 ± 8.9
Range: (21-78)
Sex ratio (male/female) 39 women (60%)
26 men
Follow-up period (months) 57.2 ± 30
Range:(18 to 144)
No. Sites 72
Posterior Mandible: 44
Posterior maxilla: 28
No. Implants 153
No. Implant-implant units 80
Table 1.Study`s Patient demographic data
36
Implant system distribution
Implant system No. %
3i internal 45 29.4
3i external 14 9.1
Astra Tech 76 49.6
Nobel Biocare
replace select
6 3.9
Nobel Biocare
speedy groovy
5 3.2
Nobel active 2 1.3
Branemark MKIIII 5 3.2
Total 153 100
Table 2.Distribution of the implant systems investigated
37
Mean horizontal inter-implant distance Mean vertical implant discrepancy
3.36 ±1.49mm 1.44 ± 0.86mm
Marginal bone loss of total inter-implant surfaces
Placement to final Placement to prosthesis Prosthesis to final
1.31±1.07mm 1.10±0.95mm 0.27±0.61mm
Table 3.Mean horizontal inter-unit distance and vertical implant
discrepancy and marginal bone loss (Mean ± SD) for total inter-
unit surfaces
Horizontal inter-implant distance < 2mm
Placement to final Placement to prosthesis Prosthesis to final
0.99 ±0.84mm 1.00 ±0.86mm 0.08 ±0.34mm
Horizontal inter-implant distance < 3mm
Placement to final Placement to prosthesis Prosthesis to final
1.38 ±1.04mm 1.24 ±0.99mm 0.22 ±0.39mm
Horizontal inter-implant distance > 2mm
Placement to final Placement to prosthesis Prosthesis to final
1.37 ±1.10mm 1.11 ±0.97mm 0.30 ±0.64mm
Horizontal inter-implant distance > 3mm
Placement to final Placement to prosthesis Prosthesis to final
1.27 ±1.11mm 1.01 ±0.93mm 0.31 ±0.73mm
Table 4.Marginal bone loss (Mean ± SD) for combined inter-
implant Surfaces based on horizontal inter-unit distances
38
Coronal implants when horizontal inter implant distance<3mm
Placement to final Placement to prosthesis Prosthesis to final
1.75±1.14mm 1.53±1.04mm 0.31±0.31mm
Apical implants when horizontal inter implant distance<3mm
Placement to final Placement to prosthesis Prosthesis to final
1.05±0.87mm 0.99±0.93mm 0.16±0.44mm
Table 5.Marginal bone loss (Mean ± SD) for inter-implant
surfaces based on horizontal inter-unit distances in cases with
vertical implant discrepancy
Horizontal inter-implant distance <3mm
Vertical implant discrepancy>1mm apical
Placement to final Placement to prosthesis Prosthesis to final
1.01±0.84mm 0.98±0.88mm 0.07±0.35mm
Horizontal inter-implant distance <3mm
Vertical implant discrepancy >1mm coronal
Placement to final Placement to prosthesis Prosthesis to final
2.03±1.25mm 1.78±0.92mm 0.35±0.35mm
Table 6.Marginal bone loss (Mean ± SD) for inter-implant
coronal and apical surfaces based on horizontal inter-unit
distances in cases with more than 1mm vertical implant
discrepancy
39
Horizontal inter-implant distance (>2mm versus<2 mm)
Placement to final Placement to prosthesis Prosthesis to final
P=0.124 P=0.628 P=0.129
Horizontal inter-implant distance (>3mm versus<3 mm)
Placement to final Placement to prosthesis Prosthesis to final
P=0.538 P=0.136 P=0.397
Table 7. Comparison of marginal bone loss for total inter-unit
surfaces in different time periods based on horizontal inter-unit
distances
Horizontal inter-implant distance <2
Coronal versus apical inter-unit surface
Placement to final Placement to prosthesis Prosthesis to final
P=0.565 P=0.124 P=0.371
Horizontal inter-implant distance <2
Coronal versus apical surfaces (> 1mm discrepancy)
Placement to final Placement to prosthesis Prosthesis to final
P=0.45 P=0.13 P=0.33
Table 8. Comparison of marginal bone loss for coronal and
apical inter-unit surfaces in different time periods based on
horizontal inter-unit distances of less or more than 2 mm
40
Horizontal inter-implant distance <3
Coronal versus apical inter-unit surface
Placement to final Placement to prosthesis Prosthesis to final
P =0.009* P =0.047* P=0.162
Horizontal inter-implant distance <3
Coronal versus apical surfaces (> 1mm discrepancy)
Placement to final Placement to prosthesis Prosthesis to final
P =0.004* P =0.018* P =0.021*
Table 9. Comparison of marginal bone loss for coronal and
apical inter-unit surfaces in different time periods based on
horizontal inter-unit distances of less or more than 3 mm (*:
Statistical significance)
Abstract (if available)
Abstract
Introduction: The purpose of the present study was to investigate the effect of relative vertical and horizontal position of adjacent implants on peri-implant marginal bone alterations. ❧ Materials & methods: Radiographic records of patients who had received multiple adjacent dental implants at two centers were examined. Inclusion criteria consisted of: 1) multiple adjacent dental implants restored with splinted or non-splinted restorations, 2) availability of diagnostic quality radiographs at time of implant installation, prosthesis connection and a minimum of one year post-loading follow-up. Parameters of interest included: horizontal distance (HID) and vertical level discrepancy (VLD) between the platform of adjacent implants, distance between the implant platform and bone level at the first implant bone contact at the mesial and distal surfaces of the implants designated as bone level. Pearson correlation coefficient was calculated to determine the relationship between implant proximity measurements and marginal bone loss (MBL). In order to determine the effect of implant position on marginal bone level, the data were stratified according to different horizontal and vertical subgroups. The data were analyzed with respect to coronal and apical implant units and their relative horizontal distance. The results were presented as mean values ± standard deviations. Two-tailed independent student t test with alpha value of .05 was used to evaluate the difference in mean marginal bone level between the compared groups. Pearson correlation test was run to investigate the possible correlation between the vertical discrepancy and MBL. ❧ Results: 65 patients with the mean age of 59 ± 8.9 years having 153 implants with the mean follow up period of 57.2 ± 0.3 months fulfilled the inclusion criteria. The mean VLD was 1.44 ± 0.86 mm and the mean horizontal distance between the implants was 3.36 ± 1.49 mm. When horizontal inter-implant distance was less than 3 mm, from the placement time to prosthesis installation, the mean MBL for the coronal and apical implants were 1.53 ± 1.04 mm and 0.99 ± 00.93 mm , respectively. The MBL of the coronal and apical implants in this category were statistically significant (P=0.04). Among implants with HID < 3mm, from implant installation to the last follow up, the coronal (MBL=1.71 ± 1.14 mm) and apical (MBL= 1.05 ± 0.87mm) implants exhibited statistical significant different MBL (P=0.009). Among implants with HID <3 mm and VLD > 1 mm, MBL for the coronal (2.03 ± 1.25 mm) and apical implants (1.01 ± 0.84 mm) from implant placement to the last follow-up were statistically significantly different (P=0.004). When examining VLD and MBL on a continuous scale, Pearson correlation test demonstrated a positive correlation between these two parameters from implant placement to the last follow-up (R²=0.29
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Creator
Khoshkam, Vahid
(author)
Core Title
The effect of vertical level discrepancy of adjacent dental implants on crestal bone resorption: a retrospective radiographic analysis
School
School of Dentistry
Degree
Master of Science
Degree Program
Craniofacial Biology
Publication Date
07/18/2017
Defense Date
05/25/2017
Publisher
University of Southern California
(original),
University of Southern California. Libraries
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Tag
dental implants,marginal bone loss,OAI-PMH Harvest,spatial inter-implant distances
Language
English
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Electronically uploaded by the author
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Zadeh, Homayoun H. (
committee chair
), Kar, Kian (
committee member
), Paine, Michael Lansdell (
committee member
)
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khoshkam@usc.edu,vahidkhoshkam75@gmail.com
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Tags
dental implants
marginal bone loss
spatial inter-implant distances