The effect of crown dimensions & implant dimensions on peri-implant marginal bone loss: a retrospective analysis

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1

A Thesis presented to the USC Graduate School in partial
fulfillment of the requirements for the degree of Master of
Science in Craniofacial Biology by

Shantia Kazemi DDS, MS

The effect of crown dimensions & implant
dimensions on peri-implant marginal bone
loss: A retrospective analysis

August 2018

2

Tables and figures: 5 tables and 8 figures
Running title: Restorative dimensions and marginal bone loss

TABLE OF CONTENTS

Abstract………………………………………………………………………………Page 2
1. Introduction….……………………………………………………………………Page 3
2. Materials & Methods……………………………………………………………...Page 5
3. Results…………..………..……………………………………………………….Page 8
4. Discussion…………………………………………………………………………Page 10
5. Conclusion…………………………………………………………………………Page 13
6. Figure Legends…………..…………………………………………………………Page 13
7. Table Legends………………..………………………………..…………………..Page 14
8. Figures……………………………………………………………………………..Page 14
9. Tables……………………..……………………………………………………….Page 19
10. References…………………………………………………………………………Page 22

Abstract:
Purpose:
The relationship between the dimensions of implant or prosthesis and implant outcomes remains
controversial with conflicting data. Accordingly, the aim of the present retrospective study was to
evaluate the relationship between implant or prosthesis dimensions and peri-implant marginal bone
loss (MBL).
Materials and Methods:
This double-center retrospective study, included data on consecutively treated patients between
January 1, 2005 to September 31, 2015, treated at USC, School of Dentistry and a private
periodontal practice. Inclusion criteria consisted of: 1) patients with single-unit, non-splinted,

3

implant restorations, being in function for more than a year in the posterior maxilla or mandible,
2) diagnostic quality intraoral radiographic images, taken at implant placement, crown delivery
and more than one year post-restoration. Radiographic images were imported into Photoshop
software (CC 2015, Adobe). Linear measurements were made after calibration of images, using
known implant dimensions, using lasso tool and ruler tool (Figure1). The relationship between
crown dimensions, implant dimensions and mesial/distal MBL was analyzed with Pearson
correlation test. Statistical significance was considered as p-value <0.05.
Results:
One hundred patients (33males, 67 females; mean age, 64 ± 10.5 years) with 100 single-unit
non-splinted posterior implants were included. A positive correlation was detected between IL
and mean MBL (P=0.02, R=0.22) (Figure2). A positive correlation was detected between crown
height space(CHS) and mean MBL (P=0.01, R=0.24) (Figure3). None of the additional
parameters, including crown-to-implant ratio, crown surface space, implant surface space, crown
width, implant diameter or follow up interval were correlated with marginal bone loss (P > 0.05).
Conclusion:
These data underscore the importance of crown height space on MBL, when restoring implants
longer than 10mm. However, crown to implant ratio was not significantly correlated with MBL.
This illustrates that C/I ratio may provide misleading information. It is recommended to consider
implant and crown length as independent variables, rather than together according to an arbitrary
formula.
Keywords: Marginal Bone Loss, Crown Height, Implant, Implant diameter, Implant length,
Crown to implant ratio.
1)Introduction:
Increasing attention has been paid on identifying the factors that interfere with the optimal
predictability of osseointegrated implants. One crucial criterion in determining long term
efficacy of dental implants is the amount of marginal bone loss around the restored implants[1].
Abrupt or incremental loss of marginal bone around implants leads to functional or esthetic
complications and ultimately loss of implant; hence in order to maintain healthy and stable bone

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implant interface, amounts of marginal bone loss and correlated etiologic factors must be
carefully taken into consideration. Decades after the introduction of osseointegrated dental
implants, researchers have been striving to promote the outcomes of replacing missing teeth with
implant supported restorations[2]. The stability of peri-implant hard and soft tissues is one of the
most critical factors for long-term implant maintenance, function and esthetics.
A crown-to-root ratio of 1:2 as a guideline and a minimum of 1:1 for a tooth abutment has been
recommended[3]. These guidelines have been adapted in implant dentistry, such that clinicians
tend to insert the longest implant that the bone volume will permit to avoid an unfavorable
crown-to-implant ratio. However, it is important to keep in mind that implants and teeth have
different biomechanical properties, since teeth have an elastic periodontal ligament, whereas
implants are directly attached to bone through osseointegration. An implant-supported prosthesis
acts as a type I lever; which means any increase in crown height will increase the force moment
that is endured by the implant and the surrounding bone[4]. Nissan et al, have demonstrated
through in vitro studies that increasing crown height space is accompanied with elevated risk of
prosthetic failure[5, 6].
A number of studies have employed finite element analysis (FEA) to demonstrate that most of
the stresses are transmitted to the crestal aspects of alveolar bone[7]. Therefore, the strategy to
increase the length of the implant to counter-act the increase in the load from elongated
restorations may not be very effective.
The relationship between changes in the length of the implant, restoration or the ratio of the two
with implant outcomes such as implant survival and marginal bone loss has been studied[8-16].
Rangert et al has demonstrated a positive correlation between an increased crown-to-implant
ratio and the amount of crestal bone loss [17]. Blanes et al, did not find a correlation between the
increased crown-to-implant ratio and marginal bone loss or implant failure[18].
Nissan et al., in two in vitro studies[5, 6], suggested that the use of crown height space is a more
significant factor than the crown-to-implant ratio in assessing biomechanics-related detrimental
effects on prosthetic complications. For each 1-mm increase in crown height space, the cervical
load is increased by 20%. Based on their data, a crown height space value greater than 15 mm
was demonstrated to have unfavorable effects on prosthetic complications. Nissan et al explained
the absence of significant correlation between the crown-to-implant ratio and crestal bone loss in
previous clinical studies by the fact that the value of crown height space was below the

5

detrimental limit of 15 mm[5, 6].
Anitua et al., investigated the effect of crown height space, crown to implant ratio on crestal
bone loss around extra-short implants and found that when an increased crown-to-implant ratio is
present, crown height space may influence crestal bone loss more significantly[9]. However, in
the study by Shan-Pao Sun et al., it was shown that higher C/I ratio and anatomical crown length
does not increase the risk of peri implant marginal bone loss during the 6 years of functional
loading[11].

Implant diameter is one of the implant related factors influencing the long term clinical outcomes
of dental implants. FEA studies have suggested that increasing implant diameter is accompanied
by reduction of the stress to the crestal bone[19]. The effects of implant diameter on the clinical
outcome of dental implants, such as implant failure and marginal bone loss have also been
studied. A number of studies have observed decreased implant survival in wider diameter
implants [20-22]. However, others have observed higher failure rate in 3.75 mm diameter group
compared to the 4 and 5 mm diameter group[23].
In addition to the role of crown height space, which is a linear vertical measurement, the
influence of the width of restoration on implant outcomes has not been examined. In view of the
fact that restorative width could potentially exert cantilever forces on implant crestal bone, the
effect of restorative width on implant outcomes remains unclear.
Accordingly, the aim of the present retrospective study was to evaluate the clinical outcomes of
implants with varying restoration diameter and length. The present study sought to accept or
reject the null hypothesis that implant and prosthetic outcomes are not correlated with restorative
width/ height or implant diameter/length.
2)Material and Methods:
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.
This double center retrospective study included data on all consecutively treated patients

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between January 1st 2004 to September 31st 2015 with single unit implants. The records of
patients were reviewed from the pool of patients treated in the Advanced Periodontology Clinic,
Ostrow School of Dentistry, University of Southern California and a private periodontal practice
in Los Angeles.
To be included in this study population, the patients were required to be over 18 years of age, in
general good health, and have received dental implant supporting a single non-splinted prosthesis
in the posterior maxilla or mandible, being in function for more than one year. The diagnostic
quality radiographs of the implant site must be available at the time of implant placement, crown
delivery and at least one year after function. The radiographs should be of sufficient diagnostic
quality without excessive angulation and showing the entire length of the implant and
restoration. Exclusion criteria consisted of heavy smoking (More than 10 cigarettes a day),
uncontrolled diabetes or multiple-unit implants with splinted restorations. Immediate placement
or previous history of grafting were not exclusion criteria.
Radiographic images of good quality that have been taken one year after restoration of single
unit prosthesis on the implant were imported into Photoshop (CC 2015, Adobe) without any
patient identifiers. Linear measurements were made after calibration of images, using known
values for implant length and diameter, or inter-thread distance for each implant system. Surface
areas of restoration and implants were measured by defining the periphery of each object using a
polygonal lasso tool. The measurement log tool was used to obtain numerical values. The linear
distance from the point of first bone-to-implant contact and platform of the implant was
measured and recorded as marginal bone level (MBL). Clinical notes were reviewed to
determine whether there was any history of complications such as implant screw fracture, screw
loosening, restoration displacement, etc.
Radiographic Assessment
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. Radiographic images were imported into
Photoshop (CC 2015, Adobe). Linear measurements were made after calibration of images using
know values for implant length and diameter. Surface areas of restoration and implants were

7

measured by defining the periphery of each object using a polygonal lasso tool. The measurement
log tool was used to obtain numerical values. The landmarks used for making numerical
measurements are illustrated in Figure 1. Accordingly, the following measurements were made:
Clinical crown length: The perpendicular distance between the implant platform and the most
coronal aspect of the crown.
Anatomical crown length (crown height space): The perpendicular distance between the plane
of occlusion and the first bone to implant contact.
Clinical width: The width of the restoration measured at height of contour of the crown.

Marginal bone loss: The distance between implant shoulder and the first visible implant-bone
contact, measured on both mesial and distal aspects of each implant from the time of crown
delivery to last follow up.
Crown height space to implant ratio: The ratio between crown height space and implant length
is calculated.
Crown Surface Space: The 2-dimensional surface area within the boarder of the restoration,
measured from the cusp tips to the bone crest and interproximal extensions of the restoration.
(The surface within the green borders in Figure 1.)
Implant Surface Space: The 2-dimensional surface area within the implant border (the surface
within the orange borders in Figure 1.)
Data and Statistical analysis:
The patient was considered the statistical unit of analyses for all measurements. Data analysis
included descriptive statistics, such as mean, median and standard deviation. All statistical
analyses were performed using the SPSS statistical software. Upon running the Shapiro-Wilk test,
it was revealed that data is not normally distributed.
The Spearman correlation was used to evaluate the association between MBL and different
variables measured at this study. Descriptive statistics was used to present the materials in terms

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of means and standard deviations.
Spearman correlation was run between MBL and each of the following parameters: crown height
space, crown surface space, crown width, implant diameter, implant length, crown to implant
ratio and implant surface space. Statistical significance was considered as p-value <0.05.
3)Results
100 patients (33male, 67female; mean age, 64 ± 10.5 years) with 100 single unit non-splinted
posterior implants were included in the analysis of this retrospective study. Table 1 summarizes
the characteristics of the included study population and sites. The implant platforms of the included
population consisted of 3 external- and 97 internal-connection implants. Both maxilla (N=48) and
mandible (N=52) were included, where 76 implants were in molar and 24 were in premolar
locations.
The descriptive analysis of variables is summarized in table 2 illustrating mean and standard
deviation of crown dimensions (height, width, space) and implant dimensions (diameter, length,
surface space), crown-to-implant ratio and also marginal bone loss. The mean follow-up time since
implant placement was 54.58 ± 27.89 months (range, 13 to 146 months) and no implants failed.
Only 30 of the patients had notes regarding their prosthesis that were screened for prosthetic
complications (screw loosening/fracture, abutment/implant fracture, ceramic chipping, and
prosthesis fracture); no complications were seen in those 30 patients.
Analysis of marginal bone loss data showed a mean of 1.0 ± 1.32 mm (range, -0.7 to 5.87 mm) of
mesial bone loss and 1.20 ± 1.42 mm (range, -1.25 to 6.95 mm) of distal bone loss.
A positive correlation was detected between IL and mean MBL (P=0.02, R=0.22) and between
crown height space(CHS) and mean MBL (P=0.01, R=0.24) (Figures 2,3). Marginal bone loss did
not exhibit any correlation (P > .05) with any of the additional parameters, including crown-to-
implant ratio, crown surface space, implant surface space, crown width and implant diameter. No
significant correlation between follow up time and marginal bone loss was detected (P>.05,
Figures 1,3,4,6,7).
To control for the possible effect of implant length on correlation between crown height space and

9

MBL, spearman correlation was run for CHS and MBL (Table3) for various ranges of implant
lengths (IL< 10mm, IL<8, IL>8, IL>10, IL>11). A positive correlation was detected between CHS
and MBL for IL>8 (P=0.001, R=0.34). No correlation between CHS and MBL was detected for
implants <8mm (n=15, P>0.05).
Additionally, to control for the possible effect of CHS on the correlation between implant length
and MBL, spearman correlation test was run between IL and MBL for implants restored with CHS
<10mm, CHS<12, CHS>12 and CHS>10 (Table4). A positive correlation was detected between
IL and mean MBL for CHS>10 (n=67, P=0. 001, R=0.37). No correlation between IL and MBL
was detected for implants restored with CHS<10 (n=33, P>0.05) or CHS<12 (n=62, P>0.05).
Regarding MBL, up to 2 years post loading the mean MBL was 1.24 mm (SD=0.12, n=12), 3 years
post loading mean MBL was 0.64mm (SD=0.43, n=12), 4 years post loading mean MBL was 1.05
mm (SD=0.09, n=26), 5 years post loading mean MBL was 0.82 mm (SD=0.10, n=17), 6 years
post loading mean MBL was 1.78 mm (SD=0.31, n=13), 7 years post loading mean MBL was
0.58mm (SD=0.0, n=6), 8 years post loading mean MBL was 1.05mm (SD=0.0, n=5), 9 years post
loading mean MBL was 1.13mm (SD=0.5, n=5), 10 years post loading mean MBL was 0.63mm
(SD=0.19, n=1), 11 years post loading mean MBL was 0.68mm (SD=0.45, n=1), 12 years post
loading mean MBL was 1.04mm (SD=1.04, n=1). There was no statistically significant correlation
between MBL and follow up time (P=0.12/P=0.29, R
2
=0.15/R
2
=0.10) respectively for
mesial/distal indicating that bone level around implants under functional loading was stable over
time (Figure 4). No implant was lost during the follow up time. The overall survival rates of
implants and prosthesis were 100% at the end of the follow-up time.
The mean MBL for implants with crown height space/implant ratio <1.5 was 0.95mm (SD=0.37,
n=90) and for implants with crown height space/implant ratio more than >1.5 was 1.88mm
(SD=0.38, n=10).
The descriptive analysis of variables is summarized in table 1, illustrating mean and standard
deviation of mesial/distal MBL for internal connection versus external connection. It should be
noted that the majority of the implants had internal prosthetic connection, while only 5 implants
had external connection platform.

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Data from 6 different implant systems have been included in the present study. The descriptive
analysis of variables is summarized in table 1 illustrating mean and standard deviation of
mesial/distal MBL for each implant system. To investigate the effect of implant system on mean
MBL, Kruskal–Wallis test was run demonstrating statistical differences between different implant
systems (p=0.001). To understand where the significance is, pairwise Wilcoxon rank sum tests
were run for all pairs indicating a significant difference between Astra system versus 3i system
(P=0.0007) and also Astra system versus Nobel system (P=0.01).
Wilcoxon rank sum test was run to investigate the effect of arch location on marginal bone loss.
No statistical difference was observed (p=0.20).
4)Discussion:
The inter-relation between implant and prosthesis dimensions (restorative height, width and
cantilever arm) and implant outcomes (survival rate and marginal bone loss) has not been
conclusively demonstrated. Often clinicians are concerned, when the crown-to-implant ratio
exceeds 1:1. The original source of the 1:1 guideline may have been extrapolated from crown-to-
root ratio recommendation of natural teeth[3]. Actual evidence for the influence of crown-to-
implant ratio and implant outcomes has remained controversial[24]. A common clinical strategy
has been to reduce the occlusal table of restorations in an effort to reduce occlusal forces [25].
However, the effect of restorative width on implant outcomes remains unknown. In view of the
fact that restorative width could potentially exert cantilever forces on implant marginal bone, the
effect of crown width on implant and prosthesis outcomes remains unclear. The aim of this
retrospective study was to investigate the correlation between prosthesis and implant dimensions
and implant outcomes. The primary outcome measure investigated was marginal bone loss.
A form of non-axial loading is displayed by implant-supported reconstructions with high C/I ratios.
The prosthesis can act as a lever arm, creating a bending moment and transferring stress to implant
prosthetic connection, as well as peri-implant bone[26]. A variety of sequelae may follow, such as
prosthetic technical complications[17], bone density changes[27], as well as, increased[28] or
marginal bone level changes. Two different definitions for C/I ratios have been considered:
anatomical C/I ratio and clinical C/I ratio. For the anatomical C/I ratio, the fulcrum is defined at
the interface between the implant shoulder and the crown–abutment junction. For the clinical C/I
ratio, fulcrum is defined at the most coronal bone–implant contact[24]. The latter may be a more

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realistic biomechanical scenario for evaluating the effect of the C/I ratio on implant-supported
prosthesis complications, because the stiffness of components connected to the implant is greater
than that of the cortical bone[26].
Due to the diversity of studies with respect to data collection and study design, the current literature
remains controversial with respect to that relationship between C/I ratios of implant-supported
reconstructions and peri-implant MBL. Some studies showing no relationship [24], while others
show a negative relationship [29].
Another consideration has been the influence of C/I ratio on prosthetic components, where some
studies have reported increased risk of technical complications, such as screw loosening, cement
failure, and framework fracture associated with increasing C/I ratio[17].
In the present study, no correlations between crown to implant ratio of single-unit implant
supported prosthesis in posterior regions and MBL was detected, which is in agreements with other
published reports[24, 30-32]. In the present study, CHS had a positive correlation with MBL. This
finding is in agreement with the previously reported data[9]. This is significant, since in the former
study, more than 75% of the implants restorations had CHS more than 15mm, compared to 9% of
the implants in the present report with CHS >15mm. It is also noteworthy that in the Anitua study,
splinted implant-supported restorations have been included, whereas splinted restorations were
excluded in the present study. The effects of splinting on implant outcomes remains
controversial[9].
Some of the confounding variables have not been considered in past studies. For example, previous
studies, examining the correlation between CHS and MBL have not accounted for indirect effects
of implant length. When IL and MBL for CHS of various sub-categories was considered, implant
length was positively correlated with MBL, only for implants longer than 10mm. One may
speculate that this may be attributed to the very low MBL of implants shorter than 10mm.
Our findings showed that implant length had a positive correlation with MBL (P=0.02, R=0.22)
(Figure2). Multiple meta-analyses have recently published, comparing survival rate, marginal
bone loss of short vs long implants[12, 33-36]. These studies failed to demonstrate a statistically
significant difference in any of the outcomes. In the meta-analysis by Fan T et al.,[36] it was
demonstrated that long implants had significantly more complication rate, as opposed to short
implants (odds ratio:3/1). In a recent RCT (Zadeh et al, COIR in press) short implants had
significantly less MBL than long implants, which is in agreement with the findings of our study.

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Considering I
2
of 99%, 66% and 43% in the published meta analyses [33, 35, 36]heterogeneity of
the analyzed papers, including different type of prosthesis, study design, implant systems could
have contributed to masking the possible association of MBL and implant length.
Recent Meta- analyses[37] revealed failure proportion, biological/prosthetic failure proportions
and marginal bone loss of 5.9%, 3.8%, 2.8% and 0.083 mm, respectively, for implants <10 mm
long, supporting single crowns in the posterior region of partially edentulous patients. Longer
implants used to be suggested to ensure sufficient surface area for bone contact, leading to more
favorable results within the same implant system[20].
An important consideration is to compare the success rate of short implants with that of advanced
surgical augmentation techniques necessary to place standard implants in atrophied posterior
jaws[38]. In the included clinical trials of Del Fabbro et al study, short implants were randomly
placed in non-augmented bone and were compared to longer implants placed in vertically
augmented mandibles [39, 40]and maxilla[41]. Their results indicated that when the bone height
over the mandibular canal or below the maxillary sinus was reduced, short implants presented
comparable short- and mid-term outcomes to longer implants placed in vertically augmented bone.
The studies agreed that short implants could be an interesting alternative to vertical augmentation
due to reduced treatment time, cost and complication rate. In the present study, MBL had a
significant positive correlation with implant length meaning short implants had less MBL
(P<0.01). Additionally, restorative width, crown surface space (2-dimensional surface area of
restoration of single unit non-splinted implant supported prosthesis in posterior regions was not
correlated with the MBL and survival rate of implants which could indicate that presence of a
cantilever was not associated with MBL.
In view of the fact that implant dimensions and prosthetic dimensions have potentially different
influences, it is prudent to consider these factors individually, rather than grouping them together
to be expressed as C/I ratio. It may be noted that some of the technical problems that may be caused
as a result of increased crown height space, cannot be readily resolved by simply increasing
implant length in an effort to reduce C/I ratio. Elongated restorations are likely to continue to have
the same adverse effects on prosthetic connections, regardless of implant length. However, it is
potentially possible that both prosthesis and implant length, at some point, may exert effects on
marginal bone. Interestingly, longer restorations (>10mm) placed on longer implants (>10mm)
were associated with increased MBL. Therefore, considering implant length and prosthesis

13

dimensions as separate parameters, allows clinician to make decisions about selection of
appropriate components for given clinical situation.
Some of the limitations of the current study includes its retrospective design, inadequate
documented cases with regards to prosthetic complications, since many of the restorations were
completed in restorative offices referring to the periodontist (only 30% of case). Another
shortcoming is exclusion of splinted cases, which could potentially have an effect on marginal
bone loss of cases with long CHS. Additionally, previous history of bone graft and immediate
implant placement were not among the exclusion criteria and could have an effect on marginal
bone level changes of implants.
There is inconclusive evidence in the literature with regards to relationship between prosthesis
dimensions and marginal bone loss and also prosthesis outcomes including prosthetic
complications. Future studies should include both splinted and non-splinted restorations, with a
wider range of implant lengths and implant diameter to address the possible associations between
implant dimensions, crown dimensions with implant outcomes and prosthesis outcomes.

5)Conclusion:
According to the results of the current retrospective study, a positive correlation between implant
length and MBL was detected. Such correlation was not detected in implants restored with
prosthesis shorter than 10mm. Conversely, CHS and MBL were positively correlated among all
implant, but not among implants shorter than 10mm. These data underscore the importance of
crown height space on MBL, when restoring implants longer than 10mm. However, crown to
implant ratio was not significantly correlated with MBL. This illustrates that C/I ratio may provide
misleading information. It is recommended to consider implant and crown length as independent
variables, rather than together according to an arbitrary formula.
6)Figure legends
Figure 1. Representative radiograph, demonstrating the landmarks used in radiographic
quantitative measurements.

Figure 2. Scatter plot illustrating the association between crown width and MBL on mesial (red)
and distal (blue) aspects of implants

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Figure 3. Scatter plot illustrating the association between crown height space and MBL on mesial
(red) and distal (blue) aspects of implants.

Figure 4. Scatter plot illustrating the association between crown surface space and MBL on
mesial (red) and distal (blue) aspects of implants.

Figure 5. Scatter plot illustrating the association between implant diameter and MBL on mesial
(red) and distal (blue) aspects of implants.

Figure 6. Scatter plot illustrating the association between implant length and MBL on mesial
(red) and distal (blue) aspects of implants.
Figure 7. Scatter plot illustrating the association between implant surface space and MBL on
mesial (red) and distal (blue) aspects of implants.
Figure 8. Scatter plot illustrating the association between C/I ratio and MBL on mesial (red) and
distal (blue) aspects of implants.
7)Table legends
Table 1. Mean + SD of MBL for different implant systems and connections. Mean + SD of study
variables

Table 2. Study population’s demographics & features

Table 3. Relationship among crown height space and marginal bone loss for different implant
length ranges

Table 4. Relationship among implant length and marginal bone loss for different crown height
space ranges

8)Figures:

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Figure 1. Representative radiograph, demonstrating the landmarks used in radiographic
quantitative measurements.

Mesial marginal bone level changes

Distal marginal bone level changes

16

Fig 2. Scatter plot illustrating the association between crown width and MBL on mesial (red) and distal (blue)
aspects of implants.
P=0.64 (Mesial: P=0.71, Distal: P=0.70)
R=0.04 (Mesial: R= 0.037, Distal: R=0.038)

Fig 3. Scatter plot illustrating the association between crown height space and MBL on mesial (red) and distal
(blue) aspects of implants.
P=0.01 (Mesial: P=0.08, Distal: P=0.006)
R=0.24 (Mesial: R=0.17, Distal: R=0.27)

-‐2
0
2
4
6
8
4 6 8 10 12 14 16 18 20 22
Marginal
bone
loss
Crown
width(mm)

-‐2
-‐1
0
1
2
3
4
5
6
7
8
4 6 8 10 12 14 16 18 Marginal
bone
loss(mm)
Crown
height
space(mm)

17

Fig 4. Scatter plot illustrating the association between crown surface space and MBL on mesial (red) and distal
(blue) aspects of implants.
P=0.77 (Mesial: P=0.46, Distal: P=0.90)
R=-0.02 (Mesial: R= -0.07, Distal: R= -0.01)

Fig 5. Scatter plot illustrating the association between implant diameter and MBL on mesial (red) and distal
(blue) aspects of implants.
P=0.65 (Mesial: P=0.57, Distal: P=0.54)
R=-0.04 (Mesial: R= -0.05, Distal: R= -0.06)
-‐2
-‐1
0
1
2
3
4
5
6
7
8
20 40 60 80 100 120 140 160
Marginal
bone
loss(mm)
Crown
surface
space
-‐2
-‐1
0
1
2
3
4
5
6
7
8
3 3.5 4 4.5 5 5.5 6 6.5
Marginal
bone
loss(mm)
Implant
diameter(mm)

18

Fig 6. Scatter plot illustrating the association between implant length and MBL on mesial (red) and distal (blue)
aspects of implants.
P=0.02 (Mesial: P=0.07, Distal: P=0. 01)
R=0.22 (Mesial: R= 0.18, Distal: R= 0.25)

Fig 7. Scatter plot illustrating the association between implant surface space and MBL on mesial (red) and distal
(blue) aspects of implants.
P=0.40 (Mesial: P=0.45, Distal: P=0.50)
R=0.08(Mesial: R= 0.07, Distal: R= 0.06)
-‐2
-‐1
0
1
2
3
4
5
6
7
8
5 6 7 8 9 10 11 12 13 14
Marginal
bone
loss(mm)
Implant
length
(mm)
-‐2
-‐1
0
1
2
3
4
5
6
7
8
15 25 35 45 55 65 75 85
Marginal
bone
loss(mm)
Implant
surface
space

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Fig 8. Scatter plot illustrating the association between C/I ratio and MBL on mesial (red) and distal (blue) aspects
of implants.
P=0.79 (Mesial: P=0.95, Distal: P=0.72)
R=0.02(Mesial: R= 0.00, Distal: R= 0.03)

9)Tables:

Table 1. mean & SD of MBL for different implant systems and connections, mean & SD of
study variables
Exploratory Variable Mean ± SD
Crown/ implant ratio 1.05±0.46
Implant surface space (mm
2
) 39.31±20.03
Implant length(mm) 10.11±1.77
Implant diameter(mm) 4.53±0.53
Crown width(mm) 9.05±1.98
Crown surface space (mm
2
) 74.38±24.62
Crown height space (mm) 11.40±2.33
MBL (overall) Mesial 1.0±1.32
Distal 1.20±1.42
MBL (Implant platform)

External

Mesial 1.45±1.43
Distal 1.29±1.30
Internal Mesial 1.31±0.13
-‐2
-‐1
0
1
2
3
4
5
6
7
8
-‐0.2 0.3 0.8 1.3 1.8 2.3 2.8
Marginal
Bone
Loss
C/I
ratio

20

Distal 1.43±0.14
MBL (Implant System) Astra
Tech(64%)
Mesial 0.66±1.16
Distal 0.87±1.30
3i Biomet(21%) Mesial 1.48±1.11
Distal 1.76±1.12
Straumann(5%) Mesial 0.98±0.96
Distal 0.94±1.06
Nobel(7%) Mesial 2.06±2.08
Distal 2.72±2.51
Genesis(2%) Mesial 3.13±1.73
Distal 2.84±2.17
Sybron(1%) Mesial 0.13
Distal 0.07

Table2. Study population’s demographics & features
Parameter Value

Population
Subjects (n) 100
Teeth (n) 100
Mean age (years) 64.03 + 10.57
Age range (years) 48 - 87
Male 33
Female 67
Sites
Maxilla 48
Mandible 52

21

Molar 76
Premolar 24
Medical history
Hypothyroidism 5
Hypertension 10
Penicillin allergy 6
Osteoarthritis 3

Table3. Relationship between crown height space and marginal bone loss for different
implant length ranges
Different Intervals of Implant
Length
N p-value Correlation coefficient:
CHS vs MBL
Implant Length>11
**
18 <0.0001 0.779
Implant Length<10 53 NS -
Implant Length>10
**
47 <0.0001 0.561
Implant Length<8 15 NS -
Implant Length>8
**
85 <0.001 0.349

NS: Not significant, NA:Not applicable

Table4. Relationship between implant length and marginal bone loss for different crown

22

height space ranges
Different Intervals of crown
height space
N p-value Correlation coefficient:
implant length vs MBL
Crown height space<10 33 NS -
Crown height space>10
**
67 <0.001 0.375
Crown height space<12 62 NS -
Crown height space>12
**
38 <0.007 0.428
NS: Not significant, NA:Not applicable

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Asset Metadata

Creator Kazemi Esfeh, Shantia (author)

Core Title The effect of crown dimensions & implant dimensions on peri-implant marginal bone loss: a retrospective analysis

Contributor Electronically uploaded by the author (provenance)

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 08/06/2018

Defense Date 05/24/2018

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag crown height,crown to implant ratio,implant,implant diameter,implant length,marginal bone loss,oai:digitallibrary.usc.edu:usctheses,OAI-PMH Harvest

Format application/pdf (imt)

Language English

Advisor Paine, Michael (committee chair), Kar, Kian (committee member), Zadeh, Homa (committee member)

Creator Email kazemies@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-55568

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Identifier etd-KazemiEsfe-6659.pdf (filename),usctheses-c89-55568 (legacy record id)

Legacy Identifier etd-KazemiEsfe-6659.pdf

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Document Type Thesis

Format application/pdf (imt)

Rights Kazemi Esfeh, Shantia

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA

Abstract (if available)

Abstract Purpose: The relationship between the dimensions of implant or prosthesis and implant outcomes remains controversial with conflicting data. Accordingly, the aim of the present retrospective study was to evaluate the relationship between implant or prosthesis dimensions and peri-implant marginal bone loss (MBL). ❧ Materials and Methods: This double-center retrospective study, included data on consecutively treated patients between January 1, 2005 to September 31, 2015, treated at USC, School of Dentistry and a private periodontal practice. Inclusion criteria consisted of: 1) patients with single-unit, non-splinted, implant restorations, being in function for more than a year in the posterior maxilla or mandible, 2) diagnostic quality intraoral radiographic images, taken at implant placement, crown delivery and more than one year post-restoration. Radiographic images were imported into Photoshop software (CC 2015, Adobe). Linear measurements were made after calibration of images, using known implant dimensions, using lasso tool and ruler tool (Figure1). The relationship between crown dimensions, implant dimensions and mesial/distal MBL was analyzed with Pearson correlation test. Statistical significance was considered as p-value <0.05. ❧ Results: One hundred patients (33 males, 67 females