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Transnasal dental implants: indication and the report of 10 cases

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Transnasal dental implants: indication and the report of 10 cases

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Transnasal Dental Implants: Indication and the Report of 10 Cases

by

Nathan Eshoiee, DDS

A Thesis Presented to the
FACULTY OF THE USC HERMAN OSTROW SCHOOL OF DENTISTRY
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfilment of the
Requirements for the Degree
MASTER OF SCIENCE
(BIOMEDICAL IMPLANTS AND TISSUE ENGINEERING)

August 2023

ii

Copyright 2023 Nathan Eshoiee
Table of Contents

Abstract........................................................................................................................................iii
Introduction..................................................................................................................................1
Chapter 1: Materials & Methods..................................................................................................9
Chapter 2: Results.........................................................................................................................11
Chapter 3: Discussion...................................................................................................................12
Chapter 4: Conclusion..................................................................................................................18
References....................................................................................................................................19
Figures...........................................................................................................................................23

iii

Abstract

Background: The rehabilitation of the atrophic maxillae with dental implants represents a
challenge that can be addressed with zygomatic dental implants and traditional axial implants. In
the event of a severely atrophic pre-maxilla, a Quad-Zygoma approach may be necessary to
provide anchorage for the fixed restoration. The proximity of anatomical features can increase the
possible morbidity of the Quad-Zygoma approach and instead, transnasal implants may serve as a
viable anterior anchorage alternative in the atrophic pre-maxilla region.

Materials and Methods: A total of 10 patients with a combined 18 transnasal implants paired
with a single zygomatic implant were included in this study. The implant placement surgeries
were performed by two experienced dental surgeons with previous clinical experience in placing
zygomatic implants. Transnasal implant marginal bone level changes were evaluated on CBCT
images taken immediately after transnasal implant placement and one year of follow-up post
loading. The reference point for the CBCT measurement of mesial and distal bone loss after one
year was the horizontal interface between the implant and the abutment.

Results: The retrospective CBCT analysis of 18 transnasal implants placed in 10 patients shows
an average marginal bone loss of 0.70mm over a time period of one year following restorative
loading, p<0.0001.

Conclusion: The marginal bone loss observed in transnasal implants one year post loading is
comparable to the marginal bone loss of conventional implants under similar conditions.
Therefore it is believed that transnasal implants can be considered as an acceptable anterior
anchorage alternative to conventional implants in the atrophic pre-maxilla region when paired
with a single posterior zygomatic implant.

1

Introduction

The rehabilitation of an atrophic maxilla with dental implants presents as a notable
challenge in implant dentistry. While in the event of severe bone loss in the mandible, a base of
bone will still remain in the apical regions that can provide an adequate amount of vertical bone
height for predictable placement of a conventional, axially directed implant
8
. Contradictorily,
vertical bone loss in the maxilla presents with a different challenge due to the anatomical
presence of the maxillary sinus posteriorly and the nasal cavity anteriorly which limit the vertical
bone height available for conventional placement of an implant.
Utilizing the Bedrossian classification to segregate the maxilla into three zones: Zone 1-
the premaxilla, Zone 2- the premolar area, and Zone-3 the molar area
7
; clinical decisions
relating to optimal implant placement in the maxillary arch of an edentulous patient need to be
made. When considering placing implants in this patient population, it is important to take into
account the anatomical limitations of the maxilla and to ensure a suitable anterior-posterior (A-P)
spread of implants. A challenge is presented particularly in Zone-1, where due to severe atrophy,
there may be ≤ 2 mm of alveolar bone present subnasally
4
. Implant placement in an atrophic
Zone-1 will provide minimal bone-implant contact with a conventional axially placed implant
with the added risk of resorption during functional stages and an increased risk of late rhino /
sinus – oral communication.
Direct solutions that address the challenge of minimal subnasal bone will generally
attempt to increase vertical height by method of vertical bone augmentation, however vertical
bone augmentation does not have consistent and predictable results. Unlike the maxillary sinus
which can be augmented in a lateral or crestal approach to increase the vertical height of bone
available to encase an implant, the nasal cavity is occupied by turbinates. In addition to
respiratory and olfactory function, nasal turbinates aid in humidifying and warming the inspired
2

air and the nasal cavity can therefore not be augmented with bone to increase vertical
dimensions. Furthermore, in a highly atrophic pre-maxilla, it is not uncommon for alveolar bone
to be relatively absent sub-nasally which may influence the clinician to place an axial implant in
a more posterior and less ideal position
25
. This compensatory and sub-ideal placement of an
implant comes with consequence, creating a short A-P spread between implants which is a
biomechanically unfavorable cantilever
25
.
Over the years, several solutions to the severely atrophic maxilla have been proposed.
The proposed alternative solutions to avoid placing a short implant subnasally include M-4
implant placement, trans-sinus implant placement, and zygomatic implant placement
27, 8
.
M-4 technique is a possible angled-implant solution in clinical situations with minimal bone
available subnasally
24
. This technique seeks to angle the apex of two implants towards what is
termed the M-point which is the maximum bone mass at the lateral pyriform rim above the nasal
fossa, where implant apices can engage cortical bone for primary stability
25
. In the M-4
technique, the anterior implant has the apex angled distally, while the posterior implant has the
apex angled mesially. The benefit of angling the implants allows the clinician to avoid bone
grafting as well as the ability to place a 10-13 mm implant in areas of severe atrophy with
otherwise less than 7 mm of available vertical bony height available
24
. To compensate for the
angulated placement of the implants, the utilization of the M-technique requires angled
abutments of 17º or 30º. However even with this approach, this technique requires at least 5 mm
of vertical bone height to allow for angulation into the lateral pyriform rim
24
. The advantage
provided by this technique is the increased biomechanical advantage available for the provisional
and definitive restorative phases.

3

Trans-sinus implant placement with engagement of the nasal cortical bone in
combination with short subnasal implants is another proposed method in for use in clinical
presentations where atrophy of the maxilla prevents insertion of traditionally tilted implants
where the apex of the implant is directed posteriorly
27, 30
. The trans-sinus implant body is placed
with the apex angled mesially, minimally transversing through the maxillary sinus with
engagement in the inferior and anterior cortical walls of the maxillary sinus and additionally
extending the apex of the implant into the nasal cortical wall for what is described as a double bi-
cortical anchorage
27
. A double bi-cortical anchorage is defined as implant anchorage into the
crestal, sinus, and nasal cortical bone
27
. An alternative method would be to place the implant
with a similar trajectory, while not traversing into the interior of the sinus yet still engaging the
cortical bone anterior to the sinus in what is described as a bicortical anchorage technique
27
. The
benefit of this is good implant anchorage with a large inter-implant distance without undertaking
a technically demanding approach of zygomatic implant placement or undergoing bone grafting
procedures. However, this technique may still require adequate subnasal bone in order to place
axially directed implants to support the prosthesis in unison with the tilted trans-sinus implant.
Trans-sinus implant approach was reported to show similar and comparable survival rates to
implants in immediate function placed in grafted bone and zygomatic anchored implants through
the extra-maxillary technique
29, 40
.
An additional proposed solution to avoid complex bone grafting procedures with the
associated co-morbidities includes zygomatic and pterygoid implants
32
. The pterygoid implant
placement is an approach which places the implant platform in the location of the second or third
molar location. Although it may circumvent the need for a bone grafting procedure of the sinus,
the posteriorly placed pterygoid implant position does increase the difficulty of prosthetic
4

procedures
4, 9
. An additional approach available is the zygomatic implant which was first
proposed by Bothur and colleagues for specific use in patients with severe maxillary atrophy
10
.
Since their introduction, zygomatic implants present with high success rates among patients with
severe maxillary atrophy and wishing to increase their masticatory function and quality of life
1
.
Previous studies on survival rates related to the rehabilitation of zygomatic implants in
immediate function are reported to be around 96.4% and 100%
28,6
. Further, in regards to the use
of zygomatic implants for maxillary rehabilitation, survival rates of 97.9% after a 3 year follow
up period and 96.7% over a 12 year follow up period were reported
4, 21, 13
.
Utilizing the Zygoma Anatomy-Guided Approach (ZAGA), the zygomatic implants are
placed in accordance to the patient’s specific anatomical characteristics, allowing for the implant
to be placed as either intra-sinus, extra-sinus, or intermediately-placed, the latter of which uses
the maxillary wall as a source of anchorage
4
. In accordance with the original Branemark
protocol, the direction of the zygoma implant is selected with the objective of maximizing the
primary stability of a prosthetically driven zygomatic implant
9
. A total of two zygomatic
implants distributed bilaterally are commonly utilized in combination with two anterior implants
in fully edentulous patients as per the original zygomatic Brå nemark protocol. However in the
absence of adequate vertical bone height subnasally in Zone-1, a Quad Zygoma approach has
also been utilized where a total of four implants are placed bilaterally in the zygomatic arch
14, 19,
38, 17, 16
.
In cases of extensive atrophy in the anterior and posterior regions of the maxilla, a quad
zygoma approach is a proposed solution involving a total of four zygomatic implants with an
adequate anteroposterior spread to allow for immediate rehabilitation
19, 38, 17, 16
. An indication to
consider a quad-zygoma approach would be in clinical situations when there is a lack of
5

adequate of bone height for conventional implant placement in Zones 1, 2 and 3
2, 4
. In spite of
being a safe technique and well documented in the literature, a Quad-zygoma approach is a more
complex and technically commanding approach and does require more experience of the surgeon
due to an increase in possible surgical risks and complications
1,17,39
. Potential complications of
zygomatic implant placement may include sinusitis, oral-nasal and extraoral fistula, and orbital
injury
14, 17, 39
.
In situations where alveolar bone is absent in zones 2 and 3, a trans-sinus alternative
method to placing zygomatic implants is the utilization of extended length subcrestal angulated
implants. As opposed to the conventional distally angled implants inserted anterior to the sinus,
extended length implants with the apex tilted mesially will be able to provide adequate
separation between the posterior and anterior implants and provide a biomechanically favorable
fixed full-arch occlusal scheme by providing greater posterior implant support which is critical
for successful rehabilitation
41, 31
. In this method, the implant head is placed in the location of the
1
st
molar and the mesially angulated implant apex will transverse the grafted sinus cavity and
engage the anterior maxilla as it extends to and engages the lateral cortical wall of the nasal
bone
41
. The extended length of the implant is believed to promote favorable implant primary
stability for immediate loading while also maximizing the inter-implant distance of the posterior
and anterior implants
41
. Additionally, one of the benefits of placing the posterior implant in
position of the 1
st
molar is the avoidance of large cantilevers which can increase the risk of
mechanical complications, especially in the presence of bruxism
30, 4
.
Another approach that shares similarities with the previous methods is the All-on-4
approach. In this protocol, the posterior implants may be angled anteriorly and ideally also
engaging the cortical bone of the lateral nasal wall, however a transsinus approach is also
6

possible when there is minimal crestal bone available
23, 25
. Additionally two anterior implants
are placed axially in Zone-1 or they may also be angled posteriorly to engage the lateral pyriform
rim or mesially towards the midline when vertical bone height is inadequate
23
. However, as with
most of the proposed solutions regarding patients with atrophic pre-maxilla, considerations need
to be made if there is an inadequate amount of subnasal bone available for implant placement.
When seeking to place an implant in the pre-maxilla region, there are a few options available
when seeking to engage an implant into cortical bone and achieve adequate primary stability.
Apart from the cortical bone of the alveolar crest, an additional source of cortical bone located in
Zone-1 can be accessed by engaging the implant into the parasnasal cortical bone
22
. Possible
cortical paranasal implant site locations include the nasal crest located inferiorly and the lateral
pyriform rim
25
.
The focus of this study is the introduction of extra-long transnasal implants as a viable
solution, chiefly as a complement to a unilateral zygomatic implants
11
. Previously, implants
placed in the pre-maxilla region were believed to be contraindicated due to increased chance of
infection
34
. The benefit of the transnasal dental implant placement technique is that the
paranasal cortical bone can be utilized to gain increased torque values in cases of Zone 1 atrophy
while maintaining a favorable A-P spread. Considering the lateral nasal wall as a source of
cortical bone, a thickness of 2 mm of paranasal bone is adequate to consider the engagement of a
transnasal implant with the goal to increase primary stability
36
. Transnasal implant placement is
a possibility to consider for many patients with severe Zone-1 atrophy due to the pattern of bone
loss observed during midface osseous atrophy. Specifically, the pyriform, nasal crest, and
zygomatic bones were found to be somewhat unaffected by disuse atrophy of the maxilla, with
the zygomatic bone being least affected
25, 36
. The transnasal implant placement procedure
7

involves detaching the distal portion of the nasal mucosa in order to expose the lateral wall and
floor of the nasal cavity, although membrane perforation of the nasal mucosa is possible, it is
thicker than the sinus membrane and therefore not as likely to rupture
2
. Recommended implant
diameter is commonly 3.75 mm with lengths ranging from 20-25 mm
2
. After the placement of
the implant, particulate bone graft may be placed on the floor and lateral position of the nasal
cavity to avoid the possibility of mucosa adherence to the implant thread and potentially causing
an implant thread exposure.
Candidates for placement of extra-long dental implants would include patients with
Zone-1 atrophy, in which subnasal implant placement would require the use of a short dental
implant (6 mm). In patients where a Quad Zygoma approach is being considered, it may be
feasible to also consider a transnasal implant in the pre-maxilla region as a substitute for a
conventionally placed anterior implant with an axial trajectory. A transnasal implant in
combination with a unilateral zygomatic implant may be a more predictable alternative solution
to a Quad Zygoma in certain clinical presentations such as when the zygomatic implant is placed
in what is termed “intermediately” placed. During intermediately placement, the maxillary wall
is used as the source of anchorage and a portion of the zygomatic implant is without full bone
coverage and is partially covered by soft tissue
3
. When a zygomatic implant is placed in these
situations, there is an increased risk for dehiscence and exposure of the implant threads
7
.
Further positive indications for consideration of extra-long trans nasal implants includes
insufficient bone height in the pre-maxilla region for placement of conventional implants, ≥ 4
mm subnasal bone if planning for immediate loading, location of the infraorbital foramen within
the trajectory of the second zygomatic implant in a Quad-zygoma approach, and in the presence
of large concavities in the anterior maxilla which increases the risk of implant exposure of
8

zygomatic implant
2,11
. Additionally, candidates may include patients in which there is
insufficient volume of the zygomatic bone or elderly patients with low density zygomatic bone
which makes the placement of two zygomatic implants with primary stability questionable if
utilizing the Quad Zygoma approach
11, 2
. Therefore, replacing the anterior zygomatic implant
with a transnasal implant is a feasible option to consider that will reduce the surgical risk and
complexity of placing a second zygomatic implant in certain clinical presentations
39
.
Additionally, the transnasal implant approach allows a greater number of surgeons to consider
the technique as an alternative solution due to the lower complexity as compared to a Quad
Zygoma approach.
The purpose of this retrospective analysis is to evaluate the outcome of 10 patients treated
via the extra-long transnasal implant as an anterior anchorage in combination with a single
posterior zygomatic implant. This transnasal dental implant with a complementing zygomatic
implant will be considered as an alternative solution to both the Quad Zygoma approach and the
use a conventional implant as the anterior anchorage to a posterior zygomatic implant. The
dental transnasal implant marginal bone loss after 1 year of function will be reported as the
primary finding. Additionally, this study aims to provide quantitative data related to amount of
cortical apical engagement, cortical lateral engagement of paranasal bone, and the subnasal bone
available for conventional implant placement.

9

Chapter 1: Materials and Methods
A total of 10 patients (mean age 59 years) with pre-maxilla atrophy were included in this
study. The total number of transnasal implants included in this study is 18 (Neodent Helix Long
implants; Noris Tuff implants) with an average length 23.9 mm. The patient cases were
performed by two experienced dental surgeons with prior clinical experience in placing
zygomatic implants. Patients were excluded from this study if they had oral infections, acute or
chronic sinus diseases. Additionally, medical exclusions included pregnancy, insulin-dependent
diabetes, undergoing treatment/medications affecting bone turnover or diseases affecting bone
metabolism
32
. All patients received a preoperative CBCT in order to create a proposed 3-
dimensional implant position simulation in order to measure the available bone between the
nasal lateral wall and the residual alveolar crest. Additional considerations were the angle of the
lateral nasal wall and any possible nerve variants to avoid possible nerve impingements and
subsequent complications during placement of a zygomatic implant
32
.
Peri-implant marginal bone level changes were evaluated on the CBCT image
immediately after implant placement, and 1 year post loading follow-up. The reference point for
the CBCT measurement of mesial and distal bone loss was assessed via the horizontal interface
between the implant and the abutment (implant platform). Image analysis software utilized was
[BlueSkyPlan4, version 4.7.55]. Marginal bone remodeling was defined as the difference in
marginal bone level at 1 year post loading in comparison to the marginal bone level present
immediately after surgical placement of the implants.
The available subnasal bone for implant placement was measured at two different
locations, the midline and proposed transnasal implant position. The midline measurement was
taken at the site of the anterior nasal spine whilst the subnasal bone at the site of the proposed
10

implant was measured directly mesial to the proposed site of the transnasal implant.
Furthermore, subnasal bone was defined as the amount of alveolar bone located inferior to the
nasal fossa and was measured from the crest of the alveolar ridge to the internal cortical border
of the nasal fossa. Lateral cortical contact was defined as the lateral portion of the transnasal
implant that engaged primarily with the cortical paranasal bone as the implant transects the nasal
cavity. Specifically, this measurement of the cortical bone to lateral implant contact was a linear
value spanning from the internal border of the cortical nasal bone (where the implant initially
enters the nasal fossa inferiorly) and ending at where the implant fully enters the lateral border of
the nasal fossa after completely traversing the fossa. The cortical apical engagement of implant is
defined as the portion of the apical end of the transnasal implant that was fully encased in the
cortical lateral paranasal bone after the implant transversed the nasal fossa. This was a linear
measurement beginning from the internal cortical border of the lateral nasal fossa (after the
implant transversed the nasal fossa) and ending at the most apical location of the implant.

11

Chapter 2: Results
Results are reported at baseline and 12 months after restorative functional loading. A total
of 10 patients were evaluated with a total of 18 transnasal dental implants. Variables were
assessed for normality using a Shapiro-Wilk test and found to be normally distributed. CBCT
analysis was utilized to provide linear measurements regarding: marginal bone loss of transnasal
implant at mesial and distal sites (n=36), availability of subnasal bone at the proposed implant
site (n=18), implant lateral contact with cortical paranasal bone (n=18), and implant apical
engagement in cortical paranasal bone (n=18). Statistical analysis reveals 12 months post
placement and functional loading of transnasal implants, the mean marginal bone loss was 0.70
mm (95% CI: -0.90 - -0.50 mm); paired t-test reveals that the amount of bone loss is statistically
significant (p<0.0001), Figure 1. Furthermore, subnasal bone availability at site of proposed
implants was found to have a mean value of 5.46 mm (95% CI: 4.94 - 5.98 mm), while subnasal
bone available at maxillary midline had a mean value of 4.69 mm (95% CI: 3.48 - 5.92 mm).
Additionally, when evaluating the linear amount of lateral contact with cortical paranasal bone, a
value of 12.92 mm (95% CI: 11.28 – 14.56 mm) was observed. Regarding the linear
measurement of the apical engagement in cortical paranasal bone, the value was measured to be
2.70 mm (95% CI: 2.31 – 3.09 mm).

12

Chapter 3: Discussion
Transnasal implants are an emerging alternative to placing conventional implants as an
anterior anchorage to zygomatic implants. Due to the novelty of these implants, there is minimal
research available documenting their use and their marginal bone loss as compared to
conventional implants. Therefore, it is unclear if transnasal dental implants can be considered as
an alternative to conventional implants for use in clinical cases of severe pre-maxilla atrophy.
The purpose of this study is therefore to provide objective and comparative data to better clarify
if transnasal implants can be considered an appropriate alternative solution to conventional
implants in clinical cases presenting with severe pre-maxilla atrophy. The significance of this
study is that it will be one of the first to document the marginal bone loss of transnasal dental
implants as a means to directly compare them with conventional implants.
In examining the marginal bone loss surrounding transnasal dental implants at one year
post loading, it was found to have a mean value of 0.70 mm with a 95% confidence that the
population mean is between -0.90 mm and -0.50 mm. Additionally a paired t-test reveals that the
amount of bone loss one year post transnasal implant placement is statistically significant
(p<0.0001). The significance of this finding is in the comparison of the marginal bone loss of
transnasal implants after one year as compared to conventional implants. The results suggest that
transnasal implants undergo a similar amount of marginal bone loss as conventional implants and
this marginal bone loss of transnasal implants is within the accepted range of peri-implant bone
loss one year after placement of conventional implants. According to the According to the 2017
World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions,
an acceptable amount of peri-implant bone loss after one year is defined as 1-1.5 mm of bone
loss, and <0.2 mm annually thereafter
37, 12
. Therefore, specifically in relation to the observed
13

marginal bone loss, it is suggested by this study that the placement of transnasal implants is
comparable to and therefore an acceptable alternative to conventional implants to achieve
anterior anchorage when paired with an zygomatic implant. Although conventional implants
have significantly more studies examining their success, the patient population seeking
rehabilitation due to an atrophic maxilla are not typically considered suitable candidates for
conventionally placed implants due to a limitation of vertical bone present subnasally. In this
study, the amount of subnasal bone present at the intended anterior implant site was measured to
be 5.46 mm with a 95% confidence that the population mean is between 4.94 mm and 5.98 mm,
but other studies report as little as 2 mm of available subnasal bone
4
. Patients with this clinical
presentation present a notable challenge in implant dentistry and in these clinical presentations of
severe pre-maxilla atrophy, even substituting a short (6 mm) implant will not be a sensible
solution due to the amount of subnasal bone atrophy. In cases of severe Zone-1 atrophy,
transnasal implant placement is a valid alternative to consider as the nasal crest and zygomatic
bones are less affected relative to atrophy of the maxilla
25, 36
. One of the primary advantages of
utilizing extra-long transnasal implants is that the amount of subnasal bone is not as significant
of a limiting factor, as it would have otherwise been if limited to only placing conventional
implants in the pre-maxilla region. Additionally, utilizing a transnasal approach removes the
necessity and complexity of proceeding with a Quad Zygoma approach where two zygomatic
implants are placed per zygoma. Another advantage to take into consideration is that, compared
to a conventional implant, a transnasal implant provides greater bone to implant contact due to its
longer length. This longer implant length is important, especially when considering its
contribution to gaining lateral engagement of the cortical paranasal bone as the transnasal
14

implant transects the nasal cavity and additionally the apical engagement where the apex of the
implant is fully encased within cortical paranasal bone.
In order to further compare the utilization of transnasal implants versus a conventional
implant as the anterior anchorage to a paired zygomatic implant, additional measurements were
included to analyze the bone to implant engagement. The three measurements regarding bone to
implant contact for comparative analysis between conventional implants and transnasal implants
includes subnasal bone engagement, apical bone engagement, and lateral bone engagement. The
amount of subnasal bone present at the proposed anterior implant site was measured to access
specific factors. Firstly, is there adequate subnasal bone present to place a conventional short (6
mm) length implant in patients with severe pre-maxilla atrophy? Secondly, how much bone to
implant engagement was utilized by transnasal implants placed in the subnasal region? In the
intended anterior anchorage implant position, the amount of available subnasal bone for implant
engagement was measured to be 5.46 mm with a 95% confidence that the population mean is
between 4.94 mm and 5.98 mm. Additionally, at the midline region inferior to the anterior nasal
spine, the amount of bone available for implant placement was 4.69 mm with a 95% confidence
that the population mean is between 3.48 mm and 5.92 mm. The significance of these values are
two-fold. As previously discussed, this value is a critical factor to determine if the placement of a
short conventional dental implant is feasible or if an alternative solution such as a transnasal
dental implant should be employed.
This measurement of subnasal bone provides objective data related to the amount of bone
to implant engagement by the transnasal implant in the coronal section of the implant. In addition
to subnasal bone, measurements were taken to access the amount of bone to implant contact in
the apical region of the transnasal implant. This linear measurement begins where the apical end
15

of the transnasal implant has fully transversed the nasal cavity and is fully housed into the
cortical paranasal bone. In this study, the apical bone to implant contact of the transnasal implant
was observed to be 2.70 mm with a 95% confidence that the population mean is between 2.31
mm and 3.09 mm. The significance of this apical bone engagement is that it provides, possibly
for the first time, objective data relating to the amount of cortical bone to implant contact at the
apical end of the transnasal implant. It is perhaps with the combined values of the transnasal
implants’ apical and subnasal bone engagement that an equivalent bone to implant contact
comparison can be established between transnasal implants and conventional implants. This
comparison is of significance because without long-term studies evaluating transnasal implants,
the success rate of transnasal implants may possibly be predicted by comparing them to
conventional implants with a similar amount of bone engagement. Moreover, the success rates of
conventional short dental implants of 6 mm or 8 mm length implants has been extensively
researched and documented. A systematic review and meta-analysis examining the success of
short 6 mm implants reported a 97.7% success rate in the maxillary arch after 4 years
35
.
Similarly, a separate systematic review reported a 94.1% success rate for short implants placed in
the maxillary arch after 5.8 years
33
. Likewise for 8 mm implants placed in the maxillary arch,
two separate systematic reviews determined a success rate of 95.5% and 92.6% with a follow up
of 4 and 5.5 years, respectively
5, 26
. Compared conventional short implants, there is currently
limited long term documentation of the transnasal implant success due to the relative novelty of
their use. However, by summation of the coronal and apical bone to implant contact, the
transnasal implant is seen to have a mean bone to implant contact value of 8.16 mm. This value
represents the linear length of the transnasal implant that, like a conventional implant, is fully
encased by bone. The significance of this measurement is that, possibly for the first time, an
16

objective bone to implant contact comparison can be made between conventional dental implants
and transnasal dental implants. This value of 8.16 mm of bone to implant contact of transnasal
implants allows for two key deductions: transnasal dental implants may possibly be comparable
to conventional implants of similar 8 mm length, additionally, that transnasal implants may
possibly have a similar success rate as 8 mm conventional implants under similar conditions.
Moreover, as an addition to the amount of bone to implant contact in the apical and coronal
regions, transnasal implants also have the benefit of lateral engagement with the paranasal bone
in which this study also sought to measure. The lateral contact was defined as the portion of the
transnasal implant that laterally engaged the cortical paranasal bone as the implant is traversing
the nasal cavity. The lateral bone to implant contact of the transnasal implants in this study was
measured to be 12.8 mm with a 95% confidence that the population mean is between 11.28 mm
and 14.56 mm. The significance of this value is supplementary to the previous measurements of
the coronal and apical bony engagement of the transnasal implant. Contrarily to a conventional
short implant, transnasal implants are significantly longer and due to their trajectory through the
nasal cavity, they also have lateral engagement to the cortical paranasal bone. Although no direct
correlation to conventional implants may be made, the additional lateral bone to implant contact
of the transnasal implant allows one to infer that transnasal implants have additional anchorage
and therefore a potentially higher primary stability and functional load capacity than a similarly
placed 6 or 8 mm conventional implant.
This present study has a number of limitations primarily due to the retrospective nature of
the study. The limitations include: (1) having a limited sample size and population; therefore, it
cannot be concluded if the obtained results are also indicative of a broader population; (2) having
a short term length of study; therefore, the results of this study can only be interpreted and
17

compared to conventional implants within the first year post functional loading; (3) not having a
control group; due to the clinical wants and needs of the patients to undergo full mouth
rehabilitation via a zygomatic approach due to severe maxillary atrophy, conventional implants
were not placed or present to serve as a direct control to this study, rather the acceptable range of
marginal bone loss around conventional implants one year post loading was determined previous
research studies.
Future directions can be recommended which will primarily be focused on the limitations
of this present study. If an insufficiency of participants exists, a prospective split mouth study
design can include patients with an atrophic pre-maxilla that have adequate subnasal bone
available to place a short (6 mm) conventional dental implant and a transnasal implant on the
contralateral side, both of which will be paired with a zygomatic implant and compared to one
another after functional loading at 1, 3, 5, and 10 years. Otherwise if there is an ample population
size available, a prospective study can be undertaken where patients with an atrophic pre-maxilla
will be grouped as having >6 mm subnasal bone (to receive conventional implants) and those
with <6 mm bone (to receive transnasal implants). This study design will compare conventional
implants vs transnasal implants as the anterior anchorage in patients with pre-maxilla atrophy
when paired with zygomatic implants with post functional loading compared at 1, 3, 5, and 10
years.

18

Chapter 4: Conclusion
In conclusion, the main objective of this study was to investigate whether transnasal implants
may be deemed a viable substitute for conventional implants when utilized as an anterior
anchorage to a zygomatic implant. This was achieved by accessing whether transnasal implants
exhibit comparable rates of marginal bone loss as documented with conventional implants in the
same time period. This study determined that the marginal bone loss of transnasal dental
implants at one year post loading was found to have a mean value of 0.70 mm ( 95% CI: -0.90 -
0.50 mm). The significance of this finding is the presentation of preliminary short term data
which suggests that transnasal implants undergo a similar and acceptable range of peri-implant
bone loss as do conventional implants one year post loading. Therefore, it is concluded that
under the short-term comparison timeframe of one year post loading, transnasal dental implants
may be considered as an acceptable alternative to conventional implants when utilized as an
anterior anchorage to a zygomatic implant, especially in clinical cases where there is minimal
(<6 mm) subnasal bone available due to severe atrophy in the pre-maxilla region.

19

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23

Figures

Figure 1. Marginal bone level of transnasal dental implants. Marginal bone levels of
transnasal dental implants were assessed during surgical placement and one year post loading.
Error bars represent standard error of the mean (SEM). Statistical analysis is via paired t-test.
*p<0.0001.

-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
initial 1 year
Marginal Bone Level (mm)
*

Abstract (if available)

Abstract Background: The rehabilitation of the atrophic maxillae with dental implants represents a challenge that can be addressed with zygomatic dental implants and traditional axial implants. In the event of a severely atrophic pre-maxilla, a Quad-Zygoma approach may be necessary to provide anchorage for the fixed restoration. The proximity of anatomical features can increase the possible morbidity of the Quad-Zygoma approach and instead, transnasal implants may serve as a viable anterior anchorage alternative in the atrophic pre-maxilla region.

Materials and Methods: A total of 10 patients with a combined 18 transnasal implants paired with a single zygomatic implant were included in this study. The implant placement surgeries were performed by two experienced dental surgeons with previous clinical experience in placing zygomatic implants. Transnasal implant marginal bone level changes were evaluated on CBCT images taken immediately after transnasal implant placement and one year of follow-up post loading. The reference point for the CBCT measurement of mesial and distal bone loss after one year was the horizontal interface between the implant and the abutment.

Results: The retrospective CBCT analysis of 18 transnasal implants placed in 10 patients shows an average marginal bone loss of 0.70mm over a time period of one year following restorative loading, p<0.0001.

Conclusion: The marginal bone loss observed in transnasal implants one year post loading is comparable to the marginal bone loss of conventional implants under similar conditions. Therefore it is believed that transnasal implants can be considered as an acceptable anterior anchorage alternative to conventional implants in the atrophic pre-maxilla region when paired with a single posterior zygomatic implant.

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Creator Eshoiee, Nathan (author)

Core Title Transnasal dental implants: indication and the report of 10 cases

School School of Dentistry

Degree Master of Science

Degree Program Biomedical Implants and Tissue Engineering

Degree Conferral Date 2023-08

Publication Date 07/17/2023

Defense Date 05/24/2023

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

Tag dental implants,OAI-PMH Harvest,transnasal

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Advisor Bakhshalian, Neema (committee chair), Aalam, Alexandre (committee member), Chen, Casey (committee member), Kar, Kian (committee member)

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