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Retrospective analysis of early implant placement in non-grafted extraction sites: Need for grafting and crestal bone remodeling

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Retrospective analysis of early implant placement in non-grafted extraction sites: Need for grafting and crestal bone remodeling

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Content Retrospective analysis of early implant placement in non-grafted extraction sites:
Need for grafting and crestal bone remodeling
By
Anahita Behshadpour, DDS
A Thesis Presented to the
FACULTY OF THE USC HERMAN OSTROW SCHOOL OF DENTISTRY
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(BIOMEDICAL IMPLANTS AND TISSUE ENGINEERING)
August 2024
Copyright 2024 Anahita Behshadpour

Table of Contents
List of Tables ……………………………………………………………………………… iii
List of Figures ……………………………………………………………………………… iv
Abstract …………………………………………………………………………………… v
Introduction ………………………………………………………………………………… 1
Chapter1: Methods & Materials …………………………………………………………… 3
Chapter2:Results …………………………………………………………………………… 6
Chapter3:Discussion ………………………………………………………………………… 7
Chapter4: Conclusion ……………………………………………………………………… 12
References …………………………………………………………………………………. 13
Figures, tables, pie charts………………………………………………………………… 17-23
ii

List of Tables
Table 1: The various implant systems used from September 2012 to December 2023 at
the University of Southern California Dental Faculty Practice ……………………………… 18
Table 2: The different implant platforms and their corresponding quantities that
were included in this study ………………………………………………………………… 18
Table 3: The number of sites that received bone augmentation at the time of
extraction, simultaneous with implant placement, or no bone augmentation ………………….. 18
iii

List of Figures
Figure 1. Sample of Excel Data Sheet …………………………………………………… 17
Figure 2. Example of 2D Radiographs of Straumann Bone Level Implant and calibration
measuring tool …………………………………………………………………………. 17
Figure 3: Illustration of the total number of implants with internal, external, and transmucosal
connections …………………………………………………………………………….. 19
Figure 4: Illustration of the different types of implant systems that were used in the faculty
practice of USC from 2012 to December 2023 …………………………………………… 19
Figure 5: Illustration of the posterior vs anterior location of the implants that were placed
in the faculty practice of USC from 2012 to December 2023 ……………………………… 20
Figure 6: Illustration of internal connection platforms presented with average bone loss
greater than 1mm in one year versus average bone loss of less than or equal to 1 mm ……… 20
Figure 7: Illustration of external connection platforms presented with average bone loss
greater than 1mm in one year versus average bone loss of less than or equal to 1 mm ……… 21
Figure 8: Illustration of the need for bone augmentation at the time of extraction,
simultaneous with implant placement, and no bone augmentation at all …………………… 21
Figure 9: Illustration of the sites with implant platforms greater than 4 mm
that required bone augmentation versus sites with implant platforms less than or
equal to 4 mm that required bone augmentation…………………………………………… 22
Fig 10: Illustration of the sites with implant platforms greater than 4 mm (60.91%)
versus sites with implant platforms less than or equal to 4 mm (39.09%) ………………….. 22
Fig 11: Illustration of the anterior sites with the need for grafting (60%) vs posterior sites
with the need for grafting (40%) ………………………………………………………… 23
iv

Abstract
Post-extraction ridge remodeling commonly occurs. Extraction socket grafting (ridge
preservation) is proposed to reduce the post-extraction ridge remodeling. One of the reasons for ridge
preservation is to reduce the need for future bone augmentation. Despite dimensional changes of the
alveolar ridge, placement of implants in proper prosthetic position is feasible as reported in
prospective studies utilizing early placement protocols and implant site development when needed.
The aim of this retrospective analysis is to assess the need for bone augmentation for implant
placement at non-grafted extraction sites with early implant placement protocol.
Electronic dental records were obtained from patients who underwent dental implant placement
in USC’s faculty practice from 2012 till December 2023. Implant placement was done by one
experienced periodontist. The implant systems represented in the study were Straumann Bone Level
NC or RC, Straumann TL, Dentium, Zimmer Biomet 3i Certain, and Zimmer Biomet 3i Osseotite.
Implants were placed at sites with history of simple or surgical extractions with or without ridge
preservation by providers at USC’s faculty practice. Part of this study focused on which sites received
bone graft at the time of extraction or at the time of implant placement. Two-dimensional radiographs
were taken at implant placement, impression stage and 6 months to 1 year follow up after implant
crown delivery. These radiographs were used to evaluate mesial and distal crestal bone level changes
from the platform of the dental implants to the first bone to implant contact. The marginal bone loss on
mesial and distal were recorded at the time of implant placement, impression and 6 months to 1 year
follow up intervals.
Out of the 280 charts evaluated radiographically, 158 met the study criteria. Charts that did not
have proper 2D periapical radiographs at specific time points were excluded. In total 158 charts and
197 implants were included in this study.
Descriptive statistics were calculated for all variables of interest. Continuous measures were
summarized using means and standard deviations whereas categorical measures were summarized
using counts and percentages. The variables were assessed to determine the correct ranking of values
between the two groups of internal and external platforms using a Wilcoxon Rank Sum test. Changes
over time in variables such as mesial bone depth and distal depth were analyzed using paired t-tests (p
< 0.001). Bone level changes from the platform of the dental implants to the first bone-to-implant
contact at different time intervals—implant placement, impression, and 6 months to 1 year
follow-up—were assessed using analysis involving two variables adjusting for the correlation among
observations taken on the same aspect, mesial or distal. Comparisons between continuous variables
were run using Pearson correlation coefficients. All analyses were carried out using SAS Version 9.4
(SAS Institute, Cary, NC, USA).
v

Among the total of 197 implants placed, 84 (42.63%) were external hex and 113 (57.36%) were
internal hex and 13 (11.5%) were TL platforms. The number of implants more than 4 mm in diameter
was 120 (60.91%) and less than or equal to 4 mm was 57 (39.09%). Additionally, 1% of cases
required separate grafting, which was in the anterior region. Furthermore, 7.58% of cases necessitated
simultaneous grafting, with 60% of those sites being anterior. The percentage of sites requiring
grafting at the time of implant placement with a platform diameter greater than 4 mm was 39.97%.
The percentage of sites requiring grafting at the time of implant placement with a platform diameter
equal to or less than 4mm was 60.03%.
vi

Introduction
Extraction socket grafting, also known as ridge preservation, has emerged as a promising
technique aimed at mitigating post-extraction ridge remodeling and optimizing conditions for
successful implant placement. The abundance of biomaterial options available has led to a surge in
socket grafting procedures, seemingly considered necessary following every tooth extraction.
However, the pertinent question to be explored is whether it is indeed imperative to graft every socket
post-extraction.
Comparable implant placement feasibility, success rates, and marginal bone loss can be anticipated
in both alveolar ridge preservation and naturally healing socket sites. However, there appears to be
considerable uncertainty or a notable risk of bias in many studies within this domain, given that a
significant portion of them receive funding from industry sources.
Post-extraction ridge remodeling is a well-documented phenomenon that often presents challenges
in dental implantology. The formation of a stable intra-socket fibrin coagulum is essential for
hemostasis and new bone formation. Following tooth extraction, the alveolar ridge undergoes
resorption, leading to significant dimensional changes that can complicate the placement of dental
implants and compromise long-term esthetic and functional outcomes. According to Van der Weijden
& Slot in 2009, mean clinical mid-facial height loss post-extraction is nearly 1.5 mm, and horizontal
width reduction averages 3.8 mm (1,2,3). Patients seeking implant restoration for areas where teeth
are missing frequently exhibit significant bone loss, leading to a variety of proposed grafting methods
and procedures. In some cases, both bone and gum tissue reconstruction are required to achieve both
functional and aesthetic outcomes in implant rehabilitation.
The primary objective of extraction socket grafting is to minimize the loss of alveolar bone volume
and preserve the natural contours of the ridge following tooth extraction. By maintaining adequate
bone volume and architecture, ridge preservation not only enhances the aesthetic outcome of dental
implant treatment but also provides a stable foundation for implant osseointegration.
One of the key motivations for ridge preservation is to reduce the necessity for future bone
augmentation procedures. By preserving the dimensions of the alveolar ridge at the time of extraction,
clinicians can potentially avoid the need for more extensive bone grafting surgeries, thereby
streamlining the implant placement process and minimizing patient morbidity.
The potential for bone regeneration in the extraction socket allows for the development and
strengthening of a trabecular bone framework, which typically increases in size 8–12 weeks after the
extraction procedure. Between the 12th and 16th weeks, this newly formed bone stabilizes,
establishing a more robust foundation. The highest osteogenic potential and presence of bone-building
cells (osteoblasts) occur around the 10–12-week mark post-extraction. As time progresses, the area of
active new bone formation shifts upwards from the initial blood clot at the apex, becoming more
coronal by the 12-week mark.
1

Socket grafting procedures may potentially impede this upward movement of bone growth by
reducing the formation of new blood vessels (neoangiogenesis) at the crestal part of the socket. These
biological processes, along with the development of new blood vessels within the socket, appear to be
affected when bone substitutes are used for socket grafting in an effort to minimize changes in the
dimensions of the alveolar ridge.
One study by Becker & Tibbetts in 2017 has explored potential factors contributing to the
significant rise in dental implant complications in recent years. Machtei, Mayer, Horwitz, &
Zigdon-Giladi in 2019 used human histological studies to demonstrate that up to a 60% reduction in
new bone formation occurs when sockets are grafted with bone substitutes. Within just four months,
non-grafted sockets exhibited 81.5% new bone formation compared to 21.5% in sockets grafted with
xenograft material. Delayed new bone formation and shortened healing times could contribute to the
increased incidence of implant complications. Defects smaller than 0.5 cc can achieve up to 89%
filling without the need for bone grafting, provided adequate time is allotted for healing (Verdugo,
Simonian, D’Addona, Pontón, & Nowzari, 2010).
Despite the inevitable dimensional changes that occur in the alveolar ridge post-extraction, recent
prospective studies have demonstrated the feasibility of placing dental implants in the proper
prosthetic position using early placement protocols and implant site development techniques when
necessary. These findings underscore the importance of ridge preservation as a proactive strategy to
optimize implant outcomes and minimize the need for additional surgical interventions. (2)
A meta-analysis highlighted frequent adverse events, with three studies reporting a high incidence
of complications and two indicating increased risks associated with alveolar ridge preservation (ARP)
(MacBeth, Trullenque-Eriksson, Donos, & Mardas, 2017). Common complications reported in ARP
included inflammation, edema, infection, facial pain, particle loosening and exposure, fibrous
encapsulation, and inadequate socket fill (MacBeth et al., 2017). The standardized mean difference in
mid-facial vertical bone height between ARP and natural socket healing was 0.7 mm (MacBeth et al.,
2017). As conscientious clinicians, we must conduct a risk assessment to determine whether a 0.7 mm
gain in height justifies the potential complications and financial impact on our patients. Additionally,
ARP was associated with a mean reduction in alveolar bone width resorption of 1.2 mm, though this
was not statistically significant compared to unassisted socket healing (MacBeth et al., 2017).
In general, there has been extensive research examining the bone remodeling process subsequent
to dental implant placement. Thus, a retrospective two-dimensional radiographic analysis was
undertaken to investigate the correlation between implant placement and alveolar bone remodeling in
extraction sockets that underwent bone augmentation either as a separate procedure prior to implant
placement or concurrently with implant placement. This assessment aimed to compare the remodeling
in these augmented sites with those that did not undergo any bone grafting.
2

Chapter 1: Methods and Materials
Study Design:
This study was conducted using the Herman Ostrow School of Dentistry of USC patient
records. The University of Southern California Institutional Review Board (IRB) approved the
use of patient records for this retrospective study (HS-23-00563). Radiographs, and chart note
documentation records for 280 charts were acquired from the Herman Ostrow School of
Dentistry of USC Axium Records from September 2012 to December 2023.
Start ( Axium records from September 2012 to December 2023)
|
Record of data for extractions performed with or without simultaneous bone augmentation procedure.
|
Record of data for dental implant placement with or without simultaneous bone augmentation
procedure.
|
Two-Dimensional Radiographic Analysis
|
Investigation of correlation between Implant Placement & Alveolar Bone Remodeling at sites with or
without bone augmentation. ( Compare remodeling in augmented sites with those without bone
grafting)
|
End
This flowchart outlines the sequential steps involved in conducting a retrospective radiographic analysis to assess the
relationship between dental implant placement, bone augmentation procedures, and alveolar bone remodeling.
3

Study Population:
The study population consisted of patients treated by a single experienced periodontist at the
faculty practice for implant placement. Implant placement was performed by the same experienced
periodontist. The implant systems represented in the study included Straumann BL/ BLT (NC/RC)
(80) , Straumann TL(13) , Dentium (17) , Zimmer Biomet 3i Certain (3) , and Zimmer Biomet 3i
Osseotite (84). Implants were placed at sites with a history of simple or surgical extractions without
ridge preservation by providers at USC’s faculty practice.
Part of this study focused on determining which sites received bone grafts at the time of
extraction or at the time of implant placement. Two-dimensional radiographs were taken at implant
placement, the impression stage, and during the 6-month to 1-year follow-up after implant crown
delivery. These radiographs were utilized to evaluate mesial and distal crestal bone level changes from
the platform of the dental implants to the first bone-to-implant contact. Marginal bone loss on the
mesial and distal aspects was recorded at the time of implant placement, during the impression stage,
and at 6-month to 1-year follow-up intervals
Inclusion criteria:
The inclusion criteria for the study are as follows:
1. Adults over 18 years old.
2. Record of extraction available at USC.
3. Extraction and placement done by the two different practitioners: 41% of extractions were
performed by the same periodontist; records for the remaining extractions were difficult to
ascertain.
Extraction techniques were not standardized by all providers. For one provider the description of
extraction procedures were more descriptive and included the following: The extraction process
involved:
● Sectioning of teeth Bucco-Lingually (mandible) or Mesio-Distally along the furcation.
● Creation of mesial and distal troughs, approximately 3-4 mm deep, around the roots followed
by the use of periotomes, elevators, and forceps.
● Occasionally, teeth were extracted in fragments or as a single piece.
● Single-rooted teeth were extracted using mesial and distal troughing techniques alongside
periotomes.
Exclusion Criteria:
The exclusion criteria for the study are as follows:
1. Existing healed sites without a record of extraction at USC.
2. Medically compromised patients with uncontrolled medical conditions.
3. Current smokers.
4. History of previous implant failure.
5. Radiographs that were non-diagnostic, where the mesial and distal bone levels could not be
discerned.
4

Clinical Records Assessment:
An Axium search query was conducted using simple or surgical extraction codes (D7140, D7120)
and the surgical implant body placement code (D6010). Subsequently, 280 charts were identified, and
two-dimensional radiographs, medical history records, clinical chart notes, and scanned implant
identifications were obtained.
Chart notes were meticulously reviewed (Figure:1) to identify instances of separate bone
augmentation performed at the time of extraction, as well as bone augmentation carried out at the time
of implant placement. Additionally, information regarding the implant site (anterior vs. posterior), the
specific implant system used, and the size of the implant placed was recorded.
Radiographic Assessment:
The mesial and distal radiographic measurements, extending from the height of the implant
platform to the first bone to implant contact, were calibrated using the Schick radiographic
calibrating measuring tool (Figure 1) according to the diameter of the implants documented in
the clinical chart notes and uploaded implant serial number. Alveolar ridge remodeling was
radiographically evaluated at three-time intervals: 'At the time of implant placement', 'At the
time of impression coping placement', and '6 months to 1 year follow-up.
5

Chapter 2: Results
Out of the 280 charts evaluated radiographically, 158 met the study criteria. Charts that did not
have proper 2D periapical radiographs at specific time points were excluded. In total 158 charts and
197 implants were included in this study.
All two-dimensional radiographic measurements were taken by two individuals. Calibration of
the two examiners was conducted on 10 charts and tested to eliminate any inter-examiner
measurement discrepancies. To evaluate the relationship between the implant’s platform and the
amount of bone remodeling, the level of the implant’s platform to the first bone- to- implant contact on
the mesial and distal of the implant was measured based on two-dimensional radiographs at the time of
implant placement, impression coping placement, and 6 months to one-year follow-up ( Fig 1-3)
Descriptive statistics were calculated for all variables of interest. Continuous measures were
summarized using means and standard deviations whereas categorical measures were summarized
using counts and percentages. The variables were assessed to determine the correct ranking of values
between the two groups of internal and external platforms using a Wilcoxon Rank Sum test. Changes
over time in variables such as mesial bone depth and distal depth were analyzed using paired t-tests (p
< 0.001). Bone level changes from the platform of the dental implants to the first bone-to-implant
contact at different time intervals—implant placement, impression, and 6 months to 1 year
follow-up—were assessed using analysis involving two variables adjusting for the correlation among
observations taken on the same aspect, mesial or distal. Comparisons between continuous variables
were run using Pearson correlation coefficients. All analyses were carried out using SAS Version 9.4
(SAS Institute, Cary, NC, USA).
Among the total of 197 implants placed, 84 (42.63%) were external hex and 113 (57.36%) were
internal hex. Of the total number of implants placed 13 (11.5%) were TL platforms. 143 (72.58%) of
the implants were placed in the posterior and 54 (27.41%) were placed in the anterior region. The
number of implants with platform width more than 4 mm in diameter was 120 (60.91%) and less than
or equal to 4 mm was 77 (39.09%). Additionally, 1% of cases required separate grafting, which was in
the anterior region. Furthermore, 7.58% of cases necessitated simultaneous grafting, with 60% of
those sites being anterior. The percentage of sites requiring grafting at the time of implant placement
with a platform diameter greater than 4 mm was 39.97%. The percentage of sites requiring grafting at
the time of implant placement with a platform diameter equal to or less than 4mm was 60.03%.
85.71% of external hex platforms presented with average bone loss less than 1 mm over a one year
period, while 14.29 % of external hex platforms presented with average bone loss greater than 1 mm
over a one year period. 97.4% of external hex platforms presented with average bone loss less than 1
mm over a one year period, while 2.6 % of external hex platforms presented with average bone loss
greater than 1 mm over a one year period.
6

Chapter 3: Discussion
When extracting teeth, the surgeon may elect to perform bone augmentation, known as a
ridge preservation procedure. Our study challenges the traditional paradigm regarding the
necessity of bone augmentation in extraction sites. Some of these patients received bone
augmentation at the time of extraction, while in some cases, bone augmentation was performed
simultaneously at the time of implant placement, and some did not require any bone
augmentation. We evaluated marginal bone remodeling on the mesial and distal aspects during
three different time intervals: at the time of implant placement, during impression coping, and at
the 6-month to 1-year follow-up. While ridge preservation procedures remain valuable tools in
certain clinical scenarios, our findings suggest that careful patient selection and individualized
treatment planning are paramount. Our hypothesis was that not every extraction site requires
separate bone augmentation at the time of extraction.
Previous pre-clinical and clinical studies have evaluated two-dimensional radiographic marginal
bone remodeling around implants placed at extraction sites, where bone augmentation was performed
at the time of extraction, implant placement, or no bone augmentation was conducted at all. After
tooth extraction, alveolar bone remodeling is unavoidable. The formation of a stable intra-socket fibrin
coagulum is essential for hemostasis and new bone formation. On average, post-extraction clinical
mid-facial height loss is nearly 1.5 mm, and horizontal width reduction averages 3.8 mm. (3)
Additionally, a descriptive study by Heberer in 2011 indicated that bone formation in Bio-Oss
Collagen-grafted human extraction sockets was lower than in ungrafted sockets. Bone formation
occurred in all specimens with varying degrees of maturation independent of the grafting material and
was initiated from the apical region. (7)
Mardas in 2015 illustrated that there is limited evidence to support the clinical benefit of alveolar
ridge preservation over unassisted socket healing in improving implant-related outcomes despite a
decrease in the need for further ridge augmentation during implant placement. Similar implant
placement feasibility, survival/success rates, and marginal bone loss should be anticipated following
alveolar ridge preservation or unassisted socket healing. (8,9,10)
The potential for bone regeneration within the extraction socket allows for the development and
maturation of a trabecular bone matrix, which typically increases in volume between 8 and 12 weeks
post-extraction. By the 12th to 16th weeks, the newly formed bone stabilizes, establishing a firmer
trabecular foundation. (11)
On average, clinical and radiographic mid-buccal height loss following extraction falls within the
range of approximately 1.5–1.6 mm, while horizontal bone width reduction averages 3.8 mm.
Post-extraction bone loss tends to be most pronounced in the horizontal dimension, particularly on the
facial aspect of the alveolar process. (3)
7

The mean difference in horizontal bone width reduction six months post-extraction in non-molar
teeth between sites undergoing ridge preservation and those left for "extraction-only" was found to be
1.2 mm versus 2.7 mm, resulting in a 1.5 mm discrepancy . Posterior teeth typically exhibit a greater
bone volume, compensating for a higher degree of horizontal ridge reduction, hence an anticipated
difference of less than 1.5 mm. (12)
Some studies have suggested that thicker flaps may enhance circulation to the underlying bone
structures, thereby influencing the initial phases of wound healing (13). Clinically, manipulating and
suturing thin tissues can pose greater challenges and may result in increased trauma, loss of papillae,
and scar formation post-surgery. While tissue phenotype may impact the initial stages of wound
healing during ridge augmentation, it does not appear to have a detrimental effect on long-term facial
graft stability. (14)
Implant positioning can also impact esthetics, blood supply, and buccal bone formation, particularly
if the implant is placed too far facially, leading to unfavorable outcomes (11). Research indicates that
individuals with thin gingival phenotypes can retain approximately 97% of the augmented
bucco-lingual width 52 months post-augmentation. A staged implant placement following
augmentation has been shown to be predictable after a short-healing reconstructive protocol in the
esthetic zone, maintaining stable peri-implant tissues in the long term. Periosteal guided bone
regeneration appears to be a reliable protocol for achieving stable facial bone regeneration after
autogenous grafting in advanced osseous defects (14).
Anterior teeth pose a greater esthetic challenge due to the thin facial bone, typically around one
millimeter thick, and the presence of dehiscences, which may easily collapse, resulting in increased
bone atrophy and dimensional changes. (16, 34)
Socket dehiscences may also lead to less favorable healing outcomes and reduced bone fill if the
extraction process is traumatic. However, preserving the facial periosteum may compensate for this
and facilitate the formation of new buccal bone plate. (15)
Human bone repair and the formation of new buccal bone will occur on large bony defects filled
solely with osseous coagulum (14). Following tooth extraction, it's crucial for the clinician to ensure
prompt blood clot formation. If the socket fails to fill with blood, intra-marrow penetrations (cortical
perforations) may be employed to stimulate intra-socket bleeding and angiogenesis.
A recent meta-analysis indicates that socket grafting may offer notable advantages in preventing
horizontal bone resorption, potentially reducing such loss by an additional 1.9 mm compared to tooth
extraction alone . However, no definitive conclusions can be drawn regarding the positive impact on
implant-related outcomes, such as changes in bone level or the occurrence of biological complications
in the short and long term. Overall, the scientific evidence quality of the included studies was deemed
average to low, with a high risk of bias. (10)
8

The timing of implant placement following socket grafting remains a subject of debate, with
certain grafting materials demonstrating superior performance in facilitating new bone formation
compared to others. Patients should be informed that when a socket is grafted with a bone substitute,
they should anticipate a significant waiting period of 6–9 months to ensure stable intra-socket bone
healing before implant placement. This delay primarily aims to gain an additional 1−2 mm of bone
width, which may be unnecessary for implants with diameters ranging from 4.1 to 4.8 mm. (35)
Furthermore, healing responses exhibit a broad spectrum of individual variability. The rationale for
extended waiting periods more than 5–6 months, stems from human studies indicating incomplete
osseointegration even at 12 months post-implant placement in grafted sockets. (17)
Research on molar extraction sites, augmented with bovine bone and exhibiting wide and shallow
facial dehiscences, demonstrated less favorable outcomes compared to implants inserted in
non-grafted sites that had undergone healing. These grafted sites exhibited incomplete
osseointegration at the 12-month mark, with increased probing depths and bleeding upon probing.
Additionally, original human research outlining the principles of guided bone regeneration in young,
healthy individuals revealed that small socket-like bony defects (2.5 mm in diameter by 2 mm deep)
still exhibited undermineralized tissue and limited bone fill even after 9 months. (18)
Grafted sockets seem to require substantially longer healing periods. Comparatively, only 4 months
after extraction, non-grafted sockets exhibit significantly higher levels of bone fill (81.5%) and new
bone formation. (19)
After an average healing period of 12 weeks, new cortical bone formation and adequate bone width
provided the feasibility for implant placement in both sites with and without dehiscences at the time of
extraction. The naturally regenerated bone within the socket ensures long-term functional stability of
the implants. This prompts the question of whether socket grafting is indispensable for achieving
long-term functional implant stability, particularly considering that non-grafted sockets exhibit 81.5%
of new bone formation four months post-extraction. Grafted sockets appear to require significantly
longer healing times, indicating a potential delay in achieving optimal conditions for implant
placement. (19)
At least 6–7 months or potentially longer, depending on the size of the defect and the type of bone
substitute utilized, are typically required for adequate healing. Subsequent shrinkage of the bone width
occurs most extensively during the initial six months following extraction and gradually thereafter.
During this post-extraction period, the alveolar bone lacks proper mechanical stimulation for volume
maintenance. The relatively low level of new bone formation of 21.5% within the socket, as observed
in studies such as Machtei et al., 2019, resulting from alveolar ridge preservation with bone
substitutes, has the potential to compromise primary stability and hinder osteogenesis required for the
formation of a new cortical bony wall. This can lead to failure if implants are loaded too early,
possibly contributing to the observed increase in implant complications and failures reported by
clinicians (20). Patients should be informed about these risks and the necessity for treatment delay
following socket grafting, as the authors believe that these outweigh the potential benefits.
9

Becker et al. demonstrated through human biopsies of grafted sockets, using either bovine bone
or DFDBA, taken 3–6 months post-extraction, that implanted bovine and DFDBA particles were often
surrounded by dense connective tissue. Similarly, micro-screws implanted in these sockets also
showed dead bovine or DFDBA particles entrapped within fibrous tissue. Consequently, the authors
concluded that xenogenic bovine bone and DFDBA did not contribute to bone-to-micro-screw contact
and are not recommended for vital bone enhancement around implants. (21)
Histological analysis conducted 7 months post-extraction revealed that grafted sockets filled with
bovine bone still exhibited a notable presence of connective tissue alongside limited amounts of newly
formed bone surrounding the graft particles. Only 40% of the perimeter of the xenograft particles was
observed to be in contact with immature woven bone at this stage (22).
The presence of fibrous or connective tissue may impede new bone formation, primary stability,
and osseointegration if implants are prematurely loaded or if adequate osteogenesis fails to occur
within the socket shortly after implant placement. The significantly higher level of new bone
formation observed in non-grafted sockets at 12 weeks post-extraction makes them a safer choice for
early implant placement and achieving primary stability compared to grafted sockets (7). Additionally,
it has been noted that the active zone of bone formation shifts coronally from the initial apical region
by the 12-week post-extraction mark (23). Socket grafting may compromise and delay this coronal
shifting by potentially reducing angiogenesis at the crestal aspect of the socket may be hindered by
socket grafting. Additionally, older individuals may exhibit reduced intra-socket angiogenesis (23).
Considering that vertical and horizontal loss post-extraction typically ranges from approximately
1.5–3.8 mm (3), respectively, and that socket grafting may or may not halve this loss while potentially
impeding healing (23), clinicians must conduct a risk analysis to determine whether postponing
implant placement for 7–9 months after socket grafting to gain a few millimeters of vertical height and
horizontal bone width is warranted. Socket grafting may compromise the blood supply crucial for
facial cortical bone repair, raising questions about its role as the standard of care. (25, 26)
A study by Atieh et al. in 2015 illustrated that there is limited evidence indicating that socket
preservation (ARP) can reduce bone loss compared to tooth extraction alone, thus allowing for dental
implant placement. There is no evidence suggesting that socket preservation makes any important
differences in the appearance or lasting quality of crowns or bridges. Furthermore, there is no
convincing evidence of any significant differences between different materials and barriers used for
socket preservation. (32)
A 6-month prospective study demonstrated that smoking significantly impacted healing following
tooth extraction, resulting in increased dimensional changes, including higher alveolar width and
height loss. Smokers exhibited 0.5 mm more crestal bone loss post-extraction compared to
non-smokers (24). However, conclusions regarding smoking's impact could not be drawn from the
present study due to the limited number of smokers, with only one patient identified as a light smoker,
and no complications were observed during follow-up.
10

In our study, we evaluated the amount of bone remodeling on the mesial and distal aspects of
implants placed in sites where bone augmentation was done at the time of extraction, performed
simultaneously with implant placement, or where no bone augmentation was performed at all. This
evaluation of bone remodeling was conducted at three time intervals using the measuring tool on
Axium, with measurements calibrated to the reported diameter of the dental implant platform. Our
results support the concept of an implant surgery without socket grafting and early implant placement.
Dehiscence sockets have a propensity to undergo self-repair through the formation of a new cortical
plate. The spontaneously regenerated intra-socket bone provides sufficient support for long-term
functional implant stability. More studies with greater sample size are needed to confirm the present
data.
This study has several limitations. Firstly, due to its retrospective nature using two-dimensional
radiographs, it is impossible to ascertain whether the radiographic angulation was consistent at
the time of implant placement and uncovery. Future prospective studies should consider
incorporating impression radiographic jigs to standardize radiographic angulations.
Secondly, the total number of implants included in this study was limited. To overcome this
limitation, future research could be expanded to include data from the USC Perio resident clinic,
thereby increasing the sample size and enhancing the generalizability of the findings.
Lastly, this study evaluated three different implant systems: Straumann, Dentium, and Zimmer
Biomet 3i Certain & Osseotite. Each system possesses unique designs, sizes, thread presentations, and
surface treatments. Consequently, numerous variables must be considered. Future studies should be
designed with implants manufactured specifically for controlled research studies to minimize such
variables and ensure more reliable results (4, 5, 6). Therefore, there are many variables to take into
consideration. Future studies should be designed with implants manufactured specifically for a more
controlled research study to eliminate such variables.
11

Chapter 4: Conclusion
In conclusion, we conducted a retrospective evaluation of two-dimensional radiographs on
implants placed at extraction sites, where some received bone augmentation at the time of
extraction and prior to implant placement, some received bone augmentation at the time of
implant placement, and some did not receive any form of bone augmentation at all. We assessed
alveolar bone remodeling by measuring from the implant platform to the first implant- to - bone
contact on the mesial and distal aspects at three different time intervals. Our calibrated
measurements revealed that, within the limitations of this retrospective observation, favorable
clinical outcomes in implant placement and crestal bone maintenance can be anticipated in
non-grafted extraction sites. The need for bone augmentation at implant sites can be deferred
using early placement protocols. Minor crestal bone remodeling differences can be expected with
different restorative platforms. Risk-benefit considerations must be employed when choosing
different restorative platforms.
12

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16

Figure 1. Sample of Excel Data Sheet
Figure 2. Example of 2D Radiographs and calibration measuring tool. Implant Placement ( Straumann BL at
sites #13 (A and B). Impression coping stage (C and D). 1 year follow up after crown delivery(E,F).
Measurements are taken from the level of the implant platform to the level of the mesial and distal bone height.
17

Implant System Representation Count
Straumann BL/BLT (NC/RC) 80
Straumann TL 13
Dentium 17
Zimmer Biomet 3i Certain 3
Zimmer Biomet 3i Osseotite 84
Table 1: The various implant systems used from September 2012 to December 2023 at the University of
Southern California Dental Faculty Practice
Type of Implant Platform Quantity:
Internal Connection 100
External Connection 84
Transmucosal Connection 13
Table 2: The different implant platforms and their corresponding quantities that were included in this
study.
Table 3: The number of sites that received bone augmentation at the time of extraction, simultaneous with implant
placement, or no bone augmentation.
No Bone Augmentation 180 Sites
Separate Bone Augmentation 2 Sites ( 100% Anterior)
Simultaneous Bone Augmentation &
Implant placement
15 Sites ( 60% Anterior)
18

Fig 3: Illustration of the total number of implants with internal, external, and transmucosal connections.
Fig 4: Illustration of the different types of implant systems that were used in the faculty practice of USC from
2012 to December 2023
19

Fig 5: Illustration of the posterior (72.6%) vs anterior (27.4%) location of the implants that were placed in the
faculty practice of USC from 2012 to December 2023
Fig 6: Illustration of internal connection platforms presented with average bone loss greater than 1mm in one
year versus average bone loss of less than or equal to 1 mm.
20

Fig 7: Illustration of external connection platforms presented with average bone loss greater than 1mm in one
year versus average bone loss of less than or equal to 1 mm.
Fig 8: Illustration of the need for bone augmentation at the time of extraction, simultaneous with implant
placement, and no bone augmentation at all.
21

Fig 9: Illustration of the sites with implant platforms greater than 4 mm that required bone augmentation versus
sites with implant platforms less than or equal to 4 mm that required bone augmentation
Fig 10: Illustration of the sites with implant platforms greater than 4 mm (60.91%) versus sites with implant
platforms less than or equal to 4 mm (39.09%)
22

Fig 11: Illustration of the anterior sites with the need for grafting (60%) vs posterior sites with the need for
grafting (40%)
23

Abstract (if available)

Abstract Post-extraction ridge remodeling commonly occurs. Extraction socket grafting (ridge preservation) is proposed to reduce the post-extraction ridge remodeling. One of the reasons for ridge preservation is to reduce the need for future bone augmentation. Despite dimensional changes of the alveolar ridge, placement of implants in proper prosthetic position is feasible as reported in prospective studies utilizing early placement protocols and implant site development when needed. The aim of this retrospective analysis is to assess the need for bone augmentation for implant placement at non-grafted extraction sites with early implant placement protocol. Out of the 280 charts evaluated radiographically, 158 met the study criteria. Charts that did not have proper 2D periapical radiographs at specific time points were excluded. In total 158 charts and 197 implants were included in this study. Among the total of 197 implants placed, 84 (42.63%) were external hex and 113 (57.36%) were internal hex and 13 (11.5%) were TL platforms. Additionally, 1% of cases required separate grafting, which was in the anterior region. Furthermore, 7.58% of cases necessitated simultaneous grafting, with 60% of those sites being anterior. Our calibrated measurements revealed that, within the limitations of this retrospective observation, favorable clinical outcomes in implant placement and crestal bone maintenance can be anticipated in non-grafted extraction sites.

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Creator Behshadpour, Anahita (author)

Core Title Retrospective analysis of early implant placement in non-grafted extraction sites: Need for grafting and crestal bone remodeling

School School of Dentistry

Degree Master of Science

Degree Program Biomedical Implants and Tissue Engineering

Degree Conferral Date 2024-08

Publication Date 07/12/2024

Defense Date 06/05/2024

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

Tag Astra,bone,bone graft,certain,dentium,external hex,extraction,implant,implant platform,internal hex,OAI-PMH Harvest,osseotite,Straumann,tissue level,zimmer

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