The Use of Temporary Anchorage Devices for Ridge Preservation After Tooth Extraction
Phase: NA
Conditions: Ridge Preservation
Sponsor: University of Maryland, Baltimore

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Cover Page 
 
Official Title of the Study: 
 
The Use of Temporary Anchorage Devices for Ridge Preservation after Tooth Extraction 
 
NCT number: 
 
NCT03205800 
 
Date of the Document: 
 
October 17, 2019 
 

2 
 
 
Research Team Members 
1) Se-Lim Oh: PI 
• 
Developing the research protocol 
• 
Obtaining the IRB approval and the approval of continuing review  
• 
Confirming the subject eligibility and supervising research procedures 
• 
Data analysis 
 
2) Dianna (Hyun San) Lee: a research team member 
• 
Performing the research procedures 
 
 
Abstract 
 
The remodeling of the alveolar bone following tooth extraction results in significant bone loss at the extraction site. An 
excessive bone loss hampers the implementation of treatment plans, prediction of esthetic outcomes, and patient satisfaction. 
Placing bone substitute materials in an extraction socket may reduce the alveolar bone resorption. However, postoperative 
infection and inflammation are common side effects following bone graft surgeries. Finding a less invasive approach to 
preserve the alveolar ridge would be amenable to dental clinic. An animal study reported that bone density significantly 
increased in the extraction site with transcortical mini-screw placements, exhibiting markedly less atrophied alveolar ridge. 
In addition, the side effects from a mini-screw placement are minimal and no antibiotics are required. Therefore, we propose 
the placement of a transcortical mini-screw at the buccal plate of an extraction socket as a minimally invasive approach to 
preserve the alveolar ridge. The objective of this study is to determine the effects of transcortical mini-screws placed at the 
buccal plates of the extraction sockets in humans. We hypothesize that placement of a transcortical mini-screw at the buccal 
plate will significantly reduce bone loss at the site. To test this hypothesis, we are performing a prospective split-mouth 
design study. We are recruiting patients who need extraction of two maxillary premolars for orthodontic treatments. Cone 
beam computed tomography (CBCT) is exposed after the extraction of two premolars and before a transcortical mini-screw 
placement (T0). One 8-mm length mini-screw is placed at the buccal plate of the extraction socket on one side. The 
contralateral extraction socket is untreated. The mini-screw is removed at 6 months and the follow-up CBCT is obtained 
(T6). We will compare changes in the alveolar bone width at both extraction sides using the CBCTs. We predict that the 
placement of a transcortical mini-screw at the buccal plate of the extraction socket significantly reduces bone loss at the 
extraction site. Results of this study will offer a useful measure to sustain an edentulous alveolar ridge for a lengthy period 
without losing bone proper. 
 

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Research Plan 
SIGNIFICANCE AND INNOVATION 
Bone loss following tooth extraction is inevitable but current available procedures for preserving bone after tooth 
extraction are not satisfactory. Teeth develop from tooth buds in the jaw bone, known as alveolar bone. The alveolar bone 
undergoes constant remodeling process throughout the 
life of teeth. When teeth are extracted, the surrounding 
alveolar bone remodels and undergoes atrophy, 
resulting in reduced alveolar ridge in width and height,1–
3 most of which takes place in the first 3 months after 
tooth extraction (Fig 1).4 Within six to eight weeks, the 
total ridge thickness was reduced by 15% of the original 
value in average.5 The ridge width was reduced from 12 
mm at baseline to 6 mm at 12 months.3 Such bone 
reduction hampers the success of treatments such as 
implant placements, esthetics for ideal fixed dental 
restorations, and orthodontic teeth treatment through the 
edentulous space.6,7 To modify bone remodeling after 
tooth extraction, various surgical ridge preservation 
procedures were proposed using bone substitute 
materials in conjunction with barrier membranes.8 
However, extractions often occur without planning. Bone graft/ridge preservation surgeries may not be feasible at the time 
of extraction due to a lack of finance, insufficient time, and/or a lack of treatment plan. In addition, inflammation and 
postoperative swellings commonly occur after ridge preservation surgeries, thus,  antibiotics are prescribed after the 
surgeries.8 A minimally invasive and cost-effective approach to preserve the alveolar ridge following tooth extraction is 
desirable. 
We propose a transcortical mini-screw insertion in order to preserve edentulous ridge as a minimally invasive (no 
antibiotics prescription requiring) and cost-effective ($180) approach. Transcortical mini-screws are widely used in 
orthodontic treatments for temporary anchorage purposes. Transcortical orthodontic mini-screws are not fully integrated 
but maintain contact with alveolar bone ranged from 10% to 58% of surface,9 which makes it easy to be removed after 
orthodontic treatments. In addition, the side effects of transcortical mini-screws such as per-implant inflammation are 
extremely low.9 One of the premises of our proposal is an animal study showing that a placement of transcortical mini-
screw at the buccal plate of an extraction socket significantly increased bone density in the extraction site, which resulted 
in markedly less atrophy of alveolar ridge.10 Furthermore, a case report11 indicates that insertion of  transcortical mini-
screws in the alveolar plate may result in increased bone density in the region. However, clinical studies determining the 
effects of a transcortical mini-screw placement on ridge preservation is lacking. The objective of our study is to investigate 
effects of a transcortical mini-screw placement on alveolar ridge preservation after tooth extraction. Successful outcomes 
will suggest the potential novel clinical application of the mini-screw for ridge preservation after tooth extraction, which 
can greatly enhance dental practice.  

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THE OBJECTIVE 
The objective of our study is to investigate effects of a transcortical mini-screw placement on alveolar ridge preservation 
after tooth extraction. 
SPECIFIC AIMS 
Specific Aim 1: To evaluate the clinical outcomes between the treated sites with a transcortical screw (the experimental 
group) and the non-treated sites (the control group) 
Null Hypothesis: There will be no differences in clinical parameters between the two groups.  
Approach: The investigators will conduct a prospective split-mouth design clinical study. The investigators will compare 
the clinical changes in the vertical ridge height and the horizontal ridge width at 3 months and 6 months from baseline (tooth 
extraction).  
Specific Aim 2: To evaluate the radiographic outcome between the experimental and the control group  
Null Hypothesis: There will be no difference in alveolar bone height and width between the two groups. 
Approach: The study will measure the alveolar bone heights and widths using cone beam computed tomographies (CBCTs) 
at baseline and 6 months. 
 
APPROACH 
This is an on-going prospective clinical study under a protocol approved by the IRB (HP-00076020). Six subjects completed 
the study protocol. Interim data analysis was performed from these six subjects.  
 
1. Sample size determination: The original sample size was determined to provide 80% power to recognize a significant 
difference of 1 mm between the two sides with a 95% confidence interval (α=0.05) and standard deviation of 1.0 mm, 
considering the difference in the mean width of the edentulous alveolar ridge as the primary outcome variable. Based on the 
power analysis reperformed by following the formula described by Faul et al12 using the interim data from the 6 subjects, 
14 subjects will provide 80% power to recognize a significant difference of 0.5 mm in the width of the alveolar ridge 
between the two sides.  
 
2. The Study Population: Patients with the following conditions are included: a) age ≥ 18 years, and b) two maxillary 
premolars (one from the left side and the other from the right side) required to be extracted in accordance with recommended 
dental treatment plans. Exclusion criteria are as follows: a) hyper-/hypothyroid dysfunctions, b) diabetes mellitus, c) subjects 
with a history of a chronic use of corticosteroid (> 6 months), d) subjects with a history of taking oral/IV bisphosphonates 
within the past 2 years, e) smokers, and f) other systemic conditions influencing bone integrity. 
 
3. Research Procedures (Figure 2) 
1) Obtaining signatures on the consent form at screening visit. 
The PI and the POC will follow the protocol in the approved IRB application while we are obtaining signatures from the 
potential subject. The information will be given to the potential subject in the separate room. The potential subject will be 
encouraged to ask the PI and the POC any questions regarding this protocol. (Approximately 40 to 60 minutes)  
 
2) Placement of a mini-screw at the buccal plate of the extraction socket in one side (left or right) one week after the 
atraumatic extraction of maxillary premolars  

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- Limited volume CBCT with high resolution will be exposed before the mini-screw placement; this is standard of care. 
- Clinical photographs and intraoral images will be obtained for both sites.  
- One mini-screw (8 mm length) will be placed at the buccal plate of one extraction site. After bone sounding, a mini screw 
will be placed at the position 3 mm from the alveolar crest. The other extraction site will be untreated. (Approximately 30 
minutes) 
• 
The PI and the POC will monitor subjects closely.  
• 
Local anesthesia with lidocaine will be administered to minimize patients’ discomfort. 
• 
Postoperative instruction will be given to subjects. 
 
3) 3 months follow-up (30 minutes); Clinical photographs and intraoral images will be obtained for both sites. 
 
4) 6 months follow-up (40 minutes) 
- The mini-screws will be removed. 
- Clinical photographs and intraoral images will be obtained for both sites. 
- Limited volume CBCT with high resolution will be exposed; this is a study procedure. 
 
4. Radiographic Measurements: CBCT will be exposed after teeth extraction and before the mini-screw placement (T0). One 
mini-screw will be placed at the buccal plate of the extraction socket one week following the extraction of maxillary 
premolars in one side. The other extraction socket site will be untreated. At 6 months, the follow-up CBCT will be exposed 
for the maxilla after removal of the mini-screws. A blinded evaluator will measure the width of alveolar ridge on the CBCTs 
made at T0 and T6. Changes in the width of alveolar ridge were measured from the outer wall at T0 to the outer wall at T6. 
A positive value indicates bone loss. In the sagittal section, three levels will be determined by measuring from the crest to 
the apex and dividing the socket length into thirds. The measurements will be performed in coronal and axial sections (Figs 
3a and 3b).  
 
Figure 3. measurements of bone loss 
after tooth extraction on CBCTs. (a-b) 
Examples of coronal (a) or axial (b) 
measurements. Changes of bone level 
from T0 to T6 was measured. 
Superimposition of two CBCT images 
(T6, blue; T0, Grey) was performed 
using Invivo 6.0 software. Right side 
images present magnification of insets 
in left panels. (c-d) Changes in the 
width of alveolar ridge (meanSD) in 
the experimental (exp) and the control 
(con) side at the crestal (C), middle 
(M), and apex (A) level in coronal or 
axial sections.  

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5. Interim data and statistical analysis: No inflammation and infection related to the mini-screw placements were observed 
in all 6 subjects. Miniscrews were removed at 6 months from 3 subjects and at 8 months from 3 subjects (the mean of 7-
month) in keeping with planned dental treatments. Overall, the experimental side with the miniscrew placement showed 
less bone loss than the control side at the crestal, middle, and apex level in both coronal and axial measurements (Figs 3c 
and 3d). Upon completion of the study, a paired t-test will be performed to compare the changes in the width of alveolar 
ridge from the two sides. We will also measure mineral density distribution at the extraction sites from the two sides using 
CBCTs.  
 
6. Expected outcomes: We predict that the experimental side with mini-screw placements will exhibit a significantly less 
bone loss than the control side. Bone density in the experimental side will be significantly greater than the control side.  
 
7. Research Related Risks 
Clinical risks for mini-screw are low. Overall failure rate of mini-screws is about 10% with orthodontic loading. Four to 
five weeks after the mini screw placement, failure rate dropped to 5%. Failures of mini-screw are mainly from loosen screws, 
which mean the mini-screws are mobile and are not firmly attached (or engaged) to the bone. Our incidence of loosen screws 
will be very low because the mini-screw will not be loaded for 6 months. 
Some of the potential risks are as follows: 
• Participants may experience inflammation, mild pain, or discomfort at the mini-screw site for about 2 days. Pain 
medication (Tylenol or Ibuprofen) will be enough to solve this problem. 
• Infection rarely develops. If it occurs, antibiotics will be prescribed. 
• The screw could become loose. If this occurs, the participant should contact the clinic immediately. We will remove the 
loosen screw and replace with a new one. 
• The incidence of broken screws is very rare although a screw breaks might occur during the removal of a screw. A broken 
screw can be easily removed with an instrument.  
• The mini-screw may not prevent bone loss. 
• As with any study, there is a risk that the study data may not be kept confidential. We will minimize this risk by storing 
data in a secure location, such as a locked cabinet in a locked office. Electronic data will be password-protected. 
 
8. Potential limitation: Not all measurements at the three levels may be significantly different. Preserving bone at the crestal 
and the middle level is critical in implant dentistry. Preserving bone at the apex level is clinically meaningful in orthodontics. 
It is difficult to measure bone loss in the palatal side with coronal sections of CBCTs. Therefore, we will also measure bone 
loss using axial sections of CBCTs. CT based bone density measurement may not be as accurate as direct measurement 
using bone biopsy. However, it is a very powerful non-invasive tool to measure mineral density.13  
 
9. Study period-time table for completion of the project 
Research procedures 
5 months 
6 months 
1 month 
Recruitments 
X 
 
 
Research procedures 
X 
X 
 
Data analysis and preparing manuscript 
 
 
X 
 

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