1. INTRODUCTION, INCLUDING
RATIONALE OF THE STUDY
Orthodontic root resorption (ORR) is a common undesirable
consequence of orthodontic treatment. Dentin sialoprotein (DSP) is a potential
biomarker for assessing root resorption severity. While premolar extractions
are a standard practice in orthodontic treatment, the timing of extraction whether
conventional or delayed can influence the magnitude of root resorption.
However, comprehensive evidence comparing DSP levels and ORR severity in these
two extraction protocols remains scarce. Understanding the relationship between
the timing of premolar extractions, DSP changes, and root resorption severity
is critical to optimizing treatment outcomes and minimizing adverse effects in
orthodontic patients.
One of the common and undesirable sequelae associated with the
orthodontic tooth movement is root resorption, clinically referred to as
Orthodontic Root Resorption (ORR). Brezniak and Wasserstein described ORR as an
unavoidable pathological process during orthodontic tooth movement,
characterized by loss of material from the dentin or cementum of the root.
Heavy orthodontic forces result in development of hyalinized areas in
periodontal spaces. Cells and blood vessels from the surrounding healthy
periodontium then remove these tissues, resulting in the loss of cementoid and
mature collagen near the cementum. This disrupts the normal barriers protecting
the root from resorption.
The incidence of ORR ranges from 44% to 91%, according to several
studies. Though in most of the cases, only mild to moderate root
resorption is experienced by the patient, which is clinically insignificant and
does not affect dental health, severe cases can lead to tooth mobility and
potentially jeopardize the success of orthodontic treatment. The likelihood of
ORR is higher in anterior teeth compared to posterior teeth, with maxillary
central and lateral incisors being the most affected, followed by canines.
Within the dental arch, the severity of ORR follows the order: anterior
maxilla, anterior mandible, posterior mandible, and posterior maxilla. Genetic
characteristics, biological factors, orthodontic treatment techniques and age
of patient all play a role in increasing the likelihood of root resorption.
Orthodontic factors include magnitude, duration, and type of the orthodontic
force applied. Studies suggest that pausing orthodontic forces during treatment
may help reduce root resorption, likely due to cementum repair during inactive
periods. Radiographic techniques are commonly used to diagnose root resorption,
offering advantages such as wide accessibility, ease of use, and
cost-effectiveness. However, the downside of this method includes difficulties
in early detection, technique errors, and radiation exposure. Radiographs are
also unable to show whether the progression of root resorption is active. While
CT and CBCT offer improved sensitivity, their expense and increased radiation
exposure make them unfeasible for routine use. Hence, a safer and more reliable
alternative for diagnosing root resorption, especially in earlier stages, is
essential.
GCF (Gingival Crevicular Fluid) is an inflammatory transudate that
flows through the gingival crevice. The quantity and composition of the fluid
varies depending on health of the periodontium. GCF contains a variety of
biochemical and cellular factors that reflect the condition of the underlying
periodontium.
Dentin Sialoprotein (DSP) is an N terminal cleavage product of
dentine sialophosphoprotein (DSPP) and part of the small integrin-binding
ligand N linked glycoprotein family. Immunolocalization studies reveal its
presence in odontoblasts, dental pulp, predentine, and dentine, but not in
bone, cartilage, ameloblasts, soft tissues, or other oral components,
indicating its high specificity to dentin. Balducci et al. (2006) have
confirmed the presence of DSP in GCF of patients diagnosed with both mild and
severe resorption after at least one year of treatment with fixed appliances.
Hence, in conclusion, DSP can serve as biomarker for detecting root resorption
associated with the orthodontic treatment, providing an alternative to
radiographic methods.
In orthodontics, therapeutic extractions are a common practice.
Traditionally, these extractions are performed prior to the initiation of the
treatment to simplify biomechanics, prevent roundtripping, and eliminate
appliance interference during extractions. Certain other strategies
recommend extracting the teeth at a later stage, prior to the retraction phase.
Tooth removal also triggers the regional acceleratory phenomenon (RAP) in the
localized area, sparking debate over the optimal timing for initiating space
closure. Clinical evidence suggests that fresh extraction sites may be
beneficial for tooth movement by leveraging a planned regional accelerated
phenomenon shortly after extractions. Prolonged treatment can increase the risk
of iatrogenic damage, such as root resorption, demineralization, and
periodontal issues. Additionally, patient compliance may decline over time,
leading to a higher likelihood of adverse effects and less favourable outcomes.
Novelty
This study explores a novel perspective by investigating the
association between DSP levels and severity of ORR in cases involving
conventional versus delayed premolar extractions. A distinctive aspect of this
research is its focus on differences in rate of the tooth movement during
retraction between these two extraction timings and its consequent effect on
orthodontic root resorption, an area that has been inadequately explored in
previous studies. By comparing biochemical markers like DSP in GCF with radiographic
parameters, this study aims to provide a thorough understanding of how
extraction timing influences both the biological response and efficiency of
space closure.
2. RESEARCH QUESTION
How do changes in dentin sialoprotein (DSP) levels in GCF compare
with the severity and progression of orthodontic root resorption in patients
with Angle’s Class I malocclusion with bimaxillary dentoalveolar protrusion
undergoing two therapeutic extraction protocols—conventional therapeutic
extraction and delayed extraction, at three time periods, in the Department of
Orthodontics, MES Dental College?
3. AIM AND OBJECTIVES
To compare the changes in DSP levels in GCF with severity of ORR
using RVG (Radiovisiography) at 3 points in patients with Angle’s Class I
bimaxillary protrusion undergoing two therapeutic extraction protocols conventional
therapeutic extraction and delayed therapeutic extraction protocols, who report
to the Department of Orthodontics and Dentofacial Orthopaedics, MES Dental
College, Perinthalmanna.
OBJECTIVE
To compare the changes in DSP and severity of orthodontic root
resorption assessed using RVG.
4. STUDY DESIGN
A Prospective Cohort Study
5. SETTING
The study will be conducted among patients with Angle’s Class I
bimaxillary dentoalveoloar protrusion malocclusion who report to the Department
of Orthodontics and Dentofacial Orthopaedics, MES Dental College,
Perinthalmanna seeking fixed orthodontic treatment.
6. SAMPLING
a. Sample Size Calculation
Variable used for sample size
calculations - DSP
n = 6 per group, there will be a
minimum of 6 patients in each group
b. Inclusion Criteria
• Patients with complete dentition.
• Patients in the age group 18 – 25
yrs.
• Patients should be having healthy
gingival and periodontal status.
• Patients with no radiographic signs
of root resorption.
c. Exclusion Criteria
• Missing molars or any of the anterior
teeth.
• Previous history of orthodontic
treatment.
• Erupted or unerupted supernumeraries
in the maxillary anterior segment.
• Impacted canines, Endodontically
treated teeth.
• Upper anterior crowding greater than or equal to 4mm.
• Periodontitis
• History of avulsion or replantation.
• History of prolonged use of systemic
steroids and NSAIDs
• History of systemic disorders
d. Sampling Procedure
Sampling will be
done by consecutive sampling methods from the patients reporting to the
Department of Orthodontics, MES Dental College, Perinthalmanna, who satisfy the
inclusion and exclusion criteria.
Study Period
10th
September 2025 to 31st
December 2026
7. METHODOLOGY
a. Methods Of Data Collection
Patients with
Angle’s Class I bimaxillary proclination will be selected based on specific
inclusion and exclusion criteria. Using consecutive sampling, they will be
divided into two groups: conventional therapeutic extraction (Group 1) and
delayed therapeutic extraction (Group 2). In Group 1, the first premolars will
be extracted immediately before the initiation of orthodontic treatment.
Following this, orthodontic treatment will begin for both groups using 0.022”
prescription Ormco Mini Diamond Brackets. The anterior segment levelling and
alignment will be performed using a standardized sequence of NiTi wires:
0.014”, 0.016” x 0.022”, 0.017” x 0.025”, and 0.019” x 0.025”, with each wire
retained for 4 weeks. After this alignment of 6 months duration, subsequently
the retraction mechanics will be initiated by placing 0.019” x 0.025” stainless
steel working wires for an additional 4 weeks. At the completion of this stage,
Group 2 patients will undergo therapeutic extraction of the first premolars.
Retraction for both groups will then be carried out with active tiebacks (ORMCO
– 0.010” SS ligature wire) using a force of 200g with 0.19”x 0.25” stainless
steel wires, with monthly activations. Oral hygiene will be maintained
throughout the treatment through periodic oral prophylaxis. Treatment
of patients in both groups will be done by the same faculty (VA) and data will
be collected by the principal investigator for the purpose of the observational
study.
Group 1 – Patients with Angle’s Class I bimaxillary dentoalveolar
protrusion malocclusion who will be treated with fixed orthodontic treatment
for retraction of anterior teeth following conventional therapeutic extraction
of maxillary first premolar teeth.
Group 2 – Patients with Angle’s Class I bimaxillary dentoalveolar
protrusion malocclusion who will be treated with fixed orthodontic treatment
for retraction of anterior teeth following delayed therapeutic extraction of
maxillary first premolar teeth.
GCF Collection
All samples will be
collected after thorough cleansing of the oral cavity. The maxillary anterior
teeth (12, 11, 21, and 22), from which samples will be obtained, will first be
isolated with cotton rolls and dried with air. GCF collection will be done by
placing PerioPaper strips (Oraflow Inc., Hewlett, New York, USA) into the
gingival sulcus of maxillary central incisors and lateral incisors. The strips
will be placed into the mesio-buccal and disto-buccal aspects of the gingival
sulcus to the point of slight resistance and kept in position for 30 seconds.
Strips that are contaminated with blood will be excluded from the analysis. The
time points of sample collection are outlined in Table-1, and all samples will
consistently be taken from the same sites. The PerioPaper strips containing GCF
will be stored in sterile Eppendorf vials containing phosphate-buffered saline.
These vials will be centrifuged for 10 minutes at 4°C and then stored at -80°C
in the Department of Microbiology, MES Medical College, Perinthalmanna, until
the collection of all samples is complete. Each aliquot will be thawed to room
temperature before testing. The samples will be analyzed using an ELISA kit
(96T) from Origin Diagnostics and Research, Kollam, Kerala. All assay
procedures will be done according to the manufacturer’s protocol. Quantitative
analysis will be conducted at the conclusion of the assay in the Department of
Microbiology, MES Medical College, Perinthalmanna.
RVG
RVG will be taken
for the maxillary anterior teeth (12, 11, 21, and 22) using the parallelling
cone technique and the images will be analyzed. The Modified Malmgren Grading
Criteria(12,13)will be applied to assess extent of the external apical root
resorption.
Gingival crevicular
fluid (GCF) and radiographic (RVG) assessments were done at different time
points. Both GCF and RVG were recorded before treatment (T1). At the beginning
of retraction, six months into treatment (T2), only GCF was assessed. Finally,
at the end of one year (T3), both GCF and RVG were recorded again.
Outcome Measurement
In this study, the
severity of orthodontic root resorption will be assessed using the Modified
Malmgren grading scale according to Beck and Harris, based on RVG. For each
grade of root resorption, the number of patients corresponding to that grade
will be identified, and the mean DSP value of these patients will be calculated
at the same time point as the RVG assessment. This process will be repeated
across all grades for both Group 1 and Group 2 separately to analyse whether
increasing root resorption severity corresponds to significant changes in mean
DSP levels.
8. DATA ANALYSIS PLAN
List Of Variables and Their
Measurement Methods with Standardization Techniques
·
Independent Variables
·
Group 1 - Conventional
Therapeutic Extraction
·
Group 2 - Delayed Therapeutic
Extraction
·
Dependent Variables
·
Dentin Sialoprotein (DSP)
levels
·
Severity of orthodontic root
resorption as seen on an RVG
List of Variable Wise Statistical
Tests to Be Used for Data Analysis
The data will be entered
into Microsoft Excel and processed using SPSS. Quantitative variables will be
presented as percentages with mean and standard deviation. All continuous
variables will be evaluated regarding normality using the Shapiro- Wilk test.
According to the normality tests, parametric (t-test) and non-parametric (Mann
Whitney tests) will be used to compare variations in the levels of DSP and
grading of radiographs in the two groups. P less than 0.05 will be considered
statistically significant. |