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Effect of a submucosal injection of platelet-rich plasma on the rate of orthodontic tooth movement – A split-mouth, single-blind randomized controlled trial
Asavari Desai1, Supriya Nambiar2, Bhaskaran Unnikrishnan3, Sharada Rai4, Sangeeta Nayak5, Srikant Natarajan6
1 Associate Professor, Department of Orthodontics, Manipal College of Dental Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
2 Head, Department of Orthodontics, Manipal College of Dental Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
3 Professor and Dean, Department of Community Medicine, Kasturba Medical College Mangalore, Manipal Academy of Higher Education, Manipal, India
4 Professor and Head, Department of Pathology, Kasturba Medical College Mangalore, Manipal Academy of Higher Education, Manipal, India
5 Associate Professor, Department of Periodontics, Manipal College of Dental Sciences Mangalore, Manipal Academy of Higher Education, Manipal, India
6 Professor and Head, Department of Oral Pathology, Manipal College of Dental Sciences Mangalore, Manipal Academy of Higher Education, Manipal, India
|Date of Submission||31-May-2021|
|Date of Decision||22-Oct-2021|
|Date of Acceptance||15-Jan-2022|
|Date of Web Publication||11-Nov-2022|
Associate Professor, Department of Orthodontics, Manipal College of Dental Sciences, Mangalore - 575 001, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: To investigate the effect of submucosal injection of platelet-rich plasma (PRP) on the rate of mini-implant-supported retraction, using a split-mouth randomized clinical design. Materials and Methods: Twenty subjects of either gender between 16 and 25 years of age with bimaxillary dentoalveolar protrusion and crowding of <4 mm scheduled to undergo fixed mechanotherapy with the extraction of 1st premolars; were recruited for the study. Those with a periodontally compromised dentition, blood dyscrasias, smoking/alcoholism, or with a history of fixed orthodontic treatment were not considered. The intervention side received a submucosal injection of autologous PRP which was prepared using 10 ml of the patient's blood. The rate of extraction space closure on both sides was recorded and compared monthly for 3 months using a digital caliper. Results: Mean overall retraction was faster on the intervention side as compared to the control side by 1.5 times and was statistically significant with a P value of 0.001. There was no influence of gender on the rate of retraction. There was no reported swelling or discomfort associated with the PRP injection. Conclusions: Submucosal injection of PRP significantly accelerates orthodontic tooth movement and can therefore be used as an effective, safe, and minimally invasive method to expedite orthodontic treatment.
Keywords: Accelerated orthodontics, platelet-rich plasma, split-mouth trial
|How to cite this URL:|
Desai A, Nambiar S, Unnikrishnan B, Rai S, Nayak S, Natarajan S. Effect of a submucosal injection of platelet-rich plasma on the rate of orthodontic tooth movement – A split-mouth, single-blind randomized controlled trial. Contemp Clin Dent [Epub ahead of print] [cited 2023 Feb 2]. Available from: https://www.contempclindent.org/preprintarticle.asp?id=360899
| Introduction|| |
Orthodontic treatment on an average takes 18–24 months depending on the complexity of the particular case, patient compliance, and biomechanics employed. This long duration of treatment is a major drawback and also one of the most common reasons for patients to avoid orthodontic treatment. Hence, the acceleration of orthodontic tooth movement has been a subject of great interest for clinicians and researchers alike. Several techniques have been devised over the years to expedite the duration of treatment.
Noninvasive methods include the use of pharmacological agents,, micro impulses, and low dose laser therapy. Invasive techniques consist of surgically assisted approaches such as periodontal ligament distraction distraction,, periodontally accelerated osteogenic orthodontics,, corticision, micro-osteoperforation, and piezocision.
Although the invasive techniques have been proved clinically and experimentally to be the most effective at accelerating tooth movement, they come with the inherent risks of surgical intervention. These procedures make use of the regional acceleratory phenomenon described by Frost in 1983, based on the principle that when the bone is irritated surgically, an inflammation cascade is initiated which caused increased osteoclastogenesis, hence causing faster tooth movement. The biggest disadvantages are patient reluctance and the loss of alveolar bone that undermines the periodontal support of the target teeth. To avoid this, surgically assisted techniques have, over the years shifted from a radical, aggressive approach to a more conservative approach. However, a minimal insult to the bone may fail to trigger a strong and long-lasting effect on the alveolar bone to hasten orthodontic tooth movement, as has been previously proved experimentally. Local injection of cytokines or hormones could be a substitute, but it is not advisable to use these due to their systemic effects and need for frequent injections.
Recently, the idea that platelet-rich plasma (PRP) can be used to overcome all these limitations, was put forth by Liou. It was first used in dentistry by Robert Marx in 1998 as an adjunct in a mandibular reconstructive procedure. PRP is nothing but an autologous concentration of platelets in a small volume of plasma and is composed of 5% red blood cells (RBCs), 1% white blood cells (WBCs), and 94% of platelets. Platelets contain seven fundamental growth factors as well as cytokines, all of which play an important role in the wound healing process as well as several cellular processes such as mitogenesis, chemotaxis, differentiation, and metabolism.
Orthodontic tooth movement is essentially an inflammatory response to force and involves the release of several inflammatory mediators, which in turn bring about cellular differentiation. This leads to bone remodeling and ultimately tooth movement. An increase in osteoclastic activity and concurrent decrease in alveolar bone density is required to accelerate tooth movement. The findings of previous histomorphometric computed tomography, and cell culture studies have reported an inhibitory effect of PRP on bone cell division and a decrease in bone density thereby leading to the hypothesis that PRP can effectively accelerate tooth movement.,,
So far, the efficacy of this technique has been assessed in animal studies with very promising results. Empirical evidence shows that it is effective in humans as well, however, no clinical trial has been published so far. Keeping this in mind, this study was taken up with the aim of evaluating the efficacy of this technique in human subjects.
Aims and objectives
To determine the effect of submucosal injection of PRP on the rate of orthodontic tooth movement.
- To assess the interval at which the effect of PRP on tooth movement is the maximum
- To determine whether the platelet fold influences the rate of tooth movement.
| Materials and Methods|| |
This split-mouth, single-blind, randomized controlled trial which was conducted at the Department of Orthodontics of the host institute after obtaining the required approval from the Institutional Ethics Committee (MCODS/198/2017, dated September 12, 2017) and is registered with the Clinical Trials Registry of India (CTRI-CTRI/2017/12/010870). The trial was conducted according to 1975 Helsinki declaration guidelines as revised in 2013. Informed written consent was acquired from all participants, after a full explanation of the study aspects.
This project was taken up as a pilot study and the rate of extraction space closure was considered as the primary factor in calculating the sample size. We assumed the rate of tooth movement to be faster by an average of 1.5 times in the intervention arm as compared to the control, based on the results of previous studies. For a confidence interval of 95% and power of 80% with a ratio of 1:1 between the intervention and control group, a sample size of 20 was arrived at.
Subjects with permanent dentition, of either gender between 16 and 25 years of age and presenting with bimaxillary dentoalveolar protrusion and crowding of <4 mm, scheduled to undergo fixed mechanotherapy with the extraction of 1st premolars; were included in the study. Those with a periodontally compromised dentition, history of fixed orthodontic treatment, history of smoking or alcoholism, and presenting with any blood dyscrasias, were not considered.
The principal investigator was responsible for examining subjects and determining their eligibility. Initially, 23 subjects were recruited for this study out of which three were excluded as they did not keep up with their appointment schedule.
Block randomization was used to carry out the intervention and allocation concealment was achieved using sealed, sequentially numbered opaque envelopes which were prepared before the trial commencement.
The intervention was administered by the principal investigator. The outcome assessment was blinded and was carried out by another investigator.
The subjects were referred for extraction of first premolars to the same surgeon, to decrease variability. Treatment was initiated by bonding fixed appliances in both arches (0.022 inch, MBT prescription). Leveling and aligning were carried out conventionally after which 0.019 × 0.025” stainless steel arch base archwires were placed and the patient was prepared for the injection of PRP.
Preparation of the platelet-rich plasma
It was prepared according to the protocol suggested by Liou.
We found that a volume of 10 ml of whole blood was sufficient to obtain the required volume of 1 ml of injectable PRP. To this, one ml of 10% sodium citrate solution was then added as an anticoagulant. Thereafter, 1 ml was used to assess the concentration of platelets.
The remaining 9 ml of whole blood was then centrifuged under 800 rpm for 12 min at room temperature. The blood was separated into its three basic components with platelet-poor plasma (PPP) at the top, the buffy coat comprising platelets in the middle, and the RBCs at the bottom [Figure 1].
|Figure 1: Separation of whole blood into 3 components -platelet poor plasma at the top, platelets in the middle and red blood cells at the bottom|
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The RBCs were discarded, and the remaining buffy coat and PPP was centrifuged again under 2700 rpm for 8 min. After the second centrifugation, most of the PPP was removed until 2 ml remained which was mixed with the buffy coat to become PRP. This contained a high concentration of platelets, few WBCs and RBCs, and anticoagulants. One ml of this preparation was injected at the target site immediately after preparation, i.e., on the buccal and palatal side distal to the maxillary canine, on the intervention side [Figure 2]. Although an injection of PRP on the palatal aspect of the incisors in addition to the distal aspect of the canine is recommended in en-masse retraction cases, we wanted to assess whether only a single injection of PRP around the canine area will be sufficient. This also prevented the patient from being subjected to multiple pricks.
|Figure 2: Injection of platelet rich plasma at the target site on the buccal and palatal side|
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The remaining PRP was used to assess the platelet concentration to determine the platelet fold (platelet count in PRP/platelet count in blood). In addition, one ml of saline was injected as a placebo on the control side to rule out the possibility of faster tooth movement occurring due to pressure of the fluid on the adjacent tissues, on the intervention side.
Since the density of the cancellous bone varies in the maxilla and the mandible, the mandibular arch was not included in this study to eliminate the effect of bone density on orthodontic tooth movement. In the maxillary arch, left and right sides of the arch were randomly assigned to the experimental group, to avoid the risk of selection bias.
Retraction was initiated in both maxillary and mandibular arches simultaneously using a calibrated force of 150 g applied bilaterally, attached to a postsoldered between the lateral incisor and canine anteriorly, and a temporary anchorage device (TAD) posteriorly between the second premolar and first molar [Figure 3]. TADs were used in all cases to ensure there was no loss of posterior anchorage.
|Figure 3: Retraction using NiTi coil spring attached to a soldered postanteriorly and a mini implant placed between second premolar and 1st molar|
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Impressions of the maxillary arch were made every 4 weeks at the regular orthodontic appointment for 3 months, to assess and compare the rate of retraction on the intervention and control side. The extraction space between the canine and second premolar was measured using a digital caliper with an accuracy of 0.01 mm. Ten models were randomly selected and measured after an interval of 2 weeks to evaluate intra-observer error. For inter-observer error, a second investigator measured the models and these values were compared with those recorded by the first investigator. Both random and systemic errors were measured and were found to be trivial and insignificant.
Patients were instructed to use acetaminophen for postinjection pain control if any. Nonsteroidal anti-inflammatory drugs were not prescribed to avoid any potential neutralizing effects on PRP.
| Results|| |
This split mouth randomised controlled trial (RCT) recruited 23 subjects with a mean age of 19.8 ± 8 years. Three subjects did not keep up with their regular appointment schedules and were hence excluded from the study. The trial commenced in February 2019 and ended in March 2020.
The baseline sample characteristics are presented in [Table 1]. The rate of extraction space closure on both sides was recorded monthly for 3 months using a digital caliper.
On subjecting the data to paired t-test, it was observed that the rate of retraction was faster in the intervention side as compared to the control side during each of the 3 months of observation and the difference was statistically significant with P < 0.001. Tooth movement was fastest in the 1st month (T1), by 1.6 times compared to the control. It reduced to 1.4 times in the second (T2) and 3rd month (T3) [Figure 4] and [Table 2].
|Figure 4: Rate of retraction in intervention and control sides during each assessment interval|
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|Table 2: Comparison of the rate of retraction between intervention and control sides during each interval and at the end of the assessment period|
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The mean tooth movement at the end of the assessment period of 3 months (T3) was found to be 1.5 times faster on the intervention side compared to the control side with a space closure of 2.58 mm/month and 1.73 mm/month respectively. This value was statistically significant with P < 0.001 [Table 2].
The platelet fold was found to have a positive effect on the rate of tooth movement with significantly faster tooth movement in patients with higher platelet fold, with a P value of 0.001, as shown by the Pearson's correlation test [Figure 5].
|Figure 5: Association between platelet fold and the rate of anterior teeth retraction|
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The gender of the patient was found to have no significant influence on the rate of retraction as assessed by the Independent t-test [Figure 6].
The intervention was well tolerated by all the patients with no reported itching, mucosal swelling, or pain.
The recruitment and flow of patients in the trial is depicted in [Figure 7], as per the CONSORT guidelines.
| Discussion|| |
Orthodontic treatment, with the therapeutic extraction of teeth, on an average takes up to 31 months. Due to the lengthy treatment duration, many potential orthodontic patients decline treatment and jeopardize their oral health. Prolonged treatment has also been linked to increased risk of decalcification, caries, gingival inflammation as well as root resorption. The quest for a practical, minimally invasive, and cost-effective method to accelerate tooth movement has always eluded orthodontists.
Therefore, this split-mouth RCT was undertaken to primarily evaluate whether a submucosal injection of autologous PRP accelerates orthodontic tooth movement. The rate of anterior teeth retraction on intervention and control sides was assessed monthly, for 3 months.
There are numerous factors that have a significant impact on the rate of tooth movement. To eliminate the effect of the forces of occlusion, only patients with similar severity of malocclusion were selected. Furthermore, the intervention was randomly assigned to the left or right sides to rule out the impact of unequal occlusal forces arising due to habitual occlusion on one side.
The age of the patient is another factor that can significantly alter the rate of tooth movement due to differences in bone density and osteoclast recruitment., To minimize the effect of age, only patients between 16 and 25 years of age were included in the study.
The type of tooth movement is another confounding variable that can affect the rate of tooth movement. We attempted to achieve bodily movement of anterior teeth using soldered retraction hooks placed between the canine and lateral incisor with a uniformly calibrated force of 150 g bilaterally. Anchorage was reinforced with mini implants inserted between the second premolar and first molar.
The results of our study indicated that PRP does indeed have a positive effect on the rate of orthodontic tooth movement. This corroborates the results of studies conducted by Liou and Güleç et al. on rats. In our study, the rate of anterior tooth retraction was found to be 1.5–2 times faster in the intervention arm, as compared to the control arm in all the subjects. This resulted in a transient midline shift of the maxillary dental arch to the intervention side, which was subsequently self-corrected as the retraction proceeded on the control side.
Tooth movement was found to be marginally higher in males compared to females in both intervention and control arms, but the difference was statistically insignificant. These findings are in agreement with previous studies conducted by Guram et al.
The platelet folds of the subjects ranged from 9.6 to 16.2. It was observed that the difference in the rate of tooth movement between intervention and control sides was the maximum in the subject with a platelet fold of 16.2 and the lowest in the subject with a platelet fold of 9.6. The difference was also found to be statistically significant with a P value of 0.001. Therefore, it can be concluded that a higher platelet fold results in faster tooth movement. This is in agreement with the findings of a study done by Güleç et al. on rats where they found that the rate of tooth movement was dependent on the concentration of the PRP injected.
One of the limitations of this study was that the effect of platelet rich plasma on the expression of biomarkers was not assessed. Also, since the patients were followed up for a duration of 3 months, the association between PRP and root resorption was not assessed. Long term studies can be done in the future to examine this aspect.
Within the limitations of the present study, it can be implicated that this technique will be a major step forwards in the exciting field of accelerated orthodontics .Clinicians will be able to routinely use it for their patients thereby making it possible to deliver high standards of care in a much shorter duration.
| Conclusions|| |
Submucosal injection of PRP increased the rate of retraction by 1.5 times on the experimental side as compared to the control side. Patients reported no discomfort at the time of injection or at subsequent appointments.
PRP can be safely used as a minimally invasive and cost-effective method to reduce the otherwise lengthy duration of orthodontic treatment and thereby improve patient compliance.
The author would like to acknowledge the contribution of Ms. Priya Shenoy who helped with withdrawing the patient's blood as well as the centrifugation process.
Financial support and sponsorship
Extramural grant from Indian Council of Medical Research, New Delhi.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2]