Introduction
Non-surgical methods to accelerate orthodontic tooth movement employ various physical, biological and pharmacological approaches to increase bone turnover, thereby mimicking a regional accelerated phenomenon (RAP) in the alveolar bone and periodontium.
Attempts to understand the biological mechanism of tooth movement have elaborated the role of various cellular and molecular mediators that influence bone metabolism. Induction of an inflammatory response can be catered directly by the surgical insult of the bone or indirectly by stimulation and proliferation of cells that involve an inflammatory cascade.
Although surgical methods are effective in accelerating tooth movement, they come with short-term risks such as pain, swelling, increased gingival inflammation, compromised oral hygiene and long-term risks, including reduced inter-radicular distance with interdental bone loss, periodontal defects around osteotomy site, increased probing depth, diminished attached gingival width, root resorption and scar formation ( Table 95.1 ). Corticotomy-induced periodontal damage was observed in rhesus monkeys around the incisor region. The actual impact of surgical techniques on gingival and periodontal parameters on humans needs a serious attention from clinicians and researchers.
TABLE 95.1
Risks and limitations of surgically assisted accelerated tooth movement
Source: From Aboul et al., Sirri et al., Charavet et al., Pouliezou et al.
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The effect of clinically acceptable RAP phenomenon peaks for only 1–2 months after the surgical insult, demanding repeated exposure of the intervention for a continuous acceleratory movement. Hence, the innate traumatic nature of the surgical methods and their need for repeated exposure have shifted the focus from invasive to non-invasive or minimally invasive modalities.
The non-surgical methods that can help stimulate the movement of teeth during orthodontic treatment are compiled in Table 95.2 .
TABLE 95.2
Non surgical approaches to enhance rate of orthodontic tooth movement
| Physical and mechanical | Blood derivatives biological activities products | Bio-modulating agents |
|---|---|---|
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Physical methods influencing the biological process of tooth movement
Low level laser therapy
Theodore H. Maimen , introduced LASER (Light Amplification by Stimulated Emission of Radiation) applications in dentistry. In contemporary clinical practice, soft tissue laser devices are used for gingivectomy, frenectomy and surgical exposure of impacted teeth.
‘Cold lasers’ have a wavelength of 600–1000 nm and emit non-thermal photons, which can traverse into some depth of soft tissue. Soft lasers are synonyms of low-level laser therapy (LLLT). LLLT influences the subcellular photoreceptors, thereby activating the cellular metabolic process. Studies on the potential bio-stimulative effects of the laser peaked after Cruz et al.’s work in 2004. He reported a 34% increase in tooth movement after administration of low-level laser. The window of therapeutic specificity of a laser depends upon the wavelength, frequency, power, duration and energy of the laser. Studies have found that the high-level laser (>20 J/cm 2 ) causes increased tissue temperature exhibiting photo-ablative and photo-thermal properties. In comparison, soft lasers had photo-bio stimulation effects at low levels (<20 J/cm 2 ). They exhibit stimulative effects on the periodontium, triggering osteoblastic lineage’s cellular proliferation and differentiation.
Diode lasers, such as gallium, aluminium, and arsenic semiconductors, are the most frequently used, apart from helium-neon and CO 2 lasers. They can be used intraorally in either continuous or pulsed mode on the buccal and lingual sides. According to Camacho et al. the suitable wavelength of laser therapy employed in the literature is 780 and 830 nm.
Mechanism of action: The mechanism of action of laser irradiation has been postulated based on the cell’s ability to absorb the light stimulus and initiate cell differentiation. The effects of laser in the stimulation of RANK/RANKL gene expression and osteoclastogenesis is assumed to be because of the absorption of light by cellular mitochondria and increased ATP production that alters intracellular homeostasis and initiates the proliferation of macrophage colony-stimulating factor (MCSF) and their differentiation into osteoblasts. , ATP production can also be increased by activation of cytochrome C oxidase and porphyrins by generating reactive oxygen species. Ge et al. have concluded that the low levels of 2.5, 5 and 8 J/cm 2 can be used with an application time of 10 s. Although moderate level of effectiveness of lasers have been found, some studies have reported no additive effect on laser therapy due to heterogeneous study designs.
Huang et al. has graphically depicted a model of cellular and biological mechanisms underlying accelerated tooth movement ( Fig. 95.1 ).
Summary of various methods of acceleration and their impact on cellular and molecular cascade of events in orthodontic tooth movement.
Red arrow depicts various methods of acceleration and blue arrow depicts stimulation and red-blunted arrow depicts inhibition. MSC , Mesenchymal cells; HSC , haematopoietic stem cells; HIF , hypoxia inducible factor; FGF , fibroblast growth factor.
Source: Reproduced with permission from Huang H, Williams RC, Kyrkanides S. Accelerated orthodontic tooth movement: molecular mechanisms. Am J Orthod Dentofacial Orthop 2014;146(5):620–32. doi:10.1016/j.ajodo.2014.07.007. PubMed PMID: 25439213.
Clinical application: Nevertheless, the non-invasive nature, ease of application, portable device and the possibility of repeated exposure make low-level laser therapy a viable alternative in accelerative orthodontics. Although several clinical research studies have reported benefits, these devices have not been used extensively. A need for a dedicated space, stringent safety protocols for patient and operator, cost of the equipment and a lack of uniform evidence-based protocol in the literature may be the possible reasons. However, the first study by Cruz in 2004 used 780 nm 20 mW Ga-Al-As diode applied four times a month (day 0, 3, 7, 14, 21 of each month) for 2 months, which benefitted in a statistically significant increase in the rate of tooth movement in the laser group by 34%.
Vibration stimulus
Resonance vibration is based on the principle of generating intermittent forces matching the natural frequency of the teeth and the surrounding periodontal ligament capable of initiating cellular responses. Thus, vibrational devices have the potential to effectively generate stress-induced charges through the rapid and intermittent application of force. Mechanical vibration of bone was observed to maintain the bone mass in patients with prolonged bed rest and post-menopausal women. Nishimura et al. studied the effects of resonance vibration in 6-week-old Wistar rats and concluded that 60 Hz of vibration applied to the first molar tooth of the rats for 8 min per week caused a 15% increased tooth movement.
Mechanism of action: The application of vibratory stimulus is believed to activate the RANK-RANKL pathway and increase osteoclastic activity by co-activating mechanoreceptors. Superficial Meissner corpuscles sense vibrations at a range of 5–150 Hz, with a peak sensitivity around 10–65 Hz and Pacinian corpuscles, that are present deep, sense vibrations at a range of 20–1000 Hz, with a peak sensitivity around 250 Hz. It is also assumed that they reduce the stick-slip phenomenon between the arch wires and bracket sliding, and reduce the pain caused during tooth movement.
The effectiveness of the stimulus depends upon three factors: frequency, magnitude and total displacement. The device’s frequency indicates the number of oscillations per second, expressed in Hertz. The induced peak acceleration magnitude (1 g = 9.81 m/s ) and the displacement is expressed in centimetre or millimetre. Vibration is a relatively safe, predictable and acceptable method of acceleration.
The vibrations that elicit a physiologic response are divided into high frequency (>45 Hz) and low frequency (<45 Hz). Commercially available devices like Acceledent work on low-frequency vibration. Acceledent (OrthoAccel Technologies, Inc., Bellaire, TX, USA) is used for 20 min per day. It is a handheld device with a thermoplastic occlusal wafer to bite, delivering 0.2 N force at 30 Hz frequency. The high frequency vibration device available in the market is VPro5 (Propel Orthodontics, Ossining, NY, USA). The recommended wear time is 5 minutes/day at 120 Hz. A few commercially available other devices are listed in Table 95.3 .
TABLE 95.3
Vibration devices for enhancing rate of tooth movement: protocol of uses
Source: From Liao Z et al., Leethanakul et al., Azeem et al., Alansari et al., Kannan et al.
| S.no. | Vibrating device | Time per day | Frequency |
|---|---|---|---|
| 1. | VPro5 (Propel Orthodontics, Ossining, NY, USA) | 5 min daily | 120 Hz |
| 2. | Acceledent (OrthoAccel Technologies, Inc., Bellaire, TX, USA) | 20 min daily | 30 Hz |
| 3. | Oral B (USA) Hummingbird Vibrating Unit | 10 min daily | 50 Hz |
| 4. | Tooth Masseuse | 20 min daily | 111 Hz |
| 5. | Colgate Motion-Multi Action electric toothbrush | 15 min daily | 125 Hz |
| 6. | Oral B CrossAction Dual Power Clean electric toothbrush (100–105 Hz) | 15 min daily | 100–105 Hz |
Clinical application of vibration device
Although few randomised controlled studies , , have concluded the positive effects of vibration on the rate of tooth movement with high frequency, current evidence still lacks support for the vibratory stimulus’ accelerating effects as a successful modality. ,
Table 95.3 summaries studies and their findings on effect of vibrating devices protocols.
Pulsed electromagnetic stimulation
The effect of pulsed electromagnetic field (PEMF) influence on bone remodelling became a scientific interest when Bassett et al. reported the successful union of the ununited bones after applying PEMF. PEMF is weak, magnetic non-thermal and can alter the resting electric state of the bone and cartilage by inducing cell division and proliferation. Applying high frequency and low magnitude vibrations produced by static magnetic fields increases the anabolic activity of the bone.
Mechanism of action
The magnetic forces work on the basic piezoelectric principle and inductive coupling. The pressure areas form the electropositive state, attracting osteoclastic action, and tension areas serving as the electronegative sides with osteoblastic activity. Vibratory stimulus changes the tension and pressure sides in cycles, causing repeated alveolar bone remodelling and reducing the lag phase. , Magnetic field influences the cyclic adenosine monophosphate (AMP) and guanosine monophosphate (GMP) of the cells and increases the expression of E cadherin, contributing to increased cell-to-cell interaction and proliferation. This causes an increased influx of sodium, calcium and potassium ions through increased cell membrane permeability, thereby increasing cellular proliferation and osteogenic differentiation. , Microscopic evaluation through transmission microscopy confirmed that magnetic field application caused elevated cell numbers causing transient osteoclastogenesis, noted in the first 2 weeks.
Darendeilier et al. evaluated the effects of PEMF in Wistar rats by bonding the neodymium-iron-boron magnets in a Helmholtz configuration, resulting in a vibratory stimulus 8 h per day. He concluded that the magnetic group showed more molar movement than the sham group. The intraoral placement of the magnets is achieved by embedding the magnets in the removable appliance. A statistically significant increase in tooth movement was noted upon 8–10 h of appliance wear.
An Intersil NE555 integrated circuit (IC) was placed in an acrylic appliance, producing an electromagnetic field with a strength of 0.5 mT and a frequency of 1 Hz. This field, when applied to the canine for a duration of 8 h daily, specifically overnight, resulted in a positive acceleratory effect. Although the PEMF depicts potential effects in acceleration, there is little evidence to date. , Split mouth studies are challenging as the control side should be neutralised simultaneously.
Their use is still at bay due to their dependence on patient compliance and the bulkiness of the magnets, which makes them inconvenient for intraoral placement.
Biological methods influencing the biological process of tooth movement
Blood derivatives
In orthopaedics and sports medicine, blood derivatives were initially used as fibrin glue for bone healing and haemostasis. Whitman et al. replaced the fibrin glue with the platelet concentrates to enhance healing and reduce contamination risk. Dohan et al. have classified platelet concentrates into four types based on their fibrin architecture: leukocyte content as, pure platelet-rich plasma (P-PRP), leukocyte-rich PRP (L-PRP), pure platelet-rich fibrin (P-PRF) and leukocyte-rich platelet-rich fibrin (L-PRF).
Recently, the use of platelet concentrates has gained popularity in accelerated orthodontics. Platelet-rich plasma (PRP) is the first-generation platelet derivative prepared by double centrifugation method, while PRF is considered the second-generation platelet concentrate extracted using a single centrifugation protocol. Third generations of platelet concentrates, including advanced PRF (A-PRF), injectable PRF(I-PRF), sticky bone PRF (S-PRF) and titanium PRF(T-PRF) , have also been introduced lately.
Mechanism of action.
Platelets are the source of various growth factors and proteins that are majorly involved in angiogenesis, osteoclastogenesis, osteoblastogenesis and matrix remodelling. They promote a pro-inflammatory action by TGF β and PDGF BB that stimulates osteoprogenitor cells and osteoclastogenesis, causing bone resorption. The fibrinogen, fibronectin and hyaluron in plasma are suppose to induce sterile inflammation and cytokine release. The plasma proteins in PRP activate the macrophages and increase the release of TNF, IL 1, IL 6 and VEGF. Thus, in higher concentrations, PRP is said to have catabolic effects on bone metabolism, which is dose dependent.
Platelet-rich plasma
PRP is the classical concentration of platelets up to 0.5 × 10 11 platelets per unit. PRP is prepared by a double centrifugation method in an anticoagulant-coated tube; the first soft spin separates the blood into three components: RBC at the bottom, plasma at the top layer and the buffy coat in the middle. The RBCs are discarded, and the test tube is subjected to second hard spin centrifugation. The resultant tube will have residual RBC, platelet-poor plasma (PPP) in the top and a platelet buffy coat in the middle. PRP is made after discarding the PPP and diluting the platelet in fibrin-rich plasma. Liou explained the initial protocol of PRP using 60 mL of blood for orthodontic application. The first centrifugation was at 1000 rpm for 12 min while second centrifugation was done at 3000 rpm for 8 min at room temperature and achieved a 1.7-fold increase in tooth movement. According to Angel et al., centrifugation of blood at 160 g for 10 min at 22°C followed by 400 g for 10 min at 22°C yielded a 6.6-time concentrated PRP resulting in 35% increase in tooth movement. The PRP can be injected locally via the submucosal or intra-ligamentary routes for the acceleratory phenomenon with less pain. , ,
The platelets are believed to have both anti-inflammatory and pro-inflammatory action based on the concentration of platelets. Gulec et al. injected PRP at moderate and high concentrations in sprague dawley rats and found that the alveolar bone density was reduced in both groups, with 1.7 times faster tooth movement in the high concentration group. Similarly, Nakornnoi et al. also confirmed the increased osteoclast numbers in the L-PRP group through histological examination. The transient osteopenia induced by the release of growth factors induces osteoclastogenesis, thereby accelerating tooth movement. The levels of OPG decreased, and RANKL increased in the first and third week of injection, regulating the early osteoclastogenesis. The split mouth-designed randomised controlled trials have concluded that the PRP has an accelerating potential in the rate of tooth movement when compared to the control groups. , There is ample evidence of the positive accelerating potential of the PRP, but some studies have reported conflicting results. , Recent studies comparing the effectiveness of the PRP and PRF have also concluded that the platelet derivatives effectively induce the regional acceleratory phenomenon.
The advantages of the PRP include its autologous nature, can be repeated with minimal discomfort and is a relatively safe intervention. The liquid form enables easy injection and sustained release in the desired area. Yao et al. have reported that the PRP has a definite short-term effect on bone metabolism up to 3 months after the injection and may need repeated injections for a stable rate of tooth movement. PRP can be activated to release growth factors externally using thrombin or CaCl 2 or innately release the contents once they come in contact with the extracellular matrix after injection. Hence, the PRP can be freshly prepared and injected for up to 8 h when stored in a sterile temperature-controlled environment. Using allogeneic or heterogeneous-activating agents have raised concerns about the risk of cross-contamination in rare situations.
Platelet-rich fibrin
The preparation of platelet-rich fibrin (PRF) was established by Joseph Choukroun and colleagues in France in 2001 and found it to stimulate the proliferation of bone mesenchymal stem cells. Since then, numerous specialties have employed the clinical use of anticoagulant-free fibrin matrices, such as periodontics, oral and maxillofacial surgery, and orthopaedics. Recently, PRF has also been tested to accelerate orthodontic tooth movement. The PRF is prepared by a single centrifugation method that activates platelets and fibrin plugs. The plug can be placed in the extracted sites to allow the release of growth factors. About 70% of growth factors are released in the first 10 min, and 100% are released within an hour. Hence, fresh preparation, fast handling and immediate placement are essential for adequate effects. The injectable PRF (i-PRF) is the third-generation PRF developed to overcome this drawback of the PRF, and this formulation involves the use of plastic tubes to delay the activation of platelets. This is the injectable form of PRF, which is easy to prepare and inject with less resistance. PRF is inexpensive, safe and has less blood requirement than PRP and is technically a more straightforward platelet derivative. Randomised controlled trials have presented compatible results regarding the effects of PRF on bone metabolism. The i-PRF is believed to increase the RANKL levels and induce osteoclastogenesis. Hence, the form of preparation, platelet concentration and injection time plays a critical role in the pro- or anti-inflammatory response of the blood derivatives.
Fig. 95.2 depicts steps in preparation of PRP and i-PRF.
Steps involved in preparation of platelet concentrates: PRP and i-PRF.
Blood is withdrawn and double centrifugation is done to obtain PRP; i-PRF is obtained from single centrifugation.
Pharmacological methods influencing the biological process of tooth movement
Pharmacological substances
Minimally invasive methods that have been attempted for faster tooth movement include the local injection of biologically active pharmacological substances. Injection of synthetically prepared bioactive materials like prostaglandin, misoprostol, parathyroid hormone and osteocalcin have been investigated with some success and also complications.
Pharmacological methods
All the acceleratory methods focus on initiating the inflammatory process in addition to the orthodontic force using minimally invasive agents. It is well-established that anti-inflammatory drugs reduce the rate of tooth movement. Hence, pro-inflammatory drugs can be used to fasten the tooth movement.
Synthetic drug analogues, including the human relaxin hormone, tenoxicam, prostaglandin E1, calcitriol (Vit D3), and fluorides have been investigated in humans to increase the rate of tooth movement. Animal studies revealed a synergistic effect of the drugs in influencing tooth movement by triggering the cyclooxygenase inflammation pathway. The effect of dinoprostone, an analogue of prostaglandin E 2 , was studied in the monkeys and indicated that ingestion of 40 µg in 4-day intervals resulted in faster tooth movement.
Two trials investigated the PGE1 effect on tooth movement and concluded that the PGE1 causes bone resorption and increased tooth movement by a 2.14:1 ratio compared to the control side. A similar study claimed a 1.7:1 ratio with no significant side effects of prostaglandin injection. , , Al-Hasani et al. evaluated the effects of calcitriol in split-mouth design and found a dose-dependent acceleratory effect on tooth movement. Potential role of RANKL and Vitamin C has also been studied for their acceleratory effect. Although studies have not reported any adverse effects, some studies have reported significant pain upon injection.
Moreover, the systemic effects of these drugs pose a risk to older patients with a risk of arthritis, diabetes and cardiovascular diseases. In light of more adult patients with varying systemic diseases seeking orthodontic treatment, drug interactions should be discussed with the physician prior to intervention. The effect of the drugs is dose-dependent, and repeated injections may be necessary due to the short half-life for continued effect on bone turnover. Current evidence of the efficacy of non-surgical methods in accelerating orthodontic tooth movement are summarised in Table 95.4 . , ,
TABLE 95.4
Current evidence of the efficacy of non-surgical methods in accelerating orthodontic tooth movement
Source: From Ferrillo et al., Shirude et al., Arqub et al., Eltimamy et al., Kaklamanos et al.
| S.no. | Study | Purpose | Population | Studies included | Conclusion(s) |
|---|---|---|---|---|---|
| 1. | Aljabaa et al. (2018, American Journal of Orthodontics and Dentofacial Orthopedics ) | Effects of vibrational devices on orthodontic tooth movement: a systematic review | Human population | 6 studies | The results from all but one of the included studies indicate no advantage from the use of vibrational devices during orthodontic treatment. |
| 2. | Yi et al. (2017, Journal of Oral Rehabilitation ) | Effectiveness of adjunctive interventions for accelerating orthodontic tooth movement: a systematic review of systematic reviews | Human population | 11 systematic reviews | LLLT (5 and 8 J/cm 2 ) has a low quality of evidence, to promote orthodontic tooth movement (OTM) at least in the short term. |
| 3. | Ferrillo et al. (2024, Korean Journal of Orthodontics ) | Role of vitamin D for orthodontic tooth movement, external apical root resorption and bone biomarker expression and remodelling: a systematic review | Animal and human population | 19 articles | Vitamin D has a biological effect on the bone metabolism but there is lack of studies as substantial evidence of its influence on the rate of tooth movement. |
| 4. | Shirude et al. (2018, Journal of Indian Orthodontic Society ) | Interventions for accelerating orthodontic tooth movement: a systematic review | Human population | 10 articles |
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| 5. | Arqub et al. (2021, Progress in Orthodontics ) | The effect of the local administration of biological substances on the rate of orthodontic tooth movement: systematic review of human studies | Human population | 11 articles | Administration of biological agents have a different effect of the rate of tooth movement. Hence there is a need for robust methodology and results should be read with caution. |
| 6. | El Timamy et al. (2019, Macedonian Journal of Medical Sciences ) | The effect of local pharmacological agents in acceleration of orthodontic tooth movement: a systematic review | Human population | 2 articles | Below moderate and inconclusive evidence of the effects of relaxin and prostaglandin on the rate of tooth movement. |
| 7. | Kaklamanos et al. (2020, European Journal of Orthodontics ) | Does medication administration affect the rate of orthodontic tooth movement and root resorption development in humans? A systematic review | Human population | 8 articles | Different effects observed by medicinal substances, inconclusive. |
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