Nociceptor mechanisms underlying pain and bone remodeling via orthodontic forces: toward no pain, big gain

Orthodontic forces are strongly associated with pain, the primary complaint among patients wearing orthodontic braces. Compared to other side effects of orthodontic treatment, orthodontic pain is often overlooked, with limited clinical management. Orthodontic forces lead to inflammatory responses in the periodontium, which triggers bone remodeling and eventually induces tooth movement. Mechanical forces and subsequent inflammation in the periodontium activate and sensitize periodontal nociceptors and produce orthodontic pain. Nociceptive afferents expressing transient receptor potential vanilloid subtype 1 (TRPV1) play central roles in transducing nociceptive signals, leading to transcriptional changes in the trigeminal ganglia. Nociceptive molecules, such as TRPV1, transient receptor potential ankyrin subtype 1, acid-sensing ion channel 3, and the P2X3 receptor, are believed to mediate orthodontic pain. Neuropeptides such as calcitonin gene-related peptides and substance P can also regulate orthodontic pain. While periodontal nociceptors transmit nociceptive signals to the brain, they are also known to modulate alveolar bone remodeling in periodontitis. Therefore, periodontal nociceptors and nociceptive molecules may contribute to the modulation of orthodontic tooth movement, which currently remains undetermined. Future studies are needed to better understand the fundamental mechanisms underlying neuroskeletal interactions in orthodontics to improve orthodontic treatment by developing novel methods to reduce pain and accelerate orthodontic tooth movement-thereby achieving "big gains with no pain" in clinical orthodontics.

Medication and orthodontic tooth movement

As any pharmaceutical substance may influence the events associated with orthodontic tooth movement, it is of importance for the clinician to be able to recognize any prospective patient's history and patterns of medicinal consumption. This review presents the effects of various commonly prescribed medications on the rate of orthodontic tooth movement. The article concludes that it remains, to a degree, unclear which types of medication may have a clinically significant effect in everyday clinical scenarios. However, since both prescription and over-the-counter medication use have recently increased significantly among all age groups, good practice suggests that it is important to identify patients consuming medications and consider the possible implications in orthodontic therapy.

Does long-term use of pain relievers have an impact on the rate of orthodontic tooth movement? A systematic review of animal studies

Background

Pain relief drugs are used and misused widely and may theoretically affect the events leading to orthodontic tooth movement.

Objective

To systematically investigate and appraise the quality of the available evidence regarding the effect of pain relief medications on the rate of orthodontic tooth movement.

Search methods

Search without restrictions in eight databases (including grey literature) and hand searching until October 2018.

Selection criteria

Animal controlled studies investigating the effect of pain relievers on the rate of orthodontic tooth movement.

Data collection and analysis

Following study retrieval and selection, relevant data were extracted and the risk of bias was assessed using the SYRCLE’s risk of bias tool.

Results

Fourteen studies were finally identified, most of which at unclear risk of bias. Ibuprofen and loxoprofen did not show any significant effects on the rate of orthodontic tooth movement, whereas indomethacin, ketorolac, morphine, and high doses of etoricoxib were found to decrease it. Inconsistent or conflicting effects were noted after the administration of acetaminophen, acetylsalicylic acid, celecoxib, meloxicam, and tramadol. The quality of the available evidence was considered at best as low.

Conclusions

Long-term consumption of pain relievers may affect the rate of orthodontic tooth movement. The orthodontist should be capable of identifying patients taking pain relievers independently of orthodontic treatment and consider the possible implications.

Trial registration

PROSPERO (CRD42017078208).

Effects of the highly COX-2-selective analgesic NSAID etoricoxib on the rate of orthodontic tooth movement and cranial growth

BACKGROUND

NSAID analgesics have found widespread use in the treatment of pain, inflammation and fever. The highly COX-2-selective NSAID etoricoxib has shown a favorable side effect profile and excellent analgesic efficacy, particularly for dental and orthodontic pain, surpassing the current standard analgesic in orthodontics, acetaminophen. However, potential side effects on the rate of orthodontic tooth movement (OTM) and cranial growth, relevant for clinical usability during orthodontic treatment, have not yet been investigated.

MATERIAL AND METHODS

40 male Fischer344 rats were randomly assigned to 4 groups (n=10) - controls receiving only 1.5ml tap water per day by oral gavage for a total of 5 weeks (1) as well as rats receiving an additional daily normal etoricoxib dosage of 7.8mg/kg for 3d (2) and 7d/week (3) and a high dosage of 13.1mg/kg for 7d/week (4) with serum bioavailability assessed by liquid chromatography-mass spectrometry. After one week of premedication, the first upper left molars (M1) were moved orthodontically in anterior direction for 4 weeks using a closed NiTi coil spring (0.25N) and OTM as well as sagittal cranial growth were quantified cephalometrically by CBCT imaging at the start and end of OTM.

RESULTS

OTM, quantified as anterior metric tipping of M1, was significantly inhibited by about 33% only in rats receiving high-dose etoricoxib 7d/week (p=0.046) with a respective, but insignificant tendency also detectable for the normal dosages, whereas sagittal cranial growth was by tendency slightly increased with rising etoricoxib dosages, reflected by corresponding steady-state serum concentrations, confirming etoricoxib bioavailability.

CONCLUSIONS

An etoricoxib-induced clinically relevant deceleration of OTM is not to be expected at dosage regimens used in clinical practice to treat dental or orthodontic pain in contrast to a continuously administered high dosage. Due to its favorable side effect profile and higher analgesic efficiency regarding dental and orthodontic pain, etoricoxib should be a clinically valid alternative to the current standard orthodontic analgesic acetaminophen with its associated higher risk profile.

Effectiveness of biologic methods of inhibiting orthodontic tooth movement in animal studies

INTRODUCTION

A number of biologic methods leading to decreased rates of orthodontic tooth movement (OTM) can be found in the recent literature. The aim of this systematic review was to provide an overview of biologic methods and their effects on OTM inhibition.

METHODS

An electronic search was performed up to January 2016. Two researchers independently selected the studies (kappa index, 0.8) using the selection criteria established in the PRISMA statement. The methodologic quality of the articles was assessed objectively according to the Methodological Index for Non-Randomized Studies scale.

RESULTS

We retrieved 861 articles in the initial electronic search, and 57 were finally analyzed. Three biologic techniques were identified as reducing the rate of OTM: chemical methods, low-level laser therapy, and gene therapy. When the experimental objective was to slow down OTM, pharmacologic modulation was the most frequently described method (53 articles). Rats were the most frequent model (38 of 57 articles), followed by mice (9 of 57), rabbits (4 of 57), guinea pigs (2 of 57), dogs (2 of 57), cats (1 of 57), and monkeys (1 of 57). The sample sizes seldom exceeded 25 subjects per group (6 of 57 articles). The application protocols, quality, and effectiveness of the different biologic methods in reducing OTM varied widely.

CONCLUSIONS

OTM inhibition was experimentally tested with various biologic methods that were notably effective at bench scale, although their clinical applicability to humans was rarely tested further. Rigorous randomized clinical trials are therefore needed to allow the orthodontist to improve the effect of translating them from bench to clinic.

Escaping the Adverse Impacts of NSAIDs on Tooth Movement During Orthodontics: Current Evidence Based on a Meta-Analysis

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to relieve pain during orthodontic treatments; however, the possible inhibition of orthodontic tooth movement (OTM) by NSAIDs has been debated. The aim of this study was to evaluate the influence of some commonly used NSAIDs on OTM during orthodontic treatments. A review of the literature identified relevant studies up to August 2014. A meta-analysis was performed following the guidelines of the Cochrane review group and the PRISMA statement. Studies were identified by searching PUBMED, EMBASE, Web of Science, the Cochrane Central Register of Controlled Trials, and the WHO Clinical Trials Registry Platform. Meta-analysis was performed in a fixed/random-effect model using Revman 5.1.1.Five studies, including 128 subjects and 3 main NSAIDs (celecoxib, acetaminophen, and aspirin), were included for quantitative synthesis and analysis. Celecoxib did not inhibit OTM except with middle-term use (2-3 weeks) (95% CI [-6.47 to -0.43], P = 0.03). Acetaminophen did not inhibit OTM except with long-term use (>1 month) and low-dose use (∼100 mg/kg per day), (95% CI [-2.96 to -0.78], P = 0.0008; 95%CI [-2.42, -0.46], P = 0.004; respectively). Aspirin was found to inhibit OTM (95%CI [-2.40 to -0.64], P = 0.0008). Our systematic review with meta-analysis suggests that aspirin might inhibit OTM in rat models, whereas the short-term (<1 week) use of celecoxib and acetaminophen for relieving orthodontic pain would not inhibit OTM. Well-designed human research should be completed before a solid conclusion can be reached.

Experimental evidence of pharmacological management of anchorage in Orthodontics: A systematic review

INTRODUCTION

Orthodontic anchorage is one of the most challenging aspects of Orthodontics. Preventing undesired movement of teeth could result in safer and less complicated orthodontic treatment. Recently, several reviews have been published about the effects of different molecules on bone physiology and the clinical side effects in Orthodontics. However, the effects of local application of these substances on the rate of orthodontic tooth movement have not been assessed.

OBJECTIVES

The aim of this research was to analyze the scientific evidence published in the literature about the effects of different molecules on orthodontic anchorage.

METHODS

The literature was systematically reviewed using PubMed/Medline, Scopus and Cochrane databases from 2000 up to July 31st, 2014. Articles were independently selected by two different researchers based on previously established inclusion and exclusion criteria, with a concordance Kappa index of 0.86. The methodological quality of the reviewed papers was performed.

RESULTS

Search strategy identified 270 articles. Twenty-five of them were selected after application of inclusion/exclusion criteria, and only 11 qualified for final analysis. Molecules involved in orthodontic anchorage were divided into three main groups: osteoprotegerin (OPG), bisphosphonates (BPs) and other molecules (OMs).

CONCLUSIONS

Different drugs are able to alter the bone remodeling cycle, influencing osteoclast function and, therefore, tooth movement. Thus, they could be used in order to provide maximal anchorage while preventing undesired movements. OPG was found the most effective molecule in blocking the action of osteoclasts, thereby reducing undesired movements.

The effect of celecoxib on orthodontic tooth movement and root resorption in rat

OBJECTIVE

Inhibition of prostaglandin (PGs) production leads to decrease in orthodontic tooth movement (OTM). It is not known whether inhibition of cyclooxygenase-1 (COX-1) or cyclooxygenase-2 (COX-2) is the key mechanism for this effect. In this study, the effect of celecoxib, a highly-selective COX-2 inhibitor, was investigated on OTM in rats.

MATERIALS AND METHODS

Four groups of male rats (seven animals in each goup) were used in the study. A 5mm-long nickel-titanium closed-coil spring was ligated between the right maxillary incisor and the first molar of each rat to deliver an initial force of 60g. All four groups recieved orthodontic appliances, group 1 received no injections, group 2 received celecoxib injections (0.3 mg in 0.1 ml saline solution), group 3 recieved normal saline injections (0.1 ml saline solution), and group 4 recieved needle penetration without injecting any solution. The local injections were carried out every 3 days for 18 days. All injections were subperiosteal and given in the upper right first molar mucosa. The animals were sacrificed 21 days after appliance insertion and OTM was measured.

RESULTS

In the animals treated with celecoxib a statistically significant decrease in OTM was observed compared with the other groups. Histological findings revealed that osteoclast count was significantly lower in group 2 compared with the other groups (P<0.05). The amount of root resorption showed a slight, but nonsignificant decrease in group 3.

CONCLUSION

This study suggests that celecoxib decreases OTM and osteoclast count. This might be the result of COX-2 enzyme inhibition and subsequent decrease in prostaglandin production.

Celecoxib treatment does not alter recruitment and activation of osteoclasts in the initial phase of experimental tooth movement

In a previous study, we reported that the short-term treatment with celecoxib, a non-steroidal anti-inflammatory drug (NSAID) attenuates the activation of brain structures related to nociception and does not interfere with orthodontic incisor separation in rats. The conclusion was that celecoxib could possibly be prescribed for pain in orthodontic patients. However, we did not analyze the effects of this drug in periodontium. The aim of this follow-up study was to analyze effects of celecoxib treatment on recruitment and activation of osteoclasts and alveolar bone resorption after inserting an activated orthodontic appliance between the incisors in our rat model. Twenty rats (400–420 g) were pretreated through oral gavage with celecoxib (50 mg/kg) or vehicle (carboxymethyl-cellulose 0.4%). After 30 min, they received an activated (30 g) orthodontic appliance, set not to cause any palate disjunction. In sham animals, the appliance was immediately removed after introduction. All animals received ground food and, every 12 h, celecoxib or vehicle. After 48 h, they were anesthetized and transcardiacally perfused through the aorta with 4% formaldehyde. Subsequently, maxillae were removed, post-fixed and processed for histomorphometry or immunohistochemical analyses. As expected, incisor distalization induced an inflammatory response with certain histological changes, including an increase in the number of active osteoclasts at the compression side in group treated with vehicle (appliance:32.2±2.49 vs sham: 4.8±1.79, P<0.05) and celecoxib (appliance: 31.0±1.45 vs sham: 4.6±1.82, P<0.05). The treatment with celecoxib did not modify substantially the histological alterations and the number of active osteoclasts after activation of orthodontic appliance. Moreover, we did not see any difference between the groups with respect to percentage of bone resorption area. Taken together with our previous results we conclude that short-term treatment with celecoxib can indeed be a therapeutic alternative for pain relieve during orthodontic procedures.