Inferior alveolar nerve damage secondary to orthodontic treatment: A systematic scoping review

Abstract

BACKGROUND:

Neurosensory impairment is a common complication following inferior alveolar nerve (IAN) damage.

OBJECTIVE:

To document and report the various causes, diagnosis, and management of IAN damage secondary to orthodontic treatment.

METHODS:

An electronic search for studies that reported IAN damage in patients undergoing orthodontic treatment was performed up to July 15, 2020 using MEDLINE, Embase, and PubMed databases. Descriptive analyses and linear regression model were performed.

RESULTS:

A total of 15 case reports were identified including 16 patients with an overall mean age of 23.3. All the included studies reported temporary sensory alterations which manifested as anesthesia (19%, n = 3), paresthesia (75%, n = 12), or combined (6%, n = 1). The majority of cases managed by stopping the orthodontic force (75%, n = 12), followed by appliance adjustments (19%, n = 3), providing a bite plate (13%, n = 2), and/or providing pharmacological management (38%, n = 6). Full recovery median duration reported in all cases following the aforementioned managements was 17.5 days.

CONCLUSIONS:

IAN damage secondary to orthodontic treatment is emerging in the literature in recent years. Identifying high risk patients with close proximity to the IAN canal is a must to formulate a proper treatment plan to avoid such complications.

Keywords

Inferior alveolar nerve injury IAN damage nerve damage neuropraxia orthodontics paresthesia

1. Introduction

Inferior alveolar nerve (IAN) damage has been extensively reported in the literature on a wide range of dental and surgical procedures, which can be broken down into local or systemic factors. Systemic factors that may cause nerve damage or altered sensation include multiple sclerosis, metastases, bacterial infection, viral infection, sarcoidosis, drug and blood induced diseases [1]. While local factors mediate neural damage through mechanical, chemical or thermal stimuli [2]. The local factor with the highest incidence of IAN damage is orthognathic surgery with a frequency of up to 83% in the first week and 18.4% at one year [3]. Moreover, third molar surgeries are a more common cause of IAN damage as there is a reported prevalence of 1.5% at 1 month and 0.6% at 1 year postoperatively [4]. Trauma, local tumors, endodontic surgery, and pre-prosthetic surgery may also induce IAN damage [5].

Damage of the IAN manifests differently amongst affected patients including altered sensation associated with the ipsilateral lower lip, chin, buccal mandibular gingivae, and teeth. These altered sensations include paresthesia, anesthesia, dysesthesia, hyperalgesia, allodynia, hypoesthesia, or hyperesthesia as classified by The International Association for the Study of Pain (IASP) [6]. These reported altered sensations could either be temporary or permanent depending on the performed procedure and its pertaining risks. However, it has been shown that about 90% of the IAN damages are temporary and resolve within eight weeks but should be considered as permanent if the damage persists more than six months [7]. Although cases of IAN damage have been widely reported in oral and maxillofacial surgical procedures, the aim of this review was to explore IAN damage related to nonsurgical orthodontics, which is a much rarer cause. There has been an increase in the number of case reports on temporary paresthesia following orthodontic procedures in recent years. This scoping review was conducted to document and report in depth, the various causes, diagnosis and management of IAN damage secondary to orthodontic treatment.

2. Materials and methods

2.1. Search protocol and study selection

An electronic search using MEDLINE via Ovid, Embase via Ovid, and PubMed databases was performed up to July 15, 2020 independently by two authors using the following search strategy: ((Orthodontic* OR Braces) AND (Inferior Alveolar Nerve OR Inferior Dental Nerve OR IAN) AND (Injur∗ OR Damage∗)). Additional records were also identified manually through searching the reference lists of the relevant publications. Following the duplicates removal using EndNote X9, records were screened through titles and/or abstracts for relevancy. Full-text articles then were assessed for eligibility.

2.2. Study criteria and data extraction

All clinical studies that reported inferior alveolar nerve damage in patients undergoing orthodontic treatment were included in the review. No restrictions on age or language were implemented. Studies that reported IAN damage due to a surgical intervention were excluded.

The following data were extracted from each included study: study information, patients details including their dental abnormalities and orthodontic managements applied. Moreover, type of IAN damage complication, the causative tooth and orthodontic force, and management applied and outcome (e.g. time to recovery) were sought. Any disagreements between the authors on study selection or data extraction were resolved by consensus and discussion with other reviewers if needed. The reporting of this scoping review follows the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) checklist [8].

2.3. Statistical analyses

Descriptive analyses were performed including the mean, median, and range of various variables from the data extracted. We also fitted a linear regression with recovery time as the outcome to investigate the effects of age, sex, side and region. Results were presented as tables and charts including scatter plot, and box and whisker plot.

Fig. 1.

PRISMA flow diagram.

3. Results

The electronic and manual search yielded a total of 237 records. After duplicates removal, 153 records were screened, of which 124 records were excluded due to irrelevancy. Twenty-nine full-text articles then fully assessed for eligibility and only 15 articles of them met the inclusion criteria (Fig. 1). The main reason for excluding most of the full-text articles was reporting cases with no IAN damage during orthodontic treatment (Appendix). Table 1 shows a summary of the data extracted from the included studies.

Table 1
A summary of the data extracted from the included studies

Study Year of publication and country Age Gender Orthodontic diagnosis Orthodontic treatment/material used prior to the complication Complication Area Causative tooth/movement Management Time to full recovery

Stirrups [11] 1985 UK 15 F LR5 lingually displaced Edgewise fixed appliance A band was placed, and traction applied by tying it to 0.016 in. Nitinol auxiliary arch with elastic thread Temporary anaesthesia and paraesthesia Right mental region LR5 Long root, crown had moved labially about 3 mm in 2 months Force stopped One month

15 F LR5 lingually displaced Removable appliance Using 0.5 mm T looped buccal spring to provide a labial and extrusive force Temporary anaesthesia Lower right lip LR5 Long root, labial and extrusive force Appliance adjustment for extrusion only One week

Tang [12] 1994 UK 39 F Class II Div 1 malocclusion on moderate skeletal II base overjet of 10 mm overbite increased and complete to the palate Fixed edgewise appliance. Insertion of a heavy rectangular archwire for LR7 intrusion Temporary paraesthesia Lower right lip LR7 Close proximity to the ID canal Antibiotics (suspected periapical abscess from LR4) Adjustments of the archwires and the occlusion Two weeks

Krogstad [23] 1997 Norway 21 M Class III malocclusion Edgewise fixed appliance Using round 0.014 in. Australian S.S. Temporary paraesthesia Left mental region LL7 Root buccally to and in close contact with the IA canal/uprighting the lingually inclined tooth Force stopped Couple of days

Study	Year of publication and country	Age	Gender	Orthodontic diagnosis	Orthodontic treatment/material used prior to the complication	Complication	Area	Causative tooth/movement	Management	Time to full recovery
Stirrups [11]	1985 UK	15	F	LR5 lingually displaced	Edgewise fixed appliance A band was placed, and traction applied by tying it to 0.016 in. Nitinol auxiliary arch with elastic thread	Temporary anaesthesia and paraesthesia	Right mental region	LR5 Long root, crown had moved labially about 3 mm in 2 months	Force stopped	One month
		15	F	LR5 lingually displaced	Removable appliance Using 0.5 mm T looped buccal spring to provide a labial and extrusive force	Temporary anaesthesia	Lower right lip	LR5 Long root, labial and extrusive force	Appliance adjustment for extrusion only	One week
Tang [12]	1994 UK	39	F	Class II Div 1 malocclusion on moderate skeletal II base overjet of 10 mm overbite increased and complete to the palate	Fixed edgewise appliance. Insertion of a heavy rectangular archwire for LR7 intrusion	Temporary paraesthesia	Lower right lip	LR7 Close proximity to the ID canal	Antibiotics (suspected periapical abscess from LR4) Adjustments of the archwires and the occlusion	Two weeks
Krogstad [23]	1997 Norway	21	M	Class III malocclusion	Edgewise fixed appliance Using round 0.014 in. Australian S.S.	Temporary paraesthesia	Left mental region	LL7 Root buccally to and in close contact with the IA canal/uprighting the lingually inclined tooth	Force stopped	Couple of days

Table 1 (Continued).

Study	Year of publication and country	Age	Gender	Orthodontic diagnosis	Orthodontic treatment/material used prior to the complication	Complication	Area	Causative tooth/movement	Management	Time to full recovery
Erickson [17]	2003 USA	57	F	Class II molar relationship due to the absent maxillary canines and a buccal crossbite of the lower right second molar	Fixed appliance with buccal and lingual buttons with elastics for LR7	Temporary paraesthesia	Lower right lip	LR7 IAN ran lingual to the LR7 and that the root apex was penetrating the neurovascular canal/Correcting the crossbite of LR7	Discontinuing the elastics for 7 days but with no improvement. The maxillary bite plate with a relief above the LR7 were provided	Two weeks
Willy [13]	2004 UK	17	M	Crowded Class II Div 2 malocclusion on skeletal I base	Pre-adjusted edgewise fixed appliance Placement of a lower 0.020 steel aligning archwire	Temporary paraesthesia	Left mental region	LL5 Apex located immediately superior to the mental foramen/mesially angulated with uprighting movement	Archwire adjustment	Four weeks
Baxmann [21]	2006 Germany	23	F	Class II Div 2 malocclusion on mild class II skeletal base, average FMA, and chin point to the left	Pre-adjusted edgewise fixed appliance placement of 0.018-inch HANT (heat-activated nickel titanium wire)	Temporary anaesthesia	Right mental region	LR5 Lingually displaced and impacted, very close proximity to mental foramen/freeing the LR5	Force stopped	Two days

Table 1 (Continued).

Study	Year of publication and country	Age	Gender	Orthodontic diagnosis	Orthodontic treatment/material used prior to the complication	Complication	Area	Causative tooth/movement	Management	Time to full recovery
Farronato [22]	2008 Italy	16	M	Skeletal Class I malocclusion, dental deepbite with biprotrusion, and vertical growth prediction	Rapid palatal expander and fixed orthodontic appliances open-coil springs, applied between the first and second mandibular molars to distalize them, were activated periodically	Temporary paraesthesia	Area innervated by right mandibular nerve	LR7 Excessive growth and length of roots/tooth distalization leading to interference and compression of IA canal and nerve	Removing the coil springs and bands. Pharmacological: an anti-inflammatory drug serratiopeptidase (10 mg, orally, 3 times a day for 1 week) and vitamin B (100 mg, daily for 10 days)	Two weeks
Noordhoek [18]	2010 USA	29	F	Uprighting LR7 and LR8 to provide a space for implant placement to replace the edentulous LR6 space	Fixed appliance Not available	Temporary paraesthesia	Area innervated by right mandibular nerve (including teeth, gingiva, and the lower lip)	LR8 Extra third root buccal to IAN resulted in impingement of IAN during distal movement and uprighting of the tooth	Force stopped Pharmacological: Medron Dosepak as an anti-inflammatory agent	More than nine weeks

Table 1 (Continued).

Study	Year of publication and country	Age	Gender	Orthodontic diagnosis	Orthodontic treatment/material used prior to the complication	Complication	Area	Causative tooth/movement	Management	Time to full recovery
Pithon [19]	2010 Brazil	31	F	Angle Class II Division 1 malocclusion, a supernumerary lower incisor, diastema between the upper incisors, impaction of the lower right second premolar with extrusion of the upper right second premolar in its space	Fixed appliance spring with helices welded in a 0.019 in. 0.025 in. lower archwire	Temporary paraesthesia	Lower right lip	LR5 Close proximity of the root to the mandibular canal while traction the tooth	Pharmacological: non-steroidal anti-inflammatory and vitamin B	13 months
Monini [20]	2011 Brazil	24	F	Class II div 1 malocclusion, excessive buccal tipping of the mandibular incisors, and a deep curve of Spee	Fixed appliance Leveling initiated with 0.016 3 0.016-inch nickel-titanium (Ni-Ti) archwire,	Temporary paraesthesia	Lower left lip	LL7 Close contact between the IA nerve and the root of the tooth	Force stopped	Four weeks
Chana [24]	2013 Canada	27	M	Severe crowded teeth	Fixed appliance Placement of temporary skeletal anchorage device and Blugloo	Temporary paraesthesia	Left mental region	LL8 Mesiobuccal root invading the space of IAN, intruded by the placement of Blugloo	Bluegloo removed and anterior bite turbos were placed to facilitate disclusion	Two months

Table 1 (Continued).

Study	Year of publication and country	Age	Gender	Orthodontic diagnosis	Orthodontic treatment/material used prior to the complication	Complication	Area	Causative tooth/movement	Management	Time to full recovery
Sham [14]	2014 UK	12	M	Class II Div 2 complicated by generalized spacing associated and retained, infra-occluded primary teeth	Fixed appliance Placement of rigid rectangular stainless steel archwires	Temporary paraesthesia	Lower left lip	LL7 Intimate contact between the mesiolingual and distal root apices of the tooth and the IA canal	Force stopped	Seven days
Abad [5]	2016 Spain	15		Class II skeletal pattern as a result of maxillary hypoplasia and a Class III dental dolichofacial pattern, maxillary compression with a left posterior cross bite, anterior open bite and agenesis of the second upper and lower premolars	Fixed appliance Placing a 0.16 × 0.16^′′ Nitinol archwire	Temporary paraesthesia	Left mental region	LL7 Close relationship between the apex of the lower second molar and the alveolar nerve canal located lingual to the roots of the molar	Force stopped Pharmacological: NSAIDs (Ibuprofen 600 mg, 1 tablet every 8 hours for 3 days) and a vitamin B complex group (Hydroxyl B1-B6-B12^®, 1 capsule daily for 2 weeks) were prescribed	Three weeks

Table 1 (Continued).

Study	Year of publication and country	Age	Gender	Orthodontic diagnosis	Orthodontic treatment/material used prior to the complication	Complication	Area	Causative tooth/movement	Management	Time to full recovery
Mahmood [13]	2019 UK	16	F	Crowded dentition with a Class II div 2 incisor relationship on a skeletal 1 base	Pre-adjusted edgewise fixed appliance Placement of lower 17 × 25 rectangular nickel titanium (NiTi) archwire	Temporary anaesthesia	Right mental region	LR7 Inferior dental canal to be sandwiched between the root apices of the lower right second molar and the lingual cortex of the jaw/ significant torque and strength of the archwire to upright the roots of a lingually tilted tooth	Inactivation of appliance Pharmacological: reducing dose of oral prednisolone (30–50 mg) for 10 days	Two weeks
Sharkouskaya [14]	2019 UK	16	F	Class II div 2 malocclusion on a Class I skeletal base with average vertical proportions. There was no crowding in the lower arch and the lower left lateral incisor was absent	Pre-adjusted edgewise fixed appliances Placement of a lower 0.019^′′×0.025^′′ NiTi archwire	Temporary paraesthesia	The cutaneous distribution of the right mental nerve including the gingivae of the lower right quadrant	LR5, LR6, and LR7 Intimate relationship between the inferior dental canal and the root apices of the above teeth	Removing the fixed appliance from the lower right posterior segment	Six months

3.1. Description of the studies

The 15 included studies were case reports only and published between 1985 and 2019 from the United Kingdom [9–14], United States of America [15,16], Brazil [17,18], Germany [19], Italy [20], Spain [5], Norway [21], and Canada [22].

3.2. Gender and age distribution

A total of 16 patients were included in this review; females (63%, n = 10), males (31%, n = 5), and unknown (6%, n = 1). The overall mean age (SD) was 23.3 (11.6) and the median (min, max) was 19 (12, 57).

3.3. Orthodontic management applied to lower dentition

Different indications that warranted orthodontic treatment were observed in the included studies and managed with fixed appliances (88%, n = 14), removable appliance (6%, n = 1), or fixed appliance with temporary anchorage device (TAD) (6%, n = 1).

3.4. The complications of IAN damage and areas affected

All the included cases reported temporary sensory alterations following IAN damage and manifested as anesthesia (19%, n = 3), paresthesia (75%, n = 12), or combined (6%, n = 1); mostly on the right side (62.5% RHS n = 10 and 37.5% LHS n = 6). The majority of the damages have affected the mental region (50%, n = 8; RHS n = 4, LHS n = 4) including the lower lip and chin followed by the lower lip only (37.5%, n = 6; RHS n = 4, LHS n = 2). In addition to the extraoral areas, intraoral areas have also been reported to be affected in two cases, one affected the area that innervated by the right IAN and one case affected the area innervated by the right mental nerve branch only. Table 2 shows the descriptive analyses of the included cases regarding the affected areas and the time reported to full recovery.

Table 2
Descriptive analyses of the included cases in this review

Female Male Overall

(N = 10) (N = S) (N = 16)

Age

Mean (SD) 26.5 (13.4) 18.6 (5.68) 23.3 (11.6)

Median [min, max] 23.5 [15.0, 57.0] 17.0 [12.0, 27.0] 19.0 [12.0, 57.0]

Associated factor – country

Other 5 (50.0%) 3 (60.0%) 9 (56.2%)

UK 5 (50.0%) 2 (40.0%) 7 (43.8%)

Associated factor - side

Left 1 (10.0%) 4 (80.0%) 6 (37.5%)

Right 9 (90.0%) 1 (20.0%) 10 (62.5%)

Associated factor - area

Lower lip 5 (50.0%) 1 (20.0%) 6 (37.5%)

Mandibular region 1 (10.0%) 1 (20.0%) 2 (12.5%)

Mental region 4 (40.0%) 3 (60.0%) 8 (50.0%)

Recovery

Mean (SD) 74.2 (123) 22.2 (23.3) 54.6 (99.4)

Median [min, max] 21.0 [2.00, 390] 14.0 [2.00, 60.0] 17.5 [2.00, 390]

	Female	Male	Overall
Age
Mean (SD)	26.5 (13.4)	18.6 (5.68)	23.3 (11.6)
Median [min, max]	23.5 [15.0, 57.0]	17.0 [12.0, 27.0]	19.0 [12.0, 57.0]
Associated factor – country
Other	5 (50.0%)	3 (60.0%)	9 (56.2%)
UK	5 (50.0%)	2 (40.0%)	7 (43.8%)
Associated factor - side
Left	1 (10.0%)	4 (80.0%)	6 (37.5%)
Right	9 (90.0%)	1 (20.0%)	10 (62.5%)
Associated factor - area
Lower lip	5 (50.0%)	1 (20.0%)	6 (37.5%)
Mandibular region	1 (10.0%)	1 (20.0%)	2 (12.5%)
Mental region	4 (40.0%)	3 (60.0%)	8 (50.0%)
Recovery
Mean (SD)	74.2 (123)	22.2 (23.3)	54.6 (99.4)
Median [min, max]	21.0 [2.00, 390]	14.0 [2.00, 60.0]	17.5 [2.00, 390]

3.5. The causative tooth and orthodontic force

The IAN damage was caused by orthodontic movement of all mandibular molars and second premolars following an application of specific orthodontic force such as placement of new archwires, elastics, springs, TAD, or orthodontic adhesive material. The mandibular molars that reported to be the causative factor include lower right first molar/LR6 (n = 1), lower right second molar/LR7 (n = 5), lower right third molar/LR8 (n = 1), lower left second molar/LL7 (n = 4), and lower left third molar/LL8 (n = 1). Whereas mandibular second premolars were reported in six cases including lower right second premolar/LR5 (n = 5) and lower left second premolar/LL5 (n = 1). Most of the studies reported that long roots and close proximity to the IAN canal, or mental foramen while orthodontically moving the teeth were the most likely explanations of such complication.

Fig. 2.

Scatter plot showing the effect of age on recovery duration.

Fig. 3.

Box and whisker plot showing the effect of gender on recovery duration.

3.6. Management applied and outcome

The management of the affected patients were stopping the orthodontic force by inactivating or removing the appliance (75%, n = 12), adjusting the appliance (19%, n = 3), providing a bite plate (13%, n = 2), and/or providing pharmacological management (38%, n = 6). Following the aforementioned managements, all the cases reported to be fully recovered to normal sensation. The time required to fully recover in days calculated as a median (min, max) was 17.5 (2, 390). Figures 2 and 3 show the reported time to recovery in days by age and gender.

4. Discussion

In this scoping review we identified 15 studies published between 1985 to 2019 which reported 16 different cases of temporary sensory alterations of the IAN secondary to orthodontic treatment. We found that female patients were reported more than male patients with almost two-thirds of overall cases being affected on the right-hand side. The majority of the reported cases with IAN damage due to orthodontics have experienced temporary paresthesia, whereas anesthesia or combined of both alterations were also reported. The temporary altered sensations reported were affecting the mental region including the lower lip and chin, lower lip only, or the intraoral and/or extraoral areas innervated by the IAN. The majority of cases were managed by stopping the orthodontic forces, while the median duration to reach full recovery was 17.5 days.

Fig. 4.

Intraoral dermatomes innervated by IAN in blue and mental nerve (as IAN branch) in green (including the lower lips).

In order to comprehend the orthodontic movements that may cause IAN damage, one must grasp the basic anatomical course of the IAN (branch of the mandibular nerve V3). The mylohyoid and lingual nerves branch from the main trunk of the mandibular nerve before it enters the mandibular foramen, thus the tongue, lingual mucosa and lower mental symphysis regions were not affected in the included studies of this review [23]. Figure 4 shows the intraoral dermatomes that IAN innervates including its mental nerve (branch of the IAN) as described by Renton and Egbuniwe [23].

Although it is uncommon for a close relationship to exist between the apices of first and second molars or premolars and the IAN canal, it should not be immediately excluded. There are well-documented radiographic signs used, that convey a close proximity of roots to the IAN canal, especially for third molar surgery. Some of these signs are darkening of the root, interruption of white lines of the canal, diversion of canal, deflection of the root, and narrowing of the root or the canal [24,25]. From the studies included in this review, only two studies have reported these signs, one reported darkening of the root and the second reported deviation of the canal [9,13]. In the remainder of the studies none of the previous signs were reported, however excessively long roots were reported in the mandibular second molar in three studies, which may be a specific risk factor [11,19,20]. It has been shown that 2% of lower second molars roots are radiographically related to the IAN canal [26]. Therefore, it is somewhat surprising that paresthesia during orthodontic treatment is not more common.

The majority of studies used panoramic radiographs as pre-operatives. However, if intimate contact between the IAN canal and tooth root is suspected it would be best to take a cone beam computed tomography (CBCT) to investigate these cases and leave the treatment plan uncompromised [12]. The introduction of CBCT imaging provides a more efficient and accurate method to predict the position of teeth roots and the IAN canal especially the bucco-lingual relationship, as it is not revealed in conventional radiography [16]. Numerous studies have been published to compare the sensitivity and specificity of CBCT imaging and panoramic radiographs. In a study by Tantanapornkul et al. [27], CBCT images versus panoramic radiographs were used to determine the diagnostic accuracy of the location of the IAN canal and the roots of third molars prior to extractions. The CBCT images had a higher sensitivity (93% vs 70%) and specificity (77% vs 63%) compared to panoramic radiographs. However, it is not recommended to use CBCT routinely for all orthodontic patients. CBCT should be prescribed only when there is an expected diagnostic benefit for the patient or when there is a significant improvement in the clinical outcome [28]. Moreover, in the advent that paresthesia does develop during orthodontic treatment it is imperative to take a CBCT to rule out a more serious cause.

The main classification method of peripheral nerve injuries is Seddon’s classification [29], which provides important insight in determining the prognosis and treatment strategy. A brief outline of the classification is described below:

Neuropraxia: temporary interruptions in conductions of impulse down the nerve fiber, as a result of blunt trauma. Recovery takes place without Wallerian degeneration; hence it is considered to be the mildest form of nerve injury.

Axonotmesis: it is a loss of the relative continuity of the axon and its covering of myelin, but preservation of the connective tissue framework of the nerve.

Neurotmesis: is the most severe nerve injury, where the nerve is divided. No conduction occur in the nerve and surgical intervention is warranted.

In the majority of the studies that reported mental nerve paresthesia the main teeth affected are the lower second molar and lower second premolar. Moreover, these teeth in the included studies were lingually inclined, which may predispose them to a closer relationship to the IAN canal. The leveling and uprighting would result in the apical part of the root to tilt against the IAN. Additionally, two studies included lower third molars, in one of the studies an intrusive force was applied which compressed the mandibular canal [22]. In the second study, distal movement and uprighting was applied on the lower right third molar, which impinged on the IAN canal [16]. The injuries described earlier are of a mechanical nature due to compression of the nerve by the tooth root during its movement. These compression injuries correspond to neuropraxia in Seddon’s classification. Although clinically they result in sensory dysfunction, but the injury is mild in nature and full recovery is seen within 12 weeks. However, the median recovery duration in the included studies was 17.5 days. If the reported symptoms do not resolve or improve within 2–4 weeks an immediate referral should be made to rule out systemic, intracranial, or extracranial causes. Patel and O’Neill [30] reported a case of a 14-year old male patient who complained of unexplained right-sided facial paresthesia after 9 months of commencing orthodontic treatment; further investigations revealed the patient had a cavernous hemangioma and the symptoms subsided after surgical intervention.

In a total of six studies adjunctive pharmacological management was given, which included steroids, vitamin B, and anti-inflammatory medications. Three out of the six studies provided Vitamin B supplementation. The importance of Vitamin B has been highlighted in several studies which have shown that Vitamin B1, B6, and B12 interact synergistically to improve neuropathy, motor control, nociception, and neuropathic pain [31]. Additionally, an animal study by Altun and Kurutas [32] has shown that supplementation of Vitamin B complex and Vitamin B12 in tissue levels following crush injuries, may be beneficial to nerve regeneration. Moreover, a clinical study by Sun et al. [33] reported that early steroid therapy has been successful in reducing nerve injury associated neuroinflammation, which may lead to accelerated function recovery of nerves. However, no current evidence exists to favor prescribing medication to alleviate the inferior alveolar anesthesia or paresthesia. In the remainder of the studies the clinicians either removed the appliance and stopped the orthodontic treatment or commenced forced interruption followed by tooth extrusion. A systemic review by Coulthard et al. [7] found the quality of evidence to be very low to investigate the effectiveness of surgical, medical and psychological factors for iatrogenic inferior alveolar and lingual nerve damage. Under the current scope of evidence, no recommendation can be made on prescribing medication to help alleviate the paresthesia.

To emphasize, using clear aligners as an orthodontic option is increasing dramatically, especially with the current advances and technologies available in the orthodontic field. There is a clear trend of providing such treatment not only by orthodontists, but general dentists as well. The studies included in this review have been affected with IAN damage secondary to orthodontic treatment, even though almost all cases were treated by orthodontists. Thus, experienced clinicians in orthodontics should be the orthodontic treatment providers for patients with high or unclear proximity to the IAN. Moreover, several companies have launched their services to provide a direct-to-consumer or “DIY” orthodontics, in which the patients might not be examined or evaluated clinically in person, but remotely and asked to take their own impression or having an intraoral scan in-store [34]. The legal and ethical implications will not be discussed, but its clinical implications should be clearly emphasized. No studies so far have been carried out to investigate whether clear aligner providers of the aforementioned services are relying on intraoral scans or self-impressions mainly to provide such treatment and if further radiographic investigation were taken such as panoramic or CBCT for patients with close or unclear proximity to the IAN. Also, a new teleorthodontics concept has been utilized for clear aligner providers to monitor the orthodontic progress with their patients remotely; in which intraoral images be taken by the patients’ smartphones regularly [35]. However, whether radiographic evaluation was implemented in such new technology during the remote orthodontic treatment journey was not clear. Therefore, questioning the radiographic surveillance in orthodontic patients with high risk of IAN damage is inevitable.

The main limitation of this scoping review was the number of cases identified due to the rarity of the complication reviewed. However, IAN damage secondary to orthodontic treatment is emerging in the literature and worth emphasizing the etiological factors and management modalities in such cases. Proper clinical examination including radiographical investigations is a standard of care, and dental practitioners should only provide orthodontic treatment with competency within their scope of clinical practice. Identifying patients with high or unclear proximity to the IAN canal should be dealt professionally while putting the patients’ best interests first.

Footnotes

Acknowledgements

The authors would like to thank Dr Barrak Alahmad from Harvard T.H. Chan School of Public Health, Harvard University, for his genuine help in performing the statistical analyses of this study.

Conflict of interest

None of the authors declare any conflict of interest relevant to this article.

Ethical approval

Not applicable.

Table showing the reasons for studies exclusion

No.	Study	Exclusion reason
10	Celebi N, Canakci GY, Sakin C, Kurt G, Alkan A. Combined orthodontic and surgical therapy for a deeply impacted third molar related with a dentigerous cyst. J Maxillofac Oral Surg. 2015;14(Suppl 1):93–5.	No IAN damage reported during orthodontic treatment.
11	Kalantar Motamedi MR, Heidarpour M, Siadat S, Kalantar Motamedi A, Bahreman AA. Orthodontic Extraction of High-Risk Impacted Mandibular Third Molars in Close Proximity to the Mandibular Canal: A Systematic Review. J Oral Maxillofac Surg. 2015;73(9):1672–85.	Not a clinical study. Systematic review on orthodontic extraction.
12	Ma Z, Xu G, Yang C, Xie Q, Shen Y, Zhang S. Efficacy of the technique of piezoelectric corticotomy for orthodontic traction of impacted mandibular third molars. Br J Oral Maxillofac Surg. 2015;53(4):326–31.	No IAN damage reported during orthodontic treatment.
13	Huang TT, Chang CJ, Chen KC, Lo JB, Chen MY, Huang JS. Outcome Analysis and Unexpected-Scenario Prediction in 2-Stage Orthodontic Lower Third Molar Extraction. J Oral Maxillofac Surg. 2018;76(3):503.e1–.e8.	No IAN damage reported during orthodontic treatment.
14	Wang Z, Liu Z, Shi Y, Fang D, Li S, Zhang D. A Novel Orthodontic Extraction Method for Removal of Impacted Mandibular Third Molars in Close Proximity to Inferior Alveolar Nerve. Journal of Oral and Maxillofacial Surgery. 2019;77(8):1575.e1–.e6.	No IAN damage reported during orthodontic treatment.

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