Knowledge and experience of dentists with patients with trigeminal neuralgia: A prospective, cross-sectional survey study

ABSTRACT Objective Trigeminal neuralgia (TN) and orofacial pain (OFP) patients frequently refer to dentists. It is often confused with odontogenic pain and dental procedures are performed. In this study, the authors aimed to reveal the knowledge and experience of dentists about TN. Methods This is a cross-sectional study that includes dentists who participate in volunteering via an online questionnaire. The questionnaire form contains demographic data, TN treatment, and diagnosis consisting of 18 questions. Results The data of 229 dentists were examined. Almost 82% of the participants reportedly knew the diagnostic criteria of TN and 61.6% reported that they had previously referred patients with TN. The most frequently confused diagnosis was odontogenic pains (45.9%). Conclusion TN diagnostic criteria should be included more often in the education of dentists. Thus, it is possible to prevent unnecessary dental procedures. There is a need to increase knowledge on this subject with further studies involving dental students.


Introduction
The American Academy of Orofacial Pain defines OFP as a group.This group includes disorders of different entities such as temporomandibular joint disorders (TMJ), masticatory musculoskeletal pain, cervical musculoskeletal pain, neurovascular pain, neuropathic pain, OFP-related sleep disorders, orofacial dystonias, headaches, intraoral-intracranial-extracranial and systemic disorders that may be associated with OFP.The reported prevalence of various OFP symptoms ranges from 21% to 42% [1][2][3].The International Headache Society (IHS) made an International Classification of Orofacial Pain, 1 st edition (ICOP) which was published in 2020.They grouped orofacial pains under 6 main headings and the 7 th heading is a psychosocial assessment of patients with orofacial pain.Pain related to the disease is attributed to the trigeminal nerve, which is gathered under two subheadings as trigeminal neuralgia and other trigeminal neuropathic pain, is included in the 4 th main article as pain attributed to the cranial nerves [4,5].
Although the face is anatomically part of the head, a clear diagnostic classification has been made due to a large number of misdiagnosed and mistreated cases.The difference in anatomical boundaries also exacerbates this problem.As a case in point, IHS defines facial pain as "pain below the orbitomeatal line, anterior to the pinnae and above the neck".While other definitions of facial pain also include the forehead, the term "orofacial pain" must necessarily include all structures in the oral cavity.Meanwhile, headaches can often be reflected in the orofacial regions and vice versa.All this leads to complex clinical phenotypes [5].
Trigeminal neuralgia (TN) is a disorder characterized by abrupt onset and ending, repetitive unilateral brief electric shock-like pain, triggered by harmless stimuli limited to the distribution of at least one division of the trigeminal nerve.In addition, there may or may not be associated with persistent pain of moderate intensity in the affected part(s).The pain is similar to a severe electric shock-like stabbing and sharp nature, which can last from seconds to two minutes (the duration of the attack may change over time).In trigeminal neuropathic pain, the pain is continuous or nearly continuous; may be burning, squeezing, aching or likened to pins.There are clinically detectable somatosensory alterations in the trigeminal distribution, and mechanical allodynia and cold hyperalgesia or allodynia which meet the International Association for the Study of Pain (IASP) criteria for neuropathic pain are common.Allodynic areas can be much larger than current punctate trigger zones [5,6].
The classic definition of TN was previously called primary TN.In classical TN, there should be a morphological change in the trigeminal nerve root seen on magnetic resonance imaging (MRI) or during neurovascular compression surgery.Classical TN is divided into two pure paroxysmal and concomitant continuous types.In secondary TN, there is an underlying spaceoccupying lesion or multiple sclerosis, or another cause.In idiopathic TN, there is no significant change in electrophysiological tests or MRI [5].
Vascular contact with the trigeminal nerve or nerve root is also commonly found in healthy patients.If such a finding is encountered in a TN patient without a morphological change such as atrophy or displacement, the term Idiopathic TN should be used, not Classical TN.
In some cases, the diagnosis is difficult as the onset and response to treatment can vary among patients.Patients find it onerous to describe their unfamiliar pain experiences.However, they often elucidate stabbing as electricity-like [7,8].The pitfall for the general dentist is to focus on its odontogenic pain component while the physician focuses on the trigeminal neuropathic pain component.Failure to identify the source of the patient's entire problem can lead to erroneous and ineffective treatment.Therefore, when trying to define the etiology and ultimately recommend treatment, it is important to consider all sources of pain [7].In the literature, the knowledge and opinions of dental students and dentists regarding the diagnosis and treatment of OFP were evaluated.There is a need for standards for this and curriculum and platforms have been proposed to encourage multidisciplinary education in dentists' diagnosis of non-dental OFP.However, today, the OFP approach is considered to be limited among dentists [3,[9][10][11].
There are many diseases in the differential diagnosis of facial pain and it is very difficult to distinguish them.Therefore, the ICOP published by IHS in 2020 is a reflection of the need to standardize the sometimes fairly intricate diagnoses of OFP.Local pain can be seen in OFP and TN, but it is necessary for dentists to distinguish between tooth-related local causes and others.Considering other pre-diagnoses, referral to the appropriate department is important for correct diagnosis and treatment.In this study, we aimed to evaluate the knowledge and experience of dentists about trigeminal neuralgia due to facial pain.

Materials and methods
The study complies with the Helsinki Declaration requirements and received local ethics committee approval (Sakarya University, Ethics Committee Decision Letter No E-71522473-050.01.04 -32,177-294).This cross-sectional observational questionnaire study includes all dentists who willingly participated in the study and were given a questionnaire form via an online link.Online links were sent to local and national groups of dentists and data were obtained and missing data excluded.Since it is not possible to clearly determine the number of people who receive messages or emails in internet groups, and there is no face-to-face survey study and it may be misleading, the response rate was not calculated.Informed consent was written on the questionnaire that was read and confirmed by all participants.
The questionnaire form consisted of 18 questions.Demographic data such as age, gender, education status, and the institutions they worked for were noted.Their opinions were asked about the presence and number of patients referred for suspected TN, which referred branch and diagnostic criteria for TN; which diagnosis is most often confused with TN in the clinic; the most common dental procedure performed in TN patients and the estimated number in the last 1 year; what is the most distinguishing feature in the differential diagnosis of TN; frequency of comorbid orofacial problems with TN; ICHD 3 classification and self-administration preferences in medical therapy; which interventional treatments are known, and whether or not more education is needed on this subject (See appendices questionnaire).This study excluded those under the age of eighteen and those who provided the missing data form.

Statistical analysis
The research data was converted from Google forms to Excel format and uploaded to SPSS for Windows 21.0 (SPSS Inc.Chicago.IL) and evaluated.Descriptive statistics were presented as mean (±) standard deviation, frequency distribution, and percentage.

Results
The data of 229 dentists were examined in the current study.It was observed that 66.4% of the participants were female; 17.0% were specialists and 8.3% were academic dentists.The highest percentage of the participants (43.7%) were working in the second-stage hospital and 29.7% were working privately.Table 1 illustrates the sociodemographic data of the participants.
The answers related to the diagnosis of trigeminal neuralgia were examined.Almost 82% of the participants claimed to know the diagnostic criteria of TN and 61.6% reported that they had previously referred patients with TN.With the highest rate of 45.9%, the most frequently confused diagnosis was odontogenic pains.Neurology (85.6%) was observed as the most consulted branch and 45.4% of the participants declared that they had no idea about the frequency of orofacial comorbidity.Table 2 shows the data on the diagnosis of trigeminal neuralgia.
Nearly 71% of dentists were reported the number of patients who had dental complaints and had dental procedures before the diagnosis of TN as 0. This may be due to the fact that dentists are more clear about nondental pain and difficulty in differential diagnosis of TN and other orofacial pain.Fifty-five and one-half percent of the participants opined that TN can be triggered by local anesthetics applied for nerve blockade during the dental procedure.In the differentiation of odontogenic pain and classic/idiopathic TN; the most distinguishing feature in favor of trigeminal neuralgia was the presence of "per second episodes of pain that resemble electric shocks" at a rate of 71.2%.When dentists were asked whether they would start the first choice for medical treatment carbamazepine on their own, only 10% said yes.When dentists were asked about the need to provide more information in training on OFP and TN, 94.8% said yes.The most known methods for treatment were observed to be Gasser Radiofrequency Thermocoagulation (RFT) (42.8%) and Gamma knife surgery (23.6%).Data on the treatment of trigeminal neuralgia are shown in Table 3.

Discussion
Although dentists often encounter orofacial pain of dental origin, recent studies have demonstrated that the prevalence of non-dental causes of chronic orofacial pain is around 7%.At the same time, these patients have pain in other parts of their bodies.Although TN is considered a rare pain, it is found to be more common than expected when looking at the databases.Patients often cannot be sure whether their pain is of dental origin or not [12].
In the present study, nearly 62% of the dentists said yes to the question of whether they have ever referred a patient with a preliminary diagnosis of TN.When asked how much orofacial comorbidity or dental problems accompany TN, the most common answer was "I have no idea" with 45.4%, followed by "less than 25%" with 20.1%.As a matter of fact, a significant number of patients may experience concurrent dental problems due to poor oral hygiene for other reasons that may exacerbate TN symptoms.Due to severe pain triggered by brushing, patients with TN may not brush their teeth for days to months [13].
Because TN is triggered by the manipulation of teeth and gums during eating, it is not uncommon for dentists to consult.Although the description of TN is typical, the misdiagnosis may be considered odontogenic pain.Because dentists do not frequently encounter TN patients in their daily practice and TN is rare, information on this subject may be scarce.Challenges in the Hadlaq et al. have a study evaluating the knowledge of dentists on OFP.Almost 80% of the participants stated that they could distinguish between odontogenic and non-odontogenic pain, but the great majority (62%) were unable to diagnose the causes of neuropathic OFP.Information questions comprising 10 queries were asked to the participants and 70% of them gave erroneous answers.Around 82% of the participants in this study stated that they knew the diagnostic criteria for TN.However, it was understood that only 5.7% knew the ICHD 3 determined by the IHS using the TN diagnostic criteria and classification.This situation prompted the authors to conclude that there is a lack of knowledge between knowing about the characteristic features of TN and knowing the diagnostic criteria.The authors did not take the ICOP determined in 2020 to the questions in the study, but since ICHD 3 is a broader and previously created classification that covers all diagnoses, this classification was used in the study.
When dentists were asked which diagnosis was most often confused with the diagnosis of TN, odontogenic pain accounted for 45.9%, persistent idiopathic facial pain was 36.7% and temporomandibular joint diseases constituted 11.8%.Differential diagnoses of TN that a dentist may consider are atypical odontalgia or neuropathic trigeminal pain and primary odontogenic pain syndromes such as pulpitis and broken tooth syndrome [15].
When dentists were asked which symptom most commonly suggested TN for the differential diagnosis of odontogenic pain and TN, 71.2% were expressed as per-second episodes of pain that resemble electric shocks, and 11.4% as pain with triggers (such as eating, brushing teeth).Only 3.9% gave the answer having a latent period during attacks.A refractory period of a few seconds or minutes in which the second paroxysm of pain cannot be triggered is another specific feature.Refractory periods do not occur in any form of mechanical allodynia [16,17].Inevitably, the features mentioned in the definition of TN are known as the most distinctive.However, the fact that an important feature such as the latent period between paroxysmal attacks in classical and idiopathic TN is not widely known may indicate the paucity of knowledge on this subject.
Dental pain is often aggravated by percussion or hotcold application to the tooth.Radiating towards the ear and eye suggests TN, even if the pain is persistent or episodic.Ram et al. reported that dental pain is aggravated at night and disrupted sleep is an inverse feature of TN [18].However, Devor et al. stated that, contrary to popular belief, painful awakenings are quite common [19].
Interestingly, routine dental practice often involves damage to small sensory fibers.Every tooth extraction, along with all root canal treatments and surgical procedures, is capable of causing neuronal damage.The use of local analgesic agents is almost universal, and neuropathy has been reported rarely following direct needle or local anesthetic injury [20].According to Benoliel et al., sensory neuropathy and neuropathic pain are among the common neuronal complications following dental implant placement due to the risk of trauma to adjacent nerves.They also added that even in the absence of nerve damage, perineural inflammation may lead to neuropathy by inducing secondary nerve damage resulting from pressure build-up [20].However, this situation is above the definition of painful post-traumatic trigeminal neuropathy (PTTN) stated in ICHD 3, despite the controversy surrounding the definition.Baad-Hansen et al. stated in their review that atypical odontalgia, which is one of the OFPs, has criteria overlapping with PTTN and that there may be difficulties in distinguishing it due to its symptomatology.PTTN can be confused with one of the neuralgias or other OFPs.The early stages of intraoral PTTN are often misdiagnosed as odontogenic pain and this group of patients is at risk of undergoing unnecessary dental procedures to eliminate the cause of the pain [21].
Almost 71% of the dentists answered "0" to the question of how many of your patients had dental procedures in the last 1 year before being diagnosed with TN.Since the patients diagnosed with TN were not surveyed, it is not clear how many patients diagnosed with TN actually underwent treatment, but based on our observation, the majority of the patients went to the dentist before applying to neurology or neurosurgery and had undergone dental procedures.Most of the participants gave this answer, which may be due to the exclusion of patients from follow-up or because true TN patients were mistakenly considered and treated as odontogenic pain.
De Siqueira et al. conducted a study in 2004 wherein 48 TN patients received 83 dental procedures, 32 of which were single tooth extractions.They did not find any linkage between intraoral triggers, such as dental procedures, and TN when compared with extraoral triggers [15].In a study conducted in 2014, Eckardstein et al. stated that 82% of 51 patients initially applied to the dentist, and 53% of them underwent invasive dental treatment.The majority of the patients in this study reported that dentists could not fully recognize the existing situation [22].Tripathi et al. similarly, in their study, found that 65.8% of the patients applied to the dentist because of their pain, and 41.8% of them underwent dental procedures, and 19% experienced an exacerbation of pain after these procedures [14].In the current study, 55.5% of the participants answered yes to the question of whether local anesthetics applied for dental procedures triggered TN pain.Meanwhile, in their study investigating the relationship between mandibular local anesthetic injections and trigeminal nerve injury, Renton et al. stated that although inferior alveolar and lingual nerve injuries are rare, chronic pain is a common condition after injury and it is permanent in 88% of those with inferior alveolar nerve damage [24].The diagnosis of non-dental facial pain is mostly made by careful anamnesis and examination, which underscores the need to take a detailed anamnesis from the patient with facial pain and to take time to describe the patient's pain [23].
When dentists were asked whether they would start the first choice for medical treatment carbamazepine on their own, only 10% said yes.When asked which of the interventional treatment alternatives they knew, the participants were given the opportunity to mark multiple answers.It was then observed that Gasser RFT was the most common among these procedures.The fact that microvascular decompression (MVD) was known at 19.2% may suggest that it should be included in education.
Carbamazepine or oxcarbazepine is recommended as first-line therapy for pain control.Early surgical treatment may be considered in patients with TN refractory to medical therapy.MVD is a treatment for the etiological problem that can be applied in a relatively small percentage of patients as a result of the widely accepted opinion that neurovascular compression plays an important role in the etiology of TN.MVD can be considered a priority over other open surgical techniques as it provides the longest painlessness [25,25].
When dentists were asked about the need to provide more information in training on OFP and TN, 94.8% said yes.In a study conducted by Devor et al.,76.6%stated that more information is needed during training on TN [19].
There were several limitations in this study.First, the study has a relatively small sample size and the results of this study should be validated by multicenter, large sample studies.Second, we were unable to determine geographic distribution because the questionnaire did not contain a geographically descriptive question.

Conclusion
This study aimed to determine the knowledge and experiences of dentists in TN, considering that dentists were the first to encounter OFP and TN.Difficulties persist in the differential diagnosis of TN and OFP.The authors are of the view that dentists should have more place in their education about TN, where patients may have unnecessary dental procedures and the physician's effort is spent on an unsatisfactory treatment result.There is a need to increase awareness and knowledge on this subject with further