C.E. Credit. Diagnosing Non-Odontogenic Sources of Dental Pain: A Case Report and Review of the International Classification of Orofacial Pain, 1^st Edition

ABSTRACT

Background

Diagnosing the source of dental pain can be challenging for even the most experienced dentist, particularly in cases of patients with chronic pain, which may present with less localized and nonspecific symptoms.

Case description

The International Classification of Orofacial Pain, 1^st edition (ICOP-1) is a comprehensive classification of orofacial pain that includes both odontogenic and non-odontogenic pain conditions and can help dentists determine the cause of dental pain. In this article, we present a case of a patient presenting with chronic orofacial pain and review the clinical features and diagnostic tests that help distinguish between odontogenic and non-odontogenic pain as defined by the ICOP-1.

Practical implications

An accurate diagnosis of orofacial pain requires a detailed history, a thorough clinical and radiographic examination, and up-to-date knowledge of the current classification system of orofacial pain.

Continuing Education Credit Available

The practice worksheet is available online in the supplemental material tab for this article. A CDA Continuing Education quiz is online for this article: https://www.cdapresents360.com/learn/catalog/view/20.

KEYWORDS:

• Persistent idiopathic dentoalveolar pain
• orofacial pain
• oral diagnosis
• dental pain

Introduction

Orofacial pain serves as a symptom associated with a multitude of distinct diseases. While dental pain, the most prevalent form of orofacial pain, predominantly arises from odontogenic sources, there are various non-odontogenic conditions that can imitate dental pain or manifest similarly. Nonodontogenic pain originates in the absence of clinically evident pathology in the teeth, periapical tissues, or periodontal tissues and adjoining structures.¹ Examples of such conditions include myofascial pain, neuropathic pain, orofacial neurovascular pain, cardiac pain, and sinus disorders, among others.¹ It can be challenging for even experienced dentists when patients present with atypical or unusual dental pain symptoms.

The process of distinguishing between various potential causes of toothache is crucial. Conducting a thorough differential diagnosis for dental pain ensures that the source of the pain is accurately determined, leading to more precise and appropriate dental treatment. Considering all the potential causes of tooth pain also reduces the likelihood of ineffective or unnecessary procedures and ultimately improves patient outcomes.²

The International Classification of Orofacial Pain, 1st edition (ICOP-1) was published in 2020 to help healthcare providers better distinguish between various types of pain, whether dental, musculoskeletal, or neuropathic in origin.¹ Specifically, ICOP-1 is a comprehensive classification of the various types of pain affecting the oral cavity, face, and head. Herein, we examine a clinical case of a patient who presents with dental pain and explore the clinical characteristics and diagnostic methods that aid in differentiating between odontogenic and non-odontogenic pain, as per the ICOP-1 definition.

Clinical Case

A 33-year-old male patient presented upon referral from his dentist with a chief concern of pain in his upper left jaw. He stated his pain began 2 years prior, beginning after he had a crown prepared on the opposing arch in the lower left jaw (pointing to tooth #19). The constant pain was described as a sensation of sensitivity “like a dental drill in [his] upper left molar.” He was not aware of any aggravating factors like sensitivity to hot, cold, or chewing. He confirmed no numbness or tingling. He also reported a history of similar pain symptoms in his lower left jaw and upper right jaw, but as of lately, the pain was being felt primarily in the upper left molar area. There were no symptoms of extra-oral or intra-oral swelling.

Additionally, he reported a longstanding history of temporomandibular joint (TMJ) pain, which he described as a milder pain in his jaws, pointing to his bilateral preauricular and masseteric area. He described this pain as tension and “like a sore muscle.” He shared that he had a diagnosis of obsessive-compulsive disorder (OCD) and anxiety and admitted to a habit of day-time clenching when stressed as well as nighttime grinding. The patient otherwise reported no history of headaches or migraines. He had no history of trauma to the head or neck.

His past medical history was significant for obsessive-compulsive disorder (OCD), anxiety (as described above) as well as insomnia and was on duloxetine 60 mg nightly, lorazepam 2 mg three times a day and zolpidem 10 mg nightly as needed, respectively. He also had irritable bowel syndrome (on pregabalin 75 mg TID) and severe obstructive sleep apnea with poor adherence to his CPAP machine.

He lived alone and was working part-time in finance. He mentioned he had to reduce his hours because of his current jaw pain, which in turn had exacerbated his OCD and anxiety. He did not drink alcohol. He was a current smoker with a 4.5 pack-year history. He did not use any other drugs recreationally.

A clinical examination revealed no facial asymmetry or swelling. Cranial nerves V and VII were intact with no sensory deficits. His mandibular range of motion on opening was normal at 47 mm with a straight path of opening and no joint noises. The lateral excursions of his mandible were similarly normal with 8 mm of movement in either direction and without pain or joint noises. He was tender to palpation of his bilateral masseter and temporalis muscles, which he stated was a familiar sensation to his secondary concern of jaw pain but did not reproduce his pain in his upper left molar area. The joint loading test was negative for TMJ arthralgia.

Intraorally, there were no lesions or swelling indicative of an acute odontogenic infection and no evidence of gross caries on visual inspection. Tooth #14 had a provisional crown in place which appeared well-adapted to the margins. The surrounding gingiva appeared pink, healthy, and knife-edged in appearance. Periapical and bitewing radiographs were taken, which revealed a well-filled root canal with no periapical pathology (Figure 1). Cold testing was negative on tooth #14 as compared to neighboring teeth, as expected given the root canal treatment. He did report tenderness to palpation of the buccal alveolar bone overlying tooth #14, but this occurred only once and was not consistent or reproducible. The tooth was negative to percussion with no mobility and probing depths of 2–3 mm with mild bleeding on probing. Testing with the Tooth Slooth® was negative.

Figure 1. (a) Periapical radiograph shows that tooth #14 is root canal treated, well-filled, restored with a post and core-build up, with a provisional crown in place. There is no widening of the periodontal ligament space or other periapical or bony pathology. (b) Bitewing radiograph shows likely open margin of provisional crown on distal aspect.

Combining the history of present illness with the lack of any clinical or radiographic signs of an odontogenic infection, he was diagnosed with persistent idiopathic dentoalveolar pain, a neuropathic pain condition. He also was diagnosed with chronic myofascial pain of his masticatory muscles secondary to self-reported bruxism in the setting of a diagnosis of severe OCD and anxiety.

To rule out the role of his myofascial pain causing referred pain in his left posterior maxilla, a diagnostic trigger point injection to the left superficial masseter near the zygomatic attachment was performed. He reported this relieved his muscle soreness but that he still had discomfort associated with tooth #14. Interestingly, nerve blocks to his left posterior superior alveolar nerve and left greater palatine nerve produced anesthesia but the patient reported still being able to feel “sensitivity” in tooth #14, which indicates a role of central sensitization, i.e., the neurophysiological mechanism that leads to amplification of pain signals from the central nervous system³ in producing his pain.

Ultimately, given his complex medical history with current use of multiple medications for chronic pain and mood (i.e., duloxetine 60 mg QD, pregabalin 75 mg TID, lorazepam 2 mg TID, zolpidem 10 mg QHS), multidisciplinary care was sought out in coordination with his primary care provider, psychiatrist, psychologist, and pain management specialist. He began meeting with his psychologist more regularly to emphasize coping skills and increasing his daily activities to live with his OCD and anxiety regarding his facial pain. The role of poor sleep quality in perpetuating or worsening chronic pain was discussed, and he was recommended to return to his sleep medicine physician to resume CPAP treatment for severe obstructive sleep apnea. His orofacial pain was improved with medical management with the addition of lamotrigine 25 mg BID, with which he reported partial improvement, though his symptoms continued to wax and wane. He also received periodic trigger point injections to treat his masticatory myofascial pain while avoiding any additional systemic medication, which he found helpful and resolved any jaw pain. Of note, he did not tolerate an occlusal appliance as he felt it worsened his insomnia. He also continued monthly follow-up visits with his orofacial pain specialist, which helped him reduce his anxiety and OCD and reduce urgent visits to the dentist due to concerns of dental disease. He overall felt that with the combination of more frequent and specialized psychological care combined with lamotrigine 25 mg BID that his symptoms were tolerable and about 60% improved.

Discussion

The ICOP-1 serves as an integral diagnostic reference and guide for management for not only all pulpal, periapical, and dental pain, but also for non-odontogenic sources of pain. Neuropathic pain in the oral cavity is often a diagnosis of exclusion, meaning that other sources of pain, such as an odontogenic infection, a cracked tooth, or musculoskeletal pain referring to the teeth, must be ruled out with a comprehensive clinical and radiographic examination. In the case above, the patient reports symptoms that are atypical for odontogenic pain. His symptoms are not aggravated by typical triggers for odontogenic pain, such as exposure to hot, cold, or sweet foods or biting, but rather are continuous and unchanging in severity. This, along with the changing location of his pain brings us to the diagnosis of persistent idiopathic dentoalveolar pain.

The ICOP defines persistent idiopathic dentoalveolar pain (PIDP), formerly known as atypical odontalgia or phantom tooth pain, as neuropathic pain in the dentoalveolar region of unknown origin. The pain is chronic, recurring daily for >2 hours per day for >3 months. Patients most commonly report their pain as deep, dull, with a pressure-like quality. It has also been described as burning, tingling, throbbing, aching, and sometimes sharp.⁴ In addition, while pain is typically localized to one dentoalveolar site, such as a tooth, some patients may report pain in multiple sites. These patients may present with somatosensory changes, that is, decreased or increased sensation to pain or pain with light touch. As an idiopathic neuropathic pain condition, this diagnosis represents a diagnosis of exclusion, meaning that the clinical and radiographic examination is otherwise normal. Of note, a separate diagnosis, known as persistent idiopathic facial pain, has similar diagnostic criteria to PIDP, but its location is present outside of the dentoalveolar region. Its various pain characteristics, along with a lack of apparent tissue damage, mark the pathophysiology of PIDP as nociplastic or involving central sensitization.

Nociplastic pain refers to pain occurring from “altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain”.⁵ In our case, the patient has a history of dental pain of 2-year duration despite interventions with a root canal and crown. He states the pain in tooth #14 began after a crown preparation of tooth #19. While dentoalveolar pain beginning after dental treatment is concerning for a post-traumatic trigeminal neuropathy, it is not neuroanatomically plausible that a patient would develop pain in tooth #14 after a crown preparation in tooth #19. Tooth #14 was checked to have adequate occlusion with no interfering contacts or hyper occlusion.

The ICOP-1 defines post-traumatic trigeminal neuropathic (PTTN) pain as chronic orofacial pain in the distribution of the trigeminal nerve that occurs following trauma to the nerve and/or findings of a lesion of the nerve. The pain should arise within 6 months of an injury, whether mechanical, thermal, chemical, or a radiation injury to the peripheral trigeminal nerve. Unlike an acute injury that resolves with healing, post-traumatic neuropathic pain should be persistent or recurring for >3 months. Common causes of post-traumatic trigeminal neuropathic pain include the third molar extractions (which accounts for 48% of cases), dental implants (13%), dental extractions (non-third molar; 13%), local anesthetic injections (11%), endodontic treatment (8%), and trauma (7%).⁶ In these patients, symptoms can vary widely in quality, chronicity, and intensity, with pain being mild to severe depending on the extent of nerve injury. With these defining characteristics in mind, an evidence-based decision was made to deem PIDP as the diagnosis for our patient and PTTN as a differential diagnosis, given the changing location of the patient’s pain. A typical classification of PTTN would consist of pain in the same anatomical region as the supposed nerve injury.

Another trigeminal neuropathic pain condition warranting discussion is trigeminal neuralgia. Trigeminal neuralgia is a neuropathic pain condition that is typically seen in older adults and presents as unilateral, sharp, shooting, or electric shock-like pain that is felt in one or more branches of the trigeminal nerve, most commonly in V2 and V3 branches. Notably, the pain should be paroxysmal, lasting from less than a second up to 2 minutes, though usually no more than a few seconds. The paroxysms of pain can be spontaneous or caused by benign stimuli, such as touching the face, brushing the teeth, chewing, or even a breeze felt against the face.⁷ In addition to paroxysmal pain, an estimated 24–49% of patients will present with concomitant background pain of more moderate pain.⁷ Notably, up to 80% of patients with trigeminal neuralgia seek out consultation from their dentist, and up to 53% will be treated for odontogenic pain, indicating that dentists must be aware of this condition and consider it in the differential diagnosis for patients who present without clear evidence of odontogenic pathology.² Trigeminal neuralgia is categorized based on etiology. Classical trigeminal neuralgia occurs due to vascular compression of the trigeminal nerve leading to demyelination and/or atrophy, whereas secondary trigeminal neuralgia occurs due to a disease or lesion, such as multiple sclerosis or a mass lesion in the brain compressing the trigeminal nerve. An MRI brain with trigeminal protocol is recommended at the time of presentation to identify vascular comperssion and rule out secondary causes.⁷

In the case presented, the patient had persistent idiopathic dentoalveolar pain of the left maxilla and also bilateral jaw pain consistent with myofascial pain of the masticatory muscles, a type of temporomandibular disorder (TMD). TMDs are estimated to affect 5–12% of the population and are the most commonly experienced form of musculoskeletal pain following chronic low back pain.⁸ TMD is a broad term that includes both joint-based or muscle-based conditions of the masticatory structures. The ICOP-1 defines subtypes of muscle-based, or myofascial, orofacial pain as well as joint-based pain, which were created for the most part in concordance with the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD).⁸ The ICOP-1 differs from the DC/TMD in that it notes the distinction between primary versus secondary pain conditions.⁹ In a primary pain condition, the pathophysiology may be known, but the cause of pain is idiopathic; in contrast, a secondary pain condition refers to pain originating from a known cause or medical condition.¹⁰

• Temporomandibular joint (TMJ) pain, or TMJ arthralgia, refers to pain localized to the TMJ that may be present at rest and/or during jaw movement. Patients typically report this pain as being in or in front of the ear. This pain should be replicated by either palpation along the lateral pole of the mandibular condyle with 0.5 kg of pressure or with pain with jaw movements (i.e., opening, lateral excursions, protrusive excursion), function (i.e., chewing, talking), or parafunction (i.e., bruxism).⁸ TMJ pain may occur secondary to an underlying disorder, such as inflammation from trauma, infection, crystal deposition, or an autoimmune disorder. Other secondary factors that increase risk for TMJ pain include the structural changes attributed to an articular disc disorder, osteoarthritis, or recurrent subluxations.

• Myofascial orofacial pain is defined as pain in the masticatory muscles, which may or may not be accompanied by a functional impairment, such as a limited mandibular range of motion. Myofascial orofacial pain is typically described as being felt in the jaw, temple, ear, or preauricular area and is aggravated by jaw movement (jaw opening, chewing, parafunctional habits such as bruxism). It is often mild to moderate in intensity and described as a deep, aching, and pressure-type pain. Objectively, there should be findings of pain on palpation of the temporalis or masseter muscles with a recommendation of 1 kg of force applied for 2 seconds. Given the difficulty in reliably palpating the medial and lateral pterygoid muscles, both the ICOP-1 and DC/TMD recommend relying on palpation of the temporalis and masseter muscles to determine the presence of myofascial orofacial pain. The ICOP-1 details that myofascial orofacial pain can be primary, or idiopathic, in nature, or occurring secondary to an underlying disorder, such as inflammation, infection, or a muscle spasm. Of note, while the DC/TMD differentiates between subtypes of myogenous pain (i.e., myalgia vs. myofascial pain), the ICOP-1 utilizes the broader term myofascial orofacial pain, as the pathophysiological difference between these diagnoses remains unclear.

Referral Patterns of Myofascial Pain to the Dentition

It is important to note that TMJ disorders – namely, trigger points within the masticatory muscles – have been known to cause referred pain felt in the teeth. A trigger point refers to a palpable, taut band of muscle that is hyperirritable and painful when palpated, causing referral of pain felt in a location separate from the area of compression. Trigger points are thought to be caused by either repetitive movement of the muscle (i.e., bruxism) or an acute muscle injury (i.e., trauma, prolonged mouth opening).

In the orofacial region, pain originating from the superficial layer of the masseter muscle is known to refer to the lower jaw, upper and lower molars, gingiva, as well as the middle third of the zygomatic arch.¹¹ These patients may even report symptoms of hypersensitivity in teeth, presenting with positive occlusal pressure, percussion, heat, and cold. Pain referral from the temporalis muscle most commonly causes tension type headaches but can also be referred to the maxillary teeth.¹² Specifically, the anterior temporalis can refer pain to the upper incisors along with the supraorbital ridge. The middle temporalis can refer pain to the rest of the maxillary teeth, along with the mid-temple area. Lastly, pain referral from the anterior digastric muscle may refer to lower four incisor teeth.

In the case presented, the patient had myofascial pain of the masticatory muscles attributed to a tender trigger point in the left masseter near the zygomatic attachment which was treated with a trigger point injection (TPI). While the TPI did relieve his muscle soreness, his pain associated with tooth #14 did not improve, ultimately leading to his diagnosis of neuropathic pain. Following the trigger point injection with a left posterior superior alveolar and left greater palatine nerve block led the patient to report numbness of his left maxilla but with persistent pain with tooth #14, indicating that there was a component of central sensitization leading to persistent pain.

Conclusion

The case above both involve a patient who presents with chronic dental and jaw pain that had been persistent for months to years. To identify the correct treatment to ameliorate their pain, an accurate diagnosis must first be made. A detailed history combined with a clinical and radiographic examination, along with an understanding of the current diagnostic criteria in dentistry and orofacial pain, are essential to identify whether pain is odontogenic or non-odontogenic origin.

In the case featured in this report, the patient had a 2-year history of multifocal pain in the left posterior maxilla, left posterior mandible, and right posterior maxilla, although his chief concern was pain and sensitivity associated with tooth #14. A thorough clinical and radiographic examination, combined with diagnostic injections to rule out the role of referred myofascial pain, ultimately led to a diagnosis of persistent idiopathic dentoalveolar pain, a neuropathic pain condition.

The ICOP-1 represents the most recently published classification system of pain originating from the head and neck, containing diagnostic criteria for dentoalveolar pain, myofascial pain of the masticatory muscles, TMJ arthralgia, neuropathic pain, and headache disorders. The ICOP-1, in combination with a detailed history and clinical and radiographic examination, can help dentists diagnose cases of chronic or otherwise complex orofacial pain.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/19424396.2023.2280283.

Additional information

Notes on contributors

Ifrana Zaman

Ifrana Zaman, DDS, is the chief resident in orofacial pain at Harvard School of Dental Medicine and Massachusetts General Hospital.

Shaiba Sandhu

Shaiba Sandhu, BDS, DDS, MS, is an assistant professor of oral medicine and orofacial pain at Workman School of Dental Medicine at High Point Univeristy.

Roxanne Bavarian

Roxanne Bavarian, DMD, DMSc, is an instructor and clinical faculty of orofacial pain, oral medicine, and dental sleep medicine at Harvard School of Dental Medicine and Massachusetts General Hospital.