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02 August 2021

How to avoid post-implantology neuropathic trigeminal pain

Lara Figini


Since the placement of dental implants is an increasingly frequent rehabilitation treatment, it is imperative to consider the possible complications. Surgical complications such as bleeding (24%) and sensorineural disorders (7%) can be included with a combined incidence of 30%. Chronic pain, such as post-traumatic trigeminal neuropathic pain (PTNP) secondary to implant placement is also a possible complication; however, the prevalence is unclear. In the case of PTNP, patients report persistent pain symptoms secondary to implant therapy. This is accompanied by positive or negative sensory abnormalities, which interfere with routine activities such as chewing, and speech. These complications can compromise the success of the implant and have a potential impact on the patient's quality of life. According to the International Association for the Study of Pain, pain that lasts longer than 3 months is classified as chronic. Chronic pain is defined as pain that occurs for more than 15 days per month, lasting more than 2 hours per day for at least 3 months. 

Type of research and methods of analysis 

In a recent JADA publication, June 2021, the authors conducted a review of the causes, methods of prevention, treatment and management of PTNP. The exact epidemiology of PTNP secondary to implant placement is unclear. It has been reported that the neuronal damage secondary to the placement of implants varies from 0.5% to a value higher than 37%. DIAGNOSIS According to the International Classification of Orofacial Pain 2020, the diagnostic criteria for PTNPs require the following features: - presence of persistent or recurrent pain within the trigeminal nerve distribution for more than 3 months with onset within 6 months of injury and associated with somatosensory symptoms and signs, or both. Injuries of the peripheral branches of the trigeminal nerve can be mechanical, thermal, radiant, or chemical. 

ETIOLOGY

Iatrogenic nerve injuries due to dental implants can result from: 

1) direct trauma or 

2) indirect trauma. 

1) Direct trauma includes preparation or osteotomy which is more commonly associated with nerve injury than the placement of the implant itself. 

2) The indirect trauma is secondary to mechanical or chemical causes including the extrusion of debris in the lower alveolar canal, bleeding and inflammation. The prevalence of nerve injury induced by haemorrhage is about 24%, in which persistent nerve ischemia occurs due to bleeding caused during placement. Iron or hemoglobin from the blood can result in chemical nerve injury, and bleeding can cause direct mechanical damage to the nerve. It is also possible to cause nerve injury while administering a local anesthetic (LA).

Clinical features:
The type of nerve fibers involved in the nerve injury determines the clinical phenotype exhibited. An injury to the A beta nerve fibers, normally responsible for the sensation of a light painful impulse, can result in slight positive (allodynia) and negative (numbness) light alterations to the touch, while an injury to the type A delta and C fibers, normally responsible of the transmission of noxious stimuli, can manifest itself as an exaggerated response to painful stimuli (hyperalgesia). The clinical features of pain are variable and mostly described as continuous, with unilateral pain (occurring most of the day and most days) in the dermatome of the affected nerve. 

How to avoid nerve injuries in implantology:
Nerve injuries related to implantology are avoidable and therefore PTNP is preventable. Dentists must give adequate importance to preventive measures, which can be divided according to the procedural phases: preoperative, intraoperative and postoperative.

Preoperative phase:
In addition to the evaluation of the biopsychosocial profile of the patients (age, sex, anxiety, depression, catastrophic pain, pre-existing chronic pain conditions, systemic pathologies and the presence of preoperative pain, at the site where the implant will be placed, are some of the known factors associated with higher levels of postoperative pain), presurgical planning of the type of incision and flap, the type of surgery and the implant technique to be used is recommended to minimize the risk of causing nerve injury. Site assessment radiographically plays an important role in avoiding nerve injury. 

The American Academy of Oral and Maxillofacial Radiology recommends cross-sectional cone-beam computed tomographic imaging as the imaging of choice for assessing the implant placement site. Vital anatomical structures and their probable anomalies must be carefully evaluated. It is essential to educate patients about possible complications, to prepare them adequately in the event of their development. When implant treatment planning is performed, it is imperative to obtain informed consent based on an individualized and patient-specific risk assessment. 

Intraoperative phase:
The implantologist must pay particular attention to the guidelines to maintain an adequate safety margin (2-4 millimeters) and the use of shorter implants is recommended to minimize the risk of injury. The extension of the required safety zone is determined individually on the basis of the operator's skill and radiographic interpretation. However, it is imperative to emphasize that even a 4 mm safety zone is not always preventative, and in the presence of significant inflammation it could generate the onset of a slow course of symptoms and eventually lead to PTNP. Furthermore, perineural inflammation secondary to the insertion of a well positioned implant can also cause PTNP. Intraoperative radiographs are suggested during implant bed preparation. It should be noted that some preparation drills are longer than the implant. If sudden failure occurs during preparation, this may indicate penetration of the vestibular or lingual cortical plate or roof fracture of the inferior alveolar nerve canal. The implant procedure should be stopped and prompt action should be taken in case of bleeding, or severe pain. 

Postoperative phase:
Early follow-up is critical in preventing the development of chronic pain. The implantologist must regularly contact the patient within 6-12 hours after surgery to detect any symptoms of potential nerve damage. In the event that the patient reports symptoms of neuropathy, an immediate follow-up visit and implant removal are indicated. If numbness persists after LA has subsided, the implant should be removed within 24 hours, through a 36-hour window to facilitate recovery and prevent the development of chronic pain. Delayed implant removal, waiting, observation, and conservative modalities are useless in relieving neuropathy and pain. 

PTNP treatment:
Treatment of PTNP remains challenging and evidence of the effectiveness of available interventions it is inconclusive; therefore, an interdisciplinary approach is indicated. Management of PTNP includes pharmacotherapy, surgery and complementary therapies. The first step in management is patient education. Communication with the patient, clarification regarding the condition and support are part of the initial psychological treatment. Patient expectation is critical for effective management of PTNP; therefore, patients should be educated about prognosis and treatment and should understand that partial pain relief is a good and expected outcome. Many times, the dentist does not communicate properly with the patient, and this increases the uncertainty, anxiety and stress in the patient. First-line drug therapy includes tricyclic antidepressants and serotonin and norepinephrine reuptake inhibitors or gabapentinoids. To improve efficacy and reduce adverse effects, a combination of 2 different drugs is suggested. The choice of drug depends on several factors, such as the presence of systemic comorbidities, age and the adverse effect profile of the drug. The use of drug therapy in PTNP for implantology has been shown to reduce pain especially if you start an early intervention. Overall, these drugs have limited effectiveness and often provide only partial pain relief. It has been reported that only 10% of patients report more than 50% of pain relief, indicating a poor PTNP response to pharmacotherapy. The use of topical products with various drug combinations may also be considered, including ketamine, carbamazepine, gabapentin, pregabalin, clonidine, lidocaine, capsaicin, and ketoprofen in varying concentrations. Treatments for intraoral PTNP with neurostent have also been reported in the literature for the increased administration and delivery of specific topical drugs at the site of the lesion, and non-pharmacological and complementary and alternative medicine interventions have also been reported.

Referral to a microneurosurgeon is recommended when no obvious pathology is visible on imaging and symptoms of anesthesia and hypoesthesia persist for more than 3 months without improvement, or dysesthesia persists for more than 3 months with resolution as a response to peripheral nerve blocks. 


CONCLUSIONS
Implant therapy can cause nerve damage to the TN trigeminal branches. The implantologist must be aware of the risks of such injuries, discuss them with the patient during treatment planning and ask the patient to sign an appropriate informed consent. Fortunately, most injuries are preventable through preoperative evaluation, including careful patient care and choice of implant site. Prevention of nerve injury by implementing appropriate preoperative and intraoperative strategies is critical. The clinician should be aware of the signs and symptoms of a nerve injury during and immediately following a procedure and should contact the patient the next day to ensure there are no such complications. Timely recognition is essential to prevent the progression to irreversible chronic neuropathy. Persistent pain and sensory distortions can be debilitating for the patient and can adversely affect the quality of life, causing a significant psychological burden. It is essential to promptly consult a pain or orofacial pain specialist for appropriate multidisciplinary pain management. The key to success is prevention. 

Keywords: 

implant; pain; trigeminal neuropathic pain; diagnosis; management plant

Bibliography 

Orofacial Pain Neuroscience Diagnosis and management of persistent posttraumatic trigeminal neuropathic pain secondary to implant therapy: A review 

Divya Kohli; Giannina Katzmann; Rafael Benoliel; Olga A. Korczeniewska 

JADA Jun 2021: 152 (6): 483-490


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