Impact of Cannabis Use on the Provision of Dental Care

Cannabis is a plant-based drug that has historical use dating back to 500 AD in ancient Egypt, Rome, China, and India. More recently, cannabis has gained much attention as many states have legalized cannabis products in one form or another. To date, 18 states, two territories, and the District of Columbia have legalized cannabis for recreational use.¹ Whereas, 36 states and four territories have legalized cannabis for medical use.² More recently, South Dakota voted to allow recreational use, yet final approval is pending an ongoing legal battle. Under federal law, however, cannabis is classified as an illegal Schedule I substance under the Controlled Substance Act.¹ But in recent months, the United States Congress has inched closer to legalizing cannabis at the federal level.

As the legalization of cannabis and cannabis derivatives gains more support, oral healthcare providers are more likely to encounter patients who may have used cannabis products, including smoking or vaping marijuana, prior to dental appointments. While cannabis or marijuana use may have noticeable effects on oral health conditions, practitioners may also notice increased anxieties, paranoia, and negative outcomes when administering local anesthetics containing epinephrine or providing general anesthesia.³

Marijuana is just one of many names given to the psychoactive products that originate from the female Cannabis plant.^4,5 Cannabis serves as an antiemetic and analgesic for the clinical user while providing mild sedation and serving as a mood enhancer for the recreational user.⁵ According to the US Centers for Disease Control and Prevention, cannabis is one of the most commonly used illegal drugs with approximately 22.2 million users.^4,6 As cannabis is classified as a Schedule I drug—meaning it is without an accepted medical use and exhibits a high potential for abuse—researchers in the US are unable to study the effects of other cannabis products. In fact, previously, the only federally approved source for research on cannabis was the University of Mississippi’s National Center for Natural Products Research.^4,7 In 2016, the US Drug Enforcement Agency updated its interpretation of the 1961 Single Convention on Narcotic Drugs and the 1970 Controlled Substance Act, which opened the door for other growers to cultivate marijuana for research.

Chemical Compounds Found in Cannabis

Three of the most widely known cannabis products are marijuana, cannabinoids, and cannabidiol (CBD). Laboratory-derived synthetic cannabinoids—such as the US Food and Drug Administration (FDA)-approved nabilone, or abusive drugs, (eg, K2 and spice, which are not FDA approved)—are also commonly used.⁴ Delta-9-tetrahydrocannabinol (THC) is the most potent psychoactive.^4,5 THC is the active chemical compound that is extracted from the flowering buds, leaves, stems, and seeds of the cannabis plant. It is responsible for the euphoric high that most users report. The concentration of THC within the cannabis product as well as the method of use are correlational to the final user experience.⁵ The level of THC determines the aggregated effects on the brain and body after use.^4,5,8

Over the years, cannabis growers have sought to increase the concentration of THC to produce desired recreational effects. Hybridization combined with more sophisticated extraction techniques may elevate concentrations of THC to as high as 90%, which is approximately 212% higher than the THC levels common in marijuana used during the 1960s.^4,8,9 Marijuana extracts used in dabbing and edibles may have THC concentrations of 50% to 90%.⁸

Increases in THC levels also elevate addiction risk. Research shows that one in 10 cannabis users become addicted, with an increase in risk if the patient begins using prior to age 18.⁶ Mental health experts report an increased risk of psychosis or schizophrenia in some users based on the duration and frequency of use. This risk increases with family history of mental illnesses (genetic vulnerability) or when use begins at a younger age when the frontal lobe of the brain is not fully developed.^6,8 In fact, a Swiss study found that heavy use of marijuana by the age of 18 increases the risk of schizophrenia by six times and showed positive relationships between use and schizophrenia even 15 years following use.¹⁰

The second most active ingredient found in cannabis is CBD, which does not impair cognition or induce psychotic effects.^8,11 While research is ongoing, CBD has shown to be effective as a therapeutic drug for epilepsy and anxiety disorders.¹¹ In therapeutic doses, CBD demonstrates efficacy as an analgesic, muscle relaxant, anticonvulsant, anxiolytic, and antipsychotic. Furthermore, CBD has demonstrated anti-inflammatory and antioxidant properties. Scientific research has not caught up with the demand for CBD in medicine, leaving healthcare providers without sufficient information regarding the most effective therapeutic doses of CBD.¹¹

In the US, CBD is sold as a supplement and can be purchased in many forms including lotions, tinctures, sublingual sprays, liquids, pills, and edibles. However, like many other herbal supplements, none of these carry FDA approval, thus, no controls are in place to monitor for the safety and purity of the ingredients contained in CBD mixtures. Many believe that CBD is safe because it is a natural substance, but it can cause liver damage, reproductive toxicity, and infertility in animals.¹¹ The FDA has approved one CBD medication, Epidiolex, for use in seizure disorders associated with Lennox-Gastaut syndrome and Dravet syndrome in patients older than 1 year.¹² Recently, the FDA removed the Schedule V listing for Epidiolex due to the safety rating and minimal potential for abuse.

Pharmacology and Mechanism of Action of Cannabis

Predicting the outcome of cannabis products is challenging as the concentration of THC and the method of delivery impact results. When cannabis products are inhaled as in smoking or vaping, the user will experience a more rapid onset and increase in THC concentration into the body. As cannabinoids are rapidly distributed in vessel-rich areas, many effects are felt within seconds to minutes of inhalation, although, they could also be delayed 1 hour to 2 hours.⁴

In 1992, Lumir Hanus, PhD, DSc, identified the endocannabinoid system (ECS), which is responsible for a range of functions (Table 1) that contribute to the body’s ability to maintain homeostasis. Endocannabinoids are endogenous cannabinoids that are naturally produced.^13,14 Hanus identified two main endocannabinoid receptors—CB1 and CB2—located throughout the body. CB1 receptors are specific to the central nervous system, while CB2 receptors are specific to the peripheral nervous system. He also identified the enzymes responsible for breaking down endocannabinoids within the ECS system.^13,14

Once ingested or inhaled, cannabinoids act on both receptors. THC can bind to both the CB1 and CB2 receptors, which causes both desirable and undesirable effects.^11,15 On the other hand, CBD does not produce a high or negative effects, thus, researchers continue to explore how CBD interacts with the ECS.^13–15 Researchers believe that CBD prevents endocannabinoids from breaking down.¹⁵

Because CB1 receptors are found in the cardiovascular tissues, central nervous system, and peripheral vascular tissues, when THC binds to these receptors, it causes an increase in blood pressure and heart rate (Table 2). Research shows an increase in myocardial infarctions and cardiac arrhythmias with an increased frequency of use.¹⁶ In fact, studies indicate a possible fivefold increase in the risk of a myocardial infarction in the first hour following the inhalation of cannabis.⁴ This multifactorial risk results from an increased heart rate and peripheral vasodilation, which causes compensatory orthostatic hypotension combined with an increase in cardiac output and high oxygen demand.⁴ In the central nervous system, THC decreases cerebrovascular blood flow, raising the risk of a cerebral vascular accident or transient ischemic attack.¹⁶ Sudden cardiac deaths have occurred following use.^17,18

Dental Care Implications

Drug interactions with cannabis or CBD products may be difficult to predict. Oral health professionals should learn the signs and symptoms of active intoxication—paranoia, anxiety, tachycardia, hallucinations, hyperactivity, and euphoric highs—as cannabis users will often not self-report.¹⁷ The use of nonFDA-approved synthetic cannabinoids has been connected with unexplained, persistent bleeding, which may impact surgical interventions such as extractions, grafting, or periodontal therapy.⁴

With the increased heart rate and cardiorespiratory effects of THC, the use of local anesthetic containing epinephrine could be life threatening in this population.^17,18 Tachycardia and acute hypertension may occur if drugs with sympathomimetic activity, such as epinephrine, are introduced to a recent cannabis user. This is because the vasoconstrictor present in epinephrine fights against the vasodilation that occurs after inhalation of cannabis as the body systems struggle to return to homeostasis. Postponing treatment of a patient who appears to be intoxicated is prudent.¹⁷ All risks must be assessed prior to the initiation of any dental procedures.

As cannabis and anesthesia both affect the central nervous system, consideration should be given prior to prescribing anxiolytics or providing sedation procedures for a patient with suspected or known history of cannabis use. Research has shown that patients who use cannabis products regularly require higher doses of pain medications and sedatives.^4,19 Sedatives, such as benzodiazepines, barbiturates, nonbenzodiazepine hypnotics, and opioids or narcotics, reduce brain activity.^4,17 These sedatives are often used to control pain and address anxiety and sleep disorders; they are commonly used in general anesthesia procedures.⁴

In dentistry, providers may prescribe a mild sedative to relax patients with known dental phobias or anxiety disorders. Anxious patients may use cannabis in an attempt to “settle their nerves” without knowing the consequences and possible reactions of using both a sedative and cannabis. Additionally, when sedation or general anesthesia is provided for orthognathic surgeries, dental providers must understand possible inherent risk associated with anesthesia medications and cannabis use. Postural hypotension and tachycardia have been noted in humans after any THC exposure.⁴ Research shows an increased risk for cannabis users who have used prior to surgery, especially if the cannabis was smoked or vaped.^4,17–19

Negative outcomes with general anesthesia administration following cannabis use is caused by bronchodilation and decreased airway resistance.⁴ Given the possibility of known or unknown drug interactions, dental providers should not provide additional pharmaceuticals for cannabis users. With cannabis use becoming more widespread, more research is needed to determine drug interactions. If emergency dental treatment is required, nitrous oxide is a safer alternative.¹⁷

Research shows that cannabis users have a higher tolerance to anesthesia, a cross-tolerance for anesthesia agents, an increased risk of myocardial infarction, and may have increased airway reactivity.⁴ In addition, patients who routinely use cannabis products may require increased pain medications following treatment or surgery.⁴ A recent study by the American Osteopathic Association showed that marijuana users required an increase in common anesthesia medications during endoscopy procedures. The findings demonstrated an average increase of 14% more fentanyl, 20% more midazolam, and 200% more propofol was needed for patients who had a history of routine cannabis use.¹⁹

Cannabis Effects on Oral Tissues and Structures

Cannabis use is associated with poor oral health especially when there is concomitant use of tobacco, alcohol, or other substances are combined with less frequent dental visits.²² Smoking or vaping cannabis causes xerostomia, which contributes to the acceleration of tooth decay.²⁰

Gingival enlargement, chronic inflammation, hyperkeratosis, leukoplakia, and erythroplakia have been identified in patients who smoke cannabis. When cannabis is combined with tobacco, research has shown an increase in oral and neck cancers.²⁰ Periodontitis, candidiasis, and other dental sequela have been identified in patients with chronic cannabis use.

Conclusion

As states continue to legalize marijuana for a variety of uses, it is likely oral health professionals will encounter patients who may be under the influence of cannabis. In addition to increased mental health concerns, the dental team must also be able to identify signs and symptoms of use and possible abuse of cannabis and cannabis products. This is especially true in situations where dental patients require additional pain management techniques such anxiolytics, local anesthetics with epinephrine, or general anesthesia. Additionally, there could be legal implications with informed consent especially for irreversible procedures. Patients with acute cannabis intoxication have shown impairments with both memory and perception, which could influence their ability to give informed consent for treatment.

As licensed health care providers, oral health professionals have the right and responsibility to know the type of cannabis product that has been used, route of administration, and the frequency of use. In order to obtain this information, clinicians must have these discussions with their patients. Dental providers should include a drug screening assessment in their initial health assessment to assist in identifying the risk of possible drug interactions.

References

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From Dimensions of Dental Hygiene. August 2022; 20(8)28,31-33.