The previous editorial in JOI 48(6) provided statistics on the use Cannabis (marijuana) and how to peri-operatively manage the patient who is an occasional or chronic marijuana user. This Editorial will review the short- and long-term effects of Cannabis (marijuana) on peri-operative sedation, sympathetic drug interactions, patient stress reactions, immune response, periodontal disease, bone-to-implant contact (BIC) changes, and bone mineral density (BMD) effects.
Marijuana effects the central nervous system (CNS) in multiple ways in a dose-dependent manner that often leads to unpredictable or bizarre reactions. The mesolimbic dopamine pathway in the CNS is affected by cannabinoids. Marijuana increases dopamine signals at cannabinoid receptors, which results in the neural processing of reward, habit formation, and altered cognition.1 Within minutes of inhaling marijuana smoke, the typical user reports feelings of euphoria, uncontrollable laughter, depersonalization, alterations in judgment of time and space, and sharpened vision. Mild visual hallucinations may occur, particularly when the eyes are closed.2 These CNS effects would potentially interfere with patient cooperation during a procedure.
These observable CNS reactions are known; however, little is known about the neurobiological mechanisms involved. There have been advances in research spanning animal models to humans which are focused on the neurobiological mechanisms following acute and chronic marijuana exposure; however, there are limitations of evidence and gaps in our knowledge on the complete CNS effects.3 Therefore, clinicians must proceed with caution when doing sedations on the marijuana user.
Tetrahydrocannabinol (THC) preparations are β-adrenergic sympathomimetic agents capable of inducing tachycardia, bronchodilatation, and some peripheral vasodilation. They also have parasympatholytic properties and can produce the clinical symptoms of xerostomia, tachycardia, hyperemia, drowsiness, and orthostatic hypotension which can lead to vertigo. Because marijuana is both a sympathomimetic and parasympatholytic agent, it interferes with natural cardiovascular and stress-response mechanisms. The mechanism for marijuana causing an increased heart rate is likely to be threefold:1,4
It is a sympathomimetic agent that causes increased pulse rate resulting from a beta-adrenergic sympathetic stimulating effect
It is a parasympatholytic agent that inhibits the parasympathetic cholinergic innervation of the heart and works synergistically with atropine
A reflex tachycardia may occur because of the peripheral vasodilating effects of the drug
There are dose-related drug interactions between cannabis metabolites and the epinephrine contained within dental local anesthetic agents. This drug interaction can result in cardiac arrhythmias and syncopal hypotensive episodes and should be anticipated when treating these patients. One of the first effects of marijuana is a consistent increase of pulse rate. When local anesthetic agents containing 1:100 000 epinephrine are administered non-benign cardiac arrhythmias are often induced.1 Marijuana is vasoactive, cardiotropic, steroidogenic, and sympathomimetic and therefore could complicate the management of a dental patient.1 During a cardiovascular medical emergency, a patient's vascular response when under the influence of marijuana, might not be as rapid or as widespread as usual.1,4 Management of cardiovascular emergencies can be unpredictable.
Patient peri-operative cannabis use is not a contraindication to the use of nonsteroidal anti-inflammatory drugs (NSAIDs), regional local anesthetic without epinephrine, or acetaminophen.5,6 As noted above, epinephrine should be used with caution as it may exacerbate marijuana induced cardiac arrythmias.
There is a detrimental effect of the cannabis smoke on gingival healing which could be partly attributed to (1) the nicotine found in the marijuana “joint” and (2) a negative effect of cannabidiol (CBD) on cell proliferation.7 Additionally, cellular exposure to cannabis smoke results in reduced levels of IL-8, which is necessary for wound healing.8,9 Thus, marijuana smoke interferes with predictable and efficient healing of implant surgical sites.
The above are immediate peri-operative considerations with cannabis use; however, long term cannabis use may lead to negative bone responses proximal to titanium implants.10
The Nogeueira-Filho et al. animal study found that with 60 days of daily marijuana smoke exposure, the degree of cortical bone-implant contact (cortical-BIC) was no different between the marijuana exposure group and the comparative non-exposure group. However, there was a significant deleterious impact on cancellous-BIC for the marijuana exposure group. This study does have limitations when extrapolating the results to humans, but it may highlight a valid concern for implant success in patients consuming cannabis on a routine basis. Future studies to establish the impact of cannabis smoke on bone healing in humans need to be performed.10
A 2016 human study by Sophocleous et al., found that heavy cannabis users had: (1) lower total hip-Bone Mineral Density (hip-BMD), (2) lower spine-BMD, (3) lower Body Mass Index (BMI), (4) increased bone fracture rates, and (5) reduced serum total 25-hydroxyvitamin D concentrations than non-users. When considering all these factors, cannabis use negatively influences bone health.11
Evidence suggests that inhalation of cannabis smoke negatively affects periodontal health.
The mechanisms are unknown, but marijuana has long been associated with anti-inflammatory properties. This anti-inflammatory effect reduces the body's immune response and damages the defense of the host against viral and bacterial infections. Cannabinoids compromise the resistance of the host through modification of the primary and secondary immune systems. This is especially true regarding the function of lymphocyte T and B cells and macrophages. A compromised immune response could promote periodontal disease by enabling colonization during dysbiotic shifts or the incorporation of new pathogens into dental plaque.12–14
Marijuana use is becoming more common place with its legalization. The Implant Dentist must be aware of the possible peri-operative effects when treating the patient that is a frequent or recent user of marijuana. All the above-mentioned immediate peri-operative and long-term effects of cannabis can lead to compromised implant success. Confounding factors such as: advanced age, cigarette smoking, vaping, use of medications that interfere with bone turnover or localized angiogenesis would be additive or synergistic and further interfere with implant success. Clinicians need to have an interactive dialogue with patients regarding the use of marijuana and educate the patient on the deleterious effects.
