The use of Botulinum toxins (Myoblock, Botox, Reloxin) for aesthetic and therapeutic dental and facial treatments is becoming increasingly popular. Dentists, physicians and patients are choosing these treatment modalities as an easier, safer alternative to typical irreversible dental and surgical procedures that offer no guarantee of success. These treatments are still prone to undesirable side-effects that are typically site and dose-related. This article discusses the causes, treatments and prevention of the most common undesirable side effects.
Protective masticatory functions prolong the life and health of the entire masticatory system. Ideally the human body maintains perfect tone to the masticatory muscle to prevent the side-effects caused by abnormal muscle function. The consequences of masticatory muscle hypertonicity are not limited to dental and periodontal trauma and disease. Other effects of masticatory muscle hypertonicity include:
• Delayed healing to periodontium after trauma
• Difficulty chewing
• Dysphagia (difficulty swallowing)
• Facial and pericranial muscle pain (nonspecific)
• Flared upper anterior teeth
• Fractured cusps and restorations
• Gingival recession
• Limited mouth opening
• Masseteric hypertrophy
• Neck pain
• Open interproximal contacts
• Painful teeth
• Scalloping of lateral border of tongue
• Temperature sensitive teeth (hot and cold)
• Tinnitus (ringing in the ears)
• Tooth mobility
• Wear facets in the tooth enamel
Dentistry has had limited success in attempting to treat and prevent transient painful TMD diseases with methods that have historically proven to be ineffective and risky. This is because malocclusions are generally not the cause of TMJ symptoms. Ideal dental procedures and restorations will not have any effect on a neuropeptide mediated sympathetically innervated hypertonic muscle clenching, the underlying cause of unnecessary pain. Most people with bad bites do not have TMJ. However, malocclusions combined with parafunctional clenching often result in TMJ pain.
Any ideal intraoral device or splint made with the greatest of intentions will not work if the patient has poor compliance, which includes the majority of patients when it comes to wearing orthotics or most other intraoral devices.
The profession obviously has a need for a conservative reversible non-invasive treatment that is quick, easy, relatively inexpensive, long acting, and effective.
A longer acting, more reliable method of obtaining masticatory muscle relaxation can be achieved by injecting measured doses of botulinum toxin (BTX) into specific sites in the major muscles of mastication.
These doses reduce teeth-clenching as they are sufficient to shut down the efferent response from spindle sensor cells within the temporalis muscles that are implicated in initiating and potentiating the sympathetic masticatory muscle dystonic cycle.
The effect of BTX is to act locally as a governor on sympathetically driven trigeminal innervation to the injected masticatory muscles. Alternative yet often ineffective cures include analgesics, splints, moist heat, exercises, transcutaneous electrical nerve stimulation, muscle relaxants, low-dose tricyclic antidepressants, local anesthetics, alpha adrenergic receptor antagonists, occlusal adjustments,full mouth rehabilitation, orthodontics, orthognathic surgery, or a combination of these treatments.
Another risky option is to prescribe narcotic or tricyclic anti-depressant drugs to control excessive clenching. Major occlusal adjustments are risky, expensive, and have no guarantee of success. The obvious treatment goal using Botox is to reduce spasm but not to interfere with normal function. A reduction in the dental pathologic consequences of dystonia with optimisation of function is easily achievable with a site-specific and dose-specific BTX injection protocol. BTX, a natural protein, is one of the most potent biological muscle relaxant substances known. The toxin inhibits the release of acetylcholine (ACH), and other neurotransmitters responsible for muscular contraction.
The injection sites for these therapeutic injections are into masticatory and facial “hatband” musculature. Injection sites include the frontalis muscles responsible for the horizontal forehead lines and position of the eyebrow, the procerus and corrugator supercillius muscles responsible for the vertical lines between the eyes, the masseter muscles, temporalis muscles and occipitalis muscles.
It is therefore essential for the injector to be familiar with all the injection sites that effect facial expression to avoid unwarranted side effects while treating therapeutic and aesthetic conditions. These side effects may include drooping (ptosis) of the mouth, eyebrow and/or eyelid, bruising, pain, headaches, bleeding, tenderness, swelling, redness at injection sites; allergic reactions, infection; numbness, tingling, paralysis or partial paralysis; loss of facial expressions.
As the popularity of these treatments increase so dentists and physicians are confronted with unwanted and unnecessary side effects associated with these injections. The purpose of this article is to describe the recognition of these and to prevent them.
Failure of treatment
The most common undesirable effect of Botox treatment for masticatory muscle pain is that the treatment does not work. This is usually caused by inadequate dosage or injections into the wrong sites, or a combination of both. This can be ascertained by monitoring the response from injections given across the forehead into the frontalis muscle. The disappearance of horizontal frown lines demonstrates that the medication is working. In the event of these muscles remaining active, the Botox has been overdiluted or the vial of Botox is ineffective. Ineffectiveness may be due to leakage of the vial before reconstitution or the mixed solution being kept too long before injecting.
The vial of Botox should be stored at a consistent temperature in the refrigerator. When the vial is allowed to defrost then be refrozen repeatedly, the rubber plunger may denature allowing air to leak into the vial. This renders the drug ineffectual. A simple way to determine if there has been leakage into the vial is the apparent lack of vacuum when saline is added. If there is insufficient vacuum to aspirate all the saline into vial then the vial has leaked and the drug will be ineffective.
A mixture containing normal saline should ideally be used on the first day of mixing. A mixture containing bacteriostatic saline can be use for two-three weeks provided it has been stored correctly. The reconstituted solution should be stored in a refrigerator before use. During reconstitution, the vial should not be vigorously shaken as the large botulinum neurotoxin molecules are extremely fragile. The molecule has a large binding chain that is responsible for the molecule attaching to a nerve cell membrane, and a smaller chain that cleaves the protein responsible for the secretion of acetyl choline from the nerve cell ending across the neuro-muscular junction into the muscle leading to muscle contraction.
When the vial is shaken vigorously the large chain separates off the molecule and the drug cannot enter the nerve cell ending. Patients that demonstrate no effect should be re-injected with a freshly mixed new vial that has been diluted with no more than 4ccs of saline. Occasionally the patient may be immune to the effects of Botox. In the rare event of the patient being immune to the effects of Botox then one can always try another type of botulinum toxin like type B (Myoblock®).
There is no cross-immunity between type A (Botox) or type B (Myoblock) unless the patient has been immunized against these. Patients who were exposed to high doses of Botox in the 1990s developed immunity. This was caused by residual protein tags left behind from the manufacturing process.
This process was refined and improved so the protein responsible for the immunity has now been removed.
‘Jack Nicholson’ eyebrows
Ptosis (drooping of the corner) of the mouth is generally caused by accidently injecting into the muscles that elevate the corner of the mouth, namely the levator anguli oris muscles and the zygomaticus muscles. These muscles may be erroneously injected while attempting to inject into the masseter muscles. Injections into the masseter muscles should not be given in the upper cheek area above an imaginary line below the zygomatic arch from the tragus of the ear to the commissure of the lips. A droopy or pulled-down mouth can be corrected by injecting the depessor anguli oris muscle which antagonises a weakened zygomaticus and levator anguli oris muscles.This injection is given midway between the corner of the mouth and the undersurface of the chin at right angles to the skin. The insertion point of the needle is medial to the marionette line.
Ptosis of the upper eyelid is caused by injecting in the frontalis muscles immediately above the eyebrow. The frontalis muscle is an elevator of the eyebrow. The muscle is antagonised by the orbicularis oculi muscle which pulls the eyebrow down towards the eye. If the frontalis muscle is weakened sufficiently the orbicularis muscles dominate and pull the eyebrow downwards.
Many injectors are overly cautious and avoid injecting the sides of the forehead wider than the eyes altogether. This leaves the outer fibres of the frontalis muscles active. These fibres will compensate for the relaxed more medial fibres. The outer margins of the eyebrows will elevate giving the patient ‘Jack Nicholson’ eyebrows.
The undesirable side-effect of bruising is most common by injecting into the veins on the inferior lateral sides of the eyes, and into the vertical opthalmic and frontal veins running up the centre of the forehead. It is almost impossible to puncture an arteriole because the ultra-fine needle is deflected by the musculature of the vessel wall . The injector should be vigilant to identify these blood vessels before injecting. When a vein is punctured the injector will know almost immediately that the patient is going to bruise. The elevated bluish subdermal hematoma appears almost before the needle is withdrawn. Allow a punctured vein to bleed freely through the injection puncture hole. Any blood trapped under the skin will form a bruise. Do not try to aspirate the bruise as the needle trauma usually increases the size of the hematoma. Conversely it a subdermal blue-ness or swelling begins to appear, the injector should immediately stop and apply finger pressure over the area.
For the most part, bruising is inevitable. Arnica Montana micro-tablets placed under the tongue and Arnica gel topical cream assist in rapid dissolution of a bruise. Other useful treatments for bruising include applying a cotton swab moistened with vinegar for an hour. For severe bruising, the patient can disguise the bruise using a masking make-up like Derma-Blend.
Botox headaches are common with multiple injections. The needle should always be angled to avoid puncturing or tearing the periosteum. These headaches respond well to OTC painkillers like Tylenol or Advil. Analgesics can be avoided by drinking two glasses of Gatorade at the time of injection. Infection from Botox injections is atypical. However patients may develop a a skin rash or dermitis around the injection sites from organisms that flourish in non-sterile normal saline.
It is recommended that the vial be disposed of once the desired quantity of saline has been extracted. Saline is sold in 10cc vials. This is recommended size to order from your supplier when less than 10 ccs are required. Do not attempt to save the saline for future use.
Bacteriostatic saline remains sterile after opening the vial. However the diaphragm cap is not sterile. It is recommended that the diaphragm be wiped with an alcohol swab before saline is aspirated from the saline vial.
Loss of facial expression
Although certain individuals desire that not a trace of an expression line be visible on their faces, it is no longer considered ideal to blanket the entire face with Botox injections rendering the patient totally expressionless. Fewer injections should be given. The glabella should be dosed with half the dose necessary to cause full paralysis of the procerus and corrugator muscles. Injections around the eye should be given at least one inch away from the outer margin of the eye. This will allow the patient to smile ‘with their eyes’ but eliminate these lines extending from the eyes to the sideburns.