March 2012, Volume 8, Issue 3
Published by AEGIS Communications
How is local anesthesia changing?
Our school carried out much of the research required for the FDA approval of a local anesthesia reversal agent, one of the most recent and unique advances in dental pain control. The product (OraVerse®, Septodont USA) was first marketed 2 years ago as a means of reducing the prolonged soft-tissue anesthesia following dental treatment. By injecting a solution of phentolamine, the active drug found in OraVerse, the action of epinephrine is inhibited, thereby causing vasodilation at the site of the injection. For patients who dislike the lip numbness experienced after a dental procedure, this is an effective mechanism for limiting the duration of the anesthesia after leaving the office. At our dental school, we find the use of phentolamine to be valuable for young or special-needs patients who may chew on their numb lip after treatment.
I am also aware of two other advances in local anesthesia currently under investigation and development. A start-up company, St. Renatus, has initiated clinical trials of an intranasally administered local anesthetic formulation that can provide pulpal anesthesia for maxillary teeth. Because the technique only requires spraying a fine mist of anesthetic into the nostrils, anesthesia is established without the use of needles or injections. Although the FDA approval process has not been completed and clinical experience has not yet been reported, this novel needleless administration technique may become very popular for apprehensive children and adults who are fearful of injections.
The other promising advancement in local anesthesia currently under development by OnPharma is a simplified method for buffering local anesthetic solutions by adding a small amount of sodium bicarbonate. A dental anesthetic cartridge containing a vasoconstrictor (2% lidocaine with 1:100,000 epinephrine) has a pH in the range of 4 to 5. It is thought that the stinging that occurs when the anesthetic solution is deposited in the tissue is due in part to the acidity of the solution. Buffering the solution will neutralize the acidity and may limit the discomfort that some patients experience. I am looking forward to seeing the impact of these innovative methods for pain control in the coming years.
Local anesthesia remains the foundation of pain control in dentistry. The ability to obtain reproducible, profound, and relatively painless local and regional anesthesia is the hallmark of modern dentistry and allows not only for access to care for millions of patients, but the performance of advanced techniques and procedures. Dentistry has long understood that as a dynamic profession, it continues to make great strides in dental and surgical advances, but the ability to provide safe and effective and tolerable local anesthesia is the key in obtaining patient cooperation and satisfaction.
Dentistry has never had such a wide range of choices in the selection of an appropriate local anesthetic tailored to patient, onset, duration of procedure and anticipated postoperative discomfort, and presence or not of a vasoconstrictor. When properly manufactured, stored, and used, the standard dental cartridge coupled with an aspirating syringe is one of the most reliable drug-delivery systems known in medicine.
Techniques continue to evolve based on anatomical and pharmacological advances. The traditional inferior alveolar nerve block via the classical or standard approach is being supplemented by the Gow-Gates mandibular block and the Akinosi-Variani closed nerve block techniques, which hinge upon different anatomical accesses.
Advances in instrumentation have led to the ability to anesthetize individual teeth via the periodontal ligament injection (PDL) and intraosseous injection (IO) approaches. These single tooth anesthetics are becoming more popular as equipment for these procedures are being further refined. The ability to anesthetize a single tooth rather than an entire mandibular arch is gaining popularity in professional and patient approval.
The future continues to be bright in the evolution of newer local anesthetics and delivery systems. Still, the most important aspect is the respect for and an understanding of the psychological impact of treating an awake patient. The combination of proper drug selection, equipment and technique, and a compassionate and skilled dentist can make local anesthesia an almost “painless” experience.
Local anesthesia has been one of the major contributions to medicine and dentistry in the last century. It enabled surgeons and dentists to be involved in more invasive procedures that not only saved lives, but also improved patient outcome by eliminating or reducing the pain factor that significantly contributed to intraoperative and postoperative surgical procedure results and patient satisfaction. Historic changes within the last couple of decades first include modified techniques for a less invasive and more efficacious delivery of intraoral local anesthesia. This includes the periodontal ligament and intraosseous anesthetic injection techniques as an alternative to the inferior alveolar nerve block. Both of these techniques are effective and safe especially in managing nerve block failures and localized anesthesia. The second advancement is the introduction of hybrid agents that are metabolized in both the liver and plasma, such as articaine. These agents are very efficacious, potent, and may have a shorter duration of action and recovery, therefore minimizing the postoperative discomfort time and definitely the possible chance of trauma (cheek and lip biting) in children and special-needs patients. The latest breakthrough is the reformulation of phentolamine mesylate (OraVerse) for intraoral submucosal injection and used for the reversal of soft anesthesia after dental procedures in adults and children 6 years of age and older. Phentolamine mesylate is a nonselective a-adrenergic blocking drug and was used previously as an antihypertensive medication for the prevention of such episodes in patients with pheochromocytoma. Multiple studies reported recovery times were reduced by 75 to 85 minutes. Facial deficits, such as drooling and difficulty in drinking, smiling, or talking, were consistently resolved by the time sensation to touch had returned to normal. Adverse effects of phentolamine injected in approved doses for reversal of local anesthesia were similar in incidence to those of placebo injections, and no serious adverse events caused by such use were reported. Because pain during dental treatment is a major obstacle for seeking oral care, these advancements will hopefully minimize the patient’s preoperative anxiety and aid in better oral healthcare access.
About the Authors
Paul A. Moore, DMD, PhD, MPH | Dr. Moore is a professor of pharmacology and epidemiology, and chair of the Department of Dental Anesthesiology at the University of Pittsburgh School of Dental Medicine.
Morton Rosenberg, DMD | Dr. Rosenberg is a professor of oral and maxillofacial surgery, head of the Department of Anesthesia and Pain Control, Tufts University School of Dental Medicine, and an associate professor of anesthesiology at Tufts University School of Medicine.
Suher Baker, DMD, BDS, MS | Dr. Baker is the program director and section chief of pediatric dentistry at Yale–New Haven Hospital.