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PHARMACOLOGY - Case Report ABSTRACT See Exercise No. 67 for Self Instruction Questions. Atropine sulfate -- a current review of a useful agent for controlling salivation during dental procedures
Craig R. Sherman, MD The oral cavity is a particularly difficult place in which to work. One challenge it presents is the nature and content of saliva, which can complicate operating conditions by making visibility difficult, leaving tooth surfaces wet, and interfering with various procedures that involve adhesion or bonding. Another challenge is salivary flow tends to increase during dental procedures. Dental clinicians have various methods for controlling moisture during dental procedures, including cotton roll isolation, saliva evacuators, and rubber dams. These traditional methods are useful, but each has certain drawbacks and limitations. Some clinicians, particularly orthodontists, use pharmaceutical drying agents instead. Methantheline bromide and propantheline bromide are two drying agents that have been used for decades, but their variable effectiveness and systemic effects can be problematic. In recent years, the American Dental Association Council on Scientific Affairs approved atropine sulfate 0.4 mg tablets as an alternative for effectively achieving moisture control during dental procedures. The necessity for maintaining a dry field during various dental treatments is reviewed here, and we discuss various benefits that atropine sulfate offers to both dentists and patients. Consequences of Inadequate Moisture Control Sufficient moisture control is crucial during many dental procedures. In restorations, for instance, saliva contacting with teeth can create mucinous deposits.1 If the saliva invades a cavity preparation or mixes with the restorative material, it can affect the marginal adaptation, hardness, and accuracy after setting. Silver amalgam is particularly susceptible to moisture contamination, because such contamination causes a severe, delayed expansion of the material and a blister typically forms on the metal's surface. The dry tooth surface is also important in such cases because it makes it possible to clearly see and assess caries excavation and to detect the presence of remaining caries, which has a characteristic moist, leathery texture that can be more easily distinguished in a dry field.1 Moisture control is also essential for endodontic procedures2 and for bonding orthodontic brackets successfully, as saliva affects the ability of various bonding materials to adhere to the tooth surfaces.3,4 Saliva contamination has also been shown to significantly decrease the adhesive bond strength of some impression adhesives.5 During periodontal procedures, some researchers have theorized, the protein-rich coating that saliva creates can interfere with proper clot adhesion an important factor in reliable periodontal therapy.6 In at least one in vitro study, saliva coating appeared to inhibit the attachment and movement of gingival fibroblasts, those cells needed to regenerate the periodontium, on tissue culture plastic and on cementum.7 However, a small-scale in vivo study in dogs suggested that saliva coating may not necessarily compromise connective tissue reattachment to the tooth surface.6 Saliva contamination of the etched tooth surfaces has been cited as the most frequent cause of failure for sealant adherence.8 Evans and Silverston found that as little as one second of saliva contamination on the etched surfaces resulted in a tenacious coating that blocked micropores in the enamel surface. This may explain why saliva interferes with proper adherence. In this study, washing did not appear to remove the coating for any specimens except those exposed for a half-second or less.9 Traditional Options for Moisture Control Clearly, maintaining a dry operative field is imperative to achieving an acceptable result during many dental procedures. Traditional methods of controlling saliva contamination in the work area include cotton roll isolation, the use of a rubber dam, and saliva evacuators. Cotton roll isolation involves placing cylinders of cotton along the buccal mucosa and over the parotid gland ducts. These are generally used in conjunction with a high-speed saliva evacuator. Cotton roll isolation can be useful, but clearly only for very short-term procedures since as the cotton merely absorbs saliva. To be effective, cotton rolls must be changed frequently. They also can be cumbersome to both patients and the clinician.10 For longer procedures, rubber dams have traditionally been used. The dam is made of latex and is punched to fit the teeth and then placed around them to isolate the area from the oral environment. Rubber dams can be a useful way to keep the area dry, except for moisture inherent in the tooth structure. They also partially retract the jaw. In many cases, their use requires that the gingiva be anesthetized, which can make them difficult to use for the pediatric patient.10 In general, although rubber dams take extra time to prepare, they appear to better control moisture than do cotton rolls.11 However, they are not foolproof. In some cases, particularly those involving treatment of splint or bridge abutments, rubber dams can fail to control saliva seepage when dams cannot be tucked into the interproximal spaces around the tooth being treated and when the shape of the crown is not normal due to caries, loss of a restoration, or an abnormal axial inclination.10 A third traditional method is the use of saliva evacuators. These can be satisfactory, but nevertheless carry both the risk of backflow and that of increasing tension and anxiety in the patient. For these reasons, some clinicians prefer to administer pharmaceutical drying agents instead of, or in addition to, the traditional methods. Methantheline bromide (Banthine, Searle & Co., San Juan, Puerto Rico) was a medication used for treating patients with peptic ulcers. A frequent side effect with this medication was xerostomia. Although this dryness was tolerable for brief dental procedures, medical patients taking the drug for prolonged periods often complained of feeling parched and would request alternate therapy. Addressing the concerns of internists and their patients, the manufacturer of methantheline replaced this drug with a new one less likely to affect salivary secretions. Propantheline bromide (Pro-Banthine, Searle & Co., San Juan, Puerto Rico) has proven effective in the treatment of peptic ulcers; but, reports in the dental literature indicate that its effectiveness as a drying agent in dental applications is variable.12,13 Furthermore, safety of this new agent for pediatric patients has not been established.14 Administration by sublingual injection instead of tablets tends to increase the effectiveness in reducing salivary flow; however, clinicians have been cautioned against the use of sublingual injections for this purpose.3 Atropine Sulfate as an Adjunct to Traditional Methods Atropine sulfate 0.4 mg tablets (Sal-Tropine, Hope Pharmaceuticals, Scottsdale, Arizona) offers several advantages over these various methods for maintaining adequate moisture control. Like methantheline and propantheline, atropine is a competitive antagonist of the muscarinic actions of acetylcholine. Atropine blocks the attachment of acetylcholine to receptors on the salivary glands; and consequently, the glands are not stimulated to produce saliva. Intravenous atropine sulfate (0.25 mg, 0.4 mg, 0.75 mg, and 1.5 mg) given to 72 healthy medical students was found to inhibit salivation at all doses.15 Intramuscular and orally administered atropine sulfate also inhibit salivation, but require higher doses. Based on peak inhibition of salivation in one study, 0.9-1.4 mg of orally administered drug was estimated to be approximately equivalent in effect to 0.6 mg administered by intramuscular injection.16 This was confirmed in a second study in which the ratio of oral to intramuscular doses of atropine sulfate on salivary secretion was 2:1.17 Drug effect was further documented with the oral administration of atropine sulfate to a patient with closed head injury and significant drooling. Testing doses between 0.3 and 1.2 mg, the researchers reported reduction by more than 50% of base line levels, in the amount of resting secretion, intraoral accumulation, and pharyngeal-laryngeal pooling of saliva with doses of 0.6 mg or greater.18 Table 1 shows a comparison of atropine sulfate with propantheline bromide.
Atropine is well absorbed from the GI tract and begins to inhibit saliva flow within one hour. Peak inhibition occurs approximately 2 hours after oral administration, and the effects persist for up to four hours. The drug is metabolized by the liver and excreted by the kidney. Salivary secretions are generally inhibited by atropine at doses lower than those required to affect other organs.19 Thus, it is possible to administer a low dose of medication sufficient to achieve the desired oral effect while minimizing systemic effects. Although individual tolerance varies greatly, the effects highlighted in Table 2 may be encountered with the corresponding doses.20
Atropine has been reported to reduce the saliva mucus secretion response to anesthesia and diminishes the amount of anesthesia that must be used during operative procedures.21 It can help prevent laryngospasm because there is less tendency for excessive saliva to irritate the larynx.22 It also eliminates any concern about potential backflow in saliva evacuators or about hypersensitivity reactions to latex used to construct rubber dams.23-25 The use of atropine during selected procedures has been reported to enhance office productivity and to reduce chair time.26 Less preparation time is required because the patient comes to the operatory with reduced salivary flow after having taken the medication as directed. Fewer interruptions during dental procedures are required to replace saturated cotton rolls, reposition saliva evacuators, or redry tooth surfaces, and the likelihood is that a single operator may perform the intended procedure. Also, the need to repeat procedures to achieve suitable technical results may be reduced. An example is bonding during orthodontic bracket placement which can fail due to saliva contamination of tooth surfaces. Atropine sulfate tablets are approved, safe, and effective for use in both adults and children. Dosing guidelines are available for infant patients as small as 7 pounds.20 The conservative starting dose for patients weighing more than 65 pounds is one tablet. This dose may be exceeded in certain cases, such as when treating large patients and heavy salivators or when performing very sensitive procedures. A practical dosing guideline to achieve suitable salivary inhibition in adult dental patients is one tablet per 75 pounds of body weight.27 This is consistent with a statement published by the American Dental Association: "Most adults require a minimum of 0.6 mg and as much as 1.0 mg of atropine before a real mouth drying effect is noted clinically."21 A corresponding dosing guideline for small children is 0.01 mg/kg body weight, not to exceed 0.4 mg in a four to six hour period.16 The tablets are tasteless and soluble to facilitate administration to children. Atropine sulfate is contraindicated in patients with glaucoma and synechiae (adhesions between the iris and lens of the eye). These two conditions are characterized by elevated intraocular pressure due to impediments to the flow of aqueous humor. In some patients, the impediment is caused by narrowing in the angle between the pupil and lateral cornea. This narrowed angle becomes further obstructed when the pupil dilates. Atropine sulfate can cause dilation of the pupil; and consequently, it must be avoided in susceptible patients. Atropine sulfate is also contraindicated for patients with asthma. In addition to inhibiting salivation, the medication can also reduce bronchial secretions. Asthmatics rely on these secretions to trap and expel inhaled allergens. Reducing the efficacy of this cleansing system in such patients may cause retention of these inhaled allergens and trigger bronchospasm. Although not formally contraindicated, some practitioners advise patients not to wear contact lenses or undertake heavy physical activity within a few hours following the dental procedure because of temporary reductions of tear and sweat secretions.12,26 The potential of atropine to reduce salivation and other secretions may be increased if it is given with other drugs that have anticholinergic action, including tricyclic antidepressants, antipsychotics, some antihistamines, and antiparkinsonism drugs. The safety and efficacy of atropine sulfate are well documented by several decades of clinical experience. Table 3 reviews the product features and patient benefits of atropine sulfate tablets. Published reports from dental practitioners on the use of this agent are positive, indicating that it increases patient comfort during procedures and also increases the speed at which various procedures can be completed successfully.26,28
After reviewing clinical literature and surveying expert opinions, the American Dental Association Council for Scientific Affairs awarded its Seal of Acceptance to atropine sulfate tablets as an antisialagogue during dental procedures. Summary Control of saliva during many dental procedures is imperative for achieving acceptable treatment results. Indicated to temporarily reduce salivation in children and adults, atropine sulfate tablets have been awarded the American Dental Association Seal of Acceptance as an effective antisialagogue for use during dental procedures. Used in conjunction with cotton roll isolation, saliva ejectors, and rubber dams, atropine tablets can improve patient comfort and enhance office productivity. Author Information Craig R. Sherman, MD, is medical director, Hope Pharmaceuticals, Scottsdale, AZ. Beryl R. Sherman, DDS, is a consultant to Hope Pharmaceuticals, Dental Affairs, Lancaster, PA. Address correspondence to: Craig Sherman, MD, Medical Director, Hope Pharmaceuticals, 7626 E. Greenway Rd., Suite 101, Scottsdale, AZ 85260. See Exercise No. 67 for Self Instruction Questions. References
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