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J Am Dent Assoc, Vol 140, No 1, 68-72.
© 2009 American Dental Association |  |
RESEARCH |
A clinical evaluation
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ABSTRACT |
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 TOP ABSTRACT SUBJECTS, METHODS AND MATERIALSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
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Methods. Sixteen participants received a five-second application of a refrigerant (1,1,1,3,3-pentafluoropropane/1,1,1,2-tetrafluoroethane) and a two-minute application of a topical anesthetic gel (20 percent benzocaine gel) in the posterior palatal area before an injection of a local anesthetic solution was administered with a 30-gauge needle. Participants rated the pain they experienced after each injection by using a 100-millimeter visual analog scale (VAS) with endpoints of "no pain" and "worst possible pain." The authors calculated VAS scores by measuring the distance in millimeters from the no pain end of the scale. They analyzed data with a paired t test (
= .05).
Results. The group receiving the refrigerant had a mean VAS score of 17.7 ± 15.3 mm, and the group receiving the topical anesthetic gel had a VAS score of 26.2 ± 18.0 mm. The use of the refrigerant compared with the use of topical anesthetic gel significantly reduced the pain experienced during administration of local anesthetic injections (P = .02).
Conclusions. The use of a refrigerant as a preinjection anesthetic was more effective compared with the use of a topical anesthetic gel in reducing the pain experienced by participants who received a posterior palatal injection.
Clinical Implications. The potential benefits of using a refrigerant rather than a topical anesthetic gel are pain reduction, decreased application time, ease of application and avoidance of displeasing taste.
Key Words: Pain measurement; palate; anesthetics; local anesthetics; topical anesthetics
Abbreviations: VAS: Visual analog scale.
The fear of pain attributed to anesthetic needle injections is cited as an obstacle in providing appropriate dental care.1,2 As a result, different treatment strategies such as applying topical anesthetics, vibrating the surrounding tissue while administering the injection, applying pressure to the injection site and using a mechanical delivery system have been used to minimize the pain experienced during administration of dental anesthetic injections.3–6 Another technique described in the dental literature is the use of a refrigerant to lessen injection pain.7,8 Although refrigerants have been used as a preinjection anesthetic for various medical procedures such as venipunctures and immunizations, they have not been used routinely in dentistry.9–13
Topical anesthetic is used routinely and widely to prepare the injection site and is recommended to decrease pain.3 Multiple studies have documented the effectiveness of intraoral topical anesthetics with different formulations and concentrations in reducing injection pain.14–19 The results of other studies have shown that the benefit of using topical anesthetic is inconclusive when it is compared with placebos or other methods.20–23 Other disadvantages of using topical anesthetics include application time (for example, two minutes minimum), displeasing taste and spread of the anesthetic agent to noninjection site areas.
Alternatives to topical anesthetics, such as applying pressure to the injection site and vibrating the surrounding tissue while administering the injection, have been described in textbooks and anecdotal reports in the literature. Clinical research demonstrating the effectiveness of these methods, however, is limited.3,6 The use of a mechanical anesthetic delivery system is effective, but it has a slower anesthetic application time and higher cost of equipment than does an injection with a syringe.5
The use of a refrigerant such as ice and a refrigerant spray to reduce the pain experienced during administration of a maxillary palatal injection has been described in technique articles in the dental literature.8,9 The authors of one article described a technique in which a cotton pellet was saturated with a dichlorodifluoromethane refrigerant spray and then was placed in contact with the palatal tissue for five seconds before the injection was administered.8 The authors of another article described the use of ice frozen on a stick that was applied to the palatal tissue in conjunction with the injection.9 There also is anecdotal evidence that dental providers have used off-label products such as 1,1,1,2 tetrafluoroethane (Endo-Ice, Hygenic, Akron, Ohio) for this purpose; however, to our knowledge, no researchers have investigated the effectiveness of a refrigerant in reducing injection pain for dental procedures.
The refrigerant 1,1,1,3,3-pentafluoropropane/ 1,1,1,2-tetrafluoroethane (Pain Ease, Gebauer, Cleveland) received U.S. Food and Drug Administration approval in March 2004, and it is safe for use on "skin, intact mucous membranes (oral cavity, nasal passages and lips) and minor open wounds."24 Oral biocompatibility studies were conducted in which the refrigerant was applied to the oral cavities of hamsters. Five doses of the refrigerant were applied across four hours, and the mucosa showed irritation that ranged from no erythema to slight erythema.25 On the basis of the histopathology report, 1,1,1,3,3-pentafluoro-propane/1,1,1,2-tetrafluoroethane has been classified as a nonirritant when applied to the oral mucosa. The results of animal studies showed that 1,1,1,3,3-pentafluoropropane/1,1,1,2-tetrafluoroethane was nontoxic when inhaled.26
In regard to precautions, the manufacturer states, "[D]o not use product on diabetics or persons with poor circulation or insensitive skin. Use of cold products on these patients may cause discomfort, skin irritation and/or frostbite." 24 For adverse reactions, the manufacturer states that "freezing of the skin can occasionally alter the skin pigmentation."24 The extreme cold may create postinflammatory hypopigmentation due to the death of melanocytes in the epidermal layer of the skin.27 This latter reaction is listed for skin but is not identified specifically for mucosa.
The null hypothesis we investigated in this study was that the use of a refrigerant does not reduce the pain experienced during administration of a palatal anesthetic injection compared with use of a popular topical anesthetic.
We used a randomized, split-mouth design with an anesthetic injection administered in the maxillary left and right posterior palatal areas. The same operator (A.K.) administered the site injections to standardize the flow rate and delivery style, and the same dental assistant prepared the tissue site. The participants received two palatal injections with a five-minute interval between injections. The sequence and site of treatment for each participant was randomized by means of a coin toss to determine which preinjection anesthetic and site were first. Participants compared the efficacy of a refrigerant versus a topical gel as preinjection anesthetics on bilateral palatal injection sites in their mouths.
We used the refrigerant 1,1,1,3,3-pentafluoropropane/1,1,1,2-tetrafluoroethane to prepare the tissue site before injection. The application and site preparation methods we followed were as follows: a 5-milliliter liquid sample of the refrigerant was collected in a small medicine cup; the mucosa was dried with a 2- by 2-inch piece of gauze; a cotton-tipped applicator was soaked in the refrigerant and then placed on the palatal tissue site for five seconds; with the refrigerant-soaked cotton-tipped applicator in place, an injection of 0.3 mL (6 milligrams) of 2 percent lidocaine with 1:100,000 epinephrine was administered into the injection site via a 30-gauge short needle during a 10-second interval (needle penetration was 1 to 2 millimeters into tissue, limiting contact with the periosteum) (FigureThe use of a refrigerant as a preinjection anesthetic was more effective than the use of a topical anesthetic gel in reducing the pain experienced by patients who received posterior palatal injections.
SUBJECTS, METHODS AND MATERIALS
TOP
ABSTRACT
SUBJECTS, METHODS AND MATERIALS
RESULTS
DISCUSSION
CONCLUSION
REFERENCES
The participants in this study were adults who required full-mouth scaling and root planing with local anesthesia or routine operative treatment. We selected them from a pool of patients available for treatment at Dunn Dental Clinic, Lackland Air Force Base, San Antonio. All participants were in good general health and classified as P1 and P2 (commonly referred to as ASA I and ASA II, respectively) according to the American Society of Anesthesiologists Physical Status Classification System. We needed to have 16 participants in our study population to show a one SD at 80 percent power at the level by using a paired t test. Our inclusion criteria were that each participant must be at least 18 years of age and have intact mucous membranes in bilateral posterior areas. We excluded from the study patients with a history of diabetes, poor circulation or insensitive skin. The institutional review board at Wilford Hall Medical Center, Lackland Air Force Base, approved the protocol and informed consent. We obtained written informed consent from each of the 16 participants before enrolling him or her in the study. 
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We evaluated participants’ self-reports of injection pain by having them use the visual analog scale (VAS) that often is used to measure pain intensity.28–31 The VAS was a 100-mm horizontal line with descriptive anchors at each end. The left end was labeled "no pain" and the right end was labeled "worst possible pain." The participants were instructed to make a vertical mark within the 100-mm line to indicate the level of discomfort they experienced after receiving the injection. We calculated the VAS pain score by measuring the distance in millimeters from the left end of the scale. The higher the score, the higher pain intensity experienced by the participant. We determined a mean and SD for the group (n = 16). We analyzed data with a paired t test ( = .05) by using a software package (Excel 2007, Microsoft, Redmond, Wash.).
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RESULTS |
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DISCUSSION |
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TOPABSTRACTSUBJECTS, METHODS AND MATERIALSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
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Physicians have used refrigerants as preinjection anesthetic for a variety of purposes such as intramuscular and subcutaneous injections, immunizations, starting intravenous lines and venipuncture.9–13 In one study, investigators assessed the efficacy of a refrigerant in reducing the injection pain experienced by preschool-aged children receiving a routine diphtheria-pertussistetanus vaccine.9 In this double-blind, placebo-controlled study with 90 subjects, the investigators compared the use of the refrigerant spray, a placebo spray and a no-spray control. They found that the placebo spray and the refrigerant spray significantly reduced injection pain. Although the results of the study did not firmly establish the efficacy of the refrigerant, they did support the use of a refrigerant as an effective treatment strategy for the reduction of pain for procedures involving injections.9
In another study, investigators compared the use of a refrigerant and a 2.5 percent lidocaine, 2.5 percent prilocaine topical anesthetic cream in school-aged children receiving the diphtheria-pertussistetanus vaccine.10 In this randomized, placebo-controlled clinical study, the investigators compared topical anesthetic cream and distraction, refrigerant and distraction and distraction alone (control). They found that all pain measures and crying durations were similar for the topical anesthetic cream and distraction, and that pain measures were lower and crying durations were shorter for the refrigerant and distraction compared with those for the control. The authors of this study concluded that when vapocoolant spray was combined with distraction, it significantly reduced immediate injection pain compared with distraction alone and was equally effective as, less expensive than and faster acting than the topical anesthetic cream. The authors further concluded that vapocoolant spray may help physicians and parents overcome their resistance to multiple injections, which can lead to missed opportunities to immunize.10
The medical use of a refrigerant as preinjection topical anesthetic is effective in reducing patients’ pain, and, on the basis of the results of our study, those same benefits and advantages can be applied to pain experienced during the administration of dental anesthetic injections. The shorter application time of refrigerants (five to 10 seconds) as compared with that of topical anesthetic gel (a minimum of two minutes) could increase provider compliance by improving clinical efficiency. Another benefit is the ease of application, as the refrigerant is applied locally and there is potential for the topical anesthetic gel to anesthetize areas other than the injection site owing to the gel’s mixing with saliva and the patient’s swallowing. Although we used a 30-gauge needle in our study, the use of thinner-gauge needles has not been shown to reduce dental injection pain when compared with the use of larger-gauge needles, and thinner-gauge needles may be associated with a greater risk of needle deflection and breakage and more difficulty in aspirating.32
The limitations of our study include our inability to control confounding variables such as application of pressure, rate of injection administration, needle contact depth and refrigerant tissue temperature. Having a larger sample size in future studies would minimize the effect of these variables and provide a more conclusive result. The blinding of patients to the treatment would be ideal, as it would eliminate the possibility of a placebo effect; however, it would be problematic owing to the cold sensation patients would experience with use of the refrigerant. A study design that included negative controls such as a placebo gel and a cotton-tipped applicator soaked in water or saline instead of use of a topical gel and a refrigerant, respectively, would provide strong evidence to support the effectiveness of refrigerant. Future studies can expand on our research and examine other materials and techniques to compare their effectiveness as a preinjection anesthetic with that of a refrigerant. Such studies may include the use of a mechanical delivery system, the use of pressure to minimize injection pain or varying the application times and topical anesthetics used.
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CONCLUSION |
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TOPABSTRACTSUBJECTS, METHODS AND MATERIALSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
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FOOTNOTES |
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This article has been cited by other articles:
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  L. Ernstgard, M. Andersen, W. Dekant, B. Sjogren, and G. Johanson Experimental Exposure to 1,1,1,3,3-Pentafluoropropane (HFC-245fa): Uptake and Disposition in Humans Toxicol. Sci., February 1, 2010; 113(2): 326 - 336. [Abstract] [Full Text] [PDF]
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