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Iontophoresis for surface local anesthesia
Iontophoresis for surface local anesthesia
Because local anesthetics are positively charged molecules, deep surface anesthesia may be obtained by the use o f iontophoresis. This can be useful for preparation o f injection sites, and it can eliminate the need for injections in procedures in which only surface anesthesia is needed.
Louis P. Gangarosa, Sr., DDS, PhD, Augusta, Ga
Twelve of 13 retained deciduous teeth were ex tracted w ithout patient discom fort with use of only deep surface anesthesia obtained by ionto phoresis of a local anesthetic. Most of the teeth were extracted after the electrical current had been applied fo r ten minutes.
Methods of procedure During three years, 13 retained deciduous ante rior teeth were extracted from three children, ages 6 to 13. Four dentists participated in the procedures. For each procedure two o f the den tists agreed that local anesthesia by infiltration injection would have been advisable for all of these extractions, if iontophoresis had not been used. The Table gives relevant data about the chil dren and the conditions of procedures. Radio graphs were taken of all the teeth, but they are not included since they merely verified the diag nosis o f routine retained deciduous teeth.
In this paper, the results o f the use of iontophore sis as the sole local anesthetic for extraction of retained deciduous teeth are reported. Ionto phoresis is a process o f medication of tissues by an electrical current to aid penetration o f a drug into tissue. This process is accepted as a method of drug application1 and has been used in dentistry to desensitize teeth.2"4 It is possible to medicate any surface tissue electrically with drugs that have a positive or negative charge.5 The possibilities for this technique have been almost totally neglected in dentistry and med icine.
Table ■ Deciduous teeth extracted by iontophoresis. Patient Boy
Girl
Tooth Age num ber 12
1
13
2
7
3
8
4
8
5
8
Girl
6
6
7
6
8
7
9
7
10
7
11
7
12
8
13
M o bility* (mm)
Root length (cm)
Method of anesthesiat
Current duration (min)
2
0.4
E
10
0
1.3
E & injection
10
Mandibular left central in ciso r Mandibular right lateral in ciso r M axillary right central incisor M axillary left central in ciso r
3
0.3
E
10
2
0.5
E
10
3
0.4
E
10
3
0.4
E
10
M andibular right central in ciso r Mandibular left central in ciso r M andibular left lateral incisor Mandibular right lateral in ciso r M axillary right central in ciso r M axillary left central in ciso r M axillary right lateral in ciso r
3
0.4
E
10
4
0.2
E
10
Tooth M axillary right canine M axillary left canine
2
0.3
E
10
3
0.3
E
10
2
0.4
E
5
2
0.4
E
5
1
0.3$
E
15
'L a b ia l-lin g u a l movement at incisal edge fo r discom fort end point. tE, e le ctrical m edication (iontophoresis). ¿This root was not com pletely resorbed lingually; th is accounts for the lack of m obility.
JADA, Vol. 8 8 , January 1974 ■ 125
The mouth electrode (Fig 1) was constructed to fit over the tooth to be extracted and to sur round the soft tissue around the tooth. Figure 1 shows the components of the iontophoresis apparatus. The indifferent electrode (Fig 1, D) is an electrode used for cystic fibrosis analysis; it is applied to the skin over the volar surface of the wrist. Figure 2 shows the iontophoresis apparatus* completely connected for use. The iontophoresor is an early model used for cystic fibrosis analysis. It supplies a low-voltage direct cur rent that can be varied between 0 and 3 ma. When the patient is ready for current application, the rheostat is gradually increased until the patient feels a slight tingling sensation. The rheostat is then turned down slightly so that no sensation is noticed. The iontophoresor must be turned on with the rheostat setting at zero before the mouth electrode is placed on the patient. If this precaution is not observed the patient may ob tain a slight, unpleasant shock. A lso, an unpleas ant feeling can occur if the current level is al tered too rapidly. The medication for iontophoresis was pre pared by the addition of lidocaine hydrochlor ide crystals! to solvent containing ultrapure wa ter (90%) and ethyl alcohol (10%) o f sufficient quantity to make a 2% solution with respect to lidocaine. Epinephrine? was added to a final concentration o f 1:50,000. The solution used for the indifferent electrode was either physiologic saline solution or isotonic sodium nitrate. For one tooth having a long root, injections were made with commercial 2% lidocaine hydrochlor ide with 1:100,000 epinephrine. The tissue site of the indifferent electrode was dried and swabbed with ethyl alcohol (70%) before application to remove surface oils and ensure good contact.
Results For extraction o f teeth 1 through 10 (Table) ion tophoresis of the local anesthetic was performed for ten minutes. Current was applied to teeth 11 and 12 for only five minutes, whereas for tooth 13 the current was applied for 15 minutes. Two to three minutes after the removal of electrodes, the teeth were luxated by finger pressure to de termine any change in sensation. The patients indicated that this procedure was without dis comfort as compared to that experienced be fore application of iontophoresis, although they 126 ■ JADA, V ol. 8 8 , January 1974
still felt pressure. A straight elevator and for ceps were then used to complete the extractions. Tw elve o f the 13 teeth were extracted satisfac torily, and the patients experienced no pain or discomfort. One patient experienced a slight de gree o f unpleasantness during the extraction of tooth 9. The mouth electrode was still under de velopment at that time; adaptation of the elec trode to tissue was not considered adequate. Tooth 2 showed such a long remaining root on the radiograph that it was decided to infil trate local anesthetic by injection into the site previously anesthetized by iontophoresis in or der to obtain deeper anesthesia around the bony attachment. The patient felt no discomfort from needle insertion on either the labial or the pal atal aspect. Because o f a lack o f mobility, cur rent was applied to tooth 13 for 15 minutes. A completely satisfactory anesthesia for more than an hour was obtained.
Discussion With the use o f only deep surface anesthesia obtained by iontophoresis, 12 of 13 deciduous teeth were extracted without patient discom fort. One extraction was considered to be un successful, probably because of poor adapta tion o f electrode to tissue during electrode de velopment. This patient returned for four more extractions with use of iontophoresis for sur face anesthesia with the improved electrode shown in Figure 1; she experienced no discom fort. Another deciduous tooth with a long root was extracted after iontophoretic surface anes thesia followed by infiltration injections into the sites already anesthetized. It is the author’s opinion that the extraction of loose deciduous teeth after iontophoretic ap plication o f local anesthetics is a satisfactory procedure. If the tooth has minimal bony at tachment, the deep mucosal anesthesia obtained is adequate to eliminate discomfort. Patient ac ceptance of the procedure was high; no anxiety was evident at return appointments for further extractions by this method. If the tooth has a bony attachment, local anes thetics can be infiltrated into the iontophoretically anesthetized areas surrounding the tooth even on the hard palate, without patient discomfort. The successful use o f iontophoretic local an esthesia requires that the operator carefully ob serve some details o f the method.
Fig 1 » A (left to right): Electrode plug that fits into iontophoresis apparatus; alum inum foil adapter, cov ered w ith cotton, tha t fits into mouth electrode; saddle-shaped electrode tha t holds drug against tissue to be anesthetized. B: alum inum foil adapted to m outh electrode. C: m outh electrode com pletely assembled. D: in different electrode applied to skin over wrist.
Fig 2 ■ lonto pho resor (AC rectifier) com pletely connected fo r use. Note w hite electrode (positive) attached at area of local anesthesia application. Gangarosa: IONTOPHORESIS FOR ANESTHESIA ■ 127
Positive and negative electrodes should be of approximately equal size' so that current density is not higher at one electrode than at the other. A high current density may cause a bum. Extraneous ions should not be introduced at the medicating electrode since a competition for current results with ions o f similar charge. There fore, commercially prepared local anesthetic solutions would probably not be suitable for iontophoretic local anesthesia. Epinephrine may be combined with local an esthetics in the same solution for iontophoresis since both vasoconstrictor and local anesthetic are positively charged ions. It was found that epinephrine in ratios o f 1:20,000 to 1:50,000 was satisfactory for prolonging the deep sur face anesthesia obtained by iontophoresis. After iontophoretic anesthetic application, a latent period o f two to three minutes was noted. A similar latent period has been observed in more than 100 experimental applications to the skin (personal observations). The use o f iontophoresis cited in this paper is in agreement with that in the report by Har ris,5 who considered iontophoresis an excellent method for obtaining surface anesthesia as well as for medicating other tissues with many types o f drugs. Further studies o f iontophoretic anes thesia under different conditions of use in den tal and medical offices should be carried out to confirm the usefulness and feasibility o f the tech nique.
Summary With the use o f only electrical medication (ion tophoresis) for anesthesia of the periodontal mu cosa, 12 deciduous anterior teeth were extract ed. The time o f iontophoresis varied from 5 to 15 minutes. One other tooth was extracted after the use o f iontophoresis and the painless injec
128 ■ JADA, Vol. 8 8 , January 1974
tion o f local anesthetic into the anesthetized mucosa. Local anesthesia by injection would have been advisable for extraction o f all 13 teeth if iontophoresis had not been used. Twelve of the 13 extractions were considered successful in that the patients felt no discomfort. Discom fort in one patient during an extraction was at tributed to technical difficulties during develop ment o f the mouth electrode. Failure o f the technique may result if careful attention to details is not observed. Possible causes o f discouragement with the technique are patient discomfort, bum s, improper elec trode matching, competing ions in the medicat ing solution, and the connection o f the medicat ing electrode to the wrong electrode. The use of this procedure could eliminate fear of hypodermic injection and promote a better dentist-patient relationship. The technique could be used as a topical anesthetic before needle in sertion. It appears simple enough for an auxiliary to perform under dentist supervision, thus saving professional time. Experiments are in progress to evaluate further the usefulness o f iontophore sis for deep mucosal anesthesia as well as for other uses in dentistry.
Dr. Gangarosa is professor of oral biology and pharm acology and coo rdinator o f pharm acology at the School of Dentistry, Medical C ollege of Georgia, Augusta, 30902. * HTL, Inc., Huntsville, Ala. TAstra Pharmaceutical Products Co., W orcester, Mass 01606. t Eli Lilly & Co., Indianapolis, 46206. 1. Bonnycastle, D.D. D rill’s pharm acology in medicine, ed 3. New York, McGraw-Hill B ook Co., 1965, p 17. 2. Scott, H.M. Reduction of sensitivity by electrophoresis. J Dent Child 29:225 4th quart 1962. 3. C ollins, E.M. Desensitization of hypersensitive teeth. Dent Dig 68:360 Aug 1962. 4. Jensen, A.L. H ypersensitivity con trolled by iontophoresis: double blind clinical investigation. JADA 68:216 Feb 1964. 5. Harris, R. Therapeutic electricity and ultraviolet radiation, ed 2. Baltim ore, Elizabeth Licht, 1967, p 156.
Because local anesthetics are positively charged molecules, deep surface anesthesia may be obtained by the use o f iontophoresis. This can be useful for preparation o f injection sites, and it can eliminate the need for injections in procedures in which only surface anesthesia is needed.
Louis P. Gangarosa, Sr., DDS, PhD, Augusta, Ga
Twelve of 13 retained deciduous teeth were ex tracted w ithout patient discom fort with use of only deep surface anesthesia obtained by ionto phoresis of a local anesthetic. Most of the teeth were extracted after the electrical current had been applied fo r ten minutes.
Methods of procedure During three years, 13 retained deciduous ante rior teeth were extracted from three children, ages 6 to 13. Four dentists participated in the procedures. For each procedure two o f the den tists agreed that local anesthesia by infiltration injection would have been advisable for all of these extractions, if iontophoresis had not been used. The Table gives relevant data about the chil dren and the conditions of procedures. Radio graphs were taken of all the teeth, but they are not included since they merely verified the diag nosis o f routine retained deciduous teeth.
In this paper, the results o f the use of iontophore sis as the sole local anesthetic for extraction of retained deciduous teeth are reported. Ionto phoresis is a process o f medication of tissues by an electrical current to aid penetration o f a drug into tissue. This process is accepted as a method of drug application1 and has been used in dentistry to desensitize teeth.2"4 It is possible to medicate any surface tissue electrically with drugs that have a positive or negative charge.5 The possibilities for this technique have been almost totally neglected in dentistry and med icine.
Table ■ Deciduous teeth extracted by iontophoresis. Patient Boy
Girl
Tooth Age num ber 12
1
13
2
7
3
8
4
8
5
8
Girl
6
6
7
6
8
7
9
7
10
7
11
7
12
8
13
M o bility* (mm)
Root length (cm)
Method of anesthesiat
Current duration (min)
2
0.4
E
10
0
1.3
E & injection
10
Mandibular left central in ciso r Mandibular right lateral in ciso r M axillary right central incisor M axillary left central in ciso r
3
0.3
E
10
2
0.5
E
10
3
0.4
E
10
3
0.4
E
10
M andibular right central in ciso r Mandibular left central in ciso r M andibular left lateral incisor Mandibular right lateral in ciso r M axillary right central in ciso r M axillary left central in ciso r M axillary right lateral in ciso r
3
0.4
E
10
4
0.2
E
10
Tooth M axillary right canine M axillary left canine
2
0.3
E
10
3
0.3
E
10
2
0.4
E
5
2
0.4
E
5
1
0.3$
E
15
'L a b ia l-lin g u a l movement at incisal edge fo r discom fort end point. tE, e le ctrical m edication (iontophoresis). ¿This root was not com pletely resorbed lingually; th is accounts for the lack of m obility.
JADA, Vol. 8 8 , January 1974 ■ 125
The mouth electrode (Fig 1) was constructed to fit over the tooth to be extracted and to sur round the soft tissue around the tooth. Figure 1 shows the components of the iontophoresis apparatus. The indifferent electrode (Fig 1, D) is an electrode used for cystic fibrosis analysis; it is applied to the skin over the volar surface of the wrist. Figure 2 shows the iontophoresis apparatus* completely connected for use. The iontophoresor is an early model used for cystic fibrosis analysis. It supplies a low-voltage direct cur rent that can be varied between 0 and 3 ma. When the patient is ready for current application, the rheostat is gradually increased until the patient feels a slight tingling sensation. The rheostat is then turned down slightly so that no sensation is noticed. The iontophoresor must be turned on with the rheostat setting at zero before the mouth electrode is placed on the patient. If this precaution is not observed the patient may ob tain a slight, unpleasant shock. A lso, an unpleas ant feeling can occur if the current level is al tered too rapidly. The medication for iontophoresis was pre pared by the addition of lidocaine hydrochlor ide crystals! to solvent containing ultrapure wa ter (90%) and ethyl alcohol (10%) o f sufficient quantity to make a 2% solution with respect to lidocaine. Epinephrine? was added to a final concentration o f 1:50,000. The solution used for the indifferent electrode was either physiologic saline solution or isotonic sodium nitrate. For one tooth having a long root, injections were made with commercial 2% lidocaine hydrochlor ide with 1:100,000 epinephrine. The tissue site of the indifferent electrode was dried and swabbed with ethyl alcohol (70%) before application to remove surface oils and ensure good contact.
Results For extraction o f teeth 1 through 10 (Table) ion tophoresis of the local anesthetic was performed for ten minutes. Current was applied to teeth 11 and 12 for only five minutes, whereas for tooth 13 the current was applied for 15 minutes. Two to three minutes after the removal of electrodes, the teeth were luxated by finger pressure to de termine any change in sensation. The patients indicated that this procedure was without dis comfort as compared to that experienced be fore application of iontophoresis, although they 126 ■ JADA, V ol. 8 8 , January 1974
still felt pressure. A straight elevator and for ceps were then used to complete the extractions. Tw elve o f the 13 teeth were extracted satisfac torily, and the patients experienced no pain or discomfort. One patient experienced a slight de gree o f unpleasantness during the extraction of tooth 9. The mouth electrode was still under de velopment at that time; adaptation of the elec trode to tissue was not considered adequate. Tooth 2 showed such a long remaining root on the radiograph that it was decided to infil trate local anesthetic by injection into the site previously anesthetized by iontophoresis in or der to obtain deeper anesthesia around the bony attachment. The patient felt no discomfort from needle insertion on either the labial or the pal atal aspect. Because o f a lack o f mobility, cur rent was applied to tooth 13 for 15 minutes. A completely satisfactory anesthesia for more than an hour was obtained.
Discussion With the use o f only deep surface anesthesia obtained by iontophoresis, 12 of 13 deciduous teeth were extracted without patient discom fort. One extraction was considered to be un successful, probably because of poor adapta tion o f electrode to tissue during electrode de velopment. This patient returned for four more extractions with use of iontophoresis for sur face anesthesia with the improved electrode shown in Figure 1; she experienced no discom fort. Another deciduous tooth with a long root was extracted after iontophoretic surface anes thesia followed by infiltration injections into the sites already anesthetized. It is the author’s opinion that the extraction of loose deciduous teeth after iontophoretic ap plication o f local anesthetics is a satisfactory procedure. If the tooth has minimal bony at tachment, the deep mucosal anesthesia obtained is adequate to eliminate discomfort. Patient ac ceptance of the procedure was high; no anxiety was evident at return appointments for further extractions by this method. If the tooth has a bony attachment, local anes thetics can be infiltrated into the iontophoretically anesthetized areas surrounding the tooth even on the hard palate, without patient discomfort. The successful use o f iontophoretic local an esthesia requires that the operator carefully ob serve some details o f the method.
Fig 1 » A (left to right): Electrode plug that fits into iontophoresis apparatus; alum inum foil adapter, cov ered w ith cotton, tha t fits into mouth electrode; saddle-shaped electrode tha t holds drug against tissue to be anesthetized. B: alum inum foil adapted to m outh electrode. C: m outh electrode com pletely assembled. D: in different electrode applied to skin over wrist.
Fig 2 ■ lonto pho resor (AC rectifier) com pletely connected fo r use. Note w hite electrode (positive) attached at area of local anesthesia application. Gangarosa: IONTOPHORESIS FOR ANESTHESIA ■ 127
Positive and negative electrodes should be of approximately equal size' so that current density is not higher at one electrode than at the other. A high current density may cause a bum. Extraneous ions should not be introduced at the medicating electrode since a competition for current results with ions o f similar charge. There fore, commercially prepared local anesthetic solutions would probably not be suitable for iontophoretic local anesthesia. Epinephrine may be combined with local an esthetics in the same solution for iontophoresis since both vasoconstrictor and local anesthetic are positively charged ions. It was found that epinephrine in ratios o f 1:20,000 to 1:50,000 was satisfactory for prolonging the deep sur face anesthesia obtained by iontophoresis. After iontophoretic anesthetic application, a latent period o f two to three minutes was noted. A similar latent period has been observed in more than 100 experimental applications to the skin (personal observations). The use o f iontophoresis cited in this paper is in agreement with that in the report by Har ris,5 who considered iontophoresis an excellent method for obtaining surface anesthesia as well as for medicating other tissues with many types o f drugs. Further studies o f iontophoretic anes thesia under different conditions of use in den tal and medical offices should be carried out to confirm the usefulness and feasibility o f the tech nique.
Summary With the use o f only electrical medication (ion tophoresis) for anesthesia of the periodontal mu cosa, 12 deciduous anterior teeth were extract ed. The time o f iontophoresis varied from 5 to 15 minutes. One other tooth was extracted after the use o f iontophoresis and the painless injec
128 ■ JADA, Vol. 8 8 , January 1974
tion o f local anesthetic into the anesthetized mucosa. Local anesthesia by injection would have been advisable for extraction o f all 13 teeth if iontophoresis had not been used. Twelve of the 13 extractions were considered successful in that the patients felt no discomfort. Discom fort in one patient during an extraction was at tributed to technical difficulties during develop ment o f the mouth electrode. Failure o f the technique may result if careful attention to details is not observed. Possible causes o f discouragement with the technique are patient discomfort, bum s, improper elec trode matching, competing ions in the medicat ing solution, and the connection o f the medicat ing electrode to the wrong electrode. The use of this procedure could eliminate fear of hypodermic injection and promote a better dentist-patient relationship. The technique could be used as a topical anesthetic before needle in sertion. It appears simple enough for an auxiliary to perform under dentist supervision, thus saving professional time. Experiments are in progress to evaluate further the usefulness o f iontophore sis for deep mucosal anesthesia as well as for other uses in dentistry.
Dr. Gangarosa is professor of oral biology and pharm acology and coo rdinator o f pharm acology at the School of Dentistry, Medical C ollege of Georgia, Augusta, 30902. * HTL, Inc., Huntsville, Ala. TAstra Pharmaceutical Products Co., W orcester, Mass 01606. t Eli Lilly & Co., Indianapolis, 46206. 1. Bonnycastle, D.D. D rill’s pharm acology in medicine, ed 3. New York, McGraw-Hill B ook Co., 1965, p 17. 2. Scott, H.M. Reduction of sensitivity by electrophoresis. J Dent Child 29:225 4th quart 1962. 3. C ollins, E.M. Desensitization of hypersensitive teeth. Dent Dig 68:360 Aug 1962. 4. Jensen, A.L. H ypersensitivity con trolled by iontophoresis: double blind clinical investigation. JADA 68:216 Feb 1964. 5. Harris, R. Therapeutic electricity and ultraviolet radiation, ed 2. Baltim ore, Elizabeth Licht, 1967, p 156.