Int. Y .Oral Surg. 1975: 4:151-156 (Key words: analgesia; anesthesia; pain)
Pain and temperature sensations related to local analgesia VALLE J. OIKARINEN, PEKKA YLIPAAVALNIEMI AND HANS EVERS
Department of Oral Surgery, Institute of Dentistry, University of Helsinki, Finland and Astra Medical Department, S6dertiil]e, Sweden
m3STI~CT -- Following the injection of local analgesic solutions at room temperature (21~ and at normal body temperature (37~ respectively, in the oral submucosal region, it was found that most of the subjects experienced the solutions as being of body temperature, regardless of whether the temperature of the solution was 37~ or 21~ The duration of soft tissue anesthesia was not influenced by the temperature of the solutions. After the anesthetic effect had subsided, prilocaine 4 % caused post-analgesic pain less frequently than did lidocaine 2 % with adrenalin 12.5 btg/ml. Following injections with different mepivacaine solutions it was found that a low pH caused more frequent pain than a high pI-I, that the addition of a vasoconstrictor caused more frequent pa~n than a plain solution, and that there was a tendency for more frequent pain with increasing concentrations of the local anesthetic agent. In this study the addition of adrenalin was not found to prolong the period of soft tissue anesthesia.
(Received for publication 2 May, accepted 14 June 1975)
Sometimes the injection of a local analgesic may cause an unpleasant pain or pressure sensation, and the area of injection may feel tender after the termination of the local anesthesia. The causative factors can be mechanical, such as tissue trauma caused by the advancing needle or the rapid injection of a relatively large volume of solution into the soft tissue under pressureS. The area of injection is also of great importance because in oral regions pain receptors are the most abundant in the mucous membranes, periodontal tissues and periosteum, and minimal in the submucosa. It is not
clear to what extent thermal and chemical factors of an injected local analgesic solution irritate the tissues. It is known that the temperature difference between the injected solution and the body must be of a certain magnitude to excite the free nerve endings and initiate an action potentialS. Furthermore, it has been shown that the activity of injected solutions at pH 6.2 causes subcutaneous pain and that a maximum effect is reached when using acid solutions with a pH of 3.2~,4. After conducting anesthesia experiments in the oral region, WIDMALM 7 concluded that the pH value may be of only
152
OIKARINEN, YLIPAAVALNIEMI AND EVERS
marginal importance in influencing the degree of pain sensation. Th e p u r p o s e of the present study was twofold: (1) to test whether, in terms of sensory perception, a group of healthy volunteers could distinguish between injections of dental local anesthetic solutions at r o o m temperature (21~ and at normal body temperature (37~ respectively, and (2) to determine h o w the concentration and pH of the local anesthetic influenced injection site pain at different phases during the injection procedure, during soft tissue anesthesia, and following termination of anesthesia, and what effects were caused by adding a vasoconstrictor.
Material and methods Seventeen dental students took part in the study, 10 males and 7 females. Their average age was 23 years, ranging from 21 to 25. The investigation was divided into two parts: 1. To test the ability of volunteers to perceive the difference between two standardized local anesthetic injections, where the only experimentally controlled variable was the difference in temperature of the solution. One solution was at normal room temperature (21 ~) while the other was warmed to normal body temperature (37~ 2. To register pain at specified points of time throughout the injection procedure and to register the onset of pain during the postanesthetic period when the effect of the local anesthetic was subsiding. Observations were made only at the injection site. The degree of pain was related to the concentration of the local anesthetic and other factors such as the presence of a vasoconstrictor or variation in pH. Duration of soft tissue analgesia was also recorded.
(Sterex). The test cartridges containing the solution for injection at normal body temperature were slowly warmed to 37~ in a heated bath which was kept in a thermostatically controlled box prior to the experiments. All injections were made submucosally in the buccol sulcus in the maxillary premolar region. The control solution, which was the same temperature as the room in which the investigation took place (21~ was injected into the corresponding region on the opposite side of the oral cavity. The injections were made under double-blind conditions so that neither the operator nor the volunteer knew which comb i n a t i o n they had or even whether the t w o temperatures were different. This latter information was known only by the operator's assistant. The entire contents of the cartridges were injected during a standardized period of 30 seconds. Immediately after injection, the volunteer was asked whether he felt the injected solution to be warmer or colder than his own body temperature. Additionally, the subject reported the duration of soft tissue anesthesia, experienced as numbness in the upper lip. R E G I S T R A T I O N OF P A I N Seventeen dental students took part in this study, 9 males and 8 females. Their average age was 25 years, ranging fl'om 21 to 32. The local analgesic solutions used were 4 % prilocaine (Citanest, Astra) and 2 % lidocaine with adrenalin (12.5 ~g/ml) (Astra); pH values were 6.7 and 3.8 respectively. The materials used, as well as the test procedures, were identical to those used in the previously described series. The temperature of the local analgesic solutions equalled that of the investigation room (21~ The following parameters were studied: pain on insertion of the needle (yes/no), pain on starting to inject the solution, and pain at the termination of the injection after 30 seconds (intensive/ slight/none) as well as onset of pain after the termination of anesthesia (yes/no) and duration of anesthesia in the soft tissues. Group A -
Sixty-one dental students took part in the study, 28 males and 33 females. Their average age was 23 years, ranging from 21. to 31. The test solutions used were as follows; 1 % mepivacaine (Carbocaine| Bofors),pH 6.7, 2 % mepivacaine, pH 6.7, 3 % mepivacaine, pH 6.7, 3 % mepivacaine, pH 4.0, and 3 % mepivacaine with adrenalin (5 ~g/ml), pH 4. In this series Group B -
P E R C E P T I O N OF S O L U T I O N TEMPERATURE Pfilocaine 4 % (Citanest| Astra) in LS-mI cartridges was used and the injections were made with disposable, self-aspirating syringes (Astra) with 27-gauge, long, disposable needles
PAIN RELATED TO LOCAL ANALGESIA the injection volume of 1.0 ml was injected at a constant rate over a period of 30 seconds. The syringes were disposable (Pharma-Plast), 2 ml, with Luer-Lok 23-gauge, 1-inch needles (Everett). The area of injection was the same as in Series 1 and 2 A. All injections were made by the same operator who did the previous series. In addition to the parameters investigated in the previous tests, 15 seconds after the start of injection the volunteers were asked about pain sensations. The study comprised six pairwise comparisons, in each of which a number of volunteers (.~--.10) received one solution on the left side and another on the contralateral side according to a random procedure. For the statistical analysis a number of independent groups were formed in order to get efficient comparisons between those solutions of potential interest. Each group included some subjects who received the same solution on both sides. Thus, each subject belongs to two different groups. The statistical tests used were the Fiseher's exact test for the pain data and the Student's t-test for the duration data. The Group 2 study was designed as a double-blind test. The codes were broken when all the data were collected and processed. The statistical evaluations were made at the Statistical Section of the Medical Department, Astra Lgkemedel AB, Sweden, by Bernhard Huitfeldt Ph.D.
Results PERCEPTION OF T E M P E R A T U R E A s u m m a r y of the results is presented in T a b l e 1. I n testing the hypothesis as to whether
Table 1. Proportion of subjects identifying correctly, or incorrectly, injected solutions at normal body temperature (37~ and at room temperature (21~ respectively
W a r m = Solution at normal body temperature 37~ Cold = Solution at room temperature 21~
Correct
Incorrect
14/17
3/17
5/17
12/17
153
the subjects could identify injected solutions of normal body temperature and of room temperature, respectively, the result shows a statistical significance (P < 0.001). This significance indicates that injected solutions of normal body temperature are identified as warm more often than solutions at room temperature are identified as being cold. Without attempting to explain the working mechanisms involved in these observations, the clinical implication would seem to be that there is no indication for warming up the solution to body temperature prior to injection. REGISTRATION OF PAIN Group A - On inserting the needle through the membrane into the submucosa, about one in every four subjects felt slight pain with both solutions. The majority of them felt slight pain at the start of the injection. However, none of them experienced this type of pain at the termination of the injection. No differences were found in the frequency of injection pain between the two local analgesic solutions tested in this series (4 % prilocaine and 2 % lidocaine with adrenalin). After termination of anesthesia, pain at the injected area was experienced more often when 2 % lidocaine with adrenalin had been injected (50 %) than when 4 % prilocaine had been injected (16 %), a difference obviously statistically significant (P < 0.05). N o differences were found between the two solutions regarding the duration of soft tissue anesthesia. Group B - A summary of the results is presented in Table 2. The following identification symbols are used in the Table: 1 % mepivacaine (pH 6.7) solution A, 2 % mepivacaine (pH 6.7) solution B, 3 % mepivacaine (pH 6.7) solution C, 3 % mepivacaine (pH 4.0) solution D, and 3 % mepivacaine with adrenalin (pH 4.0) solution E.
154
OIKARINEN, YL[PAAVALNIEMI AND EVERS
Table 2. Parameters. Observed order of compared solutions. Symbol " > " means greater pain or longer duration, respectively Solution comparison ~B
~C B/C ~D D/E
1
2
3
4
5
6
A>B A>C
AB A>C
A
Pain and temperature sensations related to local analgesia VALLE J. OIKARINEN, PEKKA YLIPAAVALNIEMI AND HANS EVERS
Department of Oral Surgery, Institute of Dentistry, University of Helsinki, Finland and Astra Medical Department, S6dertiil]e, Sweden
m3STI~CT -- Following the injection of local analgesic solutions at room temperature (21~ and at normal body temperature (37~ respectively, in the oral submucosal region, it was found that most of the subjects experienced the solutions as being of body temperature, regardless of whether the temperature of the solution was 37~ or 21~ The duration of soft tissue anesthesia was not influenced by the temperature of the solutions. After the anesthetic effect had subsided, prilocaine 4 % caused post-analgesic pain less frequently than did lidocaine 2 % with adrenalin 12.5 btg/ml. Following injections with different mepivacaine solutions it was found that a low pH caused more frequent pain than a high pI-I, that the addition of a vasoconstrictor caused more frequent pa~n than a plain solution, and that there was a tendency for more frequent pain with increasing concentrations of the local anesthetic agent. In this study the addition of adrenalin was not found to prolong the period of soft tissue anesthesia.
(Received for publication 2 May, accepted 14 June 1975)
Sometimes the injection of a local analgesic may cause an unpleasant pain or pressure sensation, and the area of injection may feel tender after the termination of the local anesthesia. The causative factors can be mechanical, such as tissue trauma caused by the advancing needle or the rapid injection of a relatively large volume of solution into the soft tissue under pressureS. The area of injection is also of great importance because in oral regions pain receptors are the most abundant in the mucous membranes, periodontal tissues and periosteum, and minimal in the submucosa. It is not
clear to what extent thermal and chemical factors of an injected local analgesic solution irritate the tissues. It is known that the temperature difference between the injected solution and the body must be of a certain magnitude to excite the free nerve endings and initiate an action potentialS. Furthermore, it has been shown that the activity of injected solutions at pH 6.2 causes subcutaneous pain and that a maximum effect is reached when using acid solutions with a pH of 3.2~,4. After conducting anesthesia experiments in the oral region, WIDMALM 7 concluded that the pH value may be of only
152
OIKARINEN, YLIPAAVALNIEMI AND EVERS
marginal importance in influencing the degree of pain sensation. Th e p u r p o s e of the present study was twofold: (1) to test whether, in terms of sensory perception, a group of healthy volunteers could distinguish between injections of dental local anesthetic solutions at r o o m temperature (21~ and at normal body temperature (37~ respectively, and (2) to determine h o w the concentration and pH of the local anesthetic influenced injection site pain at different phases during the injection procedure, during soft tissue anesthesia, and following termination of anesthesia, and what effects were caused by adding a vasoconstrictor.
Material and methods Seventeen dental students took part in the study, 10 males and 7 females. Their average age was 23 years, ranging from 21 to 25. The investigation was divided into two parts: 1. To test the ability of volunteers to perceive the difference between two standardized local anesthetic injections, where the only experimentally controlled variable was the difference in temperature of the solution. One solution was at normal room temperature (21 ~) while the other was warmed to normal body temperature (37~ 2. To register pain at specified points of time throughout the injection procedure and to register the onset of pain during the postanesthetic period when the effect of the local anesthetic was subsiding. Observations were made only at the injection site. The degree of pain was related to the concentration of the local anesthetic and other factors such as the presence of a vasoconstrictor or variation in pH. Duration of soft tissue analgesia was also recorded.
(Sterex). The test cartridges containing the solution for injection at normal body temperature were slowly warmed to 37~ in a heated bath which was kept in a thermostatically controlled box prior to the experiments. All injections were made submucosally in the buccol sulcus in the maxillary premolar region. The control solution, which was the same temperature as the room in which the investigation took place (21~ was injected into the corresponding region on the opposite side of the oral cavity. The injections were made under double-blind conditions so that neither the operator nor the volunteer knew which comb i n a t i o n they had or even whether the t w o temperatures were different. This latter information was known only by the operator's assistant. The entire contents of the cartridges were injected during a standardized period of 30 seconds. Immediately after injection, the volunteer was asked whether he felt the injected solution to be warmer or colder than his own body temperature. Additionally, the subject reported the duration of soft tissue anesthesia, experienced as numbness in the upper lip. R E G I S T R A T I O N OF P A I N Seventeen dental students took part in this study, 9 males and 8 females. Their average age was 25 years, ranging fl'om 21 to 32. The local analgesic solutions used were 4 % prilocaine (Citanest, Astra) and 2 % lidocaine with adrenalin (12.5 ~g/ml) (Astra); pH values were 6.7 and 3.8 respectively. The materials used, as well as the test procedures, were identical to those used in the previously described series. The temperature of the local analgesic solutions equalled that of the investigation room (21~ The following parameters were studied: pain on insertion of the needle (yes/no), pain on starting to inject the solution, and pain at the termination of the injection after 30 seconds (intensive/ slight/none) as well as onset of pain after the termination of anesthesia (yes/no) and duration of anesthesia in the soft tissues. Group A -
Sixty-one dental students took part in the study, 28 males and 33 females. Their average age was 23 years, ranging from 21. to 31. The test solutions used were as follows; 1 % mepivacaine (Carbocaine| Bofors),pH 6.7, 2 % mepivacaine, pH 6.7, 3 % mepivacaine, pH 6.7, 3 % mepivacaine, pH 4.0, and 3 % mepivacaine with adrenalin (5 ~g/ml), pH 4. In this series Group B -
P E R C E P T I O N OF S O L U T I O N TEMPERATURE Pfilocaine 4 % (Citanest| Astra) in LS-mI cartridges was used and the injections were made with disposable, self-aspirating syringes (Astra) with 27-gauge, long, disposable needles
PAIN RELATED TO LOCAL ANALGESIA the injection volume of 1.0 ml was injected at a constant rate over a period of 30 seconds. The syringes were disposable (Pharma-Plast), 2 ml, with Luer-Lok 23-gauge, 1-inch needles (Everett). The area of injection was the same as in Series 1 and 2 A. All injections were made by the same operator who did the previous series. In addition to the parameters investigated in the previous tests, 15 seconds after the start of injection the volunteers were asked about pain sensations. The study comprised six pairwise comparisons, in each of which a number of volunteers (.~--.10) received one solution on the left side and another on the contralateral side according to a random procedure. For the statistical analysis a number of independent groups were formed in order to get efficient comparisons between those solutions of potential interest. Each group included some subjects who received the same solution on both sides. Thus, each subject belongs to two different groups. The statistical tests used were the Fiseher's exact test for the pain data and the Student's t-test for the duration data. The Group 2 study was designed as a double-blind test. The codes were broken when all the data were collected and processed. The statistical evaluations were made at the Statistical Section of the Medical Department, Astra Lgkemedel AB, Sweden, by Bernhard Huitfeldt Ph.D.
Results PERCEPTION OF T E M P E R A T U R E A s u m m a r y of the results is presented in T a b l e 1. I n testing the hypothesis as to whether
Table 1. Proportion of subjects identifying correctly, or incorrectly, injected solutions at normal body temperature (37~ and at room temperature (21~ respectively
W a r m = Solution at normal body temperature 37~ Cold = Solution at room temperature 21~
Correct
Incorrect
14/17
3/17
5/17
12/17
153
the subjects could identify injected solutions of normal body temperature and of room temperature, respectively, the result shows a statistical significance (P < 0.001). This significance indicates that injected solutions of normal body temperature are identified as warm more often than solutions at room temperature are identified as being cold. Without attempting to explain the working mechanisms involved in these observations, the clinical implication would seem to be that there is no indication for warming up the solution to body temperature prior to injection. REGISTRATION OF PAIN Group A - On inserting the needle through the membrane into the submucosa, about one in every four subjects felt slight pain with both solutions. The majority of them felt slight pain at the start of the injection. However, none of them experienced this type of pain at the termination of the injection. No differences were found in the frequency of injection pain between the two local analgesic solutions tested in this series (4 % prilocaine and 2 % lidocaine with adrenalin). After termination of anesthesia, pain at the injected area was experienced more often when 2 % lidocaine with adrenalin had been injected (50 %) than when 4 % prilocaine had been injected (16 %), a difference obviously statistically significant (P < 0.05). N o differences were found between the two solutions regarding the duration of soft tissue anesthesia. Group B - A summary of the results is presented in Table 2. The following identification symbols are used in the Table: 1 % mepivacaine (pH 6.7) solution A, 2 % mepivacaine (pH 6.7) solution B, 3 % mepivacaine (pH 6.7) solution C, 3 % mepivacaine (pH 4.0) solution D, and 3 % mepivacaine with adrenalin (pH 4.0) solution E.
154
OIKARINEN, YL[PAAVALNIEMI AND EVERS
Table 2. Parameters. Observed order of compared solutions. Symbol " > " means greater pain or longer duration, respectively Solution comparison ~B
~C B/C ~D D/E
1
2
3
4
5
6
A>B A>C
AB A>C
A
