The effects of 2% lidocaine with 1:100,000 epinephrine on pulpal and gingival blood flow

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1 Vol. 85 No. 2 February 1998 ~!~ ~,~o%%~,#~ ~% ~%~ ~!~~~!~!~!~,~ u ~, ~, ~ ~i ~ ~:~%~%~i~ ~,~1~ ~%~i~i~@~?~~n~~,~ ~' ~'~ ~ ~ % ~ :~ ~ ENDODONTICS Editor." Richard E. Walton The effects of 2% lidocaine with 1:100,000 epinephrine on pulpal and gingival blood flow Junil Ahn, BS, a and M. Anthony Pogrel, DDS, MD, FRCS, FACS, b San Francisco, Calif. UNIVERSITY OF CALIFORNIA, SAN FRANCISCO Objective. The dental pulp is a low-compliance system that is particularly vulnerable to physiologic changes. Prolonged vasoconstriction may have detrimental effects. This goal of this study was to determine whether 2% Iidocaine with 1:100,000 epinephrine, as used for buccal infiltration, decreases the blood flow in the dental pulp and adjacent gingival tissue. Study design. The Perifhx PF3 laser Doppler monitored pulpal and gingival blood flow before and after injection with local anesthetic. Ten human volunteers with at least one healthy and unrestored maxillary premolar were used in this study. Results. After injection of 0.9 ml of 2% Iidocaine with epinephrine, there was a significant reduction from baseline values (p > 0.05) in both pulpal (73%) and gingivai (5t%) blood flow rate in all volunteers. Blood flow had not returned to baseline values after 1 hour. Conclusion. This study showed that 2% lidocaine with 1:100,000 epinephrine significantly reduced blood flow pulpally and gingivally. Pulpal blood flow reduction was more than gingival blood flow reduction, which may be critical for compromised pulps with already reduced blood flow. The gingival effects may be of relevance with soft tissue protcedures. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85: ) Local anesthetics with vasoconstrictors have been widely used in dentistry since the late 1940s for pain control. Until recently, however, few studies have looked at the effects of local anesthetics with vasoconstrictors on pulpal and gingival circulation. Research shows that pulpal circulation is a better indicator of pulpal vitality than sensory response. 1,2 Pulpal circulation and its flow regulation play an important role in inflammatory processes and pulpal pathophysiology) Because circulation is more related to pulpal health than innervation, it is important to assess how pulpal blood flow is changed by injections of local anesthetics with vasoconstrictors. Epinephrine is the most commonly used vasoconstrictor. It has been added to local anesthetics in concentrations from 1:50,000 to 1:300,000 to produce several beneficial effects: decrease in plasma concentration of local anesthetic, increase in duration and quality of anesthesia, reduction in amount of anesthetic needed, and decrease in blood loss during surgical procedures. 4 astudent, School of Dentistry. bprofessor and Chair, Department of Oral and Maxillofacial Surgery, School of Dentistry. Received for publication Feb. 24, 1997; returned for revision Apr. 16, 1997; accepted for publication Sept. 30, Copyright by Mosby, Inc /98/$ /15/86761 All of these benefits are derived from the vasoconstrictor properties of epinephrine on blood vessels in close proximity to the injection site. The vasoconstriction helps to contain the anesthetic in a localized area to prolong its effects; this also decreases blood flow and may lead to ischemia of the pulp and other tissues. Several properties of the pulp make it a low-compliance system and particularly vulnerable to insults. It is enclosed within a rigid structure of enamel and dentin, unable to expand or permeate other tissues. It also represents a terminal circulation. Because of these characteristics, prolonged vasoconstriction of the pulpal blood flow may more readily damage the pulp than vasoconstriction of other areas, such as the gingiva, which has more collateral circulation. The goal of the present study was to monitor pulpal and gingival blood flow changes using laser Doppler flowmetry, an effective and noninvasive method of monitoring blood flow in pulp and gingiva. Recent studies have applied laser Doppler flowmetry to measure human gingival sulcus blood flow, pulpal blood flow in dog canine teeth, and dental pulpal blood flow in humans MATERIAL AND METHODS Subjects The study involved 10 subjects (8 men, 2 women), 197

2 198 Ahn andpogrel ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY February 1998 Fig. 2. Dental impression used as a stabilizer for laser Doppler probe with probe tip visible on facial surface of impression of upper right first bicuspid tooth. Fig. 1. Periflux PF3 laser Doppler flowmeter. aged years with at least one healthy unrestored maxillary first premolar. Apparatus The Periflux PF3, a laser Doppler flowmeter (Perimed, Stockholm, Sweden) was used (Fig. 1). A probe that encloses an LED (light-emitting diode) and optical fibers is directed toward the facial surface of the cervical portion of the crown of the premolar and adjacent gingiva. The enclosed LED projects a low power laser light of nm in wavelength through the enamel and soft tissue. When the photons of the laser light come in contact with moving opaque cells (erythrocytes), the photons are Doppler shifted, whereas photons that strike stationary tissue cells are not. A portion of the back scattered laser light (mixture of both Doppler shifted and nonshifted light)is then absorbed by two optical fibers in the probe. The optical fibers transmit the light to a photodetector that converts the back-scattered light into an electrical signal. The electrical signal is then converted into a numerical value known as perfusion units (PU), which is proportional to blood flow, volume, and velocity. The PU is related only to the Perimed unit. It is callibrated by means of a Motility Standard, which is a b o n e containing 2 to 5 cm 3 of a colloidal suspension of latex particles. At 22 C the Motility Standard produces a standard reading on the laser Doppler Of 250 PU. The probes are rinsed in a 2% solution of glutaraldehyde, and the flowmeter is calibrated before each data session. The artifact filter, a component of the Periflux PF3, reduced artifact readings caused by probe movement. Procedure An asymptomatic maxillary first premolar, which was caries-free, vital to electrical pulp testing, and without restorations, was identified by clinical examination and review of dental history on 10 volunteers. No teeth had a history of trauma. An impression of the maxillary teeth was made with a disposable rigid plastic impression trayand silicone putty to serve as a stabilizer for the laser Doppler flowmetry probe (Fig. 2). Two holes were placed on the facial surface of the stabilizer, one at the cervical third of the facial surface of the upper premolar and another 3 mm apical to the gingival margin for stable and reproducible positioning of the laser Doppler probe. Measurement of the dental pulpal and gingival tissue baseline blood flow was taken before the administration of local anesthetic. This was performed by allowing the reading to stabilize for 2 minutes and then recording data for 1 minute at 10 second intervals to determine an average baseline value. The single local anesthetic injection was administered by local infiltration given apical to the maxillary premolar at the mucobuccal fold. The local anesthetic was 0.9 ml of 2% lidocaine with 1:100,000 epinephrine (2% Xylocaine, Astra USA, Westborough, MA). After the injection, a new reading of the pulpal blood flow was taken at 5, I0, 20, 30, 45, and 60 minutes; readings of the gingival blood flow were taken at 8, 15, 25, 35, 50, and 65 minutes. Before each reading, 2 minutes were allowed for stabilization, and the average value over 10 seconds was recorded. The Periflux PF3 updates the perfusion unit reading every 2 seconds. Negative controls were incorporated by evaluating endodontically treated teeth with the laser Doppler flowmetry. Statistical methods The primary outcome measure was the minimum observed blood flow as a percentage of the baseline value, calculated for each subject and each site. This

3 ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 85, Number 2 Ahn and Pogrel O e" e",o Pulpal Gingival Fig. 3. Baseline pulpal and gingival blood flow expressed in perfusion units C 0 1: o J Minutes Fig. 4. Pulpal blood flow with time. Zero represents time that local anesthetic with vasoconstrictor was given. measure was likely to be most relevant biologically because tissue damage may result when blood flow drops below some (currently unknown) threshold. In addition, percentage of baseline must be used because raw values depend on the angle of measurement and the shape and size of the tooth and so are not directly interpretable. The maximal percentage decrease in blood flow was compared between the pulpal and gingival sites using the Wilcoxon signed-rank test for matched data because parametric assumptions for a t-test were not met. In addition, the null hypothesis of no change in blood flow was tested separately for both sites by calculating the logarithm of the ratio of the first measurement under anesthesia to the baseline measurement and

4 200 Ahn and Pogrel ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY February ~.O 80 n I Minutes Fig. 5. Gingival blood flow with time. Zero represents time that local anesthetic with vasoconstrictor was given. Table I. Minimum percentage of baseline blood flow recorded in pulp and gingiva in each subject Minimal pulpal Minimal gingival Subject blood flow (%) blood flow (%) Mean Deviation applying the Wilcoxon signed-rank test. Secondary analyses included comparisons between sites of the percentage reduction in blood flow at the time of the first measurement at each site, the second measurement, and the average of the first and second measurements. Data on all measurements are presented graphically, but later measurements were not analyzed because of their lesser biologic relevance. RESULTS The mean baseline pulpal blood flow value was 1.97 PU (range 0.6 to 4.2 PU) with a standard deviation of 1.22 PU. The mean baseline gingival blood flow value was PU (range 7.0 to 39.6 PU) with a standard deviation of 9.54 PU (Fig. 3). After administration of 0.9 ml of 2% Xylocaine, there was significant reduction from baseline values (p < 0.05) in both pulpal and gingival blood flow rate in all volunteers. Pulpal blood flow showed a rapid decrease and a gradual return toward the baseline value within 60 minutes (Fig. 4). The maximum decrease was observed at 5 minutes, with a 73% reduction in pulpal blood flow. The gingiva also showed a rapid decrease in blood flow, although not as rapid as pulpal blood flow, and a gradual return toward the baseline value within 65 minutes (Fig. 5). The maximum decrease was observed at 15 minutes, with a 51% reduction in gingival blood flow. Neither reading had returned to baseline values after 1 hour. Because of the small number of subjects and the irregular distribution of datal the parametric assumptions for a t-test were not met; therefore, the Wilcoxon signed-rank test for matched data was used to analyze the significance of changes in pulpal and gingival blood flow at different points. Using the Wilcoxon signed - rank test on the logarithm ratio of first pulpal measurement (5 minutes) and first gingival measurement (8 minutes) separately, the percentage change from baseline values of pulpal blood flow (p = ) and gingival blood flow (p = ) was statistically significant. The mean pulpal and gingival minimal blood flow were compared (Table I), with a statistically significant difference between the pulpal and gingival minimal blood flow (p = ). In addition, the difference in

5 ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 85, Number 2 mean percentage values of pulpal and gingival blood flow at the first measurement after anesthesia, second measurement after anesthesia, and the average of the first and second measurement after anesthesia was compared using the Wilcoxon signed-rank test. Statistical significance in the average of the first and second measurement (p = ) was shown, but not in the first (p ) or second measurement (p = ). Three additional volunteers were identified who had a root treated but noncrowned upper central incisor while the contralateral central incisor was vital, as confirmed with electrical pulp testing; these individuals served as control subjects. When subjected to laser Doppler flowmetry, the root-treated teeth showed no reading, whereas the vital teeth showed a mean pulpal blood flow of 2.1 PU. DISCUSSION Pulpal blood flow showed a much more rapid and profound decrease than gingival blood flow, but the duration of decreased blood flow was about equal. Although blood flow measurements were not continued past 65 minutes, a rebound hyperemic effect may be expected. 9 The reduction in pulpal blood flow closely agrees with the experimental values found using radioisotope-labeled microspheres in dogs, 5 and laser Doppler studies on humans. 12 Gingival blood flow was not reduced as much as, and was slower to develop than, the pulpal blood flow. These data agree with the fact that gingival tissue has an extensive collateral circulation as compared to the terminal circulation of the pulpal tissue. Pulpal blood flow rate was highest of all oral tissues in an animal study using radioisotope-labeled microspheres. 13 In contrast, the data from the present study and another laser Doppler study 2 on humans showed the baseline gingival blood flow was approximately nine times greater than the baseline pulpal blood flow. This contradiction is likely due to the enamel and dentin of the tooth, which decreases the detection of the blood flow by the laser Doppler. The blood vessels of the gingiva are in closer proximity to the surface tissue and to the laser Doppler probe, which would then give a higher perfusion unit reading. Although the pulpal blood flow is high compared to the amount of pulpal tissue, the metabolic oxygen needs are assumed to be small. A high perfusion rate may be required to eliminate various substances such as bacterial toxins or irritants and to help dissipate heat. Dental procedures such as cavity preparations are performed after administration of local anesthetics with vasoconstrictors and may cause inflammatory changes. Clearance of pulpal toxins is related to the pulpal circulation, and the reduction of pulpal blood flow can result Ahn and Pogrel 201 in excessive accumulation of inflammatory mediators and heat. 14 This accumulation may then lead to local inflammation and possible pulpal necrosis. Another adverse effect of prolonged vasoconstriction may be an inadequate oxygen supply to the pulpal tissue. This may lead to direct pulpal necrosis, particularly in teeth that have a severely compromised blood supply, such as traumatized teeth. Although laser Doppler flowmetry was not initially developed to measure pulpal blood flow, recent studies I5-17 have shown that this method is accurate. Vongsavan and Matthews 16 showed a near-linear relationship between laser Doppler readings and blood flow rate through extracted human and pig teeth. The most important factor in the reading of blood flow is the accurate, stable, and consistent placement of the probe. Pulpal blood flow readings vary with different positions on the tooth and the angulation of the probe, but Ramsay et al. 17 showed that the construction of a stabilizing splint ensured accurate and reproducible readings. The splint used in the present study allowed for the accurate repositioning of the probe against the surface of the tooth and gingiva. Although the stabilizer was used, other variables, such as patient movement during breathing and swallowing, are difficult to eliminate. Other variables were fluctuations in the pulpal and gingival blood flow, which were picked up by the laser Doppler. The artifact filter eliminated large spikes in readings resulting from sudden movements. The large variances in patient-topatient readings were also due to the differences in pulpal and gingival circulation and individual response to local anesthetics and epinephrine. Some subjects showed more profound reduction in blood flow than others. Each subject also has a different enamel thickness, which can alter the absolute laser Doppler readings. In conclusion, 2% lidocaine with 1:100,000 epinephrine significantly reduced both pulpal and gingival blood flow. The pulpal blood flow was reduced to a greater degree, wl~ich may have adverse effects on pulps under certain conditions. REFERENCES 1. Ingolfsson AR, Tronstad L, Hersh EV, Riva CE. Efficacy of laser Doppler flowmetry in determining pulp vitality of human teeth. Endod Dent Traumato11994;10: Watson ADM, Pitt Ford TR, McDonald E Blood flow changes in dental pulp during limited exercise measured by laser Doppler flowmetry. Int Endod J 1992;25: Ebihara A, Suda H. Pulpal blood flow assessed by laser Doppler flowmetry in a tooth with a horizontal root fracture. Oral Surg Oral Med Oral Pathol Oral Radiol Endod t996;81: Sisk AL. Vasoconstrictors in local anesthesia for dentistry. Anesth Prog 1993;39:

6 202 Ahn and Pogrel 5. Kim S, Edwall L, Trowbridge H, Chien S. Effect of local anesthetics on pulpal blood flow in dogs. J Dent Res 1984;63: Kim S, Liu M, Markowitz K, Bilotto G, Dorscher-Kim J. Comparison of pulpal blood flow in dog canine teeth determined by the laser Doppler and the 133xenon washout methods. Arch Oral Biol 1990;35: Kim S, Liu M, Markowitz K, Bilotto G, Dorscher-Kim J. Comparison of the effects of intraarterial and locally applied vasoactive agents on pulpal blood flow in dog canine teeth determined by laser Doppler velocimetry. Arch Oral Biol 1990;35: Odor TM, Pitt Ford TR, McDonald E Adrenaline in local anesthesia: the effect of concentration on dental pulpal circulation and anesthesia. Endod Dent Traumatol 1994; 10: Odor TM, Pitt Ford TR, McDonald E Effect of inferior alveolar nerve block anesthesia on the lower teeth. Endod Dent Traumatol 1994;10: Pitt Ford TR, Scare MA, McDonald E Action of adrenaline on the effect of dental local anaesthetic solutions. Endod Dent Tranmatol 1993;9: Wilder-Srrfith PEEB. A new method for the noninvasive measurement of pulpal blood flow. Int Endod J 1988;21: Hinrichs JE, Labelle LL, Aeppli D. An evaluation of laser ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY February 1998 Doppler readings obtained from human gingival sulci. J Periodontal 1995;66: Gazelius B, Olgart L, Edwall B, Edwall L. Noninvasive recording of blood flow in human dental pulpl Endod Dent Tranmatol 1986;2: Kim S. Regulation of pulpal blood flow. J Dent Res 1985;64(special issue): Pashley DH. The influence of dentin permeability and pulpal blood flow on pulpal solute concentrations. J Endodon 1979;5: Vongsavan N, Matthews B. Experiments on extracted teeth into the validity of using laser Doppler techniques for recording pulpal blood flow. Arch Oral Biol 1993;38: Ramsay S, Artun J, Martinen SS. Reliability of pulpal bloodflow measurements utilizing laser Doppler flowmetry. Dent Res 1991 ;70: Reprint requests: M. Anthony Pogrel, DDS, MD, FACS, FRCS Departmen( of Oral and Maxillofacial Surgery University of California, San Francisco 521 Parnassus Avenue, C-522 San Francisco, CA CALL FOR LETTERS TO THE EDITOR A separate and distinct space for Letters to the Editor was established by Larry J. Peterson, editor in chief of Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics in his Editorial in the January 1993 issue. Dr. Peterson also encouraged brief reports on interesting observations and new developments to be submitted to appear in this letters section as well as Letters commenting on earlier published articles. Please submit your letters and brief reports for inclusion in this section. Information for authors for the Journal appears in this issue of Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics. We look forward to hearing from you.