A clinical comparison of pain perception and extent of area anesthetized by Wand(®) and a traditional syringe.

BACKGROUND: In the contemporary dental practice, alleviation of pain is the most important factor to ameliorate patient's condition and to gain one's confidence towards the skills of the operator. Such confidence aids to the ultimate success of the treatment procedures. AIMS AND
OBJECTIVES: This study compares the pain response of a group of 10 subjects to the Wand(®) with the response to traditional syringe injections and also compares the extent of the area anesthetized.
MATERIALS AND METHODS: 10 subjects were selected for the study and 20 injections were given contralaterally to them, 10 with Wand(®), and rest with the traditional aspirating syringe. Each subject received 2 injections on the palate, Left side with Wand(®) (test) and Right side with Traditional syringe (control). All injections were given by the same investigator without the use of topical anesthetic spray/gel. Pain perception levels were recorded with a visual analogue scale. Also the extent of area anesthetized with a single palatal injection was assessed by probing.
RESULTS: The results showed injections with the syringe were more painful than injections with the Wand(®) in 2 of 10 subjects. Also the extent of the area anesthetized by both the techniques was similar except in 2 patients.
CONCLUSION: The Wand(®) results in less painful injections; however, mean ratings of pain for both the groups, were mostly below the annoying level of pain. Also, the areas covered by the anesthetic effect of both the injections were comparatively similar.

INTRODUCTION

Local anesthesia has allowed dentistry to become what it is today – enabling dentistry to be transformed from a mere trade to a highly regarded profession. For the success of any dental procedure, profoundness of anesthesia is of paramount importance. Painless anesthesia is critical for achieving confidence of the patient towards the operator from the inception of the treatment procedure. Administering the local anesthetic injection may not only provoke anxiety in patients, but also in the dentist.[1] Many dental patients experience fear and anxiety related to the pain from the injection of local anesthetics. Such pain could be the result of mechanical trauma of needle insertion into the site of injection, due to the the sudden distention of the tissues by the anesthetic agent or from a rapid discharge of contents of the syringe.[2]

The amount of anesthetic solution injected for particular procedure is another crucial factor. It is always advisable to administer the optimum amount of anesthetic for which the technique of administration is one of the governing factors.

A supraperiosteal injection in the mucobuccal fold is the most commonly utilized route of administration to achieve local anesthesia of maxillary teeth. This injection is referred to as an infiltration or field block and was first described by William Halsted in the late 1800s.[3] Anesthetic solution diffuses from the injection site, penetrating through the soft tissues, periosteum, and porous maxillary bone, and results in anesthesia of the radicular nerve fibers of the teeth in proximity to the injection site.[4]

Adequacy of the anesthesia depends upon multiple factors which include density and thickness of the bone in the area, access to the anatomy, type and dosage of the anesthetic employed, and the patient's subjective pain threshold and response to painful stimuli.[4]

MATERIALS AND METHODS

10 subjects, five males and five females, in the age range of 30–65 years were selected for the study. All the selected subjects had no past experience of intraoral injections. Medical history of each subject was reviewed. Subjects were familiarized with the procedures, evaluation forms, pain description scale (visual analogue scale) and an informed consent was obtained. The ethical committee approval was obtained from M. A. Rangoonwala College Ethical Committee for the study. All subjects were taken up for periodontal surgical treatment procedures immediately after the administration of the anesthesia to evaluate the profoundness and depth of the anesthesia. All the subjects served as their own controls. All the injections were given by the same operator who was skilled in the Wand® as well as the traditional technique. The Wand® injection was given on the left side of the palate and the traditional aspirating syringe injection on the right side of the palate. Thus, each subject was given two injections, one on each side of the palate. The Anterior Middle Superior Alveolar (AMSA) injection technique was performed for the study to determine the extent of anesthesia. AMSA is the clinical technique for anesthetizing the anterior and middle superior alveolar neurovascular bundles from a single, virtually imperceptible palatal injection. This new and highly predictable block injection simplifies the anesthesia of maxillary teeth and has a significant positive impact on clinical procedures and patient comfort.[5-7]

Wand®

The Wand® Local Anesthesia System is computer-controlled injection device, the size of a paperback book [Figure 1]. It accommodates a conventional local anesthetic cartridge that is linked by micro-tubing to a disposable, lightweight, pen like handle with a Luer lock needle attached [Figures 2 and 3]. The system is activated by a foot control that regulates the flow of the anesthetic at precise pressure and volume ratios, resulting in an effective and comfortable injection. This eliminates the variability of the thumb-operated plunger used in a traditional syringe. The computer control sustains a constant pressure and volume ratios of an anesthetic fluid regardless of variations in tissue resistance. This system has two flow speeds – slow flow and fast flow speed with adjustable flow rates.[8]

Figure 1

The Wand® Plus – computer controlled anesthesia system

Figure 2

Wand® hand piece with Luer Lock needle and tubing

Figure 3

30 gauge half inch Luer Lock needle

Anterior middle superior alveolar nerve block

The injection site is located at a point that bisects the maxillary first and second premolars and is midway between the crest of the free gingival margin and the midpalatine suture[4] [Figure 4]. The use of a 30-gauge extra-short needle is ideal for the administration of the anesthetic. To ensure the most comfortable and painless injection, Pre-Puncture technique of needle penetration is followed, which relies on the torque of the Wand® motor that can generate a high fluid pressure at low volume. The needle is oriented at a 45° angle with the bevel facing the palatal tissue. The needle is secured in place by a sterile cotton tip applicator on the back of the bevel. This is followed by activation of the Wand® unit on slow flow rate for 6-8 seconds to force anesthetic solution into the tissue. The excess amount of anesthetic is absorbed by the cotton tip applicator. The needle is then penetrated with a simultaneous bi-axial rotation for around 2-3 seconds, moving 1-2 mm, followed by a brief pause for 3-4 seconds.[5] The same procedure of needle advancement was repeated until the palatal bone is reached. Once the bone is reached, axial rotation is stopped; however, the slow flow rate of the anesthetic is maintained until the desired amount of anesthetic is administered. The flow is now stopped and the needle is retracted slowly. Cotton tip applicator was used to catch drips as the needle was withdrawn. The ability of the computer – assisted device to deliver anesthetic at a high pressure, but a slow rate of volume flow, is the core technology of the system. The core technology is the precision fluid metering of the flow rate, limiting the pressure, regardless of variations in tissue resistance.[9] This results in a controlled, highly effective and comfortable injection even in resilient tissues such as the palate and periodontal ligament.[10] In this study, the anesthetic used was same for both the injection systems – Lidocaine hydrochloride 2% with 1:100000 Adrenaline (1.7 ml cartridge – Septanest®). For the traditional injection system, a 30 gauge, one inch short needle was used. The amount of anesthesia administered was also same for both the techniques, that is, 0.9 ml.

Figure 4

Site of Wand® injection

In five subjects, the Wand® injection on the left side of the palate was given first followed by the traditional one on the other side. In the other subjects, the Traditional ones were given first on the right side of the palate. Two minute interval was given between each injection in all the subjects to note the Visual Analogue Scale (VAS) [Figure 5], and for patients to rinse their mouth. Immediately following the injection, VAS was marked on the 100 mm VAS strip. Also the area anesthetized was assessed by probing the the palatal mucosa, interdental areas and the buccal mucosa of the ipsilateral teeth with the William's Graduated probe. Same procedure was repeated to check the area anesthetized after 10 minutes for both the injections. The results were then subjected to the statistical analysis using GraphPad InStat[11] software. Paired t-test, Fisher's Exact test and percentage value were analyzed.

Figure 5

Visual analogue scale used in this study. It is a 10 cm long scale where 0 is No pain and 10 is agonizing pain

RESULTS

The study evaluated and compared the results of the Wand® and traditional syringe injections. Only one of the control group subjects showed that the Wand® was more painful then the traditional injection system. Rest of all showed that Wand® was comparatively same or less painful then the traditional one Tables 1 and 2. Only one subject from the test group and two subjects from the control group gave the VAS responses above the annoying level of pain, whereas rest reported VAS below or at the annoying level of pain [Table 1, Figure 6]. The mean shows that the overall pain response for both the techniques was below the annoying level of VAS [Figure 7]. On evaluation of the extent of the area anesthetized immediately after the injections, 100% of the subjects in the Test Group showed complete palatal anesthesia [Figure 8], whereas 80% of the subjects in the Control Group showed the same extent of palatal anesthesia [Figure 9].

Table 1

Recording of the visual analogue scale following injections

Table 2

Comparison of pain response for the test and the control groups in different regions of the maxilla

Figure 6

Graphical representation of the [Table 1]. X-axis shows the number of subjects and Y-axis shows the readings on the visual analogue scale. On the VAS: 0 – No pain, 2 – Annoying pain, 4 – Uncomfortable pain, 6 – Dreadful pain, 8 – Horrible pain, 10 – Agonizing pain

Figure 7

Mean values of visual analogue scale readings in graphical manner for test and control groups where both the groups show the average response below the annoying level of pain

Figure 8

Extent of the effect of anesthesia given by Wand®

Figure 9

Extent of the effect of anesthesia given by traditional syringe

When re-examined after 10 minutes, 100% of the subjects in Test Group as well as Control Group showed the complete ipsilateral palatal anesthesia [Figures 10 and 11]. After 10 minutes, 40% of the test group subjects and 20% of the control group subjects showed the anesthetized marginal gingiva on the buccal aspect extending from ipsilateral central incisor to the 1st molar teeth [Figures 12 and 13]. 40% of the patients complained of discomfort during periodontal surgical treatment procedure on the right side of the palate where the anesthesia was given with the traditional technique, and required additional amount of anesthesia to alleviate the pain. Overall, 68% of the patients had pain, whereas only 32% patients experienced no pain on injection irrespective of the technique utilized [Table 3]. The two-tailed P value for the pain assessment was 0.4961, which was not considered to be significant [Table 4]. Different sites with the pain response immediately and 10 minutes after injections for both the groups were also analyzed [Table 2]. Based on which the Fisher's Exact Test, the – two-sided P value [Table 3] was 0.5796, which was not statistically significant.

Figure 10

Extent of the effect of anesthesia given by Wand® after 10 minutes

Figure 11

Extent of the effect of anesthesia given by traditional syringe after 10 minutes

Figure 12

Extent of the effect of anesthesia given by Wand® on the buccal aspect – marginal gingiva from mesial of the ipsilateral central incisor tooth to the distal of the first molar tooth

Figure 13

Extent of the effect of anesthesia given by traditional syringe on the buccal aspect – marginal gingiva from mesial of the ipsilateral central incisor tooth to the distal of the first molar tooth

Table 3

Data analyzed based on Table 2 for Fisher's exact test

Table 4

Summary of data

DISCUSSION

The challenge for clinicians is to provide an environment that allows technically complex dental treatments. This starts with the injection of local anesthesia being delivered without inflicting adverse psychological impact or physical harm to the patient.[8] Numerous modifications have been done in the local anesthesia techniques through the years to reduce the perception of pain. For example, reduction in the gauge of the needle reduces pain. More recently, a computerized anesthetic system known as Wand® has been developed as a possible solution to reduce the pain related to the local anesthetic injection[12] and to provide more profound anesthesia.

Krochak et al. in their study on 80 adult patients reported that the levels of anxiety were significantly decreased in patients when the Wand system was used. Another conclusion was that there was an optimal flow rate of anesthetic solution at which the perception of pain during an injection was minimized.[13] Liberman et al. in their study found that the Wand was the most comfortable method, and it was a good tool for building positive dentist-patient relationships.[14] Wand® is believed to be superior to the syringe because it can provide slow injections that are regulated more precisely by a computer than the hand pressure of a conventional syringe. The overall result of this study did not show a significant difference between pain perception following conventional injection and the Wand® system, which is also in the favor of studies done by Asarch et al.,[15] Fodi et al.,[16] and Koyuturk et al.[17] Gibson et al. also stated that a palatal injection given with the Wand was comparable to a traditional buccal injection and was not found to produce any significant benefit over a traditional buccal injection.[18] Ram and Peretz reached the same conclusion by comparing the Wand and the conventional technique in an intraligamentary manner by giving intraligamental injections.[8] The difference between our findings and the others may be attributed to the fact that the previous studies did not compare the Wand and the conventional technique in the intraligamentary manner following the AMSA injection. In the present study, Wand was compared with the conventional syringe subjectively in the intraligamentary manner following AMSA injection. The previous studies assessed the pain perception by subjecting the patient to electric pulp testing[19] following AMSA injection. Intraligamentary method was used in this study as periodontal surgical procedures were planned for these patients.

Palatal injections are generally the most painful injections.[6] Recent studies suggest that needle penetration in the palate does not differ between conventional and computerized syringe systems, but that the discomfort produced by deposition of solution varies among syringe types.[2] The discomfort also depends upon the speed of delivery.[20] Meechan et al. stated that discomfort of needle penetration varies in different parts of the palate, and penetrations in the anterior palate are more uncomfortable as compared to the others.[2]

Topical anesthetic is the most widely used method to reduce pain associated with dental injections. Most patients are accustomed to topical agent being applied before injections; they can taste the anesthetic agent and can feel the effect of the agent on their soft tissue. Topical anesthetic can increase the subjective anesthetic effect, and can serve to reduce the anticipatory anxiety associated with dental injections.[21] Kincheloe et al.,[22] found that using topical anesthetic or informing the patient of the effects of topical anesthetic had no effect on the amount of pain the patient perceived. They also found that the patients with high expectations of pain significantly perceived a dental injection as being more painful than did the patients with low expectations. To eliminate the effect of subjective response to pain after application of topical anesthetic, the latter was not used in our study.

Meechan et al. concluded in their study that the use of the same needle for a second needle penetration at a different location produces more discomfort than the use of a fresh needle.[2] The advantage of AMSA injection technique is the elimination of multiple needle penetrations as it has wider distribution of the anesthesia. This is fulfilled by the porous nature of the maxillary bone. Slow and constant diffusion with constant pressure pushes the anesthetic against the resistance and results in wider distribution. If the conventional anesthetic injections are are also given in a manner of slow and constant flow with nearly constant pressure, they can also give comparable results. In the current study following AMSA injection, we observed palatal blanching extending anteriorly to the incisive papilla and posteriorly to include the soft palate. The palatal blanching did not cross the midpalatine raphe which is in accordance with Lee's[19] work.

The pain perception of all the subjects to both the injection systems was below the annoying levels of pain except for two subjects, one in the traditional technique group and one in the Wand® group because of the higher apprehension level. The reduced pain perception towards Wand® anesthetic injection technique is due to the larger gauge needle and Pre-puncture technique where anesthetic solution precedes the needle making an anesthetic pathway for the needle. Such results can be achieved with the traditional anesthetic system by slow and gradual advancement of the needle with constant diffusion of the anesthetic solution.

The reason for wider distribution of the effect of anesthesia immediately following the injection is slower and gradual diffusion of the anesthetic solution and a highly porous maxillary bone. The results of this study were not in accordance with the results of the study conducted by Hochman et al., who found that the Wand® injection was 2 to 3 times less painful than the normal injection.[10]

CONCLUSION

The time-honored mindset for any injection is pain and local anesthetic injections are bestowed upon by the same credence. Such factualness has resulted in many researches to part the word pain from the word injection. One of the fruit of such researches is the development of the Wand® system of anesthesia. In this study, we compared the Wand® system with the traditional injection system for pain during administration of local anesthesia and profoundness of anesthesia. We did not find significant difference between the two techniques. However, further studies are required to substantiate the results of this study.