Use of Pre-Injection Diffusion of Local Anaesthetic as a Means of Reducing Needle Penetration Discomfort

Abstract

Aim

To determine if pre-injection diffusion of local anaesthetic solution influences the discomfort of needle penetration in the palate.

Methods

A placebo-controlled, randomised, double-blind split-mouth investigation was conducted. 25 healthy adult volunteers were recruited and each received two needle penetrations in a random order during one visit. The penetration sites were 1 cm from the gingival margin of the first maxillary premolars on each side of the mouth. 30 gauge-13 mm needles which were attached to syringes that contained either 2% lidocaine with 0.125mg/ml epinephrine or physiological saline were used. For each penetration an operator encouraged a drop of solution to appear at the end of the needle and placed this drop with the bevel of the needle flat on the palate for 20 seconds. The discomfort was noted on a 100 mm visual analogue scale with end points marked “No pain” and “Unbearable pain”.

Results

There was no significant difference in penetration discomfort between solutions, (mean VAS = 26.80±19.36mm for lidocaine and 26.20±18.39mm for saline) however the 2nd penetration was significantly more uncomfortable than the first (mean VAS = 31.00±19.84 mm and 22.00±16.65 mm respectively).

Conclusion

Pre-injection diffusion of local anaesthetic solution did not influence the discomfort of needle penetration in the palate.

Introduction

Anxiety is a barrier to dental attendance (1). The most anxiety-provoking procedure for both children and adults is the local anaesthetic (LA) injection (2-7). However, the most common and efficient method of pain-anxiety control in dentistry is the local anaesthetic injection which also offers patients comfort and co-operation, and also better performance by the practitioner (8-11).

In order to provide optimal dental care it is important to deliver an LA that is pain free and does not give rise to patient anxiety. Previous studies have examined variables that might be involved in painful LA injections and tested possible ways of minimizing the discomfort perceived at the time of injection. Variables included tissue distensibility, speed of injection, age, personality, previous experience and patient characteristics (7, 12, 13). A variety of techniques have been used to overcome injection discomfort, including the use of topical anaesthetic gel, patches, electronic anaesthesia prior to injection (14-16), or electronic computerized devices which offer controlled injection speed regardless of tissue density such as the Wand^®(later rebranded as CompuDent^®, Milestone Scientific, Livingston, NJ, USA (6-9, 17-21). Furthermore, some techniques have been suggested and evaluated to ease the discomfort of intra-oral injections, which have required a prolonged injection time, warmed-up anaesthetic solution (22-24), the possible significance of the needle gauge and the sharpness of the bevel (25-30). None of these techniques by themselves have been able to completely manage the pain connected with injections nor do the papers describing them address the question of the most significant variable(s) and technique(s) in pain perception. However, currently it is reported that following a two-minute topical anaesthetic application, slow and low-pressure injections are the key to pain free and comfortable delivery of local anaesthetic and named as “Pain free local anaesthesia technique”. (31)

Thus, the significant, influential factor(s) in pain perception has not yet been clearly addressed. The present study, aims to determine if the pre-injection diffusion of local anaesthetic solution influences the discomfort of needle penetration in the palate.

Material and Methods

The study protocol was in agreement with the guidelines of the Helsinki Declaration as revised in 1975 and approved by the Ethical Committee of Yeditepe University. Written consent was obtained from all participants after explaining the objectives of the present study.

Participants

Twenty five healthy adult volunteers aged 20 (12 F, 13 M) were recruited and each received two needle penetrations in a random order during one visit. Exclusion criteria included: under 18 years of age, pregnancy, inability to provide written informed consent, allergy to amide local anaesthetic solutions, bleeding disorders and neurological disturbances.

Injection Sites and Injection of LA Solution

A placebo-controlled, randomised, double-blind split-mouth investigation was conducted. A pediatric dentist (OOK: Ozgur Onder Kuscu) gave the injections according to the previously defined injection sites formulated randomly by a computer programme (Table 1). The penetration sites were one centimetre from the gingival margin of the maxillary first premolars on each side of the mouth which is standardized to reach the apex of the tooth (Figure 1). 30 gauge-13 mm needles which were attached to traditional plastic injectors (Hayat Tıbbi Aletler^®, Istanbul, Turkey) that contained either 2% lidocaine with 0.125mg/ml epinephrine (Jetokain^®, I.E.Ulugay, Istanbul, Turkey) or physiological saline were used (Figure 2). For each penetration the same operator who was blinded to the solution in the syringe encouraged a drop of solution to appear at the end of the needle and placed this drop with the bevel of the needle flat on the palate for 20 seconds (Figure 3). In the study method, the contact time of the solution (saline or Lidocaine) can be verified, since we cannot be sure if this 20 seconds of contact time would happen in clinical practice. After that, the needle was gently advanced perpendicularly to the tissue until the bone was contacted (Figure 4).

Table 1. Injection site table used for random allocation of the subjects.

Reg.no	Name	1. Penetration Right buccal	2. Penetration Left buccal
1		Lidocaine	Saline
2		Lidocaine	Saline
3		Saline	Lidocaine
4		Lidocaine	Saline
5		Lidocaine	Saline
6		Lidocaine	Saline
7		Saline	Lidocaine
8		Lidocaine	Saline
9		Saline	Lidocaine
10		Lidocaine	Saline
11		Saline	Lidocaine
12		Saline	Lidocaine
13		Lidocaine	Saline
14		Saline	Lidocaine
15		Lidocaine	Saline
16		Saline	Lidocaine
17		Lidocaine	Saline
18		Saline	Lidocaine
19		Saline	Lidocaine
20		Lidocaine	Saline
21		Saline	Lidocaine
22		Lidocaine	Saline
23		Saline	Lidocaine
24		Saline	Lidocaine
25		Saline	Lidocaine

Figure 1.

Each volunteer received two needle penetrations using 30 gauge-13 mm needles in a random order during one visit

Figure 2.

The needle and the analgesic solution used

Figure 3.

A drop of solution, at the bevel of the needle was positioned flat on the palate for 20 seconds

Figure 4.

The route of the needle

Assessment of pain and anxiety

The discomfort of each penetration was noted on a 100 mm visual analogue scale (VAS) with end points marked “No pain” and “Unbearable pain” (Figure 5). At the end of the first and second injection, the subjects were asked to point out the VAS pain score.

Figure 5.

Visual Analogue Scale (VAS) used for determining the perceived pain.

Statistical Analysis

The data were processed with the GraphPad Prisma V.3 programme using Paired t test. A p-value less than 0.05 was considered statistically significant.

Results

There was no significant difference in penetration discomfort between the test and control solutions (mean VAS = 26.80±19.36mm for lidocaine and 26.20±18.39mm for saline)(p > 0.05). Regarding penetration comfort, however, the second penetration was significantly more uncomfortable than the first (mean VAS = 22.00±16.65 mm and 31.00±19.84 mm respectively, t = 2.89; p = 0.008) (Table 2).

Table 2. Pain perception and related mean VAS (Visual Analog Scale) pain scores ± S.D.

	Lidocaine	Saline	1. penetration	2. penetration
mean VAS pain scores ± S.D median	26.80±19.36mm 20	26.20±18.39mm 20	22.00±16.65 mm* 10	31.00±19.84 mm* 30

Paired t test * p = 0.008

Discussion

An aspect of dental treatment that produces anxiety in patients is local anaesthesia (32). The delivery of LA injections also produces anxiety among dentists. Simon et al. (33) recorded that 19% of dentists in their study reported that the administration of local anaesthesia caused them distress; 6% considered this problem was serious. Only 2% of the respondents in that study reported no negative reaction to the administration of local anaesthesia.

Today, patient comfort and co-operation, a pain free treatment, and better performance of the dental practitioner can be achieved by proper administration of dental injections. Within this perspective, every practitioner should strive to master delivering relatively painless injections (18) and a new generation of dentists should be educated properly (34). A number of factors may influence injection pain during the administration of dental LA. Controlling pre-injection diffusion of LA as a means of reducing needle penetration discomfort might be helpful in eliminating related confounding factors.

The critical part in dental injections is at the beginning when the target tissue is first punctured by the needle and a few drops of solution are injected slowly, without any pressure; then the analgesia spreads in the tissue which permits a relatively faster injection. A recent study showed that topical anaesthetic reduced the pain of needle insertion if left on the palatal mucosa for 2, 5, or 10 minutes, but had no clinical benefit for the actual anaesthetic injection (35). Recently it was concluded that higher gauge needles such as 27 and 30 are sometimes used in the belief that they cause less discomfort of intraoral needle penetrations (1). Studies carried out on the subject all point to the fact that needle gauge did not affect pain upon insertion (26, 27). In the present study, pre-injection diffusion of LA itself did not affect pain. However, the second application of pre-injection was significantly more uncomfortable than the first.

The present study used the VAS, which is the most commonly used pain-measuring tool. The studies by Revill (36) and McCormack (37) found the VAS to be a reproducible method for measuring pain. Seymour (38), in a clinical trial on postoperative dental pain, found the VAS to be more sensitive than other pain scales and one that could discriminate between small changes in pain intensity. Most of the subjects in the study were comfortable in its use after receiving instructions and did not need any further directions.

The present study is the first study to show that there is no benefit in keeping LA while pre-injecting as a topical anaesthetic to reduce the pain of needle insertion. In conclusion, pre-injection diffusion of local anaesthetic solution did not influence the discomfort of needle penetration in the palate.