Pain perception following computer-controlled versus conventional dental anesthesia: randomized controlled trial

Since the first described use of local anesthesia (LA) in 1884, the goal of pain-free or pain-reduced treatment in dentistry has been achievable [1]. Several treatment procedures in clinical dentistry and oral and maxillofacial surgery are associated with pain, for which the adjuvant of LA is essential in terms of pain reduction [2]. In the USA, about 300 million cartridges of LA have been applied annually [3, 4]; in Germany, an estimated 70 million carpels are used annually [5], and in Australia, this figure is about 11 million [6]. Dentists often give more than 1,500 cartridges of LA every year to their patients [7]. This magnitude demonstrates LA relevance in the fields of dentistry and oral and maxillofacial surgery [8].

The administration of LA in dental practice requires an injection which is the leading cause of patients’ fear and anxiety [9]. The failure to provide adequate pain management can be a significant source of worry for dental practitioners [10]. Continuous developments at the pharmacological level, e.g., active substances, and the technical level, e.g., the application form, should enable optimisation of the sufficient LA use [4, 11]. The associated adverse effects such as injection pain, the latency of effects onset after injection, risks associated with accidental intravascular injection require further research for improvement [11]. Therefore, dental students -as future dentists- need to be well-trained to administer efficient and safe dental LA. Additionally, dental anesthesia educational courses should include all modern local anesthesia equipment in order to provide up-to-date dental education and improve the dental students’ LA training skills [12, 13]. This includes also the pre-anesthesia approach by using topical anesthetic on the needle insertion site, which has been proven to reduce the needle insertion pain in inferior alveolar nerve block [14].

One aspect of this advancement is the launch of a computer-controlled local anesthetic injector Calaject^®, (Rønvig Dental MFG, Daugaard, Denmark), designed to reduce the pain of performing local anesthesia [15]. The principle of this device is based on the fact that the less pressure and flow of a local anesthetic injection, the less painful the procedure will be [16]. Each device has an installed pressure sensor as well as a three-button display that allows you to choose the most appropriate program in terms of different speeds and pressure. According to the anesthesia technique, the manufacture recommends program I for intraligamentary and palatinally injections, program II for infiltration, and III for alveolar nerve block techniques. Conventional carpules and needles can be used in a pen-shaped part connecting to the main unit. The anesthetic administration can be achieved using a foot control pedal adapted to the main unit. The speed of injection is related to acoustic signals [17].

Evaluating the effectiveness of the computer-controlled local anesthesia (CCLA) compared to the conventional methods in a clinical trial setting is essential and required in the literature [18, 19]. Dental students as the test and operator group and an experienced dentist as an additional operator can give a better understanding of whether the dentist’s experience plays a role in terms of pain perception and demographic and medical risk factors [20]. To the best of the authors’ knowledge, this is the first trial that used this setting with two operator’s “students” and “dentist”. As we apply the CCLA and conventual LA in the dental education (student-to-student) and correlate the result with applying the two methods by an experienced dentist. Additionally, we consider two types of pain in this study: the first at the puncture site and the second during the application.

Pain perception may vary between male and female [21, 22], smoker and non-smoker [23, 24] ,and healthy and diseased patients [25]. Several studies reported a correlation between dental anxiety and pain perception in different dental treatments [26‐28]. An evaluation of pain perception by applying LA in both CCLA and conventional form would help develop a gender/ patients-specific LA administration technique.

Dental phobia is one of the main barriers which make patients avoid routine check-ups and early treatments [39]. Indeed, patients seek to avoid pain caused by dental procedures [40] For pain prevention or reduction, profound dental anesthesia is required. Nevertheless, LA is also related to pain sensation due to the injection and application, which makes this problem unsolvable [41]. Consequently, many new devices and techniques were developed to minimise pain during the application of local dental anesthesia [42]. CCLA is one of these attempts and many commercially available instruments [43, 44]. This study aimed to evaluate and compare the pain sensation resulting from using conventional and CCLA.

The study sample included a majority of females (68.3%), medically-free (90%) and non-smokers. These results are associated with the study subject selection as they are all dental students. Dental students as a study subject to test two different LA methods offers several advantages. Participants’ homogeneity, better evaluation of the pain sensation and giving the future dentists the opportunity to have their own experience with the two LA methods are among other the most essential reasons for choosing the study group. The investigation in the study included regarding the operator two groups, the “students” group in which dental students performed all anesthesia to dental students as a part of the local anesthesia course [45] and the “dentist” where an experienced oral surgeon was the operator.

On evaluating the ease of handling, 54% of the participating students rated the conventional syringe as easier, while 41.9% preferred the computer-controlled and 12.9% rated both equally. It is also worth mentioning that each subject found the signal tone of the computer-assisted Calaject^® system disturbing during treatment. This disturbance caused a further increase in the stress level of some subjects and thus presumably a subjective increase in the perception of pain. Therefore, it is advised to reduce the signal tone on the volume button to a minimum.

Pain perception on puncture was assessed in both groups. We used in all interventions the same needle (Transcodent^® painless needle) which was proved to produce less pain than the regular needle tips [46]. The difference between the injections administered by the students and the experienced dentist was statistically significant (Sig. = 0.016) with a trend towards lesser pain experienced after the dentist-administered injections. The student group performed the LA technique for the first time on their peers [47] whereas the dentist had performed numerous LA shots throughout his 15 years of practice. This may clarify the differences between the two groups.

Similarly, the infiltration technique was significantly associated (Sig. = 0.014) with less pain than the nerve block technique. This result is in accordance with findings reported that infiltrations were less painful than inferiors alveolar nerve block technique [48, 49]. Additionally, pain perception on puncture between computer-controlled and conventional injections was not statistically significant (Sig. = 0.285). This seems to be a logical result as the same needle was used in both techniques. A similar result was reported by Flisfisch et al. by testing computer assistant LA versus conventional one; there was no difference in the mean sensation of mucosal puncture [50].

Pain perception during the injection was evaluated in both groups and techniques. The student-administered injections (2.49 ± 2.26) and nerve block injections (2.92 ± 2.65) had significantly higher VAS scores than the dentist-administered injections (1.63 ± 1.97) and infiltration injections (1.78 ± 1.89), respectively. Also, here the operator’s experience seems to play an essential role in the pain reduction during the injection [19].

The difference in pain sensation during the injection between the computer-controlled (1.65 ± 1.93) and conventional injections (2.49 ± 2.31) was less painful for the computer-controlled method and statistically significant (Sig. = 0.029). Computer-controlled devices, which control the administered anesthetic rate to the soft tissues are used to lessen discomfort during local anesthesia for dental procedures [51]. Several studies with similar study designs conclude pain reduction with using a computer-assisted device [50, 52, 53]. Although, both operators of the study (dentist and students) were trained to administrate the LA very slowly, the computer-controlled devices still applied slower and less painful injections [43]. This notion underscores the importance of keeping a consistently slow administration the LA to reduce the pain perception [42, 54, 55].

On the other hand, dental practice requires both clinically-effective and time-efficient treatments; therefore, injections with higher speed are more likely to be used [56]. In this case it is recommended to use computer-controlled devices [57]. One advantage of using the CCLA system is the self-aspiration function. The device performs this automatically before the start of the injection. This significantly reduces the risk of accidental intravascular injection. Intra-arterial injection of the LA includes vasoconstrictor, which can lead to severe complications such as permanent blindness [58], cardiovascular and central nervous system toxicity [59, 60]. In the hectic of the everyday professional life a forgotten aspiration can cause a severe complication which is unlikely to occur if a computer-controlled LA device is used.

In the study sample, female students had a significantly higher DAS score compared to their male counterparts. Several studies investigating dental anxiety levels across the gender groups came to the same conclusion [61‐63]; however, other studies reported no significant differences between the gender [64, 65]. The high anxiety level of females might be due to the gender-specific socialization patterns related to pain beliefs, expectations, and subsequent behaviors [66, 67]. Unlike previous studies, DAS was not significantly different between student-administered versus dentist-administered injections (Sig. = 0.454), infiltration versus nerve bloc injections (Sig. = 0.669), or computer-controlled versus conventional injections (Sig. = 1.000). These findings should be interpreted with caution, as DAS may not have been an appropriate tool for this type of clinical trials [68].

CCLA is less painful when applying the injection than the conventional syringe, even though the two methods’ pain perception on puncture was not significantly different. Sex, chronic illnesses, medications, and smoking were not predictors of pain perception. Clinical experience seems to help in reduction of pain perception. Therefore, the dentist-administered injections were less painful compared to the student-administered injections.