Dental caries remains a serious problem in children, affecting 37.9% of five-year olds in England and 27.9% of two- to five-year olds in the United States of America (NHANES 2004; Davies 2013). If untreated, caries may lead to pain, infection, malnutrition and disturbed growth (Acs 1999; Low 1999). Social and financial consequences may include days off school or work, referral to specialised care and general anaesthetic resulting in increased costs (Thikkurissy 2010). Surgical approaches and new preventive strategies have been developed and widely researched (Innes 2007; Kandiah 2010). Once dentinal caries is established, restorative or surgical treatment is needed, traditionally requiring local anaesthetic.
Description of the condition
Dental anxiety is a well-known barrier to treatment, commonly developing during childhood or adolescence (Locker 1999). Early onset of dental anxiety may have significant consequences, being associated with behavioural problems that may lead to increased pain perception and interference with the treatment provided (Klingberg 1995; Ayer 2005; van Wijk 2008). Ultimately, children's dental anxiety may lead to avoidance of treatment and irregular attendance in adulthood (Skaret 2003).
The aetiology of dental anxiety is multifactorial. Children's cognitive abilities, parental anxiety and previous negative dental or medical experiences seem to play a crucial role in the development of dental anxiety (Townend 2000; Versloot 2008). Invasive procedures, injections and drilling in particular, appear to be the most anxiety-inducing treatments in children (Majstorovic 2004).
Dental injection phobia is a subtype of blood-injury-injection phobia. Milgrom considers general fear of injections, including pain and fear of injury, to be the main aspects of dental injection fear (Milgrom 1997). In children, needle phobia was found to be significant, with a prevalence of 19% in four- to six-year olds. Fear of needles seems to decrease with age, possibly due to cognitive maturation or development of coping behaviours (Majstorovic 2004). Nevertheless, a prevalence of 11% for 10- to 11-year olds and for 18-year olds, show the significant importance of fear of intraoral injections (Majstorovic 2004; Vika 2008). Furthermore, authors have found a strong relationship between blood-injury-injection phobia and dental anxiety (Vika 2008). Additionally, dental anxiety and pain of injection seem to be strongly correlated, with highly anxious patients reporting increased pain perception and duration (van Wijk 2008). Weisman showed that inadequate analgesia for invasive medical procedures in young children may reduce the effect of appropriate analgesia in the future (Weisman 1998). Similarly, it appears that previous experiences with dental injections may lead to behavioural problems in subsequent treatment sessions (Versloot 2008).
Delivery of pain-free dentistry is crucial for reducing fear and anxiety, facilitating delivery of treatment, developing a trusting dentist/patient relationship and accepting future treatment. Delivery of local anaesthetic is a vital part of this, however it remains one of the most challenging aspects of paediatric dentistry.
Description of the intervention
Delivery of high quality dentistry to children is closely linked to a non-threatening approach and pain-free treatment. A number of behaviour management techniques have been proposed and are consistently applied during treatment, in order to achieve successful outcomes (Campbell 2011; Ashley 2012; Lourenço-Matharu 2012). Delivery and acceptance of dental local anaesthetic is one of the most trying aspects of treatment. In order to facilitate this, several specific techniques and materials have been developed and researched. This review will focus on interventions specifically used for delivery of local anaesthetic. The use of other behaviour management techniques is implied during all steps of dental treatment. Although these may indirectly influence acceptance of local anaesthetics, they will not be discussed.
Meechan described three factors that influence discomfort during delivery of local anaesthetic: factors related to the patient, equipment factors and aspects that are under control of the dentist (Meechan 2009). The two latter will be the focus of this review.
1. Patient factors
As previously discussed, dental anxiety seems to have a multifactorial aetiology, being closely related to child psychological factors (ten Berge 1999). The level of generalised anxiety and psychological function seem to be determinant factors in children's dental anxiety (Versloot 2008; Krikken 2010). This may, in turn, influence children's acceptance to dental treatment, including delivery of local anaesthetic.
2. Equipment factors
The use of visual or auditory technology has been suggested as a distraction technique in order to reduce anxiety and pain perception during delivery of dental treatment (including local anaesthetic) for children.
Baghdadi 2000; Aitken 2002; Marwah 2005 and Prabhakar 2007 studied the effect of music distraction on anxiety, pain or behaviour for children undergoing dental treatment with local anaesthetic. Similarly, the use of videos either prior or during treatment (including audiovisual glasses) has been studied as a possible distraction technique by Melamed 1975; Ingersoll 1984; Ram 2010; Aminabadi 2012; El-Sharkawi 2012 and Hoge 2012. These were used independently or in conjunction with pharmacological behaviour management techniques.
Although topical anaesthetic is commonly used, controversy remains on its efficacy in reducing pain of dental injections in children (Meechan 1994; Tulga 1999; Kreider 2001; Primosch 2001; Nayak 2006; Paschos 2006; Berg 2007; Bågesund 2008; Deepika 2012). Similarly, Aminabadi 2009a studied the effect of pre-cooling the injection site, followed by topical anaesthetic, for delivery of local anaesthetic. The gauge or length of the needle (Brownbill 1987; Ram 2007) and the temperature of the cartridge (Ram 2002) have equally been investigated for their influence on pain perception and anxiety of children during delivery of local anaesthetic.
In recent years, several electronic delivery devices for local anaesthetic have been developed, that promote distraction by vibration, needleless injections or transcutaneous electrical nerve stimulation.
The influence of electronic devices for infiltration or intraligamental anaesthesia on children's anxiety and pain has been investigated by a number of authors (Wilson 1999; Baghdadi 2000; Palm 2004; Oztaş 2005; Versloot 2005; Ram 2006; Kuscu 2008; Versloot 2008; Tahmassebi 2009; Hembrecht 2013; Nieuwenhuizen 2013). Sixou 2008 studied treatment success rates following local anaesthetic with an electronic device for intraosseous local anaesthetic. In 2009, the same author assessed children's pain perception using the same device (Sixou 2009). Roeber evaluated the effects of using a vibrating attachment to the syringe for local anaesthetic in children (Roeber 2011). Arapostathis compared acceptance, preference and efficacy of a needleless injection device when compared to conventional syringes in children (Arapostathis 2010). Similarly, transcutaneous nerve stimulation was studied as an alternative to conventional local anaesthetic in children (Harvey 1995; Oztaş 1997; Munshi 2000).
3. Dentist factors
3.1 Non-pharmacological interventions
Non-pharmacological interventions have been suggested in order to increase acceptance of local anaesthetic. These methods may include verbal distraction by the dentist, the use of non-threatening words (or 'childrenese') to describe dental injections (Fayle 1997), imagery suggestion, systematic desensitisation or counter stimulation during local anaesthetic.
A number of case reports and review articles have focused on systematic desensitisation for dental treatment in children. Although several randomised controlled trials have been undertaken in adults, there is a paucity of these studies in children (Levitt 2000). A distraction technique involving repeated breathing and blowing out air was studied as an alternative distraction for children receiving dental local anaesthetic (Peretz 1999). The same author studied the benefits of imagery suggestion during delivery of local anaesthetic for children's dental treatment. This technique involves selection of a pleasant image in which the child is asked to concentrate during treatment (Peretz 2000). Aminabadi studied the influence of counter stimulation and distraction on pain perception of children during delivery of local anaesthetic (Aminabadi 2008).
Hypnosis has been used and researched for delivery of treatment and local anaesthetic (Al-Harasi 2010; Huet 2011). Viewing/hiding the needle prior to injection has also been subject of research (Maragakis 2006). Several authors found that the time taken to deliver local anaesthetic has an influence on injection pain (Jones 1995; Maragakis 1996). Similarly, the site of injection may influence pain perception and anxiety, hence certain authors suggesting adoption of treatment sequences that contemplate these parameters (Aminabadi 2009b).
3.2 Pharmacological interventions
Ultimately, pharmacological techniques such as inhalation, oral, intranasal or intravenous sedation have been widely used as adjuvants to delivery and acceptance of local anaesthetic. A recent Cochrane systematic review investigated the efficacy of conscious sedation for paediatric dental treatment (Lourenço-Matharu 2012). The authors found weak and very weak evidence supporting the effectiveness of oral midazolam and nitrous oxide, respectively.
In general terms, interventions were considered successful when treatment was completed or anxiety and pain reduced in comparison to control groups. These interventions are aimed at increasing acceptance of local anaesthetic, often with completion of the proposed dental treatment as an end result. In other studies, authors undertook assessments of children's pain and anxiety by using physiological assessment questionnaires or interviews, anxiety scales and behavioural assessment (Peretz 2000; Sixou 2009).
How the intervention might work
Provision of pain and anxiety-free local anaesthetic is of utmost importance. A number of interventions to help children cope with delivery of local anaesthetic have been discussed in the literature.
A common aim of interventions is to reduce pain and anxiety during injection. Equipment factors may work differently in order to achieve this goal: music and audiovisual technologies aim to redirect the child's attention away from the procedure. Furthermore, it has been suggested that music provides comfort and induces relaxation at a neurological level (Bradt 2013). The use of topical anaesthetic, the influence of the gauge of the needle, site (order) of injection and time taken to deliver local anaesthetic are all factors that have implications on pain perception during injection (Meechan 2009). One may argue that an additional benefit of topical anaesthetic may be reassurance of using an anaesthetic agent prior to injection. The use of electronic devices, similarly, may influence pain perception during delivery of local anaesthetic. These devices may also benefit from a different appearance to traditional syringes, possibly increasing children's acceptance (Kuscu 2008). Clinician's factors as counter stimulation, breathing techniques or imagery suggestion may act as distraction methods. The two latter also aim to induce relaxation (Peretz 2000). Similarly, systematic desensitisation will promote a relaxed state, while exposing children to fear-inducing stimuli (Levitt 2000). Finally hypnosis will very similarly work by redirecting children's attention away from the procedure while influencing their feelings, perception and behaviour (Al-Harasi 2010).
Short-term benefits of successful interventions include delivery of local anaesthetic and completion of dental treatment. This would occur at current or subsequent appointments or both, ultimately leading to restoration of oral health. The long-term benefit may involve reduction of dental anxiety, leading to acceptance of future treatment and development of positive attitudes towards oral health.
Why it is important to do this review
Local anaesthetic is still required for a number of procedures in paediatric dentistry. There is, however, no consensus on what is the best intervention to increase its acceptance.
Several authors looked at interventions for increasing children's acceptance to invasive medical treatment. One Cochrane systematic review looked at psychological interventions for needle-related procedural pain and distress in children and adolescents. This review focused on cognitive techniques, behavioural interventions and combined (cognitive-behavioural) interventions. The authors concluded that psychological interventions, especially distraction, hypnosis and combined cognitive-behavioural interventions, can be successful (Uman 2013). Similarly, another Cochrane review looking at interventions to assist induction of anaesthesia in children, studied psychological interventions, environmental interventions, equipment modification, social interventions and anaesthetic communication. The authors concluded that acupuncture, clown doctors, hypnosis, low sensory stimulation and hand held video games are likely to be helpful in reducing anxiety and improving cooperation (Yip 2009).
A number of studies and reviews have researched the effect of interventions to reduce pre-operative anxiety in adults. Bradt looked at music interventions and concluded that listening to music may have a beneficial effect on pre-operative anxiety (Bradt 2013). Adult studies interestingly include alternative therapies as acupuncture for reducing anxiety prior to dental treatment (Michalek-Sauberer 2012). This technique has been researched in children for reduction of gag reflex during impressions for orthodontic treatment, however, the authors are not aware of any published studies on its use for increasing acceptance of local anaesthetic (Sari 2010).
To our knowledge, there are no comprehensive systematic reviews on interventions to facilitate delivery of dental local anaesthetic in children. Although certain interventions have shown to be successful, controversy remains regarding a number of techniques, leading to confusion and empiric application in clinical settings.
Reviewing the available evidence will further our understanding of existing techniques, as well as determine whether further research on this topic is warranted.