Introduction
Dental phobia is highly pervasive. Some 80% of adults reported being apprehensive about dental treatment and up to 5% avoid dental treatment altogether (Getka and Glass, Reference Getka and Glass1992), thereby meeting criteria of a diagnosis of specific phobia. Dental phobia has an early onset at a mean age of 12 years (Öst, Reference Öst1987) but can occur throughout the life-time. Additional to the discomfort engendered by the phobia, avoidance of dental treatment imposes a considerable health risk (Mostofsky, Forgione and Giddon, Reference Mostofsky, Forgione and Giddon2006). A dental examination revealed the presence of eight to nine decaying teeth in dental phobia patients (Thom, Sartory and Jöhren, Reference Thom, Sartory and Jöhren2000) compared with one or two teeth that require treatment in the general population at any one time.
There are discrepant findings with regard to the mode of acquisition of dental phobia, with some studies finding a conditioning origin and others failing to do so. In an epidemiological study of unselected adults, few reported negative dental experiences that, moreover, were only moderately related to subsequent dental fear (Armfield, Reference Armfield2010). Similarly, in unselected children, type and number of dental treatments could not be shown to be clearly associated with dental fear (Ten Berge, Veerkamp and Hoogstraten, Reference Ten Berge, Veerkamp and Hoogstraten2002). In contrast, Öst (Reference Öst1991) reported a conditioning onset in some 50% of patients with blood and injury phobia, a partly related disorder. In our own study of 272 dental phobia patients, 79.4% remembered a distinct event after which they started to avoid dental treatment. The majority of these patients experienced strong pain and others loss of control or a combination of the two during dental treatment (Sartory and Wannemüller, Reference Sartory and Wannemüller2010).
A number of treatment studies attest to the effectiveness of cognitive behavioural techniques in dental phobia. A meta-analysis of 38 randomized controlled studies resulted in an ES of 1.8 regarding the reduction of subjectively reported dental fear (Kvale, Berggren and Milgrom, Reference Kvale, Breggren and Milgrom2004). There are fewer long-term investigations of the treatment effect. However, on average, 77% of treated dental phobics still attended regular dental check-ups within 4 years following psychological treatment. The results show that cognitive-behavioural treatment is highly successful but also that not all of the patients benefit from treatment. One of the reasons for the failure of treatment could be the difference in environmental cues between exposure during psychological treatment and the subsequent dental treatment situation. Recently, there have been attempts to reformulate processes occurring during fear extinction.
According to Rescorla (Reference Rescorla, Mowrer and Klein2001) and Bouton et al. (Bouton, Woods, Moody, Sunsay and García-Gutiérrez, Reference Bouton, Woods, Moody, Sunsay, García-Gutiérrez, Craske, Hermans, Vansteenwegen, Craske, Hermans and Vansteenwegen2006) the extinction process consists not of unlearning or the destruction of the originally learned response but of the instalment of a new neuronal network that has an inhibiting or suppressing effect on the former. There are a number of learning phenomena supporting the assumption of an unrelated extinction network such as spontaneous recovery, renewal, i.e. the return of the originally learned response with a change of context following extinction (Bouton, Reference Bouton2004), or reinstatement, i.e. the return of an extinguished reaction after renewed exposure to the unconditioned stimulus. Similar to findings in animal research, conditioning studies in humans also found a renewal effect upon presentation of an acquisition retrieval cue (Vansteenwegen et al., Reference Vansteenwegen, Vervliet, Hermans, Beckers, Baeyens and Eelen2006). In the clinical context, reinstatement is a well-known cause of relapse in substance related disorders (e.g. McFarland and Kalivas, Reference McFarland and Kalivas2001). In turn, cues retrieving the extinction context could reverse this process.
Findings from animal research indicate that the presentation of cues associated with extinction could attenuate the recovery of a conditioned response (Brooks and Bouton, Reference Brooks and Bouton1993). Similar results were reported in human conditioning experiments (Vansteenwegen et al., Reference Vansteenwegen, Vervliet, Hermans, Beckers, Baeyens and Eelen2006; Dibbets, Havermans and Arntz, Reference Dibbets, Havermans and Arntz2008). The memory enhancing effect of the mental retrieval of environmental cues of the learning context has been investigated some time ago. Studies on learning of word lists showed that recall is superior if conducted in the same context in which learning has taken place (Smith, Reference Smith, Davies and Thomson1988). However, the original context can also be recalled mentally in a different environment. Smith (Reference Smith1979) instructed participants to recall the original learning environment prior to recall of a list of words in a different environment and found their recall performance to be enhanced. Similar studies have confirmed that environmental-context dependent memory, tested by cued and free recall, is enhanced when participants are asked to recall the original learning context while being confronted with a novel test context (e.g. Frerk, Holcombe, Johnson and Nelson, Reference Frerk, Holcombe, Johnson and Nelson1985).
There are first indications that similar processes might occur during emotional learning. Mystowski, Craske, Echiverri and Labus (Reference Mystkowski, Craske, Echiverri and Labus2006) reported a beneficial effect in spider-fearful individuals by mental retrieval of the extinction context during a follow-up test. (The authors employed the term “reinstatement”, which has, however, been previously defined as the re-emergence of a conditioned response, e.g. a craving response, which is why the term “retrieval” is used here in preference). Before retest participants were instructed to mentally retrieve the exposure treatment context whereas the control condition consisted of recalling neutral memories. The cognitive strategy of mental retrieval of the treatment context had a fear-reducing effect. Mental retrieval could therefore become a useful tool among therapeutic techniques of exposure treatment. Studies so far have been carried out on animals or analogue participants who were either conditioned or fearful student samples. In order to assess whether retrieval of extinction or rather of the treatment context could serve as a therapeutic tool, the present study was carried out in individuals with a diagnosed specific dental phobia. Additionally, to assess the benefit in clinical use, patients received a full session of exposure treatment as in the Mystkowski et al. (Reference Mystkowski, Craske, Echiverri and Labus2006) study instead of an experimentally standardized and limited extinction procedure.
One-session treatment has been found to be considerably effective, with long-lasting benefits in individuals with spider phobia (Öst, Reference Öst1989). Single exposure sessions were similarly successful in dental phobia patients (Thom et al., Reference Thom, Sartory and Jöhren2000) with 73% of them continuing to observe dental appointments over the following 6 months (Schmid-Leuz, Elsesser, Lohrmann, Jöhren and Sartory, Reference Schmid-Leuz, Elsesser, Lohrmann, Jöhren and Sartory2007). In an attempt to investigate factors predictive of adherence to dental appointments, Sartory, Heinen, Pundt and Jöhren (Reference Sartory, Heinen, Pundt and Jöhren2006) found that a high desire for control coupled with low perceived control over dental treatment as assessed by the Iowa Dental Control Index (Logan, Baron, Keeley, Law and Stein, Reference Logan, Baron, Keeley, Law and Stein1991) was a significant predictor of avoidance of dental appointments. Other cognitive factors such as dysfunctional cognitions or degree of self-efficacy in dealing with problems and, in particular, with health problems may conceivably also have an effect on adherence. Perceived ability to control symptoms has previously been found to be related to dental anxiety (Kent and Gibbons, Reference Kent and Gibbons1987).
In the present study, dental phobia patients were given exposure treatment in the psychology unit with a follow-up test being carried out a week later prior to dental treatment. Half the participants were instructed to mentally retrieve the context of the exposure treatment and the other half was asked to recall a neutral memory. We expected to find fear reduction due to the retrieval of the treatment context. Additionally, we aimed to replicate the result of desire for control as partly determining adherence to dental treatment and to explore further contributory factors.
Method
Participants
A total of 72 dental phobic patients (42 women and 30 men) with a mean age of 36 years (SD = 10.9; range 19 to 62) were included in the study. They were consecutive referrals from the Dental Clinic of the Augusta Hospital in Bochum. Patients were included in the study if they met DSM-IV criteria of specific (dental) phobia, required invasive dental treatment (extraction or filling), took no anxiolytic medication or medication affecting the cardiovascular system and took part in the complete programme of three sessions. Additional 14 patients failed the latter criterion (one failed to take part in therapy and 13 in the follow-up). Data of another 8 patients were excluded because of equipment malfunction. Those participating had avoided dental treatment for a mean of 9.7 years (SD = 8.1; range 1 to 38 years). An average of nine of their teeth required treatment. Single or multiple comorbid disorders were diagnosed in 25 participants (9 specific phobia, 9 social phobia, 4 panic disorder with or without agoraphobia, 2 OCD, 2 major depression, 3 previous substance related disorder, 2 generalized anxiety disorder and one each of hypochondriasis and bipolar disorder). All patients gave their informed consent before taking part in the study. The study was approved by the Ethics Committee of the University of Wuppertal.
Design
Patients were allocated randomly to two groups (mental retrieval of treatment context vs. recall of everyday activities). Randomization was carried out according to an odd/even procedure, with the first patient being allocated to the retrieval group, the second to the control group, and so on. Both groups were treated with one exposure session. A week later, at the follow-up (FU) preceding dental treatment, half the participants were instructed to mentally retrieve the treatment session (mental retrieval) and the other half were instructed to think about everyday activities such as getting up and having breakfast (control memory).
Patients were given questionnaires to complete during the week before and at FU. Also, before and after treatment and again after the retrieval instruction at FU, patients underwent a laboratory procedure during which they were shown three dental instruments (dental probe, forceps, drill) while heart rate (HR), avoidance in terms of latency in picking them up, and SUD were recorded.
Screening and clinical assessment
The study was carried out at the Dental Clinic of the Augusta Hospital, Bochum and the Department of Psychology at the University of Wuppertal. Upon entering the Dental Clinic, patients were routinely asked whether they were afraid of dental treatment. In case of an affirmative answer they were asked to complete the Hierarchical Anxiety Questionnaire (HAF; Jöhren, Reference Jöhren1999). This self-rating questionnaire consists of 11 hierarchically ordered situations that dental phobics typically fear. Patients are asked to indicate how much anxiety they would experience in each of them on a scale from 1 to 5. Scores can range from 11 to 55 and 35 is considered the cut-off score for dental phobia (Jöhren and Sartory, Reference Jöhren and Sartory2002). An internal consistency index of Cronbach's α = .80 has been reported (Sartory et al., Reference Sartory, Heinen, Pundt and Jöhren2006). Patients with a score >35 were referred to the clinical psychologist. Data regarding the number of decayed, missing and filled teeth (DMFT- Index) were provided by an initial dental examination (on the basis of 28 teeth).
A clinical psychologist assessed the patients with a structured interview (Diagnostisches Interview bei psychischen Störungen [DIPS]; Schneider and Margraf, Reference Schneider and Margraf2006, the German adaptation of the Anxiety Disorders Interview Schedule for DSM-IV (ADIS-IV), Brown, Di Nardo and Barlow, Reference Brown, Di Nardo and Barlow1994) to confirm DSM-IV criteria of a specific dental phobia and determine comorbid disorders. The DIPS has a good test-retest reliability (r = .64 - .89) and inter-rater reliability (kappa r = .80 – 1.00; Schneider and Margraf, Reference Schneider and Margraf2006). Additionally, an exploration was carried out as to the individual bodily symptoms, thoughts and type of situations that the patient has experienced.
Questionnaires
Dental Anxiety Scale (DAS; Corah, Reference Corah1969; German version translated by the authors). This self-rating questionnaire is the most frequently used instrument in dental anxiety research and consists of four items relating to dental treatment. Patients are asked to rate how anxious they would be if they had to submit to these situations the following day. Scores range from 4 to 20. Corah, Gale and Illig (Reference Corah, Gale and Illig1978) reported a mean score of 9.07 in 2,103 non-selected participants, with women having a significantly higher score (M = 9.53) than men (M = 8.56). Dental phobic patients had a mean score of 17.20 (SD = 1.80). A score of 15 is considered the cut-off for dental phobia (Corah et al., Reference Corah, Gale and Illig1978). An internal consistency index of Cronbach's α = .64 has been reported for the German version (Sartory et al., Reference Sartory, Heinen, Pundt and Jöhren2006).
Dental Cognitions Questionnaire (DCQ; De Jongh, Muris, Schoenmakers and Ter Horst, 1995; German version translated by the authors). This self-rating questionnaire consists of 38 negative cognitions (beliefs and self-statements) related to dental treatment. Fourteen items concern negative beliefs pertaining to dentistry in general (e.g. “Dentists don't care. . .”) and to the patients themselves (e.g. “I can't stand pain”); the remaining 24 items contain negative self-statements (e.g. “Everything is going wrong”). Patients are asked to indicate whether these negative beliefs occur to them during dental treatment resulting in the frequency score of negative cognitions (DCQ: range = 0–38). Individuals with dental phobia were found to have a significantly higher number of negative cognitions than non-phobic controls (De Jongh et al., Reference De Jongh, Muris, Schoenmakers and Ter Horst1995). Data of a previous study yielded a Cronbach's α = .90 (Sartory et al., Reference Sartory, Heinen, Pundt and Jöhren2006).
Revised Iowa Dental Control Index (IDCI; Brunsman, Logan, Patil and Baron, Reference Brunsman, Logan, Patil and Baron2003; German version translated by the authors). This self-rating questionnaire consists of nine items, five of which concern the desire for control (e.g. “To what degree would you like control over what will happen to you in the dental chair?”) (Cronbach's α > .78–.79) and the other four concern perceived control during dental treatment (e.g. “How much do you think you can control what will happen to you while in the dental chair?”) (Cronbach's α > .75–.80). Items are rated from 1 (none) to 5 (totally) and summed. Dental patients with a high desire for control coupled with a low feeling of control reported high levels of dental distress compared to low scorers (Logan et al., Reference Logan, Baron, Keeley, Law and Stein1991).
State-Trait Anxiety Inventory (STAI X1, X2; German version by Laux, Glanzmann, Schaffner and Spielberger, Reference Laux, Glanzmann, Schaffner and Spielberger1981). Both scales contain 20 items describing emotional states. Participants are asked to indicate the degree to which a given statement applies to them at present (state) and during the last two weeks (trait version). Scores range from 20 (no anxiety) to 80 (high anxiety). An internal consistency score of Cronbach's α >.90 was reported (Laux et al., Reference Laux, Glanzmann, Schaffner and Spielberger1981).
Beck Depression Inventory (BDI). The German version by Hautzinger, Bailer, Worall and Keller (Reference Hautzinger, Bailer, Worall and Keller1994) was used. This 21-item inventory indexes depression intensity with a score range of 0–63. A score between 11 and 17 is considered indicative of mild depressive symptoms, and a score of 18 or above is indicative of severe depression. Internal consistency scores have been reported to exceed Cronbach's α >.74 in healthy subjects and .92 in depressed patients (Hautzinger et al., Reference Hautzinger, Bailer, Worall and Keller1994).
Aachen Self Efficacy Questionnaire (ASF; Wälte, Ebe, Brandenburg and Kröger, Reference Wälte, Ebe, Brandenburg, Kröger, Kröger and Petzold1999). This self-rating questionnaire consists of 20 items detailing a variety of problem situations and a successful way of dealing with them. Participants are asked to indicate from 1 to 5 whether the behaviour applies to them. The total score can range from 20 to 100. A study of 650 attendants of a clinic for psychosomatic disorders found the internal consistency to be high (Cronbach's α = .90). A factor analysis allocated the items to four subscales, one of which concerns self-efficacy in terms of health (e.g. “I can deal with health problems”) which was analyzed separately.
Treatment
Patients were first shown a video film that had been produced professionally by a local television crew. It showed a number of scenes from the perspective of a patient going to have dental treatment, i.e. being in the area in front of the practice and entering it, being seen by the receptionist, sitting in the waiting room, entering the treatment room, sitting in the dental chair and seeing the instruments. Finally, a dentist appears with a face mask, handles the instruments and moves them towards the viewer's face. The film lasted for 12 min and was projected by a beamer (NEC MultiSync MT 830+, Tokyo, Japan) onto a screen with a picture size of 100 × 75 cm and participants viewing at a distance of 1.6 m. Having seen the video film, participants were instructed to visualize the scenes as vividly as possible with themselves in place of the patient. During that time a clinical psychologist described the scenes, together with anxious thoughts and bodily fear reactions that the patient had reported during the initial interview. Patients were asked repeatedly as to the extent of their fear between 0 and 100 regarding the imagined scenes. Over time, imagery was progressively directed toward scenes that were particularly anxiety-provoking. Treatment duration was 90 min.
Laboratory procedure
Participants were shown three dental instruments in randomized order (dental probe, forceps and the hand piece of a slow drill). They were placed in the drawers of a small chest and presented consecutively. At first, each drawer was opened for 20 s and patients were instructed to look at the instrument while heart-rate was recorded (HR). Afterwards, the instruments were shown again and patients were instructed to hold them for 10 s. Time until picking up the instrument was recorded (avoidance). If patients failed to pick up an instrument within 10 s, the experimenter proceeded to the next one. After each instrument display, patients were asked to give a fear rating from 0 to 100 (subjective units of discomfort, SUD).
Heart-rate (HR)
The electro-cardiogram was recorded using chest electrodes with a BIOPAC amplifier system (med-NATIC, Germany). The sampling rate was 1000 Hz. R-waves were detected online and interbeat intervals converted with one RR-interval delay into HR in beats per minute (bpm). Resting HR was determined as mean HR of the last of a 3-min rest period before stimuli were administered. Mean HR reaction to the instruments was calculated over 10 s after onset of stimuli and baseline-corrected taking 1s before stimulus onset into account. Respiration was recorded with a respiratory belt that was placed around the chest. Recordings were inspected and employed for artefact control in regard to the HR analysis.
Procedure
After the initial screening and dental examination at the Dental Clinic, patients were given the psychological assessment and questionnaires there a week later. Those meeting DSM-IV criteria for specific dental phobia were invited to take part in the study. Treatment was carried out a week later at the Department of Clinical Psychology of Wuppertal University where they were shown the video with exposure in imagery. Before (pre) and after (post) treatment, participants underwent the laboratory procedure. The follow-up assessment (FU) was carried out back at the Dental Clinic where participants were asked to complete the questionnaires again. Afterwards, they were seated in a dental chair awaiting dental treatment. They were instructed to either mentally retrieve the treatment session or remember activities they had carried out since getting up earlier that day. Afterwards they received the laboratory procedure again (FU) and went into dental treatment. All dental treatments involved invasive procedures, i.e. an extraction or a filling.
Data reduction and analysis
Only participants who took part in all three sessions (assessment, treatment and follow-up) were included in the study. Missing data were replaced by the group mean of the measure at that measurement occasion. ANOVAs were carried out comparing the retrieval and control group with regard to demographic and dental health data as well as questionnaire scores before and after exposure. Similarly, patients with and without comorbid disorder were compared in regard to questionnaire scores. Laboratory measures were then submitted to MANOVA comparing groups, instruments and measurement occasions. Furthermore, patients adhering to the dental appointment after FU (N = 58) were compared with those not adhering (N = 13) with regard to the questionnaire data before and after exposure by means of T-tests (in consideration of the large difference in group sizes). Finally, relations between questionnaire and laboratory data were explored. In order to reduce data sets, a principal component analysis (PCA) was carried out on the questionnaire scores and laboratory data averaged over instruments. The PCA resulted in three components: a general anxiety factor (23.6 % of the variance) with loadings of BDI, STAI trait and ASF (self-efficacy); a dental phobia factor (23.6 %) with loadings of DAS, HAF, DCQ and STAI state; and finally, a perceived control factor (13.6 %). The factor scores were then correlated with the averaged laboratory data.
Results
There were no significant group differences with regard to demographic or dental health variables between the retrieval and the control group (Table 1). There were, however, more patients with comorbid disorders in the retrieval (N = 18) than the control group (N = 7) (χ2 = 5.0, p < .03). There were no significant group differences (neither between retrieval and control nor between patients with and without comorbid disorders) with regard to the number of patients undergoing dental treatment after the psychological intervention. Overall, 81.7% of the patients proceeded with dental treatment; the remaining ones left after completing the testing procedure at FU.
Group means and SDs of demographic and dental health data
Notes: DAS – Dental Anxiety Scale; DMF-T – decayed, missing, filled teeth)
Questionnaires
There were no significant differences between the retrieval and control group with regard to the questionnaire measures at either occasion and data were therefore pooled across groups. Means and SDs are shown in Table 2, together with F-ratios comparing measures before and after exposure treatment. There were significant pre - post measurement effects in regard to all questionnaires apart from ASF health (self-efficacy). All phobia and anxiety/depression-related scores decreased highly significantly from before to after treatment, with IDCI (desired control) decreasing only moderately (Table 2). The comparison of patients with (N = 25) and without (N = 47) comorbid disorders yielded significantly elevated scores in the former with regard to trait anxiety and depression (both p < .01). There was no significant group × measurement occasion effect.
Group means and SDs of questionnaire data before and after exposure treatment (total sample)
Notes: HAF – Hierarchical Anxiety Questionnaire; DAS – Dental Anxiety Scale; DCQ – Dental Cognitions Questionnaire; ICDI – Iowa Dental Control Index; STAI – State-Trait Anxiety Inventory; BDI – Beck Depression Inventory; ASF – Aachen Self Efficacy Questionnaire)
Laboratory measures. Pre, post and FU measurements of SUDs, HR reaction and avoidance of the two retrieval conditions were entered into ANOVA.
Subjective Units of Discomfort (SUDs). SUDs regarding the dental instruments were subjected to MANOVA with a 2 × 3 × 3 (retrieval × instrument × measurement) design. SUDs differed significantly with regard to instruments (F(2,136) = 13.08, p < .001, η2 = .16), measurement (F(2,136) = 39.3, p < .001, η2 = .37) and instruments × measurement (F(4,272) = 5.04, p < .001, η2 = .07). Post-hoc analyses showed that SUDs of the drill were significantly higher than those of the dental probe (p < .01) with SUDs of the forceps in-between (Figure 1). ANOVA of individual instruments yielded significant measurement effects. In case of the dental probe, SUDs decreased significantly from before to after treatment and again at follow-up (all ps < .01). In case of both forceps and drill, SUDs decreased significantly from before to after treatment (all ps < .01) and were stable to FU.
Group means and standard errors of subjective units of discomfort (SUD) while patients were exposed to dental instruments before and after the exposure treatment session (pre, post) and at follow-up a week later while sitting in the dental chair prior to dental treatment. The data represent the total sample
Avoidance test. Patients who failed to pick up the instrument within 10 s were given a set avoidance time of 10. Of the 72 patients, 56 picked up all instruments before exposure treatment and 62 picked them up afterwards and at FU, respectively. There were no significant group differences. Avoidance time was submitted to MANOVA with a 2 × 3 × 3 (retrieval × instrument × measurement) design. There was a significant measurement effect (F(2,136) = 16.59, p < .001, η2 = .20) and a significant retrieval × instrument × measurement effect (F(1,68) = 4.46, p < .04, η2 = .06). Post-hoc tests revealed a significantly greater avoidance time with regard to the forceps in the control than the retrieval group at follow-up (p < .04; Figure 2). As to the other instruments, there were no significant group differences but significant measurement effects with a decrease from before to after exposure treatment (all ps < .01) and no further significant decrease to FU (Table 3).
Group means and SDs of avoidance(s) of dental instruments pre and post exposure treatment and at FU (follow-up)
Group means and standard errors of time to pick up the forceps after exposure treatment and during follow-up a week later as a function of retrieval of exposure vs. control memory
Heart-rate. Resting HR was submitted to ANOVA with a 2 × 3 (retrieval × measurement) design. There was a significant measurement effect (F(2,67) = 40.58, p < .001, η2 = .55). Resting HR decreased from before to after treatment (p<.01) and increased again during follow-up (p < .01) when it was higher than before treatment (p<.02) (Pre: 77.4 bpm (11.5), post: 72.4 bpm (10.7), FU: 79.9 bpm (11.5).
HR reaction to instruments was submitted to MANOVA with a 2 × 3 × 3 (retrieval × instrument × measurement) design. There was only a significant measurement effect (F(2,67) = 7.0, p < .01, η2 = .17) indicating that HR reactions decreased over measurements (Pre: .93 bpm (SE = .31), post: −.31, (SE = .32), FU: −.50, (SE = .25)).
Adherence
Patients undergoing the dental treatment session after FU (N = 58) were compared with those not adhering (N = 13) in regard to questionnaire measures completed before the exposure session. Groups differed significantly with regard to number of dysfunctional Dental Cognitions (t (df = 69) = 2.01, p < .05; adherence: 18.4 (6.7), non-adherence: 22.3 (4.3); Figure 3) and Desire for Control (t(df = 69) = 2.24, p < .03; adherence: 20.46 (2.7), non-adherence: 22.38 (3.1)). A group comparison of questionnaire data after exposure revealed significant group differences with regard to the two former variables but also to the Dental Anxiety Scale (t(df = 69) = 3.68, p < .01; adherence: 13.3 (3.1), non-adherence: 16.8 (2.6). Accordingly, patients not undergoing dental treatment after FU showed initially and after exposure more dysfunctional dental cognitions and desired greater control over dental procedures than patients undergoing dental treatment. The former also maintained a higher fear level after exposure.
Group means and standard errors of the Dental Cognitions Questionnaire before and after exposure treatment. The total sample was divided into patients subsequently undergoing vs. not undergoing the dental treatment session
Relations between measures
In order to elucidate the data structure, correlational analyses were carried out between the initial questionnaires and the pre-exposure laboratory data. Both data sets were reduced, the questionnaire data by principal component analysis and the laboratory data were averaged across instruments (see Data reduction and analysis). The dental phobia factor was significantly correlated with mean avoidance (r(df = 71) = .26; p < .03) and mean SUD (r(df = 71) = .25; p < .04) and the two laboratory measures were also significantly intercorrelated (r(df = 71) = 39; p < .01). Furthermore, perceived control was significantly and inversely correlated with SUD (r(df = 71) = −.30; p < .01) indicating that the less perceived control over dental treatment the greater the fear of the dental instruments.
Discussion
The one-session exposure treatment of dental phobia was considerably successful in terms of the subsequent attendance of the dental treatment session. Having avoided dental treatment for an average of over 9 years, some 80% of the psychologically treated patients submitted to it. Questionnaire data indicated a significant exposure treatment effect but, at the same time, patients were still markedly fearful. Similarly, mental retrieval of the treatment had only a moderate effect. Patients who were asked to mentally retrieve the treatment picked up one of the three dental instruments, namely, the forceps, faster than patients who were asked to remember morning activities. Retrieval had no significant effect on undergoing the dental treatment session. Instead, an initially inflated number of dysfunctional cognitions and desire for control over dental treatment was predictive of later non-adherence. These patients also benefited less from exposure as indicated by their higher phobic severity after exposure.
The effect of mental retrieval of exposure was only evident in the behavioural domain in the present study whereas it was manifest with regard to self-report in the study in highly spider-fearful participants by Mystkowski et al. (Reference Mystkowski, Craske, Echiverri and Labus2006). A major difference between the two studies is that in the present study the follow-up took place with the threat of impending dental treatment, whereas Mystkowski et al.'s participants had been exposed to the highest fear item during their past treatment. The marked increase in resting HR while participants were seated in the dental chair supports the conclusion that patients were highly anxious during FU in the present study. As dental treatment is invariably the aim of psychological treatment of dental phobia, participants cannot be spared its impending threat. It is worth considering whether retrieval should take place after the first dental treatment session when it may be effective as a prophylactic means against relapse.
Cognitive factors have so far not been shown to have an extant role in the treatment of spider phobia. The present study was carried out in dental phobia patients in whom dysfunctional cognitions are thought to play a role in maintaining the disorder. One of the reasons is conceivably the age of onset, which is later in dental than spider phobia, at an age when cognitive factors are presumably of greater importance. De Jongh et al. (Reference De Jongh, Muris, Schoenmakers and Ter Horst1995) compiled the Dental Cognitions Questionnaire (DCQ), a list of dysfunctional cognitions dental phobia patients admit to having. The authors grouped cognitions into those relating to beliefs about the lack of competence or care in dentists (e.g. “Dentists don't care”) and the state of the patient's teeth (e.g. “I should be ashamed of my teeth”). The questionnaire is correlated with extent of phobic anxiety (Schmid-Leuz et al., Reference Schmid-Leuz, Elsesser, Lohrmann, Jöhren and Sartory2007) and the present results indicate that an inflated number of dysfunctional cognitions contribute to non-adherence to dental appointments. Interestingly, the DCQ was not related to non-adherence in an untreated sample of dental phobia patients (Sartory et al., Reference Sartory, Heinen, Pundt and Jöhren2006). However, non-adherence was also more pervasive in the previous study than after the present single-session exposure treatment. It is conceivable that patients with marked dysfunctional cognitions need more treatment sessions or else that these cognitions need to be addressed during treatment.
Another cognitive factor contributing to non-adherence in the present study was desire for control over dental treatment procedures as assessed by the Iowa Dental Control Index (IDCI; Logan et al., Reference Logan, Baron, Keeley, Law and Stein1991). A similar finding has been reported previously (Sartory et al., Reference Sartory, Heinen, Pundt and Jöhren2006). As in the previous study, the IDCI was not correlated with severity of dental phobia as was reported by Logan et al. (Reference Logan, Baron, Keeley, Law and Stein1991). However, their sample was not selected for dental phobia as was the case in the present study. The desire for control in the dental setting was also not correlated with other measures of self-efficacy or locus of control (Sartory et al., Reference Sartory, Heinen, Pundt and Jöhren2006). Rather than being a personality trait, the ICDI desire for control appears to be specific to dental anxiety. Instrumental control was previously found to have an anxiety-relieving effect in phobia (Sartory and Daum, Reference Sartory and Daum1992). It is conceivable that patients desiring more control experienced its anxiety-relieving effect or, rather, the fear-inducing effect of its lack during the lengthy course of their phobic history. With regard to the clinical management of dental phobia, the results suggest that patients should be given more control over treatment procedures.
A high proportion of dental phobia patients have comorbid disorders. In the present study a third of the patients suffered from a variety of other anxiety disorders, of depression and even, in one case, of bipolar disorder. These patients indicated higher levels of anxiety and depression in the questionnaire measures. However, exposure treatment was just as effective in this subgroup in regard to undergoing the subsequent dental treatment session. It is one of the limitations of this study that the effect of psychological treatment could not be evaluated for separate comorbid disorders as the sample size of the subgroups was too small.
Summarizing, the results provide only moderate indication that mental retrieval of exposure treatment could constitute an additional therapeutic tool, at least, not when patients are faced with the threat of a highly fear-inducing event. Additionally, cognitive factors such as desire for control over dental treatment procedures and dysfunctional cognitions appear to have a maintaining effect on dental phobia and need to be taken into account during both psychological and dental treatment. Among the limitations of the present study is the failure to include the data of patients who failed to complete the experiment in an “intention-to-treat” analysis.
Acknowledgments
This study was supported by the Deutsche Forschungsgemeinschaft (SA 735/16-1). We thank all participants for their help with the study. We are grateful for the help in data collection and analysis by S. Dette, K. Haag, N. Liebrecht, N. Splittgerber, K. Walla, D. Wünneberg and L. Münsterkötter.
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