Symptom provocation in dental anxiety using cross-phobic video stimulation

Cerebral activation caused by dental sounds: a functional magnetic resonance imaging study

Dental drilling sounds can induce anxiety in some patients. This study aimed to use functional magnetic resonance imaging (fMRI) to assess the relationship between dental fear and auditory stimuli. Thirty-four right-handed individuals (21 women and 13 men; average age, 31.2 years) were selected. The level of dental fear was assessed using the dental fear survey (DFS). Based on a threshold DFS score > 52, participants were categorized into two groups: dental fear (DF) group (n = 12) and control group (n = 22). Two types of stimuli were presented in a single session: dental and neutral sounds. Cerebral activation during the presentation of these sounds was evaluated using contrast-enhanced blood oxygenation level-dependent fMRI. In the DF group, dental sounds induced significantly stronger activation in the left inferior frontal gyrus and left caudate nucleus (one-sample t test, P < 0.001). In contrast, in the control group, significantly stronger activation was observed in the bilateral Heschl's gyri and left middle frontal gyrus (one-sample t test, P < 0.001). Additionally, a two-sample t test revealed that dental sounds induced a significantly stronger activation in the left caudate nucleus in the DF group than in the control group (P < 0.005). These findings suggest that the cerebral activation pattern in individuals with DF differs from that in controls. Increased activation of subcortical regions may be associated with sound memory during dental treatment.

Impact of maternal and child dental anxiety on oral health-related quality of life of 5-6-year-old preschool children

BACKGROUND

There is a lack of evidence with regards to the association between both maternal and child dental anxiety and the mother's perception of her child's oral health-related quality of life (COHRQoL). The aim of this study was to investigate the association of maternal and child dental anxiety with COHRQoL and the effect of demographic factors as moderators in this relationship. In addition, the association between child's dental caries experience and the COHRQoL was also assessed.

METHODS

A cross-sectional study was conducted involving 1150, 5-6 year-old preschool children in Selangor, Malaysia. Mothers answered a questionnaire on socio-economic status, the Malay-Modified Dental Anxiety Scale to assess maternal dental anxiety, and the Malay-Early Childhood Oral Health Impact Scale to assess COHRQoL. Child's dental anxiety was assessed using the Malay-Modified Child Dental Anxiety Scale via a face-to-face interview prior to oral examination to assess dental caries. Data were analysed using structural equation modelling to assess the relationship between maternal and child dental anxiety and COHRQoL.

RESULTS

Overall, complete data on 842 mother-child dyads were analysed. The mean scores of total ECOHIS, the child impacts section (CIS), and the family impacts section (FIS) were 17.7 (SD = 4.9), 12.6 (SD = 3.7), and 5.1 (SD = 1.9), respectively. The mean dental anxiety scores for mothers and children were 11.8 (SD = 4.5) and 16.9 (SD = 4.3), respectively. Maternal dental anxiety was associated with the CIS (b = 0.08, p < 0.001), the FIS (b = 0.01, p = 0.001), and the total ECOHIS (b = 0.14, p < 0.001). Maternal education level, income, urban/rural location, and kindergarten type were moderators to the relationship. In addition, there was also a significant relationship between child's dental caries experience and COHRQoL (p < 0.001).

CONCLUSIONS

Maternal dental anxiety and child's dental caries experience have significantly impacted the COHRQoL, the CIS, and the FIS domains. Demographic factors such as maternal education, income, urban/rural location, and kindergarten type acted as moderators that can strengthen or weaken the relationship between maternal dental anxiety and COHRQoL of 5-6-year-old preschool children.

Verification of the Korean Version of the Dental Fear Survey

Background

Although studies on dental fear in relation to sex and age have been conducted, there have been few nationwide studies particularly on the youth sector. In addition, no validity and reliability verifications have been implemented for new research groups on the Korean version of the Dental Fear Survey (K-DFS). Therefore, this study aimed to apply the K-DFS developed in a previous study on Korean youth to draw conclusions on dental fear among the youth.

Methods

This study used the K-DFS, a Korean translation of Kleinknecht's Dental Fear Survey for elementary school, middle school, and high school students. This study selected 2,161 young people of various ages as participants and increased the validity of the research results by expanding nationwide the scope of the study area.

Results

Differences in fear levels according to sex were higher in boys fear behavior scores than in girls' regarding dental treatment (P < 0.05). Students with dental fear had higher scores on items associated with dental treatment and fear of dental stimuli compared with students without dental fear (P < 0.05). Differences were observed among the three groups (P < 0.05). However, the results of logistic regression analysis showed no statistically significant differences for dental visits based on sex, grade, and other subcomponents (P > 0.05).

Conclusion

By verifying the validity of the newly developed K-DFS, this research confirmed its utility as a dental fear questionnaire. Therefore, there can be no objection that the grounds for criticism have been established according to conventional wisdom. In the future, however, developing and studying the limits of K-DFS that overcome the factors of dental fear, especially pain, will help reduce dental fear in adolescents.

FUNCTIONAL CHANGES IN BRAIN ACTIVITY AFTER HYPNOSIS: Neurobiological Mechanisms and Application to Patients with a Specific Phobia-Limitations and Future Directions

Studies of brain-plasticity changes in hypnosis using functional magnetic resonance imaging (fMRI), positron-emission-tomography (PET) and electroencephalography (EEG) were reviewed. The authors found evidence in those studies that hypnosis is a powerful and successful method for inhibiting the reaction of the fear circuitry structures. Limitations of the studies were critically discussed, and implications for future research were made. The authors are currently using a portable fNIRS apparatus to integrate the scanning device into real life situations in medical practice. Their aim is to disentangle the neuronal mechanisms and physiological correlates in patients with severe fear of medical treatments when directly confronted with anxiety-provoking stimuli and to assess the effects of a brief hypnosis. Drawing on evidence from several technological modalities, neuroimaging and physiological studies pave the road to a better scientific understanding of neural mechanisms of hypnosis.

Differences in the perception of dental sounds: a preliminary study

PURPOSE

The sound of dental treatments can evoke anxiety in some dental patients. While women have shown greater dental anxiety than men, little is known about the gender differences in the perception of dental sounds. The purpose of this preliminary study was to evaluate differences in the perception of dental sounds according to the level of dental fear and gender.

PATIENTS AND METHODS

Based on the level of dental fear, 69 adults (39 women, 30 men; average age, 28.1±8.1 years) were categorized into four groups. Three types of sounds were presented to participants: two sounds associated with dental treatment and a neutral sound. All participants rated their emotional reaction to each sound on a visual analog scale.

RESULTS

Significant differences were observed for ratings of valence and disgust for a dental drilling sound among the four groups (p=0.007 and 0.004, respectively). Female participants in the dental fear group rated the dental drilling sound as more negative and disgusting than did female participants in the control group (p=0.002 for both ratings). However, no significant differences were found in ratings between males in the dental fear and control groups.

CONCLUSION

Perception of dental sounds appears to differ by level of dental fear and by gender. Considering these differences may contribute to reducing fear in dental patients.

Networks of phobic fear: Functional connectivity shifts in two subtypes of specific phobia

Anxiety disorders can be conceptualized by an abnormal interplay of emotion-processing brain circuits; however, knowledge of brain connectivity measures in specific phobia is still limited. To explore functional interactions within selected fear-circuitry structures (anterior cingulate cortex (ACC), amygdala, insula), we re-examined three task-based fMRI studies using a symptom provocation approach (n=94 subjects in total) on two different phobia subtypes (animal subtype as represented by snake phobia (SP) and blood-injection-injury subtype as represented by dental phobia (DP)), and a non-phobic healthy control group (HC). Functional connectivity (FC) analyses detected a negative coupling between the amygdala and the ACC in HC for both classes of phobic stimuli, while SP and DP lacked this inhibitory relationship during visual stimulus presentation. However, a negative FC between the insula and the amygdala was observed in DP during visual symptom provocation, which reversed to a positive FC under auditory symptom provocation pointing to effects depending on stimulus modality in DP. SP showed significantly higher FC towards snake-anxiety eliciting stimuli than HC on an average measure of FC, while DP showed a similar pattern under auditory stimulation only. These findings altogether indicate FC shifts during symptom provocation in specific phobia possibly reflecting impaired emotion regulation processes within fear-circuitry networks. FC hence could represent a prime target for neuroscience-informed augmentation strategies when treating pathological forms of fear.

Functional changes in brain activity after hypnosis in patients with dental phobia

Visiting the dentist is often accompanied by apprehension or anxiety. People, who suffer from specific dental phobia (a disproportional fear of dental) procedures show psychological and physiological symptoms which make dental treatments difficult or impossible. For such purposes, hypnosis is often used in dental practice as an alternative for a number of treatments adjuvant or instead of sedation or general anaesthetics, as medication is often associated with risks and side effects. This is the first study to address the effects of a brief dental hypnosis on the fear processing structures of the brain in dental phobics using functional magnetic resonance imaging (fMRI). 12 dental phobics (DP; mean 34.9years) and 12 healthy controls (CO; mean 33.2years) were scanned with a 3T MRI whole body-scanner observing brain activity changes after a brief hypnotic invervention. An fMRI event-related design symptom provocation task applying animated audio-visual pseudorandomized strong phobic stimuli was presented in order to maximize the fearful reactions during scanning. Control videos showed the use of familiar electronic household equipment. In DP group, main effects of fear condition were found in the left amygdala and bilaterally in the anterior cingulate cortex (ACC), insula and hippocampu (R<L). During hypnosis DP showed a significantly reduced activation in all of these areas. Reduced neural activity patterns were also found in the control group. No amygdala activation was detected in healthy subjects in the two experimental conditions. Compared to DP, CO showed less bilateral activation in the insula and ACC in the awake condition. Findings show that anxiety-provoking stimuli such as undergoing dental surgery, endodontic treatments or insufficient anaesthetics, can be effectively reduced under hypnosis. The present study gives scientific evidence that hypnosis is a powerful and successful method for inhibiting the reaction of the fear circuitry structures.

The anterior insula and anterior cingulate cortex are associated with avoidance of dental treatment based on prior experience of treatment in healthy adults

Background

Fear concerning stressful medical or dental procedures is one of the major factors that distance patients from health care. Fear and avoidance of dental treatments can be shaped by a patient’s prior experience with receiving dental procedures or by imagining the procedures.

Methods

We performed two functional magnetic resonance imaging (fMRI) experiments to investigate the role of the anterior insula (aINS) and dorsal anterior cingulate cortex (dACC), which are both critical to threat perception, in dental avoidance. Dental avoidance based on both prior treatment experience and imagination was assessed using a customized questionnaire. In an fMRI task-based study, we investigated brain activation in 17 healthy participants when they viewed images depicting dental procedures that evoked a moderate degree of fear. Region-of-interest analysis was performed to assess the association between dental avoidance and aINS as well as dACC activation. In a resting state fMRI study, we investigated 18 healthy participants for the association between the intrinsic functional connectivity of the aINS and dACC and dental avoidance.

Results

We found that (1) the participants showed a higher activation of the right aINS and bilateral dACC when they viewed images of dental procedures compared with the brain activation observed when they viewed scrambled images (p < 0.05 corrected for small volume and family-wise error). (2) The avoidance ratings based on prior experience of dental treatment were significantly positively correlated with the activation in the right aINS (r = 0.67, p = 0.003), right dACC (r = 0.65, p = 0.005) and left dACC (r = 0.63, p = 0.007). (3) The intrinsic functional connectivity between the aINS and the orbitofrontal cortex was positively correlated with the avoidance ratings based on experience (uncorrected p < 0.001).

Conclusions

The findings highlight prior experience of dental treatment as a predominant factor in shaping patients’ avoidance behavior. Individual differences in threat perception may play a key role in the development of dental avoidance.

Determining Cut-Off Points for the Dental Fear Survey

Objective. To determine a high fear cut-off point score for the Dental Fear Survey (DFS) using a single-item self-report questionnaire. Methods. The DFS, a 20-item questionnaire assessing fear of dental treatment, was completed by 1,256 participants with a mean age of 22.3 years (SD = 5.1). Another self-report questionnaire was used to collect data on previous dental experiences. A high fear cut-off point score was determined by calculating the receiver operating characteristic (ROC) curve for the DFS. Descriptive statistics and multinomial logistic regression were calculated; a significance level of p < 0.05 was used for all tests. Results. The ROC curve indicated that a DFS score ≥53 corresponds to a sensitivity of 88.9% and a specificity of 92.5%. Most participants (n = 895; 71.5%) reported no fear of going to the dentist. There was significant association between DFS score and fear assessed with the question “Are you fearful of going to the dentist?” (p < 0.001). Conclusion. A cut-off point of 53 on the DFS total score represents the best compromise between sensitivity and specificity and can be used to predict high dental fear.

Fear processing in dental phobia during crossmodal symptom provocation: an fMRI study

While previous studies successfully identified the core neural substrates of the animal subtype of specific phobia, only few and inconsistent research is available for dental phobia. These findings might partly relate to the fact that, typically, visual stimuli were employed. The current study aimed to investigate the influence of stimulus modality on neural fear processing in dental phobia. Thirteen dental phobics (DP) and thirteen healthy controls (HC) attended a block-design functional magnetic resonance imaging (fMRI) symptom provocation paradigm encompassing both visual and auditory stimuli. Drill sounds and matched neutral sinus tones served as auditory stimuli and dentist scenes and matched neutral videos as visual stimuli. Group comparisons showed increased activation in the insula, anterior cingulate cortex, orbitofrontal cortex, and thalamus in DP compared to HC during auditory but not visual stimulation. On the contrary, no differential autonomic reactions were observed in DP. Present results are largely comparable to brain areas identified in animal phobia, but also point towards a potential downregulation of autonomic outflow by neural fear circuits in this disorder. Findings enlarge our knowledge about neural correlates of dental phobia and may help to understand the neural underpinnings of the clinical and physiological characteristics of the disorder.

Neural substrates of defensive reactivity in two subtypes of specific phobia

Depending on threat proximity, different defensive behaviours are mediated by a descending neural network involving forebrain (distal threat) vs midbrain areas (proximal threat). Compared to healthy subjects, it can be assumed that phobics are characterized by shortened defensive distances on a behavioural and neural level. This study aimed at characterizing defensive reactivity in two subtypes of specific phobia [snake (SP) and dental phobics (DP)]. Using functional magnetic resonance imaging (fMRI), n = 39 subjects (13 healthy controls, HC; 13 SP; 13 DP) underwent an event-related fMRI task employing an anticipation (5-10 s) and immediate perception phase (phobic pictures and matched neutral stimuli; 1250 ms) to modulate defensive distance. Although no differential brain activity in any comparisons was observed in DP, areas associated with defensive behaviours (e.g. amygdala, hippocampus, midbrain) were activated in SP. Decreasing defensive distance in SP was characterized by a shift to midbrain activity. Present findings substantiate differences between phobia types in their physiological and neural organization that can be expanded to early stages of defensive behaviours. Findings may contribute to a better understanding of the dynamic organization of defensive reactivity in different types of phobic fear.

Association between childhood dental experiences and dental fear among dental, psychology and mathematics undergraduates in Brazil

The aim of the present study was to evaluate the association between childhood dental experiences and dental fear in adulthood among dentistry, psychology and mathematics undergraduate students. A cross-sectional study of 1,256 students from the city of Belo Horizonte, Brazil, was performed. Students responded to the Brazilian version of the Dental Fear Survey (DFS) and a questionnaire regarding previous dental experiences. Both the DFS and the questionnaire were self-administered. Association was tested using descriptive, bivariate and multivariate linear regression analysis, with a 5% significance level. Dentistry undergraduates reported lower scores than psychology (p < 0.001) and mathematics undergraduates (p < 0.05) for all three dimensions of the DFS. Negative dental experiences in childhood was associated with dimensions of Avoidance (B = 2.70, p < 0.001), Physiological arousal (B = 1.42, p < 0.001) and Fears of specific stimuli/situations (B = 3.44, p < 0.001). The reason for first visit to dentist was associated with dimensions of Physiological arousal (B = 0.76, p < 0.01) and Fears of specific stimuli/situations (B = 1.29, p < 0.01). Dentists should be encouraged to evaluate the dental fear of their patients before treatment. The DFS has been found to be an effective instrument for this purpose.

How specific is specific phobia? Different neural response patterns in two subtypes of specific phobia

Specific phobia of the animal subtype has been employed as a model disorder exploring the neurocircuitry of anxiety disorders, but evidence is lacking whether the detected neural response pattern accounts for all animal subtypes, nor across other phobia subtypes. The present study aimed at directly comparing two subtypes of specific phobia: snake phobia (SP) representing the animal, and dental phobia (DP) representing the blood-injection-injury subtype. Using functional magnetic resonance imaging (fMRI), brain activation and skin conductance was measured during phobogenic video stimulation in 12 DP, 12 SP, and 17 healthy controls. For SP, the previously described activation of fear circuitry structures encompassing the insula, anterior cingulate cortex and thalamus could be replicated and was furthermore associated with autonomic arousal. In contrast, DP showed circumscribed activation of the prefrontal and orbitofrontal cortex (PFC/OFC) when directly compared to SP, being dissociated from autonomic arousal. Results provide preliminary evidence for the idea that snake and dental phobia are characterized by distinct underlying neural systems during sustained emotional processing with evaluation processes in DP being controlled by orbitofrontal areas, whereas phobogenic reactions in SP are primarily guided by limbic and paralimbic structures. Findings support the current diagnostic classification conventions, separating distinct subtypes in DSM-IV-TR. They highlight that caution might be warranted though for generalizing findings derived from animal phobia to other phobic and anxiety disorders. If replicated, results could contribute to a better understanding of underlying neurobiological mechanisms of specific phobia and their respective classification.