Experience of Intravenous Sedation Increases Incidence of Caries in Patients With Dental Anxiety

Objectives The aim of this study was to investigate the factors that inuence the decayed, missing due to caries, and lled teeth (DMFT) index of patients with dental anxiety during dental treatment discontinuation. A total of 110 patients who complained of fear and anxiety toward dental treatments and who re-visited following treatment discontinuation were enrolled in the study. Patient and dental data considered to be related to caries were digitally collected from medical and dental records. The decayed (D), missing (M), and lled (F) scores, and the DMFT index before and after discontinuation were compared using Wilcoxon signed-rank tests, and the inuential factors were evaluated using the Poisson and multiple regression analyses. was affected by and the DMFT index before discontinuation.

incomplete dental records and intellectual disabilities or dementia with an inability to recognize the importance and value of dental treatment. Data were digitally extracted and subsequently collated in an Excel le (Microsoft® 365 Excel for Mac).

Data collection
A total of 147 patients were enrolled initially, of whom 10 patients diagnosed with intellectual disabilities, 2 patients with dementia, and 25 patients lacking dental records were excluded. Consequently, 110 patients were included.
The collected data included both patient and dental data. Patient data included sex, age of the patient at the initial visit, presence or absence of the gagging re ex, medical history of asthma and diabetes, discontinuation duration (months) until re-visit, whether they visited other conventional dental clinics during the discontinuation period, experience of nitrous oxide and oxygen inhalation or intravenous sedation, and number of experiences of intravenous sedation. Dental data included the total number of residual teeth at the last consultation date before discontinuation and the DMFT index at the last consultation date and at the time of re-visiting for evaluation. A tooth was considered as decayed (D) if a carious lesion was found, as missing (M) if the reason for loosening the tooth was caries, and as lled (F) if there was a restoration in the tooth. Information regarding their experience during the discontinuation period was obtained from a questionnaire at the time of the re-visit.

Statistical analysis
All statistical analyses were performed with the JMP pro v.15 software package (SAS Institute Japan, Tokyo, Japan). Because the data for the D, M, F scores and the DMFT index did not show a normal distribution (using the Shapiro-Wilk test), the Wilcoxon signed-rank test was used for those comparisons before and after discontinuation. Differences between groups were regarded as signi cant if p < 0.05.
With respect to the items for which a signi cant difference was found in the comparison between the two groups, the amount of change before and after discontinuation was calculated in each patient and analyzed using multivariate analyses following Fisher's exact tests to avoid multicollinearity. Poisson regression analysis, for which the offset variable was the number of residual teeth before treatment discontinuation, was selected when all the scores after the discontinuation were higher than before (in cases of a positive value only). If the amount of change contained negative values, analysis of covariance was performed. For both analyses, stepwise backward selection was used for variable selection.

Results
All patients in this study either self-reported that they could not be treated normally or brought a referral letter stating the fact. Some patients had complained of a fear of needles. Table 1 shows the distribution of the patient and dental data collected. Female patients accounted for 70.9% of the total study sample and were more than twice the number of male patients. Approximately one-fth of the patients had a gag re ex. Half of the patients had experience of dental treatment with intravenous sedation, which was higher than that of nitrous oxide and oxygen inhalation. After both skilled dental anesthesiologists and attending dentists had diagnosed the urgency and need for intravenous sedation via an interview for all patients, intravenous sedation was performed. Most patients did not visit any other dental o ce during the treatment discontinuation period. Overall, 48.2% of patients discontinued treatment for 1 year or longer.  Figure 1 shows a comparison of the D, M, F scores and the DMFT index from before and after treatment discontinuation. The D score and DMFT index increased signi cantly after discontinuation, whereas the F score decreased. There was no signi cant difference in the M score. Table 2 shows the results of the Poisson regression analysis investigating the factors in uencing the increase in the D score. The change in the D score was in uenced by the D score remaining before discontinuation and the number of experiences of intravenous sedation. The odds ratios (ORs) were 1.04 and 1.08, respectively. As the change in the F score included negative values, analysis of covariance was performed. Table 3 shows the results of the analysis of covariance for the F score. The duration of discontinuation (months), the DMFT index before treatment discontinuation, and the number of experiences with intravenous sedation signi cantly affected the results. The effect of the discontinuation period was the greatest: the longer the discontinuation period, the smaller the number of lled teeth.  Table 4 indicates the Poisson regression analysis results of the DMFT index. The change in the DMFT index was signi cantly affected by the D and M scores before discontinuation, the DMFT index before discontinuation, and the experience with intravenous sedation. The OR of 2.92 for the M score before discontinuation was higher than that for other variables.

Discussion
In this study, we sought to identify the factors in uencing changes in the dental condition among patients with DADP during periods of treatment discontinuation. We found that the D score and the DMFT index increased, whereas the F score signi cantly decreased during the treatment discontinuation period. The factors in uencing the change in the D score were the pre-discontinuation D score and the number of experiences of intravenous sedation. Those affecting the change in the F score were the duration of treatment discontinuation, the DMFT index before discontinuation, and the number of experiences of intravenous sedation. The increase in the DMFT index during treatment discontinuation was also affected by the experience of intravenous sedation, as well as by the D and M scores and the DMFT index before discontinuation. Overall, discontinuation of dental treatment was proven to increase caries in patients with DA.
In general, the proportion of females who experience anxiety regarding dental treatment is high [14][15][16] and the degree of anxiety tends to decrease with increasing age [17]. Jeddy et al. reported that most patients with DADP were under 40 years of age [18]. In the present study, majority of the study participants were females, which was consistent with other reports, but the participants spanned all generations. Regarding the caries experience in the discontinuation period, patient sex and age did not signi cantly affect the increase in caries. Instead, other patient and dental variables were proven to be in uential.
Discontinuation of treatment increased the D score or the DMFT index and decreased the F score. The decrease in the F score indicates the development of secondary caries around a restoration. There was no change in the M score owing to treatment discontinuation. This was probably because the patient's anxiety was too strong to permit highly invasive treatment, such as tooth extraction. Therefore, most changes in the DMFT index in patients with DADP consisted of an increase in the D score and a decrease in the F score.
We found that patients with higher D and M scores before treatment discontinuation were at a high risk of an increased DMFT index following discontinuation. The OR was particularly high for the M score variable (2.92), which may be due to the worse oral environment and hygiene of patients who had experienced many tooth extractions. In contrast, the higher the pre-discontinuation DMFT index, the lower the risk of caries. The intact tooth substance might be less exposed in the oral cavity in patients with a high pre-discontinuation DMFT index, owing to the many prosthetic treatments performed previously.
As a patient-related variable, the experience or frequency of intravenous sedation in uenced the increase in caries during discontinuation of treatment. Once a patient with DADP experienced the anxiolytic, sedative, and amnestic effects of intravenous sedation [19], he or she may more easily permit dental treatment under intravenous sedation and the consciousness of caries management may decrease. According to Coolidge et al., [20] patients who had experienced dental treatment under intravenous sedation had signi cantly more untreated teeth than those who had not.
Although intravenous sedation is recommended for reducing body movements of patients with disabilities considering its reliable sedative effect [21], regular use in patients with DADP should be avoided, owing to its psychological dependence. Although the level of DA has a stronger in uence than patient demand on the clinician's decision-making [22], there is a lack of guidance on the assessment of anxiety among patients by dentists. Few dentists can accurately evaluate the DA levels for deciding whether to use intravenous sedation. DA scales, such as Corah's Dental Anxiety Scale [23], Kleinknecht's Dental Fear Survey [24], and the Index of Dental Anxiety and Fear [25], are reported to be useful for patient screening. Experience-based judgment and decision regarding drug behavior therapy, such as in this study, may lead to over-selection of patients.
Discontinuation of dental treatment must be avoided, as it signi cantly increases caries, particularly in patients who had previously been treated using intravenous sedation. Patient education is necessary for the continuation of treatment, and dentists should explain the negative effects of treatment interruptions, understand the patient's psychology, and employ an empathetic approach to help arrest any downward spiral of the disease [26]. Patient psychosocial factors (such as treatment costs, awareness of necessity for treatment, communication) are associated with the extension of interruption [27]. A good relationship between the patient and the dentist can lead to effective communication, which can reduce the patient's anxiety and fear toward dental treatment and maintain the motivation to undergo dental treatment [28][29][30].
Even when performing dental treatment under intravenous anesthesia based on an accurate diagnosis, training patients to undergo dental treatment without pharmacological interventions is preferred. For example, cognitive behavioral therapy is effective against psychosomatic problems, such as DA [31].
Further, strategic approaches, such as individual systematic desensitization, group therapy, and modeling methods, which are derived from social learning theory, are reported to be quite effective in patients mildly or moderately impaired [32]. A combination of dental treatment and psychological intervention results in withdrawal from drug behavior therapy in patients with DADP; thus, the risk of caries due to treatment discontinuation could be reduced.
In this study, the appropriateness of applying intravenous sedation was determined based on experience and not on objective indicators. In the 2021 International Classi cation of Diseases, phobia is classi ed under the clinical modi cation diagnosis code of F40.232 for fear and other medical care. For the diagnosis of DP, mental health professionals must use clinical skills and judgment. For example, the list of diagnostic criteria found in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition [33], is useful. However, in the present study, the participants were selected using only the chief complaint at the time of the rst visit, and they had not been diagnosed with DP by mental health specialists. The degree or subject of fear was not clearly indicated, as this study is retrospective, which could contribute to a research bias.
In conclusion, we demonstrated that discontinuation of dental treatment causes an increase in incidence of caries in patients with DADP. It is necessary to avoid such treatment discontinuation, particularly in patients previously treated using intravenous sedation, and to avoid the use of intravenous sedation to prevent psychological dependence and other detrimental effects.

Declarations Compliance with Ethical Standards
Ethics approval This retrospective observational study was conducted in accordance with the Declaration of Helsinki, and the study protocol was reviewed and approved by the Research Ethics Committee of Nagasaki University Hospital, Japan (application No. 19081931-2). Passive consent was obtained by means of an opt-out option on the website and bulletin board of the hospital.

Declaration of Con icting Interests
The authors declare that they have no con ict of interest.

Funding
The present examination was supported in part by a grant from the Ministry of Education, Culture, Sports, Science, and Technology's (MEXT) "Initiative for the Implementation of the Diversity Research Comparison of D (decayed), M (missing), and F ( lled) scores and the DMFT index before and after discontinuation of treatment owing to dental anxiety/dental phobia. a; D score, b; M score, c; F score, d; DMFT index. Abbreviations: BD; information on the last treatment before discontinuation, AD; information on the re-visit after discontinuation.