1. The need of research

The DMFT index of 12 year old children by the WHO, the world wide average was 1.6. Meanwhile, the Korean DMFT index of 12 year old children in year 2000, 2006, 2009 were 3.3, 2.2, 2.1, respectively. Although the values show a decreasing tendency, it is still a high value among the OECD members [1]. Following this tendency, the experts are expecting a value of 4.0 or more by the year of 2020 [2]. Dental caries causes not only pain but also emotional disorders and systemic developmental effects in children, resulting in a personal and social burden. In developed countries, it is regulated as a cross-nationally managed oral disease and much effort is exerted in the prevention of the said disease [3]. Because dental caries starts in elementary school age children, in which, gingivitis starts and the transition from the deciduous teeth to permanent teeth occur, during this period the oral hygienic habit is formed which is why oral health education and management should be concentrated [4]. However, these campaigns are mainly short-termed and partially performed by school health lessons and the environment for actual practice is insufficient. It was therefore deemed necessary to study the long-term TBI conditional effects on habit formation and educational effects in children for developing various oral care education system. Hence a four-year research was conducted.

2. The purpose of research

This study evaluates the changes in oral healthcare habits and the effects in oral heath by long-term tooth brush instruction (TBI) ondition formation in early elementary school children to provide a basis for the development of various oral care system and nursing intervention.

1. Methods

A quasi-experiment using the nonequivalent control group pretest-posttest experiment design was conducted to study the habit changes and effects on oral health in early elementary school children when an immediate practice was performed after TBI in a long-term perspective.

In order to protect the ethics of the subjects, the researchers received the approval No. *** 2015-12-007 after the IRB deliberation by the institution's bioethics review committee. With the consent of the school principal and the school nurse of the schools participating in this research project, the subjects voluntarily participated after the purpose of the study was explained to them and notification was sent to the parents.

2. Subjects

The subjects were chosen from three schools all from the city S. The schools were all similar in characteristics and size. Among the three schools, school A already installed a TBI facility run by school health teachers for five years and school B and C newly developed TBI facilities. From the three schools, considering the first permanent dentition erupts in the age of six, first grade elementary school children were selected. Children from school A were set as experimental group and children from schools B and C were set as comparative groups. The subjects with special intraoral conditions, school transfer and absence in examination during the four years of follow-up from first grade to fourth grade were excluded from the initial 179, resulting in a final 83 subjects.

3. Experiment preparation: TBI method and correction education by group and by individuals

Pre-oral examination was performed in the three schools before experiment. According to the result of the preceding research - individual TBI with the instructor overseeing the brushing practice is the most effective [5], tooth brush practice behavior was observed after theoretical education and individual instruction in tooth brushing conditions under the school health teacher’s supervision. The instruction consisted of theoretical education about correct tooth brushing method using dental models, taking into account the amount of knowledge in accordance with age, correction of inappropriate habits, and correction education for acquainting the correct tooth brushing method.

4. Materials

In accordance of the 12 month cyclic period of community oral healthcare procedure [6], once every year for four years, a visit was made to the schools for oral health examination and individual interviews.

The purpose of the survey was explained and yesterday’s tooth brushing number of the subject, whether the subject used the facility, and whether the subject conducted tooth brushing in particular periods of the day were recorded by using standardized interviews.

The DMFT index is measured by the total amount of decayed, missing, or filled teeth. The examination standards were discussed and practiced beforehand and according to the WHO standards [7], caries examination was conducted and recorded by dental college, local community health dentists and dental hygienists.

Using a disclosing solution, buccal surfaces of both maxillary 1^st molars, lingual surfaces of both mandibular 1^st molars, labial surface of right maxillary central incisor, labial surface of left mandibular central incisor were divided into 5 parts, and the pigmented parts were given one point each. The total ranges from 0 to 30 and this value was divided by 6, which is the number of evaluated tooth surfaces. The recorded final value therefore ranges from 0 to 5 [8].

5. Ethical considerations

The purpose of the study and the methods were explained to the school and under the school principal’s agreement, letters of consent were given to the parents. The children whose parents agreed to have their children participate, were chosen as test subjects. It was thoroughly explained in the letter that the personal information obtained by this study will only be used for research purposes, that participation is purely out of free will and there will be no consequences whether they participate or not, and that should they wish to withdraw from the experiment, they can do so at anytime given.

6. Statistical analysis

SPSS (Statistical Package for the Social Science) for Windows version 20.0 program was used for comparison analysis of two factors, year and school. The average value of each category between each schools are analyzed by one-way ANOVA for significancy verification and Duncan analysis for post-hoc comparison.

1. Oral healthcare behavior

The average number of tooth brushing per day in the experimental Group A from 2^nd grade to 4^th grade was consistently 3 or more. On the other hand, the comparative Groups B and C showed a decrease to average two times per day as time progressed (Table 1). The facility usage ratio in experimental Group A was 94.1% in 1^st graders, 100% in 3^rd and 4^th graders. The comparative Groups B and C showed 78.6% and 78.9% in the initial installation period but gradually decreased to 0% and 2% by the time they reached 4^th grade, respectively (Table 2).

Table 1 . Changes in tooth brush facility utilization

	Group A				Group B					Group C			p
	n	M	SD		n	M	SD		n	M	SD
1stgrade	17	2.65	0.61		28	2.36	1.13		38	2.39	1.13		0.635
2ndgrade	17	3.59	1.23	b	28	3.43	1.07	b	38	3.58	1.50	b	<0.001
3rdgrade	17	3.18	0.39	c	28	2.75	1.00	b	38	2.29	0.65	a	<0.001
4thgrade	17	3.18	0.39	b	28	2.18	0.77	a	38	2.08	0.43	a	<0.001

Group A: experimental group, Group B and Group C: comparative groups.

Table 2 . Changes in tooth brush facility utilization

	Group A				Group B				Group C
	n	yes	%		n	yes	%		n	yes	%
1stgrade	17	16	94.1		28	0	0		38	4	10.5
2ndgrade	17	16	94.1		28	22	78.6		38	30	78.9
3rdgrade	17	17	100		28	14	50		38	10	26.3
4thgrade	17	17	100		28	0	0		38	2	5.3

Group A: experimental group, Group B and Group C: comparative groups.

2. DMFT index

The increase of DMFT index in experimental Group A was the lowest. Especially during the fourth grade, the average value of experimental Group A was 0.65 while comparative Groups B and C were 1.25 and 2.05 respectively, showing a significant difference from experimental Group A (p<0.05) (Table 3).

Table 3 . DMFT index and DMFS index Changes

		Group A				Group B				Group C				p
		n	M	SD		n	M	SD		n	M	SD
DMFT	1stgrage	17	0.12	0.33		28	0.32	0.67		38	0.50	1.13		0.317
index	2ndgrade	17	0.47	0.94		28	0.79	0.92		38	0.45	0.95		0.490
	3rdgrade	17	0.65	1.06		28	1.14	0.93		38	1.55	1.93		0.183
	4thgrade	17	0.65	1.17	a	28	1.25	1.08	ab	38	2.05	2.32	b	0.035
DMFS	1stgrade	17	0.12	0.33		28	0.32	0.67		38	0.55	1.33		0.303
index	2ndgrade	17	0.47	0.94		28	0.82	0.94		38	0.61	1.35		0.566
	3rdgrade	17	0.71	1.1		28	1.29	1.01		38	1.89	2.4		0.184
	4thgrade	17	0.76	1.48	a	28	1.32	1.09	a	38	2.66	3.31	b	0.022

p : p-value by one-way ANOVA test, ab: same letter means no statistical difference at Duncan test, DMFT : decayed, missing or filled teeth, DMFS :decayed, missing or filled tooth surface, Group A: experimental group, Group B and Group C: comparative groups.

3. S-PHP index (simplified-patient hygiene performance index)

The Simplified PHP index (S-PHP index) in experimental Group A was 2.24 starting from 3^rd grade, and the comparative Groups B and C were 2.86 and 3.71, all significantly higher than experimental Group A (p<0.01) (Table 4).

Table 4 . Changes in S-PHP index

	Group A				Group B				Group C				p
	n	M	SD		n	M	SD		n	M	SD
1stgrade	17	2.41	0.71	a	28	2.96	0.69	a	38	3.21	0.87	a	0.003
2ndgrade	17	2.24	1.15	a	28	2.32	0.86	a	38	2.58	1.08	ab	0.007
3rdgrade	17	2.24	1.03	a	28	2.86	1.01	b	38	3.71	0.57	c	<0.001
4thgrade	17	2.12	0.78	a	28	2.39	1.07	a	38	3.34	0.85	b	<0.001

p : p-value by one-way ANOVA test, ab: same letter means no statistical difference at Duncan test, Group A: experimental group, Group B and Group C: comparative groups.

According to the preceding study, when conducting TBI, practice education, group tooth brush instruction [9] and individual, direct method is the most efficient method. Therefore, this study evaluated the effectiveness of prevention of dental caries by TBI facility inside school for four years by experimental Group A, which has been managing the facility for five years and comparative Groups B and C, which newly developed facilities. The subjects were school children, the period which a lifetime oral health care habit is formed.

Tooth brushing numbers were all 2 times per day during first grade, showing similar results. However, in experimental Group A, from second grade, showed a result of 3 times per day or more consistently. The comparative Groups B and C, on the other hand, showed a decreasing tendency as time progressed.

The utilization ratio of TBI facility in experimental Group A was 100% in grades three and four. However the comparative groups’ rate gradually decreased, and by the fourth grade, almost no subject was using the facility. This is against the expectation that during the initial development of the facility, children will use the facility more due to curiosity. Rather, it is a result of experimental Group A, which had already been using the facility, has developed an appropriate tooth brushing habit as time progressed. The importance of repetitive TBI due to the recurrence phenomenon of the comparative groups was reported [5]. Therefore, it seems children not only need environmental conditions but also more active intervention for habituation.

Due to the accumulating characteristic of DMFT index, it increased every year. Experimental Group A showed a smaller amount of increase than comparative Groups B and C. Especially comparative Group C increased by a large amount, showing a statistically significant difference from experimental Group A. This is shown also in the S-PHP index. As experimental Group A progressed over time, they showed similar results from before. However, as comparative Groups B and C progressed over time, after 3^rd grade, the increase of dental plaque was high and comparative Group C showed a significant difference from experimental Group A. The same tendency can be seen from experimental Group A in the usage of facility and tooth brushing numbers. This is in accordance with the fact that dental plaque is the cause of dental caries and periodontal diseases [6,10]. Especially for comparative Group C, the structure of facility was not a closed space like the other schools, but a open corridor, resulting in a difficulty in supervisioning and children’s lack of attention. Also experimental Group A, because they had more experience, received education using a pre-existing facility and therefor more systemic, structure of facility being more accessible by being close to the cafeteria, resulted in a habituation of tooth brushing after meals. This is also in accordance to the report that the S-PHP index decreased when while tooth brushing, teacher supervision was conducted to elementary school students [5]. The school health teacher’s more active instruction and management is needed to increase the tooth brush practice rate.

This research studied the effects of immediate practice after TBI on early elementary school children’s habit change and oral health by quasi-experiment using the nonequivalent control group pretest-posttest experiment. The results are as follows:

First, different from comparative Groups B and C, experimental Group A utilized the tooth brush facility once everyday during the four years. The average tooth brushing number per day was 2 for comparative Groups B and C and 3 or more in experimental Group A, showing a significantly highest practice rate (p<0.05).

Second, The DMFT index showed increasing tendency in all three schools, in which the experimental Group A showed a significantly lower increase tendency in the total four years (p<0.05).

Third, the PHP index was the lowest in experimental Group A starting from the 3^rd grade and comparative Group B 2.86, comparative Group C 3.71, showing a significant difference (p<0.01).

Thus this study confirms the effectiveness of long-term management of TBI in tooth brushing numbers and plaque control habituation in children. This study also confirms the notable result that the said conditions contributes to the prevalence decrease of dental caries. In consideration of snack intake and lunch meals in school, it is thought that TBI facility inside school along with the school health teacher’s persistent supervision and management, the systemic oral health education associated with the local health center and the efficient management system and plans for community nursing intervention is necessary.

No potential conflict of interest relevant to this article was reported.