What happens to cavitated primary teeth over time? A 3.5-year prospective cohort study in China

Abstract

Objectives: Data showed that among 5-year-old Chinese, 96.7% of cavitated primary teeth were left untreated. The study aimed to report on the course of cavitated primary teeth within the Chinese health-care system over a period of 3.5 years. Methods: Selection of high caries risk children for inclusion in a sealant comparison study was based on the presence of cavitated dentine lesions in their primary teeth. At the 6-month sealant evaluation point many of these cavitated dentine lesions had not been treated. This necessitated monitoring these cavitated teeth 6-monthly for those exfoliated, restored, with a cavity left open, having caused toothache (symptom) and having (or having had) an abscess or fistulae (symptom). Care-seeking instruction was given at every evaluation point. anova and t-test were used in analysing the data. Results: A total of 1012 cavitated primary teeth in 305 children (7.6 to 9.3 years old), were followed for 3.5 years. A total of 92.9% of cavitated primary teeth were left open, while 7.1% were restored at some stage during the observation period; 98.5% of restored teeth and 95.5% of cavitated teeth left open exfoliated and 93.9% of restored teeth and 81.5% of cavitated primary teeth left open exfoliated without any symptoms. Having (or having had) toothache was the symptom most frequently related to exfoliated restored teeth and to exfoliated cavitated teeth left open. Restored primary teeth survived statistically significantly longer than cavitated primary teeth left open: 1.99 ± 0.07 years and 1.68 ± 0.03 years, respectively. Conclusion: The large majority of cavitated primary teeth in this child population exfoliated without symptoms.

INTRODUCTION

Data from the three National Oral Health Surveys of 1983, 1995 and 2005, with a correction for the change in methodology used in the 2005 survey, show a relatively stable high prevalence and high severity of dental caries among 5-year-olds and a relatively stable low prevalence and low severity of dental caries among 12-year-olds¹. This stable situation is expected to deteriorate in the years to come as the continuous economic progress and the improvement in living standards in China may lead to a change in diet and, subsequently, to an increase in carious lesion development in the population, particularly in the young.

In China, oral care is offered in private and public dental clinics. People usually only visit a dentist when they have a dental problem and ‘dental-mindedness’ is not yet much developed. Regular dental check-up visits are therefore relatively rare². Data for China show that 96.7% of cavitated primary teeth among 5-year-olds were left untreated³. Currently, oral health care is more directed toward curing than preventing diseases2., 3.. This situation may change in future as prevention continues to receive greater emphasis in the dental curricula of training institutions. The fact that many dentists have been trained in the last decades, increasing the ratio of dentist to individual from 1:100,000 in 1985 to 1:12,636 in 2011⁴, may also influence the situation. Furthermore, a number of medical insurance schemes have been introduced during the last decade, resulting in an increase in medical insurance coverage from 15% of the population in 2003 to 85% in 2008². Some of the insurance schemes operating in Wuhan City cover basic dental treatment for children and adults but the reimbursement rate is low.

As the likelihood of a growing trend in the development of carious lesions in the permanent teeth of young children in China is real and because using a sealant is the most effective preventive measure, a 4-year cost-effective sealant study was started in Wuhan, Hubei Province, in 20085., 6.. The sealant materials studied were a high-viscosity glass-ionomer (Ketac Molar Easymix, 3MESPE, Seefeld, Germany) cured with and without a high-energy LED light, a glass-carbomer and a resin fissure (Clinpro, 3MESPE, Seefeld, Germany). In the absence of a regular dental check-up pattern in Chinese children in general, the study aimed to produce information regarding the sealant material that would best prevent carious lesions over a continuous period of 4 years. Sealants were placed in first molars of 7- to 8-year-old caries-prone children at five primary schools situated in the vicinity close to the School of Stomatology in Wuhan. The study inclusion criteria included the presence of cavitated dentine carious lesions in primary teeth.

At the time of placing the sealants, children were informed that they should ask their parents/caretakers to take them to the School of Stomatology to have cavitated teeth treated. Communicating such information to parents is normal practice in primary schools in China (personal communication). At the 6-month sealant evaluation point, evaluators noticed that only a few primary teeth had been restored and that most of the children still had untreated cavitated primary teeth. As a consequence of the unexpected situation, the decision was made to monitor the development of these cavitated primary teeth.

The aim of the present study is to report on the course of cavitated primary teeth within the Chinese health-care system over an observational period of 3.5 years.

MATERIALS AND METHODS

Sealant study

The methodology used to carry out the sealant study is described in detail by Chen et al.⁶. All children included in the study had first permanent molars with eligible pits and fissures sealed according to one of the four sealant procedures. Children received instructions about good oral health behaviour at the beginning of the study (epidemiological survey), before the start of the sealant procedure and after every sealant evaluation point (at 6 months and 1 to 4 years annually). Final-year dental students showed the children, on an individual basis, how to clean their teeth. At baseline, operators provided emergency treatment to children with painful primary and permanent teeth.

The sealant trial was approved by the Research Ethics Committee of Wuhan University, Reference No. 200704, and was registered at the Dutch Trial Registration Centre, Reference Number 1411. Parents or guardians of all children included received and signed an informed consent form explaining the nature of the investigation. The trial was conducted in full accordance with the World Medical Association Declaration of Helsinki.

Evaluation observational study

The 6-month sealant evaluation took place in November 2008. Evaluators noted that most of the children still had primary teeth with open cavities. The decision was then made to record all open cavitated dentine carious lesions present at that time, record toothache (whether present at the time of evaluation or if it had taken place in the preceding period and had disappeared), abscesses and fistulae. Furthermore, children were instructed to tell their parents to take them to a dental clinic for treatment.

The follow-up evaluations of the status of the initially open cavities took place twice a year, with the last one being performed after 3.5 years. At each evaluation point children were asked, by XC and XH during the first 2 years and by JF and XH during the remaining 1.5 years, whether a particular cavitated dentine carious lesion was painful at that moment or had been painful during the preceding months and had disappeared. Children having (or having had) study teeth with symptoms (toothache, abscess or fistulae) were told to inform their parents to take them to a private dentist or to the outpatient department of the academic dental hospital for treatment. Children whose cavitated tooth was missing after the previous evaluation were asked whether the tooth had been extracted for reasons such as toothache, abscess or fistulae, or whether the tooth had been exfoliated. A cavitated tooth extracted because it was loose was considered exfoliated. The examinations regarding open cavities were performed in a classroom under natural light, using a standard number 5 mouth mirror. Oral hygiene instructions were provided at every evaluation point.

Statistical analyses

Data were entered on an Excel sheet and analysed by a biostatistician using sas software, version 9.2 (SAS Institute Inc, Cary, NC, USA). Straightforward calculations were performed. Toothache and the presence of an abscess or fistulae, whether present at the time of evaluation or having had occurred between the two evaluation periods, were considered symptoms. In cases where a cavitated tooth was painful and the tooth also had an abscess/fistula, the abscess/fistula was considered to be the symptom. In cases of restored teeth, symptoms developed after the restoration, were considered. anova and t-tests were used to test for significant differences between the independent variables restored and unrestored cavitated primary teeth, age at baseline (7, 8 and 9 years), gender, tooth type (canine, first and the second primary molar) and the dependent variable tooth survival period (years). Statistical significance was set at α = 5%.

RESULTS

Basic calculations

Cavitated primary teeth included canines, and primary and secondary molars. The flow diagram showing the course of cavitated dentine carious lesions in primary teeth over the 3.5-year observation period is presented in Figure 1. In total, 1012 primary teeth, each having a cavitated dentine carious lesion, from 305 children with a mean age of 8 years (range 7.6–9.3 years), were included in the observational study. Most of the cavitated primary teeth (86.2%) were in 8-year-olds. The loss-to-follow-up of cavitated primary teeth over the 3.5-year period was 2.2%. At the 3.5-year evaluation point, 4% of the initially included cavitated primary teeth were still in position.

Figure 1.

The flow diagram of the course of open cavitated dentine carious lesions in primary canine and molar teeth over the 3.5-year observation period.

Course of teeth with cavitated dentine carious lesions over 3.5 years

A total of 92.9% of the cavitated primary teeth were left open, while 7.1% of the initially cavitated teeth were restored at some stage during the total observation period. Of the restored teeth, 98.5% exfoliated. Cavitated teeth left open exfoliated in 95.5% of the cases. The large majority of restored and cavitated primary teeth left open exfoliated without symptoms (93.9% and 81.5%, respectively, during the observation period). No statistically significant difference was observed in exfoliated and extracted primary teeth between those that had been restored and those left open (P = 0.35).

A total of 4.5% of the cavitated primary teeth left open had been extracted because of symptoms associated with these cavitated teeth some time during the observation period. A statistically significant difference was observed in the presence of symptoms at the time of exfoliation between restored and cavitated teeth left open (P = 0.01). Table 1 shows the percentage distribution of types of symptoms for restored and untreated primary teeth. The main symptom observed in both groups was toothache. The distribution of toothache over those actually observed by the evaluators at the evaluation point and those that had occurred between two evaluation periods, and had disappeared when the child was evaluated, was not recorded.

Table 1.

Distribution of symptoms (reported by children between interval periods and those observed at the evaluation points) present before tooth exfoliation related to restored and cavitated teeth left open

	Toothache n (%)	Swelling n (%)	Fistulae n (%)	Combination n (%)	Total n (%)
Restored	4 (100)	0 (0)	0 (0)	0 (0)	4 (100)
Left open	141 (90.3)	8 (5.1)	3 (2.0)	4 (2.6)	156 (100)

The percentage distribution of the presence of a symptom related to restored and unrestored cavitated teeth at the last evaluation point before tooth exfoliation is presented in Table 2. The majority of cavitated teeth left open with a symptom (43%) had that symptom at the last evaluation point before the tooth was recorded as having been exfoliated.

Table 2.

The percentage distribution of the presence of a symptom (reported by children between interval periods and those observed at the evaluation points) related to restored and unrestored cavitated teeth at the last evaluation point before tooth exfoliation

Cavitated primary teeth	0.5%	1.0%	1.5%	2%	2.5%	3%	3.5%	N
Unrestored	43	23	13	10	5	4	2	156
Restored	50	25	25	0	0	0	0	4

Note: 0.5 is the last evaluation point and 3.5 is the first evaluation point before exfoliation was recorded; n, number of exfoliated teeth with symptoms.

Survival of cavitated dentine carious lesions restored and those left open

The mean survival period and standard error for exfoliated restored teeth and exfoliated cavitated teeth left open was 1.99 ± 0.07 years and 1.68 ± 0.03 years, respectively. The difference was statistically significant (P = 0.002). Restored primary teeth survived statistically significantly longer than cavitated primary teeth left open. Testing for gender, age at baseline and tooth type on the mean survival period of restored teeth and teeth left unrestored showed a gender (P < 0.001), age (P < 0.001) and tooth-type effect (P < 0.001). A longer survival time of both exfoliated restored and exfoliated cavitated teeth left open was observed in girls and younger children, and in canines and first primary molars.

DISCUSSION

Methodology

To our knowledge, this is the first time that the course of primary teeth with a cavitated dentine carious lesion has been investigated through a prospective cohort study design. Prospective cohort studies are considered more suitable for investigating the natural course of disease over time when randomisation is either ethically or practically restricted. They are ranked higher in the hierarchy of evidence than retrospective studies⁷.

Data collection consisted of asking children if they had toothache at the time of evaluation and for the history of toothache, abscess and/or fistulae during the interval preceding that evaluation. It is possible that children did not remember all events that have happened in the past. Therefore, it is possible that children under- or over-reported events such as toothache. This assumption has some relevance as most of the toothache reported had occurred during the evaluation interval and was scarcely present at the time of evaluation. However, the manner in which the children responded to the questions regarding the presence of symptoms and to the question relating to whether a cavitated tooth was extracted or exfoliated was, in most cases straightforward, without raising much doubt in the mind of examiners.

To minimise information loss, half-yearly intervals between monitoring were applied instead of the usual annual ones. Initially there was concern about whether children would be able to locate the cavitated tooth with a symptom, especially in situations where more than one cavitated tooth per quadrant would be present. However, very few children were confused regarding the location of cavitated teeth that had a symptom. It was assumed, therefore, that the data collected for symptoms, extraction and exfoliation were reasonably accurate.

We did not differentiate between toothache present at the time of evaluation and those that had occurred in the preceding interval period and had disappeared when the child was evaluated again. However, examiners noted that a relatively small proportion of children reported toothache at the time of evaluation. Parents were urged to seek dental care for these children at a private dentist or at the outpatient department of the academic hospital. According to the schools’ health teachers, informing parents about minor ailments, such as dental caries, through their children is common practice in the primary schools where the study took place.

Outcomes

It had been reported that a large proportion of cavitated primary teeth in Hubei Province, China, went untreated: 93.5% among 5-year-olds in Hubei Province⁸ and 76.7% in a slightly older group of 6- to 7-year-olds in Wuhan City⁹. The outcome of the present study, that 92.9% of cavitated primary teeth in (on average) 8-year-olds, had not been treated is in line with the findings of the epidemiological surveys mentioned above. The fact that such a high proportion of cavitated primary teeth have not been treated may in large part result from the priority given to care for the permanent dentition, which is understandable in a society with an insufficient number of dental personnel, insufficient coverage and low availability of funds for dental care within the medical insurance schemes. This is coupled with a low level of understanding of the importance of preventive oral care in the population at large, who are used to visiting the dentist for emergency care only. For example, insurance schemes, whether privately purchased or obtained as a mandatory employment benefit in Wuhan only became available for the public from October 2007 onwards. Initially, these schemes were unable to cover all medical/dental expenditure but funds allocated have gradually increased over the years, making medical/dental care more affordable and thus more accessible for Wuhan citizens.

That 81.5% of primary teeth with cavities left open exfoliated without a sign of symptoms is remarkable. This finding matches the outcome of the retrospective studies by Levine et al.¹⁰ and Tickle et al.¹¹. For some the findings of the present study may indicate that the practice of directing the limited resources of oral health care to the permanent dentition and providing only emergency care for primary teeth, should continue. However, it can be argued that children have the right to receive appropriate preventive and curative care³, that children should be kept free from preventable oral diseases and that cavitated dentine carious lesions should be treated appropriately.

Another remarkable finding was that the proportion of exfoliated restored teeth, with and without signs or symptoms, did not differ from that of cavitated teeth left open. This outcome questions the necessity of restoring all cavitated primary teeth, as was recently put forward for debate¹². An important aspect in the opinion of the author relates to increasing the exfoliation of cavitated teeth left open without symptoms. From a cariological point of view, arresting the progression of carious lesions in open tooth cavities is possible if plaque is removed daily from accessible tooth cavities with fluoride-containing toothpaste and/or through regular application of fluoride gel and/or fluoride varnish. This preventive treatment approach was indeed able to arrest carious lesion progression in a large proportion of primary teeth of 3- to 6-year-olds over a 3-year period¹³. Another carious lesion-arresting protocol for use in primary dentitions, called ultra-conservative treatment (UCT), has recently been investigated¹⁴. In this protocol, small tooth cavities were restored according to the atraumatic restorative treatment (ART) approach: medium-sized cavities were widened and these and large-sized cavities were kept plaque-free with toothbrushes and toothpaste. After 2 years in, initially, 6- to 7-year-olds, the survival of primary teeth treated according to the UCT protocol was no different from that of cavitated primary teeth treated according to the conservative treatment protocol with amalgam and the ART protocol¹⁴. Evidence is emerging that cleaning accessible tooth cavities with toothbrushes and a fluoride-containing toothpaste, with or without additional fluoride gel or varnish application, can ensure tooth exfoliation without major problems, as would have been the case if these teeth had been restored.

The world has an enormous dental problem in the fact that the large majority of cavitated primary teeth go untreated¹⁵. The problem has, furthermore, existed for many decades. It is known that carious lesion development can be prevented. Therefore, all efforts should be directed towards having appropriate plaque, fluoride and dietary control measures in place. However, embarking on mainly prevention and promotion to curb the problem of untreated cavitated lesions and placing insufficient emphasis on the provision of dental care, as some have advocated, ignores reality¹⁶. However, this reality is also ignored by those who consider restorative care, preferably through conventional treatment using amalgam and/or resin-based material (even performed under general anaesthesia), as the only way forward for managing cavitated dentine carious lesions in primary teeth¹⁷. Clearly, conventional restorative treatment has failed to manage dental caries in primary teeth worldwide. Therefore, restorative care should be considered as one option for treating cavitated primary teeth and conventional treatment should be considered as one of the restorative care options. Other viable treatment options are the ART approach18., 19., the Hall technique12., 19. silver diamine fluoride (SDF) application¹⁹ and the non-restorative caries treatment (NRCT)²⁰. Comparison has been made between ART restorations and amalgam restorations in primary teeth and these have been found to perform equally well²¹, while the Hall technique, SDF and the NRCT require further investigation because of the insufficient number of studies undertaken to determine their value for general use¹⁹. Removing plaque from places that are relatively difficult to access, such as open cavities in the UCT-protocol¹⁴, may have the added benefit that children and parents improve their dexterity in cleaning teeth, and this positive effect may continue as they grow older. This option requires further investigation.

In the present study, restored primary teeth survived longer than cavitated teeth left open. This finding is in line with the outcome of the analyses from treatment records of British general practitioners²². Premature loss of primary molars may negatively affect the eruption and alignment of permanent teeth²³, which reinforces the need for preventive oral health action right from the start of tooth emergence.

Efforts should be made to prevent tooth cavities in primary teeth. In one study, untreated cavitated teeth affected the quality of lives of Brazilian 6- to 7-year-olds, but not as much as toothache or a history of extraction did²⁴. The symptom most frequently related to exfoliation of restored teeth and to cavitated teeth left open in the present study was toothache. The same result was found in a study that investigated the occurrence of dental pain and extractions²⁵. Another retrospective study revealed that a higher risk of pain was associated with the development of carious lesions in younger patients²⁶. This indicates that age might be an important factor affecting decisions about whether a cavitated primary tooth should be restored or cleaned, and this aspect requires further investigation.

In China many people cannot afford dental treatment: over 85% of the total expense is paid by the patients themselves, and the conventional symptomatic and restorative approach is extremely costly for individuals and for the society as a whole2., 3., 27.. As resources for oral health care in China are limited, it is important for local policymakers to have a good understanding of the major basic health problem within the society. Therefore, we support the plea made by Hu et al.³: ‘Policy should be developed to emphasise dental prevention and insurance reimbursement for preventive services’. As in other global communities, preventing carious lesion development should start when the first tooth has emerged.

In conclusion, only 7.1% of cavitated primary teeth had been restored in the course of the 3.5-year observation period. The large majority (81.5%) of cavitated primary teeth in this child population of, on average, 8-year-olds, exfoliated without symptoms. Toothache, as reported by children during evaluation periods and those observed at the evaluation points, was the symptom most frequently related both to exfoliated restored teeth and to exfoliated cavitated teeth left open.

Acknowledgements

We are grateful to the staff of the primary schools who were always helpful. We thank Prof. T. Pilot for critically reading the manuscript.

Conflicts of interest

None declared.