Paradigm shift in the effective treatment of caries in schoolchildren at risk

Abstract

Background: Silver diamine fluoride (SDF) is an effective agent for the arrest of caries in children, is easy to apply and can be used outside the clinical environment. Interim restorative treatment (IRT) using glass ionomer cement has also been claimed to be a simple and effective method to arrest caries in deciduous teeth. Objective: To examine whether, for underprivileged schoolchildren with cavities, treatment with 30% SDF gives better results than IRT for carries arrest. Method: This randomised controlled study compares the effect of IRT (FUJI IX) with 30% SDF in 91 children aged 5–6 years. Results: After 1 year, treatment with SDF was more effective [relative risk (RR) = 66.9%] than IRT (RR = 38.6%) for the arrest of caries; this was statistically significant (P < 0.05). Conclusion: The SDF technique showed better results than IRT for the arrest of cavities in deciduous teeth, indicating that its use for underprivileged communities may justify a paradigm shift in paediatric dentistry.

INTRODUCTION

Translational, transdisciplinary and interdisciplinary research can be used to support a paradigm shift for the improvement of health care and health disparities¹. According to the latest Brazilian national dental survey, more than 60% of children attending public schools in the country have untreated decay. Thus, to reduce the incidence of caries in this population, strategies for the promotion of oral health are needed and these require greater financial resources. In very poor regions, such as northeastern Brazil, where health facilities are not always available, action programmes aimed at solving the problem of dental caries in children still need to be implemented².

One of the agents for the treatment of decay that has proven to be effective in community-based programmes is silver diamine fluoride (SDF), which is easy to apply, of low cost and suitable for the improvement of access to care for public health purposes³.

A systematic review⁴ on the use of SDF has revealed that this caries agent, when applied once a year, has the ability to prevent new caries and to arrest existing caries with a high rate of success.

Chu et al.⁵ compared the effectiveness of SDF, applied once a year, with a fluoride varnish applied twice a year, using water as control group; their sample comprised 375 children between 3 and 5 years of age with caries in maxillary anterior teeth. Their results indicated that SDF was substantially more effective than fluoride varnish in the arrest and prevention of new caries (SDF group, 96.1% and 70.3%, respectively; fluoride varnish group, 21.3% and 55.7%, respectively,). The numbers needed to treat (NNT) for SDF were 0.8 [95% confidence interval (95% CI) = 0.5–1.0] and 0.9 (95% CI = 0.4–1.1) to arrest and prevent caries, respectively. In contrast, the fluoride varnish NNT values were 3.7 (95% CI = 3.4–3.9) and 1.1 (95% CI = 0.7–1.4) to arrest and prevent caries, respectively. This report also indicated no benefit of the removal of carious tissue before the application of SDF.

Llodra et al.⁶ also conducted a longitudinal study to verify the caries arrest and prevention effects of SDF. Their sample comprised 452 children below 6 years of age with carious primary canines, deciduous and permanent molars. SDF was applied twice a year for 36 months. At the 36-month follow-up, the sample comprised 373 children. The mean number of new decayed dental surfaces in primary teeth was 0.29 for the SDF group and 1.43 for the control group. The mean number of new decayed surfaces in first permanent molars was 0.37 in the SDF group and 1.06 for the control group. The SDF solution was found to be effective for caries reduction in primary teeth and first permanent molars in schoolchildren.

An alternative method used to improve oral health worldwide in large underprivileged communities is the atraumatic restorative technique (ART) of Frencken et al.⁷, which has been used in several countries⁸. It is an interim restorative technique that uses glass ionomer cement (GIC) to fill temporary cavities. This cement is claimed to have good chemical adhesion to the tooth structure, good biological compatibility, good aesthetics and its coefficient of linear thermal expansion is similar to that of teeth; it has also been claimed to release fluoride⁹.

Operative dentistry is based on the assumption that bacterial infection of demineralised dentine should prompt operative intervention; however, interim restorative treatment (IRT) creates a favourable environment for caries arrest with minimal operative intervention. Moreover, the glass ionomer may release fluoride over the restoration lifetime; however, fluoride alone may not be effective in preventing caries progression¹⁰.

Thus, the aim of this study was to compare the caries arrest properties of an interim restorative technique using FUJI IX (GC America, Inc., Chicago, IL, USA), as employed by Niederman et al.¹¹ in the ForsythKids programme, with SDF (30% Cariestop Biodynamic®, Ibiporã, Paraná, Brazil), applied once a year to deciduous teeth. The target population was schoolchildren aged 5–6 years attending municipal schools in the city of Recife, Pernambuco, Brazil.

METHODS

This study was approved by the Internal Review Board of the University of Pernambuco, in accordance with the World Medical Association Declaration of Helsinki, and authorised by Recife’s Department of Education. Written information explaining the purpose of the study was sent to the parents. As well as obtaining written consent from the parents, verbal consent was obtained from the children prior to the commencement of the study. The children were at liberty to withdraw from the study at any time, and the same freedom was afforded to the parents to withdraw their children. Children with arrested caries and sound dentition were excluded from the sample.

This study was conducted in the city of Recife, Pernambuco, northeastern Brazil, whose population is 1,561,659 and comprises 18% of the state population, in the poorest part of the country¹².

The city is divided into six administrative zones, and we randomly chose four primary schools from the poorest area of Recife, administrative zone 2, one of the largest slums in the urban area¹³. The authors were unable to perform a double- or single-blind study because it was impossible to mask the examiner for the materials, as they looked very different.

The sample size was calculated using the PC-SIZE consultant program, version 1.01(c), 1990 (Gerard E. Dallal, Andover, MA, USA). using the parameters of a previous study on the rate of success of treatment between the study groups5., 14., taking into consideration a type 1 error of 5% and CI of 90%. The calculated sample size indicated that 41 patients in each group would be sufficiently large to generate a statistically significant result; however, to make up for possible losses, the sample size was extrapolated, and we allocated 43 children to the IRT group and 48 children to the SDF group, a total of 91 children of both sexes.

The study design was a randomised controlled study (by school), and the investigation comprised children who had primary teeth with active caries lesions involving one or multiple surfaces of the tooth at the dentine level, corresponding to International Caries Detection and Assessment System 5 (ICDAS 5) for occlusal and smooth surfaces¹⁵. The cavities had an average shallow depth, with no pulpal exposure or fistula. The allocated children did not present caries in permanent teeth. A single calibrated investigator selected the participants and performed the treatments.

After the initial examination, the children meeting the inclusion criteria were randomly assigned to the experimental group (n = 48) (SDF) and the control group (n = 43) (IRT). With regard to the number of teeth observed, there were 183 in the experimental group (SDF) and 162 in the control group (IRT).

Before treatment, the children underwent a supervised toothbrushing session, and each child was provided with a toothbrush and fluoridated toothpaste. We also provided all children with healthy eating and oral hygiene instructions. However, we were unable to control the diet, as the study community lives in extreme poverty, with hunger and malnutrition still of great concern, and school meals often consist of a sweet biscuit or sweetened maize porridge. In addition, drinking water is not fluoridated and some schools do not have running tap water.

For caries treatment for both techniques, no effort was made to remove caries or unsupported enamel5., 11.. For both techniques, we used cotton rolls to isolate the teeth from saliva and, for the IRT group, we used a cavity conditioner (GC Corporation, Tokyo, Japan) before sealing the cavities with GIC (GC FUJI IX GP, GC America, Inc.). All participants were advised not to eat or drink for 1 h after treatment. For the 30% SDF (Cariestop Biodynamic®) treatment, vaseline was applied to the soft tissues in order to avoid contact lesions caused by the caustic properties of SDF³. The SDF solution was left in contact with the tooth surface for 3 min, before the child was asked to rinse the mouth with water from a cup and spit.

The criterion used to classify active caries lesions in the SDF group was based on the classic study of Miller¹⁶. Thus, fabric with a hard consistency and dark colour was thought to be inactive caries. Active caries was recorded when the probe, applied with light force, easily penetrated the dentine. Arrested caries was recorded if dentine could not be penetrated by the probe. For the IRT group, we examined whether GIC was still present in the cavity and whether there was failure of the sealant; we checked the consistency of the dentine by its resistance to probing.

According to Kidd¹⁷, perfect sealing of the cavity with filling material, such as GIC, is able to arrest dentine caries. Thus, dentine caries was considered to be arrested when restorative material was present in the evaluations at 6 and 12 months.

A senior examiner with extensive experience in epidemiological studies was chosen to calibrate the examiner and to correctly codify the cavities according to the ICDAS 2010 criteria of Assaf et al.¹⁸.

On separate occasions, 10% of the sample was randomly selected to be re-examined for inter-examiner reproducibility. For data analysis, we used descriptive statistical techniques and the chi-squared test and Fisher’s exact test. Statistical tests were performed with a margin of error of 5.0%. Data were stored on an EXCEL spreadsheet and statistics were calculated using the Statistical Package for the Social Sciences (SPSS) version 15 (IBM, Chicago, IL, USA). Intra-examiner reproducibility for caries diagnosis was calculated by Cohen’s kappa test. The kappa for intra-examiner agreement was 0.86 for caries and 1 for arrested caries.

RESULTS

The group comprised 326 schoolchildren aged between 5 and 6 years; of these, 165 (50.6%) were male and 161 (49.4%) were female; 76.96% had carious lesions, 16.49% had teeth to be extracted and 6.55% had some type of restoration filling. Thus, the mean DMFT (decayed, missing and filled teeth) was 3.8 (Table 1).

Table 1.

Assessment of DMFT (decayed, missing and filled teeth) at baseline, group study

	Mean	Standard deviation	Median	Prevalence (%)
Caries	2.94	3.05	2.00	76.96
Indicated for extraction or teeth with pulp exposure	0.63	1.39	0.00	16.49
Filled	0.25	0.85	0.00	6.55
DMFT	3.82	3.68	3.00

After 6 months, children in the SDF group had 85% of their caries arrested, whereas those in the IRT group had lost 43.4% of their GIC fillings and their dentine was soft.

After 12 months, we found that SDF was again more effective [relative risk (RR) = 66.9%] than IRT (RR = 38.6%) for the arrest of caries, showing a statistically significant difference (P < 0.05) (Table 2).

Table 2.

Evaluation of the effectiveness of the treatments for arrest of decay

Group	Success				Failure				Total				P value		RR (95.0% CI)
	6 months		12 months		6 months		12 months		6 months		12 months		6 months	12 months	6 months	12 months
	n	%	n	%	n	%	n	%	n	%	n	%
SDF	155	84.7	113	66.9	28	15.3	56	33.1	183	100.0	169	100.0	<0.001*	<0.001*	1.59 (1.36–1.87)	1.73 (1.38–2.18)
IRT	86	53.1	59	38.6	76	46.9	94	61.4	162	100.0	153	100.0
Total group	241	69.9	172	53.0	104	30.1	150	46.6	345	100.0	322	100.0

CI, confidence interval; IRT, interim restorative treatment; SDF, silver diamine fluoride.

^*P values obtained by Pearson’s chi-squared test.

There was a higher rate of failure when the GIC filling involved multiple surfaces (two or more) (52.2%) relative to a single surface (47.8%) (Table 3).

Table 3.

Number of surfaces involved in cases of failure in the interim restorative treatment (IRT) group

Number of surfaces	n	%
Single	33	47.8
Multiple (two or more)	36	52.2
Total	69	100.0

DISCUSSION

This study was conducted in the city of Recife, in the northwestern part of Brazil, renowned for its high poverty, where access to free health care is poor and children have a high incidence of untreated caries. Our aim was to search for an alternative method for the treatment of caries in children that would increase access to oral health care.

We compared a modified ART technique, using GIC¹¹, with the application of 30% SDF. The reason for such a comparison was that GIC is recommended by the World Health Organization (WHO) as the material of choice for ART⁷, for the arrest of caries, and 38% SDF has also been proven to be effective in the arrest of caries⁴. However, this may be a difficult comparison to perform given the different nature of the two target procedures. Nevertheless, as our aim was to look for a successful method to arrest caries in children outside a clinical setting, it should be noted that IRT has been used in refugee camps in Cambodia⁸, and the SDF technique requires only a paint brush to administer and can be applied in schools in rural areas of Pernambuco where dental facilities are not available.

The results of this study showed that 30% SDF (Cariestop Biodynamic®) was more effective than IRT (FUJI IX GP, GC America, Inc.) for the arrest of caries. After a 12-month follow-up, SDF proved to be 1.73 times more effective than IRT: SDF, RR = 66.9%; IRT, RR = 38.6%.

The results of this study are in agreement with a systematic review conducted by Niederman et al.¹¹, which revealed very promising results favouring the use of 38% SDF for caries reduction, when applied once a year, ranging from a 96% reduction in caries for deciduous teeth to a 55.6% reduction in caries for newly erupted permanent molars⁵. In our study, we applied 30% SDF, given that 38% SDF is approved by the Brazilian health authorities for dental use; however, it is not currently available in the market.

The current literature shows that the rate of failure of GIC fillings after 12 months varies over a large range according to the type of cavity and different brands of GIC. The variation is in the range 12–96%¹⁹, which is consistent with the results for IRT in this study: RR of 38.6% after 1 year.

With regard to the reported effectiveness of GIC in the arrest of caries because of its claimed ability to release fluoride in the mouth, as a result of the high failure rate shown in this work, we were unable to observe this positive outcome; the loss of the filling material left open cavities in which caries progression occurred before replacement of the GIC sealant; this agrees with the previous study by Weerheijm et al.¹⁰. The latter authors reported that the sealing property of the GIC filling material is more effective in preventing caries than its so-called cariostatic property, claimed to prevent secondary caries²⁰.

However, according to Tantbirojn et al.²¹, the fluoride released by GIC would only be effective in preventing the progression of incipient carious lesions, which does not apply to lesions involving dentine. Moreover, the potential caries-preventive effect of GIC on dentine caries is claimed to be a result of its adhesive property to hard dental tissues; this is dependent on the ability of the material to hermetically seal cavities and prevent marginal linkage of the restoration, isolating the cavity from the external environment and reducing the chances of bacterial growth caused by the infiltration of biofilms, saliva, etc.¹⁷

This study also showed that there was no significant difference in the failure rate for fillings involving multiple or single dental surfaces: 52.2% and 47.8%, respectively; this indicates that the size of the cavity is not related to the loss of the restoration.

At this point, it is important to raise two very important questions. What do we mean by temporary restoration? What is the time line expected for the survival of a filling in deciduous teeth? According to Opdam et al.²², there is a need to enhance the evidence base with regard to the longevity of restorations. Currently, there is a lack of appreciation of the differences between survival data based on the age of failed restorations when compared with gold standard statistics. Opdam et al.²² conducted a study to compare and contrast longevity data for a number of datasets, and investigated whether restoration longevity, as calculated by the Kaplan–Meier method, differed from the longevity calculated according to the median survival time of failed restorations. Their results indicated that the median age of failed restorations may be considered as a deceptive measure of restoration longevity. Looking into the duration of the available longitudinal studies, their results showed higher values for the median age of failed restorations. Restoration materials that tend to exhibit early failures may yield lower values for the median age of failed restorations, compared with restoration materials which tend to exhibit failures later in clinical service, thereby not giving a true measure of the overall restoration longevity. In conclusion, Opdam et al.²² suggested that, in the absence of all dates of placement and failure for a series of restorations, a reliable measure of restoration longevity is not yet available. However, in poor geographical regions of the world, such as Recife, where the expected longevity of interim fillings is dependent on the need to prevent poor children from suffering from caries progression, this time line may be determined by socio-economic issues, rather than by the desired longevity of restorations.

At this point, we must stress that FUJI IX, the GIC brand recommended by WHO for ART, is not available on the market in developing countries, and its cost is almost 20 times higher than that of SDF ($800–$15,000). The same applies to fluoride varnish, the cariostatic agent of choice for developed countries, but still very difficult to access in poor communities, especially in South America.

The advantages of the use of 30% SDF over IRT suggest that its application may contribute significantly to improved access to a low-cost, effective method for reducing the burden of pain and suffering caused by dental disease in children. As we aim to reduce health disparities in the world, it would be useful to disseminate our scientific knowledge about the SDF technique to underserved communities at risk for caries, and to use it on a larger scale. As we shift from a conservative paradigm of treating caries to a more advanced philosophical approach, we must make a stronger effort to reduce health disparities in order to achieve social justice over a shorter time line.

CONCLUSION

The use of 30% SDF may be the method of choice for the arrest of caries worldwide in socioeconomically disadvantaged populations, shifting the paradigm from the sealing or filling of cavities in order to reduce active caries.

Acknowledgements

The authors wish to thank the Brazilian Ministry of Education (CAPES), the Brazilian Ministry of Science and Technology (CNPq) and the State of Pernambuco Department of Science, Technology and the Environment (FACEPE).

Conflict of interest

This study was funded by the Ministry of Education of Brazil. Thus, there is no conflict of interest between competing materials, nor any interference with the results of this article.