Abstract
Objective
To compare the effectiveness of three applications of silver diammine fluoride (SDF) solution at yearly interval and three applications of SDF solution or sodium fluoride (NaF) varnish at weekly interval at baseline in arresting active caries in the primary teeth of preschool children.
Methods
Children aged 3–4 years (n = 371) who had at least one active caries lesion (ICDAS codes 3–6) in their primary teeth were randomly allocated into three groups: Group 1 – annual application of 30% SDF solution; Group 2 – three applications of 30% SDF at weekly intervals; and Group 3 – three applications of 5% NaF varnish at weekly intervals. Follow-up examinations were performed every 6 mo nths by the same masked examiner.
Results
After 30 months, 309 (83%) children with 1877 caries lesions remained in the study. For cavitated lesions (ICDAS code 5 or 6), the caries arrest rate of Group 1 (48%) was significantly higher than those of Group 2 (33%) and Group 3 (34%), (p < 0.001). Results of multi-level survival analysis showed that the arrest times of cavitated lesions in both SDF groups (Groups 1 and 2) were significantly shorter than that of the NaF varnish group. For moderate caries lesions without visible dentine (ICDAS code 3 or 4), the caries arrest rates were 45%, 44% and 51% in Groups 1, 2 and 3, respectively (p > 0.05). Presence of plaque on caries lesion, tooth type and tooth surface type had an influence on caries arrest.
Conclusion
Over a 30-month period, annual applications of SDF solution is more effective than three weekly applications of NaF varnish or SDF solution at baseline in arresting active cavitated dentine caries lesions in primary teeth.
Clinical significance
As annual application of SDF solution was found to be more effective than 3 weekly applications of NaF varnish or SDF solution at baseline in arresting active cavitated dentine caries lesions, the former application protocol is preferred for young children who are available for regular caries arrest treatment.
1
Introduction
Early childhood caries is highly prevalent, particularly in socially disadvantaged children and in the developing countries [ ]. Using restorative approach alone is insufficient to tackle this problem and may perpetuate oral health inequalities, translating a skewed distribution of tooth decay into filled teeth [ ]. A systematic review found that progression of dental caries can be halted by topical application of fluorides without any operative treatments [ ]. Application of silver diammine fluoride (SDF) solution has been proposed for arresting caries that has extended into dentine [ , ]. SDF solution is professionally applied once or twice a year, but these application protocols may not be feasible in mobile populations or effective in high caries risk children. Few studies investigated the effectiveness of repeated topical fluoride applications within a short period of time on caries management and the results were inconclusive [ , ].
Earlier studies on caries arrest treatment using SDF were mostly conducted in children with incipient enamel caries [ ], or those with frank cavitated lesions [ , ].There is limited information regarding the efficacy of caries arrest treatment in moderate caries lesions, such as those coded 3 or 4 in the International Caries Detection and Assessment System (ICDAS) [ ]. Since the severity and the extent of caries lesion may affect the success of caries arrest treatment, it would be necessary to conduct a randomized clinical trial to find out which fluoride application protocol would be more effective in slowing down the progression of tooth decay at different stages of dental caries development. This trial aimed to compare the effectiveness of three applications of SDF solution at yearly interval and three applications of SDF solution or NaF varnish at weekly interval at baseline in arresting active caries in the primary teeth of preschool children. The null hypothesis was there is no difference between the three topical fluoride application protocols in their effectiveness in arresting active dental caries in primary teeth over a 30-month period. The intermediate (18-month) results on cavitated dentine caries lesions (ICDAS codes 5–6) were reported earlier [ ].
2
Materials and methods
A randomized controlled trial was conducted in kindergartens in Hong Kong where the fluoride concentration in drinking water is 0.5 ppm. Ethical approval was granted from the Institutional Review Board of the University of Hong Kong. This study was registered (clinicaltrials.gov #NCT02426619). Sixteen kindergartens were selected from the 120 participant kindergartens of an oral health promotion program, based on a previous finding that they had a high proportion of children with untreated dental caries. All children aged 3–4 years who had at least one untreated active caries lesion (ICDAS codes 3–6) were invited to participate. Exclusion criteria were children who suffered from major systemic diseases, required long term medication, or refused the study intervention. A single examiner (DD) with training in paediatric dentistry was calibrated with an experienced epidemiologist (EL). Clinical examination was performed in kindergarten with the use of a ball-end Community Periodontal Index (CPI) probe (Ash/Dentsply, Addlestone, UK) and a disposable dental mirror attached to a handle with an intra-oral LED light. Saliva, food debris and plaque obscuring visual inspection of tooth surfaces were removed but the teeth were not dried. At child level, the decayed, missing and filled tooth surface (dmfs) index and the visible plaque index (VPI) were adopted for recording dental caries experience and oral hygiene status, respectively. At tooth surface level, caries activity (arrested/active), extent of caries lesion (ICDAS codes 3 to 6), colour of lesion (yellow, light brown, hard brown, or black) and presence of plaque (yes/no) was evaluated. A decayed tooth was excluded when there were sign/symptoms suggesting pulpal pathology such as acute pain, pulpal exposure and abscess.
The sample size was estimated based on a caries arrest rate of 70% [ ], a 10% absolute difference in caries arrest rate being clinically significant, a statistical power of 80% (β = 0.2) and a statistical significance level of 5% (α = 0.05). Calculation results showed that 360 carious tooth surfaces per group were required. Since the mean number of carious tooth surfaces in Hong Kong preschool children was four [ ], approximately 90 children would be required in each group. With an anticipated 10% annual dropout rate, over 300 children were recruited at baseline.
After baseline examination, the children were classified into two strata by the number of carious tooth surfaces they had (1–4 or >4 tooth surfaces). Then, they were allocated to one of the three intervention groups according to computer-generated random numbers using stratified block randomization (block size of 6):
| Group 1: | 30% SDF solution (Cariestop, Biodinamica, Brazil) applied 3 times at yearly interval. |
| The first, second and third applications were at baseline, 12-month and 24-month examinations, respectively. | |
| Group 2: | 30% SDF solution (Cariestop, Biodinamica, Brazil) applied 3 times at weekly intervals after baseline. |
| Group 3: | 5% NaF varnish (Duraphat, Colgate Palmolive, USA) applied 3 times at weekly intervals after baseline. |
| For Groups 2 and 3, the first application was done shortly after the baseline examination, then followed by the second and the third applications after 1 week and 2 weeks, respectively. No further application was carried out. |
The randomization process was carried out confidentially by a research assistant who held the random allocation list and prepared the materials according to the child’s assigned group. A dentist who was not involved in the clinical examination carried out the fluoride application in the kindergarten. Steps of SDF solution application were as follows: 1) position the child supine on a table; 2) remove food debris, if any, from the caries cavity; 3) isolate the decayed tooth; 4) remove excess saliva by a gauze or cotton pellet, if needed, but no air drying; 5) apply the solution on the carious tooth surfaces with a microbrush and rub for 10 s; 6) inform the class teacher that the child should not eat, drink, or rinse mouth in the next 30 min. The same technique, applying either fluoride agent or placebo (water) with a disposable microbrush, was employed in the follow-up interventions. The study children, their parents, kindergarten teachers, treatment providers and the sole examiner were blinded to the children’s group allocation.
Information regarding the children’s background (demographic and socio-economic background, behaviors related to oral health) was collected by a questionnaire filled by their parents at baseline and 24-month follow-up. Parental satisfaction with their child’s oral health status was also assessed. Follow-up examinations were performed every 6 months by the same masked examiner to assess whether the active caries lesions had become arrested after receiving the topical fluoride treatment.
For cavitated dentine caries lesions diagnosed as ICDAS code 5 or 6, visual inspection and tactile detection using a 0.5 mm ball-ended CPI probe were used for assessing caries activity. If a wall or floor of the lesion was soft and easily penetrated by the probe using light force, then it was diagnosed as active ( Fig. 1 ). A lesion with all surfaces being hard and smooth was diagnosed as arrested caries [ , ].For a moderate caries lesion with no visible dentine (ICDAS code 3 or 4) at baseline, it was classified as arrested caries at follow-up examinations if the lesion did not progress to become a cavitated lesion with visible dentine (ICDAS code 5 or 6) [ ].
At baseline and follow-up examinations, duplicate examinations were conducted on 10% of the study children selected randomly. Cohen’s Kappa statistics was used to assess the intra-examiner reliability. An intention-to-treat analysis, without imputation of outcomes, was adopted. Data were analyzed using the software SPSS 20.0 for Windows (SPSS Inc., Chicago, USA). The level of statistical significance was set at 0.05.
For moderate caries lesions, multi-level logistic regression analysis using GLIMMIX procedure, SAS/STAT ® software version 9.3 (SAS Institute Inc., Cary, NC, USA), was performed to analyze the effects of independent factors on caries arrest at the 30-month examination. The independent factors included gender, age, frequency of tooth brushing, use of toothpaste, frequency of snacking, tooth type, tooth surface and the intervention group.
For cavitated dentine caries lesions, multi-level survival analysis was adopted using the software WinBUGS, version 1.4. The statistical procedures used in the analysis were similar to those described in detail in the 18-month results paper [ ].
2
Materials and methods
A randomized controlled trial was conducted in kindergartens in Hong Kong where the fluoride concentration in drinking water is 0.5 ppm. Ethical approval was granted from the Institutional Review Board of the University of Hong Kong. This study was registered (clinicaltrials.gov #NCT02426619). Sixteen kindergartens were selected from the 120 participant kindergartens of an oral health promotion program, based on a previous finding that they had a high proportion of children with untreated dental caries. All children aged 3–4 years who had at least one untreated active caries lesion (ICDAS codes 3–6) were invited to participate. Exclusion criteria were children who suffered from major systemic diseases, required long term medication, or refused the study intervention. A single examiner (DD) with training in paediatric dentistry was calibrated with an experienced epidemiologist (EL). Clinical examination was performed in kindergarten with the use of a ball-end Community Periodontal Index (CPI) probe (Ash/Dentsply, Addlestone, UK) and a disposable dental mirror attached to a handle with an intra-oral LED light. Saliva, food debris and plaque obscuring visual inspection of tooth surfaces were removed but the teeth were not dried. At child level, the decayed, missing and filled tooth surface (dmfs) index and the visible plaque index (VPI) were adopted for recording dental caries experience and oral hygiene status, respectively. At tooth surface level, caries activity (arrested/active), extent of caries lesion (ICDAS codes 3 to 6), colour of lesion (yellow, light brown, hard brown, or black) and presence of plaque (yes/no) was evaluated. A decayed tooth was excluded when there were sign/symptoms suggesting pulpal pathology such as acute pain, pulpal exposure and abscess.
The sample size was estimated based on a caries arrest rate of 70% [ ], a 10% absolute difference in caries arrest rate being clinically significant, a statistical power of 80% (β = 0.2) and a statistical significance level of 5% (α = 0.05). Calculation results showed that 360 carious tooth surfaces per group were required. Since the mean number of carious tooth surfaces in Hong Kong preschool children was four [ ], approximately 90 children would be required in each group. With an anticipated 10% annual dropout rate, over 300 children were recruited at baseline.
After baseline examination, the children were classified into two strata by the number of carious tooth surfaces they had (1–4 or >4 tooth surfaces). Then, they were allocated to one of the three intervention groups according to computer-generated random numbers using stratified block randomization (block size of 6):
| Group 1: | 30% SDF solution (Cariestop, Biodinamica, Brazil) applied 3 times at yearly interval. |
| The first, second and third applications were at baseline, 12-month and 24-month examinations, respectively. | |
| Group 2: | 30% SDF solution (Cariestop, Biodinamica, Brazil) applied 3 times at weekly intervals after baseline. |
| Group 3: | 5% NaF varnish (Duraphat, Colgate Palmolive, USA) applied 3 times at weekly intervals after baseline. |
| For Groups 2 and 3, the first application was done shortly after the baseline examination, then followed by the second and the third applications after 1 week and 2 weeks, respectively. No further application was carried out. |
The randomization process was carried out confidentially by a research assistant who held the random allocation list and prepared the materials according to the child’s assigned group. A dentist who was not involved in the clinical examination carried out the fluoride application in the kindergarten. Steps of SDF solution application were as follows: 1) position the child supine on a table; 2) remove food debris, if any, from the caries cavity; 3) isolate the decayed tooth; 4) remove excess saliva by a gauze or cotton pellet, if needed, but no air drying; 5) apply the solution on the carious tooth surfaces with a microbrush and rub for 10 s; 6) inform the class teacher that the child should not eat, drink, or rinse mouth in the next 30 min. The same technique, applying either fluoride agent or placebo (water) with a disposable microbrush, was employed in the follow-up interventions. The study children, their parents, kindergarten teachers, treatment providers and the sole examiner were blinded to the children’s group allocation.
Information regarding the children’s background (demographic and socio-economic background, behaviors related to oral health) was collected by a questionnaire filled by their parents at baseline and 24-month follow-up. Parental satisfaction with their child’s oral health status was also assessed. Follow-up examinations were performed every 6 months by the same masked examiner to assess whether the active caries lesions had become arrested after receiving the topical fluoride treatment.
For cavitated dentine caries lesions diagnosed as ICDAS code 5 or 6, visual inspection and tactile detection using a 0.5 mm ball-ended CPI probe were used for assessing caries activity. If a wall or floor of the lesion was soft and easily penetrated by the probe using light force, then it was diagnosed as active ( Fig. 1 ). A lesion with all surfaces being hard and smooth was diagnosed as arrested caries [ , ].For a moderate caries lesion with no visible dentine (ICDAS code 3 or 4) at baseline, it was classified as arrested caries at follow-up examinations if the lesion did not progress to become a cavitated lesion with visible dentine (ICDAS code 5 or 6) [ ].
At baseline and follow-up examinations, duplicate examinations were conducted on 10% of the study children selected randomly. Cohen’s Kappa statistics was used to assess the intra-examiner reliability. An intention-to-treat analysis, without imputation of outcomes, was adopted. Data were analyzed using the software SPSS 20.0 for Windows (SPSS Inc., Chicago, USA). The level of statistical significance was set at 0.05.
For moderate caries lesions, multi-level logistic regression analysis using GLIMMIX procedure, SAS/STAT ® software version 9.3 (SAS Institute Inc., Cary, NC, USA), was performed to analyze the effects of independent factors on caries arrest at the 30-month examination. The independent factors included gender, age, frequency of tooth brushing, use of toothpaste, frequency of snacking, tooth type, tooth surface and the intervention group.
For cavitated dentine caries lesions, multi-level survival analysis was adopted using the software WinBUGS, version 1.4. The statistical procedures used in the analysis were similar to those described in detail in the 18-month results paper [ ].
3
Results
At baseline, 371 preschool children were included in this study. Their mean (±SD) age was 41 + 4 months and 222 (60%) of them were boys. The numbers of children in Group 1 (three SDF applications at yearly interval), Group 2 (three SDF applications at weekly interval at baseline) and Group 3 (three NaF applications at weekly interval at baseline) were 124, 122 and 125, respectively. There were 880, 799 and 847 active caries lesions in the Groups 1 to 3, respectively. The children’s mean (±SD) dmft score was 3.7 ± 3.5 and the dmfs score was 5.6 ±6.8. The distribution of caries lesions with ICDAS codes 3, 4, 5 and 6 were 28%, 6%, 46% and 20%, respectively. Regarding the colour of the lesions at baseline, yellowish lesions were commonly found (73%), followed by light brown lesions (23%), while dark brown and black lesions were uncommon ( < 5%). Approximately half of the lesions were located in primary molars. At baseline examination, most of the lesions had visible plaque present on the surface. There were no statistically significant differences among the three groups regarding the children’s demographic background, oral hygiene status and caries experience ( Table 1 ). All parents returned the baseline questionnaire. Most (83%) of the study children used toothpaste and 85% of them brushed their teeth daily. Regarding the children’s oral health related behaviors and parental satisfaction with their child’s oral health, no significant differences were found among the three intervention groups (χ 2 test, p > 0.05).
| At baseline examination | At 30-month examination | |||||
|---|---|---|---|---|---|---|
| Gp1 a (n = 124) | Gp 2 a (n = 122) | Gp 3 a (n = 125) | Gp1 a (n = 101) | Gp 2 a (n = 102) | Gp 3 a (n = 106) | |
| Mean VPI score | 56% | 55% | 53% | 56% | 56% | 52% |
| Mean dmfs (SD) score | 5.6 (6.4) | 5.0 (6.3) | 6.1 (7.7) | 5.5 (6.2) b | 4.9 (6.5) b | 6.4 (8.0) b |
| Tooth type included | ||||||
| % Anterior teeth | 50% | 48% | 52% | 50% | 48% | 54% |
| Tooth surfaces included | ||||||
|
36% | 40% | 37% | 37% | 39% | 36% |
|
35% | 33% | 39% | 36% | 33% | 40% |
|
29% | 27% | 24% | 27% | 28% | 24% |
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