Randomized clinical trial on arresting dental root caries through silver diammine fluoride applications in community-dwelling elders

Abstract

Objectives

To investigate the effectiveness of silver diammine fluoride (SDF) solution application in arresting dental root caries and to assess the color of arrested caries lesions.

Methods

This study was conducted in elderly centers in Hong Kong. A total of 83 elders with 157 root surfaces with active caries lesion were randomly allocated into 3 groups: Gp1 (placebo control)—annual application of soda water; Gp2–annual application of SDF solution; Gp3–annual application of SDF solution immediately followed by potassium iodide (KI) solution. Color of the arrested root caries lesion was assessed with reference to PANTONE color plates and classified into one of the followings: yellow (7401U); light brown (1245U); dark brown (4635U); and black (Black U). Status of root surfaces was assessed every 6 months by the same independent examiner.

Results

After 30 months, 100 (64%) of the included root caries lesions were reviewed. The arrest rates of root caries were 45%, 90%, and 93% in Gp1 (control), Gp2 (SDF) and Gp3 (SDF/KI), respectively (χ 2 test, p < 0.001). Pairwise comparisons showed elders in the control group had a lower proportion of the active root caries changed to arrested (p < 0.001) and the proportions of root caries being arrested in the SDF and SDF/KI groups were not significantly different (p > 0.05). The distributions of arrested caries lesions by color were not significantly different between the SDF and SDF/KI groups (χ 2 test, p > 0.05).

Conclusions

Application of SDF solution, with or without application of KI afterwards, is effective in arresting root caries among elders in a water fluoridated area. In the long term, blackening of arrested root caries is not reduced by immediate application of KI after the application of SDF.

Clinical significance

In a water fluoridated area, annual application of SDF solution or SDF/KI solution can arrest dental root caries in elders. In the long term, application of KI does not reduce the blackening of arrested caries lesions caused by SDF.

Introduction

Dental root caries is a prevalent oral disease among elders world-wide and the incidence increases with age . The reported prevalence of root caries in elders varies in different countries but a high proportion of the caries lesions being untreated active decay is common . A recent oral health survey conducted in Hong Kong found that 25% of the community-dwelling adults aged 65–74 years had root caries experience and 80% of the caries lesions were untreated . Poor oral health knowledge, infrequent tooth brushing and low utilization of dental care services among the elders are some possible explanations for the high proportion of untreated caries . Since advanced root caries can cause pain, tooth loss, and impact on general health, there is a need to develop affordable and effective treatment approaches to manage the untreated caries lesions on root surfaces in the elders.

Nonsurgical intervention for shallow dentin caries lesion has been advocated . Topical application of fluoride agents is a conservative treatment and a potentially good alternative to the surgical approach. Silver diammine fluoride (SDF) has been shown to be effective in arresting dentin caries in primary teeth of young children , and recommended for preventing and arresting root caries lesions . However, so far, only one clinical trial on using SDF to arrest dental root caries among community-dwelling elders can be found in the literature which reported that annual application of 38% SDF solution was effective and that oral health education had synergetic action with SDF application . It should be noted that the final 24-month follow-up examination in that study was conducted after only two applications of SDF solution on the study root surfaces, i.e. at baseline and after one year. The longer term effectiveness of SDF needs further investigation.

Previous clinical studies on SDF reported that it was common to have black stain on the arrested caries lesions which may cause an aesthetic concern . It has been suggested that by applying a saturated solution of potassium iodide (KI) immediately after the application of silver fluoride, staining of the dentin caries lesion can be minimized while the caries arrest effect of silver fluoride is not affected . The proposed explanation is that the iodide ions from the KI solution will react with the excess silver ions from the silver fluoride solution to form a precipitate of silver iodide. It would be a win-win situation if KI can prevent the staining associated with SDF without reducing its effectiveness in arresting caries. However, evidence from clinical trial is lacking to support this claim.

This study focused on promoting oral health among elders, including preventing new root caries and arresting existing active root caries. This paper reports on the effectiveness of the following three methods in arresting dental root surface caries among community-dwelling elders: (1) annual application of soda water (placebo); (2) annual application of 38% SDF solution; and (3) annual application of SDF solution immediately followed by KI solution. Another objective was to assess whether application of KI solution immediately after SDF application could affect the color of the arrested root caries lesions. The first null hypothesis to be tested was that there is no difference in the effectiveness of the three methods in arresting root caries. The second null hypothesis was that there is no difference in the distribution of arrested root caries lesions by color between the SDF group and the SDF/KI group.

Materials and methods

This study was a randomized clinical trial conducted in community elderly centers in Hong Kong, a city with water optimally fluoridated at 0.5 ppm, using a parallel group design. Ethical approval was obtained from the Institutional Review Board of the University of Hong Kong and the trial was registered (clinicaltrials.gov # NCT02360124).

Subject recruitment

The study population was community-dwelling elders without serious health problems. These elders lived independently in their own home and could participate in various activities organized by community centers. Notices regarding a free oral health talk were put up in 12 selected community centers for elders located in different districts of Hong Kong. Members of the elderly centers freely chose to attend the function. Details of this clinical trial were given at the end of the talk and elders who were interested were clinically examined by a dentist in the center. Subject inclusion criteria were having one or more teeth (not indicated for extraction) with active root surface caries; no cognitive problems in communication; and having self-care ability for normal daily activities. Elders whose salivary gland function had been significantly affected by disease, medication, or treatment such as radiotherapy in the head and neck region were excluded. Written informed consent was obtained before commencement of the study.

Baseline examination

The baseline examination was carried out by a trained examiner. A portable dental chair, intra-oral LED light, disposable dental mirrors, CPI probes and graduated (in mm) periodontal probes were used in the examination. Status of the exposed root surfaces of each natural tooth was assessed. Plaque and calculus obscuring visual inspection of the root surfaces was removed using cotton buds and hand instruments. Four surfaces per tooth (mesial, distal, buccal and lingual) were examined and the status was diagnosed according to the criteria recommended by the International Caries Detection and Assessment System (ICDAS II) Coordinating Committee . Root caries lesion and its activity status was detected by visual-tactile examination. Active caries was recorded when the lesion surface could be easily penetrated by a blunt (0.5 mm ball-ended) probe with light force. Inactive (arrested) caries was recorded if the lesion surface was hard and smooth . Caries lesion that have an extension of at least 1 mm beyond the cementum-enamel junction was recorded as root caries lesion. A caries lesion was recorded as involving more than one root surface when it extended beyond the line angle to involve at least one-third of the adjacent tooth surface. Other clinical parameters recorded on each included root surface were: presence or absence of plaque seen visually, greatest gingival recession (in mm), and close proximity (within 3 mm) to a partial denture.

Intervention

After the baseline examination, subjects satisfying the study inclusion criteria were randomly allocated to three groups using block randomization. A list was produced with a block size of 6 which contained 90 different combinations. A dental surgery assistant carried out the subject allocation according to the combinations randomly generated by computer. Both the examiner and the subjects were blinded to group assignment. Interventions were provided by another dentist. In Group 1, placebo control, soda water with a bitter flavor (to mimic the bitter metallic taste of SDF) was painted onto root surfaces with active caries by using a disposable microbrush. In Group 2, a 38% SDF solution (Saforide, Toyo Seiyaku Kasei Co., Ltd., Osaka, Japan) was painted onto the active caries lesions. In Group 3, KI solution (2.36 mol/l) was painted onto the caries lesion immediately after the application of 38% SDF solution. The KI solution was prepared in laboratory with distilled water and KI powder (SIGMA-ALDRICH Co., St. Louis, USA). The above procedures were repeated after 12 and 24 months. In addition, individualized oral hygiene instructions, including how to properly brush the teeth with a manual toothbrush and use of interdental brush, and a tube of fluoride toothpaste (1450 ppm fluoride, Colgate, USA) were given to all study subjects at each examination.

Follow-up

Follow-up lasted for 30 months and clinical examination was carried out every 6 months after baseline by the same examiner. The same equipment and diagnostic criteria were used in all examinations. Arrested root caries was recorded when an active root caries lesion found at baseline changed into inactive at follow-up. Color of the arrested root caries lesion was classified into one of four categories according to PANTONE ® color plates placed next to the lesion ( Fig. 1 ), namely yellow (7401U), light brown (1245U), dark brown (4635U), and black (BlackU). A random sample of 10% of the subjects were re-examined at baseline and follow-up examinations to monitor examiner reproducibility.

Fig. 1
Assessment of the color of arrested caries lesion using color plates: a) the lesion was light brown; b) the lesion was dark brown; and c) the lesion was black.

Sample size

While this paper reports on the effects of SDF solution on arresting active root caries, this clinical trial also studied prevention of new root caries in the elders and the findings will be reported in another paper. The study sample size calculation was based on the primary outcome which was development of new root caries over 30 months. An annual increment of 0.8 carious tooth root surface was found in the control group elders in a previous clinical trial in Hong Kong . In order to show that a 50% difference between the highest and the lowest mean caries increments in the three study groups was statistically significant at a 5% significance level and at a 80% power, a sample size of 80 subjects in each group was required. Allowing for a drop-out rate of around 25% over 30 months, an initial sample size of slightly over 100 subjects in each group was used.

Data analysis

All collected data were input into computer and analyzed using the statistical software SPSS for Windows version 20. The intention-to-treat approach for data analysis was adopted. One way analysis of variance (ANOVA) was used to assess the differences among the three study groups regarding the mean number of exposed sound root surfaces, root caries experience and active decayed root caries lesions at baseline. Chi-square test was used to find out if there were statistically significant differences among the three groups in the distribution of active root caries lesion which became arrested after intervention. Chi-square test was also used to assess the distribution of the arrested caries lesion according to color in the SDF group and the SDF/KI group. The statistical significance level for all tests was set at 5%.

In addition, multilevel survival analysis was conducted using the grouped proportional hazards (PH) model in WinBUGS (version 14) to assess factors that affected the time for an active root caries lesion to change into arrested (the arrest time). In the 2-level model adopted in this analysis (root surface as level-1 and subject as level-2), the arrest times of active root caries lesion in the three study groups were compared. Education level, frequency of sweet snack intake, tooth brushing frequency, visible plaque index (VPI) score at baseline, close proximity to a denture, and presence of plaque on lesion surface at baseline were included in the model as covariates. Survival functions were used to estimate the caries arrest rates.

Materials and methods

This study was a randomized clinical trial conducted in community elderly centers in Hong Kong, a city with water optimally fluoridated at 0.5 ppm, using a parallel group design. Ethical approval was obtained from the Institutional Review Board of the University of Hong Kong and the trial was registered (clinicaltrials.gov # NCT02360124).

Subject recruitment

The study population was community-dwelling elders without serious health problems. These elders lived independently in their own home and could participate in various activities organized by community centers. Notices regarding a free oral health talk were put up in 12 selected community centers for elders located in different districts of Hong Kong. Members of the elderly centers freely chose to attend the function. Details of this clinical trial were given at the end of the talk and elders who were interested were clinically examined by a dentist in the center. Subject inclusion criteria were having one or more teeth (not indicated for extraction) with active root surface caries; no cognitive problems in communication; and having self-care ability for normal daily activities. Elders whose salivary gland function had been significantly affected by disease, medication, or treatment such as radiotherapy in the head and neck region were excluded. Written informed consent was obtained before commencement of the study.

Baseline examination

The baseline examination was carried out by a trained examiner. A portable dental chair, intra-oral LED light, disposable dental mirrors, CPI probes and graduated (in mm) periodontal probes were used in the examination. Status of the exposed root surfaces of each natural tooth was assessed. Plaque and calculus obscuring visual inspection of the root surfaces was removed using cotton buds and hand instruments. Four surfaces per tooth (mesial, distal, buccal and lingual) were examined and the status was diagnosed according to the criteria recommended by the International Caries Detection and Assessment System (ICDAS II) Coordinating Committee . Root caries lesion and its activity status was detected by visual-tactile examination. Active caries was recorded when the lesion surface could be easily penetrated by a blunt (0.5 mm ball-ended) probe with light force. Inactive (arrested) caries was recorded if the lesion surface was hard and smooth . Caries lesion that have an extension of at least 1 mm beyond the cementum-enamel junction was recorded as root caries lesion. A caries lesion was recorded as involving more than one root surface when it extended beyond the line angle to involve at least one-third of the adjacent tooth surface. Other clinical parameters recorded on each included root surface were: presence or absence of plaque seen visually, greatest gingival recession (in mm), and close proximity (within 3 mm) to a partial denture.

Intervention

After the baseline examination, subjects satisfying the study inclusion criteria were randomly allocated to three groups using block randomization. A list was produced with a block size of 6 which contained 90 different combinations. A dental surgery assistant carried out the subject allocation according to the combinations randomly generated by computer. Both the examiner and the subjects were blinded to group assignment. Interventions were provided by another dentist. In Group 1, placebo control, soda water with a bitter flavor (to mimic the bitter metallic taste of SDF) was painted onto root surfaces with active caries by using a disposable microbrush. In Group 2, a 38% SDF solution (Saforide, Toyo Seiyaku Kasei Co., Ltd., Osaka, Japan) was painted onto the active caries lesions. In Group 3, KI solution (2.36 mol/l) was painted onto the caries lesion immediately after the application of 38% SDF solution. The KI solution was prepared in laboratory with distilled water and KI powder (SIGMA-ALDRICH Co., St. Louis, USA). The above procedures were repeated after 12 and 24 months. In addition, individualized oral hygiene instructions, including how to properly brush the teeth with a manual toothbrush and use of interdental brush, and a tube of fluoride toothpaste (1450 ppm fluoride, Colgate, USA) were given to all study subjects at each examination.

Follow-up

Follow-up lasted for 30 months and clinical examination was carried out every 6 months after baseline by the same examiner. The same equipment and diagnostic criteria were used in all examinations. Arrested root caries was recorded when an active root caries lesion found at baseline changed into inactive at follow-up. Color of the arrested root caries lesion was classified into one of four categories according to PANTONE ® color plates placed next to the lesion ( Fig. 1 ), namely yellow (7401U), light brown (1245U), dark brown (4635U), and black (BlackU). A random sample of 10% of the subjects were re-examined at baseline and follow-up examinations to monitor examiner reproducibility.

Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Randomized clinical trial on arresting dental root caries through silver diammine fluoride applications in community-dwelling elders
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