This study focus on the pharmacokinetic characteristic of silver diamine fluoride (SDF) in healthy children. All of the children received treatment for the decayed teeth in the same way. A medication called silver diamine fluoride is used to treat the decayed teeth. It contains a high concentration of fluoride (range from 14100 ppm to 51013 ppm) and silver. This medication halts the decay process through the combined effects of anti-bacterial from silver and remineralization from fluoride. As this product contains the highest concentration of fluoride level found in the market and the metal element of silver, the investigators aim to study the body's reaction towards SDF. The investigators collect the hair and urine samples at different time points and then analyze them to determine the silver and/or fluoride levels. The outcomes include 1. the silver level in the hair and urine samples 2. the fluoride level in the urine samples. The investigators analyze the silver level in hair and urine samples using Inductively Coupled Plasma Mass Spectrometry (ICP-MS); fluoride level in urine samples using Ion-Selective Electrode.

This research aims to determine the pharmacokinetics characteristics of silver and fluoride following topical application of Silver Diamine Fluoride (SDF) in healthy children. The use of Silver Diamine Fluoride is increasingly widespread since the device is approved by the Food and Drug Administration (FDA) of the United States in 2014, especially among the pediatric population. It is a single-arm, clinical study with the specific objectives: 1. to assess the level of silver and fluoride in the urine sample of patients receiving the SDF treatment; 2. to evaluate the pharmacokinetics of silver, based on the hair sample of patients receiving the SDF treatment. The investigators hypothesize that the pharmacokinetic characteristics of silver diamine fluoride in healthy children are different from that of silver diamine fluoride in healthy adults. The research is taking place at the Paediatrics Dentistry Specialist Clinic, Faculty of Dentistry, University of Malaya. The investigators have used a convenience sampling method to recruit children aged 4-10 years old to join the study. The investigators have calculated the sample size based on the alpha error probability of 0.05 and the power of study at 95%. The investigators have recruited children with at least one decayed primary tooth without clinical signs or symptoms. Radiographically the deepest layer of caries lesion does not involve the pulp. The investigators have excluded children with known medical illness, having glass ionomer or stainless steel crown restorations in the oral cavity. All of the recruited patients received the same intervention, the application of SDF onto the tooth cavity. The investigators have taken the patients' biological samples (urine and hair) to assess the silver and/or fluoride levels. The urine samples are collected before the SDF treatment, in the first and second 24 hours after the SDF treatment. Besides that, hair samples are collected before the SDF treatment, followed by days 7,14,30,60,75, and 90 after the SDF treatment. The silver level in hair and urine samples were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS); fluoride level in urine samples using Ion-Selective Electrode. After review at days 90, if caries remains active despite the SDF treatment, the investigators will restore the SDF treated teeth or continue the six-monthly application of SDF depending on the patient's ability to cope with the procedure and the caries status.

Inclusion Criteria:

1. Healthy children aged between 4 to 10 years old

• With at least one decayed primary tooth without clinical signs or symptoms suggesting reversible or irreversible pulpitis.
• Radiographically the deepest layer of caries lesion does not encroach on pulp, and inter-radicular supporting structures appear normal

Exclusion Criteria:

1. Children aged below 4 years and above 10 years

2. Healthy children aged between 4 to 10 years old

   • Do not have decayed teeth
   • The decayed tooth with clinical signs or symptoms suggesting reversible or irreversible pulpitis
   • Radiographically the deepest layer of caries lesion does encroach on pulp, and inter-radicular supporting structures appear abnormal
   • No consent and permission to join the study
   • Taking medications/over the counter medications/supplements
   • Known allergy to silver or fluoride
   • Presence of ulcer in the mouth which has not heal completely
   • Presence of at least one tooth treated with silver fillings or stainless steel crown.
   • Presence of at least one tooth filled with a material that contains glass particles known as glass ionomer within a year before this research.
   • Children with medical problems