36 eligible participants will be randomly divided into three groups (n=12) according to the tested chewing gum (A), where (A1) represents participants exposed to xylitol chewing gum, (A2) represents participants exposed to bicarbonate and xylitol chewing gum and (A3) represents control group where participants are exposed to paraffin pellet chewing. The pH of saliva will be evaluated according to time in relation to the gum chewing (T) where (T0) represent the pH before chewing, (T1) represent 5 minutes after gum chewing at fixed time of the day (in the morning from 10 to 11 am).

Direct benefit of the research to the human volunteer:

It is important for high caries risk patients to decrease caries susceptibility as this will eventually decrease their dental treatments and subsequently the treatment cost.

Scientific value and social benefits:

This study will benefit the dentist as the main goal of a dentist is to prevent rather than cure. Also, it will decrease the restorative work carried out by dentist and save this time for educating more patients about caries prevention methods.

Expected risk to the human subjects:

Allergic reactions due to any of the components of the materials used which is rare to occur.

Inclusion Criteria:

• Patients eligible for the trial must comply with all of the following at randomization.

  1. Age range from 20-50 years
  2. High caries risk patients defined according to American Dental Association (ADA)
  3. Acidic baseline saliva pH
  4. Systematically healthy
  5. Not taking any medication interfering with saliva secretion
  6. Subjects who signed informed consent

Exclusion Criteria:

• (1) Subjects who wore orthodontic appliances or removable prosthesis (2) Subjects suffering from any medical or systematic disease (3) Smokers (4) Pregnant females (5) Allergy to any of chewing gum ingredients