The objective of this research is to evaluate the oral modifications caused by different types of coke drinks (regular coke and diet coke). The salivary and the dental biofilm pH will be determined in the first minutes after their consumption. Additionally, the bacterial proliferation of dental biofilm will be evaluated.

Sugary soft drinks modify oral pH and favor bacterial proliferation and are associated with the development of caries. Information on the effects of consuming carbonated drinks without sucrose is limited.

In this crossover clinical trial, salivary pH and dental biofilm pH will be determined. These will be registered at 0, 5, 10, 15, 30, 45, and 60 min after the participants ingested 355 ml of natural water, soft drink with sucrose, soft drink with aspartame/acesulfame K or carbonated water on different days (1 week between each other). In addition, dental biofilm cultures will be conducted at 0 and 120 minutes after intake of each beverage to determine Streptococcus mutans biofilm formation.

The patients will be invited to participate and informed of the potential risks. Those who signed informed consent and have eligibility requirements will be randomized in a double-blind manner.

The data collection will be carried out in records forms, including verifying the patient's previous conditions, identification data (ID, age, gender,) and possible adverse events. If any adverse effect could exist, the research team will be notified for the implementation of possible changes.

A HANNA HI 221 potentiometer (HANNA Instruments Inc. Woonsocket-RI-USA, Romania) will be used to determine salivary pH and dental biofilm pH. The electrode will be calibrated using buffer solutions of pH 4.0 and 7.0 for correct records. The electrode will be washed with distilled water before and after each sample. The data will be collected by 2 verifiers, guaranteeing that the information obtained is the same as that indicated on the potentiometer; a stopwatch will indicate the exact time for obtaining the pH values.

Samples of dental biofilm will be taken, and Streptococcus mutans biofilm formation will be evaluated at 0 and 120 minutes after taking each beverage. The samples will be cultivated in suitable conditions, identified and compared with ATCC. The samples obtained will be analyzed in the same place of collection to avoid possible contamination.

Sample size with an alpha=0.05 and a beta=0.8 include 22, considering 20% losses.

Variables will be described with frequencies and percentages or medians and interquartile range (IQR) according to the variable type. Salivary pH and dental biofilm at different times will be compared using ANOVA analysis with adjustment for multiple comparisons using Bonferroni correction. Changes in the bacterial proliferation of the dental biofilm at 0 and 120 min will be compared using the Wilcoxon test and intergroup changes will be compared using the Kruskal-Wallis test. The statistical program SPSS v. 22 will be used and statistical significance will be considered with a p ≤ 0.05

Inclusion Criteria:

• Habitual consumption of soft drinks
• DMFT (Decayed, Missing, and Filled Teeth) index of at least 3
• Agree to participate in the study and sign informed consent
• Parents sign informed consent
• Any nutritional condition

Exclusion Criteria:

• Undergoing orthodontic treatment
• Received a topical application of fluoride during the last 3 months
• Having a motor disability that interfered with tooth brushing
• Consuming drugs or being carriers of diseases that cause xerostomia
• Being under antibiotic therapy during the study period
• Having active periodontal infections.

IPD that underlie results in a publication

when summary data are published

The data will be shared with researchers interested in data analysis, request to email: americaml@hotmail.com, review of the request by MSc., PhD. America Liliana Miranda Lora

colors were designated for each drink