Salivary Flow, pH, and Buffering Capacity in Fixed and Clear Aligner Orthodontic Treatment

February 2, 2026 updated by: Omar Alkadhi, Riyadh Elm University

Changes in Salivary Parameters in Patients Undergoing Clear Aligner Orthodontic Treatment: A Randomized Controlled Trial

Study Design: A randomized controlled trial with two parallel arms and an allocation ratio of 1:1.

Setting: The study will be conducted in the orthodontic department of Riyadh Elm University hospitals in Riyadh City, Saudi Arabia.

Participants: Patients undergoing fixed or clear aligner orthodontic treatment referred to REU dental hospital will be randomly allocated to either the clear aligner group or the fixed orthodontic appliance group.

Intervention: Prior to orthodontic treatment, all patients will receive phase I periodontal therapy and oral hygiene instructions. Fixed orthodontic appliances will be bonded using metallic brackets with a 0.022-inch slot and 0.014-inch NiTi archwires. Clear aligner patients will receive Invisalign® treatment.

Outcomes and Saliva Collection: Salivary samples will be collected using the spitting method at baseline (T0) and follow-up time points according to the study protocol. Salivary flow rate, pH, and buffering capacity will be assessed as described in the proposal.

Randomization and Blinding: Randomization will be performed using a random number generator with allocation concealment via opaque envelopes. The investigators involved in outcome assessment and data analysis will be blinded.

Ethical Considerations: The study will be submitted to the Institutional Review Board at Riyadh Elm University and conducted in accordance with IRB policies.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

This study is a randomized controlled clinical trial designed to evaluate changes in salivary parameters in patients undergoing fixed orthodontic treatment or clear aligner therapy. Patients referred to the orthodontic department of Riyadh Elm University dental hospital will be screened for eligibility and randomly allocated into two parallel groups with an allocation ratio of 1:1.

Prior to the initiation of orthodontic treatment, all participants will undergo phase I periodontal therapy and receive standardized oral hygiene instructions. Patients in the fixed orthodontic appliance group will be treated using metallic brackets with a 0.022-inch slot and initial 0.014-inch nickel-titanium archwires. Patients in the clear aligner group will receive clear aligner treatment according to the prescribed protocol.

Salivary samples will be collected using the spitting method at baseline before the start of orthodontic treatment (T0) and at subsequent follow-up time points as specified in the study protocol. Salivary flow rate, salivary pH, and buffering capacity will be assessed at each time point using standardized methods described in the proposal.

Randomization will be carried out using a random number generator, with allocation concealment ensured through the use of opaque sealed envelopes. The investigators involved in outcome assessment and data analysis will be blinded to group allocation.

This study will be conducted following approval from the Institutional Review Board (IRB) of Riyadh Elm University and in accordance with institutional ethical guidelines.

Study Type

Interventional

Enrollment (Estimated)

40

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Class I, II and III skeletal malocclusion.
  • Age ≥18 undergoing fixed or Clear aligner orthodontic treatment.

Exclusion Criteria:

  • Current medications including antibiotic use within the past 3 months that affect salivary flow and composition.
  • Active smoking including vaping and E-cigarette use.
  • Diagnosis of systemic diseases/conditions such as Sjogren's syndrome, diabetes, chronic kidney diseases, neurological conditions.
  • Active dental caries or signs of gingivitis and/or periodontitis
  • Less than three months of orthodontic treatment since it is characterized by acute, temporary changes and patient adaptation to the new appliances.
  • Requiring single arch treatment to standardize the research and eliminate a potential confounding variable
  • Crown restoration is excluded due to their material properties which may affect salivary composition.
  • Pregnancy due to the physiological variation in salivary flow and composition due to hormonal changes.
  • Presence of mouth breathing may lead to inconsistent salivary flow rate, Changes in Salivary Composition and pH
  • Poor oral hygiene with high levels of dental plaque, calculus, and gingival inflammation can independently alter salivary flow rate, pH, and buffer capacity there by acting as confounding variable.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Fixed orthodontic treatment control group
Study subjects in control group will receive fixed orthodontic appliances with metallic brackets of 0.022-inch slot size (American Orthodontics). The bonding process will be performed using the same adhesive (BracePaste, American Orthodontics) for all patients, and treatment will be initiated with 0.014-inch NiTi archwires (Highland Metals).
Device: Fixed orthodontic appliances
Study subjects in control group will receive fixed orthodontic appliances with metallic brackets of 0.022-inch slot size (American Orthodontics).
Experimental: Clear Aligner Treatment Group
Study subjects in Clear Aligner treatment group will receive Invisalign® (Align Technology, Inc., Tempe, AZ, USA). The Clear Aligner treatment protocol will be followed until the end of the treatment.
Device: Clear Aligner Treatment
Study subjects in Clear Aligner treatment group will receive Invisalign® (Align Technology, Inc., Tempe, AZ, USA). The Clear Aligner treatment protocol will be followed until the end of the treatment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Salivary flow rate
Time Frame: The outcome measure will be assessed at (T0) just before the commencement of fixed appliance and Clear Aligner therapy, at one week (T1), at two weeks (T2), after three months (T3), and at six months (T4) of treatment.
The salivary flow rate will be recorded in each patient. Two mL of whole unstimulated saliva will be collected in a graduated tube. The salivary flow rate will be recorded in all the four time points T0, T1, T3 and T4.
The outcome measure will be assessed at (T0) just before the commencement of fixed appliance and Clear Aligner therapy, at one week (T1), at two weeks (T2), after three months (T3), and at six months (T4) of treatment.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Salivary pH
Time Frame: The outcome measure will be assessed at (T0) just before the commencement of fixed appliance and Clear Aligner therapy, at one week (T1), at two weeks (T2), after three months (T3), and at six months (T4) of treatment.
The pH values will be assessed using portable pH meter strips at the same four time points. Salivary pH will be measured at T0, T1, T3 and T4.
The outcome measure will be assessed at (T0) just before the commencement of fixed appliance and Clear Aligner therapy, at one week (T1), at two weeks (T2), after three months (T3), and at six months (T4) of treatment.
Salivary buffering capacity
Time Frame: The outcome measure will be assessed at (T0) just before the commencement of fixed appliance and Clear Aligner therapy, at one week (T1), at two weeks (T2), after three months (T3), and at six months (T4) of treatment.
Buffer capacity will be determined by quantitative test using a hand-held pH meter method. This method will involve addition of 0.5 ml of saliva to 1.5 ml of 5 mmol/L HCl. Mixtures will be vigorously shaken. Then stream of Nitrogen will be passed through the mixture for 20 min to eliminate carbon dioxide from the sample and allowed to stand for 10 min when the final pH will be measured. The salivary buffering capacity will be measured at T0, T1, T3 and T4.
The outcome measure will be assessed at (T0) just before the commencement of fixed appliance and Clear Aligner therapy, at one week (T1), at two weeks (T2), after three months (T3), and at six months (T4) of treatment.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Riyadh Elm University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

March 15, 2026

Primary Completion (Estimated)

February 15, 2027

Study Completion (Estimated)

May 29, 2027

Study Registration Dates

First Submitted

February 2, 2026

First Submitted That Met QC Criteria

February 2, 2026

First Posted (Actual)

February 9, 2026

Study Record Updates

Last Update Posted (Actual)

February 9, 2026

Last Update Submitted That Met QC Criteria

February 2, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • REU-CA-SALIVA-RCT-001

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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