Adjunctive Effects of a 2% Zinc Citrate Toothpaste on Plaque and Oral Microbiota in Orthodontic Patients: A Randomized Controlled Trial.

Abstract

Introduction: Zinc citrate trihydrate (ZCT) has antibacterial and anti-inflammatory properties and is widely used in oral-care products. However, evidence regarding its effectiveness in orthodontic patients remains limited. This study aimed to evaluate the effects of a toothpaste containing 2% ZCT on gingival inflammation, plaque accumulation, and plaque-associated bacterial load in patients wearing fixed orthodontic appliances.

Methods: A randomized controlled clinical trial was conducted among 102 patients with plaque-induced gingivitis undergoing fixed orthodontic treatment. Participants were randomly assigned to use either a toothpaste containing 2% ZCT (test group) or a conventional toothpaste without ZCT (control group). The gingival index (GI) and Modified Quigley-Hein Plaque Index (MQHPI) were recorded at baseline, after 1 week, and after 4 weeks. Supragingival plaque samples were collected at baseline and after 4 weeks and analyzed using real-time polymerase chain reaction to quantify selected plaque-associated bacterial species. Linear mixed-effects models were used to evaluate the effects of time, treatment, and their interaction on GI and MQHPI.

Results: Exploratory time-specific comparisons at 4 weeks showed lower GI and MQHPI and lower loads of Fusobacterium nucleatum (Fn), Tannerella forsythia (Tf), and Solobacterium moorei (Sm) in the ZCT group. However, the longitudinal mixed-effects analyses showed no significant treatment-by-time interaction for either the clinical outcomes or the quantitatively assessable bacterial species.

Conclusions: Both groups showed clinical improvement over time. However, the longitudinal analyses did not demonstrate an additional clinical or microbiological effect attributable to the 2% ZCT toothpaste during the 4-week study period.