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

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.