Assessment of colour modifications in two different composite resins induced by the influence of chlorhexidine mouthwashes and gels, with and without anti-staining properties: An in vitro study

Objectives: Chlorhexidine (CHX)-based products are the most effective chemical agents used in plaque control and oral disinfection. One of their side effects is tooth and restoration staining. For this reason, CHX products with anti-discolouration systems (ADS) have been developed. The aim of this in vitro study was to compare different CHX-based products (gel and mouthwash) with or without ADS in composite colour modification.Methods: Two hundred specimens were created, 100 of which were made of packable composite and 100 of flowable composite. After 24 h, colour coordinates (L*, a*, b*, C*, h degrees) were recorded using a spectrophotometer (T0). Then, all samples were subjected to a CHX/tea staining model and immersed in human saliva for 2 min. Composite specimens were divided in 10 groups (N = 20). Control groups (PC, FC) were soaked in distilled water and test groups (PG, PGads, FG, FGads, PM, PMads, FM and FMads) were immersed in CHX-based solutions or brushed with CHX gel. Then the cycle was repeated 6 times, and colour differences (Delta E-ab and Delta E-00) were finally calculated.Results: Through flowable composites, FC and FG showed the highest colour differences, respectively Delta E-ab = 3.48 +/- 1.0, Delta E-00 = 2.24 +/- 0.6 and Delta E-ab = 2.95 +/- 1.3, Delta E-00 = 1.53 +/- 0.6. In the composite groups instead, PM and PMads showed the highest colour differences, respectively Delta Eab = 2.78 +/- 1.3,Delta E00 = 1.94 +/- 0.8 and Delta E-ab = 2.71 +/- 1.4, Delta E-00 = 1.84 +/- 0.9.Conclusions: CHX-containing products are able to cause stains on restorative composite materials. Discolouration is more likely to occur in flowable composites than packable composites, and ADS-containing products cause fewer pigmentations than CHX products without ADS. Packable composites showed more staining after mouthwash treatment, whereas flowable composites underwent higher discolouration after treatment with gels.