The development of modern dentistry, by improving the properties of materials and techniques used in clinical practice, also changed the approach to the treatment of hard dental tissue. The basic postulate and goal to which every dental practitioner of the twenty-first century should strive is to avoid invasive procedures, to preserve hard dental tissue, natural anatomy and tooth morphology to the greatest extent possible. One of the modern methods that allows us to achieve this goal and whose research and introduction into wider clinical application is still being done is infiltration technique. It is a microinvasive method that was originally intended for the treatment of initial carious lesions, especially those located on the proximal tooth surfaces but has been more frequently used in the treatment of aesthetically unsatisfying discolorations on vestibular, smooth surfaces. The principle of action of infiltration technique is based on penetration of low-viscosity resin, with high penetration coefficient into the pores caused by demineralization or disorder in the mineralization of enamel during tooth development. This increases mechanical tooth strength and allows remineralization of the demineralized area, but also corrects aesthetic defects as the refractory index of demineralized dental tissue approximates with the one of healthy enamel by penetrating the resin. It was the most efficient in therapy of discolorations caused by dental fluorosis, while in the cases of discolorations of different etiology the results were somewhat modest and the masking was incomplete. If we are talking about carious indication, ICON can be used in lesions that radiographically reach the inner enamel layer, or up to the outer third of the dentine, while in the case of deeper lesions its application is not indicated.