Objective: To demonstrate the importance of using a matrix for treatment of root perforations with MTA (mineral trioxide aggregate), and to describe the treatment technique. Methods: The matrix can be created with calcium sulphate, resorbable collagen or calcium hydroxide. When calcium sulphate is used, the material should be carried through the perforation into the bone cavity in the periodontium until the material reaches the level of the external root surface. MTA is then placed in the perforation. Conclusions: Utilisation of a calcium sulphate, resorbable collagen or calcium hydroxide matrix is advisable when treating perforations with MTA, in order to avoid material extrusion into the periodontium. Keywords: calcium hydroxide, calcium sulphate, collagen