A nozzle element (1) for a dental treatment device, in particular for a dental treatment device intended for a subgingival cleaning of at least a part of a surface of a root of a tooth (3), comprising:- a basic body (2) being elongated in a longitudinal direction (L) and configured to be introduced at least partially into a periodontal pocket (7)- a first feed channel (10) for transporting a powder - gas - mixture (12), wherein said first feed channel (10) is incorporated inside the basic body (2),- a first outlet opening (11) of said first feed channel (10) in an end region (E) of the elongated basic body (2) for ejecting the powder - gas - mixture (12), wherein said first outlet opening (11) is preferably configured for a lateral ejection of the powder - gas - mixture (12) in a first ejection (E1) direction being slanted relative to the longitudinal direction (L),wherein the nozzle element (1) is configured for providing at least a part of at least one pressure relief channel at the end region (E) of the basic body (2).
