While pronouncing S, T, D, N, Z sounds, tip of tongue makes contact with:
Linguopalatal sounds (Anterior Palate):

The linguopalatal sounds are “C (soft), D, T, N, Z and R”
Produced by: When the tip of the tongue contacts the anterior portion of the palate or the lingual side of anterior teeth.
Importance of Linguopalatal sounds: When the denture base in the rugae area is too thick and can produce a similar effect. “S” sounds produced by the position of the tongue so that air stream released through a small gap between tongue and rugae, “S” will sound as “SH” when anterior teeth are anteroposteriorly displaced.
Anterior 2/3rd of plate
Maxillary canines
Inner 2/3rd of lower lip
Does not make any contact