Dentals.
These sounds are formed with the tongue tip behind the
upper front teeth. The symbol used for this sound is (Ө)
usually referred as "theta". which is voiceless, and the
voiced dental is represented by the symbol ( ð ) usually
called "eth".
Alveolars.
These are sounds formed with the front part of the
tongue on the alveolar ridge, which is the rough, bony
ridge inmediately behind and above the upper teeth.
The alveolar symbols are: (t), (s) which are voiceless,
(z), (d) & (n) are voiced.