I'd like to suggest you that, if you're dealing with StoreProcedure then only use
cmd.Parameters
, otherwise for inline query (like you've written for UPDATE) you can directly set the values...
Now let me correct your query by this way (I'll not write entire query):
string UpdateQuery = "UPDATE teet SET teethmodel='"+comboBox1.SelectedItem.ToString()+"',noteeth='"+comboBox2.SelectedItem.ToString()+"' WHERE teethmodel='"+comboBox1.SelectedItem.ToString()+"'";
cmd.CommandText=UpdateQuery;
cmd.Connection=con;
cmd.ExecuteNonQuery();