The clinic doesn't take appointments except for ongoing treatments.
Initially I too was feeling inconvenience but then I spoke to my ex classmate who is a dentist & he said this:
The advantage of group practice is having dentists who are good in a particular field of treatment and being assigned accordingly is certainly good for the patient!
I understood what he was saying...
If a clinic has a mix of newly hired & experience dentists, it is better to regulate the traffic.
"Oh...6 monthly checkup? No other issue right? Let's see ... Maybe Dr Teng,... he's friendly & bubbly....& good looking too
"
"Pain huh?...I think Dr Ramakrishnan is good at that. He's our expert in pain trauma...you won't feel a thing."
So Dental CH Tee assigns the best available dentists for the patients' needs/urgencies instead of an appointment.