Its the reality of any tight appointment based service
Im not actually dentist but work in a nhs based service, where we often run over, cancel appts last minute etc. All of the spare excess in the system is being trimmed, for example I would often have a buffer between some appointments that would limit the knock on effect of a patient taking longer than anticipated, and would be able to book a 25 min appt in a 30 min slot to give flex. That's all gone so the second I run over its a cascade of issues and often the slot times arent sufficient to do the actual work in practicality.
This is especially true in things like dentistry when non clinicians, contractors and payment by slots, all are used to determine the most that can be fit in a day which often massively under estimates admin time for tasks.
Our admin are now only funded to work the surgery opening times, we used to have admin that started earlier than the slots so if I called in sick, the first slot of the day could be at least cancelled with 30 to spare, now it gets cancelled at 9 when I (and the admin) starts and the patient is probably due in.
Equally the number of spare slots is slim (and you are under significant pressure to be fully booked, and not be operating under 95% capacity). When for example my car broke down on a way to an appt, I knew that the patients house who i was already meant to be at would be rebooked in a terrible time frame because I simply dont have slots. I booked her in a very urgent slot, was told off as she wasn't urgent and then had an actual emergency that I sent to a+e because I couldn't do it. The rest of the patients cancelled on that day waited about 6 months
Theres limited spare capacity so an unexpected call, a broken bit of machinery, child going home sick from school in the middle of the day all can tip a mundane day into cancellations past appointment times and big delays.
Unless people are happy to campaign for funding for spare clinicians to cover unforseen events and for slack in the system then it will continue