Yes, for healthcare degrees usually the emphasis is more on you experiencing a caring role and then you reflecting on your experiences in that

There's a reference thread in the medicine forum about volunteering and work experience here that might be helpful to read:
https://www.thestudentroom.co.uk/showthread.php?t=6929328It's more medicine focused in terms of specifics but I imagine some of the general points apply for dentistry as well

I think for securing a placement it would just be case of contacting different places, make sure you also leave your details so if they have something open up in future they can let you know.
Also try asking about shadowing opportunities - and not just for your desired role (e.g. dentist) but also other roles which work around/support them (e.g. dental hygienists/nurses, even perhaps the office/admin staff in a dental surgery) as that will likely all give you a better idea of how dentistry works overall as a profession (remembering you'll need to work with all those kinds of people as a dentist on a daily basis too so knowing what they do and where their care ends and yours begins and vice versa is probably useful!). It will also give you opportunities to understand the overall patient journey in dentistry beyond when they're in your chair which will hopefully give you lots of things to reflect on

For other things though try casting a wide net and not just within dentistry - care homes, hospices, charities supporting vulnerable people/people with long term conditions, GP surgeries, hospitals, etc, all might have opportunities to experience work experience/observation in/of a caring role to reflect on.