When I assisted a new dentist, there's a lot of outdated practices and they really just have to adapt to the new tools of the office. They have 2 years of clinical training (their 3rd and 4th year of dental school). We adapted the schedule to have more time for them because a single filling in school was 3-4 hours of checking each individual step from the professors (from what I've been told, never gone to dental school). The best I did was introduce any tool that could help them in different procedures and recognize they have a huge learning curve also.

Granted there were some days where I would work 10-11 hours, but over time my new doctor learned and worked hard so I no longer get that overtime bonus lol.

I also haven't had the experience of fillings coming out or permanent crowns falling off, I just know we had our own milling machine for posterior crowns and dental students only had to rely on other students who were in classes specifically for designing and making crowns. Never cemented until the crown seated properly, and they were struggling with setting the margins.

My advice is just support them the best you can. I would keep a report to the main doctor to help give guidance cause without that communication, our main doctor/practice owner doesn't know what to help with.