Following on from my recent post: Making Mistakes, I have decided to start up this thread which will constantly be updated to include some of my personal encounters on clinics as a dental student.
I will always try to be as honest as possible, offering my own hindsight thoughts, commentary and lessons. I guess I just want to create an outlet that I can use to put my experiences in writing, first and foremost for my own benefit, but also hopefully to share my journey with fellow dental students, dental professionals and prospective dentistry applicants.
The most recent ‘diary posts’ will be added at the top of this thread.
As always: any feedback, comments or ideas you might have – please share!
I couldn’t get my temporary crown off the prepped tooth!
Exciting times. I was doing my first anterior crown prep. It was a discoloured upper right lateral incisor that had been root treated (by me). I was looking forward to this appointment for a few weeks’ leading up to it – and had done my homework the night before so was mentally prepared for it. There was a pre-exisiting composite in the tooth’s crown- placed by a previous dentist. The appointment got off to a fine starty, my preparation went well. Fast forward one hour, I was doing the final refinements and was using the red band fine diamond to smooth the prep when all of a sudden the old composite just came out! Just like that, in the blink of an eye it flew out and was sucked up immediately by the high power suction tube. With my absolute inexperience when it comes to indirect restorations, I went into a mode of internal panic – trying my best not to outwardly express my panic to the patient. I stopped, asked my supervising clinical tutor to come over to check up on me as and they reassured me that it was relatively easily to address: I just needed to replace the composite and then refine the prep before continuing. I re-restored the tooth and made my preparation refinements – it didn’t take long at all. Then came the time to construct the temporary crown – I applied a light layer of petroleum jelly to the prepped tooth and adjacent teeth then injected the ProTemp bisacryl composite material into my putty matrix. My temporary crown didn’t come off! I tried to off as carefully as possible, whilst applying controlled force with my flat plastic – it wasn’t budging. After ~5 minutes of me struggling to get the temp crown off, I accepted it and just broke the temp crown off and made a new one. The rest of the appointment went fine – I took my impressions, refined the new temp crown and cemented it. Here’s the big lesson I learnt from this experience: the bisacryl composite temp crown material WILL bond to any freshly placed composite. That’s why I couldn’t get the first temp off – it had bonded to the surface layer of the resin material I had just placed in the tooth. Here’s hoping I don’t make the same mistake again – next time: more petroleum jelly and prep away oxygen-inhibited surface layer of any ‘freshly placed’ composite. And that is why we need to know our dental materials science!
Don’t place blind faith into old/existing restorations when working on a tooth. They might let you down
The lesson of the day was to replace old composites in a tooth before starting with a crown prep. The tooth being treated was a lower premolar, which was treatment planned for a full metal crown.
The tooth in question has been in the restorative cycle for many years. It had a large DO amalgam that had fractured then eventually came out during function after many years of service, which I then temporarily replaced with a GIC before then removing the temporary dressing and placing a composite core. The tooth also had a buccal composite, which had some staining around it at the restoration-tooth interface but no signs of secondary decay. The patient could not recall exactly how long ago the buccal composite was placed, but it looked like it had been there a long time. Anyway, the crown preparation was going fine until I was prepping the buccal surface – just minimally to acheive the ideal 0.5mm reduction with a chamfer margin. As I was doing so, the buccal composite just came out leaving a little hole in the side of the tooth. After a moment of panic from me, I resolved to quickly replacing it with a fresh well-bonded resin then refine the prep. The rest of the appointment went fine, although my temporary crown left a lot to be desired (I need to practice making temporary crowns more!).
One of the main learning points for me from this appointment was to examine any existing restorations before doing further work on a tooth, because you can never be sure of how well placed they were, how well looked after they have been by the patient etc. In hindsight, I should have anticipated this and replaced the old composite from the start – the staining around its margins was the big clue for me which I just ignored. Lesson learned.
This was my first experience with a patient who has a maxillary flabby ridge. The patient is an elderly gentleman with a relatively complex treatment plan. In this appointment, I was intending to take the master impression for his upper complete denture. Given his flabby ridge, I made a light-cured acrylic special tray and then cut out a window anteriorly into the special tray – because the plan was to use the selective displacement technique. I was really excited for this appointment as I knew I was going to be doing something totally new, but I did not expect it to be such a challenge! I’d done lots of prep for the appointment: I was mentally prepared about what I needed to do, I had read lots of information about the selctive displacement technique online and from published papers in the dental journals – I’d even watched videos on YouTube about it so felt I had a good grasp of what I needed to do. It did not go to plan, at all. I was optimistic when I was taking the first impression.
After presenting to my tutor, I called the patient in and got started – checking the tray in the patient’s mouth for over/under-extension etc. My first attempt at taking the impression left a lot to be desired – it was not clinically acceptable. Any dental technician would have taken one look at it and sent it back saying it was not even close to being good enough to work with. When using the selective displacement technique, you need to take the mucodisplasive aspect of the impression first, then cut out any material within the window before taking the mucostatic aspect of the impression (i.e. impression of the flabby ridge) by syringing a light body silicone into the window. It seemed so simple but I found it difficult to execute. After showing the tutor my first attempt, she agreed it had to be redone so I proceeded to remove the material from my tray and get it ready to go again. The second attempt wasn’t much better. I had to apologise to the patient, thank him for his patience and do it again. The tutor helped me with the third attempt. Watching her, I learnt some little tricks – such as using the 3-in-1 syringe to blow air against the light-body material as it is starting to set against the flabby ridge. The third attempt was better, but still not good enough. But by this point, time left in the appointment was running out and the patient had had enough. Don’t forget that the silicone material takes ~4 minutes to set, and each time I took the impression I had to wait for the medium-body mucodisplasive to set first, then cut my window and wait another four minutes for the light-body to set.
With the benefit of hindsight, I now appreciate how important the tray design was, and always is. In this case, the main reason the impression was not good enough any of the times I tried was that the window I had cut out in my special tray was far too big, and the frame anteriorly in the tray was far to thin – meaning it could not support much of the silicone material and therefore was now allowing my impression material to be supported in the correct position. This was an incredibly frustrating afternoon for me, and the patient wasn’t best pleased. I am grateful as always for the lessons learnt from this experience and have since made a new special tray with a smaller window and a better anterior frame, which I am sure will allow me to take a great impression when the time comes to go again very soon.
As soon as I get to the lab I will take a photo of the two special trays and post them here to help you understand what I mean! I will also link a few great articles about managing patients with flabby ridge.
Today I learnt how important it is to take your time and follow every single step properly when using resin-based cement to place a full coverage non-precious metal crown.
Although I have used a resin cement before, it was Rely-X and they are different systems with their own specific multi-step instructions for use. I got onto clinic early, checked my labwork, disinfected everything, set up the bay and checked the crown on the die. All was looking good.
I removed the temporary crown, cleaned the prepared tooth of any temporary cement and checked the fit of the crown. Internal fit was fine, occlusion was fine, contacts fine, margins fine, aesthetics fine – patient happy. I placed an optragate to help with moisture control, open my field of view to help with the crown cementation. I had the instructions in front of me and followed them exactly step by step. Time to mix the two paste Panavia 21 cement and insert it into the crown. The instructions clearly state it should be mixed and left as a THIN LAYER! My assistant helped with the mixing and they did not present it to me as a thin layer, there was a mini clump of the cement on the pad and it was already setting (given the chemical nature of how this cement sets). Despite this, silly me, I continued to use the thin mix cement and some of the clumpy part-set cement as well. This was my crucial mistake. I know this with the frustrating benefit of hindsight. Because there was a small amount of set cement already inside the crown, as I seated it, despite me applying lots of finger pressure it didn’t seat 100% (as it had done so when I checked the fit without cement just a moment before). I hesitated at the time when I was scooping up the clumpy cement I felt like something was not quite right, but I proceeded wrongly to use it anyway. This was my first time using Panavia 21 and I will make sure to do it completely right next time.
I have learnt how important it is to follow the instructions exactly. It is very technique sensitive using resin cement and I appreciate this a little more now. Without doubt there are countless more mini mistakes for me to make as I continue to learn how to properly do adhesive dentistry with indirect restorations. Any sort of open margin will compromise the longevity and clinical success of the restoration – ultimately, this is a compromise that is not fair on the patient. Poor cementation can immediately destine an restoration for inevitable early failure and therefore should be cut off and redone.
An open margin will lead to the ingress of bacteria and other micro-organisms that will cause secondary caries, leakage under the crown/cement and undermine the underlying tooth tissue until the tooth can no longer be saved. It is an absolute neccessity for the margins to be within clinically acceptable limits.
Has this ever happened to any of you? I hope I am not the only one, but regardless, I have appreciated this frustrating experience as it has led to my greater respect for the importance of good cementation.