First patient and Immediate denture impression technique

 In my new role the very first patient I met was a difficult denture case. There are upper and lower canine to canines were remaining and the periodontal condition was so severe that the lower teeth are grade 3 mobile and less than 1mm of bone is holding the upper teeth in. In the public system, this would be an open and shut full clearance and delayed denture case as the teeth would clearly come out in the impression but in the private setting, the boss had treatment planned a phased immediate denture and had already extracted the posteriors. I had told him that I enjoy the denture process and mysteriously I have found all of his denture cases have been transferred to me. 

So walking into the practice having this case in front of me I was faced with a challenge as I had a situation I had not encountered previously and had time pressure as he wanted the dentures made before his birthday in 3 weeks. It occurs to me that private patient's demands are more reasonable as they are paying and so have more control in the direction of their treatment than public patients. Not so much as to control how we treatment plan, but we will tend to comply with their requests given that they are reasonable.

The challenges that I perceived in the first appointment was initially to bring the patient's expectations down. To boost his confidence in the incoming dentist they had said I was very good at dentures and he'd like me very much. About half of the first appointment was spent disabusing him of that notion. One mistake I made in the first appointment was to not to approach the case the way that I normally would. I was overstimulated by the new environment, new systems and new staff and didn't examine the patient the way I would normally. I noted in the second appointment, in the posterior maxilla he had bony exostoses which are not bony undercuts which would make denture construction and retention difficult. I failed to discuss this in the first visit and so I perceive that I lost face when I mentioned it in the second visit. 

The second challenge in the first visit was how to take the impression without pulling out the teeth. The teeth were so loose I don't even know how they were still in place. The upper teeth were only grade 2 mobile so I was confident that an alginate wouldn't pull them out if I could block out the black triangles so I placed tray wax in between the teeth and took the upper impression. On removing the impression I was sure to lift the lip and place one finger under the periphery of the impression and pull down on that and the handle to break the seal of the impression. I also made sure to pull the impression out slightly anteriorly and downwards along the long axis of the teeth.

With the lower teeth, it was much more challenging as the lower incisors were much looser and they had massive chunks of calculus on the lingual surfaces which were larger than the teeth themselves and produced a massive undercut on the teeth. I considered taking an ultrasonic and removing the calculus but I supposed that the force would remove the teeth and although the teeth weren't joined, the calculus of each incisor contacting the next gave some measure of support to the teeth. Additionally, removing the calculus would increase the interproximal undercuts. My technique was to put a very bulky amount of periphery wax between the teeth to remove any interproximal undercuts as well on the labial embrasures and on the lingual area underneath the calculus so the material wouldn't flow. One downside of the wax is that it can be dislodged when the impression is seated and will be pushed to the periphery and if it is picked up in the impression it can be distorted easier than the impression material as it does not set firm. I covered the upper and lower teeth in vaseline to reduce the "stickiness" of the alginate and took the impressions uneventfully. 

The next challenge was to plan the sequence of appointments in a way that allowed a predictable and timely result. This was not a problem in previous jobs as my first 2 jobs I didn't do any denture work and in my public job, I would approach the case completely differently. I figured I could take the secondary impressions (which were needed as the primary impressions were inadequately accurate due to the copious amounts of wax) and the bite registration at the second visit. As the patient's teeth were overerupted and uneven, the bite registration in the posterior segments would not allow me to convey to the technician where I wanted the anterior teeth placed to achieve a good aesthetic result. I got around this in the second visit by marking on the primary case the area I wanted to place the incisal edge and midline to guide the technician. The final difficulty was how to try the teeth in to ensure an adequate result. The patient is paying for this treatment and any gross malpositions of the denture teeth would necessitate a remake of the denture with the cost borne by the patient. I discussed this with him and we settled on him agreeing to have all the teeth extracted at the try in stage which would allow me to try in the whole denture and once the aesthetics was approved, he would stay at home until the denture was processed. This would give us the ability to see how the denture would look while it could still be altered and I could reset the teeth if they were completely off. 

Moving forwards, the second appointment was the secondary impressions and bite registration appointment. I'm fairly happy with the quality of lab work given by this technician but there are a few things I will be requesting in the future for him to do with our denture cases. A benefit of private is that you can choose which technician you want to work with and can develop a relationship with them as they are financially incentivised to do a good job for you. I marked on his tooth with a pencil where I wanted the final incisal edge to go and carved the upper wax rim to this level taking into account the ala-tragus line and interpupillary line. The lower rim I carved to get the OVD and to fit well against the upper rim to allow me to take the bite. I took the bite in wax.

The secondary impressions were done with a technique I hadn't used previously. I couldn't use the same bulk of wax underneath the calculus as it encroached on the lingual sulcus and the lingual periphery of the denture would be inaccurate. I asked for some advice from a prosthetist at my public job and he suggested using light or heavy body PVS to block out the undercuts. I thought this not a bad idea as it would set firm but still be flexible enough to be removed, would hold in well enough to not be dislodged by seating the tray and if picked up in the impression wouldn't distort as much as wax. However, I didn't trust my ability to manpilate the unset PVS in between the teeth and under the bulk of calculus keeping away from the lingual sulcus depth. Instead I took a lesson from one of Dr. Findlay Sutton's lectures on immediate dentures where he would cut out the whole labial flange of a stock tray so that the alginate would only lay on the lingual. He would then lay PVS bite registration material on the exposed tooth labial surface which would set and he would remove the 2 pieces separately and superglue them together outside the mouth to make one impression. I used a bur to cut the labial flange off the tray covering the lower teeth, border moulded with greenstick and took the alginate impression. One thing I noted was that even though I tried to underfill the tray in the tooth area, the alginate would flow out on seating the tray and covered the tooth labial surfaces. I considered leaving it like that initially thinking that the material would be flexible enough to flex around the tooth but decided not to risk it and used my fingers to push the material back away from the teeth. Without removing the tray (because I thought I may not be able to get it back in), I extruded fast set heavy body PVS on the labial surfaces and border moulded. The irregularities of the alginate surfaces and the tray were enough to allow me to reseat the PVS outside the mouth. The benefit of this technique is that the impression material is not surrounding the tooth in any location and so can't provide an extracting force on removal. Especially in this case as the undercut was on the lingual, I removed the PVS first and lifted the posterior segment first and pushed the tray posteriorly to disengage the lingual undercut. I then disinfected the impression, dried and superglued the impressions together. If doing this again, I would use a stiffer material as this brand of PVS was still quite flexible but considering the time it took me, I wouldn't use fast set bite registration if there was a large tooth borne area to be captured as I think it would set by the time I border moulded. Perhaps a different brand of heavy body PVS or something like impregum which would still give a good working time but would set much stiffer. Some of the wax from between the teeth came out in the alginate and hindered seating of the PVS so I just flicked this out of the impression and could confirm that the impressions fit together well.

 I will see how this denture case goes and I am sure that I will learn a lot in any case. A new job brings a new environment, new possibilities and new challenges and I will see how things play out in the near future.