tips and tricks

For some reason, I had a long period of no denture cases coming in. For maybe 1-2 years I did a couple of fractured denture repairs but no new denture cases. Lately there have been some new ones coming in which have been enjoyable to work with. I thought I would make a post regarding modification vs remaking of dentures. Of course by modification I don't mean something simple like adjusting a denture sore spot, where we obviously wouldn't remake a denture, but for where there is a significant discrepancy between what the denture should be like and what it is like e.g changes to the fit or teeth. One common dilemma when a patient comes in with an old set of dentures is do we do nothing, do we try to improve the current denture, or do we start again and create a new set for the patient. My take on this is simple, if I can make an improvement to their current denture and this improvement will make a significant difference to the patient then it is justifiable to do something for t...

It has been countless times that I or the technician have broken teeth off the stone model. Gluing the tooth back onto the model leads to unnecessary fragility and inaccuracy of the model. I am breaking them off less frequently these days but this involves identifying the risk factors for breaking teeth and employing strategies to avoid this occurence. Risk factors: Essentially, anything that introduces an undercut or a thin isthmus of stone.  - Tilted teeth especially proclined or retroclined incisors. Breaking off molars is less frequent as they are short and wide and have less severe undercuts -Teeth with reduced periodontium. This introduces black triangles for material to lock into and increases the undercut as the root diameter is less than the crown diameter. The more severe there perio, the thinner and weaker the root will become. -Triangular teeth: Same issue with black triangles -Porous stone: If the stone is poured with lots of bubbles, the void in the stone will act as ...

 The special tray material I have encountered come in the light cured and chemical cure varieties. The light cured variety is rougher and are premade in thin sheets. Therefore they are simpler to use as an acrylic baseplate for wax rims/bite blocks and the wax can stick to the rougher surface and they can be made thin to leave space to set teeth. They also seem stronger in thinner sections compared to the chemical cure variety. One thing to note is hat although the chemical cure variety comes out a lot smoother and may be nicer for the patient, if it is heated, it tends to soften and melt slightly. This can be beneficial as adjusting it on a trimming wheel, the excess slumps together and can be peeled off compared to light cured tray material which will produce a lot more dust. However, the downside is that for denture impressions, heating the tray in a flame is ill advised as the tray will soften and become deformable. For crown and bridge, and other impressions where the extensio...

When you are adjusting the dentures to remove overextensions which cause instability or for sore spots, look at the tissues and see how they match up with the denture base. I don't put a lot of trust and faith in indicators such as pressure indicating pase because it is very dependant on the amount you put and the pressure at which you apply the denture to the tissues. If you put a very thick layer on the denture it may not be removed even with significant pressure. If the pressure spot is also quite light, it may not have enough pressure to displace even a thin layer of PIP. The material itself is quite viscous and sticky. Half the time, it will stick to the tissue and be removed from the denture surface. Other times, the viscosity will displace tissue at the sulcus and won't reveal overextensions. A light bodied material won't displace tissue as much and instead will be displaced off the denture revealing pressure spots. Inspecting the tissues is especially important at t...

 Lately I've been using alginate in a stock tray for the final impression for chrome dentures. If poured up quickly after the impression, alginate is a fantastically accurate material and has proven more than adequate for chrome impressions. One issue that can arise is bubbles in the mix and on tissue surfaces. To minimise bubbles in the mix, invest in an alginate mixer as this will minimise the problem. Take some alginate on your finger and smear it onto tooth surfaces especially occlusal surfaces and the distal surface of the most distal tooth to explude bubbles from the impression surface. Do this wile your assistant is loading the tray and seat the tray shortly after. For dentures that will be significantly tissue borne e.g free end saddles, avoid over seating the tray which will displace the tissues too far and result in an overextended denture. For kennedy class 3 dentures it is not so critical as the dentures will be mainly tooth supported.

A few months ago I went for another day to observe a prosthodontist in private practice. I had the notes from the day written down but had put off posting it due to laziness. Below are some of the procedures I observed on the day: - Review of suckdown resins to close black triangles: The patient whose consultation that I observed at a prvious visit had had his resin additions done with a suckdown technique to close the black triangles. His black triangles were as a result of triangular teeth with mild recession therefore required a prosthodontic solution. I was observing the review appointment where the teeth were to be separated. Embrasures were cut into the teeth a the bonding visit and spaces opened to allow piksters to go through. Line angles and the location of the proximal contact was defined with the waxup but the teeth were still stuck together. Suck down resin veneers will stain at edges making areas that aren't bonded easier to see staining at first review but doesn'...

A few months back I encountered a patient in the public clinics who had had an all on 4 prosthesis placed in the maxilla and mandible a few months prior. Personally, I felt as though he was an incredibly highly strung person and at the state at which I met him I would be hesitant to do any large scale dentistry on. His personality may have been a true reflection of himself or it may have had something to do with the state he was in about his all on 4 treatment. The patient had gone through a few sets of full dentures over quite a number of years and actually didn't mind the dentures too much but his story was that he had come into some money and felt as though he wanted to make some positive changes to his health and transition to a fixed prosthesis. He spent the money he had on this treatment but had recently fallen on harder times due to the pandemic.  The patient percieved nothing but problems from the treatment and reported he had chronic sinusitis since the treatment and belie...

Setting an ideal position of  teeth for a lower full denture is of the utmost importance due to the almost universal instability of the lower full denture. One of my pet peeves is how the technician wants to set everything with an "anatomic" class 1 relationship. Tooth position can be in a wide range in the natural dentition but this is anchored in bone with periodontal ligament support. Because of this, natural dentition tooth position can exist outside the zone of soft tissue influence a la the neutral zone concept. The influence of external factors on tooth position becomes more obvious as there is loss of periodontal support in diseased states which allows buccal and lingual soft tissues as well as the occlusion to move the teeth resulting in flared teeth and diastemas.  In contrast to the natural dentition, full dentures are at the mercy of the movement of soft tissues during speech and function which can affect their success if denture base extensions are improperly des...

 Today an elderly man dropped off a broken lower full denture which belonged to his wife. She was in a nursing home due to her severe dementia and had thrown her denture on the floor. It had split in half and was a clean break so was definitely repairable. I had a bit of free time and we had some cold cure acrylic in the back lab so I thought I would attempt the repair rather than send it out to our lab as they didn't offer same day work. The steps I followed are below: -Inspect the denture: If the break is clean and there aren't too many pieces then the denture is deemed repairable. With traumatic fractures, the denture usually breaks at the thinnest part of the denture which tends to be down the midline with lower full dentures or at the flanges for upper full dentures. If there is a fracture through the tooth arches it will almost always pass through the contact point and not fracture a tooth in half as this point is a weak spot. Put the pieces together and if they fit toget...

 Today I had the worst denture try in that I've ever had. The situation was the construction of a full over partial denture. The patient has a current full denture which he doesn't like the aesthetics of feeling the teeth aren't visible enough. He is a person who is a bit past a mid life crisis and spends his days chasing after women half his age. But to be fair, the incisal display was inadequate and unless he had a very wide smile, he looked edentulous and unsupported lip-wise. Naturally I took my jaw registration intending to increase the incisal display and ordered the A1 teeth to be set.  I don't know how it was so wrong but the midline was off by about 5mm and the incisal edge was down by about 5mm. I have never seen a sight more horrible. To my annoyance, the wax rims I had sent up were still sitting in the lab box meaning the technician had supposedly used them to mount the case and then set the teeth up without it. They can make an index over the lower cast to ...

Following up on the difficult impression appointment from a previous post: https://dental-tidbits.blogspot.com/2021/04/difficult-impression-appointment.html The aim of preparation is to convert a difficult task to an easier one. The impression that I sent off that day turned out the be absolute rubbish and completely inappropriate for the final impression.  I could approach the case with a clear head and cleaned the old impression off the tray and placed adhesive long before the appointment. This way there was enough time for the solvent to evaporate and the adhesive to be effective.  I used light body PVS in every single cavity to block it out. I thought this would be difficult to handle but it was quite simple and if excess bled out of the cavity I could push it back in with an instrument. I had to change tips half way through because I was too slow in the placement and the material had early set half way through the blocking out. One thing I would change is to dry the teeth...

 Today I had a difficult impression appointment. The case is for a full upper immediate denture and the patient has almost all of his upper teeth that are badly broken down and carious. The issue with the impressions is that the material kept flowing into the carious areas, locking in and when I tried to remove the tray, the alginate would peel off the tray and tear. I retook the impression 4 times and in the end accepted a compromised result. I don't know how it will come back to bite me down the line but I know it will in some form or another. An important failure of mine here is that I didn't analyse how the first few impressions failed and try to learn from them for the next impression. Some thoughts: -The combination of locking in on the anterior and posterior teeth was enough to overcome the adhesion to the tray. When considering impression debonding it is merely a tug of war between the impression sticking to the tray and the impression sticking to the teeth. I think the...

 Today I spent another day at the prosthodontic practice. It was a pretty packed day with a mixed bag of treatment, some cases just starting, some far along both surgery and fixed prosthodontics. -Bonded gold restorations lower canine buldup: The patient had a history of bruxism and had worn teeth. The anteriors had been restored as veneers in composite resin and the patient requested a gold restoration for the upper right premolar. The preparation was essentially a veneer with a buccal path of insertion. The veneer wrapped around over the buccal cusp with the finish line at the position of the cusp tip. It extended equigingival and mesially and distally between the line angles and the contact point, just far enough to mask tooth structure. In the middle of the facial surface there was a round 0.8mm diameter dent prepared into it for resistance form. The temporary restoration was a shrink wrap bisacryl which was locked into the interproximal undercut. There was an enamel chip on th...