Observing prosthodontics again

Recently I spent another day observing at a prosthodontic practice. It was a mixed day with some implant work, fixed pros, composite resin and denture work. Below is a summary of the day with some thoughts and observations:

-The first appointment was the jaw registration appointment in the construction of a new full lower over denture retained by a bar. As the old denture suprastructure was made at another practice whose scanner files were lost in a software update, a new suprastructure had to be designed. The impressions were taken in the previous appointment using the layering technique described in his denture course. One issue with impressions around these structures is the material locking in and tearing. This isn't an issue as he flows light body under the bar and lets it set to block it out and uses ultra light body PVS around the bar to take the impression in the final wash which is one reason he doesn't like polyether for these cases due to its stiffness. The suprastructure had been placed on the model and a wax rim constructed around it. It didn't need an acrylic base as the titanium suprastructure is sufficient to reinforce the rim. The issue in this appointment was that the suprastructure didn't seat properly initially. This was clear to him as when he seated the wax rim it fit very actively (as opposed to passively) as is bound very tightly at certain points. He surmised that this was because the lab didn't adjust the suprastructure properly and the act of taking it on and off the model caused abrasion to the stone at certain points which made it fit seemingly. He said that what can be done is to pour up the impression in pattern resin which won't abrade and will force the lab to adjust the suprastructure till it fits. To fit check, he used light body PVS in the suprastructure and seated it on the bar. Once this had set, he removed the denture and checked the thickness of the PVS. Initially it was about 3mm thick which indicated that the denture was not seating by a long way. Before making any adjustments to the suprastructure, he confirmed that the wax rim fully seated on the model by using light body PVS as a fit checked. If the fit checking PVS was thick in the mouth due to a wax rim fabrication error it would be silly to start adjusting the suprastructure. Once fit checking on the model henoted that the PVS was paper thin therefore the wax rim was fabricated correctly. He then used occlude spray to check the points where the suprastructure was binding. He blows triplex air to dry the surface before and after spraying the occlude spray. Spraying before allows the spray to adhere to the surface and spraying after evaporates the solvent. He used a thin red band bur in a straight handpiece to adjust the binding points until the occlude spray was even all the way around. He removed the occlude with air and water and confirmed seating by placing three small blobs of PVS around the suprastructure. The idea of this is that he didn't need to cover the whole suprastructure with PVS because the aim wasn't to see where the showthrough was but rather to check the thickness of the fit checker. As he was making a spare set of dentures, to copy the old set which the patient was happy with he used a willis gauge to measure the vertical dimension with the older dentures and adjusted the wax rims until the vertical dimension after was the same. He used the heated spatula to round off the posterior part of the rim as it was interfering with seating. He used the tip of the spatula to form 3 V shaped notches on each side to locate the bite registration material.

-The next patient was explanting a molar implant and replacing it with a wider implant. The original implant was fibrointegrated and initially it all seemed fine possibly because it was integrated at the apex and fibrointegrated everywhere else and came loose after it was loaded. It was important to notice that the xray appeared perfectly sound as the fibrointegrated layer was very thin "like cling wrap around the implant". He removed the screw retained crown and noted that the tissue and implant appeared perfect. Fibrointegration will appear perfectly sound except there is pain to bite and very subtle movement of the implant. Removal of the implant basically involved reverse torquing it with the surgical handpiece. He curetted the soft tissue on the bony walls and used a rotary tool on the surgical handpiece to scrape soft tissue off the walls. He prepared the osteotomy for a wider implant and placed the new implant in. The wider implant was possible because there was plenty of bone thickness around the original implant. When he places implants he usually buries the implant with a cover screw as opposed to leaving it uncovered with a healing abutment. This is to avoid any force on the implant while healing. An immediate load would have the most force but a healing abutment would still allow the implant to be contacted with food during function. After implant placement he used a sickle scaler to feel around the bony collar over the implant (As it was placed slightly deeper) to make sure no soft tissue was trapped against the implant. He is careful when switching to the implant placement to run the handpiece and driver for a few seconds to check that the setting is right to avoid spinning the implant at an osteotomy speed with the implant on it which would fly across the room. He shook the implant over a sterile site to make sure it was seated on the handpiece properly. When he uses a hand driver he makes sure that the screw is dry as the fit of the driver should be well enough to ensure a friction fit so that the screw won't fall off. If the screw is wet or has debris in it the driver won't seat fully and the screw may fall off in the patient's mouth. The surgical driver will have a fitting that fits the implant surface e.g hex as the slow speed type latch connection isn't strong enough to handle the torque and it would break without the internal fitting. Placing in the implant is done in stages with the implant placed in, backed out and placed in further after 30 seconds or so. This is to let the bone expand and will increase the stability of the implant. Hand tightening will tend to make a max torque of 15N/cm and so you can't technically overtighten any screws if the torque required is above this. Put the torque wrench on after hand tightening to get the right torque. To close the wound, he didn't raise a flap but placed gelatamp over the implant. He flattened the block of gelatamp with his fingers and placed it over the socket. He then sutured with fine non resorbable sutures in a network over the gelatamp. Gelatamp is quite difficult to handle once wet and it was comforting to see that it stuck to the tweezers with him as it does me. To avoid trapping the suture needle on the gelatamp he moved the needle from the wound edge towards the gelatamp and then back out tucking the needle tip under the gum surface and displacing the gelatamp away from the tissues with the first movement. The sutures were placed across the socket in a buccal-palatal direction in 3 parallel lines along the socket to keep the gelatamp secure. The suture direction is something like mid buccal to mid palatal to mesiobuccal to mesiopalatal to distobuccal to distopalatal and secured to the initial suture. This makes a network of the suture which is more effective than just having sutures diagonally across which won't secure the mesial and distal parts of the gelatamp. Before tying the knot he pulls both ends of the sutures tight to tighten the suture across the gelatamp. As this particular suture was quite elastic this tightening of the suture doesn't over tension the wound. The suture was quite fine and snapped while tightening the suture and due to the elasticity of the sutures he was able to pull on the tal and get enough length to tie the knot. He leaves the tails of the sutures long ~3mm long and secured them down with periacryl which was dispansed into a sterile dappens dish and microbrush. The gelatamp acts as a collagen plug with iodine antibacterial to seal the socket and the periacryl sets this in place and provides a seal. The sutures are in place to secure the gelatamp. The periacryl may be enough but the sutures are used as added security. If there was any gap in the gelatamp e.g it can be pulled away from the wound edges on tightening the sutures, he will tear a bit more gelatamp and place it over the gap before applying periacryl. Before applying periacryl he will use gauze to mop up the blood overlying the wound as periacryl will set in contact with liquid. After placing the periacryl he will spray the area with water to set the material. After a surgery he will inject 1ml of 4ml/ml dexamethasone into the buccal sulcus to reduce post operative swelling.

-Preoperatively he gets patients to rinse with ozonated water as an antibacterial rinse. He uses the wrapping of the sterile surgical gloves as a barrier to use the computer mouse if required. This is useful as it is sterile and an impermeable barrier.

-The next appointment was the bonding on of a zirconia crown on a lower 7 in a heavy bruxer. It was bonded on with resin cement, the crown surface prepared with scotchbond universal uncured and left on for a while and the tooth cleaned with etch and prepared with scotchbond universal uncured. The relyx automix was put into the crown and seated. with firm pressure. The excess was wiped away with a microbrush flowing onto the tissues and the interproximal excess was wiped away with a thin and long microbrush tip. The whole lot was cured and excess below the margins cleaned with a yellow band flame bur. This particular case had the temporary crown fall off 6 weeks prior so the tooth had moved and the crown didn't seat on the mesial due to the tight contact. He checked the contact point to adjust the crown by marking the interproximal with green whiteboard marker, jiggled the crown on and off and adjusted the areas which wiped off with a bur. This is much easier than trying to fit articulating paper between the teeth and it can be wiped off after adjustments. According to him if you use a fine diamond bur: yellow band to adjust the crown surface with light pressure it is smooth enough without requiring further polishing. The more pressure you put on the bur the greater the heat generation and water spray is required. The more pressure put with the bur the rougher the surface because there is more risk of ditching the bur.

-After that was an extraction and bone graft of a 18. The grafting was performed because there wasbone loss around the neighbouring 17 implant due to caries and food packing around the 18.He used a hufriedy flat plastic which is quite thin to remove the attachment of the soft tissue. Periotomes tend to be too long to reach difficult areas and a flat plastic is much easier to handle. He provided apical pressure and side to side motions rather than back and forward to avoid bending the flat plastic instrument. This release of soft tissue allows the forceps to slide underneath atraumatically. He extracted the tooth by sectioning because the crown fractured off. The bone graft is usually mixed with metronidazole but he used local anaesthetic which is sterile as they didn't have any in stock. To pick up the bone graft he used a metal injecting tool and just tapped the opening over the bone particles to pick it up. First he curetted the socket well to clear the infection but didn't irrigate it with anything. He filled up the socket with bone graft and put a fair bit of pressure to compress the buccal plate which will reduce the size of the wound so the soft tissue would close faster. He mopped up excess blood with sterile cotton rolls or gauze before placing the gelatamp then sutures and periacryl. The bone graft acted to preserve the bone around the 17 implant and in the unlikely event that the patient wanted an implant in the 18 region in the future as it was a tooth in function and the patient had put a lot of time and effort in preserving the 18 with RCT, re treatments and fixed pros.

-If the optragate is pressing too hard into the labial sulcus then place a cotton roll in the sulcus which will take the pressure of the optragate

- The next patient was the issue of a screw retained 22 implant crown. The healing abutment was removed and the crown screwed in. As the anterior teeth were crowded, initially he had difficulty locating the crown onto the implant but he was attempting to do it in a rotated position i.e the next position along the hex. It is important to remember the orientation of the crown on the model as this is how you will be inserting the crown. There is some discomfort when inserting an implant crown as the tissue is stretched by the crown fitting surface. This is true if a custom healing abutment isn't used as by definition the crown will be a different shape to the soft tissue under the stock healing abutment. Warn the patient that it will feel tight on the tissues for 5-10 minutes and tighten slowly screwing it on a little but then waiting a minute then tightening more. keep staging this until the screw is torqued correctly. If there is slight tissue blanching then this is fine but excessive blanching that doesn't go away in a few minutes may result in soft tissue necrosis and recession. The patient had a partial cobalt chrome denture and he cut the tooth pontic off so that it would fit against the new implant crown. He used a diamond bur to cut off the framework as it cuts faster than an acrylic bur. He used a cylindrical diamond ot cut off the tooth at the metal framework and adjust it until the framework seated then used a yellow band football diamond bur to polish it smooth.

-The next patient was a stage 2 surgery to uncover a central incisor implant. During the healing he buries his implants to reduce the forces on the fixture. The missing space was temporised with a bridge with the abutment on the adjacent central incisor and bonded with a wing to the adjacent lateral incisor. He cut the pontic off with a bur leaving the adjacent central incisor and removing the wing on the lateral incisor. His uncovering procedure is pretty simple, he doesn't raise any fancy flaps, just cuts a horizontal incison over the cover screw and pushes the tissue to the buccal and palatal. This is a vascularised pedicle and will heal attached to the buccal and palatal tissues and thicken up the tissue. He prepares the temporary cylinder with composite resin for the temporary crown. He uses titanium cylinders and avoids peek abutments because although they may be more aesthetic he prefers the stiffness/strength of titanium. He puts scotchond on the cylinder and cures it. To handle the cylinder the puts the screwdriver through it with the platform at the handle and holds the handle of the screwdriver to avoid touching the cylinder and distorting the composite. He puts opaquer as the first thin layer over the cylinder to block out the metallic colour. He then uses dentine shade composite to form a sausage shape around the cylinder about 2mm thick. He uses modelling resin on his gloved fingers to avoid the composite sticking and forms the shape with his fingers. At the platform he blends the composite to a taper and avoids getting any on the platform itself which would stop it seating. He then screws in the temporary cylinder. At this point he has the base of the temporary composite resin against the cylinder and just needs to build a tooth around it. If he has added too much to the labial surface he trims this back with a bur. He uses a clear strip against the adjacent tooth and puts in flowable composite until he has established both contacts one side at a time. Then he uses his fingers to paste on composite to the labial and incisal surfaces to form a rough tooth shape. He takes the temporary crown off here and fills in any missing areas with composite using modelling resin to smooth everything off especially at the tissue surface. He pinches his fingers around the platform area and spins the cylinder around to form a natural concavity which will encourage tissue formation into the area and develop the soft tissue shape and volume. He then screws the temporary crown in and polishes everything with burs. There is moisture contamination from the bleeding tissues but he isn't worried about the integrity of bonding, just getting composite in there for aesthetics and to develop the soft tissue site during healing. He then uses a football bur to cut down the palatal surface including the cylinder which is designed to be too tall. As it is titanium, sparking from the bur friction is normal.

-Don't pull back on flowable composite syringes as it will pull air in and bubbles will form all along the tubing causing voids in restorations.

-There are methods to digitise facebow but they aren't that sophisticated at the moment. He just uses average values in his digital dentistry. If you think about this, in cases where you would use a physical triple tray average values are even more accurate as the hinge of a triple tray mounting is quite close to the teeth whereas with digital average value articulators there is at least an attempt to approximate the relationship of the maxilla to the TMJ. As long as there is the canines present then the guidance should be taken care of and the contralateral canine should take care of non working side interferences. Building in canine guidance is a cheat way to control the occlusion as it causes posterior disocclusion and makes the recording of joint position and eminance angle less vital to designing things like custal inclines. During his full mouth rehabilitations he will transfer the digital waxup to the mouth as a bonded mockup and refine the occlusion till he is happy. This then becomes his master scan which the final restorations will mimic. This way any inaccuracy of not taking a facebow is corrected.

-The next appointment was a issue of an occlusal splint. He Takes a scan of the dentition and a leaf gauge bite scan and the hard-soft splint is made on that. Just like dentures he doesn't do many adjustments at the insert appointment but lets the patient take it away and sees them in about 4-6 weeks to review.

-The next appointment was a review of a set of composite resin veneers. This patient likely had body dysmorphia and was very demanding about the aesthetics of their teeth including the brand and shade of composite resin that had to be used. The patient had changed their mind multiple times about the shade and he had cut back the veeners and redone them about 3 times. This time the patient wanted the posterior teeth changed from B2 to B1. The good thing about composite resin is that it can be cut back and changed as many times as necessary.as compared to ceramic which has to be completely removed, reprepped, impressed and recemented. He cut the restorations back and etched, used schotchbond and did a single layer of composite resin as a veneer. He used modelling resin to avoid instruments sticking and used a clean gloved finger and a button attachment on a hand instrument to shape the composite resin. When he does his initial composite resin veneers he uses a clear stent and injection technique with packable composite. All the teeth are stuck together and at the review appointment he separates the teeth with a fine bur into the embrasures. At this step he didn't have to worry about contacts and just stuck the teeth together to separate at a later date. The concept of this kind of patient is one which puts me off the idea of specialisation. Knowing that these patients are the ones we would be wanting to get out of our general practice and refer off to the specialists is scary because specialist practices are probably full of these patients and there aren't really places that you can offer to palm them off to as a specialist.

-The last patient of the day was referred in for bleeding and bone loss around an implant bridge. The bridge was cemented in and he could see cement still remaining when he dried the crowns and surmised that there may be cement subgingivally. The aim was to remove the bridge and clean around the implants, leave the bridge off for a few weeks and see if the periimplantitis could be stabilised before recementing the bridge. The patient was using a waterpik and he suggested the use of peroxyl mouthrinse in the irrigation under the bridge to increase the oxygen tension and kill off the anaerobic bacteria.