Observing specialists Day 2

 Today I spent another day in the upstairs specialist clinics but this time spent my day in the prosthodontic department. This will likely be the last day that I can do this for a while if my teaching job comes through as I will not have any free time to pop in and do so. There was nothing mindblowing but I observed a few patients including some crown preparations, some head and neck cancer patients who had had fibular reconstructions and a hypodontia case who had canine substitutions for lateral incisors. Some things I picked up are below:

-    Look at the shank of the bur when you are preparing a tooth for a crown. This will be the reference point for producing parallelism perfectly parallel preps are more appropriate for gold work but porcelain doesn't tend to do so well with parallelism and requires some taper. If your preps are too parallel, take an endo Z bur (tungesten carbide, non end cutting bur) and run it around your prep a couple of times with the non cutting tip sitting on the margin. For anterior preparations, resting a finger of your non dominant hand on the head of the handpiece can further stabilise the handpiece. Care has to be taken to watch the shank of the bur to avoid excessive tapering. Think of the bur like the rod of a surveyor. 

-If you tend to produce parallel preparations, consider using a tapering bur. If you tend to overtaper your preps, use a parallel sided bur.

-To gain extra ferrule, if you plan to go subgingival, do gross reduction and pack cord around the tooth. This can result in quite a lot of vertical displacement of the tissues and allow you to prepare the tooth with deeper margins that will be subgingival once the tissue rebounds. 

-When packing cord, you don't want to force the cord downwards but roll the cord with with the cord packer rolling along the gingival margin rather than a pure apical thrust. 

-Instead of double cord, very long single cord can be used and be wrapped around the tooth twice or as many times as is required to achieve adequate gingival retraction and hemostasis. 

-Hold a finger against the gingival margin when you are packing cord to support the gingiva and stop it from being excessively displaced. 

-Time is needed for the tissue to displace and for hemostasis to be achieved. In the meantime, you can take a bite registration and polish your temporaries. She packed single cord for the preparation, removed it after producing temporaries, refining the bite and taking an alginate to communicate the shape of the final crowns to the lab. She then packed the single cord around the tooth twice before the impression.

-Use a probe to expose some part of the cord on all teeth so that they can be removed with tweezers rapidly.

-If the impression is mostly good other than one tooth, you can retake the whole impression or just use a sectional tray to take the impression of the area where you were inadequate, the lab can use that to produce the die and index it to the original master cast.

-Put the bur against adjacent teeth to gain a reference of the angulation of your prep. Keep moving the bur from the buccal to the lingual surface to ensure your preps are parallel. Use a football shaped bur to make the palatal reduction of anterior teeth as it is the correct shape for this purpose. Use a soflex disc to round the corners of the prep before finalising the preparation.

-Use cotton rolls in the buccal sulcus to keep the teeth dry and retract the cheeks. Use two fingers to hold the cheeks out of the way with pressure on these cotton rolls.

-Dry the teeth before removing the cord, once you remove the cords it may be difficult to dry the teeth. Once you have injected light body around the teeth you can plow air to displace this and to confirm that the light body has coated all the surfaces you want to cover. Then inject light body again before you seat the tray

-For upper impressions, you can put a horseshoe of tray wax on the palate to stop the material from flowing down the back of the throat.

-For jaw resections, fibular grafts are most commonly used taken from the leg bone. This is left as is and bo plating is added to the leg with no adverse effects. Surgical guides can be printed and used to place implants in the fibula and allowed to integrate before another surgery occurs with a guide to locate cuts to harvest the bone and free flap. 

-After the implants are placed they can be scanned with scanning flags and a prosthesis made in preparation for the harvest appointment. Once the bone is harvested with the implants, the prosthesis can be screwed on and a guide can be made for this e.g an essix retainer or a bite wafer with the opposing jaw to locate the prosthesis-fibula assembly while the plates are screwed on to secure the graft.

-There is an issue with fibula in the mandible as over the span of the bone there can be flexure which can disrupt the occlusion during function and theoretically the movement can stop implants from osseointegrating if placed after grafting.

-Ideally, after implant placement in the fibula, a connective tissue graft can be taken from the surgical skin site and placed around the implants under the muscle. This will result in a fixed skin tissue around the implants ready for harvesting. This results in fixed tissue in the oral site without which there would be moveable mucosa around the implants.

-When the angle of the mandible and/or TMJ is removed and repla

ced with fibula, the issue is that there is no muscle attachment to this side of the mandible and the mandible will tend to drift to the side of the defect as the opposing TMJ is guided forwards.

-All of the surgeries should be prosthetically driven. Reconstructive surgery without planning the end goal will result in surgeries where there is bone and soft tissue in the wrong place or the wrong type of bone or soft tissue. A maxillofacial prosthodontist should be part of the team planning for the management of whatever lesion results in resection in the first place.

 -Obturators can be useful but especially in young people, surgery to graft maxillary jaw defects can be beneficial considering the length of time that they have to wear a removable appliance. Psychologically, the appliance can be a reminder of the accident or the surgery that caused their defect and have an impact on their mental health. Also considering the need for maintenance and remaking of the appliance over their lifetime. It amounts to approximately $400K of public money to rehabilitate these patients with fixed solutions.