Observing prosthodontics 4

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't tend to stain that much after. This may be something to do with oxygen inhibited layer. 

To clean tooth before bonding to avoid stains from debonding you can sandblast or pumice the teeth and use diamond strips interproximally. Be careful with sandblasting because once the gum bleeds the bonding will be much more difficult. 

Injection moulding is done to place the composite. Put flowable composite on the teeth and paste composite in stent. The paste will displace most of the flowable as it seats but the flowable will seal the gaps and wet the surface.

Process for separating teeth: Use a flame bur for to remove the excess composite where the teeth may be overcontoured or overhanging. Use a fine mosquito bur for separation of the teeth by opening up the embrasures. Take the fine bur under the contact and use upward strokes with the tip. Then use the flame bur downwards with downwards and side to side strokes to widen the embrasures slightly. Then use a sickle scaler to click the teeth apart by poking it in between the teeth and twisting the handle. Use a finger to push anterior teeth labially to produce forces in the direction that flares them outwards in their socket. If you do this while you are twisting the sickle scaler it will allow for more separation and add more control to the break. Then use a long interproximal saw strip to separate the teeth if they don't click open from this method. Some of the teeth will have already clicked apart before the review appointment and these didn't need any of the previous steps. 

Refine the shape: Use soflex discs to round the incisal corners and shape the embrasures further. Use a rubber flat disc polisher to finish the embrasures then a white spiral wheel. 

Polishing the teeth: Use a diamond strip under the contact point to remove sharp edges and make the surfaces cleansable. Then use eve twist polishing wheels white, green and pink to provide shine to the surface.

For reproducible photos, once you have taken a photo and want to have the same framing and zoom for subsequent photos, have the focus set to manual and hold the edge of the ring flash with your non dominant hand to avoid the temptation of changing the focus. This allows stability of the tip of the camera and by not changing the focus all you have to do is ensure the same framing and move closer or further from the object till the image is focused.

For retracted shots it is much easier to use an optragate and have the patient lying down. Make sure you use the camera strap a the last thing you want is the camera dropping on the patient's face.

-Extraction of lower premolars, socket augmentation graft and issue lower partial chrome denture with tooth additions.

Once you have a good purchase point and wish to elevate the tooth, hold the elevators in pointing down for lowers in your fist and rotate it with write strength with no apical force. Use forceps in an underhanded grip initially only with fingers holding it and finger strength used to turn the forceps. This lets you have a feel for the movement of the tooth before you apply force that may fracture it.

If the tooth is not coming out with traditional forceps delivery and you want to avoid a forceps delivery you can section even single rooted teeth in a mesiodistal direction with long shanked, high speed surgical bur. 

Sectioning the tooth is in the mesiodistal direction and not to the apex. A buccolingual section can defeat purpose and damage the buccal plate.

Have a metal kidney dish for bits of tooth, scalpel and suture to keep your tray table clean. Sectioning the tooth is to make space to elevate from the mesial and distal into this space. 

Once the graft material is in you don't want the suction near it so if blood is collecting on top of the graft and you want to clean it to allow suturing etc use sterile gauze or a sterile cotton roll to soak it up. 

Suture the graft (figure 1) to form a web like network starting from mid buccal to midlingual to distobuccal (from inside socket), to mesiolingual to distolingual to mesiobuccal and tie the knot to the tail at the buccal. This will be to retain the gelatamp sponge and the periacryl will form a seal over the top to avoid the graft being contaminated or lost from the socket.

Figure 1: Sutures to retain a socket graft. 1: Mid buccal to mid lingual, 2. Mid lingual to distobuccal, 3. Distobuccal to mesiolingual, 4. Mesiolingual to distolingual, 5. Distolingual to mesiobuccal and tie a knot to 1.

Hold the clasp of a chrome denture picked between your fingers while polishing on a lathe or it the lathe may catch the clasp and dig it into your finger. 

In this case the denture teeth added were too short so he bonded some resin to them to make them longer. Sandblast and steam clean the surface to allow bonding of composite resin to acrylic. The MDP monomer in scotchbond universal allows bonding to most materials.

Avoiding movement is the most important thing in graft success. Even if without bony walls, bone has the potential to vertically if there is no movement. If there is soft tissue ingrowth into the graft it is essentiall a bone particle reinforced soft tissue graft but volume is the key. Do we really care if there is real bone there or just soft tissue? It depends on the case.

-Implant crown impression:

This was a fairly straight forward appointment. To support the soft tissues put the impression coping on and inject flowable composite into the space around it. You have about 30-60 seconds before soft tissue collapses so don't rush but don't take too long in doing this or the shape you have spent time developing with the temporary crown will be wasted. During the impression, inject light body in the interproximal spaces of all the teeth so they break and the impression is easier to remove.

When uncovering the healing cap, the location of the M-D incison depends on the soft tissue profile. If the tissues are deficient on the buccal, cut slightly palatally to move the tissue buccally. If there is enough volume then cut in the middle of the implant site.

-Equilibration: A review of an overerupted wisdom tooth causing functional issues. If an occlusal splint doesn't cover the wisdom teeth you can find they overerupt. The 8s then hit first and the patient will posture forwards to maintain contact. Protruding will cause posterior disclusion due to the angle of the eminance. This will allow them to maintain contact for function but posterior disclusion during day function will cause more overeruption. Use a fluted tungsten carbide bur for smooth, slow reduction of tooth structure.

-Issue maryland bridge: To remove a temporary maryland bridge section first get crown forceps on it and give it a twist. If it doesn't come off with slight pressure then section the pontic in half and flick it off with a sickle scaler. If it still isn't coming off it may be the resin locking interproximally that is the issue. Get some gorilla floss underneath this resin interproximally and pull lingually to knock the resin off. 

If the porcelain retainer wing is quite fine then it has to be pressed as milling can't make ceraimcs too fine. Pressed ceramics are still the most accurate type of technique. It is essentially like a gold casting but isntead of spinning the casting with molten metal the porcelain is melted and pushed into the mould under pressure. An issue with this is that the fineness of the ceramic can cause flash past the margins which can stop the ceramic from seating. 

If the final restoration isn't seating, check the edges of the restoration flash and also check for bonding resin at the place you have spot etched at the preparation appointment. Also run over the preparation with a sickle scaler to make sure no resin is locked in at the margins. A yellow band football bur at the spot etched areas is useful to clean excess bond off. If the surface is still shiny once etched there is excess bond that needs to be cleaned before the restoration will seat.

Hold the automix cement syringe with your middle finger and thumb around the shaft and use your index finger to extrude the plunger.

-Issue invisalign trays and bonding attachments:

An optragate very handy for bonding the attachments. It is much slower without some sort of hands free retractive device as you can't bond as many teeth at the same time without saliva contamination.

There is a soft tray that acts as the template to bond your attachments on. Use a red band, wide, flat cone bur to roughen the tooth prior to bonding. Keep looking back and forth at the tray and teeth to see where the attachments will be and see where you need to grind the tooth and place etch.

Bond one quadrant at a time so the etch isn't there for too long resulting in over etching. Use a highspeed suction to clean off the etchbefore rinsing with water to stop a blob of etch going down the patient's throat. Place and cure your bond and put flowable composite in the tray where the space is for the attachment.

Place the tray on and hold it down with your finger on the occlusal surface to make sure it is fully seated while you are curing. Spot cure each attachment for a few seconds then do a full cure with the finger pressure off.

Use a flat plastic to peel the tray off. If the attachment debonds while you are doing this then immediately reapply bond on tooth, put more flowable in tray, reseat and cure.

Use the flat cone bur and flame bur to clean the flash off the tooth and diamond strips to separate teeth if stuck together.

When explaining how to use the invisalign trays, hand the patient the mirror: explain how to tell the trays apart "Big front teeth go on top, little front teeth go down the bottom. Line up midline, then seat the front first then slowly work your way backwards"

Sometimes to insert and remove the aligner tray you need to toll the tray buccolingually to flex the tray over the contours of the teeth and attachments. 

Whenever the tray is out of the mouth make sure it is in the box provided or it will get lost. Only take the trays out to eat and clean them. 

 When removing the trays, it is easier to use the opposite side hand to lower one posterior side. This ensures the buccal is pulled off first helping it flex around the attachments. After the first day of use it is easier to remove. 

When the patient is stressed, get them to chew a bite tab (piece of mouth guard material) to stratch the ligaments and help the teeth move. Do this for 5 minutes a few times a day.

Avoid staining foods and liquds e.g coffee or the attachments and trays will stain.