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Taking impressions...

rambo2006

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    Just recently we have been taking impressions and I feel like I go the hang of it. It reminds me of an auto body-work summer job I had in my early undergrad years. Anyhow, we have been taking these impressions on typodonts and I just wanted to hear your thoughts on how very different it may or may be from taking it from a patient. Are there any extra steps or caution? Do u take more than 1 alginate impression so that if after you make your cast you see voids, u can do it again? Or do you get the hang of it till the point that you dont get void?

    thanks. :)
     

    crazy_sherm

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      Taking alginates on patients is easier than on the typodont. You usually don't need as huge a tray and the saliva helps a lot. The gagging part sucks though, have to work on distracting your patients and making sure they're comfortable. Don't worry too much about voids, anything less than 3mm across is small enough to flick off later, plus, it's usually just a study model. PVS and polyether impressions are a totally different story. Having about 6 extra hands help the first few times you take a final impression.
       
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      dheav005

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        Well that is probably because you dont have the same typodont that we have at our school. Ours has a gag reflex and it also comes with synthetic throw-up. JK. that would indeed be nasty though :)

        holy crap! the cheeks, hyperflexible neck and soulless eyes on ours was what really freaked me out. as you improve in your speed, get some fast set alginate if your school doesnt have any on hand. pt really appreciate the shortened time of the goo in their mouths. taper the fill of your MX tray toward the posterior to minimize overflow down the pharynx. as for PVS, get an extra set of hands. trying to cover preps in wash while a full tray of medium body sets on the alabama cart in something like trying to herd cats, except not as much fun
         

        QM1

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          Creating a posterior dam with compound on the max tray really helps. The few minutes extra in prep is saved by not repeating an impression due to gag reflex.
          Oh yeah, don't overfill your tray.
           

          aphistis

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            Creating a posterior dam with compound on the max tray really helps. The few minutes extra in prep is saved by not repeating an impression due to gag reflex.
            Oh yeah, don't overfill your tray.
            Use periphery wax instead of compound. Takes seconds instead of minutes, and works just as well.
             

            ivorinedust

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              A few more alginate impression tips:

              1. Select the proper size impression tray. A very basic and important step, but often neglected. Rimlocks are best to use with alginate. When seating the impression, make sure the labial frenum is aligned with the corresponding notch on the tray.

              2. Use accurate powder/liquid ratio. Too little water, and the material gets crumbly. Too much and it will flow back to your patient's mouth causing him to gag.

              3. Check your patient's palatal vault...If it is too high, you'd always have a large bubble in the middle of your impression. Pad the tray accordingly on the palatal with wax.

              4. Take the impression of the lower arch BEFORE the upper, specially for pedo. Why? Because if you begin with the upper arch and the patient begins to gag, you've blown it. It will be very hard to get his cooperation after that. You're gonna have to reappoint. Lower impressions rarely cause gagging. If you start with the lower impression and then patient gags on the upper, at least you have the lower one to pour, right?

              5. A wax posterior dam helps, but raise the patient's back rest to upright and have him tilt his head down too. Tell him that drooling is okay, but be sure to protect his clothing with the bib. Keep the saliva ejector handy.

              6. Put a little blob of alginate somewhere near(bracket table or patients bib perhaps?) while waiting for the impression to set. Use this as a "tester" to check for setting in the mouth. Obviously when the tester gets firm as you lovingly squeeze it, so is the impression inside the mouth. Then it will be safe to withdraw your impression.

              7. If it gets difficult to withdraw the upper impression, have the patient say "kay...kay...kay" while trying to rock the tray by rotating the handle. The "kay" syllable raises the soft palate and allows air to come between it an the impression, breaking the "palatal seal".

              Hope that helps.

              Ivorinedust

              "Apolonia, relieve my toothache"

              P.S. St. Apolonia is the patron saint of dentistry. Feast day celebrated tomorrow, February 9. FYI for Catholic dentists.:)
               

              FreshBreath

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                The only tip I would like to add, is before seating the tray, take some excess alginate from the mixing bowl and place a little on hard to reach areas (eg. thrid molars) to assure capturing them in the impression. In addition, place some algiante in the vestibule and frenal attachments areas to help capture it everytime.
                 

                aphistis

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                  The only tip I would like to add, is before seating the tray, take some excess alginate from the mixing bowl and place a little on hard to reach areas (eg. thrid molars) to assure capturing them in the impression. In addition, place some algiante in the vestibule and frenal attachments areas to help capture it everytime.
                  That's kinda time-consuming. Wouldn't it be easier to just make sure the impression tray fits, and is fully seated? :)
                   

                  rambo2006

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                    Takes a little more time, but not more than a few seconds, and will guarantee a better capture of soft tissue or a hard to reach area.

                    I've been doing that actually and it works great. It really helps keep the voids to a minimum when you take the aliginate and push it into the occulusal surfaces and embrasures. I figured out after messing up 3 times that you dont use hot water for alginate. I know now that u can use room temp but cold water gives me more time to make sure I can get it in all the embrasures, occlusal tables, and behind the 3rd molars.
                     

                    dheav005

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                      ...extractions dont count.

                      for pts. with narrow openings and tight vestibules or tori/exostosis, i like to have a big surgical syringe with the plastic tip cut down to an opening a couple of mm wide. after you load the tray, force alginate into the open end of the tube and replace the plunger. syringe it into the areas where you would have restricted flow of alginate to pick up those areas, works just like PVS wash and limits remakes due to missed borders.
                       

                      ivorinedust

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                        Before pouring your impressions, be sure to remove all saliva and blood from it.
                        Running water will not do the trick as you will know. I put a little bit of "terra alba"--pulverized plaster(calcium sulfate) in its dihydrate state-- in a bowl of water and wash my impressions in it. Works like a charm.

                        Ivorinedust

                        "Apolonia, relieve my toothache!"
                         
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