One sure-fire way to get a shell provisional is to have it fabricated by a laboratory. The first piece of this puzzle is to make sure that the fees you quoted for the case include the extra lab expense for the provisional. The second challenge is depending on how the lab fabricates the provisional you may have adjusting to do in order to seat it over your preps. Often what the lab does is prep a duplicate model to make the shell. Depending on how much they prep and the orientation, the shell may bind on your preps and require internal relief. I utilize a shell technique that we do in the office. It is another process I have trained my assistant to complete. This transfers the lab fee for the shell to an hourly rate for a team member plus expenses.
Wax-Up Model
What I love about the technique is that it allows the shell to fit universally over the preps without needing to be adjusted internally. The first step is to take a stone model of the final wax-up. Run a 1-2mm wide bead of wax along the gingival margin of every tooth buccal and lingual.
Silicone Matrix
Using silicone lab putty fabricate a full arch matrix on the stone model. Once the matrix has set, lightly paint all of the internal surfaces with bisacryl provisional material. I do this using the tip of the material on the gun. Allow the bisacryl to reach a full set, which can be up to five minutes or more bench top depending on what material you use.
Using a Bard Parker blade, slice the silicone matrix material from the cervical edge to the occlusal table over the interproximal of every pair of teeth around the arch.
Silicone Matrix Loaded with Bisacryl
Bend these tabs of silicone down until they snap off near the occlusal table, exposing the shell. This step is necessary due to the delicate nature of the shell, do not try and tease it out of the matrix.
Matrix Sliced
Once the buccal wall of the matrix has been removed, the shell will ease off. Carefully trim the excess bisacryl off back to the wax line you created at the gingival margin. The air inhibited layer of bisacryl can be removed first with rubbing alcohol to prevent clogging up your bur. Once trimmed it is ready to be relined over the preps. If the shell breaks when you are trimming, simply place back in the silicone matrix and repair with bonding agent and flowable.
excellent technique.thank you in advance.
This is a great post. The technique looks very simple and easy to troubleshoot. Thank you for sharing!
Dr. Lee can you post a video for this. Thank you
I’ll put one together!
This may be a stupid question, but what is the advantage of making the shell indirectly only to reline it in the mouth vs. using your silicone matrix and fabricating the provisional directly in the mouth?
Thanks, Chris
Chris,
Thanks for a great question. I tried this technique many times with frustration prior to learning this technique. The challenges come from the lack of occlusal stops to seat the matrix as every tooth has been prepared. Relying solely on sift tissue stops for a flexible matrix is tricky, You tend to over seat and get short temps, or under seat, or worse seat differently right to left and introduce a cant in the temps. Even if you leave the second molars unprepared, the matrix tends to seat to far in the anterior so capturing the proposed tooth length and VDO can be an exercise that is challenging. this technique takes all of that uncertainty out.
Lee
Thanks, Lee!
I’m a new dentist and have not actually tried either technique so I was just curious.
I attended one of your courses at the greater ny meeting and am an avid reader of your blog. Thanks for all your helpful tips n tricks:)
Hi Lee, great idea! Could you please explain what the purpose of the wax around the stone model is…….wouldn’t this mean you don’t have an accurate margin to trim to or am I missing something?
Cheers
Jared
Jared,
The bead of wax moves the shell out away from the gingival one third of the teeth to make sure the shell seats over the preps. You want to run the bead on the teeth at the gingival margin so you can still see where to trim to.
Lee
This looks like a great technique! As I understand this, adding the wax beads will mean the buccal and lingual contours of the provisionals will not initially match the buccal and lingual contours of the waxup and overlap the gingivae slightly. Does this mean you have a fair bit of trimming to do on the bucal and lingual of the provisionals to get them flush with the tooth margins? Am i correct in thinking the wax bead is placed on the tooth an over onto the gingiva slightly? Many thanks.
When relining the thin shell intraorally with Bisacryl, should I place bonding agent onto the fit surface, or is that stage not necessary? I use scotchbond universal as my composite bond. Would that do? Many thanks! Your blog is fantastic by the way.
Chris
Chris,
When you reline the shell you do not need to add dentin adhesive unless you have removed the air inhibited layer ont he internal of the shell with rubbing alcohol.
Lee
Should the wax bead be extended slightly onto the gingival margin, or the gingival margin avoided to avoid an excess of temporary material on the provisional?
It looks like a great technique, but I am a little confused as surely there will be a lot of trimming bucco-lingually to trim the extra bulk of temporary material (caused by the wax bead) to get the tooth provisionals back to the correct contour of the waxup, especially if the bead extends onto the gumline slightly? Sorry for being a little slow! Many thanks. Chris
The wax bead is placed right at and above the Free gingival margin on the model. You are correct that there will be trimming at the margins to remove some excess thickness. However without placing the wax bead you will have more issues with draw of the different preps, and placing the shell to the margins and picking the margins up when you reline the shell.
Lee
Thank you. I will give it a try!
Q1 – How do you compensate for the slight shrinkage of the bisacryl when multiple units are temporized in 1 piece? I find the shrinkage, especially with bridges, prevents accurate fit. And if I leave it on for full cure, I have a lot of trouble getting it off. Sometimes I separate one of the retainers and then bond it back with light-cured resin. What’s your solution?
Q2 – I’ve never used pre-fabricated temps. What are they made of? Does the bisacryl bond to those materials well? If not, what do you do to aid in the retention of the bisacryl. Also, what about the margins of the pre-fab temps and the margins of your preps – does the bis-acryl establish them well? Are the pre-fab temps mad to be over extended so that we can trim them back after lining them?
Thanks.
We relieve the inside of the provisional to make sure it can seat all the way to the margins.
Pre-fab temps can be made of lab processed bisacryl or milled or printed PMMA or conposite.