Blog

*Here is a great blog from one of our Mentors Dr. Darin O'Bryan.  He posted this on the Spear Education site and we thought it would be a great blog for the CEREC guys as well.

If you asked most of your patients if money was no object would they fix their teeth, the vast majority of them would say yes.  We all have patients in our practice that need our services and want to have the best that dentistry can do for them.  How many times have you talked to a patient and they realize they have needs that should be addressed but financially they just can not afford the multitude of crown and bridge that are necessary?  With the current economic trend more people are being frugal with their discretionary income.  I don't know about you but I don't have a ton of patients with a bunch of cash set aside to fix their teeth.  How can we make it possible for them to have the quality care they want and make it feasible financially?

For the patient that wants the best but can not afford complete restorative care at this time it is necessary stage their therapy over time.  Long term provisionals with composite are an ideal way to accomplish this objective. 

Once the patients restorative needs are determined an ideal wax up is created.  The wax up is then duplicated in stone and a vacuform matrix is created.  The matrix is trimmed to the gingival margin to make easier clean up.  Caries removal is done on teeth with disease.  Restorations can either be left or removed depending on their condition.  For metal crowns retention grooves can be cut into their surface.  Crowns with a porcelain surface can be abraded and then conditioned to bond to the resin. 

Once this is done the patient is isolated and the proper bonding protocol followed for the underlying structure.  The matrix is then filled with composite and seated on the arch.  The gross excess is trimmed away and the whole thing is cured. The teeth are then sectioned if so desired with fine finishing burs, cera-saws and finishing strips.  The same is then done for the opposing arch if needed.  

There are a number of benefits to staging a patients therapy in this way.  It allows the patient to have the crown and bridge work done over the course of years if necessary.  If they are an insurance mind set patient now their insurance will cover the crowns one or two a year.  It is also a great way for the patient to test drive their new occlusion and pathways of function.  If the patient has GERD's or acid reflux it is also a way to verify control of the condition before moving on to more costly procedures.

Now biocopy is your friend.  One, two or the entire thing can be duplicated with biocopy.  If this is a patient that can only afford or wants to only do 1-2 crowns a year then you can leave the others until such time as their insurance rolls or the patient decides to do a few more crowns. 

The combination of the composite mock up and CEREC is a powerful tool that allows the delivery of ideal dentistry over time with amazing results.

One of the things that I am a firm believer in is the ability to bond porcelain to teeth. Lets face it, it works. It works well and it's proven. 

With so many bonding agents out there and companies working on ways to make the process easier and easier, what we are finding is that we have the ability to really have great bond strengths with our materials. So as I've moved more toward self-etching bonding agents such as the 3M Scotchbond Ultimate or the Kerr XTR bonding agents -- I still like to selectively etch the enamel. If there is a lot of enamel remaining, I feel that you still get the best bond strengths to enamel by etching it.  Keep the etch on the enamel and not on the dentin. Even if I use one of my favorite cements such as Multilink, I still like to etch the enamel.

This may change in the future but for now- enamel etching is where its at.

There are many places where dentists can get education. I’m especially proud of the courses, CEREC and Spear, that my colleagues present at Scottsdale Center for Dentistry. The facility is top-notch, the faculty are some of the best around and the resources available to the attendees are tremendous. However, I want to point you to a website that I use extensively to do research and find the latest information on the trends in dentistry. This website is called pubmed. www.pubmed.com

A compilation of all dental research and dental journals, this site has a tremendous amount of articles and research at the disposal of the user to peruse and read. Everything from anesthesia to cementation. Especially notable are the "Systematic Review" articles, which are a compilation of various research efforts that summarize the different camps of thought and give the user a concise summary of the latest research.

www.cerecdoctors.com is your go-to source for all things CEREC and will continue to remain so; however, for in-depth research analysis, visit www.pubmed.com and you will find some interesting features and articles.

What’s the best way to cool down a restoration when it comes out of the oven? Next time, try a coffee mug. Not a paper cup from Starbucks or anything like that –a ceramic coffee mug.

When the restoration comes out of the oven, set the entire tray aside on the metal tray beside the oven. This will allow the tray to cool a bit. Put your tongs in the muffle of the oven to warm them. You never want to touch hot porcelain with cold metal.

Once the tongs get a bit warm, move the restoration from the firing tray to the bottom of a coffee mug. The ceramic acts as a heat sink and helps to suck up some of the excess heat, allowing the restoration to cool a bit faster. What’s great is that the mug acts as a great device to transfer the restoration from your lab to the chair.

By the time you walk over, your restoration has cooled enough where you can handle it with ease. This is a super-cheap and inexpensive way to transfer your restoration and cool it at the same time.

"Do I need the inLab MC XL?"

This is a question that is constantly asked on the message boards of www.cerecdoctors.com. Many doctors want to get into the inLab system so that they can fabricate their own abutments, create bridge frameworks and really take advantage of the different features of the inLab software.

So if you have the inLab software, this means you need the inLab MC XL, right? Wrong! In reality, there is really no reason for any CEREC owner – inLab software or not – to use anything other than the regular MC XL.

With the regular MC XL, the doctor can take advantage of all of the inLab features except one: model milling. In reality, this is a laboratory need and not really indicated for the chairside doctor. Abutments, bridge frameworks, everything can be done with your regular chairside MC XL, except milling models.

If you get the inLab MC XL, you are tied into the inLab software product cycle and miss out on a lot because now you have dongle incompatibility and other issues.

Stick with the regular chairside milling unit. There is no reason for the average CEREC doctor to go with the inLab unit.

What’s the best material to use in the anterior? There isn’t a day that goes by that I don’t get asked this question.

My answer is always the same: It depends. In reality, there is no "best material." There are different materials for different situations.

Ideally, we want to use the most translucent material possible when restoring teeth for the optimal esthetics. A translucent material gives us the most depth and esthetics in a restoration. The more opaque the material, the less depth and lack of esthetics it contains.

Increased translucency can be good and bad. It’s good for the reason we already discussed – enhanced esthetics. It’s bad because if the underlying tooth structure is dark, then that dark tooth structure will shine through, leading to a decrease in the esthetics by showing a dark root. This is ok if the patient has a low lip line, but not so good if the patient has a high smile.

So what, then, is the "best" material to use in the anterior? I use the list below as a guideline for when you have normal and dark stumps:

NORMAL SUBSTRUCTURE:

1a           Vita TriLuxe

1b           Empress Multi

1c            e.max HT

2              Vita Real Life (Single tooth only)

3              Vita TriLuxe Forte (older patients with dark cervicals)

4              e.max LT

DARK SUBSTRUCTURE:

1              e.max LT

2              Vita TriLuxe Forte

One of the keys to success with anterior CEREC restorations is the ability to create an esthetic surface texture. Too often, when restorations come out of the milling unit, doctors simply assume that they can just glaze them without any other work and place them in the mouth. This leads to a good restoration but not a great one. To get a great restoration, you must take the time to remove the bur marks from the milling unit prior to stain and glaze.

In the example below, a patient presented to the office with a fractured central incisor. The patient had received porcelain veneers approximately six years earlier in another office. When the restoration fractured, we used Biogeneric Reference to match the adjacent central incisor.

Now, when the images are taken, the clinician must – and this is mandatory – follow the appropriate sequence to ensure that the surface texture and luster of the restoration matches what is on the other restorations.

Typically, when the restoration comes out, I will contour the restoration using a fine diamond. This most often is done in the mouth due to the nature of CEREC one-visit dentistry, but can obviously be done off a model.

Once the restoration is contoured, the convex areas are polished with a rubber wheel. You can typically leave the concave areas a bit dull, but polish anything that is convex. After polishing is when we do our stain and glaze.

Now here is the critical part- after stain and glaze: rubber wheel the glaze off the restoration. You want to remove the shiny look and simply have a dull finish.

It’s not the stain and glaze that gives the restoration its luster, it’s the saliva in the mouth. Prove this to yourself by looking at an extracted tooth. It’s rarely shiny, but the surface is polished. It’s the saliva that gives it the luster.

This is exactly the sequence that was followed on tooth #8 below. You can see the luster and shade matches the adjacent teeth. If I had to rate this restoration, Id rate it an 8/10 because what I should have done was given it a bit more surface texture to match #9. Close, but no cigar. Regardless, I hope you get the concept of treating anteriors with the CEREC.

In my last blog, I talked about how to go about restoring a posterior tooth after it had been treated endodontically. The consensus in the literature clearly states that when you have a posterior tooth treated by endo, do a full-coverage restoration. No ifs, ands or buts.

However, how should you go about treating an anterior tooth that has had root canal therapy but needs restorative work?

Below is a case that was posted on the forum. It was posted for other reasons; however, what caught my eye was the restoration on #9 with the endo access in the lingual.

So my question is, would you have prepped the same way or would you have done a full-coverage restoration? This comes up quite a bit and the answer may surprise you. As we discussed, in the posterior, we want full coverage. In the anterior, however, do all you can to preserve the cingulum and avoid doing a full coverage. 

In fact, I would have treated this tooth exactly the same way, as two separate restorations. An anterior all-ceramic with a separate composite closing off the endo access.

The weakest area in anterior teeth is the lingual fossa, and this is the area that causes the tooth to flex significantly when it is undergoing excursive movements.

What compensates for the flexing is the cingulum. If you cut the cingulum away, you significantly weaken the tooth. 

To summarize: Posterior teeth, full coverage.  Anterior teeth, partial coverage if a restoration is needed. If this was a virgin tooth, close the access with composite and call it a day.

One of the big questions that constantly gets asked in our courses is, “How do you restore endodontically treated teeth?” Especially if there is a small access opening on a large molar. Suffice it to say, I’ve heard some speakers espouse the merits of simply doing an occlusal inlay for a molar that has been endodontically treated. If you have heard the same, my advice to you is don’t listen to this and do your patient a disservice.

This one paper summarizes it nicely:

Are full cast crowns mandatory after endodontic treatment in posterior teeth?

Tikku AP, Chandra A, Bharti R.

J Conserv Dent. 2010 Oct;13(4):246-8.

The main take-away from the article is summarized below:

"Root canal treated posterior teeth without crowns are lost at a much higher rate than teeth supported with full cast crowns. The risk involved in losing the endodontically treated posterior teeth to fracture if not supported by full cast crown is too high to take."

One of the most exciting materials available to CEREC owners is the e.max block. With a compressive strength in the neighborhood of 400 mpa, this porcelain block is two to three times stronger than other available blocks. Clinically it has performed beyond expectations, and recently Ivoclar has published a 10-year retrospective on the studies that have been done on this material. As soon as it’s available from Ivoclar, a digital version will be placed in the download section of this website.

The bottom line on the research is that the material works, and it works well.  A summary of the IPS e.max Press system showed a failure rate of 1.6%. (Boning et al., 2006; Etman and Woolford, 2010; Guess et al., 2009; Gehrt et al., 2010; Dental Advisor 2010, and internal Ivoclar study) The studies tracked 499 restorations with a survival rate of 98.6% after a mean observation period of four years. Chipping only occurred in 1.4% of the restorations, and the other failures were due to endodontic failure, caries and fracture. These studies used a combination of adhesive and conventional cementation techniques, which I thought was interesting.

Now us CEREC guys are more interested in milling, so what were the results of the milling studies with e.max CAD?  Six clinical studies were reviewed (Richter et al., 2009; Nathanson, 2008; Reich et al., 2010; Fasbinder et al., 2010; Bindl, 2011; Sorensen et al., 2009) with a total of 237 restorations (crowns) that showed that 97.9% of the restorations survived after a mean observation period of 2.5 years. The 2.1% failure rate included chipping, fractures and caries.

So no doubt those of you that have been using e.max in your practices can relate to these results. The material works, and it works well. The blocks have been available in both an HT (high translucency blocks) and an LT block (low translucency). The one shortcoming of the blocks (if there is one) is that esthetically, unless you cut back and layer porcelain, you are dealing with a monolithic material – which means monolithic esthetics. Unlike their Empress Multi counterparts, the blocks are the same shade and translucency throughout.

Until now. At the Midwinter meeting in Chicago next month, Ivoclar is expected to release the e.max Multi blocks graduated shade and graduated translucency from one end of the block to the other. Initially, these blocks will be available for the pressed version only. Once the pressed version is released, we will eventually get our hands on milled versions of these blocks for our milling units. They have not set a release date yet, but I would imagine that it will be after the Chicago meeting for the pressed version, and my hope is that we have milled versions of the e.max Multi blocks by CEREC 27 and a half in the summer.

So all you CEREC owners can salivate at what I expect will become the most popular block for CEREC, giving you the appropriate opacity to block out any dark underlying tooth structure with the appropriate incisal edge translucency for the appropriate esthetics. As more information becomes available on these blocks, we will keep you updated on www.cerecdoctors.com