TBU # 007: Biomimetic Tip Tuesday: 3 Tips to Improve Your Peripheral Seal Zone in Your Preps

This month's focus is on understanding the importance of the peripheral seal zone in our preps.  This can be very stressful stage of our treatment.  First let me explain what the peripheral seal zone is.

The Peripheral Seal Zone (PSZ) is a 2-3mm wide circumferential area, caries free zone, around the pulp horns.  The intent of this technique has two main benefits:

1. To preserve the pulp when faced with deep decay

2. To create a bondable surface that we can use to build our restorations

Both are equally important and needed. This steps is what allows a biomimetic dentist to claim the reduced need for root canal treatments in their office.  For me personally, I have seen the need for root canal treatments decrease about 85%.  If we are able to intervene with treatment earlier enough, we can have great success.  This is a huge practice builder as patients love that you are caring for them and trying to save their teeth.  

Ok so how do we do it and how can we be successful? Here are some tips of improving our Peripheral Seal Zone that that I have learned along the way.

1. Improve your ability to see

This really involves two things.  We need to first be able to see what we are doing.  That sounds so obvious but it can get lost while we are focusing.  I recommend loupes of at least 4.5x.  Anything in the range of 6x-10x is preferred.  I started with 3.5x in school and made the jump to 5x and now to 6x.  It really is worth it when we are trying to do such detailed work.  How can we treat what we cant see? 

The second portion of this is to not let the tooth limit what we can see.  We all love being conservative, but there are times when we need to remove a corner of a wall or improve our occlusal reduction so that we can see the prep.  Keeping the tooth alive and responding properly is our first priority.   

2. Use Caries Detecting Dye

You’ve heard me talk about this before but it really is such a useful tool.  In my opinion, its really impossible to get a clean peripheral seal zone without using this. In a simple explanation, and how I explain it to my patients, is that its a dye that attaches to anything bad, and washes off whatever is good.  Once again patients love that I  am using a systematic approach to cleaning and treating their teeth.  They know that I am attempting to rid the human guesswork and making it more standardized. 

Caries detecting dye is super cheap, easy, and doesn’t have any negative effects with it. This is the kind that I use. If you are concerned with false readings from it, start simple.  You can use a Diagnodent to test the area to see how clean the location is. 

Keep in mind that we should also be removing decay and doing this step following measurements.  Following the 3 x 5 rule will help ensure that we aren’t getting closer to the pulp than what we should be. 

The 3 x 5 rule for doing our Peripheral Seal Zone states that we should not extend our prep beyond 3mm from any outside surface of the tooth (the interproximal, buccal, etc. ) and not extend further than 5mm from the occlusal surface of the tooth.  These numbers are based off of anatomical averages.  Keep in mind that there might occasionally be a pulp horn that extend into this area.  We need to use our best judgment, caries detecting dye, and experience to avoid pulpal exposures. 

3. Use Specialized Burs

My three favorite burs for this step are: a 330, a surgical length small round bur, and the CeraBur (a small round zirconia bur).  I have them in a kit by Komet.

330

This is a classic. I love it because its small and won’t remove tons of excess tooth structure due to its size.  The width of this bur is about 1mm so I can roughly gauge the width of the zone based off of this.  I  use an electric handpiece so I  can turn the speed down low for controlled movements.

Surgical Small Round

The added length to the bur shank is what really makes this nice.  Especially in deeper areas where access is hard.  These can come in different size heads.  Pick the one that you feel most comfortable with.  I like to measure the tip of the bur to know the width of my outline, as I mentioned before. 

CeraBur

These burs are nice for the bulk removal of the decay.  I use these once I have the cavity opened up and can see what I’m doing.  I like this bur for this step because I can be sure that this bur won’t remove excess.  These burs are good but its not the final clean out. I  save those for the above two burs.  Ceramic burs tend to not remove enough and leaves some decay.  But when applied for our caries removal endpoints, this works perfectly well.  These burs can also be a good way to get started doing deeper clean outs if you often find yourself a bit timid or nervous.   

Komet says this on their site. “The CeraBur K1SM facilitates controlled, intuitive excavation, enabling the user to feel when the instrument leaves the carious, soft dentin.
The outstanding efficiency of the CeraBur K1SM was shown in a study compiled by the University of Münster, Germany. On top, a study prepared by the Queen Mary University of London showed that the service life of the K1SM is three times as long as that of a round tungsten carbide bur."

The same principles applies to creating our peripheral seal zone as with any other procedure to be successful.  It takes time, practice, and patience.  Follow these three tips and I know you’ll get it in no time!