#DNotes Memo Concerning Tools for Dental Tooth Reduction

Most dentists are well aware of the documented requirements for tooth reduction in various situations. For example:

PFM: Incisal = 1.5 – 2.0 mm ; Facial = 1.5 – 2.0 mm ; Lingual = 0.5 – 1.0 mm

PFZ: Incisal = 1.5 – 2.0 mm ; Facial = 1.5 – 2.0 mm ; Lingual = 0.5 – 1.0 mm

FZ: Incisal = 1.5 – 2.0 mm ; Facial = 1.0 – 1.5 mm ; Lingual = 1.0 – 1.5mm 

e.Max: Incisal = 1.0 – 2.0 mm ; Facial = 0.5 – 1.0 mm ; Lingual = 1.0 mm

Yet a very large number of unaesthetic as well as weak dental restorations are ultimately caused by under-reduction, simply because the dentist is unaware how to measure! 

Very useful tools do exist to help the dentist know how much to reduce teeth in order to get both aesthetic and strong results? At Shanto, the most useful tool, we know of is the Flexible Clearance Guide – made by Belle de St.Claire, and sold locally by Patterson Dental. We use it in the lab all the time, but it is particularly useful chairside because it is flexible! 

When you use it, please note that you must be able to pull the Flexible Clearance Guide through WITHOUT RESISTANCE in order to know that you have at least as much clearance as what the guide indicates (0.5, 1.0, 1.5, 2.0, 2.5, or 3.0 mm)! 

Also, please note that there is an important difference between clearance and reduction!!! Clearance is the space created between the prepped tooth and the opposing. Reduction is how much you have reduced in relation to the planned shape of the restored tooth. For example on facial surfaces, clearance is irrelevant because there is no opposing dentition, but appropriate reduction is still important because you don’t want the facial of the restoration to be “sticking out” after the restoration is made. 

In addition, premolars and molars actually have occlusal surface areas that need reduction which has little or nothing to do with clearance – such as marginal ridges (where opposing cusps should not occlude), or situations where there is no opposing tooth (i.e. lots of clearance) but where measuring reduction is still important to get the correct restorative anatomy! 

Please remember that on its own in the mouth the Flexible Clearance Guide measures only (not reduction). In order to make accurate measurement of reduction (e.g. facial surfaces), you need to use the Flexible Clearance Guide in conjunction with another tool – a Reduction Guide – which can be a putty index of say the pre-op tooth or a wax-up! This is the reason you should ALWAYS use a Reduction Guide when you are prepping anterior teeth, because appropriate reduction of facial surfaces is of course super important and has nothing to do with clearance! Hence when you are planning to prep anterior teeth, should ALWAYS do a wax-up – even for singles! All wax-ups you send to Shanto, will always be returned to you with a Reduction Guide. 

Questions about this month’s DNotes? Feel free to reach out to us below:

#DNotes Who’s fault it is? It is the distolingual cuspid fault…

We find in the laboratory that the most common area needing additional reduction in the disto-lingual cuspid. Why? Well, we cannot assure the reason; but we believe it is related to the fact that it is the area of most difficult access when preparing the tooth; and the area which is not very convenient to check for adequate reduction.

Requirements Chart

Keep that in mind when preparing the tooth and take a look of this pocket chart with the minimal required reduction for a strong long lasting crown. Another culprit for minimal material space is an opposing cusp. Almost always the palatal of the 16 or 17. Don’t be afraid to reshape these with consent of course.

Have any questions about how we can assist? Feel free to email us at info@shantodental.com or fill in the form below:

#DNotes Ideal Access Hole – Middle of the Crowns or Axial

Is the implant crowns access hole decision made for aesthetic, convenience or mechanical reasons? 

As Technicians, we do understand dentist’s desire for screw-retention. However, we also want dentists to understand that in certain circumstances prioritizing screw-retention can lead to unwanted compromises which can be solved by deciding on cement retention instead! 

These days it is technically possible to screw-retain almost every implant case. But that should not lead to the conclusion that it is always desirable to do so! In other words, screw-retention does have some negative consequences. It is important to know what those consequences are so that you can make an informed decision when you decide on screw-vs. cement-retention. 

Have any questions about how we can assist? Feel free to email us at info@shantodental.com or fill in the form below:

#DNotes Splinting implants to natural teeth

Combined implant and tooth support

Technically, splinting implants to natural teeth can be done and we are asked to do it from time to time. So, it happens! However, finding published studies or literature on this treatment is as challenging as navigating a calcified MB2 on 16.

There is no doubt we will find lots of conflicting opinions; it is an ongoing and hotly debated issue.

This publication shares some good perspectives and situations to do, or not to do. It also suggests some great engineering options that we can surely provide if a treatment like this was accepted by your patient.

We always recommend full disclosure as to potential outcome. Make sure you have your patient review and sign a risk assessment form and document your case ! Not only for your own benefit, but also because we all need more information.

Have any questions about how we can assist? Feel free to email us at info@shantodental.com or fill in the form below:

#DNotes Triple Trays

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