Written by Andrew Sedler

Written by Andrew Sedler

Written by Andrew Sedler

Porcelain Veneer Prepping
TREATING WITH PORCELAIN VENEERS
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Porcelain Veneers

Porcelain veneers were introduced by Dr. Charles Pincus in Hollywood in 1928, to enhance an actor’s appearance for close-ups in the movie industry. Dr. Pincus used thin methyl-methacrylate veneers that he affixed temporarily with denture adhesive for filming and then removed afterward. Today, everyone wants a HOLLYWOOD Smile.

"The cornerstone of every good treatment plan is an accurate diagnosis. An esthetic treatment plan requires an esthetic diagnosis. The truly esthetic dentist devises an attractive dental composition not only from stereotypical guidelines of form and function but also as an organic expression of personality, status, lifestyle, gender, occupation, and other characteristics that distinguish one individual from another. The smile is perceived as an integral part of the face and, in a larger sense, of the whole person. It is an expression of beauty, youth, age, or persona. In addition, the esthetic dentist must have an awareness of contemporary fashions, a perception of patient expectations and self-image, and the creativity and technical skill to orchestrate this information into a successful therapeutic result." Pocket Dentistry,  Porcelain Veneers: An Esthetic Therapeutic Alternative, Chapter 12, by Robert L. Nixon.

The prep for a veneer needs to be designed to be complementary to the end goal for the individual patient, and take into consideration the existing conditions and the final desired results.

The Perennial Debate
About Veneer Preps 

There are many philosophies about how to prep for a porcelain veneer, each camp is fiercely loyal to the dogma of their methods. The truth is, as with many techniques in dentistry, it should be dependent on the individual patient's specific situation and goals. What I seek to accomplish in this article is to present three variations of veneer preps and what conditions are best addressed by each prep style.

The first step in deciding the appropriate prep for a given patient is to ask, why are veneers a considered treatment plan for this patient?

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Factors for Treating With Porcelain Veneers

The following indications may be managed by more conservative preparation:

  • Mildly discolored teeth
  • Teeth with enamel defect
  • Worn or foreshortened teeth
  • Chipped or broken teeth

The following indications require a more aggressive preparation:

  • Multiple unsatisfactory with spacing
  • Misaligned teeth
  • Insufficient display of teeth incisally, facially, or buccally
  • Badly discolored teeth, especially those with grey, black, or dark banding

The NO Prep Veneer - Myth or Magic?

One of the valid arguments for being as conservative as possible is the fact that research on adhesive dentistry tells us preserving as much enamel as possible facilitates the maximum adhesive bond strength. While on the topic of conservative veneers, the NO prep veneer needs to be discussed. Even the legendary Dr. Robert Ibsen, the creator of Lumineers®, did "enamel contouring" in strategic areas, and “freshened-up” the enamel by bur-etching the surface and creating some finish lines with a diamond bur. The point is that literally, all veneer cases needs to be touched with a bur. The debate is, how much is too little and how much is too much?

Below are a few considerations that must drive the decision making process regarding how much to prep.

1. The material properties of ceramic veneers

The minimal thickness of even the strongest materials is realistically .5 mm.

a. Fabrication limitations - While it is possible to make veneers thinner than .5 mm, it becomes unpredictable both in the fabrication process and in being able to seat the veneer safely if the veneer is made much thinner than .5 mm.

b. Optical limitations - As thickness decreases, there is a diminishing ability to block out underlying color, and still have a vital appearance. Some veneers companies boast the ability to make veneers that are approximately .2 mm thick and are highly translucent, allowing them to replicate the natural appearance of enamel. We find that most patients want some shape change and a brighter smile, but they do not want their teeth to look like white Chiclets. What patients want is a beautiful brighter smile that looks natural. That requires some prepping and a layered ceramic.

c. Finish-line margins are important to allow accurate seating and minimize the resin cement junction, which can stain in the future.

Veneers that have proper room can yield natural vital looking results vs. opaque monochromatic veneers that are the result of too little preparation for a vital natural result. (Fig. 1 & 2)

Burbank Dental Lab smile after porcelain veneers
Figure 1
Veneers - After
Figure 2

2. Adhesive properties of tooth structures

It is generally accepted that the bond strength to etched enamel is higher than that of the bond to dentin. So maintaining as much enamel as possible is a worthy goal, but it is not the only element to consider. Dentist bond-in ceramic crowns every day and they bond them primarily to dentin. Today’s adhesive has increased their ability to bond to dentin. This can vary significantly between which brand and generation of adhesive that you use. Some systems have virtually the same bond strength to both dentin and enamel depending on how they are used. You need to be aware of how much dentin you are bonding to as you choose your adhesive material and protocols.

It is up to the clinician to determine how to achieve the goals of each case best.

There is no one style fits all. As with all cases, it is essential for clinicians to be the bridge between patient and laboratory, but especially with elective cosmetic cases like veneers. There is an important line to walk between the cosmetic goals of the patient and the clinical requirements of each case. Knowing, and accepting that there are choices in ceramic materials, and understanding the subsequent preparation and adhesive requirements is a critical ingredient for success in cosmetic veneer cases.

Types of Veneers 

Before I outline preparation variables, It is important to have a basic understanding of the ceramic materials typically used for veneers. They can be broken down into 3 basic groups:

1. IPS e.max - Ivoclar Vivadent

  • Pressed or milled Lithium Disilicate - Is typically pressed and layered for veneers.
  • Flexural strength of 500 MPa

2. IPS Empress - Ivoclar Vivadent

  • Pressed or milled Lucite reinforced ceramic - Is typically pressed and layered for veneers.
  • Flexural strength of 160 MPa

3. Feldspathic Veneers

  • Hand-layered on platinum foil or on a refractory die
  • Flexural strength of 100 MPa

Three Basic Preparation Groups

1. Minimal Preparation VeneersThese are best used when minimal shade or shape change is desired.

Prep parameters

  • .5 mm to .7 mm facial tooth preparation
  • Margin prep, .3 mm chamfer margin at or slightly subgingival
  • Preparation extending into the interproximal, 1/2 of the way through the contacts.
  • Incisal edge prep can be .75 mm to 1.5 mm - 90º “butt joint” prep is best.

This prep style is best used in teeth that:

  • Are aligned properly
  • Have no significant diastemas
  • Only minor color change is desired

Best material choices for this preparation:

  • Pressed monolithic ceramic-like e.max.
  • Feldspathic layered veneers are the indicated restorations.
  • Pressed e.max can be layered if the incisal edge length is prepped at least 1mm and the incisal facial plane also must be prepped to be slightly retroclined to allow for layering porcelain. (Fig.3)
Burbank Dental Lab minimal porcelain veneer prep
Figure 3

The incisal can also be layered if the tooth is being lengthened, but facial incisal plane must still be prepped back.

It is important to note that a minimal facial prep can be used if it is acceptable to build out the veneer to >.5mm, for example, a .3 mm prep with a final veneer thickness of .5mm.

2. Classic Veneer Preparation  - This is most often used for veneer preparation and can accomplish moderate shade and shape changes.

Prep parameters

  • .8 mm to 1.00 mm facial preparation
  • .3 mm chamfer margin at or slightly subgingival
  • 1 mm to 2 mm incisal edge reduction 90º “butt joint”prep is best.
  • Prep into the interproximal contact about 1/2 of the way through the contact
  • The incisal facial plane also be must be prepped to be slightly retroclined to allow for layering porcelain.
  • Interproximal Dog Leg / Elbow

It is essential to prep a “dog leg” lingual from gingival margin up under and into the contact slightly. This will prevent side views of the interproximal to reveal underlying tooth color in the area emerging from the papilla. (Fig.4)

Burbank Dental Lab nano prep guide for porcelain veneers
Figure 4

This prep style is best used in teeth that:

  • Need moderate alignment corrections
  • Have diastema correction of less than 1mm
  • Have shade changes up to 3 steps in chroma or value.  (eg. A4 to A1)

Best material choices for this preparation:

  • Pressed layered ceramic like e.max.
  • Feldspathic layered veneers

Either veneer material can be used depending on the goals and preferences of the clinician.

3. More Aggressive Veneer Preparation  - This prep is used to correct for deficits like flat papilla, instant ortho, and diastemas.

Prep parameters

  • 1 mm to 1.5 mm facial preparation
  • .3 mm chamfer margin at or slightly subgingival
  • 1 mm to 2 mm incisal edge reduction 90º “butt joint”prep is best.
  • A “slice prep” through the contact to cingulum, and needs to be at least .5 mm subgingival

The incisal facial plane also be must be prepped to be slightly retroclined to allow for layering porcelain. (Fig.5)

Burbank Dental Lab veneer preparation
Figure 5

This prep style is best used in teeth that:

  • Need more severe alignment corrections - "Instant Orthodontics"
  • Have diastema correction that exceeds 1mm, especially multiple diastemas
  • Have shade changes up to 3 steps in chroma or value.  (Eg. A4 to A1)

Greater shade correction can be achieved with the use of opacious ingots or opaque layers built into feldspathic veneers.

Best material choices for this preparation:

  • Pressed layered ceramic like e.max.
  • Feldspathic layered veneers

Either veneer material can be used depending on the goals and preferences of the clinician.

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Focus on Patient-Centered Treatment

Understanding patient goals is the critical element of an esthetic veneer case. The materials and prep requirements fall into place once you focus your clinical knowledge on patient-centered treatment. Then coordinating that desired outcome with a cosmetic dental lab like Burbank Dental Lab will deliver the WOW factor for your patient.

Look for upcoming topics regarding veneer tips, such as:

  • To Break or Not To Break Contacts
  • How To Avoid Black Triangles

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is here!

Burbank Dental Lab has three new state-of-the-art Carbon M2 printers. We are very excited about the options that these cutting-edge printers will allow us to offer our dental clients. Here are some of the advantages that these printers will begin to deliver to you and your dental practice.

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Carbon offers a highly dependable 3D manufacturing solution for many dental applications with its breakthrough Digital Light Synthesis™ technology, enabled by a wide range of dental materials.

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