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 Veneers - These 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)