The catalyst behind the development of veneer restorations
involved the combination of two innovative processes: mechanical and chemical
bonding. The introduction of surface treatment to enamel1 and
porcelain,2 followed by the development of the first composite resin
system,3 were responsible for the evolution of bonding technology
that led to the laminate veneer. During its inception, this concept of placing
custom-formed thin shells of plastic or ceramic over the tooth structure was
considered a departure from the conventional treatment methods and considered
highly suspicious by the dental profession.4
The veneer concept was developed in 1938 by
Pincus, who described a technique for masking defects and improving the
appearance of actors’ teeth by utilizing a thin plastic or porcelain veneer
that was retained by a denture adhesive. The early 1970s introduced a composite
catalyzed by ultraviolet light, which allowed adequate working time for
developing direct veneers. These restorations, however, had limitations that included
poor resistance to abrasion, limited shade selection, increased susceptibility
to staining, lack of color stability, and questionable durability of polish.5
In the late 1970s, a prefabricated acrylic veneer (ie, chemically bonded to
etched tooth structure with a thin layer of self-curing composite resin) was
advocated by Faunce.6 While this technique increased stain resistance and the
durability of polish, its use was
discontinued because of adhesive failure at the laminate-composite interface
and negative gingival responses.5
The 1980s brought the introduction of the
fabrication and the cementation of the porcelain veneer. While the fabrication
and cementation procedures were described by Horn,7 the studies of
Calamia and Simonsen outlined the surface preparation time and procedure (eg, hydrofluoric
acid etching, silination) for improved retention.2,8 This technique,
along with advancements in adhesive formulations and resin cements over the
past 20 years, have expanded the conservative treatment possibilities that
simplify the clinical application of aesthetic techniques and ultimately improve
the level of patient oral healthcare.
Indications and Contraindications
Veneers can now be
fabricated out of two different materials: composite resin (via either direct
or indirect methods) and porcelain. Although not a panacea to all restorative
challenges, the veneer can offer alternatives to various clinical situations
without compromising the natural tooth or periodontium. These clinical
situations include the management of carious lesions, fractured or discolored
teeth, worn anterior dentition, and other noncarious enamel defects.9 Accepted
clinical applications for these restorations include masking discolorations,
improving anterior guidance, modifying occlusal relationships, and altering
tooth size, shape, alignment, and color along with other well-documented
indications. Contraindications for these biomaterials include patients with
poor oral hygiene, bruxism, teeth with only dentin present or minimal enamel,
teeth that exhibit severe crowding, and teeth in severe labial version.10
Porcelain Laminate Veneers (PLVs)
Indirect porcelain veneers provide several advantages to
direct resin veneers. With PLVs, discolorations and underlying irregularities
can be more easily controlled and monitored using ceramic opaquers and
modifiers. In addition, porcelain systems are unsurpassed in color stability,
gloss, and wear resistance, and the gingival response to them is excellent
since porcelain retains less plaque than other restorative materials11;
plaque can also be removed more rapidly from the surface of porcelain.12
Furthermore, when properly fabricated and bonded, these restorations require
minimal finishing. Their disadvantages include the fact that porcelain
modifications (eg, contacts, fractured margins) are time-consuming chairside
tasks, the bonding protocol for porcelain to composite requires attention to
detail, the need for multiple patient visits, and the potential need for provisionalization.
The indirect method requires close communication between the technician and
clinician for optimal aesthetic results (Figures 1-2-3-4).
(Continued from page 1 )
Although the original concept of the veneer technique had
not evidenced the development of improved dentin bonding systems, the
conservative preparation and placement of the restoration in enamel has proven
to be beneficial for the longevity of the restoration and tooth. A long-term
clinical trial suggests that resin-retained porcelain veneer restorations that
did not meet enamel ceramic criteria had a greater risk of failure through
microleakage, fracture, and debonding.13
While various conservative preparation techniques have been
advocated, the diagnostic waxup can aid in the management of tooth removal
through the development of a silicone matrix guide. This process also provides
the patient with a visual image of the anticipated restorative outcome and
should occur prior to finalization of the treatment plan to ensure that the
patient is satisfied. The following
guidelines should be considered to improve patient understanding and to provide
optimal long-term clinical results.
- Inform the patient of other treatment alternatives,
beginning with most conservative, and discuss long-term consequences and replacements;
- A diagnostic waxup should be finalized and reviewed by the patient
prior to completion of the treatment plan and initiation of restorative
- Only prepare teeth when the gingival tissue is healthy;
- Keep as much of the preparation in the enamel layer as
- If dentin is exposed during preparation, seal (ie, hybridize)
to prevent sensitivity and bacterial invasion;
- All internal line angles should be rounded to prevent stress
that can lead to fracture;
- Margins should be placed supragingivally when possible;
- Provisional restorations, fabricated from the diagnostic
waxup, should be developed to allow the patient to visualize and function with
- Utilize adhesive techniques according to manufacturer’s
- Individual placement or sequence placement in series of two
beginning at midline (ie, central incisors, laterals, canines) and avoid
complete placement of numerous veneers at the same time to prevent micromovement
and possible microleakage;
- Inspect margins and gingival adaptation, and completely
finish and polish; and
- Evaluate occlusion in centric, protrusive, and lateral excursions,
adjust as needed and repolish.
The longevity of a bonded veneer is a direct function to the
amount of enamel substrate supporting it.14 The primary consideration
for the success of PLVs is one’s knowledge of the enamel thickness and how it varies
throughout the given tooth. Unfortunately, many clinicians continue to use
preparation guidelines that suggest a standard geometric design, failing to
consider the anticipated final restorative dimension or variations in enamel
thickness on one tooth to another or from one area of the tooth to another (eg,
cervical, body, incisal).15 This approach of removing predetermined
tooth thickness without consideration of anatomic variations and final
restorative dimension can result in improper removal of tooth structure and
postoperative sensitivity (Figure 5). A more appropriate method is using a medium
grit, round-ended diamond bur to remove a uniform thickness of facial enamel by
joining the pre-cut depth-cut grooves, then using a diamond bur to bevel back
the incisal edge (Figures 6 and 7).
Current “makeover” trends promote this more aggressive tooth
preparation with less consideration for conservative dental concepts, the needs
of the patient, and interdisciplinary diagnosis and treatment planning.16
Alternatively, the modern restorative concept seeks to minimize the biologic
cost of the natural tooth, combining the prevention, preservation, and
perpetuation of longevity of the restoration (Figures 8-9-10).Clinicians
should correct restorative challenges by selecting a progressive treatment
concept that begins with the most conservative restorative option and
progresses to more invasive procedures only as required.17 Additionally,
the method of informing patients to ensure proper decision-making should be
directed toward the long-term biomechanical risks associated with more invasive
Veneers have undergone quite a transformation since their
inception as a conservative option was met with skepticism decades ago. Today,
however, PLVs are a sound treatment option if conservative preparation designs
and precise adhesive techniques are followed. Those clinicians who practice
aggressive restorative procedures and improper adhesive protocols leave their
colleagues in disbelief and their patients in peril.
*Assistant Professor, Department of
Restorative Dentistry and Biomaterials, University of Texas Health Science
Center Dental Branch, Houston, TX; private practice, Institute of Esthetic and
Restorative Dentistry, Houston, TX.
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