Dental Veneer Placement

The porcelain laminate veneer (PLV) has gained significant notoriety throughout popular culture. The use of this treatment modality has elicited a discussion of its appropriateness and ethical usage.[1, 2] Currently, there are no universally accepted guidelines as to the suitability of this treatment modality.

PLVs are routinely used in the correction of malposition and minor dental diastemas (see images below). In addition, malformations, minor chips, and discolorations not responsive to chemical bleaching are being remedied via the application of PLVs.

Preoperative view of a diastema.

Postoperative view of a diastema closure.

Successful implementation of PLVs requires meticulous planning, as well as a clear understanding of the patient’s expectations. With routine care and good oral hygiene, PLVs can be a conservative and ideal treatment option.

Two methods are currently being used to manufacture dental veneers—direct and indirect techniques. The direct method involves the direct application of composite resin on the tooth surface without laboratory fabrication. In most cases, the direct technique does not require the temporization of the dentition and may be completed in a single dental visit. The indirect method utilizes a dental laboratory for the manufacturing of the veneers. The indirect technique requires that an impression be recorded, which is an additional step. With the advent of computer-aided design and computer-aided manufacturing (CAD-CAM) technology, it is now possible to complete an indirect restorative procedure in a single dental visit.

Treatment via the direct or indirect protocol may or may not require the reduction of natural tooth structures.

Preoperative protocol for dental veneer treatment requires that all sound dental and medical principles be followed. In doing so, the following should have been addressed and resolved preoperatively:

• Active periodontal disease

• Occlusal imbalances

• Other active pathologies

For the vast majority of cases, the placement of a porcelain laminate veneer (PLV) is elective. The patient’s objectives and expectations should be thoroughly studied. The limitations and risks should be explained to the patient and fully understood. Alternatives such as traditional orthodontics, bleaching, and crown treatment must be explored prior to intervention. It is not uncommon for several treatment modalities to be combined in achieving the patient’s objectives.

A study of the current masticatory system requires the recording of impressions for the fabrication of study models (see image below).

Preoperative study models.

To simulate the postoperative esthetics and functional prognosis, an esthetic wax-up may be constructed upon articulated models (see image below). This aids in evaluating treatment objectives and potential for additional needs in varying the periodontal architecture. Gingival architecture plays a crucial role in the smile design process.[3]

Wax teeth planning (wax up) for planned veneers.

Besides an articulated model, a survey of the patient’s extra-oral anatomy is ideal. The smile line, midline, interpupillary distance, and other pertinent anatomical landmarks are registered and considered.[4] The recording and analysis of such data is best conducted through the use of digital photography (see image below).

Preoperative view.

Having interpreted the above, the clinician, in cooperation with the patient, can better select the appropriate veneering technique, along with the optimal substrate for the veneers.

The preparation design for a porcelain laminate veneer (PLV) varies, and several preparation techniques exist. Overall, the tooth preparation should be optimized for the removal of the least amount of tooth structure.

The following necessitates the removal of tooth structure during the preparation phase:

• Providing sufficient thickness for the structural integrity of the PLV

• Providing optimal clearance in relation to the opposing dentition

• Accommodating space for the new morphology

• Accommodating for a shift in the midline

• Accommodating for change in tooth inclination

• Removal of decay

It cannot be overemphasized that the mechanical properties and constraints of the materials used for the fabrication process be respected during preparation. With the variety of substrates available on the market, the minimum preparation depth for mechanical integrity varies. In general, when overlaying a veneer, it is important that a minimum of 1-2 mm of tooth structure be reduced. These guidelines exist for the consideration of occlusal and shear forces.

A study by Otani et al assessed an automated robotic tooth preparation system for porcelain laminate veneers for accuracy and precision compared with conventional freehand tooth preparation. The study concluded that the automated robotic procedure was able to prepare the tooth model as accurately as the conventional freehand procedure and the conventional procedure was able to prepare the tooth model with better precision.[5]

Other guiding principles in veneer preparations include the following:

• Maintaining enamel for bond strength

• Terminating the veneer preparation at or above the gingiva for moisture control during cementation

• Ensuring that occlusal contact points do not rest upon margins

• Avoiding all sharp angles within the preparation as to mitigate force aggregation

• Considering preparation characterizations that aid visualization for the laboratory technicians

• Accommodating appropriate lines of draw

  Veneer preperation.

The lack of temporization has become unacceptable to patients for reasons of esthetics and sensitivity. Besides patient needs, temporization serves as a diagnostic tool. The transitional restoration allows patients to visualize the final prosthesis. For the clinician, the temporaries permit an in vivo examination of functional esthetics. Concepts of guidance and occlusal stability derived in the study model phase may be reconfirmed. It is not uncommon for the patient to use temporaries for several weeks so that both the doctor and the patient can evaluate suitability.

A common technique used in the fabrication of temporary veneers utilizes a matrix, which is synthesized from a copy of the diagnostic wax-up. Numerous brands of acrylic resins may be introduced into the matrix and onto the prepared teeth for the fabrication of an accurate and acceptable transitional restoration. The temporaries are retained on the prepared teeth through mechanical and/or other bonding techniques. It is prudent that this restoration permits an efficient and effective oral hygiene regimen. Violation of this provision could result in gingival irritation, making the cementation phase of the final prosthesis nearly impossible.

After the trial phase of the transitional veneers, an impression is taken of the temporaries, along with the prepared teeth. This vital information will guide the laboratory technician in fabricating veneers that conform to form and function.

Temporary veneers.

Porcelain laminate veneer (PLV) cementation requires a high degree of technical skill.

All prepared teeth should be isolated with reliable moisture-control protocol. Contamination from blood, saliva, or any other fluid will compromise maximum bond strength and long-term stability.

The retention and removal of the temporary depends on the technique implemented by the clinician. After removal, the prepared teeth must be thoroughly cleansed of all residual cements and debris. Failure to do so will impede the precise seating of the veneers. Pumice may be used as an effective debridement material.

The use of a light-cured or dual-cured resin for the cementation of the final product is indicated.

Cemented veneers.

Numerous complications can contribute to failure of the porcelain laminate veneer (PLV) restoration. These include the following:

• Dislodgement of the PLV owing to bond failure

• Fracture of the PLV due to occlusal interference, bruxism, trauma, and/or excess unsupported porcelain (>2 mm)

• Discoloration of margins

• Recurrent decay

• Occlusal interferences

A 10-year study by Mazzetti et al reported annual failure rates for ceramic veneers of 2.9% at 5 years and 2.8% at 10 years.[6] A systematic review found that the success rate of PLVs over a 20-year period is high; however, few studies have examined the longevity of PLVs beyond 20 years.[7]