Consultants’ Comments

• “I have been very pleased with the Lava restorations.”
• “My patients love the life-like quality of Lava restorations and prefer them over the grayness of PFM crowns.”
• “The esthetics and clinical longevity of anterior restorations over a ten year period have been exceptional.”
• “Lava has been my restoration of choice for anterior and pre-molar crowns.”

Description

3M ESPE Lava™ Crowns and Bridges are CAD/CAM processed, zirconia based restorations overlaid with an appropriate zirconia veneering ceramic. The zirconia copings and frameworks provide the long-term strength while the veneering material is designed for optimal esthetics and shape. The zirconia substructure is colored with one of the seven available shades, to coordinate with the final restorations. The system is used for anterior and posterior crowns, implant crowns, bridges with a span of up to 48 mm in length and two-piece abutments.

Clinical Evaluation Protocol

Over 1300 Lava restorations have been placed and documented since 2003. These restorations include anterior and posterior crowns, three- to six-unit bridges and implant crowns. Most restorations were cemented with 3M ESPE RelyX Unicem Self-Adhesive Universal Resin Cement.

• One thousand and eight restorations were recalled at year ten. The distribution of restorations evaluated is shown in Figure 1.
• Restorations were rated on a 1-5 scale, 1=poor, 2=fair, 3=good, 4=very good, 5=excellent.

Figure 1

Clinical Observations

Resistance to Fracture and Chipping

The fracture and chipping of Lava restorations at 1, 5, and 10 years of service
are shown in Figure 2. The majority (89%) of Lava restorations showed no evidence of fracture or chipping at 10 years (Figure 3). Of the recalled restorations, 61 fractured and therefore were replaced because they received a rating of 1 or 2 out of 5. In many cases the fractures resulted in the delamination of a large portion of the veneering ceramic, and the restorations could not be polished or repaired. Forty-seven restorations received a rating of 3 or 4. These restorations were chipped restorations that either did not need any smoothing or polishing or were polished and smoothed satisfactorily. In most cases the patient was not aware that the restoration had chipped. The causes of the fractures may be the result of:

• rapid heating or cooling of the veneering ceramic or
• the thickness of unsupported porcelain.

Rapid cooling of the restoration can result in the buildup of undesirable stresses within the restoration. Failure from rapid heating or cooling is normally experienced shortly after cementation of the restoration. The veneering porcelain disintegrated in these instances. This type of failure occurred in less than 10% of the failed restorations. None of the fractures involved a zirconia substructure or coping failure. The overlay fracture rate (6.1%) at 10 years is higher by 1.8% than all-ceramic restorations documented by THE DENTAL ADVISOR over a 10-year period but in the same range of published PFM performance statistics. Molar crowns fractured twice as often as pre-molar crowns and anterior crowns (Table 1). Upper anterior crowns fractured more often than lower anterior crowns. Upper anterior crowns are especially prone to fracture in people who are bruxers.

Esthetics
The vast majority of Lava restorations received a 5 or excellent rating for esthetics (Figure 3). Only 50, or 4.8%, of 1008 restorations received a rating less than 5. Lava restorations definitely have superior esthetics when compared to PFM restorations, especially because the Lava coping can be shaded to closely simulate dentin, eliminating the graying caused by a metal substructure. Once the patient experiences the esthetics of a Lava zirconia-based restoration, they are elated with the outcome.

Resistance to Marginal Discoloration
Over 97% of Lava restorations received an excellent rating for resistance to marginal discoloration (Figure 3). One advantage of Lava crowns is that the margin of the opaque core is very close to the margin of the preparation. These thin opaque margins reduce or eliminate graying due to microleakage that can be visible in more translucent restorations. During the 10-year evaluation, only 2.4% of the restorations exhibited graying at the margins.

Wear Resistance
Over 97% of Lava restorations received an excellent rating for resistance to wear (Figure 3). A small number (2.8%) of the recalled restorations exhibited some wear of the overlaid ceramic at 10 years. Minimal to moderate wear was noted in about 15% of the teeth opposing Lava restorations; this wear was mostly visible in anterior teeth.

Figure 2

Figure 3

Summary

3M ESPE Lava Crowns and Bridges performed well over the 10-year evaluation period with very good resistance to fracture and marginal discoloration and minimal wear. 3M ESPE Lava Crowns and Bridges received a 93% clinical performance rating at 10 years.