3M ESPE Lava Crowns and Bridges (7 yr)

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  THE DENTAL ADVISOR was the first to publish Long-term Clinical Performance Report results on ceramics, cements, composites, laboratory composites, and bonding agents. With over 24 years of data on these materials, THE DENTAL ADVISOR is capable of providing the long-term data many customers require.

7-Year Clinical Performance

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.”
• “Over 1500 zirconia-based restorations have been placed in our office during the past seven years. The results have been phenomenal.”

Laboratory Comments

• “As the owner of a dental laboratory, it is much more gratifying to work with zirconia as compared to metal, because the esthetic results are superior.”

Description

3M ESPE Lava Crowns and Bridges are Lava zirconia-based restorations overlaid with an approved veneering ceramic. The zirconia copings and frameworks provide the strength while the veneering material provides the esthetics. The system is used for crowns, implant abutments, and bridges with a span of up to 48 mm in length. Tooth preparation is similar to PFM preparations but with slightly less reduction occlusally and circumferentially. Dies are scanned and then the copings or frameworks are milled and sintered. The process can also be carried out through the 3M ESPE Lava Chairside Oral Scanner C.O.S. The zirconia substructure is colored with one of seven available shades to coordinate with the final restoration. Lava restorations can be cemented with traditional or self-adhesive resin cements. Lava received a 95% clinical rating.

Clinical Evaluation Protocol

• Lava restorations were placed beginning in 2003. Since then well over 1500 restorations have been placed and documented. These restorations include anterior and posterior crowns, 3- to 6-unit bridges and implant abutments. Most restorations were cemented with 3M ESPE RelyX Unicem Self-Adhesive Universal Resin Cement.
• Five hundred and seventy-four restorations were recalled over a six-month period. 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=v good, 5=excellent.

Clinical Observations

Resistance to Fracture and Chipping
The fracture and chipping of Lava restorations at 1, 3, and 7 years of service are shown in Figure 2. Of the recalled restorations 16 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 ceramic. When a large piece would shear off the coping material, it could not be polished or repaired. Thirty-five restorations received a rating of 3 or 4. These were chipped restorations that either did not need any smoothing or polishing or could be polished and smoothed satisfactorily. In many cases the patient was not aware that the restoration had chipped. The causes of the fractures could be the thickness of unsupported porcelain or possibly too rapid heating or cooling of the veneering ceramic. Rapid cooling of the restoration can result in the build up of undesirable stresses within the restoration. None of the fractures involved a zirconia substructure or coping failure.

Esthetics
The majority of the recalled restorations had excellent esthetics, and 57 restorations or 10% had a good to very good rating (Figure 3). Lava restorations have improved esthetics compared to PFM restorations, because the Lava coping can be shaded to act as a good dentin simulator and the grayish appearance of the metal at the cervical is eliminated. Lava restorations are also vital in appearance.

Resistance to Marginal Discoloration
Over 95% of Lava restorations received an excellent rating for resistance to marginal discoloration (Figure 3). Advantages of Lava crowns are the opaque core and the zirconia coping margins can be very close to the margin of the preparation. These characteristics reduce or eliminate graying at the margin due to microleakage that can be visible in more translucent restorations. During the seven-year evaluation, only 2.8% of the restorations exhibited slight graying at the margins.

Wear Resistance
Over 96% of Lava restorations received an excellent rating for resistance to wear. A small number (3.2%) of the recalled restorations exhibited some wear of the overlaid ceramic at seven years. Minimal to moderate wear was noted in about 15% of the teeth opposing Lava restorations; this wear was mostly visible in anterior teeth.

Summary

3M ESPE Lava Crowns and Bridges performed exceptionally well over the seven-year evaluation period with excellent resistance to fracture and marginal discoloration and minimal wear.