Consultants’ Comments:

• “Well done, even the shade. I wish they all this looked this way.”
• “Great‚Ķno adjustment needed.”
• “Crown is opaque but the patient loved it.”

Description

Zenostar® Zr Translucent is a pre-shaded zirconia with a flexural strength in the range of 1200 MPa. The purpose of this study was to determine the clinical performance of Zenostar® Zr Translucent restorations at placement and over a 12-month period.

Placement Protocol

Dentists placed 101 full-contour Zenostar Zr Translucent, including:
• 60 second molar crowns
• 32 fi rst molar crowns
• six premolar crowns
• one, three-unit bridge (teeth #4-6).
All restorations were designed, milled and finished by Apex Dental Milling, Ann Arbor, MI. Seventy-four percent of cases were completed with traditional impressions that were scanned by the milling center and converted into digital files. Dentists obtained impressions digitally through intraoral scanning in 26% of the cases (True Definition, 3M ESPE, and iTero, Align Technologies). The restorations were stained and glazed to achieve the requested shade. The majority of crowns (74%) were cemented with adhesive resin cements (Figure 1).

Placement Results

The following parameters were evaluated at placement: esthetics, marginal integrity, fit to tooth, interproximal contacts, and occlusion. Categories evaluated were rated on a scale of 1 (poor) to 5 (excellent) (Figure 2).

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Fit, Marginal Integrity, Contacts and Occlusion

These design features had excellent ratings with few exceptions. Both traditional and digital impressions produced crowns with excellent fit, requiring minimal to no adjustment.

Esthetics

The majority of Zenostar® Zr Translucent restorations received a rating of 5 (excellent) for esthetics. Crowns that received lower ratings were too opaque or had a higher shade value than adjacent teeth. Because the majority of these crowns were placed on molars, the crowns were considered clinically acceptable. In cases where occlusal adjustment removed the glaze from the surface, the exposed zirconia could be polished to a high gloss but had a visible color difference.

Recall Results

Eighty-six units were evaluated at recall. Age of the restorations at recall is shown in Figure 3. At recall the following parameters were documented: esthetics, resistance to fracture/chipping, resistance to marginal discoloration, and wear resistance. Categories evaluated were rated on a scale of 1 (poor) to 5 (excellent) (Figure 4).

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Esthetics

Esthetics at recall was unchanged from placement (Figure 4). Color was stable, and the glaze maintained a high level of gloss.

Resistance to Fracture/Chipping and Wear

Zenostar® Zr Translucent restorations were strong and durable, with no fracture, chipping or wear (including the glaze) noted during this recall period (Figure 4).

Resistance to Marginal Discoloration

Resistance to marginal discoloration was rated excellent (Figure 4). The accuracy of marginal fit contributed to lack of staining at the cement line.

Retention

Two crowns debonded to date. One mandibular, second molar crown debonded at five months; the crown was re-cemented. One mandibular, first molar crown debonded at the zirconia/cement interface. Both of these crowns were cemented with adhesive resin cements.

Summary

At placement, Zenostar® Zr Translucent restorations received excellent ratings for fit, marginal integrity, contacts and occlusion. The majority of Zenostar® Zr Translucent restorations received a rating of 5 (excellent) for esthetics, but some crowns were too opaque or had a value that was too high at the 12-month recall. The rating at placement was 96%. At one-year recall, Zenostar® Zr Translucent restorations received excellent ratings for esthetics, resistance to fracture/chipping, resistance to marginal discoloration and wear resistance. Zenostar® Zr Translucent received a clinical performance rating of 98% at one year.