Onlay treatment on severely damaged molar with secondary caries

Clinical case by MDDr. Alžbeta Kršáková

Case characteristics

Age: 46 years old

Gender: Female

Area of restoration: Molar

Tooth number: 46

Reason for treatment: Damaged tooth crown with multiple fillings and secondary caries


Patient came to our clinic for preventive check-up. Along with the clinical examination, a set of Bite-wing x-rays was made. Some problems were identified after examination: secondary caries on second maxillary premolar (15), unsatisfactory fit of PFM crown on second mandibular premolar (45) and secondary caries on first mandibular molar (46). (Fig.1)

Figure 1: Bite-wing projection, right side

Tooth no. 46 was assessed as the biggest problem due to a large carious lesion in dentine, close to a vital pulp, and severe loss of crown structure, together with old restorations. Patient refused to have the PFM crown changed as, she stated, it did not cause any problems.


Caries removal and removal of all restorations was done under rubber dam insulation under local anaesthesia. After all infected dentine and unsupported enamel was removed there were very few structures left for direct restoration, so a decision was made to restore the tooth with onlay using MyCrown.

First, margin relocation on distal margin was done using composite material because gingival margin was placed subgingivally. Then, we did Immediate Dentine Sealing (IDS) using the same composite material.

After the initial phase, preparation for onlay was done. We removed rubber dam and placed aluminium chloride infused retraction cord inside sulcus to retract the gingiva and enable scanning. (Fig.2)

Figure 2: Tooth 46 after onlay preparation with retraction cord placed

Administration of the case in MyCrown was done by an assistant. Prior to scanning we secured a dry working field by placing an OptraGate Dry Tip on the parotid, coupled with suction.

After scanning the area of restoration, we scanned the opposite jaw, and finally performed a buccal scan to register the occlusion.  Digital models were created and the software correlated them according to bite registration.

We placed the restoration correctly along the dental arch and then drew the margin of preparation. (Fig. 3) According to the models and margin, the software designed the onlay restoration. (Fig.4)

Figure 3: Margin of preparation, as shown on a digital model, in MyCrown Design

Figure 4: Design proposal, colours on occlusal side indicate strength of contact with antagonists

After checking contact points and all details of the proposed onlay, small adjustments were made and we proceeded to manufacturing phase. The onlay was milled from Celtra Duo Block – zirconium-reinforced lithium silicate. After milling we carefully polished the restoration as we opted for mill and polish procedure. (Fig. 5)

Figure 5: Onlay after polishing


We checked the fit of the restoration to the preparation area and moved to cementation. Adhesive cementation by Variolink was done under rubber dam insulation to secure safe adhesion. (Fig.6)

Figure 6: Tooth 46 prior to adhesive cementation of the onlay


After removal of excess cement and polishing the margins we checked the fit to the occlusion and polished points of contact once more. Colour match seemed to be very good immediately after cementation. (Fig.7)

Figure 7: Onlay restoration performed using MyCrown on tooth number 46 immediately after cementation


This clinical case shows how we can deal with severe loss of dental structure and reconstruct a crown in one visit using modern technology. Chairside CAD/CAM can help to solve more complex cases quickly and effectively, so that both the dentist and patient are happy with the result.

About Doctor

MDDr. Alžbeta Kršáková

General dentist, working in private clinic 3S DENT based in Bratislava since Graduation.  Interested in Prosthodontics and Esthetic dentistry.

Graduated at Palacky University in Olomouc, Czech Republic in 2011.