Conventional single crowns (SCs)

CHAPTER 4

Anterior regions

2.4.1 Anterior SC with non-discolored abutment tooth

2.4.2 Anterior SCs with discolored abutment teeth

Posterior regions

2.4.3 Posterior SC with non-discolored abutment tooth

2.4.4 Posterior SC with a discolored abutment tooth

Complex situations

2.4.5 Conventional SCs and fixed dental prostheses (FDPs)

2.4.6 SCs in combination with an implant

2.4.1 Anterior SC with non-discolored abutment tooth

■ Anterior regions, crown with non-discolored abutment tooth

This first section describes the replacement of an esthetically displeasing existing porcelain-fused-to-metal (PFM) crown with an all-ceramic crown.

Assessment and treatment planning

A 37-year-old healthy and caries-free female presented herself at the clinic, seeking treatment for her esthetically unpleasing central incisor PFM crown at position 11. Furthermore, she disliked the pronounced buccally oriented shape of the old crown.

As a consequence of an accident several years ago, she received the conventional PFM crown based on a conventional and quite invasive 360-degree preparation of her abutment tooth 11.

In agreement with the patient, a step-by-step treatment plan was established. The first step consisted of a revaluation after the removal of the old crown to have a better understanding for the quality and shade of the abutment tooth. Depending on the shade of the abutment tooth and the available space, an all-ceramic restoration was planned based on a buccally veneered reinforced glass-ceramic crown. In case of any discoloration, bleaching in combination with a zirconia-based crown was considered (Fig 2-4-1).

Redefining the crown preparation and impression

A silicone index was fabricated based on a wax-up to facilitate the correct repreparation of the tooth.

According to the patient’s wishes, the tooth shape was now planned to be oriented slightly more palatally. The old crown was removed and the non-discolored tooth was re-prepared, which consisted mainly of a minimal rounding of the incisal border and a smoothening of the finish line (Universal Prep Set, Intensiv, Montagnola, Switzerland).

The final impression was taken using two retraction cords. In order to avoid traumatization of the gingiva and to minimize the risk of recessions, a surgical suturing material (size 4-0, Vicryl Ethicon, Johnson & Johnson, NJ, USA) was used as the first retraction cord. The second retraction cord was the thinnest cord available on the market (000 Ultrapak, UP Dental, Cologne, Germany) (Fig 2-4-2).

Provisional

To transfer the wax-up into the patient’s mouth, a second silicone index of the wax-up was prepared in order to fabricate an eggshell provisional on the cast. This eggshell was fabricated with a classic acrylic PMMA material (New Outline, Anaxdent, Stuttgart, Germany) that was later on easy to reline and adjust to the actual intraoral preparation. The provisional was then relined with a self-curing resin (Tab 2000, Kerr, Brea, CA, USA) extraorally polished and provisionally cemented (Protemp, 3M, Seefeld, Germany). The resulting provisional integrated very nicely and already showed the patient the new, more palatally oriented shape of the crown.

Fabrication of the crown

The first step toward the final restoration was the fabrication of a master cast. For the fabrication of the crown, a backward planning concept was applied and with the silicone index fabricated based on the wax-up, the dentin core coping was modeled and prepared for the lost wax technique. The coping was then embedded in a special investment material for press ceramics (IPS PressVest Premium, Ivoclar Vivadent, Schaan, Liechtenstein) and pressed with a feldspathic glass-ceramic (Creation Press A2, Willi Geller, Meiningen, Austria). Once again, the laboratory work was guided by the information from the wax-up, which was transferred by the aid of silicone indexes (Matrix Form 60, Anaxdent). The ceramic masses were then applied (Creation Classic, Willi Geller) according to the custom shade that was developed by the dental technician in collaboration with the patient. After one dentin firing, the surface texture and the final shape was done with stones and diamond burs. The glaze firing was followed by an additional stain firing and a mechanical polishing procedure (Fig 2-4-3).

Integration of the crown

A try-in session was carried out where the crown was inserted with a try-in paste (Variolink Esthetic neutral and warm, Ivoclar Vivadent) in order to improve color assessment and optical integration. In a dry environment (rubber dam) the all-ceramic crown was cemented. The abutment tooth was pretreated and bonded with a multistep adhesive system (Syntac Classic, Ivoclar Vivadent). The bond was not light-cured in order not to compromise the fit of the ultra-thin veneers. The crown was etched with hydrofluoric acid (9% concentration for 1 min) (Porcelain Etch, Ultradent Products, South Jordan, UT, USA). A silane-containing primer (Monobond Plus, Ivoclar Vivadent) and a bonding system (Heliobond, Ivoclar Vivadent) was applied. Then the crown was cemented with a dual-curing resin cement (Variolink Esthetic neutral, Ivoclar Vivadent). Excess cement was removed with rotating and oscillating diamond instruments (Universal Prep Set, Intensiv). The occlusal and functional contacts were analyzed, and only very minor adjustments were necessary. The patient and the entire treatment team were very satisfied with the final treatment outcome (Fig 2-4-4 and 2-4-5).

(Dental Practitioner: Prof Dr I Sailer; Technician: DT B Thiévent.)

Comparing zirconia and metal-based restorations

(discolored abutment teeth)

2.4.2 Anterior SCs with discolored abutment teeth

■ Anterior regions, crowns with discolored abutment teeth

■ Comparing zirconia and metal-based restorations

The following section describes the replacement of two esthetically displeasing existing porcelain fused-to-metal (PFM) crowns with an all-ceramic crown.

Assessment and treatment planning

A 46-year-old healthy female presented herself at the clinic seeking treatment for her esthetically unpleasing central incisors with PFM crowns at position 11 and 21. Furthermore, she disliked the grayish discoloration apical of the crown 21 caused by the discolored root of the non-vital tooth and the crowns that showed no ceramic shoulders.

She received the conventional PFM crowns based on a quite invasive 360 degrees preparation of her abutment teeth several years ago and was never really happy with the appearance of her smile.

In agreement with the patient, a step-by-step treatment plan was established. The first step consisted of a revaluation of the abutment teeth after the removal of the old crowns to gain a better understanding of their quality and shade. Finally, and depending on the degree of discoloration of the abutment teeth, either an all-ceramic zirconia or metal-based restoration with an enlarged ceramic shoulder was planned.

In the process of restoring the patient, both zirconia and metal-ceramic restorations were fabricated and the patient could choose which version she preferred (Fig 2-4-6).

Diagnostics

The patient’s chief complaint was her compromised esthetic appearance. In addition to this, she was also aware of the grayish discoloration of her mucosa caused by the dark root of tooth 21.

She also mentioned that she disliked the monochromatic appearance of her crowns and understood that especially in cooperation to her existing natural teeth the crowns were too opaque.

So, her wish was not only to achieve a better shape of the restorations and hide the cervical exposure of the gold margins but also to have two natural looking esthetic crowns (Fig 2-4-7).

Redefining the crown preparation, impression, and provisionalization

A silicone index was fabricated based on a first wax-up to facilitate the correct repreparation of the teeth. The old crowns were removed and both the non-discolored as well as the discolored teeth were re-prepared, which consisted mainly in a minimal rounding of the incisal border and a smoothening of the finish line (Universal Prep Set, Intensiv, Montagnola, Switzerland).

The final impression was taken using two retraction cords. In order to avoid traumatization of the gingiva and to minimize the risk of recessions, a surgical suturing material (size 4-0, Vicryl Ethicon, Johnson & Johnson, New Brunswick, NJ, USA) was used as the first retraction cord. The second retraction cord was the thinnest cord available on the market (000 Ultrapak, UP Dental, Cologne, Germany) (Fig 2-4-8).

To then fabricate the provisionals, the dental laboratory already prepared an eggshell provisional on the first cast. This eggshell was fabricated with a classic acrylic PMMA material (New Outline, Anaxdent, Stuttgart, Germany) that was later on easy to reline and adjust to the actual intraoral preparation. The provisional was then relined with a self-curing resin (Tab 2000, Kerr, Brea, CA, USA) extraorally polished and provisionally cemented (Protemp, 3M, Seefeld, Germany) (Fig 2-4-9).

Wax-up try-in

As the patient was not really satisfied or convinced during this phase with her eggshell provisional, it was decided to verify the exact crown shapes with an additional wax-up try-in.

So, after the master cast was produced in the laboratory, a wax-up was fabricated using esthetic wax in order to verify the exact shape of the final restoration before the actual restoration and its framework was created.

The patient was now happy with the achieved shape and contour of her crowns; however, the grayish discoloration was still visible (Fig 2-4-10).

Fabrication of the restorations

As the custom shade was developed by the dental technician during the wax-up try-in, it was discussed that in this particular case, also due to the different degrees of discoloration of the abutment teeth, a classic opaque zirconia should serve as the restorative material of choice.

In the laboratory the casts were scanned using a lab scanner (inEos X5, Dentsply Sirona, Bensheim, Germany). Based on the scans, the frameworks were digitally designed (Cerec inLab 16.1, Dentsply Sirona). The generated crown files were then milled in a five-axis milling unit (Zenotec Select Hybrid, Ivoclar Vivadent, Schaan, Liechtenstein) using a classic 98-mm zirconia disk in a dry milling environment (Lava Plus, 3M).

The milled restorations were adjusted in the white stage and sintered to their final density and prepared for a framework try-in (Fig 2-4-11).

Framework try-in

During the framework try-in it became immediately evident that despite the selection of the classic opaque zirconia used for the frameworks, it was not possible to mask the strongly discolored abutment tooth 21. Therefore, and especially due to the very challenging patient, it was decided to take a step back and fabricate conventional PFM frameworks with XL ceramic shoulders as they would mask the discoloration without any question (Fig 2-4-12).

Finalization of the restorations

Thereafter both crown pairs were veneered according to the individually developed custom shade. The PFM crowns were veneered with a classic feldspathic veneering ceramic (Creation Classic CC, Willi Geller, Meiningen, Austria) and the zirconia frameworks with a conventional glass-ceramic (Creation ZI, Willi Geller).

After two dentin firings, the surface texture and the final shape were developed with stones and diamond burs before both pairs were superficially characterized applying stains and glaze (Fig 2-4-13).

Integration of the restorations

A try-in session was carried out in which the two crown pairs were inserted with a try-in paste (Variolink Esthetic neutral, Ivoclar Vivadent) in order to assess the final outcomes and allow the patient to choose between them.

Interestingly enough, once the crowns were placed in the oral cavity for the patient as well as the restorative team it was absolutely evident that the PFM restorations integrated much better and appeared more natural. Additionally, the PFM crowns with their XL ceramic shoulder also managed to reduce the grayish marginal discoloration substantially. As the choice was made for the PFM crowns, they were then conventionally cemented applying a glass-ionomer luting cement (Ketac Cem, 3M). Excess cement was removed with rotating and oscillating diamond instruments (Universal Prep Set, Intensiv). The occlusal and functional contacts were analyzed, and only very minor adjustments were necessary. The patient and the entire treatment team were very satisfied (and relieved) with the final treatment outcome (Fig 2-4-14).

(Dental practitioner: Prof Dr I Sailer; Technician: DT W Gebhard.)

2.4.3 Posterior SC with non-discolored abutment tooth

■ Posterior crown with non-discolored abutment tooth

■ Chairside dentistry

The following section describes the monolithic restoration of a first molar by means of a full digital workflow and the fabrication of a chairside lithium disilicate crown.

Assessment and treatment planning

A 39-year-old male presented himself at the clinic seeking treatment for his several years ago endodontically treated maxillary first molar. He observed a strange feeling during the preceding few weeks as if the old composite had become loose and applying his dental floss in the distal area always led to a torn floss.

After the re-evaluation of the root canal treatment the patient was planned to be restored chairside with an all-ceramic crown to provide fracture prophylaxis.

As restorative material, a lithium disilicate (IPS e.max, Ivoclar Vivadent, Schaan, Liechtenstein) was used and milled in the pre-sintered blue stage.

However, today this full crown preparation would be considered too invasive and to protect the devitalized tooth from fracturing only an overlay preparation would have been envisaged. To achieve an efficient treatment and not to cause any additional costs by the dental laboratory it was also planned to perform an optical impression and finalize the restoration by means of a cast free chairside computer-aided design/computer-aided manufacturing (CAD/CAM) workflow (Cerec, Dentsply Sirona, Bensheim, Germany) (Fig 2-4-15).

Crown preparation and optical impression

The initial partial crown preparation was extended to a minimally invasive crown design, with the aim to cover the crown completely to facilitate a fracture prophylaxis. Today, however, the extension of the preparation would be considered too invasive and in order to preserve the maximum of tooth substrate only an overlay would have been considered as treatment of choice. Additionally, as a very important step to achieve a good fit in the chairside workflow, the incisal boarders were smoothened off to allow for a good reproducibility of the chairside three-axis milling unit (MCXL, Dentsply Sirona).

Then a powder-free optical quadrant impression (Omicam, Dentsply Sirona) was acquired.

Directly after the data acquisition, the files were processed and the marginal line, as well as the insertion pass were semi-automatically detected (Fig 2-4-16).