Defect-oriented restorations

CHAPTER 3

Posterior regions

2.3.1 Defect-oriented partial crowns and overlay in posterior regions

2.3.2 Defect-oriented overlays in posterior regions

2.3.3 Defect-oriented restoration of endodontically treated posterior tooth

2.3.4 Defect-oriented restorations (direct computer-aided composite build-up)

2.3.1 Defect-oriented partial crowns and overlay in posterior regions

■ Anterior regions (360-degree veneers)

■ Posterior regions (defect-oriented partial crowns and overlays)

■ Full-mouth rehabilitation

This section covers the minimally invasive rehabilitation of a patient to re-establish esthetic and oral function by means of minimal invasive restoration. This involved the application of individual veneered feldspathic veneers to the anterior regions and monolithic lithium disilicate partial crowns to the posterior regions.

Assessment and treatment planning

A 41-year-old male with severe erosion and abrasions in his entire dentition presented himself at the clinic seeking treatment for his compromised esthetics. He also suffered from sensitivities when drinking or eating hot or cold beverages. Hence, for this patient the potential changes were quite dramatic, as they involved the raising of the vertical dimension of occlusion (VDO), functional aspects, and a complete change in his esthetic appearance. The importance of the diagnostic analyses and the mock-up try-in played a fundamental role to make sure that the treatment goal was set according to the patient’s wishes and their functional needs.

The patient was quite young for such a comprehensive rehabilitation. With this in mind, a minimally invasive treatment plan was established and tested with an extensive splint phase. This involved not only the esthetic anterior segments but also a change of vertical dimension. It would also allow the patient to test the new appearance not only during a mock-up try-in session but also with an adapted Michigan splint. As the splint was fabricated like a tooth-shaped provisional, the patient could wear this before the actual preparation had to be created.

Another advantage of these detailed diagnostics was that the later treatment could easily be sequenced; this would mean the appointments for both patient and clinician could be shorter and less stressful (Fig 2-3-1).

Diagnostics

The patient’s chief complaint was his compromised esthetic appearance, especially in the maxillary anterior teeth. However, he was also aware that due to the abrasion of his teeth, he had not only lost vertical dimension but also his teeth had become more sensitive. He was afraid that if there was no intervention at this point in time, things would only become worse.

In all his teeth, dentin was already exposed to a high degree, which also explained the sensitivity he reported. Despite the long-exposed dentin, his teeth remained vital and showed no signs of decay (Fig 2-3-2).

Wax-up and direct mock-up

In order to visualize the final treatment outcome and also its potential limitations, a purely additive wax-up was performed on two conventional plaster casts that were articulated by means of a facebow.

To then transfer the wax-up into the patient’s mouth, two silicone indexes of the wax-up were prepared in order to fabricate a direct mock-up (Memosil 2, Kulzer, Hanau, Germany). These silicone indexes were filled with a chemically curing composite material, in shade Vita A2 (Protemp, 3M, Rüschlikon, Switzerland) and placed over the maxillary and mandibular teeth.

The resulting direct mock-up served as a communication tool, to visualize the prospective treatment outcome (Fig 2-3-3).

The patient was very happy with the mock-up try-in and immediately felt very comfortable with the raised vertical dimension and agreed to the proposed treatment plan (see Fig 2-3-4, showing an adapted Michigan splint with planned VDO in the mandibular arch).

To allow the patient to adjust to his new vertical dimension and reassure that he is compliant and comfortable with it, a Michigan splint was fabricated in the dental laboratory. It was fabricated in a way that the anterior segment already looked like his future teeth and in the posterior segment the new vertical detention was incorporated. The overall splint design was kept thin so that it was convenient for the patient to wear during the day (Fig 2-3-5).

Provisional: Maxillary anterior teeth

To fabricate the provisional according to the same shape of the wax-up and transfer it into the patient’s mouth, the same silicone index from the mock-up try-in of the maxillary anterior teeth was used 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 (Fig 2-3-6).

Preparation and impression of the maxillary arch

A silicone index was fabricated based on the wax-up to facilitate the correct preparation of the teeth. Teeth 13–23 were prepared with a minor epigingival course to preserve the maximum of tooth substrate, while the teeth 17–14 and 27–24 basically could be restored with no preparation at all. 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 2-3-7).

The anterior eggshell provisional was then relined with a self-curing resin (Tab 2000, Kerr, Brea, CA, USA) extraorally polished and provisionally cemented (Protemp, 3M). The posterior region was provisionally restored by a direct provisional (Fig 2-3-8).

Fabrication of maxillary arch restorations in the laboratory

The first step for the final restoration was the fabrication of an alveolar cast. In order to achieve an individualized shape and shade for the anterior restorations, refractory dies were manufactured (anaxVest, Anaxdent) to then directly veneer them. Due to the use of refractory dies, the best possible fit of the veneers could also be guaranteed.

For the fabrication of the partial crowns, however, a new, slightly softer silicone key was fabricated, based on the initial wax-up. With this new silicone index, the wax-up was transferred to the new master cast. As a next step, all margin lines were adjusted in wax and then the partial crowns prepared for the lost wax technique. They were embedded (IPS PressVEST Speed, Ivoclar Vivadent, Schaan, Liechtenstein) and pressed (Programat EP 5010, Ivoclar Vivadent) with a lithium disilicate press ceramic (IPS e.max press MT A2, Ivoclar Vivadent), divested, adjusted, and finalized by the application of stain and glaze (IPS Ivocolor, Ivoclar Vivadent) according to the custom shade that was developed by the dental technician in collaboration with the patient.

Meanwhile, the anterior veneers were individually layered with ceramic masses (Creation Classic, Willi Geller, Meiningen, Austria). After two dentin firings, 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. The polished veneers were carefully removed from the refractory dies by airborne-particle abrasion with glass beads and cleaned in an ultrasonic waterbed (Fig 2-3-9 and Fig 2-3-10).

Integration of maxillary veneers and overlays

A try-in session was carried out where the overlays were inserted with a try-in paste (Variolink Esthetic neutral and warm, Ivoclar Vivadent) in order to improve color assessment and optical integration. Subsequently, in a dry environment (rubber dam), the ceramic veneers were cemented. The abutment teeth were etched with 35% phosphoric acid (Ultra-Etch, Ultradent Products) 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 veneers were etched with hydrofluoric acid (9% concentration for 1 min) (Porcelain Etch, Ultradent Products). A silane-containing primer (Monobond Plus, Ivoclar Vivadent) and a bonding system (Heliobond, Ivoclar Vivadent) were applied. Then the overlays were etched with hydrofluoric acid (5% concentration for 20 s) (IPS Ceramic Etching Gel, Ivoclar Vivadent). A silane-containing primer (Monobond S, Ivoclar Vivadent) and a bonding system (Heliobond, Ivoclar Vivadent) were applied.

Finally, the partial crowns were cemented with a dual-curing resin cement (Variolink Esthetic Neutral, Ivoclar Vivadent, FL, USA). Excess cement was removed with rotating and oscillating diamond instruments (Universal Prep Set, Intensiv, Montagnola, Switzerland) (Fig 2-3-11).

Transfer of the maxillary arch

Once the maxillary restorations were placed, a conventional impression was performed and sent to the dental laboratory. Due to the initial wax-up and diagnostics, the dental technician was able to cross-articulate the new maxillary arch against the initial wax-up and in a second phase replace the initial wax-up model by the newly prepared master cast for the mandibular arch.

With this cross-articulation, all initial data from the orientation of the cast in the articulator according to the facebow to the planned vertical dimension and the wax-up could be maintained efficiently (Fig 2-3-12).

Preparation and impression: Mandibular arch

A silicone index was fabricated, based on the wax-up, to facilitate the correct preparation of the teeth. Teeth 31–37 and 41–47 were prepared with no epigingival course to preserve the maximum of tooth substrate and stay in the enamel wherever possible. Due to erosion and abrasion, the teeth already appeared as if they were prepared and therefore the actual preparation was quite efficient. Due to the opening of the vertical dimension during the diagnostic phase and its verification with the mock-up, the minimum thickness of both maxillary and mandibular restorations was already taken into account and therefore there was no need for a subtractive preparation. Only sharp margins and edges were rounded, and the preparation mainly consisted of smoothing of the surfaces.

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) was used as the first retraction cord. The second retraction cord was the thinnest cord available on the market (000 Ultrapak, UP Dental) (Fig 2-3-13).