Minimally invasive restorations (resin-bonded fixed dental prostheses [RBFDPs])

Anterior regions

2.2.1 Failing central incisor after many years of periodontal treatment

2.2.2 Congenitally missing lateral incisor (RBFDP after orthodontic pretreatment)

2.2.3 Congenitally missing lateral incisors (RBFDP after orthodontic pretreatment)

2.2.4 Full-mouth rehabilitation with congenitally missing teeth (RBFDPs, veneers, and overlays after orthodontic treatment)

Complex situations

2.2.5 Complex situations (RBFDP and additional veneer in combination with orthodontic pretreatment)

2.2.1 Failing central incisor after many years of periodontal treatment

This first case shows the minimally invasive rehabilitation of a patient who was refusing surgical interventions, with a follow-up of 10 years.

Assessment and treatment planning

A 47-year-old female patient was referred by her periodontist (Dr Frank Paqué) with a central incisor (tooth number 11) with a poor prognosis. Over the previous 7 years the patient did everything possible to maintain her compromised tooth, that now unfortunately after several successful interventions had finally failed. A periradicular chronic infection, two fistulas in the buccal area of tooth 11, could be detected, and a radiograph clearly showed the bone loss as consequence of the inflammatory process and the previous interventions.

Two treatment options for the replacement with a fixed restoration were discussed and elaborated with the patient: a single-retainer resin-bonded fixed dental prosthesis (RBFDP) bonded to tooth 21, and a single implant. After both treatment options were presented, the patient strongly insisted on a surgery-free treatment which in her case was reflected by the RBFDP. No restorative limitations were posed by the position and angulation of the teeth and therefore the replacement of the missing tooth by means of a fixed tooth-borne restoration was possible and a single retained RBFDP made from zirconia was planned (Fig 2-2-1).

Diagnostics

The patient’s chief complaint was to receive a fixed dental restoration. The patient liked the shape and the slight crowding of her teeth and also saw a small color change in her affected central incisor that she did not like. She requested the same position and shape for her final restoration. Due to the mesial rotation of the adjacent central 21 and the slightly inverted position of the designated pontic, the conditions were close to ideal for the anchorage of a palatal backing.

Usually the adjacent central incisors offer a longer approximal contact area than canines, first to develop a sufficient connector dimension and second, but at least as important, to then hide the connector and its minimally invasive preparation. In this case the adjacent central incisor 21 was chosen to serve as an anchorage tooth (Fig 2-2-2).

Extraction

Despite the extremely careful extraction, the tooth immediately broke into two pieces. The remaining root of tooth 11 was extracted and a lot of granulation tissue had to be removed.

Finally, the socket was curettaged and rinsed with neomycin solution (Fig 2-2-3).

Ridge preservation

After the extraction and cleaning of the socket a xenogeneic bone substitute (Bio-Oss Collagen, Geistlich, Wolhusen, Switzerland) was inserted in combination with a subepithelial connective tissue grafts harvested from the palate to perform a ridge preservation (Fig 2-2-4).

Conditioning of the pontic

Prior to the prosthetic replacement of missing tooth 11, the gingival area in the pontic region was shaped (ie, conditioned according to the desired emergence profile of the restoration). The conditioning was performed in order to shape the soft tissues into an “ovate-pontic-like” shape and, hence, to allow for a natural emergence profile of the pontics. For the conditioning, flowable composite (Tetric Flow, Ivoclar Vivadent, Liechtenstein) was applied in a stepwise approach to the basal region of the provisional pontic, inducing pressure to the soft tissues in the edentulous area and thereby shaping of this region. This procedure was repeated three times at intervals of 8–10 days until the desired shape of the pontic area was achieved (Fig 2-2-5).

Preparation and conventional impression

Finally, the respective abutment tooth 21 was prepared in order to allow for retention of the RBFDP and in order to simplify the positioning during the laboratory work as well as the cementation procedure. The minimally invasive preparation design for anterior zirconia-based RBFDPs encompassed the preparation of a mesial and a distal vertical groove (6-degree taper) and a tiny slot at the palatal/lingual cingulum region (Universal Prep Set, Intensiv, Montagnola, Switzerland). After that, a conventional impression was performed using an elastomeric impression material (President, Coltene, Langenau, Germany).

Fabrication of the RBFDP in the laboratory

The single-retainer zirconia-ceramic RBFDP was virtually designed with respect to the minimum requirements of the framework and connector dimensions. This was manufactured by means of a CAD/CAM system (Cares Visual, Straumann, Basel, Switzerland) and milled from Lava Plus (3M, Seefeld, Germany).

The minimum dimensions for zirconia frameworks in the anterior region were:

■ thickness of retainer 0.5 mm;

■ cross-section of connector 6 mm2 (2 mm of width, 3 mm of height);

■ shape and size of pontic according to the emergence profile of the respective site and with an anatomical support for the veneering ceramic.

Framework and wax-up try-in

The framework was clinically checked with respect to its fit and in the same appointment a wax-up verification of the designated final shape of the central incisor was carried out.

The patient and the restorative team were very satisfied with the shape and the fit of the framework and thereafter the final veneering could be done in the dental laboratory.

Creation ZI-F (Creation Willi Geller, Meiningen, Austria) was used according to an individualized custom shade developed with the patient in the dental laboratory (Fig 2-2-6).

Biscuit bake try-in

The biscuit bake was clinically checked with respect to its fit and shape of the central incisor.

The patient and the restorative team were very satisfied with the final shade and the fit of the veneered framework; however, in the pontic area the RBFDP was slightly buccal and appeared as if it was sitting in front of the ridge and not emerging from the defined pontic. Therefore, it was discussed with the technician to create a little cementoenamel junction, basically capping the adjacent central incisor. With this, the cervical Part could be shaped less noticeably and the RBFDP, without changing its well-developed shape, appear as it would emerge from the pontic (Fig 2-2-7).

Finalization of the RBFDP in the laboratory

After the biscuit try-in of the RBFDP veneered with Creation ZI-F (Creation Willi Geller, Meiningen, Austria) the surface with its micro and macro texture was created by means of diamond burs, stones, and polishing wheels and then finally glazed without the application of vacuum in the ceramic oven.

Integration of the restorations

The RBFDP was adhesively cemented using a resin cement Panavia 21 (TC, Kuraray, Tokyo, Japan). For the cementation rubber dam was applied, and the abutment tooth was meticulously cleaned with pumice. Then, the palatal/lingual retention area of the abutment tooth was etched with a 37% phosphoric acid (1 min application). Furthermore, the corresponding primer of the resin cement ED Primer (Kuraray) was used as pretreatment as recommended by the manufacturer.

The zirconia surface was cleaned with alcohol and a silane-containing primer, Clearfil Porcelain Bond (Kuraray) was applied according to the manufacturer’s recommendations (Fig 2-2-8).

Finally, the cement was applied to the RBFDP retainer and the restoration was seated. A glycerin gel, Oxyguard (Kuraray), was used to cover the margins for the setting of the resin cement. Constant finger pressure was applied during the setting time.

Adjustments were performed where needed, after which the ceramic surfaces were meticulously polished with the Optrafine Kit (Ivoclar, Schaan, Liechtenstein) (Fig 2-2-9). (Dental practitioner: Prof Dr I Sailer; Technician: DT X Zahno.)

Final outcome after 10 years of clinical function

No technical or biological complications occurred, and the patient was still very satisfied with her RBFDP. The mesial and distal papilla, as well as the volume, could be maintained over the years. Along with a visible continuing growth of the maxillary segment the emergence profile continued to show a very natural contour (Fig 2-2-10).

2.2.2 Congenitally missing lateral incisor (RBFDP after orthodontic pretreatment)

Minimally invasive rehabilitation after orthodontic pretreatment with 8 years’ follow-up.

Assessment and treatment planning

A 15-year-old female patient was referred by the Clinic of Orthodontics after alignment of the maxillary incisors for the prosthetic replacement of missing tooth 12. Tooth 12 was congenitally missing and the space was nicely distributed by the orthodontic department and maintained by a removable provisional.

Two treatment options for replacement with a fixed restoration were discussed: a single-retainer RBFDP bonded to tooth 13 or 11, and a single implant. The RBFDP was considered the most appropriate at the time of the treatment due to the very young age of the patient. It was likely, though, that at a later stage a singlediameter reduced implant would be a good alternative.

After the orthodontic alignment, for both treatment options no restorative limitations were posed by the position and angulation of the teeth. The replacement of the missing tooth by means of either the fixed tooth- or implant-borne restoration would have been possible.

However, due to the young age of the patient and the associated potential growth, a single retained resin-bonded fixed dental prosthesis made from zirconia was planned (Fig 2-2-11).

Diagnostics and provisionalization

The patient’s chief complaint after the orthodontic alignment of her teeth was to receive a fixed dental restoration and no longer having to rely on the removable restoration.

As the removable provisional, however, looked and integrated quite nicely, it could perfectly be used as a diagnostic set-up and function at the same time as a mock-up to determine which of the two neighboring teeth would offer the best anchorage.

Usually the central incisors offer a longer approximal contact area than canines; this first allows development of a sufficient connector dimension and second, but at least as important, to then hide the connector and its minimally invasive preparation. However, in this case, the canine 13 was chosen to serve as an anchorage tooth as the central incisor on its distal contact area was quite round and triangular.

Conditioning of the pontic

Prior to the prosthetic replacement of missing tooth 12, the gingival area in the pontic region was shaped (ie, conditioned according to the desired emergence profile of the restoration). The conditioning was performed in order to shape the soft tissues into an “ovate-ponticlike” shape and, hence, to allow for a natural emergence profile of the pontics. For the conditioning, flowable composite (Tetric Flow, Ivoclar Vivadent, Schaan, Liechtenstein) was applied in a stepwise approach to the basal region of the provisional pontic, inducing pressure to the soft tissues in the edentulous area and thereby shaping of this region. This procedure was repeated twice at intervals of 8 to 10 days until the desired shape of the pontic area was achieved (Fig 2-2-12).

Preparation and optical impression

Finally, the respective abutment tooth 13 was prepared in order to allow for retention of the RBFDP and in order to simplify the positioning at cementation. The minimally invasive preparation design for anterior zirconia-based RBFDPs encompassed the preparation of a mesial and a distal vertical groove (6-degree taper) and a tiny slot at the palatal/lingual cingulum region (Universal Prep Set, Intensiv, Montagnola, Switzerland). After that, the optical impression was carried out using an iTero intraoral scanner (Align Technology, San Jose, CA, USA) (Fig 2-2-13).