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Repair of an Implant-Supported Porcelain-Fused-to-Metal Restoration in Under-Occlusion: A Case Report [Dental News (Middle East)]
[September 21, 2014]

Repair of an Implant-Supported Porcelain-Fused-to-Metal Restoration in Under-Occlusion: A Case Report [Dental News (Middle East)]


(Dental News (Middle East) Via Acquire Media NewsEdge) Dr. Norma Ziadeh [email protected] Dr. Danielle El Hakim [email protected] Abstract This paper presents an indirect intraoral repair procedure that may be used to overcome an under-occlusion defect on an implant-support- ed porcelain-fused-to-metal (PFM) fixed partial denture. In the present technique, onlay ceramic restorations were adhesively bonded to the original PFM. The reparation was quick, relatively affordable and easier than removing the bridge and making a new one. This procedure provided good aesthetic and functional results.



Introduction Fracture of porcelain is a frequent mechanical complication in implant-supported prosthesis. The reparation can present difficult challenges to the practitioner. Due to the brittle nature of the porcelain and its fabrication process requiring firing, new porcelain can hardly be added to an existing restoration intra-orally. Intra-oral repair options provide the possibility of repairing the porcelain in the patient's mouth preventing replacement of the complete restorations.

Repair alternatives are classified in two categories: the direct and the indirect techniques. In the direct technique, composite resin is applied directly to the fractured restoration with the aim to reestablish function and aesthetics. Several articles have been published describing the in- direct technique whereby the remainder of the restoration is prepared and a lab-fabricated restoration is cemented or bonded on the remain- ing substrate. This technique is more appropriate for large fractured surfaces, in posterior areas with heavy functional load, or where aesthetic result is important; however, it requires a second appointment.


No previous publications have reported the use of this approach to adjust the occlusal plane. This paper describes an indirect intraoral repair technique for an implant-supported porcelain- fused-to-metal fixed partial denture in under- occlusion. CAD/CAM onlay ceramic restorations were used to treat the defect.

Case-report A 45-year old woman came to the dental of- fice complaining of unaesthetic smile and poor chewing ability on the left side. Clinical examination revealed a disharmony of the occlusal plane, poor restorations, missing teeth and a 4 unit implant-supported PFM bridge in the lower left area in under-occlusion Radiographic examination (fig 2) showed the presence of radiolucency around one implant (the third most distal) and an unfamiliar screw element in the last implant all this with good clinical and radiographic adaptation of the prosthesis. Probing of the third implant was executed, of 5mm depth, no pus or bleeding signs were found around it. A slight redness on the gingival margins around the implants due to plaque retention caused by poor mouth hygiene.

A full-mouth rehabilitation was indicated, changing all the deteriorated restorations and crowns, placing implants in edentulous areas, to adjust the occlusal plane including 2 implants in upper maxilla facing the 4 unit implant supported PFM's. The patient was informed about his problem and treatment alternatives; After all options discussion, a deep scaling of the implant surface in question was implemented and an indirect repair was decided without removing the existing 4-element restoration. Since removal of the bridge could potentially result in deterioration of the abutments especially the most distal one where an unknown metallic screw is used to fix the abutment, which may lead to loosing the last implant as well as the implant with bone resorption and the inability to place 2 other implants in this site because of the insufficient bone height above the inferior dental nerve.

Repair technique Study casts were mounted in articulator and a full wax-up was carried out to evaluate the height or space to be corrected.

Buccal, palatal, mesial and distal preparations of 1 mm depth and 1.5 mm height were created using fine grit 25 micron burs (Komet Dental, Lemgo, Germany) to prevent cracks in the prepared ceramic. With the occlusal present defect, no occlusal reduction was needed (fig 3). A provisional restoration was made using a silicon key as mold copying the morphology of the wax-up. The temporary used between the two appointments (fig 4) helped in testing the new occlusion.

A one-step polyether impression (ImpregumTM PentaTM medium-bodied and ImpregumTM GarantTM L DuoSoftTM light-bodied consistency) (3M ESPE, Ger- many) in custom tray was taken for the fabrication of the master cast. Bite registration, shade selection was done to match the new onlays with the exist- ing bridge.

The plaster cast was scanned with the indirect in lab technique and CAD/CAM onlays were milled (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein). The onlays were tried in mouth and checked for marginal adaptation and final outcome prior to bonding.

Internal surfaces of the IPS e.max onlays were etched with 9.5% hydrofluoric acid for 20 seconds. For control of the oral cavity humidity and patient protec- tion due to the inherent risks of the hydrofluoric acid, field isolation was ob- tained with the aid of a rubber dam, a lip expander and the use of a protection eyewear. The prepared surface of the feldspathic restoration was etched for 2 minutes with the same acid (fig 5). After rinsing with water for 30s and drying the ceramics with an air stream, a one bottle silane coupling agent (Monobond S, Ivoclar Vivadent, Schaan, Liechtenstein) was applied on both surfaces, left undisturbed for 1 minute and then air dried.

Finally, the ceramic onlays were adhesively bonded to the prepared surface using the dual-curing luting composite, Variolinc N (Ivoclar Vivadent, Schaan, Liechtenstein), and the interface margin was polished (fig 6). At the end of the bonding session, occlusal contact points were verified with 12 Microns articulating paper (Arti-fol, Bausch, Koln, Germany), for any occlusal or lateral prematurity contacts, to achieve a harmonic distribution of the occlusion. After the contacts adjustments a ceramic polishing kit (Komet Dental, Düssel- dorf, Germany) was used with 3 progressive granulometries and a polishing paste (Inten- sive Unigloss Paste, Intensiv, Montagnola, Switzerland) After 6 months of treatment, the full-mouth re- habilitation was completed and the patient re- established function and esthetics. The comfort in chewing food was expressed by the patient in the one-year follow up. The prosthesis has been in the mouth for 2 years (fig 7), and no visible alterations have been observed so far.

Discussion Other treatment modalities could have been considered in this case; Total replacement of the bridge or, even more, replacement of the defect- ed implant(s). This would have made the treatment extremely expensive and time-consuming, besides leaving the patient vulnerable to a more complicated situation.

The CAD/CAM restorations allow less stress on the ceramic to ceramic interface and more ac- curacy of fit. IPS e. max CAD is a high-strength lithium-disilicate-based glass ceramic with high edge stability. With strength of 360 to 400 MPa, the material is suited to the fabrication of fully anatomical and partially reduced anterior and posterior crowns.

When repair of ceramic restorations is considered, a strong and durable bond between the crown and repairing ceramic must be achieved. A strong resin bond relies on micromechanical interlocking and chemical bonding to the si- lanized ceramic and bridge surfaces, which requires roughening (HF) and clean- ing for adequate surface activation.

Several considerations should be accounted for when choosing the material of the repair onlay restorations. Feldspathic ceramics, used as veneering porcelain in PFM restorations and lithium disilicate onlays are both glass-ceramic materi- als3 allowing etching process. Ceramic-ceramic compatibility is important for enhanced esthetic outcome and better bond. Successful material combinations should have close thermal expansion coefficients to avoid any thermal stresses that may lead to a future cracking or debonding. It is known that lithium disilicate is a brittle material but it gets its strength when bonded correctly.

Many studies were published describing how to prepare the surface of a fractured restoration for intraoral repair. For glass-ceramic surfaces, the use of silane seems to be essential, whereas an appropriate etching and a mechanical treatment depend on the kind of the ceramic.

Hydrofluoric (HF) etching can achieve a proper surface roughness, because the glassy matrix is selectively removed and crystalline structure is exposed.3-7 For instance, with the lithium disilicate, 9,5% HF acid applied for only 20 seconds is successful to provide a proper etch, while for the feldspathic ceramic,8,9 a 2-2.5 minutes is needed (9,5% HF). Intraoral use of hydrofluoric acid is controversial because of its hazardous properties.1,3,4 Therefore, clinicians should never use it without a rubber dam and eyewear protection.

Chemical bonding is achieved by application of a silane.Silane solutions are bifunctional molecules that bond silicone dioxide (SiO ) with hydroxyl groups 2 on the ceramic surface and silane is a crutial agent for a satisfying resin bond to glass ceramics; it has also a functional group that co-polymerizes with the organic matrix of the resin. Additionally, silanization increases the wettability of the bonded surface. As a general rule, for most systems, fresh chemically active silane (one to two coats) should be applied and allowed to dry for a minimum of 30 seconds to 1 minute in room temperature followed by a gentle warm-air drying (for 60 seconds). To be noted that extended time of silanized ceramic could lead to losing the bonding properties by chemical transformation of si- lane into siloxane (inactive saturated formula).

VariolinkN is a dual-curing luting composite product for adhesive luting of glass-ceramic, lithium disilicate and composite restorations. It is composite resin cement,5 with modified formula and has the advantages of high strength, high adhesion, low solubility, and aesthetic results. This allows it to be used with brittle, esthetic restoration types such as glass-ceramics and indirect composite or in cases where retention is critical.

The ultimate success and longevity of intraoral porcelain reparations is a multi- factor chain. The extent of the repair, occlusal forces applied on it, and the patient's oral habits, oral hygiene, and esthetic demands are some of the factors that might contribute to the survival of the reparation. The use of a rubber dam is essential to provide adequate isolation for the adhesive steps, and the occlusion must be carefully adjusted after the bonding. This technique was never described in the litterature.

Conclusion The replacement of a multi-unit implant sup- ported bridge with under-occlusion problem may not necessarily be the most suitable solution because of added cost, chair time required and related removal complications. Indirect intraoral reparation using ceramic onlays restorations may offer appropriate therapeutic alternative with short-term clinical success. Further clinical cases and long term follow up are needed in order to implement this technique as a long term solution for under-occlusion metal ceramic prosthesis.

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