Case Reports in Dentistry

Hindawi Publishing Corporation

Case Reports in Dentistry

Volume 2014, Article ID 629786, 7 pages

http://dx.doi.org/10.1155/2014/629786

Case Report

Inlay-Retained Fixed Dental Prosthesis: A Clinical Option Using

Monolithic Zirconia

Davide Augusti,1 Gabriele Augusti,1 Andrea Borgonovo,2 Massimo Amato,3 and Dino Re1

1 Department of Oral Rehabilitation, Istituto Stomatologico Italiano, University of Milan, Milan, Italy

2 Department of Oral Surgery, Dental Clinic, Ospedale maggiore Policlinico, Fondazione IRCCS Ca’ Granda, Milan, Italy 3 Department of Medicine and Surgery, University of Salerno, Salerno, Italy

Correspondence should be addressed to Gabriele Augusti; g.augusti@libero.it

Received 21 February 2014; Accepted 5 May 2014; Published 21 May 2014

Academic Editor: Mine Dundar¨

Copyright © 2014 Davide Augusti et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Different indirect restorations to replace a single missing tooth in the posterior region are available in dentistry: traditional full-coverage fixed dental prostheses (FDPs), implant-supported crowns (ISC), and inlay-retained FDPs (IRFDP). Resin bonded FDPs represent a minimally invasive procedure; preexisting fillings can minimize tooth structure removal and give retention to the IRFDP, transforming it into an ultraconservative option. New high strength zirconia ceramics, with their stiffness and high mechanical properties, could be considered a right choice for an IRFDP rehabilitation. The case report presented describes an IRFDP treatment using a CAD/CAM monolithic zirconia IRFDP; clinical and laboratory steps are illustrated, according to the most recent scientific protocols. Adhesive procedures are focused on the Y-TZP and tooth substrate conditioning methods. Nice esthetic and functional integration of indirect restoration at two-year follow-up confirmed the success of this conservative approach.

1. Introduction

The availability of new treatments or technologies in dentistry has two consequences: on one side it expands the range of therapies given to patients and on the other hand it stimulates the development of decision-making algorithms for specific medical conditions [1, 2].

Different indirect restorations to replace a single missing tooth in the posterior region are available in dentistry: tradi-tional full-coverage fixed dental prostheses (FDPs), implant-supported crowns (ISC), and inlay-retained FDPs (IRFDP) [3–5]. The last one is considered a less time and expensive solution compared to the others. Resin bonded FDPs rep-resent a minimally invasive procedure; preexisting fillings can minimize tooth structure removal and give retention to the IRFDP, transforming it into an ultraconservative option [6]. In fact, it has been demonstrated that a high amount of coronal dentin is lost during the prosthetic preparations of abutments for conventional full-coverage FDPs with an overall calculated tooth substance removal of 63% to 73% [7].

Historically, cast resin bonded FDPs were produced exclusively using noble metals like high-gold alloys; nowa-days a wide range of new materials are available: hybrid microfilled or fiber-reinforced composites (FRC), ceramics with a high content of glass particles (i.e., lithium disili-cate, glass-infiltrated zirconia. or alumina), or high strength ceramics (densely sintered zirconia/alumina polycrystal) to be used as frameworks for subsequent veneering or to fabri-cate monolithic restorations [8, 9]. All-ceramic restorations offer an excellent optical behavior promoting biomimetic integration and their surfaces showed minimal plaque accu-mulation when exposed intraorally [10].

During clinical function, dental restorations are subjected to biting and chewing forces; stress applied during mastica-tion may range between 441 and 981 N in the molar region. According to DIN standards and to some authors, FDPs should withstand occlusal forces of more than 1000 N in a static fracture resistance test [11].

New high strength ceramics, with their stiffness and high mechanical properties (i.e., resistance to fracture and/or

2 Case Reports in Dentistry

(a) (b)

Figure 1: (a) Intraoral occlusal view of edentulous area before treatment. (b) Intraoral lateral view of tooth gap; the interabutment distance measured was 11 mm.

Figure 2: Standardized inlay preparations; previous composite fillings were removed.

fatigue), could be considered a right choice in an IRFDP rehabilitation [12].

New zirconia color infiltration techniques can improve the color matching when monolithic restorations were planned [13].

Zirconia still presents a challenge when used with adhe-sive techniques due to their single-phase tetragonal crys-talline structure that is not etchable by commonly used agents such as hydrofluoric acid. Debonding of the adhesive interface and delimitation and microcracks of the ceramic veneering material were the most long term failures observed and reported [14–16].

A correct FDP and tooth cavity surfaces conditioning before adhesive cementation procedures is necessary to avoid mechanical and biological complications [17, 18].

2. Diagnosis and Treatment Planning

A 52-year-old patient referred to the Department of Oral Rehabilitation (Istituto Stomatologico Italiano, University of Milan) with a need for a 3-unit FDP.

The patient rejected any implant therapy planned with a previous reconstructive surgery procedure (major sinus lift).

Good oral hygiene, low susceptibility to caries, coronal height over 5 mm, parallel abutments previously restored with composite fillings, and a mesiodistal edentulous gap of 11 mm were suggested for an IRFDP rehabilitation, with a minimally invasive approach compared to conventional retained full-coverage FDP (Figures 1(a) and 1(b)).

The bone level of the vital abutment teeth was radi-ologically investigated; no signs of active bone resorption or any periodontal and periapical pathology was revealed. The maximum mobility of grade 1 for the element 1.7 was

considered acceptable; no marginal leakage, discoloration, or secondary caries of the previous composite restorations were clinically detected.

Informed consent was obtained from the patient and the inlay-retained full zirconia FDP treatment planning was approved.

3. Preparation and Impression

The inlay preparations were designed with rounded proxi-mal boxes and internal edges, smooth round corners, and rectangular-based preparation floors with 2.5 mm occlusal reduction, without bevels at occlusal or gingival margins. T he isthmus width of the preparation was 2 mm for premolar and 3 mm for molar abutments. The minimum axial reduction (shoulder with rounded internal angle) was set at 1.5 mm and the convergence preparation angle was added up to approximately 6 degrees (Figure 2).

The minimum dimensions of the connector were 3 × 3mm, to enhance optimum mechanical stress distribution.

Prepared dentin was sealed with an adhesive system (Scotch Bond Universal, 3M ESPE) to prevent contamination by bacteria and components coming from the impression and provisional cementation materials.

The impression was made using a VPS material with a one-step technique (Elite HD + putty soft, Elite HD + regular body, and Elite HD + light body, Zhermack SpA, Badia Polesine, Italy) (Figures 3(a) and 3(b)). Alginate impression of the lower arch and occlusal registration were finally performed. Inlay cavities were then filled with temporary restorations.

4. Try-In Fabrication

Impressions were poured with Type IV gypsum (GC-Fuji Rock EP) and stone casts were mounted in an articulator. An IRFDP resin mock-up was fabricated for the clinical try-in; two different indirect laboratory light cured composite resins were used for the inlays (Sinfony, 3M ESPE) and the intermediate crown (Rigid Transparent-Blue Resin, Zirkon-zahn GmbH) fabrication. Complete indirect resin photo polymerization was obtained using a laboratory curing unit (3M ESPE Alfa Light Unit) (Figures 4(a) and 4(b)).

The fit of the structure in the oral cavity was controlled using a low-viscosity silicone material (Fit-Checker, GC,

Case Reports in Dentistry 3

(a) (b)

Figure 3: (a) Occlusal view of the final elastomeric impression. (b) Close-up of silicon impression; light body material reproduced every preparation fine details.

(a) (b)

Figure 4: (a) Type IV gypsum master cast with the composite resin

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