|Year : 2013 | Volume
| Issue : 4 | Page : 143-147
Challenges in reconstructing an isolated anterior tooth with a metal-free crown
Max Doria Costa1, Marcelo Barbosa Ramos1, Jefferson Ricardo Pereira2, Daniel Sartorelli Marques de Castro1, Saulo Pamato3, Fabio Cesar Lorenzoni1, Luiz Fernando Pegoraro4
1 Postgraduate Student - Department of Prosthodontics, Bauru School of Dentistry (USP), University of São Paulo (USP), Brazil
2 Professor in Mastering Program of Health Sciences, University of Southern Santa Catarina (UNISUL), Brazil
3 Postgraduate Student in Mastering Program of Health Sciences, University of Southern Santa Catarina (UNISUL), Brazil
4 Professor, Department of Prosthodontics, Bauru School of Dentistry (USP), Bauru, SP, Brazil
|Date of Web Publication||4-Dec-2013|
Jefferson Ricardo Pereira
Rua Recife 200, Apto 601 Bairro Recife, CEP 88701-420, Tubarão/SC
Source of Support: None, Conflict of Interest: None
Introduction: Currently, new esthetic treatments are available to the dentist due to the advent of ceramic-ceramic prostheses. A new option has become part of daily clinical practice, with the promise of esthetic optimization through the elimination of metal in prosthetic crowns. The translucence of these new systems allows the transmission of light through the tooth structure, minimizing gingival darkness and producing a vibrant and natural appearance. Case Report: The patient, 30 years old, female, showed with a fractured tooth crown at the cervical level in the right lateral incisive. It was observed that the tooth had prior adequate endodontic treatment. A metal-free restorative system was selected. A plaster model was obtained for subsequent tooth preparative scanning and manufacture of ceramic framework. After receiving the framework, adjustments were made and the color choice of covering ceramic, following the protocol of choice for a chroma suboptimal aiming further characterization. After the ceramics application, adjustments in shape, texture, and occlusion were made. The crown was characterized by exterior paint, getting a favorable result, restoring esthetics and function. Discussion : The metal-free systems are a viable alternative to the restorative treatment when esthetics is desired, allowing a natural and harmonious smile, combined with the reliability of the restorative material.
Keywords: Crowns, dental materials, dental porcelain, esthetics
|How to cite this article:|
Costa MD, Ramos MB, Pereira JR, de Castro DM, Pamato S, Lorenzoni FC, Pegoraro LF. Challenges in reconstructing an isolated anterior tooth with a metal-free crown. Dent Hypotheses 2013;4:143-7
|How to cite this URL:|
Costa MD, Ramos MB, Pereira JR, de Castro DM, Pamato S, Lorenzoni FC, Pegoraro LF. Challenges in reconstructing an isolated anterior tooth with a metal-free crown. Dent Hypotheses [serial online] 2013 [cited 2020 Jul 13];4:143-7. Available from: http://www.dentalhypotheses.com/text.asp?2013/4/4/143/122678
| Introduction|| |
All-ceramic crowns are preferred in reconstructive dentistry since metal-ceramic esthetic problems are related with the graying discoloration around soft tissue and also with the metal margin exposition, when recession occurs.  These factors have driven the development of new ceramics material.  In addition, unlike the metal-ceramic system, all-ceramics restorations present framework without the need for masking by an opaque porcelain layer, facilitating the application of the esthetic porcelain veneer. Several characteristics are attractive in all-ceramic crowns especially esthetic and biocompatibility,  as well as the low plaque accumulation and low thermal conductibility.  Currently, the all-ceramic systems are the choice when placing full crowns in the anterior segment. 
In the beginning, the strength characteristic of these all-ceramic systems was one of the most important limitations of its use. The first attempt to solve this issue involved strengthening a feldspathic porcelain by adding aluminous oxide.  Currently, the mechanical properties are improved, especially after the development of yttrium tetragonal zirconia partially stabilized; thus, all-ceramic restorations can replace single or multiple teeth in the high-load molar region. , Recent systematic review of crowns failures showed, in the anterior region, fracture rates similar among all-ceramic systems (Procera alumina, In-Ceram alumina and Empress glass-ceramic crowns) compared with metal-ceramic crowns.  Therefore, this region does not require high strength of the ceramic and choice of what system should be employed in this segment might be based on the esthetic characteristic instead of the mechanical properties (fracture strength, elastic modulus, hardness, etc.).
However, currently there are many ceramic materials in the market  that present enough technologies to satisfy the demand of the dental profession, , but still there is no evidence that supports the use of one ceramic system in all clinical situations.  The challenge isto choose the best ceramic system for a specific clinical situation. There are several major factors involved during the selection of an all-ceramic system, such as the inherent translucency of the ceramic material and adjacent tooth, the color of the prepared tooth, and the forces that will be in the region. For the anterior segment, the correct choice of the ceramic material should be based on the subjacent tooth color. When there is a subjacent dark color, the glass-ceramic should not be employed  because it needs up to 2 mm of porcelain to black out this darkness. , So, in these specific clinical situations alumina- or zirconia-based material could be used since they are less translucence than glass-ceramic.  ProceraAllCeram system was developed by Anderssonand Odιn, and it embraces the concept of computer-assisted design-computer-assisted machining (CAD/CAM) to produce dental restoration, , resulting in crowns composted of densely sintered high-purity aluminum oxide (Al 2 O 3 > 99.9%).  ProceraAllCeram system has shown high mechanical properties when compared with other ceramic materials,  presenting flexural resistance of 600MPa,  as well as high fracture resistance and rupture modulus. , Several restorative possibilities were development  including the CAD/CAM system. , However, for these levels of precision to be achieved, some care must be taken during clinical procedures. ,, To achieve esthetic success, extrinsic dye on veneer porcelain can reproducethe characterization of the color crown,  but the success of its use depends on factors such as optical properties, thickness, and the correct choice of ceramic materials.  So, the aim of this workis to relate clinical steps, the CAD/CAM system, and the challenges in reconstructing an isolated anterior tooth with a metal-free crown.
| Case Report|| |
A 30-year-old woman was referred to the Postgraduate Oral Rehabilitation Clinic at Bauru Dental School, São Paulo University, to restore the esthetic of the anterior segment. The main complaint was related to the coronal structure fracture on the maxillary right lateral incisor [Figure 1]. After clinical and radiographic examinations, the root was not fractured, was disregarded, and the endodontic treatment was judged as satisfactory [Figure 2]. The patient's medical history was unremarkable. The treatment plan was discussed with patient and consisted of maintain the root and constructing an all-ceramic crown.
The clinical procedure began with preparing the remaining coronal structure with a diamond rotary cutting instrument (#3216; KG Sorensen, Barueri, São Paulo, Brazil) in a high-speed handpiece with water spray (Super Torque 625 Autofix; Kavo do Brazil Ind, Com, Ltd, Joinville, SC, Brazil). Considering that the amount of remaining coronal tooth structure was lower than 2.0 mm, a cast posts in a Ni-Cr alloy (Durabond, Sao Paulo, Brazil) was chosen to restore the endodontic-treated tooth instead of a fiber post.  After that, 12 mm of gutta-percha was removed with diameter bur compatible with canal roots (Fibrekor drill, Pentron Clinical Technologies, LLC., Wallingford, CT, USA). An acrylic resin post replica was made directly on the tooth using an acrylic resin Duralay (Reliance Dental Mfg Co. Worth Il. USA), took into account the amount of space required for getting the minimal thickness necessary to make an all-ceramic crown (2.0 mm incisal reduction and 1.5 mm axial reduction). After that, the acrylic resin post replica was casted, adjusted, and cemented with a resin-cement RelyX U100 (3M ESPE, St. Paul, MN, USA) [Figure 3]. After the postcementation procedures, the tooth was prepared with a 1.2 mm circumferential chamfer shoulder and its margin was placed 0.5 mm inside of the gingival sulcus.
A provisional crown was made through direct technique with the resin acrylic Dencor (Clαssico, São Paulo, Brazil), which contributed to both the conditioning and the stability of soft tissues and to ease impression procedures [Figure 4]. The glass-ceramic system was not selected, because it advocated to be more translucent than alumina and zirconia; so the ProceraAllCeram (Nobel Biocare'sProcera® System, Göteborg, Sweden) was chosen.
|Figure 4: Provisional crown and soft tissue adaptation after 7 days|
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After 15 days, an evaluation of the soft tissue health was performed and an impression was made using vinyl polysiloxane material (Express - 3M ESPE, St. Paul, MN, USA) and poured with stone (Durone Dentsplay Ind. Com. Ltd-Petropolis - Brazil). Next, the stone dye was ditched below the finish line to define the extension of the preparation. Prior to scanning, it was vertically oriented in the scanner's die holder and then a sapphire ball forms probed the surfaces of the die. When scanning was finished, data were analyzed and sent via modem to Stockholm, Sweden, where the coping was manufactured. The core was made thicker due to the need to black out the dark color from the metal post and to allow better esthetic outcomes [Figure 5]. During the selection of the color, some important features were found, including the presence of a spot more chromatized at cervical region, a highly fluorescence at central region, and a slight translucence across the incisal edge extending about 1 mm at proximal faces. A map showing the color choice was sent to dental laboratory to guide the application of esthetic porcelain veneer. After that, the shade Vita Lumin Vacuum (VitaZahnfabrik - Bad SäckingenGmbH) was used to choose the color. The predominant shade was A3, but a shade below (A2) was selected to allow the subsequent application of the extrinsic dyes. The ceramic coverage application was proved and adjusted, based on form and texture of adjacent teeth. We observed the need to intensify thechroma at the cervical region and for this an ochre pigment was used to ensure the color accuracy with adjacent teeth. After the glaze, the crown was cemented with resin-modified glass ionomer cement (RelyX Luting 2-3M ESPE, St. Paul, MN, USA). The final outcome reflected the care taken, especially during the selection of the ceramic system and also due to color selection and extrinsic dye [Figure 6] and [Figure 7].
|Figure 5: ProceraAllCeram coping. Prior to application of the esthetic porcelain veneer, the core was checked on the marginal settlement|
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|Figure 6: Final restoration with successful aesthetic results 1 month after final cementation. View after color crown characterization|
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|Figure 7: Postoperative facial contour demonstrating adequate reconstruction of the tooth with acceptable support to the face soft tissues|
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| Discussion|| |
The development of ceramic materials allows several restorative possibilities;  however, mimicking intrinsic and extrinsic features of the color, form, superficial texture, and other elements of the natural dentition is still a challenge. In this context, ceramic materials selection is complex and it will directly influence the final outcome of the prosthetic treatment. Although the best esthetic results may be found with glass-ceramic materials,  this choice is based on the presence of a dark color from the metal post, and in this case, the selection of a glass-ceramic system could result an unexpected esthetic result.  The ProceraAllCeram system was chosen because it presents the same failure rate in both all-ceramic system (In-Ceram alumina and glass-ceramic Empress) and metal-ceramic.  Another reason for the selection of ProceraAllCeram was the CAD/CAM manufacturing process instead of the hand process, which is employed in In-Ceram Alumina slip cast. The CAD/CAM system was developed in order to eliminate the potential origin of mistakes that are observed in conventional craftsmanship techniques.  Furthermore, Procera core can be more easily produced in a laboratory process than In-Ceram crown. 
One of the most important steps of all prosthetic treatment is the correct color choice, as well as the way that this choice is sent to the dental laboratory. In this report, a map was used to inform and guide the dental technician about how to apply the porcelain veneer. Moreover, teeth are not flat and monochromatic structures; in fact, they present forms and textures that reflect light, individual optical effects possible which must be added to the final prosthetic treatment. Advantages of the extrinsic dye on veneer porcelain include details in the reproduction and characterization of the color crown  to ensure the matching color with natural dentition. Thus, the color restoration depends on factors such as optical properties, thickness, and the correct choice of ceramic materials. ,
The adaptation and polishing of the provisional crown are fundamental to periodontal health and it helps to future steps such as during the impression. The Procera (Nobel Biocare's Procera® System, Göteborg, Sweden) allows a marginal fit between 50 and 70 μm  and this was reported as clinically acceptable.  However, for these levels of precision to be achieved, some care must be taken during clinical procedures such as the utilization of a vinyl polysiloxane material to ensure the better reproduction of details of the prepared tooth. 
This case report showed some advantages and esthetics benefits of ProceraAllCeram system. The esthetic benefits were mainly attributed to reproduction of the form and texture surface and through a careful color selection and extrinsic dye. The crown was also physiologically advantageous, because it allows good hygiene due to the optimal characteristics of biocompatibility  and low plaque accumulation,  observed in all-ceramic systems.
The use of single crowns in the anterior segment is still a challenge due to inherent difficulties to ensure the matching color, form, and texture with the adjacent teeth. The use of metal-free system in the restoration of single crowns in the anterior region is indicated, because it can provide strength and reliability combined with high esthetic features.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]