In case of a serious tooth decay, the treatment often requires an inter-disciplinary approach. The dentist can be required to restore aesthetic and function of an upper tooth, where the aesthetic and the entity of the masticatory loads are often influencing the choice of procedures and materials and even the general prognosis of the tooth. In particular, the factors that had to be considered in this case were the position and size of the cavity, the requirement to complete an endodontic treatment and the size of the final restoration. Moreover, having planned a prosthetic crown, the authors also considered the requirement of endodontic post, the position of the bone crest in respect to the cavity margins, the length of the root, the status of the adjacent teeth, the overall oral hygiene and the patient’s compliance and, as important consideration, the cost/benefit ratio to explain to patient. In many cases where the rehabilitation plan of a premolar includes different and complex procedures such as endodontic treatments, posts or extensive restorations, the dentist tends to choose an implant-supported prosthetic rehabilitation, because the costs of the alternative conservative treatments could be similar to those of the implant-supported ones, but the overall prognosis of a tooth-supported prosthesis may result, in the mind of professionals and in a certain part of literature,1 lower than that of a crown over implant. In fact, the prognosis of different rehabilitations is strongly affected by many factors, mainly the dentist and his skills, but also the used materials.
However, considering the overall length in terms of months, the rehabilitative treatment of a natural tooth is usually faster and the conservative treatment represents always the best choice biologically, if allowed. In this case the right selection of the prosthetic material could be decisive.
Clinical case presentation
A 45-year-old female patient, B.S., referring intensive pain in her upper left dental arch, asked for a visit at the dental clinic of the IRCCS Istituto Ortopedico Galeazzi (Milan, Italy). During the anamnesis she told to be in good health status, without being affected by any chronic disease, and no smoking.
During the clinical oral examination, she didn’t exhibit any mucosal lesions, she presented an optimal level of oral hygiene but there were a lot of incongruous restorations and an apparently provisional restoration on tooth #25.
This element was not stimulated with the cold test and the radiographic image revealed an incomplete endodontic treatment (Figs. 1-2). The element seemed to present a suitable root length for a conservative restoration, but the apical position of the carious lesion and the proximity of the interdental bone ridge didn’t allow a correct rehabilitation with prosthetic crown, respecting the biological width.2
Considering the patient’s factors (e.g. age, level of oral hygiene, absence of smoking or other risk factors) and status of the tooth (e.g. length of the root, endodontic access, periodontal status), it was communicated to the patient that the treatment plan would include an endodontic-prosthetic restoration through conservative therapies and CAD-CAM restoration in lithium-disilicate.3-6
The patient at the first appointment immediately required a quick solution for the pain, consecutive to an incomplete endodontic treatment and a partially removed carious lesion. So, the first step consisted in the removal of the decayed tissue of the distal face of the tooth 25 in its coronal portion and in the first third of the root.
The cervical limit of the decay was exposed; then the wall was restored with a glass hybrid material (EQUIA ForteTM, GC) coated with the light-curable EQUIA Forte CoatTM to obtain a more resistant material even in case of occlusal loads.7-9 A glass hybrid material was chosen because the apical edge of the tooth cavity was under the gingival margin, so it was impossible to obtain a correct isolation for a composite restoration: it’s known that the glass hybrid materials can tolerate acid and humid environments more than composite. 7-9
The glass hybrid EQUIA Forte was preferred to glass ionomer because better long-term results are reported in literature.7-10
After that, the tooth was endodontically treated. The tooth had only one root canal, processed with a hand file READY STEEL K-FileTM (Dentsply Sirona) and for the shaping and refinement with mechanical file PROTAPER GOLDTM (Dentsply Sirona) at a working length of 20 mm.
The canal was sealed with a ThermafilTM cone (Dentsply Sirona) with an apical diameter of 0.30 mm (Figs. 3-4).
After the surgical flap elevation of the tissue and the bone remodeling, the flap was repositioned apically and sutured with a vertical mattress suture anchored in the periosteum (Figs. 5-6). The suture was removed after 7 days (Fig. 7).
After the restoration, the tooth was prepared with the BOPT technique5-6 . A provisional PMMA crown, obtained with an optical scan done before the preparation of the element with a AADVA IOS100 scanner (GC), was placed. During this phase the obsolete restorations of the teeth 24 and 26 were replaced. (Figs. 9-12)
The dental impression was sent to the laboratory, where it was optically scanned and a CAD-CAM path was set.
As a consequence of the newly surgically modified prosthetic margin, the appropriate length of the abutment for an adhesive cementation had been obtained, and the high aesthetic requirement and the contemporary need of containing costs with a monolithic crown, led the clinical choice to a lithium-disilicate crown with high translucency and suitable for the CAD-CAM technology.
The chosen material was the Initial LiSi BlockTM (GC), because the ultra-thin structure of the Initial LiSi Block’s has two important advantages: first of all, the block is easy to be milled with the use of chairside milling machine in the lab, and secondly this material doesn’t require other steps in the oven to be sintered or glazed. In fact, Initial LiSi Block is the first completely crystalized lithium-disilicate block, so the time for its crystallization could be saved and the software for the finishing and glazing would not have to compensate for any material contraction due to the temperature in the crystallizing oven.
In this way, margins remain extremely thin and clear and it’s particularly useful in this case. It’s also possible to reduce costs compared to the use of a highly aesthetic and functional material.
rinsed and then dried with compressed air. The definitive crown was etched with 9% hydrofluoric acid for 20 seconds (Fig. 19), rinsed and dried with compressed air. According to manufacturer’s instruction, it is not recommended to etch Initial LiSi Block for more than 20 seconds, in order to preserve all properties of the material. Since the acid etching with the hydrofluoric acid may result the formation of crystals of lithium salts on the inner surface of the crown,10 it’s important to put the crown in hot water for 1 minute after the acid removal, to eliminate the crystals and prevent any interference with the adhesive cementation, and then it must be carefully dried. Before the placement of the adhesive cement, a specific coupling agent was placed on the internal surface of the crown, in order to obtain a stronger adherence between the ceramic and the luting resin. For this reason, G-Multi Primer (GC) was selected and applied (Fig. 20). The luting phase was finally performed with the G-CEM LinkForceTM (GC), after the placement of the dedicated adhesive system (G-Premio Bond) on the tooth, blowing them with compressed air for 20 seconds, without curing them before the luting phase in order to allow a correct fit of the crown. Each crown surface was cured for 40 seconds (120” in total in order to correctly cure both adhesive and resin cement even through the ceramic) and the excesses of the luting material were finally removed.
At the end of the procedures, the restoration was precisely seated at equigingival level of the margins, it appeared to be morphologically integrated in the dental arch, with correct contact points and with a good chromatic match with the adjacent elements (Figs. 21-24). Upon X-ray examination, it was possible to see that the subgingival margins were also integrated, without any step or any plaque-retaining area that could be a problem for the home dental hygiene
(Fig. 25). The patient didn’t refer pain anymore and was completely satisfied with the prosthetic rehabilitation, that she found perfectly integrated at both functional and chromatic levels. She also found the colour of the prosthesis was better than her natural teeth.
CAD-CAM technology and chairside procedures, including the milling process that takes place completely inside the dental clinic, are actually a solid reality and these kind of digital machines are easily available for many years8.
The required time for the a complete crown production inside the dental clinic, from projecting, milling to finishing, may vary depending on the material: the required production time ranges normally from 1 hour (for the simplest materials) to more than 4 hours (for the materials that after milling require more tests and passages in finishing furnaces. For this reason, and due to the diffusion of CAD-CAM procedures in laboratories as well, chairside procedures are actually less appreciated by many dentists, who see them as a possible waste of time, diverting dentists from the real clinical activity
However, the reliability of modern CAD-CAM systems and new materials allow dentists and laboratories to make new choices, even in the name of a smoother workflow and cost control, when possible. A millable material that has considerable aesthetic properties is in any case
indispensable, whether a clinician decides for a full chairside procedure, or for sending the impression to the laboratory. Also the “monolithic” materials cannot actually afford to be
opaque, not very natural and not very translucent, because very few professionals and patients are inclined to accept aesthetic compromises in modern times.
Moreover, from the dentist’s point of view, polishing procedures after possible occlusal adjustments should not require much time, neither dedicated instruments and burs, which mean expenses for the clinic and less time to dedicate to dental activities.
An ideal monolithic material must have some fundamental characteristics, in order to make it an adequate choice for aesthetic and functional rehabilitations:
• High mechanical strength.
• Adequate translucency.
• Ease of processing and milling.
• Availability of different shades.
• Possibility of effective and durable luting with the most common adhesive systems or cements.
• Easy polishing phase involving few steps and burs.
• Availability for the most common chairside and laboratory milling machines (compatibility).
There is not an ideal, universal material that could be chosen for all prosthetic procedures. By the way, while selecting the material that could appear clinically ideal for a specific case, only a good mix of these characteristics can determine a clinical success of a prosthetic rehabilitation procedure with monolithic materials and, ultimately, full patient satisfaction.