Restoration of Discoloured Incisors with Ceramic Veneers: A Workflow Case Report

Tooth discolouration is one of the most common outcomes associated with traumatic events.¹ Colour changes can occur due to different causes, such as pulp necrosis or penetration of endodontic cement into the dentinal tubules.^2,3 In light of this, proposed treatments should consider effective approaches to masking the darkened substrate. Ideally, the proposed treatment should only include the affected elements and not involve the adjacent teeth with the aim of achieving chromatic harmony.⁴ The decision-making process should consider the patient's expectations and demands regarding the restorative material and longevity of the treatment.^5,6

Conservative treatments, such as tooth bleaching techniques, can be adequate to resolve or minimize tooth discolouration.^7,8,9 However, some cases require restorative treatments, such as direct composite resin restorations.¹⁰ The masking ability of resin composites is highly related to the technique and influenced by the thickness of the restoration and the use of opacifier agents and/or opaque resin composites.¹¹ Additionally, the substrate-masking process needs to be balanced against compromising other aesthetic properties, such as translucency.^10,12 Furthermore, the ageing of resin composites can result in long-term colour instability¹² and require interventions such as polishing or refurbishment.¹³

The aesthetics of the anterior dental region may require particular thought. The dental optical properties of translucency and opalescence owing to natural layering and the different opacities within tooth structure) should also be considered.^10,12 Dental materials may not always be able to perform these effects. Most restorative materials reproduce dental effects in two main forms either by adding pigments (reproducing these proprieties in a static configuration), or by trying to recreate the same relation between light and teeth, by producing tooth-similar optical restorative materials. Also, as space is required to apply these different layers, the preparations can be more invasive, resulting in a great loss of biological and non-recoverable tissues.^10,11,12,13

In contrast, ceramics have lower discolouration potential when compared to resin composites and might present better colour stability over time.^14,15,16 Additionally, as ceramic restorations are manufactured in the laboratory, they are less dependent on the technical ability of the dental practitioner to obtain excellent masking results. To achieve success, when performing indirect restorations, good communication between the dental practitioner and technician is essential.^17,18 Sometimes, the dental technicians can actively participate in the treatment planning, by being present at the dental office, having a close examination of the patient, and discussing technical aspects of the treatment with the dental practitioner.^19,20 Although ceramic restorations do require tooth preparation, it is possible to fabricate restorations with reduced thicknesses, thus minimizing the extent of the required preparation.²¹

This case report presents the treatment of two discoloured maxillary incisors with feldspar ceramic veneers using an integrated work approach, involving the active participation of the technician in the treatment planning.

Case report

This report followed the principles recommended by the CARE guidelines.²² CARE is a guideline that helps authors to provide a complete case description, and ensure that all the important details are mentioned while making the reading of case reports easier for the readers.

A 34-year-old male presented for aesthetic treatment. During the anamnesis, the patient reported a history of trauma in the anterior maxillary area related to a childhood bicycle accident. The clinical examination revealed a cervical discolouration in the central and lateral maxillary right incisors (UL1 and UL2). Both teeth had undergone endodontic treatment after the trauma. The left central incisor had been fractured by trauma and had been restored with resin composite. The left lateral incisor had not fractured, but was affected by a discolouration process after the endodontic treatment (Figure 1).

The patient reported previous multiple attempts at tooth bleaching using different techniques, but none could achieve the desired results. The attempts at whitening appeared to have been carried out in a clinic using hydrogen peroxide gel, in association with an at-home technique with carbamide peroxide gel. The patient did not know what concentrations of either had been used.

The patient was also unsatisfied with the resin composite restoration on the right maxillary central incisor, which did not mask the cervical discolouration. Hence, considering that the tooth had previously been prepared for the direct resin composite restoration (i.e. preparation for discolouration cases), the patient and dental practitioner agreed on an indirect restorative treatment with the placement of feldspar ceramic veneers. After preparation, the hypothesis that UL1 presented minor discolouration owing to partial masking of resin composite was confirmed. It was considered that both teeth presented with the same level of discolouration, justifying the restorative planning.

For the integrated work approach, the technician was invited to the dental office during the initial appointments. This way, the technician could better understand the patient's demands and help in the treatment planning. The association between dentist and laboratory technician, in a consistent line of communication, can provide more desirable and reliable results. The workflow philosophy is described for a better understanding of the process.

First, it is important to highlight that, although the technician was present in the clinical sessions, the patient's expectations and desires were considered. As aesthetics is a subjective topic, when this principle is not followed, there is likely to be less patient satisfaction with the final results.

After dental prophylaxis, an impression using polyvinyl siloxane (Silagum, DMG, Hamburg, Germany) was taken to obtain models. The shade of the teeth was recorded using a shade guide (VITA classical, VITA Zahnfabrik, Bad Säckingen, Germany). Using photographic analysis, it was established that the best match for colour selection would be Vita shade B1 because the patient had undergone previous bleaching procedures. One concern was that masking ceramics may not provide the necessary translucency proprieties. However, considering the shade map studies for the specific case, it was noticed that the cervical region was the most affected. It is known that this area does not present these optical effects, so feldspar ceramic was the chosen option.

A silicone guide was obtained from the model made before the tooth preparation. Since this case did not require alteration in dental form, the unprepared structure could guide important aspects of the treatment, such as dental preparation depth and temporary restoration placement. The operative field was isolated with a rubber dam and dental preparation was performed with 12-fluted tungsten carbide burs (H375R, Cosmedent, Chicago, Il, USA). The preparation consisted of removing the existing restoration on the central incisor, limited to the supragingival level, to create the necessary space for the veneer (Figure 2).

Both restored teeth presented with previous restorative material (resin composite), with the central incisor having a large restoration involving both labial and incisal surfaces, which could explain the discolouration perception in this tooth. The restorative plan was to remove 0.8 mm of the restoration labially, and 1.0 mm incisally.

The lateral incisor presented with a minor mesial restoration. Thus, planning for this tooth aimed to achieve the necessary space for an adequate adaptation to a thin laminate ceramic veneer as well as complete masking of the background. The restorative plan was to remove 0.6 mm of the tooth labially, and 0.8 mm incisally. After preparations, a new impression was performed, and the models and photographs were sent to the dental technician (Figure 3).

In this intregrative workflow approach, the dental technician manufactured the feldspar veneers in a reduced time compared to the conventional protocol, and the provisionals remained in place for less than 1 week. This process avoids the need for replacing the temporary restorations, which is a common procedure for ‘long-term’ bisacryl restorations. Additionally, reducing the length of time temporary restorations are in place also avoids inflammation of gingival tissues.

Regarding the chosen material and patient request (that once underwent a previous restorative procedure with direct resin composite), it was defined that an indirect procedure could produce better results, considering clinical time and the possibility to stay in a less-invasive field. Feldspar ceramics was elected as the best option, from a range of possibilities. Despite the clinical and technical experience of the operators, the material can provide adequate results for non-severe discolouration cases.

The feldspar ceramic veneers were placed on the substrate using a try-in paste with the same colour as the intended cement (NX3, Kerr Corp A2) to confirm its masking ability and overall colour match (Figure 4). After the patient's approval, the dental substrate was conditioned with 37% phosphoric acid (Power Etching; BM4, Palhoça, SC, Brazil), and two layers of the adhesive system (Adper Single Bond 2; 3M ESPE, St Paul, MN, USA). The ceramic veneers were etched with 10% hydrofluoric acid (Power etching 10%; BM4) for 120 seconds. A silane coupling agent (Silane Primer; Kerr Corp, Orange, CA, USA) was applied for 60 seconds and air-dried (Figure 5).

The veneers were bonded to the prepared teeth using a light-cured resin-based cement, shade A2 (NX3; Kerr Corp). After removing the excesses, a photocuring unit (Demi; Kerr Corp) was used. A layer of glycerine gel was applied before the final photoactivation. The rubber dam was removed, remaining cement was removed with a #12 blade, and the contacts were checked and adjusted (Figure 6).

A slight open margin can be identified in UL2 owing to the cementation process and veneer margin adaptation. Despite this undesirable event, the clinicians and patient agreed to carry out monitoring and intervene only if necessary. This management was considered acceptable because the patient had no biofilm retention areas or dentine hypersensitivity (Figure 7).

The patient was satisfied with the final result of the restorations, considering that the superior lip could hide the high cervical surface. In 3-month follow up no alterations were identified (Figure 8). The case continues to be monitored.

Discussion

In this case report, the treatment of two discoloured maxillary incisors with feldspar ceramic veneers was performed with an integrative workflow approach in collaboration with the dental technician. The high aesthetic demand of the patient and the decision to intervene for only the two discoloured teeth increased the complexity of the case. However, the technician's presence during the appointments favoured communication and facilitated the manufacturing of the veneers once the technician could see in person the critical areas for masking the substrate and had a better overview of the case.

Cases that require only colour changes have the advantage of allowing the patient's initial model to be used as a guide for temporary restorations, eliminating the need for diagnostic wax-up.^23,24 From an initial impression, before dental preparations, it was possible to obtain a model that presented the exact dimensions in size and volume as the original teeth. This model allowed the creation of a silicone guide, which can be used as a tray for applying bisacryl resin and as a guide for teeth preparation, thus, aiding essential steps of restorative treatment.^23,24

Tooth discolouration should preferably be treated with conservative approaches, such as tooth bleaching techniques.^3,25 The decision-making process should take into account the patient's history and demands.^26,27 In the present case, the patient had previously undergone different tooth bleaching techniques without reaching the desired outcome. However, the previous tooth bleaching may have contributed to reducing the initial discolouration within the biological limits for the patient,^7,26,27 making it possible, in this case, to reduce the preparation to the minimum necessary for masking with indirect veneers.⁷

Internal bleaching could have been a possibility for reducing discolouration and allowing less invasive preparations. However, the clinician and patient agreed that it would be best not to interfere with the well-performed endodontic treatment. Internal bleaching requires access through the palatal surface, and this procedure could remove healthy dental structure. It was considered that performing the preparation over the resin composite, on both the labial and incisal surfaces, would reduce dental wear and be the least invasive course of action.

Resin composite can be valuable for masking discolourations.¹⁰ In general, this material does not require dental preparation and has good adhesion properties. However, for certain types of discolouration, preparation may be necessary to allow an adequate thickness of the restorative material to mask it fully.^10,12,27 Since the patient already had a direct resin composite restoration on his maxillary right central incisor, and the discolouration was still noticeable, this indicated the need for an extra thickness of the restorative material. This indication and the aesthetic demand of the patient were considered for the decision of adopting ceramic veneer as the chosen approach.

Ceramic restorations can be made with different materials and in different thicknesses. While, in the past, ceramic veneers had to be had to be formed in many layers, necessitating heavy tooth preparation, it is now possible to produce thin veneers, called laminates. Laminates have been studied over the past decades with favourable results. Interventions with laminates show a high rate of survival and do not jeopardize the tooth's lifespan and/or function.²⁸ Considering the development of dental science and materials, it is possible to perform long-term ceramic restorations. Individual patient characteristics, such as age and habits, can directly influence the restoration lifetime, but in general, adequate results can be achieved, once material characteristics and biological principles are respected.²⁸

Given a conservative strategy, the decision was made to intervene only on the two discoloured teeth in the present case, increasing the challenge of masking the discoloured substrate while mimicking the characteristics of the adjacent teeth.^27,30 Our report emphasizes the possibility of achieving excellent results without involving adjacent teeth based on an integrated work approach.^19,20

Body image and self-perception represent important aspects of human beings. Although it is common sense that the perfect body, face, or teeth are not possible achievements, human beings keep looking for different approaches, to improve their physical characteristics.³¹ Slight changes and alterations can produce good benefits psychologically; however, when it becomes an obsession, a dysmorphic condition may be present. In the present case, the patient presented with a high aesthetic demand and concerns about his teeth, which could configure an important warning for dentists in anamnesis and clinical examinations. Dysmorphia is not an easy condition to identify, although it is quite common at present. Dental literature is still scarce, although it is an important field for further research.³¹

As a limitation, it is possible to address that this is one case of good results for masking discoloured teeth with feldspar ceramics in an integrated workflow, so it would be interesting for other practitioners to describe similar cases and help to enrich the literature. It is also possible to address as a limitation the slight cervical margin on UL2, considering that this weakness could lead the treatment to be less satisfactory. Overall, patient satisfaction is the strongest point for using this integrated workflow approach and it might be a good alternative for similar cases.

Conclusion

Masking discoloured teeth can be a challenge for clinicians. This case highlights the importance of communication between the patient, clinician and technician to achieve excellent results. After more conservative options have been explored, restorative options can be used to meet a patient's aesthetic demands. Feldspar ceramic veneers may be a good option for masking discoloured substrates because they can be manufactured with a small thickness, which avoids extensive dental preparations. The patient was satisfied with the final result.