Occlusal and Esthetic Enhancement: A Noninvasive Approach to an Old Dilemma Open Access

Diastema closure is a common clinical procedure that may be used to address inadequate tooth size, occlusal misalignments and undesirable esthetic features.^1–3  The most common treatment modality is tooth preparation and porcelain veneer placement or direct composite resin restoration.^4–6  For porcelain veneer preparations, there is usually a need for the removal of sound tooth structure, while direct composite resin restorations are “no prep” in most clinical situations. Still, sometimes “no prep” may not always be the best choice because esthetics may eventually be compromised due to a color mismatch when substrate masking is required.⁷  Thus, the treatment plan has to consider the tooth shape and size, determine the need for substrate masking, and indicate the most conservative treatment that properly matches function and esthetics.

In this case, the lengthening of the central incisors and a diastema closure were requested by the patient. They were also necessary for protrusive guide adjustment, because of the presence of posterior premature contacts that were impairing the patient’s occlusion. Beyond that, in this clinical case, the diastema closure was done to prevent tooth movement after orthodontic treatment. The treatment plan for the patient consisted of two indirect composite resin veneers without any kind of tooth preparation. This was possible because there were adequate substrate color and space to perform the restoration. The present technique report describes an indirect composite restoration with a noninvasive approach using simple materials to establish occlusal improvement and esthetic appearance.

The initial clinical situation was assessed and the amount of tooth structure to be restored was determined (Figure 1). A protrusive guide was assessed for planning the wax-up (Figure 2). One maxillary cast (Type IV Dental Die Stone GC FujiRock EP Golden Brown, GC America Inc, Alsip, IL, USA) was used in a semiadjustable articulator for the wax-up and to obtain a silicone matrix guide (Honigum Heavy Body, DMG America, Ridgefield Park, NJ, USA; Figure 3A).

On a second cast (working cast), a 0.2-mm thick light wax layer relief was applied to the central incisors (Cera Kota, Kota Ind e Com Ltda, Cotia, SP, Brazil) to facilitate the removal of the restoration after its manufacture and prevent it from adhering to the model, as shown in Figure 3B. It is important to note that no dental preparation was performed, and what appears to be a gingival finish line in the maxillary right central incisor was, in fact, a variation of the normality of the enamel dental anatomy, coinciding with the anatomical neck of the tooth. First, the composite resin was applied to the restoration on the palatal area (Z350 XT WB White Body, 3M ESPE, St Paul, MN, USA; Figure 3C). Then, the same resin (A1) was added for dentin replacement followed by B1 resin for incisal buildup.

Characterization for a more natural aspect of restorations was achieved using the Resin Color Modifier and Opaquing Kit (Kerr Corporation, Orange, CA, USA), Kolor + Plus–White (Figure 4A) and Kolor + Plus–Ochre (Figure 4B) pigments. The last two layers were made with B0 resin (Renamel Microhybrid, Cosmedent, Chicago, IL, USA; Figure 5A). Abrasive ceramic rubbers were used for finishing (Gray Edenta, Labordental Ltda, São Paulo, SP, Brazil), and the texture was achieved with diamond burs (HF257SPE-023 and HF364CE-023, Cosmedent; Figure 5B,C).

The two veneers were removed from the cast using abundant boiling water, which melted the wax layer relief and released the veneers easily, and then their marginal adaptation was assessed in the patient. A try-in (NX3 Light Cure, Kerr Corporation) was used to test and choose the cement color. The veneers were placed in a silicone matrix to protect the buccal face during the surface treatment before the cementation procedure. This preparation consisted of air abrading the inside of the veneers with aluminum oxide (20 μm), rinsing with water, etching with phosphoric acid (power etching 37%; BM4, Maringá, PR, Brazil; Figure 6A), rinsing with water (Figure 6B), and air drying. Silane (Silane Primer, Kerr Corporation) was applied, the excess was dried off (Figure 6C), and an adhesive layer was then applied (Adper Scotch Bond Multi-Purpose, 3M ESPE).

In the tooth substrate, a total etching technique was carried out using phosphoric acid for 30 seconds. The acid was subsequently removed with water and air dried, and the adhesive system was then applied (Adper Scotch Bond Multi-Purpose, 3M ESPE). The surface was gently air dried for removal of the solvent.

For the veneer adhesive procedures, a thin layer of a resin-based cement (NX3 Light Cure [clear], Kerr Corporation) was applied to the inside of each veneer before seating on the tooth (Figure 6D). The emergence profile was checked after cementation (Figure 6E).

An evaluation of the diastema closure, occlusion (Accufilm, Parkell Inc, Edgewood, NY, USA), and the increase of the central incisors’ length (Figure 7) was performed as well as the assessment of the correct anterior guidance (protrusion), where space was created to adjust the previous posterior premature contacts (Figure 8). The restoration provided natural tooth color, texture, anatomic shape, and proportion of the central incisors.

The 2.5-year follow-up of the treatment was satisfactory, with adequate polishing of the restoration, contours, and color and without cracks or fractures. The patient’s periodontal health is shown in Figure 9.

The main potential problems of this technique may be related to the limitations of composite resin, such as short-term color mismatch, loss of brightness and polishing, or a restoration fracture.⁸  Another issue that should be considered is the need for an additional lab step and also a dental lab technician if the dentist does not have the skills to perform an indirect restoration.

The advantage of this technique is the possibility of using a low-cost combination of simple materials and techniques that may be manufactured by the dentist without the need for a dental laboratory. Indirect techniques allow for a preoperative design with a wax-up or digital wax-up and better management of the occlusion. As in this case, in which optimal form and esthetics are required, indirect techniques have advantages,⁹  such as allowing for the reproduction of the natural appearance of the teeth with less chair time and enabling intraoral repair using the same material and also the enhancement of resin mechanical and chemical properties (eg, additional polymerization with an optimized degree of conversion).^9,10 

The optimal performance of the restorations depends on the proper polymerization of the resin components, featured by transforming monomers into polymers, and volumetric reduction of the material, which is known as polymerization shrinkage. ^11,12  With the indirect restorative procedure, the polymerization shrinkage stress at the adhesive interface will be restricted to the resin cement and not the entire restoration, contributing to a reduction in stress.¹³  However, there is a need for caution with the wax relief, as a thicker relief may result in a thicker layer of cement.

Although there is no reliable evidence to show a better approach of direct or indirect veneer restoration regarding the longevity of the restoration,¹⁴  studies show that anterior composite restorations have adequate clinical performance.^15,16  A minimally invasive approach to the final restoration is generally preferred, and the removal of a sound tooth structure should be avoided when possible.⁹  No tooth preparation was performed on the tooth substrate to achieve the outcome. The minimally invasive approach is still controversial in the literature because of periodontal problems, due to overcontouring, possible pigmentation of the margins, and because long-term results are not available. ¹⁷  However, some studies have shown that this approach is successful^1,18,19  and has clinical advantages such as enamel preservation, absence of postoperative sensitivity, no need for provisional restoration, and, mainly, the possibility of treatment reversal. An underlying feature of this rehabilitation was the achievement of adequate protrusive guidance, which previously produced posterior premature contacts and impaired the occlusion. This feature can easily be adjusted by waxing up in a semiadjustable articulator.^20,21  The 2.5-year follow-up showed that this technique performed satisfactorily, restoring function and esthetics properly. However, as with any other resin restoration, failures may occur and the patient needs to be regularly monitored for treatment maintenance.

The authors thank Francisco Mello and Osmar Gradnar for technical assistance. This study was conducted in a graduate program supported by CAPES, Brazil.