A guided, conservative approach for the management of localized mandibular anterior tooth wear

Methods of direct composite resin application

A variety of techniques have been described in the contemporary literature, as a means for applying resin composite for the direct restoration of anterior tooth wear.^5,6 These can be broadly divided into those advocating a ‘free-hand approach’, the use of a guiding ‘silicone key’ or the use of a ‘custom, thermoplastic template’. The latter two are reliant on the taking of study casts, mounted on a semi-adjustable articulator, followed by the fabrication of a diagnostic wax-up based on a carefully prescribed occlusal scheme and aesthetic prescription.

The use of a free-hand technique offers a cost-effective approach. However, it is highly reliant on the operator having a good knowledge of the concepts of functional occlusion, aesthetics and skill with resin placement. A failure to appreciate the dynamic occlusal scheme may culminate in premature restorative failure or possible consequences elsewhere in the dentition.⁷

The use of a silicone key derived from the wax-up provides the operator with a template to duplicate the occlusal form established extra-orally. Resin layering becomes a controlled process permitting the anatomical development of the desired morphology and colour by using a variety of shades which may be light cured in suitable increments. The silicone key also offers an important default, should there be a need to revise restorations in the future. The use of a translucent polyvinyl siloxane material (such as Memosil 2, Heraeus Kulzer, Hanau, Germany) also offers the potential to cure transversely through the matrix. However, difficulties with matrix placement, unwanted flexion of the matrix and the management of the inter-proximal areas may be factors to consider. In the lower arch, additional difficulties may be encountered with the use of a silicone key, such as the inability to attain adequate moisture control in the presence of a bulky, lingually placed key, interference with the tongue, access in particular where teeth may be retroclined or where there may be copious loss of dental hard tissues.

Figures 1 and 2 depict an example where a transparent silicone key has been used to restore worn lower anterior teeth using resin composite.

Use of an unmodified thermoplastic matrix has been described which involves the insertion of resin composite into the matrix, and then seating this following the preparation of the enamel and dentine for bonding and light curing in situ. The management of unwanted material excess (particularly in the inter-proximal areas), the inability to apply the material incrementally, the high polymerization exotherm and contraction, coupled with the tendency towards air entrapment within the material with potential subsequent voids, are clear disadvantages with this technique.⁵

However, the use of a ‘modified template’ to permit the ‘injection moulding of pre-warmed resin composite’ offers considerable advantages, and overcomes many of the concerns associated with the use of an unmodified template.

This technique has been described below as part of a case report.

Case presentation

A 46-year-old male patient complained of thermal sensitivity from his lower anterior teeth upon consumption of cold food and beverages and a lack of ability to chew his food properly, which had been noticed over the past year. The patient's medical history was unremarkable. However, his past dental history revealed the undertaking of numerous occlusal adjustments to the antagonistic dentition following the cementation of multiple unit maxillary anterior teeth restorations of an indirect, ceramic variety placed 15 years previously.

A careful extra-oral examination revealed that both the masseter and temporalis muscles displayed signs of muscular hypertrophy and tenderness on palpation. However, a normal range of mandibular motion was observed with the absence of any clicking, displacement or deviation of the mandible during opening and closing movements of the temporomandibular joint(s).

Intra-orally, the patient displayed the presence of a heavily restored dentition, with signs of localized moderate pathological tooth wear of the lower anterior teeth with the presence of exposed dentine on the incisal edges (Figures 3–5). A detailed occlusal assessment was undertaken and revealed a slide from CR to ICP with a larger horizontal component and wear of the canine teeth resulting in the loss of canine guidance, with subsequent balancing side interferences on the second molars on both sides.

The patient also presented with a low lip line and was satisfied with the appearance of his maxillary teeth. The gingival deficiency around an implant-retained crown at UR2 was not visible. The discoloration and morphology of the incisal edges of lower anterior teeth that were visible during speech were, however, a concern for this patient.

A preventive programme was initiated comprising simple scaling, polishing, diet assessment, and oral hygiene instruction.

Following an evaluation period of 6 months, to ensure stability and compliance with the preventive regimen, a direct composite mock-up was first carried out to predetermine the aesthetic and functional outcome. This involved drying the lower affected teeth (canine to canine) and an appropriate shade of resin composite was placed onto the worn surfaces without any prior preparation for adhesive bonding. An alginate impression (Palgat™ Plus, 3M ESPE, MN, USA) of this mock-up guides the dental technician whilst fabricating the wax-up to the aesthetic and functional prescription.

Composite was then removed and accurate pre-operative upper and lower impressions were taken in Express™ PVS (polyvinylsiloxane) (3M ESPE, MN, USA) using metal rim-lock trays. A facebow record and a centric relation record was taken using an anterior deprogrammer with the aid of Dawson's bimanual manipulation technique, along with a comprehensive selection of clinical photographs.

Impressions were cast in Fujirock EP (GC Corp, Tokyo, Japan). The casts were mounted on a semi-adjustable articulator Artex CP (Amman Girrbach, Pforzheim, Germany), using the CR and facebow records.

An analysis of the mounted casts in centric relation (CR) revealed the presence of a sizeable discrepancy with a dominant horizontal component between RCP (retruded contact position) and ICP (intercuspation position). In the RCP, only bilateral posterior tooth contacts were observed, thus leaving an inter-occlusal space of 1.5–2.0 mm, which may be used to restore the lower anterior teeth using direct resin composite in a predictable manner, without the concomitant need for any further tooth reduction or, indeed, an increase in the occlusal vertical dimension, thereby leaving the patient with fewer changes to which to adapt (Figure 6).

The lower six anterior teeth were waxed-up considering all elements of functional smile design and the impression from the mock-up to provide even centric contact in CR (Figure 7), with immediate disclusion of all the posterior teeth in eccentric movements.²¹Figure 8 provides a view of the waxed-up lower cast in relation to the upper cast, mounted in CR.

Using a stone duplicate model of the diagnostic wax-up, a 0.5 mm PVC thermoplastic template was formed by the vacuum processing of a template sheet (Acorn Plastics Ltd, Burford, Oxon) over the lower cast, including all but the distal-most teeth. The template was extended 3mm beyond the gingival margin to ensure rigidity post customization and finished with a flat marginal outline.

The template was then tried in to ascertain the desired fit, and an intra-oral mock-up performed in order to gain patient consent. The teeth to receive restorative care were lightly coated with petroleum jelly, and a suitable quantity of bis-acryl resin Luxatemp Automix Plus (DMG, Hamburg, Germany) placed into the template, which was then carefully seated in situ. Upon setting, the template was carefully removed and flash excess trimmed away. This enabled the patient to visualize the finished result.

A preheated blade # 15 (Swann-Morton, Sheffield, UK) was used to section the template interdentally in the area of the lower anterior teeth, and loading holes were created on the buccal surfaces of those teeth using a large football bur OS1 023 (Brasseler, GA, USA) (Figures 9–12). Slits were extended 3–4 mm beyond the desired inter-proximal contact area, and the loading holes positioned approximately midway between the existing occlusal surface and the desired incisal edge position. Loading holes were also carefully assessed pre-operatively to ensure that the tip of the desired resin compule was able to fit passively. A second template was prepared in an analogous manner, to serve in a contingency purpose.

The fit of the stent was verified intra-orally, making sure that the desired metal matrices Flutrec (Pulpodent, MA, USA) could be positioned inter-proximally (as shown below) placed in a relatively passive manner. Please note, the placement of the slits extending a few millimetres beyond the contact area (as discussed above) should allow the metal matrix to extend into this area. In some cases, however, in order to attain this, a small amount of inter-proximal reduction may be required, which can be achieved using a suitable diamond-polishing strip. However, this process was not required in this case.

The lower anterior teeth were subsequently cleaned using an air abrasion device (50 μm) (Microetcher llA, Danville, CA, USA) so as to remove stains and increase the bonding strength without sacrificing any tooth structures.²²

Isolation was achieved using cotton wool rolls and copious suction. Teeth were total etched with 32% orthophosphoric acid Uni-etch (Bisco Inc, IL, USA) for 15 sec. The etchant was rinsed and teeth dried (avoiding over desiccation); caution was also taken not to dehydrate the exposed dentine. Opti Bond Solo (Kerr Corp, CA, USA) was applied to both the enamel and dentine using a micro brush, dried with an air gun to permit solvent evaporation and cured for 30 seconds on each surface per tooth. G-aenial composite (GC Corp, Tokyo, Japan) was chosen for this case. Enamel composite from the selected Patient's shade (AE) was pre-heated to 39°C using a composite heater ENA Heat (Micerium Spa, GE, Italy) to improve the physical and handling characteristics of the composite.²³ However, some clinicians may choose to negate the use of a resin warmer, where there may be a preference for a resin composite material that is less viscous and more readily sculptable.

The template was placed in the patient's mouth. Thin metal matrixes were inserted interdentally between template sectioning. The preheated composite was then injected through the labial holes on the template (Figures 13, 14). During this process, digital pressure was applied to the lingual aspect of the template to avoid undesired overflow. Resin was also inserted in a careful manner, using a back-flow technique so as to avoid air entrapment. Once it was evident that an adequate quantity of resin had been inserted, the template was gently squeezed to ensure material adaptation using a flat plastic instrument. Excess resin in the sprue region was wiped away using the flat plastic instrument prior to light curing, which could otherwise render the removal of the template challenging (Figure 15).

In this case, there was only a need to replace the lost enamel tissues. However, in cases of more severe wear, it is possible to restore lost dentine using a layered approach. The latter involves the placement of ‘dentine cones’, using an appropriate shade of dentine placed in a manner to replace lost dentine. This is carried out prior to the injection moulding process. The above technique may then be used to replace the lost enamel tissue.

The restorations were then light cured with Demi™ Ultra LED (Kerr Corp, CA, USA). After curing of the composite material for 60 seconds per surface, the matrices were removed and template lifted off (Figure 16).

A 20 minute interval was then applied prior to the commencement of the finishing and polishing protocol (Figure 17), so as to permit time for undisturbed delayed polymerization, commonly referred to as dark polymerization.²⁴

Finishing was initially performed using a fine diamond bur followed by fine carbide burs (Brasseler, GA, USA) so as to remove gross excess. Final polishing was carried out using Mini Flex disks. At this stage the occlusal scheme was evaluated. Final lustre was then achieved with Astrobrush (Ivoclar Vivadent AG, Schaan, Lichtenstein). The goal was to attain an effective anterior guidance that would provide immediate disclusion of all the posterior teeth in eccentric movement (Figure 18), and at the same time avoid interference with the envelope of function. Achieving a balanced mutually protected occlusion is desirable. Figure 19 provides a final post-operative view.

Conclusions

The restoration of worn lower anterior teeth can pose the clinician with some difficult challenges. This technique, using direct resin composite and a modified template, simplifies finishing by allowing the information gathered using a diagnostic wax-up to be translated into the clinical scenario. It also permits the use of interdental matrices.