Tooth discoloration: regaining aesthetic harmony
Michelle is a natural beauty with flowing red hair and a gorgeous face. As a child she was given medication containing tetracycline, resulting in severe discolouration of her adult teeth. When I first met her, through one of my clients, her maxillary teeth had previously been crowned in an attempt to mask the discolouration, but the restorations had subsequently failed and gingival recession had occurred.
The mandibular teeth remained untouched, thus no attempt had been made to mask the staining or correct the occlusal discrepancies apparent on both sides of the arch (Fig. 1a – f). Michelle was looking for oral health, good function and an aesthetic smile with harmony between her face and both the soft and hard oral tissues.
Alginate impressions, a facebow and jaw registration were taken. The impressions were poured twice and the resulting casts mounted on a semi-adjustable articulator (Denar Mk 2).
One set was kept as a record and a full contour wax up carried out on the second set (Figs. 2a – e). By evaluating the wax up, the appropriate restoration for each tooth was decided upon.
The Failed crowns were removed, selective electro-surgery carried out on the gingiva and the teeth re-prepared as necessary. Minimal tooth reduction was carried out, but the margins were placed just below the gingival crevice to optimise the aesthetic outcome. Tooth 14 was prepared for a veneer and tooth 26 for an onlay (Figs. 3a – b). In the mandible, teeth 34, 36, 44 and 46 were prepared for onlays to correct the occlusal discrepancy.
Indices were made from the wax up (lab putty- Whaledent) and subsequently used to fabricate the interim temporary restorations at the chair side (Figs. 4a – e). The defect in the lower arch was corrected and temporisation allowed the aesthetics and function to be assessed. Shade selection for the definitive restorations was carried out in the laboratory under colour corrected light conditions (Fig. 5).
Following minor adjustments to the occlusion and time allowed for the tissues to heal and stabilise, the temporary restorations were removed, retraction cord placed to clearly expose the margins and the definitive impressions taken. Working casts were fabricated and mounted on a semi adjustable articulator (Denar Mk 2) using a facebow and intercuspal jaw registration (Fig. 6).
Fabrication of Crowns
Zirconia based crowns were chosen for their ability to mask underlying discolouration. A set of dies suitable for scanning were fabricated and trimmed to expose the margins. The Zirconia copings were designed and milled (inEos and inLab – Cerec). The Zirconia blocks are milled 25% larger. In their soft green state they are trimmed and then cleansed in a porcelain furnace at 700°C for 5 minutes before being sintered at 1530°C in a ZYrcomat furnace overnight during which they shrink to fit and harden. Finally they are fitted to the dies and the margins carefully trimmed before being regenerated in the porcelain furnace at 1000°C for 10 minutes. This process converts the structure from its monoclinic crystalline phase to its tetragonal crystalline phase, maximising its strength and resistance to crack propagation. After this process the copings should not be ground or abraded (Figs. 7a – e). The prepared copings were veneered with ceramic (VM9- Vita) (Figs. 8a & b).
Fabrication of the Veneer and Onlays
The veneer (tooth 14) and the onlays (teeth 26, 34, 36, 44 and 46) were waxed to full contour (Fig. 9a), sprued and invested in a ringless mould using a refractory investment (Matchpress – Schottlander) (Figs. 9b & c). The wax was burnt out of the mould in a furnace at 900°C for 1 hour 15 minutes. The units were then pressed from ceramic ingots (Herapress – Heraeus Kulzer) (Fig. 9d) in a pressing furnace (Mulitmat Touchpress – Dentsply) (Fig. 9e) at 1050°C under vacuum.
The pressed mould was left to bench cool before being carefully devested (Figs. 10a – c) using 50μ aluminium oxide to remove the bulk of the investment then 50μ glass bead so not to damage the delicate margins of the pressings. The sprues were removed with a disc and the pressings carefully trimmed with a green stone and fitted to the dies (Fig. 10d). Using ceramic stains (Fig. 11) the pressings were stained and fix fired on a platinum foil in a porcelain furnace at 840°C (Fig. 12a). Small additions such as contacts can be made using compatible porcelain (HeraCeram – Heraeus Kulzer) (Fig. 12b). Glaze was applied in thin layers and fired in a porcelain furnace. Two or three glaze layers are applied to ensure that the stain layer is buried and a high lustre obtained (Figs. 12c – f).
The discrepancies in the mandibular arch were corrected with minimally invasive pressed ceramic onlays (Figs. 13a & b). All the completed restorations were checked for function on the articulated casts (Figs. 14a – c). On cementation the gingival tissues showed some slight inflammation but this soon settled (Figs. 15a – c). Michelle’s smile is now very much in harmony with her face, be it close up, or from a distance (figs. 16a – b). Two years on (Fig. 16c) and four years on (Fig. 16d), the tissues are healthy and the freshness of her smile sustained.
Aesthetic harmony – that balance between the facial form and a smile – can often be the elusive element in a dental reconstruction: ‘The Wow Factor!’ For Michelle her restored smile achieved this promise and complimented her natural beauty so well. She is delighted with the outcome, as are the minions who fall for her winning smile!