A single non-vital central incisor is a challenge to mask using adhesive porcelain. This case illustrates a successful result in alleviating crowding and masking a non-vital tooth with four anterior bonded porcelain restorations.
A 34-year-old female company director presented complaining of dissatisfaction with her smile, which she felt was crooked and discoloured. She wanted her teeth to be more even and whiter.
She had carried out research on the internet into possible solutions. She had experienced trauma during a horse-riding accident to her upper right central that had turned brown over recent years. She was also interested in replacing her posterior amalgams with tooth-coloured restorations.
There was no relevant medical history. The patient smoked five cigarettes per day. A full clinical examination was carried out including evaluation of the hard and soft tissues, full periodontal charting and oral cancer screening.
There were no TMJ symptoms recorded. Canine guidance right and left and posterior disclusion on protrusion. No posterior interferences were noted lateral excursions, and there were no obvious signs of occlusal instability.
Failing posterior amalgams were on all first molars and 54 2 mesial early caries. There was mild imbrication of the lower incisors but no chipping of the incisal edges, while guidance in protrusion was smooth.
No abnormalities detected in the soft tissues. Radiographic examination of 1 revealed a periapical radiolucency, which indicated endodontic therapy.
Smile design evaluation
Lip-line: moderate to low i.e. the upper lip just covered the gingival margins of the upper anteriors in a full smile. The midline was currently correct for the upper, i.e. parallel to the long axis of the face. There was a slight discrepancy to the lower midline which was not significant or of relevance.
Centrals and canines had good position in relation to the curve formed by the lower lip. The long axis of the upper laterals were distally inclined with a buccal flaring of the distal incisal edges. The premolars were palatally positioned relative to the molars.
The lateral incisors’ gingival position was higher than the ideal smile design parameters – it should be slightly below a line drawn between the central and canine gingival zeniths (height of contour). However, due to the patient’s low lip-line, this was not considered a problem that needed addressing.
Initial hygiene therapy was appointed for the patient, including advice on interdental cleaning and fluoride therapy. The options for the failing amalgams were discussed and indirect inlay/onlay restorations were the treatment of choice.
The patient’s main concerns were her upper anteriors. Although widening the buccal corridor and including 8-10 teeth could make improvements, the patient preferred to treat only the upper four anterior teeth at present. A wax-up of these teeth was carried out on articulated study models to identify the final appearance that could be obtained from modifying the width of the incisors in order to alleviate the crowding. This was also used to produce a silicone preparation guide to identify the amount and exact position of required tooth reduction to obtain the desired result.
Observing the guidelines of golden proportion (Levin, 1978), we were able to identify that it was possible to reduce the widths of the incisors and still maintain appropriate width to length ratios: 70-80% for central incisors (Chiche, 1994). It was possible to correct the long axes of the lateral incisors to be closer to a five degree taper lateral as suggested by smile design principals (Preparation – silicone preparation guide). The patient was pleased by the final appearance of the wax-up and informed consent was obtained to commence treatment.
Following successful endodontic therapy of 1, the patient underwent an in-surgery whitening procedure (Zoom2). She used the home whitening trays for two weeks and we then allowed two weeks for the colour to stabilise. At the preparation appointment, the 1, 2 and 1 were anaesthetised and prepared using the silicone preparation guide. The 1 was more heavily prepared buccally in order to allow for the masking of the discolouration by the laboratory.
Clinical digital photography using an SLR camera (Nikon D100) and varying the f-stops was used to evaluate the shade of the canines and to illustrate the exact shade of the
underlying preps – the obvious challenge being the discoloration of 1 being matched to otherwise natural coloured teeth. The techniques for shade-photography advocated by Ed McLaren (AACD San Diego 2006) were used, including keeping the shade tab in the same plane as the tooth and photographing from a 90o angle. This prevents uneven light distribution between the shade tab and the tooth surface.
The photography also communicated the texture and surface anatomy of the surrounding dentition. Silicone impressions, bite registration and stick-bite were obtained. Temporaries were made using Luxatemp B1 (Minerva Dental) in a stent made over the wax-up. The patient was evaluated the next day where minor adjustments to the temporaries were prepared.
Phonetics were evaluated (E-position, f and s sounds – Dawson Functional Aesthetics, Dawson Centre for Advanced Dental Study, Florida) and the position of the incisal edges relative to the lower lip in both a horizontal and a vertical plane were assessed. The final length of the central incisor was established at 11mm, which is ideal (Magne et al, 2003). An alginate was taken of their final shape to send to the laboratory to communicate the exact dimensions.
The case was made using Shofu Halo porcelain for the veneers and Belleglass (Kerr) for the onlays. The blocking out of the darker tooth 1 was achieved by the careful application of Opaque dentine at crack-firing stage.
The temporaries were removed and the final restorations tried in with try-in paste to assess the colour especially in relation to 1. 25% opaque for 1 was mixed in with the shade used to cement all restorations. (Variolink, Ivoclar Vivadent).
The patient was delighted with the results. The main challenge in this case was matching a single non-vital tooth to natural teeth underlying veneers. This was overcome using careful laboratory communication including the use of high quality digital photography. My thanks go to Luke Barnett Ceramics.
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