Aesthetic composite veneers for an adult patient with amelogenesis imperfecta: a case report

Clinical presentation of amelogenesis imperfecta

In the case of Witkop Type I hypoplastic AI, there is a defect in the enamel matrix formation, however mineralization of the enamel matrix proceeds in a physiological manner, culminating in a mechanically strong enamel layer, but of a reduced level of thickness.

For cases presenting with hypocalcified AI (Witkop Type III), the matrix is of normal thickness but mineralization is poor; hence the enamel tissue present is of a relatively softer consistency, and is thus susceptible to rapid wear.

In hypomaturation AI (Witkop Type II) defect, the enamel layer has a normal, physiological thickness, but is slightly softer than normal enamel and thus may chip readily from the clinical crown. Often these teeth have a mottled appearance.4Figure 2 provides clinical examples of AI defects as described above.

Enamel formation by ameloblasts is a complex process, with interactions occurring between organic matrix molecules including enamelin, amelogenin, ameloblastin, tuftelin, amelotin, dentine sialophosphoprotein and various enzymes, including kallikrein 4 and matrix metalloproteinase 20, which have been genomically identified.5

Whilst historically it was thought that AI was a pure enamel defect (often associated with marked tooth sensitivity), it has since been reported that a plethora of other dental hard tissue anomalies have been observed to occur commonly in conjunction with the presence of this enamel disorder. The latter list of anomalies includes:

Such features are often AI Type dependent. Poor oral hygiene is also a concomitant finding frequently reported. Amelogenesis imperfecta also appears to be associated with other somatic findings,5 including reported associations with nephrocalcinosis,8 raising the question of whether hypoplastic AI patients should have a renal function assessment as part of whole patient care. The diagnosis of AI has also been linked with tricho-dento-osseous syndrome,4,5 whereby the dental condition is seen in conjunction with curly hair, nail defects and skeletal changes, including bone sclerosis. Cases have also been reported of AI combined with cone rod dystrophy, platyspondyly and as part of Kohlscutter syndrome, amongst other medical conditions.5

Not surprisingly, the altered tooth appearance may result in grievous psychosocial concerns amongst patients affected by the condition,5,9 which, especially amongst younger adults, may result in the patient developing a tendency towards suicide. A report has also been published in the contemporary literature, describing a single incident of an AI patient resorting to theft to fund his/her dental treatment.10

Management strategies for amelogensis imperfecta

On account of the heterogeneous mode of presentation of AI, there is no simple generic formula for treatment. However, consensus opinion appears to indicate a distinct tendency towards minimally invasive adhesive dental restorations (where possible).7,11–16 The traditional application of conventional indirect restorations has been associated with a high incidence of subsequent pulpal pathology17 and the extensive loss of coronal tissue.18 However, as a pre-requisite for successful adhesive dentistry, it is generally considered that the presence of copious, high quality dental enamel is essential.

In spite of the obvious concerns which remain with regards to resin bonding to altered enamel, Lygidakis et al19 have described the formation of adequate adhesive bonds between hypomineralized enamel on molar teeth, provided the soft, obviously defective superficial enamel has been removed. Venezie et al20 have described the pre-treatment of hypocalcified AI teeth with sodium hypochlorite prior to adhesive bonding, to improve bond strengths attainable with resin-based materials.

Whilst aiming to be as minimally destructive as possible posteriorly, Sengun and Özer13 have described the placement of adhesive metal onlays in supra-occlusion to reduce any unnecessary substantial tooth reduction, whilst increasing the vertical dimension that was lost due to increased toothwear. Others, such as Yamaguti et al15 and Türkün16 have used composite onlays, while Sabatini and Guzmán-Armstrong12 and Yiğit-Özer and Bahşi,14 have used direct composites. Anteriorly, many authors have used either adhesive composite11–16 or porcelain veneer 7,21,22 restorations. In some instances, however, metallo-ceramic or dentine-bonded crowns may still be the anterior or posterior treatment of choice.7,21,22

Treatment planning for AI cases is seldom straightforward. The plan needs to take into account a multitude of factors including:

Whatever the personal views of the clinician, the patient must be fully informed of all options and his/her opinions and preferences sought. Needless to say, with any restorative option, good preventive care is absolutely paramount for long term clinical success.

Described below is a case report of a patient presenting in general dental practice with AI, which has been managed utilizing a minimally invasive approach. This case has been presented as part of the continual assessment requirement for the MSc in Aesthetic Dentistry, King's College Dental Institute.

A case report

A 24-year-old, well-educated adult female patient, who had previously accepted her poor dental aesthetics, requested an improvement, ideally without ‘cutting into the teeth’ (Figure 3).

A detailed history was recorded, followed by a meticulous extra- and intra-oral examination. The latter revealed the presence of a healthy, minimally restored dentition with excellent oral hygiene and periodontal condition. Significant pitting was noted to be present on the labial, buccal and palatal surfaces of all teeth with the occlusal surfaces being relatively spared, resulting in no loss of vertical dimension (Figure 4). Her mother had less severe pitting on most teeth, whilst her sister had been unaffected. She had no significant history of caries or having suffered sensitivity.

Fluorosis and chronological enamel hypoplasia were excluded on the basis of history and clinical appearance.

The condition generally appeared consistent with Witkop's Type IA Hypoplastic pitted AI,4 which is the most commonly occurring, with Bäckman and Holm¹ finding this in 47/105 of those cases studied. This is thought to be due to a defect in the enamelin gene-ENAM 4q215 and is generally transmitted by autosomal dominant inheritance, which agrees with the family pattern found. However, Witkop's detailed descriptive classification4 states pitting as being only on the labial and buccal surfaces. Bite-wing radiographs (Figure 5) showed what appeared to be a mild case of taurodontism-hypotaurodontism23 (while her mother had no taurodontism) which potentially could imply that this is a Witkop Type IV, though good enamel density was present. In view of the variability of the nature of AI, even within families, this case appears to back the call of Aldred et al6 for a more flexible classification system.

Options for treatment

Orthodontics to align the upper and lower anterior teeth fully prior to any other treatment was an option which was discussed, but which the patient was not keen to pursue. Crowns, while not relying on adhesive bonding, were dismissed on the basis of amount of the tooth reduction required.18 Porcelain veneers and composite veneers were discussed with the patient, along with the theoretical issues of bonding, the amounts of tooth preparation necessary, potential problems that may be encountered and respective longevities. The patient was keen to keep treatment as conservative as possible and was willing to accept a reduced longevity of the composite resin restorations compared to porcelain, in return for a lesser biological price.

A smile analysis was carried out, a full set of photographs was taken and alginate impressions carried out to allow a technician's wax-up (Figures 6–9). Whilst noted as being present, the disparity in the gingival margin heights across the midline was not considered important in this case. While the patient had a classic UR5/UL5 premolar smile (which were planned to be restored), the wax-up was carried out on UR3/UL3, with the premolars being intended to be built freehand. It was agreed that minimal recontouring would be carried out on the mesio-incisal edge of UL2.

The bis-acryl mock-up

An alginate impression was taken of the wax-up and loaded with a bis-acryl composite (Protemp 4 – 3M ESPE). The impression was then inserted into the mouth and the material allowed to set, before the impression was removed. This procedure allowed the patient to preview what was being planned and give her approval. Note the more relaxed lip posture than that seen in the pre-treatment images with the proposed incisal edge contour following the curve of the lower lip.

An initial course of home tray whitening was carried out over a 3-week period with 10% carbamide peroxide gel (Illuminé, Dentsply, Weybridge, UK). A period of 6 weeks then lapsed owing to work commitments and an initial stabilization period before the composite build-up procedure.

The build-up procedure

A putty index impression (Provil, Heraeus Kulzer, Newbury, Berks) extending to the labio-incisal edges was taken of the wax-up (Figures 10–12). This index (often described as a silicone key) was then transferred to the mouth to act as a template for the palatal and incisal aspects of the layered build-up.24,25

The teeth were carefully isolated with cotton wool rolls, cleaned with pumice and the labial and palatal surfaces etched as appropriate with 30% phosphoric acid for 20 seconds. To maintain control, the teeth were treated in groups, with the four incisors being built first. Opti-Bond Solo (Kerr, Peterborough, Cambs), a 5th generation, 2-step etch and rinse bonding agent was applied to all etched surfaces. Treatment was in fact carried out over two appointments, with the incisors and canines being built at the first appointment, and the premolars at the second.

The material chosen for the veneers was ‘HFO’ composite resin (Mycerium, Optident UK, Ilkley, W Yorkshire), an anatomically layered composite system, which was ‘pre-warmed’ to 39 °C (Figure 13). An initial palatal layer of high value GE3 enamel composite was placed using the matrix to achieve the desired outline, dentine shade UD1 was subsequently applied across the pitted surface, whilst forming the shape of the dentinal lobes and line angles. Intensive white IW was applied as a thin layer in areas where discoloration showed through and OBN translucent shade applied to the mamelon areas. A thin layer of ‘glass connector’ (a highly fluorescent material that lifts the vitality of the enamel) was applied and subsequently covered with a single layer of shade GE3 enamel.

Curing was carried out in 10 second increments using a Translux Power Blue curing light (Heraeus Kulzer) with a 60 second cure of the final enamel layer. Such short increments of curing time are feasible with this technique because of the cumulative effect achieved during subsequent curing of the various layers. In this particular case, as contact points were not being rebuilt, interproximal separation and contouring was achieved using clear matrix strips.

Little shaping was necessary as this was addressed in the build-up process, but where indicated was carried out with fine diamond burs, along with the creation of secondary anatomy. Polishing of the labial and palatal surfaces was performed using the Astropol kit (Ivoclar Vivadent, Enderby, Leics) (Figure 14) of specially fabricated silicone finishers and polishers, which come in three different grades (F, P, HP) and a variety of shapes. Groovy Diamond diamond-impregnated bristle polishing brushes (Clinicians' Choice, Optident UK) (Figure 15) were used to produce the final high sheen. Interproximal polishing was performed with Epitex strips (GC) (Figure 16).

The occlusion was checked in both centric occlusion and excursions using thin articulating paper and Miller's forceps. Adjustments were made to provide shared contacts in protrusive guidance (Figures 17 and 18). Lateral guidances were not disturbed and remained as group function. Figures 19 and 20 show the final appearance attained.

Discussion

Patients with amelogenesis imperfecta are susceptible to the restorative cycle of replacement restorations,26 just like any other patient, but start with a distinct disadvantage. Many AI patients are treated as children when pulp sizes are large. Despite the difficulties, treatment to address wear, sensitivity and aesthetics needs to be as conservative as possible for as long as possible. This approach will provide the patient with the best chance of maintaining his/her dentition for the longest period of time.

Composite veneers are a very conservative and cost-effective way to enhance a smile, with excellent aesthetic results and high patient satisfaction27 in the adult population. The layering used in this case, while more complex, provides a natural depth and allows characterization of the restoration. These aspects significantly improve the aesthetics and are not seen in the simple single shade build-up, which is often seen used in the literature on children.

At room temperature, HFO has a relatively stiff consistency which may not always be conducive to its application in thin layers/increments. However, when pre-warmed (as described above), the ability to adapt the latter material to the tooth surface increases significantly, allowing it to be easily placed in thinner sections. A study by Deb et al,28 which assessed a variety of different commercially available resin composites, showed that all of the six composite resins tested as part of their study exhibited this phenomenon. However, Da Costa et al,29 in a study looking solely at the property of rheology (flow) amongst 18 different commercially available composite resin brands, found the increase in flow to be product specific.

The pre-warming of resin composites is also thought to be associated with a higher degree of polymerization conversion.30 Whilst it would be reasonable to assume that the ability to adapt a pre-warmed resin would be better than that of material which has not been warmed and would, in turn, culminate in reduced microleakage, Deb et al28 found that this was not the case; equally there were no adverse affects reported either (when assessing marginal adaptation). The latter group also found that pre-warming resulted in only a minimal increase in the flexural strength of the cured material(s) (apart from two products which displayed significant gains with respect to this mechanical property). In addition, no concomitant increases in cytotoxicity were reported amongst the products tested as a result of the application of a heat source.28

The only adverse effect of pre-warming, reported by Deb et al,28 was an increase in overall shrinkage, perhaps due to the increased level of overall polymerization attained. However, the shrinkage was deemed not to be clinically significant, possibly due to it being offset by the improved adaptation.

The use of the silicone matrix provides a high degree of accuracy in transferring information from the smile design planning stage to the mouth. As can be seen in the occlusal views, minor rotations have been masked, while the slightly instanding UL5 has been built out more buccally than the others, so as to give a natural progression to the visible tooth surfaces. Carrying out the treatment in two stages allowed photographs to be taken, assessed and adjustments made. It also allowed time for complete dark polymerization to occur before final polishing of the anterior teeth.

The initial high lustre of the composite does tend to be lost with time and superficial repolishing is needed, probably at six-monthly intervals. There is a risk of chipping though, unlike porcelain, this can be easily repaired intra-orally without complete replacement. Longer term, a cut-back and resurfacing procedure can be carried out rather than complete replacement. The choice of this particular patient tied in with the findings of Nalbandian and Millar27 regarding patient concern about maintaining the integrity of the original teeth. As with any restorative treatment, ongoing monitoring and preventive care is essential.

Conclusion

Because of the nature of AI, this treatment is certainly not suitable for all, as there is a clear pre-requisite for the availability of adequate, well mineralized enamel, which may not be present in all forms of AI. Careful evaluation of the quality and quantity of enamel, along with the patient's oral hygiene, age, and fully informed personal preferences, are necessary to ensure the most desirable result. As Yamaguti et al15 also commented, increased reporting and correlation needs to be made of the longer term clinical behaviour of modern conservative materials, in patients with AI, to establish their success and rationalize future treatment options.