Minimally invasive adhesive full mouth reconstruction of a patient with amelogenesis imperfecta

Amelogenesis imperfecta

Amelogenesis imperfecta (AI) is a dental condition affecting the structure and condition of dental enamel with occasional involvement of other oral structures. AI has been classified many times, both clinically and genetically; Table 1 demonstrates an example of one such classification.

Management

Amelogenesis imperfecta has traditionally been managed in a hospital setting and, depending on the severity of the enamel condition, the treatment has involved paediatrics, orthodontics and restorative departments.³

Historically, treatment has involved conventional cast restoration for posterior teeth using gold or porcelain bonded to metal crowns to overcome problems with fracture and sensitivity, while anterior teeth were restored using porcelain veneers to improve aesthetic deficiencies caused by discoloration associated with amelogenesis imperfecta.

However, such approaches are destructive to tooth structure with the potential for irreversible damage to pulpal status.⁴ Preparation of teeth for indirect conventional cast restorations have been demonstrated to cause pulpal necrosis and subsequent periapical periodontitis.⁴ This, in combination with the fact that the presenting patients are very young individuals, reduces the long-term prognosis of the dentition, thereby speeding up the restorative cycle.

In this case report, a minimally invasive approach will be demonstrated to treat both anterior and posterior teeth, improving both function and aesthetics. The benefits of such management strategy are improved prognoses of the dentition and reduction of speed in the restorative cycle by preserving tooth structure.

Case report

A 21-year-old student was referred, by the Paediatrics Department at Eastman Dental Institute, UCL, regarding continuing restorative management of his dentition. He presented complaining of yellow discoloration of his anterior teeth and multiple fractures of his posterior teeth.

He had no symptoms associated with fractured teeth, however, concerns were raised over the future prognoses of these teeth by the patient. He had unremarkable health and, on extra-oral examination, no abnormalities were detected. He had competent lips with a medium smile line with 4 mm papilla visible.

On intra-oral soft tissue examination, no abnormalities were detected, the gingiva was highly scalloped and of thin biotype. On hard tissue examination, the anterior teeth had been previously restored with direct composite restorations, with yellow discoloration and marginal discrepancy due to gingival maturation. The majority of posterior teeth were restored using metal onlay restorations. All posterior teeth, including restored teeth and maxillary canines, had areas of enamel fracture exposing the underlying dentine.

On occlusal examination, the patient had a Class I incisal relationship, with canine guidance on lateral excursions and RCP contact between UR6 and LR5 (Figure 1).

Tooth whitening/Bleaching

Tooth whitening involves the use of oxidizing chemical agents to remove extrinsic and intrinsic staining via oxidation of the organic matrix in tooth tissue. Currently, the most commonly used oxidizing agent is carbamide peroxide (CP), which can be used at concentrations from 5–16%.⁵ Over the years, various techniques have evolved, in an attempt to optimize the effect of carbamide peroxide, to treat both vital and non-vital teeth. Examples of such techniques are the use of heat or light to activate the faster release of free radicals. Currently, the most commonly used method involves the use of custom vacuum-formed thermoplastic trays that are loaded by the patient with various concentrations of CP and worn during the day or at night-time (night-time bleaching).⁵

The home bleaching technique is minimally invasive with little or no damage to tooth tissue and should be the first line of treatment in cases of tooth discoloration.⁶ It has been demonstrated to be highly effective in the management of patients with fluorosis, amelogenesis imperfecta and patients with mild tetracycline staining.

At presentation, one of the patient's main concerns was deteriorating discoloration of anterior teeth, therefore, as the first line of treatment, home bleaching technique was carried out using 10% CP in vacuum-formed thermoplastic trays for 4 hours daily for 14 days (Figure 2)

Diagnostic phase

Hard acrylic maxillary splint (Michigan)

In consideration of the fact that most teeth required restoration with potential for full mouth reconstruction, a Michigan splint was utilized Figure 3. The aim of the splint was to enable assessment of reproducible mandibular position at the intended increased occluso-vertical dimension (OVD).

Mounted casts in retruded axis position (RAP) and diagnostic wax-ups

Articulated casts were mounted in a semi-adjustable articulator (Denar Mark II) to allow assessment of retruded contact position (RCP) followed by full mouth diagnostic wax-up at the intended increased OVD. The wax-up was tried in intra-orally using putty matrices made on casts from diagnostic wax-ups. The putty matrices were filled with Biascryl (Integrity, Dentsply) and fitted over existing teeth to assess aesthetics and function at this OVD.⁷ At this stage, the treatment objectives and plan was confirmed with the patient and informed consent was gained for full mouth rehabilitation (Figure 4).

Core investigations

The individual tooth assessment was carried out after removing existing direct and indirect restorations. The hypoplastic/hypomineralized unsupported enamel was removed using an ultrasonic scaler (Figure 5 a–n).

Direct composite build-up: anterior teeth

The maxillary and mandibular anterior teeth (canine to canine) were built-up directly in composite resin (Gradia, GC). The teeth were isolated using rubber dam, each tooth was cleaned, and sandblasted followed by preparation using 3-step bonding system (Optibond FL, Kerr). Using silicone records (Memosil, Kulzer) of diagnostic wax-ups, the anterior teeth were built up lingually, starting with the lower teeth. Each tooth was then built-up labially using layered technique to mask staining and provide sufficient translucency (Figure 6).

At this stage, the OVD vertical space between the posterior teeth and dynamic occlusion, was checked and confirmed to ensure adequate thickness of material for the posterior teeth, as well as canine guidance in excursions.

Posterior teeth preparations

With the OVD and dynamic occlusion set on the anterior teeth, the maxillary and mandibular second molars were prepared for cast gold restoration. Due to the patient's wide buccal corridor and aesthetic concerns, the first molars (except for UL6) were prepared for adhesive Emax onlay restorations (Figure 7).

All molars were provisionally restored using chairside polyethyl methacrylate resin (PEMA, Trim II, Bosworth) with glass ionomer cement (GIC, Fuji IV, GC) occlusal stops on maxillary premolars (Figure 8).

The patient was reviewed on a weekly basis for 6 weeks to assess the stability of occlusion in static and dynamic positions. At this stage, polyvinyl siloxane upper and lower impressions were taken to produce static maxillary and mandibular casts. The maxillary and mandibular positions were recorded using facebow record in compound relined with Temp bond and jaw registration in self-polymerizing acrylic resin (Duralay, Reliance) (Figure 9).

The working casts were mounted in a semi-adjustable articulator (Denar, Mark II) and individual dies were prepared for definitive wax-up (Figure 10).

The second molars were constructed in high content gold and first molars in pressed Emax (Figure 11).

All posterior teeth were tried in intra-orally to check for marginal fit, interproximal and occlusal contacts, as well as aesthetics. On the day of the fit, the gold adhesive restorations were sandblasted with 50 micron aluminium oxide (AlO) and heat-treated ready for cementation (Figure 12).

The Emax adhesive restorations were steam cleaned prior to hydrofluoric acid (5%) treatment. At the time of fit, each unit was treated with phosphoric acid (37%) and silanated.

All adhesive units were cemented under rubber dam using opaque adhesive resin cement (Panavia F2.0) after cleaning teeth surfaces using pumice and sandblasting using 50 micron AlO (Figure 13).

Direct composite onlay restoration of premolars

For direct composite resin restoration of premolar teeth, upper and lower casts were mounted in MK II articulator and wax-ups were carried out. Memosil indices of the wax-ups were produced to replicate the occlusal morphology and contacts. The lingual and labial segments were then built-up free-hand to achieve ideal aesthetics (Figure 14).

The teeth were isolated using rubber dam, sandblasted, treated with 3 step bonding system (Optibond FL) and restored with direct posterior composite (Gradia) (Figure 15).

Conclusion

In management of this patient the concerns were addressed in the most conservative manner and objectives were met.

The minimally invasive approach of this adhesive treatment reduces the chances of pulpal complications in the future, while allowing for easier maintenance by the GDP.

Although conventional cast restorations have shown better longevity,^{8, 9} the conservative nature of this treatment plan is more appropriate for the patient's age as it slows down the restorative cycle by allowing conventional treatment in the future.

The prognosis of the treatment provided is good considering the presence of enamel on all margins, however, most of the bonding substrate is dentine which can have an effect on the longevity of these restorations.¹⁰

Direct inlay/onlay composite restorations have been shown to have comparable longevity to that of other composite restorations used to restore carious cavities¹¹ and, in the present case, an even better longevity can be expected, considering the surface treatments for mechanical retention and presence of enamel on all margins.

The bonded gold alloy adhesively-retained restorations have been shown to have good long-term prognoses,^{10, 12} however, considering the patient's condition, the question was bonding quality to the enamel. In this case, the previous adhesive treatment has proven to have good bonding ability.