Indirect adhesive cementation with Maxcem Elite Chroma
This clinical case describes the latest equipment, materials and evidence-based techniques that are available to help dentists optimise all clinical stages of indirect adhesive restorative procedures.
A 45-year-old male patient came to the office for the cosmetic replacement of a ceramic crown on the maxillary left central incisor (Fig. 1). Aesthetic co-diagnosis determined that the patient’s main complaint was asymmetry between the restored and adjacent central incisors in terms of shape, length, surface texture, shade and labial margin position. The patient had no concerns regarding his midline diastema and requested no aesthetic treatment for any other teeth. Radiographic examination (which is mandatory prior to indirect restorative dental procedures), along with periodontal examination, occlusal analysis and pulp testing, revealed no pathology (Fig. 2).
The restoration of a single central incisor adjacent to an unrestored central incisor is considered to be the greatest aesthetic challenge in dentistry.1 The restorative design was communicated in the following stages:
- Shade selection was carried out immediately to reduce the risk of inaccuracies resulting from tooth dehydration, using a VITAPAN 3D-Master shade guide (VITA Zahnfabrik).
- A range of intra- and extra-oral preoperative photographs were taken using a digital SLR camera, macro lens and ring flash.
- A 1:1 magnification photograph of the central incisors was digitally enhanced by increasing contrast. This is a useful aid for optimising colour and surface texture diagnosis.
- Design images were then inserted into an MS PowerPoint slide and annotated with detailed technical instructions (Fig. 3).
- The annotated slide was e-mailed to the ceramist. Patient consent was obtained for data protection purposes prior to sending the file to the ceramist.
During the preparation appointment, a preoperative impression was taken to enable fabrication of a provisional restoration using an adjustable, perforated aluminium sectional tray (Kwik Tray, Kerr) with addition-cured silicone putty, which was trimmed and vented as shown in Figure 4. After anaesthesia, the existing restoration was sectioned labially using a diamond bur and carefully fractured using a specialist crown remover and airway protection (Fig. 5). Study of the preparation and fit surface of the ceramic crown revealed previously undiagnosed marginal leakage. Tooth preparation was then carried out according to established protocols,1–4 to maximise retention and resistance form and to reposition the labial shoulder margin apically.
As demonstrated in Figure 6, a round-ended, tapered diamond bur was used to optimise the occlusal convergence angle and to create a rounded line angle between the axial walls and the shoulder. The shoulder margin was then refined and measured with a 1 mm end-cutting diamond bur. A retraction cord was placed prior to marginal finishing to protect the periodontal tissue and obviate the risk of biological width violation.
The generally recommended minimum incisal thickness for all-ceramic crowns is 1.5– 2.0 mm,1, 3, 4 in order to allow adequate room for porcelain (Fig. 7). Incisal clearance was measured in the intercuspal position and in all protrusive and lateral excursions using a flexible silicone feeler gauge (Flex Tab, Kerr), which is available in a range of thicknesses (1.0, 1.5 and 2.0 mm). Line angles were then smoothed with fine finishing discs (OptiDisc, Kerr).
The most convenient and reliable way of recording putty/wash impressions is to use a one-stage technique with the addition of polymerised silicone putty material in a rigid metal tray.5 After removal of the retraction cord, low-viscosity impression material was injected subgingivally and on to the preparation surface. The wash material was then air-thinned and the preparation reloaded with a second increment of wash (Fig. 8) before inserting the silicone putty. This technique is designed to eliminate the risk of impression inaccuracies, such as air bubbles. Once set, the impression was removed, washed, dried and inspected under magnification (Fig. 9). An opposing impression was captured in a rigid metal tray with Take 1 Alginate (Kerr).
Using the void impression technique,5 the preoperative sectional silicone impression was loaded with acrylic resin (Fig. 10) and inserted over the prepared tooth. Vented acrylic was tested intermittently to determine the optimal removal time before it completely set. The provisional restoration was adjusted using OptiDisc to optimise marginal fit and make occlusal and aesthetic refinements.
The inhibiting effect of eugenol-containing cements on the polymerisation of resin cements6 is the subject of debate, and in this case, a non-eugenol temporary cement was used (TempBond NE, Kerr). The quantity of temporary cement was limited to a thin layer, approximately 2 mm beyond the internal crown margin (Fig. 11). This technique would have allowed ease of removal and potential re-use of the provisional crown had adjustments to the definitive restoration been necessary. Once cemented, the provisional restoration was painted with a specialist low-viscosity light-cured resin glaze to optimise aesthetics and minimise staining (Fig. 12).
After casting, die stone models were prepared and mounted on a semi-adjustable articulator (Fig. 13), and an all-ceramic crown was constructed to match the functional and aesthetic prescription (Fig. 14).
During the fitting appointment, after anaesthesia, the provisional crown and residual temporary cement were removed and the crown was tried on (Fig. 15). An OptiClean rotary instrument may also be employed to facilitate the removal of provisional cement from the preparation. The crown was filled with a water-soluble try-in gel (NX3, Kerr) to stabilise the crown during the assessment of marginal fit, occlusion and aesthetics (Fig. 16). The try-in gel allowed the patient to study the restoration in detail to confirm that all aesthetic requirements had been met. After assessment, the NX3 gel was easily rinsed off and the fitting surface of the lithium disilicate crown (Fig. 17) was etched with 5% hydrofluoric acid and treated with a silane primer, according to the manufacturer’s instructions.
The luting cement used in this case was Maxcem Elite Chroma (Kerr), a self-etching/self-adhesive resin cement with a clean-up indicator. Moisture control is essential during adhesive cementation procedures, and in this clinical case, optimal isolation was obtained by using cotton wool rolls and a saliva ejector. The preparation was air-dried with care not to desiccate the dentine. (The split-dam technique may also be used to enhance isolation).
The clear version of Maxcem Elite Chroma was selected (white and yellow shades are also available). The dual-barrel resin cement syringe was removed from its foil packaging. The syringe cap was then removed and a very small quantity of the material was dispensed on to a pad to equalise the base and catalyst pastes in the syringe. The restoration, including the margins, was then light-polymerised for 1 minute from all angles (Fig. 22), using the high-quality Demi Ultra LED curing light (Kerr).
Maxcem Elite Chroma is a very versatile material and may also be used with the following alternative protocols, depending on the operator’s preference:
- The luting resin may be tack-cured for approximately 2–3 seconds (the pink colour will disappear immediately), followed by immediate removal of excess.
- Unset excess may be removed immediately using a sponge pellet or micro-brush and left to self-cure for a minimum of 4 minutes, while maintaining pressure on the restoration. (This is a useful technique when cementing opaque restorations that will not transmit light, such as zirconia or metal–ceramic crowns).
- When polymerising marginal luting resin, a glycerine or NX3 try-in gel barrier may also be used to preclude formation of an oxygen inhibition layer.
After light polymerisation, Maxcem Elite Chroma was left to completely self-cure for 4 minutes before final finishing, which was carried out using a sharp scaler and a double-thickness dental tape (Fig. 23). If required, fine abrasive strips may be used to finish proximal areas, and margins may be polished with HiLusterPLUS (Kerr) discs, cups or points for a final high-lustre polish. Final occlusal and aesthetic assessments were carried out, and the restoration was evaluated two weeks postoperatively (Fig. 24).
Composite resins are the optimal luting materials for adhesively bonded ceramic restorations, as they have the highest strength and lowest solubility.3 Use of Maxcem Elite Chroma reduced technique sensitivity and ensured an efficient and predictable outcome that was pleasing for both the patient and the operator.
Furthermore, Maxcem Elite Chroma is radiopaque and enables improved radiographic monitoring of ceramic restorations over time.
A list of references can be requested from the publisher.