Written by G. Franklin Shull, DMD, and Matt Roberts Thursday, 09 December 2010 14:42
A very significant part of any case is material selection. Due to the likelihood of porcelain chips and fractures as a result of a patient’s bruxing habit, dentists have a tendency to fear cases that present with signs of occlusal disease. The purpose of this article is to present such a case and to talk about the dental materials needed for a successful aesthetic outcome and predictable restorative longevity.
Diagnosis and Treatment Planning
A 40-year-old male patient initially presented with a broken anterior tooth. Specifically, a large Class IV composite resin restoration was missing from tooth No. 9 (Figures 1 to 4). Throughout the years, the patient had experienced problems with his anterior teeth due to the enamel not forming properly. The patient had received multiple large Class III and Class IV composite resin restorations and PFM crowns on teeth Nos. 22 and 27. He was aware of a bruxism habit, but had never worn an appliance. Embarrassed by the appearance of his smile, he felt it held him back in his career. He wanted to be able to smile and feel confident in himself. The patient had no medical contributing factors, and no contraindications to restorative dentistry.
|Figure 1. Preoperative (retracted 1:2) view of the patient showing severe wear and irregular incisal edges.||Figure 2. Preoperative view of the patient’s full natural smile enabling evaluation of the potential gingival display.|
|Figure 3. Preoperative (1:1 view) of the patient’s maxillary anterior teeth showing large Class IV composite restorations and an obvious pattern of wear. All of these signs combined point to a need for a sound occlusal philosophy and the use of a strong restorative material.||Figure 4. View of the patient’s mandibular anterior teeth, revealing enamel malformation and old existing PFM crowns on the right and left cuspids.|
Tooth No. 9 was repaired with direct composite, and the patient was appointed for a comprehensive examination and records appointment.
The comprehensive examination appointment included the following diagnostic tools: study models, face-bow transfer, centric relation bite record, stick bite, and a complete series of photographs and radiographs. In addition, a hard- and soft-tissue examination was documented. The clinical examination, aided by the digital photographs, helped to evaluate the patient’s gingival display (Figure 2), soft-tissue symmetry, and pattern of wear (Figure 3).
To create the optimal environment in which to place aesthetic restorations, the patient was scheduled for and underwent hygiene appointments, as well as general posterior operative care.
After this work was completed, during a consultation to review findings and to discuss the treatment alternatives, the preoperative photographs were reviewed with the patient. Articulated models mounted in centric relation were used to demonstrate the significant interference to maximum intercuspation.1,2 Occlusal equilibration would be utilized prior to reestablishing anterior guidance. Nightguard vital bleaching would be used to lighten the teeth not being covered by crowns.
The patient agreed to the above recommended treatment, as well as all-ceramic crowns on teeth Nos. 6 to 11 and Nos. 22 to 27, followed by the delivery of an occlusal guard.
Material Selection: A Team Effort
The key component to the treatment plan was restoring the dentition with a metal-free material that would provide optimal aesthetics and strength, particularly since the patient presented with a bruxing habit. Material selection would be critical to ensuring the aesthetic and functional success of this case.
A copy of the patient’s records and information was sent to the dental laboratory team for review. A request was made to create a diagnostic wax-up to be used in evaluating and restoring aesthetics and function. The doctor and ceramist agreed that a strong lithium disilicate all-ceramic material (IPS e.max Press [Ivoclar Vivadent]) would be an ideal choice to use in fabricating the restorations. To address the primary concern of ceramic chipping and fracture, a “monolithic” restoration design was chosen. The monolithic technique involves waxing and pressing the restoration to full contour, without doing a cutback to allow room for a layering ceramic. This technique has been shown to provide long-term predictability, resisting both chipping and fracture. For the technician, the relative ease of fabrication also was an important factor that was considered as an indication for selecting this material for the case. In addition, for the doctor, the ability of this material to be pressed into very thin restorations is important. This, when combined with the availability of a full range of translucency levels, reduces the need for aggressive tooth reduction allowing for conservation of the patient’s existing tooth structure.
Prior to the preparation appointment, the patient completed the hygiene appointments, as well as the occlusal equilibration. Also, his teeth were bleached to a basic B1 (Vita Lumin Shade Guide [Vident]) shade.
Using a matrix created from the diagnostic wax-up as a reduction guide, teeth Nos. 22 to 27 were prepared first for full-coverage all-ceramic crowns. Then, using a putty matrix (Siltech [Ivoclar Vivadent]) that was also fabricated from the diagnostic wax-up, provisionals were made for teeth Nos. 22 to 27 using a strong and aesthetic bisacryl provisional material (Luxatemp [DMG America]). This was then set aside to be temporarily cemented later.
Teeth Nos. 6 to 11 were then prepared for full-coverage all-ceramic crowns using the same technique as for the lower arch. Similarly, provisional restorations were fabricated and set aside.
When treating a patient utilizing all-ceramic restorations, it is important to evaluate the color of the underlying tooth structure and provide adequate thickness of the veneering material to achieve the final desired shade of the new restorations, as well as the chroma gradient from gingival to incisal. This is especially important when working with a monolithic ceramic; there will be no laboratory layering in this situation, so the major tool used in controlling color gradient is the thickness of the ceramic. Gingival areas in which a stronger color is desired are left thinner, and very shallow chamfer margin preparations are used to facilitate a contact lens-like blending into the neck of the tooth. Deeper preparation at the incisal of the tooth lets the effect of the underlying color fade out, simulating the normal gingival to incisal color gradient seen in natural teeth.
When using lithium disilicate, clinicians and their dental laboratory team can deliver very aesthetic restorations that demonstrate a soft progression of chroma gradient and nondynamic incisal effects, as frequently seen in natural teeth. However, it must be noted that without layering, it may not always be possible to create very translucent incisal effects, such as detailed dentine lobe structure and dynamic translucency.
When the preparations were completed, these parameters were verified using the silicone (Siltech) matrix from the diagnostic wax-up to evaluate proper incisal and facial reduction. Prior to taking final impressions, the thickness of the provisional restorations was double-checked to ensure that ideal thickness had been achieved to accomplish the restorative goals. Final impressions of the upper and lower arches, a new face-bow transfer, bite registration, and preparation photographs (Which included shade tab comparisons to communicate colors of the preparations) were obtained.
The provisional restorations then were seated using a spot etch and flowable provisional material (LuxaFlow [DMG America]) technique, after which the occlusion was adjusted and the restorations polished (Figures 5 and 6). Well-done provisional restorations are important to complex restorative cases, since they enable patients to evaluate the fit, aesthetics, and function of the proposed treatment before any definitive work is initiated.
|Figure 5. View of teeth Nos. 6 to 11 after being prepared for all-ceramic crowns. Teeth Nos. 22 to 27 were also prepared and provisionalized.||Figure 6. Smile view of the mandibular and maxillary provisional restorations in place.|
The patient returned in 4 days to check the provisional restorations: speech, occlusion, and aesthetics were evaluated. Minor adjustments were made to the lateral excursions and crossover. At this time, the patient also approved the aesthetics, and a decision about the final color of the restorations was made. To assist the dental ceramist in creating optimal restorations, impressions of the provisionals were taken to convey the proper contour and incisal edge positions, and a full series of photographs was taken.
Dental Laboratory Fabrication of the Restorations
At the dental laboratory, all impressions were poured, and the models were pinned and articulated. A full-contour wax-up of the restorations was created by taking a silicone (Siltech) matrix of the provisional model and placing it over the prepared tooth model. Next, molten wax was injected through a hole (made with a No. 8 round bur) in the incisal area using a hot wax injection pump. This technique reproduced the form and position of the provisional restorations in the final wax-up (Figure 7). The contour of the wax-up was then evaluated and compared to the photos of the patient’s provisional restorations. Contour, surface morphology, and the functional envelope were idealized in wax.
|Figure 7. The initial diagnostic wax-up fabricated in the laboratory was derived from the provisional restorations via wax injection.||Figure 8. After pressing with lithium disilicate (IPS e.max [Ivoclar Vivadent]), composite dies in the color of the preparations were then fabricated for the restorations.|
|Figure 9. Final contour and surface texture was achieved prior to shading and glazing the restorations.|
|Figures 10 and 11. The glazed restorations were fit carefully to a solid model.|
|Figure 12. Centric and excursive positions were carefully adjusted on the articulator.|
Next, the wax-up was sprued onto the ring former, invested, burned out, and high translucency B1 IPS e.max Press ingots were pressed into the resulting voids. After pressing, composite dies in the color of the preparations were fabricated for the restorations (Figure 8). The restorations were then removed from the investment by sandblasting with glass bead, and the restorations were fit to the master model. Final contour and surface morphology was achieved by grinding with rotary diamond burs (Figure 9). Canine guidance, protrusive guidance and crossover were all checked on the semi-adjustable articulator. The restorations were then be stained and characterized, fired, and then glazed (Figures 10 and 11). Finally, centric and excursive positions were carefully adjusted on the articulator (Figure 12).
At the seating appointment, the provisional restorations were removed using a carbide ET bur. To verify fit, all restorations were tried-in individually. All the restorations were tried-in at the same time with a try-in paste to verify the interproximal contacts, aesthetics, and occlusion.
|Figure 13. Postoperative view of the patient in natural smile. A reasonable blend with the natural dentition is exhibited by the restorations.||Figure 14. Retracted postoperative view of the final maxillary and mandibular restorations, revealing enhanced aesthetics, color and incisal symmetry.|
|Figure 15. Retracted close-up postoperative view of the definitive maxillary anterior restorations.||Figure 16. Postoperative (right lateral) view of the completed restorations.|
|Figure 17. Postoperative (left lateral) view of the completed all-ceramic restorations.|
The preparations and restorations were then cleansed and prepared for bonding. (Restorations fabricated with the lithium disilicate glass ceramic can be conventionally cemented or adhesively bonded.) Using a rubber dam for isolation, the restorations were bonded utilizing the “total etch” technique with a single-bottle adhesive system (Adper Single Bond Plus [3M ESPE]) and adhesive resin cement (RelyX ARC, shade A1 [3M ESPE]). Excess cement was removed from the facial and lingual surfaces with cotton rolls and brushes. Excess cement was removed interproximally using dental floss, after which the restorations were then fully light-cured. The rubber dam was removed, and the occlusion was again verified and adjusted. The restorations then were polished.
A new set of maxillary and mandibular impressions were taken for use in fabricating an acrylic bite splint. This was delivered to the patient when he returned the following week for his postoperative occlusal check (Figures 13 to 17).
DISCUSSION: LITHIUM DISILICATE
The IPS e.max all-ceramic system, as demonstrated in this case report, provides dentists and their laboratory team with a predictable and productive way to create all-ceramic restorations for use in both the anterior and posterior segments.
This universal system includes a pressable monolithic fabrication option with IPS e.max Press; a lithium disilicate glass ceramic that delivers the fit, form, and function expected from pressable ceramics, but with enhanced strength and optimized optical properties. Pressable lithium disilicate is indicated for inlays, onlays, thin veneers, veneers, partial crowns, anterior and posterior crowns, 3-unit anterior bridges, 3-unit premolar bridges, telescope primary crowns, and implant superstructures.3-5
Historically, a choice between strength and aesthetics has plagued the dental profession. The most aesthetic materials have often failed when under the stress of parafunctional habits. As a result, metal-based ceramics have been the restorations of choice for many years in high-stress situations, but often with compromising to aesthetics. Unfortunately, chipping of the weak ceramic materials covering the strong metal copings is still being seen today. For the dentist and dental technician team, IPS e.max is a welcome addition to indirect restorative materials. The IPS e.max system represents a solution to this dilemma by providing a monolithic technique with IPS e.max Press. Using lithium disilicate pressed to full contour (without cutback and layering) can provide clinicians with a strong and easy-to-use indirect restorative material for such cases. When treating patients with a high risk of incisal chipping, it is preferable to fabricate the incisal edge from lithium disilicate (400 Mpa flexural strength), rather than the layering ceramic (85 Mpa flexural strength) that is veneered over it.
The latest studies from New York University College of Dentistry show that monolithic lithium disilicate restorations are one of the strongest restorative materials available today.6 In simulated chewing tests, the occlusal load on restorations was progressively increased through repetitive chewing cycles; at 350 Newton load and 100,000 cycles restorations with a zirconia core showed a 90% failure rate, in contrast to lithium disilicate restorations which showed no failures after 1,000,000 cycles at a load of 1,000 Newtons of force.
This article demonstrates the need for teamwork in making a selection of restorative materials. In this case, the challenge was to meet the need for excellent aesthetics while recognizing the patient’s high risk for porcelain chips and fractures as a result of his bruxing habit. By using lithium disilicate pressed-to-full-contour restorations, the patient’s expectations were met with final restorations that were predictable, aesthetic, and strong (Figures 13 to 17).
- Parker MW. The significance of occlusion in restorative dentistry. Dent Clin North Am. 1993;37:341-351.
- Dawson PE. Functional Occlusion: From TMJ to Smile Design. St. Louis, MO: Mosby; 2007.
- Sorensen JA, Cruz M, Mito WT, Raffeiner O, Meredith HR, Foser HP. A clinical investigation on three-unit fixed partial dentures fabricated with a dual-curing adhesive system and a self-curing resin cement. J Adhes Dent. 2006;8:427-431.
- Höland W, Schweiger M, Frank M, et al. A comparison of the microstructure and properties of the IPS Empress 2 and the IPS Empress glass-ceramics. J Biomed Mater Res. 2000;53:297-303.
- Kheradmandan S, Koutayas SO, Bernhard M, et al. Fracture strength of four different types of anterior 3-unit bridges after thermo-mechanical fatigue in the dual-axis chewing simulator. J Oral Rehabil. 2001;28:361-369.
- Guess PC, Zavanelli R, Silva NR, et al. Clinically relevant testing of dental porcelains for fatigue and durability with an innovative mouth motion simulator. Presented at: 39th Annual Session of the American Academy of Fixed Prosthodontics, Chicago, Ill.
Disclosure: Dr. Shull reports no disclosures.
Disclosure: Mr. Roberts is owner of CMR Dental Lab and Team Aesthetic Education.
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