Matt Roberts, AAACD, and John Roberts, DDS

	Laboratory ceramists and their dentists often are faced with restorative cases that demand the use of a singular material capable of simultaneously providing conservative esthetics and sufficient functional strength. Lithium disilicate is increasingly being used in clinical situations demanding the highest physical and optical characteristics.

	Unlike conventional PFM restorations, lithium disilicate ­restorations are uniformly strong and esthetic and allow dental professionals to provide highly cosmetic restorations in a conservative manner. Additionally, the enhanced strength and presence of a glassy matrix allows dentists to either conventionally cement or adhesively bond lithium disilicate restorations.

 line of ingots expands the restorative possibilities for smile design and is ideal for enamel replacement with minimally invasive preparations. The new Impulse ingots include three Value shaded ingots in an intermediate translucency and two Opal ingots that provide dental professionals with a high level of natural opalescence to beautifully mimic the look of ­natural dentition.

	Created to meet the demands of dental professionals around the world, IPS e.max Press Impulse ingots can be used in single tooth restorations, bridges in the anterior, implant super structures, veneers and thin veneers. With a strength of 400 MPa, IPS e.max Press Impulse ingots demonstrate the same flexural strength of the original IPS e.max Press ingots and can be reliably pressed to as thin as 0.3 mm for veneers.

	The IPS e.max Press ingot product line, originally available in four translucencies (High Translucency, Low Translucency, Medium Opacity, High Opacity) and two sizes, has been greatly expanded with the introduction of IPS e.max Impulse ingots. By providing translucencies and new shades with the same exceptional strength of the original IPS e.max Press ingots, Impulse ingots enable dental professionals to provide their patients with the most functional and life-like esthetics possible in restorations requiring the use of lithium disilicate glass-ceramics.

	Developed with the same quality of Ivoclar Vivadent materials, IPS e.max Ceram Impulse veneering materials are specially developed to create individual characterization. Pressable lithium disilicate restorations (IPS e.max Press, Ivoclar Vivadent) are fabricated utilizing a hot wax press technique, and due to crystal size and length, the flexural strength of pressable lithium disilicate is 400 MPa.

	A healthy 61-year-old woman presented with the intention of replacing the bridge spanning tooth Nos. 10-12 for cosmetic reasons, but didn’t want her otherwise healthy tooth Nos. 6-9 prepared (Fig. A). The right-hand bicuspids (Nos. 4 and 5) previously had been treated with titanium post and cores, but at the time of presentation, the patient was uninterested in post build-ups and desired only composite build-ups.

	However, during a discussion of treatment options, the patient was informed that it would be possible to create a uniform appearance to her smile (i.e., including Nos. 6-9) by keeping tooth preparation to a minimum (e.g., only 0.3 mm). After demonstrating the proposed changes using intraoral mock-ups, she accepted the proposed treatment plan.

	The need to provide patients with minimal preparations while simultaneously addressing esthetic and color blocking issues (e.g., old dark tooth structure from root canal therapy) can require a combination of restorations that range from thin, for esthetics and conservation of tooth structure, to thick, for adequate strength. In this case, the restorative material of choice was lithium disilicate (IPS e.max), and in particular the recently introduced Opal ingot.

	Based on the diagnostic wax-up (Fig. B) and final impressions of the provisional restorations, the laboratory ceramist followed the following protocol to fabricate the lithium disilicate (IPS e.max Press Opal) veneer and bridge restorations:

 A wax-up for pressing was created using a matrix of the provisional model, which was trimmed to remove any areas without clear tissue detail, leaving a small piece of the palatal area to stabilize the matrix during injection.

 The matrix was placed on the model, wax was injected, and the wax was allowed to set for 3 minutes, after which the matrix was removed from the model.

 Using a scaler (Hollenbeck, Kerr Corporation), the margins were exposed, wax removed from the gingival area and any flash from waxing removed.

 After observing the clinical photographs, the midline of the provisional model was marked, along with the incisal edge positions of all teeth, and the width was checked with an electronic caliper (6425A Caliper, Central Tools Inc.).

 The stick-bite photograph then was studied to ensure the midline was in the proper position, and wax was added to create lobes to work with and reinforce the dominant line angle.

 The mesial and distal line angles were built-up with hot wax, followed by the emergence lobes. The middle was then filled, allowing the wax to flow to the newly established areas, ensuring that the middle lobe was high and that the mesial reflected more forward.

 Surface morphology was refined using a wax carving instrument (Premier Dental). After shaping the facial areas, the mesial and middle lobes were refined and their boundaries established.

 The incisal embrasures were worked and opened. Utilizing the back side of the carving instrument, the mesial lobe symmetry was refined. The emergence profile was controlled by building out just enough to set the facial plane and vertical axis.

 At this time, the contacts were checked to ensure they ran all the way to the papilla. To prevent the formation of black triangles, the interproximal areas were extended.

 To separate the embrasures, the contact was melted with the waxing instrument and cut through with a thin porcelain slicing blade (Tanaka Dental Products). The wax was then cut back to allow room for layering ceramic on the facial incisal aspect. Margins were resealed and the ­restorations were sprued for pressing. 

	After the interproximal embrasures were complete, the wax model (Figs. C and D) was sprued, invested and pressed with the appropriate shade of IPS e.max Press Impulse ingot. Then, the following ceramic layering protocol was followed:

 The midline was marked, the incisal edges were refined using a diamond bur (854 Bur, Brasseler USA), and the sprues were removed.

 Utilizing a sharp diamond (Brasseler USA) with light pressure and high speed, a rough reduction was completed to remove any scale layer left from investment. Every surface area of the restorations was freshened with the diamond, since lithium disilicate cannot be sandblasted, as per manufacturer instruction.

 A football-shaped diamond (Brasseler USA) was used to set up the dentin lobes and remove the reaction layer up to the contacts. With a diamond bur (863 Bur, Brasseler USA), the emergence profile and surface was worked to remove any remaining reaction layer and reestablish the desired morphology.

 Once the desired surface morphology was achieved, the color of the restorations was modified using a ceramic stain (IPS e.max Stain, Ivoclar Vivadent) and brush (Tanaka Dental Products), and color was added from the gingival to incisal. A ceramic glaze (Ivoclar Vivadent) was then applied to the restorations, which were fired at 770°F (Fig. E).

 To begin esthetic development, it was necessary to separate the lobes and extend slightly past the cut-back (Fig. F).

 Effect enamels (IPS e.max Ceram) were placed, beginning with Opal (OE 1) to create a silhouette, while translucency was reduced with a translucent incisal (TI 1) ceramic. Keeping the midline straight, the silhouette shape was built with incisal ceramic enamel. To create the mammelon effects, a light-colored ceramic (MM Light) was feathered on the tips of the dentin lobes. Salmon effect enamel (MM Salmon) also was used and carried to the incisal edge (Fig. G).

 Prior to firing, shape, color and value were evaluated and corrections made. The restorations then underwent the first bake (Fig. H).

 After baking, the lithium disilicate restorations underwent full contouring with an Opal enamel ceramic (OE 1) to replace what was cut-back during waxing (Fig. I). The lobe structures were filled and rebuilt to final anatomy prior to the second bake, after which any deficient areas were corrected, beginning at the midline and working out. The incisal embrasures were then reopened and the restorations fired a third time.

 After baking, the lithium disilicate restorations underwent a corrective procedure utilizing adjusting diamonds (Brasseler USA) to modify the contacts at the midline, based on the stick-bite. Excess ceramic was removed from the surfaces, and the incisal was blended into the surface morphology and embrasure form with an 863 diamond bur. Lines from the gingival two-third were extended into the incisal, without over-grinding the stained and glazed pressed ceramic (Fig. J).

 After smoothing the lingual incisal, functional movements were checked with an articulator and articulator paper. Once occlusion was verified, the distal line angle was softened, the lobes began to take form, and a natural flowing contour was created, with incisal spacing smallest at the midline and the dental lobes flowing into the incisal edge. The lobes were smoothed and shaped with soft angles to achieve ideal esthetics (Fig. K).

 Excess material was removed, the restorations were glazed (IPS e.max Glaze, Ivoclar Vivadent), and a final firing was completed at 725°F (Fig. L).

 After firing, excess glaze was removed from the surface with a diamond bur (850-016 Bur, Brasseler USA), beginning at the midline and working out. Minimal adjustments to the contacts were made to ensure a proper seal from the tip of the papilla to the incisal embrasure (Fig. M).

 A polishing wheel (Brasseler Gray, Brasseler USA) and light rubber wheel were used to smooth the surface of the restorations. A diamond strip was used to adjust the interproximal contacts, without pulling it all the way through, which would damage the restorations (Fig. N).

 To achieve a natural appearance, a rubber wheel was used to polish and smooth any high points in the restorations, which were then placed back on the articulator for assessment of functional movements. A diamond paste (Diashine, VH Technologies Ltd.) and a soft bristle brush (Robinson Brush, Bolton Dental Manufacturing Inc.) brought the surface to high luster, making the restorations ready for final cementation (Fig. O).

	Lithium disilicate restorations (IPS e.max) can be conventionally cemented or adhesively bonded. The patient was anesthetized, the provisionals removed, and the preparations thoroughly cleaned. After try-in of the restorations, the internal aspects were conditions with a single-component bonding agent (Excite F single), after which the selected shade of resin cement (Variolink Veneer +3) was applied. Proper isolation and gingival retraction was accomplished, and the preparations were conditioned with the single-component bonding agent (Excite F), desensitized (Gluma, Heraeus Kulzer), and cured. The restorations were seated individually, cured into place, and cleaned with glycerin and dental floss.

	Lithium disilicate restorations (IPS e.max Press) enable dentists to offer patients a conservative alternative for replacing previously placed PFM restorations and transforming the appearance of their smiles. In the case presented here, the patient was very pleased with the function and esthetics of the IPS e.max Press restorations (Fig. P), as well as the fact that only minimal tooth reduction was required.

	For a video of this technique, visit the Team Aesthetics and CMR Dental website at 

Articles

 Laboratory ceramists and their dentists often are faced with restorative cases that demand the use of a singular material capable of simultaneously providing conservative esthetics and sufficient functional strength. Lithium disilicate is increasingly being used in clinical situations demanding the highest physical and optical characteristics.

Matt Roberts, AAACD, and John Roberts, DDS

Articles

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