Volume 9, Issue 6
Published by AEGIS Communications
Solving a Complex Case
Selecting the right pressed ceramic materials for an extensive restoration
It is becoming more and more common for dentists to rely on the ceramist for advice on material selection and case planning when treating a complex case. The ceramist works with these materials on a daily basis and should therefore have a good understanding of the limitations of the materials as well as their various properties.
The objective for any ceramist is to fabricate the case from materials that are as translucent and vital as the teeth they are restoring. However, the ultimate determination of the material to be used is based on several factors. The stump shade determines the level of translucency that can be used and whether an opaceous liner or core is needed. Ivoclar Vivadent has expanded its range of IPS e.max® (www.ivoclarvivadent.com) ingots to allow the ceramist to select a high-opacity (HO) ingot, one that provides close to full block-out of the underlying prep or abutment. Five shades of the IPS e.max Press HO Ingots are available, and due to their opacity, they can be used as copings, which are then layered using IPS e.max Ceram. The level of opacity decreases as the translucency increases until the other end of the ingot scale—O1 ingot or opalescent 1 ingot—is reached. The O1 ingot is used whenever the objective is to use the underlying stump color and achieve a contact lens effect at the margins. Usually, the dentist’s preparation will be minimal to none, maintaining the enamel unless the preparation is for an occlusal inlay.
The habitual function, classification of the bite, and type of occlusion dictate the material to be selected based on degrees of strength. If the patient tends to be a bruxer or has a Class III or edge-to-edge bite, it may be advisable to select a material such as lithium disilicate for its 400 MPa of strength.
The ultimate goal when restoring any large case is to maintain harmonious muscle function and eliminate posterior occlusal interference to ensure that function is a priority while still achieving natural esthetics.
A 27-year-old man was dissatisfied with his “old man” smile, which he said was negatively affecting his self-confidence (Figure 1). He presented to his dentist with a pseudo Class III occlusion. He had two anterior porcelain-fused-to-metal (PFM) bridges (teeth No. 6 through No. 8 and No. 9 through No. 11) that were in atraumatic (hyper) occlusion with his lower teeth (Figure 2 and Figure 3).
The patient had been missing teeth No. 7 and No. 10 since the age of 12 years. During that period, he had been restored initially with Encore™ (Pentron Clinical, www.pentron.com) bridges, then later with the two PFM bridges. Due to the length of time that elapsed, some atrophy of the ridge had occurred in the upper lateral area. During the clinical examination, it was determined that the patient was in the beginning stages of posterior bite collapse. A significant amount of enamel was missing from his posterior teeth, resulting in a decreased vertical dimension.
At the initial consultation, a multiple treatment phase was determined. The first part of the treatment was to restore the patient’s collapsed vertical. Doing so would both restore a more youthful appearance to the patient and allow an increase in the anterior vertical dimension, thus possibly reducing the severity of his Class III bite by increasing his over-jet to as close to a Class I as possible.
A mock-up was done at the consultation by adding to the vertical and lengthening the existing anteriors with bonding (Figure 4). During the second phase of the treatment, the patient would undergo gum grafts and plumping as well as addition of bovine bone material to compensate for the severe bone loss on the maxillary ridge in the area of the laterals. Two implants would then be inserted, and finally the upper anteriors would be restored.
Lithium disilicate (IPS e.max Press) was selected as the material of choice to restore the patient. The reason for this selection was the strength and versatility of the material, in consideration of the patient’s bite classification, occlusal habits, and esthetic demands. In terms of versatility, three different ingots were to be used due to the manner in which the case was to be restored and the types of preparations that were needed to achieve the expectations of the patient.
The patient’s vertical dimension was increased using a fixed orthotic (Figure 5). After several months, a vertical that was harmonious to the patient’s muscles was established and temporomandibular joint dysfunction had been eliminated. A platform had been set for achieving occlusal stability and eliminating the patient’s previous posterior interferences and allowing anterior guidance to be achieved. The two PFM bridges were removed, and a set of temporaries was fabricated chairside (Figure 6 and Figure 7). Enough anterior clearance had also been established to allow a change in classification from an anterior Class III to a Class I.
A total of 18 teeth were to be restored, all as single units. The first phase was the lower molars and lower second premolars. To maintain the exact vertical of the orthotic, one lower posterior quadrant was replaced at a time and the first premolars were left untouched as occlusal reference points. The preparation was conservative and the margins were kept supragingival (Figure 8).
The underlying preparatory shade was not excessively dark. For that reason, a monolithic high-translucency (HT) ingot was selected to ensure an esthetic blend at the marginal junction without any concern about bleed-through of a discolored preparation. Due to the preparation, the crown thickness was not excessive, and therefore the brightness was maintained and the value was not lowered (Figure 9). The thicker the HT crown is, the more it reflects gray due to the black oral cavity. To maintain strength and brightness, the crowns were not layered, but instead were meticulously stained to achieve a layered appearance and depth of color.
During the period in which the vertical was established, the patient was undergoing gum grafts and plumping of the anterior maxilla, as well as the insertion of bovine bone mineral to restore the severely resorbed anterior region of the upper laterals. After treatment, implants were placed at sites No. 7 and No. 10 (Figure 10).
The next phase was to fabricate two custom gold abutments, which were opaqued in preparation for the lithium-disilicate crowns (Figure 11). Initially the crowns were pressed using a HT ingot and layered at the incisal one third (Figure 12). However, due to the labial thickness of the crowns caused by correcting the anterior Class III occlusion, the value was lowered too much, giving a grayer than normal appearance in the mouth and not matching the natural value of the lower anteriors (Figure 13).
The layering process used at the time also added to a drop in value, because layering the incisal one-third on an already translucent ingot created too much translucency. On future cases, when an HT IPS e.max ingot is used, only micro-layering will be done on a shallow cutback, where the incisal one-fifth will be feathered and layered only to create an internal mamelon effect and natural halo.
Teeth No. 4 through No. 13 were redone using an LT ingot, which was waxed to full contour and pressed. Six full crowns were pressed for teeth No. 6 through No. 11 and four onlays were placed on the upper premolars. The full-contoured crowns were then cut back on the labial and buccal thirds. The incisal was internally stained to create a natural mamelon effect and halo and was glazed to match the lower anteriors and recently placed lower posteriors. The anterior crowns were layered with a combination of essence powders (EO2 and EO4) to highlight the internal effects of the stains and to give a natural incisal effect, followed by Opal Effect 1 (OE1) impulse powder to create a slight halo and finally the Transparent Incisal (Ti1) from Ivoclar Vivadent.
The final shaping and length differed from the temporaries, as the patient wanted a more masculine shape and smile design and additional length to show more tooth by increasing his overbite (Figure 14). The upper crowns and onlays were bonded in with a clear resin.
The final phase of treatment on the patient was the preparation of the mandibular first premolars. The preparation was minimal, and the buccal margin was finished just below the incisal one third on the buccal. Due to the amount of reduction and the fact that the final shade and the underlying shade were going to be the same, an Opalescent 1 ingot was selected (Figure 15). This ingot is the most translucent of all the IPS e.max Press ingots. Because the preparation was more of an onlay-type preparation, it was important to get a very natural blend between the restoration and the tooth at the supra-gingivally exposed buccal margin. This was a stain-and-glaze procedure only, keeping the marginal area as thin as possible to create the contact lens effect. In this instance, only the occlusal one-third of the restoration was lightly stained, because this is where the material tends to be thicker and therefore pick up less of the underlying tooth color. Because the ingot is very translucent, the thicker it becomes, the more its value tends to decrease, and therefore it should be limited to minimally prepared cases as well as selective occlusal inlays. The final restorations were bonded with a clear resin cement to ensure that the marginal junction was unnoticeable (Figure 16).
The color between the first and second premolars was barely distinguishable, even though two different ingots—the HT and the O1—were used with varying degrees of translucency.
Often on a larger combination case that is being pressed, it is ideal to use the same ingot for the entire case to have the same degree of translucency and chroma and ultimately a harmonious color match. However, a certain preparation shade, implant abutment, or design such as a bridge should not determine the ingot selection for the entire case if it is not ideal.
For this particular patient, it was important to use different degrees of translucencies to accommodate the differences in thickness of the restorations between the upper and lower preparations. The upper anteriors had been previously prepped for PFM bridges; therefore, the reduction was more aggressive and the result was less tooth structure and thicker restorations. In addition, the objective was to achieve a more ideal classification of the anterior bite and added thickness to the restorations. The initially selected HT ingot for the anteriors resulted in the shade of the restorations having a value that was too low; therefore, a more opaceous LT ingot was used to press those crowns to achieve the correct shade.
Alternatively, had the same LT ingot been maintained on the lowers with the preparation design and supra-gingival margins, it would not have been possible to achieve the same result as the HT ingot and create the contact lens effect at the margins. The HT restorations were not cut back, but were stained and glazed only to achieve the correct value and ensure that the strength was maintained to accommodate the occlusal habits of the patient. The upper crowns were cut back to increase the translucency and create a more natural-looking restoration and a closer match to the lower anteriors (Figure 17).
daVinci Dental Studios
Los Angeles, California