Esthetic Implant Abutment Solutions Using Pressable Lithium Disilicate
Combining lifelike functional and optical characteristics
Many factors contribute to the long-term success or eventual failure of dental implants and their respective restorations. Among these are esthetics; ease of retrieval, fabrication, and placement; fit; occlusion; and cost.1 Whether cement- or screw-retained, the type of dental implant restoration clinicians select for a given case must take these considerations into account.1
In weighing the challenges associated with both options at the time of placement, screw-retained implant crown restorations have been demanding, requiring management of screw-access channel closure to ensure proper occlusal anatomy, function, and esthetics.2 As a result, dentists have elected to attach implant crowns to the underlying abutment using cementation techniques.2 Although dental implants have commonly been restored with cement-retained restorations,3 residual cement adjacent to implant margins unfortunately has proven to be deleterious to periodontal tissues, as well as a contributing—if not causative—factor in peri-implantitis.4
The introduction of pressable lithium disilicate (IPS e.max® Press, Ivoclar Vivadent, www.ivoclarvivadent.com) has offered laboratory ceramists the means to provide dentists and their patients with durable, esthetic, and functional abutment solutions that eliminate the procedural challenges and potential clinical complications associated with cement-retained, implant-supported restorations. Lithium disilicate demonstrates strength of 400 MPa and is suitable for a range of indications, including thin veneers (ie, 0.3 mm), monolithic molar crowns, anterior and premolar bridges, and now hybrid abutment restorations. Its clinical success in a variety of indications has been documented in the literature.5,6
Pressed Implant Abutment Solutions
In combination with a titanium abutment, lithium disilicate represents a solution for hybrid abutments with separate crowns or hybrid abutment crowns. Both options enable laboratory ceramists and dentists to efficiently deliver implant restorations that demonstrate the lifelike functional and optical characteristics that today’s patients demand.
Hybrid abutment crowns combine a lithium-disilicate abutment and monolithic crown in one and represent an efficient two-in-one solution. To maximize esthetics and optical properties, restorations can be characterized simply using stains (IPS e.max® Ceram, Ivoclar Vivadent).
The monolithically pressed hybrid abutment crown is luted to the titanium abutment using a universal restorative primer and self-curing luting composite with light-curing option (eg, Monobond® Plus and Multilink Implant®, Ivoclar Vivadent), after which the restoration is screwed onto the implant in one piece. This eliminates the need to remove excess cement intraorally and greatly reduces the risk of cementoma, a known contributor to peri-implantitis and implant failure.7
The screw-access channel is subsequently sealed using composite material (eg, Tetric EvoCeram®, Ivoclar Vivadent). The screw can be accessed at any time, if necessary, which affords the dental team clinical flexibility.
Additionally, hybrid abutment crowns fabricated with pressable lithium disilicate also represent an economically attractive alternative to conventional implant-supported restorations. This is particularly significant for the posterior area, where strength, durability, and convenient clinical handling impact procedural efficiency and success.
For a more individualized solution, a hybrid abutment fabricated from pressed lithium disilicate allows for a superior adjustment of shape and emergence profile, as well as excellent esthetic properties, based on the clinical situation. Individual characterization produces a lifelike appearance near the root and transition area to the crown, which is particularly important for anterior implant treatments.
Because the crown preparation margin is located at the gingival level, the hybrid abutment geometry facilitates easy integration of the restoration, making removal of excess cementation material easy.7 Additionally, because the pressed abutment is extraorally luted to a titanium abutment using a universal restorative primer and self-curing luting composite with light-curing option and then screwed into place in the oral cavity, the process is time efficient and flexible. It then can be restored with a permanent lithium-disilicate crown.
As with all dental treatment options, success with dental implants is predicated on comprehensive diagnosis, patient selection, and treatment planning.8 Cases requiring titanium abutments that do not satisfy geometric requirements are contraindicated for pressed hybrid abutment and hybrid abutment crown restorations. Additionally, when hybrid abutment crowns are fabricated, the opening of the screw channel must not be located in contact point or masticatory function areas. If this is not possible, hybrid abutments with separate crowns are preferred.
Case Presentation
A 45-year-old man presented after losing tooth No. 4. The treatment plan involved placing a narrow-neck, 3.5-mm platform implant (NobelReplace®, Nobel Biocare, www.nobelbiocare.com) to be restored with a hybrid abutment crown restoration. The implant was placed, a punch technique was performed, and a healing cap was provided by the oral surgeon. As is standard for maxillary implants, 6 months were allowed for healing.
At the 6-month follow-up, the general dentist took a final shade for the lithium-disilicate-pressed hybrid abutment crown restoration (Figure 1), after which an impression coping (NobelReplace 3.5 mm) was placed (Figure 2). A coping impression was taken using an open-tray technique, which has been shown to be more accurate than closed-tray impression techniques.9,10 This coping impression—along with the final shade selection—was forwarded to the laboratory ceramist.
Laboratory Protocol
The laboratory ceramist selected a suitably sized titanium abutment (Snappy Abutment™, Nobel Biocare) (Figure 3). In general, it is advisable to select a titanium abutment with a size matching the clinical situation and chosen implant system. Geometry requirements must be observed, because adequate space is required for pressing the crown restoration. Titanium abutments with undercuts, such as retention grooves, are suitable to some extent; however, the undercuts must be blocked out to allow a path of draw for the subsequent wax-up.
A full-contour wax-up of the hybrid abutment crown restoration that detailed the occlusal access hole was created (Figure 4). The wax-up was contoured and designed to functional and esthetic criteria and checked in relation to the opposing dentition. Additionally, the emergence profile was verified, along with the transition to the titanium abutment. The wax-up then was invested and pressed with the selected ingot.
To best match the final shade selected by the dentist, a low-translucency (LT) pressable ingot (IPS e.max Press) in shade A3 was selected for fabricating the hybrid abutment crown. After pressing, the lithium-disilicate crown fit the titanium abutment perfectly (Figure 5).
Note that the fit of the abutment crown is verified on the titanium abutment prior to separating the sprue. Additionally, the inner aspect and screw channel should be checked for bubbles in the ceramic and, if present, removed with suitable instruments.
The pressed hybrid abutment crown was cut back for layering (Figure 6). The facial incisal edge was then layered with veneering ceramic (IPS e.max Ceram) (Figure 7), characterized, and glazed (Figure 8).
To complete the hybrid abutment crown complex, the titanium abutment base was sandblasted and treated with a universal primer (Monobond Plus, Ivoclar Vivadent) for 1 minute (Figure 9). Likewise, the inside of the pressed abutment crown was etched and then treated with Monobond Plus (Figure 10).
An opaque shade of self-curing/light-curing option resin implant cement (Multilink® Implant) was applied to the titanium abutment base (Figure 11), and the lithium-disilicate crown restoration was seated onto the abutment and cleaned (Figure 12). Liquid Strip (glycerin gel) was applied to the hybrid abutment crown, after which it was light cured (Figure 13) and prepared for delivery to the dentist (Figure 14).
Seating Appointment
During the delivery appointment, the IPS e.max Press hybrid abutment crown restoration was tightened into place (Figure 15). The restoration then was torqued to 30 nm (Figure 16). To seal the access hole, Vanilla Bite™ (DenMat, www.denmat.com) was first placed, followed by 1 mm of composite in shade A4 (Tetric EvoCeram) that was cured for 20 seconds. Then, a 1-mm increment of IPS e.max Ceram Incisal Bleach (Ivoclar Vivadent) in a shade matching the composite was placed and cured. Articulation and occlusion were verified, and the patient was re-appointed for a follow-up.
Conclusion
When placing implants for patients, the goal is to provide them with functional and esthetically pleasing treatments that help maintain their oral health. It is also important to achieve this objective with minimal changes to the soft-tissue areas and surrounding dentition, which can occur when excess cement in gingival areas results in cementoma and peri-implantitis, which is the main cause of implant failure. Fortunately, IPS e.max Press abutment solutions enables laboratory ceramists and dentists to efficiently restore implants in predictable, lifelike, and flexible ways (Figure 17 and Figure 18).
References
1. Cicciù M, Beretta M, Risitano G, Maiorana C. Cemented-retained vs screw-retained implant restorations: an investigation on 1939 dental implants. Minerva Stomatol. 2008;57(4):167-179.
2. Wadhwani C, Piñeyro A, Avots J. An esthetic solution to the screw-retained implant restoration: introduction to the implant crown adhesive plug: clinical report. J Esthet Restor Dent. 2011;23(3):138-143.
3. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: a prospective clinical endoscopic study. J Periodontol. 2009;80
(9):1388-1392.
4. Santosa RE, Martin W, Morton D. Effects of a cementing technique in addition to luting agent on the uniaxial retention force of a single-tooth implant-supported restoration: an in vitro study. Int J Oral Maxillofac Implants. 2010;25(6):1145-1152.
5. Gehrt M, Wolfart S, Rafai N, et al. Clinical results of lithium-disilicate crowns after up to 9 years of service [published online ahead of print Mar 7 2012]. Clin Oral Investig. 2013;17(1):275-284.
6. Silva NR, Thompson VP, Valverde GB, et al. Comparative reliability analyses of zirconium oxide and lithium disilicate restorations in vitro and in vivo. J Am Dent Assoc. 2011;142(Suppl 2):S4-S9.
7. Wadhwani C, Piñeyro A, Hess T, et al. Effect of implant abutment modification on the extrusion of excess cement at the crown-abutment margin for cement-retained implant restorations. Int J Oral Maxillofac Implants. 2011;26(6):1241-1246.
8. Liddelow G, Klineberg I. Patient-related risk factors for implant therapy. A critique of pertinent literature. Aust Dent J. 2011;56(4):417-426.
9. Al Quran FA, Rashdan BA, Zomar AA, Weiner S. Passive fit and accuracy of three dental implant impression techniques. Quintessence Int. 2012;43(2):119-125.
10. Kwon JH, Son YH, Han CH, Kim S. Accuracy of implant impressions without impression copings: a three-dimensional analysis. J Prosthet Dent. 2011;105(6):
367-373.
About the Author
Michael Koczarski, DDS
Private Practice
Woodinville, Washington
Nelson Rego, CDT
Smile Designs by Rego
Santa Fe Springs, California
