Use of CAD/CAM in Second-Stage Implant Surgery to Achieve Improved Final Restoration Esthetics and Natural Gingival Appearance

David Dano, DMD; Laila Khalid, DMD; Eihab Mously, BDS, MSD; and Russell Giordano, DMD

Over the past several decades, use of implant-supported crowns for rehabilitation of an edentulous space has been a remarkable accomplishment in the field of dentistry. However, as patients have become increasingly aware of esthetics and clinicians have been compelled to step up efforts to improve this facet of implant dentistry, this type of restoration has become more challenging. As technology advances, highly intricate details are being incorporated into these restorations to attain a natural emergence profile around the implant crown.

This case report describes the use of computer-aided design/computer-aided manufacturing (CAD/CAM) technology in the second stage of implant surgery to scan, mill, and restore the implant site all in one office visit.

Case Report

A 30-year-old healthy female patient presented to the student clinic at Boston University's School of Dental Medicine for a single-implant restoration in an edentulous area of the upper right maxillary first molar, tooth No. 3. Six months prior, a sinus augmentation procedure using a lateral window approach and placement of 3 cc of freeze-dried bone allograft, followed by placement of a 5-mm x 10-mm Nobel Replace Select implant (Nobel Biocare, nobelbiocare.com) was performed in the BU Periodontology Department (Figure 1 through Figure 3).

The patient presented for a stage-two uncovering of the implant with same-day delivery of the final restoration. This approach would allow for the creation of an enhanced emergence profile and a highly esthetic result.¹ One carpule lidocaine 2% with 1:100,000 epinephrine was administrated via local infiltration, and a mid-crestal incision with a buccal surface full-thickness flap design was performed to uncover the implant (Figure 4).

A ScanPost impression post (Dentsply Sirona, dentsplysirona.com) was placed on the implant, and a bitewing radiograph was taken to verify proper seating (Figure 5). A digital impression of the implant position was taken with a CEREC^® AC Omnicam (Dentsply Sirona), followed by an impression of the opposing arch, the patient's correct bite, and gingiva using the Gingival Mask tool of the CEREC^® 4.4 software. This software was used to design the final restoration, which was produced using VITA ENAMIC^® IS (VITA Zahnfabrik, vita-zahnfabrik.com) block shade 2M, machined on a CEREC MC XL mill (Figure 6 through Figure 9).

The crown was tried-in intraorally and a bitewing radiograph was taken to verify proper seating of the various implant restoration components (Figure 10 and Figure 11). The final restoration was polished according to the manufacturer's recommendation and cemented to the TiBase (Dentsply Sirona) using Multilink^® Hybrid Abutment cement (Ivoclar Vivadent, ivoclarvivadent.com). Then, 3-0 chromic gut sutures were placed on the mesial and distal sides of the crown to approximate the buccal and lingual flaps. This was done to promote healing of tissue to attain the shape of papillae on both sides.

The patient returned for follow-up at 2 weeks (Figure 12) and 4 weeks (Figure 13) to evaluate the status of the peri-implant soft tissue, including its height, level, color, texture, and contour. At 4 weeks postoperative it was noted that the color, contour, and all other parameters of the peri-implant soft tissue matched that of the adjacent reference teeth, and natural soft-tissue appearance was achieved.

Discussion

As the paradigms of dental prosthetics continue to evolve, esthetics has become equally as vital as functionality. A wide demand now exists for the restoration of single missing-tooth spaces with implant-supported crowns, especially for esthetic reasons. To meet patients' desires for lifelike restorations, there is an inference that “pink esthetics,” also known as soft-tissue esthetics, are as important as “white esthetics” (ie, superstructure for implants).²

To attain an optimal reconstruction of the soft-tissue architecture, several objective parameters must be accomplished. Embrasures that fill with papillae, contours, and morphology of the mucosal margin, as well as the color similarity with adjacent mucosa, need to be evaluated. Fürhauser et al introduced an objective index, the Pink Esthetic Score (PES), to evaluate the soft-tissue architecture around a single implant that might change over time. PES is a reproducible index and could be a useful tool for monitoring long-term soft-tissue alterations.^3,4 To meet patients' esthetic demands, clinicians and researchers have experimented with different biomaterials to compare outcomes.^2,5

CAD/CAM-milled customized abutments have shown superior results relative to conventional standard abutments in maintaining the papillary fill and natural emergence profile.^6,7 Not only do they provide the natural scalloping of the peri-implant soft tissue, but they also meet the white esthetic criteria and, due to the direct chairside fabrication, offer a faster approach for restoring a missing-tooth space. CAD/CAM-produced implant crowns in a complete digital workflow represent a feasible treatment option for rehabilitation of a missing-tooth space in either the esthetic zone or a posterior region where strength is of utmost importance.⁸

Use of an intraoral camera to obtain 3-dimensional digital scans for both the implant and soft tissue affords the clinician an opportunity to record the implant platform with the aid of a standardized implant scanbody and mucosal architecture chairside with precise details. These STL files are incorporated in the CAD/CAM system for milling the CEREC crowns, which can be provided to the patient in the same office visit.⁹ For a predictable esthetic outcome of the emergence profile, digital impressions provide a fast and simple approach to capture the hard- and soft-tissue details and plays a pivotal role in a full digital workflow.¹⁰

There are various biomaterial options for successfully restoring an implant, including full-contour zirconia, full-contour glass-ceramic (eg, e.max^®, Ivoclar Vivadent), a zirconia abutment with a machined ceramic crown, or porcelain-fused-to-metal. For this case the authors used a CAD/CAM-milled ENAMIC crown to restore the implant for several reasons. Besides being the only alternative to glass-ceramic currently approved for full-contour restorations, this material does not require post-machining processing other than polishing, which helps significantly decrease delivery time. Also, it may be easily adjusted as needed to further improve the proper emergence profile and tissue contours. ENAMIC is a polymer-infiltrated-ceramic-network (PICN) that offers outstanding esthetics and mechanical properties that closely resemble the natural dentition, including excellent fracture resistance.^11,12 This interpenetrating phase ceramic matrix material is designed to improve resistance to fracture and decrease stress transmitted to the implant. Its interconnected network of ceramic and polymer creates an infrastructure aimed at ensuring adequate stiffness and resistance and preventing crack propagations. The material has a response to stress that is similar to tooth enamel, and its high fracture toughness is due to a crack deflection mechanism related to the interconnected structure.¹³

Resistance to damage under stress is particularly important for restorative materials used with implants, because loads placed on the implants by the patient can be several times higher than normal biting force due to lack of proprioception. A study by Coldea examined damage tolerance of a variety of materials, including glass-ceramics, porcelain materials, zirconia, and a PICN, and the latter material demonstrated the highest resistance to indentation damage.¹² This study replicated the high occlusal stress that might be placed on a restoration and demonstrated that the microstructure of an interpenetrating phase material provides resistance damage that may occur clinically. Natural teeth have a microstructure that allows for damage to be contained, as many teeth have multiple cracks yet survive for the lifetime of the patient. Materials that can sustain damage yet survive are needed clinically, which is one reason why zirconia-type materials are in widespread use.¹⁴

Conclusion

Biomaterial options for chairside restoration of dental implants include zirconia (many types), lithium-disilicate glass-ceramics, such as e.max, and interpenetrating phase ceramics, such as ENAMIC. A variety of considerations must be taken into account when selecting a material, including fabrication time, post-machining processing, ease of adjustment, resistance to stress, and esthetics. As shown in this case report, the polymer-infiltrated-ceramic-network material offers an efficient workflow, with decreased machining time required, an ability to be easily contoured, and needing only polishing, leading to significant time savings. The PICN material may also provide decreased stress transfer and enhanced damage resistance, helping to make it a viable option for restoration of implants.

DISCLOSURE

Dr. Giordano conducts research with numerous companies that provide materials and monetary support, including Dentsply Sirona, Ivoclar Vivadent, and Vita Zahnfabrik. He is the inventor of the ENAMIC material.

ABOUT THE AUTHORS

David Dano, DMD

Clinical Assistant Professor, Department of General Dentistry, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts

Laila Khalid, DMD

Private Practice, Nashua, New Hampshire

Eihab Mously, BDS, MSD

Assistant Professor, Periodontology Department, Taibah University, Medina, Saudi Arabia

Russell Giordano, DMD

Associate Professor, Department Restorative Sciences & Biomaterials, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts

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