Digital Workflows in the Management of the Esthetically Discriminating Patient

Traditional methods of designing and creating restorations are being increasingly replaced by digital processes. Software and hardware platforms for esthetic restoration design allow for local computer-aided design/computer-aided manufacturing (CAD/CAM) production. These systems are becoming ubiquitous and their strengths can be applied to the management of the esthetically discerning patient. This article takes a critical look at the effectiveness of digital workflows, including digital treatment planning using multiple datasets, linked digital workflows, digital restorative design, milled prototypes, and minimally veneered zirconia restorations. A complete digital workflow can be used in the treatment of the esthetically discriminating prosthodontic rehabilitation patient.

Key points

  • Digital CAD/CAM workflows are used in the preview, prototype and definitive esthetic prosthodontic rehabilitation.

  • New workflows allow for local CAD/CAM production of restorations for teeth and implants.

  • Intra-oral capture can be used as an entry point into the digital workflow.

  • CAD/CAM compatable materials in use are improving in esthetic and functional capabilities.

Introduction

The advent of digital pathways for the restoration of teeth and implants has matured in recent years. Digital design software is now an important tool that can assist in the dental rehabilitation of the esthetically discerning patient. When combined with direct digital capture of a patient’s pretreatment and prepared teeth, digital design software is used to simulate the patient’s eventual esthetic outcome. In addition, once approved by the patient and the dentist, the laboratory technician has the ability to convert these designs into durable precision restorations for use as prototypes of the patient’s eventual definitive restorative designs. Testing these restorations in function allows the patient and the dental team to confirm or to modify the designs before manufacture of the definitive restorations. The ability to efficiently design and manufacture esthetic and well-adapted restorations is now easier due to the advances in computer-assisted design and computer-assisted manufacturing (CAD/CAM) technology in the clinical and laboratory settings.

Intraoral scanning has been suggested as providing improved efficiency and accuracy for clinicians and laboratory technicians. Digital workflows for the design and manufacture of restorations have proved to be accurate and efficient in laboratories. Simultaneously, new restorative materials used in digital manufacturing are proving to be safe and effective. Esthetic performance is improving as manufacturers continue to adapt nontraditional materials such as translucent zirconia to the digital workflow. Technicians have become increasingly proficient with new colorants and new digital restorative designs and material manufacturing strategies. This article is written to illustrate the clinical and laboratory digital workflows and material advances that have taken place that can be effectively used for the efficient dental management of the esthetically focused rehabilitation patient.

Many investigators have validated the accuracy of intraoral scanning for the restoration of individual teeth and quadrants. Achieving cross-arch accuracy still presents a challenge when using intraoral scanning. The full-arch scan is an assembly of multiple smaller individual images. The reconstruction of the images to create a full-arch surface scan relies on built-in software to stitch images together. Theoretically, this may present distortions and may result in a misfit in the full-arch splinted or long-span restoration. Investigators are working to understand and validate the trueness and accuracy of the full-arch scanned intraoral impression.

However, when direct intraoral scanning is used in the individual tooth nonsplinted full-arch rehabilitation, the process yields highly accurate individual restorations with only minimal risk of discrepancy from cross-arch distortions. Individual tooth size is smaller than the field of view of the scanner image size. Therefore, the actual dimension of the tooth is not extrapolated from stitching. Cross-arch imaging can only be achieved by stitching multiple smaller images, and therefore cross-arch distortions can and do exist. Multiple accurately fitting individual restorations made from intraoral scans are registered for the laboratory and remounted with physical interocclusal registrations on an appropriate physical articulator and adjusted before delivery. In addition, the restorations are commonly adapted intraorally at the time of try-in for remounting in the laboratory and adjusted again before final delivery.

The patient presented in this article was treated using a complete digital process for the diagnosis, design, and manufacture of the complete maxillary arch restorations on teeth and implants along with multiple opposing mandibular restorations. The mandibular restorations included all mandibular molars and several incisor teeth. Digital intraoral scans yielded 3-dimensional (3D) digital diagnostic casts. Consultation with the patient was performed regarding her needs and a treatment plan was developed to achieve the esthetic and functional goals the patient requested. Conservative full crown preparations were performed on all treated teeth and conservative inlay preparations were used for the mandibular second molars. Optical capture was used for all final impressions and interocclusal registrations including the optical capture of implant scan-body positions for 2 molar implants. Multiple single-tooth restorations including provisional restorations and implant abutments were digitally designed. The contour of the restorations was designed in collaboration with the patient and laboratory with the dentist and patient present in front of the design station. Minor esthetic adjustments were facilitated through this process. All abutments and restorations were produced in-house using a digital design station and a 5-axis milling system, including an additional prototype set of milled provisional restorations (Zirkonzahn). The definitive restorative designs were made from the same initial files as the prototype files. The design chosen for the crowns used minimally veneered zirconia, and a monolithic lithium disilicate (Emax, Ivoclar, Liechtenstein) material was chosen for the bonded ceramic inlays.

Why use a digital process?

The use of a complete digital workflow in the treatment of this patient resulted in increased efficiency, accuracy, and overall effectiveness not previously realized by this investigator when compared with conventional means. In addition, an enhanced overall experience for the patient was noted as compared with past patients receiving traditional treatment methods. Digital design and manufacture of restorations from an optical impression allows for both laboratory and clinical effectiveness that might not otherwise be possible. Once the data are received by the laboratory, no impressions have to be poured. Implant analogs do not have to be adapted to a physical impression and no soft tissue casts have to be created around the implant impression posts. No casts have to be separated. No dies have to be trimmed or ditched. All of these steps are performed digitally in a fraction of the time, including the addition of die spacer and undercut block out. Digital waxing from tooth libraries occurs rapidly because global changes can be made to adapt the tooth forms to the patient’s tooth preparations in the virtual environment. Using a virtual articulator, adjustments can be made to the vertical dimension if needed and eccentric movements can be accomplished via the virtual articulation including the adaption of the digital restorative designs to prescribed average motion pathways.

Esthetics in tooth form, proportion, smile design, color, and texture can all be achieved via a digital tooth library and 3D modeling software. High-strength esthetic materials can be milled to make prototype provisional restorations. The milled provisional restorations have similar marginal accuracy as a final restoration and can serve to validate the impression accuracy, esthetics, and the interocclusal relationship on try-in. If the provisional is accepted by the patient or requires only minor modifications, then the delivery of the final restorations becomes a routine process because the final design files can be derived from the exact same files that created the provisional prototype. This can be done in collaboration with the patient. The definitive restoration files can be modified easily if desired and usually requires some modifications before final export for manufacturing. Moving from provisional acceptance to final restoration can be completed with confidence because the final restorations are not started from scratch, but rather they are improved versions of the same files. The manufacturing of the final crowns is performed digitally and robotically. Ceramists are able to input the most artistic effects in the finished result via a 0.8 mm facial cutback for conventional customized feldspathic porcelain layering. Ceramists now focus more on the artistry rather than managing the traditional porcelain buildup and compensations for feldspathic porcelain firing shrinkage and distortion.

Diagnosis, planning, treatment confirmation, and clinical workflows

The patient presented 7 years before treatment with a severely worn dentition. In addition, there were many broken down and carious involved teeth and restorations ( Figs. 1–5 ). A treatment plan was developed to address these concerns and also to address the etiological factors causing the destructive process. She was also interested in lightening her teeth and improving her overall smile while maintaining a natural color and appearance in order to match her untreated teeth. It was determined that in order to control the color and shape of the teeth a maxillary arch reconstruction would be indicated. The mandibular arch would receive multiple crowns as needed to control the occlusion and manage the excessive spacing. For many of the mandibular teeth, bleaching and direct composite restorations were indicated. The patient delayed the overall plan and had the maxillary right first and second molars extracted and wide-diameter implants placed. After waiting several years, the patient returned and requested to initiate the rehabilitative plan.

Fig. 1
Relaxed smile of the patient’s pretreatment condition revealing worn dentition.

Fig. 2
Retracted open-mouth view of the pretreatment condition revealing worn, carious, and fractured dentition with mandibular anterior spacing.

Fig. 3
Maxillary arch image of the pretreatment condition.

Fig. 4
Mandibular arch image of the pretreatment condition.

Fig. 5
Pretreatment panoramic radiograph reveals worn, carious, and fractured teeth.

Updated intraoral and extraoral photographs were made. Esthetic consultation was performed and treatment time and expectations were discussed and agreed on. Preliminary composite restorations and in-house bleaching with light activated carbamide peroxide was performed.

The patient was then appointed for tooth preparation and was treated with the assistance of an MD anesthesiologist using intravenous sedation. The 3Shape Trios Color scanner (3Shape Inc., Copenhagen, Denmark) was used for impressioning. The scanner software prescription was filled out including the implant locations, type of abutment designs and restorative material, and the design and shade desired for each restoration. Direct intraoral 3D optical scans of the unprepared teeth were made and stored. Local anesthetics were administered in the maxillary arch. Tooth preparations were performed using a minimally invasive thinly reduced crown preparation design described by Guess. Tissue displacement was accomplished using retraction cord, and local hemorrhage control was achieved using 3M ESPE Astringent Retraction Paste. Implant scan-bodies (Biodenta) were positioned on the implants in the maxillary right first and second molar positions. Final maxillary tooth preparation scans were completed and confirmed as well as scans of the implant scan-bodies ( Fig. 6 ). The scan data were copied, stored, and secured from automatic deletion. The patient received direct chairside provisional restorations created from a bisacryl material (Integrity Shade A1, Dentsply) using an irreversible hydrocolloid impression made before tooth preparation. The trimmed and polished provisional restorations were cemented with Temp Bond temporary cement (Kerr Dental).

Aug 9, 2020 | Posted by in General Dentistry | Comments Off on Digital Workflows in the Management of the Esthetically Discriminating Patient
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