Effective Use of Dental Software Systems to Achieve Predictable Results: A Novel Approach

There has never been a more fertile field for the prosthodontist in search of pristine restorative solutions. The advent of a plethora of digital technologies puts various new tools at clinicians' fingertips with untold capabilities, and when studiously blended together, these digital innovations can repetitiously produce dramatic, dynamic results.

Evolving software applications for greater artistic understanding of ideal function and smile esthetics,¹ coupled with the ability to robotically produce precise replications of the design, afford practitioners a more streamlined treatment plan and the confidence to produce highly predicable outcomes. Software systems that employ a toolbox of extraoral instrumentation allow clinicians to both architecturally and artistically create a smile design that can be pre-approved by the patient.^2,3 Additional digital resources can then be relied upon to enable the clinician to assimilate data and commence the manufacturing of appropriate surgical guides, interim prostheses, and, ultimately, computer-aided design/computer-aided manufacturing (CAD/CAM) final prostheses that will precisely mimic the digital design.

The following case report describes a fixed full-mouth restoration. It discusses the basis for prosthetic smile design through digital workflows and describes how planning is predictably executed at the time of surgery. Innovative digital CAD/CAM processes are used to replicate the original planning for fabrication of the definitive restorations.

A 64-year-old systemically healthy Caucasian man presented with an edentulous mandible and six severely compromised remaining teeth in the maxilla (Figure 1). He was suffering from mild lack of self-esteem incongruent with an outgoing personality and was struggling to overcome this deficit. An accomplished guitarist and singer, he had become reluctant to open his mouth wide in public. The patient, whose spouse was employed at an oral surgery office, presented with high expectations, hoping to achieve a complete restoration of his smile despite lacking the economic means to pursue a conventional restorative solution. Such a solution might include fixed dental prosthetics made with porcelain-fused-to-gold alloy materials delivered through a delayed therapy with multiple surgical interventions for bone augmentation and implant placement. Mature patients with sophisticated dental knowledge and the need for cost-effective conservative solutions are driving the rapid acceleration of digital combinations to achieve desirable results. This case required skilled patient management, careful selection of materials, and streamlined clinical efficiency to effect the result.

A highly comprehensive diagnostic visit took place. Because the patient had no apparent health issues to circumvent, the clinician could immediately collect traditional clinical data and then move to a dentofacial analysis incorporating the digital smile design (DSD) protocol.⁴ This digital workflow concept prescribes the use of videography rather than still photography to determine ideal tooth size and shape as well as the curvature of the smile, with the premise being that "dento-labial parameters vary according to lip dynamic."⁵ Extensive still photographs of this patient from various angles incorporated with video clips indicating subtle differences in exposure with specific movements equipped the clinician with a comprehensive oral and extraoral profile.

Using a digital ruler and DSD guidelines, and beginning with the maxillary central incisors, the clinician selected tooth size and shape appropriate for the patient. Then, working with a precise mathematical formula, the clinician moved sequentially to the posterior teeth, creating the esthetic visual to be shared with the patient (Figure 2 through Figure 4). This patient "preview" of the anticipated clinical result in conjunction with a succinct written treatment plan can have a positive influence on patient acceptance while promoting realistic patient expectations in esthetic results.

Extraction of the six compromised teeth in the maxilla was indicated; therefore, the DSD dictated a plan for full upper and lower fixed prostheses. Adhering to Bidra's directives for photographically determining the midline and smile curvature,⁶ and following Coachman's protocol,¹the clinician established a working 2-dimensional (2D) smile design. By overlaying the 2D design on a 3-dimensional (3D) software program, occlusion was established and a surgical guide was generated for the placement of dental implants (NobelActive^®, Nobel Biocare, nobelbiocare.com) (Figure 5).

At the second clinical visit six implants were placed in the maxilla using traditional All-on-4^® treatment concept placement guidelines⁷ with two additional anterior implants (Figure 6). Tipping the implants distally helps reduce the length of the prosthetic cantilever to create a better distribution of implants.⁸ Five implants were placed in the mandible (Figure 7). The conversion prostheses fabricated from the data of the DSD were immediately loaded onto the implants (Figure 8). All postoperative indications confirmed that functionally and esthetically the interim prostheses had a precision fit.

The patient, who experienced little discomfort and no complications, was carefully monitored for 6 months after the surgical procedure. During this time the digital workflow to create the final prostheses was set in motion. For economic reasons but with full confidence in the viability of the product, the clinician opted to use an acrylic monolithic polychromatic restoration stabilized by a titanium bar (Nobel) for the milled final prostheses.

After confirmation radiographically that the patient's healing was ideal, final impressions were taken and articulated (Figure 9). The fabrication of the final prostheses then moved to the realm of the digital laboratory where burgeoning technology has elevated the importance of prosthodontic lab support to new levels. Partnering with a "sharp end"⁹ laboratory fluent in sophisticated scanning techniques and the biomedical engineering necessary to ensure selected materials for the prostheses will endure long-term functionality is critical to success.

According to Balshi and Balshi, most important to the outcome is the proper and accurate digitization of records. The ability to design and manufacture the substructure, superstructure, and milled custom teeth simultaneously reduces laboratory production time, translating to cost savings for both the clinician and patient while affording the dental team a comprehensive digital record if needed for replacement or repair.¹⁰

For this patient the clinician elected to use AvaDent^® Signature Teeth (AvaDent Digital Dental Solutions, avadent.com) for the final prostheses. In the author's experience, this system allows the clinician to control the size, shape, and color of each individual tooth, therefore enabling exact duplication of the DSD in the final restoration.

The scanning process for the manufacture of the prostheses included scans of the impressions both by themselves and with the conversion prostheses in place. The resulting STL files provided the manufacturer with the information needed to robotically mill the titanium bar and create the acrylic restoration with precision dental anatomy. The digital tooth positions and interocclusal record from the impression scans provided the manufacturer with the data needed to design the bar. The design STL files are then transmitted to an outsource service (NobelProcera^®, Nobel Biocare) for the fabrication of the stabilizing bar, which, lastly, is returned to AvaDent for the milling of the definitive restorations (Figure 10).

As defined by Bidra, this process is a "subtractive method of manufacturing that uses images from a digital file for the creation of an object by machining to physically remove material to achieve desired geometry."¹¹ For this patient, the resulting prostheses were exacting to the DSD in every detail. Once delivered at the second clinical appointment after healing (the first appointment being final impressions and scanning), no clinical adjustments were required. Moreover, the patient had no phonetic learning curve or occlusal variation from the conversion prostheses.

The digital workflow, from the patient's diagnostic visit to case completion, was seamless. An alternative restoration using milled monolithic zirconia was considered; however, current protocols with this material indicate an additional step for verification of fit and do not guarantee exact replication of esthetics, especially if the restoration is microlayered with veneering porcelain for esthetics. Additionally, concern has been expressed that not all patients can tolerate the mating of zirconia restorative abutments with titanium implants.¹² Abduo in a comparative analysis of CAD/CAM frameworks utilizing titanium versus zirconia concluded that the reliability of fit with both materials is similar, though for larger spans titanium may enhance durability.¹³ In the present case, the choice of acrylic to fulfill the patient's esthetic and economic requirements dictated that the titanium bar serve as the prostheses' stabilizer.

Approaching 1 year after the delivery of the final prostheses (at the time of this writing), the patient was clinically sound and well satisfied with both comfort and esthetics. His systemic health remained robust and he appeared to be much less reclusive, as can be seen when comparing his preoperative full-face smile (Figure 11) to his postoperative full-face smile (Figure 12). The implants were stable and the acrylic prostheses indicated minimum wear.

Effective fixed full-mouth restorations can be achieved with the use of a variety of primarily digital protocols. By incorporating a smile design system into the diagnostic visit, potentially heightened patient engagement in the outcome may increase the perceived value of the case. The combination of JPEG, STL, and DICOM files provides the volume of precise information necessary for the generation of the milled restoration. Materials for the final prostheses are chosen with consideration given to such factors as arch-span engineering, functional longevity, esthetic expectations, and patient economics.

Though the use of a monolithic polychromatic acrylic hybrid restoration empowered by DSD is a new dental solution in the marketplace, the predictability of the outcome, streamlining of clinical time to effect the restoration, and significant cost conservation are factors that could help usher this workflow into the mainstream. Also, the avoidance of denture therapy has wide appeal to most patients. According to Marinello, by the year 2050 there will be 2 billion people older than age 60 requiring complex restorative dental care that demands minimally invasive clinical analysis, high predictability, a quality product, and less patient involvement.⁹ The present case serves as an example of one meeting these requirements.

In the author's estimation, the most significant aspect of this approach is the involvement of highly skilled and knowledgeable digital laboratory support personnel to ensure that complex files are systematically and chronologically passed to the manufacturer. Thus, the DSD may then be translated into a tangible, custom-designed smile.

The author is a paid consultant for Nobel Biocare and receives honoraria from Nobel Biocare and AvaDent.

The author thanks Joanne M. Balshi for editorial assistance in generating this article.

Sundeep Rawal, DMD

Private Practice, Orlando, Florida