Can Indirect Restorations Be Produced With the Same Level of Quality Without Using Digital Technology?

Russell Giordano II,DMD, DMSc, is an associate professor and the director of biomaterials in the Department of Restorative Sciences and Biomaterials at Boston University's Goldman School of Dental Medicine.

Jack Ringer, DDS, maintains a private practice in Anaheim Hills, California.

Amanda Seay, DDS: Whether or not digital tools are used in treatment, the critical foundations of quality clinical practice remain the same. Dentists must have the experience and wisdom to determine the correct diagnosis and appropriate clinical endpoint. They also must possess the understanding and skill to execute the treatment plan that was developed. If any of these foundations are missing, it makes no difference whether analog or digital tools are used-a successful result will not be obtained. In clinical practice, digital technology is a tool that can be used to achieve a quality outcome for the patient, but the tool is less important than the clinician's ability and will not compensate for any lack of foundational skills.

A digital workflow may be more efficient in achieving the same result that, historically, was created manually, but digital tools have many of the same shortcomings. If we consider the example of taking an impression, a good preparation design and a clear tooth/tissue interface must be present. A margin obscured by blood or debris will result in inaccuracy and a poor outcome whether the clinician uses a vinyl polysiloxane material in a tray or a digital intraoral scanner. Similarly, neither of these impression-taking techniques will compensate for a poor preparation design.

However, digital technology does offer workflow advantages when a well-designed and well-defined preparation is present. A scanned impression can save chairtime and may feel less invasive to the patient, particularly one with a strong gag reflex. Stone models will not need to be poured and shipped, and the impression information remains retrievable from the electronic file.

In summary, the tools-digital or analog-are only as strong as the clinician who uses them.

Russell Giordano II, DMD, DMSc: There are many different types of indirect restorations, including inlays, onlays, bridges, and single and multiple implant restorations. I believe that the type of restoration needs to be considered in the answer to the question. Inlays or Class II restorations are generally restored with direct composite resins. Although these are good materials, the restorations often suffer from porosity and poor contours and contacts. A machined restoration will be denser, and the contours and contacts may be better designed. Ultimately, I think that machined restorations are of higher quality.

As we move on to larger restorations, such as crowns and bridges, some type of impression must be made. A conventional physical impression is subject to distortion, both during impression-taking and after it is made. Oftentimes, the impression is put in a bag and transported to the dental laboratory. During transport, heat or cold can cause significant changes to the impression. In addition, steps involving cast fabrication and metal casting, or even ceramic pressing, have more potential for error inherent in the fabrication process. Digital impressions do not suffer from distortion, and machined restorations are generally made from blocks that are highly reliable due to consistent and highly controlled fabrication methods. There are numerous ceramic materials that can be machined for every clinical situation. Furthermore, 3D printing/selective laser sintering can produce full contour and metal frameworks with improved mechanical and physical properties. Yes, high-quality restorations have been made by hand for years, and they will continue to be made. However, digital technology may provide further improvements.

With respect to implants, I believe it is absolutely necessary to use digital technology to plan implant placement and the restoration design. Combining intraoral scanning with cone-beam computed tomography (CBCT) allows for placement of an implant in the ideal position so that it can be restored with proper function and esthetics. The use of a surgical guide based on the digital planning facilitates precise placement of the implant. This should become the standard of care. In fact, DMD students at Boston University use this technology to treatment plan and place implants with faculty supervision.

While I was a dental student, one of my favorite professors told me that there is a "range of acceptability" for dental treatments. Although all conventional and digital restorations can be made to fall within the range of acceptability, I believe that digital technology moves us to the high end of the range with improved and more reliable quality.

Jack Ringer, DDS: With change comes skepticism (eg, cameras going from film to digital), and as digital technology has been introduced into dental practices and laboratories, this skepticism has been evident in the dental community.

However, the continuing and expanding evolution and revolution of technology in dentistry has dramatically improved the quality of dental treatment due to one major factor: the reduction and/or elimination of the human element (and therefore the potential for human error) from the equation (ie, from the beginning to the end of indirect restoration).

Digital technology has made its greatest impact on dentistry in two primary areas. The first is diagnostics and design. Digital x-ray and CBCT scanners have given the practitioner the ability to diagnose disease (eg, carious lesions, cracks, etc) more easily and accurately than with analog methods. Studies have shown that, in addition to being as accurate or even more accurate than analog impressions, digital impressions make for an overwhelmingly better experience for the patient. Various design software applications have allowed the practitioner and laboratory technician to accurately design the proposed shape, position, and size of a patient's tooth/teeth before therapies such as orthodontics, implant placement, or entire smile makeovers are employed.

The second area in which digital technology has had the greatest impact is in the manufacture of restorations. With the advent of design software, strengthened ceramics and zirconia materials, and sophisticated milling machines, practitioners and laboratory technicians are capable of creating remarkably strong and esthetic restorations that fit with extreme accuracy without utilizing conventional, human-labor-intensive procedures, which potentially allow for the introduction of more errors and are more expensive for the practitioner and the laboratory.

Based on these and other factors, it's this author's opinion that a practitioner and laboratory cannot achieve the same overall quality of treatment without utilizing digital technology for diagnostics, design, and manufacturing.