Digital Designs and Fabrication in Restorative Practice

Even if a dental office does not utilize impression scanning or custom fabrication via in-office computer aided design/computer aided manufacturing (CAD/CAM), nearly all modern restorative procedures involve digital designs and manufacturing. For example, traditional impressions that are sent out are generally digitized by the laboratory, which uses the data to design and manufacture the prosthesis using CAD/CAM techniques. And with improvements in software and hardware, including milling units and three-dimensional (3D) printers — along with dropping prices — more offices are embracing in-house design and manufacturing.

To gain perspective on the digital aspect of restorative treatment, we asked SEUNG KEE CHOI, DMD, MS,of the Department of Advanced Oral Sciences and Therapeutics at the University of Maryland School of Dentistry to discuss strategies that will allow dental teams to take full advantage of CAD/CAM workflows.

Whether clinicians use an intraoral scanner to create digital impressions or a commercial laboratory digitizes traditional impression materials, digital scans are a cornerstone of restorative CAD/CAM practice. What are the advantages of intraoral scanning?

One clear advantage over conventional impression-making and wax-ups is the ability to form images of patient’s intraoral condition almost instantaneously. The advantages are analogous to obtaining radiographic images using a digital sensor versus conventional film. Using digital data, the clinician can quickly gain diagnostic values, such as occlusion and positions and proportions of teeth. Moreover, digital designs can be created in less time than diagnostic wax-ups, and can serve as an effective visual tool to communicate various problems to the patient, as well as when discussing treatment plan options.</p

Overall, clinicians and patients may find the evaluation/consult appointments more efficient using data obtained from intraoral scanning than those obtained via conventional impressions and wax-ups. In addition, the quality of treatment outcomes can be improved with intraoral scanning. Clinicians can evaluate tooth preparations immediately after an intraoral acquisition of the preparations, which can be magnified and visualized for details such as occlusal clearance, taper and smoothness. If necessary, modifications can be made chairside and the existing intraoral scan can either be modified or a new intraoral scan obtained in minutes. Based on the evidence that digitally fabricated restorations can provide equal or greater accuracy than conventional restorations, this quality assurance measurement should further increase clinicians’ and patients’ confidence in the outcome.^1,2

Digital systems have their own challenges in terms of data security and storage, but maintaining digital data does not involve the same issues as maintaining physical patient data in the form of casts, paper records and impressions. The use of dental stones and impression materials can be reduced or even eliminated from the clinic, increasing physical space while reducing cost and issues with storing and handling the material. Disasters, such as fire and flooding, can render physical patient data useless, but may not affect the integrity of digital data (especially if it is constantly backed up in a remote location). The efficiency of communicating with patients and colleagues (e.g., referring dentists, specialists and laboratory technicians) can also be enhanced through digital data.

Are there instances in which conventional impressions might be more appropriate than an intraoral scan?

In spite of the clear advantages of intraoral scanning, there are instances in which a conventional impression is more appropriate. One instance is difficulty in accessing the area of interest with the intraoral scanner. If the intraoral scanner utilizes a camera head design that is too large for the patient or the patient has a limited mouth opening, conventional impression technique should be used. In the areas of the mouth where space is limited (e.g., teeth #2, 15, 18 and 31), capturing the finish line around the interproximal area of the tooth preparation — which may require tilting the camera tip — can be extremely difficult. Last but not least, a patient who is not able to remain still may affect the accuracy of the scan or even make it difficult to acquire intraoral scans entirely. For these instances, conventional impressions should be considered.

When it comes to CAD software and designing restorations in-house, what’s involved in terms of costs, training and staffing needs? Are time constraints a factor in clinical practice?

Most CAD software programs are not free. In fact, in addition to the initial purchase price, many require an additional fee to receive software support and updates, which are often necessary to fix bugs in the programs. Companies may provide initial training at no cost. Beyond this, online media (e.g., social media and online digital study clubs) may provide useful forums for exchanging ideas for troubleshooting and creating solutions to challenges. However, users may find such forums inadequate to attain the necessary training to deal with daily hardware and software issues. In this instance, advanced training in the form of continuing education provided by an experienced clinician or company technician/ clinician will be useful — but typically entails additional costs.

A properly trained staff member should be designated as the in-house “expert” in digital technologies. An in-house laboratory technician may be the preferred arrangement for a very productive clinic since she or he can provide the necessary laboratory support. Of course, hiring a technician adds to the cost of operating a digital clinic.

Time is another cost associated with designing restorations in-house. It is likely that dentists will need to design the restorations themselves if their clinic lacks support staff (as mentioned above). Most clinicians will experience a learning curve, which can require considerable time initially. Furthermore, clinicians inexperienced with CAD software will find designing errors not only time-consuming to resolve, but also frustrating and discouraging.

For most routine restorations (single-unit crowns, for example), designing restorations using CAD software should be a relatively straightforward and efficient process, even in an office where additional trained staff members are not available. Still, a clinic that has the potential to be efficient with CAD/CAM should consider having a CAD/CAM-trained staff member so doctors can focus on maximizing their chairtime, rather than spending time with digital designs.

Workflow demands, clinician preference, and the dental team’s skill set will all affect this decision, so it really becomes an individual choice based on the practice. Speaking personally, the only reason I would ask the laboratory to design the restoration would be if I didn’t have time to design it myself and/or I didn’t have personnel in my clinic who were trained to handle the task. Other clinicians may prefer to delegate the design function to the lab, freeing the team for other procedures.

The same thinking applies to the fabrication process, as there are pros and cons to handling fabrication in-house or using the lab to manufacture the prosthesis. Table 1 provides an overview of the advantages and disadvantages of each approach.