Occlusal appliances are frequently used for diagnostic, therapeutic, or protective purposes. Depending on the goal for an occlusal appliance, a specific design will be prescribed, including the selected arch, maxillary-mandibular relationship, and the desired occlusion (Fig. 1). Analog approaches are well documented, but increasingly, a digital approach to occlusal appliance fabrication is becoming more popular due to reduced costs and desired results.

occlusal appliances in clinical practice - segmental appliance (left), full coverage appliance (center), and specialty appliance (right)
Figure 1: Most occlusal appliances fall into one of three categories: segmental appliances (left), in which only some teeth are in occlusal contact with the appliance; full coverage appliances (center), which include occlusal contacts on all the opposing teeth; and what could be considered “specialty” or somewhat less common appliances (right).

Digital Approach to Occlusal Appliance Fabrication: Three Components

Classically, occlusal appliances have been fabricated from gypsum casts. While the analog approach is time-tested and can produce an occlusal appliance that fits well to the teeth and requires minimal occlusal adjustment at the time of insertion, it is also time-consuming for the clinician to acquire the clinical information, as well as for the technician fabricating the appliance.

With the rapid increase in clinicians using chairside digital scanning technologies, a digital approach to occlusal appliance fabrication is increasingly common, and workflows are emerging. As with all digital approaches to fabrication, the process may be broken down into three main components: acquisition, design, and manufacture (Fig. 2).

When most clinicians imagine a digital approach to occlusal appliance fabrication, they picture beginning the process with direct, chairside scanning of the patient. This is the acquisition stage. While it is certainly possible to scan an analog cast or even an analog impression doing so would limit the potential for improved efficiency with the direct digital approach. Accurate acquisition of the patient's clinical information is a key first step in fabricating an accurate occlusal appliance.

CAD (computer-aided design) — the digital design stage of appliance fabrication — is the most overlooked of the three components. Before any manufacturing may begin, a design for the appliance must be developed. This design step should follow the clinician's selected appliance design; it most closely follows the waxing stage of an appliance in an analog approach. Therefore, CAD requires specific software and associated learning curves for clinicians and is the last step that clinicians decide they want to perform in-house. (As an interesting side note: manufacturers and developers are hopeful that occlusal appliance design will soon be successful using artificial intelligence. SprintRay and 3Shape both currently offer A.I. designs for occlusal appliances.)

The third and final component in the digital fabrication process is actual manufacturing, or CAM (computer-aided manufacturing). Early digital approach to occlusal appliance fabrication, used a subtractive approach to the manufacturing process through the milling of a pre-polymerized puck and a large five-axis laboratory milling unit. However, milling acrylic resins is a slow process and is increasingly being replaced by additive manufacturing in dental laboratories and clinical practices. Since clinicians have already invested, or are considering investing, in desktop 3D print technology, occlusal appliances are a natural fit for in-house manufacture.

The following case illustrates how these concepts come together in a digital approach to occlusal appliance fabrication.

Digital approaches to occusal fabrication - acquisition scan of patient teeth (left), CAD design of casts in laboratory (center), CAM manufacture of final occlusal appliance (right)
Figure 2: Digital approaches to fabricating an occlusal appliance have three distinct components: acquisition, design, and manufacture. The clinician is often responsible for the acquisition, particularly if a chairside scanner is used rather than scanning gypsum casts in the laboratory. The design and manufacturing stages may be managed by the clinician or outsourced to a technician.

Clinical Example with Digital Fabrication

In this clinical example (Fig 3), a middle-aged male patient has been prescribed a protective occlusal appliance. The design selected is a full-coverage appliance for the lower arch with little to no steepness to the anterior guidance (often described as a “flat plane”). The appliance will have an occlusion developed with the condyles in a seated position (centric relation).

Appliance fabrication - scan of patient teeth
Figure 3: In the simplest form, a digital approach to occlusal appliance fabrication requires the clinician only to scan the patient chairside, record the interocclusal record, and transfer the information with the desired design to the technician.

Clinical information collected during acquisition must be accurate for the definitive occlusal appliance to fit well to the patient's teeth and require a minimum adjustment to the insertion appointment. Both arches were scanned directly following the manufacturer's instructions (Fig. 4 and 5).

photo of patient teeth (left), digital scan of lower and upper arches (right)
Figure 4: Successful and efficient occlusal appliances must fit well to the teeth and the patient's occlusion. Here, direct (or chairside) scans were made of the patient's lower and upper arches using Cerec Primescan (Dentsply Sirona), following the manufacturer's suggested protocol.
headshot of patient with articulator (left), digital scan of teeth (right)
Figure 5: Like the analog approach, the scanned arches will be positioned in a virtual articulator. While not critical for appliance fabrication, the maxillary “model” can be manipulated in the software to better transfer the esthetic position of the maxilla relative to the rest of the patient's face, following a clinical photograph.

Since the selected appliance is to function from a fully seated condylar position, the interocclusal record must capture the inter-arch relationship in this condylar position. In a fashion like what was described in my previous article on analog fabrications, the condyles are seated using a Lucia Jig (Great Lakes Dental Technologies, Buffalo, New York). For this patient, the prefabricated Lucia Jig increased the occlusal vertical dimension sufficiently to allow for a minimum of 2 mm of occlusal appliance material thickness. A leaf-gauge or bimanual approach could also have been used (Fig. 6).

Following a direct scan of both arches and fabrication of the interocclusal record at the desired occlusal vertical dimension, the jaw relationship was digitally acquired as the “buccal bite.” During this step, the silicone bite segments were left between the posterior teeth while scanning to minimize the risk of mandibular movement. The anterior deprogrammer is inconsequential for this step and was removed before scanning. In some cases, the buccal aspect of the bite registration material may need to be trimmed for the chairside scanner to detect enough common points to allow the files to stitch (Fig.7).

bite record (left), digital scan of teeth (right)
Figure 6: Here, the condyles are seated using a premanufactured anterior deprogrammer. If a different occlusal vertical dimension had been desired, the deprogrammer could have been adjusted, or a different approach to making the bite record could have been selected.
digital scans of patient teeth, front and side views
Figure 7: Since the clinical information is acquired digitally, the patient's interocclusal relationship will also be acquired directly. In this case, both segments of the PVS bite record were left in place while the “buccal bite” was scanned. An advantage to leaving the bite record in place is that mandibular movement is minimized, therefore also minimizing the risk of introducing error.

Since the interocclusal relationship was determined and recorded clinically, there should be little to no need to alter the occlusal vertical dimension in the virtual articulator. Minimizing alterations to the pin setting will also minimize the introduction of error into the case. Should the occlusal vertical dimension require alteration, clinicians should anticipate the possibility of increased occlusal adjustment at the insertion appointment (Fig. 8).

digital scan (left) and virtual articulator (right)
Figure 8: Because most currently available virtual articulators use average values, recording the interocclusal relationship at the occlusal vertical dimension required for the occlusal appliance will minimize the introduction of error in the occlusal relationships.

The acquired clinical information may now be transferred to the technician and the prescribed appliance design. While technology is required, specifically a chairside scanner for acquisition, the design and manufacture are now outsourced to the dental technician. An advantage to this approach is that no clinical staff time is required for either CAD or CAM, making it a great entry point for clinicians who are not currently printing in their offices (Fig 9).

Digital approaches to occusal fabrication - acquisition scan of patient teeth (left), CAD design of casts in laboratory (center), CAM manufacture of final occlusal appliance (right) with CAD and CAM highlighted
Figure 9: Clinicians have emerging potential workflow options for digitally fabricating an occlusal appliance. The most efficient is outsourcing the CAD (design) and CAM (manufacture) to a dental technician. In-office desktop 3D printers are becoming increasingly common, as are printable resins suitable for occlusal appliances.

The technician will design the appliance digitally and complete the digital manufacture using a milled approach. This approach closely follows the concepts clinicians are familiar with from analog occlusal appliance fabrication (Fig. 10-13).

Alternatively, the case design can be outsourced, and the design file returned to the clinician for in-house manufacturing. This approach is increasingly common with practitioners interested in desktop 3D printing but who do not want to spend time designing the case. Should a clinician want to exert full control over digital fabrication, a number of design software programs are available.

appliance inserted, patient teeth in MIP (left) and digital scan of teeth (right)
Figure 10: The interocclusal relationship captured clinically (right) and the appliance inserted (left). No alteration was required in the virtual articulator, and no adjustment to the occlusion was required at the insertion appointment. Maximum intercuspal position on the occlusal appliance is coincident with fully seated condyles.
Dynamic occlusal relationship in left and right lateral excursion.
Figure 11: Dynamic occlusal relationship in left and right lateral excursion. The anterior guidance is not flat but only has steepness sufficient to disclude the posterior teeth in excursions.
patient teeth in protrusive excursion
Figure 12: The anterior “ramp” is also visible in protrusive excursion.
milled occusal appliance
Figure 13: The occlusal contacts evaluated clinically required no adjustment on the milled occlusal appliance.

Why it Pays to Get this Right

With assorted designs and goals, occlusal appliances are common treatment options in many clinical practices. Since they are so common, small improvements in predictability and efficiency can add up to large savings over a year.

While it may seem overly labor intensive to virtually articulate casts with precise accuracy when fabricating something as ubiquitous as a protective occlusal appliance, the investment in time and effort spent during the acquisition phase is returned at the time of insertion in the form of minimal need for occlusal adjustment. A digital approach to occlusal appliance fabrication is the future.

Darin Dichter, D.M.D., is a member of the Spear Resident Faculty.


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