Once considered a niche service, in-office milling is now a familiar concept for practitioners, as the ability to effectively restore patients’ teeth in just one simple office visit represents the most efficient means of restoring straightforward, single-unit posterior cases. With the adoption rate of digital impression technology continuing to climb, the introduction of lower cost and open-architecture digital impression scanners and milling units is allowing dentists to more readily implement a digital workflow into their practice.
“In the past, typical milling blocks required a two-step, technique-sensitive baking process. However, more recent advances have introduced milling blocks (BruxZir NOW, manufactured by Glidewell Dental) that are made from high-strength post-sintered solid zirconia and require no staining or glazing,” says Dr. Patel. When used with an in-office mill, restorations can be designed and fabricated in about an hour, then delivered to the patient immediately, affording valuable time savings for doctors and patients alike.
In-office milling is ideally indicated for single-unit posterior cases, such as molar and premolar crowns (Fig. 1). To get started, clinicians prepare the tooth and scan the preparation with an intraoral scanning device. The scanned image is transmitted to a dedicated computer workstation that is connected to the chairside mill. After a simple setup, the software quickly and accurately proposes crown designs based on the tooth being restored; the multitude of crown design tools require little effort to master.
Next, the doctor-approved design information is sent to the onsite mill where the clinician inserts the milling block and bur. At that point, the patient may step into the waiting room, opening up the chair for the next appointment.
After milling is complete, the crown is removed from the machine (Fig. 2). The clinician uses a high-speed diamond or carbonium disc to cut the sprue, and user-friendly polishing tools aid in achieving a highly esthetic luster.
The crown is then tried in. The occlusion and contacts may be adjusted; however, no adjustments, or very minimal ones, are typically required. After fit verification, the restoration is cemented to the tooth. The final delivery is straightforward and can be performed with ease (Figs. 3, 4).
“In my opinion, cutting-edge technology has made it seamless to implement an in-office delivery system. Crowns can be designed, milled, and readied for placement in about an hour with equipment such as the TS150 mill, manufactured by Glidewell Dental,” says Dr. Patel. While clinicians have successfully outsourced zirconia crowns to the lab in the past, performing the procedure chairside, on demand, allows for ultimate control over the case.