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The digitization of fixed restorations in dentistry is becoming the norm rather than the exception. Larger dental laboratories are reporting as much as 90% of fixed restorations being somehow digitally involved. In contrast, progress toward digitizing the removable prosthetic process has been slower. However, more digital options are becoming available, such as Pala Digital Dentures (Heraeus Kulzer, paladigitaldentures.com). In the following case, the authors and patient experienced an excellent clinical result while enjoying a very efficient, streamlined process that required half the chairtime usually associated with complete denture fabrication.
A patient presented with a reasonably functional and esthetic existing complete maxillary denture, requesting a replacement. The Pala Digital Denture was prescribed. The authors decided this was the perfect opportunity to work together with this new technology.
From a clinician’s point of view, the tray selection and impression making for a Pala Digital Denture turned 3 appointments into 1. Once the tray size was determined by try-in, final impressions were made without the need for preliminary impressions and custom trays.
A heavy bodied PVS material (FlexiTime VPS, Heraeus Kulzer, heraeus-kulzer-us.com) was used in the tray to capture the impression. Any spots that rubbed through to the tray were adjusted and the impression was relined with light-bodied material (Figure 1).
During the reline, border movements were captured by manipulating and pulling on the patient’s lips and cheeks while holding the tray in place on the hard palate.
To cut and remove posterior tray segments, a line was drawn with a fine-tipped marker to coincide with the posterior portion of the maxillary impression tray. It needed to be accurately separated so that the mandibular impression (or bite plate) could be placed and bite record and tracing could be taken without interference from the posterior border, preventing closure.
For the Centric Relations Record, using the Gothic Arch Tracing Device on the maxillary impression, and VDO pin on the mandibular impression or bite plate, the VDO was established by screwing the pin to the desired height to coincide with the patient’s preoperative OVD (Figure 2). The existing VDO was recorded.
To establish VDO to match, once the vertical height of the pin correctly matched the preoperative VDO, a tracing was performed to record mandibular border movements.
The Gothic Arch Tracing was performed by the pin on the slate, which had been applied to the center (palate) of the maxillary impression. The Centric Relation position was recorded by the pin on the slate, and that position was “dimpled” into the maxillary tray so the patient could repeatedly close into CR accurately. The maxillary and mandibular trays (or bite plane) were secured together with bite registration material in the Centric Relation position (Figure 3).
A special tool was used to measure lip length at rest and smiling, and those numbers were recorded on the prescription. The remainder of the information on the prescription was filled out—any special instructions are noted here—and the case was sent to the authorized Pala laboratory for scanning of the impressions.
Upon receipt of the case from the dentist, the technician read the prescription thoroughly.
The technician scanned the impressions and bite registration, utilizing a D900 scanner (3Shape, 3shape.com). The STL files were sent to the Heraeus Kulzer Pala facility for the fabrication of a 3D-printed prototype, which was then returned to the laboratory for try-in.
The printed try-in allowed the dentist to evaluate retention, VDO, tooth function and esthetics, phonetics, and occlusion. At this stage, any necessary changes can be noted and another try-in made if necessary. Minimal changes can be incorporated into the final prosthesis without the need for a second try-in visit (Figure 4). Retention, VDO, anterior tooth position for esthetics and phonetics, and centric occlusion were changed in this case.
Upon successful completion of the try-in, the case was returned to the laboratory for completion. The technician digitally requested that the case be completed in the appropriate tooth and base resin shades. The case was completed at the Heraeus Kulzer facility and returned for delivery.
Upon delivery of the case, the same parameters of retention, VDO, esthetics, phonetics, and occlusion were evaluated. Minor adjustments to occlusion were accomplished using articulating paper and acrylic burs to ensure maximum intercuspation in centric occlusion (Figure 5).
In this era of a shrinking technician labor pool and diminishing educational programs, the dental laboratory industry is faced with a catastrophic lack of qualified dental technicians. Nowhere is this more concerning than in the removable prosthetics arena. Pala Digital Dentures allow laboratories to provide high-quality complete dentures to their clients and patients without the overhead and inventory typically associated with this service. It also provides an opportunity to enhance the working relationship with the dentist by bringing predictable, streamlined techniques into the operatory and improving efficiency and profitability.
This article was supplied by Heraeus Kulzer.
About the Authors
David Avery, CDT Consultant Charlotte, North Carolina
Robert A. Lowe, DDS Private Practice Charlotte, North Carolina