A new digital denture procedure: a first practitioners appraisal

Abstract

Background: Historically, the complete removable denture is the last prosthetic procedure to switch to digital techniques whose advantages are mainly observed in the laboratory stages; however, it is not possible to measure the depressibility of the oral mucosa using optical cameras, thus conventional impression techniques are still necessary. This article describes the clinical and laboratory procedure and practitioners appraisal of the first fifteen digitally designed complete removable dental prostheses.

Methods: Several systems are now available including the Wieland® Digital Denture® which offers a complete procedure. This system is composed of a five axis-milling machine combined with a laboratory scanner and a design software application. Fifteen rehabilitations were carried out using the Wieland® system.

Results: The practitioner's role is simplified by intraoral recording with a central point and a reduced number of sessions. The prosthesis laboratory requires considerable investment in learning and equipment, making it possible to obtain ideal mounting assemblies in accordance with the occluso-prosthetic concept of bilateral balanced occlusion. The absence of polymerization and therefore of base deformation risks reduce the equilibration step. Finally, the creation of templates as an alternative to the assembly of teeth on wax makes it possible to functionally validate (masticatory and phonatory) the future dentures. However, this procedure still presented some limitations in terms of scanning and software scope of applications.

Conclusion: Digital denture design software is relatively efficient and helps to standardize clinical results. However, to this date, improvements of the software are still required for a routine use.

Keywords: Cad-cam; Complete denture; Digital denture; Milling.

Fig. 1

Centric Tray®

Fig. 2

Recording of preliminary inter-arch report with the Centric Tray® and high viscosity elastomer

Fig. 3

UTS CAD®

Fig. 4

UTS CAD® device connected to the Centric Tray® for recording deviations from the reference planes

Fig. 5

Measure of deviation from sagittal Camper plan

Fig. 6

Measure of deviation from frontal bi-pupillary plan

Fig. 7

Superimposition of Centric Tray® bound impressions with primary impressions

Fig. 8

Values of the UTS CAD® device are used to create primary digital model positioned on a virtual articulator

Fig. 9

The edges of the individual trays are drawn according to conventional recommendations

Fig. 10

A cutback is integrated to leave sufficient space for the intra-oral center-point recording system (Gnathometer®) and to avoid any interference between the antagonist occlusal rims

Fig. 11

Maxillary individual milled tray

Fig. 12

Mandibular individual milled tray

Fig. 13

Maxillary conventional functional impression with the manufactured tray

Fig. 14

Mandibular conventional functional impression with the manufactured tray

Fig. 15

Gnathometer®

Fig. 16

Gnathometer® can be easily clipped to tray impressions and does not require bonding or retention

Fig. 17

Gysi Gothic arch registered with Gnathometer®

Fig. 18

Gysi Gothic arch paths meet at an equilibrium area used as a reference during the inter-arch relationship recording step

Fig. 19

The use of elastomer material (silicone bites) allows shaping the lip support and locating the horizontal joint line of the lips

Fig. 20

The embedded functional impressions are scanned

Fig. 21

Numerical models are placed on the virtual articulator and identified reference points

Fig. 22

Drawing of the limit of the future denture base

Fig. 23

A teeth setting is proposed by the 3shape software with posterior teeth positioned in an ideally bilateral balanced occlusion concept

Fig. 24

Virtual waxes finishing step

Fig. 25

Manufactured template on a white PMMA disc

Fig. 26

Mandibular template

Fig. 27

Maxillary template

Fig. 28

The occlusion rims are validated and patients use their manufactured template for functional validation (mastication and phonation) for a while at home

Fig. 29

A retention silicone (Retention.Sil® Bredent®) can be used to replace the intra-prosthetic retention part if the patient already wears complementary retention system

Fig. 30

Milling of the denture extrados on a pink resin disc with specific alveoli for the prosthetic teeth, depending on the brand and model of the teeth selected

Fig. 31

A positioning key is milled to ensure the ideal setting of the teeth during the bonding process with a PMMA resin

Fig. 32

Once the bonding is complete, the disc is put back into the machine to mill the denture intrados. If a prosthetic tooth base interferes with the virtual model, it will be machined according to the correct intrados

Fig. 33

The dentures are tried and primary equilibration is performed

Fig. 34

First equilibration session, as all steps are validated