Two-visit CAD/CAM milled dentures in the rehabilitation of edentulous arches: A case series.

Computer-aided design-computer-aided manufacturing (CAD-CAM) has now found its place in the field of removable prosthodontics with the advent of its use in the fabrication of complete dentures. The conventional technique, by injection or compression molding using heat-polymerized resins, requires cumbersome laboratory procedures and up to five patient visits. For patients with time constraints and clinicians with a higher throughput rate, the CAD-CAM approach with a digital workflow can reduce the number of appointments and ensure speedy delivery of the prosthesis. This article describes the rehabilitation of completely edentulous arches using the Baltic Denture System (Merz Dental GmbH®) in just two patient visits.

INTRODUCTION

Complete removable dentures have been the mainstay of rehabilitating edentulous arches to date, though implant-supported prostheses are now gaining popularity. Prosthodontic therapy with implants may not always be feasible due to constraints and contra-indications.[1] The introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) technology in the field of removable complete denture prosthetics has now effectively reduced patient visits and decreased chairside time, thus expediting the otherwise cumbersome process.[2] This article describes the rehabilitation of 15 patients with a CAD-CAM removable prosthesis using the Baltic Denture System (Merz Dental® GmbH).

CASE REPORT

This article describes the rehabilitation of 15 edentulous older adults, five females and ten males, in the age range of 61–79 years with an average of 67.7 years. Among the patients, 12 of them were previous denture wearers, who were dissatisfied with their current prosthesis. A comprehensive examination was carried out with the aid of the Prosthodontic Diagnostic Index (PDI) Complete Edentulism Checklist,[3] based on the PDI classification system[4] by the American College of Prosthodontists. Twelve patients were classified as PDI Class I, which represented favorable diagnostic criteria with a good prognosis. The remaining three patients presented with a greater loss of residual alveolar bone height (16–20 mm) and hence were classified as PDI Class II. Due to the time constraints and a favorable ridge relationship, a CAD-CAM complete denture was planned for the patients using the Baltic Denture System after obtaining informed consent from them.[56]

The occlusal vertical dimension (OVD) was measured using conventional techniques, and an OVD reference was fabricated using a wooden tongue depressor, which was kept aside

The upper impression tray (BD Key®) of the appropriate size was selected and the extensions adjusted as necessitated [Figure 1a and b]

Figure 1

(a) The BD Key® Sets corresponding to the Load Blanks of various shades and sizes. (b) Armamentarium for impression making and registration of maxillomandibular relationship

Four tissue stops were incorporated in the stress-bearing areas on the inner surface of the maxillary tray using a pliable putty such as thermoplastic impression material (BD Impress®), which is softened at 75–85°C and later hardens to a plastic compound at the oral temperature [Figure 2]

Figure 2

Tissue stops incorporated in the upper key

The occlusal plane analyzer (BDKEY Plane® and the BDKEY Fin®) was attached to the upper impression tray following which the occlusal plane was oriented parallel to the interpupillary line and the Camper's plane. The facial midline and anterior tooth visibility were also verified [Figure 3]

Figure 3

Using BD Key® plane and Fin for orientation occlusal plane

Once the material set, the tray was removed from the mouth, and border molding accomplished using the thermoplastic impression material (BD Impress®). The orientation of the occlusal plane was reassessed initially and following border molding, using the easily detachable plane analyzer

The final wash impression was then made with light-bodied polyvinyl siloxane (PVS) (Virtual® Light Body, Ivoclar Vivadent AG, Liechtenstein) [Figure 4]

Figure 4

The maxillary final impression using polyvinyl siloxane

A centric lock (BD Key® Lock) was used to secure the lower impression tray onto the upper tray, following the application of three tissue stops (two in the molar region and one in the anterior region) [Figure 5a]

Figure 5

(a) Tissue stops incorporated in the lower key. (b) Making mandibular final impression using polyvinyl siloxane

The patient was guided into centric relation and made to the close the mouth until the appropriate vertical dimension was obtained

Mandibular border molding and the final impression procedure, using light-bodied PVS (Virtual® Light Body (Ivoclar Vivadent AG, Liechtenstein), were then carried out. The OVD was established and reassessed intermittently during this step [Figure 5b]

Frontal and lateral view photographs with the lips at rest and in smile were taken to assist the dental laboratory technician with the design fabrication and tooth shade selection

Once the esthetics and functions were reevaluated and the patient satisfied, the impressions were sent to the dental laboratory following the standard disinfection protocols

In the laboratory, an extraoral scanner (D2000, 3Shape®, Denmark) was used to scan the impressions and the bite registration [Figure 6a and b]

Figure 6

(a) Completed impressions with key set bite registration. (b) Extraoral scanning of the impressions and bite registration

A virtual three-dimensional model was obtained by importing the scanned data into the specialized software (BD Creator®). The functional borders and reference points such as the center of the ridge, the incisal papilla, and midpalatal suture were marked for aiding in aligning the teeth and even generating milling paths

The appropriate milling block (BD Load®) size and jaw width were selected along with the teeth. The software allows altering the vertical dimension of the scanned records by about 1.5 mm and any changes to the three-dimensional orientation of the occlusal plane could be brought about

The teeth setting could be rotated or moved to any position as desired, conforming to the anatomic landmarks. The denture base design with a border thickness of 2 mm (which could be increased if necessary) was generated by the CAD software, and the necessary relief was provided where desired [Figure 7]

Figure 7

Computer-aided designing using specialized software

The stereolithography file was then exported to the CAM software (WorkNC®, Vero India Software Pvt Ltd), and the final prosthesis was milled from the milling blank using a 5-axis milling machine (imes-icore® 350i Gmbh, Germany) [Figure 8a and b]

Figure 8

(a) Milling the computer-aided design/computer-aided manufacturing denture using a 5-axis milling machine. (b) Milled dentures ready for conventional finishing and polishing

Following the milling, the dentures were separated from the blank using rotary instruments, and conventional finishing and polishing were performed

The dentures were inserted at the second appointment and minor occlusal adjustments were carried out [Figure 9]. Overextensions of the denture flanges, if present, were altered, and the denture was finished and polished before delivery to the patient

Figure 9

Final prosthesis post insertion and adjustment

The patients were recalled after a week and then after 6 weeks for evaluation. They were visibly satisfied with the new dentures and did not face any problem in function [Figure 10]. The patients are scheduled for 6 months and yearly follow-up to evaluate the functional stability of the new CAD-CAM dentures.

Figure 10

Happy patient with his new dentures, in just two visits

DISCUSSION

Compared to conventional dentures, CAD-CAM dentures have been found to have reduced resin volume and weight, which can increase patients’ comfort and adaptability.[7] These dentures release little monomer; however, it has not been found to be statistically significant when compared to longtime, water bath, heat-polymerized dentures fabricated conventionally.[7] Studies have shown that CAD-CAM dentures fit better than that of conventional ones, which again increase patients’ tolerance and acceptability.[89] The intaglio surface trueness of the milled CAD-CAM dentures has been found to comparable to injection-molded and conventional techniques, which contributes to the success of the prosthesis.[10] Polymerization shrinkage is not an issue with these dentures as they are milled from resin blanks and hence result in fewer microporosities.[11] The absence of shrinkage also enhances the adaptation of the denture base.[89] However, it has been reported that CAD/CAM denture base resins do not generally have a higher fracture tolerance than manually processed heat-polymerizing resins.[12]

The biggest advantage of the Baltic Denture System is the reduced clinical visits, which is appealing to both the clinician (especially those with a higher throughput rate) and patients alike. The denture delivery is ensured at the second visit in comparison with other CAD-CAM systems currently available.[7] There is no concern of debonding of denture teeth from the denture base, unlike other systems,[7] as the teeth have already been incorporated in the milling blank in eugnathic lingualized occlusion. However, the inability to digitally customize the dentures and accurately verify centric relation is one of the drawbacks. This denture system is presently applicable only to patients with a favorable Class I maxillomandibular relationship, which is another limitation when compared with conventional techniques. However, there is a scope for extensive research, backed by long-term clinical studies in this relatively new technology, CAD-CAM dentures are here to stay!

Declaration of patient consent

The authors certify that they have obtained all the appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This research was supported by the DentCare Dental Lab Pvt. Ltd.

Conflicts of interest

There are no conflicts of interest.