Discussion
Extreme residual ridge resorption is a challenging clinical situation
for the fabrication of complete dental prostheses and there are no
clinical reports of CAD/CAM workflows for complete prosthesis solving
this complicated situation. This workflow combines traditional and novel
techniques in order to fabricate digital complete dentures in patients
presenting extreme alveolar ridge atrophy. Due to the short height of
the ridge, it was decided to make the conventional final impression
following the functional impression technique using her current complete
dentures. Making the final impression using the patient’s existing
denture as the impression tray has been shown to be a successful
approach for atrophic ridges.31,32 Conventional
mounted master casts and can be either scanned by the clinician or
simply mail them to the dental laboratory. Once the digital file is
created, the computerized designs of the complete removal dentures are
made, and the clinician can access online and have full control of the
tooth shape, shade and arrangement, denture plate color and anatomical
features. After the dentist approves all the features, the company ships
the restorations in short time.
Wearing complete denture for several years may have adverse effects on
the alveolar ridge bone as well as on the keratinized mucosa, and
unstable denture wearing may cause adverse undesirable such as extreme
alveolar atrophy of alveolar ridge.33-39 Mandibular
atrophic ridge sometimes can be so advanced that the short mandibular
height40 makes it almost impossible to deliver a
stable and well-functioning complete dentures with conventional
techniques, and as a result it leads to chewing difficulties, pain, sore
spots and poor oral health-related to quality of
life.41,42 Unfortunately, due to high costs involving
implant therapy, complete dentures still the first choice of treatment
for patients with financial constraints, so it is imperative to have a
well-fitting prosthesis in order to improve the patients’ quality of
life.
Milled complete dentures can be either fabricated all in one piece with
base plate and teeth together or separated as this case report whereas
the denture based is milled from a puck and the milling of the teeth
from another puck. Milling both pieces separated provides higher
esthetic results because there are multi-chromatic discs offering shade
degradation to give high esthetics to milling of teeth. Moreover, in a
situation whereas the patients break the teeth, there could be an option
merely to mill the teeth and bond them to the existing plate without the
need of milling a new entire base plate.
There are numerous techniques for the final impressions making in the
edentulous arches.43-47 This clinical situation was
complex because the patient had been wearing the existing complete
dentures for the last 15 years and the residual alveolar ridges in the
mandible were excessively reabsorbed and atrophied. Due to the short
height of the ridge, it was decided to make the conventional final
impression following the functional impression technique using her
current complete dentures. Making the final impression using the
patient’s existing denture as the impression tray has been shown to be a
successful approach for atrophic ridges.48,49Unfortunately, the patient needs to wait in the dental clinic while the
clinicians pours the impression and fabricate the conventional master
cast.
Milled complete dentures, including the teeth, are made out of
prepolymerized resin acrylic pucks and teeth are bonded to the plate
using a proprietary bonding mechanism in the milled recesses. This resin
puck is produced under higher pressure and heat, so polymerization
shrinkage does not happen and the porosity decreases and the adherence
of Candida Albicans to the base plate decrease.14Polymerization shrinkage absence in the complete milled dentures results
in a highly accurate denture fitting and improvement of
retention.50,51 The CAD/CAM company (AvaDent Digital
Dental Solutions, Scottsdale, Arizona, USA) offers all the tooth shades
and shapes that are available in conventional denture fabrication for
the milled prosthesis. Moreover, the digital construction of the
complete dentures allows the designer to define the minimal thickness of
the denture base and to include anatomic features on the denture base
plate. The company provides the clinician the opportunity to logging
into their website to modify the teeth set-up before milling the final
prosthesis.52-56 The Avadent®(AvaDent Digital Dental Solutions, Scottsdale, Arizona, USA) order form
demands the clinician to select the type of occlusal scheme, tooth
shade, denture base colour, the set-up of position of the anterior
teeth, and optional anatomical details for the denture base. The type of
occlusal schemes offered are the anatomical, lingualized and
flat-on-flat, which resembles the options provided by traditional
denture teeth companies. The denture base color options include light
shade, original, standard, medium and extra dark; these shades could be
selected to match the patient’s gingival color.
The anterior teeth position and arrangement are also available options
for the clinician and patient, it offers the regular set-up, and other
options such as flared out central incisors, rotated lateral incisors,
palatalized lateral incisors, with small overlap among them, and with
small diastemas between all anterior teeth. The extra anatomical options
for the denture base include the root prominence, stippling, rugae,
gingival staining, frenum depth to match impression, posterior palatal
seal, buccal roll and engraving the patients name on the base. The
company (AvaDent Digital Dental Solutions, Scottsdale, Arizona) also
offers a wide variety of teeth shape and shades including the designs of
the traditional denture teeth.
Trying to incorporate new technology or clinical techniques can be
challenging because clinician needs to become familiar with the software
and operating equipment by the dental laboratories to maximize the
dental care options for patient care. Due to the investment in novel
equipment, laboratory costs may be increased compared with conventional
methods.57 The laboratory companies may offer the
clinical non-color trial dentures before the milling of the final
prostheses however those trial dentures also have extra costs and its
try-in will require an additional appointment for the patient. A
previous study comparing the trueness fit of the intaglio surface of
conventional and CAD/CAM dentures demonstrated significant improvements
for the conventional prosthesos.58 However, as
technology improves, newer studies have shown improvements of the
CAD/CAM prosthesis.18
Several studies have indicated that prosthodontic management of
anthropic mandibular ridges can be very
challenging.59,60 The present case report successfully
combines the advantage of CAD/CAM technology and traditional clinical
recording methods for the construction of complete dentures in atrophic
alveolar ridges. The presented workflow is completely functional because
the clinician does not need to have either an intra-oral or laboratory
scanner to offer CAD/CAM dentures to patients. Following this protocol,
the clinician can do conventional final impressions, jaw relation
records and mounting, then it can be either sending those mounted
records to the laboratory in order to fabricate CAD/CAM dentures. If the
dental office has a laboratory scanner, the records could be scanned and
the STL file would be sent to the company. The combination of this
workflow provides the necessary critical information of
maxillomandibular relationship with conventional techniques and the
improved material properties and fit of the milled dentures.