June 2017
Volume 38, Issue 6

Peer-Reviewed

Today’s Solutions for Edentulous Patients: Implants, Digital Dentures, and Streamlined Technologies

David Little, DDS

Dentists and an increasingly widespread patient population are more keenly aware today that implant-retained dentures resolve many of the issues associated with conventional removable full-arch prostheses. Dentures supported by up to six implants provide patients with a more secure and stable fit, greater overall comfort, enhanced facial support, and improved functionality. Additionally, when implants are placed to support a full-arch overdenture, a decrease in bone loss and resorption is usually observed.1,2

The benefits of implant-supported overdentures, however, extend beyond those that are physical and are perhaps most dramatic in terms of the positive psychological and social effects they can have on the lives of edentulous patients. Improved self-esteem, better satisfaction with their appearance, greater confidence when speaking and chewing, and more comfortable social interactions are among the many emotionally based advantages of having secure and comfortably fitting overdentures supported by dental implants.3

A number of digitally based technologies have contributed to the predictability with which dental implants can be placed and overall treatments planned, including those involving overdentures. Three-dimensional (3D) imaging, such as cone-beam computed tomography (CBCT), enables dentists and specialists to precisely plan implant treatments in the ideal location and at the proper angulation, and determine the appropriate implant size, length, and diameter to help ensure predictable outcomes. Computer-aided design (CAD) software facilitates implant treatment planning using 3D images, whereas computer-aided manufacturing (CAM) processes are used to produce accurate surgical guides for precise implant placement. Today, however, the power of these same CAD/CAM technologies can be harnessed to streamline the processes involved in fabricating full-arch denture prostheses.

Digital Denture Fabrication Process

Using digital technologies and dental implants, dentists can provide edentulous patients with solutions that are more stable and lifelike than conventional removable denture prostheses. Because they are planned and fabricated using digital processes, these alternatives can usually be delivered in less time and with fewer appointments than traditional dentures, thereby contributing to a better overall patient experience and creating less frustration for dental professionals. Whereas the processes involved with generating conventional full-arch denture prostheses are time-consuming and require multiple patient appointments, digital denture processes, whether CAD/CAM or 3D printing, enable final dentures to be treatment planned, tried in, and delivered in as few as two or three appointments.

For example, during the first patient appointment in conventional denture processes, a preliminary impression is taken and sent to a dental laboratory to make a custom tray. This tray is then returned to the dentist to use when taking the final impression during the second patient appointment. The final impression is sent to the laboratory and a base plate and occlusal rims for the denture are made.

The patient then returns for a third appointment, at which the completed base plate and occlusal rims are used for mounting and setting up the denture teeth, and the patient’s vertical dimension and centric relation records are taken. This information is sent to the laboratory, where an analog wax-up of the denture prosthesis is created for the patient to try in during the fourth appointment. Unfortunately, the wax rim/base plate molding process has considerable potential for discrepancies, and the resulting try-in usually does not represent how the final removable prosthesis will fit, feel, or function.4

During this appointment, the wax-up denture is tried in the patient’s mouth, after which it is returned to the laboratory for processing and finishing of the final denture. During yet a fifth appointment, the patient receives the final denture, and any adjustments are performed at subsequent appointments.

With digital processes, however, all of the information required for designing a patient’s dentures is acquired and/or captured during the first appointment and converted and/or stored in a digital format.5,6 Either traditional analog impressions can be taken, or an intraoral 3D digital impression scanner can be used to capture various digital impressions for use in establishing vertical dimension, centric relation, etc, when wax-free, rapid 3D prototyping is performed at the laboratory. The laboratory uses the digital impression file to create a virtual wax-up using CAD software on a computer to set and move the denture teeth, after which a CAM-produced try-in prototype (ie, wax-up) is made, which is typically a better representation of how the final dentures will look, fit, and function.5,6 The highly accurate prototype makes the try-in appointment much easier and less time-consuming.7 Alternatively, the dentist could choose to forego the try-in phase and a final denture could be made; therefore, only a single patient appointment would be needed before delivery of the final denture.

Other Benefits

Besides fewer appointments and a streamlined workflow, digital dentures offer a variety of other benefits. First, dentists typically do not need to invest in digital hardware or software, although digital intraoral scanning is proving to be more efficient and accurate than conventional analog methods for many restorative procedures and is, therefore, a worthwhile investment.8 Also, the digital denture process involves fewer record-taking and fabrication steps than traditional denture procedures. Because they are not as labor-intensive as conventional removable prostheses, digital dentures could be more accurate, cost-effective, and efficient options for edentulous patients. Finally, because the information necessary to design an accurate, comfortable, and esthetic denture is retained in a digital format, a permanent record can be maintained for future use if a replacement or duplicate denture is required or if modifications to a previous denture are needed.

Several manufacturers offer digital denture solutions, including AvaDent, DENTCA, Digital Dental Lab, Pala Digital Dentures, and 3Shape. Each uses a similar method for capturing and digitizing impression records. However, they differ in terms of how the final denture is fabricated (ie, either milled or 3D printed). Digital dentures that are milled (eg, AvaDent, Digital Dental Lab) are fabricated using solid blocks of ceramic or composite resin through subtractive manufacturing. With this method, the denture teeth must be placed in the milled denture, a process that takes longer than 3D printing. When digital dentures are fabricated through 3D printing, such as those from Pala Digital Dentures, additive manufacturing—or fabrication via a traditional injection mold process—is used.

Abutment and Attachment Options

Today, a variety of implant abutment/attachment options are available for retaining and securing full-arch dentures, depending on the clinical situation. These include screw- or cement-retained attachments as well as hybrid abutment/attachments. Hybrid solutions (eg, SynCone® or Atlantis™ Conus, Dentsply Sirona Implants, dentsplyimplants.com; Straumann® CARES® System 8.0, Straumann, straumann.us; BruxZir® Shaded Zirconia Hybrid Abutments, Glidewell Laboratories, glidewelldental.com) incorporate a cement-retainable prosthetic component positioned on an abutment that is used with a screw-retained metal cylinder; this option is ideal when angled abutments are required. The benefits of newer abutment/attachment systems include reduced stress levels at the implant/prosthetic component, lower stress concentration in supporting tissues compared with the splinted bars or frames used in years past, and overall predictable stability and retention for implant-supported overdentures.9

Thoughtful care and planning are required, however, when using these abutment/attachment systems. Retained cement is a known risk factor for peri-implant diseases and subsequent implant failure.10 Also, when using screw-retained systems, planning is needed to determine the ideal location of the screw-access hole to ensure it does not negatively affect esthetics or function. Hybrid abutment/attachment systems can be affected by both of these issues.

Despite advancements in abutment/attachment systems, some common complications can affect the long-term predictability of full-arch prostheses when they are fixed to dental implants. These include abutment screw loosening and fracture, frame/bar fracture, acrylic resin denture base crack/fracture, and the need to replace a denture tooth, among others.11 When such problems arise, the prosthesis often must be removed and sent to a laboratory for repair, which could take days or weeks. This underscores the benefit of digital dentures and the almost immediate nature of their fabrication based on digital records. It also reinforces the fact that removable implant-retained full-arch prostheses are easier and more cost-effective to repair than those that are screw or cement retained.

An alternative to cement- or screw-retained abutment/attachment systems or hybrid attachment systems for implant-retained full-arch prostheses are locator systems.9,12 For example, LOCATOR F-Tx™ (Zest Dental Solutions, zestanchors.com) can be used for implant-retained removable full-arch overdentures and for those that are fixed and only removable by a dentist. These abutment/attachments do not require prosthetic screws, screw-access channels, or cement.

Durable Full-Arch Fixed Alternatives

The benefits that can be achieved with today’s removable implant-retained full-arch prostheses are impressive. However, these treatments for edentulism remain prone to several problems, including wear and breakage of the denture base, body, and prosthetic teeth.13,14 Fortunately, digital CAM technologies combined with advancements in material science make it possible to provide patients with predictable and durable implant-supported full-arch monolithic zirconia prostheses. When treatment planned and executed using a team approach that begins by envisioning the ultimate outcome, fixed implant-supported monolithic zirconia restorations can be produced in an efficient manner. The results can be a more esthetic, lifelike, and comfortable restoration, one that is a well-accepted treatment for edentulous arches.

Conclusion

By using a team approach and innovations in technologies and material sciences, dentists can provide edentulous patients with optimal treatments based on their individual needs, clinical condition, and financial situation. With digital diagnostics and treatment-planning technologies, such as CBCT and implant surgical guides, immediate implant placement can be performed the same day teeth are extracted. Similar digital technologies, such as intraoral impression scanners, make it possible to obtain impression records necessary for fabricating a full-arch prosthesis on the same day that implant-planning CBCTs are taken. As a result, a patient could be scheduled for one subsequent appointment to undergo tooth extraction, implant placement, and delivery of a final denture. The implant-retained full-arch prostheses could be fabricated using digital technology for a more comfortable and convenient patient experience that ultimately achieves highly accurate and well-fitting dentures.

About The Author

David Little, DDS
Private Practice
Professionals in Dentistry
San Antonio, Texas
Adjunct Clinical Professor
UT Health San Antonio, School of Dentistry
San Antonio, Texas

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