Prosthodontics - A Quarterly Newsletter on Dental SpecialtiesJADA Specialty Scan

Measuring the impact of implants

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The advantages of implant-supported fixed complete dentures (ISFDs) over conventional dentures are long established, and include better stability, comfort, speech, chewing ability and bone preservation.

Meanwhile, oral health-related quality of life (OHQOL) and the impact of clinical procedures on patients is drawing more attention and research. An assessment tool called the Oral Health Impact Profile (OHIP) measures oral health-related quality of life.

Scientists publishing in the November/December 2014 issue of The International Journal of Periodontics & Restorative Dentistry used a version of OHIP to assess the impact of replacing conventional mandibular complete dentures with ISFDs on the OHQOL of completely edentulous patients. They also sought to learn how treatment with ISFDs influences parameters as measured by kinesiographic assessments, which included movement during opening and closing of the mouth and movement of the maxillary complete denture and mandible during chewing.

To investigate, 16 subjects – 10 women and six men – who had volunteered to receive new complete dentures at the Araraquara Dental School in Sao Paulo, Brazil, were recruited. Three researchers and a dental technician sought to provide subjects with ideal fit, esthetics and fabrication of the new dentures.
After a functional adaptation phase, researchers performed a baseline assessment. They performed surgical and prosthetic procedures up to a week after baseline, and all ISFDs were placed within 48 hours after the surgical procedures. Researchers assessed patients at one, two, three, six and 12 months after insertion of the ISFDs. Each of the assessments included the OHIP questionnaire and kinesiographic records.

Results showed that OHQOL improved significantly after two months and remained constant up to six months. Subjects reported a significant improvement again at one year after the insertion of the ISFDs, when compared to baseline, when they were wearing their complete dentures.

Among kinesiographic findings, analysis of opening and closing movement limits showed that 60 days after treatment with the ISFDs, a statistically significant increase of 5.6 millimeters was found for vertical opening, and the values remained almost constant until the end of the assessment period.

Authors noted previous research showing that older people consider the impact of oral heath on functions such as eating to be the most important variable in terms of OHQOL.

“The results of the present study could be attributed to retention and greater confidence in eating provided by the implants, as opposed to conventional denture treatment, which only has tissue support,” they commented.


Consulting Editor: Lars O. Bouma, DDS
American Board of Prosthodontics

Cement- and screw-retained prostheses performance explored

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Implant-supported prostheses have long used screws for retention, and the evidence confirms their success. But screw loosening or fracture is a possible complication. Cement-retained prostheses have become a popular alternative, primarily in treatments for single and fixed prostheses, yet comparative studies of the differences in biomechanical behavior between the two retention methods have yielded inconsistent results.

Scientists at Federal University in Brazil compared the preload maintenance, stresses and displacements of prosthetic components of screw- and cement-retained implant supported prostheses by simulating identical loads in three-dimensional models of each retention type. They published their findings in the December 2014 issue of the Journal of Prosthetic Dentistry.

“The presence of an intermediate layer of cement in addition to the engaging feature of the abutment seems to favorably alter the biomechanical behavior of cement-retained prostheses,” authors noted in discussion of results that found that cement-retained prostheses performed better. However, even with a higher risk of mechanical issues, screw-retained prostheses are reliable and may have some biological advantages.

According to the researchers, “newer prosthetic connections seem to present fewer technical issues such as screw loosening.” They also said when using screw-retained prostheses, special attention should be given to factors that can minimize the loads and stresses on the prosthetic complex, including:     

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Grow your practice with 3D

As dental technology continues to accelerate, practitioners are searching for information on when to invest, how to select equipment, and the best way to integrate it into the workflow.
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Cost-effective CAD/CAM technique described

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Researchers at the University of Louisville School of Dentistry outline a digital workflow that offers a cost-effective, single-step conversion process for fabricating an implant-supported fixed complete dental prosthesis in the December 2014 Journal of Prosthetic Dentistry.

The dental technique report describes the steps of the digital workflow, supported by newly developed software. The process incorporates digital data acquisition at the implant level, computer-aided design and computer-aided manufacturing-fabricated titanium framework, individually luted zirconium oxide restorations and autopolymerizing injection-molded acrylic resin for placement in an edentulous mandible.

The authors describe and illustrate the process that encompassed five clinical appointments and four laboratory stages.

Researchers say “the capability and flexibility of CAD/CAM software allow the trial tooth arrangement to be converted to the titanium framework and ceramic restorations design in a single step,” decreasing treatment time and cost compared to a double-scan technique.

The software also allows access openings to be analyzed and placed on the selected restorations for an implant-supported, screw-retained fixed complete dental prosthesis and can incorporate luting restorations with interim cement to make them retrievable if the trajectory of screw access doesn't allow for access openings on the restorations.

A benefit of this method is that preserved digital data can be used if the definitive cast and/or prosthesis need to be repaired or refabricated.
Possible disadvantages are risk of lost retention between the framework and the restorations, acrylic resin veneer fracture and a higher fabrication cost than the conventional technique with acrylic resin dentures.

Although the CAD/CAM fabricating process may not achieve optimal esthetic results, veneering porcelain and low-fusing nanofluorapatite glass ceramic can be used to characterize the restorations with additional laboratory cost and time.


Common tool is functional for screw fractures

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While many appreciate the cotton swab’s variety of uses, the December 2014 issue of the Journal of Prosthetic Dentistry reported on a useful adaptation of the swab for clinicians: screwdriver.

Although screw loosening and fractures are uncommon in implant supported restorations, they can compromise the viability of both the implant and the prosthesis. Retrieving fractured screw fragments is time consuming and may require multiple appointments. Potential risks include damage to the internal threads of the implant.

Scientists at New York University College of Dentistry explored a procedure they describe as “a simplified technique” that uses the cotton swab as a screwdriver. “This procedure allows the screw fragment to be retrieved without the risk of damaging or altering the surface characteristics of the components and avoids potential damage to the internal threads of the implant,” authors reported.


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Showing patients how implants can restore smiles

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The ADA is offering a 15 percent discount on the patient education brochure, “Dental Implants: Are They an Option for You?

This comprehensive brochure helps patients understand the value of implant treatment. With illustrations and step-by-step explanations, it describes the major points of implant placement, healing and prosthesis placement. Single tooth implants are covered, as well as implant-supported bridges and dentures. “Dental Implants” is well suited to send home with patients who need to discuss treatment with a spouse.

The eight-panel brochure is available in packs of 50 from the ADA Catalog, 1-800-947-4746 or This educational resource is also available personalized or in Spanish. Specialty Scan readers who use campaign code 15407E before April 10 can save 15 percent on all ADA Catalog products.

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What is Specialty Scan?

This is one in a series of quarterly newsletters updating dentists on selected specialties in dentistry. Information presented is aggregated and summarized from previously published materials, each item attributed to its publication of origin. This issue of JADA Specialty Scan focuses on prosthodontics, the first in the series on this topic for 2015. Other Specialty Scan issues are devoted to endodontics, orthodontics, oral and maxillofacial pathology, oral and maxillofacial radiology, pediatric dentistry and periodontics. The ADA has engaged the specialty organizations in these areas as well as its own Science Institute and Division of Legal Affairs to assist with these newsletters. We welcome your feedback on this and all Specialty Scan issues.

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