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American Dental Association

JADA Specialty Scan: Prosthodontics

IMAGE: dentures

Overdentures vs. conventional dentures

Findings from a survey of prosthodontists
As noted in an earlier issue of JADA Specialty Scan, a group of 15 scientists gathered in a symposium at Montreal's McGill University in 2002 to discuss the relative merits of overdentures versus conventional dentures for edentulous patients.

IMAGE: JADA coverRelying heavily on randomized controlled trials comparing overdentures to conventional dentures, the group issued a brief consensus statement declaring the two-implant retained mandibular overdenture (IRMOD) the "first choice" for edentulous patients, despite the higher cost.

Then in 2009, the consensus statement from the McGill group was reviewed and supported at the annual conference of the British Society for the Study of Prosthetic Dentistry.

More recently, a research team from New York University published findings from a survey they conducted on this topic in the August 2012 edition of The Journal of the American Dental Association.

The authors administered a Delphi method survey to an expert panel of 16 nationally representative academic prosthodontists to determine whether there was, in fact, a consensus among them on a first-choice standard of care for an edentulous mandible.

Developed by the Rand Corp. in 1950, the Delphi method survey is designed to gather expert opinion on a topic and assess whether a consensus can be found. Consensus in this case was defined as a 70 percent agreement among the panelists.

The panel evaluated performance in relation to 10 parameters: retention, stability, esthetics, speech, masticatory efficiency, comfort while eating soft and hard foods, confidence in intimate situations, satisfaction and self-esteem.

The group came to the consensus that they would recommend an IRMOD instead of a conventional denture as the first-choice for mandibular edentulous patients who are otherwise healthy or have mild systemic disease‹but not for patients with severe systemic disease. They favored the IRMOD for nine of the 10 parameters. The lone exception: esthetics, for which only a majority (51­69 percent) favored the IRMOD.

"Dentists should be encouraged to at least advise their edentulous patients about the benefits of this treatment option [IRMOD] and provide care or make provisions for an appropriate referral," the researchers concluded.

"On the basis of results of our study, we also suggest that education regarding the IRMOD should be offered by dental schools to students, as well as in continuing education course and professional development programs."

Case Report

Advanced implant-supported prostheses

Thanks to advances in implant restorative and surgical technologies, patients with the most severe dental and skeletal anomalies can regain optimal facial esthetics and function.

Consider the case of a 74-year-old man suffering from advanced periodontal disease and periapical pathology, with extensive loss of hard and soft tissues and just nine remaining, highly mobile teeth (five maxillary, four mandibular).

His treatment, provided by a three-member team from Johannesburg, South Africa, is described in a clinical report that appeared in the July 2012 issue of the Journal of Prosthodontics, the official publication of the American College of Prosthodontists.

"The purpose of this paper," the authors note, "is to illustrate how the use of an advanced implant-restorative protocol can enable successful treatment of even the most challenging clinical situations."

In this case, the patient's remaining teeth were declared hopeless and extracted. Dental implants were then placed along, with interim, fixed-margin abutments and abutment protection caps.

Two days later, acrylic resin fixed-interim prostheses restored the patient¹s esthetics and partial masticatory function. After implant osseointegration, maxillary and mandibular frameworks for definitive prostheses were milled from Ti alloy, using CAD/CAM technology.

The authors note in their conclusion that the CAD/CAM technology used in this protocol "enabled creation of accurately fitting titanium-alloy frameworks more efficiently than earlier casting technologies."

They added, "Additional laboratory and clinical research is warranted to confirm the long-term validity of these processes."

Is there a gender difference in masticatory function?

Assuming an equal number of teeth, do men and women perform differently when it comes to chewing?

Researchers at Japan's Nippon Dental University pursued an answer to that question and published their findings in the July 2012 issue of the Journal of Prosthodontic Research www.elsevier.com/locate/jpor.

The research team assembled 60 dentate subjects‹30 female and 30 male‹and asked them to chew gummy jelly on their habitual chewing side for 10, 15 and 20 seconds, and the amounts of glucose were measured. The changes of both glucose extraction and standardized glucose extraction from 10 to 20 seconds were investigated differently for males and females.

The amount of glucose extraction was compared between males and females for each chewing duration. Also, the maximum occlusal force was compared between males and females to assess a gender difference.

It was determined that the amount of glucose extraction was significantly larger for males than females for all chewing durations, and the maximum occlusal force was significantly larger for males.

The researchers concluded that any activity or study that involves analyzing masticatory performance should take gender differences into account.

Rehabilitating the edentulous maxilla

The preponderance of evidence shows that typical survival rates for dental implants range from 80 to 95 percent over 10 years. But higher failure rates have been reported for implant treatments in the edentulous maxilla than in the mandible.

The July 2012 issue of The Journal of Prosthetic Dentistry included a clinical report of a 72-year-old man who came to the University of Rochester, Eastman Institute for Oral Health with multiple fractured denture teeth on his maxillary implant-supported milled bar overdenture. It turned out the patient had experienced seven implant failures over a decade. He also reported a history of bruxism.

In a case of failed implants, the treatment team noted, reimplantation often is the only treatment option that will satisfy a patient seeking a fixed dental prosthesis.

"Both patient and clinician should be aware of the difficulties and potential risks of reimplantation before any attempt is considered," they wrote. "It has been recommended that a failing/failed implant should be removed as soon as is practical or when diagnosed as hopeless."

In this case, the failed dental implants were removed and replaced with eight new implants in the previously failed implant sites. An alternative design for implant supported metal ceramic fixed complete denture with metal occlusal surface retained with three sections of milled bars and three lateral screws was implemented.

A hard stabilization splint for nightly use was provided, and clinical guidelines for treating patients with bruxism were followed. Of critical importance, the patient demonstrated an ability to follow home-care protocol and enrolled in a six-month recall program with satisfactory clinical results.

Product Spotlight

BruxZir restorations report esthetic improvements

When Glidewell Laboratories introduced BruxZir Solid Zirconia crowns and bridges in 2009, the plan was to offer a monolithic zirconia restoration for bruxers and grinders-an esthetic alternative to posterior metal occlusal PFMs and full-cast metal restorations.

What was a restoration mainly for posterior teeth is moving more and more to the anterior, with what the company called "promising results." Thanks to a processing method developed in Glidewell's Research and Development Department, BruxZir zirconia exhibits higher translucency in the warm color spectral wavelength (>550 nanometers) allowing for more natural-looking restorations.

"BruxZir Solid Zirconia-which undergoes a unique, colloidal processing technique-has been shown to exhibit improved optical transmission compared to zirconia that has undergone conventional processing such as cold isostatic pressing (CIP)," said Robin Carden, Glidewell VP for research and development.

These esthetic enhancements, the company says, are accomplished without reducing BruxZir's strength and performance capabilities.

Dr. Michael DiTolla, director of Clinical Education and Research at Glidewell Laboratories, said he was hesitant to use bruxzir in the anterior, but has been impressed with its improved esthetics.

He added, "For the patient who has broken other restorations or shows higher-than-average wear, BruxZir restorations can be an excellent anterior restorative option."

For more information, visit www.bruxzir.com.

In this Issue

Product Spotlight


What is Specialty Scan?

This is one in a series of quarterly newsletters updating dentists on selected specialties in dental care. This issue of JADA Specialty Scan is focused on prosthodontics and is the third issue in the prosthodontics series. Other Specialty Scan issues explore orthodontics, oral and maxillofacial radiology and endodontics. The ADA has engaged the specialty organizations in these areas, as well as its own divisions of Science and Dental Practice, to offer content that we hope will be of interest to all dentists, generalists and specialists alike. You will receive four issues of Specialty Scan each quarter for a total of 16 issues in 2012. We hope you find these newsletters enlightening and useful, and we welcome your feedback on this and every issue of Specialty Scan.

Consulting Editor

Thomas J. McGarry, DDS
Past President, American
College of Prosthodontists

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