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JADA Specialty Scan - Prosthodontics
Prosthodontics - A Quarterly Newsletter on Dental SpecialtiesJADA Specialty Scan

Digital workflow and implant crowns

Recent advances in technology enable clinicians to place dental implants using an array of digital processing methods, including cone-beam computed tomography, three-dimensional surface planning software, intraoral surface scanning and computer-aided design/computer-aided manufacturing (CAD/CAM) technology. Some of the benefits of digital workflows reported in the literature include reduced clinical treatment time, simplified technical production and precision in prosthetic construction.

Yet, scientists at the University of Bern in Switzerland found that only a few studies have compared efficiency parameters of digital workflows with those of conventional methods. Furthermore, even when studied, the focus has been limited to single treatment steps, such as intraoral scanning compared with conventional impression-taking procedures. To their knowledge, only one clinical case series examined the efficiency of the complete digital implant prosthetic workflow, starting with intraoral scanning, followed by CAD/CAM fabrication and final placement of the prosthesis. Conventional impression techniques with transfer posts in combination with plaster master casts and porcelain-fused-to-metal (PFM) crowns remain the gold standard in the manufacturing process for fixed implant-supported reconstructions, according to the researchers.

“Particularly for evaluating time-efficiency in implant prosthodontics, it is essential to understand the impact of this digitalization trend on modifying well-established conventional protocols,” the researchers said. Considering this, they conducted their own prospective clinical crossover trial and published the findings in the September/October 2015 issue of The International Journal of Oral & Maxillofacial Implants.

The researchers investigated whether the digital workflow to produce implant-supported single-unit reconstructions is more time efficient than the traditional method in 20 participants who needed a single-tooth replacement in posterior sites. Each patient received two different implant crowns in a prospective clinical crossover design, as follows: 20 customized titanium abutments plus CAD/CAM-fabricated zirconia superstructures (test group) and 20 standardized titanium abutments plus PFM crowns (control group). Researchers measured time efficiency for every clinical and laboratory work step for the test and control groups.   

All study participants were treated successfully in two appointments and the manufacturing process did not affect the success rate for the placement of the final prosthesis.

However, the total production time — clinical plus laboratory work steps — was significantly different between the digital workflow and the conventional method. Digital processing for overall treatment was 16 percent faster, with overall chair time demonstrating a wide range of 27.0 to 44.5 minutes for the control group as opposed to 9.0 to 18.5 minutes for the test group (digital workflows). Scientists found similar results for laboratory work, with significantly reduced mean time in the test group versus the control group.

In discussion, authors noted the value of measuring efficiency as it describes the extent of the effort needed for a certain procedure or goal. “At first sight, time-efficiency does not seem to be an applicable parameter to analyze implant prosthetic reconstructions in clinical trials,” the authors noted in the discussion. “However, time resources are of great interest in daily practice.” Researchers highlighted patient expectations for convenience-oriented treatment requiring shortened treatment sequences, as well as fewer appointments.

“The digital protocol resulted in a more efficient technique than the conventional procedure,” they said, while also acknowledging that the learning curves for dentists, dental assistants and technicians have to be considered when interpreting the results.

Read the original article.


Consulting Editor: Donald A. Curtis, DMD, FACP
Diplomate, American Board of Prosthodontics
Professor, University of California San Francisco

Avoiding visibility of screw-retained restorations

Even though cement-retained restorations can accommodate more implant positions, clinicians may choose screw-retained restorations because they are easier to retrieve and may be easier to maintain. In addition, a growing body of literature demonstrates that peri-implant soft tissues respond more favorably to crowns that are screw-retained rather than cement-retained. Despite this evidence, screw retention often isn’t even considered in the maxillary arch, where screw access may compromise esthetics.

The November 2015 issue of The Journal of Prosthetic Dentistry features a clinical report about a treatment with a new method of fabricating a custom abutment-crown combination for a screw-retained restoration. The technique allows the channel for the screw to be placed at an angle other than parallel to the implant body, thereby avoiding the facial access hole and not sacrificing esthetics.

To demonstrate their findings, researchers at the University of Michigan in Ann Arbor outlined the case of a 34-year-old woman seeking a restoration after implant placement at the site of the maxillary right lateral incisor.

“New technology allows clinicians to offer screw-retained restorations in a practical and esthetic way that previously may not have been possible,” researchers noted about the protocol.

Read the original article.


3M helps dentists make great first impressions
3M Oral Care has updated its Impression Troubleshooting 
Guide, an interactive digital tool allowing dentists to quickly find answers to 12 of the most common issues in the impression taking procedure. With the newly optimized online guide, dentists can feel confident throughout the impression taking process, helping to ensure accurate outcomes each and every time.


Internal and marginal fit in cobalt-chromium restorations

One of the more cost-effective and increasingly used methods for fabricating cobalt-chromium restorations demonstrated the poorest internal and marginal fit, new research published in the November 2015 issue of The Journal of Prosthetic Dentistry reported.

The finding is important because poor fit increases the chance a patient will develop periodontal disease and caries.

Interested in how fabrication methods affected internal and marginal fit, scientists in Norway made 30 cobalt-chromium metal frameworks using three different methods: conventional casting, milling and selective laser melting (SLM). They evaluated marginal fit with a direct-sight technique and internal fit with scanning electron microscopy.

Results showed significant differences in both internal and marginal fit among the three fabrication methods, with the milled group having the best internal fit, followed by the conventional casting and, lastly, the SLM group. Scientists found a statistically significant correlation between internal and marginal fit among the three groups.

“Other studies have found internal fit of SLM-fabricated restorations that were both better and poorer than that of conventional casting and milling,” the authors said in discussion. “Precision may differ among the production systems; furthermore, the method will certainly be further developed and refined in the future.”

Read the original article.

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New edition of Tooth Replacement Options brochure

The ADA brochure Three Tooth Replacement Options has been reformatted into a larger booklet to help dentist and patient more thoroughly review each option for replacement: implants, fixed bridges and removable partial dentures. The brochure reviews the steps of each process, its advantages and disadvantages and which patients are good candidates.

Additionally, it now includes a glossary of dental terms to ensure the patient’s comprehension. A “Pros and Cons” chart helps start a dialogue with the patient on weighing options. Three Tooth Replacement Options is a 12-page booklet sold in packs of 50. A personalized version is also available. To order, call 1-800-947-4746 or go to adacatalog.org. Readers who use the code 16403E before March 11 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 2016. Other Specialty Scan issues are devoted to endodontics, orthodontics, oral pathology, oral and maxillofacial radiology 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.

Editorial and Advertising Policies

Any statements of opinion or fact are those of the authors and do not necessarily reflect the views of the American Dental Association. Neither the ADA nor any of its subsidiaries have any financial interest in any products mentioned in this publication. Any reference to a product or service, whether in advertisements or otherwise, is not intended as an endorsement or as approval by the ADA or any of its affiliated organizations unless accompanied by an authorized statement that such approval or endorsement has been granted.

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