Better chewing for denture-wearers
Dental adhesives improve chewing function for denture wearers with both normal and poor bone status, even when prostheses are well-fitted.
These observations come from research conducted by Brazilian scientists who explored the effects of adhesives on chewing performance, chewing ability and chewing cycle movements in denture wearers, particularly among subjects with a resorbed denture-bearing ridge.
Encountering conflicting results in the conclusions of previous studies, the researchers conducted their own clinical trial. Their study involved 30 volunteer subjects who received new well-fitting dentures at the Graduate Dental Clinic in the Piraciacaba Dental School in Sao Paulo, Brazil. These 30 subjects were classified into two groups, according to their ridge status: normal or resorbed. During the same session, the researchers evaluated the subjects’ chewing ability, masticatory performance and chewing cycle movements.
The parameters were assessed in the subjects as they used their dentures in three different ways:
• without adhesive (control);
• with dental adhesive cream;
• with dental adhesive strips.
For each group, researchers implemented a chewing test with a sieve method to analyze masticatory performance. A kinesiolographic device evaluated chewing cycle and a visual analog scale (VAS) measured masticatory ability.
The results showed that dental adhesive use enhanced chewing performance and ability in patients with both ridge types. Subjects with resorbed ridges showed the best masticatory performance and lowest chewing cycle time with dental adhesive cream, followed by those using dental adhesive strips and the group using no adhesive. Denture-bearing ridge status alone did not alter masticatory function for any of the parameters evaluated.
In addition, chewing improvement in denture wearers was greater after dental adhesive cream application than dental adhesive strips. The authors noted previous research that determined the possible reason for the difference between cream and strips may be due to a long-acting synthetic polymer in the cream, which increases adhesive strength and resistance to dislocation of the resin base.
“DA cream seems to be more efficient and lasts longer than DA strips,” authors said.
Two test materials (peanuts and Optocal) were used to test chewing cycle movements. Although patients are accustomed to chewing natural foods, they vary in consistency and texture, which is why researchers also evaluated chewing with a standardized artificial material. The results of the present study were in agreement with those of a previous study finding that dental adhesive cream was associated with a faster chewing cycle.
By shortening the chewing cycle and enhancing chewing ability and performance, dental adhesives improve mastication, authors said in conclusion. The research was published in the March 2014 issue of The International Journal of Prosthodontics.
Consulting Editor: Lars O. Bouma, DDS
New CAD/CAM materials studied
A new class of materials for CAD/CAM blocks performed well in a study evaluating fatigue, failure and wear of complete molar crowns.
Strong drivers for the gains in computer-aided design and computer-aided manufacturing (CAD/CAM) include an ever-increasing demand for better esthetics and new and improved treatment options. Advantages, disadvantages and similarities about the performance of ceramic versus composite resin materials are well-reported in the dental literature.
What’s missing, according to authors publishing in the April 2014 issue of The Journal of Prosthetic Dentistry, is a consensus on the best material for restoring posterior teeth.
To evaluate, the scientists conducted a simulated study to determine the fatigue resistance, load-to-failure, failure mode and antagonistic wear of complete molar CAD/CAM crowns made of three different materials. They examined lithium disilicate (LD), feldspathic glass ceramic (FEL) and resin nanoceramic (RCN)—a newer material recently classified by the American Dental Association as a porcelain-ceramic (60 percent in volume).
The scientists milled 15 specimens of each material to restore 45 molars with a standardized complete CAD/CAM crown of 1.5 millimeters thickness. Among their analyses, they simulated chewing for the fatigue test and applied cyclic load for the load-to-failure test starting with 200 newtons (N), for 5,000 cycles, followed by six stages from 400 to 1,400 N to a maximum of 30,000 cycles each.
Failures were categorized into three groups: reparable tooth fracture, possibly repairable or catastrophic tooth-root fracture.
The results showed that mean fracture loads for all three materials exceeded the values of maximum posterior chewing forces, which lie in the 600 to 900 N ranges. The LD and RNC groups demonstrated a significantly higher survival rate (93.3 percent and 80 percent, respectively), after the fatigue test than the FEL (6.6 percent). The survival of the molars restored with LD and RNC was not significantly different. Whereas no catastrophic failure occurred during the fatigue test, all of the specimens in the load-to-failure test exhibited catastrophic fractures.
After the fatigue test, the RNC crowns showed less wear at the antagonist sphere than the LD or FEL crowns. However, the opposite was found about the actual material because well-defined wear facets could be seen at the contact with the RNC specimens, whereas researchers could barely notice contact areas in the LD and FEL groups.
The findings for mean fracture strength of FEL crowns were within the range reported in previous research. The performance agrees with the work of previous investigators, and correlates with its lower flexural strength compared with the other two materials, authors said in discussion.
“By contrast, the performance of RNC and LD crowns was similar in spite of their different flexural strength” they said. “This situation can be explained by the elastic modulus of the material.”
The work of fracture, they advised, is inversely related to the stiffness of the material.
Practical advantages of resin nanoceramic were discussed, including less mill time. Authors called for further research to explore the bondability of the new RNC and the potential for adding contacts or esthetic characterizations with light polymerized composite resin, as no esthetic characterizations were applied in this invitro study.
BruxZir Full-Arch Implant Prosthesis
Constructed from 100% BruxZir Solid Zirconia, this fixed, full-arch implant solution for edentulous patients attaches to implants via titanium connections, dramatically improving speech and chewing function. Strong, biocompatible, and affordably priced, the prosthesis exhibits natural esthetics while offering exceptional resistance to chips, fractures, and stains.
Dental caries and risk assessment
New information about risk factors for dental caries may lead to more targeted therapies, an article published in the April 2014 issue of The Journal of Prosthetic Dentistry reported.
Historically, caries-damaged teeth were treated surgically with restorations. More recent evidence supports a philosophy that identifies specific risk factors and disease indicators for individual patients. Called Caries Management by Risk Assessment, or CAMBRA, the approach is based on research published in the dental literature.
The author describes CAMBRA as a simple process of assessment, diagnosis and prescription, with a single challenging aspect. The approach entails culturing saliva to measure mutans streptococcal and Lactobacillus levels.
Usually assigned to an overtasked hygiene appointment, time constraints may be problematic. A caries risk assessment form developed for clinical practice to address this inconvenience is suggested. It enables patients to self-report risk factors prior to the dental hygiene appointment. The clinician then can identify disease indicators and discuss risk factors with patients.
Endeavoring to make CAMBRA more adaptable to the private practitioner, the author also discussed known risk factors and disease indicators, as well as new risk factors acknowledged in contemporary research.
“These new data have added to the factors and changed the picture for dental caries, but this change has simplified the situation for those in clinical practice,” the author said. “Designing an appropriate and effective treatment strategy for an individual patient is straightforward. The causes drive the treatment strategies.”
A discussion of prescriptive treatment based on risk factors and disease patterns was organized into three categories: reparative strategies, therapeutic materials and behavioral therapies.
The research showed that although it is important for a clinician to understand the complexity of the dental caries biofilm disease, the ability to identify common disease patterns and associated therapies may be more important to enabling CAMBRA, an approach that the author said, “provides the next step toward precision medicine and the more effective treatment of dental caries in clinical practice.”
The caries risk assessment form adapted for practice is included with the article.
C.diff and patient susceptibility
Patients taking antibiotics may not realize they’re more susceptible to C. diff, an infection that can cause diarrhea and may irritate or even damage the colon.
The July 2014 issue of The Journal of the American Dental Association includes a patient education piece about Clostridium difficile infection providing information about risks, symptoms, prevention and treatment.
People who recently received medical care in a hospital, a nursing home, a physician’s office or an outpatient surgical center account for 94 percent of all cases, according to reported Center for Disease Control and Prevention data. In the United States, some 14,000 deaths are attributed to the infection.
Restoring the edentulous arch
By Michael McCracken, DDS, Ph.D.; and Jonathan P. Ouellette, DMD
The following case report illustrates the protocol for restoring an edentulous arch with the BruxZir Full-Arch Implant Prosthesis. Clinicians can substantially improve the lives of their patients by providing a fixed, esthetic and long-lasting full-arch implant restoration.
The patient is a 58-year-old male with 11 implants placed: six in the maxilla, five in the mandible.
Step 1: Impressions were made using stock trays and closed-tray impression copings. The copings were placed back into the impressions before the case was sent to the laboratory.
Step 2: Bite blocks were seated, occlusal rims were contoured, the vertical dimension was established, and jaw relation records were taken.
Step 3: The patient required four multi-unit abutments in the anterior maxilla
and five in the mandible to correct implant angulation and raise the prosthetic platform (Fig. 1). Wax denture setups were evaluated and adjusted for proper esthetics, phonetics, contours, occlusion and tooth arrangement. Then, the sectioned and numbered acrylic pieces of the lab-fabricated implant verification jigwere seated and luted together (Figs. 2a, 2b). A final impression using an open-tray impression technique picked up the jig.
Step 4: PMMA provisionals provided by the laboratory allowed the patient to live with the proposed restoration during a trial period. The patient approved the CAD/CAM provisionals.
Step 5: The final restoration was fabricated from BruxZir Solid Zirconia using the CAD design confirmed during the provisional trial (Figs. 3a, 3b). The fit, occlusion and esthetics of the final restoration were excellent, and the patient was pleased.
The BruxZir Full-Arch Implant Prosthesis offers excellent esthetics and durability, and maximizes prosthetic stability, function and comfort. This option should be part of the treatment plan discussion for every edentulous patient.
Figure 1: Without correction, the screw access hole for the implant (reflected by the silver driver) would be visible on the facial surface of the restoration. The angled multi-unit abutment corrects the angulation (green carrier).
Figures 2a, 2b: The acrylic sections of the implant verification jig were luted together, with material flowed completely through and around the gaps.
Figures 3a, 3b: The lab fabricated, stained and glazed each prosthesis from a single block of BruxZir Solid Zirconia.
To read the full article, visit www.inclusivemagazine.com.
Encode Impression System
The Encode Impression System streamlines the implant restorative process and mitigates gingival trauma by eliminating the need for component-swapping during the impression phase. Available in titanium, all-zirconia, or zirconia with titanium base, each Encode Healing Abutment is “encoded” with special markings that transmit implant information with no implant-level impression.
ADA offers discount on implant brochure
Now through Aug. 31, the ADA is offering members a patient education brochure on immediate load implants at a 15 percent discount.
Members can order “Immediate Load Implants” (W305) through the ADA Catalog, using promo code 14359E. The 8-panel brochure is available in packets of 50 for $27; retail price $40.50. Discounts are also available in higher quantities.
Written for the dental patient, the brochure conveys the benefits of implants, as well as the advantages of immediate load implants. It also explores who is eligible for dental implants while outlining the general steps of placement.
Members can preview this and other ADA brochures online at adacatalog.org. Orders can be placed online or by calling the ADA Member Service Center at 1-800-947-4746. Remember to use promo code 14359E to receive the 15 percent discount.
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 third in the series on this topic for 2014. Other Specialty Scan issues are devoted to periodontics, orthodontics, endodontics, and oral and maxillofacial radiology. The ADA has engaged the specialty organizations in these areas as well as its own divisions of Science and Legal 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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