JCDA Express Issue 7, 2011

Cite this as: J Can Dent Assoc 2011;77:12

November 17, 2011

Issue 7, 2011

A member service that keeps you up-to-date on important new literature relevant to your practice.

In this issue of JCDA Express our contributors highlight articles on the use of ionizing radiation in dentistry, experimental strategies to prevent dentin bond degradation, NSAIDs and the risk of cardiovascular events, and the evaluation of mandibular implant overdentures.

JCDA would like to gratefully acknowledge the publishers of these articles, who have granted free access to the full-text papers until December 17, 2011. Follow the links in the Notes and News sidebar to discover more about these publications.

The British Columbia Dental Association is hosting its 12th Annual Toothfairy Gala on March 10, 2012. This event, held during the Pacific Dental Conference, honours the accomplishments of BC dentists and raises funds in support of oral health-related charities in the province. The BC Cancer Agency and AboutFace are the beneficiaries of the upcoming gala. These two organizations are partnering to help adult survivors of childhood cancers who have dentofacial abnormalities.

The response to my recent Editorial, in which I seek help with a new JCDA project, has been most encouraging. I am looking for 100 dentists to assist with reviewing and distilling clinical information into existing templates—and this will all be done within a safe, comfortable environment. Once again, if you are interested in contributing to this project, please contact me by phone or email.

Sincerely,

Dr. John P. O'Keefe
Editor-in-chief, JCDA
1-800-267-6354, ext. 2297
jokeefe@cda-adc.ca

Ionizing Radiation in Dentistry

Dr. Bob Wood is chief of dental oncology, ocular and maxillofacial prosthetics at Princess Margaret Hospital, Toronto, Ontario. Dr. Wood recommends:

Lam E. Considerations for the use of ionizing radiation in dentistry. Dispatch. 2011;25(3 Suppl):1-12.

Full-text access to this article has expired.

JCDA Clinical Pearl: Radiologic investigation, like any form of testing, should be performed thoughtfully in order to minimize risk and maximize useful information.

Key points:

This article reinforces the principle that dentists should use every reasonable means at their disposal to ensure that radiation doses to patients, particularly children and adolescents, are as low as reasonably achievable (ALARA).
No exposure to radiation should be permitted without first considering the benefits that may be derived from that exposure, and the relative risks of alternative clinical approaches. Radiologic examinations should not be used in a bid to detect occult disease.
With the introduction of CBCT systems in dentistry, the potential to harm patients is considerably greater because of the higher effective doses. For some CBCT systems, the risks of developing a fatal cancer are comparable to contemporary medical CT examination. This has many concerned.
The estimated radiation absorbed dose equivalent calculated in 2007 for a full mouth series of intraoral radiographs is now more than 4 times the value calculated in 1992.
The idea that panoramic imaging can replace periapical or bitewing radiography, or be used as a "screening tool" at predefined time intervals in normal community practice, should be considered inappropriate given the inherent artefacts of panoramic imaging and the lower image resolution.
Although collimators of varying lengths are available for intraoral x-ray systems, use of long collimation is the preferred choice. Also, rectangular restrictions have been reported to decrease patient radiation absorbed dose by a factor of between 4 to 5 times without impacting image quality.
The use of personal lead protection, consisting of 0.25 mm lead equivalent in the form of a thyroid collar, should be mandatory because the thyroid is radiosensitive and close to the field. Although aprons may not afford additional gonadal protection, they do protect tissues closer to the beam and are highly recommended.

Reasons for recommending this article:

This article provides important information of practical use in protecting our patients from excess radiation. It is an excellent summary of current thinking, dosages and risk estimates from authoritative sources. The information is presented in a language and format that are readily understood and is thoroughly referenced should the reader want to delve deeper into the subject matter. There are numerous practical tips that dentists can use in their practice (e.g., examination prior to radiography, personal lead protective devices, narrower collimation, and avoidance of calendar-based radiography). If implemented, the tenets of this article will reduce the radiation burden on the Canadian public and allow dentists to use this special testing technique responsibly.

Dentin Bonding Degradation

Dr. Denis Robert is a professor of restorative dentistry at Laval University. Dr. Robert recommends:

Liu Y, Tjäderhane L, Breschi L, Mazzoni A, Li N, Mao J, et al. Limitations in bonding to dentin and experimental strategies to prevent bond degradation. J Dent Res. 2011;90(8):953-68. Epub 2011 Jan 10.

Full-text access to this article has expired.

JCDA Clinical Pearl: Contemporary resin-dentin bonding is not as durable as some may believe. Although degradation of the bond will always occur, experimental treatment strategies are being studied to help overcome this challenge.

Key points:

The degradation of resin-dentin bonds is caused primarily by 2 mechanisms: slow hydrolysis of resin components caused by water sorption or esterases, and the degradation of water-rich, resin-sparse collagen fibrils within hybrid layers by the activation of host-derived matrix metalloproteinases (MMPs) and possibly cysteine cathepsins during bonding procedures.
Resin-dentin bonds are less durable than resin-enamel bonds because dentin bonding relies on organic components. Although moisture is essential for successful dentin bonding, it can also adversely affect long-term bonding results.
Bond durability is critical for the longevity of tooth-coloured restorations, because degradation can weaken adhesion and lead to gaps between teeth and restoratives.
Many experimental techniques are being examined to determine if they can prevent degradation and therefore increase the service life of resin-based bonding procedures.
This article looks at 5 experimental strategies that address problems encountered in dentin bonding: 1) increasing the degree of conversion and esterase resistance of hydrophilic adhesives; 2) inhibitors of collagenolytic enzymes; 3) MMP and cathepsin silencing via the use of cross-linking agents; 4) ethanol wet-bonding with hydrophobic resins; and 5) biomimetic remineralization of resin-dentin bonds.
While each of these 5 strategies has its own merits and limitations, the blending of several of these strategies into a single treatment approach may overcome the barriers currently encountered in bonding to dentin.
Replacing the free and loosely bound water within collagen water compartments and silencing collagenolytic enzymes are goals for improving the durability of resin-dentin bonds.

Reasons for recommending this article:

Dentists should remember that bonding composite to dentin is not permanent and that degradation of the bond will occur in all cases. This might explain many of the postoperative sensitivities observed in clinical practice. The article also shows that more research is required on this subject and that such future research should be transferable to the clinic setting.

NSAIDs and cardiovascular risk

Dr. Stephen Ahing is an oral medicine and pathology specialist who directs the TMD/maxillofacial pain/sleep disorders clinic at the University of Manitoba. Dr. Ahing recommends:

Schjerning Olsen AM, Fosbøl EL, Lindhardsen J, Folke F, Charlot M, Selmer C, et al. Duration of treatment with nonsteroidal anti-inflammatory drugs and impact on risk of death and recurrent myocardial infarction in patients with prior myocardial infarction: a nationwide cohort study. Circulation. 2011;123(20):2226-35. Epub 2011 May 9.

Full-text access to this article has expired.

JCDA Clinical Pearl: Neither short- nor long-term treatment with non-steroidal anti-inflammatory drugs (NSAIDs) is advised in patients with prior myocardial infarction.

Key points:

This nationwide cohort study prospectively examined NSAID treatment and cardiovascular risk in 83 675 Danish patients with prior myocardial infarction (MI).

Patients over 30 years of age who were admitted to hospital with first-time MI between 1997 and 2006 were identified and their subsequent NSAID use was studied.

Overall, NSAID treatment was significantly associated with an increased risk of death or recurrent MI at the beginning of treatment, and the risk persisted throughout the course of treatment.

Diclofenac was the NSAID associated with the highest cardiovascular risk, while naproxen had the lowest cardiovascular risk.

The authors conclude that even short-term (1 week or less) NSAID treatment is associated with increased cardiovascular risk in patients with prior MI. There appears to be "no safe therapeutic window for NSAIDs in patients with prior MI."

The study results challenge the 2007 recommendations of the American Heart Association regarding NSAID treatment in patients with established cardiovascular disease, which focused on long-term NSAID use. The AHA advocated concurrent prophylactic strategies with low-dose aspirin prophylaxis, proton pump inhibitors, selection of patients with low thromboembolic risk and continuous monitoring of blood pressure as well as renal and gastrointestinal function.

The main limitation of the study was its observational design, which could not exclude the effect of unmeasured confounding factors such as blood pressure, body mass index or smoking habits—although the authors felt the comorbid factors would not have significantly altered the results.

It was not discussed if cardiovascular risk was greater in special circumstances such as sustained release preparations or for NSAID/prophylactic aspirin combinations. It should be noted that the latter combination has been reported to have adverse cardiovascular effects.

Reasons for recommending this article:

All NSAIDs increase the cardiovascular risk of patients who have had previous cardiovascular events—even after short-term use of 1 week or less for some NSAIDS. Many patients with tempomandibular disorders (TMD) are prescribed NSAIDS or self-medicate with variable doses of NSAIDs. Many dentists use NSAIDs for 1 week pre- or post-operatively to manage orofacial pain associated with toothache, odontogenic infection, arthritis of the temporomandibular joint, and various TMD and non-TMD head and neck chronic pain disorders. This article challenges the dental profession to examine how drugs such as acetaminophen, prednisone, methotrexate, narcotics, neutraceuticals and non-pharmacological pain management can be incorporated into the management of chronic pain or inflammatory pain in the head and neck.

Mandibular Overdenture Treatments

Dr. Randall Mazurat is an associate professor of restorative dentistry at the University of Manitoba. Dr. Mazurat recommends:

Burns DR, Unger JW, Coffey JP, Waldrop TC, Elswick RK Jr. Randomized, prospective, clinical evaluation of prosthodontic modalities for mandibular implant overdenture treatment. J Prosthet Dent. 2011;106(1):12-22.

Full-text access to this article has expired.

JCDA Clinical Pearl: Patients preferred mandibular overdentures using 2-implant independent ball attachments over more costly and complex 2-implant bar and 4-implant bar overdenture treatments.

Key points:

This crossover study evaluated multiple treatment outcomes for 30 patients being treated with 3 different overdentures.

The patients received 4 implants in the anterior mandible and then randomly received 1 of 3 treatment types—a 4-implant bar attachment, a 2-implant bar attachment, or 2 independent ball attachments.

Patients were randomly assigned to wear each of the 3 different overdentures sequentially, for a wear period of 1 year for each type of overdenture.

The treatment outcomes examined were denture retention, tissue response, patient preference and satisfaction, and complications.

The study outcomes favoured the 2 independent ball attachments for all parameters except denture retention; for this parameter, the 4-implant bar attachment was best.

More than half of the patients (52%) preferred the 2-implant independent ball overdenture.

The study results demonstrate that a relatively inexpensive and less complex overdenture modality can provide an equivalent or more satisfactory outcome than treatment modalities that employ a greater number of implants and are more expensive and complex.

Reasons for recommending this article:

Most clinicians would recommend an implant-supported overdenture to patients having difficulty wearing a conventional denture. However, they may not feel confident recommending the specific number of implants or the attachment mechanism. This article can help dentists in the decision-making process by showing that, given the opportunity to try different treatment modalities, patients often prefer a simple and less costly treatment. In terms of cost, ease of use and long-term maintenance, the use of 2 implants with independent ball attachments to retain an overdenture is my preferred option. The fabrication procedures are similar to those used to fabricate conventional dentures and the timing of implant and attachment placement is also less critical than with bar-retained overdenture systems.

JCDA is the authoritative written voice of the Canadian Dental Association, providing dialogue between the national association and the dental community. It is dedicated to publishing worthy scientific and clinical articles and informing dentists of issues significant to the profession.