Issue 2, 2010

Welcome to the second issue of JCDA Express, an e-newsletter that brings you concise information about important developments in the dental and biomedical literature pertinent to Canadian dental practitioners.

For this issue, our contributors have selected articles on curing lights, orthodontic relapse and dental materials. We are pleased to provide you with access to the full text of all the articles until May 8, 2010. This temporary access is made possible through the support of the American Dental Association (ADA) and Elsevier. To find out more about the publications featured in this issue, click on the links in the Notes and News sidebar.

Yours sincerely,

Dr. John P. O'Keefe
Editor in chief
jokeefe@cda-adc.ca

Curing Lights

Dr. Richard Price is a professor in the department of dental clinical sciences at Dalhousie University. Dr. Price, a JCDA editorial consultant, recommends:

Curing lights. ADA Professional Product Review. Fall 2009; Volume 4, Issue 4.

View article
Full-text access to this article has expired.

 
Key points:

• Measuring light output (irradiance) at the tip of a curing light is not clinically relevant. Irradiance decreases as the distance from the tip of the light guide increases. In this study, the light output of 9 curing lights was assessed at distances of 2 mm and 9 mm.


• In all cases, light output decreased dramatically at the 9-mm distance. For example, the irradiance delivered from one light decreased by 68% from the 2- to the 9-mm distance.


• Manufacturers’ depth of cure recommendations are based on having the tip of the curing light at 0 mm from the composite. However, the depth of cure decreases as the distance between the material and the tip of the light guide increases due to the reduction in irradiance.


• QTH and PAC lights deliver a broad spectral emission. For optimal curing, some composites require a broader spectrum of light than some LED curing lights deliver.


• Each light produces a rise in temperature. Some of the LED lights produced a greater increase in temperature than the Optilux 501 (a QTH light).


• The review includes a web-based survey of 710 dentists that provides practitioner ratings of the curing lights based on factors such as access in the mouth, ease of use, durability, counter space requirements, purchase price, technical support, acceptable cure time and availability of different light guides.

NOTES AND NEWS

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June 10–13
Tampa, Florida
(OSAP) Annual Symposium

CHECK OUT THE PUBLICATIONS FEATURED IN THIS ISSUE

ADA’s Professional Product Review
www.ada.org/271.aspx

American Journal of Orthodontics and Dentofacial Orthopedics www.journals.elsevierhealth.com

Dental Materials
www.elsevier.com

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Reasons for recommending this article:

This review is an unbiased report on the capabilities of 9 different dental curing lights of various types (7 LED, 1 PAC and 1 QTH). The information is clinically relevant and of clear importance to practising dentists. A world expert on the topic of curing lights, Dr. Fred Rueggeberg of the Medical College of Georgia in the U.S., also provides an excellent review of what to look for when purchasing a curing light.

Listen to an interview with Dr. Price about this review.

Free e-subscription to the ADA Professional Product Review: Special offer for Canadian dentists

The ADA is now offering Canadian dental professionals a chance to receive a complimentary e-subscription to 4 issues of the ADA Professional Product Review in 2010—a savings of $99 USD.

ADA Professional Product Review is a quarterly publication that provides unbiased, scientifically sound comparisons of professional dental products. It is designed to help dental professionals make informed purchase decisions about products they currently use or that they are considering purchasing in the future.

Learn more about this limited time offer at: www.ada.org/prof/resources/pubs/ppr/ppr_login.asp

Orthodontic Relapse

Dr. Kathy Russell is head of the division of orthodontics at Dalhousie University. Dr. Russell, a JCDA editorial consultant, recommends:

Olsen TM, Kokich VG Sr. Postorthodontic root approximation after opening space for maxillary lateral incisor implants. Am J Orthod Dentofacial Orthop. 2010;137(2):158.e1-158.e8.

View article
Full-text access to this article has expired.

Key points:

• Magnification using panoramic radiographs to assess coronal and radicular space for lateral implants varied between 8% and 21%. Use of periapical radiographs is recommended instead of panoramic radiographs.


• 11% of patients experienced relapse severe enough to require orthodontic retreatment before implant placement.


• More relapse was seen in patients who finished orthodontic treatment at a younger age (16 y vs. 21 y).


• More relapse was seen with removable retainers than with fixed lingual retainers or (fixed) resin-bonded bridges.


• Relapse was caused by 1) the tipping of the adjacent teeth into the lateral space due to patients not wearing their removable retainer full-time; or 2) continuation of vertical growth past the end of orthodontic treatment.


• Use of a resin-retained bridge or fixed bonded lingual wire retainers is recommended as postorthodontic treatment until definitive implants can be placed.

Reasons for recommending this article:

This study is a large retrospective, evidence-based clinical research study that addresses a clinical challenge. The topic represents an interdisciplinary clinical area that general practitioners and specialists may likely see in their practice. The study is logically presented and includes a self-critique of the methods as well as a clear discussion of the possible reasons for the orthodontic relapse. Fixed retention, a feasible clinical treatment, is recommended as a method to alleviate the problem of post-treatment root convergence.

Related article

Kokich VG. Maxillary lateral incisor implants: planning with the aid of orthodontics. J Oral Maxillofac Surg.
2004;62(9 Suppl 2):48-56.

Dental Materials

Dr. N. Dorin Ruse is chair of the division of biomaterials at the faculty of dentistry, University of British Columbia. Dr. Ruse, a JCDA editorial consultant, recommends 2 articles:

Article 1: Vrochari AD, Eliades G, Hellwig E, Wrbas KT. Curing efficiency of four self-etching, self-adhesive resin cements. Dent Mater. 2009;25(9):1104-8. Epub 2009 May 8.

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Full-text access to this article has expired.

Key points:

• The literature concerning some properties of self-etching, self-adhesive cements is limited. This study evaluated the degree of cure (% DC) of 4 self-etching, self-adhesive resin cements and 1 conventional resin cement.


• Half the specimens were treated as dual-cured (irradiated with a halogen curing light) and half were treated as self-cured (not irradiated).


• In all cases, the % DC was much lower in the self-cured group than in the dual-cured group, although the values for the dual-cured group were still considered low (with the exception of Multilink Automix).


• The % DC for all resin cements was much lower than what has been reported in the literature.


• The materials tested are used to cement fixed prostheses. In such applications, some light attenuation will occur due to the overlying prosthesis. The low % DC therefore raises questions as to the clinical performance of these materials. In situations where the light is not completely blocked by an overlying restoration, longer irradiation times may probably result in higher % DC.

Reasons for recommending this article:

Over the last several years, the use of self-etching materials, both in dental adhesive systems and in resin cements, has increased dramatically. Personally, I believe there are quite a few issues with these systems that have not been fully addressed and could compromise the success of restorations. For example, the article identifies a concernedly low degree of conversion in the 4 self-etching, self-adhesive resin cements being investigated. The low degree of conversion, coupled with the possibility of continuous etching of the substratum, raises some as yet unanswered questions regarding the long-term performance of these materials.

Article 2: Erickson RL, Barkmeier WW, Kimmes NS. Fatigue of enamel bonds with self-etch adhesives. Dent Mater. 2009;25(6):716-20.

Key points:

• This study measured the shear bond strength and shear fatigue limit of composite to enamel bonds using an etch-and-rinse system and 4 self-etch adhesives.


• The etch-and-rinse system had significantly greater shear bond strength and shear fatigue limit than the 4 self-etch adhesives. Among the self-etch systems, Clearfil SE had the highest shear bond strength and shear fatigue limit.


• The etch-and-rinse system also had the highest ratio of shear fatigue limit to shear bond strength. As for the self-etch systems, the ratio decreased as the shear bond strengths decreased.


• Because of their lower fatigue limits, the self-etch adhesive systems may lead to greater enamel margin breakdown when these systems are used.

Reasons for recommending this article:

I found this article interesting from 2 points of view. First, the study uses a fatigue methodology (I am a strong believer that to have the slightest in vivo predictability, in vitro investigations should include fatigue testing) and, second, it raises awareness of possible shortfalls related to the use of self-etching bonding systems (see the article by Vrochari et al. above). The authors identified a significantly shorter fatigue life of composite–enamel bonds mediated by self-etching bonding systems compared to those mediated by etch-and-rinse systems.

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