September 1, 2013
by Dr. Len Boksman
It was a pleasure to read your July 2013 Issue of Oral Health and Dr. Freedman is to be congratulated for editing the issue.
Dr. Strassler in his excellent overview on “Successful Light Curing — Not As Easy As it Looks,” reinforces the fact that there are many variables affecting the polymerization and the resultant success or failure of composite resins, not the least of which is the curing light.
Dr. Strassler rightly points out that there is no single recipe that the clinician can use for adequately curing composites. There is research documenting that there are variations in distance from and depth of the restoration, type of composite, type and reactivity of the photo-initiator, colour of the composite, beam profile, wavelength, light energy output, and deviations from the manufacturer’s claimed output. The importance of placing the light at ninety degrees to the surface to achieve maximum penetration is well supported in the article, as is the importance of knowing how much energy is lost at distance, as we must compensate by increasing our curing time.
Figure 6 of the article, which shows how to properly place the light close to, and at 90 degrees to a Class V composite resin however, shows a curing light with an angled light guide that is impossible to place at ninety degrees to the occlusal surfaces of posterior molar.
Class II restorations. This antiquated tip design has been replaced with curing lights that effectively place the light at ninety degrees in all classifications of clinical preparations. Similarly Figure 4 seems to show a turbo tip placed into a Class II preparation. It has been well-documented in the scientific literature that these tips, while having good energy at the tip, should never be used for curing composites in the proximal boxes of Class II restorations, as turbo type tips show a hight drop off of energy at distance.
Dr. Price and Dr. Strassler continue to help make us aware with their research work, that doing clinical restorative dentistry necessitates exquisite attention to detail and a thorough knowledge of all the principles involved in placing composite restorations.
I applaud their efforts.
Dr. Len Boksman,
Thank you for your letter to the editor. My article “Successful Light Curing — Not As Easy As it Looks” provides important information to the clinician to best evaluate their light curing practices and the adequacy of their own curing lights. Key to concepts of light curing is the amount of energy that is delivered to the restoration being placed. You pointed out that the curing light shown in figure 6 has an angled light guide. Tthe statement in your letter that the angled light guide shown is “impossible to place at ninety degrees to the occlusal surfaces of posterior molar Class II restorations.” Depending on the light used, some light angled guides depending on tooth position (even second molars) and patient mouth opening allow their tips to be placed at right angles. Some do not. The article makes a point in the section on restoration characteristics on this aspect of curing. It is not an absolute yes or no, but rather, based upon patient mouth opening each clinician needs to evaluate their curing light so that they can achieve a proper orientation. Also, you note that Figure 4 shows a turbo tip on a curing light. You state that turbo tips should “never” be used for cuirng composites in Class II proximal boxes. I agree that turbo tips have irradiance decreases based upon the distance from the tip, but since curing composite is about energy delivered to the restorative material, one merely needs to increase curing time taking care to cool the tooth for longer curing times. It would be better to use a non-turbo tip but for purpose of illustration, the guide is correctly oriented and the curing time was appropriately increased. Your letter’s points of “never use” really points to a clinician needs to make informative choices in the curing light they select and for curing lights they currently are using to achieve adequate photopolymerization of composite resins.
Howard E. Strassler,
DMD, FADM, FAGD
University of Maryland School of Dentistry, Department of Endodontics, Prosthodontics and Operative Dentistry,