Forums Laser Resources Laser Restorative Related Literature Lasers and Tensile Dentin Strength

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  • #3243 Reply

    Glenn van As

    Found this on pubmed where I occasionally look to see what is new in laser research…..suggesting that deeper penetrating wavelengths (diode , Nd Yag ) may have a greater effect on the dentin due to heat generation and affect perhaps the tensile bond strength of dentin.

    I have always said that a diode or soft tissue laser cant do much damage to a tooth. Do I worry now?

    I personally dont think so but here is the abstract.


    Photomed Laser Surg. 2005 Jun;23(3):278-83. Related Articles, Links

    Effects of laser irradiation on tensile strength of bovine dentin.

    Tonami K, Takahashi H, Kato J, Nakano F, Nishimura F, Takagi Y, Kurosaki N.

    Oral Diagnosis and General Dentistry, Dental Hospital, Tokyo Medical and Dental University, Tokyo, Japan.

    OBJECTIVE: The purpose of the present study was to investigate the tensile strengths of dentin after laser irradiation using three kinds of dental lasers to elucidate the laser-irradiation effect on dentin properties. BACKGROUND DATA: Different kinds of laser devices have been developed in dentistry. The characteristics of each laser are determined by its original wavelength; however, one common feature is to generate heat in irradiated tissues, and such heat possibly affects dentin collagen, which contributes to tensile strength of the tissues. MATERIALS AND METHODS: Er:YAG, CO2, and diode (GaAlAs) lasers were used to irradiate bovine dentin. Subsequently, tensile test specimens were made from the irradiated dentin and tensile tests were conducted. The tensile strengths were analyzed using the paired-t test and Weibull analysis. Irradiated dentin was also observed transversally using light microscopy. RESULTS: The tensile strengths of the lased dentin and the control group for the Er:YAG, CO2, and diode lasers were 73.1 and 78.5, 70.3 and 74.3, and 64.3 and 71.0 MPa, respectively. The tensile strength of the dentin had a tendency to decrease with laser irradiation. Weibull analysis indicated that the laser influence was different among the three kinds of laser apparatuses and seemed to correspond to the depths the laser beam reached, which were suggested by light microscopy observation. CONCLUSION: Laser irradiation could possibly decrease dentin tensile strength, which suggests the importance of careful use of laser for hard tissue treatment, considering its energy-transforming characteristics.

    #9592 Reply

    Robert Gregg DDS

    Hey Glenn,

    I know from years of previous research with Nd:YAG that dentin tensile strength is increased.

    I can’t speak to any diode studies, but I would not think it likely, especially since I don’t know anyone who is directly irradiating dentin as we do with FRP Nd:YAG.

    I’d chaulk this one up to academic curiosity………or the “A-Files” for wierd and unexplained phenomenons!


    #9591 Reply

    Glenn van As

    Bob, it is interesting how so much of the research on certain wavelengths keeps coming out of the same camps. For instance Aoki and his group does a ton of the research on Er:YAG lasers.

    I think that one of the problem with many of the studies (for example microleakage studies for Er:YAG lasers) that the researchers have zero idea of what settings to use that are clinically relevant. They rely on the companies supporting the study to tell them. THe reps dont know what is going on in the real world either in alot of cases.

    That is why so much of the research is useless at times in these early stages and so conflicting in nature. Now I have noticed that recently more microleakage studies are being done with Er:YAG lasers but many fire away with huge energy settings (ie enamel settings) on the enamel and then dont acid etch and compare to acid etched.

    Meanwhile in the real world those of us using the lasers have figured out that bevels need to be at much much lower settings and we either scrape the eneamel with a spoon or air abrade, diamond scrape etc the margins.

    Why cant researchers ask real world clinicians to look at the design (M and M) of their studies to make them more clinically relevant to us. I know that Hack amongst other things taught me to look more closely at the M and M – in so many cases it just has very little clinical relevance to how we are doing things in the real world.

    I actually like the literature search that I do every few months. I read the abstracts, occasionally get an article for download (got one yesterday on diodes and periodontal therapy) and read it to find out if there is clinical science to back up what I am doing in the real world.

    It shows how far the pioneers in this field are out there, when we are 2-3 years ahead of the researchers trying things out. Its also amazing how many times the research eventually shows that the stuff we bantered around on LDF and to a lesser extent on DT helped solve problems and that eventually the research backed up our claims.

    For Er:YAG eventually a study will compare power settings on enamel and look at microleakage……guess what they will find.

    Largest microleakage will occur with higher energy settings.

    Lowest will occur with caries or less settings , slightly defocussed with scraping of enamel or AA on the enamel to remove loose prisms.

    Its just a shame that we as clinicians have such a good idea how to do a relevant study but the researchers in their ivory towers keep missing the mark that clinicians have figured out a LONG time ago.

    All the best


    #9593 Reply

    Robert Gregg DDS


    I know what you mean.

    It is the nature of acdemicians to feel that clinicians have nothing to contribute. It is their bias on the heirarchy of evidence that all discoveries stem first from basic science instead of an observed clinical phenomenon. I’ve been seeing it just as you so eloquently described for the 15 years I’ve been using lasers

    Early adopters have been pretty good at adjusting their intra-operative parameters and getting around some manufacturer originated deficiencies in dosimetries.

    Why do they (academicians) listen so intently to the operating parameters that a PhD came up with on extracted teeth or dead cow tongue?!

    They need a Glenn van As or Ron Kaminer, or a Mark Colonna or an Eric Bornstein. Sometimes they listen, but usually only after considerable time has passed and they are so many frustrations with the manufacturer (and academically “researched”) recommended settings.

    Look at Nd:YAG and perio. The entire WORLD of lasers experts–save but a few like George Romonos–decided years ago (thanks in part to poor research desgin and execution by the UMKC studies and irrational negative bias of Zachariasen and Dederich) that Nd:YAG was the worst wavelength for perio. A dangerous Nylad Laser 35 with 800 usec and fixed 50 Hz didn’t help (again manufacturer-based and designed parameters)

    Del and I just said, “How can they be so sure of their conclusions and be so emphatically wrong?”

    So much of what Del and I have done, and continue to do with respect to science and research, is to overcome the ingrained negative conclusions by those in academia and research about Nd:YAG and perio.

    All that could be much less if university investigators would partner with clincians like we have done with Prof Yukna and is research team.

    Arrogance and exaggerated self-importance by academic researchers prevents many from partnership, from my humble observations. And often when it does happen, the university researcher wants to take all the glory and dismiss their clinical partners. We went through that as well early on with someone we thought was trustworthy. Not Ray Yukna. It’s been a great partnership that continues to benefit both entities.


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