A NEWSLETTER FOR DENTISTS FROM RTD
WELCOME TO OUR SECOND EDITION since they are the company that invented, Feature article: patented and commercialized them, in the The effects of mechanical properties on clinical performance of fiber posts.
Feature Interview Link to a revealing interview with Professor Simone Grandini, of Univ. Sienna; “father” of the Anatomic Post and Core
IN THIS ISSUE • New products from RTD • RTD’s new Mini-WebSite for Macro-Lock Post Illusion X-RO • More dentist testimonials for RTD posts • Feature Article: Characterizing Superior Fiber Posts: Flexure Strengths • Clinical Case: Anatomic Post & Core • Interview with Prof. Simone Grandini, Siena, Italy • Selected published research summaries
Fiber reinforced composite posts have been available to clinicians in most parts of the world for almost 20 years. As with composite resin filling materials and resin cements, there are a number of compositions available from different manufacturers, offering dentists a number of choices for their practice. Sometimes many choices leads to confusion, and to an erroneous conclusion that the products are “all the same”. It is a fact that the fiber posts in today’s market have similar characteristics in common. They all have an elastic modulus similar to that of dentin. They are all available in a aesthetic translucent or tooth- color shade. Fiber posts can generally be removed atraumatically, by hollowing from the inside out, unless they have a wire running down the middle of the structure. The similarities and between brands of fiber posts end about here. No company in the world has more expertise in the design, composition and manufacture of these products than RTD,
1980s. In this leadership role, it is important that we provide information that distinguishes our products from the many (good and bad) imitation products that exist in the market. There are at least four areas where it has clearly be shown, by in- vitro testing, that RTD products have an advantage: • flexural strength • fatigue resistance • radiopacity • light transmission Beginning with this issue of the RTD newsletter, and continuing with the next several issues, the editorial team will address one of these important clinically important areas in each issue. In this issue we address the importance and the reasons for the differences in flexural strength. The academic literature is rife with studies and abstracts comparing Fig. 1
Comparative Radiopacity* (Fig. 1)
(mm) % d’alluminium equivalent
300 300 250 250
Fiber Kleer 1.5mm
the Flexural Strength of different fiber posts, mostly resulting from the “competition” in a 3 point pending test. While this type of testing is easy 200 for a student or researcher to perform, it is often contradictory to previous, similar studies1-6 and misleading least to the readers.
200 150 100
WHY, then are some fiber posts so much stronger than others? RESISTENCIA
Flexural Strength (Fig. 2)
SNOWPOST 1.6 MM**
MACRO-LOCK POST™ ™ & ***
MACRO-LOCK POST™ X-RO™ * & ***
Over the years, many researchers 6 - 11 have noticed a clear observations correlating the in vitro performance (eg Flexural Strength, Cyclic Fatigue) and the composition of the posts :
The principal reason for this is because the very short span afforded On the typical Instron® machine, and the relatively short length of the 100 typical fiber post (16-22mm) do not allow adequate “span” for a sophisticated, authentic flexural test. Knowing this, RTD has always used the 50 50 MACRO-LOCK POST X-RO ISO standard test protocol #14125, which prescribes a Radiopacity flexural tests using a specimen of the raw material that is 20 times the length of its diameter (Fig. 1). Manufacturing companies that are ISO certified and CE marked are also obliged to follow this test protocol. And because of Latoradiopacidad del Macro-Lock X-RO mejora en ~50% ostentada porinfluence la generación precedente de postes this, it is then possible compare the flexural strength of the material fiber post is madelafrom, without the of post surface characteristics, degree of taper, post diameter, an options of the test equipment. (Fig. 2). The difference , using this methodology, is profound, and consistent.
Rely X **
Fiber Kleer 1.5 mm**
• the type and quality of fibers used (Quartz, S-Glass, e-glass, r-glass, Zirconia fibers, Carbon, and proprietary fibers) • the density of the fibers used (the ratio / % of resin matrix to the fibers) • the nature and quality of the bond between these fibers and the matrix (Interlaminate Shear Strength) to eliminate bubbles and voids Flexural strength test • the overall quality control of the manufacturing, that create weak points (Fig 3a-c) filler particles (Fig. 4), whichundisplace the fibers thatde enlace silano que incrementa la resistencia adhesiva • the inclusion of radiopacifiying Las fibras X-RO también incluyen exclusivo agente contribute to strength. manteniendo una alta resistencia a la fatiga. Fig. 3 a-c* 200 a: Multiple voids 200 180 Thermocycling Test* (Fig. 3) 180 (Angelus Post) 160 400 200 0
10 000 CYCLES
10 000 CYCLES
5 000 CYCLES
c. No voids (RTD post) 5 000 CYCLES
5 000 CYCLES
10 000 CYCLES
5 000 CYCLES
10 000 CYCLES
b. Some voids (Parapost Fiber White)
Having pioneered the fiber post, RTD made a huge development investment and 5 years’20 time to obtain a special fiber exclusively for use in 0 their range of endodontic posts and other potential dental reinforcement products. MACRO-LOCK POST MACRO-LOCK POST MACRO-LOCK POST MACRO-LOCK POST Thermocycling test
This proprietary process involves creating a special Silica (Quartz) glass (Fig 5) with an elevated content of radiopacifier, for added tensile strength and radiopacity. In developing its resiste la captación de agua en pruebas de termociclado extremo entre 50°C – 55°C* (Fig. 3). own expertise, RTD had concluded that it is more advantageous to make the base fibers more radiopaque, than to put the radiopacifiers into the resin matrix between the fibers. Under a sophisticated heat & stretching process, the glass is turned into the patented X-RO® fibers. These fibers are industrially coated / saturated with a proprietary, coupling agent formulated for this application, to promote an exceptional Interlaminate Shear Strength. The X-RO fibers, saturated in the matrix, are “pultruded” (maybe pre-tensed) under tension and heat to create an industrial composite mass that is several millimeters in diameter and more than 99% cross-linked, as confirmed by DSC testing. The move from one fiber to the next (X-RO) generation was done without sacrificing Flexural Strength, (~1800 MPa) or Fatigue Resistance (>10 million cycles). In summary, having a stronger raw material leads to a stronger final clinical product, allowing for modifications for shape, surface characteristics and anatomical considerations without compromising clinical performance.
References on page 10 * Scanning Electron Micrographs courtesy of Dra Karla Daniela Mora Barrios, University of the Andes, Venezuela
80 60 40 20 0
New Published Research RTD keeps an eye on the in vitro and clinical research that is being published on nearly every continent. There is plenty, and we use this newsletter to share some of what we consider to be the most significant studies, many of which distinguish RTD products and technology from the plain and ordinary. Influence of masticatory fatigue on the fracture resistance of the pulpless teeth restored with quartz-fiber post core and crown. Er-Min Nie, Xia-Yun Chen, Chun-Yuan Zhang, Li-Li Qi and Ying-He Huang. International Journal of Oral Science (2012) 4, 218–220; doi:10.1038/ijos.2012.78; published online 10 January 2013 The aim was to investigate whether masticatory fatigue affects the fracture resistance and pattern of lower premolars restored with quartz-fiber post, (DT Light-Post, RTD, St Egreve France) , core and full crown, 44 single rooted lower premolars recently extracted from orthodontic patients were divided into two groups of 22 each. The crowns of all teeth were removed and endodontically treated and then restored with quartz-fiber post–core and full crown. Twenty-two teeth in one group were selected randomly and circularly loaded at 456 to the long axis of the teeth of 127.4 N at a 6 Hz frequency, and the other group was not delivered to cyclic loading and considered as control. Subsequently, all teeth in two groups were continually loaded to fail at 45 degrees to the long axis of the teeth at a crosshead speed of 1 mm/min. The mean destructive force values were (733.886254.99) and (869.146280.26) N for the experimental and the control group, respectively, and no statistically significant differences were found between two groups (P .0.05). Bevel fracture and horizontal fracture in the neck of root were the major fracture mode of the specimens. Under the circumstances of this study, it seems that cyclic loading does not affect the fracture strength and pattern of the quartz-fiber post–core–crown complex. Within the limitations of this study, no significant differences were found for their fracture resistance and pattern of the quartz-fiber post– core–crown complex before and after cyclic loading, and the quartzfiber post–core and crown restoration exhibit a good fatigue resistance. Editor comment: In vitro testing has progressed during years of research with fiber posts.The use of cyclic loading improves the research and creates a situation closer to the clinical one but with some considerations. Under the circumstances this research was done, cyclic loading did not show differences between both groups. The premolars restored with D.T. Light-Post exhibited good results and cyclic loading did not reduce significantly its resistance to fracture. These results , under the circumstances of which he research was done, shows the adequate resistance D.T. Light-Post posts gives to the overall rehabilitation.
Randomized clinical trial comparing the effects of post placement on failure rate of post-endodontic restorations: Preliminary results of a mean period of 32 months. Kerstin Bitter, Jorn Noetzel,Oliver Stamm, Juliane Vaudt, Hendrik MeyerLueckel, Konrad Neumann, and Andrej M. Kielbassa, J Endod 2009;35:1477–1482 The aim of this randomized clinical trial was to assess whether the placement of a fiber post (DT Light Post, RTD, St Egreve, France) (DT) and the amount of residual coronal dentin affect the time to failure of single-unit post-endodontic restorations. Methods: Ninety patients providing 120 teeth were selected. Three groups (n = 40) were defined on the basis of the amount of residual coronal dentin: 2-walls group, 2 or more coronal walls; 1-wall group, 1 coronal wall; no-wall group, no wall exceeding 2 mm above the gingival level. Within each group teeth were randomized and allocated to 2 intervention groups (n = 20), including subgroups no post (no root canal retention) and subgroups post (placement of DT). Results: After a mean observation period of 32.4 (13.7) months in subgroups no post, the failure rates were 10%, whereas in subgroups post, failure rates of 7% were observed (P = .318). In no-wall group post placement significantly affected the time to failure of total restorations (P = .029, log-rank test). Teeth without post retention revealed a significantly higher failure rate (31%) compared with teeth restored with post retention (7%). Conclusions: Within the observation time of the present study, fiber post placement was efficacious to reduce failures of post-endodontic restorations only with teeth that exhibited no coronal walls. Post insertion for teeth showing a minor substance loss should be critically reconsidered. Within the limitations of the present study (inclusion of various coronal single-unit restorations, unequal distribution of the various tooth types, as well as a mean observation period of 32.4 [13.7] months), it can be concluded that quartz fiber post placement is efficacious to reduce failures of post-endodontic restorations of teeth that exhibit no coronal wall above 2 mm of the gingival level. Post insertion for teeth showing a minor substance loss should be critically reconsidered to avoid overuse. Editor comment: To consider all of the dental issues when a post and crown is used is very important. It is necessary with a proper clinical criteria , to evaluate the position of the tooth, occlusal aspects, patient needs, esthetics, and to conserve as much dentin as possible and to evaluate the remaining dentin to select the appropriate alternative for the restoration. Under the circumstances of this research, the indication and use of quartz fiber posts (D.T. Light-Post) with the adequate resistance are able to be used for the rehabilitation of clinical situations where a minimum dentin is kept with lower risk of failure compared with other options.
CLINICAL CASE STUDY
Each issue will feature at least one case study showing clinical steps using RTD products. The complete cases, with as many as 24 step photos, can be reviewed at www.rtd.fr website. The clinical cases have been donated by recognized clinicians and teachers from all over the world. The cases are selected by a committee and the editor does not bear responsibility for the accuracy or appropriateness of the treatment plans or step sequence. Fig.1
ANATOMIC POST AND CORE This case was donated by Dr. Alejandro Bertoldi Hepburn, of Universidad de Desorolla, Concepcion, Chile.
Fig. 2 Fig. 3
When the opening of the post space is 25% - 50% wider than the selected fiber post, there are additional low-modulus techniques available. Direct-indirect chair-side techniques, using composite resin over the post, allow good adaptation. A light-cured composite can fill the flared space. Once the post is removed, the â€œsupplementalâ€? composite can be additionally cured, to enhance several of its properties. This patient presented with a failed cast post and core which was exhibiting dark-root syndrome (Fig.1) When the post is removed, it is obvious that there is corrosion and corrosion by-product left inside the tooth.
After removing the corrosion by-product and additional debris, the depth of the post space is established using the universal starter drill to remove any remaining gutta percha. The post space is then customized, removing undercuts, using the sequence of finishing drills provided in the system (Fig. 2). Clearly, there is a exceptional flare toward the coronal opening of this space (Fig. 3). Because cement is not inherently strong in bulk, a light cured hybrid composite will ultimately be used to fill this space. In this particular case, the number 3 size Macro-Lock Illusion post has the best fit in the apical 3rd. (note the intrinsic color-coding) This post is tried- in to confirm the fit (Fig. 4), still noting the profound space at the neck of the post.
After the Try-In, a water-soluble separating medium was applied to all exposed hard surfaces (Fig. 5), to prevent sticking of the hybrid composite when pressed against the interior surfaces of the tooth.
After cleaning the post, a compatible resin adhesive such as Sealbond Ultima is applied to the post, air-dried and light-cured.and a high-strength, light-cured composite (eg Lumiglass) is adapted over the coronal third of the root-canal portion of the post (Fig. 6).
The post and composite is re-inserted, and the composite is adapted to the flared open space (Fig. 7). It is “spot-cured” from the occlusal aspect, then withdrawn. A felt tip pen is used to mark the post as to orientation for re-seating. the same mark can also be used to designate the preferred length of the post and where to trim off the excess post length. It is further cured extra-orally, to increase its degree of conversion and, in this way, it’s flexural resistance. You can see how the composite has taken the adapted shape of the flare of the post space (Fig. 8). The custom-fitted post assembly can now be cemented or bonded back into the space, following the manufacturer’s directions (Fig. 9). A dual-cure, resin cement (such as Corecem or Sealbond Cement from RTD) is the least soluble, and is compatible with the airinhibited surface of the cured composite on the post. Immediate light-curing from the occlusal aspect stabilizes the post.
The excess resin cement / can be left in place (Fig. 10) as part of the core build-up, which is carried out with resin composite (Fig. 11), then temporized. As the soft tissue healed, and the final crown is placed (Fig. 12), the discoloration disappeared. Fig. 12
PRODUCT NEWS CORECEM™ ILLUSION®
Corecem Illusion® is exactly like regular Corecem, except that it incorporates the patented Illusion Color -On Command technology like used in DT Light-Post® Illusion and Macro-Lock™ Post Illusion. This presents as a BLUE posterior core composite while being manipulated, for easy contrast against natural tooth structure. After finishing, the BLUE color disappears, leaving a popular A1 shade.
PROFESSIONALS’ TESTIMONIALS “Corecem Illusion not only enhances clinical efficiency by allowing one to cement a post and build up a core with the same outstanding material, but the color change feature also completely solves the problem of visualizing the core in sub-gingival preparations, without compromising esthetics. I highly recommend Corecem Illusion.” Dr. Tony Pensak, Calgary, Alberta, Canada “I prefer the stackability and handling of Corecem to other materials I have used for this purpose. Corecem is a very friendly material to use and solves both cementation and core build up together.” Prof. Dr. Daniel Torassa Universidad Nacional de Córdoba, Universidad Católica de Córdoba, Argentina "I enjoy using Corecem Illusion in my practice because it couldn't be any easier to dispense, cuts just like dentin and the on-demand blue color shows me exactly where the core margins are while I'm prepping." Dr. Mark L. Pitel, Associate Clinical Professor, University College of Dental Medicine Professor of Operative Dentistry, Director of Predoctoral and CDE Esthetic Studies, Columbia University, New York City
WHY DENTISTS LOVE MACRO-LOCK™ILLUSION® X-RO® The MACRO-LOCK Post was introduced in 2009 at the very height of the DT Light-Post’s ascent to being the world’s leading fiber post. It was a gamble for RTD to launch its own brand that might compete with the DT Light-Post, however, there were good reasons. There are, and will always be, dentists who lack of access to good bonding materials, light curing equipment or lower confidence in bonding to internal dentin, prefer to use a more “traditional” type of cement (such as Glass Ionomers or RMGIs) and therefore will want the added security of a “macro-retentive surface” , such as provided on the Macro-Lock post family. Today many, MANY dentists are bonding the Macro-Lock posts, with and without Fibercone™ Accessory Posts, and most markets are capable of supporting both the Macro-Lock and DT Light-Post. We asked a number of dentists who have been using the Macro-Lock Post shape, or testing them in the laboratory. Here are some of these testimonials, which will also be available for viewing by your clients on RTD’s updated website.
Dra. Sandra Costa Zamboni Dept. of Dental Materials and Prosthodontics, São Paulo State University at São José dos Campos, Brazil
Dr. Yining Wang Director of Prosthodontics Department, School of Stomatology, Wuhan University, China
Dr. Christine Berthold, Dept. of Endodontics, Univ. of British Columbia, Canada, Department for Operative Dentistry and Periodontology, Univ. Erlangen, Germany
Dr. Manfred Friedman Private Practice, Adjunct Professor, Schulich School of Medicine & Dentistry, Univ. of Western Ontario, London, Ontario, Canada
"I have used RTD fiber posts since 1997 and do not have cases of breaking or failure in my treatments. Moreover, these Macro-Lock posts offer the best versatility and perfect adaptation on the root canals of the many posts I have evaluated in the laboratory, and in the clinic. I can observe and quantify that they always present the best results in terms of fatigue resistance, adhesion and conductivity of light. RTD fiber posts provide me confidence as a professional, and security for the patient."
“The validity of fiber post has been confirmed by both of the clinical data and experimental studies. I have been using Macro-Lock fiber post for more than three years. The clinic outcome is excellent. Meanwhile, the mechanical properties of Macro-Lock fiber post have been tested in our studies, experimental or numerical analysis. The quality of Macro-Lock fiber post is outstanding.”
"I have used these RTD (Macro-Lock) posts clinically with satisfaction, and appreciate their properties and their quality. But perhaps just as importantly, my research team and I have tested them in the laboratory over several years' time. We have found that even with a variety of cement types they demonstrate good- to -excellent retention, especially compared to similar fiber posts that are without the retention features, and to cemented metal posts used as the controls."
“I have placed over 500 Macro-Lock posts without a single failure. The tapered shape facilitates minimal removal of tooth structure and ensures a minimal amount cement, which minimizes polymerization shrinkage and micro-leakage. Superior physical properties, along with macro and micro-retention, and anti-rotational features make this my post of choice for extensively broken down teeth.”
INTERVIEW WITH PROFESSOR SIMONE GRANDINI Professor Simone Grandini, DDS, MSc ,PhD is the Chair of Endodontics and Restorative Dentistry Department of Endodontics and Restorative Dentistry, Dean of the School of Dental Hygienists at the Tuscan School of Dental Medicine, University of Siena, Italy. Since 1996 he has published and collaborated on numerous articles and invitro and clinical studies involving post-endodontic rehabilitation using the low-modulus approach. Dr Grandini is credited with “officializing” the chair-side Anatomic Post and Core. 1. Dr. Grandini, in several publications you have described/defined the Anatomical Post as “a translucent fiber post covered by a layer of light curing resin -cured outside of the mouth - which allows for an individual, anatomic shaping of the post through its insertion into the prepared canal”. What do you consider to be the greatest clinical advantage(s) of this technique?
“The “Anatomical post” has a main advantage: a uniform layer of cement. This will reduce the chance of debonding, leading to an ideal condition for post retention, and possibly to a higher strength of the whole system.” 2. What are the primary indications, seen by most general dentists, for this technique, and would you consider it to be a bona fide alternative to a custom cast post?
“This kind of post is basically a resin based cast post! In those clinical situations where the dentist finds an oval canal, the anatomical post will be able to fit very well, reducing the amount of material used during cementation procedures. A lower amount of cement during polymerization will lead to less voids in the cement layer, again reducing the de-bonding which is the main problem of fiber posts in non rounded canals.” 3. In your SEM evaluations of this type of restoration, what was the most important finding?
“The resin cement thickness was significantly lower when using anatomic posts than when using a normal post (standardized posts), especially at the coronal and middle third of the canal. A good adaptation of the anatomical post was evident, and the clinical advantages during cementation became obvious at that point.”
4. Why do you feel that the Anatomic Post and Core technique might be superior to filling this space with light-cure or dualcure composite alone (without a post), as some recommend?
“When using only light-cure or dual-cure composite alone (without a post), there is no “reinforcement” of the inner part of that structure, which is mainly used for “retention” of the unit and for “strengthening” the tooth itself. It has been demonstrated that when some kind of fiber post is cemented in the canal, a favorable failure (restorable fracture) occurs.” 5.The technique steps are demonstrated in a another part of this newsletter, but generally what do you consider to be the most critical, or technique-sensitive step or aspect in this technique?
“Relining the post inside the canal is the only difficult step. The dentist must be aware that a lubricant must be used, and that all undercuts must be taken off. If these rules are respected, a good result and an easy procedure are guaranteed.” 6. You first describe this technique at the beginning of the century in your thesis and in a textbook. Since then, new cement formulations have emerged, including self -etching and self adhesive varieties of resin cement. In your view, can any or all of these be recommended for use in placement of the Anatomic Post and Core, or is the technique dependent upon the “totaletch” cementation technique, and is there anything more that you and your colleagues have learned, since your original publications nearly a decade ago, by repeated application and observation of this technique?
“Henry Pickering, Dean of the Harvard Medical School, in 1965 said that: “Half of what you are taught will be wrong in 10 years and the problem is none of your teachers knows which half”. If you asked me this question 10 years ago I would have answered “total -etch” is the only way. I see a lot of interesting results even with self-etch systems, and self-adhesive cements are getting better, even if up to now they’re not exactly as total- or self-etch systems. We have to keep in mind that the dentist is an important variable in the system, so anything that simplifies the cementation procedure is welcomed. I have to say I am used to etch the canal and I don’t find it particularly difficult!”
VISIT RTDâ€™S MACRO-LOCK ILLUSION X-RO MINI-SITE RTD has created a unique mini-website, dedicated to the Macro-Lock Illusion X-RO SYSTEM. It includes multiple animations and data to quickly address all the benefits of the system. It is available in English only at this time.
References from feature article 1. Galhano, GA, Valandro, LP, deMelo, R., Scotti, R., Bottino, MA. Evaluation of the flexural strength of carbon fiber, quartz fiber and glass fiber â€“ based posts. JOE Vol. 31. No. 3, March 2005, 209-211 2. Seefeld, F, Wenz, HJ, Ludwig, K, Kern, M. Resistance to fracture and structural characteristics of different fiber reinforced post systems. Dent Mater. 2007 Mar;23(3): 265-71 3. Tomazinho, F.S.F., Zaitter, S., Silva, S.R.C., Alfredo, E. and Y.T.C. Silva-Sousa, Y.T.C. Flexural properties of fiber reinforced root canal posts. J Dent Res. Vol 89 (Spec. Iss. B) Abstract #3115, 2010 (www.dentalresearch.org) 4. Plotino, G, Grande, NM, Bedini, R, Pameijer, CH, Somma, F. Flexural properties of endodontic posts and human root dentin. Dent Mater J. 2006 Vol 231129-1135 5. Novais, V.R., Quagliatto, P.S., Bona, A.D., Correr-Sobrinho, L, Soares, C.J.. Flexural modulus, flexural strength, and stiffness of fiber-reinforced posts. Indian J Dent Res. 2009 Jul-Sep;20(3):277-81. 6. Beck, P., Ghuman, T., Cakir, D. Ramp, L. Burgess, J. Evaluation of flexural strength and elastic modulus of endodontic posts. J Dent Res. Vol 88 (Spec. Iss. A) Abstract # 3065, 2009. (www.dentalresearch.org) 7. Stewardson, DA, Shortall, AC, Marquis, PM, Lumley, PJ. The flexural properties of endodontic post materials. Dent Mater. 2010 Aug;26(8):730-6. Epub 2010 Apr 21 8. Cheleux, N., Sharrock, P.J., Mechanical properties of glass fiber-reinforced endodontic posts. Acta Biomater. 2009 Oct;5(8):3224-30. Epub 2009 Apr 24. 9. Grandini, S., Goracci, C., Monticelli, F., Borracchini, A., Ferrari, M. An evaluation, using a three-point bending test, of the fatigue resistance of certain fiber posts. II Dentista Moderno, March, 2004, 70-74 10. Stewardson, DA, Shortall, AC, Marquis, PM. The effect of clinically relevant thermocycling on the flexural properties of endodontic post materials. J Dent. 2010 May; 38(5):437-42. Epub 2010 Feb 25. 11.Marco Ferrari & Roberto Scotti. Fiber Posts: Characteristics and clinical applications. Masson Publishing 2002