Stress Distribution Analysis on Mandibular Implant Supported Overdentures

VOLUME 2, NO. 9 NOVEMBER 2010 The Journal of Implant & Advanced Clinical Dentistry Stress Distribution Analysis on Mandibular Implant Supported Overdentures Rapid Smile Makeover Dr. David Garber





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The Journal of Implant & Advanced Clinical Dentistry VOLUME 2, NO. 9 • NOVEMBER 2010 Table of Contents 19 Case of the Month Rapid Smile Makeover: A Pictorial Essay David Garber 27 Case Reports Describing The “Bump”: A New Phenomenon in Implant Healing Paul S. Rosen, Neil Meredith, Mark A. Reynolds 41 “Toronto” Screwed Mandibular Overdenture on Dental Implants: FEM and Von Mises Analysis of Stress Distribution M. Cicciù, G. Risitano, C. Maiorana, A. Herford, G. Oteri, D. Cicciù The Journal of Implant & Advanced Clinical Dentistry • 5

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The Journal of Implant & Advanced Clinical Dentistry VOLUME 2, NO. 9 • NOVEMBER 2010 Table of Contents 63 The Twin Implant: A New Subperiosteal Dental Implant Antonio T. Di Giulio,, Giancarlo Di Giulio, Enrico Gallucci 69 Restoration of a Partial-Maxillectomy Patient with a Prosthesis Supported by Dental Implants in Both the Reconstuctive Bone Graft and the Residual Bone: An 8-Year Follow-up Kosuke Honda, Kazuki Takaoka, Yoko Yasukawa, Hiromitsu Kishimoto, Masao Kakibuchi, Masahiro Urade 75 Dental Practice Marketing for the Next Decade Shannon Mackey The Journal of Implant & Advanced Clinical Dentistry • 7



The Journal of Implant & Advanced Clinical Dentistry VOLUME 2, NO. 9 • NOVEMBER 2010 Publisher Copyright © 2010 by SpecOps Media, LLC. All rights SpecOps Media, LLC reserved under United States and International Copyright Conventions. No part of this journal may be reproduced Design or transmitted in any form or by any means, electronic or Jimmydog Design Group mechanical, including photocopying or any other information www.jimmydog.com retrieval system, without prior written permission from the publisher. Production Manager Stephanie Belcher Disclaimer: Reading an article in JIACD does not qualify 336-201-7475 the reader to incorporate new techniques or procedures discussed in JIACD into their scope of practice. JIACD Copy Editor readers should exercise judgment according to their JIACD staff educational training, clinical experience, and professional expertise when attempting new procedures. JIACD, its Digital Conversion staff, and parent company SpecOps Media, LLC (hereinafter NxtBook Media referred to as JIACD-SOM) assume no responsibility or liability for the actions of its readers. Internet Management InfoSwell Media Opinions expressed in JIACD articles and communications are those of the authors and not necessarily those of JIACD- Subscription Information: Annual rates as follows: SOM. JIACD-SOM disclaims any responsibility or liability Non-qualified individual: $99(USD) Institutional: $99(USD). for such material and does not guarantee, warrant, nor For more information regarding subscriptions, endorse any product, procedure, or technique discussed in contact [email protected] or 1-888-923-0002. JIACD, its affiliated websites, or affiliated communications. Additionally, JIACD-SOM does not guarantee any claims Advertising Policy: All advertisements appearing in the made by manufact-urers of products advertised in JIACD, its Journal of Implant and Advanced Clinical Dentistry (JIACD) affiliated websites, or affiliated communications. must be approved by the editorial staff which has the right to reject or request changes to submitted advertisements. Conflicts of Interest: Authors submitting articles to JIACD The publication of an advertisement in JIACD does not must declare, in writing, any potential conflicts of interest, constitute an endorsement by the publisher. Additionally, monetary or otherwise, that may exist with the article. the publisher does not guarantee or warrant any claims Failure to submit a conflict of interest declaration will result made by JIACD advertisers. in suspension of manuscript peer review. For advertising information, please contact: Erratum: Please notify JIACD of article discrepancies or [email protected] or 1-888-923-0002 errors by contacting [email protected] Manuscript Submission: JIACD publishing guidelines JIACD (ISSN 1947-5284) is published on a monthly basis can be found at http://www.jiacd.com/author-guidelines by SpecOps Media, LLC, Saint James, New York, USA. or by calling 1-888-923-0002. The Journal of Implant & Advanced Clinical Dentistry • 9



The Journal of Implant & Advanced Clinical Dentistry Founder, Co-Editor in Chief Founder, Co-Editor in Chief Dan Holtzclaw, DDS, MS Nicholas Toscano, DDS, MS Editorial Advisory Board Tara Aghaloo, DDS, MD Robert Horowitz, DDS Michele Ravenel, DMD, MS Faizan Alawi, DDS Michael Huber, DDS Terry Rees, DDS Michael Apa, DDS Richard Hughes, DDS Laurence Rifkin, DDS Alan M. Atlas, DMD Debby Hwang, DMD Georgios E. Romanos, DDS, PhD Charles Babbush, DMD, MS Mian Iqbal, DMD, MS Paul Rosen, DMD, MS Thomas Balshi, DDS Tassos Irinakis, DDS, MSc Joel Rosenlicht, DMD Barry Bartee, DDS, MD James Jacobs, DMD Larry Rosenthal, DDS Lorin Berland, DDS Ziad N. Jalbout, DDS Steven Roser, DMD, MD Peter Bertrand, DDS John Johnson, DDS, MS Salvatore Ruggiero, DMD, MD Michael Block, DMD Sascha Jovanovic, DDS, MS Henry Salama, DMD Chris Bonacci, DDS, MD John Kois, DMD, MSD Maurice Salama, DMD Hugo Bonilla, DDS, MS Jack T Krauser, DMD Anthony Sclar, DMD Gary F. Bouloux, MD, DDS Gregori Kurtzman, DDS Frank Setzer, DDS Ronald Brown, DDS, MS Burton Langer, DMD Maurizio Silvestri, DDS, MD Bobby Butler, DDS Aldo Leopardi, DDS, MS Dennis Smiler, DDS, MScD Donald Callan, DDS Edward Lowe, DMD Dong-Seok Sohn, DDS, PhD Nicholas Caplanis, DMD, MS Shannon Mackey Muna Soltan, DDS Daniele Cardaropoli, DDS Miles Madison, DDS Michael Sonick, DMD Giuseppe Cardaropoli DDS, PhD Carlo Maiorana, MD, DDS Ahmad Soolari, DMD John Cavallaro, DDS Jay Malmquist, DMD Neil L. Starr, DDS Stepehn Chu, DMD, MSD Louis Mandel, DDS Eric Stoopler, DMD David Clark, DDS Michael Martin, DDS, PhD Scott Synnott, DMD Charles Cobb, DDS, PhD Ziv Mazor, DMD Haim Tal, DMD, PhD Spyridon Condos, DDS Dale Miles, DDS, MS Gregory Tarantola, DDS Sally Cram, DDS Robert Miller, DDS Dennis Tarnow, DDS Tomell DeBose, DDS John Minichetti, DMD Geza Terezhalmy, DDS, MA Massimo Del Fabbro, PhD Uwe Mohr, MDT Tiziano Testori, MD, DDS Douglas Deporter, DDS, PhD Dwight Moss, DMD, MS Michael Tischler, DDS Alex Ehrlich, DDS, MS Peter K. Moy, DMD Michael Toffler, DDS Nicolas Elian, DDS Mel Mupparapu, DMD Tolga Tozum, DDS, PhD Paul Fugazzotto, DDS Ross Nash, DDS Leonardo Trombelli, DDS, PhD Scott Ganz, DMD Gregory Naylor, DDS Ilser Turkyilmaz, DDS, PhD David Garber, DMD Marcel Noujeim, DDS, MS Dean Vafiadis, DDS Arun K. Garg, DMD Sammy Noumbissi, DDS, MS Emil Verban, DDS Ronald Goldstein, DDS Arthur Novaes, DDS, MS Hom-Lay Wang, DDS, PhD David Guichet, DDS Charles Orth, DDS Benjamin O. Watkins, III, DDS Kenneth Hamlett, DDS Jacinthe Paquette, DDS Alan Winter, DDS Istvan Hargitai, DDS, MS Adriano Piattelli, MD, DDS Glenn Wolfinger, DDS Michael Herndon, DDS George Priest, DMD Richard K. Yoon, DDS Giulio Rasperini, DDS The Journal of Implant & Advanced Clinical Dentistry • 11

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Letters to the Editors JIACD has been a great addition for and a camaraderie building experience with your dentists to learn about the latest in peers. Additionally, you can receive feedback techniques and interdisciplinary care. from readers in over 80 countries in as quickly as The thing that has impressed me the most 3 to 6 months following submission. TRY IT! about this journal is that the information Dr. Tom Wilcko, Erie, Pennsylvania, USA is online, easy to access, and the quality of the photos and case presentations is JIACD brings to all aspects of dentistry some amazing. things that are lacking with other journals. Dr. Paul Rosen, Philadelphia, The articles are timely, relate to all aspects of Pennsylvania, USA dentistry, and are relevant to all readers. As a researcher and clinician, I appreciate the I really appreciate JIACD because it’s a timeliness of getting my articles published fundamental tool for both practitioner and AND reading the current research performed researcher in the field of Periodontology and by others in the field. This is what dentistry dental implant continuing education. What I has needed for a long time to help us all move prefer most is the reliability, the friendly use, and forward more quickly to deliver the best, latest, the extremely high quality of the images and the state-of-the-art care to our patients. interesting topics. Clinicians and scientists can Dr. Robert Horowitz, Scarsdale, New York, USA find clear clinical suggestions and solutions to new and old problems for daily practice. My complements on what you have Dr. Giulio Rasperini, Italy accomplished with this online publication. Content has been superb. What a service JIACD is a very informative and educational to implantology. online journal. Each issue educates with cutting Dr. Gary Henkel, Horsham, Pennsylvania, USA edge clinical technology. The best advantages of JIACD are unlimited openness to clinicians After reading several informative, well written all over the world. I highly recommend dental articles by highly respected educators and clinicians to become subscribers of JIACD. clinicians I was inspired to submit my own article Dr. Dong-Seok Sohn, Republic of Korea to JIACD. The editorial process was speedy and painless and the reviewers made some very The internet is now the medium of choice helpful suggestions actually improving my original for the timely distribution and collection of submission. I intend to continue writing for the knowledge. The editors and reviewers of journal as I am anxious to be a part of this superb JIACD understand the concept of “timely”. The online educational process. JIACD review process is thorough but streamlined Dr. Michael Toffler, New York, New York, USA The Journal of Implant & Advanced Clinical Dentistry • 13

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Editorial Commentary Different Worlds Over time, I have had the great fortune to in an interesting and intellectually stimulating be a part of many different subcultures of atmosphere. You typically are on the cutting edge dentistry including private practice, public regarding new procedures and materials. You do service, and academia. It is very interesting not have to worry about finding patients for your to reflect upon the different experiences practice, they find you. While academia has many that each of these types of practice provide. of the same drawbacks as public service, it also has certain unique challenges of its own. First of Public service dental practice can entail many all, advancement in academia is often difficult as things ranging from military service to working people in power such as department chairs can on Native American Indian reservations. With sometimes hold their position for decades. You this type of practice, you make certain sacrifices also have the added pressures of obtaining tenure with the biggest being a lack of control. By this, and constantly producing publishable research. I mean that you are not your own boss. You have certain limitations on what you can and cannot do. Finally, there is private practice. This is the You have certain limitations on what you can and type of practice that most are familiar with. Private cannot buy. You have to abide by policies that practice is capitalism at its best. The harder you are established by others and you may not exactly work, the more you earn. If you are more creative agree with them. You often have to move your and provide better service than the competition, family every few years to work where your public you generate more income. Best of all, you are service organization needs you. Motivation is the boss. You can do what you want, buy what sometimes a problem because if you work harder, you want, and set your own policies. Like other you still receive the same pay as the guy who is a types of practice, private practice has its own slacker. Finally, the pay you receive is usually fairly unique issues. First and foremost is risk. If you low in comparison to those in private practice. fail in private practice, you can go bankrupt. On the flip side, with this type of practice you There is no guaranteed income. There are major have a guaranteed income, fringe benefits such expenses such as practice loans, real estate, as excellent health care, and typically a generous employees, equipment, supplies, and advertising. retirement plan. You do not have to worry about Patients don’t automatically find you, you have to paying employees, buying equipment on your own find them. dime, or other business related matters such as providing health insurance and retirement plans. When interacting with our colleagues, we Additionally, you get the personal satisfaction should respect one another and realize that of knowing that you are contributing to the everyone’s practice has their own unique set of greater good of something larger than yourself. benefits and hardships. Depending on where your organization, you may be serving your country and fellow citizen or Dan Holtzclaw, DDS, MS Nick Toscano, DDS, MS helping those less fortunate than others. Founder, Co-Editor-In-Chief Founder, Co-Editor-In-Chief Like public service, academia has many The Journal of Implant & Advanced Clinical Dentistry • 15 benefits such as guaranteed income, excellent fringe benefits, and often a generous retirement plan. You work daily with many other colleagues

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Case of the month Garber Rapid Smile Makeover: A Pictorial Essay David Garber, DDS1 Abstract Long term research data on dental porce- and complex. 3) Use of a wax up and silicone lain veneers have demonstrated the need stent to develop a trial smile directly in the mouth: to retain as much enamel as possible dur- allows evaluation of function and esthetics. ing the preparation phase. With this in mind, the preparation process has evolved through With a trial smile, one can re-impress to cre- 3 distinct generations. 1) Arbitrary controlled ate a guide for final pressed veneers and then depth cuts of the remaining tooth substance: prepare directly through the Trial Smile acrylic. but this inevitably extends through to dentin cre- This technique limits preparations to predomi- ating potential predictable long term bonding nantly enamel, ensuring longevity and allows the issues. 2) Wax up the desired new tooth form patient the opportunity to evaluate the poten- extending slightly labially (0.25mm) and develop tial final case form directly in the mouth. There silicone indices/matrices to evaluate controlled are no surprises and a simpler, more predict- intra-enamel preparation relative to new position- able seating appointment is achieved. This ing of teeth: a good system but time consuming paper is a pictorial essay of a rapid smile makeover utilizing the trial smile technique. KEY WORDS: Dental veneers, prosthodontics, dental atraumatic restorative treatment, dental esthetics, tooth preparation 1. Private practice, Atlanta, Georgia, USA The Journal of Implant & Advanced Clinical Dentistry • 19

Garber Figure 1: Preoperative view of a patient desiring ultra-conservative but rapid solution to the wear, shape and relative spacing of his anterior teeth and overall smile. Figure 2: Wax up to redevelop normal tooth form, lengthen the teeth and close proximal spacing, and then evaluate the relative proportion of waxed tooth form relative to the lip drape, within the context of a “trial smile”. Figure 3: Arbitrary depth guide. Figure 4: Silicon index guide. 20 • Vol. 2, No. 9 • November 2010

Garber Figure 5: Prep through a direct composite mock up. Figure 6: Preoperative lateral oblique view of smile showing spacing and attrition/wear. Figure 7: Vinyl polysiloxane (VPS) matrix developed Figure 8: Trial smile step 1: Block out interproximal from wax-up. This matrix should extend 2 teeth beyond undercuts with Opal Dam (Ultradent, South Jordan, Utah, proposed teeth to be treated and 6mm beyond the free USA) gingival margins on the buccal and palatal aspects. Figure 9: Trial smile step 2: Apply Mucolube to soft tissues Figure 10: Trial smile step 3: Fill silicone index with ethyl- and any proximal block out material. methacrylate temporary acrylic and place over unprepared teeth. The Journal of Implant & Advanced Clinical Dentistry • 21

Garber Figure 11: Trial smile step 4: Place silicone index over Figure 12: Trial smile step 5: Peel excess material from unprepared teeth & bottom out over distal stops and soft lubricated tissue using Hugh-Friedy CRNT 12 (Hu-Friedy, tissue. Let set and then remove matrix leaving acrylic trial Chicago, Illinois, USA) smile in place over teeth. Figure 13: Trial smile step 6: Add composite tints to create Figure 14: Preparation done through the Trial Smile with separation, coat with Biscover (Bisco, Schaumburg, Illinois, Brasseler LVS 4151 Kit (Brasseler USA, Savannah, Georgia, USA) and cure. Then reevaluate for length, form, and USA) not dependant on arbitrary depth-cuts but directly position within the smile. related to the proposed nal result. Results in conservative intra enamel reduction. Figure 16: Post-operative veneers are luted in position. Figure 15: Conservative Mock-up Guided completed intra- enamel preparations to optimize long term bonding and retention. 22 • Vol. 2, No. 9 • November 2010

Garber Figure 17: Before rapid smile makeover. Figure 18: Postperative view of veneers in position and change in smile esthetics. Figure 19: Lateral oblique view before veneers. Figure 20: Lateral oblique smile line before veneers. Disclosure: The author reports no conflicts of interest with anything mentioned in this article. Correspondence: Dr. Garber 600 Galleria Parkway SE Suite 800 Atlanta, Georgia 30339 USA Figure 21: Post-operative lateral oblique view of smile. The Journal of Implant & Advanced Clinical Dentistry • 23

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Case Reports Describing The “Bump”: Rosen et al A New Phenomenon in Implant Healing Paul S. Rosen, DMD, MS1 • Neil Meredith BDS, PhD2 Mark A. Reynolds, DDS, PhD3 Abstract This article presents 28 cases demonstrat- from those seen at placement until osseointe- ing a phenomenon that will be termed the gration causes an increase back to and quite “Bump”. Historically, implants have seen possibly greater than those initially measured. an early decrease in their stability as healing The patients presented in these case reports progressed from primary mechanical stability to were treated with enhanced surface implants biologic bone remodeling and formation better exhibiting electro-wetting and demonstrated known as osseointegration. The lag between ISQ values during early healing periods of 2 the predominance of biologic over mechani- and 4 weeks that were significantly higher than cal stability has been termed the dip. This can those measured at insertion. The possibility that be quantitatively measured by resonance fre- this may relate to accelerated wound healing quency analysis (RFA) where the implant sta- should be considered, expanding the option for bility quotient (ISQ) values decrease with time loading such implants at an earlier time frame. KEY WORDS: Dental implants, bone, remodeling, osseointegration, implant stability quotient, electrowetting 1. Private practice limited to Periodontics and Dental Implants, Yardley, Pennsylvania, USA. Clinical Associate Professor of Periodontics, Baltimore College of Dental Surgery, University of Maryland Dental School, Baltimore, Maryland, USA 2 CEO of Neoss Ltd., Professor of Restorative Dentistry and Biomaterials at Leeds Dental Institute, University of Leeds, United Kingdom 3 Chairman of the Department of Periodontics, Baltimore College of Dental Surgery, University of Maryland Dental School, Baltimore, Maryland, USA The Journal of Implant & Advanced Clinical Dentistry • 27

Rosen et al INTRODUCTION osseointegration, it has not obviated the dip. A more recent approach to increasing the Implant osseointegration has revolutionized the way that we treat our patients today. Ini- speed of osseointegration has been to reduce tially, implants provided a means for the den- surface contamination and to increase bio-adhe- tally compromised patient to regain mastication sion/surface retention of the clot. This may be and phonetics.1,2 Today however, patient achieved by a combination of titanium particle expectations have also come to include receiv- blasting and acid etching of the surface followed ing an implant-supported prostheses that is by submitting it to electrochemical wetting to more esthetic while being delivered on a more decrease surface tension enhance clot adhesion timely basis. Dental implant surface rough- and bone deposition. By eliminating surface ten- ening has reduced the time for implant heal- sion and overcoming bridging effects, electro- ing while enabling greater success rates.3-5 wetting an implant allows blood and tissue fluids containing growth factors and other essential The process for achieving successful osseo- proteins to be drawn into intimate contact with integration progresses from initial primary/ its roughened surface. In vivo studies have dem- mechanical stability of the dental implant where onstrated that by placing ions on the ProActive® non-integrated bone and blood clot contact the implant’s surface, an electrical charge is gener- implant’s surface upon its placement to second- ated when contacting a patient’s blood, leading to ary or biologic stability where both are replaced greater clot stability and earlier bone deposition. by contact or distant osteogenesis.6 Histori- cally, this transition in implant stabilization from It is the purpose of this paper to present mechanical to biological has demonstrated a clinical cases where electro-wetted implants phenomenon known as the “dip”,7 coinciding with have been placed and RFA values have dem- the first 2-8 weeks of healing, depending upon onstrated no dip, but on the contrary, rises in the implant’s surface and the nature of the bone- values at intervals of two and four weeks post implant interface.8 Changes in implant stabil- insertion. These values suggest that the dip may ity have been quantitatively measured historically be eliminated and replaced by a “bump” in osse- through the use of resonance frequency analysis ous healing which may allow for consideration (RFA)9,10. In the case of a dip, the implant stabil- to earlier restoration of these particular implants. ity quotient (ISQ) would initially diminish owing to a decrease in implant micro stiffness, only CASE TREATMENTS to recover to the initial reading at implant place- ment or quite possibly to a value that might be Patients were referred to a practice limited to peri- higher based on an increase in bone to implant odontics and dental implants for the replacement contact. Until there is evidence of an increase of missing or failing teeth. All received informed or maintenance in stability in ISQ from the dip’s consent prior to the planned care. Immediately nadir, patients are typically expected to wait prior to the surgical procedure, patients rinsed for restoration of their implants. While rough- and brushed with a 0.12% chlorhexidine mouth- ening the surface has increased the speed of wash. Anesthesia was obtained using local infiltra- tion with articaine 4% with 1:100,000 epinephrine 28 • Vol. 2, No. 9 • November 2010

Rosen et al Table 1: Patient Information Implant Patient Patient Insertion ISQ 1 ISQ 2 ISQ 1 ISQ 2 ISQ 1 ISQ 2 ID Gender Age Torque Measurement Measurement Measurement Measurement Measurement Measurement (Ncm) at Placement at Placement at 2 weeks at 2 weeks at 4 weeks at 4 weeks 1 F 2 F 68 32 80 80 84 85 NR NR 3 F 4 M 59 32 79 82 83 85 85 85 5 M 6 M 70 32 70 78 78 78 76 76 7 M 8 M 55 32 71 75 77 80 79 79 9 M 10 F 69 32 72 75 72 79 79 80 11 F 12 M 63 32 71 71 76 72 75 77 13 F 14 F 63 32 58 77 75 70 77 77 15 M 16 M 52 32 75 78 85 80 85 84 17 F 18 M 65 32 70 80 78 80 79 79 19 M 20 M 62 32 65 76 76 76 77 77 21 F 22 M 63 32 74 79 79 80 74 76 23 M 24 M 55 32 66 75 71 71 70 70 25 F 26 M 40 32 65 66 74 76 80 80 27 F 28 F 69 32 77 84 85 84 85 84 61 32 60 66 71 71 64 65 53 32 60 76 73 76 72 74 66 32 78 78 77 82 81 82 55 32 65 80 79 80 NR NR 76 32 72 77 77 77 75 75 76 32 75 79 80 80 79 80 59 32 76 81 81 81 81 81 62 32 76 83 84 84 86 86 65 32 73 73 78 78 77 77 68 32 74 74 81 80 80 77 50 32 75 75 75 80 73 77 48 32 75 75 75 79 73 77 51 32 67 67 71 72 74 73 51 32 67 72 72 72 64 72 or articaine 4% with 1:200,000 epinephrine (Sep- Sites included both those that had completely tocaine®, Septodont, Inc. New Castle, Delaware healed following tooth extraction or where imme- 19720). Full thickness flaps were elevated and diate removal of a tooth had been performed. the surgical area was fully visualized. Implant Following the preparation of the osteotomy, an placement followed the manufacturer’s protocol. implant whose surface had been micro rough- The Journal of Implant & Advanced Clinical Dentistry • 29

Rosen et al Figure 1a: Pretreatment view of the maxillary left canine Figure 1b: Conebeam radiograph reveals that the site in this healthy 53 year old healthy male. The tooth had permanent canine will limit the length of implant been extracted 3 months prior to the implant being placed. placement. A mocked up rendition of a 4X7 mm implant is placed to determine its appropriateness. Figure 1c: Flap re ection of the site suggests good bone Figure 1d: A smartpeg has been placed on the 4x7 mm width for implant placement. implant at initial insertion. The insertion was 32 Ncm with ISQ readings of 60 in the buccal-palatal direction and 76 ened by both blasting followed by acid etching mesio-distally. and electro-wetting (Proactive®, Neoss, Harro- gate, England) was fully seated and resonance ized allograft (LifeNet Health, Virginia Beach, Vir- frequency analysis (Osstell ISQ Instrument, Oss- ginia) hydrated with recombinant platelet derived tell AB, Gothenburg, Sweden) was performed growth factor-BB (rh-PDGF-BB) (Osteohealth, with values recorded in both the buccal-lingual Shirley, New York). Implant abutments made and mesial-distal directions. Any necessary bone from polyetherether-ketone (PEEK), which came augmentation was performed using a mineral- packaged with the implants, were placed and kept transgingival enabling RFA’s to be obtained at subsequent visits. Suturing of the flaps was 30 • Vol. 2, No. 9 • November 2010

Rosen et al Figure 1e: A 2mm titanium abutment will allow for Figure 1f: Two week healing with the smartpeg in place. transgingival suturing of the implant. The ISQ’s are now 73 in the buccal-palatal direction which has shown a substantial bump and 76 mesio-distally. Figure 1g: Four week healing shows good soft tissue Figure 1h: Final radiograph suggests good crown margins response. A bump from baseline is still present with the and the implant just avoiding the impacted cuspid. ISQ’s now reading 72 buccal-palatally and 74 mesio- distally. achieved using 6-0 expanded polytetrafluoroethyl- Figure 1i: Clinical view of the nal crown at 6 months ene (W.L. Gore & Associates. Flagstaff, Arizona). following implant placement. Postoperative management included the use of amoxicillin 875 mg twice daily for 7 days along with the use of 0.12% chlorhexidine glu- conate mouthrinse topically applied twice daily for at least the first 28 days. If the patient was allergic to amoxicillin, then either clindamycin The Journal of Implant & Advanced Clinical Dentistry • 31

Rosen et al Figure 2a: Pretreatment clinical view of the maxillary right Figure 2b: The rst premolar has vertical root fracture in rst premolar in this 62 year old whose medical history addition to recent crown loss that make it untreatable. includes osteopenia. No medication is taken for this other than vitamin D and calcium. Figure 2c: Extraction is performed and immediate Figure 2d: Suturing of the ap with 7-0 ePTFE was placement of the implant is accomplished. The nal performed to further assist in graft containment. insertion torque is 32Ncm. There is a 1 mm labial gap that will be subsequently grafted with FDBA combined with times per day or acetaminophen with codeine PDGF-BB. The smartpeg has been positioned and the ISQ # 3 taken every four-six hours if non-steroidal values are 65 for buccal-palatal and 76 for the mesial-distal anti-inflammatory agents could not be taken. direction. Suture removal took place at 14 ± 3 days 150 mg taken four times daily for seven days post-implant insertion. At the time of the visit, or azithromycin 500 mg taken on the first day RFA was repeated and recorded in the same followed by 250 mg per day for the next four directions as at the time of implant place- days was substituted. For pain management, ment. If a removable prosthesis was worn it was patients used ibuprofen 600-800 mg up to four checked, adjusted, relined or replaced if neces- 32 • Vol. 2, No. 9 • November 2010

Rosen et al Figure 2e: RFA values taken at the time of 2 weeks Figure 2f: RFA values at 4 weeks are 77 for both the following implant placement. The ISQ is 76 for both buccal- buccal-palatal and mesial-distal directions. Soft tissue palatal and mesial-distal directions. healing has progressed favorably as well. Figure 2g: Clinical view of the nal crown placement at 8 Figure 2h: Periapical radiograph of the seated nal crown months post surgery. The crown is screw retained with the suggests good bone stability. soft tissue response being quite favorable. RESULTS sary and lightly adherent plaque was removed by topical application of a 0.12% chlorhexi- The patients reported on here were a part of a dine mouth rinse. The subsequent postopera- larger group that was consecutively treated and tive visit was at 28 ± 3 days at which time RFA all followed this protocol and will be detailed in was repeated and recorded along with appli- a subsequent paper. All had bone that could be ance evaluation and plaque removal. If RFA val- categorized as type I-III, achieved an insertion ues remained stable or improved, impressions torque of 25Ncm or better (average of 31.8)and were taken for the final prosthesis was sched- had an ISQ reading of 58 or greater. The ISQ uled with the restorative dentist/prosthodontist. values were all obtained from the same Osstell The Journal of Implant & Advanced Clinical Dentistry • 33

Rosen et al Figure 3a: Preoperative clinical view of the mandibular Figure 3b: Implant was placed into Type II bone to 32Ncm. left rst molar site in a 53 year old male who was a former ISQ values are 75 in the buccal-lingual direction and 78 in smoker until one year prior. the mesio-distal direction. Figure 3c: Implant received a 4 mm PEEK healing Figure 3d: Radiograph of the placed implant. abutment which was sutured transgingivally with 4-0 gut. DISCUSSION device. Table 1 summarizes the initial and sub- sequent ISQ values along with insertion torques These case reports appear to indicate that obtained for these implants. The accuracy of an implant with a microroughened elec- the Osstell is +/- 2 ISQ units 11 and so implants tro-wetted surface to achieve rapid clini- exhibiting increases in ISQ of 3 or greater in cal healing. While no patients received at least one direction with the other, remain- restorations immediately, this did serve as ing at least stable, were considered significant the basis to further explore this possibility. and included. Figures 1a-i to 3a-i present sev- eral representative cases amongst the group. Efforts have traditionally focused on increas- ing the speed of osseointegration by modify- ing the macro and/or micro geometry of the 34 • Vol. 2, No. 9 • November 2010

Rosen et al Figure 3e: Smartpeg in place at 2 week post-op. ISQ values Figure 3f: Post-operative view of tissue healing at 4 weeks. are 85 in the buccal-lingual and 80 in the mesial-distal directions. Figure 3g: Smartpeg placed at 4 weeks. ISQ’s are 85 in the Figure 3h: Clinical view of the nal crown placement at 4 buccal-lingual and 84 in the mesial-distal directions. months post surgery. dental implant surface. While roughening an More recently, efforts have shifted toward sur- implant surface has enhanced osseointegra- face modifications in surface chemistry that tion3,7, increasing the roughness of a surface would lead to greater reactivity. Manufacturing may also create pits causing air to be trapped an implant in a nitrogen rich environment with under a liquid layer preventing wetting. Fur- subsequent storage in a solution of physiologic thermore, the aspect ratio (height or depth of saline is one method that looks to enhance the troughs or porosities in relation to their width chemical purity and retained surface energy of or circumference) of the topography is critical an implant’s surface to give it enhanced hydro- as this may cause bridge formation resulting in philic properties13. Baier14 has discussed that a failure of a fluid to penetrate such features.12 there is a correlation between biocompatibility, The Journal of Implant & Advanced Clinical Dentistry • 35

Rosen et al Figure 3i: Radiograph of the nal crown suggests good ing placement and breaks down the interfacial maintenance of bone levels at 4 months post-placement. surface tension between the blood and implant surface (Electro-wetting on Dielectric [EWOD]). bio-adhesion and surface tension or contact The contact angle of such a treated implant is angle on a substrate or implant surface. By implant is 0°. Animal studies have corroborated improving adherence of the blood clot to the this phenomenon with animal histology dem- implant’s surface, the process of healing may onstrating bone deposition outpacing resorp- proceed more quickly, allowing for an implant tion as early as 10 days.16 Removal torque to be placed into earlier function. If the dental was consistent with the histology since val- implant’s surface could become more “reac- ues were higher versus other implant surfaces tive” by increasing surface energy in the form as early as 10 days lasting up to 6 weeks.16 of hydrophilicity and surface charge, it might be While animal data serves as a good first step, possible to accelerate the speed of bone-to- this needs to be corroborated in humans. implant contact. In vivo studies have suggested that the shift from primary to secondary stabil- These cases were all treated in a clini- ity takes place over approximately eight weeks cian’s private practice and serve as initial clini- for rough surface implants while chemical sur- cal evidence to corroborate the in-vivo animal face modifications have reduced this further.15 data. RFA has been used in practice as it is a noninvasive, safe method of obtaining objec- Electro-wetting is a possible method that tive information on healing to make the clini- attempts to enhance the reactivity of a dental cal decision of when to provisionalize or load implant’s surface. The electro-wetting process the implant. While these patients are only 28 on a titanium surface enables increased hydro- in number, they are a significant sample to say philicity, maximizing the penetration of blood and with confidence that this is simply not a chance its components, fibrin, complement and growth finding but rather a consequence of enhanced factors into the implant surface. This is achieved conductive properties to this implant surface. by an ionic surface treatment that creates an The value of 3 ISQ was used to determine a electrical charge on the implant surface dur- bump in healing as the accuracy of the Oss- tell machine is ± 2 units. What is interesting is that the vast majority of the sites retained this bump phenomenon at 4 weeks and that none demonstrated a dip from the baseline through- out the 4 week time period. Furthermore, there needs to be controlled corroboration of whether the high level of surface conductiv- ity coupled with a high value of early stability make these implants better candidates for rou- tine immediate or very early provisionalization. Several trends are worth noting in these 36 • Vol. 2, No. 9 • November 2010

Rosen et al case reports. The majority of the bumps Disclosures occurred in a buccal-lingual/palatal direc- Dr. Reynolds reports no conflicts associated with this article. tion rather than mesiodistally and that this Dr. Rosen has lectured for Neoss and Osstell. trend remained true for the majority of the Dr. Meredith is one of the founders and is currently employed by Neoss. implants at 4 weeks as well as at 2. This may relate to the higher ISQ values at inser- Acknowledgements tion at mesial and distal sites and there being The authors wish to thank Nyree Divitini for assistance in the preparation of this a lower likelihood for an increase to have manuscript. occurred. In those implants that were immedi- ately placed, there appeared to be a trend for References fixtures with high ISQ levels to decrease and 1. Zarb GA, Schmitt A. The longitudinal clinical effectiveness of osseointegrated low ISQ levels to increase over time (Table 1). dental implants: the Toronto Study. Part II: The prosthetic results. J Prosthet In conclusion, this preliminary observa- Dent. Jul 1990;64(1):53-61. tion from a clinical private practice is an excit- ing finding. To our knowledge, no one else 2. Zarb GA, Schmitt A. The longitudinal clinical effectiveness of osseointegrated has reported on this nor has there been any in dental implants: the Toronto study. Part I: Surgical results. J Prosthet Dent. Apr depth evaluation of its implication on clinical 1990;63(4):451-457. practice. It certainly suggests, at the very least, that this electro-wetted surface implant, when 3. Cochran DL. A comparison of endosseous dental implant surfaces. J placed in a healthy patient, heals quite rapidly. Periodontol. Dec 1999;70(12):1523-1539. Further study in larger controlled trials appear warranted to determine what is or are the exact 4. Shalabi MM, Gortemaker A, Van’t Hof MA, Jansen JA, Creugers NH. Implant reasons for this faster healing, if this could pos- surface roughness and bone healing: a systematic review. J Dent Res. Jun sibly translate to more frequently provisional- 2006;85(6):496-500. izing/loading this implant either immediately or very early, i.e. at 2 weeks, with the risk of failure 5. Wennerberg A, Albrektsson T. Effects of titanium surface topography on bone being less likely usher in an era of implant care integration: a systematic review. Clin Oral Implants Res. Sep 2009;20 Suppl that comes closer to meeting the desire of our 4:172-184. patients to achieve final outcomes sooner. 6. Schouten C, Meijer GJ, van den Beucken JJ, Spauwen PH, Jansen Correspondence: JA. The quantitative assessment of peri-implant bone responses using histomorphometry and micro-computed tomography. Biomaterials. Sep Dr. Paul S. Rosen 2009;30(27):4539-4549. 907 Floral Vale Blvd 7. Raghavendra S, Wood MC, Taylor TD. Early wound healing around endosseous implants: a review of the literature. Int J Oral Maxillofac Implants. May-Jun Yardley, PA 19067-5515 2005;20(3):425-431. (215) 579-0907 8. Friberg B, Sennerby L, Linden B, Grondahl K, Lekholm U. Stability measurements of one-stage Branemark implants during healing in mandibles. A clinical resonance frequency analysis study. Int J Oral Maxillofac Surg. Aug 1999;28(4):266-272. 9. Meredith N, Alleyne D, Cawley P. Quantitative determination of the stability of the implant-tissue interface using resonance frequency analysis. Clin Oral Implants Res. Sep 1996;7(3):261-267. 10. Meredith N, Book K, Friberg B, Jemt T, Sennerby L. Resonance frequency measurements of implant stability in vivo. A cross-sectional and longitudinal study of resonance frequency measurements on implants in the edentulous and partially dentate maxilla. Clin Oral Implants Res. Jun 1997;8(3):226-233. 11. Nedir R, Bischof M, Szmukler-Moncler S, Bernard JP, Samson J. Predicting osseointegration by means of implant primary stability. Clin Oral Implants Res. Oct 2004;15(5):520-528. 12. Le Guehennec L, Soueidan A, Layrolle P, Amouriq Y. Surface treatments of titanium dental implants for rapid osseointegration. Dent Mater. Jul 2007;23(7):844-854. 13. Rupp F, Scheideler L, Olshanska N, de Wild M, Wieland M, Geis-Gerstorfer J. Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces. J Biomed Mater Res A. Feb 2006;76(2):323-334. 14. Baier RE. The role of surface energy in thrombogenesis. Bull N Y Acad Med. Feb 1972;48(2):257-272. 15. Oates TW, Valderrama P, Bischof M, et al. Enhanced implant stability with a chemically modified SLA surface: a randomized pilot study. Int J Oral Maxillofac Implants. Sep-Oct 2007;22(5):755-760. 16. Gottlow JS, Sennerby L. Influence of surface and implant design on stability of five commerical titanium implants: A biomechanical study in the rabbit. Academy of Osseointegration. Orlando, 2010. The Journal of Implant & Advanced Clinical Dentistry • 37

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“Toronto” Screwed Mandibular Overdenture Cicciù et al on Dental Implants: FEM and Von Mises Analysis of Stress Distribution M. Cicciù, DDS, PhD1 • G. Risitano, PhD, ED2 • C. Maiorana, MD, DDS3 A. Herford, MD, DDS 4 • G. Oteri, MD, DDS5 • D. Cicciù, MD, DDS6 Abstract Background: The aim of this work was to Results: Data from virtual 3D models were ana- analyze how different distributions of chew- lyzed. The study investigated frontal and hori- ing load could be related to dental prosthesis zontal planes and vertical directions of occlusal fractures of the Toronto restoration via a vir- forces. Results showed how position and per- tual parametric model. We also investigated spective of fixtures strongly influenced the stress implant positions and perspectives in compari- distribution on the bone of the jaw. Prostheses son with a virtual medial plane, to evaluate the elements such as cantilever, passing screws, incidence of screw and prosthesis breakage. and dental implants are strictly related to the correct selection of dental implant position. Methods: Finite element analysis of the lower jaw was performed to underline parameters and Conclusions: The three-dimensional geometry mechanical features of dental implants con- of the jaw is an important factor influencing the nected with the fractures of a prosthetic res- choice of position, number, diameter, and length of toration. A “virtual jaw” model and 3D fixtures dental implants used for Toronto prostheses. This were created. The distribution of a non-specific study would suggest a “virtual” method to help the chewing phase, analyzing the overall load on surgeon choose a correct model for prosthetic the fixtures of the lower jaw was performed. rehabilitation, evaluating position, perspective, and stress distribution of the chewing strengths. KEY WORDS: Dental implants, mandibular overdenture, Von Mises Stress analysis, finite stress analysis 1. Department of Oral Surgery, I.R.C.S.S. Dental School University of Milan, Milano, Italy, 2. University of Perugia, Department of Industrial Eng, Perugia, Italy 3. Department of Oral Surgery, I.R.C.S.S. Dental School University of Milan, Milano, Italy, Chief Oral Surgery 4. Loma Linda University, Chief Oral Maxillofacial Department, Loma Linda, CA Usa, 5. University of Messina, School of Dentistry Assistant Professor 6. University of Messina, School of Dentistry Head and Director The Journal of Implant & Advanced Clinical Dentistry • 41

Cicciù et al INTRODUCTION jaw atrophy, using the classification of the eden- tulous jaws described by Cawood and Howell.5 The significance of mechanical stimuli in the main- Prior to implant dentistries predictable and safety tenance and structure of skeletal tissues has techniques, the only treatment for edentulous been investigated since the middle of the 19th patient was the traditional removable prosthesis. century.1,2 The skeleton is continuously remodel- Today, the Toronto overdenture prosthetic resto- ling itself during its life by the osteoclast resorbing ration over dental implants can be considered a old bone and the osteoblast subsequently form- good choice for treatment of edentulous patient ing new bone. Bone resorption and bone forma- with atrophy of the jaw. Toronto rehabilitation is tion are therefore said to be coupled, a process a removable screw – retained prosthesis made of renewing the skeleton while maintaining its by a golden girder bridge with lateral extension structural integrity. Alveolar bone is loaded inter- covered with resin prosthetic dental crowns. mittently during mastication, but is subject to a continuous deformation or strain. Atrophy condi- Literary reviews demonstrated that tion of the jaws is tightly related to missing teeth. the problem with this type of restora- tion, such as fracture of cantilever prosthe- The surgical and prosthodontic rehabilita- sis and fracture of passant screw, could tion of the edentulous patient aims to restore be associated with several conditions. oral function and facial form. Planning treatment requires an understanding of the effect of pro- Past literature analyzed only the ratio between gressive jaw atrophy, and the concomitant effect distal cantilever and length of the basis of the on the soft tissues of the face. Loss of the natu- prosthesis.6-9 Today the tendency is to analyze ral dentition results in gradual resorption of the the risk factors related to length and diameter alveolar process and consequently a change in of dental implants, the ratio between anterior natural jaw relationship, at the same time there and posterior cantilevers,10 the distribution of are changes in the facial musculature and con- load,11 the mesial cantilever structure,12 and con- sequently a change in facial morphology.3 Tall- siderations upon material of prosthetic struc- gren observed that the greatest proportion of the ture.13 von Mises (or equivalent) strain stimulus alveolar bone loss occurs in the first year,4 how- of all components was analyzed and then evalu- ever this is a chronic process and bone loss con- ated. Von Mises stress is a norm (i.e. a sca- tinued over the subsequent 25 years of her study. lar) that is calculated from the three principal In addition, it is known that the rate of this chronic stresses of the local stress tensor (i.e. a matrix).14 process varies not only between individuals, but also within the same individual over a period of For considering axial load, the masticatory time. Relatively little has been published regard- load working on the molar region was reported ing the progressive soft tissue changes conse- to be 75–300 N, and 300 N was therefore quent to the loss of the dentition. Accordingly adopted as the masticatory force and was the aim of the study was to examine the changes applied to the right-side cantilever portion of the in facial form, using recognized anthropometric superstructure.15 In the treatment of the eden- measurements, and relate these to the extent of tulous mandible, fixtures are generally embed- ded between the mental foramina to avoid 42 • Vol. 2, No. 9 • November 2010

Cicciù et al Figure 1: Mucoperiosteal Flap elevated before dental Figure 2: Implants placed between mental nerve implant positioning in the mandible. emergences. Figure 3: Healing abutments on the dental implants. Figure 4: Toronto prosthesis model. injuring the inferior alveolar nerve.16 The aim of Direction, intensity and frequency (working cycles) the present study was to use FEM to perform a of loads have to be considered for a correct eval- comparative analysis of the strength distribu- uation of the force distribution. The analysis was tion in the lower jaw related to implant position performed on Toronto prosthesis in order to evalu- evaluating the mandible bone stress. Cosmos - ate the possible failure related to the fracture of Solid Works®, Matlab® and Matchad 14® were the passant screws or the cantilevers (Figs. 1-10). used to recreate a virtual 3D model and to study the difference in the variation of the load This kind of analysis required the perfect despite dental implant positions and numbers. reproduction of the mandible anatomy with all asymmetric and irregular characteristics. Solid- MATERIAL AND METHODS Works program® was used to recreate the CAD of the mandibular 3D model. Global dental The ratio between chewing/deglutition is related implant virtual model CAD Ø 4.3 mm was recre- to the quality and quantity of the masticatory loads. ated by SOLIDWORKS 2007® using engineer- The Journal of Implant & Advanced Clinical Dentistry • 43

Cicciù et al Figure 5: Toronto prosthesis model screwed on the dental Figure 6: A real model of Toronto screwed prosthesis, implants. Frontal clinical view. frontal view. Figure 7: Occlusal view of the Toronto prosthesis. Figure 8: Size and length of the cantilevers in a standard Toronto prosthesis. Figure 9: Clinical problems related to the fracture of the Figure 10: Particular of the passant screw fracture. passant screws. 44 • Vol. 2, No. 9 • November 2010

Cicciù et al Figure 11: Tridimensional model of dental implant. The Figure 12: Dental Implant 3D model. model underlines the three di erent parts: Fixture, Passant Screw and Abutment. ability related to results of the previous models. Mandible geometry reproduction with CAD ing draws of the implant (Sweden & Martina®). Titanium 4th grade was used to characterize the model was not easy due to the several curve and dental implant screws and abutment. SOLID- irregularities of the bone. For this reason profes- WORKS 2007® is also able to offer Wohler curve sional scanner (Micro System – Copy Mate®) for dynamic-fatigue FEM of each implant (Figs. was used to create the ideal CAD model of the 11-15). At the same time, Matlab program® was mandible. The created file was an STL file and it used to achieve the model of the force distribution resulted being too heavy (very high resolution) to over dental implants during a generic chewing be used with the next rendering processes. So cycle. The force distribution model is influenced Rhinocerus® program was used to change the by dental implant positions (Figs. 16-20). format file IGES. The mechanical forces applica- tion to the model was the next step of the study. Afterwards, FEA mandible-fixture was per- formed by COSMOS 2007®. FEA evaluation Several resources illustrated the mechanical showed the reaction (strength and deformation) proprieties of the bone, however no investigation between bone and implant surface. Therefore could be considered reliable to generally classify FEA of dental implant was analyzed by COSMOS the results. Bone characteristic are directly con- 2007® to evaluate the titanium structure’s reli- The Journal of Implant & Advanced Clinical Dentistry • 45

Cicciù et al Figure 13: 3D view of Figure 14: 3D model of Figure 15: 3D model of Figure 16: 3D model of the 3 dental implant the passant screw. the dental implant. the abutment. components all together. nected with individual physical features and so These following conditions applied there is a high variability. The bone values and Matlab 7 program® and Mathcad 14® parameters were chosen by literary references.9,14 were used to elaborate axial loads: Mandibulaar bone could be classified in cortical bone and marrowbone. Mandible areas could Analysis performed on a sagittal plane be divided in seven different chewing load areas Occlusion over all transversal planes (Table 1). Bone elastic module 17,300 MPa; Pois- Force of 250 N for incisive; Force of 800 N son coefficient 0,3; bone density 1800 kg/m³; for molars compression resistance 190 Mpa (Figs. 21-26). Masticatory cycle is studied by a sinusoidal semi-wave (ratio of load R=0, force by origin). The right value of the axial loads dur- The structure of the prosthesis frame was ing chewing movement is very debated in considered rigid. Programs results (corre- the literature. Axial load characteristic is not lated with the size and with the position of den- simple to be characterized. The subject Bio tal implants placed) gave the exact axial load individuality, the different muscle systems, the for each screw and showed the screw safe curve and the angles of the upper and lower coefficients and cantilever safe coefficients. jaw and the teeth occlusal surface are influ- 4 different trials were performed by COSMOS encing parameters to determine axial load. 2007®. The number and the dental implants posi- 46 • Vol. 2, No. 9 • November 2010

Cicciù et al Figure 19: Mandibular bone. Di erent elastic proprieties related to the area. Figure 17: 3D model of Figure 18: Real model of Figure 20: (below) 3D virtual model of the human skull the three components in the dental implants and and mandible. ratio. components. The Journal of Implant & Advanced Clinical Dentistry • 47

Cicciù et al Table 1: Mechanical Characteristics of the Seven Areas of Bone N° area Cortical bone Spongy Bone v Cortical vSpongy Zona 1 E [N/m2] E [N/m2] 0,345 0,345 Zona 2 1,68E+10 7,27E+08 0,345 0,345 Zona 3 168E+10 7,27E+08 0,236 0,236 Zona 4 193E+10 8,35E+08 0,236 0,236 Zona 5 193E+10 8,35E+08 0,236 0,236 Zona 6 240E+10 1,04E+09 0,236 0,236 Zona 7 240E+10 1,04E+09 0,236 0,236 240E+10 8,83E+08 tion placing were the variables for each analysis obtained. Moreover two dynamic virtual mod- (Table 3). von Mises analysis was performed to els and investigations were performed for the investigate the strengths of the passant screws two more negative fatigue conditions over den- and of the Toronto structure too (Figs. 27-29). tal implants and passant screws (Figs. 30-35). Trials 1 and 2 were performed with a number of five dental implants supporting Toronto pros- RESULTS thesis. However, central dental implants posi- tioned in the first trial are closer each other, while Trials 1 and 2 models results’ are found on tab.1- in the second trial central dental implants’ dis- 2. The bone areas around dental implants n°5-4 tance is the same as that of the lateral implants (preomalar area) are the most solicited during (Table 4). For this reason, cantilever length load simulation of the first trial. The bone area was longer in the first trial then in the second. around dental implant n°1 (central implant) is the most solicited during load simulation of the sec- Trials 3 and 4 analyzed 6 dental implants ond trial. The reason of this change is related to supporting Toronto prosthesis. Trial 3 and trial a different new distance between the three cen- 4 difference is due to the diameter of the den- tral implants and the two laterals. When the lat- tal implant placed in the lateral (premolar) area eral dental implants are closer to the central (Table 5). FEM analysis was performed for each implants, the mesial cantilever is shorter and trial with Matchad 14® - Matlab 7®. Static evalu- the load is directed to the implant in the central ation related to dental implant position was position. Specifically, implant n°1 load increases 48 • Vol. 2, No. 9 • November 2010