See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/315989141 Rehabilitation of the atrophic mandible with short implants in different positions: A finite elements study Article · April 2017 DOI: 10.1016/j.msec.2017.03.310 CITATIONS READS 0 20 6 authors, including: Fernanda Faot Bruno Salles Sotto Maior Universidade Federal de Pelotas Federal University of Juiz de Fora 60 PUBLICATIONS 185 CITATIONS 56 PUBLICATIONS 153 CITATIONS SEE PROFILE SEE PROFILE Elizabeth Martinez Daiane Cristina Peruzzo Faculdade São Leopoldo Mandic Faculdade São Leopoldo Mandic 70 PUBLICATIONS 220 CITATIONS 45 PUBLICATIONS 335 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Features of maxillo-mandibular profile in edentulous patients. View project Teledentistry View project All content following this page was uploaded by Fernanda Faot on 31 May 2017. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. Materials Science and Engineering C 80 (2017) 122–128 Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec Rehabilitation of the atrophic mandible with short implants in different positions: A finite elements study Hugo E. Peixoto a, Paulo R. Camati b, Fernanda Faot c, Bruno S. Sotto-Maior d,f, Elizabeth F. Martinez e,DaianeC.Peruzzoe,⁎ a São Leopoldo Mandic Dental Institute and Research Center, Campinas, SP, Brazil b Curitiba, PR, Brazil c Federal University of Pelotas, Department of Restorative Dentistry, Pelotas, RS, Brazil d Federal University of Juiz de Fora, Department of Restorative Dentistry, Juiz de Fora, MG, Brazil e São Leopoldo Mandic Dental Institute and Research Center, Campinas, SP, Brazil f Brazil and São Leopoldo Mandic Dental Institute and Research Center, Campinas, SP, Brazil article info abstract Article history: Objective: The aim of this study was to analyze whether the use of inclined short implants without lower Received 19 September 2016 transcortical involvement (test model - SI), thus preserving the mandibular lower cortical bone, could optimize Received in revised form 7 March 2017 stress distribution. Accepted 12 March 2017 Materials and methods: Six identical atrophic mandible models were created featuring 8 mm of height at the sym- Available online 07 April 2017 physis. Two study factors were evaluated: implant length and angulation. Implant length was represented either by short implants (7 mm) with preservation of the mandibular lower cortical bone or standard implants (9 mm) Keywords: with a bicortical approach and 3 possible implant positioning configurations: 4 distally-inclined implants at 45° Atrophic mandible Dental implants (experimental model), all-on-four, 4 vertical implants. All tridimensional (3D) models were analyzed using the Finite element analysis Finite Element Method (FEM) and the Ansys Workbench software. Results: The maximum stress on the bone at the cervical region of the implants in the experimental model was 132 MPa and transcortical involvement with implant inclination yielded higher values (171 MPa). Regarding von Mises stress on the retaining screw of the prosthesis, 61 MPa was recorded for the experimental model while upright implants had the highest values (223 MPa). At the acrylic base, 4 MPa was recorded for the exper- imental model whereas models with upright implants showed the highest stress values (11 MPa). Conclusion: Rehabilitation of severely resorbed mandibles with 4 short implants placed distally at 45°, without lower transcortical involvement, were biomechanically more favorable, generating lower stress peaks, than the models with short implants on an all-on-four, or on an upright configuration, with or without lower transcortical involvement. © 2017 Published by Elsevier B.V. 1. Introduction report pain, difficulty chewing and speech impairment, which compro- mise their quality of life [2–6]. The increase in life expectancy in recent decades described by the The use of osseointegrated titanium implants is considered an effec- World Health Organization has increased the number of people wearing tive method for functional and esthetic replacement of lost teeth. Treat- lower dentures for many years [1]. As alveolar ridge volume is dictated ment success has always been related to variables such as volume and by the presence of natural teeth, a lack thereof inevitably triggers bone anatomy of the remaining bone, the longer the implant the more favor- resorption. In the case of complete teeth loss, replacement of natural able the prognosis [2,7,8]. However, in many situations, placement of teeth using soft tissue supported dentures generates unfavorable forces long implants is hindered by severely resorbed alveolar ridges, anatom- that may accelerate this process, exacerbating the instability of full den- ical limitations such as the mental foramen or inferior alveolar nerve tures as well as the degree of patient dissatisfaction. Patients often and mandibular canal and shape of the mandible [1,9–14]. Placement of short implants (≤8 mm long) may be considered an ef- fective option to rehabilitate edentulous patients whenever conven- ⁎ Corresponding author at: Rua José Rocha Junqueira, 13, Campinas, SP, Brazil. tional implants cannot be placed without prior bone augmentation E-mail address: [email protected] (D.C. Peruzzo). procedures [3,4,9–18], such as autologous bone graft, osteogenic http://dx.doi.org/10.1016/j.msec.2017.03.310 0928-4931/© 2017 Published by Elsevier B.V. H.E. Peixoto et al. / Materials Science and Engineering C 80 (2017) 122–128 123 One way to improve the distribution of functional forces on the prosthesis, implants and peri-implant tissues in patients with little bone is the use of angled implants. Biomechanical justification for distal inclination of implants is based on decreased distal extension of the prosthesis and favorable anteroposterior distribution of im- plants. Furthermore, the use of tilted implants can increase its prima- ry cortical anchoring and stability, allowing the use of longer Fig. 1. Illustration of the 6 models generated: SI - short inclined implants; IT – inclined implants [1,23–26]. transcortical implants; SA - short implants positioned as all-on-four; TA – transcortical The all-on-four concept consists of a relatively less invasive treat- short implants positioned as all-on-four; SU - short upright implants; UT - upright ment option with a high success rate [27–29]. Distally inclined im- transcortical implants. plants at 45° decrease the concentration of stresses on the peri- implant bone [23] and compressive forces on the distal bone/implant distraction or mental foramen transposition, which increase surgical interface compared to the configuration with four upright implants morbidity and treatment time [1,3,4,9–12,14–16,19]. [1,13,24,25,30–33]. A survey on the occurrence of mandibular fractures associated with Based on the aforementioned arguments, the aim of this study dental implants concluded that mandibles with b10 mm of bone height was to evaluate stress distribution on severely resorbed mandibles, at the region of the symphysis are at risk of fracture and associated com- with 8 mm of remaining bone height at the symphysis, restored plications [20]. One factor that may favor the occurrence of a mandibu- with implants at varying angulations and length (bicorticated and lar fracture is the penetration of the lower mandibular cortical ridge, by non-bicorticated) using the tridimensional Finite Element Method the implant, i.e. bicortication. Thus, the installation of shorter implants, (FEM) [33–35]. The null-hypothesis tested was that different im- keeping the integrity of the lower mandibular cortex, might reduce plant angulations and length would not affect biomechanical the risk of mandibular fragilization [21,22]. behavior. Fig. 2. Implant dimensions. An implant with an external hexagonal interface Titamax TI Cortical (Neodent®, Curitiba, Brasil) was used. 124 H.E. Peixoto et al. / Materials Science and Engineering C 80 (2017) 122–128 2. Materials and methods 2.1. Experimental design This study involved the establishment of models of the mandible in silico with severe alveolar bone resorption and average bone height of 8 mm in the region of the symphysis. The mandibles were dentally reha- bilitated using implant-supported fixed dentures over 4 implants. Both the mandible and denture models were the same for all simulations. The study factors were the angulation of implants and implant length. Three possibilities were considered for the angulation of implants: (1) verti- cally positioned implants; (2) all-on-four (2 vertical anterior implants and 2 posterior implants distally inclined at 45° inclined); (3) 4 im- plants distally inclined implants at 45°. In addition, for each implant an- gulation model two implant lengths were used, a 7-mm short implant placement preserving the lower cortical bone of the mandible and a 9- mm implant model, which penetrates the lower cortical bone of the mandible. Six models were therefore generated: SI - short inclined im- plants; IT – inclined transcortical implants; SA - short implants posi- tioned as all-on-four; TA – transcortical short implants positioned as all-on-four; SU - short upright implants; UT - upright transcortical