TECHNICAL ARTICLE—PEER-REVIEWED A Microstructural and Fractographic Study on the Failure of Surgical Torch Meters Cassio Barbosa • Ibrahim de Cerqueira Abud • Tatiana Silva Barros • Sheyla Santana de Carvalho • Ieda Maria Vieira Caminha Submitted: 22 May 2013 / in revised form: 30 August 2013 / Published online: 28 September 2013 Ó ASM International 2013 Abstract As in the case of implants, the increase of the life expectancy and of the risk of accidents, thus causing a higher incidence of surgeries, has led to an increased use of surgical instruments. The reliability of these instruments, used in applications of considerable responsibility, depends on the characteristics of the materials, as well as on the conditions of manufacture. Using some techniques such as optical microscopy, scanning electron microscopy, and hardness tests, this work has as purpose the identification of the possible causes of failure of surgical torch meters used for dental implants fixation, trying to correlate with the microstructural characteristics of the austenitic and mar- tensitic stainless steels used in their manufacture. The results thus obtained allowed the identification of the main causes of the failure, primarily related to microstructural heterogeneities which resulted from inadequate heat treat- ment and with the presence of non-metallic inclusions, which favored brittle fracture and corrosion. Keywords Failure analysis Á Torch meters Á Stainless steels Á Fracture Á Microcopy Introduction The increasing lifetime of the world population in the past decades has led to a significant increase in the amount of surgeries of different types, although other factors, such as scientific/technological progress and enhanced exposure of individuals to trauma risk, for instance, also contribute to this tendency [1, 2]. Several articles have been published about surgical implants, either orthopedic or dental, reporting their characteristics such as: biocompatibility, mechanical strength (both static and dynamic), resistance to degradation (corrosion and wear), bioadhesion (to bones), and ease of manufacture by different thermomechanical processes and availability/low cost [3–5]. In general, the requirements of chemical composition, microstructure and mechanical properties are well established in standards edited by international institutions such as ISO (Interna- tional Organization for Standardization) and ASTM (American Society for Testing and Materials) [6–11]. However, little information is available in the technical literature about instruments used in these surgeries [12], either cutting ones such as scissors or lancet or non-cutting ones such as tweezers, beside specific technical standards about these instruments [13–15]. Surgical torch meters are devices designed for the application of forces on screws and similar components subjected to torsion loads and simultaneous measurement of this force, in order to avoid either loosening or excessive force that can cause damages to the dental implants, which are components designed to replace lost teeth, thus enabling the complete recovery of the chewing function. Usually, these implants are based on screws inserted in the jaw bone and attached to a piece of porcelain, which is manufactured similar to a tooth. The titanium screw must have sufficient biocompatibility to become naturally integrated to the bone and thus mechanically and biologically stable. If the torsion force is very low, the implant will be loose, but, on the other hand, if the torsion force is too high, the implant can be damaged. Therefore, surgical torch meters are very important devices to guarantee adequate attachment of the implant to the jaw bone. C. Barbosa (&) Á I. de Cerqueira Abud Á T. S. Barros Á S. S. de Carvalho Á I. M. V. Caminha Instituto Nacional de Tecnologia (INT), Avenida Venezuela 82, Sala 620, Rio de Janeiro CEP 20.081-312, Brazil e-mail: cassio.barbosa@int.gov.br 123 J Fail. Anal. and Preven. (2013) 13:765–770 DOI 10.1007/s11668-013-9748-4