Stress amplifications in dental non-carious cervical lesions Jackeline Coutinho Guimarães a , Gabriela Guimarães Soella a , Letícia Brandão Durand b , Françoà Horn c , Luiz Narciso Baratieri d , Sylvio Monteiro Jr. d , Renan Belli e,n a Department of Prosthodontics, School of Dentistry, Federal University of Espírito Santo, Vitória, Brazil b Department of Operative Dentistry, School of Dentistry, Federal University of Santa Maria, Santa Maria, Brazil c Biomechanics Engineering Laboratory, Federal University of Santa Catarina, Florianópolis, Brazil d Department of Operative Dentistry, School of Dentistry, Federal University of Santa Catarina, Brazil e Laboratory for Biomaterials Research, Dental Clinic 1, Operative Dentistry and Periodontology, Friederich-Alexander University of Erlangen-Nuremberg, Glueckstraße 11, 91054 Erlangen, Germany article info Article history: Accepted 6 November 2013 Keywords: Non-carious cervical lesions Finite element analysis U-shaped lesions V-shaped lesions Tooth deflection abstract This study aims to investigate the influence of the presence, shape and depth of NCCLs on the mechanical response of a maxillary second premolar subjected to functional and non-functional occlusal loadings using 3-D finite element (FE) analysis. A three-dimensional model of a maxillary second premolar and its supporting bone was constructed based on the contours of their cross-sections. From the sound model, cervical defects having either V- or U-shapes, as found clinically, were subtracted in three different depths. The models were loaded with 105 N to simulate normal chewing forces according to a functional occlusal loading (F1) vertically applied and two non-functional loadings (F2 and F3) obliquely oriented. Two alveolar bone crest heights were tested. Ansys™ FE software was used to compute stress distributions and maximum principal stress for each of the models. The presence of a lesion had no effect on the overall stress distribution of the system, but affected local stress concentrations. Non- functional loadings exhibited tensile stresses concentrating at the cervical areas and root surfaces, while the functional loading resulted in homogeneous stress distributions within the tooth. V-shaped lesions showed higher stress levels concentrated at the zenith of the lesion, whereas in U-shaped defect stresses concentrated over a wider area. As the lesions advanced in depth, the stress was amplified at their deepest part. A trend of stress amplification was observed with decreasing bone height. These results suggest a non-linear lesion progression with time, with the progression rate increasing with patient's age (deeper lesions and lower bone support). & 2013 Elsevier Ltd. All rights reserved. 1. Introduction The scientific endeavor that seeks to clarify the etiology of dental non-carious cervical lesions (NCCLs) has been so far inconclusive (Bartlett and Shah, 2006; Wood et al., 2008). Early theories on abrasion or erosion mechanisms, having leading parts in the forma- tion of NCCLs, recently gave room to a biomechanical perspective (McCoy, 1982; Lee and Eakle, 1984), according to which tensile stresses caused by tooth deflection progressively disrupt the miner- alized tissues in the cervical region of teeth. Experimental validations have been supplied by analytical simulations showing the develop- ment of tensile stress on the cervical bulge of working cusps for non- functional loadings (Goel et al., 1991; Rees, 1998; Palamara et al., 2000; Rees, 2002; Rees et al., 2003; Rees and Hammadeh, 2004; Borcic et al., 2005; Dejak et al., 2005; Palamara et al., 2006). The correlation of occlusal factors with NCCLs in some population-based surveys (Mayhew et al., 1998; Miller et al., 2003; Takehara et al., 2008) and the higher prevalence of NCCLs in bruxism subjects (Xhonga, 1977; Ommerborn et al., 2007) further substantiates this theory. However, in vitro and clinical investigations (Litonjua et al., 2004; Estafan et al., 2005) still find it difficult to establish a clear association between parafunctional loading and NCCLs. Instead, studies have pointed the joint action of occlusal factors and acid corrosion (Khan et al., 1999; Rees and Hammadeh, 2004; Staninec et al., 2005) in the progressive cyclic process of fatigue microcracking and tissue dissolu- tion. Added to the early belief that abrasion resulting from tooth- brushing was linked to a higher prevalence of NCCLs (Radentz et al., 1976; Bergstrom and Lavstedt, 1979) and evidences of a combined effect of abrasion and acid corrosion in cervical wear from more recent studies (Eisenburger et al., 2003; Attin et al., 2004), the current scientific judgement tends to support the multicausality of NCCLs (Bartlett and Shah, 2006). The superposition of three-body wear, acid corrosion and bending stresses at the cervical region of teeth and the severity of each of these causative components over a period of time generate, typically, V-shaped (or wedge-shaped) or U-shaped Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com Journal of Biomechanics 0021-9290/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbiomech.2013.11.012 n Corresponding author. Tel.: þ49 9131 854 3741; fax: þ49 9131 853 4207. E-mail address: rbelli@dent.uni-erlangen.de (R. Belli). Journal of Biomechanics 47 (2014) 410–416