Dynamic mechanical properties of oral mucosa: Comparison with polymeric soft denture liners

Abstract

The purpose of this work was to characterize the viscoelastic behaviour of oral mucosa and compare it with the dynamic mechanical properties of different soft liners. For this purpose, a sample of pig oral mucosa and six commercialized soft liner samples have been investigated. A comparison was also carried with the first suitable hard rubber for dental prosthetics: vulcanite. Creep recovery (CR) and dynamic mechanical analysis (DMA) have been used to determine the mechanical modulus of oral mucosa and soft liners respectively. The Poisson ratio is used to compare mucosa bulk modulus and soft liner shear modulus. The biomechanical concept of conventional complete dentures needs a good adjustment of dynamic mechanical impedance between the base and oral mucosa. The viscoelastic mechanical property of the oral mucosa as a referent biopolymer has been confirmed in vitro. The modulus value, adjusted for old patients in physiological conditions, is in the order of 3 MPa. This study underlines the plasticization effect of absorbed water on the mechanical properties of the underlying tissue. This study allows us to define some characteristics of the most adapted biomaterial according to the clinical exigency. The required biomaterial must display the following properties: compatibility and chemical resistance with biological environment perpetuated mechanical properties during physiological conditions and clinical use, good adjustment of dynamic mechanical impedance with supporting mucosa and easy sample processing.

Effect of long-time immersion of soft denture liners in water on viscoelastic properties

“…In case of non-uniform distribution of the occlusal force on the thin mucosal tissue covering the alveolar ridge, the biting force may result in pain sensations and advancing alveolar bone absorption. Resilient denture liners are frequently used when complete denture wearers suffer from the symptoms mentioned, and clinical data have proven that soft denture liners improve the masticatory function when compared with conventional hard denture bases [1][2][3][4][5][6][7] .…”

“…They can be categorized as acrylic resin-based and silicone-based materials, and their main characteristics vary according to the chemical type 4) . The soft denture liner must fulfill several essential requirements, such as high biocompatibility, good dimensional stability, permanent softness, compliance, viscoelasticity, strong bonding to the hard denture base, low water sorption and water solubility and color stability 4) . There is however no ideal soft lining material available, complying with all the requirements.…”

Determination of oral mucosal Poisson’s ratio and coefficient of friction fromin-vivocontact pressure measurements

“…Significant interest has arisen and extensive studies have been undertaken regarding the biomechanical responses of mucosa under denture treatment. Both instant nonlinear elastic responses (Scapino 1967;Kishi 1972;Kydd et al 1974;Kanbara et al 2012) and time-dependent viscous responses (Inoue et al 1985;Lacoste-Ferré et al 2011;Sawada et al 2011;Wakabayashi and Suzuki 2013) of the mucosa have been examined via experimental and numerical approaches. This highly vascularized tissue consists of considerable amount of interstitial fluids, and the substantial fluidic exchange occurs with surrounding tissues under compression (Scapino 1967;Kydd and Daly 1982).…”

“…In fact, apparent Poisson's ratio (n) of mucosa has not been considered as a critical factor in some literature (Inoue et al 1985). Previous FE studies have assumed a rather broad range of possible values, from 0.30 to 0.49 (Lacoste-Ferré et al 2011;Sawada et al 2011;Kanbara et al 2012;Ż mudzki et al 2012a, 2012bWakabayashi and Suzuki 2013). From a biomechanics perspective, the effect of apparent Poisson's ratio has not been adequately addressed thus far.…”

“…(a) Masks segmented for individual components from two individual CT scans, patient jaw and denture, presenting mucosa (transparent maroon), cortical bone (transparent yellow), cancellous bone (opaque orange), teeth (opaque grey), denture base (transparent cyan), frame (opaque blue), and artificial crowns (opaque red); (b) solidified model with NURBS representation after visual insertion of the removable partial denture; (c) finite element models meshed in ABAQUS 6.9.2 and (d) loading conditions (orange: native teeth; blue: artificial crowns) and boundary conditions (cyan triangles) assigned to the model.Computer Methods in Biomechanics and BiomedicalEngineering 3 range of n (from 0.30 to 0.49) has been assumed in the literature(Lacoste-Ferré et al 2011;Sawada et al 2011;Kanbara et al 2012;Ż mudzki et al 2012a, 2012bWakabayashi and Suzuki 2013). Soft tissue is often considered to be nearly incompressible by taking a very high Poisson's ratio of 0.499.…”