Evaluation of Synthetic Materials for An in-vitro Mandibular Edentulous Model

Objectives: The aim of this investigation was to indentify a suitable synthetic material that will replicate the soft tissue overlying the edentulous mandibular ridge with a view to creating an in-vitro model of a human edentulous mandible to test the retention of mandibular complete dentures. Methods: A range of synthetic materials to replicate the soft tissues of the oral mucosa were evaluated. Ten elastic materials were assessed: Addition-reaction silicone (Provil Novo L-Body, Heraeus, Germany; Aquasil Putty, Dentsply, Germany; Extrude Extra H-Body, Kerr, USA; ProGel Outer skin, Princibality, UK; M517 Coform Soft, Princibality, UK; Elite soft relining, Zhermack, Italy ), condensation reaction silicone (Xantoprin L-Blue L-Body, Heraeus, Germany), polysulphide (Permlastic L-Body Kerr, Italy), polyether (Impregum M-Body, 3M, Germany) and Alginate (Codent,UK,). The viscoelastic recovery and dimensional stability were measured in accordance with EN ISO standard 4823:2000 for elastomeric materials. The wettability of the elastomeric materials and the cohesive union of PMMA to these materials was also assessed. Results: The results for elastic recovery showed that Progel was the only material to reach 100% recovery; the remaining materials did not demonstrate true visco-elastic behaviour. All the materials showed resistance to vertical displacement of the PMMA discs, Codent alginate showed a significantly greater resistance at a crosshead speed of 5-60mm/min (p<0.05). Contact angle measurements revealed that all tested materials were hydrophobic, Provil novo showed the lowest hydrophobicity (p<0.05). All materials showed a mean linear shrinkage of 0.7% (SD=0.2) after 24 h. but then remained dimensionally stable over a 14-week period. Conclusions: The results of this investigation show that no single material showed optimal properties as a human mandibular-ridge soft tissue replacement. However, a combination of materials used in a multi-laminar arrangement may provide the required properties.