Novel Molecular Spectroscopic Multimethod Approach for Monitoring Water Absorption/Desorption Kinetics of CAD/CAM Poly(Methyl Methacrylate) Prosthodontics

Abstract

Water absorbed to poly(methyl methacrylate) (PMMA)-based CAD/CAM (computer-assisted design/computer-assisted manufacturing) prosthodontics can alter their properties including hardness and stability. In the present contribution, water absorption and desorption kinetics under defined experimental conditions were monitored employing several supplementary and advanced Fourier transform infrared (FT-IR) spectroscopic techniques in combination with multivariate analysis (MVA). In this synergistic vibrational spectroscopic multimethod approach, first a novel near-infrared (NIR) diffuse fiber optic probe reflection spectroscopic method was established for time-resolved analysis of water uptake within seven days under controlled conditions. Near-infrared water absorbance spectra in a wavenumber range between 5288-5100 cm (combination band) and 5424-5352 cm (second overtone) were used establishing corresponding calibration and validation models to quantify the amount of water in the milligram range. Therefore, 14 well-defined samples exposed to prior optimized experimental conditions were taken into consideration. The average daily water uptake conducting reference analysis was calculated as 22 mg/day for one week. Additionally, in this study for the first time NIR two-dimensional correlation spectroscopy (2D-COS) was conducted to monitor and interpret the spectral dynamics of water absorption on the prosthodontics in a wavenumber range of 5100-5300 cm. For sensitive time-resolved recording of water desorption, a recently developed high-temperature, high-pressure FT-IR reaction cell with water-free ultra-dry in situ and operando operation was applied. The reaction cell, as well as the sample holder, was fully made of quartz glass, with no hot metal or ceramic parts in the vicinity of the high temperature zone. Applying a temperature gradient in the range of 25-150 ℃, mid-infrared (MIR) 2D-COS was successfully conducted to get insights into the dynamic behavior of O-H (1400-1800 cm) absorption bands with increasing temperature over time and the release of CO (2450 cm) from the polymers. In addition, an ATR FT-IR imaging setup was optimized in order to investigate the surface homogeneity of the PMMA-based resins with a spatial resolution to 2 µm. From this vibrational spectroscopic multimethod approach and the collection of several analytical data, conclusions were drawn as to which degree the surface structure and/or its porosity have an impact onto the amount of water absorption.

Near-Infrared Spectroscopic Method for Monitoring Water Content in Epoxy Resins and Fiber-Reinforced Composites

“…Based on study by Falk et al [ 35 ], this band corresponds to a combination mode of stretching and bending of the water molecule’s OH group. This observation is also consistent with a recent study by Muroga et al on spectroscopic evaluation of water content in polylactide (PLA) and with a novel work on water monitoring methods in PMMA by Wiedemair et al [ 21 , 36 ]. Thus, this absorption band is chosen to monitor the water content of the epoxy resin.…”

Spectroscopic and Quantum Mechanical Calculation Study of the Effect of Isotopic Substitution on NIR Spectra of Methanol

“…The development of near-infrared (NIR) spectroscopy during the last two decades resulted in its growing importance in science and technology. − It is currently a well-established method, with strong application record in basic physicochemical studies, i.e., on anharmonicity of molecular vibrations, , molecular structure, , intermolecular interactions and association mechanisms, ,, various aspects of hydrogen bonding, ,− solution chemistry, microheterogeneity of binary mixtures, solvent effects, , etc. It offers considerable advantages compared to other vibrational spectroscopies, i.e., affordability of the instrumentation and general versatility. , Thus, it is often preferred in both academic and industrial laboratories for qualitative and quantitative analysis of natural products, food, pharmaceuticals, medical tools, and medical diagnosis …”

Infrared spectroscopic imaging studies of medicinal plants

“…Molecular stretching, bending and deformation vibrations in the MIR contain absorptions in a range between 400 and 4000 cm À1 . NIR spectroscopy 35,[39][40][41][42][43][44] is concerned with the absorption, emission, reflection and diffuse-reflection of light and is not only vibrational but also electronic spectroscopy dealing with overtones and combination modes. 36 The MIR region can be divided into four parts: (1) X-H stretching region (4000-2500 cm À1 ); (2) triple-bond region (2500-2000 cm À1 ); (3) double-bond region (2000-1500 cm À1 ); (4) fingerprint region (1500-600 cm À1 ).…”