Lídia Carvalho

Application of Bragg Grating Sensors in Dental Biomechanics

This paper describes the use of fibre Bragg grating (FBG) sensors to measure strains at a mandible surface that are caused by static or impact loads on a dental implant. The measuring apparatus uses a fixed optical filter reference scheme and is able to detect dynamic signals with frequency components of up to 10 kHz. A dried implanted cadaveric mandible was used with strain gauges and FBG sensors placed at the outer surface in the direction of the longitudinal axis of the implant. The implants were loaded statically and dynamically and uniaxial strains recorded. The study demonstrates the ability of the FBG as a biomechanical sensor.

In the trail of a new bio-sensor for measuring strain in bone: osteoblastic biocompatibility.

Fibre Bragg Grating (FBG) is an optical sensor recorded within the core of a standard optical fibre, which responds faithfully to strain and temperature. FBG sensors are a promising alternative to other sensing methodologies to assess bone mechanics in vivo. However, response of bone cells/bone tissue to FBGs and its sensing capability in this environment have not been recorded yet. The present study addressed these issues in long-term human osteoblastic cell cultures. Results showed that osteoblastic cells were able to adhere and proliferate over the fibre and, also, the protective polymer coating. RT-PCR analysis showed the expression of Col I, ALP, BMP-2, M-CSF, RANKL and OPG. In addition, cultures presented high ALP activity and the formation of a calcium phosphate mineralized extracellular matrix. Cell behavior over the fibre without and with the coating polymer was similar to that found in cultures grown in standard tissue culture plates (control). In addition to the excellent osteoblastic cytocompatibility, FBGs maintained the physical integrity and functionality, as its sensing capability was not affected through the culture period. Results suggest the possibility of in vivo osseointegration of the optical fibre/FBGs anticipating a variety of applications in bone mechanical dynamics.

Fibre Bragg grating sensing and finite element analysis of the biomechanics of the mandible

This paper describes the application of fibre Bragg grating (FBG) sensors to measure strains at the outer surface of a mandible. The strains were correlated to identical ones obtained with a numerical finite element model. For this purpose, a synthetic mandible was used and 4 Bragg sensors were glued to the mandible. Strain patterns were assessed for different load configurations which included the forces of the masseter and temporal muscles and occlusion loads on different tooth (incisor, canine and molar). Overall the strains obtained using different measuring methods were identical, namely for the case of symmetric loading. When loading was non-symmetric, strain differences were observed at one sensor.

FBG applied in dynamic analysis of an implanted cadaveric mandible

This work describes the use of a fiber Bragg grating sensor (FBG) to measure strains at a mandible surface caused by impact loads on a dental implant. The apparatus uses a tuneable optical filter reference scheme and is able to detect dynamic signals with frequency components up to 10 kHz. A dried cadaveric mandible with a dental implant, and a FBG placed on the outer surface was used. The results demonstrate the ability of the FBG as a biomechanical sensor.

Evaluation of the efficacy and influence of the decontamination and sterilization of FBGs exposed to S. aureus and E. coli

The FBGs (Fibre Bragg Grating) are adequate sensors for measuring strain in biomedical applications. This work evaluates the efficacy of some products and processes, which are used for the decontamination and sterilization of these sensors. Fibre optic samples, partially stripped of the primary coating, were contaminated by E. coli and S. aureus and suffered decontamination processes by autoclave heating, immersion in ethylene oxide, sodium hypochlorite, chloramine T or peracetic acid and illumination ultra-violet radiation. After each process fibre samples were removed, washed in sterile saline and placed individually in BHI broth tubes. Tubes that showed turbidity of the BHI broth were considered positive. The sterilization practices by heating and immersionand avoided the formation of bacteria colonies, whereas illumination processes were not effective to avoid the bacteria colony growth.

FBG application in the determination of setting expansion of dental materials

The use of Fibre Bragg Grating sensors to study the setting expansion of dental materials like resin based composites and gypsum is reported. Temperature and strain evolution during the hardening phase of the material are obtained.