PubMed · 9352785
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B Negus. 1997. Gauze bite block.. https://pubmed.ncbi.nlm.nih.gov/9352785/
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In order to evaluate interdental forces as a benchmark for mesial drift, a measurement technique was tested and evaluated on a human specimen. The measurement technique is based on the principle that a mesially directed horizontal force (FH) within a complete dental arch has an effect on interdental friction at the points of contact. The dynamic force (FZ), needed to pull out a defined metal strip from the interdental space is equal to the interdental frictional force (FR). Assuming unmodified approximal surfaces and unchanged tooth mobility in a complete dental arch, relative modifications of the interdental frictional force level provide a way of measuring horizontal force fluctuations. The validity of this measurement technique was measured by applying mesially directed forces of 1 to 5 N to the distal surface of the 2nd molar in a human specimen. The frictional forces measured increased in proportion to the distally applied force. The mesially directed force on the 2nd molar was transmitted in the dental arch anteriorly up to the incisor region and resulted in an increase of frictional forces. The reproducibility of this measurement technique was tested by quantitative analysis of potential measurement errors in the human specimen. The effect on interdental force measurement of the speed at which the metal strip is pulled was evaluated in a range of 50 to 500 mm/min. At the maximum pulling speed of 500 mm/min, a maximum scatter of 8% was recorded. Dependency of the dynamic force on direction of pull was measurable only when the metal strip was angled at more than 15 degrees. Experimental tests on the human specimen confirmed that the measurement technique presented here is sufficiently valid and reproducible for clinical long-term studies of interdental forces.
Four three-dimensional numerical models of a fixed partial denture were constructed, analyzed, and compared by means of the finite element method. Each model consisted of three elements destined to compensate the loss of a first molar. The second proemolar and the second molar were used as abutments. The connector surface was varied and then tested. A unidirectional axial force was applied to the center of the occlusal surface of the pontic. For each model, we measured the strain undergone by the connectors that link the pontic to each abutment. Results show that the strain measured in the mesio-distal direction was much more significant than in any other direction. Strain originated on either side of the loading point, centrally located on the cervical side of the pontic. The 0.15% strain threshold, beyond which rupture is possible, was only reached in one model (connector surface = 3.3 mm2). Increasing both the height and the width of the connectors by 1 mm resulted in extending the surface by 3.3 to 7.95 mm2. Although the surface increased by 141%, the strain threshold was not reached. This first result indicates that extending the surface of the connectors, which is less consistent with periodontal clinical requirements, is not necessary to ensure resistance to rupture.
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