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Displaying 1 - 25 of 101

Hydraulically Pumped Cone Fracture in Bilayers With Brittle Coatings

October 12, 2021
Author(s)
H Chai, Brian R. Lawn
An earlier FEM analysis of inner cone cracks in monolithic brittle solids subject to cyclic indentation in liquids is extended to include the case of a brittle layer bonded to a compliant substrate, using a model glass/polycarbonate bilayer system as an

Margin Failures in Brittle Dome Structures: Relevance to Failure of Dental Crowns

October 12, 2021
Author(s)
T Qasim, Chris Ford, M T. Bush, X Z. Hu, Kenneth Malament, Brian R. Lawn
Margin cracks in loaded brittle dome structures are investigated. Dome structures consisting of glass shells filled with polymer resin, simulating the essential features of brittle crowns on tooth dentin, provide model test specimens. Disk indenters of

Role of Substrate Material in Failure of Crown-Like Layer Structures

October 12, 2021
Author(s)
Jeonghwan Kim, Sanjit Bhowmick, Herzl Chai, Brian R. Lawn
The role of substrate modulus on critical loads to initiate and propagate radial cracks to failure in curved brittle glass shells on compliant polymeric substrates is investigated. Flat glass disks are used to drive the crack system. This configuration is

NOVEL ZIRCONIA MATERIALS IN DENTISTRY

October 16, 2017
Author(s)
Yu Zhang, Brian R. Lawn
Zirconias, the most durable of the dental ceramics, are increasingly being fabricated in monolithic form for a range of clinical applications, circumventing issues associated with weak porcelain veneers. Yttria-based tetragonal zirconia polycrystal (Y-TZP)

Materials Design for Biomechanical Layer Structures

February 19, 2017
Author(s)
Brian R. Lawn, Antonia Pajares, P Miranda, Y N. Deng
A survey of recent advances in the analysis of ceramic-based layer structures for biomechanial applications is presented. Data on model layer systems, facilitating development of explicit fracture mechanics relations for predicting critical loads to

THE COMPELLING CASE FOR INDENTATION AS A FUNCTIONAL EXPLORATORY AND CHARACTERIZATION TOOL

September 15, 2015
Author(s)
Robert F. Cook, David B. Marshall, Nitin P. Padture, Michelle L. Oyen, Antonia Pajares, Jodie E. Bradby, Ivar E. Reimanis, Rajan Tandon, Trevor F. Page, George M. Pharr, Brian R. Lawn
The utility of indentation testing for characterizing a wide range of mechanical properties of brittle materials is highlighted in light of recent articles questioning its validity, specifically in relation to the measurement of toughness. Contrary to

MECHANICS ANALYSIS OF MOLAR TOOTH SPLITTING

December 12, 2014
Author(s)
Amir Barani, Brian R. Lawn, Mark Bush, Herzl Chai
A model for the splitting of teeth from wedge loading of molar cusps from a round indenting object is presented. The model is developed in two parts: first, a simple 2D fracture mechanics configuration with the wedged tooth simulated by a compact tension

THE ROLE OF TOOTH ENAMEL MECHANICAL PROPERTIES IN PRIMATE DIETARY ADAPTATION

June 27, 2012
Author(s)
Paul Constantino, James J. Lee, Yvonne B. Gerbig, Adam Hartstone-Rose, Mauricio Talebi, Brian R. Lawn, Peter Lucas
Primate teeth adapt to the physical properties of foods in a variety of ways including changes in occlusal morphology, enamel thickness, and overall size. We conducted a comparative study of extant primates to examine whether their teeth also adapt to

PROBING MATERIAL PROPERTIES WITH SHARP INDENTERS: A REVIEW

January 2, 2012
Author(s)
Brian R. Lawn, Robert F. Cook
A review on the use of sharp, fixed-profile indenters as materials probes is presented. Indentation is proposed as a simple but powerful methodology for evaluating basic mechanical properties—elastic modulus, hardness, toughness, etc.—in all classes of

Tooth chipping can reveal bite forces and diets of fossil hominins

June 16, 2010
Author(s)
Paul Constantino, James J. Lee, H Chai, Bernhard Zipfel, Charles Ziscovici, Brian R. Lawn, Peter Lucas
Fossil hominin tooth enamel often exhibits antemortem edge chipping (Robinson 1954; Tobias 1967; Wallace 1973). Here we apply a simple fracture equation to estimate peak bite forces from the sizes of such chips. This equation, previously validated by

FRACTURE OF TOOTH ENAMEL FROM INCIPIENT MICROSTRUCTURAL DEFECTS

June 14, 2010
Author(s)
H Chai, James J. Lee, Brian R. Lawn
We present definitive evidence for crack growth from internal defects called 'tufts' in human enamel. Side walls of slices sawn from extracted human teeth are observed during loading to 'failure'. 'Longitudinal' and 'transverse' slices (parallel and normal

GRADED STRUCTURES FOR ALL-CERAMIC RESTORATIONS

May 17, 2010
Author(s)
Yu Zhang, H Chai, Brian R. Lawn
One failure mode of all-ceramic crown restorations is radial cracking at the cementation surface, from occlusally-induced flexure of the stiffer crown layer on the softer dentin underlayer. We hypothesize that such failure may be substantially mitigated by

Teeth: Among Nature's Most Durable Biocomposites

April 6, 2010
Author(s)
Brian R. Lawn, James J. Lee, H Chai
This paper addresses the durability of natural teeth from a materials perspective. Teeth are depicted as 'smart' biocomposites, highly resistant to cumulative deformation and fracture. Favorable morphological features of teeth at both macroscopic and

MORPHOLOGY AND FRACTURE OF ENAMEL

September 16, 2009
Author(s)
Sang-Won Myoung, James J. Lee, Paul Constantino, Peter Lucas, Brian R. Lawn
Teeth are remarkable biological structures, brittle but resilient. Here we examine the inter-relation between enamel morphology and crack resistance by sectioning human molar teeth after loading to fracture. The sections reveal that many cracks start from

The feeding biomechanics and dietary ecology of Australopithecus africanus

February 19, 2009
Author(s)
Brian R. Lawn, David Strait, Gerhard Weber, Simon Neubauer, Janine Chalk, Brian Richmond, Peter Lucas, Mark Spencer, Caitlin Schrein, Paul Dechow, Callum Ross, Ian Grosse, Barth Wright, Paul Constantino, Bernard Wood, Qian Wang, Dennis Slice, Craig Byron, Amanda Smith
The African Plio-Pleistocene hominins known as australopiths evolved a distinctive craniofacial morphology that traditionally has been interpreted as a dietary adaptation1 for feeding on small, hard objects2. This adaptive complex includes large postcanine

Predicting Failure in Mammalian Enamel

January 16, 2009
Author(s)
Brian R. Lawn, James J. Lee, Paul Constantino, Peter Lucas
Dentition is a vital element of human and animal function, yet there is little fundamental knowledge about how tooth enamel endures under stringent oral conditions. This paper describes a novel approach to the issue. Model glass dome specimens fabricated

Hydraulically Pumped Cone Fracture in Brittle Solids

October 21, 2008
Author(s)
Herzl Chai, Brian R. Lawn
An analysis of inner cone cracks in brittle solids subject to cyclic indentation in liquid is presented. These inner cone cracks, so named because they form well within the maximum contact circle, are postulated to be driven by a hydraulic pumping

Fracture Modes in Brittle Coatings With Large Interlayer Modulus Mismatch

October 16, 2008
Author(s)
Herzl Chai, Brian R. Lawn, S Wuttiphan
Fracture modes in a model glass/polymer coating/substrate system indented with hard spheres are investigated. The large modulus mismatch between the glass and polymer results in distinctive transverse fracture modes in the brittle coating: exaggerated