Dental Materials Science Rama Krishna Alla
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1Basic Dental Materials Science
Chapter Outline
  • • Properties of Tooth Structure
  • • Standards for Dental Materials
  • • General Properties of Dental Materials
  • • Chemistry of Synthetic Resins
  • • Physical Metallurgy2

Properties of Tooth Structure1

A brief outline of the structure and the properties of the tooth are required as any conservative treatment is to replace the missing part of tooth or missing teeth with artificial materials that ideally should have similar properties.
 
CROWN AND ROOT
Crown is the visible part of the tooth above gingiva, which is about 1/3rd of the total length. The remaining 2/3rd is the root, which is stably positioned in the alveolar bone sockets.
 
ENAMEL
Enamel is a highly calcified substance covers that part of the tooth, which is visible. It is the hardest tissue in the body. The mineral phase has hydroxyapatite structure and it is in the form of rod-shaped units termed enamel prisms. Small quantities of organic matter consist of soluble proteins, peptides, insoluble proteins and citric acid.
The organic material is mostly present on the enamel surface. The prismatic rods have different refractive indices, dispersed at different densities; the structure is optically anisotropic medium, which shows different color parameters in different directions for different wavelengths. Hence it is impossible to do perfect matching of color parameters with artificial materials.
 
DENTIN
The bulk of the tooth substance is dentin, which resembles base in many respects. As with enamel the mineral content is hydroxyapatite and organic matter about 20% by weight is mostly collagen and small quantities of citric acid, insoluble protein, mucopolysaccharide and lipid.
 
PULP
The pulp of the tooth is soft tissue containing nerves and blood vessels. The pulp is very sen­si­tive to chemical, thermal and electrical stimulation.
 
CEMENTUM
Cementum is the mineralized dental tissue covering the anatomic roots of human teeth. It begins at the cervical portion of the tooth at the cementoenamel junction and continues to the apex.
 
Composition
Cementum contains 45–50% inorganic sub­stances and 50–55% organic material and water. Inorganic portion consists of calcium and phosphate in the form of hydroxyapatite. Cementum has the highest fluoride content of all the mineralized tissues. Organic portion consists of type-I collagen and protein poly­saccharides.
 
Physical Properties
  • The hardness of fully mineralized cementum is less than that of dentin.
  • It is light yellow in color.
  • 4 Lighter in color than dentin.
zoom view
Fig. 1.1: Cross-section of tooth structure
 
PERIODONTAL LIGAMENT
The periodontal ligament is a fibrous connective tissue that is noticeably cellular and contains numerous blood vessels. The periodontal ligament occupies the periodontal space, which is located between the cementum and the periodontal surface of the alveolar bone. The majority of the fibers of the periodontal ligament are collagen, and the matrix is composed of variety of macromolecules.
 
Functions
  • Attachment and support
  • Nutrition
  • Synthesis and resorption
  • Proprioception.
 
PROPERTIES
The properties of enamel may vary somewhat with its position on the tooth, i.e. cuspal enamel being stronger than enamel on the sides of the tooth. The proportional limit, ultimate compres­sive strength, modulus of elasticity of enamel are greater than corresponding values for dentin. However, dentin is capable of sustaining signi­ficant plastic deformation under compressive loading before fracture. Thus, enamel is stiffer and more brittle material than dentin. Dentin is more flexible and tougher. The high modulus of elasticity results in less resilience of enamel in comparison with dentin (Table 1.1).
TABLE 1.1   Properties of tooth
Property­
Enamel­
Dentin­
Density (cm3
2.97­
2.14­
Proportional limit (MPa)­
224­
148­
MOE (MPa)­
88,900­
18,600­
Ultimate compressive ­strength (MPa)
380­
300­
UTS (MPa)­
10­
57­
Shear strength (MPa)­
90­
135­
Modulus of resilience ­(MJ/m3)
0.55­
0.94­
Surface hardness (KHN) ­(Kg/mm2)
343­
68­
Specific heat (cal/gm/°C)­
0.18­
0.28­
Thermal conductivity ­(cal/sec/cm2)
0.0022­
0.0015­
Thermal diffusivity ­(mm2/sec)
0.469­
0.783­
COTE (X10–6 or ppm)­
11.4­
8.3­
Dentin is considerably stronger in tension than enamel. The low thermal conductivity of enamel and dentin aids in preventing thermal shock and pulpal pain when hot or cold foods or drinks taken into the mouth. Enamel is trans­lucent and exhibits a property called fluorescence.
SUGGESTED READING
  1. Bertassoni LE, Habelitz S, Kinney JH, Marshall SJ, Marshall GW Jr. Biomechanical perspective on the remineralization of dentin, Caries Res. 2009; 43: 70-7.
  1. Chai Y, Slavkin HC. Prospects for tooth regene­ration in the 21st century: a perspective. Microsc Res Tech. 2003; 60 (5): 469–79.
  1. Dhoble A, Padole P, Dhoble M. Bone mechanical properties: a brief review, trends biomater. Artif Organs. 2012; 26 (1): 25–30.
  1. Du C, Moradian-Oldak J. Tooth regeneration: challenges and opportunities for biomedical material research. Biomed Mater. 2006; 1 (1): R 10-7.
  1. Harold C Slavkin. The future of dentistry.5 Dent Today. 2006; 25 (10): 90-2.
  1. Hassan R, Caputo AA, Bunshah RF. Fracture toughness of human enamel. J Dent Res. 1981; 60 (4): 820-7.
  1. Ho SP, Balooch M, Goodis HE, Marshall GW, Marshall SJ. Ultrastructure and nanomechanical properties of cementum dentin junction. J Biomed Mater Res A. 2004; 68 (2): 343–51.
  1. Ho SP, Goodis HE, Balooch M, Nonomura G, Marshall SJ, Marshall GW. The effect of sample preparation technique on determination of struc­ture and nanomechanical properties of human cementum hard tissue. Biomaterials. 2004; 25 (19): 4847–57.
  1. Ho SP, Marshall SJ, Ryder MI, Marshall GW. The tooth attachment mechanism defined by structure, chemical composition and mecha­ni­cal properties of collagen fibers in the perio­dontium. Bio­materials. 2007; 28 (35): 5238–45.
  1. Solheim T. A new method for dental age estima­tion in adults. Forensic Science International. 1993; 59: 137–47.
  1. Thesleff I, Tummers M. Stem cells and tissue engineering: prospects for regenerating tissues in dental practice. Med Princ Pract. 2003; 12(Suppl 1): 43–50.
  1. Vasudeva G, Pawah S. Dentistry in the 21st century: a look into the future. J Oral Health Comm Dent. 2009; 3 (1): 9–14.
  1. Vystrèilová M, Novotný V. Estimation of age at death using teeth. Variability and Evolution. 2000; 8: 39–49.