Compressive and tensile zones in the cement interface of full crowns: a technical note on the concept of resistance.

PURPOSE The objectives of the study were: 1) to map the stresses acting on the cement interface of crown and abutment analogs during loading; and 2) to provide a theoretical basis for the hypothesis that resistance to lateral dislodgment is a function of the distribution of compressive force vectors acting on the cement lute. MATERIALS AND METHODS Three-dimensional finite element (FE) meshes of crown and abutment analogs were constructed and loaded in a direction perpendicular to the axes of symmetry of the abutments. Three parameters were investigated: taper (10 degrees and 20 degrees of convergence), abutment substrate (Ni-Cr alloy and dentin), and type of cement (zinc oxide eugenol, zinc phosphate, glass ionomer, and composite resin). The tensile and compressive components of the resulting force systems were plotted along two axes (z: parallel to the axis of symmetry of the crown/abutment complex; and y: perpendicular to z, i.e., parallel to the direction of loading). Von Mises stresses were also generated. RESULTS First, it was shown that the restoration's axis of rotation was located inside the abutment cone and was perpendicular to and intersected the axis of symmetry of the crown/abutment complex. Second, stress distribution was dependent on the three parameters investigated. Varying taper led to shifts due mainly to alterations in specimen geometry, whereas the abutment substrate and the cement type had a bearing on the level of the axis of rotation. The smaller the modulus of elasticity of the abutment substrate or the cement lute, the farther apical the location of the axis of rotation. CONCLUSIONS Conventional schemes for explaining crown dislodgment in which the restoration rotates around an axis located at the preparation margin should be reassessed. The results of the FE analysis are compatible with the hypothesis that resistance to lateral dislodgment is a function of the distribution of compressive force vectors acting on the cement interface.

[1]  A Morikawa [Investigation of occlusal force on lower first molar in function]. , 1994, Kokubyo Gakkai zasshi. The Journal of the Stomatological Society, Japan.

[2]  K. Dreyer,et al.  The relationship between retention and convergence angle in cemented veneer crowns. , 1955 .

[3]  N. Gjerdet,et al.  Dental casting alloys with a low content of noble metals: physical properties. , 1983, Acta odontologica Scandinavica.

[4]  A. Wilson,et al.  The relationship between preparation convergence and retention of extracoronal retainers. , 1994, Journal of prosthodontics : official journal of the American College of Prosthodontists.

[5]  H T Shillingburg,et al.  Retention and resistance of preparations for cast restorations. , 1980, The Journal of prosthetic dentistry.

[6]  G. E. Myers,et al.  The retentive qualities of bridge retainers. , 1968, Journal of the American Dental Association.

[7]  David R. Hall,et al.  Elastic Constants of Three Representative Dental Cements , 1973 .

[8]  H F Morris,et al.  Veterans Administration Cooperative Studies Project No. 147/242. Part VII: The mechanical properties of metal ceramic alloys as cast and after simulated porcelain firing. , 1989, The Journal of prosthetic dentistry.

[9]  Herbert T.Shillingburg...,et al.  Fundamentals of fixed prosthodontics , 1979 .

[10]  J I Nicholls,et al.  The effect of tooth preparation height and diameter on the resistance of complete crowns to fatigue loading. , 1997, The International journal of prosthodontics.

[11]  Stanley Daniel Tylman,et al.  Tylman's Theory and Practice of Fixed Prosthodontics , 1989 .

[12]  D. E. Smith,et al.  The measurement of forces transmitted to abutment teeth of removable partial dentures. , 1979, The Journal of prosthetic dentistry.

[13]  P. S. Lund,et al.  The effect of tooth preparation on retention and microleakage of cemented cast posts. , 1994, Journal of prosthodontics : official journal of the American College of Prosthodontists.

[14]  Zuckerman Gr Resistance form for the complete veneer crown: principles of design and analysis. , 1988 .

[15]  Jon P Standlee,et al.  Biomechanics in Clinical Dentistry , 1987 .

[16]  P. Wilson,et al.  The effect of die-spacing on crown retention. , 1996, The International journal of prosthodontics.

[17]  Edward G. Kaufman,et al.  Factors influencing the retention of cemented gold castings , 1961 .

[18]  M. Georgescu,et al.  Effect of two dentinal desensitizing agents on retention of complete cast coping using four cements. , 1996, The Journal of prosthetic dentistry.

[19]  S F Rosenstiel,et al.  Influence of tooth surface roughness and type of cement on retention of complete cast crowns. , 1997, The Journal of prosthetic dentistry.

[20]  J. Katz,et al.  Elastic Properties of Dental Resin Restorative Materials , 1974, Journal of dental research.

[21]  R M LEWIS,et al.  A mathematical solution of a problem in full crown construction. , 1959, Journal of the American Dental Association.

[22]  R G Craig,et al.  Finite element analysis of three- and four-unit bridges. , 1989, Journal of oral rehabilitation.

[23]  F. M. Gardner,et al.  Quantitative determination of taper adequate to provide resistance form: concept of limiting taper. , 1988, The Journal of prosthetic dentistry.

[24]  U. Belser,et al.  Fatigue resistance of soldered joints: a methodological study. , 1994, Dental materials : official publication of the Academy of Dental Materials.

[25]  H. T. Shillingburg,et al.  Preparations for cast gold restorations , 1974 .

[26]  W B Eames,et al.  Techniques to improve the seating of castings. , 1978, Quintessence of dental technology.

[27]  F. M. Gardner,et al.  New guidelines for preparation taper. , 1993, Journal of prosthodontics : official journal of the American College of Prosthodontists.

[28]  P J Mack,et al.  A theoretical and clinical investigation into the taper achieved on crown and inlay preparations. , 1980, Journal of oral rehabilitation.

[29]  J I Nicholls,et al.  The relationship between abutment taper and resistance of cemented crowns to dynamic loading. , 1996, The International journal of prosthodontics.

[30]  G Willems,et al.  A classification of dental composites according to their morphological and mechanical characteristics. , 1992, Dental materials : official publication of the Academy of Dental Materials.

[31]  R. Mericske-Stern,et al.  Simultaneous force measurements in 3 dimensions on oral endosseous implants in vitro and in vivo. A methodological study. , 1996, Clinical oral implants research.

[32]  R. G. Craig,et al.  Modulus of elasticity and strength properties of dental cements. , 1976, Journal of the American Dental Association.

[33]  D. McComb,et al.  Physical properties of calcium hydroxide and glass-ionomer base and lining materials. , 1989, Dental materials : official publication of the Academy of Dental Materials.

[34]  U. Belser,et al.  A rationale for a simplified occlusal design in restorative dentistry: historical review and clinical guidelines. , 1995, The Journal of prosthetic dentistry.

[35]  Robert L. Willey Retention in the preparation of teeth for cast restorations , 1976 .

[36]  S. Ochi,et al.  The taper of clinical preparations for fixed prosthodontics. , 1988, The Journal of prosthetic dentistry.

[37]  R J Baez,et al.  A method for determining adequate resistance form of complete cast crown preparations. , 1984, The Journal of prosthetic dentistry.

[38]  J Silness,et al.  Preparation areas resisting displacement of artificial crowns. , 1977, Journal of oral rehabilitation.

[39]  T W Korioth,et al.  Forces and moments generated at the dental incisors during forceful biting in humans. , 1997, Journal of biomechanics.

[40]  E Ohm,et al.  The convergence angle in teeth prepared for artificial crowns. , 1978, Journal of oral rehabilitation.

[41]  R. Bryant,et al.  Modulus of elasticity in bending of composites and amalgams. , 1986, The Journal of prosthetic dentistry.

[42]  J. A. Tesk,et al.  Elastic constants of three Ni-Cr dental alloys at room and elevated temperatures. , 1989, Dental materials : official publication of the Academy of Dental Materials.

[43]  W. G. Matthews,et al.  Tensile Properties of Mineralized and Demineralized Human and Bovine Dentin , 1994, Journal of dental research.