Stress pattern generated by different post and core material combinations: A photoelastic study.

Objective: To analyze the effect of different combinations of post and core materials on stress distribution in dentin of an endodontically treated tooth. Materials and Methods: This was an experimental stress analysis study. Models were made in photoelastic material, i.e., epoxy resin. Different combinations of post and core materials used were: Glass fiber post with composite core, stainless steel post with composite core, and cast metal post and core. Stresses generated were frozen, models were sliced and viewed under circular polariscope, and photographs were taken. Stress was calculated by counting the number of fringes. Results: For the combination of glass fiber post with composite core, the shear stresses calculated were 1.196, 1.196, and 2.898 MPa in the apical, mid-root, and cervical region, respectively. For the combination of stainless steel post with composite core, the apical, mid-root and cervical stresses were 1.534, 0.511, and 2.557 MPa, respectively. For cast metal post and core, the apical, mid-root, and cervical stresses were 0.852, 0.511, and 1.534 MPa, respectively. Conclusion: The cervical region of the teeth is subjected to the highest stresses irrespective of the material used. The stainless steel post with the composite core generated the highest stress concentration in different regions. A glass fiber post generated a uniform stress distribution. A cast metal post and core combination generated lesser stress than the other combinations. The vast difference in the elastic modulus of the restorative materials can lead to nonuniform stress distribution and concentration of stresses in different areas which can have deleterious effect on the survival of already compromised teeth and restoration. Such combinations should be avoided and the material which has an elastic modulus close to that of dentin should be preferred.

Neutral zone and oral submucous fibrosis.

Oral submucous fibrosis is a premalignant condition in which rigidity of the lip, tongue, and palate results in reduced mouth opening and tongue movement. Limited mouth opening, mucosal rigidity, and reduced salivary flow makes prosthodontic procedures difficult in these patients and affects the stability, retention, and the support of removable prostheses. The burning sensation in the mouth that these patients experience reduces the tolerance to prostheses. We report a case of oral submucous fibrosis where the conventional neutral zone technique with certain modifications was utilized to rehabilitate a completely edentulous patient with this condition.

Collarless metal ceramic restorations to obscure the umbrella effect.

Esthetics with porcelain fused to metal restoration in the anterior region can be adversely affected due to the inadequate teeth preparations and design of the prosthesis. We presented here a case report where esthetics was compromised due to darkening of the interdental papilla and marginal gingival and overcontoured restorations in relation to porcelain fused to metal restorations. Good esthetic results were obtained by using basic principles of tooth preparation and using collarless metal ceramic restorations.