Effect of Different Sprue Designs on the Internal Porosity of Cast Titanium Crowns

Mahshid, M.; Darabi, R.; Sazegara, H.; Seyyedan, K.; Varshosaz, M.; Ejlali, M.; Nikoobazl, M.; Eslami, B.

Effect of Different Sprue Designs on the Internal Porosity of Cast Titanium Crowns

Document Type : Original Article

Authors

M. Mahshid ¹

R. Darabi ²

H. Sazegara ¹

K. Seyyedan ³

M. Varshosaz ⁴

M. Ejlali ⁵

M. Nikoobazl ⁶

B. Eslami ⁷

¹ Associate Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences

² Prosthodontist

³ Assistant Professor, Department of Fixed Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences

⁴ Assistant Professor, Department of Oral and Maxillofacial Radiology, School of Dentistry, Shahid Beheshti University of Medical Sciences

⁵ Academic Staff, Department of Removable Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences

⁶ Academic Staff, Central laboratory, School of Dentistry, Shahid Beheshti University of Medical Sciences

⁷ Associate Professor, Department of Oral Pathology, Dental School, School of Dentistry, Shahid Beheshti University of Medical Sciences

Abstract

Statement of Problem: Porosity is a frequently observed casting defect in titanium dental casting.Purpose: This study measured the effects of different sprue design on the internal porosity of cast titanium crowns. Materials and Method: Sixty complete veneer crowns were fabricated on a stainless steel die with a 150- degree sloping shoulder using customized wax patterns. All wax patterns were sprued with 3 different sprue design (Reservoir, Runner bar and Rousseau) and were invested with an alumina- magnesia investment. Castings were made with commercially pure titanium (CP Ti (grade II)) according to the manufacturer's instructions. The castings were carefully cleaned. Internal porosities were quantified with photographs and radiographs by computerized image analyses. Data were analyzed with an ANOVA with a confidence level of 95%.Results: There were statistically significant differences in the values of porosity between 3 types of sprue design. The reservoir sprue design had the least internal porosity comparing to the other designs.Conclusions: Improvements in the porosity of titanium crowns was the result of the Reservoir sprue design with vent. Effects of Different sprue designs on internal porosity and their effects on casting accuracy and marginal adaptation of cast titanium crown and bridges must be evaluated to achieve better evidence and clinical relevance.Key Words: Titanium, Sprue design, Internal porosity