title: A Comparison of Accuracy of Matrix Impression System with Putty Reline Technique and Multiple Mix Technique: An In Vitro Study.
abstract: BACKGROUND
  The difficulty in obtaining an acceptable impression increases exponentially as the number of abutments increases. Accuracy of the impression material and the use of a suitable impression technique are of utmost importance in the fabrication of a fixed partial denture. This study compared the accuracy of the matrix impression system with conventional putty reline and multiple mix technique for individual dies by comparing the inter-abutment distance in the casts obtained from the impressions.
  
  
  METHODS
  Three groups, 10 impressions each with three impression techniques (matrix impression system, putty reline technique and multiple mix technique) were made of a master die. Typodont teeth were embedded in a maxillary frasaco model base. The left first premolar was removed to create a three-unit fixed partial denture situation and the left canine and second premolar were prepared conservatively, and hatch marks were made on the abutment teeth. The final casts obtained from the impressions were examined under a profile projector and the inter-abutment distance was calculated for all the casts and compared.
  
  
  RESULTS
  The results from this study showed that in the mesiodistal dimensions the percentage deviation from master model in Group I was 0.1 and 0.2, in Group II was 0.9 and 0.3, and Group III was 1.6 and 1.5, respectively. In the labio-palatal dimensions the percentage deviation from master model in Group I was 0.01 and 0.4, Group II was 1.9 and 1.3, and Group III was 2.2 and 2.0, respectively. In the cervico-incisal dimensions the percentage deviation from the master model in Group I was 1.1 and 0.2, Group II was 3.9 and 1.7, and Group III was 1.9 and 3.0, respectively. In the inter-abutment dimension of dies, percentage deviation from master model in Group I was 0.1, Group II was 0.6, and Group III was 1.0.
  
  
  CONCLUSIONS
  The matrix impression system showed more accuracy of reproduction for individual dies when compared with putty reline technique and multiple mix technique in all the three directions, as well as the inter-abutment distance.
authors.affiliation: Reader, Department of Prosthodontics, MNR Dental College, Sangareddy, Telangana, India.
authors.forename: M Praveen
authors.initials: MP
authors.lastname: Kumar
authors.affiliation: Associate Professor, Department of Dentistry, Karnataka Institute of Medical Sciences, Hubli, Karnataka, India.
authors.forename: Suneel G
authors.initials: SG
authors.lastname: Patil
authors.affiliation: Reader, Department of Prosthodontics.
authors.forename: Bhandari
authors.initials: B
authors.lastname: Dheeraj
authors.affiliation: Reader, Department of Prosthodontics, Narsinh Bhai Patel Dental College, Visnagar, Gujarat, India.
authors.forename: Keshav
authors.initials: K
authors.lastname: Reddy
authors.affiliation: Reader, Department of Prosthodontics, Institute of Dental sciences, Bareily, Uttar Pradesh, India.
authors.forename: Dinker
authors.initials: D
authors.lastname: Goel
authors.affiliation: Reader, Department of Prosthodontics, Institute of Dental sciences, Bareily, Uttar Pradesh, India.
authors.forename: Gopi
authors.initials: G
authors.lastname: Krishna
keywords: Matrix impression; multiple mix; poly vinyl siloxane; putty reline