Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: An in vitro study

Abstract

Introduction:Literature reveals that masticatory load on denture bearing tissues through complete dentures should be maximum on primary stress bearing areas and least on relief area in accordance with the histology of underlying tissues. A study to validate the existing beliefs was planned to compare the pressure on mucosa using selective pressure technique and minimal pressure technique, with the incorporation of two different impression materials utilizing the pressure sensors during secondary impression procedure.Materials and Methods:The study was performed using a maxillary analog. Three pressure sensors were imbedded in the oral analog, one in the mid palatine area and the other two in the right and left ridge crest. Custom trays of two different configurations were fabricated. The two impression materials tested were light body and zinc oxide eugenol. A total of 40 impressions were made. A constant weight of 1 kg was placed, and the pressure was recorded as initial and end pressures.Results:A significant difference in the pressure produced using different impression materials was found (P < 0.001). Light body vinyl polysiloxane produced significantly lesser pressure than zinc oxide eugenol impression materials. The presence of relief did affect the magnitude of pressure at various locations.Conclusion:All impression materials produced pressure during maxillary edentulous impression making. Tray modification is an important factor in changing the amount of pressure produced. The impression materials used also had a significant role to play on the pressures acting on the tissues during impression procedure.Clinical Implication:Light body VPS impression material may be recommended to achieve minimal pressure on the denture bearing tissues in both selective as well as minimal pressure techniques.

Evaluation of the trueness and precision of complete arch digital impressions on a human maxilla using seven different intraoral digital impression systems and a laboratory scanner

“…However, when the palate was evaluated the physical impressions compressed the tissues and demonstrated a negative deviation of 120 μm while the digital impressions all demonstrated a positive deviation ranging from 106 to 236 μm. This is consistent with previous studies that show that physical impressions generate significant compressive forces which can depress the soft tissues . The lack of pressure from a digital impression may cause prosthetics to fit more loosely compared to those fabricated with physical impressions.…”

“…This is consistent with previous studies that show that physical impressions generate significant compressive forces which can depress the soft tissues. 19 The lack of pressure from a digital impression may cause prosthetics to fit more loosely compared to those fabricated with physical impressions. The ability for intraoral digital impression systems to capture and stitch soft tissue data is relatively recent.…”

“…Elastomeric impression materials have been very successful over the years and have good dimensional stability and accuracy . However on soft tissues, pressure generated by these materials have the potential to compress and therefore distort these areas . Laboratories will often pour a physical impression and then scan the stone model into a box scanner to start the digital manufacturing workflow .…”

“…18 However on soft tissues, pressure generated by these materials have the potential to compress and therefore distort these areas. 19 Laboratories will often pour a physical impression and then scan the stone model into a box scanner to start the digital manufacturing workflow. 20 These laboratory scanners have very little research describing their accuracy, however some been shown to perform better in complete arch trueness when compared to the last generation of intraoral scanners.…”

Laboratory investigation of Accuracy of Impression Materials for Border Molding

“…23,24 During the clinical impression procedure, the minimum applied pressure is 1 kg/cm 2 , which is unequal distributedbigger on the alveolar ridge, less on the midline. 25…”