title: Effects of relief space and escape holes on pressure characteristics of maxillary edentulous impressions.
abstract: BACKGROUND
  The selective pressure technique has been recommended for making impressions of maxillary edentulous residual ridges. Although various methods for making impressions have been reported, a definitive procedure has not been clearly elucidated.
  
  
  OBJECTIVE
  This in vitro study evaluated changes in impression pressure produced by different types of relief space and escape holes in the impression tray for making an impression of a simulated maxillary edentulous arch.
  
  
  METHODS
  Silicone impression material (Exadenture) and a maxillary edentulous acrylic cast were used. A miniature pressure sensor was embedded at the mid-palatal suture (point-P) and at the left first molar area on the edentulous ridge (point-R). Three types of tray relief were used: no spacer (NS), a 0.36-mm-thick sheet of wax (SS), or a 1.40-mm-thick base plate wax (BS). Four types of escape holes were made: no hole (NH), or escape holes of 0.5, 1.0, or 2.0 mm in diameter (05H, 10H, and 20H, respectively) in the area opposing point-P. Twelve trays were formed using these relief space and escape hole combinations. The cast and tray were attached to a rheometer for applying a continuous isotonic force of 5.0 kgf and compressive speed of 120 mm/min. Impressions were made and measurement of pressure (kPa) began immediately prior to compression and continued until the materials had polymerized for 2 minutes, with a sampling time of 5 Hz. Measurements were performed 5 times for each tray. The data were analyzed using 3-way analysis of variance and the Bonferroni test (alpha=.05).
  
  
  RESULTS
  At initial pressure, the data obtained at point-P showed significantly higher values for NSNH, NS05H, SSNH, and SS05H (range: 22.29 +/- 1.58 kPa to 29.96 +/- 1.41 kPa) than those at point-R (range: 18.61 +/- 1.12 kPa to 22.71 +/- 2.11 kPa). At end pressure, the data obtained from NSNH at point P showed a significantly higher value (25.36 +/- 1.69 kPa) than that of point-R (15.36 +/- 0.99 kPa) (P<.001), whereas data from NS10H and NS20H at point-P showed a significantly lower value (6.32 +/- 0.84 kPa and 4.50 +/- 0.42 kPa) than at point-R (15.50 +/- 0.49 kPa and 14.98 +/- 0.88 kPa) (P<.001). The data obtained from SS05H, SS10H, and NS20H at point-P showed significantly lower values (range: 3.72 +/- 0.44 kPa to 9.10 +/- 0.26 kPa) than those at point-R (range: 13.40 +/- 1.31 kPa to 14.40 +/- 0.98 kPa). Moreover, the data obtained from BSNH, BS05H, BS10H, and BS20H at point-P showed significantly lower values (range: 3.24 +/- 1.96 kPa to 10.20 +/- 1.84 kPa) than those of point-R (range: 11.69 +/- 1.01 kPa to 14.04 +/- 2.08 kPa).
  
  
  CONCLUSIONS
  For making impressions of an edentulous maxilla, the data suggest that a tray with an escape hole 1.0 mm or larger or a spacer thickness of base plate wax (1.40 mm) be used.
authors.affiliation: Department of Comprehensive Clinical Dentistry, Nihon University School of Dentistry at Matsudo, Chiba, Japan. komiyama@mascat.nihon-u.ac.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Komiyama
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Saeki
authors.forename: Misao
authors.initials: M
authors.lastname: Kawara
authors.forename: Kihei
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Shigeo
authors.initials: S
authors.lastname: Otake
mesh_terms: D000180:Acrylic Resins; D000704:Analysis of Variance; D003724:Dental Arch; D003760:Dental Impression Materials / Q000737:chemistry*; D003761:Dental Impression Technique / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D007575:Jaw, Edentulous; D008437:Maxilla; D003765:Models, Dental; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D012212:Rheology / Q000295:instrumentation; D012826:Silicone Elastomers / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014160:Transducers, Pressure; D014885:Waxes / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D003760:Dental Impression Materials; D011108:Polymers; D012826:Silicone Elastomers; D014885:Waxes