title: Suitability of polymers as screw post materials in primary teeth: an in vitro study.
abstract: OBJECTIVE
  Primary teeth undergo physiological root resorption during the transition to permanent dentition. The aim of  this study was to assess the potential use of screw posts in core build-up for primary teeth while adequately retaining the  crown restoration and allowing smooth physiological root resorption.
  
  
  METHODS
  To determine whether biodegradable  polymers such as polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) were appropriate as post materials, bending  strength test and bending elastic modulus test were performed according to ISO standards. The prepared screw posts were  immersed in 0.01 mol/L phosphate-buffered saline at 37 degrees Celsius, and changes due to hydrolysis were observed.  Results In the bending strength test and bending elastic modulus test, PGA and PLLA showed similar values to composite  resins used for core build-up. Although both showed adequate hydrolysis, the hydrolysis rate of PGA was higher than that of  PLLA.
  
  
  CONCLUSIONS
  PGA and PLLA may be suitable as biodegradable screw posts for primary teeth because they have  appropriate strength and hydrolysis ability.
authors.affiliation: Department of Pediatric Dentistry, Matsumoto Dental University, Nagano, Japan. t_mizutani@po.mdu.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Mizutani
authors.forename: A
authors.initials: A
authors.lastname: Nakayama
authors.forename: H
authors.initials: H
authors.lastname: Iwasaki
authors.forename: H
authors.initials: H
authors.lastname: Miyazawa
mesh_terms: D020341:Absorbable Implants; D001672:Biocompatible Materials / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D055119:Elastic Modulus; D006801:Humans; D006868:Hydrolysis; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D018583:Pliability; D011091:Polyesters / Q000737:chemistry*; D011100:Polyglycolic Acid / Q000737:chemistry*; D011176:Post and Core Technique / Q000295:instrumentation*; D019279:Resin Cements / Q000737:chemistry; D012391:Root Resorption / Q000503:physiopathology; D012965:Sodium Chloride / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D014094:Tooth, Deciduous / Q000473:pathology*
chemical_list: D001672:Biocompatible Materials; C112828:Clearfil AP-X; C469237:Clearfil Core; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011091:Polyesters; D019279:Resin Cements; D011100:Polyglycolic Acid; D012965:Sodium Chloride; C033616:poly(lactide)