title: Self-drilling and self-tapping screws: an ultrastructural study.
abstract: OBJECTIVE
  The aim of the current study was to compare self-drilling and self-tapping screws with regard to bone contact and the production of bone debris using scanning electron microscopy.
  
  
  METHODS
  Three New Zealand rabbit calvariae were used. Self-tapping and self-drilling screws were inserted into the outer surface of the skull with and without saline solution irrigation. All screws were 5 mm in length and were inserted until their tips projected through the endosteal side. Sixteen screws were used--8 with a head diameter of 1.5 mm and 8 with 2.0 mm. All self-tapping screws were inserted through a drill bit hole (1.6 mm for 2.0-mm screws and 1.3 mm for 1.5-mm screws).
  
  
  RESULTS
  There was no damage to the screws after insertion. Bone damage occurred when irrigation was not used during the installment of the self-tapping screws. Bone debris formed during the installment of the self-drilling screws, which is considered beneficial.
  
  
  CONCLUSIONS
  Because the insertion of self-drilling screws is performed with manual pressure, irrigation is not essential. Unlike the drilling that occurs with self-tapping screw, the bone debris formed with self-drilling screws is not the result of the heat generated, but rather the result of biologically active bone tissue capable of reacting with the screw and improving its performance. The animal model used proved highly appropriate for comparisons with human beings because the bone structures of the head have the same density and thickness.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Universidade de Pernambuco, Recife, Brazil. jugoelzer@hotmail.com
authors.forename: Juliana Gonçalves
authors.initials: JG
authors.lastname: Goelzer
authors.forename: Rafael Linard
authors.initials: RL
authors.lastname: Avelar
authors.forename: Rogério Belle
authors.initials: RB
authors.lastname: de Oliveira
authors.forename: Roberto
authors.initials: R
authors.lastname: Hubler
authors.forename: Roger Lanes
authors.initials: RL
authors.lastname: Silveira
authors.forename: Rosilene Andrea
authors.initials: RA
authors.lastname: Machado
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001860:Bone Plates; D001863:Bone Screws; D003399:Craniotomy / Q000379:methods; D004867:Equipment Design; D017276:Friction; D006358:Hot Temperature; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D023421:Models, Animal; D009777:Occipital Bone / Q000601:surgery* / Q000648:ultrastructure; D011312:Pressure; D011817:Rabbits; D012965:Sodium Chloride; D013499:Surface Properties; D007507:Therapeutic Irrigation; D014025:Titanium
chemical_list: D001672:Biocompatible Materials; D012965:Sodium Chloride; D014025:Titanium