Self-drilling and self-tapping screws: an ultrastructural study.
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.
Goelzer
Juliana Gonçalves
JG
Department of Oral and Maxillofacial Surgery, Universidade de Pernambuco, Recife, Brazil. jugoelzer@hotmail.com
Avelar
Rafael Linard
RL
de Oliveira
Rogério Belle
RB
Hubler
Roberto
R
Silveira
Roger Lanes
RL
Machado
Rosilene Andrea
RA
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
D001672:Biocompatible Materials; D012965:Sodium Chloride; D014025:Titanium