Changes in dentin after insertion of self-threading titanium pins with 3 methods: a scanning electron microscope pilot study.
BACKGROUND
Inserting a self-threading pin can cause dentinal cracks, but it is not known whether dentin bonding agents can penetrate these cracks.


OBJECTIVE
Part I of this in vitro pilot study was conducted to document the presence of dentinal cracks after the placement of self-threading pins with 3 methods. Part II was conducted to observe changes in dentin when a dentin bonding agent was applied before insertion of the self-threading pins.


METHODS
The crowns of 14 noncarious third molars were sectioned horizontally 2 mm above the cemento-enamel junction, and the occlusal portions were discarded. The teeth were put into a nontransparent bag and divided randomly into 2 groups. Group 1 consisted of 12 teeth. In each tooth, 4 pinholes were prepared with a handpiece at normal rotation speed (30,000 rpm). Self-threading pins were placed into 3 of the pinholes in each tooth: 1 manually, 1 by handpiece at 7000 rpm, and 1 by handpiece at 30,000 rpm. The fourth pinhole was left empty and served as the control. All group 1 teeth were sectioned vertically through the pins, dental hard tissue, and control pin holes. The examination surface of each specimen in group 1 was polished, and the smear layer was removed with Calcinase and NaOCl solutions. After dehydration in ascending grades of alcohol, specimens were coated with a 10- to 15-nm-thick layer of gold and examined with a scanning electron microscope. In the remaining 2 teeth (group 2), a dentin bonding agent was introduced into the pinholes prior to pin placement. Two pins were placed manually and 2 by handpiece at 30,000 rpm. After pin placement, sectioning, cleaning, and dehydration, the specimens were examined with a scanning electron microscope, and x-ray mapping was performed to determine the presence of titanium, silicon, and calcium.


RESULTS
Craze lines in dentin were associated with 54.5% of pins placed manually and 54.5% of pins placed with a handpiece at reduced speed (7000 rpm). Dentinal cracks were associated with 50% of pins placed with a handpiece at standard speed and with 16.7% of the control pinholes. X-ray mapping analysis revealed the presence of the dentin bonding agent between the pin and dentin wall. The dentin bonding agent was not found in the dentinal cracks except at the crack orifice.


CONCLUSIONS
Within the limitations of this pilot study, the method of pin insertion had no direct bearing on the presence of dentinal cracks. The dentin bonding agent tested did not fill the entire space of dentinal cracks but did occlude their orifices and fill the spaces between pin surface and dentin walls in the pin preparation.
Segović
Sanja
S
Department of Endodontology and Restorative Dentistry, School of Dental Medicine, University of Zagreb, Croatia.
Ferk
Suzana
S
Anić
Ivica
I
Jukić
Silvana
S
Galić
Nada
N
Sistig
Suzana
S
D003387:Cracked Tooth Syndrome / Q000209:etiology* / Q000517:prevention & control*; D003755:Dental High-Speed Technique; D003772:Dental Pins / Q000009:adverse effects*; D003799:Dental Stress Analysis; D003804:Dentin / Q000293:injuries* / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000627:therapeutic use*; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008963:Molar; D010865:Pilot Projects; D019279:Resin Cements / Q000627:therapeutic use; D014025:Titanium; D019228:Tooth Crown
D017220:Dentin-Bonding Agents; C092987:Optibond; D019279:Resin Cements; D014025:Titanium