Abstract
Sixty-four fractured commercially pure titanium (cp-Ti) narrow dental implants (NDIs) with similar macrogeometry and connection designs were studied after different implantation times in humans in order to determine their reliability and to evaluate the causes of the fracture. These NDIs were compared with other similar implants, made with alloyed titanium with 15% Zr and with 12% strained titanium. Original implants were tested under static and fatigue conditions, simulating the tri-axial loads in the mouth by means of a Bionix hydraulic test machine. Fractography was studied using field-emission scanning electron microscopy (FSEM). The results showed that cp-Ti NDI exhibits low strength for mechanical cycling, and the alloyed Ti and strained titanium increase the mechanical strength, guaranteeing long term mechanical behavior. NDIs fractured due to fatigue, and, in some cases, the presence of cracks in the original NDIs quickly led to fracture. These cracks were attributed to plastic deformation during machining were found to be exacerbated due to acid etching in the passivation process. All cases of fracture were cp-Ti dental implants due to the low fatigue limit. The results show that, when titanium is alloyed or cold-worked, the fatigue limit is higher than cp-Ti. This in vitro research will help clinicians to select a better NDI system for safer treatment.
Highlights
Sometimes, the available bone tissue is insufficient to place regular-diameter dental implants, and new surgical techniques are necessary for increasing and regenerating the hard tissue
The use of narrow dental implants (NDIs) is an alternative treatment, because these allow dental restorations in areas with limited prosthetic space and they can be inserted in places that would otherwise require grafting techniques [1,2,3,4]
All cases of fractured narrow dental implants were manufactured with commercially pure titanium (cp-Ti), and the failure mechanism was fatigue in all cases
Summary
The available bone tissue is insufficient to place regular-diameter dental implants, and new surgical techniques are necessary for increasing and regenerating the hard tissue. The yield strength for the grade 4 cp-Ti was the cold-worked Ti presented a lower value of toughness, without any effects on other lowest, and it increased for the other implants. The strain to fracture was lower for the Ti alloy and cold-worked be significantly higher for the cold-worked Ti than the other implants, due to the increase in the number of linear defects in the hexagonal microstructure of α-titanium. The cold-worked Ti presented a lower value of toughness, without any effects on other dislocations produced an increase in the hardness and the mechanical properties. The cp-Ti grade 4 presented a curve around 100 N These values demonstrate the importance of the static mechanical properties on the cyclic behavior.
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