Objective: The influences of abutments made from zirconia (Y-TZP) and cement materials on the strength of titanium implants were investigated by using the finite element method.
Methods: Non-linear analysis was performed using a finite element method program (ANSYS Ver. 11, ANSYS, Canonsburg, U. S. A.) and a personal computer. For the analysis model, the bisection, trisection, and modified trisection types, for which the reliability of analytical accuracy has been established by experiments, were used. Regarding the combination of constituent materials, fixtures made of JIS class-4 pure titanium were used for all samples, and the materials of the abutment and abutment-screw were changed. Temporary cement and resin cement were used for adhesion materials. The materials of the superstructure and abutment were the same, and compact bone was used under all conditions. A force of up to 1,000 N was loaded in the 45° oblique direction to the superstructure. The fixture, abutment, and abutment-screw were placed in contact, the bone bottom was entirely fixed, and the lateral sides were fixed excluding the longitudinal direction.
Results: When JIS class-4 pure titanium abutment-screws were used in the trisection type implant, the strength reached the maximum. In the case of the bisection and modified trisection types implants, the strength decreased greatly when using abutments made from zirconia, although their fracture strengths were equivalent to the fatigue strength of JIS class-4 pure titanium implants. The influence of the two types of cement on strength of implant depended on the structure and materials of the implant. However, no major difference due to the cement type was noted in the strength of any implant. Conclusion: When the abutment and superstructure are prepared with zirconia, the maximum strength can be obtained by using JIS class-4 pure titanium abutment-screws in the trisection type. The design appropriate for all titanium implants is not necessarily appropriate for zirconia abutments; an appropriate design for zirconia abutments needs to be investigated. For the two kinds of cement examined, the strength of implant was hardly affected by the kind of cement.
It has been reported that β-TCP can stimulate bone formation, but the mechanisms are not well understood. The enhancement of bone formation and IGFs gene expression in bone defects of Beagle dog mandibles by β-TCP were reported. IGFs are the most abundant growth factors produced by osteoblasts, and exert important effects on the proliferation and differentiation of osteoblasts. However, the mechanism of activation of IGF signaling by β-TCP has not been elucidated. In this study, an implant drill was used to make bone defects in Beagle dog mandibles, and β-TCP was filled into the bone defects. The effect of β-TCP on IGF receptor 1 (IGF1R) gene expression was analyzed by RT-PCR and real-time PCR. Moreover, the gene products in mandibles were examined by immunohistochemistry. Increased mRNA levels of IGF1R gene were observed in β-TCP implanted samples compared with controls. The enhancement of IGF1R mRNA levels by β-TCP was confirmed by RT-PCR and real-time PCR. Immunohistochemical staining revealed increased IGF1R protein expression and phosphorylation in β-TCP-implanted bone tissue. Taken together, the stimulation of IGF1R expression and phosphorylation by β-TCP might be a part of the mechanism of accelerating bone formation.
The quartz crystal microbalance (QCM) method can detect the amounts of proteins adsorbed on biomaterials by a frequency shift of an oscillating quartz crystal. In the present study, we observed the adsorption behavior of proteins onto a titanium surface by using 27-MHz QCM. As proteins, two cell adhesive proteins, fibronectin and collagen, and albumin were evaluated.
The QCM apparatus used was a 27-MHz AFFINIX QNμ (Initium Co., Ltd., Tokyo, Japan) with 500-μL cells. The temperature was maintained at 25±1℃ and the solution in the cells was stirred during the measurements. A titanium sensor was prepared by titanium sputter-coating onto an Au electrode. Bovine albumin, human plasma fibronectin and atelocollagen were dissolved in phosphate-buffered saline (PBS) solution (pH 7.4) at a concentration of 50 μg/mL. Each protein solution was injected into the PBS solution in the cells of the QCM apparatus. The decrease of frequency was monitored and the amounts of proteins adsorbed onto the titanium surface at 30 min after the injection were calculated by Sauerbrey's equation. The apparent reaction rate, Kobs, was also obtained.
A slight frequency decrease was observed upon injection of albumin, and the frequency decrease for fibronectin adsorption was larger than that for albumin adsorption. Collagen significantly showed the largest decrease of frequency shift. Significant differences in the adsorbed amounts were seen among the three proteins. Namely, collagen exhibited the significantly largest adsorption amount on titanium, and albumin showed the significantly smallest amount. Kobs for collagen was significantly the smallest, and that of albumin was significantly the largest. A small value of Kobs corresponds to rapid adsorption of protein on titanium.
It is presumed that electrostatic interaction was dominant in the protein adsorption on titanium. Both albumin and fibronectin had more electrostatic repulsion to titanium based on their isoelectric points. In contrast, the attractive force increased between collagen and titanium because of the positively charged collagen. The QCM method was found to be a useful tool for monitoring not only the adsorption amounts of proteins but also adsorption behavior including the adsorption rate.
Although dental implant placement is considered to be a safe surgical procedure, this report focuses on two cases with severe hemorrhage during implant placement in the mandible. Excessive hematoma formation in the mouth floor resulted from arterial or venous trauma that occurred during implant socket preparation. The first case was a 60-year-old man who suffered hemorrhage and the formation of a large hematoma in the mouth floor that occurred during insertion socket preparation in the lateral incisor position on the right side of the mandible. The second case was a 57-year-old woman in whom a large hematoma formed in the mouth floor 4 hours after implant placement in the first molar site on the right side of the mandible.
In the first case, the dentist did not consider that the lingual cortex had been perforated. Therefore, we suspected that a small branch of the sublingual artery had been injured in the mandible with a twist drill, and that the vessel had withdrawn into the mouth floor. In the second case, the dentist involved identified a perforation of the lingual cortex, although bleeding had been noticed during the surgery and hemostasis had been achieved at that time. Swelling occurred 4 hours after surgery, although it progressed relatively slowly. Therefore, we suspected that a small vein in the mouth floor had been injured. Severe airway obstruction did not occur in either case.
Though dental implant treatment is mainly intended for functional improvement of disorders in the stomatognathic system resulting from missing teeth, it sometimes leads to unpredictable neurological symptoms in patients. We report two cases of atypical orofacial pain following dental implant placement. The patients were two women aged 50 and 65 years old. Neither patient had established a rapport with the dentist who performed the dental implantation for them. The patients were treated by administration of paroxetine hydrochloride hydrate and milnacipran hydrochloride, in consultation with the physician. We must be conscious of the onset of orofacial pain in dental implant treatment.
The objective of this study was to identify clinical indices for the safe and appropriate determination of insertion sites in mandibular molar implant treatment. The subjects were 286 patients (153 men, 133 women; age 26-78 years) who underwent cone-beam CT scanning prior to implant surgery. The patients were immobilized at the forehead and external auditory meatus in the upright position, and the cone-beam CT image was screened in the occlusal plane horizontally in the state of centric occlusion.
The angle of inclination of the mandible and vertical bone diameter on the lingual side, which are anatomical factors that affect implant insertion planning, were measured on the cone-beam CT images.
As a result, the angle of inclination of the mandible increased from the mesial to the distal side which was consistent with previous reports.
The angle of inclination of the mandible was ≧30º in the second molar in 26.0% of patients. Vertical bone diameter on the lingual side was ≦12 mm in the first molar in 43.78% of patients and ≦12 mm in the second molar in 62.66% of patients, and a high proportion of mandibles posed problems for implant planning.
The morphology of the lingual side of the mandible is difficult to diagnose from panoramic X-ray images. We must perform accurate preoperative diagnosis, including CT scanning, and carry out implant treatment with a high degree of predictability, with safety as the basic premise.
Background: Although it is important to elucidate the deformation distribution of alveolar bone around a dental implant, there are some disadvantages in the existing experimental methods such as strain gauge method, photoelasticity method, etc. Therefore, an advanced experimental technique is required not only for problems but also for showing the validity of numerical analysis such as finite element analysis.
Objective: A new advanced experimental technique combining a bone model and digital image correlation (DIC) method is proposed to enable systematic, quantitative evaluations.
Method: A laminated test block (SAWBONES, WA, USA) having the same bilayer structure as actual bone was employed as the bone model specimen. The DIC method was used to visualize the displacement and strain distributions of alveolar bone around a dental implant.
Results: The new proposed experimental technique made it possible to analyze the deformation distribution around a dental implant systematically and quantitatively.
Conclusions: The proposed experimental technique can be used to assess the deformation distribution behavior of alveolar bone around a dental implant systematically and quantitatively.