Objective: Possible changes in the biological potential of titanium (Ti) over time have never been examined; it is assumed that the biological properties, particularly osseointegration capability, of titanium surfaces are stable. The objective of this study was to test the hypothesis that the protein adsorption capacity and cell attractiveness of Ti, which are critical to the process of osseointegration, change over time during its use.
Materials and methods: Ti disks with three different surface topographies were prepared: machined, acid-etched and sandblasted. Some disks were tested for biological capacity immediately after the processing and some after being stored under dark ambient conditions for 4 weeks. Protein adsorption capacity of Ti was examined using albumin and fibronectin. Cell attractiveness of titanium was evaluated by examining the number of rat bone marrow-derived osteoblasts attached to Ti disks.
Results: For all surface types, protein adsorption capacities of 4-week-old Ti disks were substantially lower than the matching fresh Ti disks (e.g., the amount of fibronectin adsorbed to 4-week-old acid-etched surfaces during 24 hours was approximately 50% of that on the freshly prepared acid-etched surfaces). The number of osteoblasts attached to 4-week-old acid etched surfaces was only 30% and 50%, respectively, at 6 hours and 24 hours of culture, of that seen on freshly prepared acid-etched surfaces. These biological phenomena were associated with the loss of superhydrophilicity on 4-week-old Ti surfaces.
Conclusions: The degrading trend of protein adsorption capacity and osteoblast attractiveness of Ti surfaces during 4 weeks of storage after processing was remarkable. This time-dependent biological degradation was demonstrated in three different Ti surfaces: acid-etched, machined and sandblasted surfaces. We suggest that this phenomenon requires immediate further study for possible substantial commercial, scientific and research impacts in the field.
To achieve the long-term function of superstructures inserted in titanium implants without causing dislodgement, it is necessary to maximize their adhesive strength. It is known that sand-blast treatment markedly influences the adhesive strength. Therefore, to improve the adhesive strength using sand-blast treatment of titanium materials, we evaluated the influence of blast pressure, and effects of applying blast powder coated by adhesives (Super-Bond C&B), based on tensile and compressive shear strengths.
The following results were obtained:
1. Regarding blast treatment pressure, the tensile shear strength was highest at 0.4 MPa.
2. When blast treatment was performed using alumina powder coated with adhesives, the compressive shear strength increased by approximately 13%. We considered that this was because the adhesives coated on the alumina powder remained on the surface of the titanium.
It is important to recognize the posterior superior alveolar artery (PSAA) in the lateral wall of the maxillary sinus when planning the sinus floor augmentation procedure. The aim of this study was to characterize the prevalence and vertical position of PSAA running in the posterior alveolar canal. The studied samples consisted of 208 areas of 113 patients who underwent CT examination prior to the implant surgery. Analysis was performed by coronal CT images. Four areas were observed:the area of the inferior crest of the zygomatic process (Z-area), 5 mm forward of the Z-area, and 5 mm and 10 mm behind the Z-area.
The results were as follows:
1.The prevalence of the posterior alveolar canal on CT images was the lowest in the Z-area.
2.The vertical measured point of the posterior alveolar canal was the lowest in the Z-area.
3.The vertical distance between the maxillary sinus floor and the posterior alveolar canal was 8.5±4.8 mm at the area 5 mm forward of the Z-area (the area where the lateral window technique is adopted).
4. The vertical distance between the alveolar crest and the posterior alveolar canal was 16.2±4.0 mm at the area 5 mm forward of the Z-area.
These data results will be useful for the sinus floor augmentation procedure.
Titanium is now widely used for dental implants as the most reliable material. Although titanium has excellent mechanical properties, some clinical cases of fracture of titanium implants have been reported. This study examined the cause and mechanism of splinted implant fracture by observing the fracture surface.
Seven structured implants in four cases that had been splinted and placed in the posterior molar region were investigated. The fracture surfaces were examined with stereoscopic microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Longitudinal sections of those implants were also prepared to observe their structure in detail.
Stereoscopic microscope observations revealed that a crack started at the lingual or buccal site. SEM analyses showed a striation-like geometry suggestive of metal fatigue. Corrosion of titanium could not have been relevant to the fracture, as no corrosion product or pitting corrosion was detected. Panoramic radiograph showed that the fracture occurred at the border between the osseointegration zone and bone resorption zone. The longitudinal sections and SEM photos demonstrated that the thinnest part of the implant body was 500 μm, at which the fracture line started.
Based on these results, the following was speculated. The direction of fracture of the splinted implants was not in the mesio-distal direction but in the lingual-tobuccal direction. The level of alveolar bone was positioned in the vicinity of the fractured site and was considered to have a mechanical influence on the structure. Therefore, it is suggested that bending stress was concentrated at the abutment screw tip when an occlusal force was applied to the superstructure. The pitch of the external threads and internal threads of the implant was different, and so the implant thickness changed periodically and a structurally thinnest part appeared. When such a weak part is located at the tip of the abutment screw, it will become the fulcrum of bending stress and thereby promote the concentration of stress, where fracture is the most likely to occur.
We report a case who was treated with endoscopic sinus surgery for a dental implant accidentally displaced into the maxillary sinus.
A 60-year-old female was referred to the Shiga University of Medical Science Hospital with a shedding abutment which had been placed in the upper-left second molar area. Postoperatively, she also complained of left nasal obstruction. Physical examination revealed slight swelling of the left cheek. Recess of gingiva of about 3 mm in diameter was seen in the upper-left second molar. A bone defect was also noted in this part.
A panoramic radiograph and CT examination revealed a dental implant with an abutment in the left maxillary sinus. The CT examination also showed hypertrophy of the left maxillary sinus mucosa. Functional endoscopic sinus surgery through an incision in the nasal mucosa of 1.0×1.5 cm was performed to extract the dental implant from the maxillary sinus. The postoperative clinical course was uneventful.
Endoscopic sinus surgery proved to be effective in decreasing the invasiveness in this case; hence, this method can be considered useful in the treatment of a dental implant accidentally displaced in the maxillary sinus.
Purpose: Thickness of peri-implant mucosa is an important factor in maintaining an esthetic prognosis. The purpose of this study was to evaluate the morphological features of peri-implant mucosa.
Materials and Methods: Forty-two patients, aged 26 to 72 years (average: 48, 20 males and 22 females), who had had Brånemark System® and TiUnite Replacement implants (Nobel Biocare, Göteborg, Sweden) placed in their oral cavity at Tsurumi University Dental Hospital were selected at random. Eighty-two working casts that had been used for fabricating the final prosthesis were examined. The width and height of buccal peri-implant mucosa were measured with a micro-caliper. The measurements were recorded and the means, standard deviations, and frequency were calculated. Correlation analysis was performed to describe the association between the width and the height. Analysis of variance was used to confirm the statistical differences between regions using SPSS12.
Results: The width, height and their ratio of peri-implant mucosa measured were (2.45 mm± 0.93, 1.62mm± 0.72, 1.64± 0.73:1) respectively. There was a statistically significant correlation (r=0.48, p=0.00) between the width and the height. In 10 cases, the height of peri-implant mucosa was greater than the width. According to the regions, the widths of the maxillary incisor and canine (p=0.019) and mandibular molar (p=0.000) regions were significantly greater than that of the mandibular premolar region. The heights of the mandibular premolar (p=0.050) and maxillary molar (p=0.040) regions were significantly smaller than that of the maxillary incisor and canine region. The ratio of the maxillary incisor and canine region was significantly less than that of the mandibular molar region(p=0.003).
Conclusions: The implant platform was useful as the working reference plane. The height of peri-implant mucosa was significantly less than the width. The ratio of width to height was about 1.64:1.