Rotational panoramic radiography is routinely used in dental practice. It has not been clarified, however, whether an accessory mental foramen can be demonstrated using this technique. The visibility of accessory mental foramina on rotational panoramic radiographs, including the influence of dry mandibles and their positioning, was compared with that on para-panoramic images reconstructed from cone-beam computed tomography (CBCT).
Four mandibular bones with accessory mental foramina were analyzed. Para-panoramic images were reconstructed from CBCT images with the accessory mental foramen using three-dimensional visualization and measurement software, and then the accessory mental foramen on rotational panoramic images was compared with that on para-panoramic images.
There was a difference in the rate of visualization of the accessory mental foramen on rotational panoramicradiographs from 20% to 95%.
These results indicated that some of the accessory mental foramen could be observed on rotational panoramic radiographs.
Metal ceramic restorations with high-gold alloys have been used for crowns and fixed dental prostheses (FDPs). Today, however, high-gold alloys have been largely replaced by cobalt-chromium alloy (Co-Cr alloy) for the FDP framework of the implant superstructure, due to the low cost and favorable mechanical properties such as high strength, high modulus of elasticity as well as high corrosion resistance. When fabricating the superstructure, it is necessary to use high-fusing gold solder for joining the Co-Cr alloy framework to the gold cylinder. However, the strength of solder joints between Co-Cr alloy and high-fusing gold solder has not been fully clarified. This study aimed to evaluate the tensile bond strengths of Co-Cr alloys that were joined with high-fusing gold solder in comparison with conventional gold alloys joined with high-fusing gold solder. In addition, scanning electron microscopy (SEM) of the fractured surface and electron probe microanalysis (EPMA) of the joint interface were performed.
The tensile bond strengths of Co-Cr alloy joined with high-fusing gold solder were more than 600 MPa, and were significantly larger than those of metal-ceramic gold alloys joined with high-fusing gold solder. The cohesive fracture pattern in solder was observed in the fractured surface of all specimens by SEM observation. EPMA analyses revealed that the elements of the gold solder had diffused into the Co-Cr alloy, leading to firm bonding between the alloy and solder.
These results indicated that the joining technique of Co-Cr alloy using a high-fusing gold solder is promising for fabricating implant superstructures.
Purpose: The purpose of the present clinical study was to examine the effect of differences in the surface materials of implants on the achievement of osseointegration and its long-term maintenance during a 10- to 15-year follow-up for two systems of cylinder implant, titanium implant and hydroxyapatite-coated implant, which were used for the prosthesis of posterior partially edentulous jaws.
Materials and Methods: The study evaluated 221 titanium implants in 75 patients (Ti implants) and 181 hydroxyapatite-coated implants in 66 patients (HA im plants), all of which were installed in available bone of posterior partially edentulous jaws during the period from 1994 to 1999 at a single center in Japan. The cumulative survival rates after 10 to 15 years were calculated by life table analysis and compared to evaluate the clinical courses.
Results: The cumulative survival rates after 10 to 15 years were 94.2% for Ti implants and 92.5% for HA implants, showing no significant difference in survival rate between the different implant bodies.
On comparison of survival rates of the implant bodies by elapsed period, Ti implants and HA implants showed 99.5% and 99.4%, respectively, for less than one year post-implantation, and 92.2% and 89.5%, respectively, for one year or more post-implantation, demonstrating no significant difference in survival rate during either period. However, in both implant bodies the survival rate tended to decrease over time at 4 to 5 years after loading.
In addition, incidence rates of implantation failure during the elapsed period showed no significant difference between Ti implants and HA implants in the cases of implant loss due to failed osseointegration, with 0.5% and 0.6%, respectively, during the post-implantation period of less than one year. Meanwhile, after one year or more post-implantation, the incidence of implant loss due to failed osseointegration was 6.1% for Ti implants and 0% for HA implants, and the incidence of implant loss due to peri-implantitis was 1.7% for Ti implants and 10.5% for HA implants, demonstrating a significant difference in incidence rate between the different implant bodies.
Discussion and Conclusion: No significant differences were found in the long-term survival rates between Ti implant bodies and HA implant bodies.
In addition, while both types of implant body showed successful survival rates during a post-implantation period of less than one year, at one year or more after implantation, the survival rates tended to decrease over time due to the development of failed osseointegration in Ti implants and the occurrence of peri-implantitis in HA implants.
Thus, it is suggested that, in order to achieve better long-term outcomes, occlusal adjustment for avoiding overloading on specific implant bodies is important for Ti implant bodies, whereas maintaining good oral hygiene for avoiding peri-implantitis is important for HA implant bodies, during a follow-up period of one year or more.
Purpose: To evaluate the sinus lift procedure in conjunction with autogenous bone harvested from the mandible.
Materials and Methods: The study group comprised 10 patients who underwent a total of 11 sinus lift procedures. The donor sites in the mandible included the symphysis, ramus or retro-molar region. Each implant site was radiographically evaluated preoperatively; at superstructure placement 6 to 10 months later; and 1, 2, 3, 5, and 10 years after loading. Panoramic radiography and cross-sectional imaging were performed as needed. Preoperative bone height was measured to determine the distance between the primitive sinus floor and the crest of the alveolar ridge. Postoperative bone height was measured to determine the distance between the sinus floor after the sinus lift procedure and the crest of the alveolar ridge and the apical end of the implant body in the area. We analyzed the difference of measurement using two way ANOVA with IBM SPSS, and analyzed the difference of the average value with multiple comparisons (Tukey). The change in bone density was also observed on the radiograph.
Results: The average distance between the primitive sinus floor and the crest of the alveolar ridge in the plan of the implant placement area was 3.5±1.4 mm. The mean distance between the sinus floor after the sinus lift procedure and the crest of the alveolar ridge was 12.4±1.6 mm at the time of superstructure placement and 11.8±1.9 mm and 11.3±1.9 mm after 1 and 10 years of loading, respectively. The distance between the sinus floor after the sinus lift procedure and the apical end of the implant body was 1.6±1.2 mm at the time of superstructure placement and 1.4±1.5 mm and 1.0±1.8 mm after 1 and 10 years of loading, respectively. A statistical significance was detected between at the time of superstructure placement and after 10 years. Regarding the change in bone density, in 5 of the 11 sinuses, the grafted bone was highly radiopaque compared to the native bone at the time of superstructure placement, but it showed the same density as that of the native bone about 2 years after loading.
Conclusion: The height of the grafted bone decreased gradually, and its rate was very low. The change in density of the grafted bone was approximately stable between 1.5 to 2.5 years. This appearance was maintained during the observation.