Implant Body Displacement into Medullary Cavity of Mandible: A Case Report.

One serious complication in implant surgery is displacement of the implant body into the surrounding tissue. This occurs only rarely in the mandible, however. This report describes a case of an implant body displacing into the medullary cavity of the mandible and discusses this in reference to the literature. The patient was a 72-year-old woman who was referred to our department at Tokyo Dental College Chiba Hospital (now Chiba Dental Center) by her regular dentist after an implant inserted in the left mandible in 2010 showed loosening in October 2016. Panoramic X-rays obtained at the initial examination revealed that 2 implants had been inserted into the left mandible, one on top of the other. Removal of both was recommended to prevent infection at the implant site and any potential effects on the alveolar nerve. In the absence of subjective symptoms other than implant loosening, however, the patient did not consent to this proposal. Therefore, only the broken abutment was removed. The patient was instructed to contact us immediately should infection or any other symptoms appear once the mucosa had healed, and the dental clinic that had referred her to us was requested to make her a set of dentures. To our knowledge, only 11 reports have been published to date describing displacement of an implant body into the mandible, and these address a total of just 20 cases. The possibility that an implant body in the mandible may become displaced must be kept in mind during treatment.

Lightweight acrylic resin facial prosthesis for maxillofacial defects: a fabrication and retention method.

Extraoral maxillofacial rehabilitation for compromised or lost facial anatomy resulting from the surgical eradication of malignancy, trauma, or congenital anomalies is commonly accomplished with a silicone prosthesis. However, with increasing size and weight, a silicone prosthesis can lose retention. This report presents 2 patient treatments to introduce a fabrication and retention method for a lightweight acrylic resin facial prosthesis. The prosthesis was fabricated by bonding an acrylic resin facial shell to a computer-edited facial image printed with iron-on transfers. The completed prosthesis was attached to the skin with medical-grade double-sided adhesive tape, which maintained a tight marginal seal even when in contact with saliva and water. The strong prosthetic retention of the lightweight prosthesis enabled orofacial and speech rehabilitation, which makes it a promising alternative to the conventional silicone prosthesis, especially for the restoration of extensive maxillofacial defects.

Peri-implant bone density in senile osteoporosis-changes from implant placement to osseointegration.

PURPOSE: The aim of this study was to examine healing over time after implant body placement in a senile osteoporosis model and a control group. MATERIALS AND METHODS: In this study, 16-week-old male mice were used. The senile osteoporosis model consisted of senescence-accelerated prone 6 mice and the control group consisted of senescence-accelerated resistant 1 mice. Titanium-coated plastic implants were used as experimental implants whose dimensions were 3.0 mm in length, 1.1 mm in apical diameter, and 1.2 mm in coronal diameter. Bone samples were collected at 5, 7, 14, 21, and 28 days after implant placement. A micro-quantitative computed tomography (QCT) system was used to scan these samples and a phantom in order to quantitate bone mineral measurements. Bone mineral density (BMD) of each sample was measured. Each sample was also examined by light microscopy after QCT imaging. At 14 and 28 days after implant placement, the bone-implant contact (BIC) ratios were calculated from light microscopy images and were divided into cortical bone and bone marrow regions. RESULTS: When BMD was compared between the osteoporosis and control groups using micro-QCT, the osteoporosis group had a significantly lower BMD in the region 0-20 µm from the implant surface in the bone marrow region at 14 days onward after implant placement. Compared with the control group, the osteoporosis model also had significantly lower BMD in all regions 0-100 µm from the implant surface in the bone marrow region at 14 days after placement. However, in the cortical bone region, no statistically significant difference was observed in the regions at the bone-implant interface. Light microscopy revealed osseointegration for all implants 28 days after implant placement. The osteoporosis model tended to have lower BICs compared with that of the control group, although this did not reach statistical significance. DISCUSSION: Our results showed that osseointegration was achieved in the osteoporosis model. However, the BMD was 30-40% lower than that of the control group in the region closest to the implant surface in bone marrow region. Peri-implant BMD was lower in a relatively large area in the osteoporosis model during an important time for osseointegration. Therefore, this result suggests that osteoporosis might be considered as a risk factor in implant therapy. CONCLUSION: The osteoporosis model had a lower BMD than the control group in the region closest to the implant during an important time for osseointegration. This result suggests that senile osteoporosis might be a risk factor in implant therapy. However, the osteoporosis model and the control group had no difference in peri-implant BMD in the cortical bone region. This suggests that risk might be avoided by implant placement that effectively uses the cortical bone.

Human mandibular trabecular bone density correlation with mechanical strength: implications for implant dentistry.

PURPOSE: The prognosis of a dental implant depends on the mechanical properties of the bone. The preoperative diagnosis of bone quality has become more important, because the immediate loading procedure is now widely used, and a firm initial stability is required. Quantitative computed tomography (QCT) is an effective method of determining selectively the bone mineral density (BMD) of the trabecular bone mostly responsible for the survival of the implant. In this project, we investigated the relationship between the BMD measured by QCT and the mechanical strength of the mandible. MATERIALS AND METHODS: The BMD (mg/mL) of 58 trabecular bone specimens from 6 embalmed human cadaver mandibles were obtained using QCT. The compressive strength to break point was performed with a mechanical device. Each specimen was washed and weighed. RESULTS: The mean values of BMD for the anterior, premolar, and molar region were 633.3, 571.0, and 518.3 mg/mL, respectively. The mean values of compressive strength were 0.237, 0.216, and 0.196 kN, and the ash weights were 0.047, 0.044, and 0.039 g, respectively. There was a positive correlation between the BMD and the mechanical strength (R = 0.77) and between the ash weight and the mechanical strength (R = 0.84). CONCLUSION: There was strong correlation of bone strength, bone mineral, and bone density by QCT. QCT is an excellent preoperative diagnostic tool to select the most mechanically appropriate implant for initial stability and improve the survival prognosis.

Students' opinion of a predoctoral implant training program.

Implant treatment today is highly predictable and provides valid restorative options for the completely or partially edentulous patient. In Japan, many dental care facilities have incorporated implant treatment, and such treatment is no longer rare. For predoctoral students, the educational environment related to implants is not always applicable in present clinical settings. In this article, we describe the implant training program developed at our university for predoctoral education, and we report the changes in student opinions regarding implant treatment by comparing pre- and post-training opinions. The newly developed models for implant training were effective in increasing student understanding that implant treatment is one prosthetic option for restoring missing teeth. In a survey of predoctoral students, responses indicating negative opinions toward implant treatment decreased after training, and responses indicating positive opinions increased. These findings indicated that this training was effective in deepening student understanding of implant treatment.

Chronological changes in the ultrastructure of titanium-bone interfaces: analysis by light microscopy, transmission electron microscopy, and micro-computed tomography.

PURPOSES: The objectives of this study were to chronologically examine the titanium-bone interfaces and to clarify the process of osseointegration using light microscopy, transmission electron microscopy (TEM), and micro-computed tomography (CT). MATERIALS AND METHODS: Experimental implants (Ti-coating plastic implants) were placed into tibiae of 8-week-old rats. Animals were sacrificed at 1 to 28 days after implant placement and prepared tissue specimens for a light microscope, a TEM, and micro-CT. RESULTS: New bone formation began 5 days after implant placement, and osseointegration was obtained by 14 days after implant placement. Osseointegration was well developed by 28 days after implant placement. DISCUSSION: TEM and quantitative computer tomography (QCT) results indicated that bone formation in osseointegration of titanium implants did not occur from the surfaces of the implant or preexisting bone, but it was likely that bone formation progressed at a site a small distance away from the surface. The bone formation took place in a scattered manner. Small bone fragments adhered to each other and transformed into reticular-shaped bone, and finally these bones became lamellar bone. CONCLUSION: Comparative analysis of the titanium-bone interfaces using light microscopy, TEM, and QCT by micro-CT revealed the precise process of osseointegration.

Effect on the amount of bone-implant contact when splinting immediate-loaded dental implants.

PURPOSE: Much attention has been focused on the immediate or early loading of implants with or without splinting. The purpose of this study was to evaluate the contact rate between bones and implants, with or without splinting. MATERIALS AND METHODS: Under general anesthesia, an 8-mm-deep cavity for a dental implant was drilled in the mandibular ridge of dogs where teeth had been extracted 4 months earlier. Rough-surfaced, cylindrical screw implants (International Team for Implantology [ITI] monotype implants 4 mm diameter and 8 mm long, Straumann, Basel, Switzerland) were placed with splinting on the right side and without splinting on the left side using gold abutment. Resin plates for the maxilla were adjusted to attach to the gold abutment in each mandible. At 4, 8, or 12 weeks after the implantation, specimens were stained using toluidine blue and fuchsin. The sections were observed and morphometric analysis was performed to measure the rates of bone-implant contact and new bone-implant contact. RESULTS: The ratio of bone-implant contact on the lingual side was higher than on the buccal side in both the splinted and the unsplinted groups, and the rates in the splinted group were also higher than in the unsplinted group. The ratio of new bone-implant contact was not significantly different between the splinted and unsplinted groups, except for spongy bone at 4 weeks. CONCLUSION: Splinting of immediate-loading dental implants can be adequate for osseointegration, particularly in spongy bone.

Ultrastructure of the interface between titanium and surrounding tissue in rat tibiae--a comparison study on titanium-coated and -uncoated plastic implants.

PURPOSES: The purposes of this study were to prepare experimental titanium-coated plastic implants suitable for electron microscopy examination of the titanium-bone interface and the response of tissue surrounding titanium, and to histologically compare surrounding tissue responses in coated and uncoated implants. MATERIALS AND METHODS: Experimental plastic implants were prepared from a plastic rod coated with a thin film of titanium. Plastic implants without coatings were used as controls. The implants were placed into tibiae of 10-week-old male rats. The specimens with implants were harvested 4 weeks after placement and observed under a light microscope, a transmission electron microscope, and a scanning electron microscope. RESULTS: In the transmission electron microscopy, the titanium layer of the experimental implant was a uniform layer that was approximately 150- to 250-nm wide. The new bone formation was observed around both titanium-coated implants and plastic implants. However, there was no direct bone contact with the plastic implant. DISCUSSION: The responses of tissue surrounding the experimental implants varied. Under an electron microscope, the following areas were observed: (1) an area with a direct contact between the titanium and bone, (2) an area at the interface where an amorphous layer was observed, (3) an area with progressing calcification in the surrounding tissue where the cells were adjacent to the titanium surface, and (4) an area in which bone resorption and apposition were observed and remodeling was thought to be occurring. CONCLUSION: The experimental titanium was homogenous and was considered to be highly useful in observing the responses of the surrounding tissue to the titanium surface.