To fabricate improved biocompatible implants that undergo rapid bone remodeling and provide long-term osteoconductivity, a commercial titanium screw implant was coated with stoichiometric hydroxyapatite (HAp) at a thickness of 50 nm using the pulsed laser deposition (PLD) technique. Bovine hydroxyapatite (BAp) , which is significantly more biocompatible than HAp, was subsequently coated on the HAp layer at a thickness of 300 nm.The PLD technique is capable of coating implants with hydroxyapatite films at nano-scale thickness while allowing easy interaction between the initial material and the coated film. Nano-scale films are preferred because the fracture toughness of thin films is greater than that observed for thick films. Thinner films also create less distortion in the ultimate shape of the substrate of implants than do thicker films. In the present study, including the above bilayered implants (BAp/HAp/Ti) , simple CP-titanium implants (Ti) as control specimens, implants coated with HAp at a thickness of 20 μm using flame spraying (HA/Ti) and implants coated with only BAp at 300 nm thickness (BAp/Ti) were used. The osteoconductivity of all of the specimens was histologically evaluated after implantation in canine femurs for 2～24 weeks.
At 4 weeks following implantation, large gaps and connective tissues were intermingled at the Ti-bone interface, while no gaps were detectable at the BAp/HAp/Ti-bone, HA/Ti-bone or BAp/Ti-bone interfaces. At 8 weeks after implantation, direct adhesion of the titanium substrates of both BAp/HAp/Ti and BAp/Ti to the bone along the full length of the interface was observed, with practically no hydroxyapatite film remaining. Only in the case of the sprayed HA/Ti coating was the HA film still clearly seen. In this latter case, the fixation between the bone and the HA/Ti implant would certainly collapse if the HA thick coating cracked or peeled from the substrate. By 24 weeks after implantation, normal bony structures surrounded all four implants. Notably, a thin layer of newly formed bone had also developed along the interface between the implants coated with hydroxyapatite and the normal bones.
BAp coatings can ensure more active bone remodeling, and unlike with Ti, remodeling takes place quickly along the surface of the coating. This effect is realized as long as the structure of the coating remains intact. The thin bilayer hydroxyapatite coating assists good biocompatibility and long-term fixation of implants to bone due to the continued osteoconductivity provided by the BAp film and the greater fracture toughness of such thin films.
Recently, implant therapy is applied to not only healthy patients but also those with various medical conditions. However, there are no clear guidelines for implant treatment for patients with intellectual disabilities such as Downʼs syndrome.
A 25-years old patient with Downʼs syndrome was treated with implants. Three endosseous implants were placed in the anterior maxilla and a cement-retained superstructure was delivered 10 weeks after the implant placement. The patient had regularly attended for 7 years. Healthy peri-implant soft tissue had been maintained and no radiographic sign of bone resorption was found during the observation period.
This case report indicates that the clinician should pay careful attention to the systemic and oral conditions of Downʼs syndrome patients when implant therapy is required. Support from their family as well as the dental team is essential for long-term success of implant treatment.
It is suggested that implant therapy could be a reliable prosthetic option for Downʼs syndrome patients and would improve their QOL, if proper treatment and maintenance are provided.
Purpose: Accurate placement of the implant is essential for the clinical success of implant therapy. Recently, computer-assisted navigation systems have been widely used to ensure precision in implant surgery. We have also developed a new navigation system equipped with a motion control sensor (AMI 602; Aichi Steel, Japan) that can detect three-dimensional inclination. The aims of this study were to evaluate the efficacy of our navigation system by comparing it with the surgical guide plate model, and to review other implant navigation systems reported in the literature.
Materials and methods: Mandibular plastic models (Kennedy Class II; Nissin, Japan) were prepared for this study. The crown forms of the missing teeth were reconstructed using an autopolymerizing resin for use as the surgical guide plate. Three parallel guide holes were drilled at appropriate positions for each crown form, and extended into the plastic model. The positions of these holes into the model were defined as the ideal implant holes. The guide holes of the surgical plate were reinforced with stainless steel tubes. Five dentists having no experience in implant treatment were asked to create three implant holes in the practice models. The holes were created using either the surgical guide plate or our newly developed navigation system. Straight stainless steel rods were inserted into the holes, and the angles of each rod were measured by photographic analyses (mesial and buccal sides) . The data between the two models were compared statistically using twoway ANOVA and the Mann-Whitney test.
Results: The mean absolute error was 3.2±2.4 degrees for our navigation system, whereas it was 2.7±2.2 degrees for the surgical guide plate; however, the difference was not significant.
Conclusion: It is suggested that our computer assisted navigation system equipped with a motion control sensor may be useful in implant surgery. Our navigation system could facilitate cheaper implant placement as compared to other systems. Our system can also be used for practical training for undergraduate students and general dentists who are less experienced in implant treatment.
Nowadays, many basic and clinical research papers have been reported and oral implantology has become organized in dentistry. In recent years, questions on implantology have been set in national board examinations, and so almost all dental schools have introduced programs and syllabuses accordingly. In August 2008, the Japan Society of Oral Implantology was requested by the Japanese Association for Dental Science to conduct a questionnaire survey on undergraduate programs for implant education for 29 dental schools. The answers were analyzed and the following results were obtained.
1. All of the dental schools had an oral implantology undergraduate curriculum.
2. Regarding the grade in which oral implantology is taught, the fourth grade accounted for 43%, the fifth grade 36%, the sixth grade 14% and the third grade 7%.
3. Lectures were conducted by the assigned department in 76% of cases, by one department in 17%, and 7% gave no answer. In the case of an assigned department, the prosthodontics department accounted for 25%, oral maxillofacial surgery 23%, periodontology 14%, dental implantology 11%, dental radiology 7% and pathology, dental materials, oral anatomy 4% each.
4. Basic practice using models was conducted in 52% of dental schools, and 3% of schools are planning to do so.
5. Some 96% regarded that a standardized curriculum in the future is “necessary”;4% gave no answer.