Implant therapy is an important means of improving esthetics and compensating for loss of masticatory function due to tooth defects, but it is difficult to achieve early fixation when residual bone mass is inadequate, and so bone substituties are often used. In this study we applied bioactive bone cement (CAP cement) when embedding implants into spaces experimentally created and enlarged in the mandible of dogs and assessed the possibility of its application as a bone substitute. In addition, after 8 weeks had elapsed we conducted 3-dimensional observations by a Micro-focus X-ray computed tomography device (ELE SCAN®; :μ-CT), bone density analyses, and pathohistological examinations. We also conducted a mechanical study in pig mandibles to assess mechanical strength and obtained the following results in comparison with a control group.
1. Bone density analyzed by μ-CT was 39.7% in the experimental group and 72.4% in the control group.
2. Histopathological examination
1) In the control group, penetration of epithelium along the implants was observed in the alveolar bone defect area, and examination of the bone around the implant revealed the addition of immature new osteoid tissue. There was no inflammatory reaction of the surrounding tissue.
2) In the experimental group, penetration by epithelium was not observed along the surface of the implant, and examination of the bone around the implant revealed immature new osteoid tissue between the CAP cement and the bone. The implant and the cement were joined without any intervening fibrous connective tissue.
3) Mechanical tensile strength was 344.6±69.4 N in the experimental group and 114.8±108.5 N in the control group,and the difference was statistically significant.
The fact that at 8 weeks postoperatively the CAP cement had not induced an inflammatory reaction in the surrounding tissue and that it possessed mechanical strength suggests that it is a useful artificial biomaterial as a bone substitute.
YDA filler (a silver ion inorganic system antibacterial agent) has been shown to stabilize antimicrobial activity when added to dental resin. Due to this property, this study examined the application of YDA filler to temporary cements and its effects on bacteria.
The sample materials used were zinc oxide eugenol cements and impression paste with YDA filler. Streptococcus mutans, and Actinomyces viscosus were used as the test bacteria. Anaerobic culturing was done for 10-12 hours, at 37℃ after the trial bacteria had taken in 5 ml TSBY including 0.5% yeast extract. Afterwards, they were adjusted using RTF at 1×106 RTF/ml. Next, the trial cement pieces were immersed in adjustment bacterial liquid, with anaerobic culturing for 12 hours, at 37℃. Bacterial quantities, after 10 X serial dilution, were measured using RTF. Each dilution liquid (0.1ml) was dropped in the TSBY plane culture medium with 4 days of anaerobic culturing at 37℃. Culture media with 100 colonies were chosen and the number of bacteria counted. The cement pieces were soaked in 10 ml RTF for 12 hours to measure the Ag ion concentration that dissolved from the cement, using inductive coupling plasma emission analysis. Other examinations researched:the physical properties, surface quality, and Ag ion uptake in bovine dentin.
0.1-30.0%wt YDA-filled impression paste had no bacteriocidal effects on all test bacteria. However, 5.0%wt YDA-filled zinc oxide eugenol (ZOE) cement showed bacteriocidal effects on all trial bacteria. For leachability, there was Ag＋ elution from 5.0% or 30.0% wt YDA-filled ZOE cement. For physical properties, YDA-filled ZOE cement had similar results to the control high-bond cement. However, YDA-filled ZOE cement displayed adhesion for titanium different from that of the control cement. Using SEM and EPMA, Ag ion was not observed on the cement surface. Also, there was no Ag＋ uptake in bovine dentin.
YDA-filled temporary cements have bacteriocidal properties and so have the potential to be used as a temporary adhesive for prosthetic dental implants, because of its characteristics of bonding with titanium.
The purpose of this study was to investigate the influence of occlusal contact conditions during intercuspation on masticatory functions in patients with osseointegrated implants. Osseointegrated implant bridges were placed in 23 patients presenting with unilateral defects in the molar region. They were classified into 2 groups:an even occlusal contact (EOC) group, and a lower occlusal contact (LOC) group, on the osseointegrated implant bridge, according to the height of occlusal contact on the implant bridge, which was measured by the Addpicture system.
We studied their mandibular kinesiographs (MKG) and electromyograms (EMG) of the masseter and anterior temporal muscles during unilateral gum chewing. We compared their dentate side with the osseointegrated implant bridge side, and the EOC-group implant side with the LOC-group implant side.
The results were as follows:
1. No statistically significant difference was seen between the implant and the dentate side on MKG of both groups.
2. On EMG parameters of the EOC-group implant side during implant side chewing, the value of the coefficient of variation on the implant side was stable and very similar to EMG on the dentate side.
3. On EMG parameters of the LOC-group implant side during implant side chewing, the value of coefficient of variation on the implant side was higher than that on the dentate side.
4. On EMG parameters of the anterior temporal muscles during ipsilateral and contralateral side, the value of the coefficient of variation on the LOC-group implant side was higher than that on the EOC-group implant side.
The results suggested that we should equalize occlusal contact heights in both molar regions, which could lead to the stability of masticatory movements for osseointegrated implant bridge placed in patients presenting with unilateral molar region, or it might affect on masticatory functions.
Thirty patients who required Midazolam intravenous conscious sedation for dental implant surgery in a dental office, were statistically examined. The results were as follows:
1. The mean age was 58±10 years (range, 36～70 years). The mean duration of surgery was 62±48 minutes (range, 7～175 minutes). The mean dosage of Midazolam required for induction of sedation was 0.059±0.017 mg/kg (range, 0.027～0.088 mg/kg). The mean Midazolam administration rate for maintenance of adequate sedation was 3.8±1.4mg/hr (range, 1.8～6.5 mg/hr). The mean recovery time was 29±10 minutes (range, 10～50 minutes).
2. The preoperative medical questionnaire was important to understand patients' physical status, and to decide the surgical plan. However, 2 patients did not report their preoperative complications. As such, physical examination was very important just before surgery.
3. ST segment depression was observed on ECG in 10 patients, systolic blood pressure increased over 160 mmHg in 15 patients, and diastolic blood pressure increased over 100 mmHg in 7 patients, just before surgery.
4. Hypertension before surgery was decreased to the normal blood pressure level by Midazolam administration intravenously. However, blood pressure increased again during surgery (SBP＞160 mmHg, DBP＞100 mmHg) in the patients who had hypertension before surgery.
5. The dose of Midazolam and the sedation level did not affect SpO2 depression (＜95%) by Midazolam administration intravenously.
6. The postoperative survey revealed that 57% of the patients had complete amnesia about operative events, and 97% were satisfied with this sedation and would desire similar sedation for a future procedure.
7. No serious complications occurred. Safe surgery requires that the surgeon have understanding of sedation techniques and conscious sedation (monitored anesthesia care) performed by a dental anesthetist.
8. Preoperative evaluation of the general condition, considering introduction to a central hospital, was very important in intravenous sedation in the dental office.
This study was carried out to evaluate the clinical utility and complications of IAT Fit Ⅱ® dental implant, an osseointegrated dental implant. Twelve patients, consisting of four patients each with oral cancer, traumatic tooth-loss or excessive gag reflex, served as subjects. They had difficulty in using conventional soft-tissue supported dentures. According to the manual, 581AT Fit Ⅱ® fixtures were placed in the jaws and supported 20 superstructures. All patients were treated with implant-retained overdentures or implant-supported prostheses. With a median follow-up period of 25 months, 57 of 58 fixtures (98.3%) were clinically osseointegrated. Although two fixed screws were fractured and one abutment was loosened, they were successfully replaced. All 12 patients were conscious of recovery of their oral function and were satisfied with their prostheses.
These results suggested that IAT FitⅡ® dental implants are useful for the oral rehabilitation of patients with difficulty in wearing conventional removable dentures.
Using a standardized radiographic procedure for a paralleling technique, the five-year changes of crestal bone height after superstructures placement around Branemark implant fixtures were assessed. The mean crestal resorption after superstructures placement was -0.20 mm for the first year, while the annual resorption was -0.07 mm, as a mean, for the following four years. This quantity of bone resorption was less than that reported in past literature. These results strongly suggested that follow-up examination for the first one year is extremely important.
The difference of bone resorption in terms of type of teeth missing, gender, maxilla or mandible, opposing teeth, and smoking habit, revealed no significant differences, although slight differences were observed between maxilla and mandible, as well as opposing teeth condition (natural teeth and removable prostheses).
When dental implants are placed in esthetically important areas, their prognosis is likely to be affected by securement of bone volume and considerations on soft tissue. The application of guided bone regeneration (GBR) at implant installation can be divided into simultaneous approaches and staged approaches depending on the timing of the application, and either approach is selected clinically according to bone loss conditions.
If enough bone volume can be secured, the vertical position of implants tends to be deep, in order to provide a superstructure with an esthetic and appropriate contour which resembles that of natural teeth.
In order to study the prognosis of dental implants with which GBR techniques were applied, we compared GBR simultaneous and staged approaches and investigated the relationship between the degree of inflammation of peri-implant tissue and the peri-implant probing depth, the distance measured from the marginal mucosa around the dental implant and the abutment connecting part, or the fixture top.
The following measurements were obtained:
1. Peri-implant marginal bone resorption
2. Implant Crevicular Fluid (ICF)
3. Plaque Index (PLI)
4. Implant Probing Depth (IPD), the distance between the marginal mucosa around the dental implant and the fixture-abutment-connecting surface.
For the statistical analysis, the Mann-Whitney test and Wilcoxon test were used for intergroup comparison, and regression analysis was adopted for correlation analysis.
The results were as follows:
1. In the comparison between GBR simultaneous and staged approaches, no statistically significant difference was seen in terms of peri-implant marginal bone resorption, peri-implant marginal mucosal recession, and ICF.
2. Correlation was confirmed (r=0.823) between IPD and ICF after three years.
3. Correlation was not observed (r=0.440) between peri-implant marginal bone resorption and ICF.
4. Correlation was not observed (r=0.118) between peri-implant marginal bone resorption and PLI.
The above-mentioned results suggest that there is no clinical difference in the prognosis of peri-implant conditions when implants were installed by either simultaneous or staged GBR application based on conventional clinical criteria for preoperative bone loss. There were few cases of inflammation of peri-implant when the depth from the peri-implant marginal mucosa to the abutment-connecting surface, or the fixture top, was shallower.
Placement of implants in regions where placement had been impossible has become possible by guided bone regeneration (GBR). Among the various GBR methods proposed, the one using the combination of a titanium-reinforced e-PTFE membrane and autogenous bone graft is expected to give good bone regeneration. In this study, we clinically examined the GBR method (staged approach) with the combination of a titanium-reinforced e-PTFE membrane and autogenous bone graft. The subjects were 7 patients who underwent the staged approach GBR at the PDI Saitama Dental Clinic, Meikai University School of Dentistry between 1999 and 2001. The 9 patients consisted of 4 patients who underwent the staged approach GBR using a titanium-reinforced e-PTFE membrane alone (group A) and 5 patients who underwent the staged approach GBR using a titanium-reinforced e-PTFE membrane and autogenous bone graft (group B). In group A, neogenetic tissues were mostly soft tissues, and the amounts of neogenetic hard tissues were 1.8±1.3 mm in the vertical direction(Coronal direction) and 1.9±2.2 mm in the horizontal direction (Buccal-Lingual direction). Therefore, it was necessary to perform GBR again at the time of embedding implants. In all patients of group B, regeneration of the alveolar bone was noted, and implants could be embedded by the ordinary method. The amounts of regenerated bones were 4.2±1.1 mm in the vertical direction and 7.1±2.5 mm in the horizontal direction. A thin layer of soft tissues with a thickness of less than 1 mm was noted immediately below the membrane. We concluded that the GBR method with the combination of a titanium-reinforced e-PTFE membrane and autogenous bone graft is clinically useful.
The long-standing controversy on which implant: machined screw-type implant, or hydroxyapatite (HA)-coated implant, is superior to the other, has not yet been settled. This paper compares, retrospectively, the survival rates of a hydroxyapatite-coated cylindrical implant system, and a machined screw-type implant system, for non-complicated patients.
The subjects were 34 males and 40 females, of ages from 18 to 75 years, with an average age of 50.5 years. They had no systemic diseases affecting implant treatment. They had enough bone volume for implant placement. The implants used were an HA-coated cylindrical implant:Calcitek implant®(Sultzer Calcitek, USA), of either 3.25 mm or 4.0 mm in diameter, and of 8, 10, 13, or 15 mm in length, and a machined screw-type implant:Brånemark implant®(Nobel Biocare, Sweden), of 3.75 mm or 4.00 mm in diameter, and of 10, 13, or 15 mm in length. The survival rates were assessed using the Kaplan-Meier test. The factors investigated were implant position, anterior/posterior and mandible/maxilla, and implant length.
The following results were obtained:
1. The total survival rates were 97.9% for Brånemark implants up to 5 years, and 94.4% for Calcitek implants up to 7 years.
2. No statistical difference existed between these results.
3. On the length and sites of the implants, the survival rates were more than 90%, except for Calcitek implants 8 mm or 10 mm in length.
4. Overheating during placement and/or post operative infection could be causes of implant failure.
Very high survival rates could be anticipated by both implant systems in patients with enough bone volume in the implanted sites, and without basic diseases affecting the treatment. They could be further elevated by avoiding negative factors.
An attempt was made to refine platelet rich plasma (PRP) from 28 adults by 4 processes. Due to agglutinations in 7 adults and the trouble of machine in 1 adult, measurements of PRP were done on 20 adults, and the numbers of white blood cells (WBC), red blood cells (RBC), platelets (PLT), and the percentage of PLT collection, were measured.
In all processes, the amount of the measured PRP was 0.3 ml solution. The PRP of the process ① was collected from the demarcation line of the serum component and blood cell component, after serial two-differential centrifugation (the first:2,400 rpm, for 7 minutes; the second:3,000 rpm, for 10 minutes). The PRP of the process ② was collected from the bottom of the second differential centrifugation of the serum component that was collected after the first differential centrifugation. The PRP of the process ③ was collected from the demarcation line, after the second differential centrifugation of the blood component that was collected after the first differential centrifugation of process ②. The PRP of the process ④ was collected from the demarcation line after the second differential centrifugation of the portion of the demarcation line after the first differential centrifugation. In the process ②, the PRP was not refined for rare platelet. In the process ①,③, and ④, the PRP was refined, but the comparison of PRP quantities yielded no significant difference. The average of PLT number was 20.8×104/μl before the differential centrifugation, but it was 98.5×104/μl thereafter. The process ① was recommended for easy operation.
We experienced a patient with a fractured implant body, locating on the posterior partially edentulous jaws after 4 years of functional loading. He recovered by improving the design of superstructure with preserving the implant body. Scanning electron microscopic observation of the fractured part showed evidence of brittle fracture after intermittent vertical pressure. So we suspected the cause of the fracture was concentrating habitual stress on the implant body transmitted by an inappropriately designed superstructure.
It is important to perform prosthodontic design very carefully for a good functional prognosis.
We report our experience with use of an implant-type distractor (ACE OsteoGenic Distractor TM :OGD) for vertical alveolar distraction osteogenesis. The patient was a 19-year-old male with an alveolar bone defect in the anterior portion of the mandible, caused by a traffic accident. Two distractors were inserted into the distracted bone segment and the base bone, using the same procedure as for a dental implant. After a 10-day latency period, the alveolar bone was elevated vertically, at a rate of 1.0 mm/day, for 10 days. After 12 weeks of a consolidation period, the distractors were removed. When three osseointegrated implants were inserted 3 months after the removal of OGDs, new bone formation in the distraction gap was observed. The implants have shown good progress at 1 year after fitting of a superstructure (about 2 years after the distraction osteogenesis).
Although the follow-up period is still short, and long-term prognosis of the bone produced by distraction osteogenesis is unclear, alveolar distraction using OGD might be a successful technique for vertical alveolar ridge augmentation.