This study examined the application of tooth transplantation to clinical practice for prosthetic treatment. Extracted teeth that had been stored at 4℃, -80℃ or -2℃ for 4-8 weeks were transplanted, and their prognoses compared based on tooth mobility and on radiographical and histological findings for 8 weeks after transplantation. The results were as follows
1. The mobility of the teeth stored at -2℃ for 8 weeks after transplantation was grade 1, and was the same as before extraction, whereas the mobility of the teeth stored at 4℃ or-80℃ was grade 0 because ankylosis was observed.
2. Radiographical observation showed ruptured periodontal spaces in the teeth stored at 4℃ or -80℃,but the teeth stored at -2℃ had periodontal spaces.
3. Histologically, new bone was observed between the cementum resorbed area and alveolar bone, and ankylosis was observed in the teeth stored at 4℃ or -80℃. In the teeth stored at -2℃, fibrous connective tissues were observed between the transplant tooth and alveolar bone, and the run of fibrous tissues was arranged especially regularly and functionally after being stored for 4 weeks.
These results suggest that controlled freezing point storage allows the long-term storage of teeth to be transplanted and replanted, and that this method of storage can be applied to clinical practice.
Statement of problem: In order to improve denture stability, patient's satisfaction and longterm success of mandibular distal extension removable partial dentures, it seems to be effective to place an osseointegrated implant beneath the distal extension denture base for denture support. However, there is no scientific evidence which supports the biomechanical benefit of this system.
Purpose: This study investigated the effect of utilizing an osseointegrated implant as a distal support of a mandibular distal extension removable partial denture.
Material and method: The Kennedy class Ⅱ mandibular partially edentulous case was simulated. The missing teeth were the right side second premolar and molars in the mandible. An implant fixture (3 i OSSEOTITE, Implant Innovations, USA) was placed at the second molar region. Three types of prostheses were fabricated: a conventional distal extension removable partial denture without implant support (called PD model), an implant supported removable partial denture (called PDI model), and fixed partial denture using first premolar and the implant (called BR model). Strain gauges were attached to the surfaces of the abutment tooth and the implant. A vertical load of 100N was applied on each prosthesis at the second premolar, first molar and second molar region.The axial force and bending moment on the abutment tooth and the implant were measured. The disto-mesial displacement of the abutment tooth (first premolar) was measured using a CCD laser displacement sensor. The obtained data were statistically analyzed using two-way analysis of variance (p=0.05).
Results: The PD model showed the biggest vertical displacement of the prosthesis. The bending moment of the abutment tooth and the bending moment of the implant were the highest in the BR model, and were the lowest in the PDI model. Further, concerning the stress distribution of the implant, bending moment around the implant was not generated and the applied force was transmitted along the implant axis in the PDI model.
In this study, bond strengths of Ti implant substrate to Ti and 12% Au-Ag-Pd superstructure materials, using bonding agent, were investigated. The study examined the influences of blasting surfaces with different media including glass beads, alumina powder, and carborundum powder on bond strengths.
The main results were as follows:
1. The surface of the Ti substrate blasted with glass beads revealed a roundish unevenness.
2. The Ti surface blasted with alumina powder was rougher with sharp unevenness.
3. The surface blasted with carborundum powder showed simikar topological features to the alumina-blasted surface, but was much rougher.
4. The bond strengths of the glass-beads-blasted Ti substrate exhibited the minimum values for both Ti and 12% Au-Ag-Pd alloy.
5. The maximum bond strength was obtained on the alumina-blasted Ti surface for both Ti and 12% Au-Ag-Pd alloy.
Titanium has become popular not only as a dental implant material but also as a denture or Cr-Br material. Previously, we reported that 1.8% or more expansion of casting molds was required to create a suitable fit when used casting titanium for the superstructure of implants. The purpose of this study was to evaluate the fit of titanium castings obtained from some commercial investments for titanium. Four kinds of commercial investment for titanium (T-invest C＆B(TCB), Titavest CB (CB), Selevest SCB (SCB), Selevest D (SD) were selected and used according to the manufacturer's instructions. A tapered metal die for the fitting test based on the ADA standard was prepared. Using this die, dimensional changes by both MOD crowns cast by a special outer frame and ring shape casting were measured. Although CB showed no setting expansion, the titanium castings became oversized because of large thermal expansion. The MOD crown from SCB indicated the smallest gap in the investments tested. However, the ring casting from SCB was slightly contracted. This revealed that the expansion mechanism of SCB was unstable during heating. Both MOD and ring-shape castings from TCB were undersized. On the other hand, large marginal gaps were observed on the castings from SD, which were due to little mold expansion. These results indicated that the investments we tested in this study showed insufficient expansion to achieve an appropriate fit of the castings.
The present in vitro study was conducted using polyelectrolyte complexes (PECs) as drug delivery system (DDS) materials for various cytokines, which are used to actively facilitate tissue regeneration, in order to determine their potentials as macromolecular DDS materials for the regeneration of periodontal ligament tissue.
By mixing 2 polycations and 3 polyanions, a total of 6 PECs were prepared, and each PEC was coated onto several tissue culture dishes. Human periodontal ligament fibroblast (HPLF) in D-MEM containing 10% FBS was cultured, and cell adhesion was assessed 4 and 8 hours after the start of culturing; cell proliferation was determined 2, 4 and 6 days after the start of culturing by counting the number of viable cells; and type I collagen synthesis was quantified 4 days after the start of culture test by immunostaining. The results were as follows:
With one PEC (Soluble DAC 50-κ-carrageenan), clear signs of suppressed cell adhesion and proliferation were seen, but with the other PECs, relatively favorable results were obtained. Collagen synthesis was favorable with insoluble DAC 50-S-chitin 140 and with the other PECs.
These findings suggest that PECs are macromolecular complexes with a high affinity towards HPLF and can be used as macromolecular DDS materials for various cytokines.
In order to clinically utilize teeth that have been preserved for a long period of time, teeth were frozen at either -0.5 or -1℃/min in the cryoprotective agents DMSO, glycerol, or trehalose and stored at -196℃ for 2 weeks. Cellular proliferation and adhesion were evaluated in vitro. Eight weeks after the cryopreserved teeth had been grafted in vivo, X-ray and histological evaluations were assessed and compared. Cell proliferation and adhesion studies showed that cellular activity was most favorable when teeth were cryopreserved with physiological saline＋ glycerol or physiological saline＋DMSO, followed by physiological saline＋ trehalose and physiological saline, in that order. Also, the results were generally more favorable when teeth were frozen at the rate of -1℃/min compared to the rate of -0.5℃/min.
Morphological examinations showed that teeth cryopreserved with physiological saline＋ glycerol or physiological saline＋ DMSO had more favorable development of cellular processes and more active cellular proliferation. In histological examinations, teeth cryopreserved with physiological saline or physiological saline＋ trehalose showed adhesion between the dentin and the alveolar bone all around the dental root. In teeth cryopreserved with physiological saline＋ DMSO or physiological saline＋ glycerol, fibrous connective tissue was seen at the border between the grafted teeth and the alveolar bone. The results suggest that the gradual freezing of teeth at the rate of -1℃/min using glycerol or DMSO as a cryoprotective agent was extremely effective and could be applicable in routine clinical treatments.
The purpose of this study was to determine whether or not colored fluids and microorganism is microleakage along the implant-abutment interface of Non-Hexed and externally-Hexed lock (HL) Steri-Oss implant systems. Furthermore, an attempt was made to find measures against such microleakage.
The degrees of microleakage in the implant were examined when the implant-abutment assembly was closed by 10 Ncm and 20 Ncm torques. As a tracer, a plaque disclosing solution and gram-negative anaerobic short rod-shaped bacteria (Bacilli) isolated from plaque around the apical roots of extracted teeth were used. The experiment on microleakage was carried out by immersing the implant-abutment assembly into a test tube containing the solution and a BHI (brain heart infusion) broth.
In tests using the plaque disclosing agent, microleakage from the implant-abutment interface to the implant substructure decreased significantly as the closing torque was increased from 10 Ncm to 20 Ncm. However, the difference in implant type between Non-Hexed and HL implant systems did not affect liquid leakage much. The microorganisms were seen invading the inside of the implant-abutment assembly, but no significant changes in microleakage were observed even if the closing torque was increased from 10 Ncm to 20 Ncm, the implant system was changed from the Non-Hexed to the HL system, or if ultrasound vibrations were applied to the test tube or not. While three types of sealers containing 1.8% CHX(chlorhexidene) ointment were inserted between the implant and abutment while closing the assembly by a torque of 20 Ncm, leakages of microorganisms were mostly prevented.
These results demonstrated that it is possible to prevent microleakage from the interface by using sealers in addition to tightly closing the implant-abutment assembly with the torque when the implant is connected with the abutment.
Bone quality is very important for successful implant treatment. The purpose of this study was to evaluate the effect of menopause and aging on mandibular bone mineral densities (BMD).
The subjects were 28 women with mandibular distal extension defect, 13 pre-menopausal and 15 postmenopausal, ranging in age from those in their 30 s to 70 s. They were divided into pre- and postmenopausal groups and the latter was subdivided into 1-9 years after menopause group and ＞ 10 years group. Trabecular and cortical BMD were measured using quantitative computer tomography.
The results were as follows.
1. Trabecular and cortical BMD were significantly low in the postmenopausal group.
2. Trabecular BMD was not affected by aging in both the pre- and postmenopausal groups.
3. Cortical BMD was not affected by aging in the premenopausal group; however, it decreased with aging in the postmenopausal group.
These results indicate that menopause rather than aging affects the decrease in mandibular BMD.
To evaluate the risk factors of the loss of osseointegration (late failure) of titanium implants,we statistically carried out a clinical examination 392 fixtures of Brånemark implant, for which a one-year follow-up after the fitting of superstructures had been completed. Seven fixtures (1.8%) lost their osseointegration within one year after the fitting of superstructures.
The results are summarized as follows:
1. Age and sex did not affect late failure.
2. There was no significant difference in the rate of late failure between the maxilla and the mandible. In the mandible, the prognosis of fixtures installed in the posterior region to the mental foramen was worse than that of fixtures installed in the anterior region.
3. The kinds of fixtures did not affect late failure.
4. The prognosis of fixtures of 5 mm or more in diameter was poor.
5. The prognosis of fixtures of 10 mm or less in length was poor.
6. The initial stability of fixtures at the installation and the healing period between fixture installation and abutment connection did not affect late failure.
7. With regard to the number of fixtures connected in a superstructure, the fixtures connected with 6 or more frequently failed.
8. Smoking and state of opposing dentition did not affect late failure.
These results demonstrated that short fixtures,wide fixtures and large number of fixtures connected in a superstructure are risk factors in the loss of osseointegration (late failure).
This report deals with two free-end saddle bridge cases (Case 1: mandible, Case 2: maxilla), which were used as the transitional prosthesis during the postimplantation period. The wide area of the denture base was removed at the site of the implant fixtures to prevent direct mechanical forces affecting the implants. Oral hygiene around the implants and teeth was well maintained. The function of remaining teeth and denture was preserved. This appliance contributed not only to the predictability of the implants but also to the QOL of the patients.
Magnetic attachments are third-generation attachments with various characteristics, and their application to implant-supported dentures has been attempted. This attachment is useful in overdentures for difficult cases such as edentulous jaw, cleft palate, and remarkable defect of jawbone.
This report describes an implant overdenture with milling bar attachment made of a goldplatinum alloy that has magnet keepers on the top face. The denture has a titanium frame in the permanent resin baseplate. This attachment has only retentive force, and support and bracing force are demonstrated with the milling bar.
We have treated 20 cases with this type of denture in 6 years and there was no experience of disintegrated implant, broken bar or remade denture. The advantages of this method based on our clinical experiences are reliable occlusal registration because of the ease of checking the metal frame adaptation on the bar, sufficient support with rigid bar, and easy removal for aged and/or handicapped patients, as well as ease and reliability of repair and relining.