Annual examination of patients with dental implants sometimes reveals infections in the areas surrounding the implants, physiologic and pathologic resorption of supporting bone structures, and disturbance and fracture of the implant dentures. These conditions are suspected to be the result of the involvement, direct or indirect, of bacteria inhibiting dental plaque. Therefore how to reduce the number of microbes is an important factor in the prevention of these conditions. Citric acid could be utilized to get the microflora under control. After collecting masses of bacteria from implant, the effect of gingival sulci and citric acid in the growth of bacteria was compared with that of minocycline hydrochloride of ointment.
Materials and Methods: A total of 50 former patients ―20 with endosseous implants, 5 with endodontic endosseous implants and another 25 with periodontal disease― were enrolled in this study. Masses of bacteria garnered from the implant gingival sulci and periodontal pockets were cultivated by an anaerobic culture and 50 select germ stocks were obtained. By a disk method, the effects of citric acid (pH 1.0) and minocycline hydrochloride of ointment were examined to see which of the reagents more effectively inhibit the growth of bacteria. We also checked the sensitivity of bacteria before and after letting stand for three minutes. Furthermore, titanium test pieces were soaked in a citric acid solution (pH 1.0) for one hour to examine the extent to which bacteria adhered to the titanium test pieces with scanning electron microscope.
Results: Hardly any significant difference was noted in the sensitivity of bacteria to citric acid and minocycline hydrochloride of ointment, except for some strains. The sensitivity of adherent bacteria was also examined three minutes after implant gingival sulci were treated with citric acid. The result showed no difference in sensitivity between citric acid and minocycline hydrochloride of ointmeat. On the surface of titanium treated with citric acid, it was clear that adherance of bacteria was prohibited.
There are several means to judge the prognosis of endosteal implant, of which the existance or nonexistance of mobility has the most important meaning. The Periotest can measure mobility objectively and quantitatively, but it has not been clarified yet whether Periotest values really have something to do with X-rays and histological views in animal experiments using ITI Bonefit Implant. We also thought that we could presume the connection of bones and implants by measuring torque, which is deeply related to the supporting power of implants on the jawbone.
We used a mature shepherd dog, and implanted five ITI Bonefit 2-part screw implants (two 8 mm, two 10 mm and one 12 mm) into the dog's mandible. About four months later, we made an undecalcified histologic section after radiography and measured Periotest values and removal torque.
The results were as follows:
1. In the X-ray view, whether bone radiograph is absent or if present in a middle amount, the difference of amount of radiograph did not express a distinct difference of Periotest value.
2. In the histological view, if the implant body is absent or one-half of it is present, difference of Periotest values was not found; regardless of whether or not bone resorption as well as implant body and bone fusion were present, the Periotest values were found to be low.
3. Removal torque was at least 15 kgfcm (about 147 Ncm) and showed comparatively bigger value than that of man.
Histological changes surrounding hydroxyapatite-coated shape memory alloy implants, designed blade-vent type, were examined. Implant operations were performed in the mandibular premolar and molar regions in the Japanese monkey. A fixed bridge was set between the implant head and a tooth mesial to it, and the implant was applied by occlusal loading for six months. After six-month implantation, histological structures surrounding the implant, especially the implant tissue interface, were observed by means of microradiography, light microscopy, and scanning electron microscopy. In the interface between the HAP-coating layer and newly-formed bone tissue, no connective tissue could be found, and the newly-formed bone tissue tightly adhered to the HAP-coating layer on the implant similar to ankylosis. However, connective tissue fibrous elements extending from the newly-formed bone surface invaded fine pores of the HAP-coating layer. In the no-HAP-coating portion, on the flexible implant, newly-formed bone tissue was in close connection with Ti-Ni alloy, and no interpositioning of the fibrous element could be observed. The newly-formed bone tissue was composed of an irregularly lamella-like bone parallel to the surface of Ti-Ni alloy. The margin of this newly-formed bone had a smooth line without osteoclastic bone resorption. This study demonstrated that the HAP-coated shape memory alloy implants may stimulate osteogenic activity as well as accommodate masticatory and occlusal functions and may maintain great stability and fixation in the endosseous implant operation.
In an edentulous jaw bone, a certain degree of atrophy occurs causing preservation of its morphology to be difficult. In the field of oral and maxillofacial surgery, hydroxyapatite ｛Ca10(PO4)6(OH)2｝ (hereinafter referred to as“HAP”) is applied to such defects. However, most of the studies so far have related to formation of new bones, and there have been very few reports on prevention of atrophy of the mandible. In this study, we extracted posterior molars of the mandible of a dog, packed HAP porous particles, and performed histopathological observation on morphology of the jaw bone after 2, 4, 13 and 26 weeks respectively. As a result, reduction in height in early stage of packing was not suppressed, but decrease of buccolingual width was prevented thereafter. Also, broken pieces of HAP were found,which may have been generated during packing.
Two different types of carriers combined with bone morphogetic protein (BMP) were implanted in the dorsal subcutaneous tissue of the rat in order to study and compare the osteogenesis-inducting activity and histological patterns. The carriers were insoluble bone matrix (IBM) and porous particles of hydroxyapatite (PPHAP). Only carriers were implanted in control studies. Each composite and its surrounding tissues were removed after 1, 2 and 3 weeks and were observed by routine histology. Our results demonstrated that BMP-IBM induced osteogenesis in s process resembling endochondral ossification and BMP-PPHAP induced osteogenesis in a process resembling intramembranous ossification. BMP-carrier composites differentiated immature mesenchymal cells to either osteogenetic or chondrogetic cells, depending on the physicochemical nature of the carrier that affected the tissue microenvironment for cell differentiation.
Collagen bead carriers with bone morphogenetic protein (BMP) were implanted in the rat dorsal subcutaneous tissues in order to study and compare the osteoinductive capacity and histological patterns. The carriers were wet (CBw) and dry collagen beads (CBd) and of round star shaped varieties. The carrier alone was implanted as a control. Each composite and its surrounding tissue were removed 1, 2 and 3 weeks later and were studied by routine histology.
BMP-CBd induced bone tissue in a process that resembled endochondral ossification mode BMP-CBd showed an early initiation of the process.This system also induced bone formation through a direct ossification mode. One the other hand, BMP-CBw induced bone formation in a process resembling intramembranous ossification. BMP-collagen bead composites induced immature mesenchymal cells to become either osteogenetic or chondrogenetic cells or both, depending on the shape of the carrier that affected the microenvironment for cell differentiation.
Bone morphogenetic protein (BMP) membrane carrier composites were implanted into the dorsal subcutaneous tissues of rats. The carriers were fibrous collagen membrane (FCM) and fibrous glass membrane (FGM). The carriers were implanted as controls. Each composite was removed after 1, 2 and 3 weeks and was studied by histological observations. BMP-FCM and BMP-FGM induced bone tissues in a process that resembled an endochondral ossification mode. But the FCM system induced bone formation through a direct ossification mode. BMP-carrier composites differentiate immature mesenchymal cells to either osteogenetic or chondrogenetic cells or both, depending on the physico-chemical nature of the carrier that affected the microenvironment for cell differentiation.
Clinical application of bone augmentation using the guided tissue regeneration (GTR) technique has been discussed for the last decade. In this study, we investigated new bone formation around apatite implants using a membrane technique. Apatite 2-piece implants were inserted in the tibiae of rabbits and then covered with a non-resorbable membrane (Sellulose membrane) or resorbable membrane (Collagen membrane). Animals were sacrificed after two, four, and eight weeks. The specimens containing the implants and peripheral tissue were prepared for histological examination. Under light microscopic observation, significant new bone formations were seen in membrane groups as compared with non-membrane group.
The endodontic endosseous implant has been used to stabilize the mobile tooth which is affected by periodontal disease or trauma. We treated the luxated teeth of the anterior lower region using endodontic endosseous implants ten years ago. The disturbance of the masticatory function and esthetic problems of these teeth were not recognized. However, inflammation of the periapical region has reoccurred due to insufficient bonding of the implant to the canal walls. Furthermore, plaque control by the patient was not performed perfectly due to absorption of the alveolar bone and roots. Another kind of dental implant, Brånemark implant system, was installed into the mandible after removal of the endodontic endosseous implanted teeth. The occlusal function was restored completely, and mobility of the Brånemark implant was not observed.
When an implant does not lead to satisfactory progress for a long time, another kind of the dental implant should not be installed due to resorption of the alveolar bone. We recommend that if the inflammation surrounding the implant occurs occasionally and plaque control by the patient is not achieved sufficiently due to resorption of the alveolar bone, the replacement with a more predictable dental implant should be done as soon as possible.
The purpose of this study was to investigate what effects occured on the preservation of teeth when a tooth was replanted.
A total of 30 clinically healthy human teeth were employed in this study. The teeth experimented upon were divided into two groups, one in which the teeth were immediately fixed after extraction (the control group), and the second in which the teeth were kept at room temperature for a 30 minute period (the dry group). The periodontal ligaments of these teeth were observed under a light microscope and a transmission electron microscope.
The recorded result showed that numerous fibroblasts and cementoblasts were observed in the control group. However, in the dry group, cells which appeared in the periodontal ligaments exhibited disrupted membranes, swollen mitochondria, and distended and fragmented endoplasmic reticula.