The authors present a histologic analysis of 19 Branemark titanium implants retrieved for different causes: four implants were removed for abutment fracture, one for dental nerve dysesthesia, two for bone overheating, two for peri-implantitis, nine for mobility, one for unknown causes. In the implants removed for fracture a high bone-implant contact percentage was present (71.83 +/- 4.96%) with compact, mature bone at the interface. The picture of the failure due to bone overheating was characteristic with the presence of bone sequestra and of a gap between implant and bone filled by lymphocytes and plasma cells: many bacteria surrounded the necrotic bone and no newly regenerated bone was present. In peri-implantitis an inflammatory infiltrate was observed in the peri-implant tissues: a dense fibrous connective tissue was present around implants failed for mobility. The microscopical picture is certainly extremely important in identifying the causal determinants of an implant failure.

Bone and Bones↗

PubMedDate not supplied

A histologic evaluation of eight cases of failed dental implants: is bone overheating the most probable cause?

Biomechanical overloading has been stated to be, overall, the major cause of implant failures. Very important can be, however, in the etiopathogenesis of early implant failure, the overheating of the surgical site. The authors present eight cases of implant loss most probably due to bone overheating, even if other causes cannot be excluded. The microscopical picture, in all cases, was composed by the same features: (1) presence of bone sequestra; (2) no regeneration of the peri-implant bone; (3) presence of an inflammatory infiltrate in the gap between bone and implant; (4) no organization of the peri-implant bone clot; (5) presence of a compact and mature bone around the implant; (6) presence of bacteria around the implant and the necrotic bone.

Biomechanical Phenomena↗

PubMedDate not supplied

Periodontal membranes from composites of hydroxyapatite and bioresorbable block copolymers.

Biomembranes are frequently proposed as devices for "guided bone regeneration." Such membranes consist generally of a thin sheet of polymeric material, mostly textured from polymeric yarns or clots, which all have a diffuse very fine winding porosity. The cross-section size of the holes of such porosity is nanometric (diameter < 0.1 microm); thus these holes can be indicated as nanoholes. Whatever the method of production, the surface density of nanoholes (number per square centimeter) has to be as high as possible. It is important also that no variation of this density occurs. The fine dimension of these microholes allows the crossing of small molecules (O2, CO2, H2O, sugars, many nutritional organic compounds and even some simple proteins) but not other larger molecules and particulates, including cells of any kind. These biomembranes have, consequently, a semipermeable behavior, providing the functional role which is the interposition of a barrier for the cells, separating the bone from the surrounding soft tissues. The kinetic of proliferation of osteoblasts is lower than that of fibroblasts. Most membranes of this kind are not resorbable. The main problem for the resorbable ones is the speed of size increase of the holes during the time. Their diameter must not exceed a threshold value until the reconstruction of bone is complete, otherwise soft tissue cells will invade the growing bone tissue with formation of undesirable mixed tissue. The present paper deals with a resorbable membrane made with a composite polymer/ceramic. A poly(epsilon-caprolactone)-block-poly(oxyethylene)-block-poly(epsilon-caprolactone) copolymer is the polymeric matrix which contains dispersed ceramic hydroxyapatite microgranules, a stiff filling additive. The main possible use is that of periodontal membranes. The copolymer, obtained by thermal polymerization of epsilon-caprolactone onto poly(ethylene-glycol), presents good biological tolerance, is resorbable under physiological conditions and can promote cell growth. Histological tests, performed 6 months after implantation, showed that the polymeric matrix is almost totally resorbed. New-formed bone colonizes even the innermost parts of the membrane, with bone trabeculae closely surrounding the hydroxyapatite granules.

Journal Article↗

PubMedDate not supplied

Bone regeneration guided by resorbable collagen membranes in rabbits: a pilot study.

Artificial cross-shaped intrabony defects were created in the mandibles of 12 rabbits and the cavities covered with Type I highly cross-linked resorbable collagen membranes for 30 days. Similar cavities were prepared in three control animals and left uncovered for the same time period. Morphological and analytical data were obtained by means of light microscopy, scanning electron microscopy, and x-ray energy-dispersive spectrometry. After the experimental period, the membrane covered cavities were completely filled with regenerated bone. In the control specimens, the artificial cavities were occupied by fibrous connective tissue.

Animals↗

PubMedDate not supplied

Morphological and cytofluorimetric analysis of adult mesenchymal stem cells expanded ex vivo from periodontal ligament.

Many adult tissues contain a population of stem cells that have the ability of regeneration after trauma, disease or aging. Recently, there has been great interest in mesenchymal stem cells and their roles in maintaining the physiological structure of tissues, and their studies have been considered very important and intriguing, after having shown that this cell population can be expanded ex vivo to regenerate tissues not only of the mesenchymal lineage, such as intervertebral disc cartilage, bone, tooth-associated tissue, cardiomyocytes, but also to differentiate into cells derived from other embryonic layers, including neurons. Currently, different efforts have been focused on the identification of odontogenic progenitors from oral tissues. In this study we isolated and characterized a population of homogeneous human mesenchymal stem cells proliferating in culture with an attached well-spread morphology derived from periodontal ligament, a tissue of ectomesenchymal origin, with the ability to form a specialized joint between alveolar bone and tooth. The adherent cells were harvested and expanded ex vivo under specific conditions and analysed by FACScan flow cytometer and morphological analysis was carried out by light, scanning and transmission electron microscopy. Our results displayed highly evident cells with a fibroblast-like morphology and a secretory apparatus, probably indicating that the enhanced function of the secretory apparatus of the mesenchymal stem cells may be associated with the secretion of molecules that are required to survive and proliferate. Moreover, the presence in periodontal ligament of CD90, CD29, CD44,CD166, CD 105, CD13 positive cells, antigens that are also identified as stromal precursors of the bone marrow, indicate that the periodontal ligament may turn out to be a new efficient source of the cells with intrinsic capacity to self-renewal, high ability to proliferate and differentiate, that can be utilized for a new approach to regenerative medicine and tissue engineering.

Adult↗

PubMedDate not supplied

Potential markers of tongue tumor progression selected by cDNA microarray.

Squamous cell carcinoma (SCC), the most frequent malignant tumor of the oral cavity, generally exhibits a poor prognosis and metastases are the main cause of death. This tumor often arises from pre-malignant lesions. To date, it is difficult to predict if and which pre-malignant lesions may progress into oral SCC using traditional methods. For these reasons, several studies are trying to identify markers useful in the progression of pre-malignant lesions and tumors. To define the genetic expression profile of tongue tumor progression we compared 9 dysplasias (DS), 8 tumors without metastasis (TWM), 11 metastasizing SCCs (MT) of the tongue, and a baseline of 11 normal tissues by using cDNA microarray containing 19.2 K clones. We initially applied hierarchical agglomerative clustering based on information from all 6026 clones. Results were obtained by performing a two steps analysis: a Significance Analysis of Microarray (SAM) and a Gene Ontology search. One hundred and five clones have statistically significant different expression levels (FDR < 0.01) between DS and TWM, whereas 570 genes have statistically significant difference expression levels between TWM and MT (FDR < 0.01) as detected by SAM. By filtering with FatiGo only 33 genes were differentially expressed in TWN, respect to DS, whereas 155 genes were differentially expressed in MT respect to TWM. We detected some genes which encode for oncogenes, transcription factors and cell cycle regulators as potential markers of DS progression. Examples are BAG4, PAX3 and CCNI, respectively. Among potential markers of metastases are some genes related to cell mobility (TSPAN-2 and SNTA1), intercellular adhesion (integrin alpha 7) or extracellular matrix components (ADAMTS2 and cathepsin O). Additionally, under-expressed genes encoded apoptosis-related proteins (PDCD4 and CASP4). In conclusion, we identified several genes differentially expressed in tumor progression which can potentially help in better classifying pre-malignant lesions and tongue SCCs.

Adult↗

PubMedDate not supplied

Factors associated with apoptosis in symptomatic and asymptomatic carotid atherosclerotic plaques.

The aim of this study was to investigate the differences that are present between apoptosis in symptomatic (with symptoms of cerebral ischemic attack) and asymptomatic carotid atherosclerotic plaques. The apoptotic process in macrophages and smooth muscle cells was evaluated. Cellular markers and products of immune cells in symptomatic and asymptomatic atherosclerotic plaque and endoarterectomy specimen were analyzed by immunohistochemistry. No statistically significant differences were present regarding the mean SMC actin-positive area. Using double staining of alpha-smooth muscle actin and TUNEL techniques, the number of smooth muscle cells in apoptosis was statistically higher in symptomatic plaque as compared with asymptomatic plaque. Statistically significant differences (p=0.009) were also found in the CD45-positive cells in the inflammatory infiltrate. The CD68-positive macrophages showed statistically significant differences (p=0.0001). Similarly, the double staining with CD68 and TUNEL revealed that apoptotic macrophages were mainly present in asymptomatic plaques rather than symptomatic plaques. Statistically significant differences (p<0.001) were found in the Bcl-2 expression, with higher values in asymptomatic plaques. Our data showed that the increase of the inflammatory cells contributes to plaque instability and that death due to apoptosis of smooth muscle cells in symptomatic plaques could contribute to their destabilization and explains their tendency to fracture.

Aged↗

PubMedDate not supplied

Bone-hydroxyapatite interface in retrieved hydroxyapatite-coated titanium implants: a clinical and histologic report.

Two hydroxyapatite-coated implants were retrieved after 12 months of loading because of a fracture of the abutments. The specimens were treated to obtain thin ground sections, and a microprobe chemical analysis was done under a scanning electron microscope equipped with an energy-dispersive x-ray analysis and cathodoluminescence system. Under light microscopy, close contact between the bone and the hydroxyapatite coating was seen, with no gaps at the interface. In some areas of the coating a reduction of the coating thickness could be observed, along with the presence of some detached hydroxyapatite particles embedded in newly formed bone. The chemical analysis of the cathodoluminescent areas at the interface showed a reduced calcium:phosphorus ratio in this region.

Calcium↗

PubMedDate not supplied

Bone reactions to anorganic bovine bone (Bio-Oss) used in sinus augmentation procedures: a histologic long-term report of 20 cases in humans.

Many materials are used for sinus augmentation procedures. Anorganic bovine bone (Bio-Oss) has been reported to be osteoconductive, and no inflammatory responses have been observed with the use of this biomaterial. One of the main questions pertaining to Bio-Oss concerns its biodegradation and substitution by host bone. Some investigators have observed rapid replacement by host bone, while other researchers observed slow resorptive activity or no resorption at all. The aim of the present study was to conduct a long-term histologic analysis of retrieved specimens in humans where Bio-Oss was used in sinus augmentation procedures. Specimens were retrieved from 20 patients after varying periods from 6 months to 4 years and were processed to obtain thin ground sections. Bio-Oss particles were surrounded for the most part by mature, compact bone. In some Haversian canals it was possible to observe small capillaries, mesenchymal cells, and osteoblasts in conjunction with new bone. No gaps were present at the interface between the Bio-Oss particles and newly formed bone. In specimens retrieved after 18 months and 4 years, it was also possible to observe the presence of osteoclasts in the process of resorbing the Bio-Oss particles and neighboring newly formed bone. Bio-Oss appears to be highly biocompatible and osteoconductive, is slowly resorbed in humans, and can be used with success as a bone substitute in maxillary sinus augmentation procedures.

Absorbable Implants↗

PubMedDate not supplied

Synthetic bone grafts in peri-implant bone dehiscences: histological results in humans.

This study describes the histological results found in three patients treated with osseointegrated implants and Bioplant HTR (Hard Tissue Replacement) synthetic bone graft in peri-implant dehiscences adjacent to implants. This therapy was carried out without the use of barrier membranes. Bioplant HTR is reported to act as its own barrier and prevent gingival soft tissue migration ingrowth. The histologic picture demonstrated that Bioplant HTR is osteoconductive and biocompatible, and can be used both as bone substitute and as a barrier for guided bone regeneration in implant therapy.

Adult↗

PubMedDate not supplied

Tissue reactions, fluids, and bacterial infiltration in implants retrieved at autopsy: a case report.

A 72-year-old patient underwent the placement of 2 screw-type implants. After 5 months the patient died of a massive stroke, and a block section of the portion of the mandible containing the implants was done. The specimen was treated to obtain thin ground sections. A 1- to 5-micron gap was present between the implant and the healing cover screw, and this space was filled by bacteria and calculus; bacteria were also present in the most apical portion of the hollow part of the implant. An inflammatory infiltrate was present in the connective peri-implant tissues. The spaces between all implant components (implant, abutment, and healing screw) can act as conduits and reservoirs for bacteria, which could cause inflammation of the peri-implant soft tissues. In conclusion, the histologic data from this autopsy case may help to confirm the penetration by fluids and bacteria into the internal portion of the implants, obtained from previous in vitro and in vivo studies.

Aged↗

PubMedDate not supplied

Immunocytochemical detection of hMSH2 and hMLH1 expression in oral melanoma.

BACKGROUND: The DNA mismatch repair system (MMR) plays an important role in the maintenance of genomic stability. To date few studies have been performed on hMSH2 and hMLH1 expression and melanoma of the head and neck region. A study of two cases revealed no mutations of the mismatch repair genes hMSH2 and hMLH1. MATERIALS AND METHODS: To verify the possibility of implication of hMSH2 and hMLH1 alterations in melanocytic cancerogenesis, the authors examined the protein expression pattern of hMSH2 and hMLH1 by immunohistochemistry in 9 paraffin-embedded oral melanoma. RESULTS: One case (11%) showed nuclear positivity for hMSH2, 3 cases (33%) showed cytoplasmic positivity, and five cases (55%) showed no staining in the tumoral cells, even if normal squamous epithelium available in this section showed a nuclear positivity. Four cases (44%) showed no hMLH1 staining in the tumoral cells, even if normal squamous epithelium available in this section showed a nuclear positivity. Two cases (22%) showed nuclear positivity, and three cases (33%) showed cytoplasmic positivity. CONCLUSIONS: The analysis of mismatch repair genes can be a new molecular diagnostic tools for the detection of patients at high risk of developing melanoma and other neoplasia, or metastasis and recurrences.

Adaptor Proteins, Signal Transducing↗

PubMedDate not supplied

Immediate one-stage postextraction implant: a human clinical and histologic case report.

The placement of an implant immediately after tooth extraction may have the following advantages: reduction in morbidity, treatment time, and treatment costs; preservation of the residual ridge width and height; optimal esthetic result; and easier definition of implant position. The aim of the present study was the presentation of a human clinical and histologic report involving a nonsubmerged implant placed in a mandibular postextraction site and removed because of persistent pain. At low-power magnification, it was possible to see that newly formed bone with wide osteocyte lacunae was present around the implant. A 1.5-mm sulcular epithelium was visible on one side of the implant, with a 0.5-mm epithelial attachment. The thickness of the supracrestal connective tissue was 3.2 mm. This connective tissue was dense, had few cells, was well vascularized, and showed no evidence of an inflammatory infiltrate. Under polarized light, it was possible to observe that the connective fibers were arranged perpendicular to the implant surface and that these fibers became parallel near the implant. These results show that human immediate postextraction implants can have a high percentage of bone-implant contact.

Alveolar Process↗

PubMedDate not supplied

Removal torque and histomorphometric investigation of 4 different titanium surfaces: an experimental study in the rabbit tibia.

This study presents a histomorphometric and biomechanical comparison of bone response to commercially pure titanium screws with 4 different types of surface topographies placed in the tibial metaphysis of 12 rabbits. Each rabbit had 4 implants placed, 2 in each tibia. The 4 surface topographies were a machined surface, a grit-blasted surface, a plasma-sprayed surface, and an acid-etched (Osseotite) surface. After a healing period of 5 weeks, histomorphometric and removal torque data revealed a significantly higher percentage of bone-to-implant contact and removal torque for acid-etched implants compared to machined, blasted, and plasma-sprayed implants. Within the limits of this short-term experimental study, the results indicated that micro-rough titanium surfaces obtained with acid-etching procedures achieved a 33% greater bone-to-implant contact over machined titanium surfaces with an abutment-type roughness and provided enhanced mechanical interlocking.

Animals↗