Healthy Implants Research Articles

Laminin-5 gamma2-chain and collagenase-2 (MMP-8) in human peri-implant sulcular fluid.

Laminin-5 (LN-5) is an important epithelial cell-derived structural and adhesive component in hemidesmosomes and basement membranes (BM). In peri-implant tissue, gingival BM underlies the junctional epithelium (JE) and reflects the peri-implant health. Matrix metalloproteinase-8 (MMP-8 or collagenase-2) is one of the key mediators of periodontal tissue destruction. Western immunoblotting with image analysis was used to quantitate the molecular forms of LN-5 gamma2-chain and MMP-8 in peri-implant sulcular fluid (PISF) from healthy and diseased implants. These observations were related to the recorded gingival (GI) and bone resorption (BR) indices of the studied sites. Altogether, 72 PISF samples from osseointegrated dental implants were examined. Significantly elevated levels of fragmented LN-5 gamma2-chain species (45 and 70 kDa) and MMP-8 immunoreactivities were observed in diseased PISF in relation to healthy PISF. The elevated levels of both LN-5 gamma2-chain 45 and 70 kDa fragments and MMP-8 in diseased PISF from peri-mucositis (BR = 0) and peri-implantitis (BR >/= 1) lesions strongly correlated with elevated GI. Low levels - almost comparable to those seen in healthy control PISF - were seen in PISF from peri-implantitis lesions (BR >/= 1) with no GI. Activation of 75 kDa neutrophil (PMN)-type proMMP-8 to 10 kDa lower-molecular-size active forms was especially detected in PISF from peri-implantitis with elevated GI. These cross-sectional findings indicate that elevated MMP-8 and LN-5 gamma2-chain fragment levels in PISF can reflect the active phase of the inflammatory peri-implant disease. Longitudinal studies are required to assess their use, either alone or in combination as molecular biochemical PISF markers, to predict the risk of progression of peri-implantitis, as well as to monitor the impact of treatment of the disease.

Osteocalcin, deoxypyridinoline and interleukin-1beta in peri-implant crevicular fluid of patients with peri-implantitis.

The aim of the present study was to analyze the levels of osteocalcin, deoxypyridinoline (Dpd) and interleukin-1beta as markers of bone metabolism in peri-implant crevicular fluid (PICF) from peri-implantitis patients. PICF was sampled from a total of 34 endosseous titanium implants from 16 patients; nine females (mean age 52.8, range 40-62 years) and seven males (mean age 56.0, range 36-66 years). The implants had been in place for a period of 9-112 months (mean; 35.8 months) since the loading. These sites were categorized as six peri-implantitis, eight peri-implant mucositis and 20 healthy implant. PICF volume from peri-implantitis sites was significantly higher than mucositis and healthy implant sites (P < 0.01). Osteocalcin levels in PICF from mucositis sites were significantly higher than healthy implants (P < 0.05), whereas peri-implantitis sites were not significantly different from either mucositis or healthy implant sites. Dpd could not be detected in any of the samples examined. IL-1beta levels in PICF from peri-implantitis sites were significantly higher than levels from peri-implant mucositis (P < 0.05) and healthy implant sites (P < 0.01). In conclusion, osteocalcin in PICF may reflect increased local bone turnover around implants. Further, IL-1beta should be a useful marker for peri-implant inflammation.

Elastase, alpha2-macroglobulin and alkaline phosphatase in crevicular fluid from implants with and without periimplantitis.

The aim of this investigation was to determine the presence of selected enzymes and enzyme inhibitors in crevicular fluid collected from implants with and without clinical, radiographic and microbiological signs of periimplantitis. Eleven implants with symptoms of periimplantitis in eight patients (four men and four women) were compared to eleven implants in seven subjects (one man and six women) without periimplantitis. Periimplant crevicular fluid (PICF) was collected at the mesial and distal sites of each implant. Alkaline phosphatase activity (ALP) was measured by using p-nitrophenyl-phosphate as substrate, elastase activity (EA) by the use of a low molecular weight fluorogenic substrate, and the inhibitor alpha2-macroglobulin (alpha2M) by ELISA. ALP, EA and alpha2M were detected in the majority of samples in both groups. In comparison to the clinically healthy implants, total amounts of each of these substances were significantly higher in PICF collected around implants with periimplantitis. The mean total amounts of EA, alpha2M and ALP in the healthy group were: EA: 1.8 ng, alpha2M: 3.1 ng, ALP: 24.1 U, and in the periimplantitis group EA: 23.1 ng, alpha2M: 25.2 ng and ALP: 142.3 U. In addition, all three mediators were correlated with the clinical parameters. The results confirm the similarity of the inflammatory response of tissues surrounding implants and natural teeth, and suggest that ALP and EA could be promising markers of bone loss around dental implants.

Detection of platelet-activating factor in gingival tissue surrounding failed dental implants.

Dental implant therapy has entered routine clinical practice. However, the failure rate of implants at 5 years, due to biological factors, is still around 7%. The pathogenesis of implant loss involves a complex network of cells and inflammatory mediators. This study evaluated platelet-activating factor (PAF), a potent phospholipid mediator of inflammation, in soft tissue surrounding failed dental implants versus healthy implants. PAF was estimated on extracted lipids by bioassay on washed rabbit platelets; inflammatory cell populations were assessed semiquantitatively after staining, and microvessel density was evaluated after immunohistochemical staining. Biologically active PAF was detected in the lipid extracts of samples excised from gingival tissue of patients with failed implants, but not in samples from patients with osseointegrated implants or from healthy edentulous subjects. The amount of PAF detected in failed implants was significantly higher than in healthy implants, suggesting a local production of this mediator. The presence of PAF was associated with histopathological findings of local inflammation and increased blood vessel density.

Histological studies of gene-ablated mice support important functional roles for natural killer cells in the uterus during pregnancy

Maternal lymphocytes having a large and granulated morphology accumulate at healthy implantation sites in normal mice. Insight into the functions of these cells has come from a previous study of two independent lines of mice deficient in natural killer (NK) cells. In pregnant Tgϵ26 mice, vascular pathology was found that led to the major complications of either fetal death or intrauterine growth retardation. In pregnant p56 lck null × IL-2Rβ null mice, extensive distension of the decidua was observed that separated the placenta from the myometrium and appeared to be interstitial edema. To strengthen assignment of uterine large granulated lymphocytes to the NK cell lineage and to understand which aspects of NK cell biology may be important for a uterine-based, pregnancy-associated subset, mid-gestation implantation sites from a new series of mice having gene deletions which alter NK cells (IL-2Rγ null, Stat4 null, IL-12 p40 null, β 7 integrin null and Muc-1 null) have been examined histologically. The findings support the assignment of pregnancy-associated large granulated cells of mice to the NK cell lineage and suggest that the primary functions of these tissue-based NK cells are to support normal development of the decidua and/or its vasculature using pathways that involve IL-12 mediated signal transduction.

Soft tissue response to polytetrafluoroethylene and silicone rubber in humans: morphological and immunohistochemical observations.

The objective of this study was by morphological and immunohistochemical means to investigate the cellular tissue response to the alloplastic materials polytetrafluoroethylene (PTFE polymer), and soft and hard silicone rubber over time. In seven healthy volunteers implants made of Proplast-Teflon, and soft and hard silicone were inserted subcutaneously in unloaded areas in the iliac crest region. After 1, 2, 4, 12, and 26 weeks, respectively, the implants with surrounding soft tissue were removed en bloc for histological and immunohistochemical examination using a panel of antibodies to various leukocyte markers. The tissue reaction to the various alloplastic materials varied greatly with the focus on macrophage and giant cell reactions and eventual formation of a peri-implant fibrous capsule. The most extensive changes developed next to porous Proplast, both with respect to degree of changes and endurance of tissue reaction. Less intense reactions were seen, in decreasing order, to soft silicone, Teflon, and hard silicone. The study gave no clues to a toxic, allergic, or traditional immunological pathogenesis of the tissue reaction induced by the test materials.

The Use of Embryonic Spinal Cord Grafts to Replace Identified Motoneuron Pools Depleted by a Neurotoxic Lectin, Volkensin

The viability of solid pieces of embryonic spinal cord grafted into adult spinal cords that had been depleted of motoneurons by a neurotoxic lectin, volkensin, was investigated. The possibility that the grafted neurons will extend their axons via the degenerated ventral roots and reinnervate the denervated muscles was also studied. Cells in the embryonic spinal cord were prelabeled with bromodeoxyuridine and grafted into the host cord 2 or 3 weeks after volkensin treatment. Six to 24 weeks later the fluorescent dyes Fast Blue and Diamidino Yellow were applied to the peripheral nerve or muscles which were expected to be reinnervated by neurons from the graft. The grafted cells were visualized by bromodeoxyuridine immunocytochemistry. Although the transplants survived, no neurons of graft origin reinnervated the muscles via the ventral roots of the host spinal cord. Therefore, in another series of experiments axons from grafted and host neurons were guided toward an implanted extensor hallucis longus (EHL) muscle via its motor nerve. The EHL muscle was removed from either healthy or volkensin-affected hindlimb of the host, placed paravertebrally, and the proximal end of its motor nerve inserted into the spinal cord at the site of the graft. In these experiments, neurons of graft origin reinnervated the paravertebrally placed muscle implant via the muscle's own nerve. However, significantly fewer neurons were observed when volkensin-affected nerve-muscle implants were used. To establish whether grafted spinal cord neurons are necessary for reinnervation of skeletal muscles, in separate experiments embryonic neocortical tissue was transplanted into the motoneurondepleted spinal cord. These grafts were connected to healthy nerve-muscle implants. In this case little reinnervation of the muscle occurred. These results suggest that, though volkensin-affected peripheral nerve is not a good conduit for regenerating axons, other inhibitory effects located in the CNS may be responsible for the failure of growing embryonic neurons to reach their peripheral targets via the existing anatomical routes. Experiments with grafted neocortical tissue indicate that good reinnervation of implanted muscles can only be achieved by using homologous embryonic tissue.

Collagenase, gelatinase and elastase activities in sulcular fluid of osseointegrated implants and natural teeth.

Proteinases play a key rôle in the physiological degradation and remodelling of the periodontal tissues. The rôle of these enzymes in tissue remodelling remodelling in connection with the insertion of dental endosseous implants has not been elucidated. Therefore, the aim of the present study was to identify the eventual presence of collagenase, gelatinase and elastase activities in periimplant sulcus fluid (PISF) of osseointegrated implants. Gelatinolytic activity in the samples was studied with gelatin-zymograms. Collagenase activity and its susceptibility to tetracycline-inhibition were monitored with SDS-polyacrylamide gel electrophoresis and laser densitometry, and elastase activity with synthetic substrate. Low activities of elastase and collagenase were detected in both PISF of osseointegrated implant patients and gingival crevicular fluid (GCF) of the control patients whereas significantly higher activities were detected in GCF of adult periodontitis patients. Also the profiles of gelatinases were similar in PISF of osseointegrated implant patients and GCF of the controls, but differed from the profile of active gelatinases present in GCF of adult periodontitis patients. The similar activities/characteristics of these proteinases in both periimplant sulcus fluid of healthy dental implants and GCF of healthy natural teeth suggest that they comprise the major proteinases for both periodontal and periimplant tissue remodelling or destruction.

Intraepithelial antigen‐presenting cells in the keratitied mucosa around teeth and osseointegrated implants

The presence and distribution of intraepithelial antigen‐presenting cells was studied in the keratinized mucosa around healthy osseointegrated implants and teeth. Vimentin, cytokeratins, HLA‐Dr, CD18, ICAM‐I and CDla‐positive cells were assessed by a 3‐stage ABC immunoperoxidase system in serial sections from clinically characterized sites. A total of 11 biopsies (7 adjacent to osseointegrated dental implants and 4 adjacent to teeth in healthy volunteers) were qualitatively and quantitatively analyzed. All biopsies displayed the presence of a small inflammatory infiltrate subjacent to themost coronal portion of the junctional epithelium. Intraepithelial antigen‐presenting cell markers were present both around implants and teeth. The observations were consistent with the presence of functional local major histocompatibility complex Class II restricted antigen presentation. Quantitative differences were observed by analysis of variance in terms of different locations within the same section (i.e. junctional epithelium vs oral epithelium) and in terms of the source of the biopsy (i.e. implants vs teeth). The significance, if any, of the observed quantitative difference is discussed in terms of different maturity of the local immune response and possible environmental differences. It is concluded that clinically healthy keratinized mucosa around osseointegrated dental implants shares functional similarities with normal gingiva in terms ofantigen presentation. These results further contribute to the characterization of a functional local immune response that represents the basis for long‐term clinical success of osseointegrated dental implants.

Decidua-associated suppressor activity and viability of individual implantation sites of allopregnant C3H mice

Release of soluble suppressor activity from individual implant site decidua of DBA/2-mated C3H/HeJ mice was measured on days 12.5–13.5 of pregnancy. Suppressor activity varied among sites and followed a distribution curve that was displaced towards low suppression when resorption sites were compared to healthy embryonic implants. Pre-immunization against the DBA/2 strain paternal antigens failed to increase resorbtion (by loss of low suppression implants) but led instead to a reduced resorbtion rate. This was associated with an increase in soluble suppressor activity obtained from decidua. Some reduction in resorbtion occurred independent of an increase in the level of suppression suggesting additional contributing factors to the immunization effect.

Studies on the surgical induction of endometriosis in the rat

As a model to examine the pathophysiologic attributes of endometriosis, attempts were made to surgically induce the disease in the rat by autotransplanting endometrial or uterine tissue to the peritoneum. Rats (n = 46) were randomly assigned to one of four surgical techniques: (1) four uterine squares sutured to the peritoneal cavity; (2) uterine luminal lavages instilled into the peritoneal cavity; (3) endometrial scrapings flushed into the peritoneal cavity; and (4) sham-operated controls. Rats were examined at various days after surgery for the presence of endometrial implants. The autotransplantation of uterine squares to the peritoneal cavity was the only treatment that yielded healthy endometriotic implants. These implants grew into ellipsoidal cystic structures that were composed of both endometrial glands and stroma and were found to contain prostaglandin F (202 ng/mg) at concentrations similar to those measured in uterine tissue (205 ng/mg). To examine the effect of surgically induced endometriosis upon fecundity, rats (n = 40) were autotransplanted with uterine squares or were sham operated and mated. The presence of ectopic endometrial tissue reduced the number of pups at term by 48% and the number of day 14 embryos by 28% (P less than 0.05). Peritoneal adhesions were greater in rats with induced endometriosis than in sham-operated controls (P less than 0.05); however, in rats with induced endometriosis, no differences were noted in the severity of adhesions between pregnant and nonpregnant rats. Endometriotic implants underwent complete regression in the day 14 pregnant rat but had doubled in size in the nonpregnant rat. At term, the endometriotic implants were larger than in the day 14 pregnant rat (P less than 0.05) and similar to their original size. The successful growth and development of surgically transplanted endometrial tissue in the rat offers a research model that can be used to study those aspects of endometriosis that cannot be adequately investigated in women.

Interruption of pseudopregnancy in rats by hemi-ovariectomy.

Hemi-ovariectomy on days 1, 2 and 3 after the appearance of leukocytes in vaginal smears in rats (made pseudopregnant by reserpine injections at estrus) caused a return of proestrus between 2 and 3 days after operation in all animals. There was compensatory ovulation at the first or second postoperative proestrus, as shown by counting healthy implantation sites at laparotomy following a successful mating. Progesterone replacement immediately after hemiovariectomy successfully maintained the persistent leukocytic vaginal smears of pseudopregnancy in all animals so treated. Sham operation was without effect. (Endocrinology87:173,1970) THERE IS good evidence to indicate that the central nervous system chronically inhibits the secretion of prolactin in the rat (1–4). It has been postulated that the factor which stimulates luteotrophin secretion does so by suppressing this neural inhibition, and that, during pseudopregnancy, progesterone may maintain the secretion of luteotrophin by a positive feedback (3).