Barrier Epithelium Research Articles

Marginal bone and soft tissue behavior following platform switching abutment connection/disconnection– a dog model study

The effect on the marginal peri-implant tissues following repeated platform switching abutment removal and subsequent reconnection was studied. Six adult female Beagle dogs were selected, and Pm3 and Pm4 teeth, both left and right sides, were extracted and the sites healed for 3 months. At this time, 24 bone level (BL) (Straumann, Basel, Switzerland) Ø 3.3/8 mm implants were placed, 2 in each side on Pm3 and Pm4 regions. In one side (control group), 12 bone level conical Ø 3.6 mm healing abutments and, on the other side (test group), 12 Narrow CrossFit (NC) multibase abutments (Straumann) , Basel, Switzerland) were connected at time of implant surgery. On test group, all prosthetic procedures were carried out direct to multibase abutment without disconnecting it, where in the control group, the multibase abutment was connected/disconnected five times (at 6/8/10/12/14 weeks) during prosthetic procedures. Twelve fixed metal bridges were delivered 14 weeks after implant placement. A cleaning/control appointment was scheduled 6 months after implant placement. The animals were sacrificed at 9 months of the study. Clinical parameters and peri-apical x-rays were registered in every visit. Histomorphometric analysis was carried out for the 24 implants. The distance from multibase abutment shoulder to the first bone implant contact (S-BIC) was defined as the primary histomorphometric parameter. Wilcoxon comparison paired test (n = 6) found no statistically significant differences (buccal P = 0.917; Lingual P = 0.463) between test and control groups both lingually and buccally for S-BIC distance. Only Pm3 buccal aBE-BC (distance from the apical end of the barrier epithelium to the first bone implant contact) (P = 0.046) parameter presented statistically significant differences between test and control groups. Control group presented 0.57 mm more recession than test group, being this difference statistically significant between the two groups (P < 0.001). It can be conclude, within the limits of this animal study, that the connection/disconnection of platform switching abutments during prosthetic phase of implant treatment does not induce bone marginal absorption. Furthermore, it may present a negative influence in the buccal connective tissue attachment that becomes shorter anyway preventing marginal hard tissue resorption, especially in thin biotypes.

Whole-mount immunostaining of the adult Drosophila gastrointestinal tract

The gastrointestinal (GI) tract harbors an essential barrier epithelium that separates an organism from its changing external environment. As such, the gut epithelium is a fascinating nexus of stem cell biology, immunology and physiology. Investigators have sought to mine this rich interface for new biological and mechanistic insights. Many of the powerful genetic approaches developed in Drosophila have proven effective in the study of the gut. The goal of this article is to present a method for dissecting, immunostaining and mounting samples of the adult Drosophila GI tract. This protocol combines readily with techniques to label cell lineages and/or challenge the system with environmental perturbations, which are briefly discussed.

Use of donor bladder tissues for in vitro research

To evaluate deceased non-heart beating (DNHB) donors and deceased heart beating (DHB) brain-stem dead donors, as sources of viable urological tissue for use in biomedical research. To identify sources of viable human bladder tissue as an essential resource for cell biological research aimed at understanding human diseases of the bladder and for developing new tissue engineering and regenerative medicine strategies for bladder reconstruction. Typically, normal human urinary tract tissue is obtained from adult or paediatric surgical patients with benign urological conditions, but few surgical procedures yield useful quantities of healthy bladder tissue for research. Research ethics committee approval was obtained for collection of donor bladder tissue. Consent for DHB donors was undertaken by the Donor Transplant Coordinators. Tissue Donor Coordinators were responsible for consent for DNHB donors and the retrieval of bladders was coordinated through the National Blood Service Tissue Banking Service. All retrievals were performed by practicing urologists and care was taken to maintain sterility and to minimise bacterial contamination. Two bladders were retrieved from DNHB donors and four were retrieved from DHB donors. By histology, DNHB donor bladder tissue exhibited marked urothelial tissue damage and necrosis, with major loss or absence of urothelium. No cell cultures could be established from these specimens, as the urothelial cells were not viable in primary culture. Bladder urothelium from DHB donors was intact, but showed some damage, including loss of superficial cells and variable separation from the basement membrane. All four DHB bladder specimens yielded viable urothelial cells that attached in primary culture, but cell growth was slow to establish and cultures showed a limited capacity to form a functional barrier epithelium and a propensity to senesce early. We have shown that normal human bladder urothelial cell cultures can be established and serially propagated from DHB donor bladders. However, our study suggests that rapid post-mortem changes to the bladder affect the quality and viability of the urothelium, rendering tissue from DNHB donors an inadequate source for urothelial cell culture. Our experience is that whereas patients are willing to donate surgical tissue for research, there is a barrier to obtaining consent from next of kin for retrieved tissues to be used for research purposes.

Soft Tissue Healing at One-Piece Zirconia Implants Compared to Titanium and PEEK Implants of Identical Design: A Histomorphometric Study in the Dog

This study aimed to histomorphometrically evaluate the soft tissue reactions of one-piece zirconia implants versus titanium implants in regard to their insertion depth. Four one-piece implants of identical geometry were inserted on each side of six mongrel dogs: an uncoated zirconia implant, a zirconia implant coated with a calcium liberating titanium oxide, a titanium implant, and an experimental implant made of a synthetic material. Using a split-mouth design, they were inserted in both submerged and nonsubmerged healing modes. After 4 months, dissected blocks were stained with toluidine blue to histologically assess the marginal portion of the implant mucosa, apical extension of the barrier epithelium, and margin level of bone-to-implant contact. The inflammation status at the crestal part of the implant was assessed as well. The histomorphology presented the typical soft tissue configuration of barrier epithelium and connective tissue near the bone-to-implant contact. Histomorphometrically, the length of the barrier epithelium did not differ significantly concerning material type or healing modality. Furthermore, the inflammation signs were higher with nonsubmerged implants. The submerged uncoated zirconia implants, however, showed few signs of inflammation. Within the limits of this study, it is concluded that uncoated and coated zirconia implants are capable of establishing sufficient soft tissue configurations that are comparable to those of titanium implants.

Morphogenesis of peri‐implant mucosa revisited: an experimental study in humans

To apply a novel human model to evaluate the morphogenesis of the mucosal attachment to implants. Twenty one patients receiving implant-supported single-tooth replacement were enrolled in this study. After implant installation, a custom-designed experimental abutment was connected to the implant. Soft tissue biopsies representing 2, 4, 8 or 12weeks of healing were collected by the use of a circular cutting device and prepared for histological analysis. The soft tissue biopsies were retrieved, preserved and processed with a technique that was safe and reproducible. The results from the histological analysis in regards to dimensional and qualitative changes in the mucosa over time were consistent with those reported from animal experiments. At 8weeks, the soft tissue dimension was about 3.6mm and included a barrier epithelium of 1.9mm and a connective tissue portion of 1.7mm. Similar dimensions were found at 12weeks. It is suggested that the new human model provides advantages in terms of cost-effectiveness in research as well as from ethical aspects and should be considered as an alternative to pre-clinical in vivo studies in animals.

Impact of immediate loading on early soft tissue healing at two‐piece implants placed in fresh extraction sockets: an experimental study in the beagle dog

To study early soft tissue healing of immediately placed implants with or without immediate loading in the dog. Forty-eight implants were placed in the distal sockets of Pm3 and Pm4 in the lower jaw of 12 beagle dogs immediately after tooth extraction. In the control group, no loading was applied. In the test group, an immediate loading restoration with occlusal contacts was performed. Dogs were sacrificed at 2, 4, and 8 weeks for histological analysis. At the end of the study, there was a 100% implant and prosthesis survival. The biological width dimension was similar in both groups at all the studied healing periods. This dimension tended to decrease from week 2 to 8 in both groups, on both the buccal and lingual side. The barrier epithelium tended to stop at the implant-abutment interface in both groups and also decreased in length from week 2 to 8, on the buccal and the lingual side. Soft tissue recession remained low and occurred mainly in the test group. The characteristics, dimension, and healing pattern of the peri-implant soft tissues were similar around immediate implants with or without immediate loading.

Intestinal inflammation and stem cell homeostasis in aging Drosophila melanogaster

As a barrier epithelium, the intestinal epithelium has to coordinate physiological functions like digestion and nutrient resorption with the control of commensal bacteria and the prevention of pathogenic infections. It can therefore mount powerful innate immune and inflammatory responses, while, at the same time, maintaining tissue homeostasis through regenerative processes. How these different functions are coordinated remains unclear, and further insight is required to understand the age-related loss of homeostasis in this system, as well as the etiology of inflammatory and proliferative diseases of the gut. Recent work in Drosophila melanogaster has provided important new insight into the regulation of regenerative activity, innate immune homeostasis, commensal control, as well as age-related dysfunction in the intestine. Interestingly, many of the identified processes and mechanisms mirror similar homeostatic processes in the vertebrate intestine. This review summarized the current understanding of how innate immune responses, changes in commensal bacteria, and other challenges influence regenerative activity in the aging intestinal epithelium of flies and draws parallels to similar processes in mammals.

Peri‐implant tissue reactions to immediate nonocclusal loaded implants with different collar design: an experimental study in dogs

The aim of this study was to evaluate bone remodelling and soft tissue reactions around immediate nonocclusal loaded implants with different collar configuration in beagle dogs. The mandibular bilateral second, third and fourth premolars of six beagle dogs were extracted. After 3 months of healing, four implants were placed in the mandibles of each dog. Randomly, two implants with a 1.5 mm polished surface collar (TSA, control group) and two implants with a 0.7 mm polished surface collar and 2.5 mm microthreaded area (TSAA, test group) were inserted. Both groups were treated with a minimal mucoperiosteal flap elevation approach. Impressions were taken and two single screw-retained restorations were inserted in each hemi-mandible 2 days after the implant placement. The animals were sacrificed at 1, 2 and 3 months (two specimens each), and biopsies were obtained. Samples were processed for ground sectioning. Histomorphometric analysis was carried out to compare buccal and lingual bone height loss and soft tissue behaviour between the two groups. Crestal bone resorption was significantly higher in the control group (P > 0.05). The establishment of the biological width showed similar outcomes for both groups. Only the distance from the top of the peri-implant mucosa to the apical portion of the barrier epithelium at lingual aspect was significantly more pronounced in the control group (P > 0.05). The alterations that occurred in the peri-implant tissues were related to the adaptation that occurred after the loading conditions in both groups. The microthread design might have an effect in maintaining the marginal bone loss against loading.

Soft tissue response to zirconia and titanium implant abutments: an in vivo within‐subject comparison

To compare the health of the soft tissues towards zirconia and titanium abutments in man, as observed using histological data. Twenty patients received two mandibular implants with either a zirconia or titanium abutment (split mouth study design, left-right randomization). After 3months soft tissue biopsies were prepared for histological evaluation. They were subjected to blind evaluation. The number of blood vessels per surface unit and an inflammation grading scale score ranging from 1 to 4 were determined. Paired samples from 17 patients were suitable for analysis, 3 with unsevered implant-abutment connections and 14 solely containing soft tissue. All showed a well-keratinized stratified squamous epithelium which was continuous with the barrier (junctional) epithelium that faced the abutment surface. The normal epithelial build-up could be recognized with little signs of inflammation. No statistically significant difference in tissues adjacent to zirconia and titanium abutment surfaces were seen with respect to vascular density (20.5 SD 4.4 and 20.7 SD 3.2) or inflammation grading scale scores (3.2 SD 0.7 versus 3.1 SD 0.7). No differences in soft tissue health were seen in peri-implant mucosa adjacent to zirconia and titanium abutment surfaces.

Healing of peri-implant tissues after flapless and flapped implant installation

The aim of this study was to investigate the consequences of different flapless procedures for the installation of dental implants on peri-implant bone response. After bilateral extraction of the mandibular second and third premolars and a 3-month healing period, 30 SLActive(®) implants were installed for 3 months in 10 Beagle dogs according to three different surgical approaches, i.e.: (1) flapped (F), (2) tissue punch flapless (P), and (3) direct flapless (DF). At harvesting, 29 implants were analysed. Micro-computed tomography and histomorphometrical evaluation (which also included the mobile implants) showed comparable results in bone volume (F=55 ± 9, P=51 ± 4, DF=54 ± 5) and crestal bone level (F=3420 ± 762, P=5358 ± 1681, DF=3843 ± 433). However, the implants inserted using the punch approach revealed a significantly lower first bone contact (F=3420 ± 762, P=5358 ± 1681, DF=3843 ± 433) and bone-to-implant contact percentage (F=70 ± 12, P=48 ± 23, DF=73 ± 12). Considering the gingival response, the barrier epithelium was also significantly deeper around the implants installed using the punch approach (F=1383 ± 332, P=2278 ± 1154, DF=1107 ± 300). The results indicate that a flapless surgical technique can be used for the installation of oral implants. In addition, using a tissue punch wider than the implant diameter should be avoided, as it can jeopardize the outcome of the implantation procedure.

Soft tissue dimensions in flapless immediate implants with and without immediate loading: an experimental study in the beagle dog

The aim of the present study was to evaluate the peri-implant soft tissue dimensions in flapless immediate implants with and without immediate loading. This study was carried out on six beagle dogs. Four implants were placed (two per side) immediately after tooth extraction (third and fourth premolars). Flapless immediate implant placement was performed in one hemimandible (control). The same procedure was performed in the contralateral side and immediate prosthesis was connected (test). After 3 months of healing, the dogs were sacrificed. None of the implants and prosthesis were lost. Barrier epithelium in the loaded group was 2.51 mm at the buccal and 2.34 mm at the lingual aspect. In the no loaded group, the results were similar, 2.54 and 2.2 mm at the buccal and lingual side, respectively. Connective tissue in the loaded group was 1.38 mm at the buccal and 0.65 mm at the lingual aspect, and in the no loaded group 1.48 mm at the buccal and 0.53 mm at the lingual side. Biological width dimensions were 3.9 mm at the buccal and 2.95 mm at the lingual aspect for the loaded group, and 4.01 and 2.64 mm at the buccal and lingual aspect for the no loaded group. The results of the present study suggested that soft tissues dimensions around immediate implants with immediate loading were similar to immediate implants without loading.

Immortalisation of Normal Human Urothelial Cells Compromises Differentiation Capacity

BackgroundThe development of urothelial malignancy is not solely a consequence of loss of proliferation constraints but also involves loss of cellular differentiation, defined histopathologically as grade. Although tumour grade is an independent prognostic marker for urothelial carcinoma (UC), the molecular events underpinning the loss of urothelial differentiation are poorly understood. ObjectiveTo examine the effect of gene alterations implicated in UC development on the ability of human urothelial cells to undergo molecular differentiation and form a functional urothelial barrier. Design, setting, and participantsLaboratory study. InterventionNormal human urothelial (NHU) cell cultures were transduced with recombinant retroviruses to produce stable sublines overexpressing wild-type or oncogenic mutated fibroblast growth factor receptor 3 or human telomerase reverse transcriptase (hTERT). Previously generated NHU sublines carrying dominant-negative CDK4 and p53 mutant genes or immortalised with the human papillomavirus 16 E6 oncoprotein were included. MeasurementsThe activity of introduced transgenes was demonstrated by comparing phenotypes of transgene-expressing and isogenic control NHU cells. Modified and control sublines were compared for changes in generational potential (life span) and capacity to respond to differentiation-inducing signals by transcript expression of uroplakins 2 and 3. The ability to form a barrier epithelium was assessed by measuring the transepithelial electrical resistance. Results and limitationsBy contrast to tumour suppressor loss of function or oncogene overactivation, hTERT overexpression alone led to life span extension and immortalisation. The hTERT immortalised cells carried no gross genomic alterations but became progressively insensitive to differentiation signals and lost the ability to form an epithelial barrier. Further characterisation of hTERT cells revealed a downregulation of p16 cyclin-dependent kinase inhibitor expression and loss of responsiveness to peroxisome proliferator-activated receptor γ, providing mechanistic explanations for the subjugation of senescence constraints and the abrogation of differentiation capability, respectively. Although immortalised urothelial cell lines without karyotypic aberrations may be generated, such cell lines are compromised in terms of differentiation and functional capacity. ConclusionsOverexpression of hTERT promotes development of an immortalised differentiation-insensitive urothelial cell phenotype. Although such cells offer a useful insight into the grade/stage paradigm of UC, they have limited value for investigating normal urothelial cell/tissue biology and physiology.

Ce-Duox1/BLI-3 Generates Reactive Oxygen Species as a Protective Innate Immune Mechanism in Caenorhabditis elegans

Caenorhabditis elegans was recently developed as a model system to study both pathogen virulence mechanisms and host defense responses. We previously demonstrated that C. elegans produces reactive oxygen species (ROS) in response to exposure to the important gram-positive nosocomial pathogen Enterococcus faecalis. We also presented evidence of oxidative stress and upregulation of stress responses after exposure to the pathogen. As in mammalian systems, this new work shows that production of ROS for innate immune functions occurs via an NADPH oxidase. Specifically, reducing expression of a dual oxidase, Ce-Duox1/BLI-3, causes a decrease in ROS production in response to E. faecalis. We also present evidence that reduction of expression of Ce-Duox1/BLI-3 increases susceptibility to this pathogen, specifically when expression is reduced in the intestine and the hypodermis. Ce-Duox1/BLI-3 was previously characterized as having a role in cuticle cross-linking. Two C. elegans mutants with point mutations in the peroxidase domain that exhibit severe cuticle defects were discovered to be unaffected in ROS production or pathogen susceptibility. These results demonstrate an important biological role for the peroxidase domain in cuticle cross-linking that is unrelated to ROS production. To further demonstrate the protective effects of the pathogen-induced ROS production, we show that antioxidants that scavenge ROS increase the sensitivity of the nematode to the infection, in stark contrast to their longevity-promoting effects under nonpathogenic conditions. In conclusion, we postulate that the generation of ROS by NADPH oxidases in the barrier epithelium is an ancient, highly conserved innate immune defense mechanism.

The mucosal barrier at implant abutments of different materials

AbstractObjective: The aim of the present study was to analyze the soft tissue barrier formed to implant abutments made of different materials.Material and methods: Six Labrador dogs, about 1 year old, were used. All mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later four implants (OsseoSpeed™, 4.5 × 9 mm, Astra Tech Dental, Mölndal, Sweden) were placed in the edentulous premolar region on one side of the mandible and healing abutments were connected. One month later, the healing abutments were disconnected and four new abutments were placed in a randomized order. Two of the abutments were made of titanium (Ti), while the remaining abutments were made of ZrO2 or AuPt‐alloy. A 5‐months plaque control program was initiated. Three months after implant surgery, the implant installation procedure and the subsequent abutment shift were repeated in the contra‐lateral mandibular region. Two months later, the dogs were euthanized and biopsies containing the implant and the surrounding soft and hard peri‐implant tissues were collected and prepared for histological analysis.Results: It was demonstrated that the soft tissue dimensions at Ti‐ and ZrO2 abutments remained stable between 2 and 5 months of healing. At Au/Pt‐alloy abutment sites, however, an apical shift of the barrier epithelium and the marginal bone occurred between 2 and 5 months of healing. In addition, the 80‐μm‐wide connective tissue zone lateral to the Au/Pt‐alloy abutments contained lower amounts of collagen and fibroblasts and larger fractions of leukocytes than the corresponding connective tissue zone of abutments made of Ti and ZrO2.Conclusion: It is suggested that the soft tissue healing to abutments made of titanium and ZrO2 is different to that at abutments made of AuPt‐alloy.

The mucosal barrier at implant abutments of different materials

The aim of the present study was to analyze the soft tissue barrier formed to implant abutments made of different materials. Six Labrador dogs, about 1 year old, were used. All mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later four implants (OsseoSpeed, 4.5 x 9 mm, Astra Tech Dental, Mölndal, Sweden) were placed in the edentulous premolar region on one side of the mandible and healing abutments were connected. One month later, the healing abutments were disconnected and four new abutments were placed in a randomized order. Two of the abutments were made of titanium (Ti), while the remaining abutments were made of ZrO(2) or AuPt-alloy. A 5-months plaque control program was initiated. Three months after implant surgery, the implant installation procedure and the subsequent abutment shift were repeated in the contra-lateral mandibular region. Two months later, the dogs were euthanized and biopsies containing the implant and the surrounding soft and hard peri-implant tissues were collected and prepared for histological analysis. It was demonstrated that the soft tissue dimensions at Ti- and ZrO(2) abutments remained stable between 2 and 5 months of healing. At Au/Pt-alloy abutment sites, however, an apical shift of the barrier epithelium and the marginal bone occurred between 2 and 5 months of healing. In addition, the 80-mum-wide connective tissue zone lateral to the Au/Pt-alloy abutments contained lower amounts of collagen and fibroblasts and larger fractions of leukocytes than the corresponding connective tissue zone of abutments made of Ti and ZrO(2). It is suggested that the soft tissue healing to abutments made of titanium and ZrO(2) is different to that at abutments made of AuPt-alloy.

Deafness and Stria Vascularis Defects in S1P2 Receptor-null Mice

The S1P(2) receptor is a member of a family of G protein-coupled receptors that bind the extracellular sphingolipid metabolite sphingosine 1-phosphate with high affinity. The receptor is widely expressed and linked to multiple G protein signaling pathways, but its physiological function has remained elusive. Here we have demonstrated that S1P(2) receptor expression is essential for proper functioning of the auditory and vestibular systems. Auditory brainstem response analysis revealed that S1P(2) receptor-null mice were deaf by one month of age. These null mice exhibited multiple inner ear pathologies. However, some of the earliest cellular lesions in the cochlea were found within the stria vascularis, a barrier epithelium containing the primary vasculature of the inner ear. Between 2 and 4 weeks after birth, the basal and marginal epithelial cell barriers and the capillary bed within the stria vascularis of the S1P(2) receptor-null mice showed markedly disturbed structures. JTE013, an S1P(2) receptor-specific antagonist, blocked the S1P-induced vasoconstriction of the spiral modiolar artery, which supplies blood directly to the stria vascularis and protects its capillary bed from high perfusion pressure. Vascular disturbance within the stria vascularis is a potential mechanism that leads to deafness in the S1P(2) receptor-null mice.

Peri‐implant hard and soft tissue integration to dental implants made of titanium and gold

The aim of the study is to compare the peri-implant hard and soft tissue integration around dental implants made of commercially pure (c.p.) titanium or a gold alloy but with the same shape and surface roughness. In four beagle dogs, all mandibular premolars were extracted. Three months later, four experimental non-submerged implants were placed in each edentulous premolar region. Each implant comprised three different zones: zone A (coronal), zone B (central) and zone C (apical). Each zone was made of either c.p. titanium or a gold alloy. Four different combinations of metal and zone were used. A plaque control program was initiated and 6 months later, the animals were sacrificed and biopsies were obtained. The biopsies including the implant and the surrounding tissues were processed for ground sectioning. The height of the peri-implant mucosa and the length of the barrier epithelium were similar at the four experimental sites. The marginal bone level in the different metal combinations was located between 4.5 and 4.8 mm apical of the implant rim. The percent of mineralized bone that was in direct contact with the implant surface (BIC%) was consistently greater in the marginal than in the apical portion of the implants. The BIC% for the marginal and apical zone were consistently greater for implant portions made of titanium than for portions made of gold alloy (zone B: 42.7% vs. 36.5%, zone C: 33.2% vs. 19%). Osseointegration was achieved to surfaces made of both c.p. titanium and a gold alloy. BIC% was higher at titanium than at gold surfaces. Moreover, the peri-implant soft tissue dimensions were not influenced by the metal used in the 'marginal' zone of the implant.

Morphogenesis of the peri‐implant mucosa: an experimental study in dogs

The objective of the present experiment was to study the morphogenesis of the mucosal attachment to implants made of c.p. titanium. All mandibular premolars were extracted in 20 Labrador dogs. After a healing period of 3 months, four implants (ITI Dental Implant System) were placed in the right and left sides of the mandible. A non-submerged implant installation technique was used and the mucosal tissues were secured to the conical marginal portion of the implants with interrupted sutures. The sutures were removed after 2 weeks and a plaque control program including daily cleaning of the remaining teeth and the implants was initiated. The animals were sacrificed and biopsies were obtained at various intervals to provide healing periods extending from Day 0 (2 h) to 12 weeks. The mandibles were removed and placed in the fixative. The implant sites were dissected using a diamond saw and processed for histological analysis. Large numbers of neutrophils infiltrated and degraded the coagulum that occupied the compartment between the mucosa and the implant during the initial phase of healing. At 2 weeks after surgery, fibroblasts were the dominating cell population in the connective tissue interface but at 4 weeks the density of fibroblasts had decreased. Furthermore, the first signs of epithelial proliferation were observed in specimens representing 1-2 weeks of healing and a mature barrier epithelium occurred after 6-8 weeks of healing. The collagen fibers of the mucosa were organized after 4-6 weeks of healing. It is suggested that the soft-tissue attachment to implants placed using a non-submerged installation procedure is properly established after several weeks following surgery.

Probe penetration in periodontal and peri‐implant tissues: An experimental study in the beagle dog

Today, periodontal probing is the best diagnostic tool to assess the health status and attachment level of periodontal tissues. There are, however, doubts as to whether the same method could be used for implants. Experiments comparing peri-implant and periodontal probing provide conflicting results. The impact and interpretation of peri-implant probing are still not sufficiently known. The purpose of the present study was to further analyze the histological level of probe penetration in healthy periodontal and peri-implant tissues. In four beagle dogs, all mandibular premolars were extracted. Three months later, four experimental non-submerged implants were placed in each edentulous premolar region. Six months later, probing depth was determined at the buccal aspect at two of the implants and at the bilateral first mandibular molars. A pressure-controlled probe with a diameter of 0.4 mm and 0.2 N probing force was used. Following the probing depth assessment, a metal periodontal probe tip was inserted into the previously measured depth and attached to the implants and teeth using a composite material. Block biopsies were obtained and prepared for histometric examinations. The findings showed that probing resulted in similar probe extension at implants and teeth, that the probe extension corresponded to the extension of the barrier epithelium and that the distance between the probe tip and the bone was about 1 mm in both peri-implant and periodontal tissues. This experiment showed that under healthy conditions, the probe tip penetration in the soft tissues at teeth and implants is similar when a probing force of 0.2 N is used. Probing around implants using a moderate force is a valuable diagnostic tool in the maintenance of implant patients.

Tissue reactions to abutment shift: an experimental study in dogs.

Standard protocols for the clinical use of dental implants often include the placement of healing abutments prior to standard or custom-made abutments. The tissue response to a single shift from a healing abutment to a permanent abutment has not been studied. The aim of the present experiment was to study tissue reactions that may occur following the removal of a healing abutment and the placement of a permanent abutment. In six beagle dogs, all mandibular premolars were extracted. Three months later three fixtures of the Astra Tech Implants Dental System (Astra Tech AB, Mölndal, Sweden) were installed in each edentulous premolar region. An additional 3 months later, the first abutment connection was performed. In two sites on each side of the mandible, healing abutments were placed; in the remaining site, a Uni-abutment (Astra Tech AB) was used. The two healing abutments were removed 2 weeks later, and one Uni-abutment and one prepable abutment were placed. A plaque-control period was initiated, and 6 months later block biopsies were obtained. The biopsies were prepared for histometric and morphometric examination. Radiographs were obtained at fixture placement, 2 weeks after the first abutment connection, and 6 months later. The length of the barrier epithelium, the height of the connective tissue attachment, and the level of the marginal bone did not differ between the three abutment groups. The major part of the radiographic bone loss during the experiment took place prior to or immediately after abutment connection; only small bone level alterations occurred during the subsequent 6-month period. The shift from a healing abutment to a permanent abutment resulted in the establishment of a transmucosal attachment, the dimension and quality of which did not differ from those of the mucosal barrier formed to a permanent abutment placed during a second-stage surgery.