Expression of cytokeratins in enamel organ, junctional epithelium and epithelial cell rests of Malassez.

BACKGROUND AND OBJECTIVE: After tooth formation is complete, it is suggested that continuity exists between the epithelial cell rests of Malassez (ERM), reduced enamel epithelium (REE) and subsequently the junctional epithelium. However, the junctional epithelium was reported to differ from REE and ERM. The developmental relationships between and among them remain controversial. Therefore, in the present study we examined the expression of cytokeratins in the three types of epithelia to investigate the epithelial phenotypes. MATERIAL AND METHODS: The maxillae of Wistar rats, 1, 2, 3 and 7 wk of age, were used, and the expression of CK14, CK17, CK19, CK10/CK13 and AE1/AE3 was detected using immunoperoxidase techniques. RESULTS: There was negative staining for CK10/CK13 in all the epithelia. ERM stained strongly for AE1/AE3, CK14, CK17 and CK19. During the transformation of inner enamel epithelial (IEE) cells into reduced ameloblasts and subsequently into junctional epithelium, strong staining for CK14 was evident in IEE, REE and junctional epithelium, whereas the expression of AE1/AE3 and of CK19 were initially negative in IEE and then strong in REE and junctional epithelium, respectively. In particular, the expression of CK17 was strongly positive in ERM and REE, but was negative in IEE and junctional epithelium. CONCLUSION: ERM are of odontogenic origin and junctional epithelium has an epithelial phenotype different from REE and ERM. This is the first report to demonstrate that CK17 can be used as a marker to distinguish junctional epithelium from ERM.

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

AIM: To apply a novel human model to evaluate the morphogenesis of the mucosal attachment to implants. MATERIAL AND METHODS: 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 12 weeks of healing were collected by the use of a circular cutting device and prepared for histological analysis. RESULTS: 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 8 weeks, the soft tissue dimension was about 3.6 mm and included a barrier epithelium of 1.9 mm and a connective tissue portion of 1.7 mm. Similar dimensions were found at 12 weeks. CONCLUSION: 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.

Morphological and functional characteristics of human gingival junctional epithelium.

BACKGROUND: This study aims to observe the morphological characteristics and identify the function characteristics of junctional epithelium (JE) tissues and cultured JE cells. METHODS: Paraffin sections of human molar or premolar on the gingival buccolingual side were prepared from 6 subjects. HE staining and image analysis were performed to measure and compare the morphological difference among JE, oral gingival epithelium (OGE) and sulcular epithelium (SE). Immunohistochemistry was applied to detect the expression pattern of cytokeratin 5/6, 7, 8/18, 10/13, 16, 17, 19, and 20 in JE, OGE and SE. On the other hand, primary human JE and OGE cells were cultured in vitro. Cell identify was confirmed by histology and immunohistochemistry. In a co-culture model, TEM was used to observe the attachment formation between JE cells and tooth surface. RESULTS: Human JE was a unique tissue which was different from SE and OGE in morphology. Similarly, morphology of JE cells was also particular compared with OGE cells cultured in vitro. In addition, JE cells had a longer incubation period than OGE cells. Different expression of several CKs illustrated JE was in a characteristic of low differentiation and high regeneration. After being co-cultured for 14 d, multiple cell layers, basement membrane-like and hemidesmosome-like structures were appeared at the junction of JE cell membrane and tooth surface. CONCLUSIONS: JE is a specially stratified epithelium with low differentiation and high regeneration ability in gingival tissue both in vivo and in vitro. In co-culture model, human JE cells can form basement membrane-like and hemidesmosome-like structures in about 2 weeks.

Expression of odontogenic ameloblast-associated and amelotin proteins in the junctional epithelium.

Two novel proteins - odontogenic ameloblast-associated protein and amelotin - have recently been identified in maturation-stage ameloblasts and in the junctional epithelium. This article reviews the structure and function of the junctional epithelium, the pattern of expression of odontogenic ameloblast-associated and amelotin proteins and the potential involvement of these proteins in the formation and regeneration of the junctional epithelium.

Establishment of the epithelial attachment and connective tissue adaptation to implants installed under the concept of "platform switching": a histologic study in minipigs.

AIM: To validate the "platform switching" concept at oral implants with respect to the preservation of the alveolar crestal bone levels in an animal model. MATERIAL & METHODS: Five minipigs received three implants each with a 0.25 mm implant/abutment mismatch and were placed flush (T(0)), 1 mm below (T(1)) and 1 mm above (T(+1)) the alveolar bony crest, and as a control, one conventionally restored implant placed at the bone level. The implants were randomly inserted flapless into the mandible. Four months after implant insertion, the animals were sacrificed, and undecalcified block sections were obtained and used for histological analyses. RESULTS: The mean values for peri-implant bone resorption were 1.09 ± 0.59 mm (Control), 0.51 (± 0.27 mm, T(0)), 0.50 (± 0.46 mm, T(+1)) and 1.30 (± 0.21 mm, T(-1)), respectively. Statistically significant differences (P<0.05) were found among the test (T(0), T(-1)) and the control sites. Control implants presented an average biologic width length of 3.20 mm (± 0.33), with a connective tissue adaptation compartment of 1.29 mm (± 0.53) and an epithelial attachment of 1.91 mm (± 0.71). T(0), T(+1) and T(-1) implants presented with a mean biologic width of 1.97 mm (± 1.20), 2.70 mm (± 1.36) and 2.84 mm (± 0.90), respectively, with a connective tissue adaptation compartment of 1.21 mm (± 0.97), 1.21 mm (± 0.65) and 1.50 mm (± 0.70) and an epithelial attachment of 0.84 mm (± 0.93), 1.66 mm (± 0.88) and 1.35 mm (± 0.44), respectively. Differences between the configurations were mainly associated with the length of the epithelial attachment. The epithelial attachment was significantly longer in the C sites than in T(0) (P=0.014). However, no other differences between configurations were detected. CONCLUSION: If the implants are positioned at the level of the alveolar bony crest, the platform-switching concept may have a minor impact on the length of the epithelial attachment (0.84 vs. 1.91 mm), while the connective tissue adaptation compartment remains relatively unaffected. Moreover, platform switching resulted in less resorption of the alveolar crest (0.58 mm).

In vivo investigation on connective tissue healing to polished surfaces with different surface wettability.

OBJECTIVES: Connective tissue in contact to transgingival/-dermal implants presents itself as tight scar formation. Although rough surfaces support the attachment they increase bacterial colonisation as well. In contrast to surface roughness, little is known about the influence of surface wettability on soft-tissue healing in vivo. We therefore investigated the influence of different surface wettabilities on connective tissue healing at polished implant surfaces in vivo. MATERIAL AND METHODS: Three polished experimental groups (titanium, titanium coated with hydrophobic nano-crystalline diamond (H-NCD) and titanium coated with hydrophilic nano-crystalline diamond (O-NCD) were inserted into the subcutaneous connective tissue of the abdominal wall of 24 rats. Animals were sacrificed after 1 and 4 weeks resulting in eight specimen per group per time point. Specimen were subjected to histological evaluation (van Giesson's staining) and immunohistochemistry staining for proliferating cell nuclear antigen (PCNA), fibronectin and tumour necrosis factor-alpha (TNF-α). RESULTS: Histological evaluation revealed dense scar formation at the titanium and H-NCD surfaces. In contrast, the connective tissue was loose at the O-NCD surface with a significantly higher number of cells after 4 weeks. O-NCD demonstrated a strong expression of PCNA and fibronectin but a weak expression of TNF-α. In contrast, the PCNA and fibronectin expression was low at the titanium and H-NCD, with a strong signal of TNF-α at the H-NCD surface. CONCLUSIONS: Hydrophilicity influences the connective tissue healing at polished implant surfaces in vivo positively. The attachment of connective tissue and the number of cells in contact to the surface were increased. Moreover, the inflammatory response is decreased at the hydrophilic surface.

Expression pattern of odontogenic ameloblast-associated and amelotin during formation and regeneration of the junctional epithelium.

The junctional epithelium (JE) adheres to the tooth surface, and seals off periodontal tissues from the oral environment. This incompletely differentiated epithelium is formed initially by the fusion of the reduced enamel organ with the oral epithelium (OE). Two proteins, odontogenic ameloblast-associated (ODAM) and amelotin (AMTN), have been identified in the JE. The objective of this study was to evaluate their expression pattern during formation and regeneration of the JE. Cytokeratin 14 was used as a differentiation marker for oral epithelial cells, and Ki67 for cell proliferation. Immunohistochemistry was carried out on erupting rat molars, and in regenerating JE following gingivectomy. In the reducing enamel organ and in established JE, ODAM and AMTN were present at the cell-tooth interface while only ODAM and CK14 were found throughout the JE. Both were also conspicuously present in cell clusters situated between the erupting tooth and OE. During JE regeneration, ODAM was detected first at the leading wound edge and then in the regenerating JE. Some cell clusters in the subjacent connective tissue were also positive for ODAM. AMTN appeared later and both AMTN and ODAM accumulated at the interface with the tooth. Cytokeratin 14 gradually appeared in the regenerating JE but the cell clusters showed variable labeling. Cells associated with JE formation and regeneration exhibited higher division activity than adjacent epithelial cells. These findings suggest that ODAM and AMTN have a role at the cell-tooth interface, and that ODAM is likely also implicated in cellular events during formation and regeneration of the JE.

Expression and function of laminin and integrins on adhesion/migration of primary culture cells derived from rat oral epithelium.

BACKGROUND AND OBJECTIVE: It remains controversial whether or not the junctional epithelium cells that are directly attached to teeth migrate on the enamel surface, as those cells are able to adhere firmly to the enamel. The aim of this study was to investigate the expression patterns of laminin gamma(2), integrin beta(4) and integrin alpha(3), and to examine their potential function in cell migration. MATERIAL AND METHODS: Oral epithelium cells obtained from Sprague-Dawley rats were established in primary culture. We employed a wound-healing assay to characterize the direction of cell extension at the start of cell migration, and observed different localizations of laminin and integrins using immunofluorescence. For functional analyses of integrins, we employed a phosphatidylinositol-3-kinase (PI3K) activator to promote integrin beta(4) function and used P1B5 to inhibit integrin alpha(3) function, and we analyzed the percentage of re-epithelialization as the migration function. RESULTS: Marked accumulation of laminin gamma(2) was detected in the peripheral cytoplasm of cells adjacent to the wound area, as shown by the results of the migration assay. Integrin beta(4) was detected in the distal cell processes of actively migrating cells, while integrin alpha(3) was found in cell membranes of cells adjacent to the wound area. In the functional analyses, the percentage of re-epithelialization was significantly lower in the PI3K-activator group and in the P1B5-treated group (2.5% and 7.2%, respectively) than in the control group (39.0%) (p < 0.01). CONCLUSION: The results suggest that laminin gamma(2) is secreted as a foothold for cell migration, that integrin beta(4) participates in cell adhesion and that integrin alpha(3) is involved in cell migration in the primary culture cells.

Histologic evidence of a connective tissue attachment to laser microgrooved abutments: a canine study.

Previous research has demonstrated the effectiveness of laser-ablated microgrooves placed on implant collars to support direct connective tissue attachments to altered implant surfaces. Such a direct connective tissue attachment serves as a physiologic barrier to the apical migration of the junctional epithelium and prevents crestal bone resorption. The current prospective preclinical trial sought to evaluate bone and soft tissue healing patterns when laser-ablated microgrooves were placed on the abutment. A canine model was selected for comparison to previous investigations that examined the negative bone and soft tissue sequelae of the implant-abutment microgap. The results demonstrate significant improvement in peri-implant hard and soft tissue healing compared to traditional machined abutment surfaces.

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. III: soft tissue findings.

AIM: To describe histologically the early phases of soft tissue healing to implants placed into fresh extraction sockets. MATERIALS AND METHODS: In 16 beagle dogs, 64 3.25-mm-wide cylindrical screw implants were inserted into the distal sockets of the third and fourth lower premolars using a one-stage trans-mucosal healing protocol. Biopsies were then taken at 1, 2, 4 and 8 weeks and prepared for histological examination. RESULTS: One-week specimens showed a junctional epithelium and an underlying loose connective tissue rich in inflammatory cells. At 2 weeks, signs of epithelial proliferation and a more organized connective tissue were observed. At 4 and 8 weeks, inflammation was absent; the epithelium appeared mature and in close contact with the surface of the healing abutment or the implant. The connective tissue was dense in an area close to the implant surface and the fibres were aligned parallel to the implant surface. The soft tissue dimensions at 8 weeks were approximately 5 mm, including about 3-3.5 mm of epithelium and 1-1.5 mm of connective tissue. CONCLUSION: Soft tissue healing to implants placed in fresh extraction sockets may result in a longer epithelial interface than implants placed in a healed ridge.

Effects of ovariectomy and aging on tooth attachment in female mice assessed by morphometric analysis.

OBJECTIVE: Non-human primates, dogs, rats, hamsters and ferrets, have frequently been used as laboratory animals in periodontal biology and pathology. In the past, mice have been used less for this purpose, but nowadays attract a lot of interest because gene knockout and transgenic technologies utilize mice primarily. In this study, we investigate the effects of ovariectomy and aging on tooth attachment in female mice. MATERIAL AND METHODS: Eight-week-old mice (n=15) were divided into three experimental groups (control, n=5; sham-operated, n=5; ovariectomy, n=5) and ovaries removed bilaterally. Attachment level, assessed by measuring alveolar bone height and apical termination of the junctional epithelium, was determined 6 weeks post-ovariectomy by digital morphometric analysis in sagittal sections of the mandible. The plasma level of the inflammation marker serum amyloid A (SAA) was determined by ELISA. In another series of experiments, tooth attachment was determined in female mice (n=7) at 8-26 weeks of age. RESULTS: Withdrawal of female sex hormone production by ovariectomy had no effect on alveolar bone height and apical termination of the junctional epithelium. The SAA level in plasma was unaffected by removal of the ovaries, suggesting that systemic inflammation is not induced by ovariectomy. Bone height was similar in mice sacrificed at 8-26 weeks of age and apical termination of the junctional epithelium was at the cemento-enamel junction at all ages. CONCLUSIONS: Removal of ovarian production of female sex hormones by ovariectomy has no influence on tooth attachment, and further tooth attachment is preserved with age in female mice.

A Simulated Microgravity Environment Causes a Sustained Defect in Epithelial Barrier Function.

Intestinal epithelial cell (IEC) junctions constitute a robust barrier to invasion by viruses, bacteria and exposure to ingested agents. Previous studies showed that microgravity compromises the human immune system and increases enteropathogen virulence. However, the effects of microgravity on epithelial barrier function are poorly understood. The aims of this study were to identify if simulated microgravity alters intestinal epithelial barrier function (permeability), and susceptibility to barrier-disrupting agents. IECs (HT-29.cl19a) were cultured on microcarrier beads in simulated microgravity using a rotating wall vessel (RWV) for 18 days prior to seeding on semipermeable supports to measure ion flux (transepithelial electrical resistance (TER)) and FITC-dextran (FD4) permeability over 14 days. RWV cells showed delayed apical junction localization of the tight junction proteins, occludin and ZO-1. The alcohol metabolite, acetaldehyde, significantly decreased TER and reduced junctional ZO-1 localization, while increasing FD4 permeability in RWV cells compared with static, motion and flask control cells. In conclusion, simulated microgravity induced an underlying and sustained susceptibility to epithelial barrier disruption upon removal from the microgravity environment. This has implications for gastrointestinal homeostasis of astronauts in space, as well as their capability to withstand the effects of agents that compromise intestinal epithelial barrier function following return to Earth.

Visualization of junctional epithelial cell replacement by oral gingival epithelial cells over a life time and after gingivectomy.

Junctional epithelium (JE), which is derived from odontogenic epithelial cells immediately after eruption, is believed to be gradually replaced by oral gingival epithelium (OGE) over a lifetime. However, the detailed process of replacement remains unclear. The aim of the present study was to clarify the process of JE replacement by OGE cells using a green fluorescent protein (GFP)-positive tooth germ transplantation method. GFP-positive JE was partly replaced by OGE cells and completely replaced on day 200 after transplantation, whereas there was no difference in the expression of integrin ß4 (Itgb4) and laminin 5 (Lama5) between JE before and after replacement by OGE cells. Next, GFP-positive JE was partially resected. On day 14 after resection, the regenerated JE consisted of GFP-negative cells and also expressed both Itgb4 and Lama5. In addition, the gene expression profile of JE derived from odontogenic epithelium before gingivectomy was partly different from that of JE derived from OGE after gingivectomy. These results suggest that JE derived from the odontogenic epithelium is gradually replaced by OGE cells over time and JE derived from the odontogenic epithelium might have specific characteristics different to those of JE derived from OGE.

Establishment and characterization of immortalized human gingival keratinocyte cell lines.

BACKGROUND AND OBJECTIVE: Primary human keratinocytes are used to analyze the properties of the oral epithelium and the early stages of oral bacterial infections. In vitro, these cells are characterized by their short life span and restricted availability. Approaches for culturing these cells will end after approximately 6-10 passages as a result of entry into apoptosis. For this reason, it is important to generate cell lines suitable for obtaining an unlimited source of cells. Therefore, the aim of the present study was to generate gingival keratinocyte cell lines and to compare their in vitro behaviour with those of primary human gingival keratinocytes. MATERIAL AND METHODS: Primary human gingival keratinocytes were immortalized with a combination of the human papilloma virus onkoproteins E6 and E7. The pattern of the cytokeratins, involucrin and filaggrin was investigated by intracellular staining using flow cytometry. This method allows quantitative analysis of the expression of a variety of intracellular or extracellular markers. RESULTS: The immortalized cell lines showed many morphological similarities, expressing a cytokeratin pattern that is comparable with that of primary gingival keratinocytes. Furthermore, they developed transepithelial electrical resistance, which is a marker for the generation of tight junctions. These results indicate that the cells might be able to act as an epithelial barrier, reflecting the reaction of primary human cells. CONCLUSION: The establishment of a continuous line of human gingival epithelial cells with functional characteristics of the epithelial barrier provides a valuable in vitro model for using to study the early steps of gingival/periodontal infections.

Modulation of gingival epithelial phenotypes by interactions with regionally defined populations of fibroblasts.

BACKGROUND AND OBJECTIVE: The unusual structure and functions of junctional epithelium, together with its pattern of migration in periodontal disease, raise interesting questions about the factors associated with the maintenance of its unique phenotype. To explore the effects of regionally differing fibroblast populations on the growth and patterns of differentiation of oral epithelia, this study used an organotypical in vitro model in an attempt to detect interactions occurring between populations of human oral fibroblasts and keratinocytes. MATERIAL AND METHODS: Keratinocytes and fibroblasts, isolated from the gingival region and periodontal ligament, were characterized by their patterns of growth and by their expression of known differentiation markers. Changes in cell behaviour and phenotypic marker expression were examined during in vitro passage as an indication of the maintenance of in vivo phenotypic traits. Using early passage cells, organotypical cultures were generated and patterns of epithelial growth and expression of phenotypic markers were examined. RESULTS: Phenotypically different populations of junctional and oral-gingival keratinocytes, and of oral-gingival and periodontal ligament fibroblasts, were successfully isolated, cultured and characterized. In the organotypic culture system, oral-gingival fibroblasts were found to have a markedly greater ability than periodontal ligament fibroblasts to support and maintain the growth of either type of epithelium. Shifts of epithelial phenotype were induced by different fibroblasts. CONCLUSION: Periodontal and gingival fibroblast subpopulations have differential effects on the growth and patterns of differentiation of oral and junctional epithelia. By modulating the epithelial phenotype, regionally differing fibroblasts can influence the stability and behaviour of the gingival attachment apparatus in health and disease.

The effect of thick mucosa on peri-implant tissues: an experimental study in dogs.

BACKGROUND: Findings from animal studies have indicated that the implant-mucosal barrier consists of a junctional epithelium approximately 2 mm long and a connective tissue compartment about 1 to 1.5 mm high. It may be argued that different features develop in the implant-mucosal barrier when it is placed within the alveolar bone with thick mucosa. The aim of this study was to examine the influence of a thick mucosa on peri-implant tissue healing around dental implants. METHODS: The bilateral fourth mandibular premolars and all maxillary premolars were removed in six mongrel dogs. On one side (test side) of the mandible, a standardized bone defect (8.0 mm in height) was created in the premolar region, whereas no defect was created on the other side (control side). After 3 months of healing, one implant was placed on each side of the mandible; a long abutment (12 mm in height) was connected to the fixture on the bone defect side, whereas a normal abutment was connected to the fixture on the control side. After a healing period of 6 months, all dogs were sacrificed to evaluate peri-implant tissues. RESULTS: The height of the mucosa, the length of the junctional epithelium, and the height of the zone of connective tissue integration were significantly greater in the thick mucosa than in the normal mucosa (P <0.05). No significant difference was found between the control and test sides in the marginal level of bone-to-implant contact. CONCLUSIONS: The junctional epithelium extended more apically in the thick mucosa than in the normal mucosa. However, additional marginal bone resorption was not observed at the thick mucosa sites.

The effects of laser microtextured collars upon crestal bone levels of dental implants.

PURPOSE: The purpose of this study was to examine the crestal bone, connective tissue, and epithelial cell response to a laser microtextured collar compared with a machined collar, in the dog model. MATERIALS: Six mongrel dogs had mandibular premolars and first molars extracted and after healing replaced with BioLok implants 4 x 8 mm. Each dog had 3 control implants placed on one side of the mandible and 3 experimental, laser microtextured, implants placed contralaterally. After 3 months, 1 dog was killed. Bridges were placed on the implants of 4 of the dogs. The sixth dog served as a negative control for the duration of the experiment. Two of the dogs were killed 3 months after loading, of the dogs were killed 6 months after loading as was the negative (unloaded) control. Histology, electron microscopy, and histomorpho-metric analysis was done on histologic sections obtained from block sections of the mandible containing the implants. RESULTS: Initially the experimental implants showed greater bone attachment along the collar. With time the bone heights along the control and experimental collars were equivalent. However, the controls had more soft tissue downgrowth, greater osteoclastic activity, and increased saucerization compared with sites adjacent to experimental implants. There was closer adaptation of the bone to the laser microtextured collars. CONCLUSION: Use of tissue-engineered collars with microgrooving seems to promote bone and soft tissue attachment along the collar and facilitate development of a biological width.

Two-piece implants with turned versus microtextured collars.

Implant companies have been promoting two-piece implants with microtextured collars in the interest of hard tissue preservation and/or soft tissue integration. However, this rationale may not be justified. Based on comparative studies currently available, it is unclear whether microroughened implant necks reduce crestal bone loss. A possible effect may be overruled by the establishment of a biologic width or by other factors influencing crestal bone remodeling. In addition, the orientation and attachment of the collagen fibers in the peri-implant mucosa are a little different because the surface roughness varies at the level of the implant neck. The clinician should be cautious when using these modified implants because the impact of microtextured collars on the initiation and progression of peri-implant pathology is currently unknown.

Culture of human gingival fibroblasts on a biodegradable scaffold and evaluation of its effect on attached gingiva: a randomized, controlled pilot study.

BACKGROUND: An adequate width of attached gingiva is necessary to maintain healthy periodontium, especially in orthodontics or restorative treatments in periodontics. The purpose of this study was to evaluate the width of attached gingiva after clinical application of a cultured gingival graft compared to a periosteal fenestration technique. METHODS: This study was conducted on nine patients (18 sites) with insufficient attached gingiva adjacent to at least two teeth in contralateral quadrants of the same jaw. A small portion (approximately 3 x 2 x 1 mm) of attached gingiva (epithelial + connective tissue) was removed with a surgical blade. After culture of gingival fibroblasts, 2 x 10(5) cells in 250 microl nutritional medium were added to 250 microl collagen gel. One tooth in each patient was randomized to receive a periosteal fenestration technique for gingival augmentation (control) or a tissue-engineered mucosal graft (test). Clinical parameters measured at baseline and 3 months included width of keratinized tissue, probing depth, and width of attached gingiva. RESULTS: An increased amount of keratinized tissue was seen at all treated sites after 3 months. The mean increased amount of attached gingiva was 2.8 mm at test sites and 2 mm at control sites; this difference was significant (P < 0.05). CONCLUSION: Based on the results of this investigation, the tissue-engineered mucosal graft is safe and capable of generating keratinized tissue.

Preprosthetic periodontal surgery in the proximal area with modification of the col area: results following the reestablishment of the contact point.

BACKGROUND: Anatomic characteristics of interproximal areas are dependent on the anatomy, position, and proximal contact of adjacent teeth. The objective of this study was to investigate the influence of the reestablishment of the interproximal contact following the restorative alveolar interface (RAI) procedure on the interproximal gingival COL and formation of the interdental gingival papilla. METHODS: Six mongrel dogs received bilateral apically positioned flaps, crown lengthening, and the RAI procedure on the maxillary fourth bicuspid and first molar. After 2 weeks, in a randomized manner, one side was prepared to receive metallic crowns and the opposite side remained as the control. The crowns were cemented at the 4-week postoperative period, and the dogs were sacrificed after another 4 weeks, totaling a period of 4 weeks with the full crowns in position and a total of 8 postoperative weeks. Histologic specimens were stained with hematoxylin and eosin and Mallory dyes. Sections 6 micro m thick were obtained in a bucco-lingual plane allowing ample visualization of the interproximal area. RESULTS: Clinical measurements revealed that, in the restored sides, four animals had complete fill of the interdental spaces with gingival papilla, whereas the other two dogs had a distance from the contact point to the tip of papilla varying from 0.02 to 0.021 mm. In the control group, papillae were totally reepithelialized with keratinized epithelium and a convex form. The epithelium completely covered the connective tissue and showed both epithelial projections and surface desquamation. On the test group, despite the presence of the prosthesis, the COL morphology modified by preprosthetic surgery was not altered, presenting a convex papilla with a triangular form and with a keratinized epithelium. Additional histologic characteristics were the same as found in the control group. CONCLUSION: Based on the results of this study, the reestablishment of the contact point does not revert what was obtained with the RAI procedure; the interproximal tissues remain convex and keratinized.