Fate of pocket epithelium in an apically positioned flap

Functional Local Renin-Angiotensin System in Human and Rat Periodontal Tissue

The initiation or progression of periodontitis might involve a local renin-angiotensin system (RAS) in periodontal tissue. The aim of this study was to further characterize the local RAS in human and rat periodontal tissues between healthy and periodontally-affected tissue. Components of the RAS were investigated using in vitro, ex vivo and in vivo experiments involving both human and Wistar rat periodontium. Although not upregulated when challenged with P. gingivalis-lipopolysaccharide, human gingival and periodontal ligament fibroblasts expressed RAS components. Likewise, healthy and inflamed human gingiva expressed RAS components, some of which were shown to be functional, yet no differences in expression were found between healthy and diseased gingiva. However, in inflamed tissue the immunoreactivity was greater for the AT₁R compared to AT₂R in fibroblasts. When compared to healthy tissue, ACE activity was increased in human gingiva from volunteers with gingivitis. Human-gingiva homogenates generated Ang II, Ang 1-9 and Ang 1-7 when incubated with precursors. In gingiva homogenates, Ang II formation from Ang I was nearly abolished only when captopril and chymostatin were combined. Ang 1-7 formation was significantly greater when human gingiva homogenates were incubated with chymostatin alone compared to incubation without any inhibitor, only captopril, or captopril and chymostatin. In rat gingiva, RAS components were also found; their expression was not different between healthy and experimentally induced periodontitis (EP) groups. However, renin inhibition (aliskiren) and an AT₁R antagonist (losartan) significantly blocked EP-alveolar-bone loss in rats. Collectively, these data are consistent with the hypothesis that a local RAS system is not only present but is also functional in both human and rat periodontal tissue. Furthermore, blocking AT₁R and renin can significantly prevent periodontal bone loss induced by EP in rats.

Contemporary crown-lengthening therapy: a review

BACKGROUND

The authors conducted a literature review regarding the rationale, basic surgical principles, contraindications and wound healing associated with periodontal crown-lengthening surgery. They present a report of a clinical case illustrating crown lengthening with osseous resection.

TYPES OF STUDIES REVIEWED

The authors evaluated clinical and radiographic studies, as well as literature reviews. They selected only publications that pertained to the surgical exposure of the natural dentition to facilitate restorative therapy, esthetic concerns or both.

RESULTS

Periodontal crown lengthening can be used for esthetic enhancement in the presence of delayed passive eruption. Moreover, for teeth with subgingival caries, fractures or both, this treatment can establish a biological width and, if needed, a ferrule length facilitating prosthetic management. Crown-lengthening surgery involves various techniques, including gingivectomy or gingivoplasty or apically positioned flaps, which may include osseous resection. Authors of wound-healing investigations have reported that an average of 3 millimeters of supragingival soft tissue will rebound coronal to the alveolar crest and can take a minimum of three months to complete vertical growth.

CLINICAL IMPLICATIONS

Initiation of final prosthetic treatment should wait at least three months and possibly up to six months for esthetically important areas, as the free gingival margin requires a minimum of three months to establish its final vertical position. Dentists must be aware that osseous resection could affect periodontal stability and may pose a contraindication to crown-lengthening therapy.

Wound healing after mucoperiosteal surgery in the cat

The purpose of this study was to examine possible tissue-dependent differences in rate of healing after mucogingival flap surgery. After intrasulcular incision and a vertical-releasing incision distal to the maxillary and mandibular cuspids, buccal, full-thickness mucogingival flaps were raised in four quadrants of 10 adult cats. The triangular flaps were left open for 30 min and then repositioned and sutured. Tissue reactions were studied histologically after 1, 3, 7, 14, and 28 days of healing. Although new collagen occasionally was observed in the wound space in the free gingiva at 3 days, collagenous union between the cut dentogingival fibers and the flap seemed well established at 7 days. Flap reattachment to the denuded cortical bone was seen at 14 days in the region of the attached gingiva. In the region of the alveolar mucosa, however, residual coagulum and inflammatory reaction was present as late as at 28 days in several specimens. These observations indicate a marked difference in rate of healing among the different interfaces involved. These variations seem to be related to variations in size of the resulting wound space when a full-thickness mucoperiosteal flap is readapted over cervical root surfaces, alveolar bone crest, and denuded cortical bone, respectively.

Immunohistochemical analysis of cells attached to teflon membranes following guided tissue regeneration

A wide panel of monoclonal antibodies to various keratins together with an anti-vimentin antibody to label mesenchymal cells were used to label cells attached to expanded polytetrafluorethylene (ePTFE) membranes removed 6 weeks postoperatively from 7 patients. All membranes demonstrated variable amounts of adherent tissue, within which vimentin-positive cells were detected. In 8 of the 18 samples, no epithelial cells were detected. Seven of the 18 samples demonstrated small groups of epithelial cells on both sides of the membranes, staining predominantly as basal cells. The remaining 3 samples were more densely populated by epithelium which expressed a diverse keratin profile. Thus, the membranes were successful in establishing mesenchymal cell proliferation, as evidenced by vimentin positivity, but did not totally exclude epithelium.

Periodontal response to mechanical non-surgical therapy: a review

This literature review is concerned with the ability of personal oral hygiene and mechanical instrumentation to establish and maintain periodontal health. Clinical, microbiologic, and histologic responses to non-surgical therapy are evaluated to provide guidelines for expected treatment results. Factors that may limit the effectiveness of non-surgical therapy as a closed procedure are also addressed. These include length of therapy, skill of therapists, patient compliance, responsibility of clinician for maintenance, and disease activity status of the patient.