The secondary electron emission yield for 24 solid elements excited by primary electrons in the range 250-5000 ev: a theory/experiment comparison.

The secondary electron (SE) yield, delta, was measured from 24 different elements at low primary beam energy (250-5,000 eV). Surface contamination affects the intensity of delta but not its variation with primary electron energy. The experiments suggest that the mean free path of SEs varies across the d bands of transition metals in agreement with theory. Monte Carlo simulations suggest that surface plasmons may need to be included for improved agreement with experiment.

Theory experiment comparison of the electron backscattering factor from solids at low electron energy (250-5,000 eV).

The electron backscattering factor was measured from 24 different elements at low primary beam energy (250-5,000 eV). The results were compared with Monte Carlo simulations from a variety of freely available programs and an in-house developed program. The results suggest that a thin film of oxide can modify the backscattering factor at low primary energy. In addition, a number of problems have been identified with the freely available programs.

Periodontal plastic surgery in a dystrophic epidermolysis bullosa patient: review and case report.

Epidermolysis bullosa (EB) is a group of genetic disorders in which patients frequently present with fragile skin and mucosal surfaces that blister following minor trauma; 23 subtypes have been recognized, but their precise pathogenesis and etiology remain obscure. There is no treatment for EB, only palliative therapy. Oral bullae are the most common oral finding and affect all surfaces. Patients with EB present a unique challenge in terms of periodontal therapy. The following article reviews this disorder and describes the complications encountered when providing periodontal plastic surgery to a patient exhibiting this condition. A 36-year-old female with dystrophic EB presented for treatment of a 3 mm recession area with minimal attached gingiva on the facial of #24 and 25. Oral evaluation revealed multiple ulcers. The treatment consisted of a subepithelial connective tissue graft in conjunction with a coronally positioned flap and buccal frenectomy. Most of the epithelium associated with the surgical area and buccal vestibule sloughed. During the postoperative course, the frenum had regenerated at a more coronal level and was applying tension on the gingival tissues. It appeared that a connective tissue union had formed between the de-epithelialized surface of the facial flap and the buccal mucosa of the vestibule. A second frenectomy was performed, and a clear acrylic stent was fabricated to prevent the union of the connective tissue of the facial flap to the buccal mucosa. The stent prevented the fusion of both connective tissue layers and allowed time for epithelium migration.

Comparison of bioabsorbable laminar bone membrane and non-resorbable ePTFE membrane in mandibular furcations.

The purpose of the study was to compare clinical parameter changes and osseous regeneration in 12 pairs of comparable Class II mandibular molar furcation invasion defects using either a bioabsorbable demineralized laminar bone allograft membrane or a non-resorbable expanded polytetrafluoroethylene (ePTFE) membrane as a barrier in guided tissue regeneration. Measurements with calibrated periodontal probes were made to determine soft tissue recession, probing depth, and attachment levels. Defects within each pair were randomly selected for treatment with either bioabsorbable demineralized bone allograft membrane or ePTFE membrane. All defects were concurrently grafted with particulate demineralized freeze-dried bone allograft (DFDBA). Additional measurements were made at surgery to determine crestal resorption and the vertical and horizontal dimensions of the osseous defects. The temporal course and extent of membrane exposures were also recorded. The non-resorbable membrane was retrieved 6 weeks following placement. Six months following initial surgical treatment, each site was surgically re-entered and all soft and hard tissue measurements repeated. Descriptive statistical analysis revealed that both treatments resulted in significant within-group mean vertical and horizontal osseous fill, but no statistical difference emerged between the groups. As based on this pilot study, laminar bone membrane may be as effective as ePTFE when used in conjunction with DFDBA for treatment of Class II mandibular molar furcation bone defects. This pilot study of low power suggests that these two materials may be equivalent when used in conjunction with DFDBA. Further studies of much higher power and of the laminar bone alone as compared to positive and negative controls are required. Laminar bone does not require a secondary surgical procedure for removal and may undergo less frequent instances and degrees of exposure during healing.

Effect of flap design on healing and osseointegration of dental implants.

The purpose of this study was to evaluate soft tissue healing and osseointegration of dental implants after the use of vestibular incision or crestal incision flap designs during placement of the dental implant fixture. A split-mouth design was used in 10 patients. The vestibular flap technique was used for half the implant fixtures and the crestal incision for the other half. Postsurgical healing was monitored for 30 days, and osseointegration at second-stage surgery was evaluated. The short-term results suggest that the use of either the vestibular incision or the crestal incision technique did not affect overall clinical healing or osseointegration.

Comparison of DNA probe and ELISA microbial analysis methods and their association with adult periodontitis.

The purposes of this study were two-fold: to compare the DNA probe and enzyme linked immunosorbent assay (ELISA) microbial identification tests and correlate the levels of microorganisms with adult periodontitis. A single plaque sample were taken from each of 2 sites in 52 patients. Twelve of these patients were also sampled during and after treatment. The experimental site had clinical indicators of disease (bleeding on probing, probing and attachment loss of > or = 6 mm) and the contralateral site (control) was clinically healthy. A total of 176 plaque samples were collected, divided, processed, and sent for both types of quantitative microbial analyses. All of these samples were used to compare the DNA probe and ELISA methods while only the initial 104 pretreatment sites were used to correlate microorganisms/method with clinical indicators of adult periodontitis. DNA probes were used to assay for A. actinomycetemcomitans, P. gingivalis, P. intermedia, E. corrodens, F. nucleatum, T. denticola, and C. rectus. An ELISA utilizing monoclonal antibodies was used to assay for P. gingivalis, E. corrodens, T. denticola, and C. rectus. Comparison of the two methods revealed that the ELISA test identified P. gingivalis and C. rectus significantly more often than the DNA probe method and that T. denticola was detected more frequently with the DNA probe. The sensitivities and specificities varied widely among organisms and by test. P. gingivalis, as identified by ELISA, had the highest degree of sensitivity and specificity (0.90 and 0.82 respectively) to clinical indicators of adult periodontitis.

The dimensions of the human dentogingival junction.

This study examined the naturally occurring dimensions of the dentogingival junction in 10 adult human cadaver jaws. The connective tissue attachment, epithelial attachment, loss of attachment, and sulcus depth were measured histomorphometrically for 171 tooth surfaces. Mean measurements were 1.34 +/- 0.84 mm for sulcus depth; 1.14 +/- 0.49 mm for epithelial attachment; 0.77 +/- 0.32 mm for connective tissue attachment; and 2.92 +/- 1.69 mm for loss of attachment. These dimensions, as measured in this study, support the concept that the connective tissue attachment is a variable width within a more narrow distribution and range than the epithelial attachment, sulcus depth, or loss of attachment. The level of the loss of attachment was not predictive of the connective tissue attachment length.

Biologic preparation of diseased root surfaces. An in vitro study.

The study evaluated the effect of 2% sodium desoxycholate combined with whole plasma from a single donor on gingival fibroblast attachment to diseased root surfaces. Twenty extracted periodontally involved teeth were cut into halves buccolingually and sterilized by moist heat under high pressure. The diseased root surface of each control half was rubbed with a sterile cotton pellet saturated with Dulbecco's phosphate-buffered saline (PBS). The diseased root surface of each experimental half was rubbed with a sterile cotton pellet saturated with 2% sodium desoxycholate and then rubbed with a pellet soaked in human plasma. The control and experimental halves were placed in separate petri dishes, and a fibroblast cell suspension was added to each dish. The mean number of attached cells per half tooth was calculated for each group. Tooth surfaces treated with PBS (controls) showed a mean of 307 +/- 63 attached cells for 17 tooth halves; the experimental treated surfaces exhibited a mean of 650 +/- 130 attached cells for 16 halves. The difference between these numbers was statistically significant (P less than 0.01). These findings suggest that the desoxycholate/plasma combination enhanced in vitro fibroblast attachment to diseased root surfaces.