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The solubility enhancement generated by an amorphous phase over its crystalline counterpart is unaffected by the pH of the solution (at fixed ionic strength and temperature), even for a drug containing ionizable moieties, provided that both the ionized and neutral species generated through dissolution of the solids remain dissolved., (Copyright © 2020 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Amorphous phases are frequently employed to overcome the solubility limitation that is nowadays commonplace in developmental small-molecule drugs intended for oral administration. However, since the solubility enhancement has finite longevity (it is a "kinetic solubility" effect), characterizing its duration (i.e., the so-called "parachute" effect) can be important for optimizing a formulation with regard to its in vivo exposure. Two semiempirical models, based on dispersive kinetics theory, are evaluated for their ability to precisely describe experimental transients depicting a loss in supersaturation (initially generated by the dissolution of the amorphous phase) over time, as the solubilized drug recrystallizes. It is found that in cases where the drug solubility significantly exceeds that of the crystal at longer times, the mechanism has substantial "denucleation" (dissolution) character. On the other hand, "nucleation and growth" (recrystallization) kinetics best describe systems in which the recrystallization goes to completion within the experimental time frame. Kinetic solubility profiles taken from the recent literature are modeled for the following drugs: glibenclamide, indomethacin, loratadine, and terfenadine. In the last case, a combination of three different kinetic models, two classical ones plus the dispersive model, are used together in describing the entire dissolution-recrystallization transient of the drug, obtaining a fit of R 2 = 0.993. By precisely characterizing the duration of the "parachute" in vitro (e.g., under biorelevant conditions), the proposed models can be useful in predicting trends and thereby guiding formulation development and optimization.

The accurate prediction of the solubility enhancement offered by neat amorphous drugs and amorphous solid dispersions, over their crystalline (API) counterparts, has been discussed in several landmark works dating back at least two decades. Against this backdrop, an assessment of the current state-of-the-art for rigorously, yet simply (circumventing computational methods), determining the amorphous:crystalline solubility ratio based on thermo-analytical quantities is presented herein. Included in this work is a brief survey of the literature together with a discussion of the advantages and shortcomings of some of the most popular approaches, to-date. While the focus is on neat amorphous drugs, both before and after moisture sorption, the methodology presented is readily extended to more complex (e.g. ternary) systems that form a single, homogeneous phase. Six key questions are addressed in the context of how to most accurately determine the amorphous:crystalline solubility ratio: (1) How is the lattice energy of the crystalline phase assessed? (2) What is the role of heat capacity? (3) How does the pK a impact the solubility ratio prediction (for ionizable drugs)? (4) How does one incorporate the effects of moisture sorption on the amorphous phase? (5) How might one characterize (predict) the rate of drug recrystallization under various conditions (since the duration of the solubility enhancement is a kinetic phenomenon)? (6) What is the best approach for linking the (loss in) solubility enhancement to the T g -lowering of the amorphous drug (by water) and vice-versa? In addressing these questions, this work aims to put forth a standardized methodology for determining the amorphous solubility enhancement with improved accuracy., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Water is often readily absorbed by amorphous compounds, lowering their glass transition temperature (T g ) and facilitating their recrystallization (via nucleation-and-growth). At the same time, the increase in moisture content translates to a decrease in both the thermodynamic solubility and intrinsic dissolution rate, as compared to the corresponding dry (pure) amorphous phase, e.g. see [Murdande SB, Pikal MJ, Shanker RM, Bogner RH. 2010. Solubility advantage of amorphous pharmaceuticals: I. A thermodynamic analysis. J Pharm Sci 99:1254-1264.]. In the case of pure indomethacin and felodipine, the solubility advantage of each amorphous phase over its crystalline counterpart were previously determined to be 7.6 and 4.7, respectively, using a new methodology together with basic calorimetric data taken from the literature. Herein, we demonstrate that, theoretically, following the uptake of just ∼0.5% w/w water, the solubility ratios decrease to 6.9 and 4.5, in the same order. Moreover, as the predicted intrinsic dissolution rate (based on the Noyes-Whitney equation) is directly proportional to the solubility advantage of a given amorphous-crystalline pair, it decreases proportionately upon moisture uptake. Applying the methodology presented herein, one can directly predict the extent of T g -lowering observed at any moisture content, for a given amorphous phase. Knowing that value, it is possible to estimate the relative decrease in the solubility and/or intrinsic dissolution rate of the plasticized phase compared to the pure glass, and vice-versa., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Predicting the glass transition temperature (T g ) of mixtures has applications that span across industries and scientific disciplines. By plotting experimentally determined T g values as a function of the glass composition, one can usually apply the Gordon-Taylor (G-T) equation to determine the slope, k, which subsequently can be used in T g predictions. Traditionally viewed as a phenomenological/empirical model, this work proposes a physical basis for the G-T equation. The proposed equations allow for the calculation of k directly and, hence, they determine/predict the T g values of mixtures algebraically. Two derivations for k are provided, one for strong glass-formers and the other for fragile mixtures, with the modeled trehalose-water and naproxen-indomethacin systems serving as examples of each. Separately, a new equation is described for the first time that allows for the direct determination of the crossover temperature, T x , for fragile glass-formers. Lastly, the so-called "Rule of 2/3", which is commonly used to estimate the T g of a pure amorphous phase based solely on the fusion/melting temperature, T f , of the corresponding crystalline phase, is shown to be underpinned by the heat capacity ratio of the two phases referenced to a common temperature, as evidenced by the calculations put forth for indomethacin and felodipine.

Use of amorphous phases can mitigate the low in vivo exposures of poorly soluble, crystalline active pharmaceutical ingredients. However, it remains challenging to accurately predict the solubility enhancement offered even by a pure amorphous phase relative to the crystalline form. In this work, a methodology is presented that allows estimation of the amorphous:crystalline solubility ratio, α, using only measured thermodynamic quantities for each of the pure phases. With this approach, α values of 7.6 and 4.7 were calculated for indomethacin and felodipine, respectively, correlating more closely than previous predictions with the experimentally measured values of 4.9 and 4.7 reported in the literature. There are 3 key benefits to this approach. First, it uses simple mathematical functions to more precisely relate the temperature variations in the heat capacity (Cp) to allow a more accurate estimation of the configurational energy difference between the 2 phases, whereas traditional models typically assume that Cp of both phases are constant(s). Second, the Hoffman equation is leveraged in translating the free energy of crystal lattice formation to the actual temperature of interest (selected to be 25°C/298K in this work), again, for better accuracy. Finally, as only 2 modulated differential scanning calorimetry scans are required (one for each phase), it is attractive from an experimental simplicity standpoint., (Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Regeneration of the lost tissues of the periodontium is an ideal therapeutic goal and has been the subject of much research and ingenious clinical techniques. Reconstructive or regenerative techniques are used either singly or in combination for three main purposes: (1) to regain lost periodontal ligament attachment, (2) to provide a wider zone of attached gingiva, and (3) to cover previously exposed root surfaces.

The establishment of periodontal health should be a primary aim in all treatment plans. The methods by which this can be achieved have been dealt with in previous chapters, but there are a number of situations where integration of these treatment methods with other dental disciplines needs to be clarified. To simplify matters this chapter will consider periodontal implications in three main areas: treatment of drifted anterior teeth, pre-restorative procedures and replacement of missing teeth.

The characterization of orally-delivered peptide pharmaceuticals presents several challenges to analytical methods in comparison to characterization of conventional small-molecule drugs. These challenges include the analysis and characterization of difficult-to-separate impurities, secondary structure, the amorphous solid-state form, and the integrity of enteric-coated drug delivery systems. This work presents the multidisciplinary analytical characterization of a parathyroid hormone (PTH) peptide active pharmaceutical ingredient (API) and an oral formulation of this API within enteric-coated sucrose spheres. The analysis of impurities and degradation products in API and formulated drug product was facilitated by the development of an ultrahigh-performance liquid chromatography (UHPLC) method for analysis by high-resolution mass spectrometry (MS). The use of UHPLC allowed for additional resolution needed to detect impurities and degradation products of interest. The secondary structure was probed using a combination of solution-state NMR, infrared, and circular dichroism spectroscopic methods. Solid-state NMR is used to detect amorphous API in a nondestructive manner directly within the coated sucrose sphere formulation. Fluorescence and Raman microscopy were used in conjunction with Raman mapping to show enteric coating integrity and observe the distribution of API beneath the enteric-coating on the sucrose spheres. The methods are combined in a multidisciplinary approach to characterize the quality of the enteric-coated peptide product.

The isolation, characterization, and bioactivity in the feeding circuitry of a novel neuropeptide in the Aplysia californica central nervous system are reported. The 17-residue amidated peptide, NGGTADALYNLPDLEKIamide, has been termed cerebrin due to its primary location in the cerebral ganglion. Liquid chromatographic purification guided by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry allowed the isolation of the peptide with purity adequate for Edman sequencing. The cerebrin cDNA has been characterized and encodes an 86 amino acid prohormone that predicts cerebrin and one additional peptide. Mapping using in situ hybridization and immunocytochemistry showed that cerebrin containing neuronal somata are localized almost exclusively in the cerebral ganglion, mostly in the F- and C-clusters. Both immunostaining and mass spectrometry demonstrated the presence of cerebrin in the neurohemal region of the upper labial nerve. In addition, immunoreactive processes were detected in the neuropil of all of the ganglia, including the buccal ganglia, and in some interganglionic connectives, including the cerebral-buccal connective. This suggests that cerebrin may also function as a local signaling molecule. Cerebrin has a profound effect on the feeding motor pattern elicited by the command-like neuron CBI-2, dramatically shortening the duration of the radula protraction in a concentration-dependent manner, mimicking the motor-pattern alterations observed in food induced arousal states. These findings suggest that cerebrin may contribute to food-induced arousal in the animal. Cerebrin-like immunoreactivity is also present in Lymnaea stagnalis suggesting that cerebrin-like peptides may be widespread throughout gastropoda.

An HPLC NMR system is presented that integrates a commercial microbore HPLC system using a 0.5-mm column with a 500-MHz proton NMR spectrometer using a custom NMR probe with an observe volume of 1.1 microL and a coil fill factor of 68%. Careful attention to capillary connections and NMR flow cell design allows on-line NMR detection with no significant loss in separation efficiency when compared with a UV chromatogram. HPLC NMR is performed on mixtures of amino acids and small peptides with analyte injection amounts as small as 750 ng; the separations are accomplished in less than 10 min and individual NMR spectra are acquired with 12 s time resolution. Stopped-flow NMR is achieved by diversion of the chromatographic flow after observation of the beginning of the analyte band within the NMR flow cell. Isolation of the compound of interest within the NMR detection cell allows multidimensional experiments to be performed. A stopped-flow COSY spectrum of the peptide Phe-Ala is acquired in 3.5 h with an injected amount of 5 micrograms.

Neuropeptides are a ubiquitous class of signaling molecules. In our attempt to understand the generation of feeding behavior in Aplysia, we have sought to identify and fully characterize the neuropeptides operating in this system. Preliminary evidence indicated that Mytilus inhibitory peptide (MIP)-like peptides are present and operating in the circuitry that generates feeding in Aplysia. MIPs were originally isolated from the bivalve mollusc Mytilus edulis, and related peptides have been identified in other invertebrate species, but no precursor has been identified. In this study, we describe the isolation and characterization of novel Aplysia MIP-related peptides (AMRPs) and their precursor. Several AMRPs appear to have some structural and functional features similar to vertebrate opioid peptides. We use matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to confirm that all 14 AMRPs predicted by the precursor are processed in isolated neurons. Northern analysis, whole-mount in situ hybridization, and immunohistochemistry are used to map the abundant expression of these peptides in the CNS and peripheral tissues such as the digestive tract, vasculature, and the reproductive organs. Physiological studies demonstrate that the rank order of the inhibitory actions of these peptides is different for three target muscles. These results underscore the importance of using a multidisciplinary approach to identifying and characterizing the actions of neuropeptides in an effort to gain understanding of their role in systems of interest. The widespread distribution of the AMRPs indicates that they may be operating in many different systems of Aplysia.

The neuropeptidergic bag cells of the marine mollusc Aplysia californica are involved in the egg-laying behavior of the animal. These neurosecretory cells synthesize an egg-laying hormone (ELH) precursor protein, yielding multiple bioactive peptides, including ELH, several bag cell peptides (BCP) and acidic peptide (AP). While immunohistochemical studies have involved a number of species, homologous peptides have been biochemically characterized in relatively few Aplysiidae species. In this study, a combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) and electrospray ionization Fourier transform ion cyclotron resonance MS is used to characterize and compare the ELH peptides from related opisthobranch molluscs including Aplysia vaccaria and Phyllaplysia taylori. The peptide profiles of bag cells from these two Aplysiidae species are similar to that of A. californica bag cells. In an effort to characterize further several of these peptides, peptides from multiple groups of cells of each species were extracted, and microbore liquid chromatography was used to separate and isolate them. Several MS-based sequencing approaches are applied to obtain the primary structures of bag cell peptides and ELH. Our studies reveal that (&agr;)-BCPs are 100 % conserved across all species studied. In addition, the complete sequences of (&egr;)-BCP and ELH of A. vaccaria were determined. They show a high degree of homology to their counterparts in A. californica, with only a few amino acid residue substitutions.

The first Aplysia californica insulin gene is characterized and its proteolytic processing from prohormone to final peptides elucidated using a combination of biochemical and mass spectrometric methods. Aplysia insulin (AI) is one of the largest insulins found, with a molecular weight of 9146 Da, and an extended A chain compared with other invertebrate and vertebrate insulins. The AI prohormone produces a series of C peptides and also a unique N-terminally acetylated D peptide. AI-producing cells are restricted to the central region of the cerebral ganglia mostly within the F and C clusters, and AI is transported to neurohemal release sites located on the upper labial and anterior tentacular nerves. The expression of AI mRNA decreases when the animal is deprived of food, and injections of AI reduce hemolymph glucose levels, suggesting that the function of insulin-regulating metabolism has been conserved.

Matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry is used to examine the formation of N-pyroglutamate (pGlu) in single, identified neurons from Aplysia. Six pGlu peptides are identified in the R3-14 and the R15 neurons that result from in vivo processing of peptides containing either Glu or Gln at their respective N-termini. Moreover, we show that Glu-derived pGlu is not a sample collection or measurement artifact. The pGlu peptides are detected in isolated cell bodies, regenerated neurites in culture, interganglionic connective nerves, cell homogenates, and collected releasates. We also demonstrate that R3-14 cells readily convert a synthetic N-Glu peptide to its pGlu analogue, indicating the presence of novel enzymatic activity.

Liquid chromatography (LC) has been used extensively for the separation and isolation of peptides due to its high selectivity and peak capacity. An approach combining microbore LC with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS) detection is described to identify peptides in cells and guide the purification of peptides from the marine mollusc Aplysia californica. Direct MALDI-MS of neurons and processes provides molecular mass information for unknown peptides with almost no sample preparation, and LC-MALDI-MS allows the isolation and purification of these peptides from pooled samples, thus enabling new putative neuropeptides to be isolated from complex cellular samples. Both direct MALDI-MS and LC-MALDI-MS are compared in terms of detecting peptides from neuronal samples. Using both approaches, two peaks from Aplysia californica connectives having molecular masses of 5013 and 5021 have been isolated, partially sequenced and identified as novel collagen-like peptides.

Few investigations have studied the long-term fate of bone formed following the technique of guided tissue regeneration. The aim of the present study was to evaluate bone fill around implant fixtures with dehiscence defects and to study its response to loading. Ten patients were treated with overdentures supported by 2 fixtures ad modum Brånemark. A third 7 mm x 3.75 mm diameter fixture was placed for the purposes of the study in the most anterior part of the mandible with a dehiscence defect of 4 to 5 mm on the buccal aspect (and 3 to 4 threads exposed) which was covered with a Gore-Tex membrane and buried beneath the mucosa. Fixtures were exposed after 5 months (stage 2), ball abutments connected and loaded through an overdenture for 1 year. Nine fixtures were functioning well after 1 year of loading, 6 of which were retrieved with a trephine for histological examination and compared with 6 unloaded fixtures retrieved in our previously reported study. The bone area filling the thread profiles (BA%) and the bone to metal contact (BMC%) were measured in the 3 most apical and 3 most coronal thread profiles on the buccal and lingual surfaces. Statistically significant higher BMC% (P < 0.01) were observed in loaded fixtures in the apical regions (buccal: loaded 51%, unloaded 25%; lingual: loaded 49%, unloaded 24%). Differences approached significance for the regeneration site (loaded 22%, unloaded 6%) but were no different for the coronal lingual region (loaded 28%, unloaded 20%). There were no differences for BA%. This study confirms that there is an increase in bone to metal contact with time and following fixture loading and that this may also occur with bone regenerated under Gore-Tex membranes.

Intracellular concentrations of L-citrulline (Cit) and its metabolites are related to nitric oxide synthase (NOS) activity, an enzyme producing the intercellular messenger NO in animal tissues including the nervous system. A capillary electrophoresis system using laser-induced fluorescence detection is described, and methods are developed to monitor the levels of L-arginine (Arg), Cit, and related molecules in identified neurons of the marine slugs, Pleurobranchaea californica and Aplysia californica. The limits of detection for Arg, Cit, L-arginino-succinate, L-ornithine, and L-arginine phosphate range from 50 amol to 17 fmol (5 nM to 17 microM in the neurons under study); these detection limits are significantly lower than actual intracellular levels of the metabolites, allowing the direct assay of single cells. The levels of NOS metabolites in individual neurons varied form 6 (Arg) and 4 mM (Cit) in putative NOS-containing neurons down to < 1 microM (undetectable) levels in many putative NOS-negative cells. The Arg/Cit ratio is independent of cell volume, correlates with NADPH-diaphorase staining, and appears to be a characteristic parameter for the presence of NOS activity in identified neurons.

The major ganglionic connectives in Aplysia are assayed to determine putative neuropeptides. Matrix-assisted laser desorption/ionization mass spectrometry allows direct measurement of peptides in a nerve. Many previously characterized peptides are observed, including APGWamide, buccalins, small cardioactive peptides, and egg-laying hormone. Several unreported peptides are detected in specific nerves, suggesting they may have important physiological roles. Furthermore, novel processing products of the L5-67 precursor peptide and the APGWamide/cerebral peptide 1 prohormone are strongly suggested, and their interganglionic transport demonstrated.

A new design of single tooth implant (AstraTech, Molndal Sweden) featuring a microthreaded conical neck and TiO blast surface was evaluated clinically and radiographically after 2 years in function. Fifteen patients (age range 16 to 48) with missing maxillary anterior teeth (6 central incisors, 8 laterals, 1 bicuspid) had 4, 13 mm and 11, 15 mm implants placed under local anaesthesia and left for a period of 6 months before exposure and abutment connection/crown fabrication. All patients were seen at 4 to 6 monthly intervals for hygienist maintenance. Radiographs using Rinn holders and a long cone technique were taken at the crown insertion and after 1 year (14 subjects) and 2 years (12 subjects). All implants were successfully integrated at stage 2, and no implants have been lost. The internal conical seal design of the abutment/implant interface facilitated connection and there were no cases of abutment screw loosening. No soft tissue problems were observed, and the gingival morphology/health was well maintained. One crown was recemented after 18 months in function, and 1 crown was replaced because of a fracture to the porcelain incisal edge. At crown insertion, the mean bone level was 0.46 to 0.48 mm apical to the top of the implant and there were no statistically significant changes in the bone level over the 2 years of the study. In conclusion, the single tooth Astra implants were highly successful and bone changes within the first 2 years of function were comparable with other systems reporting high long-term success rates.

The aim of the present study was to compare guided tissue regeneration with conventional surgery in matched periodontal defects within the same subject. Twenty pairs of sites in nine subjects were treated. Surgery was performed at both test and control sites on the same visit. Random allocation was not performed until all preparation and root instrumentation had been completed. Test defects were covered with e-PTFE membranes (Gore-Tex) and secured with sutures. Membranes were removed after 5-6 weeks with a second surgical procedure, whereas the control sites were not re-operated. At 12 months probing depth reductions were significantly greater at the Gore-Tex treated sites (P<0.05) but no difference in probing attachment level gains were found when compared with conventional flap surgery.

Results from comparative surgical studies have shown small differences between methods when evaluated over a few years post-surgically. Early interim results suggest that apical repositioning is more effective at reducing probing depth, replaced flaps (such as the modified Widman technique) offer slight advantages in terms of gain in clinical attachment, and procedures which involve extensive bone removal or exposure result in more bone loss and loss of attachment. The replaced flaps should in theory produce better aesthetics than the apical repositioned flap. In the long term however, the former tend to recede slightly whilst there is some coronal rebound in the latter, thereby producing relatively little difference between them when good plaque control is maintained. In all procedures there is loss in height of the interdental tissues, even if the labial tissue is maintained, and this can be aesthetically displeasing to some individuals. However it should also be remembered that effective non-surgical treatment can result in similar changes in tissue height and contour, and there is no guarantee of preservation of pre-existing dentogingival aesthetics. All routine periodontal treatment results in gingival shrinkage to some degree. In many cases periodontal surgery will, in reality, involve a combination of replacement, apical repositioning and resection due to the uneven pattern of disease and different anatomical constraints of the palate, tuberosities and retromolar regions. This is shown in figure 12. In summary the surgical procedures should: 1. Produce well contoured flaps of even thickness which are tailored to the shape of the tooth surfaces and permit good coverage of the alveolar bone and any bone defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontology has witnessed some of the most intensive and extensive research in dentistry over the last 30 years. This has led to a much clearer understanding of the aetiology of periodontal diseases and clinical studies have done much to compare and improve treatment modalities. The wealth of literature can certainly lead to confusion but for the most part should ultimately result in a more rational application of diagnostic and treatment methods. This new series is based upon the authors' wide experience in clinical practice and interpretation of the scientific literature.

Bone augmentation around implant fixtures using the technique of guided tissue regeneration has been described in a number of reports. The aim of this study was to evaluate bone fill around dehiscence defects at matched defects randomly allocated to test (expanded polytetrafluoroethylene; Gore-Tex) or control treatments within the same patient. Six edentulous subjects were treated with overdentures supported by 2 fixtures ad modum Bränemark. In addition, 2 experimental 7-mm fixtures with nearly identical dehiscence defects on the labial aspect were placed in the anterior part of the mandible. Baseline defect heights ranged from 2.5 to 4.0 mm with 2 to 4 threads exposed. The test fixture dehiscence was covered with a Gore-Tex membrane secured with a cover screw. The experimental fixtures were exposed after 5 months at stage 2 surgery and measurements and photographs repeated. The fixtures were then removed with a trephine and processed for histological evaluation. Regeneration of a hard tissue resembling bone was observed in 4 of 6 cases treated with Gore-Tex, amounting to between 95 and 100% elimination of the dehiscence and total coverage of the threads. However, in one of these cases, histological evaluation showed that it was soft tissue and not bone, and in a further case soft tissue regeneration was apparent both clinically and histologically. In another case there was no significant regeneration at either test or control defects. Although there was a trend for the Gore-Tex-treated dehiscences to respond more favourably, the differences in clinical and histological measurements between test and control failed to reach statistical significance.

Immunocytochemical analysis was carried out on samples of 5-, 6-, and 9-week old regenerated soft tissue taken from healing periodontal defects treated by guided tissue regeneration using expanded polytetrafluorethylene (ePTFE) membranes. A panel of monoclonal and polyconal antibodies to cytokeratins, vimentin, and collagen was used to label cells and collagen types I, III, and IV. Epithelium was identified in 7 of the 9 samples examined, in addition to mesenchymal cells staining positively for vimentin and co-distribution of collagen types I, III, and IV in all samples. Clinical observations indicated that exposure of the ePTFE membranes during healing was a frequent occurrence, and the presence and quantity of epithelium found within the healing defect beneath the membrane may be related to the extent to which this occurs.

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.

The aim of this survey was to study the prevalence of juvenile periodontitis in schoolchildren aged 12-19 yr in Lagos, Nigeria. 1001 children, 565 boys and 436 girls, took part in the study. Initially all the children were screened clinically at school according to the recommendations of CPITN. A mirror and WHO 621 pattern probe were used for this examination. Any child with two or more sextants or teeth with CPITN code 3 or one sextant code 4 was taken for a radiographic and full clinical examination. Only 19 children, 12 boys and seven girls, fulfilled these requirements. Of these 19 children, five boys and three girls showed radiographic evidence of bone loss as well as increased probing depths, and were diagnosed as having juvenile periodontitis. The other children showed no evidence of bone loss radiographically, despite maximum probing depths of 4-5 mm. The results indicate a prevalence of juvenile periodontitis of 0.8% in this Negro population.