Parallel-stacked aromatic molecules in hydrogen-bonded inorganic frameworks.

By precisely constructing molecules and assembling these into well-defined supramolecular structures, novel physical properties and functionalities can be realized, and new areas of the chemical space can be accessed. In both materials science and biology, a deeper understanding of the properties and exploitation of the reversible character of weak bonds and interactions, such as hydrogen bonds and π-π interactions, is anticipated to lead to the development of materials with novel properties and functionalities. We apply the hydrogen-bonded organic frameworks (HOFs) strategy to inorganic materials science using the cubic octamer of orthosilicic acid, [Si8O12][OH]8, as a building block, and find that various types of hydrogen-bonded inorganic frameworks (HIFs). We succeed in parallel π-stacking pure benzene, thiophene, selenophene, p-benzoquinone, thiophene·p-benzoquinone, and benzene·p-benzoquinone polymers infinitely. These polymers interact via their π-systems by taking advantage of the flexible pores of the three-dimensional nano-honeycomb HIFs, which consist of periodic wide and narrow segments.

Treating octasilanol [Si8O12][OH]8 with tetramethoxysilane and trimethoxyvinylsilane: a halogen-free synthetic route to alkoxysilyl-substituted double-four-ring siloxanes.

The synthesis of methoxysilyl-substituted siloxanes with a double-four-ring (D4R) framework [Si8O12][OSiR(OMe)2]8 (R = OMe or vinyl) via the dealcoholative coupling between silanol [Si8O12][OH]8 and alkoxysilane was accomplished and achieved a halogen-free synthetic process. The solid-state structure of [Si8O12][OSi(OMe)3]8 was determined via a single-crystal X-ray diffraction analysis.

A catalyst- and additive-free synthesis of alkoxyhydrosiloxanes from silanols and alkoxyhydrosilanes.

A convenient method for the selective synthesis of alkoxyhydrosiloxanes that bear SiH and SiOR2 groups on the same silicon atom, R13Si-O-SiR32-n(OR2)nH (n = 0, 1, or 2), via a simple catalyst- and additive-free dealcoholization reaction between silanols and alkoxyhydrosilanes has been developed. These alkoxyhydrosiloxanes can be easily converted into Si(OR2)3-containing siloxanes by zinc catalyzed alkoxylation and alkoxy-containing silphenylene polymers by platinum catalyzed hydrosilylation.

Methanol extract of mycelia from Phytophthora infestans-induced resistance in potato.

Plants recognize certain microbial compounds as elicitors in their active defence mechanisms. It has been shown that a series of defence reactions are induced in potato plant cells after treatment with water-soluble hyphal wall components prepared from Phytophthora infestans. In this study, a methanol extract from mycelia of P. infestans (MEM), which contains lipophilic compounds, was used as another elicitor for the induction of the defence reactions in potato. MEM elicitor induced reactive oxygen species (ROS), especially O2(-) and H2O2 production, and nitric oxide (NO) generation in potato leaves and suspension-cultured cells. Hypersensitive cell death was detected in potato leaves within 6-8 h after MEM elicitor treatment. The accumulation of phytoalexins was detected by MEM elicitor treatment in potato tubers. In potato suspension-cultured cells, several defence-related genes were induced by MEM elicitors, namely Strboh, Sthsr203J, StPVS3, StPR1, and StNR5, which regulate various defence-related functions. Enhanced resistance against P. infestans was found in MEM-treated potato plants. These results suggested that MEM elicitor is recognized by host and enhances defence activities to produce substances inhibitory to pathogens.

A three-die cast technique for duplicating free gingival form in zirconia crowns: two case reports.

This report describes a duplication technique of free gingival form from a provisional restoration to a zirconia crown. Three die casts were manufactured from a silicone impression with an acrylic resin ring tray. The first die cast was for the zirconia framework, the second for the provisionalized transfer coping, and the third for relining the provisional restoration. A free gingival impression was taken using a provisionalized transfer coping, and a soft gingival cast was manufactured. The depth of free gingival transparency was measured using a zirconia shade plate. Then, the zirconia framework was customized to allow for subgingival porcelain space. This technique seems to contribute to the clinical-laboratory interface in computer-aided design/computer-assisted manufacture restorations.

Intentional Gingival Retraction With Provisional Direct Restoration: A Novel Approach to Facial Crown Lengthening.

INTRODUCTION: Achieving a harmonious marginal gingiva is an important factor in esthetic dentistry. However, surgical crown lengthening of single teeth risks asymmetry of the gingival outline in the esthetic zone. In restorative dentistry, excessive gingival retraction or deep subgingival preparation can cause facial gingival recession. This case report describes a novel approach for facial crown lengthening of single teeth using intentional gingival retraction and provisional direct restoration. CASE PRESENTATION: After administration of anesthesia, facial bone sounding was performed. Gingival retraction cords were pressed into the connective tissue attachment from the mesial to the distal line angle. A provisional direct restoration was then performed. These procedures were repeated until an ideal gingival outline was achieved. CONCLUSION: Intentional gingival retraction with provisional direct restoration appears to be useful for facial crown lengthening of single teeth in periodontal biotypes with thin bone.

A free gingival impression for achieving optimal interdental papilla height: a case report.

Failure to tend to inadequate crown contours in the crown trial can cause long-term disharmony of the free gingival form. This case report describes a novel technique for free gingival impression from a final provisional restoration to a zirconia crown. Two die casts were manufactured from a silicone impression. The first die cast was for the zirconia crown; the second die cast was for the final provisional restoration and the provisionalized transfer coping. A free gingival impression was taken using a provisionalized transfer coping, and a soft gingival model was manufactured. The proximal contact position was managed using the predicted convex curve of the interdental papillae. One year after zirconia crown placement, no inflammation was observed around the pyramidal interdental papillae, and symmetric interdental papilla heights were evident. A free gingival impression using a two die-cast technique appears to be useful for achieving optimal interdental papilla height.

The distances between the facial and palatal papillae in the maxillary anterior dentition.

This study examined the distances between the facial and palatal papillae (DFPP) in the maxillary anterior dentition. A total of 360 filled interdental papillae in 72 study models were examined (Group A: 36 young patients, Group B: 36 adult patients). The DFPP was measured directly on alginate impressions. In Group A, the average DFPP was 1.27 ± 0.6, 1.53 ± 0.42, and 1.83 ± 0.56 mm between the central incisors (CI-CI), central and lateral incisors (CI-LI), and lateral incisor and canine (LI-CA), respectively. In Group B, the respective average DFPPs were 1.3 ± 0.83, 1.38 ± 0.68, and 1.62 ± 0.58 mm. Within the limits of the present study, the average distances between the facial and palatal papillae seem to be useful for setting the proximal contact position.

Isolable p- and m-[((t)Bu2MeSi)2Si]2C6H4: disilaquinodimethane vs triplet bis(silyl radical).

Isomeric p- and m-disilaquinodimethanes 2 and 4 were synthesized by the reductive dehalogenation of the corresponding p- and m-bis(halosilyl)benzenes 1 and 3, respectively, and were isolated and structurally characterized. The X-ray diffraction and solid-state NMR studies of 2 revealed its singlet quinodimethane structure featuring two exocyclic Si═C double bonds with some singlet biradical contribution. In contrast, the X-ray crystallography and EPR measurements of 4 disclosed its biradical nature, described as a triplet ground state bis(silyl radical).

The concept of the interdental gingival midpoint line in cervical line management.

The first purpose of this study was to investigate the relationship between the lowest cervical point and the interdental gingival midpoint (IGM) line in the maxillary anterior region. After marking the lowest cervical points and the mesial and distal interdental gingival midpoints on study models of 77 patients, the shortest distances from the IGM lines that connect both interdental gingival midpoints to the lowest cervical points were measured on silicone impressions. The findings showed that the average position of the lowest cervical points in the central incisors coincides with the IGM line. This position is located 0.24 mm palatally in the lateral incisors, and in the canines 0.3 mm facially from the IGM line. The second purpose of the study was to verify the IGM line concept in cervical line management through some clinical cases. In a thick-flat biotype case using a clinical crown lengthening procedure, the lowest cervical points were adjacent to the IGM lines following long-term coronal gingival growth. In a short-term observation of a thin-scalloped biotype case, untouched facial gingiva increased following interdental gingival augmentation. In a case of Miller class 1 gingival recession, a coronally advanced flap combined with the roll technique was performed based on the IGM line concept. According to the results obtained from this study and these cases, it seems that the IGM line could become a diagnostic standard in cervical line management in periodontal plastic surgery.

Biologic height-width ratio of the buccal supra-implant mucosa.

Recently, esthetic implant dentistry has focused on changes in buccal implant mucosal height. The purpose of this article was to investigate the relationship between the height and width of buccal supra-implant mucosa based on the physiologic mucosal form surrounding the implant. Fourteen patients who had buccal supra-implant mucosal heights of more than 1.5 mm and keratinized mucosa 1 year or more after superstructure placement (average period: 3 years 5 months) were studied. Silicone impressions were taken immediately after superstructures and abutments were removed. The study model used for the measurement process was manufactured using improved dental stone. The height and width of the buccal supra-implant mucosa were measured using digital slide calipers, and the ratio of the height and width was investigated. In all cases, the widths were greater than the heights. The average height of the buccal supra-implant mucosa was 2.17 mm, while the average width was 3.44 mm. The average biologic height-width ratio was 1:1.58. The width was larger in the posterior region than in the anterior. There were no differences in the biologic height-width ratio in terms of the diameter of the implant. These findings indicate that peri-implant soft tissue augmentation procedures resulting in an average biologic height-width ratio of 1:1.5 may provide a stable buccal cervical line around the implant superstructure, even for thin periodontal biotypes.

Buccal and coronal bone augmentation using forced eruption and buccal root torque: a case report.

The following case report describes the buccal and coronal bone augmentation around an irretrievable tooth using forced eruption and buccal root torque for immediate nonsubmerged implant placement. A mandibular left second premolar with degree 2 mobility, severe buccal bone resorption, and interproximal angular bony defects was subjected to forced eruption and buccal root torque. Five months after this process, the tooth was displaced 15 mm coronally and the root apex faced buccally. Buccal and coronal bone augmentation and soft tissue enlargement were evident at reentry surgery. This technique enabled proper implant placement in a situation where the bone was compromised.

Connective tissue-bone onlay graft with enamel matrix derivative for treatment of gingival recession: a case report.

We describe a case of gingival recession in which root coverage and coronal bone regrowth were achieved after treatment with a connective tissue-bone graft and enamel matrix derivative. The connective tissue-bone graft was harvested from a maxillary edentulous area and then curved to fit the root surfaces of the maxillary left central and lateral incisors. Enamel matrix derivative was applied to the root surfaces, and the connective tissue-bone graft was fixed to the interdental bone by a titanium screw. Six months later, the exposed roots were covered with thick gingiva, and coronal regrowth of thick bone was evident at reentry surgery. This technique is useful for esthetic restoration placement with an intracrevicular margin on teeth with a thin, receding gingiva.