Preparation and Properties of Nickel Hemoglobin

Hemoglobin A reconstituted with nickel protoporphyrin IX (NiHbA) has been prepared and characterized. Kinetics of its reaction with p-mercuribenzoate and with haptoglobin, absorption and circular dichroism spectra, and x-ray crystallographic properties have been investigated as probes of its structural conformation. The results suggest that NiHbA exists in a structure that is similar to the deoxy, or T-state of HbA. It is proposed that NiHbA and its derivatives may serve as a useful model for future studies of hemoglobin allosteric changes.

Light microscopic and scanning electron microscopic retrieval analyses of implanted biomaterials retrieved from humans and experimental animals

This paper reports analysis obtained from 200 implant cases retrieved from humans and submitted to the American Academy of Implant Dentistry Research Foundation, Medical College of Georgia implant retrieval center. The samples that were not decalcified were embedded in polymethylmethacrylate and examined with scanning electron microscopy and routine light, polarized, or Nomarski microscopy. Cases included both orthopedic and dental implants, as well as entire mandibles and portions of maxillae obtained at autopsy. A significant number of submitted implants had substantial amounts of adhered bone, which permitted evaluation of human bone remodeling to osseointegrated implants. These implants failed because of implant fracture. As was observed with animal studies, healthy bone supported these implants, with the bone containing an interdigitating canaliculi network that provided communication between interfacial osteocytes and osteocytes deeper within the remodeled osteonal and trabecular bone. Early dental implants containing a coating of beads showed a connective tissue interface, which corresponded to the bead surface of specific orthopedic implants that underwent some degree of micromovement. This is in contrast with the excellent response reported for successful contemporary beaded implants. Significant numbers of osseointegrated fractured hydroxyapatite (HA)-coated dental implants demonstrated the adequate serviceability of these implants before biomaterial fracture. In contrast, the HA coating was dissociated from retrieved orthopedic implants, leading to extensive cup loosening and case failure. This study, therefore, underscores the need for evaluation of failed human dental and orthopedic implants. Correlations can be drawn between human retrieval and experimental animal studies.

Effects of triclosan on the cytotoxicity and fungal growth on a soft denture liner

STATEMENT OF PROBLEM

Contamination of removable prostheses with microorganisms, particularly Candida albicans, is a common clinical problem. Microban, a broad-spectrum antimicrobial containing triclosan, recently has been proposed to inhibit microbial growth.

PURPOSE

This study aimed to determine whether the addition of Microban to PermaSoft denture liner prevents the growth of C albicans and affects the cytotoxicity of the PermaSoft material.

MATERIAL AND METHODS

Experimental specimen disks (5 x 1 mm each) with and without incorporated Microban were fabricated aseptically (n = 6) against polyester film to produce a smooth surface. To assess the cytotoxic effect of Microban, the MTT assay was used. To determine the effect of Microban on the growth of C albicans, disks were placed in Transwell dishes, covered with Sabouraud's broth containing an ATCC strain of C albicans, and incubated at 37 degrees C for 24 hours. Wells containing fluorocarbon resin disks or broth alone served as controls. The disks were rinsed to remove unattached C albicans and then sonicated in sterile water to remove surface organisms. Serial dilutions of the water extracts were plated on Sabouraud's agar and returned to the incubator for 24 hours. Colonies were counted with a Brunswick Colony Counter. Growth of C albicans in the internal aspects of the specimens was determined in a manner as previously described, with the exception that the specimens were sonicated to remove surface organisms, minced, and sonicated once more before making serial dilutions. The results were compared with ANOVA and Tukey intervals (alpha=.05).

RESULTS

The number of colonies formed ranged from 17 to 31 x 10(5) (mean = 23 +/- 4 x 10(5)) and 14 to 69 x 10(5) (mean = 32 +/- 20 x 10(5)) for the PermaSoft with and without Microban groups, respectively. There was no statistically significant difference between PermaSoft with and without Microban.

CONCLUSION

The addition of Microban did not significantly alter the cytotoxicity of the PermaSoft denture lining material or reduce the adherence of viable C albicans to the surface of PermaSoft material after 24 hours.

Dental considerations in upper airway sleep disorders: A review of the literature

STATEMENT OF PROBLEM

Upper airway sleep disorders are becoming recognized as common medical concerns. Multiple treatment options have been advocated, including the use of dental devices. Dental practitioners are being asked by the medical profession to become a part of the treatment team. This may be a challenging task because of the large number of dental devices available, rapid advancement in the understanding of this disease, and numerous publications.

PURPOSE

This article reviews the anatomic features and etiologic factors of upper airway sleep disorders and medical and dental treatment options.

METHODS

The literature review was conducted with an accepted literature research tool, PubMed, developed by the National Library of Medicine. Key words searched included "obstructive sleep apnea," "sleep apnea," "sleep disorders," and "snoring".

CONCLUSION

Dental devices are indicated in snoring and mild-to-moderate obstructive sleep apnea patients after medical evaluation and referral.

Retrieval analyses of implanted biomaterials: light microscopic and scanning electron microscopic analyses of implants retrieved from humans

We report analyses obtained from 135 implant cases retrieved from humans and submitted to the American Academy of Implant Dentistry Research Foundation--Medical College of Georgia Implant Retrieval Center. The undecalcified samples were embedded in polymethyl-methacrylate and examined with scanning electron microscopy and with routine light via polarized or Nomarski microscopy. Cases included both orthopedic and dental implants as well as entire mandibles obtained at autopsy. Significant numbers of submitted implants had substantial amounts of adhered bone, which permitted evaluation of human bone remodeling to osseointegrated implants. These implants failed because of implant fracture. As has been observed in animal studies, an interdigitating canaliculi network provided communication between interfacial osteocytes and osteocytes deeper within the remodeled osteonal and trabecular bone. Significant numbers of osseointegrated fractured hydroxyapatite-coated dental implants demonstrated the adequate serviceability of these implants prior to biomaterial fracture. In contrast, the hydroxyapatite coating was dissociated from retrieved orthopedic implants, leading to extensive cup loosening and case failure. Caution is advised for the use of hydroxyapatite-coated acetabular implants. This study therefore underscores the need for evaluation of failed human dental and orthopedic implants. Correlations can be drawn between human retrieval and experimental animal studies.

Histologic and histomorphometric comparison of immediately placed hydroxyapatite-coated and titanium plasma-sprayed implants: a pilot study in dogs

The purpose of this pilot study was to make a histologic and histomorphometric comparison of hydroxyapatite-(HA) coated and titanium plasma-sprayed (TPS) root-form implants that were placed in 2 mongrel dogs immediately after extraction of mandibular premolars. After 8 weeks of healing, the implant-containing segments of the mandible were removed en bloc and bone blocks including implants were sectioned. Histologic and histomorphometric analyses were performed by evaluating bone sections. The mean bone contact percentage of HA-coated implants was 61.84 +/- 7.84%, with a range of 52.09% to 75.7%, and the mean bone contact percentage of TPS implants was 51.35 +/- 12.1%, with a range of 30.1% to 70.6%. This pilot study suggests that HA-coated implants placed into fresh extraction sockets can achieve better bone contact than TPS implants, but there was evidence that the surface of the HA layer can be resorbed, so long-term stability of HA coatings in immediate implantation must be investigated.

The biologic tissue responses to uncoated and coated implanted biomaterials

Ultrastructural examination of the morphology and morphometry of the bone supporting uncoated titanium and ceramic implants was assessed in an experimental animal model involving 120 implants placed into the mandibles of 30 adult mongrel dogs. Further, preliminary morphologic and morphometric observations of the bone supporting uncoated and hydroxylapatite-coated endosteal titanium implants was evaluated in a second investigation involving 72 implants placed into the mandibles and maxillae of 6 additional dogs. A densely mineralized collagen fiber matrix was observed directly interfacing with uncoated implants. The only material interposed between the implant and bone matrix was a 20- to 50-nm electron-dense material suggestive of a proteoglycan. Also seen in these same osseointegrated implants were narrow unmineralized zones interposed between the implant and bone matrix. In these zones of remodeling bone, numerous osteoblasts were observed interacting with the collagen fiber matrix. It was shown that a normal homeostasis of anabolic osteoblastic activity and catabolic osteoclastic activity resulted in bone remodeling and the resultant osseointegration of the implants. Hydroxylapatite-coated implants intimately interfaced with healthy bone. The mineralized matrix extended into the microporosity of the HA coating. This matrix contained viable osteocytes.

Physical-property comparison of a chairside- or laboratory-polymerized permanent soft-liner during 1 year

PURPOSE

This investigation examined the influence of polymerization mode and water storage duration on the Shore A hardness, water sorption, resin solubility, and glass transition temperature of Permasoft, a commercial soft denture liner that is polymerized either chairside or in the laboratory.

MATERIALS AND METHODS

Specimen disks (31-mm diameter x 10 mm thick) and bars (44 x 8.5 x 1.2 mm) were polymerized following manufacturer's recommendations. The chairside polymerization process was simulated by pouring the mixed components into a mold and processing at 70 degrees C for 15 minutes under 2-psi pressure. Laboratory-polymerized specimens of the same dimensions were fabricated by processing under 500-psi pressure at 100 degrees C for 45 minutes. Specimens were stored in distilled water at 37 degrees C for 1, 7, and 30 days, and 6 and 12 months. Specimens were tested for Shore A hardness, water sorption, resin solubility, and glass transition temperature after the prescribed interval. To determine the effects of polymerization mode and storage time on material properties, a repeated-measures ANOVA (hardness data) and a two-way ANOVA (sorption and solubility data) with appropriate post-hoc tests were used.

RESULTS

Shore A hardness values increased from a low of 9.4 (+/- 0.5) units immediately after fabrication to a maximum of 15.9 (+/- 1.1) units after 1 year. Mode of polymerization did not influence hardness (p = .9851). Water-sorption values ranged from 4.2 (+/- 0.2%) of dry weight to 14.7 (+/- 2.5%) after 1 year. Resin solubility varied from 10.3 (+/- 0.6%) of preimmersion weight to 15.4 (+/- 1.1%), and immersion duration had no effect on solubility. In addition, after 1 year of storage, no difference in resin solubility or water sorption was found with respect to cure mode. The glass transition temperature for chairside-polymerized samples approximated -10 degrees C, while that for labpolymerized samples approximated -15 degrees C.

CONCLUSIONS

With regard to the material properties evaluated in this study, clinically processed Permasoft liner was equivalent to the laboratory-processed material.

Histologic evaluation of the periodontium of abutment teeth in combination implant/tooth fixed partial denture

The histologic response of the periodontal tissues of teeth rigidly joined to implants with a fixed partial denture was evaluated using light microscopy. The fourth premolar of a dog was connected to implants placed in the first and second premolar position with a fixed partial denture. The restored teeth were under function for periods of 6, 12, 18, and 24 months, with unrestored fourth premolars as controls. The histology of the periodontal ligament on the fourth premolar was found to be similar in the control and the restored teeth. The periodontal tissues contained a minimal amount of inflammatory cell infiltrate. The crestal bone was cortical in nature, showing no periodontal breakdown. The orientation of the periodontal fibers was easily determined, indicating that minimal remodeling had taken place. The number and morphology of the blood vessels were also similar in the control and the treated teeth. The lack of inflammation and stability of the periodontal tissue suggested that the use of combination implant-to-natural-teeth restorations with rigid joints in this animal model does not result in deleterious effects on the periodontal tissues and that the forces placed on the tissues are within the remodeling capabilities of the teeth.

Ultrastructural analyses of the attachment (bonding) zone between bone and implanted biomaterials

This report presents transmission electron and high voltage transmission electron microscopic observations of bone and associated remodeling tissues directly interfacing with endosteal dental implants. Undecalcified interfacial tissues were serially sectioned from mandibular samples encasing 60 implants placed into 30 dogs. Two-dimensional ultrastructural analyses and three-dimensional stereology showed that osteogenesis adjacent to dental implants is a dynamic interaction of osseous cells and a collagenous fiber matrix. This study showed that the interfacial bone consists of a mineralized collagen fiber matrix associated with an inorganic (hydroxylapatite) matrix. This study suggested that an unmineralized collagen fiber matrix initially is laid down directly at the implant surface, and that this matrix then is mineralized. Osteoblasts interacted with this matrix, eventually becoming encased within developing lacunae during the remodeling process. This process formed the cellular (osteocyte) aspects of the developed bone. Osteocyte processes extended through canaliculi directly to the implant surface. Apparently, these processes also were entrapped within canaliculi during the mineralization events. At times, these processes paralleled the implant surface. The bone-implant interfacial zone was primarily fibrillar (both mineralized and unmineralized) in morphology, with an electron-dense, ruthenium positive deposition. This electron-dense material was approximately 20 to 50 nanometers in thickness, and only this thin layer separated the remodeled mineralized bone from the implant.

Composite morphology of the bone and associated support-tissue interfaces to osseointegrated dental implants: TEM and HVEM analyses

Correlated transmission electron and high-voltage electron microscopic analyses examined the undecalcified bone and associated support tissues of 60 endosseous titanium blade and titanium and ceramic root-form implants in dogs. The implants supported fixed partial dentures for up to 2 years. Data obtained from this investigation suggest that a range of tissues, both mineralized and unmineralized, support osseointegrated dental implants. This study examined the tissues apposing not just isolated aspects of the implant surface, but the entire length of the implant, and found that mineralized and unmineralized tissues existed concurrently. Much of the implant surface was apposed by mandibular bone, and both root-form and blade implants osseointegrated. The densely mineralized collagen fibril matrix was often separated from the implant by only a 20-nm to 50-nm electron-dense, ruthenium-positive deposit. High-voltage electron microscope stereology demonstrated that cellular processes extended directly to the implant from underlying osteocytes. In the same implants, areas containing an unmineralized collagen matrix interposed between the bone and implant surface were observed. In this region osteoblasts interacted with this matrix, and Howship's lacunae, containing vascular elements and osteoclasts, were also observed. The remodeling activities appear to be a homeostasis of catabolic activity (osteoclasts) and metabolic activity (osteoblasts). The apex of the implant was often apposed by a fibrofatty stroma. The support tissue response appears to be the result of the interrelations of osteoblasts, osteocytes, and osteoclasts in association with vascular elements. Therefore, the support tissue response to osseointegrated implants is a dynamic activity that involves the healthy interaction of these cells and tissues along the entire length of the implant.

Prosthetic rehabilitation of the cleft palate patient

This article is a brief overview of prosthodontic and restorative methods used in the treatment of unilateral and bilateral cleft palate patients. Some past, present, and future methods of rehabilitation are discussed.

Lingualized occlusion. An occlusion for all reasons

This authors make practical recommendations for a wide variety of clinical situations, including various anteroposterior and buccolingual arch discrepancies. Many of the ideals of the anatomical and mechanical schools of thought are blended. In addition to being a valuable clinical adjunct, Lingualized Occlusion also has great application in undergraduate dental education. It is a simpler occlusal scheme to teach and learn.

A comparative investigation in dogs: 2-year morphometric results of the dental implant--bone interface

One hundred twenty titanium and ceramic root-form and titanium blade implants were placed into 30 dog mandibles. Twenty-four implants in six control dogs (in situ for 5 months) did not receive prostheses. Ninety-six implants in 24 dogs supported prostheses for 6, 12, 18, or 24 months. Computerized morphometry data presented the percent of the implant surface apposed directly by bone. A three-way factorial analysis of variance was used to assess significance. Individual implant means ranged from 0% (mobile implant) to 71% bone adaptation. From these data, two-stage titanium root-form implants were shown to be apposed by more bone than the other five systems, and overall, titanium implant systems were apposed by more bone than ceramic systems. Between 41% and 50% of the surface of integrated ceramic implants were apposed by bone, whereas between 50% and 65% of the surfaces of titanium implants were apposed by bone. Also, two-stage surgery for blade implants appears important for implant success. Furthermore, the use of Nomarski differential illumination appears to be useful for examining the quality of interfacial bone to correlate with the amount of bone quantified by morphometric protocols.

Swing-lock design considerations for obturator frameworks

The conventional and swing-lock (S/L) obturator prostheses can be highly effective in restoring maxillary defects when careful attention is paid to the principles of framework design. Although the S/L modality has been available since the mid 1960s, its use in maxillofacial prosthetics has been limited, and little information is available in the literature to guide the practitioner. This modality offers a conservative design option that lies somewhere between the conventionally designed obturator prosthesis and the prosthesis designed to use extensive fixed reconstruction or endosseous implants. When the S/L obturator is considered, single, double, or dual labial bar designs are possible and may be required by the length and complexities of the arc of closure. Such designs provide a flexible labial bar that transmits less stress to abutment teeth. This article reviewed conventional obturator framework designs and compared them with S/L designs for similar patient categories.

Transmission electron and high-voltage electron microscopy of osteocyte cellular processes extending to the dental implant surface

Examination of the morphology of osteocytes within the bone supporting endosteal dental implants was performed using conventional transmission and high-voltage transmission electron microscopy (HVEM). The in vivo dog model used 72 implants inserted into the premolar region of 18 experimental animals. Forty-eight implants in 12 dogs were used as anterior abutments for fixed bridges for periods up to 12 months. The mineralized matrix of the supporting bone was either directly apposed to the implant surface or was separated from the implant by a narrow region of unmineralized matrix. Osteocytes were routinely observed to be closely associated with the bone-implant interface, as well as at a distance from the implant. Osteocytes were found to extend cellular processes directly to the implant surface through canaliculi. The osteocyte processes contained microfilaments. The three-dimensional capabilities of HVEM elucidated the nature of these cell processes at the point of exit from the osteocyte, as the processes extended through the mineralized matrix, and as the processes terminated at the implant interface. This report suggests that avenues of communication may exist between the implant and the osseous cells, providing intriguing hypotheses regarding biomechanical forces and osteogenesis at the implant interface. Furthermore, an electron-dense deposit was observed upon the inner confines of the canalicular wall, upon the outer aspects of the osteocyte lacuna, and upon the outer aspect of the bone interfacing the implant.

Osteoblast activity at the dental implant-bone interface: transmission electron microscopic and high voltage electron microscopic observations

The purpose of this report is to present transmission electron microscopic and high voltage transmission electron microscopic (HVEM) observations of a longitudinal investigation examining the activities of osteoblasts and associated tissues apposing titanium and alumina oxide ceramic endosteal dental implants. The HVEM permitted 3-dimensional stereologic observations. All observations were obtained from undecalcified interfacial tissues from this in vivo experimental dog model using commercially available implants placed into the mandible. Two similar implants were placed in both sides of the mandible, with implants in 12 of the 18 dogs supporting fixed bridges for either 6 or 12 months. From the study, we observed that a mineralized matrix exists in direct apposition to the implant. Since bone does not interface the entire length of the implant, other interfacial zones were found to exist which consisted of unmineralized tissues. In such zones, we observed that osteoblasts were routinely found directly at the implant interface to the mandibular bone. These interfacial tissues included unmineralized collagen fibers, proteinaceous material, a finely fibrillar matrix, and the osteoblasts. This study has reinforced the concept that the oral tissue-dental implant interface is a dynamic zone consisting of remodeling activities of the osseous cells and extracellular matrices.

Basic matrices for the matrix-assisted laser desorption/ionization mass spectrometry of proteins and oligonucleotides

In order to examine the importance of pH in the matrix-assisted laser desorption/ionization (MALDI) analysis of proteins and oligonucleotides, 37 highly substituted pyrimidine, pyridine, and benzene derivatives containing basic amino groups were screened as potential matrices. Several of these compounds were useful for the preparation and analysis of samples under neutral and basic pH conditions. The matrix, 2-amino-4-methyl-5-nitropyridine, gave good results with small proteins (up to approximately 12,000 Da). The best results with oligonucleotides were obtained with 2-amino-5-nitropyridine, which was a useful matrix for the analysis of mixed-base oligonucleotides smaller than 20 nucleotides in length and homopolymers of thymidine. In general, oligonucleotide analysis using basic matrices was found to be subject to similar constraints of size and base composition that hold when acidic matrices are used. A major advantage of these newly discovered matrix materials over the more commonly used acidic matrices is that they extend the utility of MALDI to the analysis of acid-sensitive species.

Morphology of the bone that supports endosteal dental implants. Transmission electron microscopic and high voltage electron microscopic observations

The morphologic features of the bone-dental implant interface were investigated using an in vivo dog model. The undecalcified bone and associated support tissues were serially sectioned and examined with both conventional and high voltage transmission electron microscopy. A varied morphologic appearance of the tissues supporting clinically and radiographically appearing integrated implants was observed. Osteoblasts were observed at the implant interface, and osteocytes were routinely seen encased within lacunae extremely close to the implant surface. Often these osteocytes extended cellular projections to the implant surface. The variable tissue types observed were suggestive of healthy lamellar and appositional type mineralization patterns adjacent to the implants.

Osteogenesis at the dental implant interface: high-voltage electron microscopic and conventional transmission electron microscopic observations

The osteogenesis of mandibular bone to endosteal dental implants was examined using an in vivo dog model. One half of the implants examined were unloaded implants, with the remaining one half prosthodontically loaded for 6 months. Undecalcified mandibular implant samples were examined with both high-voltage electron microscopy (HVEM) stereology and routine transmission electron microscopy. The osseous interface to integrated implants was shown to vary in its morphology. Mineralized bone was observed directly apposing the implant, often separated from the implant by an electron-dense deposit of approximately 50 nm. Within this densely mineralized matrix, osteocytes were routinely observed. Adjacent areas were shown to contain slightly wider zones of either a less dense mineralized matrix or, alternatively, unmineralized tissue. Other zones consisted of wider unmineralized matrices containing collagen fibers and osteoblasts. These latter zones were consistent with the appearance of an appositional type of bone growth. Because bone is a dynamic, actively remodeling tissue, a varied morphology of the support tissues to dental implant is not unexpected. Areas of mature bone interfacing with successfully integrated implants were demonstrated, as well as areas adjacent to the mature bone that were undergoing remodeling or mineralization. This study has also shown that HVEM stereology is a valuable research tool to investigate the oral tissue interface with dental implants.

Comparative implant research in dogs: a prosthodontic model

One-hundred twenty endosteal dental implants were inserted bilaterally in the mandibles of 30 adult mongrel dogs after bilateral extraction of all premolars. The 120 implants were evenly divided into one- and two-stage systems and included ceramic and titanium cylindrical root-form implants and titanium blade implants. The research design of this investigation divided the 30 animals into 10 groups of three dogs. This article describes an animal model that is useful in evaluating dental implant designs and compares the results with those from humans. In particular, this article delineates the prosthodontic approach appropriate for this model using one- and two-stage titanium implants. Rexillium alloy fixed prostheses were placed on 32 endosteal implants and 16 natural mandibular molar teeth. The implants and prosthetic components of the Sterio-Oss implant system were used. All prostheses are functional with minimal maintenance. To date, after 1-year of follow-up, none of the implants have been lost and none of the fixed prostheses have required recementation or maintenance other than normal hygiene. Histologic and survival data as well as results with other implant systems will be presented in other reports.

A light and electron microscopic comparison of osseointegration of six implant types

This study compared six commercially available implants placed in an animal model for 5 months. Twelve of the implants were used for light microscopic analysis, and the remaining 12 were used for scanning electron microscopic analysis. With the exception of one implant, newly formed bone was evident in direct apposition to portions of all control implants. The light microscopic and scanning electron microscopic evaluations of the tissues surrounding the six commercially available implant types indicated that initial osseointegration is likely with all types. Implant design, material, and submergibility do not appear to be essential for initial osseointegration to occur as long as a biocompatible material is selected and the implant is placed using minimally traumatic surgical techniques.

Transmission electron microscopic and high voltage electron microscopic observations of the bone and osteocyte activity adjacent to unloaded dental implants placed in dogs

The purpose of this report is to describe ultrastructural observations of the bone and associated tissues supporting 24 unloaded endosteal dental implants placed in mongrel dogs (canis familiaris). The following 3 specific areas of the supporting tissues were targeted: 1) the osteocyte populations; 2) the mineralized collagen fiber matrix of the bone; and 3) an electron dense interfacial deposit. To investigate these areas, transmission electron microscopy and high voltage electron microscopic (HVEM) protocols were emphasized. HVEM permitted stereologic observations. Further, all observations were obtained from undecalcified tissues obtained from animals with commercially available implants placed into the mandible. From the study we observed a mineralization pattern of the implant supporting bone that was similar to those events occurring naturally within the mandibular bone. Osteocyte morphology was similar whether the osteocytes were found well below the implant interface or close to the interface. Osteocytes within lacunae were routinely found close to the implant interface, often extending cellular processes through canaliculi to the bone-implant interface. At the interface, an electron dense deposit approximately 50 nm in thickness was often observed. In interfacial regions, densely mineralized collagen fibers were observed running primarily parallel to the implant surface. This dense mineralized tissue was separated from the interface by a mineralized, but finely fibrillar matrix of approximately 200 nm in thickness.

High-voltage electron microscopy and conventional transmission electron microscopy of the interface zone between bone and endosteal dental implants

The interface between mandibular bone and endosteal dental implants was examined with an in vivo dog model. Undecalcified mandibular implant samples were observed with both conventional transmission electron microscopy and high-voltage transmission electron microscopy (HVEM). Results demonstrated the variable nature of the interfacial support tissues. Mineralized bone was often found within 50 nm of the implant surface, separated from that surface only by an electron dense deposit. Osteocytes were observed close to the interface encased within lacunae extending numerous cellular processes through canaliculi. An osteoblast was also observed directly at the interface within a developing lacuna. Other interfacial areas exhibited a finely fibrillar and more electron lucent morphology. Furthermore, other areas were shown to be composed of wider zones of extracellular products containing collagen fibrils, ground substance, and calcified inclusions. Because bone is an actively growing and remodeling tissue, these different morphological zones around the entire area of the implants would appear to confirm the dynamic tissue response to endosteal dental implants. Further, HVEM stereology was shown to be an exciting research tool to investigate this tissue response.

Simplified technique for the fabrication of a hollow obturator prosthesis using vinyl polysiloxane

A technique in the fabrication of a heat-cured acrylic resin transitional maxillary obturator using vinyl polysiloxane putty instead of wax is demonstrated. The putty allows a decrease in the time of fabrication in both the pattern and the processing stage of the prosthesis.

Secondary structure of human interleukin-3

1. The secondary structure of human interleuken-3 in solution was determined by circular dichroism spectroscopy. 2. The results were then compared with empirical secondary structure predictions based on primary sequence structure of the protein. 3. The two approaches are in extremently close agreement showing the protein to have 40% alpha-helix, 12% total beta-structure and 48% random coil content.

Ultrastructural investigations of the bone and fibrous connective tissue interface with endosteal dental implants

The interface between the tissues of the oral cavity and ceramic and titanium cylindrical endosteal dental implants was investigated with correlated light microscopy, transmission electron microscopy and scanning electron microscopy. This study suggested that mandibular bone can directly interface and form an intimate association with one-stage endosteal dental implants. This potential attachment matrix is composed of a composite of calcified bone, and an osteoid unmineralized matrix in association with an apparent osteogenic connective tissue. Further, results from this study suggested that at a level inferior to the junctional epithelium, and superior to the level of crestal bone, fibrous connective tissue can attach to the dental implant. This non-loadbearing attachment of gingival connective tissue could, by contact inhibition, prevent apical epithelial migration. In association with previously documented epithelial attachment, such apical support and connective tissue attachment appears to suggest that endosteal dental implants can be adequately maintained in the oral cavity.

Scanning electron microscopic studies of the oral tissue responses to dental implants

Scanning electron microscopy (SEM) and its associated technologies have proven invaluable in elucidating the interfacial oral tissue responses to dental implants. Since the dental implant must extend from the mandibular or maxillary jaw, through the oral mucosa, and into the oral cavity, these tissue responses include epithelium, connective tissue and bone. The continual occlusal forces acting upon these tissues reinforce the dynamic character of these tissue responses. Immediately upon implantation, a healing phase begins as a response to the implanted biomaterial. Following this immediate response a longer healing phase occurs, beginning approximately 1 week after implantation, resulting in the modeling of bone to the implant as well as the formation of epithelial attachment to the implant. This later, delayed healing continues throughout the lifetime of the implant since these tissues must die and be replaced by similar tissues. Current dental research employing scanning electron microscopy is now documenting these tissue responses. This paper reviews, in detail, SEM observations of these tissue responses.

Modification of immediate denture sectional impression technique using vinyl polysiloxane

The labial sectional impression technique in the maxillary immediate denture can be done in many different materials with varied results. The use of vinyl polysiloxane putty for this impression technique is demonstrated and shows the superior results both in the ease of use and the detail of the impression surface.

Using a tooth-reduction guide for modifying natural teeth

A simplified method of transferring diagnostic odontoplastic information from the cast to the patient is described. This technique can be used successfully when treating fixed, removable, or combination prosthodontics patients.

Purification and characterization of pituitary bovine somatotropin

Bovine somatotropin (bST) has been isolated from pituitary glands and compared in a variety of chemical analyses and bioassays with somatotropin derived from recombinant Escherichia coli. Comparison of pituitary extracts and purified bST by Western blot analysis of two-dimensional gels suggested that the immunoreactive somatotropin species present in the extract were also present in the purified material, with no significant losses or degradation as a result of the purification method. NH2-terminal sequence analysis indicated the presence of equal quantities of Ala-Phe-Pro-Ala-Met-Ser-Leu-Ser- and Phe-Pro-Ala-Met-Ser-Leu-Ser- sequences. The Met-Ser-Leu-Ser-NH2-terminal sequence, a degradation product observed in NIH standard lots, was not detected. Assay of bioactivity in a bovine liver receptor-binding assay and in a female rat growth assay showed pituitary bST and recombinant methionyl-bovine somatotropin to be equipotent. Tryptic maps and sequence analysis of pituitary-derived somatotropin suggest the presence of isoaspartate derivatization at Asp128.

Prosthodontic principles in the framework design of maxillary obturator prostheses

The Aramany classification system of postsurgical maxillectomy defects is a useful tool for teaching and developing obturator framework designs and enhancing communication among prosthodontists. This article describes a series of Aramany-obturator design templates and discusses the relevant considerations for each. In all situations, a quadrilateral or tripodal design is favored over a linear design because this allows a more favorable leverage design application that will aid in the support, stabilization, and retention of the prosthesis.

Extending the longevity of temporary soft liners with a mono-poly coating

A method has been described that will reduce the incidence of fungal growth and increase the period of resiliency for temporary soft liners. The use of a monopoly coating procedure is limited to temporary soft liners only. The coating will not adhere to the more permanent soft liners such as Molloplast-B (Regneri & Co KG, Karlsruhe, West Germany). The coating, however, can be used on any conventional temporary soft liner with good results.

A study of roles of evolutionarily invariant proline 30 and glycine 34 of cytochrome c

The previous studies (Juillerat, M. A., and Taniuchi, H. (1986) J. Biol. Chem. 261, 2697-2711), using a three-fragment complex (1-25)H X (28-38) X (39-104) of horse cytochrome c, have shown that invariant leucine 32 and partially invariant leucine 35, both buried in the interior, exhibit a striking difference in perturbation of binding fragment (28-38) by substitution with isoleucine. Then the idea has been proposed that the energy states of leucine 32, the Met-80-S-heme-Fe bond and other distant residues such as tryptophan 59 would be coupled to generate extra force while leucine 35 would be less important for such coupling if it were involved. In the present studies we synthesized three (28-38) analogs substituting invariant proline 30 with glycine or invariant glycine 34 with alanine or serine. Thermodynamic and kinetic studies and UV CD and biological activity measurements were carried out on binding of the analogs to complex (1-25)H X (39-104). The results with the ferric form show that perturbations of delta G, delta H, and delta S associated with formation of the intermediate complex and with the ensuing process by the Gly34----Ala or Ser substitution result in weakening the Met-80-S-heme-Fe bond formed in the latter process; in contrast, perturbation by the Pro30----Gly substitution is small. However, the biological activity is more perturbed by the Pro30----Gly substitution than by the Gly34----Ala or Ser; and in the Gly34----Ala or Ser substitution the complex appears to be more readily activated for both formation and disruption of the Met-80-S-heme-Fe bond at 20 degrees C and below than without substitution. In all cases reduction of the heme strengthens the binding of fragment (28-38). However, striking are the increases in perturbation (less negative) of both delta H and delta S for binding of fragment (28-38) to form the ground state on reduction of the heme in the Pro30----Gly, Gly34----Ala or Ser (the present studies), and Leu32----norvaline (the previous studies) substitutions. It is known that fluctuation of the atomic positions of most residues of tuna ferrocytochrome c including Pro30, Leu32, and Gly34 increases on oxidation of the heme and that these three residues are among those showing the least fluctuating atomic positions (Takano, T., and Dickerson, R.E. (1982) in Electron Transport and Oxygen Utilization (Ho, C., ed) pp. 17-26, Elsevier/North-Holland Biomedical Press, New York).(ABSTRACT TRUNCATED AT 400 WORDS)

Thermographic diagnosis in athletes with patellofemoral arthralgia

Pain in front of the knee is common in athletes and is often called patellofemoral arthralgia, but it is difficult to prove that the pain arises in that joint. Thermograms of 30 athletes clinically considered to have patellofemoral arthralgia were compared with those of a similar number of unaffected athletes matched for age and sex. A comparison was also made with thermograms of two older groups of 30 patients with knee involvement from either rheumatoid arthritis or osteoarthritis. Twenty-eight of the athletes with patellofemoral arthralgia had a diagnostic pattern on thermography. The anterior knee view showed a rise in temperature on the medial side of the patella and the medialis knee view showed that this temperature rise radiated from the patellar insertion of the vastus medialis into the muscle itself. The possible aetiological role of quadriceps muscle imbalance in athletes with patellofemoral arthralgia is discussed in relation to these findings.

Titanium: the mystery metal of implant dentistry. Dental materials aspects

A number of important points concerning titanium and its alloys have been discussed. They are summarized as follows. Ti and its alloys, particularly the alpha-beta alloys, possess mechanical properties that make them ideal implant materials. Ti and its alloys oxidize readily in air. This surface oxide is extremely stable in the physiologic environment of the body. The stability and inertness of this surface oxide layer acts to protect Ti from corrosive breakdown when used in the body. The elimination of surface irregularities and contaminants is important when preparing a metal for implantation. Titanium can be coupled with equally passive metals in the body without causing galvanic corrosion.