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.

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.

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.

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.

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.

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.

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.

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.

Histologic observations of bone remodeling adjacent to endosteal dental implants.

To examine bone morphology associated with endosteal dental implants at various time intervals, we inserted 20 one-stage and 20 two-stage titanium blade implants and 20 one-stage and 20 two-stage titanium root-form implants into 30 dog mandibles. Sixteen implants in 6 control (c) dogs (in situ five months) did not receive bridgework. Sixty-four implants in 24 dogs supported bridges for six, 12, 18, or 24 months. The entire area of the mandible containing the implants was examined by routine light and Nomarski differential interference microscopy (NM) for bone morphology (including osteon orientation) at the implant surface and at regions away from the implant. Control root-form implants were apposed by woven bone, with homogenous compact bone in the cortical plate distant to the implant. After 6 mo of load, immature bone was predominant apposing the implant, but initial osteonal maturation was apparent. NM clearly demonstrated the interstitial and concentric lamellae of the bone. Surprisingly, compact bone formed internal to the cortical plate, an area where trabecular bone is expected. At later periods of load, more mature osteons were seen apposing the implants; however remodeling events were still apparent. These remodeling events extend further away from the implant than was expected if the events resulted only from surgical repair. Also, when the implant inclined so that half was totally in the cortical plate and half in the marrow (in trabecular patterns), osteonal bone appeared to remodel in both areas. Control blade implants and blades loaded for six months were apposed by immature osteons when the implant was placed into the cortical plate. A trabecular meshwork was inferior to the osteonal bone. At 12 mo of load, the bone internal to the cortical plate appeared similar to the lamina dura supporting teeth; however, no PDL existed; the lamina-dura-like pattern directly apposed the implant. Even after 24 mo of load, extensive bone remodeling was apparent adjacent to the implant, markedly different from the bone making up the existing cortical plate. From these data, remodeling activities to blade implants may involve the development of a lamina-dura-like bone morphology after longer periods of load. Osteonal bone was apparent, but only at regions where the implant was inserted into the cortical plate. Further, bone remodeling was apparent even after long periods of load.

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.

Light microscopic and scanning electron microscopic analyses of dental implants retrieved from humans.

This paper reports analyses obtained from 51 implant cases retrieved from humans and submitted to the AAIDRF-MCG Implant Retrieval Center. The undecalcified samples were embedded in PMMA and examined with scanning electron microscopy and with routine light or Nomarski microscopy. Cases included individual implants as well as 2 mandibles obtained at autopsy. Retrieved implants were sometimes shown to be encapsulated with connective tissue (CT), whereas other implants were apposed by bone, with only minimal CT association. In the latter cases, the implants were apposed by substantial amounts of viable bone. Nomarski microscopy disclosed the orientation and close apposition of the collagen bundles comprising the interfacial bone. In these cases where close bone apposition was observed to the implants, implant fracture was often the cause of failure. Periodontal lesions were reported around some implants showing a marked degree of inflammatory cell infiltrate (ICI). This study underscores the need for evaluation of failed human dental implants. Failure of implants placed longer than 10 years ago (perhaps loaded immediately) may be due to loss of bone support, CT encapsulation, and ICI (i.e., biological failure). Failure of more recently placed implants could also be due to this scenario, but failure was more often ascribed to biomaterial failure.

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.