Physical and chemical properties of resin-reinforced calcium phosphate cements.

OBJECTIVES: The purpose of this study was to improve the handling and physical properties of a self-setting, water-based calcium phosphate cement by combining it with polymerizable resins and to study the setting reactions involved. METHODS: Dual-cured composite cements were prepared from a calcium phosphate cement powder and dental monomers that contain carboxylated hydrophilic resins or resin/water mixtures. The setting reaction of the calcium phosphate cement in the presence of the resins was evaluated by pH measurements, infrared spectroscopy, diametral tensile strength, x-ray diffraction analysis, and scanning electron microscopy. RESULTS: Carboxylated resins were chosen because they can form ionic bonds to the mineral filler, which was confirmed by appearance of an infrared absorbance peak at 1552 cm-1 within 24 h after mixing due to the formation of a carboxylate salt. Hydroxyapatite did not develop in composites prepared from resin and calcium phosphate cement. However, composites from calcium phosphate cement, resin and water showed approximately 40% hydroxyapatite. The resulting composite cements have moderately high DTS of 14-15 MPa and high pH. SIGNIFICANCE: Hydrophilic acidic resins allows mixing with water and/or allow rapid diffusion of water into the resinous cement so that the dissolution and reprecipitation processes required for the conversion of the calcium phosphate components to hydroxyapatite can occur. The characteristics of the resulting composite cements suggest that the materials may be useful in pulp capping and/or cavity lining.

Molar efficiency study of chlorinated NPG substitutes in dentin bonding.

This study evaluated and compared the contributions to dentin adhesive bonding of three N-phenylglycine analogues with electron-withdrawing substituents on the aromatic ring. These electron-deficient "N-compounds" included: N-(4-chlorophenyl)-glycine (NCPG), N-methyl-N-(4-chlorophenyl)-glycine (NMNCPG), and N-(3,4-dichlorophenyl)-glycine (NDCPG). An experimental three-step dentin-bonding protocol that consisted of sequential application of acidic ferric oxalate solution, an N-compound in acetone, and a surface-active comonomer in acetone was used. The first and third steps were held constant throughout the study. Each N-compound (NCPG, NMNCPG, NDCPG) was used in step two at ten concentrations ranging from 0.0 mol/L (pure acetone) to 5 x 10(-1) mol/L, depending on solubility. After overnight storage in distilled water, the dentin-to-composite bonds were broken in tension. The data were analyzed with ANOVA, and multiple comparisons were performed with Duncan's Multiple Range test. All statistical tests were controlled at alpha = 0.05. At 5 x 10(-3) mol/L, the relative effectiveness of the three N-compounds (as measured by tensile bond strengths) was NMNCPG > NCPG > NDCPG. Of all concentrations studied, the mean bond strengths produced with NMNCPG were statistically as good as or better than those produced by the other two compounds, and NCPG was always as good as or better than NDCPG. Increased electron-withdrawing from the nitrogen of the amine group by the substituents narrowed the effective concentration range for dentin bonding and, in general, produced lower mean bond strengths between dentin and composite.

Protective coatings for tooth crowns.

Transfer of technology to the dental office could provide thin polymeric coatings over tooth crowns and accessible root surfaces. These coatings can be prepared from relatively inexpensive, commercially available materials in one-step reactions. When the monomer technique becomes available, it will provide caries protection for all of your patients.

Dentin-bonding molar efficiency using N-phenylglycine, N-phenyl-beta-alanine, or N-methyl-N-phenylglycine.

Three structurally related substituted amino acids (N-compounds) were studied in a three-step dentin-bonding protocol. The first step of an acidic ferric oxalate solution and the third step of a surface-active comonomer were held constant throughout the study. In the second step, the amount of the N-compound--either N-phenylglycine (NPG), N-methyl-N-phenylglycine (NMNPG), or N-phenyl-beta-alanine (NPBA)--was varied in acetone from 0 mol/L through 5 x 10(-1) mol/L in seven steps. At 1 x 10(-3) mol/L for NPG and NMNPG, average bond strength values were 7.4 +/- 2.2 and 10.5 +/- 2.7 MPa. The highest bond strength value for NMNPG was at 1 x 10(-2) mol/L, with 13.2 +/- 4.0 MPa. The highest value for NPG was at 1 x 10(-1) mol/L, with a value of 11.8 +/- 2.5 MPa. The average bond strength for NPBA did not differ from zero across the entire range of concentrations. Molar efficiency was defined as the bond strength per mole of these applied N-compounds. For the two N-compounds that did provide adhesion to dentin, NPG and NMNPG, the average bond strengths rose, peaked, and fell as the amounts of applied N-compound were increased. The molar efficiency dropped off as the concentration of applied N-compound rose. The least operator-sensitive and most efficient N-compound, NMNPG, delivered a bond strength equivalent to that of NPG, with 10% of the applied NPG amount.

The effect of catalyst structure on the synthesis of a dental restorative monomer.

The addition product of 2-hydroxyethyl methacrylate (HEMA) and pyromellitic dianhydride (PMDA), known as PMDM, is a mixture of two structural isomers. The para PMDM isomer--currently used in mediating adhesive bonding of restorative materials to hard tooth tissues--is a crystalline solid. The meta isomer is a liquid. In the synthesis of PMDM, the para isomer, which can be purified by crystallization, is usually present to the extent of only 50% of the product mixture. The effect of the amine catalyst structure was studied relative to its role in increasing the yield of the para isomer, either by a reduction in the amount of the meta isomer or by an increase in the extent of overall reaction. The chemical structure of the amine catalyst had an important role in the synthesis of PMDM and influenced the ratio of the isomers. Among aliphatic amines, especially noteworthy as catalysts that gave excellent yields of the para isomer in high purity were N,N-di-isopropyl-ethylamine and hexamethylenetetramine.

Substitutes for N-phenylglycine in adhesive bonding to dentin.

Using bond strength measurements, we investigated a number of related compounds in order to elucidate the role of the surface-active ingredient, N-phenylglycine (NPG), in experimental two-step and three-step bonding protocols resulting in adhesive bonding to dentin. All active compounds identified for the two-step or the three-step protocol were N-aryl-alpha-amino acids, and the results delineate some of the key features of the NPG molecule for bonding. For the three-step protocol, there was a requirement for a secondary or tertiary aromatic amino group, a carboxylic acid group, and a single (secondary or tertiary) methylene unit between those two functional groups of the amino acid. For the two-step protocol, additional substitutions at the para position of the phenyl ring on the amine improved the bond strength. In both protocols, para-methyl- and para-chloro-substituted NPG analogues ranked higher than NPG. A "catalytic" effect of the aromatic tertiary amino group on the polymerization of the adhering resin in both procedures could not be ruled out.

Mechanically-induced generation of radicals in tooth enamel.

Mechanical instrumentation of enamel leads to the formation of long-lived free radicals that can be conveniently measured by electron paramagnetic resonance (EPR) spectroscopy. Powdered enamel tissue exhibited EPR signals remarkably similar to the radicals formed by ionizing radiation. The observations described below lead to the conclusion that physical stress will induce a free-radical formation in dental tissues. These observations have significance for other areas of study such as dosimetry and archeological dating.

Adsorption of N-phenylglycine on hydroxyapatite: role in the bonding procedure of a restorative resin to dentin.

The adsorption of N-phenylglycine (NPG) onto synthetic hydroxyapatite from ethanol solutions was studied to elucidate the role of surface-active moieties in determining the character of adsorption, and to explore the role of NPG in a bonding procedure of restorative resin to dentin. The adsorption isotherm of N-phenylglycine is reversible (and Langmuirian) from ethanol (99.8%). At maximum adsorption the phenyl rings of the adsorbed molecules lie flat on the surface and the carboxylate oxygens and amino nitrogens are anchored to the surface. The N-phenylglycine serves as an amine accelerator since the peroxide containing monomer polymerizes with the adsorbate-covered apatite. The diametral tensile strength of this composite is approximately equal to the composite filled with untreated apatite. The role of various factors contributing to adhesive strength in the bonding procedure is also discussed.

Aneurysmal bone cyst of the hand.

Diagnosis of aneurysmal bone cyst in the hands is confused by rarity (2%) and overlapping characteristics of other lesions, especially benign osteoblastoma and giant-cell tumor. Pseudosinusoidal vascular channels create interfaces between liquid blood (maintained by fibrolysin) and connective tissue cells. The role of trauma is inexplicable.

Thermal effects of polymerization of methyl-methacrylate on small tubular bones.

This study was designed to investigate the thermal effects of polymerization on small tubular bones. The results demonstrated only a slight increase in temperature during cement-curing in the medullary canals of these bones. The maximum rise (11.7 degrees C) was within the levels of tolerance for living bone cells. It was demonstrated that the small volumes of methyl-methacrylate cool more rapidly, hence further decreasing the deleterious effects of heat. The histological studies showed no recognisable adverse reaction to the thermal effects of methyl-methacrylate polymerization on small tubular bones or on the overlying tissue.

Isolated blastomycotic osteomyelitis: a case simulating a malignant tumor of the distal radius.

Blastomycosis osteomyelitis frequently complicates systemic blastomycosis, but it is unusual as an isolated osteolytic lesion in the asymptomatic patient. An isolated blastomycotic osteomyelitis of the distal radius was the initial manifestation of blastomycosis in a healthy young man. The lesion was originally interpreted as a sarcoma. Fungal osteomyelitis must be differentiated from radiologically similar bone neoplasms.

Prosthetic synovitis.

The term "prosthetic synovitis" is applied to reactive changes resulting from a synovial-like membrane formed between a failed prosthesis (noninfected) and the bone interface. This report is the result of light-microscopic and clinical examination of more than 100 specimens obtained at surgery of failed previous hip replacements. The morphology and cell distribution of those tissues removed at surgery in 51 noninfected cemented total hip operations allowed a quantitative estimate of surface cell population by a "touch imprint" technique; qualitative and quantitative estimate (scale, 1 to 4+) of cell population and foreign body materials by light microscopy; and electron microscopy and biochemical analysis of selected samples. Histologic examination included the following cell population, in decreasing order of frequency: acidophilic histiocytes (95%); giant cells (80%); fibronoid material (80%); lymphocyte and plasma cells (26%); and neutrophils (8%). Microscopic examination showed that the largest particles of acrylic cement and shards of high-density polyethylene appeared to be walled off by connective tissue capsules. The majority of smaller particles were incorporated into the histiocyte/macrophage or giant cell population. Histochemistry indicated that these particles elicited "foci" of cellular activity within the synovial-like membrane. This increased activity included the appearance of increased endogenous peroxidase activity in those macrophages within the "foci"; increased betagalactosidae activity among these histiocytes; and a localization of acid phosphates activity within giant cells along the borders of inclusions within the cell cytoplasm. We conclude that wear products resulting from total hip arthroplasty, including the bone cement, can induce increased lysosomal and proteolytic activity within the histiocyte and giant cell populations. It may be important to emphasize that there were "reactive foci" within the membrane and that the entire membrane, even though infiltrated with macrophages, did not respond uniformly to the presence of prosthetic debris. We advance a theory that the first step toward a distractive phenomenon at the interface is micromotion between the cement and bone. Micromotion may be caused by removal of subchondral plate during total hip replacement, leading to fatigue and loss of trabeculae and resultant increase motion, thus bone loss. Bone loss may be the direct result of mechanical injury, increased osteoclasis, or direct lysis of bone by various enzymes released by the interface membrane.

A gross anatomic and histologic study of the innervation of the proximal interphalangeal joint.

The innervation of the proximal interphalangeal joint was studied by gross dissection with magnification and histologic analysis. The joint is innervated by a constant articular branch arising from the palmar proper digital nerve at the level of the midproximal phalanx. This articular nerve bifurcates adjacent to the joint, and its terminal branches enter the joint in the midlateral plane at the junction of the palmar plate and lateral capsule. No contribution to the articular innervation was found to arise from the sensory radial, dorsoulnar cutaneous, and collateral branches of the proper digital nerve that cross the joint. The innervation of the proximal interphalangeal joint is congruent with the palmar sensory innervation and has no relation to the dorsal sensory innervation.

Adjuvant chemotherapy of malignant fibrous histiocytoma of bone.

Malignant fibrous histiocytoma (MFH) is a pleomorphic sarcoma that is uncommon in children. It most frequently arises from the soft tissues; however, it has been recently established that primary bone MFH also exists. Surgical resection or amputation is the cornerstone of treatment for MFH of bone. But, with this modality of therapy alone the majority of patients develop either distant metastases or local recurrence. This study reports on three adolescent girls with MFH of bone who were successfully treated with radical resection and 18 months of adjuvant chemotherapy with vincristine, high dose methotrexate, Citrovorum Factor rescue, and Adriamycin. All three patients remain disease-free for a follow-up period of 42-48 months. The current regimen was well tolerated. Morbidity was minimal, with no patient developing any significant drug-related complications. The adjuvant chemotherapy regimen described appears to be effective in prolonging survival in patients with MFH of bone and appears to warrant further study in additional patients.

HLA-B27-associated spondyloarthritis and enthesopathy in childhood: clinical, pathologic, and radiographic observations in 58 patients.

HLA-B27 typing of all arthritic children helped to identify and focus attention on a subset whose disease was pathogenetically related to and demonstrated clinical features of ankylosing spondylitis and Reiter syndrome, but only rarely fulfilled current diagnostic criteria for those disorders (spondyloarthritis). In contrast to other forms of childhood arthritis, enthesopathy (inflammation at the sites of attachment of ligaments and tendons to bone) was a prominent feature in 75%; a family history of similar arthritis was obtained from 60%; boys were more frequently affected (2:1); urethritis, acute iritis, conjunctivitis, or keratoderma blennorrhagicum occurred at some time in 42%; and the initial attack followed an unexplained febrile illness, known dysentery or urethritis, or severe musculoskeletal trauma in 41%. The arthritis was generally pauciarticular, asymmetric, and primarily in the feet and large joints of the lower extremities. Distinctive radiographic features included periostitis, severe osteopenia, calcaneal erosions, and heel spurs; three of 58 had rapid destruction of a single joint. Only ten patients (all boys) were found to have radiographic sacroiliitis after an average of five years of disease, and only three had the Reiter triad. The lifetime risk of sacroiliitis and spinal ankylosis can only be determined by long-term follow-up of such prospectively identified groups of spondyloarthritic children.

Incidental appendectomy: frequency of pathologic abnormalities.

The incidence of pathologic abnormalities found in the appendix when it is removed incidentally at the time of jejunoileal bypass is reported. Thirty-one per cent of these appendices had significant histopathologic changes. In the authors' opinion these findings support the theory that the appendix may undergo bouts of acute inflammation that are self-limited and that the fibrosis observed in the appendix is a direct sequela of such episodes. In potentially contaminated primary procedures the addition of incidental appendectomy does not increase operative morbidity or mortality.

The effects of a minidose of heparin on peritonitis in rats.

Sprague-Dawley rats with peritonitis treated with either a subcutaneous or intraperitoneal minidose of heparin show a significant increase in survival time when compared with controls. In the treatment groups, adhesions and abscesses were less severe and localized to the area of gangrenous bowel. Heparin also significantly reduced the incidence of recovery of viable bacteria from the blood and peritoneal cavity. These findings may be related to a decreased deposition of fibrinogen within the abdomen or to the early mobilization of fibrin.

Adjuvant arterial embolization in the treatment of benign primary bone tumors in children.

This report presents an initial clinical experience with arterial embolization as adjuvent therapy in the surgical treatment of selected benign primary bone tumors in childhood. Embolization was dramatically effective in 4 children with spinal or pelvic vascular tumors. This technique facilitated local surgical resection and/or curettage. No child had evidence of local recurrence. Three of the 4 children had spinal cord or nerve root compression resulting in various degrees of paralysis prior to surgery. All treated patients had complete recovery from their paralysis. There were no complications of embolization or surgery. The treatment of benign primary bone tumors of the spine and pelvis is immeasurably improved by the adjuvant arterial embolization procedure. The immediate surgical treatment of these difficult tumors now becomes feasible with the greatly diminished blood flow resulting from embolization.