Biomedical subjects
Publications and source records attributed to J W Harrison.
The decision to place a tooth in the hopeless category is by no means a simple one. There is always the possibility of being wrong, the possibility that this tooth may prove to be the exception and, against all odds, survive as a functioning component of the masticatory apparatus. These are the decisions that make us dentists rather than technicians.
The antibiotic era began in the early 1940s with the clinical use of penicillin. Subsequent discovery, development, and clinical use of other antibiotics resulted in effective therapy against major bacterial pathogens. These drugs were so effective that bacterial infectious diseases were considered by many experts to be under complete therapeutic control. However, the scientific community grossly underestimated the remarkable genetic plasticity of these organisms and their ability, through mutations and genetic transfer, to develop resistance to antibiotics. Infectious diseases are now the world's major cause of death. The cause of bacterial reemergence as a threat to human health and life is the abuse of the "miracle drugs." The ubiquitous nature of antibiotics in the human ecosystem foments bacterial resistance and threatens to eliminate antibiotics as effective drugs for human therapeutic use.
The bacteria causing diseases that are now becoming serious public health threats are neither strange nor exotic, but rather shockingly familiar. Tuberculosis, typhoid fever, meningitis, pneumonia, and septicemias are emerging global threats. The infectious agents causing these serious threats are the same bacteria identified many decades ago. The only difference is that these and other microorganisms are no longer killed by the "miracle drugs" that have kept them at bay for the past six decades. Antibiotic resistance has made potential killers out of bacteria that previously posed little threat to mankind. The indiscriminate and reckless use of antibiotics has led to a fast-approaching crisis in which human dominance of the planet is threatened by single, elementary cells of the microbial world. Part I of this article detailed the causes of the crisis. Part II addresses the solutions that are recommended by national and international authorities and organizations.
Intermediate Restorative Material (IRM) has been advocated as a root-end filling material based primarily on reports of clinical success and various leakage studies. The objectives of this study were to determine the excisional wound healing responses of the periradicular tissues to IRM root-end filling material and to compare this with the wound healing responses to amalgam and orthograde gutta-percha root-end filling materials. Mandibular premolars in dogs were obturated, root-ends resected, and the healing responses associated with root-end fillings of IRM, amalgam, and orthograde gutta-percha were evaluated microscopically and radiographically at postsurgical intervals of 10 and 45 days. The excisional wound healing responses associated with IRM root-end fillings were normal at both postsurgical intervals. There was no evidence of inhibition of dentoalveolar or osseous wound healing associated with IRM, amalgam, or orthograde gutta-percha. Statistical analysis showed no difference in wound healing between the 3 root-end filling materials.
OBJECTIVES: To determine and compare osseous regeneration associated with three guided tissue regeneration membrane types (expanded polytetrafluoroethylene, dense polytetrafluoroethylene, and an absorbable polylactic acid/citric acid ester base) and removal forces required for expanded and dense polytetrafluoroethylene membranes. STUDY DESIGN: Bilateral osseous defects were created in 30 adult rat calvaria; one defect was covered with a test membrane and the other received no membrane (control). After 2 or 4 weeks, forces required for membrane removal from the tissues were electronically determined, and the calvaria removed and decalcified. Sections through the defects were stained and evaluated electronically and microscopically. Data were analyzed statistically. RESULTS: Microscopic evaluation with Mann-Whitney U test revealed that dense polytetrafluoroethylene was associated with significantly greater bone formation than expanded polytetrafluoroethylene (p = 0.02) at 2 weeks and absorbable polylactic acid/citric acid ester base (p = 0.004) at 4 weeks. Electronic evaluation of the linear degree of fill with one way ANOVA and Tukey's test found no significant difference (p > 0.05) among the experimental or the control groups. In addition, the Mann-Whitney U test indicated that removal forces required for dense polytetrafluoroethylene were significantly less than for expanded polytetrafluoroethylene (p = 0.003). CONCLUSIONS: The use of dense polytetrafluoroethylene as a membrane barrier deserves further investigation as it allows osseous regeneration, it is easier to remove from healing soft tissues, and it is inexpensive. A study with larger sample sizes should be conducted.
In the roots and root analogs of mammalian teeth a narrow zone of highly calcified tissue occupies the junction between cementum and dentin. This zone is referred to as "intermediate cementum," despite evidence that it is not a product of cementogenesis (or of dentinogenesis). Studies conducted on teeth of human and nonhuman primates indicate that the intermediate cementum layer contains enamel matrix proteins and is likely a product of Hertwig's epithelial root sheath. The available evidence regarding the development (origin), structure, and composition of intermediate cementum is reviewed, and the potential functions of this layer are assessed to include a possible role in wound healing.
The objective of this study was to determine the effect of demineralization of resected root ends on the temporal and qualitative healing of the dentoalveolar (apical attachment apparatus) and alveolar (osseous) tissues in the excisional wound site created during periradicular surgery. Root end resections to orthograde gutta-percha obturations were performed on the mandibular premolars of six mongrel dogs. Twenty-four experimental root ends were demineralized by citric acid burnishing of the resected surfaces. The remaining 24 standard treatment root ends were not demineralized. Microscopic evaluations at postsurgical intervals from 4 to 45 days revealed that the demineralized root ends were associated with more rapid and complete healing than the nondemineralized root ends. It is proposed that demineralization enhances cementogenesis, the key to dentoalveolar healing, by removing the smear layer barrier and exposing the organic component (collagen fibrils) of resected cementum and dentin.
A study was conducted to compare the marginal apical leakage of root-end filling materials under vacuum and non-vacuum conditions, and to assess the effect of demineralization by application of citric acid to the root ends on the apical marginal leakage of root end filling materials. The root canals of 148 extracted human canines and premolars were handfiled and sealed with gutta-percha and Roth's 801 sealer using cold lateral condensation. The teeth were divided into 8 groups that received retrofilling materials. The materials tested were amalgam, IRM and gutta-percha/sealer with and without successive application of citric acid. Half of the specimens were placed under vacuum conditions in methylene blue dye, and the other half were placed in the dye for the same time period without exhausting air from the flask. The teeth were split longitudinally and the extent of dye penetration was determined with a stereomicroscope and eyepiece micrometer. The most evident difference in dye penetration was found between the positive control groups. Under vacuum conditions, the positive controls showed complete penetration of the unobturated canal system with dye. With passive immersion only partial penetration of the unobturated canal system occurred. Application of citric acid to the root end did not adversely affect the seal of amalgam, IRM or gutta-percha/sealer.
Prosthetic rehabilitation of an edentulous adult with a complete residual cleft of his palates is presented. Lack of retention of his prosthesis made speech and eating difficult. Four osseointegrated dental implants were used to join the right and left maxillae and to provide mechanical retention for a complete overdenture obturator to improve function.
Surgical endodontics has become an important treatment modality in modern dentistry. The evolution and development of this modality has suffered from decades of empiricism, as techniques, concepts, and root-end filling materials were advocated without supporting scientific evidence. The techniques and concepts of periodontal surgery and oral and maxillofacial surgery were long assumed to directly apply to endodontic surgery. Evidence now suggests that certain procedures adopted from other specialties are not indicated for surgical endodontics and, in fact, may be counterproductive. During the past year, the most important developments have emerged in the area of surgical wound healing as it relates to soft tissue management procedures. New techniques and concepts that enhance rapid wound healing and decrease untoward postsurgical sequelae have been proposed.
Information regarding the presence of the free radical scavenging (inactivating, dismutating) enzyme superoxide dismutase in human dental pulp was sought. Free radicals, such as the superoxide anion radical (O2-) and the hydroxyl anion radical (OH.), are powerful biological oxidants produced by phagocytes during the normal tissue response to injury and infection. Also produced is hydrogen peroxide (H2O2), an aggressive oxygen species formed by the reaction of superoxide with itself, i.e., a dismutation in which one molecule of O2- is oxidized by the other. These three reactive oxygen intermediates serve as part of the normal host biological defense mechanism for the inactivation of microorganisms and the breakdown of their toxic products. Both normal and inflamed dental pulps were assayed for the presence of this enzyme. Superoxide dismutase activity was identified in the normal pulpal tissues. There was a slight decrease in activity with age. In the inflamed pulpal tissues, enzyme activity was markedly and significantly increased in comparison to that in the normal tissues. These observations indicate that human dental pulp possesses an endogenous defense mechanism designed to protect the tissue components (cells and matrix) from the toxic effects of the reactive oxygen intermediates. In this regard, the inflammatory response of this specialized and somewhat isolated (compartmentalized) tissue is not unlike that seen in other connective tissues.
Wound healing responses of the tissues of the periodontium following periradicular surgery in rhesus monkeys were evaluated by light microscopy. Part II of this investigation reports the responses of mucoperiosteal and osseous tissues to blunt dissectional wounding resulting from the reflection of triangular or submarginal rectangular flaps. Healing of the dissectional wound is rapid, although slower than the incisional wound. Granulation tissues replaces the fibrin clot in the wound site as early as 4 days after surgery, and is replaced by fibrous connective tissue by 14 days. Minimal differences were found in the temporal and qualitative dissectional wound-healing responses to the two types of flap designs. The periosteum does not survive the flap reflection procedure. The cells of the cambium layer are destroyed and the collagen of the fibrous layer undergoes depolymerization. It is postulated that the depolymerized periosteal collagen plays a role in rapid reattachment of flapped tissues to cortical bone.
This report provides a review of the major biological events that occur in the oral mucoperiosteal tissues following simple surgical wounding. The chronological sequence and interrelationships of mucoperiosteal tissue wound healing responses are described. The objectives of this review are to provide clarification of wound healing terminology and a basic reference source for further investigative research into the wound healing responses to endodontic surgery.
Special and specific immunohistochemical techniques as well as routine transmission electron microscopy were used to identify the presence of von Willebrand factor (vWF), a blood clotting factor essential to normal hemostasis, and Weibel-Palade bodies (WPB's), respectively, in the endothelial cells lining the blood vessels from both normal and inflamed human pulpal tissues. In human endothelial cells, WPB's are peculiar and specialized organelles which store vWF. All classes of blood vessels (capillaries, arterioles, arteries, venules, and veins) were vWF positive. The fine structural studies showed similar results with regard to the presence of WPB's. Interestingly, morphometric analyses conducted on the same tissues using either light or transmission electron microscopy showed that significantly more vWF-positive blood vessels were seen in the inflamed tissues. In agreement with the latter observation, transmission electron microscopy showed that more vascular endothelial cells contained WPB's in the inflamed tissues when compared with the normal tissues. From this it appears that during pulpal inflammation, the cascade of events associated with hemostasis may be activated with the increased synthesis and release of vWF by endothelial cells.
Periradicular surgical procedures were performed on rhesus monkeys and the wound healing responses of the tissues of the periodontium were evaluated by light microscopy. This article, Part I of the investigation, reports the mucoperiosteal tissue wound healing responses to incisional wounds of the triangular and submarginal rectangular flap designs. Little difference was found in the temporal and qualitative healing responses to incisional wounds of the two flap designs. However, the submarginal rectangular design showed less predictable results, with a greater intersample variation of wound healing responses in the earlier postsurgical evaluation periods. Vital connective tissue and epithelium, although not visible clinically, remain attached to the root surfaces following reflection of flaps which include an intrasulcular incision. Preservation of these root-attached tissues prevented apical epithelial down-growth along the root surfaces and loss of soft tissue attachment levels. Vitality of root-attached tissues was preserved by preventing dehydration, avoiding curettement of root surfaces, and using a flap reflection technique which eliminates reflective forces in the intrasulcular incisional wound site.
The antimicrobial properties of two different compositions of sodium hypochlorite were compared in a tube dilution study. Absorbent paper points were contaminated with Streptococcus faecalis or Candida albicans and exposed to 5.25% or 2.62% concentrations of "regular" or "fresh scent" sodium hypochlorite (Clorox) for periods ranging from 15 to 120 s. The points were then removed from the sodium hypochlorite solution, placed into a growth medium, incubated, and the presence or absence of growth recorded. Results showed that formulary changes involved in the manufacture of the "fresh scent" sodium hypochlorite had no apparent effect on its antimicrobial properties, as both compositions proved equally effective against the test organisms at each concentration evaluated.
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A 64-year-old male with a 40-year history of dermatologic disorders is presented. The patient carries diagnoses of neurodermatitis and suspected myosis fungoides on which has been superimposed a factitial dermatitis requiring increasingly extended hospitalizations. Given a very disturbed home life and personality style, the patient showed no incentive for change, and his family and caregivers became increasingly frustrated and distraught. An operant behavioral approach proved helpful to staff in standardizing care and setting realistic expectations. This led to a reversal of a downward course and to a coordinated discharge.