Murine model for analysis of the immune response to oral colonization

The overall aim of this work was to analyze the role of the immune response to a known periodontal pathogen, Actinomyces viscosus T14V, in orally superinfected Balb/c mice. The mice did not contain A. viscosus in the oral cavity prior to superinfection. Colonization by superinfecting A. viscosus was specific for the tooth surface.
When mice were placed on a soft, high-carbohydrate diet and superinfected with varying doses of A. viscosus T14VJ1, all mice became infected. A cell-mediated response to the bacteria was detected only in the low-dose inoculated animals, and only the low-dose mice developed bone loss. No serum antibody to the bacteria was detected in any animal. The response to the bacteria was detected in the cervical lymph nodes, which are the draining lymph nodes for the gingival tissue. The results suggest that the development of an immune response to the periodontal pathogen, A. viscosus T14V, correlated with bone loss in super-infected mice.     

Normal serum bone markers in bisphosphonate-induced osteonecrosis of the jaws

We obtained serum bone markers and other relevant endocrine assays on 5 patients with osteonecrosis of the jaw (ONJ). The assays were C-telopeptide, N-telopeptide, bone-specific alkaline phosphatase, osteocalcin, intact parathyroid hormone, T3, T4, TSH, and Vitamin D 25 hydroxy. Diagnostic criteria for ONJ were those formulated by the American Association of Oral and Maxillofacial Surgeons. Four of our patients were women. Two had metastatic breast cancer and had been treated with zoledronic acid; one had also received pamidronate. Two others had osteoporosis and had been treated with daily alendronate. One man had metastatic prostate cancer treated with zoledronic acid. All patients had been withdrawn from bisphosphonate for at least 6 months. None were taking or had taken corticosteroids. None of the lesions had shown any significant healing and all were still causing the patients considerable distress. Yet the bone markers were within the normal range as measured in our laboratory, except for intact parathyroid hormone, which was slightly elevated in one case of metastatic breast cancer (177 pg/mL). Because the jaws have a greater blood supply than other bones, and a high bone turnover rate, bisphosphonates are highly concentrated in the jaws. This anatomic concentration of bisphosphonates might cause bisphosphonate-osteonecrosis to be manifested exclusively in the jaws and is consistent with our finding of normal serum bone markers in ONJ patients.     

In vivo antibacterial efficacy of ultrasound after hand and rotary instrumentation in human mandibular molars

The purpose of this prospective, randomized, single-blind study was to compare the in vivo antibacterial efficacy of a hand/rotary technique versus a hand/rotary/ultrasound technique in mesial root canals of necrotic mandibular molars. The hand/rotary group consisted of 16 mesial roots prepared with a hand/rotary technique. The hand/rotary/ultrasound group consisted of 15 mesial roots prepared similarly, followed by 1 minute of ultrasonic irrigation per canal with an ultrasonic needle in a MiniEndo unit and 15 mL/canal of 6.0% sodium hypochlorite. Canals were sampled before and after instrumentation and after 1 minute of ultrasonic irrigation. Samples were incubated anaerobically on reduced blood agar for 7 days at 37 degrees C, and colony-forming units (CFUs) were counted. The addition of 1 minute of ultrasonic irrigation resulted in significant (p = .0006) reduction in CFU count and positive cultures (p = .0047). Logistic regression analysis indicated the addition of ultrasonic irrigation was 7 times more likely to yield a negative culture.     

Ostene, a new water-soluble bone hemostasis agent

Traditional formulations of bone wax are composed largely of beeswax and are well known to interfere with bone healing and cause inflammatory reactions. Ostene, a newly available bone hemostasis agent made of water-soluble alkylene oxide copolymers, was evaluated. The soft tissue response to Ostene was compared with bone wax and a polyethylene control after implantation into the paravertebral muscles of three rabbits. After 2 weeks, Ostene elicited no fibrous response, the polyethylene elicited a thin (less than 0.5 mm) fibrous response, and the bone wax was encased in a fibrous capsule 0.6 to 1.0 mm thick infiltrated with inflammatory cells. The effects of Ostene were compared with bone wax in a femur defect model in eight rabbits. Ostene showed no evidence of an adverse response in the cortical defect site, medullary cavity, or the surrounding tissue at 4 and 8 weeks. In contrast, bone wax at both time intervals elicited a foreign body response consisting of fibrous tissue infiltrated by macrophages, giant cells, and lymphocytes at the sites of the bone defects. Bone wax also displaced the bone marrow and interfered with bone ingrowth into the defects. Ostene provides the clinician a water-soluble bone hemostasis material that does not demonstrate the adverse tissue response or the interference with bone healing seen with the use of bone wax.     

The phenotypic characterization of lymphocyte subpopulations in established human periodontal disease

Phenotypic characterization of lymphoid cell subpopulations in the lesionof established chronic inflammatory periodontal disease in man was carried out using indirect immunofluorescence to dectct the presence of human thymocyte antigen, human myeloid antigen, IgG-and IgM-bearing cells in situ in the lesion. The majority of lymphiod cells were IgM-positive T-cells were found. These results suggest that established chronic infalmmatory periodontal disease in man should be considered as a B-cell lesion. The role of the T-cells in the lesion May be primarily one of helper activity, although cell-mediated immune mechanisms cannot be precluded.     

Microvascular changes in cheek-pouch wounds of oophorectomized hamsters following intramuscular injections of female sex hormones

The increased degree of gingivitis during pregnancy may be ascribed to both the influence of bacterial plaque and the action of sex hormones on the microvascular system. The present investigation was undertaken to elucidate the mechanism behind the changes in vascular structure and function in healthy and in slightly inflamed tissues following an increased blood concentration of estrogens, progesterone and chorionic gonadotropin. The cheek-pouch of oophorectomized female hamsters constituted the experimental model. The animals were oophorectomized 7 days prior to the start of the hormone experiments. A micro-wound was produced surgically in the cheek-pouch to leave a defect area with a slightly damaged vascular bed and a surrounding tissue with unaffected circulation as observed by vital microscopy. Irrigation with Tyrode's solution for 10–15 minutes reversed the inflammatory changes in the defect area. A hormone solution (0.2 ml of 5 mg /ml Stilbol^R or progesterone^R or 0.2 ml of 1,500 I.U./ml Gonadex^R) was injected intramuscularly in the hamster's hind leg either once (short term experiments) or daily during a five day period (long term experiments). Estrogen and chorionic gonadotropin caused only minor vascular changes. When progesterone was added to the circulating blood via the hind leg muscle, the resistance of the wound tissue seemed to be lowered and acute inflammation developed in the defect area. The surrounding tissue was unaffected. The symptoms of Inflammation in the wound were more severe than immediately after the surgical procedure as judged by the degree of swelling of the endothelium lining the veins, the number of leucocytes adhering to the vessel walls and the number of micro-thrombi. The findings are discussed in the light of present knowledge of the effects of female sex hormones on intra vascular and perivascular cell structure and function.     

Physical property investigation of contemporary glass ionomer and resin-modified glass ionomer restorative materials

Objectives

The objective of this study was to investigate selected physical properties of nine contemporary and recently marketed glass ionomer cement (GIC) and four resin-modified glass ionomer cement (RMGI) dental restorative materials.

Materials and methods

Specimens (n = 12) were fabricated for fracture toughness and flexure strength using standardized, stainless steel molds. Testing was completed on a universal testing machine until failure. Knoop hardness was obtained using failed fracture toughness specimens on a microhardness tester, while both flexural modulus and flexural toughness was obtained by analysis of the flexure strength results data. Testing was completed at 1 h, 24 h, 1 week, and then at 1, 3, 6, and 12 months. Mean data was analyzed with Kruskal-Wallis and Mann-Whitney (p = 0.05).

Results

Physical properties results were material dependent. Physical properties of the GIC and RMGI products were inferior at 1 h compared to that at 24 h. Some improvement in selected physical properties were noted over time, but development processes were basically concluded by 24 h. A few materials demonstrated improved physical properties over the course of the evaluation.

Conclusions

Under the conditions of this study:

1. 1.

   GIC and RMGI physical property performance over time was material dependent;

2. 2.

   Polyalkenoate maturation processes are essentially complete by 24 h;

3. 3.

   Although differences in GIC physical properties were noted, the small magnitude of the divergences may render such to be unlikely of clinical significance;

4. 4.

   Modest increases in some GIC physical properties were noted especially flexural modulus and hardness, which lends support to reports of a maturing hydrogel matrix;

5. 5.

   Overall, GIC product physical properties were more stable than RMGI;

6. 6.

   A similar modulus reduction at 6 months for both RMGI and GIC produced may suggest a polyalkenoate matrix change; and

7. 7.

   Globally, RMGI products demonstrated higher values of flexure strength, flexural toughness, and fracture toughness than GIC materials.

Clinical relevance

As compared to RMGI materials, conventional glass ionomer restorative materials demonstrate more stability in physical properties.

     

Mutational analysis of candidate genes in 24 amelogenesis imperfecta families

Amelogenesis imperfecta (AI) is a heterogeneous group of inherited defects in dental enamel formation. The malformed enamel can be unusually thin, soft, rough and stained. The strict definition of AI includes only those cases where enamel defects occur in the absence of other symptoms. Currently, there are seven candidate genes for AI: amelogenin, enamelin, ameloblastin, tuftelin, distal-less homeobox 3, enamelysin, and kallikrein 4. To identify sequence variations in AI candidate genes in patients with isolated enamel defects, and to deduce the likely effect of each sequence variation on protein expression and structure, families with isolated enamel defects were recruited. The coding exons and nearby intron sequences were amplified for each of the AI candidate genes by using genomic DNA from the proband as template. The amplification products for the proband were sequenced. Then, other family members were tested to determine their genotype with respect to each sequence variation. All subjects received an oral examination, and intraoral photographs and dental radiographs were obtained. Out of 24 families with isolated enamel defects, only six disease-causing mutations were identified in the AI candidate genes. This finding suggests that many additional genes potentially contribute to the etiology of AI.     

Clinical evaluation of patients with temporomandibular joint implants

PURPOSE: An undetermined number of patients with temporomandibular joint (TMJ) symptoms have been treated with intra-articular disc implants composed of Teflon ethylene/propylene or Teflon polytetrafluoroethylene and aluminum oxide (Proplast-Teflon; Vitek, Houston, TX). These implants have shown the potential to fragment in situ resulting in nonbiodegradable particles that stimulate a giant cell reaction and lead to degeneration of local structures, pain, and limitation of mandibular opening. We examined the possible relationship between TMJ implants and persistent pain, responses to sensory stimuli, quality of life, and systemic immune dysfunction. PATIENTS AND METHODS: This case series (32 patients) were referred from university-based orofacial pain centers and private practices from across the United States. Laboratory and clinical assessments evaluated orofacial pain symptoms, neurologic function, clinical signs and symptoms of rheumatologic disease, physical function, systemic measures of immune function, and behavioral measures. RESULTS: We found that TMJ implant patients appeared to have altered sensitivity to sensory stimuli, a higher number of tender points with a diagnosis of fibromyalgia, increased self-report of chemical sensitivity, higher psychologic distress and significantly lower functional ability. Systemic illness or autoimmune disease was not evident in this series of TMJ implant patients. CONCLUSIONS: Significant problems were noted on clinical assessment of TMJ implant patients. This is a US government work. There are no restrictions on its use.