Comparison of conventional and TACT (Tuned Aperture Computed Tomography) digital subtraction radiography in detection of pericrestal bone-gain

Tuned Aperture Computed Tomography or TACT is a relatively new technique that transforms correlated two-dimensional images into a three-dimensional display. Associating TACT with digital subtraction radiography (TACT-DSR) may enhance its use in the detection of diseases. This study aims to assess observer performance in the task of detecting simulated bone-gain in periodontal defects, comparing conventional and TACT DSR. Buccal, lingual and proximal pericrestal bony defects in a human dry skull were imaged with and without increments of crushed-bone and wax mixtures using standardized vertical bitewing projections, acquired with an intraoral digital receptor in a tomographic X-ray machine. One hundred and twenty pairs of baseline and follow-up images were obtained for each imaging modality. Post-acquisition processing including image-registration, density-correction and subtraction operation were applied to both transmission images and TACT-slices. Eight calibrated observers evaluated the presence or absence of pericrestal bone-gain using a 5-point confidence scale. Details about the location of periodontal defects and the amount of bone-gain for each subtracted image were recorded and used in the statistical analysis. Observer performance and study design factors were analyzed by means of receiver operating characteristic (ROC) curve analysis and ANOVA. Mean values of areas under ROC curves for bone-gain detection performance were 0.82 for conventional DSR and 0.90 for TACT-DSR. TACT-DSR provided statistically superior detection performance of simulated periodontal bone-gain over conventional DSR for tooth-obscured defects (p = 0.001) and for the smallest bone mass (p = 0.024). The findings support TACT-DSR's potential to provide greater sensitivity and technique flexibility in detecting periodontal bone-gain than standard DSR.     

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.