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Objective: To determine why some implants can appear to be well osseointegrated with no signs of infection and yet can remain sensitive to percussion and painful and unable to tolerate the weight of a restoration., Study Design: Five patients were identified who between them had 7 implants that met the criteria of being persistently painful and sensitive to percussion while appearing to be well integrated and otherwise disease free. High-definition cone beam computed tomography scans were obtained for all patients. All patients had failed medical treatment., Results: The cone beam computed tomography scans showed radiolucent channels running from the nearest nerve trunk to the vicinity of the sensitive implants. These may represent neurovascular channels that originally supplied the teeth that were present at the site of the implants, and they may have terminal neuromas that neuromas may be irritated by the implant. In all cases removal of the offending implant caused either substantial or complete relief of discomfort., Conclusion: The presence of terminal neuromas within the jaws may be responsible for persistent pain and sensitivity in an otherwise well-integrated and disease-free implant. Removal of the offending implant appears to be the only treatment., (Copyright © 2021 Elsevier Inc. All rights reserved.)

In the last years numerous investigations of the preferentially neurotropic carcinogenic action of different indirectly alkylating N-nitroso-compounds have been reported. Contrary to these the nuber of experiments, in which the effect of directly alkylating methyl methanesulphonate (MMS) and ethyl methanesulphonate (EMS) was studied is relatively small. Therefore, in own investigations on 4 groups of hooded rats of the inbred strain E the postnatal and prenatal effects of MMS and EMS were studied.

The influence of allogeneic blood transfusions (BT) on experimental tumor growth was investigated in three syngeneic, one allogeneic and one autochthonous tumor model in the rat. Con A induced T-cell response, relative distribution of lymphocyte subsets using flow cytometry and cytotoxic antibodies were determined. No differences in take rate, induction time, incidence and growth rate of tumors were observed in the different models. A significant decrease of cell-mediated immunity and a significant increase of peripheral Ia-positive cells could be observed. The relative distribution of T-cell subsets showed no differences between BT-groups and controls.

In comparison to the known carcinogenic properties of Acetoxymethyl-Methyl-Nitrosamine (AMMN) after oral or intraperitoneal application the dimethylnitrosamine derivative was tested by subcutaneous, intravenous and intrarectal route in male Sprague-Dawley or Wistar rats. AMMN proved to be primarily a locally acting carcinogen. However, a second mode of action is indicated by systemic carcinogenic properties found after i.v. and s.c. applications. The lung and heart, and to a less extent the kidney and earduct were found as target organs of distant carcinogenic response.

Groups 1, 2, and 3 of female Donryu rats were given continuously 400, 200, or 100 ppm solution of 1-methyl-1-nitrosourea (MNU) as their drinking water. The incidence of neurogenic tumors was 12/27 (44%), 39/33 (91%), and 33/36 (92%) in Groups 1, 2, and 3, respectively. Among the neurogenic tumors, neurinomas developing from the spinal nerve roots were the most frequent. In addition, tumors of the digestive tract were found in 12, 1, and 2 rats in Groups 1, 2, and 3, respectively, and tumors in hematopoietic tissues developed in 6 rats. Tumors in other organs were infrequent.

A single dose of 25--100 mg/kg 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) given to BD IX rats at the end of pregnancy gave rise to the development of 10 malignant tumors in 9 out of 39 offspring. The majority of malignomas (6 of 10) were neurogenic tumors (malignant neurinomas).