Management-related outcomes and radiographic findings of idiopathic condylar resorption: a systematic review.

Idiopathic condylar resorption (ICR) is progressive resorption of the condyle of unknown aetiology. There is no consensus on the approaches for diagnostic imaging and management of this disease. The objective of this systematic review was to examine the best practices for imaging and to appraise the success of surgical and non-surgical therapy of ICR. Eleven search engines were queried via explicit literature searches for studies describing ICR, published until 2012. Two authors independently extracted data using predetermined characteristics. Studies that identified patients as having either ICR or progressive condylar resorption and that described the radiographic findings or treatment options were included. Seventeen studies contributing 178 cases met the eligibility criteria. The major radiographic findings, as assessed mostly by two-dimensional imaging, included decreased ramus height, decreased condylar height, altered volume of the condyle, decreased SNB angle and mandibular plane angle, and a retrognathic profile. Treatments included occlusal splints with orthodontic treatment, condylectomy with costochondral graft, and other surgical approaches. This systematic review was limited by the lack of meta-analysis. Nevertheless, we identified the need for future investigations: characterization of findings on three-dimensional imaging and its contribution to treatment planning, outcomes of non-surgical and pharmacological management of ICR, and randomized trials and comparative studies with longer follow-up periods.

Update on the biological effects of ionizing radiation, relative dose factors and radiation hygiene.

Diagnostic imaging is an indispensable part of contemporary medical and dental practice. Over the last few decades there has been a dramatic increase in the use of ionizing radiation for diagnostic imaging. The carcinogenic effects of high-dose exposure are well known. Does diagnostic radiation rarely cause cancer? We don't know but we should act as if it does. Accordingly, dentists should select patients wisely - only make radiographs when there is patient-specific reason to believe there is a reasonable expectation the radiograph will offer unique information influencing diagnosis or treatment. Low-dose examinations should be made: intraoral imaging - use fast film or digital sensors, thyroid collars, rectangular collimation; panoramic and lateral cephalometric imaging - use digital systems or rare-earth film screen combinations; and cone beam computed tomography - use low-dose machines, restrict field size to region of interest, reduce mA and length of exposure arc as appropriate.

An unusual soft tissue radiopacity--radiographic appearance of a dermal filler.

We present a case that describes the radiographic findings of Radiesse, a calcium hydroxyapatitie-based dermal filler. This dermal filler was detected during radiographic examination for implant treatment planning. This case illustrates the typical radiographic appearance of this material and the importance of differentiating it from pathological conditions.

Calmodulin antagonists and cAMP inhibit ionizing-radiation-enhancement of double-strand-break repair in human cells.

Ionizing radiation (IR) enhances double-strand-break (DSB)-repair fidelity in plasmids processed in normal lymphoblasts but not in lymphoblasts from ataxia telangiectasia (A-T) patients. Putatively, signal-transduction pathways mediate this DNA-repair induction. Because IR inhibition of DNA synthesis is defective in A-T cells and is mediated by a calmodulin (caM)-dependent pathway, we evaluated the involvement of caM-dependent pathways in DSB-repair induction. Human lymphoblasts were gamma-irradiated with or without treatment with caM antagonists and the cells' abilities to repair shuttle pZ189 carrying a single DSB (linDNA) were assessed. In untreated controls, IR enhanced DSB-rejoining fidelity if transfection occurred promptly but diminished fidelity if transfection was delayed. Treatment with two caM antagonists, W-7 and W-13, prior to irradiation blocked this IR-enhancement of DSB-rejoining fidelity. Vinpocetine, a caM-dependent phosphodiesterase inhibitor, and 8-bromo-cAMP also inhibited IR enhancement of repair fidelity, but caM-dependent protein kinase II inhibitor KN62 had no effect. Other protein kinase inhibitors, staurosporine and genistein, also did not inhibit IR enhancement of DSB repair fidelity. However, staurosporine blocked the twofold reduction in DSB-repair fidelity seen if linDNA transfection was delayed 2 h after irradiation. These findings point to the involvement of caM/cAMP-dependent pathway(s) in mediating IR-enhancement of DSB-rejoining fidelity in mammalian cells.

Cyclin D1 in parathyroid disease.

Primary hyperparathyroidism (HPT), most commonly due to parathyroid adenoma, is a disorder characterized by excessive secretion of PTH. So far, abnormalities in two genes, cyclin D1 and MEN1, have been implicated in the development of parathyroid adenomas. Cyclin D1, now an established Oncogene involved in numerous human cancers, was first identified and recognized as an Oncogene in the study of parathyroid tumors. A subset of parathyroid adenomas contains a clonal rearrangement that places the PTH gene's regulatory sequences in proximity to the cyclin D1 Oncogene causing its overexpression, and 20-40% of parathyroid adenomas overexpress the cyclin D1 protein. Transgenic animal models have further confirmed the role of cyclin D1 as a driver of abnormal parathyroid cell proliferation. Future studies on the mechanism of cyclin D1's oncogenicity and its interactions with other parathyroid growth regulators will further our understanding of parathyroid cell biology and may prove useful clinically.

Requirement for p53 in ionizing-radiation-inhibition of double-strand-break rejoining by human lymphoblasts.

Ionizing radiation (IR) triggers apoptosis, cell-cycle arrest, and DNA-repair induction in mammalian cells. These responses are mediated by proteins, including p53, which are activated or induced by IR. To determine the role of p53 in double-strand break (DSB) repair following irradiation of mammalian cells, we compared the abilities of unirradiated and irradiated TK6 human lymphoblast line and its derivatives TK6-E6-20C and TK6-E6-5E to repair restriction-enzyme-linearized shuttle pZ189 and the luciferase-reporter plasmid pGL3-control. TK6-E6-20C expresses wild-type p53 like the parental TK6 line, while TK6-E6-5E is p53 null. DSB-rejoining capacity was determined from the ratio of viable progenies arising from DSB-containing plasmids (linDNA) to the number of viable progenies from undamaged, supercoiled plasmids (scDNA). The ratio from the p53wt hosts was two- to three-fold higher than that from the p53null host, using either pZ189 or pGL3-control plasmid. After exposure of both hosts to 0.5 Gy gamma-radiation, DSB-rejoining capacity of p53null increased two-fold compared to unirradiated null controls, if transfection occurred immediately after irradiation. In contrast, the DSB-rejoining capacity of p53wt was unaffected by irradiation. If transfection was delayed for 2 h following irradiation, however, DSB-rejoining declined in both p53wt and p53null hosts. Irradiation also altered DSB-rejoining fidelity, measured from the mutation frequencies, among progenies of pZ189 linDNA. But, unlike rejoining capacity, changes in DSB-rejoining fidelity were similar in p53wt and p53null hosts. Changes in cell-cycle distribution in p53wt and p53null hosts were also similar following irradiation. These findings show that IR increases DSB-rejoining capacity in mammalian cells without functional p53, suggesting that p53 participates in suppressing DSB-rejoining following exposure of mammalian cells to IR.

Heightened induction of c-jun mRNA by PMA, EGF and IL-1 in ataxia telangiectasia lymphoblasts.

PURPOSE: To determine if cells from the cancer-prone autosomal recessive disorder ataxia telangiectasia (A-T) are defective in responding to stimuli other than ionizing-radiation (IR) damage. MATERIALS AND METHODS: The induction of c-jun transcripts by IR, by phorbol 12-myristate 13-acetate (PMA), interleukin 1 (IL-1) and epidermal growth factor (EGF) in normal and A-T lymphoblasts was measured. RESULTS: Treatment with PMA increased c-jun transcripts in a dose- and time-dependent manner two- to three-fold more in A-T than in normal cells. Similarly, treatment with EGF and IL-1 also increased c-jun transcripts more in A-T than in normal lymphoblasts. In contrast, exposure to gamma-radiation increased c-jun transcripts at least twofold more in normal than in A-T lymphoblasts. CONCLUSIONS: These findings indicate that A-T cells are not only defective in responding to IR damage, but also in responding to mitogenic stimuli like IL-1 and EGF. Furthermore, these findings implicate ATM, the gene responsible for the A-T disorder, in the induction of c-jun transcripts by PMA, EGF or IL-1.

Defective modulation of double-strand break repair in ataxia telangiectasia cells by gamma radiation.

Ataxia telangiectasia (AT) cells are defective in responding to damage induced by ionizing radiation. To study the modulation of double-strand break (DSB) repair by ionizing radiation and a defect in such modulation in AT cells, we compared processing of linearized shuttle vector pZ189 (linear DNA) by unirradiated or gamma-irradiated normal and AT lymphoblast hosts. The linear DNA processed in unirradiated AT and normal host cells yielded similar mutation frequencies in the supF-tRNA target gene. Irradiation of normal but not AT host cells decreased plasmid mutation frequency 2-fold if transfection occurred immediately. However, if transfection occurred 2 h after host cell irradiation, mutation frequencies increased 2-fold above those in unirradiated controls in both normal and AT hosts. DSB rejoining capability, based on the ratio of the number of progeny arising from equal amounts of linear DNA and supercoiled, undamaged pZ189, was 25- to 50-fold higher in normal than in AT hosts when both were unirradiated. Irradiation decreased DSB rejoining capability 2- to 5-fold in normal hosts but did not alter that of AT hosts. These findings demonstrate that AT cells normally rejoin DSBs as accurately as normal cells but do so less often, and that AT cells are defective in modulation of DSB rejoining by ionizing radiation.

Evidence of the involvement of p53 in gamma-radiation-induced DNA repair in human lymphoblasts.

PURPOSE: To determine the involvement of p53 in ionizing radiation-induced excision and recombination repair. MATERIALS AND METHODS: Shuttle vector pZ189 containing radiation-induced single strand breaks plus base damage (ocDNA), ultraviolet-radiation damage (uvDNA), or a restriction enzyme-produced double strand break (linDNA) were processed in unirradiated or irradiated p53wt and p53mut lymphoblasts. Mutation frequencies in the supF-tRNA target gene and survival of plasmids processed in p53wt and p53mut hosts were compared. RESULTS: Mutation frequencies of oc-, uv- or linDNA were similar after processing in unirradiated p53wt and p53mut hosts. However, the mutation frequency of ocDNA and uvDNA decreased 50% when processed in irradiated p53wt hosts but was unaltered in irradiated p53mut hosts. In contrast, linDNA mutation frequencies varied similarly whether processed in irradiated p53wt or p53mut hosts: mutation frequency decreased twofold when linDNA was transfected immediately after host irradiation but increased twofold when transfection was delayed by 2h. Double strand break rejoining capacity, determined by the ratio of the number of progenies from linDNA to that from undamaged pZ189, differed both qualitatively and quantitatively in irradiated p53wt and p53mut hosts. CONCLUSIONS: These studies show induction of DNA repair in mammalian cells by ionizing radiation and indicate the involvement of p53 in the modulation of excision repair fidelity and double strand break rejoining capacity.