Radiographic bone level around particular laser-treated dental implants: 1 to 6 years multicenter retrospective study.

PURPOSE: The aim of the present retrospective study was to evaluate clinical and radiological outcomes, in terms of implant survival rate, marginal bone loss, and peri-implantitis incidence, of a titanium implants with an innovative laser-treated surface. MATERIALS AND METHODS: A total of 502 dental implants were inserted in four dental practices (Udine, Arezzo, Frascati, Roma) between 2008 and 2013. All inserted implants had laser-modified surface characterized by a series of 20-µm-diameter holes (7-10 µm deep) every 10 µm (Synthegra®, Geass srl, Italy). The minimum follow-up period was set at 1 year after the final restoration. Radiographs were taken after implant insertion (T0), at time of loading (T1), and during the follow-up period (last recall, T2). Marginal bone loss and peri-implant disease incidence were recorded. RESULTS: A total of 502 implants with a maximum follow-up period of 6 years were monitored. The mean differential between T0 and T2 was 0.05 ± 1.08 mm at the mesial aspect and 0.08 ± 1.11 mm at the distal with a mean follow-up period of 35.76 ± 18.05 months. After being in function for 1 to 6 years, implants reported varying behavior: 8.8% of sites did not show any radiographic changes and 38.5% of sites showed bone resorption. The bone appeared to have been growing coronally in 50.7% of the sites measured. CONCLUSION: Implants showed a maintenance of marginal bone levels over time, and in many cases, it seems that laser-modified implant surface could promote a bone growth. The low peri-implant disease incidence recorded could be attributed to the laser titanium surface features that seem to prevent bacterial colonization. Future randomized and controlled studies are needed to confirm the results of the present multi-centrical retrospective analysis.

Comparative evaluation among laser-treated, machined, and sandblasted/acid-etched implant surfaces: an in vivo histologic analysis on sheep.

PURPOSE: The aim of the present in vivo analysis was to evaluate the osseointegration process of titanium implants with three different surfaces (machined, sandblasted and acid-etched, and laser-treated) after 15 and 30 days of healing period. MATERIALS AND METHODS: Thirty-six implants with different surfaces were placed in the iliac crest of four Bergamasca sheep. The implant surfaces tested were sandblasted and acid-etched (group A), laser-treated (group B), and fully machined (group C). Two animals were sacrificed after 15 days while the other two after 30 days. Histological and histomorphometric analyses were performed. RESULTS: After 30 days, the bone tissue layer onto implant groups A and B appeared almost continuous with small marrow spaces interruption, while on the machined surface (group C), larger spaces with marrow tissue alternated with the bony trabeculae onto the titanium surface. Implants in groups A and B showed significantly higher implant contact percentage (BIC%) value than group C (P < 0.05). Moreover, it was observed a BIC% increase in both groups A and B between 15 and 30 days while in the machined group (group C), the BIC% decreased. CONCLUSION: Results from the present in vivo analysis revealed that both sandblasted/acid-etched and laser-treated titanium implants, compared to the machined ones, have higher values of osseointegration in less healing time.

cis-Dichloro(dimethyl sulfoxide-S)(2-methoxypyridine-N)platinum(II).

The title complex, [PtCl(2)(C(6)H(7)NO)(C(2)H(6)OS)], exhibits square-planar geometry. The plane of the pyridine ring makes a dihedral angle of 67.2 (3) degrees with the square plane of the metal center. The S-O bond is nearly aligned with the adjacent Pt-N bond, leaving the methyl groups of the dimethyl sulfoxide ligand to stagger the Pt-Cl bond.

The effect of O6-methylguanine DNA adducts on the adenosine nucleotide switch functions of hMSH2-hMSH6 and hMSH2-hMSH3.

The human homologs of prokaryotic mismatch repair have been shown to mediate the toxicity of certain DNA damaging agents; cells deficient in the mismatch repair pathway exhibit resistance to the killing effects of several of these agents. Although previous studies have suggested that the human MutS homologs, hMSH2-hMSH6, bind to DNA containing a variety of DNA adducts, as well as mispaired nucleotides, a number of studies have suggested that DNA binding does not correlate with repair activity. In contrast, the ability to process adenosine nucleotides by MutS homologs appears to be fundamentally linked to repair activity. In this study, oligonucleotides containing a single well defined O(6)-methylguanine adduct were used to examine the extent of lesion-provoked DNA binding, single-step ADP --> ATP exchange, and steady-state ATPase activity by hMSH2-hMSH3 and hMSH2-hMSH6 heterodimers. Interestingly, O(6)-methylguanine lesions when paired with either a C or T were found to stimulate ADP --> ATP exchange, as well as the ATPase activity of purified hMSH2-hMSH6, whereas there was no significant stimulation of hMSH2-hMSH3. These results suggest that O(6)-methylguanine uniquely activates the molecular switch functions of hMSH2-hMSH6.

DNA guanine-guanine crosslinking sequence specificity of isophosphoramide mustard, the alkylating metabolite of the clinical antitumor agent ifosfamide.

PURPOSE: The purpose of this investigation was to determine the base sequence specificity of isophosphoramide mustard (IPM), the alkylating metabolite of ifosfamide, by crosslinking of designed DNA oligomers in comparison with the clinical alkylating agents mechlorethamine (ME) (nitrogen mustard) and phosphoramide mustard (PM), the alkylating metabolite of cyclophosphamide. METHODS: IPM, as well as PM and ME were each reacted with three dodecameric duplexes, which were designed to detect interstrand crosslinking between guanines in 5'-GC-3' (I), 5'-GNC-3' (II) or 5'-GNNC-3' (III) sequences (N = A or T). RESULTS: All three agents preferentially react with 5'-GNC-3' target sequences. The 5'-GNNC-3' target sequence is less reactive by a factor of approximately 2.5- to 10-fold, while 5'-GC-3' is of even lower reactivity. CONCLUSION: These results indicate that all three agents show approximately equal preference for reaction with a 5'-GNC-3' target sequence in spite of the fact that IPM yields a 7-atom crosslink, while the other two agents yield 5-atom crosslinks.

DNA polymerase II (polB) is involved in a new DNA repair pathway for DNA interstrand cross-links in Escherichia coli.

DNA-DNA interstrand cross-links are the cytotoxic lesions for many chemotherapeutic agents. A plasmid with a single nitrogen mustard (HN2) interstrand cross-link (inter-HN2-pTZSV28) was constructed and transformed into Escherichia coli, and its replication efficiency (RE = [number of transformants from inter-HN2-pTZSV28]/[number of transformants from control]) was determined to be approximately 0.6. Previous work showed that RE was high because the cross-link was repaired by a pathway involving nucleotide excision repair (NER) but not recombination. (In fact, recombination was precluded because the cells do not receive lesion-free homologous DNA.) Herein, DNA polymerase II is shown to be in this new pathway, since the replication efficiency (RE) is higher in a polB+ ( approximately 0. 6) than in a DeltapolB (approximately 0.1) strain. Complementation with a polB+-containing plasmid restores RE to wild-type levels, which corroborates this conclusion. In separate experiments, E. coli was treated with HN2, and the relative sensitivity to killing was found to be as follows: wild type < polB < recA < polB recA approximately uvrA. Because cells deficient in either recombination (recA) or DNA polymerase II (polB) are hypersensitive to nitrogen mustard killing, E. coli appears to have two pathways for cross-link repair: an NER/recombination pathway (which is possible when the cross-links are formed in cells where recombination can occur because there are multiple copies of the genome) and an NER/DNA polymerase II pathway. Furthermore, these results show that some cross-links are uniquely repaired by each pathway. This represents one of the first clearly defined pathway in which DNA polymerase II plays a role in E. coli. It remains to be determined why this new pathway prefers DNA polymerase II and why there are two pathways to repair cross-links.

Evidence for a recombination-independent pathway for the repair of DNA interstrand cross-links based on a site-specific study with nitrogen mustard.

DNA-DNA interstrand cross-links are thought to be important for the cytotoxicity of many chemotherapeutic agents. To study this more definitively, adduct site-specific methods are used to construct a plasmid with a single nitrogen mustard interstrand cross-link (inter-HN2-pTZSV28). Replication efficiency (RE = [colonies from (inter-HN2-pTZSV28)/(control with no cross-link)]) is approximately 0.3 following transformation into Escherichia coli, implying that the cross-link is repaired. The commonly accepted pathway for cross-link repair, which involves both nucleotide excision repair (NER) and recombination, is ruled out since RE is approximately 0.3 in a delta recA strain. Non-RecA-directed recombination such as copy-choice is also unlikely. However, NER is involved since RE was approximately 0.02 in strains deficient in NER. Base excision repair is not important since RE is approximately 0.3 in strains deficient in 3-methyladenine DNA glycosylases I and II, FAPY DNA glycosylase, both known apurinic/apyrimidinic endonucleases, or DNA deoxyribophosphodiesterase. Another hypothetical repair pathway hinging on a 5' --> 3' exonuclease activity is unlikely since RE is approximately 0.3 in cells deficient in either the 5' --> 3' exonuclease activities of DNA polymerase I, exonuclease VII, or RecJ. Thus, aside from NER, it is unclear what else participates in this recombination-independent repair pathway, although a pathway involing NER followed by replicative bypass of the lesion is the current working hypothesis. Psoralen interstrand cross-links appear not to be repairable by this second pathway, which may have implications for the relative cytotoxicity of interstrand cross-links from different agents.

Early- and Late-Lanthanide Pyridinethiolates: Synthesis, Redox Stability, and Structure.

The early and late lanthanides form stable complexes with the pyridinethiolate (2-S-NC(5)H(4), or SPy) ligands. The Ce compound Ce(SPy)(3) is relatively insoluble in neutral organic donor solvents such as THF or pyridine but can be solubilized by the addition of [PEt(4)][SPy] to form the orange homoleptic cerium thiolate [PEt(4)][Ce(SPy)(4)] (1). Low-temperature structural characterization of 1 showed that the complex is isostructural with the known Eu(III) derivative. Further oxidation of Ce(III) with dipyridyl disulfide does not occur. Molecular 1 is colored due to a low-energy f(1)-to-d(1) promotion. As the size of the lanthanide ion decreases, the solubility of neutral Ln(SPy)(3) appears to increase. Colorless [PEt(4)][Ln(SPy)(4)] (Ln = Ho (2), Tm (3)) can also be isolated by fractional crystallization, and the compounds are isostructural with the Ce and Eu derivatives. The neutral complexes of Ho and Tm are also slightly soluble in acetonitrile and dimethoxyethane and very soluble in pyridine. Both divalent and trivalent Yb complexes of the pyridinethiolate ligand dissolve in and crystallize from pyridine. Divalent Yb(SPy)(2) crystallizes as the pentagonal bipyramidal molecule (py)(3)Yb(SPy)(2) (4). One pyridine nitrogen and the four donor atoms of the two pyridinethiolate ligands are bound in equatorial positions, and two neutral pyridine ligands occupy the axial sites. The Yb(III) compound crystallizes readily from pyridine as molecular 8-coordinate (py)(2)Yb(SPy)(3) (5). Compounds 4 and 5 are intensely colored; 4 has a visible Yb(II)-to-pyridine charge transfer excitation that is virtually identical in energy to the analogous excitation in SmI(2)(py)(4), while 5 has a visible S-to-Yb charge transfer absorption. Crystal data (Mo Kalpha, 153(5) K) are as follows: 1, monoclinic space group P2/n, a = 15.118(6) Å, b = 16.117(4) Å, c = 26.443(7) Å, beta = 90.14(3) degrees, Z = 4; 4, monoclinic space group Cc, a = 10.588(1) Å, b = 16.810(3) Å, c = 14.833(5) Å, beta = 109.12(2) degrees, Z = 4; 5, monoclinic space group P2(1)/n, a = 9.672(2) Å, b = 16.293(4) Å, c = 19.214(3) Å, beta = 101.51(2) degrees, Z = 4.

Electrophoretic and chromatographic separation methods used to reveal interstrand crosslinking of nucleic acids.

Several electrophoretic and chromatographic techniques, many of which have only been developed recently, provide sensitive methods for the detection and separation of DNA containing interstrand crosslinks such as those produced by many cancer chemotherapeutic drugs and photoactive psoralen derivatives. Most of the methods rely on the fact that the presence of such crosslinks prevent the complete denaturation of the two complimentary DNA strands by heat or alkali. A simple and highly sensitive neutral agarose gel electrophoresis method is particularly applicable to detailed time-course experiments of both total crosslink formation, and the "second-arm" of the crosslink reaction. This method separates denatured single-stranded from double-stranded DNA which has reannealed as a result of an interstrand crosslink. Polyacrylamide gel-based assays using denaturing gels are more suited to the separation of smaller crosslinked DNA fragments and, in particular, small oligonucleotides on high-percentage gels. In addition, they provide methods for the determination of the exact base position and sequence selectivity of crosslink formation. Sephadex chromatography and high-performance liquid chromatography can separate small crosslinked oligonucleotides from non-crosslinked duplexes, and the hydroxyapatite column chromatographic separation of single- and double-stranded cellular DNA can be used to quantitate the level of interstrand crosslinking present in the bulk of the genome. Finally, the analysis of damage by crosslinking agents, and its repair, at the level of specific genes can be achieved by hybridization with specific probes following membrane transfer from neutral agarose gels used to fractionate restricted and fully denatured genomic DNA from drug-treated cells.

Structure of a platinum(II) complex of levamisole.

Chloro(ethylenediamine)[(-)-2,3,5,6-tetrahydro-6-phenylimidazo[2, 1-b]thiazole]platinum(II) chloride, [PtCl(C2H8N2)(C11H12N2S)]Cl, M(r) = 530.39, orthorhombic, P2(1)2(1)2(1), a = 31.676 (11), b = 8.190 (2), c = 6.6242 (6) A, V = 1718.5 (7) A3, Z = 4, Dx = 2.050 g cm-3, lambda (Mo K alpha) = 0.71069 A, mu = 86.8 cm-1, F(000) = 1016, T = 296 K, final R = 0.030 for 1646 unique observed reflections [F > 4 sigma (F)]. The Pt coordination is square planar, bonded to three N atoms (one from the levamisole and two from the ethylenediamine moiety) and to one Cl atom.

Two structurally related diaziridinylbenzoquinones preferentially cross-link DNA at different sites upon reduction with DT-diaphorase.

The nucleotide sequence preferences for the formation of interstrand cross-links induced in DNA by 2,5-diaziridinyl-1,4-benzoquinone (DZQ) and 3,6-dimethyl-2,5-diaziridinyl-1,4-benzoquinone (MeDZQ) were studied using synthetic duplex oligonucleotides and denaturing polyacrylamide gel electrophoresis (PAGE). Reaction of these bifunctional alkylating agents with a DNA duplex containing several potential cross-linking sites resulted in the formation of cross-linked DNAs with different electrophoretic mobilities. Analysis of the principal cross-linked products by piperidine fragmentation revealed that the preferential site of cross-linking was altered from a 5'-GNC to a 5'-GC sequence upon reduction of DZQ to the hydroquinone form by the enzyme DT-diaphorase. In contrast, the reduced form of MeDZQ was found to preferentially cross-link at 5'-GNC sites within the same sequence. These preferences were confirmed in duplex oligonucleotides containing single potential cross-linking sites. Additional minor cross-linked products were characterized and revealed that DZQ and MeDZQ are both capable of cross-linking across four base pairs in a 5'-GNNC sequence.

Alteration in DNA cross-linking and sequence selectivity of a series of aziridinylbenzoquinones after enzymatic reduction by DT-diaphorase.

DT-diaphorase (DTD) mediated reduction of a series of 2,5-bis-substituted-3,6-diaziridinyl-1,4-benzoquinones was found to increase the level of DNA interstrand cross-linking (ISC) formed at neutral pH with an enhancement observed as the pH was decreased to 5.8. The analogues used were symmetrically alkyl-substituted carbamoyl ester analogues of AZQ (D1-D7), 3,6-diaziridinyl-1,4-benzoquinone (DZQ), the 2,5-dimethyl derivative (MeDZQ), and a 2,5-bis[(2-hydroxyethyl)amino] analogue (BZQ). At pH 5.8, the level of DNA ISC induced by enzymatic reduction was as follows: DZQ greater than MeDZQ much greater than D1 (methyl) greater than D3 (n-propyl) greater than D2 (AZQ; ethyl) greater than D5 (n-butyl) greater than D7 (sec-butyl) greater than D4 (isopropyl) D6 greater than (isobutyl). A similar trend was observed at pH 7.2. The level of DNA ISC induced by BZQ, which is not a substrate for DTD, was not increased by enzymatic reduction. Dicumarol, a known inhibitor of DTD, was capable of inhibiting the DNA ISC induced by these quinones upon enzymatic reduction. MeDZQ and DZQ reacted with guanines, as measured by Maxam and Gilbert sequencing, with a sequence selectivity similar to that of the nitrogen mustard class of antitumor agents. Enzymatic reduction of DZQ and MeDZQ by DTD was found to alter their sequence-selective alkylation. Reduced DZQ showed enhanced guanine alkylation in 5'-GC-3' sequences and new sites of adenine alkylation in 5'-(A/T)AA-3' sequences. Reduced MeDZQ only showed new sites of adenine alkylation at 5'-(A/T)AA-3' sequences but no enhancement of guanine alkylation. The new sites of adenine alkylation were found to be inhibited in the presence of magnesium and rapidly converted into apurinic sites.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA cross-linking and sequence selectivity of aziridinylbenzoquinones: a unique reaction at 5'-GC-3' sequences with 2,5-diaziridinyl-1,4-benzoquinone upon reduction.

Several bifunctional alkylating agents of the aziridinylbenzoquinone class have been evaluated as potential antitumor agents. 3,6-Bis[(2-hydroxyethyl)amino]-2,5- diaziridinyl-1,4-benzoquinone (BZQ), 2,5-diaziridinyl-1,4-benzoquinone (DZQ), 3,6-bis(carboxyamino)-2,5-diaziridinyl- 1,4-benzoquinone (AZQ), and six analogues of AZQ have been studied for their ability to induce DNA interstrand cross-linking, as measured by an agarose gel technique, and to determine whether they react with DNA in a sequence-selective manner, as determined by a modified DNA sequencing technique. At an equimolar concentration (10 microM), only DZQ and BZQ showed any detectable cross-linking at pH 7 without reduction. Cross-linking was enhanced in both cases at low pH (4). Reduction by ascorbic acid at both pH's increased the cross-linking, which was particularly striking in the case of DZQ. In contrast, AZQ and its analogues only produced a significant level of cross-linking under both low-pH and reducing conditions, the extent of cross-linking decreasing as the size of the alkyl end group increased. The compounds reacted with all guanine-N7 positions in DNA with a sequence selectivity similar to other chemotherapeutic alkylating agents, such as the nitrogen mustards, although some small differences were observed with BZQ. Nonreduced DZQ showed a qualitatively similar pattern of reactivity to the other compounds, but on reduction (at pH 4 or 7) was found to react almost exclusively with 5'-GC-3' sequences, and in particular, at 5'-TGC-3' sites. A model to explain this unique reaction is proposed.

Structure activity analysis of the formation of DNA damage induced in human tumor cells by the cyclodisone class of anti-tumor agent.

1,5,2,4-dioxadithiocane-2,2,4,4-tetraoxide (compound II) and 1,5,2,4-dioxadithionane-2,2,4,4-tetraoxide (compound III) are two structural analogues of the anticancer agent cyclodisone. Compound III was found to be more toxic to human colon carcinoma cells of the Mer- phenotype (BE) than the Mer+ phenotype (HT-29). In contrast, compound II showed little preferential toxicity with both cell lines being equally sensitive to this agent. DNA interstrand crosslinks were induced in the sensitive cell line by compound III but only at concentrations which were extremely cytotoxic. No DNA interstrand crosslinks were detected in the resistant cell line by compound III nor in either cell line by compound II. Total crosslinks which reflects both DNA interstrand and DNA-protein crosslinks, were observed in both cell lines after exposure to each agent although the kinetics of formation and repair of these lesions differed between both the compounds and each cell line. DNA strand breaks were also induced in both cell lines by each compound and were found to be totally 'protein associated' with compound III and to a lesser extend with compound II. The mechanism of action of this class of compound is thus different from other bifunctional alkylating agents and has still to be identified.

An agarose gel method for the determination of DNA interstrand crosslinking applicable to the measurement of the rate of total and "second-arm" crosslink reactions.

A simple agarose gel electrophoresis method for the determination of DNA interstrand crosslinks is described. Following complete denaturation of 32P-end-labeled DNA the presence of an interstrand crosslink results in renaturation to double-stranded DNA. The single- and double-stranded bands separated on an agarose gel can be accurately quantitated by densitometry of the autoradiograph produced from the dried gel. The technique is particularly applicable to detailed time-course experiments of both total crosslink formation and, following removal of free drug, the "second-arm" of the crosslink reaction. The method is illustrated for a number of nitrogen mustard antitumor agents, showing how the moiety attached to a bifunctional reactive group can influence the extent and rate of crosslink formation and, in particular, the conversion of monoadducts to crosslinks. It is sensitive enough to follow the formation of crosslinks by slow and inefficient cross-linking agents such as busulfan which have not previously been measured by physical procedures.