The paper presents a kinetic analysis of a reversible enzymatic reaction Sright arrow over left arrowP involving two intermediate compounds under the condition E(0) >> S(0) + P(0). For the case of ...mono-exponential behavior, we derive an equation for k (obs) as a function of E(0), which emphasizes the pitfalls of oversimplifying kinetic schemes (such as the Michaelis-Menten model) for ribozyme studies. This novel apparent rate constant, which has been arrived at through mechanistic considerations, is analyzed, and the characteristic parameters obtained. The equation, which seems to fit experimental data better than conventional approximations, is used to analyze a single turnover study on an ADC1 ribozyme drawn from hepatitis delta virus RNA. The microscopic kinetic constants for such enzyme are evaluated and its mono-exponential behavior verified.
Abstract Objective An analysis of the genes involved in both osteoporosis and modifications of the jawbone, through text mining, using a web search tool, of information regarding gene/protein ...interaction. Design The final set of genes involved in the present phenomenon was obtained by expansion-filtering loop. Using a web-available software (STRING), interactions among all genes were searched for, and a clustering procedure was performed in which only high-confidence predicted associations were considered. Results Two hundred forty-two genes potentially involved in osteoporosis and in modifications of the jawbone were recorded. Seven “leader genes” were identified (CTNNB1, IL1B, IL6, JUN, RUNX2, SPP1, TGFB1), while another 10 genes formed the cluster B group (BMP2, BMP7, COL1A1, ICAM1, IGF1, IL10, MMP9, NFKB1, TNFSF11, VEGFA). Ninety-eight genes had no interactions, and were defined as “orphan genes”. Conclusions The expansion of knowledge regarding the molecular basis causing osteoporotic traits has been brought about with the help of a de novo identification, based on the data mining of genes involved in osteoporosis and in modification of the jawbone. A comparison of the present data, in which no role was verified for 98 genes that had been previously supposed to have a role, with that of the literature, in which another 81 genes, as obtained from GWAS reviews and meta-analyses, appeared to be strongly associated with osteoporosis, probably attests to a lack of information on osteoporotic disease.
This article discusses a 3-year retrospective survey of implant clinical survival and computerized tomographic analysis of bone remodeling in atrophic alveolar crests reconstructed via various ...autogenous bone grafting procedures and in similar regions of native bone.
The retrospective chart review included consecutive edentulous patients with severe alveolar crest atrophy treated between 2000 and 2002 with onlay autogenous bone grafts in the mandible and anterior maxilla (as needed) and implant insertion. Implant recipients were followed for 3 years. Defective areas were reconstructed by bone graft harvested from the chin or iliac crest. Implants in reconstructed areas were divided into two groups according to graft source. Implants in corresponding native areas served as controls. Cumulative survival rate (CSR), survival rate, and confidence interval (CI) were calculated, and linear measurements of bone remodeling around implants were assessed on computerized tomographic scans. Results were compared for statistically significant differences by Wilcoxon signed-rank test with a significance level a = .05.
Forty patients were treated with 109 screw-type, root-form, rough-surfaced implants inserted in 48 onlay grafts; 88 implants were placed in native bone. The implant 3-year CSRs were 98.9% (CI 96.7% to 100%) in native bone and 99.1% (CI 97.3% to 100%) in onlay grafts, irrespective of bone source. Mean resorption in the maxilla was 4.6 +/- 0.9 mm buccally and 3.8 +/- 0.8 mm palatally in areas reconstructed with chin grafts, 3.4 +/- 1.7 mm buccally and 2.6 +/- 1.4 mm palatally in areas reconstructed with iliac crest grafts, and 3.2 +/- 1.2 mm buccally and 2.1 +/- 0.9 mm palatally in native areas.
Similar implant CSRs were seen in native and grafted sites. Maximal implant CSR was observed in onlay grafts from the chin despite more marked linear bone remodeling in this group as compared to iliac crest grafts or native bone.
The application of tribology in dentistry is growing rapidly, intense research has been conducted to develop an understanding of dental tribology for better selection of artificial materials and ...dental implant design. Dental biotribology, has been one of the most important branches in biotribology in recent years. The aim of this research is to investigate the tribological performances in the tooth-to-tooth contact and material-to-natural tooth contact (zirconia vs. zirconia and natural tooth vs. zirconia). The presented research was carried out by testing the above mentioned tribological pairs with the use of a reciprocating tribometer under lubricated conditions (artificial saliva). The normal force used in the tests was 20 N the time for each test was of 60 min. The stroke length was 2 mm, according to the range of displacement used in scientific literature. The wear mass loss evaluation was evaluated by using a gravimetric method. In order to characterize the wear mechanisms, present in the worn surfaces after each of tribo-tests, a topographic analysis was carried with a 3D non-contact optical profiler. The results show that the minimum value of the COF is obtained in the case of Zirconia vs. Zirconia tribo-couple. The results on the wear mass loss show a very low wear rate when coupling in tribological condition natural tooth with a ceramic restoration (a mean value of 0.5 mg was found). This rate is even lower when the contact is between two artificial zirconia teeth.
The present study was a 3-year follow-up evaluation of implant clinical success and radiographic bone remodeling in sinus floors elevated with different autogenous bone-grafting procedures and in ...similar native bone regions.
This retrospective chart review examined consecutive edentulous patients with severe jaw atrophy treated between 2000 and 2002 via sinus lift, when needed, and implant insertion. Implants in sinus lift areas were divided into four groups by graft source (iliac crest, chin area) and technique (bone block, particulate). Implants positioned in native areas beneath the sinus floor served as controls. The cumulative success rate (CSR) and success rate (SR) were calculated, and linear measurements of bone remodeling around implants were assessed on computerized tomographic scans. Results were statistically compared with the Wilcoxon signed rank test.
Twenty-eight patients were treated in the posterior maxilla via insertion of 70 screw-type, root-form, rough implants in 39 sinus-lifted areas. All surgical procedures were uneventful. Twenty-four implants were positioned in native areas beneath the sinus floor. The implant CSR was 95.8% in native areas (one failure/24 implants), 85% in sinuses lifted with particulate chin bone (three failures/20 implants), and 100% in the other three groups (eight in particulate iliac crest, 20 in chin block, and 22 in iliac crest block). Computerized tomographic scans revealed that bone remodeling around apices caused implants to bulge into the sinuses in both particulate bone graft groups. Crestal remodeling around implant necks was similar for all groups.
The use of particulate chin bone grafts in sinus lift procedures does not seem to yield optimal outcomes. Milled iliac crest and chin bone tends to remodel around the implant apices, leading to bulging within the sinuses. Grafting sinuses with either chin or.iliac crest bone blocks yields the highest implant success rates and stable sinus floors.
The purpose of this study is to analyze marginal bone levels (MBLs) around dental implants positioned in the upper and lower jaw with or without horizontal onlay grafting procedures, and to survey ...implant survival with a follow-up of 5 years. Seventeen patients were surveyed in the present retrospective chart review. A total of 27 dental implants positioned in pristine bone and 21 in horizontally grafted bone were enrolled. MBLs were recorded for 4 aspects during a radiologic survey of 5 years. Significant differences were searched for among times and surgical procedures with paired and unpaired comparison tests, respectively, and survival rates were calculated for the 2 groups. In the maxilla, no statistically-significant differences between pristine and augmented groups were obtained; the time comparisons for pristine implants showed an affection of palatal, mesial, and distal sides, whereas the resorption around implants placed into horizontally grafted bone of anterior maxilla seemed to be limited just to buccal and distal aspects. Comparisons with the pristine horizontal procedure revealed that just the buccal sides were involved. The analysis of time comparisons attested to a continuous alveolar bone remodeling during the entire time of the survey for the pristine group. Given the extremely unfavorable resorption at the buccal aspect of the augmented areas, clinicians should reserve dental implant positioning into horizontal bone graft to selected patients, in whom it may represent one of the last opportunities of rehabilitation with a fixed prosthesis.
The purpose of this study was to evaluate the recolonization patterns of the subgingival microflora of adult periodontitis patients after a single session of scaling and root planing. In each of ...eight patients, three clinically diseased sites were investigated microbiologically by darkfield microscopy and cultural analysis. After initial clinical and microbiological parameters were determined, each subject received a single session of scaling and root planing but no oral hygiene instructions. Clinical indices were measured and microbial parameters were reassessed 7, 21, and 60 days after treatment in a manner such that each of the test sites was sampled only once after treatment. Recolonization was evaluated by matching any single site with its own preoperative site. A significant improvement in probing depth was noted for up to 60 days after treatment, while the gingival index did not change markedly during the course of the study. The microbial composition of treated sites 7 days after scaling and root planing, as determined by both cultural and darkfield data, was similar to that of periodontally healthy sites. Differences between cultural and darkfield data became apparent at the 21 day sampling point. The darkfield data showed that the sites consisted of cocci with few spirochetes. Cultural data demonstrated that the majority of the cocci were anaerobic, namely Streptococcus intermedius, Veillonella parvula, and Peptostreptococcus micros. At 60 days, there was no significant variation in any of the parameters from pretreatment levels. The most prevalent anaerobic rods prior to and 60 days after therapy were Fusobacterium nucleatum, Bacteroides gingivalis, and B. intermedius.
Purpose: The aim of the study was to evaluate by Computed Tomography (CT) scan technique the alveolar ridges reconstructed through osseous grafting procedures (onlay bone grafts or sinus lift and ...grafting) for dental implant placement, and to test its suitability to differentiate pre-operative and post-operative conditions in reconstructed areas. Methods: Seventy-four CT cross-sections from 16 mandibles and 113 CT crosssections from 18 maxillae from patients treated with autogenous bone grafts, performed via either vertical or horizontal autogenous bone block grafting or sinus lift procedure and grafting, and implant positioning, from January 2000 through December 2004, were analyzed and listed according to a residual ridge resorption evaluation. Maxillary and mandibular measurements were recorded and compared by Wilcoxon tests to highlight statistically significant differences. Data were subjected to Pearson's chi-square (%2) test, with YATES correction when necessary, to show frequency differences between preoperative and post-operative conditions. Results: The comparison between pre-operative and post-operative CT cross-sections showed statistically significant differences both in maxillary and mandibular posterior regions subjected to vertical onlay grafts; no statistically significant differences, instead, were found in the anterior region of the maxilla. Clinical Significance: The presented 3D CT scan evaluation of jaw atrophies could be applied to the recognition of bone height useful for implant positioning. Future maxillomandibular atrophy evaluation schemes should include the three-dimensional relationship between the maxilla and the mandible, as well as volumetric considerations.
Abstract Objectives A long-term survey on the healing potential of large-sized parasymphyseal osseous defects. Patients and methods Ten patients, subjected to 14 bilateral and 3 unilateral ...parasymphyseal bone harvesting for alveolar ridge augmentation, were selected for the retrospective chart review. CT scans were performed immediately before bone grafting, before implant insertion, and then once annually for 6 years, and the volumes of the bone defects at the buccal aspect in the healing process were measured using a software program. Volumes from the yearly measurements were then compared statistically. Results Volumes of both the intrasurgical defects, 0.77 (0.20) cc and of those in the one-year group, 0.60 (0.26) cc were statistically different from volumes of all the other time intervals (from 24 to 72 months) with all p -values less than 0.002 and 0.004, respectively. The healing of osseous defects in the long-term radiographic survey (6 years) resulted in bony infill of 63%. Conclusion For parasymphyseal defects of 0.7 cc, a maximum possible healing of two-thirds can be expected; a re-harvesting procedure could be performed 24 months after early surgery, due to both the formation of a new buccal cortical plate and the achievement of a steady state of osseous remodelling.
Background: Tentative bioinformatic predictions were performed to comprehend the complexity of the gene interaction networks of the T lymphocyte cell cycle and of human periodontitis. This study aims ...to identify and rank genes involved in osseous augmentation or bone remodeling to obtain groups with more numerous predicted associations called the leader gene clusters.
Methods: An iterative search (consisting of a consecutive expansion‐filtering loop) was performed for which only genes involved in a specific process were identified. For each gene, predicted associations with all other involved genes were obtained from a Web‐available database (Search Tool for the Retrieval of Interacting Genes/Proteins) and the weighted number of links (WNL), given by the sum of only high‐confidence predicted associations (results with a score ≥0.9), allowing gene ranking. Genes belonging to higher clustering classes were identified.
Results: A total of 161 genes potentially involved in bone‐volume augmentation and 128 genes connected with the bone‐remodeling phenomenon were identified. For the bone‐volume augmentation process, only one gene belonged to the leader gene group, whereas six other genes were classified as cluster B genes; for the bone‐remodeling phenomenon, three leader genes were identified, whereas six other genes formed the cluster B group. No one gene belonged to leader gene clusters of both processes, whereas one gene of each higher cluster group belonged to the immediately lower cluster of the opposite process. Only three genes of the higher clusters were experimentally involved in both analyses.
Conclusions: A de novo identification was performed based on the data mining of leader genes involved in bone‐volume augmentation or bone remodeling to acquire primeval information about their molecular basis and to plan future ad hoc targeted experiments. For several genes of the upper clusters, an active role in the bone processes was already known, but the present analysis suggested that they play a major role in the analyzed phenomena. The role of the transcription factors as leader genes and the numerous orphan genes (genes with WNL = 0) recovered probably attest to a lack of information regarding these processes, which could be further clarified through specific DNA microarray experiments.
PDF
