Donato Di Iorio

Friction of Conventional and Self-Ligating Brackets Using a 10 Bracket Model

The friction generated by various bracket-archwire combinations previously has been studied using in vitro testing models that included only one or three brackets. This study was performed using a specially designed apparatus that included 10 aligned brackets to compare the frictional resistance generated by conventional stainless steel brackets, self-ligating Damon SL II brackets and Time Plus brackets coupled with stainless steel, nickel-titanium and beta-titanium archwires. All brackets had a 0.022-inch slot, and five different sizes of orthodontic wire alloys used. Each bracket-archwire combination was tested 10 times, and each test was performed with a new bracket-wire sample. Time Plus self-ligating brackets generated significantly lower friction than both the Damon SL II self-ligating brackets and Victory brackets. However, the analysis of the various bracket-archwire combinations showed that Damon SL II brackets generated significantly lower friction than the other brackets when tested with round wires and significantly higher friction than Time Plus when tested with rectangular archwires. Beta-titanium archwires generated higher frictional resistances than the other archwires. All brackets showed higher frictional forces as the wire size increased. These findings suggest that the use of an in vitro testing model that includes 10 brackets can give additional interesting information about the frictional force of the various bracket-archwires combinations to the clinician and the research worker.

Regenerative potential of human periodontal ligament derived stem cells on three-dimensional biomaterials: A morphological report

Recent studies have shown that mesenchymal stem cells obtained from periodontal ligament (PDL-MSCs) are multipotent cells that have similar features of the bone marrow and dental pulp MSCs and are capable of proliferating and producing different types of tissue such as bone and tooth associated-tissues. Human PDL-MSCs expanded ex vivo were induced to osteogenesis, seeded in three-dimensional biocompatible scaffolds (fibrin sponge, bovine-derived substitutes) and examined using light, scanning and transmission electron microscopy. Morphological observations showed extensive growth of cellular biomass partially covering the scaffolds after 4 weeks of incubation in mineralization medium. These findings indicate that periodontal ligament can be an easily and efficient autologous source of stem cells with a high expansion capacity and ability to differentiate in osteogenic cells that can colonize and grow connected to bio-compatible scaffold. It can be suggested that the use of PDL-MSCs for generating graft biomaterials is advantageous for bone tissue engineering in regenerative dentistry.

In vitro evaluation of fracture resistance and failure mode of internally restored endodontically treated maxillary incisors with differing heights of residual dentin

STATEMENT OF PROBLEM Some of the associated effects of different restorative systems placed in endodontically treated teeth with varying heights of residual dentin have yet to be examined in a comprehensive manner. There is a need for additional information regarding fracture resistance and mode of failure. PURPOSE The purpose of this in vitro study was to evaluate the effect of 3 different restorative techniques with varying amounts of remaining dentin heights on the fracture resistance and failure mode of endodontically treated teeth. MATERIAL AND METHODS Three groups of 40 human maxillary incisors were subdivided into 4 subgroups (n=10) with respect to the uniform height of the residual coronal dentin, defined as 0-, 2-, 4-, or 5-mm from the cemento-enamel junction, and then restored internally using a composite resin (Z100 MP) (control group), a cobalt-chromium ceramic alloy custom-made cast post and core (IPS d.SIGN 30; CCPC group), or a carbon fiber post system (Tech Xop 2000; CFP group). All specimens were then restored with nonprecious cast crowns. Static loading tests were performed on each specimen until failure (crack without a complete fracture). The data were analyzed with 2-way ANOVA and Bonferroni-corrected t test for independent samples (alpha=.05). Failure was classified as either favorable (allowing repair) or catastrophic (not allowing repair). RESULTS The fracture resistance values (N) for the 0-, 2-, 4-, and 5-mm residual dentin heights were: 88, 143, 154, and 202 for the control group, 230, 264, 364, and 383 for the CCPC group, and 153, 235, 346, and 357 for the CFP group, respectively. Generally, all the differences tested were statistically significant. The failure mode was catastrophic for no control specimens, for 36 CCPC specimens, and for 4 CFP specimens. CONCLUSIONS The highest and lowest fracture resistances were recorded for the CCPC and control groups, respectively, at each residual dentin height. An increased height of residual dentin generally provided greater fracture resistance. The fracture resistance of the CCPC group was, however, similar or only slightly higher than that of the CFP group when 2, 4, or 5 mm of residual dentin height was present. In contrast, the failure mode was favorable for almost all of the CFP and control groups, while it was catastrophic in most of the CCPC group.

Bacterial adhesion on commercially pure titanium and anatase-coated titanium healing screws: an in vivo human study.

BACKGROUND Little is known about the mechanisms of bacterial interaction with implant materials in the oral cavity. Other surface characteristics, in addition to surface roughness, seem to be extremely important in relation to plaque formation. Different adhesion affinities of bacteria were reported for different materials. Anatase is a nanoparticle that can be applied to titanium surfaces as a coating. The anatase coating gives special characteristics to the implant surface, including some genetic effects on osteoblasts. In this study, the antibacterial effect of anatase is investigated. The aim of this study is to characterize the percentages of surfaces covered by bacteria on commercially pure (cp) titanium and anatase-coated healing screws. METHODS Ten patients participated in this study. The protocol of the study was approved by the ethics committee of the University of Chieti-Pescara. A total of 20 healing screws (10 test and 10 control screws) were used in the study. The control screws were made of cp titanium, whereas the test screws were coated with anatase. Cleaning procedures and agents for chemical plaque control were not applied to the healing screws for the complete duration of the test period. After 7 days, all healing screws were removed, substituted, and processed under scanning electron microscopy for evaluation of the portions of the surfaces covered by bacteria. RESULTS The supracrestal screw surfaces covered by bacteria on test specimens were not significantly lower than those of control screws (P = 0.174). The subcrestal screw surfaces and threads covered by bacteria on test specimens were significantly lower than those of control screws, and P values were 0.001 and 0.000, respectively. CONCLUSION Results show that anatase could be a suitable material for coating implant abutments, with a low colonization potential.

In vitro evaluation of thermomechanic coupling in conical implant-to-abutment joint.

Purpose:This study investigates the use of thermomechanic abutment-to-implant coupling. Materials and Methods:Ten 3.5 × 1 mm commercially pure titanium Ankylos implants (Dentsply Friadent, Mannheim, Germany) and 10 standard abutment of titanium alloy Ti6Al4V were used in the present study. All fixtures were mounted on hold specimen provided of a 10-ohm electrical resistance to maintain the fixture at 37°C ± 3°C during the entire test and to evaluate the influence of the coefficient of thermal expansion on joined conical abutment. The threading part of all abutments was cut off using a diamond disc. All abutment implants were coupled at 35 N using a universal testing machine (Lloyd 30K, Lloyd Instruments Ltd. Segensworth, UK). Five abutments were heated at 37°C ± 3°C, whereas the reaming were cooled at 0°C ± 3°C before connection. To measure the difference a pull-out test was performed. Results:The results were statistically analyzed using unpaired t test at P < 0.05. The cooled specimens showed a result (mean ± SD) of 421.6 ± 55.20 N, whereas for heated specimens the result was 238.4 ± 42.27 N. The difference was statistically significant (P = 0.001). Conclusions:The thermomechanic coupling significantly increases the performance of the conical joint.

In Vitro Analysis of Resistance to Cyclic Load and Preload Distribution of Two Implant/Abutment Screwed Connections

The aim of the present research is an in vitro evaluation of the preload distribution in screw-retained implant systems under cyclic load. Two implant systems with internal connection were tested: fifteen 4.5 × 10 mm implants with internal hexagon and fifteen 4.5 × 10 mm implants with internal octagon. Samples underwent cyclic load that was between 20 N and 200 N for 1 × 10(6) cycles. After mechanical tests, samples were sectioned along the long axis and analyzed under a scanning electron microscope. Five 4.5 × 10 mm implants with internal hexagon and five 4.5 × 10 mm implants with internal octagon were collected for photoelastic analysis. Each fixture was mounted in a wax-made parallelepiped measuring 20 mm × 20 mm × 10 mm. A mold was made for each wax parallelepiped/fixture assembly using a silicone-based impression material, and an epoxy resin was poured in each mold. After setting of the resin, 25° angled titanium abutments were screwed onto each replica; afterwards, assemblies underwent photoelastic analysis. After cyclic load, screw threads and heads were still in contact with internal fixture threads and abutment holes, respectively, suggesting that preload has not been lost during load. During load, SSO and Xsigñ implants behave in a different way. SSO samples revealed the presence of fringes radiating from the base of the abutment. Xsigñ implants showed the presence of fringes radiating from the threads of the retention screw. From the present in vitro research, it is possible to state that screw-retained abutment based on an internal octagonal connection is less likely to come loose after cyclic load.

Histomorphometry of 2 Immediately Loaded Mini Implants Retrieved From Human Mandible After 3 Months: A Light and Scanning Electron Microscopy Report

Today, mini implants represent an additional choice for patients and surgeons. They are largely used as anchorage when a severely resorbed mandible is to be rehabilitated with an overdenture, their major advantages being flapless, painless surgery and easy placement in thin alveolar crests without any split-crest or bone-grafting procedure. Unfortunately, the literature provides little information on histomorphometric analysis of immediately loaded mini implants placed in the posterior region of the human mandible. The aim of the present in vivo research is to carry out a histologic evaluation of the bone surrounding 2 mini implants placed in human mandible and immediately loaded with an overdenture after 12 weeks. A patient who underwent extraction of 14 periodontally compromised teeth was selected for the present study. After the extractions, 2 mini implants with ball attachment were placed in sites 19 and 30. Mini implants were immediately loaded with a temporary immediate overdenture. Three months aft...