Giacomo Derchi

Surface morphology and mechanical properties of new-generation flowable resin composites for dental restoration

OBJECTIVES The purpose of this study was to characterize the surface morphology and the elastic properties of four dental restorative flowable composites currently on the market (Venus Diamond Flow, Vertise Flow, Filtex Supreme XT Flow, Surefil SDR Flow). Additionally, one adhesive system (Adhese One F) and one non-flowable composite (Venus Diamond) have also been characterized as the control materials. METHODS Surface morphology was studied by both scanning electron and atomic force microscopy, and the elastic modulus and the hardness measured by instrumented indentation. Grain analysis was performed on the microscopic images, and statistical analysis was carried out on the results of the nanoindentation measurements. RESULTS It was observed that Vertise, Filtek XT and Surefil SDR exhibit stiffness similar to the non-flowable Venus Diamond, whereas Venus Diamond Flow presents itself as the more compliant flowable composite, with Adhese showing intermediate stiffness. Grain analysis of the images confirmed the general rule that the mechanical properties improve with increasing filler loading, with the notable exception of Vertise Flow that shows modulus and hardness as high as 9.1±0.6 and 0.43±0.03GPa, respectively, for an estimated loading of only ∼40% by volume. SIGNIFICANCE Whereas generally flowable composites are confirmed not to possess sufficiently strong mechanical properties for bulk restorations, exceptions can eventually be found upon appropriate laboratory screening, as presently seems to be the case for Vertise Flow. However, real practice in actual restorations and respective clinical evaluation are required for final assessment of the suggested results.

Atomic force microscopy in vitro study of surface roughness and fractal character of a dental restoration composite after air-polishing

BackgroundSurface roughness is the main factor determining bacterial adhesion, biofilm growth and plaque formation on the dental surfaces in vivo. Air-polishing of dental surfaces removes biofilm but can also damage the surface by increasing its roughness. The purpose of this study was to investigate the surface damage of different conditions of air-polishing performed in vitro on a recently introduced dental restorative composite.MethodsAbrasive powders of sodium bicarbonate and glycine, combined at different treatment times (5, 10 and 30 s) and distances (2 and 7 mm), have been tested. The resulting root mean square roughness of the surfaces has been measured by means of atomic force microscopy, and the data have been analyzed statistically to assess the significance. Additionally, a fractal analysis of the samples surfaces has been carried out.ResultsThe minimum surface roughening was obtained by air-polishing with glycine powder for 5 s, at either of the considered distances, which resulted in a mean roughness of ~300 nm on a 30 × 30 μm2 surface area, whereas in the other cases it was in the range of 400-750 nm. Both untreated surfaces and surfaces treated with the maximum roughening conditions exhibited a fractal character, with comparable dimension in the 2.4-2.7 range, whereas this was not the case for the surfaces treated with the minimum roughening conditions.ConclusionsFor the dental practitioner it is of interest to learn that use of glycine in air polishing generates the least surface roughening on the considered restorative material, and thus is expected to provide the lowest rate of bacterial biofilm growth and dental plaque formation. Furthermore, the least roughening behaviour identified has been correlated with the disappearance of the surface fractal character, which could represent an integrative method for screening the air polishing treatment efficacy.

Extraction Socket Healing in Humans After Ridge Preservation Techniques: Comparison Between Flapless and Flapped Procedures in a Randomized Clinical Trial

BACKGROUND The preservation of hard and soft tissue volume, partially lost after tooth removal, can potentially reduce the need for the more demanding augmentation procedures used in implant-supported rehabilitation. The objective of this research study is to investigate the effect of filling with xenogeneic material the postextractive sockets of two surgical procedures (flapless versus flapped). METHODS In this prospective randomized clinical survey, two types of socket preservation were performed on two groups of patients: the control, treated via full-thickness mucoperiosteal flap, and the test, via a flapless procedure. Anatomic measurements and related outcome variables at the third month were analyzed using multiway analysis of variance. Multiple comparison tests, using Tukey honestly significant difference test, and appropriate pairwise comparison tests for independent samples were carried out. RESULTS Sixty-four patients were treated, 32 for each of the two socket preservation procedures. Statistically significant differences were registered for the output variables -- changes in width of keratinized gingiva, changes in bucco-lingual width, and vertical bone changes at four sites -- between the two socket preservation techniques, with P values of <0.001, <0.001, and 0.0105, respectively. CONCLUSIONS A full-thickness mucoperiosteal flap gave significantly more negative results than that of the less-demanding flapless procedure, with an increased width resorption of the postextraction site. Moreover, the increased value of the keratinized gingival width attested to the positive outcome of a flapless procedure in terms of soft tissue preservation and improvement. On the other hand, the flapped technique seemed to show less vertical bone resorption on the buccal aspect than the flapless technique.

Surface Roughness of Commercial Composites after Different Polishing Protocols: An Analysis with Atomic Force Microscopy

Background and Aims: Polishing may increase the surface roughness of composites, with a possible effect on bacterial growth and material properties. This preliminary in vitro study evaluates the effect of three different polishing systems (PoGo polishers, Enhance, Venus Supra) on six direct resin composites (Gradia Direct, Venus, Venus Diamond, Enamel Plus HFO, Tetric Evoceram, Filtek Supreme XT). Materials and Methods: For each composite, 12 square specimens were prepared: 9 specimens were polished, three for each different method, while three specimens were used as controls. Surface roughness was determined with AFM by measuring Root Mean Square (RMS) of average height. Results: PoGo polisher determined a significantly rougher surface, versus controls, in 5 out of 6 composites evaluated. Some significant differences from unpolished controls were observed also for Enhance polishing. Polishing with Venus Supra did not result in any significant difference in surface roughness versus controls. No differences were observed between different polishing systems. Conclusions: These preliminary results suggest that Venus Supra polishing system could determine a smoother composite surface if compared to the other polishing systems tested. On this basis, we are conducting an in vivo study to evaluate bacterial colonization on some combinations of composites and polishing protocols.

Relationship Between Human Periodontitis and Type 2 Diabetes at a Genomic Level: A Data-Mining Study

BACKGROUND The leader gene approach is a data-mining method based on the systematic search for the genes involved in a specific process and their ranking according to the interconnections with the other genes identified. The application of this algorithm to human periodontitis gave promising results. The present study used this algorithm to formulate new hypotheses about the association between periodontitis and type 2 diabetes. METHODS The genes involved in a given process were identified via interrelated queries of several databases. The interactions among such genes were mapped and given a significance score. The weighted number of links (sum of weighted scores for every interaction in which a gene is involved) was calculated for each gene. Genes were clustered according to this parameter; those in the highest cluster were termed leader genes. This algorithm was applied to diabetes and sinusitis. Sinusitis was chosen as a control because it is an inflammatory infectious disease like periodontitis. The results were compared to those previously calculated for periodontitis. RESULTS Periodontitis and diabetes share four leader genes; all leader genes are linked in a complex map of interactions. Periodontitis and sinusitis share no leader genes; no interactions were identified. CONCLUSIONS Even with the limitations of ab initio analyses, these theoretical results might suggest the existence of some common genomic pathways between periodontitis and type 2 diabetes, despite the different pathogenesis of these diseases. In particular, the shared leader genes could have an important role in this relationship, which may be investigated further with targeted experimentation.

The Effect of Insertion Torque on the Clinical Outcome of Single Implants: A Randomized Clinical Trial

BACKGROUND The insertion torque value has been extensively used as an indicator for implant primary stability, which is considered a determining parameter for the implants success. PURPOSE The primary goal of the present randomized clinical trial was to evaluate and compare the clinical outcome for implants placed with high insertion torque (between 50 Ncm and 100 Ncm) and regular insertion torque (within 50 Ncm) in healed ridges. MATERIALS AND METHODS Partially edentulous patients, missing one or more mandibular or maxillary teeth, having an adequate amount of bone, requiring implant placement, were randomized to receive Blossom CT implants with regular insertion torque (<50 Ncm) or CT implants with high insertion torque (≥50 Ncm). Implants were left to heal submerged for 3 months. Implants were restored with individualized abutments and cemented metal-ceramic crowns. Acquired measurements were: insertion torque values (IT), thickness of buccal bone plate after implant osteotomy preparation (BBT), marginal bone level (MBL), and facial soft tissue level (FST). All patients were followed 12 months after implant placement. RESULTS One hundred sixteen implants were placed in one hundred sixteen patients and enrolled for the study. Fifty-eight implants were randomly allocated in regular-IT and high-IT groups with a mean insertion torque ranging from 20 Ncm to 50 Ncm and from 50 Ncm to 100 Ncm, respectively. Three implants failed, and another five implants showed at the 12-month evaluation a marginal bone loss (ΔMBL) greater than 1.5 mm, being considered unsuccessful. CONCLUSIONS The findings suggested that implants inserted with high-IT (≥50 Ncm) in healed bone ridges showed more peri-implant bone remodeling and buccal soft tissue recession than implants inserted with a regular-IT (<50 Ncm). Moreover, sites with a thick buccal bone wall (≥1 mm) - after implant osteotomy site preparation - seemed to be less prone to buccal soft tissue recession after 12 months than sites with a thin buccal bone wall (<1 mm).

Tooth bleaching with hydrogen peroxide and nano-hydroxyapatite: a 9-month follow-up randomized clinical trial.

OBJECTIVES The aim of this study was to compare the amount of tooth colour change, rebound rate and tooth sensitivity in patients submitted to a bleaching technique with 6% hydrogen peroxide (HP) with or without 2% nano-hydroxyapatite (n-HA). METHODS Sixty subjects were included in this examiner-blinded, randomized clinical trial using a 6% HP gel with or without 2% n-HA. Tooth colour and tooth sensitivity were analysed before and after treatment. All data were analysed statistically. RESULTS After bleaching, both treatments demonstrated significant improvements in tooth shade (P < 0.05 for both groups). At the 9-month recall, tooth shade remained significantly lighter than at baseline (P < 0.05 for both groups). However, a relapse of the tooth shade was observed compared with the immediate post-bleaching result (P < 0.05). 6% HP with 2% n-HA produced significantly lower sensitivity (P < 0.05) than the bleaching product without n-HA. Colour change evaluation resulted in no difference between the two groups. CONCLUSION Both treatments demonstrated significant improvements in tooth shade. The bleaching effectiveness of the tested products was comparable. The use of 6% HP with 2% n-HA reduced the incidence of sensitivity during the bleaching treatment compared to a bleaching agent that did not contain n-HA.

Effectiveness of nano-hydroxyapatite toothpaste in reducing dentin hypersensitivity: A double-blind randomized controlled trial

OBJECTIVE The present double-blind randomized clinical trial aimed to compare the efficacy in reducing dentin hypersensitivity of a dentifrice formulation containing nano-hydroxyapatite with a fluoride dentifrice and a placebo. METHOD AND MATERIALS 105 subjects were recruited to participate in the study. A computer-generated random table with blocking to one of the three study treatments was used in order to have 35 subjects per group: 1) nano-hydroxyapatite 15% toothpaste, fluoride-free; 2) fluoride toothpaste; 3) placebo. Groups 1, 2, and 3 were instructed to brush their teeth for 2 minutes twice a day with the provided toothpaste. The participants dentin hypersensitivity was evaluated at baseline and after 2 and 4 weeks using airblast and tactile tests. In addition, a subjective evaluation using a visual analog scale (VAS) was used. RESULTS Significantly lower values of cold air sensitivity and tactile sensitivity (P<.001) were found for the test group at 2 weeks and 4 weeks. In addition, statistically significantly (P<.001) lower values of sensitivity were reported for group 1 compared to groups 2 and 3, at 2 and 4 weeks respectively. The VAS scores were significantly lower (P<.001) in the test group at 2 and 4 weeks compared to baseline and to the control groups. CONCLUSION The findings of the present study encourage the application of nano-hydroxyapatite in fluoride-free toothpaste as an effective desensitizing agent providing quick relief from symptoms after 2 and 4 weeks.

Esthetic Outcome of Implants Placed in Fresh Extraction Sockets by Clinicians with or without Experience: A Medium-Term Retrospective Evaluation.

PURPOSE This study discussed a 3-year retrospective survey of clinical and esthetic outcomes of immediate implants placed by experienced senior surgeons and residents in implant dentistry. MATERIALS AND METHODS The retrospective chart review included patients who received single-tooth extraction and immediate implant placement at the Tuscan Stomatology Institute between 2009 and 2011. Treated independent postextraction areas were divided into two groups according to the operators experience: expert versus nonexpert group. Patient satisfaction with the esthetic aspect, chewing, speaking, comfort, self-esteem, and ease of cleaning were assessed by visual analog scales. Changes in the marginal bone level and parameters describing the changes of the facial soft tissue and in papilla index were assessed. Proper pairwise comparison tests were applied with a significant level α = .05. RESULTS Of the 60 selected patients, 31 were in the expert group and 29 in the nonexpert group. At the 3-year follow-up, findings attested to a significantly higher bone loss in the nonexpert group (1.74 ± 0.59 mm) than those registered in the expert group (1.34 ± 0.45 mm), with a P value of .0044. The papilla index (PI) appeared very stable in the group of experts, whereas it showed a significant loss throughout the study in patients in the nonexpert group (PI = 2 at 1 year and PI = 1.5 at 3 years). Moreover, significant recessions at the buccal soft tissue were registered for all groups at both check-ups; however, in the expert group, slight soft tissue recession was evident 3 years later (0.58 ± 0.72 mm), whereas the nonexpert group showed greater recession (1.52 ± 0.74 mm). Patients reported higher overall satisfaction when treated by the group of experts (85.2%) than when treated by the nonexperts (81.1%) with P < .0001. CONCLUSION The findings from this study suggested that immediate implant procedures could be considered a successful and satisfying treatment strategy when strict selection criteria together with a high level of surgical expertise are applied.

The Clinical Outcomes of Immediate Versus Delayed Restoration Procedures on Immediate Implants: A Comparative Cohort Study for Single-Tooth Replacement

BACKGROUND Immediate implant placement into fresh extraction sockets is generally considered a reliable procedure that offers several clinical advantages. PURPOSE The primary aim of this study was to evaluate and compare the overall clinical outcomes of immediate and delayed restoration procedures for implants placed in fresh extraction sockets by means of a flapless technique and resorbable membrane stabilizing a xenograft. Total costs and operating times were also compared. MATERIALS AND METHODS In this prospective cohort study, changes of marginal bone level, facial soft tissue (ΔFST), and width of keratinized gingiva (ΔWKG), in addition to the papilla index, underwent a pairwise comparison; correlations with pristine buccal bone thickness were also investigated. RESULTS Although similar results were recorded for the two procedures, with a bone loss of -1.0 ± 0.5 mm and -0.9 ± 0.7 mm, respectively, for immediate and delayed restoration, negative remodeling in the delayed restoration procedure was seen to occur from 4 to 12 months after implant placement. No significant differences were recorded between the two procedures in terms of ΔFST and ΔWKG. A loss of the papillary soft tissues before restoration, followed by a reestablishment after restoration, seemed to be verified for the delayed group, for which the papilla index went from the minimum of 0 at 4 months to a value of 2 at 24 months. Moreover, the immediate restoration procedure seemed to be more promising in terms of healing times and costs. CONCLUSION Immediate restoration of implants installed in fresh extraction sockets was at least as effective and safe as delayed restoration.