Physical and chemical mechanisms involved in adhesion of orthodontic bonding composites: in vitro evaluations.

BACKGROUND: Bond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare bond strength of light-cure orthodontic composites by measuring debonding forces and evaluating locations of bond failure. Investigations on chemical compositions clarified adhesive behaviors and abilities, exploring effects of ageing processes in this junction materials. METHODS: Twelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT™ 3 M UNITEK, USA, Light-Cure Orthodontic Paste, LEONE, Italy and Bisco Ortho Bracket Paste LC, BISCO, Illinois) and underwent to Shear Bond Strength test. Metallic brackets were bonded to twenty-seven human premolar, with one of the adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces. Raman Spectroscopy analysis was performed on eight discs of each composites to investigate on chemical compositions, before and after accelerated aging procedures in human saliva and sugary drink. RESULTS: Orthodontic adhesive systems showed similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone at adhesive-bracket interface. Accelerated in vitro aging demonstrated good physical-chemical stability for all composites, Bisco only, was weakly contaminated with respect to the other materials. CONCLUSION: A similar, clinically adequate and acceptable bond strength to enamel for debonding maneuvers was recorded in all orthodontic adhesive systems under examination. No significant chemical alterations are recorded, even in highly critical situations, not altering the initial mechanical properties of materials.

Clinical and radiographic assessment of implant-supported rehabilitation of partial and complete edentulism: a 2 to 8 years clinical follow-up.

OBJECTIVE: The aim of this study was to find out the rates of survival and success of implant rehabilitation, and the influence of some risk indicators on the medium- and long-term prognosis. PATIENTS AND METHODS: Of the 102 patients eligible for this study rehabilitated with dental implants during the years 2009-2015, 75 patients with 156 implants of different implant systems placed and loaded by the same team were recalled. For each subject, pocket-probing depth, bleeding on probing, plaque buildup, mobility of the fixtures, and the presence/absence of prosthetic complications were recorded. Radiographic evaluation was based on the analysis of bone levels around the fixtures, as shown by intraoral radiographs. RESULTS: The average follow-up was 4.4 years, ranging from 1.5 to 7.8 years. One hundred and fifty-four of the implants survived, while two implants failed; 98.8% of the prostheses survived, while 75.9% were successful. Success was achieved in 90.4% of implants and in 80% of patients. The sample showed average radiographic bone resorption of 1.09 mm. The average pocket probing depth was 2.79 mm. Bleeding on probing was found in 18% of all sites, and 59.6% of implants showed bleeding on probing in at least one site. Mucositis was found in 90% of patients, and peri-implantitis was found in 16% of patients. CONCLUSIONS: The rates of success and survival showed the reliability of implant therapy. Plaque accumulation, smoking and upper jaw location, seem to increase the risk of failure of implant-supported rehabilitation.

Oral management of adult patients undergoing hematopoietic stem cell transplantation.

Chemotherapy and hematopoietic stem cell transplantation (HSCT) are the current treatments for patients with hematological diseases; they result in myelosuppression, and increase the susceptibility of patients to severe infections. The oral cavity is a potential site of complications in HSCT patients, because it is the entrance for agents that can cause systemic infections; it is one of the most frequent locations for side effects deriving from conditioning therapy. The importance of dental pre-chemotherapy and transplant prescription is often stressed, since both therapies depress the immune system and platelets, making each intervention at this stage a high risk. The aim of this article is to review the potential complications of HSCT, and to extrapolate from the scientific literature the treatments and timeframes in which dental therapies can be performed, avoiding important risks for patients.

A Deep Morphological Characterization and Comparison of Different Dental Restorative Materials.

Giomer is a relatively new class of restorative material with aesthetics, handling and physical properties of composite resins, and benefits of glass ionomers: high radiopacity, antiplaque effect, fluoride release, and recharge. To verify the superior properties of Giomers, in this study, a deep morphological characterization has been performed with an in vitro comparative study among a Giomer (Beautifil® II by Shofu Dental Corporation, Osaka, Japan), a Compomer (Dyract Extra by Dentsply, Caulk, Germany), glass ionomer cement (Ketac fil plus by 3M ESPE), and a composite resin (Tetric Evoceram by Ivoclar). In particular, mechanical and optical properties and ageing effects have been compared to investigate materials similarities and differences. Indentation tests, UV-Visible spectroscopy, Raman spectroscopy, and weight loss after storage in saliva or sugary drink have been carried out to analyze materials behavior in real conditions. The results confirm the high quality of Giomer material and indicate possible improvements in their usage.

Temporary anchorage devices (TADs) in orthodontics: review of the factors that influence the clinical success rate of the mini-implants.

INTRODUCTION: The mini-implant, temporary anchorage devices (TADS), are now a common method of treatment in Orthodontics with versatility, minimal invasiveness and the relationship between costs and benefits that they offer even today. Skeletal anchorage has, to a large degree, replaced conventional anchorage in situations where anchorage is considered either critical, insufficient, or likely to result in undesirable side effects such as vertical displacements generated by inter-maxillary force systems. OBJECTIVES: The objective of this study is to carry out a review about the factors that seem affect the success or failure rate of orthodontic mini-implants. A computerized literature review was performed by searching the MEDLINE database (Entrez PubMed, www.ncbi.nlm.nih.gov), Google Scholar, Scopus, Cochrane Central Register of Controlled Trials, Isi Web of Knowledge until March 2016 . The main subject heading "orthodontics" was combined with these keywords mini-implant, mini-screw, micro-implants, mini-implant success rate, mini-implant failure rate, skeletal anchorage, temporary anchorage device (TADS). In the selection process, abstracts were initially read independently by two researchers to identify potentially eligible full text papers which were then retrieved and assessed in order to decide on the final inclusion. CONCLUSIONS: The clinical success of orthodontic anchorage by mini-implants depends on the stability of the miniscrews used for fixation. For good stability, the application site must provide bone of good quantity and quality. We can reasonably assume that the stability of the anchorage of the mini-implants could be optimized by selecting a position with particular characteristics of quality and quantity of bone, in relation to cortical and total mandibular and jaw bone thickness. These expected informations are important because they indicates that the bone quality and quantity are significant when considering an implant placement site, but also that there are other confounding factors influencing the success rate.

LED Curing Lights and Temperature Changes in Different Tooth Sites.

Objectives. The aim of this in vitro study was to assess thermal changes on tooth tissues during light exposure using two different LED curing units. The hypothesis was that no temperature increase could be detected within the dental pulp during polymerization irrespective of the use of a composite resin or a light-curing unit. Methods. Caries-free human first molars were selected, pulp residues were removed after root resection, and four calibrated type-J thermocouples were positioned. Two LED lamps were tested; temperature measurements were made on intact teeth and on the same tooth during curing of composite restorations. The data was analyzed by one-way analysis of variance (ANOVA), Wilcoxon test, Kruskal-Wallis test, and Pearson's χ (2). After ANOVA, the Bonferroni multiple comparison test was performed. Results. Polymerization data analysis showed that in the pulp chamber temperature increase was higher than that without resin. Starlight PRO, in the same condition of Valo lamp, showed a lower temperature increase in pre- and intrapolymerization. A control group (without composite resin) was evaluated. Significance. Temperature increase during resin curing is a function of the rate of polymerization, due to the exothermic polymerization reaction, the energy from the light unit, and time of exposure.

The effects of host derived metalloproteinases on dentin bond and the role of MMPs inhibitors on dentin matrix degradation.

OBJECTIVES: The work has the objective to analyze the literature on the degradation of the adhesive interface. In particular the study is focused on the role of the metalloproteinase in the hydrolytic degradation of collagen matrix in the bonded interface. The survey will concern also the latest innovations to improve and increase the link between dentin and the restorative materials through the MMPs inhibitors. METHODS: The research has been carried out in the MEDLINE database by choosing keywords as "metalloproteinases" and "dentin bond" and "degradation". In vitro studies were included in the research, excluding studies with no human and deciduous teeth. Language was limited to English. RESULTS: The collagenolytic enzymes in mineralized dentin have been demonstrated to have an important role in dental hard tissue pathologies, including the degradation of the hybrid layer. CONCLUSION: The preservation of the collagen matrix integrity is a key issue in the attempts to improve the dentin bonding durability.

Periodontal bacteria in the genital tract: are they related to adverse pregnancy outcome?

One of the most important factors implicated in preterm birth (PTB) is acute genitourinary tract infection. The bacteria causing chronic periodontal inflammation include Gram-negative rods and anaerobes similar to those found in women with bacterial vaginosis. The aim of this prospective study is to investigate the relationship between oral and vaginal microflora and preterm low birth weight. Real-time polymerase chain reaction was used to detect both the presence and level of six periodontitis-related species: Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf), Treponema denticola (Td), Fusobacterium nucleatum ssp(Fn), and Prevotella intermedia (Pi) for both oral samples of subgingival plaque and cervical samples, obtained from 80 patients, during gynaecological examinations. The more representative oral pathogen (less than 60 percent) species in oral samples of preterm and term group were Tf, Td, and Fn. 24.4 percent of pregnant women presented periodontal pathogens in vaginal swab; the most representative species with a percentage over 0.1 percent of total bacteria in genital tract of preterm group were Tf, Td, and Piwith a positive correlation (less than 0.5). The presence of the bacterium T. denticolain the vagina, regardless of the amount, adversely affects preterm delivery.

pPKC α regulates through integrin ß 1 human gingival fibroblasts/Streptococcus mitis adhesion in response to HEMA.

AIM: To investigate in coculture of human gingival fibroblasts (HGFs) and Streptococcus mitis, the molecular mechanisms driving the response to 2-hydroxyethyl methacrylate (HEMA) in terms of eukaryotic/prokaryotic cell adhesion, signal transduction and apoptosis. METHODOLOGY: The clinical strain S. mitis DS12, cultured in Trypticase soy broth was added to HGFs, obtained from fragments of healthy marginal gingival tissue and cultured in DMEM, treated with 3 mmol L(-1) 2-hydroxyethyl methacrylate (HEMA) for 48 h and processed for microscopic, western blotting and flow cytometric analyses. RESULTS: 2-hydroxyethyl methacrylate (HEMA) treatment increased the adhesion between S. mitis and HGFs, which seemed to be mediated by the PKC α/integrin ß 1 signalling system, improved by the presence of saliva. It also reduced the viability and the adhesion of HGFs to polypropylene substrate in terms of procollagen I and MMP3 expression. The presence of saliva and S. mitis reduced the number of necrotic HGFs and upregulated the expression of both procollagen I and MMP3. CONCLUSIONS: These results shed more light on the biological and molecular events occurring in vitro in a coculture model that mimics the environment of the oral cavity with HEMA treatment. The key role played by oral bacteria and saliva in preventing inflammatory and toxic processes that occur in vivo in human gingival fibroblasts upon the release of dental material monomers is confirmed.

Occurrence of Candida species colonization in a population of denture-wearing immigrants.

Infection of the oral cavity and dentures by Candida species are frequent in denture wearers. C. albicans is the most common pathogen; however, other emerging Candida species are also responsible for this condition. Few data are available about the occurrence of Candida species in the oral cavities of denture-wearing immigrants to Italy. In this study, we compare the Candida species found in the oral mucosa and on dentures from a population of denture wearing immigrants to Italy to a matched Italian group. Oral swabs were collected from dentures and the underlying mucosa of patients enrolled in the study and were then cultured to test for the presence of Candida species in each sample. Out of 168 patients enrolled (73 Italians and 95 immigrants), 51 Italians (69.8 percent) and 75 immigrants (78.9 percent) tested positive for the presence of Candida. Candida albicans was the most frequently observed species overall; however, we found a higher occurrence of C. glabrata among immigrants than among Italians. In addition, immigrants displayed a higher incidence of Candida – associated stomatitis and a lower mean age than Candida-positive individuals from the Italian group. Immigrants are more prone to longer colonization of the oral mucosa and dentures by Candida. In these patients, dentures must be checked periodically to prevent the presence of Candida.

Antibacterial activity of various antibiotics against oral streptococci isolated in the oral cavity.

A total of 550 oral streptococci: 270 Streptococcus mitis, 110 Streptococcus sanguis, 90 Streptococcus anginosus, 50 Streptococcus mutans, 30 Streptococcus salivarius, were isolated from dental plaque and gengival crevices of patients and tested for their susceptibility to 12 ß-lactam antibiotics and to 5 non-ß-lactam antibiotics, using the microdiluition method. Overall, a reduced susceptibility to penicillin was recorded in 13.4% of cases. The percentage of strains resistant to penicillin appeared significantly higher in S. mitis (24%) than in S. sanguis (19%), in S. mutans (14%) and in S. salivarius (10%). No levels of penicillin resistance were shown by 90 strains of S. anginosus. In susceptibility test to antibiotics, imipenem was the most active molecule tested, confirming its general good activity against oral streptococci. Also third generation cephalosporins such as ceftriaxone and fourth generation cephalosporins such as cefepime, showed good activity. Chinolones, glycopeptides and rifampicin confirmed a good activity against oral streptococci.

Herpesviruses and periodontal disease: a cautionary tale.

Periodontitis is an inflammatory disease of bacterial origin, characterized by an inconstant progression of lesions affecting the tooth supporting tissues. In spite of more than half a century of research efforts, the clinician still lacks any specific molecular or microbial diagnostic tool to predict the progression of periodontal lesions. Recently, several reports have proposed a role for some herpesviruses in the etiology of destructive phases of periodontitis. This paper critically analyzes these data in the light of consolidated knowledge that was developed in the characterization of virus-bacteria cooperative interactions, and proposes new topics of investigation to clarify the role of herpesviral infections in periodontitis and their potential predictive role as markers of progression.

Antibacterial activity and anti-biofilm effect of chitosan against strains of Streptococcus mutans isolated in dental plaque.

Streptococcus mutans is the major cause of dental plaque and is often associated with biofilm formation. The aim of this study is to evaluate the activity of a hydrosoluble derivative of chitosan against S. mutans biofilms in vitro and in vivo. Strains of S. mutans were isolated from the dental plaque of 84 patients enrolled in the study. The antibacterial activity of chitosan was determined by broth microdilutions. The effect of chitosan at different concentrations and exposure times on S. mutans biofilms at different phases of development was assessed by a clinical study using the classical "4-day plaque regrowth" experiment in adult volunteers. The MIC values of chitosan were between 0.5 and 2 g/L. Compared to distilled water, the chitosan solution significantly decreased the vitality of plaque microflora (p

Electric-current-assisted application of self-etch adhesives to dentin.

The use of electric current during the application of etch-and-rinse adhesive systems has been recently claimed to increase bonding of etch-and-rinse adhesives by enhancing substrate impregnation. The null hypothesis tested in this study was that electrically assisted application has no effect on bond strength of self-etching bonding systems. Three self-etch adhesives (Protect-Bond, Xeno III, and Prompt L-Pop) were applied with the aid of an electric signal-generating device (ElectroBond) and tested vs. controls prepared with the same disposable sponges but without electric current. Specimens bonded under the influence of electric current exhibited increased microtensile bond strength compared with the controls (p<0.05). High-resolution SEM analysis showed that bonding under the influence of electricity reduced interfacial nanoleakage. It is speculated that resin infiltration may be improved by the attraction of polar monomers by an electric current or by modification of the dentin surface charges, resulting in better water substitution or evaporation.

Microbiological study and scanning electron microscopic analysis of root canal wall dentin following pumped Diodium Nd:YAG laser irradiation.

The capability of Nd:YAG laser in sterilizing root canals and the alterations of dentinal walls induced by laser treatment were investigated. Thirty root canals were infected by P. aeruginosa ATCC 27853 and thirty canals by A. naeslundii CH-12. Within each infection, 4 groups were selected on the basis of the treatment. Among them, 2 test groups (TGs) were treated by Nd:YAG laser at 15 Hz for 15 s, using 2 different settings: 1 Watt/70 Joule and 1.5 Watt/100 Joule, respectively (n = 10 each). The other 2 groups, used as controls (CGs), were: untreated (positive control, n = 5) and sterilized by 5.25% NaClO group (negative control, n = 5). Observations under scanning electron microscope (SEM) and quantitative bacterial counts were performed. These analyses were performed once per group after infections and treatments. Laser treatments significantly reduced the number of both bacteria. SEM investigation showed melting and crystallization of canal dentin over 1.5 W/100 J. Laser irradiation has a bactericidal effect but it does not completely sterilize the root canal as NaClO 5.25% solution does if the goal of treatment is also to avoid alterations of dentinal walls.

Temperature change within gutta-percha induced by the System-B Heat Source.

AIM: This study evaluated the temperature change within gutta-percha during the vertical compaction technique performed with a System-B Heat Source. METHODOLOGY: Extracted human teeth were prepared and divided in two equal groups depending on the apex diameter (group 1: 0.20-0.25 mm and group 2: 0.30-0.35 mm). Teeth were root treated with a combination of step-back and coronal flaring instrumentation using Gates Glidden burs and hand stainless steel K- and H-files. Two thermocouples were connected to the outer surface of the root: the first one was placed 2 mm apically from cement-enamel junction (CEJ) (point C); and the second one 1.5 mm from the apex (point A). The instrumented canals were filled with size F gutta-percha cones. All teeth were then immersed in a thermostatic bath at a constant temperature of 37 degrees C and warm vertical compaction was performed using a System-B Heat Source. delta T values were recorded by means of a digital thermometer connected to the thermocouples. RESULTS: Increments of temperature (delta T) recorded in point A revealed a mean value of 0.5 +/- 0.5 degree C for group 1 and 0.9 +/- 1.1 degrees C for group 2; delta T values recorded at point C gave a mean value of 4.1 +/- 1.7 degrees C for group 1 and 3.9 +/- 1.81 degrees C in group 2. No statistical difference was found between the groups, whilst a difference was present between the measurements at points A and C (P < 0.01). CONCLUSIONS: The use of the System-B Heat Source on root canals maintained at a constant body temperature by a thermostatic bath revealed that the increase of temperature of the gutta-percha at the apical third of the canal was negligible and that the compaction of the mass of the gutta-percha close to the apex was performed at body temperature. Minor changes in temperature of the outer surface of the root canals occurred, suggesting no danger for the periradicular tissues.

Antibiotic prescribing for dental conditions: a community-based study in southern Italy.

The aim of this study was to investigate for which conditions antibiotics are being used in community dental practice, and which clinical features represent the most common reason for an antibacterial approach to the treatment of dental conditions. The study was carried out from November 1998 to June 1999. Dentists were selected according to the different areas of southern Italy, from a list provided by the Italian Society of Dentists. Out of 87 selected dentists, 33 agreed to participate and filled in 1615 questionnaires for each therapeutic intervention ending with antibiotic treatment. Analysis of data indicated that alveolar-gingival abscesses were the most commonly treated infection, accounting for 23.6% of total treatments, followed by acute periodontitis (20.6%) and disodontiasis of the 3rd molar (18.5%). Parenteral antibiotics were chosen in 7.8% of cases. Penicillins were the most commonly used group, 40.1% of total treatments, followed by macrolides (30.2%) and cephalosporins (13.4%). Moreover, penicillins were widely used for post-surgery therapy (52.1%) and disodontiasis of the 3rd molar (50.8%), while macrolides were the most commonly used group for gingivitis (44.1%) and parodontal diseases (55.0%). The choice of parenteral antibiotics was related to severe general symptoms (odds ratios [OR], 4.4; 95% CI: 2.2-9.0), pain (OR, 2.7; 95% CI: 1.2-6.1) and lymphonodal involvement (OR, 6.4; 95% CI: 2.7-15.1). In conclusion, our study demonstrates that antibiotic treatment is often based on the eradication of as many microorganisms as possible, and on the clinical assessment of the patients, rather than on any knowledge of the pathogens involved.

Antibacterial activity and post-antibiotic effect of flurithromycin compared with other macrolides and penicillins against periodontal pathogens.

In this study the authors examined the activity of flurithromycin compared to that of erythromycin, spiramycin and penicillin against 107 strains of various species supposed to cause periodontitis. The range of MICs of flurithromycin was: < or =0.06-2 mg/l for P. gingivalis (28 isolates), 0.06-2 mg/l for P. melaninogenica (7), 0.5-4 mg/l for P. intermedia (5), 0.25-8 mg/l for Prevotella sp. (8), 1-16 mg/l for F. nucleatum (14), 0.12-0.5 mg/l for W. recta (2), 0.5-32 mg/l for E. corrodens, 0.5-2 mg/l for B. forsythus (2); < or =0.06-64 mg/l for Peptostreptococcus sp. (11), < or =0.06-1 mg/l for A. odontolyticus (11) and for A. naeslundii (7) and < or =0.06-16 mg/l for A. viscosus (7). Macrolide activity was ranked in decreasing order from flurithromycin to erythromycin to spiramycin. Beta-lactamase production was demonstrated in Prevotella sp. (20%) and in F. nucleatum (7%). Isolates which were beta-lactamase negative but resistant to penicillin were found among Peptostreptococcus sp. and Actinomyces sp. A post-antibiotic effect of 2 hours was seen for flurithromycin on P. gingivalis and E. corrodens. The good in vitro activity of flurithromycin against bacteria supposed to cause periodontitis suggests clinical potential in the treatment of these diseases.