Effect of composite resin containing antibacterial filler on sugar-induced pH drop caused by whole saliva bacteria.

STATEMENT OF PROBLEM: Secondary caries around restorations is a major problem and can be attributed to bacteria invading microgaps formed at the tooth-restoration interface. An antibacterial composite resin containing quaternary ammonium silica (QASi) filler has been reported to inhibit enamel demineralization in situ. However, whether the prevention of enamel demineralization by QASi-containing composite resin is because of the reduced metabolic activity of acid-producing saliva bacteria is unclear. PURPOSE: The purpose of this study was to compare the effects of QASi-containing composite resin and 2 other restorative materials on the viability of salivary bacteria and sugar-induced acid production. MATERIAL AND METHODS: Whole saliva from each of the 30 study participants, 14 at high risk and 16 at low risk for caries, was brought into contact with quadruplicate specimens of 3 restorative materials, Infinix Flowable Composite, an anti-bacterial composite resin containing 1.5% QASi filler (Nobio), Filtek Supreme Flowable Restorative (3M), a conventional flowable composite resin, and dental amalgam (Silmet). Bacterial growth and sugar-induced acid production on each restorative material were measured every 20 minutes for 18 hours. Caries risk groups were compared using the t test and repeated measures analysis of variance (α=.05). When significant, Bonferroni multiple comparisons were used. RESULTS: On average, the saliva with the QASi-containing composite resin specimens maintained a near-neutral pH, not dropping below pH 6.0. The saliva associated with both conventional restorative materials exhibited a pH drop below 5.5 (P<.001), the critical threshold for tooth demineralization according to the Stephan curve. Virtually no growth was measured on the surface of the antibacterial composite resin, whereas bacteria grew on the conventional composite resin and dental amalgam (P<.001). No differences were observed between participants at high and low risk of caries. CONCLUSIONS: Unlike amalgam and conventional composite resin, the QASi-containing composite resin showed a near-complete shutdown of the metabolic activity of salivary bacteria upon contact and virtually no bacterial viability. This suggests that the prevention of tooth demineralization by QASi-containing restoratives is associated with a significant reduction in bacterial metabolic activity.

Impact of dietary interventions on pre-diabetic oral and gut microbiome, metabolites and cytokines.

Diabetes and associated comorbidities are a global health threat on the rise. We conducted a six-month dietary intervention in pre-diabetic individuals (NCT03222791), to mitigate the hyperglycemia and enhance metabolic health. The current work explores early diabetes markers in the 200 individuals who completed the trial. We find 166 of 2,803 measured features, including oral and gut microbial species and pathways, serum metabolites and cytokines, show significant change in response to a personalized postprandial glucose-targeting diet or the standard of care Mediterranean diet. These changes include established markers of hyperglycemia as well as novel features that can now be investigated as potential therapeutic targets. Our results indicate the microbiome mediates the effect of diet on glycemic, metabolic and immune measurements, with gut microbiome compositional change explaining 12.25% of serum metabolites variance. Although the gut microbiome displays greater compositional changes compared to the oral microbiome, the oral microbiome demonstrates more changes at the genetic level, with trends dependent on environmental richness and species prevalence in the population. In conclusion, our study shows dietary interventions can affect the microbiome, cardiometabolic profile and immune response of the host, and that these factors are well associated with each other, and can be harnessed for new therapeutic modalities.

Deep convolution neural network for screening carotid calcification in dental panoramic radiographs.

Ischemic stroke, a leading global cause of death and disability, is commonly caused by carotid arteries atherosclerosis. Carotid artery calcification (CAC) is a well-known marker of atherosclerosis. Such calcifications are classically detected by ultrasound screening. In recent years it was shown that these calcifications can also be inferred from routine panoramic dental radiographs. In this work, we focused on panoramic dental radiographs taken from 500 patients, manually labelling each of the patients' sides (each radiograph was treated as two sides), which were used to develop an artificial intelligence (AI)-based algorithm to automatically detect carotid calcifications. The algorithm uses deep learning convolutional neural networks (CNN), with transfer learning (TL) approach that achieved true labels for each corner, and reached a sensitivity (recall) of 0.82 and a specificity of 0.97 for individual arteries, and a recall of 0.87 and specificity of 0.97 for individual patients. Applying and integrating the algorithm in healthcare units and dental clinics has the potential of reducing stroke events and their mortality and morbidity consequences.

Antibacterial performance of composite containing quaternary ammonium silica (QASi) filler - A preliminary study.

BACKGROUND: Antibacterial composite will have a significant clinical advantage in controlling caries. This study tests the antibacterial properties of a novel bulk-fill flowable composite (Infinx™, Nobio™ Ltd.) containing quaternary ammonium silica (QASi) filler particles. METHODS: Infinix™ was tested in-vitro by the direct contact test (DCT), using E. faecalis or whole saliva as inoculum. A similar formula composite without QASi served as a control. In addition, composite test samples were polymerized on three volunteers' intact buccal enamel surfaces of mandibular first premolars in a split-mouth design experiment. Traditional composite served as control (Filtek Bulk Fill Flowable, 3M). Bacterial viability on the composite surfaces weres assessed ex-vivo microscopically six months later, using a fluorescent dead/live stain. Images of each bacterial sample were taken using a fluorescent microscope (Nikon Eclipse 80i), and further live/total cell analysis was performed using ImageJ software. RESULTS: Following direct contact with one week of aged Infinix, more than 1 million E. faecalis bacteria were killed. Similarly, when using the saliva as inoculum, no single microorganism survived. Six-month in-vivo experiments supported these results by showing a reduction of 54%, 30% and 28% in live/total number of bacteria ratio retrieved from antibacterial composite vs. the control in volunteers #1, #2, #3 respectively. CONCLUSION: Within the limitations of the experimental design, the present study suggest that antibacterial activity of quaternary ammonium silica particles (QASi) is comparable to that of previously described quaternary ammonium polyethyleneimine particles (QPEI). In addition, whole saliva bacteria are effectively killed by QASi-containing composite in-vitro and in-vivo, for a period of six month at least. Long-term full-scale clinical study is needed to confirm the findings of the present study and their implication on maintaining health balance. CLINICAL SIGNIFICANCE: Antibacterial composites containing QASi filler is a novel class of restoratives that may contributes to caries lesion control.

Translation of mouse model to human gives insights into periodontitis etiology.

To suggest candidate genes involved in periodontitis, we combined gene expression data of periodontal biopsies from Collaborative Cross (CC) mouse lines, with previous reported quantitative trait loci (QTL) in mouse and with human genome-wide association studies (GWAS) associated with periodontitis. Periodontal samples from two susceptible, two resistant and two lines that showed bone formation after periodontal infection were collected during infection and naïve status. Differential expressed genes (DEGs) were analyzed in a case-control and case-only design. After infection, eleven protein-coding genes were significantly stronger expressed in resistant CC lines compared to susceptible ones. Of these, the most upregulated genes were MMP20 (P = 0.001), RSPO4 (P = 0.032), CALB1 (P = 1.06×10-4), and AMTN (P = 0.05). In addition, human orthologous of candidate genes were tested for their association in a case-controls samples of aggressive (AgP) and chronic (CP) periodontitis (5,095 cases, 9,908 controls). In this analysis, variants at two loci, TTLL11/PTGS1 (rs9695213, P = 5.77×10-5) and RNASE2 (rs2771342, P = 2.84×10-5) suggested association with both AgP and CP. In the association analysis with AgP only, the most significant associations were located at the HLA loci HLA-DQH1 (rs9271850, P = 2.52×10-14) and HLA-DPA1 (rs17214512, P = 5.14×10-5). This study demonstrates the utility of the CC RIL populations as a suitable model to investigate the mechanism of periodontal disease.

Peri-implant alveolar bone resorption in an innovative peri-implantitis murine model: Effect of implant surface and onset of infection.

PURPOSE: To compare the difference in alveolar bone resorption around implants after immediate placement in a bacterial induced experimental periimplantitis murine model. The various conditions that were examined were: Effect of implant surface characteristics and the onset of the induced infection. MATERIALS AND METHODS: Screw-shaped titanium implants, smooth-surface or sand-blasted large-grit acid-etched (SLA) coated, were inserted immediately after extraction of the first upper left molar, in 90 5-6-week-old BALB/c mice. The mice were infected with Porphyromonas gingivalis and Fusobacterium nucleatum 21 (early infection) or 42 days (delayed infection) after implantation. Six weeks post infection, bone volume around inserted implants was measured using micro-CT, and was compared to alveolar bone level around teeth. Histological analysis was also performed. RESULTS: The level of bone loss was significantly higher around the implants compared to the teeth, for smooth surface implants the bone loss was higher than of the SLA surface in both control and infected groups with no statistical significance. The survival rate of the implants in immediate infection was 75% compared of the 100% survival of the delayed infection and control mice. There is no significant difference between the early and the delayed infection in alveolar bone loss level around the implants. CONCLUSIONS: This model can assist in studying the differences in alveolar bone resorption in different implants and their effect on the development of the disease.

Surface-modified nanoparticles as anti-biofilm filler for dental polymers.

The objective of the study was to synthesis silica nanoparticles modified with (i) a tertiary amine bearing two t-cinnamaldehyde substituents or (ii) dimethyl-octyl ammonium, alongside the well-studied quaternary ammonium polyethyleneimine nanoparticles. These were to be evaluated for their chemical and mechanical properties, as well for antibacterial and antibiofilm activity. Samples were incorporated in commercial dental resin material and the degree of monomer conversion, mechanical strength, and water contact angle were tested to characterize the effect of the nanoparticles on resin material. Antibacterial activity was evaluated with the direct contact test and the biofilm inhibition test against Streptococcus mutans. Addition of cinnamaldehyde-modified particles preserved the degree of conversion and compressive strength of the base material and increased surface hydrophobicity. Quaternary ammonium functional groups led to a decrease in the degree of conversion and to low compressive strength, without altering the hydrophilic nature of the base material. In the direct contact test and the anti-biofilm test, the polyethyleneimine particles exhibited the strongest antibacterial effect. The cinnamaldehyde-modified particles displayed antibiofilm activity, silica particles with quaternary ammonium were ineffective. Immobilization of t-cinnamaldehyde onto a solid surface via amine linkers provided a better alternative to the well-known quaternary ammonium bactericides.

Testing Motor Learning Curves Among Dental Students.

Motor learning up to reaching proficiency can be registered and displayed as a learning curve. Understanding the nature of the motor learning curves will allow proper planning of teaching. The aim of this study was to measure the rate of motor learning of novice dental students in preparing dental cavities. A total of 66 first-year students (21 males and 45 females) at a dental school in Israel participated in this 12-week study. In the first and last weeks, the students prepared 12 cavities in 45 minutes in a composite material plate, using a dental high-speed burr. In the ten weeks between tests, manual performance was measured by drilling two cavities, limited to 3.5 minutes per cavity. The results showed that improvement was significant (p<0.05) at two-week intervals in all cases except for the sixth and seventh weeks, when a significant increase was observed only after three weeks. The performance of the lowest performing students (those with grades in the lowest third of the class) remained low throughout the entire course. Further subdivision of the class into two groups showed that the upper half reached the minimum required performance in week 9, whereas the lower half achieved it only three weeks later. The authors concluded that the 12-week study was not sufficiently long for the learning curve to reach a plateau. Dental students present a variety of motor learning curves and different rates of proficiency acquisition, so understanding the nature of these curves, and the differences among students, may be useful in lesson planning to support the process of motor learning.

Antibacterial Orthodontic Adhesive Incorporating Polyethyleneimine Nanoparticles.

PURPOSE: To evaluate the antibacterial, mechanical and biocompatibility characteristics of an orthodontic adhesive that contains quaternary ammonium polyethyleneimine (QPEI) nanoparticles. MATERIALS AND METHODS: QPEI nanoparticles were added to an orthodontic adhesive at 0%, 1% and 1.5% wt/wt. Antibacterial activity was tested after aging for 14 days using the direct contact test (DCT). The degree of monomer conversion (DC) was measured using Fourier transform infrared (FTIR) spectroscopy. Shear bond atrength (SBS) was tested on the etched enamel of extracted human teeth. Biocompatibility was tested using keratinocyte and neutrophil cell lines in the XTT assay. RESULTS: The DCT results showed significant bacterial growth inhibition in the test group incorporating 1.5% wt/wt QPEI nanoparticles (p < 0.05). The DC of the 0%, 1%, and 1.5% wt/wt samples measured immediately and after 10 min was 62.2-71.0%, 59.1-68.7%, and 52.9-58.6%, respectively, and the average SBS were 9.25 MPa, 11.57 MPa, and 9.10 MPa, respectively. Keratinocyte and neutrophil viability did not change following the addition of QPEI to the orthodontic adhesives. CONCLUSIONS: The incorporation of QPEI nanoparticles into orthodontic cement provides long-lasting antibacterial activity against Streptococcus mutans without reducing the strength of adhesion to enamel, the degree of double bond conversion during the polymerisation, or the biocompatibility of the orthodontic cement.

Synthesis variants of quaternary ammonium polyethyleneimine nanoparticles and their antibacterial efficacy in dental materials.

BACKGROUND: Resin-based dental materials allow bacterial growth on their surface and lack antibacterial activity, leading to functional and esthetic failure. Quaternary ammonium polyethyleneimine (QPEI) nanoparticles (NPs) incorporated in resin-based composite at 2% wt/wt have demonstrated prolonged and complete inhibition of bacterial growth. This study focused on optimization of QPEI NP synthesis to reduce the concentration required for bacterial growth inhibition. The objective here was to enhance antimicrobial efficacy by excess base neutralization, using phosphoric or hydrochloric acid, and by using surfactants. METHODS: QPEI NP variants were prepared (i) under controlled neutralization of acid, using NaHCO3, (ii) under controlled carbonate ion neutralization with HCl or H3PO4 and (iii) by treatment with N-lauroylsarcosine or glycerol monostearate. NPs incorporated in the dental materials were examined for their antibacterial effect against Enterococcus faecalis. RESULTS: Controlled addition of NaHCO3 resulted in modified QPEI NPs with an increased ability to inhibit bacterial growth. Surface treatment with N-lauroylsarcosine resulted in enhanced antibacterial activity at 0.5% wt/wt concentration in acrylate and epoxy resin-based dental materials. CONCLUSIONS: The antimicrobial efficacy of QPEI NP may be improved significantly by controlling the addition of NaHCO3, neutralization of excess base and the surface-agent effect.

Lethal bacterial trap: Cationic surface for endodontic sealing.

Insoluble antibacterial cationic nanoparticles have been previously shown to have potent and long-lasting antibacterial properties. Our tested hypothesis was that root canal pathogens will be attracted to and eliminated when exposed to epoxy resin-based surfaces incorporating cationic nanoparticles. In our research, an epoxy resin-based surface incorporating quaternary ammonium polyethyleneimine (QPEI) nanoparticles was evaluated. Surface characterization was performed using atomic force microscopy and X-ray photoelectron spectra. The surface anti-Enterococcus faecalis effect was evaluated in an anti-gravitational model. Cell membrane potential, viability, biofilm thickness, and biomass were tested using flow cytometry and confocal laser scanning microscopy. Additionally, the antibiofilm activity of the bacterial supernatant was assessed. The surface characterization showed QPEI nanoparticle embedment on the modified sealer. The epoxy resin-based surface incorporating the QPEI nanoparticles actively attracted bacteria, causing membrane destabilization, and bacterial death. The supernatant of bacteria pre-exposed to QPEI showed an antibacterial effect. In conclusion, the tested epoxy resin-based surface incorporating QPEI nanoparticles traps and kills bacteria. The nanoparticles attracted bacteria, reducing their viability, and promoting cell death.

Anti-biofilm properties of wound dressing incorporating nonrelease polycationic antimicrobials.

Polycationic nanoparticles show biocompatible, broad-spectrum bactericidal properties in vitro and in vivo when incorporated in denture lining material post-maxillectomy in head and neck cancer patients. In the present study, the synthesized Crosslinked quaternary ammonium polyethylenimine nanoparticles were found to have a strong bactericidal activity against a wide variety of microorganisms rapidly killing bacterial cells when incorporated at small concentrations into soft lining materials without compromising mechanical and biocompatibility properties. This appears advantageous over conventional released antimicrobials with regard to in vivo efficacy and safety, and may provide a convenient platform for the development of non-released antimicrobials. This is a crucial issue when it comes to giving an answer to the serious and life-threatening problems of contaminations in immunocompromised patients such as orofacial cancer patient.

Teaching New Materials and Techniques for Fixed Dental Prostheses in Dental Schools in the United States and Canada: A Survey.

PURPOSE: Tooth-supported fixed dental prostheses (FDPs) remain an extensive therapeutic option, with new materials and a digital fabrication process gradually replacing traditional methods. The variety of advances calls for dental schools to expand the teaching of this field. Our aim was to examine the nature and the amount of theoretical and practical training in clinical FDP courses, and the extent to which new methods and innovations in the field are being integrated. MATERIALS AND METHODS: Data were collected using an online questionnaire including theoretical and practical teaching regarding clinical courses, restorative materials, and new fabrication methods, which was sent to 58 dental schools in North America. RESULTS: A total of 36 schools responded to the survey for a response rate of 62.1%. All the schools teach theoretical and practical porcelain-fused-to-metal (PFM) restorations, and almost all the schools teach full-metal FDPs. In more than half (57.1%) of the schools, zirconia-based FDPs are placed by students. Students place partial veneer FDPs in less than one-fifth (17.9%) of the schools. The average number of restorations required for completion of the clinical course is 7.3 FDP units. The respondents assessed that of the total FDPs placed by students in the clinical course, tooth-color coping (zirconia/alumina/porcelain) FDPs constituted 16.2%. None of the schools produce computer-assisted design/computer-assisted manufacturing copings or crowns within the school. CONCLUSIONS: All North American dental schools include teaching and placement of PFM restorations in their curriculum, but only one-third teach ceramic-based crowns. The low average number of required crowns may lead to graduates not being exposed to and trained in up-to-date dental restorative materials and techniques.

Genetic evidence for PLASMINOGEN as a shared genetic risk factor of coronary artery disease and periodontitis.

BACKGROUND: Genetic studies demonstrated the presence of risk alleles in the genes ANRIL and CAMTA1/VAMP3 that are shared between coronary artery disease (CAD) and periodontitis. We aimed to identify further shared genetic risk factors to better understand conjoint disease mechanisms. METHODS AND RESULTS: In-depth genotyping of 46 published CAD risk loci of genome-wide significance in the worldwide largest case-control sample of the severe early-onset phenotype aggressive periodontitis (AgP) with the Illumina Immunochip (600 German AgP cases, 1448 controls) and the Affymetrix 500K array set (283 German AgP cases and 972 controls) highlighted ANRIL as the major risk gene and revealed further associations with AgP for the gene PLASMINOGEN (PLG; rs4252120: P=5.9×10(-5); odds ratio, 1.27; 95% confidence interval, 1.3-1.4 [adjusted for smoking and sex]; 818 cases; 5309 controls). Subsequent combined analyses of several genome-wide data sets of CAD and AgP suggested TGFBRAP1 to be associated with AgP (rs2679895: P=0.0016; odds ratio, 1.27 [95% confidence interval, 1.1-1.5]; 703 cases; 2.143 controls) and CAD (P=0.0003; odds ratio, 0.84 [95% confidence interval, 0.8-0.9]; n=4117 cases; 5824 controls). The study further provides evidence that in addition to PLG, the currently known shared susceptibility loci of CAD and periodontitis, ANRIL and CAMTA1/VAMP3, are subjected to transforming growth factor-ß regulation. CONCLUSIONS: PLG is the third replicated shared genetic risk factor of atherosclerosis and periodontitis. All known shared risk genes of CAD and periodontitis are members of transforming growth factor-ß signaling.

Characterisation of the antibacterial effect of polyethyleneimine nanoparticles in relation to particle distribution in resin composite.

OBJECTIVES: To characterise the antibacterial effect of resin composite incorporating cross-linked quaternised polyethyleneimine (QPEI) nanoparticles in relation to their distribution in the bulk material. METHODS: The antibacterial effect of resin composite incorporating QPEI nanoparticle was tested against various oral pathogens, including Enterococcus faecalis, Streptococcus mutans, Actinomyces viscousus, Lactobacilus casei and whole saliva. Nanoparticle distribution in the modified resin composite was assessed using X-ray photoelectron spectroscopy (XPS). Additionally, the degree of conversion was recorded. RESULTS: Total bacterial inhibition was detected against all the tested pathogens following direct contact with the outer surface of the modified resin composite. Similarly, the inner surface of the modified resin composite caused total inhibition. Electron microscope images showed bacterial death. XPS revealed surface I(-) ions on both the outer and the inner surfaces of the modified composite. No I(-) ions were detected in the unmodified composite. Nanoparticle distribution was higher on the inner surface of the modified composite. The composite's degree of conversion was unaffected by nanoparticle addition. CONCLUSIONS: QPEI nanoparticles represent a new generation of antibacterial nanoparticles which are highly promising in preventing bacterial recontamination when restoring teeth.

Topical application of slow-release simvastatin as a bone substitute in bone defects in the rat tibia: a pilot study.

PURPOSE: It is hypothesized that local application of statins positively affects bone formation. The aim of this study was to evaluate the potential effect of topical slow-release simvastatin as a bone substitute on the healing of bone defects in rat tibia. MATERIALS AND METHODS: Granules of slow-releasing hydroxypropyl methylcellulose, with or without simvastatin, were inserted into critical-size defects in the tibiae of 16 rats (8 in the study group, 8 in the control group). Bone static and dynamic histomorphometric variables were examined at 2, 4, 6, and 8 weeks postsurgery. RESULTS: All indices examined in the study group indicated improved healing relative to the control group, although statistical significance was not demonstrated for all variables. In the static histomorphometric analysis, osteoid thickness and volume were significantly higher in the study group, but the fraction of trabecular surface covered with active osteoblasts, the fraction of trabecular surface covered with osteoid, and total calcified bone volume were not significantly higher in the experimental group. In the dynamic histomorphometric analysis, the mineral apposition rate, determined by time-repeated calcein labeling, was significantly higher in the study group than in the control group. Experimental time and dosage effects were observed for most bone values in the study group. CONCLUSION: The findings indicate that topical application of simvastatin for the treatment of bone defects enhances the process of healing. Dosage and the methodology of administration require further calibration.

Heritability and coefficient of genetic variation analyses of phenotypic traits provide strong basis for high-resolution QTL mapping in the Collaborative Cross mouse genetic reference population.

Most biological traits of human importance are complex in nature; their manifestation controlled by the cumulative effect of many genetic factors interacting with one another and with the individual's life history. Because of this, mouse genetic reference populations (GRPs) consisting of collections of inbred lines or recombinant inbred lines (RIL) derived from crosses between inbred lines are of particular value in analysis of complex traits, since massive amounts of data can be accumulated on the individual lines. However, existing mouse GRPs are derived from inbred lines that share a common history, resulting in limited genetic diversity, and reduced mapping precision due to long-range gametic disequilibrium. To overcome these limitations, the Collaborative Cross (CC) a genetically highly diverse collection of mouse RIL was established. The CC, now in advanced stages of development, will eventually consist of about 500 RIL derived from reciprocal crosses of eight divergent founder strains of mice, including three wild subspecies. Previous studies have shown that the CC indeed contains enormous diversity at the DNA level, that founder haplotypes are inherited in expected frequency, and that long-range gametic disequilibrium is not present. We here present data, primarily from our own laboratory, documenting extensive genetic variation among CC lines as expressed in broad-sense heritability (H(2)) and by the well-known "coefficient of genetic variation," demonstrating the ability of the CC resource to provide unprecedented mapping precision leading to identification of strong candidate genes.

Rapid kill-novel endodontic sealer and Enterococcus faecalis.

With growing concern over bacterial resistance, the identification of new antimicrobial means is paramount. In the oral cavity microorganisms are essential to the development of periradicular diseases and are the major causative factors associated with endodontic treatment failure. As quaternary ammonium compounds have the ability to kill a wide array of bacteria through electrostatic interactions with multiple anionic targets on the bacterial surface, it is likely that they can overcome bacterial resistance. Melding these ideas, we investigated the potency of a novel endodontic sealer in limiting Enterococcus faecalis growth. We used a polyethyleneimine scaffold to synthesize nano-sized particles, optimized for incorporation into an epoxy-based endodontic sealer. The novel endodontic sealer was tested for its antimicrobial efficacy and evaluated for biocompatibility and physical eligibility. Our results show that the novel sealer foundation affixes the nanoparticles, achieving surface bactericidal properties, but at the same time impeding nanoparticle penetration into eukaryotic cells and thereby mitigating a possible toxic effect. Moreover, adequate physical properties are maintained. The nanosized quaternary amine particles interact within minutes with bacteria, triggering cell death across wide pH values. Throughout this study we demonstrate a new antibacterial perspective for endodontic sealers; a novel antibacterial, effective and safe antimicrobial means.

Genotype is an important determinant factor of host susceptibility to periodontitis in the Collaborative Cross and inbred mouse populations.

BACKGROUND: Periodontal infection (Periodontitis) is a chronic inflammatory disease, which results in the breakdown of the supporting tissues of the teeth. Previous epidemiological studies have suggested that resistance to chronic periodontitis is controlled to some extent by genetic factors of the host. The aim of this study was to determine the phenotypic response of inbred and Collaborative Cross (CC) mouse populations to periodontal bacterial challenge, using an experimental periodontitis model. In this model, mice are co-infected with Porphyromonas gingivalis and Fusobacterium nucleatum, bacterial strains associated with human periodontal disease. Six weeks following the infection, the maxillary jaws were harvested and analyzed for alveolar bone loss relative to uninfected controls, using computerized microtomography (microCT). Initially, four commercial inbred mouse strains were examined to calibrate the procedure and test for gender effects. Subsequently, we applied the same protocol to 23 lines (at inbreeding generations 10-18) from the newly developed mouse genetic reference population, the Collaborative Cross (CC) to determine heritability and genetic variation of control bone volume prior to infection (CBV, naïve bone volume around the teeth of uninfected mice), and residual bone volume (RBV, bone volume after infection) and loss of bone volume (LBV, the difference between CBV and RBV) following infection. RESULTS: BALB/CJ mice were highly susceptible (P<0.05) whereas DBA/2J, C57BL/6J and A/J mice were resistant. Six lines of the tested CC population were susceptible, whereas the remaining lines were resistant to alveolar bone loss. Gender effects on bone volume were tested across the four inbred and 23 CC lines, and found not to be significant. Based on ANOVA analyses, broad-sense heritabilities were statistically significant and equal to 0.4 for CBV and 0.2 for LBV. CONCLUSIONS: The moderate heritability values indicate that the variation in host susceptibility to the disease is controlled to an appreciable extent by genetic factors. These results strongly support the possibility of using the Collaborative Cross, as well as developing dedicated F2 (resistant x susceptible inbred strains) resource populations, for future dissection of genetic factors in periodontitis.