Antimicrobial Mechanism of Oleanolic and Ursolic Acids on Streptococcus mutans UA159

Triterpenoid saponin derivatives oleanolic acid (OA) and ursolic acid (UA), but not betulinic acid (BA), were previously found to have strong antimicrobial activity against Streptococcus mutans. OA and UA inhibited the transcription of genes related to peptidoglycan biosynthesis, thereby preventing bacterial growth. However, it is not clear whether this is the only pathway involved in the antimicrobial activity of these compounds against S. mutans. Therefore, we used quantitative real-time PCR (qPCR) and microarray analyses to examine the expression of genes related to essential metabolic pathways in S. mutans UA159 following incubation with OA, UA, or BA. An oligonucleotide array consisting of 5363 probes was designed to survey 1928 of the 1963 genes in the genome of S. mutans UA159. Genes that showed >2-fold changes in expression in response to the treatment conditions were annotated, and selected target genes involved in central metabolism were analyzed by qPCR. Microarray analysis confirmed that the gene expression patterns of the OA- and UA-treated cells differed from that of the BA-treated culture, indicating differences in the antimicrobial mechanism. In particular, the expression of pfk and pykF, coding for glycolysis regulatory proteins phosphofructokinase and pyruvate kinase, respectively, were significantly decreased in the OA and UA groups (P < 0.05), as were genes involved in fatty acid and amino acid synthesis. In addition, the microarray analysis confirmed previous qPCR results showing that peptidoglycan synthesis is down-regulated in the OA- and UA-treated groups. OA and UA also appear to decrease the generation of organic acids by S. mutans UA159, which would have an anticaries effect. Overall, these findings suggest that OA and UA affect multiple genes involved in the central metabolism of S. mutans, with inhibition of glycolysis, fatty acid synthesis, amino acid synthesis, and peptidoglycan synthesis, all contributing to their antimicrobial activity.

Prevalence of Intracranial Aneurysms in Patients with Aortic Dissection

BACKGROUND AND PURPOSE

There is an uncertainty about the association between intracranial aneurysms and aortic dissection. We aimed to determine the prevalence of intracranial aneurysms in patients with aortic dissection and evaluate the independent risk factors for the presence of intracranial aneurysms in these patients.

MATERIALS AND METHODS

Seventy-one patients with a confirmed aortic dissection who underwent additional brain imaging were enrolled as the aortic dissection group, and 2118 healthy individuals with brain imaging, as controls. Demographic data were obtained from their medical records, including age, sex, comorbidities, and arch vessel involvement of aortic dissection. Two readers reviewed all brain images independently regarding the presence, morphology, size, and location of intracranial aneurysms. Baseline characteristics were compared between the aortic dissection group and controls by propensity score matching, and logistic regression analysis was performed for independent risk factors for the presence of intracranial aneurysms.

RESULTS

The prevalence of intracranial aneurysms was 12.96% in the aortic dissection group and 1.85% in controls (P = .022). The mean diameter of intracranial aneurysms was significantly larger in the aortic dissection group (5.79 ± 3.26 mm in aortic dissection versus 3.04 ± 1.57 mm in controls; P = .008), and intracranial aneurysms of >7 mm were also more common in the aortic dissection group (28.6% in aortic dissection versus 5.3% in controls, P = .003). On multivariate analysis, arch vessel involvement of aortic dissection was an independent risk factor for the presence of intracranial aneurysms (odds ratio, 6.246; 95% confidence interval, 1.472-26.50; P = .013).

CONCLUSIONS

Patients with aortic dissection have a high prevalence of intracranial aneurysms, and selective screening for brain vessels could be considered in these patients with arch vessel involvement. A further prospective study is needed to demonstrate a substantial prevalence of intracranial aneurysms.

Antimicrobial and physical characteristics of orthodontic primers containing antimicrobial agents

OBJECTIVE

To compare the antimicrobial and physical properties of experimental primers containing chlorhexidine (CHX) or ursolic acid (UA) with a commercial primer.

MATERIALS AND METHODS

Two antibacterial agents, 3 mg each of CHX and UA were incorporated respectively into 1 ml of Transbond XT primer (TX) to form antibacterial primers, TX-CHX and TX-UA. The antimicrobial activity of the three primers (TX, TX-CHX, and TX-UA) against Streptococcus mutans in both planktonic and biofilm phases was analyzed by determining minimum inhibitory and bactericidal concentrations and by performing growth and biofilm assays. Growth and biofilm assays were performed in both the absence and presence of thermocycling in a water tank to analyze the effects of water aging on the antimicrobial activities of primers. After bonding brackets onto bovine incisors using the primers, shear bond strength and mode of fracture were analyzed to compare physical properties.

RESULTS

TX-CHX had stronger antimicrobial activity against S. mutans in the planktonic and biofilm phases than did TX or TX-UA. When applied, TX-CHX completely inhibited the growth and biofilm formation of S. mutans . In addition, the antimicrobial activity of TX-CHX was maintained after thermocycling. However, TX-UA did not show significant antimicrobial activity compared with TX. There was no significant difference in either shear bond strength or bond failure interface among the primers.

CONCLUSION

Incorporation of CHX into an orthodontic primer may help prevent enamel demineralization around surfaces without compromising its physical properties.

Changes in salivary periodontal pathogens after orthodontic treatment: An in vivo prospective study

OBJECTIVE

  To analyze the initial changes in salivary levels of periodontal pathogens after orthodontic treatment with fixed appliances.

MATERIALS AND METHODS

  The subjects consisted of 54 adult patients. The Simplified Oral Hygiene Index, Plaque Index, and Gingival Index were measured as periodontal parameters. Both the plaque and gingival indexes were obtained from the central and lateral incisors and first molars of both arches. Whole saliva and periodontal parameters were obtained at the following four time points: immediately before debonding (T1), 1 week after debonding (T2), 5 weeks after debonding (T3), and 13 weeks after debonding (T4). Repeated measures analysis of variance was used to determine salivary bacterial levels and periodontal parameters among the four time points after quantifying salivary levels of Aggregatibacter actinomycetemcomitans (Aa), Fusobacterium nucleatum (Fn), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Tannerella forsythia (Tf), and total bacteria using the real-time polymerase chain reaction.

RESULTS

  All periodontal parameters were significantly decreased immediately after debonding (T2). The salivary levels of total bacteria and Pg were decreased at T3, while Pi and Tf levels were decreased at T4. However, the amount of Aa and Fn remained at similar levels in saliva during the experimental period. Interestingly, Aa and Fn were present in saliva at higher levels than were Pg, Pi, and Tf.

CONCLUSION

  The higher salivary levels of Aa and Fn after debonding suggests that the risk of periodontal problems cannot be completely eliminated by the removal of fixed orthodontic appliances during the initial retention period, despite improved oral hygiene.

Adhesion of periodontal pathogens to self-ligating orthodontic brackets: An in-vivo prospective study

INTRODUCTION

Our aims were to analyze adhesion of periodontopathogens to self-ligating brackets (Clarity-SL [CSL], Clippy-C [CC] and Damon Q [DQ]) and to identify the relationships between bacterial adhesion and oral hygiene indexes.

METHODS

Central incisor brackets from the maxilla and mandible were collected from 60 patients at debonding after the plaque and gingival indexes were measured. Adhesions of Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Fusobacterium nucleatum (Fn), and Tannerella forsythia (Tf) were quantitatively determined using real-time polymerase chain reactions. Factorial analysis of variance was used to analyze bacterial adhesion in relation to bracket type and jaw position. Correlation coefficients were calculated to determine the relationships between bacterial adhesion and the oral hygiene indexes.

RESULTS

Total bacteria showed greater adhesion to CSL than to DQ brackets, whereas Aa, Pg, and Pi adhered more to DQ than to CSL brackets. CC brackets showed an intermediate adhesion pattern between CSL and DQ brackets, but it did not differ significantly from either bracket type. Adhesion of Fn and Tf did not differ significantly among the 3 brackets. Most bacteria were detected in greater quantities in the mandibular than in the maxillary brackets. The plaque and gingival indexes were not strongly correlated with bacterial adhesion to the brackets.

CONCLUSIONS

Because Aa, Pg, and Pi adhered more to the DQ brackets in the mandibular area, orthodontic patients with periodontal problems should be carefully monitored in the mandibular incisors where the distance between the bracket and the gingiva is small, especially when DQ brackets are used.

Reduction of Oxygen-Induced CSF Hyperintensity on FLAIR MR Images in Sedated Children: Usefulness of Magnetization-Prepared FLAIR Imaging

BACKGROUND AND PURPOSE

Oxygen-induced CSF hyperintensity on FLAIR MR imaging is often observed in sedated children. This phenomenon can mimic leptomeningeal pathology and lead to a misdiagnosis. The purpose of this study was to investigate whether magnetization-prepared FLAIR MR imaging can reduce oxygen-induced CSF hyperintensity and improve image quality compared with conventional (non-magnetization-prepared) FLAIR MR imaging.

MATERIALS AND METHODS

Bloch simulation for magnetization-prepared and non-magnetization-prepared FLAIR sequences was performed for tissue contrast. We retrospectively reviewed 85 children with epilepsy who underwent MR imaging under general anesthesia with supplemental oxygen (41 with non-magnetization-prepared FLAIR and 44 with magnetization-prepared FLAIR). CSF hyperintensity was scored from 0 to 3 points according to the degree of CSF signal intensity and was compared between the 2 sequences. The contrast-to-noise ratios among GM, WM, and CSF were evaluated to assess general image quality from both sequences. To assess the diagnostic accuracy for hemorrhage, we reviewed an additional 25 patients with hemorrhage.

RESULTS

Bloch simulation demonstrated that CSF hyperintensity can be reduced on magnetization-prepared FLAIR compared with non-magnetization-prepared FLAIR. CSF hyperintensity scores were significantly lower in magnetization-prepared FLAIR than in non-magnetization-prepared FLAIR (P < .01). The contrast-to-noise ratios for GM-WM, GM-CSF, and WM-CSF were significantly higher in magnetization-prepared FLAIR than in non-magnetization-prepared FLAIR (P < .05). Hemorrhage was clearly demarcated from CSF hyperintensity in the magnetization-prepared group (100%, 12/12) and non-magnetization-prepared group (38%, 5/13).

CONCLUSIONS

Magnetization-prepared 3D-FLAIR MR imaging can significantly reduce oxygen-induced CSF artifacts and increase the tissue contrast-to-noise ratio beyond the levels achieved with conventional non-magnetization-prepared 3D-FLAIR MR imaging.

The Revascularization Scales Dilemma: Is It Right to Apply the Treatment in Cerebral Ischemia Scale in Posterior Circulation Stroke?

BACKGROUND AND PURPOSE

Although various revascularization scales are used in the angiographic evaluation of acute ischemic stroke, observer reliability tests of these scales have been rarely performed for posterior circulation stroke. We aimed to evaluate inter- and intraobserver variability of 2 scales, the modified Treatment in Cerebral Ischemia and the Arterial Occlusive Lesion, in posterior circulation stroke.

MATERIALS AND METHODS

Three independent readers interpreted pre- and postthrombolytic angiographies of 62 patients with posterior circulation stroke by using the modified Treatment in Cerebral Ischemia and Arterial Occlusive Lesion scales. The κ statistic was used to measure observer agreement for both scales, and κ > 0.6 was considered substantial agreement.

RESULTS

For the Arterial Occlusive Lesion scale, inter- and intraobserver agreement was >0.6. While intraobserver agreement of the modified Treatment in Cerebral Ischemia scale was >0.6 except for 1 reader, interobserver agreement was lower in dichotomized and original scales. In 49 cases with solely basilar artery occlusion, inter- and intraobserver agreement of both scales was similar to that in all 62 patients with posterior circulation stroke. In 2 consecutive readings, there was a significant decrease in the proportion of mTICI 2a reads (22.58% in the first versus 13.44% in the second session, P < .03) and a reciprocal increase in the sum of proportions for modified Treatment in Cerebral Ischemia 2b and modified Treatment in Cerebral Ischemia 3 reads (62.37% in the first versus 72.58% in the second session, P < .046).

CONCLUSIONS

In angiographic assessment of posterior circulation stroke, inter- and intraobserver agreement for the Arterial Occlusive Lesion scale was reliable, while the modified Treatment in Cerebral Ischemia failed to achieve substantial interobserver agreement. The clinical impact of this result needs to be validated in future studies.

Hyperintense Vessels on T2-PROPELLER-FLAIR in Patients with Acute MCA Stroke: Prediction of Arterial Stenosis and Perfusion Abnormality

BACKGROUND AND PURPOSE

Fluid-attenuated inversion recovery hyperintense vessels in stroke represent leptomeningeal collateral flow. We presumed that FLAIR hyperintense vessels would be more closely associated with arterial stenosis and perfusion abnormality in ischemic stroke on T2-PROPELLER-FLAIR than on T2-FLAIR.

MATERIALS AND METHODS

We retrospectively reviewed 35 patients with middle cerebral territorial infarction who underwent MR imaging. FLAIR hyperintense vessel scores were graded according to the number of segments with FLAIR hyperintense vessels in the MCA ASPECTS areas. We compared the predictability of FLAIR hyperintense vessels between T2-PROPELLER-FLAIR and T2-FLAIR for large-artery stenosis. The interagreement between perfusion abnormality and FLAIR hyperintense vessels was assessed. In subgroup analysis (9 patients with MCA horizontal segment occlusion), the association of FLAIR hyperintense vessels with ischemic lesion volume and perfusion abnormality volume was evaluated.

RESULTS

FLAIR hyperintense vessel scores were significantly higher on T2-PROPELLER-FLAIR than on T2-FLAIR (3.50 ± 2.79 versus 1.21 ± 1.47, P < .01), and the sensitivity for large-artery stenosis was significantly improved on T2-PROPELLER-FLAIR (93% versus 68%, P = .03). FLAIR hyperintense vessels on T2-PROPELLER-FLAIR were more closely associated with perfusion abnormalities than they were on T2-FLAIR (κ = 0.64 and κ = 0.27, respectively). In subgroup analysis, FLAIR hyperintense vessels were positively correlated with ischemic lesion volume on T2-FLAIR, while the mismatch of FLAIR hyperintense vessels between the 2 sequences was negatively correlated with ischemic lesion volume (P = .01).

CONCLUSIONS

In MCA stroke, FLAIR hyperintense vessels were more prominent on T2-PROPELLER-FLAIR compared with T2-FLAIR. In addition, FLAIR hyperintense vessels on T2-PROPELLER-FLAIR have a significantly higher sensitivity for predicting large-artery stenosis than they do on T2-FLAIR. Moreover, the areas showing FLAIR hyperintense vessels on T2-PROPELLER-FLAIR were more closely associated with perfusion abnormality than those on T2-FLAIR.

Oleanolic acid and ursolic acid inhibit peptidoglycan biosynthesis in Streptococcus mutans UA159

In this study, we revealed that OA and UA significantly inhibited the expression of most genes related to peptidoglycan biosynthesis in S. mutans UA159. To the best of our knowledge, this is the first report to introduce the antimicrobial mechanism of OA and UA against S. mutans.

Influence of temporomandibular joint disc displacement on craniocervical posture and hyoid bone position

INTRODUCTION

The purpose of this study was to evaluate craniocervical posture and hyoid bone position in orthodontic patients with temporomandibular joint (TMJ) disc displacement.

METHODS

The subjects consisted of 170 female orthodontic patients who consented to bilateral magnetic resonance imaging of their TMJs. They were divided into 3 groups based on the results of magnetic resonance imaging of their TMJs: bilateral normal disc position, bilateral disc displacement with reduction, and bilateral disc displacement without reduction. Twenty-five variables from lateral cephalograms were analyzed with 1-way analysis of variance to investigate differences in craniocervical posture and hyoid bone position with respect to TMJ disc displacement status. Pearson correlation coefficients were calculated to analyze the relationships between craniofacial morphology and craniocervical posture or hyoid bone position.

RESULTS

Subjects with TMJ disc displacement were more likely to have an extended craniocervical posture with Class II hyperdivergent patterns. The most significant differences were found between patients with bilateral normal disc position and bilateral disc displacement without reduction. However, hyoid bone position in relation to craniofacial references was not significantly different among the TMJ disc displacement groups, except for variables related to the mandible. Pearson correlation coefficients indicated that extended craniocervical posture was significantly correlated with backward positioning and clockwise rotation of the mandible.

CONCLUSIONS

This suggests that craniocervical posture is significantly influenced by TMJ disc displacement, which may be associated with hyperdivergent skeletal patterns with a retrognathic mandible.

In vitro antimicrobial activities of 1-methoxyficifolinol, licorisoflavan A, and 6,8-diprenylgenistein against Streptococcus mutans

The objective of the study was to investigate the antimicrobial effects of purified single compounds from ethanol-extracted licorice root on Streptococcus mutans. The crude licorice root extract (CLE) was obtained from Glycyrrhiza uralensis, which was subjected to column chromatography to separate compounds. Purified compounds were identified by mass spectrometry and nuclear magnetic resonance. Antimicrobial activities of purified compounds from CLE were evaluated by determining the minimum inhibitory concentration and by performing time-kill kinetics. The inhibitory effects of the compounds on biofilm development were evaluated using crystal violet assay and confocal microscopy. Cell toxicity of substances to normal human gingival fibroblast (NHGF) cells was tested using a methyl thiazolyl tetrazolium assay. Chlorhexidine digluconate (CHX) was used in the control group. Three antimicrobial flavonoids, 1-methoxyficifolinol, licorisoflavan A, and 6,8-diprenylgenistein, were isolated from the CLE. We found that the three flavonoids and CHX had bactericidal effects on S. mutans UA159 at the concentration of ≥4 and ≥1 µg/ml, respectively. The purified compounds completely inhibited biofilm development of S. mutans UA159 at concentrations over 4 μg/ml, which was equivalent to 2 μg/ml of CHX. Confocal analysis showed that biofilms were sparsely scattered in the presence of over 4 μg/ml of the purified compounds. However, the three compounds purified from CLE showed less cytotoxic effects on NHGF cells than CHX at these biofilm-inhibitory concentrations. Our results suggest that purified flavonoids from CLE can be useful in developing oral hygiene products, such as gargling solutions and dentifrices for preventing dental caries.

The effects of TMJ symptoms on skeletal morphology in orthodontic patients with TMJ disc displacement

OBJECTIVE

The aim of this study was to investigate the effects of temporomandibular joint (TMJ) symptoms on skeletal morphologies of orthodontic patients with TMJ disc displacement (DD).

MATERIALS AND METHODS

The sample consisted of 197 women seeking orthodontic treatment. The subjects were divided into two groups according to the presence of TMJ symptoms: the presence and absence of TMJ symptoms. Each group was sub-divided into three groups based on magnetic resonance images of bilateral TMJs: bilateral normal disc position (BN), bilateral disc displacement with reduction (DDR) and bilateral disc displacement without reduction (DDNR). Seventeen variables from lateral cephalograms were analyzed by two-way analysis of variance to identify differences in skeletal morphologies with respect to TMJ symptoms and TMJ DD status.

RESULTS

Patients with TMJ DD were more likely to have short ramus height, short mandibular body length and backward positioning of the ramus and mandible. These skeletal morphologies became more severe as TMJ DD progressed to DDNR. However, the skeletal morphologies associated with TMJ DD were not significantly different between symptomatic and asymptomatic patients. As a result, patients with TMJ DD had backward positioning and clockwise rotation compared to those with bilateral normal TMJs, irrespective of the presence of TMJ symptom.

CONCLUSIONS

This study suggests that TMJ DD is associated with altered skeletal morphology, but TMJ symptoms do not significantly influence the relationships between TMJ DD and skeletal morphology.

Dentofacial characteristics in orthodontic patients with centric relation-maximum intercuspation discrepancy

INTRODUCTION

To investigate dentofacial characteristics of orthodontic patients with centric relation (CR)-maximum intercuspation (MI) discrepancy and to analyze changes in dentofacial characteristics between CR and MI positions in these patients using lateral cephalograms.

MATERIALS AND METHODS

Adult female patients were classified into two groups: large CR-MI discrepancy (greater than 2.0 mm horizontal or vertical mandibular incisor movements during CR to MI change, n  =  20) and small CR-MI discrepancy (less than 1.0 mm horizontal and vertical mandibular incisor movements during CR to MI change, n  =  22). All subjects underwent temporomandibular joint (TMJ) magnetic resonance imaging prior to treatment. Gnathological stabilizing splints were used to find a reliable CR position in patients with large CR-MI discrepancy. Sixteen variables from lateral cephalograms were analyzed to identify differences in cephalometric variables between CR and MI positions in patients with large discrepancy. Differences in dentofacial cephalometric variables at MI positions between patients with large and small CR-MI discrepancies were also analyzed.

RESULTS

Patients with large CR-MI discrepancy had backward positioning and rotation of the mandible at the MI position compared to the norm. In addition, the mandible moved more posteriorly and rotated more in a clockwise direction during MI to CR change. Interestingly, all patients with large CR-MI discrepancy had TMJ disk displacement. There were no significant differences in the cephalometric variables of the MI positions between patients with small and large CR-MI discrepancies.

CONCLUSIONS

This study suggests that adult patients with backward positioning and rotation of the mandible should be carefully evaluated as a result of the potential CR-MI discrepancy.

Efficacy of skull plain films in follow-up evaluation of cerebral aneurysms treated with detachable coils: quantitative assessment of coil mass

BACKGROUND AND PURPOSE

Skull plain films of coiled aneurysms have been used in a limited role, including morphologic comparison of the coil mass. We aimed to evaluate the efficacy of skull plain films in patients treated with detachable coils by using quantitative assessment.

MATERIALS AND METHODS

In this retrospective study, 78 pairs of the initial and follow-up skull anteroposterior and lateral images were reviewed independently by 2 neuroradiologists. The largest diameter, the perpendicular diameter, and area of the coil mass were measured separately on plain film, and quantitative changes of parameters were compared between subgroups, which were determined by consensus, depending on the need for retreatment. Subgroup analysis was also performed according to aneurysm size, packing attenuation, and ruptured status.

RESULTS

On skull lateral images, mean quantitative changes of the largest diameter (0.53 ± 0.43 mm versus 1.17 ± 0.91 mm, P < .01), the perpendicular diameter (0.56 ± 0.48 mm versus 1.20 ± 1.05 mm, P < .01), and the area of the coil mass (5.21 ± 7.51 mm(2) versus 10.55 ± 10.93 mm(2), P < .02) differed significantly between subgroups. Receiver operating characteristic analysis showed quantitative change of the largest diameter (>1.1 mm; sensitivity, 50.0%; specificity, 90.3%), the perpendicular diameter (>.9 mm; sensitivity, 62.5%; specificity, 85.5%), and the area (>8.5 mm(2); sensitivity, 50.0%; specificity, 83.9%) on skull lateral films to be indicative of aneurysm recurrence, and the diagnostic accuracy of these parameters increased significantly in the high-packing-attenuation group.

CONCLUSIONS

Quantitative measurement of the coil mass by using skull plain lateral images has the potential to predict aneurysm recurrence in follow-up evaluations of intracranial aneurysms with coiling.

Autotransplantation of mesiodens for missing maxillary lateral incisor with cone-beam CT-fabricated model and orthodontics

AIM

Autotransplantation is a viable treatment option for a missing tooth when there is a suitable donor, especially in adolescents with remaining facial growth. This report presents the aesthetic restoration of a missing maxillary lateral incisor through orthodontic treatment and autotransplantation of a mesiodens using a CBCT-fabricated rapid-prototyping model.

SUMMARY

A 14-year-old male patient with a congenitally missing maxillary lateral incisor was referred from the Department of Orthodontics. The teeth were moved orthodontically to regain space for the missing lateral incisor and to close the space of the mesiodens after transplantation. A replica of the donor tooth was fabricated from a cone-beam computed tomography scan through a rapid-prototyping machine before autotransplantation surgery. The model was used to create a socket for the graft tooth, thereby shortening the extra-oral time and minimizing the damage to the root surface. After transplantation and orthodontic tooth movement, the mesiodens was finally restored with an aesthetic laminate restoration. Over 3 years, the aesthetics remained excellent, and the transplant functioned normally without any signs or symptoms of root resorption.

KEY LEARNING POINT

Missing anterior teeth may be replaced through a combination of orthodontics, autotransplantation with a rapid-prototyping model and prosthodontic restoration, in growing patients.

Progress dissecting the oral microbiome in caries and health

Recent rapid advances in "-omics" technologies have yielded new insights into the interaction of the oral microbiome with its host. Associations of species that are usually considered to be acid-tolerant with caries have been confirmed, while some recognized as health-associated are often present in greater proportions in the absence of caries. In addition, some newly identified bacteria have been suggested as potential contributors to the caries process. In spite of this progress, two major challenges remain. The first is that there is a great deal of heterogeneity in the phenotypic capabilities of individual species of oral bacteria. The second is that the most abundant taxa in oral biofilms display remarkable phenotypic plasticity, i.e., the bacteria associated most strongly with health or with caries can morph rapidly in response to alterations in environmental pH, carbohydrate availability and source, and oxygen tension and redox environment. However, new technologic advances coupled with "old-fashioned microbiology" are starting to erode the barriers to a more complete understanding of oral biofilm physiology and ecology, and in doing so are beginning to provide insights for the creation of novel cost-effective caries control therapies.

Panoramic radiographic evaluation of the mandibular morphological changes in elderly dentate and edentulous subjects

OBJECTIVE

The aim of the present study was to analyze the changes in the gonial angle, ramus height, condyle height and cortical bone thickness in relation to gender and dental status in elderly patients.

MATERIALS AND METHODS

The study population comprised 240 patients (age ranged from 60-69 years) who had digital panoramic radiographs taken for various purposes. One group consisted of 120 patients, 60 men and 60 women, who had all natural teeth present except for third molars. The second group consisted of the remaining 120 patients (60 men and 60 women) who were in a completely edentulous state (maxilla and mandible). The gonial angle, ramus height, condylar height and cortical bone thickness of the mandible were measured by computer software on their panoramic radiographs.

RESULTS

Women showed larger gonial angles than men, while men had greater cortical bone thickness and ramus height (p < 0.05). However, no significant difference in condylar height was found between both genders (p > 0.05). Edentulous subjects had a larger gonial angle than dentate subjects, while dentate subjects had greater cortical bone thickness on both sides and left side of condylar height (p < 0.05). The gonial angle had statistically negative correlations with cortical bone thickness and ramus height, regardless of gender.

CONCLUSIONS

The outcomes of the present study indicate that the edentulous women undergo morphological changes of the mandible influenced by the dental status more than men.

Making three-dimensional Monson's sphere using virtual dental models

OBJECTIVES

The Monson's sphere and curve of Wilson can be used as reference for prosthetic reconstructions or orthodontic treatments. This study aimed to generate and measure the three-dimensional (3-D) Monson's sphere and curve of Wilson using virtual dental models and custom software.

METHODS

Mandibular dental casts from 79 young adults of Korean descent were scanned and rendered as virtual dental models using a 3-D digitizing scanner. 26 landmarks were digitized on the virtual dental models using a custom made software program. The Monson's sphere was estimated by fitting a sphere to the cusp tips using a least-squares method. Two curves of Wilson were generated by finding the intersecting circle between the Monson's sphere and two vertical planes orthogonal to a virtual occlusal plane. Non-parametric Mann-Whitney and Kruskal-Wallis tests were performed to test for difference between sex and in cusp number within tooth position.

RESULTS

The mean radius of Monson's sphere was 110.89 ± 25.75 mm. There were significant differences between males and females in all measurements taken (p<0.01), within 16.87-17.27 mm. Furthermore, morphological variation derived from variability in cusp number in the second premolar and second molar were not found to influence occlusal curvature (p>0.05).

CONCLUSIONS

This study describes a best-fit algorithm for generating 3-D Monson's sphere using occlusal curves quantified from virtual dental models. The radius of Monson's sphere in Korean subjects was greater than the original four-inch value suggested by Monson.

CLINICAL SIGNIFICANCE

The Monson's sphere and curve of Wilson can be used as a reference for prosthetic reconstruction and orthodontic treatment. The data found in this study may be applied to improve dental treatment results.