Ricky W. K. Wong

Virtual model analysis as an alternative approach to plaster model analysis: reliability and validity

The objective of this study was to assess the feasibility of virtual models as an alternative to orthodontic plaster models. Virtual dental models (obtained from OrthoCAD) and corresponding plaster models of 80 patients in the permanent dentition were randomly selected from patients seeking orthodontic care. Inter-examiner error was assessed by measuring tooth width, overjet, overbite, intermolar width, intercanine width, and midline discrepancy. Criterion validity of virtual model analysis was determined by the agreement between the measurements from virtual and plaster models. Test-retest reliability was determined by remeasuring 10 virtual models 1 week later. Comparison analysis was assessed by calculating the mean directional differences and standardized directional differences. Correlation analysis was determined by calculating the intraclass correlation coefficients (ICCs). Both intra- and inter-examiner reliability and test-retest reliability of virtual model analysis were acceptable in measuring intercanine, intermolar, overjet, overbite, midline discrepancy, space analysis, and tooth width (ICC > 0.7). Good criterion validity was indicated by agreement between the results from the plaster and virtual models (ICC > 0.8). There were substantial agreements for canine and molar relationship classifications (κ > 0.70). The results suggest that analysis performed on virtual models is as valid as traditional plaster models for intra- and inter-arch relationship.

Antimicrobial activity of Chinese medicine herbs against common bacteria in oral biofilm. A pilot study.

n Abstractn n Twenty traditional Chinese medicines (TCM) were evaluated for their antimicrobial activity against four common oral bacteria. TCMs were tested for sensitivity against Streptococcus mitis, Streptococcus sanguis, Streptococcus mutans and Porphyromonas gingivalis. Aliquots of suspension of each bacterial species were inoculated onto a horse blood agar plate with TCMs soaked separately on 6mm paper disks. The plates were incubated for 48h anaerobically and the mean diameters of growth inhibition of three different areas obtained. 0.2% (w/v) chlorhexidine was used as a positive control. Broth microdilution assay was used to determine minimum inhibitory concentration and minimum bactericidal concentration. Fructus armeniaca mume was effective against all four bacteria. Thirteen TCMs demonstrated antimicrobial activity against Porphyromonas gingivalis, including Cortex magnoliae officinalis, Cortex phellodendri, Flos caryophylli, Flos lonicerae japonicae, Fructus armeniaca mume, Fructus forsythiae suspensae, Herba cum radice violae yedoensitis, Herba menthae haplocalycis, Pericarpium granati, Radix et rhizoma rhei, Radix gentianae, Ramulus cinnamomi cassia and Rhizoma cimicifugae. Cortex phellodendri showed antimicrobial activity against Streptococcus mutans, while Radix et rhizoma rhei was effective against Streptococcus mitis and Streptococcus sanguis. Fructus armeniaca mume had inhibitory effects against Streptococcus mitis, Streptococcus sanguis, Streptococcus mutans and Porphyromonas gingivalis in vitro.n n

The effects of Rhodiola rosea extract on 5-HT level, cell proliferation and quantity of neurons at cerebral hippocampus of depressive rats

The purpose of this study was to investigate the effects of Rhodiola rosea extract and depression on the serotonin (5-HT) level, cell proliferation and quantity of neurons at cerebral hippocampus of depressive rats induced by Chronic Mild Stress (CMS). Seventy male Sprague-Dawley rats were divided into seven groups (10 per group): normal control group, untreated depressive rat model group, negative control group, positive control group, low dosage Rhodiola rosea extract (1.5g/kg) group, medium dosage Rhodiola rosea extract (3g/kg) group and high dosage Rhodiola rosea extract (6g/kg) group. After the depressive rats induced by CMS had received Rhodiola rosea extract for 3 weeks, the 5-HT levels at cerebral hippocampus were detected by high performance liquid chromatography. Bromodeoxyuridine (BrdU) was injected in vivo to label the proliferating cells at hippocampus, and morphometry was used to count the hippocampal neurons. The results showed that the 5-HT level of the three experimental groups had recovered to normal status. The immunohistochemistry of hippocampus BrdU positive cells had returned to the normal level in the group of depressive rats with low dosage Rhodiola rosea extract. In conclusion the results demonstrated that Rhodiola rosea extract could improve 5-HT level in hippocampus in depressive rats, and low dosage Rhodiola rosea could induce neural stem cell proliferation at hippocampus to return to normal level, repairing the injured neurons at hippocampus.

Use of Miniscrews and Miniplates in Orthodontics

Paradigms have started to shift in the orthodontic world since the introduction of mini-implants in the anchorage armamentarium. For example, miniscrews have allowed the management of wider discrepancies than those treatable by conventional biomechanics because force can be applied directly from the bone-borne anchor unit. Therefore, miniscrews not only free orthodontists from anchorage-demanding cases, but they also enable clinicians to have good control over tooth movement in 3 dimensions. This review will illustrate the versatility of skeletal anchorage provided by mini-implants in the correction of malocclusion, focusing on orthodontic or orthopedic movements in the 3 spatial planes. Adjunctive orthodontic treatments in adult periodontal conditions and treatment for impacted teeth with the aid of miniscrews will also be discussed.

The role of salivary factors in persistent oral carriage of Candida in humans

BACKGROUNDnCandida albicans is a commensal oral yeast in approximately one-third to one-half of the healthy population. To date, there are no studies investigating the multiple anti-candidal salivary constituents of healthy individuals with either nil or, consistent oral yeast carriage.nnnOBJECTIVEnTo compare the composition and anti-candidal activity in stimulated whole saliva of healthy consistent oral Candida carriers with Candida-free individuals.nnnMETHODSnA sub-sample of 22 consistent, Candida-free individuals and 10 consistent Candida carriers were recruited from a 12 months screening study investigating oral Candida carriage in 97 healthy patients treated by fixed orthodontic appliances. Unstimulated and stimulated saliva samples were collected. The following salivary attributes were measured using standard methodology: the flow rate, pH, lysozyme, lactoferrin and IgA concentration and, the degree of inhibition of blastoconidial growth and blastospore germination.nnnRESULTSnSaliva from the Candida-free individuals showed 20.2% higher inhibition of blastoconidial growth (p < 0.05) of a reference strain of Candida albicans. No significant differences between the other salivary attributes of the two groups were found.nnnCONCLUSIONnThe fact that saliva of Candida-free individuals significantly inhibited the blastoconidial growth more than Candida-carriers (p < 0.05) suggests that saliva may play a role in modulating oral candidal populations in health. Further studies, with a larger cohort are needed to confirm these findings and determine the factors that confer enhanced salivary anti-candidal activity.

Identification of SNP markers on 1p36 and association analysis of EPB41 with mandibular prognathism in a Chinese population

OBJECTIVEnThe results of a genome-wide scan suggested that chromosome locus 1p36 might be linked to the etiology of mandibular prognathism (MP) amongst Asian ethnicities. In this study, we performed a two-stage case-control association study to determine whether one or more genes that confer susceptibility to MP are located within this genomic region.nnnDESIGNnIn the first stage of the study, we examined 103 single nucleotide polymorphisms (SNPs) on 1p36 across an 8.6Mb critical region and within four candidate genes in 158 cases and 147 controls to identify genes associated with MP. In the second stage of the study, we examined an additional 23 SNPs within the erythrocyte membrane protein band 4.1 (EPB41) gene in 211 cases and 224 controls.nnnRESULTSnFour SNPs located in the EPB41 gene showed possible allelic and genotypic associations with MP (P<0.03 and P<0.05, respectively) in the first stage. In the analysis of single SNPs in the second stage, the allele of rs4654388 showed the strongest significant association with MP (P=0.008) and the rs4654388 G-allele was associated with a significantly increased risk of MP (OR: 1.78, 95% CI: 1.16-2.74). Haplotype analysis revealed that MP was associated significantly with haplotype GTTCAGGT (P(corrected)=0.031), which included the rs4654388 G-allele.nnnCONCLUSIONSnAn association between genetic polymorphisms in the EPB41 gene and MP has been observed. Although the polymorphisms which may contribute to MP have not been determined, the results of our study suggest that the EPB41 gene could confer susceptibility to MP.

Condylar growth and mandibular positioning with stepwise vs maximum advancement

INTRODUCTIONnThe aim of this study was to compare the effects of several Class II malocclusion treatments on condylar growth and positioning of the mandible.nnnMETHODSnThe material comprised series of lateral cephalograms obtained at the start, after about 6 months, and after about 12 months of treatment from 3 groups of consecutively treated patients who used a headgear-activator with stepwise mandibular advancement (HGA-S), a headgear-activator with maximum jumping of the mandible (HGA-M), and a headgear-Herbst appliance with stepwise advancement (HGH-S), respectively. Six-month growth data from matched controls were used to calculate the net treatment effects.nnnRESULTSnMandibular prognathism was enhanced after stepwise advancement but not after maximum jumping, and only during the initial phase of therapy; the effect was significantly greater for the fixed functional appliance than for the removable functional appliance. Lower-facial height was increased by the HGA-S, unchanged by the HGA-M, and restrained by the HGH-S. The low construction bite of the HGH-S meant that the extent of bone apposition on the posterior and superior parts of the condyle was similar, whereas the high construction bite of the HGA-S and the HGA-M meant that the effect on the superior part was greater, but only significantly so after stepwise advancement.nnnCONCLUSIONSnThe mode of jumping, the vertical opening, and whether the functional appliance is fixed or removable affect the amount and pattern of condylar growth, and the position of the mandible.

Neuroprotective effect of preadministration with Ganoderma lucidum spore on rat hippocampus.

The aim of this study was to investigate if preadministration with Ganoderma lucidum spore (GLS) could (1) alleviate oxidative stress and mitochondrial dysfunction in rat hippocampus of intracerebroventricular (ICV) injection of streptozotocin (STZ), (2) protect neurons from apoptosis, and (3) improve cognitive dysfunction. Three groups of Sprague-Dawley rats were preadministrated with GLS at doses of 2.0, 4.0 and 8.0 g/kg, respectively, for 3 weeks before the ICV STZ injury. Thereafter the rats were operated with ICV STZ (1.5 mg/kg) bilaterally on days 1 and 3. The behavioral alterations, oxidative stress indexes, ATP, cytochrome oxidase (CytOx), and histopathology of hippocampal neurons were studied. The results showed that ICV STZ model rats exhibited a significant increase of malondialdehyde (MDA), a significant decrease of glutathione reductase (GR), reduced glutathione (GSH), ATP and CytOx, accompanied with marked impairments in spatial learning and memory, and severe damage of hippocampal neuron. In conclusion, preadministration with GLS at dose of 8.0 g/kg in ICV STZ rats significantly reversed these abnormalities. In conclusion, preadministration with GLS might protect hippocampus from oxidative impairment and energy metabolism disturbance of ICV STZ. This may also provide useful information for future research on the pathogenesis and prevention of Alzheimers disease (AD).

Prunus mume extract exhibits antimicrobial activity against pathogenic oral bacteria

OBJECTIVESnPrunus mume is a common fruit in Asia, which has been used in traditional Chinese medicine. In this study, we focused on the antimicrobial properties of Prunus mume extract against oral pathogens related to dental caries and periodontal diseases.nnnSTUDY DESIGNnA total of 15 oral pathogens including Streptococcus mutans, S. sobrinus, S. mitis, S. sanguinis, Lactobacillus acidophilus, P. gingivalis, Aggregatibacter actinomycetemcomitans, and Candida species were included in the study. Initially, agar diffusion assay was performed to screen the antimicrobial activities of Prunus mume extract. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were then determined for sensitive species. Effect of Prunus mume extract on human oral keratinocytes (HOK) viability was also tested.nnnRESULTnIn the agar diffusion assay, drug suspension of 2 g/mL was able to inhibit all the bacterial species tested, but not the fungal species. MIC and MBC range of Prunus mume extract against the oral bacteria was 0.15625-0.0003 g/mL and P. gingivalis being the most susceptible species. Prune extract did not cause any detrimental effect on HOK.nnnCONCLUSIONnPrunus mume extract may be a potential candidate for developing an oral antimicrobial agent to control or prevent dental diseases associated with oral pathogenic bacteria.

3D CBCT McNamara's cephalometric analysis in an adult southern Chinese population

Preliminary results were determined for a database on 3-dimensional (3D) cephalometrics using McNamaras analysis in an adult southern Chinese population based on cone-beam computerized tomography (CBCT). 3D dentoskeletal morphology was assessed from CBCTs from 80 (39 males; 41 females; 21-30 years) consecutive adult southern Chinese without gross craniofacial deformity or asymmetry, adopting 16 variables from McNamaras cephalometric method. For variables in relation to maxilla to cranial base, mandible to cranial base and dentition, there were no significant differences between males and females. For variables in relation to mandible to maxilla, 8 of 11 showed significant differences between males and females: Cd(L)-Gn (♂: 127.65 mm; ♀: 119.56 mm, P<0.01), Cd(R)-Gn (♂: 127.85 mm; ♀: 119.94 mm, P<0.01), Cd(L)-A (♂: 99.38 mm; ♀: 94.18 mm, P<0.01), Cd(R)-A (♂: 93.93 mm; ♀: 94.99 mm, P<0.01), MxMD-DF(L) (♂: 28.26 mm; ♀: 25.40 mm, P<0.05), MxMD-DF(R) (♂: 27.74 mm; ♀: 24.02 mm, P<0.05), ANS-Me (♂: 71.09 mm; ♀: 65.84 mm, P<0.01), and MD-P(L) (♂: 22.85°; ♀: 25.25°, P<0.05). The method errors did not exceed 0.5 mm for any variables. A preliminary CBCT cephalometric database of the population was created. The significant sexual differences in the 3D McNamaras analysis indicate that gender specific data should be made available. The sample size should be increased to create a more representative database.