Dental arch form in 5 Chinese minorities was metrically analyzed for the purpose of describing their dental arch form with the use of widths and lengths and showing their affinity to other Asian populations through the application of multivariate analysis. Materials were dental impression models of 5 Chinese minorities, Hani, Dai, Naxi, Pumi and Miao in Yunnan Province. They were placed under an arm-type 3D digitizer (Micro Scribe 3DX) and the landmarks were plotted. Arch width was represented by 9 parameters and arch length was represented by 8 parameters with the use of the program CADKEY2000. Principal component analysis showed that dental arch size of Yunnan Chinese minorities was small and relatively short compared with other Asian and Pacific populations in males and females. Among the 5 groups Hani had a larger dental arch, hereas Miao had a smaller one than the other groups. In the sex-combined analysis, it was generally clear that male's arches were larger in size and broader in shape in all of the populations studied.

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Aging is a complex biological process driven by a selective class of molecules and pathways that affect overall deterioration of physiological functions to increase the risk of ageing. Bone formation steadily declines with age, resulting in significant loss of bone mass, and reactive oxygen species (ROS) are thought to be a major contributor to the ageing process. In our previous study, H₂O₂ treatment significantly reduced bone nodule formation rate on pre-osteoblastic cell, MC3T3-E1. In our previous study, RGD peptide derived from fibronectin enhanced the gene expression of baculoviral inhibitor of apoptosis repeat-containing gene 6 (BIRC6) suggesting GRGDSP may promote cell proliferation of osteoblasts and lead to matrix mineralization. In this study, effect of H₂O₂ treatment on gene expression of BIRC6 gene expression in MC3T3-E1 was carried out. The enhancement of BIRC6 mRNA level was observed by DNA microarray analysis. A significantly higher level of BIRC6 mRNA in H₂O₂-treated cells was confirmed by reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR. Since. BIRC6 is known as the inhibitor of apoptosis, the stimulation of BIRC6 gene expression by ROS may be one of molecular mechanisms in the decline of bone formation in the ageing process.

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Aggregatibacter actinomycetemcomitans is an important pathogen related to aggressively progressive periodontal breakdown in adolescents and adults. The bacterium forms a tenacious biofilm on solid surfaces is important in colonization of the oral cavity. The genes of tight adherence (tad) locus reside in a 12-kb flp operon that contains 14 genes, flp-1-flp-2-tadV-rcpCAB-tadZABCDEFG. The purpose of this study was to sequence the tad locus in a highly aggregative and adherent A. actinomycetemcomitans serotype g designated NUM-Aa 4039 strain. The tad locus of NUM-Aa 4039 strain contained 14 genes in 11,559-bp nucleotides. The similarity of the tad locus sequence was 96.5% compared with that of the well-documented, rough, adherent strain CU1000. Almost all genes were similar to the CU1000 strains. However, the flp-1 and tadG genes of NUM-Aa 4039 showed 84.0% and 71.8% homology in their amino acid sequences compared to those of CU1000, respectively. The Flp1 major pilin protein of NUM-Aa 4039 consisted of 75 amino acids and several amino acid substitutions occurred in the C-terminus of the protein. It was classified as flp-1 allelic class type 6. The sequence variations of flp-1 and tadG genes may be due to the tight adherence and aggregation of NUM-Aa 4039.

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The presence of yeasts in periodontal pockets is well documented and Candida albicans is the species most commonly isolated from the oral cavity. The immune response and anticandidal activity of oral epithelial cells play a key role in host defense against C. albicans infection. Human gingival epithelial cells were primarily cultured from healthy human gingival tissues and challenged with C. albicans ATCC90029. After 8 hours, total RNA was extracted and mRNA levels were analyzed using Affymetrix GeneChip (Human Genome U133 plus 2.0 Array, ca. 47,000 genes). Numerous genes showed altered gene expression, and among these, a pro-inflammatory cytokine, tumor necrotizing factor alpha (TNF-α), was up-regulated by more than two-fold over normal levels after C. albicans infection. Altered mRNA levels on GeneChip results were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR. Rat gingiva was infected with C. albicans cells and immunohistochemical examination for TNF-α production was then carried out. Stronger immunoreactivity against TNF-α was observed in rat gingival epithelium infected with C. albicans.

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Halo-forming colony and its variant (non-halo forming) strains, designated NUM-Aa 5014 and NUM-Aa 5016, respectively, were isolated from periodontitis. They were identified as Aggregatibacter actinomycetemcomitans serotype f. The NUM-Aa 5014 strain showed an aggregated form in the broth culture and strong biofilm formation on hard surfaces, while NUM-Aa 5016 did not show this phenomenon. In a Congo red (CR)-binding assay, the halo-forming colony strain NUM-Aa 5014 was strongly bound by CR. ATCC 33384^T and NUM-Aa 5016 showed low binding activity. The tight adherence (tad) locus of the NUM-Aa 5014 and 5016 strains contained 14 genes, flp-1-flp-2-tadV-rcpCAB-tadZABCDEFG, in 11,565 and 11,574 bp, respectively. Almost all genes were the same except the flp-1 and tadD genes between the NUM-Aa 5014 and 5016 strains. The homologies of flp-1 and tadD genes in the NUM-Aa 5014 and 5016 strains were 97.4% and 99.6% in amino acid sequences, respectively. These results suggest that the expression of genes in tad locus may play some roles in adherence and aggregation of A. actinomycetemcomitans.

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Streptococcus mutans, consisting of serotypes c, e and f is an oral aciduric organism associated with the initiation and progression of dental caries. Recently a new serotype k S. mutans was proposed. The distribution of serotype k S. mutans was investigated in 244 subjects. The ratio of S. mutans and Streptococcus sobrinus against total streptococci was approximately 1-0.1%. Mutans streptococci were found in 212 subjects (86.9%), S. mutans in 74.2% and S. sobrinus in 12.7%. No mutans streptococci were found in 32 subjects (13.1%). The predominant serotype was c with 84.9% detection in S. mutans. Serotype k was found in only 3 subjects (1.4%) : 1 of them had a coexisting serotype c strain and the other 2 were alone. Serotypes d and g of S. sobrinus were detected at equal percentages and those usually coexisted with S. mutans strains. Serotype k S. mutans isolates were confirmed by serological and genetical methods and characterized. The homologies of the rgpF gene sequence, which is related to the biosynthesis of serotype antigens, of isolates were 93-100% among serotype k type strains and 71% with serotype c to serotype k strains. Water-insoluble glucan synthesis from sucrose and artificial plaque formation of the serotype k strains were similar to those of the serotype c strain. However, acid production by the serotype k strains was comparatively lower than that of serotype c. A few years after the first investigation, serotype k S. mutans was confirmed to be maintained in the individual oral cavities of the same subjects by genetic analysis.

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The 40-kDa outer membrane protein has been cloned from the periodontal pathogen Porphyromonas gingivalis 381 as a 2.0-kbp EcoRI DNA fragment. This protein was found to have several functions, including aggregation and hemagglutination. On a functional motif search, we found that this molecule carried a hemin-binding domain, and the recombinant protein expressed hemin-binding activity. We deposited the DNA sequence into the NCBI DNA database as the 35-kDa hemin-binding protein (HBP35). However, promoter and terminator of the hbp35 gene have not been fully analyzed. In this study, we analyzed the nucleotide sequence of the EcoRI fragment to identify promoter and terminator regions and determined the structure of hbp35. A possible promoter sequence (TTGCAG in the -35 region and TATTTT in the -10 region), which were nearly identical to the predicted promoter sequences, were found upstream of the start codon (ATG). The number of bases between the regions was 17. The transcription start site (+1) was predicted to be located 53 nt upstream from the translation start codon. Palindrome analysis showed a very high matching sequence position from 1554 to 1601 on the EcoRI fragment. Hairpin loop and stem parts analysis predicted two typical terminators downstream of hbp35. Both locations partially overlapped the palindromic sequences, indicating ρ-independent transcription termination in the 3'-noncoding region. These terminator and promoter analyses therefore identified the whole gene structure of hbp35.

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Primary intraoral malignant melanoma is a rare but aggressive neoplasm. Oral melanomas represent 1-2% of all oral malignancies. In contrast to cutaneous melanoma, oral melanoma is usually asymptomatic, invades and spreads readily, and shows marked propensity for metastasis. Prognosis is thus typically very poor. Although the tumor can present at any location in the oral cavity, the maxillary gingiva and palate are frequent sites for this neoplasm. A rare case of primary intraoral malignant melanoma in a 40-year-old man involving the mandibular gingiva and alveolar mucosa is presented along with a brief review of literature. The case is unusual in that multiple sites of the gingiva and oral mucosa were involved.

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To identify gene whose expression is enhanced by low level laser irradiation (LLLI ; 830 nm Ga-Al-As diode laser), we constructed the cDNA library of osteoblastic cell line MC3T3-E1 using a subtractive gene cloning. In the present study, we focused on a gene clone designated as MCL98. DNA sequence of MCL98 indicated the high homology with inhibin beta (INHBB) gene. The enhancement of INHBB mRNA by LLLI was successfully confirmed by reverse transcription-polymerase chain reaction and real-time PCR. INHBB is shown to serve as a co-receptor for BMPs which stimulate bone cell differentiation and bone formation. Thus, the enhancement of INHBB expression by LLLI may be one of molecular mechanisms in accelerating bone formation by LLLI.

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Dental professionals and their patients are constantly exposed to a number of specific occupational hazards. In many cases, this exposure results in diseases, which are regarded as occupational illnesses. Relying on relevant literature, this paper discusses the occupational hazards present in the dental environment. These range from toxicity from chemicals routinely used in dentistry and threat of cross-infection in the dental clinic to musculoskeletal diseases consequential to sub-optimal working posture. Such hazards cause the appearance of various ailments that are specific to the profession and that develop and intensify over years. Being unaware of the potential hazards in the work environment makes dental personnel more vulnerable to injury and illness. Awareness of these occupational hazards and implementation of preventive strategies can provide a safe dental environment for all concerned.

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