European Journal of Oral Sciences

The aim of this study was to test the hypothesis of an association between hypothalamic‐pituitary‐adrenal (HPA) axis reactivity and progression of periodontal disease. Histocompatible Lewis and Fischer 344 rats respond to stressful stimuli with low and high HPA axis reactivity, respectively. Experimental periodontitis was induced by tying a silk ligature around the neck of maxillary 2nd right molar teeth in 10 Lewis and 10 Fischer 344 rats with contralateral non‐manipulated teeth as controls. Twenty non‐manipulated animals were included. Also, experimental periodontitis was induced in 10 adrenalectomized Wistar rats and in 10 sham‐operated rats. Furthermore, corticosterone pellets were subcutaneously implanted in 9 Lewis rats, while placebo pellets were implanted in 8 animals. Disease progression was evaluated histometrically and radiographically. The low‐responding Lewis rats developed significantly less periodontal breakdown than did the high‐responding Fischer 344 rats. Administration of corticosterone increased the disease development, while adrenalectomy reduced the disease severity. Our findings demonstrate the importance of genetic factors in the development of periodontal disease, and suggest that HPA axis hyper‐activation is one mechanism by which periodontal disease susceptibility may be increased.

Gingivitis and periodontitis are thought to result from an imbalance between those oral microorganisms which normally colonize tooth surfaces in close contact with the gingival margin, and the nature and efficiency of the host response. The bacteria are the triggering agents, but host defence mechanisms within the gingival/periodontal tissues seem to be responsible for most of the tissue damage and for the outcome and progression of the diseases. It has recently been shown that emotional or psychological load (stress) may influence immune activities directly via neurvoendocrine (hormone) messenger substances (neurotransmitters and neuropeptides) and/or indirectly via neuroendocrine (hormone) substances. This review discusses how emotional stressors and nervous and neuroendocrine responses to psychological stressors may modulate the immune response to bacteria, and thus be expected to influence the progression and course of gingivitis and periodontitis.

Huang Z, Kim J, Lacruz RS, Bringas P Jr, Glogauer M, Bromage TG, Kaartinen VM, Snead ML. Epithelial‐specific knockout of the Rac1 gene leads to enamel defects. 
Eur J Oral Sci 2011; 119 (Suppl. 1): 168–176. © 2011 Eur J Oral Sci

The Ras‐related C3 botulinum toxin substrate 1 (Rac1) gene encodes a 21‐kDa GTP‐binding protein belonging to the RAS superfamily. RAS members play important roles in controlling focal adhesion complex formation and cytoskeleton contraction, activities with consequences for cell growth, adhesion, migration, and differentiation. To examine the role(s) played by RAC1 protein in cell–matrix interactions and enamel matrix biomineralization, we used the Cre/loxP binary recombination system to characterize the expression of enamel matrix proteins and enamel formation in Rac1 knockout mice (Rac1^−/−). Mating between mice bearing the floxed Rac1 allele and mice bearing a cytokeratin 14‐Cre transgene generated mice in which Rac1 was absent from epithelial organs. Enamel of the Rac1 conditional knockout mouse was characterized by light microscopy, backscattered electron imaging in the scanning electron microscope, microcomputed tomography, and histochemistry. Enamel matrix protein expression was analyzed by western blotting. Major findings showed that the Tomes’ processes of Rac1^−/− ameloblasts lose contact with the forming enamel matrix in unerupted teeth, the amounts of amelogenin and ameloblastin are reduced in Rac1^−/− ameloblasts, and after eruption, the enamel from Rac1^−/− mice displays severe structural defects with a complete loss of enamel. These results support an essential role for RAC1 in the dental epithelium involving cell–matrix interactions and matrix biomineralization.

Oral‐specific measures are often preferred to examine outcomes of oral disorders. However, generic measures can add additional information, including health utility. The aim was to assess the Oral Health Impact Profile (OHIP), EuroQol (EQ‐5D), and Assessment of Quality of Life (AQoL) instruments in relation to oral health in terms of their discriminative and convergent validities. Data were collected from adults, 30–61 yr of age, in Australia by mailed survey during 2009 and 2010, including the OHIP‐14, the EQ‐5D, and the AQoL, a range of self‐reported oral health variables, and by self‐rated oral and general health. Responses were collected from 1093 subjects (a response rate of 39.1%). The OHIP, the EQ‐5D, and the AQoL were associated with oral health variables, with effect sizes ranging from 0.6 to 1.1 for the OHIP, from 0.3 to 0.5 for the EQ‐5D, and from 0.4 to 0.6 for the AQoL. The OHIP tended to be more strongly correlated with self‐rated oral health (rho = −0.5) than with general health (rho = −0.3), whilst the EQ‐5D and the AQoL were less strongly correlated with oral health (rho = −0.3 and −0.3, respectively) than with general health (rho = −0.4 and −0.5, respectively). Whilst the OHIP was more sensitive to differences in oral health, the generic measures of EQ‐5D and AQoL both exhibited discriminative validity and convergent validity in relation to oral health variables, supporting their use in oral health studies.

Radiation dose delivered from the SCANORA® radiography unit during the cross‐sectional mode for dentotangential projections was determined. With regard to oral implantology, patient situations of an edentulous maxilla and mandible as well as a single tooth gap in regions 16 and 46 were simulated. Radiation doses were measured between 0.2 and 22.5 mGy to organs and tissues in the head and neck region when the complete maxilla or mandible was examined. When examining a single tooth gap, only 8% to 40% of that radiation dose was generally observed. Based on these results, the mortality risk was estimated according to a calculation model recommended by the Committee on the Biological Effects of Ionizing Radiations. The mortality risk ranged from 31.4 × 10⁻⁶ for 20‐year‐old men to 4.8 × 10⁻⁶ for 65‐year‐old women when cross‐sectional imaging of the complete maxilla was performed. The values decreased by 70% when a single tooth gap in the molar region of the maxilla was radiographed. The figures for the mortality risk for examinations of the complete mandible were similar to those for the complete maxilla, but the mortality risk decreased by 80% if only a single tooth gap in the molar region of the mandible was examined. Calculations according to the International Commission on Radiological Protection carried out for comparison did not reveal the decrease of the mortality risk with age and resulted in a higher risk value in comparison to the group of 35‐year old individuals in calculations according to the Committee on the Biological Effects of Ionizing Radiations.

In the present study, dose measurements have been conducted following examination of the maxilla and mandible with spiral computed tomography (CT). The measurements were carried out with 2 phantoms, a head and neck phantom and a full body phantom. The analysis of applied thermoluminescent dosimeters yielded radiation doses for organs and tissues in the head and neck region between 0.6 and 16.7 mGy when 40 axial slices and 120 kV/165 mAs were used as exposure parameters. The effective dose was calculated as 0.58 and 0.48 mSv in the maxilla and mandible, respectively. Tested methods for dose reduction showed a significant decrease of radiation dose from 40 to 65%. Based on these results, the mortality risk was estimated according to calculation models recommended by the Committee on the Biological Effects of Ionizing Radiations and by the International Commission on Radiological Protection. Both models resulted in similar values. The mortality risk ranges from 46.2×10‐6 for 20‐year‐old men to 11.2×10⁻⁶ for 65‐year‐old women. Using 2 methods of dose reduction, the mortality risk decreased by ∼ 50 to 60% to 19.1×10⁻⁶ for 20‐year‐old men and 5.5×10⁻⁶ for 65‐year‐old women. It can be concluded that a CT scan of the maxillofacial complex causes a considerable radiation dose when compared with conventional radiographic examinations. Therefore, a careful indication for this imaging technique and dose reduction methods should be considered in daily practice.

Previous findings, during chewing, that boluses of larger size and harder texture result in larger amplitudes of both mandibular and head–neck movements suggest a relationship between increased chewing load and incremental recruitment of jaw and neck muscles. The present report evaluated jaw (masseter and digastric) and neck [sternocleidomastoid (SCM) and trapezius] muscle activity during the chewing of test foods of different sizes and textures by 10 healthy subjects. Muscle activity was recorded by surface electromyography and simultaneous mandibular and head movements were recorded using an optoelectronic technique. Each subject performed continuous jaw‐opening/jaw‐closing movements whilst chewing small and large boluses of chewing gum and rubber silicone (Optosil). For jaw opening/jaw closing without a bolus, SCM activity was recorded for jaw opening concomitantly with digastric activity. During chewing, SCM activity was recorded for jaw closing concomitantly with masseter activity. Trapezius activity was present in some, but not all, cycles. For the masseter and SCM muscles, higher activity was seen with larger test foods, suggesting increased demand and recruitment of these muscles in response to an increased chewing load. This result reinforces the previous notion of a close functional connection between the jaw and the neck motor systems in jaw actions and has scientific and clinical significance for studying jaw function and dysfunction.

The purpose of this study was to investigate the condensation pressure during amalgam placement in patients. Forty‐four practitioners were asked to fill two class 2 cavities in the lower jaw on their patients in their own practice with the aid of a force‐measuring plugger. This device, with semiconductor strain gauges, allowed the dentist to have an identical tactile feedback as with any other plugger. Three different amalgams, with different shapes of alloy particles, were tested. The results showed a maximum condensation pressure of 8.9±2.4 MPa and 5.5±1.8 MPa with a small and a large amalgam plugger, respectively. Average condensation pressures were 3.7±1.3 MPa for the small and 2.2±0.9 MPa for the large instrument. The total working time required to fill a cavity was on average 131 s; the amalgam was effectively condensed for 44 s. No significant differences between amalgams with different shapes of alloy particles, no influence of time of day, and no difference between female and male dentists were found. This study showed that the condensation pressure is lower than often recommended, and that it is not statistically different from the values obtained in a previous laboratory study (1).

Nghiên cứu này ước tính tỷ lệ đau răng trọn đời ở độ tuổi 6 và 12 tuổi, tỷ lệ đau răng trong tháng vừa qua và sự liên quan của chúng với các yếu tố xã hội, hành vi và lâm sàng trong suốt cuộc đời của 339 trẻ 12 tuổi từ một đoàn hệ sinh ở Pelotas, Brazil. Các biến số khám phá được thu thập từ nghiên cứu chu sinh và trong nhiều nghiên cứu theo dõi. Các tỷ lệ thịnh hành được tính toán bằng hồi quy Poisson, theo một mô hình khái niệm phân cấp. Tỷ lệ đau răng trọn đời ở độ tuổi 6 và 12 tuổi lần lượt là 39% [khoảng tin cậy 95% (CI) = (34;45)] và 63% [95% CI = (58;69)]. Đau răng trong tháng qua được báo cáo bởi 11% [95% CI = (8;15)]. Trẻ không sống cùng cha ruột khi sinh và trẻ có chỉ số dmf-t cao hơn báo cáo tỷ lệ đau răng trọn đời cao hơn ở độ tuổi 6 tuổi. Trẻ trải qua nghèo đói từ 0 đến 4 năm tuổi, có chỉ số dmf-t và DMF-T cao hơn có tỷ lệ đau răng trọn đời lớn hơn ở độ tuổi 12 tuổi. Đau răng trong tháng qua có khả năng được báo cáo nhiều hơn bởi các bé gái và trẻ không sống với cha ruột khi sinh. Chiến lược phòng ngừa nên được thực hiện ở giai đoạn đầu của vòng đời, cần tính đến bối cảnh kinh tế-xã hội và gia đình nơi mà đau đớn thường xảy ra.

Confocal laser scanning microscopy (CLSM) has been employed as a method for studying intact natural biofilm. When combined with fluorescence in situ hybridization (FISH) it is possible to analyze spatial relationships and changes of specific members of microbial populations over time. The aim of this study was to perform a systematic description of the pattern of initial dental biofilm formation by applying 16S rRNA‐targeted oligonucleotide probes to the identification of streptococci and other bacteria, and to evaluate the usefulness of the combination of CLSM and FISH for structural studies of bacterial populations in dental biofilm. Biofilms were collected on standardized glass slabs mounted in intra‐oral appliances and worn by 10 individuals for 6, 12, 24 or 48 h. After intra‐oral exposure the biofilms were labelled with probes against either streptococci (STR405) or all bacteria (EUB338) and analysed by CLSM. The current approach of using FISH techniques enabled differentiation of streptococci from other bacteria and determination of their spatio‐temporal organization. The presence of chimney‐like multilayered microcolonies with different microbial compositions demonstrated by this methodology provided information supplementary to our previous knowledge obtained by classical electron microscopic methods and increased our understanding of the structure of developing biofilms.