Makoto Kawamura

Lotka's law and the pattern of scientific productivity in the dental science literature

Statistical regularities can be observed in many natural and social phenomena. From empirical data on the authorship of scientific papers, Lotka deduced an inverse-square law: the number of authors publishing n papers is 1/n2 of those publishing one paper. The general type for the relation (1/n(c)) has a wide range of applicability to a variety of phenomena. This study examined, by means of bibliometric tools, whether Lotkas law could be applied to the literature of dental science. Data came from 20 leading dental science journals, as reported in Journal Citation Reports. The search was performed with a programme developed using Visual Basic for Applications, which counted the number of authors and analysed their contributions to the literature. Authorship for all contributions, as reported in Medline, was compiled for each of these 20 journals for the last 25 years, 1971 through 1995. The total number of authors was 43,796, responsible for 124,556 authorships. The journals published in countries other than the USA exhibited higher degrees of author concentration. The dental science literature conformed very well to Lotkas model with c = 1.95.

Caries prevalence associated with Streptococcus mutans and Streptococcus sobrinus in Japanese schoolchildren

BACKGROUND Streptococcus mutans and Streptococcus sobrinus are known to be associated with dental caries in humans. AIM We used a polymerase chain reaction method to detect S. mutans and S. sobrinus in 128 Japanese schoolchildren and then compared their presence with the dental caries experience. DESIGN Plaque samples were collected from all erupted tooth sites with a sterile toothbrush, and dental examinations were performed to determine the numbers of decayed and filled teeth in primary (dft) and permanent (DFT) dentition using the WHO caries diagnostic criteria. Fishers PLSD test was employed to compare caries scores between combinations of the detected bacteria. RESULTS Streptococcus mutans and S. sobrinus were present in 38.3% and 68.0%, respectively, whereas 14.8% were positive for S. mutans alone, 44.5% for S. sobrinus alone, and 23.5% for both S. mutans and S. sobrinus, with 17.2% negative for both. The DFT, dft, and total (DFT + dft) scores for subjects positive for both S. mutans and S. sobrinus were significantly higher than those positive for S. mutans alone (P < 0.05, in triplicate). CONCLUSION These results suggest that schoolchildren harbouring both S. mutans and S. sobrinus have a significant higher dental caries experience in both permanent and primary teeth as compared to those with S. mutans alone.

An Analytical Study on Gender Differences in Self-Reported Oral Health Care and Problems of Japanese Employees

An Analytical Study on Gender Differences in Self‐Reported Oral Health Care and Problems of Japanese Employees: Makoto Kawamura, et al. Department of Preventive Dentistry, Hiroshima University School of Dentistry—The purpose of this survey was to clarify gender differences in self‐reported oral health care and problems of Japanese employees. A 60‐item questionnaire named Dental Checker® was used in a project on oral health in the working place. Subjects were 77,845 Japanese employees (males, 52,345; females, 25,500). The Mantel‐Haenszel chi‐square test was used to clarify gender differences among respondents. Of great significance was a finding that 81.8% of females felt uncomfortable when they slept without brushing their teeth, as contrast with 58.8% of males (P<0.001, OR=3.22). Nearly one half of male employees answered that they were too busy to go to the dentist, while 36.8% of females answered in this way (P<0.001, OR=1.83). Only a minority reported occasional use of dental floss (males; 13.2%, females; 24.9%, P<0.001, OR=2.04). Significant gender differences were found for all 18 behavioral items, and in each case, females generally reported ‘healthier’ behavior than males. Although differences between genders were small with respect to their assessment of the risk factors of periodontal disease, male employees were more likely to report bad breath, enlarged spaces between teeth, food impaction, chewing restriction, and tooth mobility than females (P<0.001, OR=1.26‐1.78). Findings suggest that gender as well as age remains an important consideration when planning dental health education or other interventions at the workplace.

Effects of fluoride intake on the mineral content, acid solubility and resorption caused by experimental periodontitis of rat alveolar bone

Adult rats were given either distilled water or drinking water containing 100 parts/10(6) of fluoride. The alveolar bone of rats given fluoride for 90 days showed an increased mineral content and decreased acid solubility compared to the bone of rats given distilled water. Experimental periodontitis was initiated in both groups after 110 days of treatment to cause alveolar bone resorption. Fourteen days later, the rats were killed and it was found that the alveolar bone resorption caused by experimental periodontitis was significantly smaller in the rats given fluoride in their drinking water than in those given distilled water. The findings suggest that fluoride intake might have a protective effect on rapidly progressing alveolar bone resorption.

Changes of subgingival microflora around single-crystal sapphire endosseous implants after experimental ligature-induced plaque accumulation in monkeys

A study was performed to evaluate the change of subgingival microflora with plaque accumulation around the single-crystal sapphire implant. Four implants were inserted into mandibular and maxillary edentulous regions, and the super-structure was inserted 1 month after implant insertion in each of nine monkeys. Plaque control was maintained for 3 months after insertion to establish the baseline. Plaque was allowed to accumulate on one side by placement of ligatures around the implants and natural teeth with no plaque control. On the other side plaque control was continued for 9 months. Both the implants and natural teeth on the ligature side showed significant increases in proportions of motile rods and spirochetes. No significant difference of microflora was detected between the implants and natural teeth. These findings indicate that plaque control is necessary to maintain the normal microflora around the implant.

コンピュータ・トレーニングソフト「ダーグズ」を用いた歯周状態判断の経験が養護教諭養成課程学生に与える影響

本研究では,看護学生の養護教諭資格取得講座を履修している学生を対象に,コンピュータ・トレーニングソフト『歯グキを見る眼を養おう』(ダーグズ)を2 度(初回時ならびに3 週間後)体験させ,学生の歯周状態の判断成績の変化を見るとともに,ダーグズの歯科保健教育に対する有用性についてアンケート調査を行った.その結果,歯周状態の判定指標である一致数,再現数,的はずれ回答数のいずれにおいても成績の向上が確認されたことから,ダーグズを用い学生がトレーニングに取り組み,歯周状態判断力が向上したことが推察された.また,終了後のアンケート調査の結果では,「歯グキの健康管理に役立てたい」,「将来学校等で活用してみたい」等の肯定的な回答が得られたことから,このソフトは学生の歯科保健教育に対して有用である可能性が示唆された.

Maternal and Child Dental Health Care at a Public Health Center. II. Relationship between Caries Increment and Life Style in 1.5-year-old Children with and without Caries.

The purpose of this study was to extract the factors which affect the caries increment between 1.5 and 3 years of age by dividing the subjects into two groups, one with and the other without caries at 1.5 years of age.The subjects were 1641 children who received a 3-year-old dental health examination at a public health center in Hiroshima City between April 1990 and November 1991.Eight factors associated with caries prevalence at 3 years of age were examined using multivariate analysis. These factors were ‘Family type’, ‘Order of birth’, ‘Interruption of breast feeding’, ‘Bottle feeding at 1.5 years of age’, ‘Regularity of between-meal snacks’, ‘Drinking sugary beverages’, ‘Watching TV at meals’ and ‘Tooth brushing with mothers help’.The results were as follows.1) The factors related to caries increment from 1.5 to 3 years of age for the children without caries at 1.5 years of age were ‘Drinking sugary beverages’, ‘Interruption of breast feeding’, ‘Watching TV at meals’ and ‘Bottle feeding at 1.5 years of age’, and for the children with caries at 1.5 years of age the factor was ‘Tooth brushing with mothers help’.2) We suggest that more efficient dental health guidance should be given at a 1.5-year-old dental health examination.3) The screening method with the eight variables was valid for prediction of caries increment in the children with caries, but not in the children without caries.