Ultrastructural study of induced keratinization in sulcular gingival epithelium in rhesus monkeys

Morphological aspects of the gingiva in children with Down's syndrome during experimental gingivitis

In a previous investigation, children with Down's syndrome (DS) showed an earlier, more rapid and more extensive gingival inflammation than normal healthy control children. These differences in gingival inflammation may be the result of aberrant morphology of the gingiva related to the genetic disorder in DS children. The aims of the present study were (i) to describe the structural composition of "normal" gingiva in DS compared to control children, (ii) to analyse the histological changes in the gingiva during plaque development and (iii) to investigate whether the clinical findings could be supported by morphological observations. The study was carried out in 8 DS and 8 matched control children. Their ages ranged from 5-10 years. Gingival normality was guaranteed by strict oral hygiene procedures. During a period of 21 days in which oral hygiene was abolished, gingival biopsies were taken from buccal sites of deciduous teeth following a predetermined schedule on days 0, 7, 14 and 21. Results on day 0 showed no morphological differences between the DS and control children regarding oral epithelium, junctional epithelium or connective tissue. During the experimental phase of the study, the amount of plaque accumulation in the DS children gave rise to a more extensive gingival inflammation than in the control children. The gingival inflammation in the DS group started earlier and included: (1) an acute inflammatory response, (2) an increase of the junctional epithelium area, (3) an increase of the infiltrated connective tissue area (ICT) and (4) a decrease in collagen fibre density of about 35-40% compared to day 0. The same phenomena were not seen until 7 days later in the control group. Conversely, the development of a perivascular lymphocyte infiltrate (LI) in the DS children was delayed compared to the control group. This may be caused by the impaired delayed-type hypersensitivity response in DS children. The development of 2 separate infiltrates (ICT and LI) in this age group and the different temporal development of ICT (day 7 for the DS and day 14 for the control group) and LI (day 14 for the DS and day 7 for the control group) does suggest different immunological mechanisms for both areas and both groups.

Experimental gingivitis around deciduous teeth in children with Down's syndrome

Epidemiological studies have shown that there is a high prevalence and rapid progression of periodontal disease in children with Down's Syndrome (DS). In this respect, DS children exhibit a markedly different response compared with healthy children. In order to understand the reasons for this difference, a controlled study was set up to determine the extent and the quality of the differences in the early periodontal tissue response towards dental plaque in the deciduous dentition of DS children and matched control children. In a preliminary investigation, the gingival health was estimated by determining the bleeding tendency. 9 healthy children were selected from a group of 14 and matched with 9 DS children with respect to plaque development, sulcus depth and age. The DS children had a higher bleeding tendency than the matched controls. In the DS children, moreover, a correlation was found between bleeding tendency and age. No such correlation was found in the controls. After a period of intensive oral hygiene, all cleaning of teeth was discontinued for 21 days. The amount of plaque according to the plaque index, the gingival health according to the gingival index, and the amount of crevicular leucocytes and gingival exudate were assessed at days 0, 7, 14 and 21. During the experimental phase of the study, the amount of plaque increased at a similar rate in both groups. In the DS children, the development of gingival inflammation started earlier and was more extensive. It increased after day 14, whereas in the control children, the gingival inflammation seemed to stabilize at this time. The results of the present experimental study thus confirm earlier results from epidemiological studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Dextran penetration through nonkeratinized and keratinized epithelia in monkeys

The purpose of this study was to determine if polysaccharide dextrans would pass through intact-nonkeratinized and induced-keratinized sulcular epithelia in monkeys. Dextran penetration through normally keratinized oral gingival epithelium also was evaluated in the same gingival specimens. Each of three Rhesus monkeys received a thorough prophylaxis 1 week prior to the experiment. During this week, the monkeys also received daily IV injections of Achromycin. After the antibiotic treatment, the teeth were polished and cleaned with a rubber cup using prophylactic paste for 2 consecutive months, as follows: (1) the right maxillary and mandibular teeth received daily prophylaxes on weekdays and (2) the left maxillary and mandibular teeth received one prophylaxis weekly. These frequencies of plaque removal on one-half of the mouth maintained clinically healthy gingiva and produced keratinization of the sulcular epithelium. At the end of the 2-month prophylaxes, a 5% solution of dextrans derived from Leuconostoc mesenteroides was applied topically to the gingiva once daily for 3 consecutive weeks. During this time, the monkeys continued having dental prophylaxes following the previous time schedule. The study showed that induced-keratinized sulcular epithelium as well as normally keratinized oral gingival epithelium resisted penetration of dextrans, whereas intact-nonkeratinized sulcular epithelium apparently lacked a surface layer resistant to penetration.