Dimensionamiento de flota

vidual’s precise needs. The intervention may include reinforce- ment of oral hygiene instruction with either supragingival scaling, subgingival debridement or perhaps, a combination of the two regimes.

There appears to be no clear evidence to indicate what fre- quency of recall interval is likely to give the best long-term results, although a 3 month recall interval for patients seems to be favoured in most clinical trials and dental practice. This interval, however, appears to have evolved as a matter of convenience to both clinicians and patients rather than being based upon specific clinical and, or microbiological data. Clearly, this is an area where further research is needed to inform clinical practice.

It must be emphasized that existing periodontal disease must first be treated and optimal periodontal health established by a sustained course of treatment before scheduling a recall pro- gramme of professional cleaning. This is because a maintenance schedule comprising single-visit sessions of scaling and oral hygiene instruction at widely spaced intervals is unlikely to restore periodontal health or prevent progressive attachment loss when a significant amount of disease is present at the outset.

Preventive programmes—the classic

studies

The components of an effective preventive programme based on plaque control are dental health education, oral hygiene instruc- tion, and professional tooth cleaning. The relative importance of each component has been assessed in a number of classic studies predominantly in the 1960s and 1970s. These have measured var- ious parameters of oral cleanliness and periodontal health, namely, plaque and calculus accumulation, gingival inflammation, gingi- val bleeding, pocket depths, attachment levels, and bone resorp- tion. This work has been carried out both in children and adults. The discussion which follows concerns non-surgical methods of periodontal care, which have been standardized for testing on large groups of individuals. The participants were ‘ordinary’ members of the public rather than periodontal patients per se, and the various procedures were tested both for their effects on pre- existing periodontal disease and for their ability to prevent new or recurrent disease. Because of the ‘treatment’ element, these pro- grammes cannot be solely regarded as primary prevention.

Preventive programmes in children

It is generally assumed that good oral hygiene practices are best acquired in childhood when they may be integrated with other developing health habits. Preventive programmes in schools provide continual opportunities for peer influence and the stimu- lating effect of daily personal interaction.

Evidence for the effectiveness of dental health education pro- grammes in schools is equivocal, although there may be significant improvements in knowledge and attitudes, changes in behaviour, as measured by reduction in plaque and gingivitis, are usually short-lived. The ‘Natural Nashers’ health education programme in the UK was a large trial involving 6700 13–14-year-olds who received a teacher-mediated dental health education programme comprising three 70–80 minute sessions, at weekly intervals (Craft 1984). The programme employed active learning principles and included a slide presentation, experimental work, and use of work sheets. Improvement in plaque and gingivitis levels, while statis- tically significant, was small and faded considerably between the 5- and 28-week observation periods. Nevertheless, the exposure to such a dental health programme might conceivably improve the uptake of subsequent practice-based preventive care.

Supervised toothbrushing in schools is an alternative approach, which has been evaluated in several studies. For example, in a study of 12–13-year-old schoolchildren, a 3-year supervised daily effect of having clean teeth after a dental appointment may be the

principal benefits of polishing, while removal of fluoride from superficial layers of the enamel could be a significant drawback. Clearly, tooth polishing cannot be supported on scientific grounds as a routine procedure, but may be indicated in special instances where plaque removal is obviously inhibited by surface roughness.

Tooth surface instrumentation

• Scaling and, if necessary, polishing should produce a smooth surface which will facilitate plaque removal for the patient

• Mechanical instrumentation of the root aims to produce a surface that is biologically acceptable to the periodontal tissues

Supportive care

• After it has been successfully treated, periodontal disease will likely recur unless adequate plaque control is maintained

• Professional support is essential both to maintain good plaque control and intercept recurrent disease while still at an early stage

areas examined (in the last year), whereas a control group showed a 75 per cent increase in gingivitis, typical of this stage of child- hood (Lindhe et al. 1966).

Although supervised toothbrushing may produce an overall improvement in gingival health, a number of additional observa- tions have been made in several studies:

• the reduction of gingivitis is often unevenly distributed within the dentition with, for example, the upper anterior part of the mouth showing greater resolution of inflamma- tion than the posterior, less accessible areas;

• gingivitis scores tend to remain somewhat higher for prox- imal surfaces than for buccal and lingual surfaces;

• this type of preventive programme lacks any prolonged effect after it is withdrawn.

These limitations of supervised toothbrushing have, to some extent, been overcome in clinical trials in which dental personnel have introduced various other preventive strategies to children on an individual basis.

In 1974, Axelsson and Lindhe reported the effect of a rigorous preventive programme in school children aged initially 7–14 years. The test groups received professional tooth cleaning, oral hygiene instruction, and topical fluoride applications every 2 weeks. Parental involvement was obtained at the beginning of the study and after 1 year. The experimental group demonstrated low plaque scores and negligible signs of gingivitis after 2 years and there were no significant differences between gingivitis scores of proximal and buccal/lingual areas. Children in the control group, on the other hand, had much higher plaque and gingivitis scores. Thus, it appears that careful fortnightly interproximal cleaning with floss or polishing tips prevents gingivitis in those areas in children. Furthermore, the plaque control programme was equally effective for molars and incisors.

This study was continued for two further years. During the third year, the interval between prophylactic sessions was pro- longed to 4 weeks in the younger age groups and to 8 weeks in the oldest age group and during the fourth year, all children were recalled every 8 weeks (Lindhe et al. 1975, Axelsson and Lindhe 1977). The excellent standard of oral hygiene was maintained during the third and fourth years and there was no significant change in gingival condition. Significant differences, however, were once again observed between test and control groups. This introductory 2-year programme of fortnightly professional tooth- cleaning and oral hygiene sessions, followed by recall at intervals of one or two months during the third and fourth years, practi- cally eliminated all signs of gingivitis in school children.

A trial with a similar design assessed primarily the effect of preventive measures in a large group (1100) of schoolchildren between the ages of 7 and 17 years. Specially trained dental nurses administered oral hygiene instructions and professional tooth cleaning, and applied topical fluoride every third week. Over the 3-year trial period, the frequency of plaque-infected surfaces in

and the frequency of inflamed gingival units from 41.1 per cent to 18.8 per cent. Differences between test and control groups were highly significant at re-examination (Hamp et al. 1978).

Further studies were designed to ascertain the separate effect of each component of the prophylactic regimen.

Poulsen et al. (1976) attempted to determine the benefits that might be obtained by professional tooth-cleaning alone in 78, 7-year-old children. Thus the experimental group received thorough mechanical cleaning every 2 weeks while a control group were given no professional tooth-cleaning. Both groups received fortnightly supervised fluoride rinsing. Throughout the study, home-care standards were not intentionally influenced. After 1 year, there was a statistically significant difference in plaque accumulation between the groups and an improvement in gingivitis in the test group. This study was continued for one fur- ther year during which the interval between professional tooth- cleaning sessions was increased to 3 weeks. Plaque and gingivitis scores increased in the experimental group but remained signifi- cantly lower than in the control group, where there was no appre- ciable change in oral cleanliness or gingival health (Agerbaek

et al. 1978).

These studies demonstrate that the frequency of professional tooth-cleaning is of major importance when it is the only plaque control measure used, although it is difficult to assess the value of tooth-cleaning per se because the involvement of the children itself may have motivated them to practice better home care.

That the benefits of fortnightly professional tooth-cleaning cannot be attributed entirely to the repeated removal of 2-week old plaque has also been demonstrated in a later study involving 13–14-year-old children who received fortnightly professional tooth-cleaning in a split-mouth design (Axelsson and Lindhe 1981). The children were divided into two groups only one of which received oral hygiene instruction at 2-week intervals. There was an equal reduction in plaque and gingivitis in the untreated quadrants of both groups of children suggesting that the subjective impression of tooth cleanliness, as identified in the cleaned jaw quadrants of the group not receiving oral hygiene instruction, was sufficient to motivate the children towards a standard of home care that was equal to that achieved by the group which did receive oral hygiene instruction.

The fortnightly preventive programme of Axelsson and Lindhe (1974) which produced the most impressive reductions not only of gingivitis but also of caries, required about 160 min/child per year. Traditional dental treatment, for children not participating in the trial, required about 140 min/child per year and cost over twice as much as the preventive programme. Furthermore, the trial participants achieved a much better standard of dental health—gingivitis was negligible and practically no caries devel- oped. Attempts by others to match these results have, however, been unsuccessful. Although other studies have achieved similar reductions in plaque and gingivitis, their effect on caries has not been sufficiently large to make such programmes cost-effective.