A preliminary investigation into the ultrastructure of dental calculus and associated bacteria.

INTRODUCTION: Though dental calculus is generally recognised as comprising mineralised bacteria, areas of non-mineralised bacteria may be present. AIM: To investigate the ultrastructure of non-decalcified young and mature supragingival calculus and subgingival calculus, and the possible presence of internal viable bacteria. MATERIALS AND METHODS: Supragingival calculus was harvested from five patients, 9-10 weeks after scaling and root debridement. Five samples of mature supragingival and subgingival calculus were taken from patients presenting with adult periodontitis. Specimens were fixed and embedded for transmission electron microscopy. RESULTS: The ultrastructure of young and mature supragingival calculus was similar with various large and small crystal types. Non-mineralised channels were observed extending into the calculus, often joining extensive lacunae, both containing intact non-mineralised coccoid and rod-shaped microorganisms. Subgingival calculus possessed more uniform mineralisation without non-mineralised channels and lacunae. CONCLUSION: Supragingival calculus contains non-mineralised areas which contain bacteria and other debris. The viability of the bacteria, and their identification could not be determined in this preliminary investigation. As viable bacteria within these lacunae may provide a source of re-infection, further work needs to be done to identify the bacteria in the lacunae, and to determine their viability.

Effectiveness of an electrically active brush in the removal of overnight plaque and treatment of gingivitis.

OBJECTIVES: The purpose of the present study was to evaluate the effect of an electrically active toothbrush on established plaque and gingivitis in a 7-month clinical trial. MATERIAL AND METHODS: For this study, 66 volunteers (non-dental University students) were selected on the basis of having moderate gingival inflammation. At baseline, plaque (Quigley & Hein), bleeding upon marginal probing and the Modified Gingival index were assessed on the vestibular, mesio-vestibular, disto-vestibular and lingual surfaces at four sites per tooth. Subjects were randomly divided among two groups; one group brushed with a control brush (Butler GUM 309) while the other used the electrically active test brush. After 2 weeks, 4 weeks, 4 months and 7 months the clinical indices were again recorded. At each assessment the participants received a new brush head for the electrically active brush (test group) or a new manual control toothbrush (control group). RESULTS: All baseline indices appeared to be well balanced. A mean Quigley & Hein plaque score of 1.98 and 2.13 was found in the control and test group, respectively. Little change was observed from baseline to 7 months. The mean bleeding upon marginal probing score at baseline was 0.62 for the control group and 0.59 for the test group. Little to no improvement was observed for the manual brush, whereas an increase in bleeding was observed in the test group in the course of this study. The mean percent reduction in plaque after 1 min of brushing varied throughout the study between 36% and 46%. No difference between the brushes was observed at any time point during the 7-month test period. CONCLUSION: No beneficial effect could be shown for the 'electrically active design feature' compared to a regular manual toothbrush control.

The influence of toothbrush wear on the variables of plaque and gingivitis in clinical trials.

Although toothbrush wear has been shown not to be critical in ensuring optimal plaque removal, the degree of toothbrush wear occurring in a clinical trial may influence the results of the trial. The aim of this study was to determine the effects of toothbrush wear on the clinical variables of dental plaque and gingivitis. There were 107 subjects who participated in this six-month clinical trial in which plaque and gingivitis scores were assessed in relation to toothbrush wear at 2, 4, 12 and 24 weekly intervals. At each appointment, the toothbrushes being used were assessed for wear and replaced if necessary. It was found that 58% of the group were "rapid," and 42% were "slow" wearers. Of the group, 18.6% required replacement toothbrushes within two weeks from baseline with 50.9% of replacement toothbrushes being issued within four weeks of the start of the trial. Two subjects required as many as 10 replacement toothbrushes over the six-month trial period. "Slow" wearers had significantly lower plaque scores than "rapid" wearers at weeks 4 and 12, whereas the "rapid" wearers had significantly lower gingivitis scores than "slow" wearers at weeks 2 and 4. Clinical results show that significant toothbrush wear patterns of individuals participating in clinical trials should be taken into account when designing clinical trials assessing plaque and gingivitis scores. It may be necessary to exclude "rapid" toothbrush wearers from clinical trials that assess plaque and its removal. As the rate of toothbrush wear varied considerably among subjects, the simple classification of subjects into "rapid" and "slow" wearers may require further subgrouping. The surprising result that "rapid" wearers achieved lower levels of gingivitis requires further study to determine if this observation is valid in clinical trials designed for this purpose.

The relevance of pH to gingivitis and periodontitis.

Although the resting pH of the oral cavity is between 5 and 9, it is also known to vary widely depending on a number of factors. While this phenomenon has been extensively studied in relation to dental caries, little research has been undertaken of its possible significance in relation to gingivitis and periodontitis. This study aimed to investigate any possible correlations between pH and gingivitis and periodontal pocketing. Forty-two subjects with gingivitis and periodontitis were included in this study. Strips of pH indicator paper were placed on the floor of the mouth, soft palate, healthy gingival margins, sites of superficial gingivitis, and in periodontal pockets. It was shown that pH varies in different sites in the mouth. Statistically significant correlations between pH and gingivitis were not identified, but significant correlations between pH and periodontal pocketing were evident, although wide variations were observed between pockets. Randomly distributed pH readings ranging from 2-9 were observed within a single periodontal pocket. This implies that the physiology of processes taking place within periodontal pockets is wide ranging and complex. Different levels of pH indicate different chemical environments which may imply that different disease and reparative processes are occurring simultaneously within each periodontal pocket. The limitations of the assessment technique used in this study were highlighted and compared in relation to results obtained from other studies using more sophisticated techniques and it was found that the results obtained using this unsophisticated technique were in agreement with most of these other studies. Therefore, this technique may have applications in screening for disease activity in clinical practice. However, the need for further work to confirm the observations of this study is necessary to corroborate these associations.

A transmission electron microscopy study of supragingival calculus.

In this study the ultrastructure of human dental calculus was investigated using transmission electron microscopy (TEM). The aim of the study was to observe and clarify the calcification process and the part played by dental plaque in this process. Supragingival calculus from 10 patients was harvested and processed. It was shown that both calculus, and dental plaque within non-mineralised lacunae in calculus, are heterogeneous. Furthermore it was shown that the calculus/dental plaque interface was distinct, although also variable. As calcification occurred apparently independently of dental plaque in some places and when calcification of dental plaque bacteria occurred, it was also varied, it was concluded that supragingival calculus is not simply 'mineralised plaque' but a complex heterogeneous material consisting of numerous phases of mineralisation and non-mineralised areas. The role of dental plaque in the mineralisation process is unclear. However, calculus was not observed arising out of mineralising dental plaque. Mineralising dental calculus and maturing dental plaque are two distinct and different phases occurring simultaneously, albeit with great variability.

Management of data used in clinical trials which is unevenly distributed at baseline.

In this study, 63 healthy adult males were selected for participation in a clinical trial. After initial screening to determine their suitability for participation in the trial, an appointment was scheduled for a professional prophylaxis to derive baseline data and to instruct volunteers in the use of a standard oral hygiene regimen for the trial. Volunteers were then randomly assigned to test and control groups. Follow-up appointments were scheduled two and four weeks thereafter for collection of data. The presence of dental plaque and calculus was assessed at each appointment. Data was to be analysed by using a Student's 't'-test for paired data, but significant differences in the plaque scores were found between the test and control groups at baseline. As a result, the data could not be analysed in this way to obtain a meaningful result. An initial scatter plot of the data revealed six subjects whose plaque scores varied considerably from the group. The aim of this analysis was to evaluate how two different approaches to statistical analysis of data in which significant differences between test and control groups at baseline might affect the inferences drawn from the data. Reasons for significant differences in baseline data in randomly selected groups of volunteers were considered, as well as methods of avoiding this situation. Suggestions on the management of situations in which databases significantly differ include the elimination of 'outliers' and the use of techniques like the Standard Normal Deviate (SND). The data for this study were analysed using these techniques. Although no statistical differences were identified between the two methods of analysis, numerical differences were evident which altered with the type of analysis used. It was concluded that techniques for transformation of the data, like those used in this study, made no difference to the results of subsequent statistical analysis by comparison with the original data set. The influence of sample selection and analysis of data on the results of clinical trials are discussed. The difficulties in interpretation of the results of statistical analyses were highlighted. The influence of imbalances in the data set on the interpretation of the results of statistical analysis was shown to be minimal in this clinical trial.

Statistical analysis of data derived from clinical variables of plaque and gingivitis.

Selection of suitable subjects and statistical analysis of data derived from clinical trials presents a number of problems. In this trial, clinical data were analysed separately for pooled whole mouth data and for data including positive scores only for the variables of dental plaque and gingivitis. It was demonstrated that comparable data sets and statistical analyses were obtained using both data sets. Furthermore, it was shown that in order to achieve the best possible results in a clinical trial, the variable of gingivitis should be used in preference to plaque scores, that only individuals of high and/or moderate susceptibility to inflammation should be selected for inclusion in the statistical analysis, and that sites which have positive signs of disease only, should be included in the statistical analysis.

Supragingival calculus formation in a group of young adults.

The presence of calculus was assessed on the lingual surfaces of the mandibular anterior teeth in a randomly selected group of 63 young adults. The rate of regrowth of calculus after professional prophylaxis was also observed. Twenty-two individuals had supragingival calculus on the mandibular lingual surfaces of their teeth at baseline. Eleven of these individuals demonstrated regrowth of calculus by the end of the study, in spite of repeated professional prophylaxis. Thus, 17.5% of subjects exhibited rapid regrowth of calculus on the mandibular lingual surfaces of their teeth within 2 weeks of professional prophylaxis.

Efficacy of a new electronic toothbrush in removing bacterial dental plaque in young adults.

Although a high level of oral cleanliness is essential for long-term maintenance of dental health, many people cannot maintain good oral hygiene consistently. A new electronic toothbrush has been developed that induces a small electric charge onto tooth surfaces. This charge damages electrostatic bonding of plaque proteins to tooth surfaces; thus, plaque removal is enhanced while the toothbrush is used. Young men were issued identical toothbrushes; some were electrically active. Plaque levels were assessed at baseline, and after two and four weeks, concurrently with oral-hygiene instruction and professional prophylaxis. The electrically active toothbrushes demonstrated better plaque removal than the inactive toothbrushes. This better performance was statistically significant linguopalatally, indicating that significantly more plaque was removed where mechanical access was poorest. Thus, the electrical activity of this toothbrush significantly enhances plaque removal where toothbrushing access is limited.

Variations in plaque scores in a small group of individuals over a four week time period.

Individual plaque scores were assessed in a group of individuals over a four week period and compared to the group mean value for the group. No instruction in toothbrushing or professional prophylaxis was undertaken during the period of study. While the mean values for the group remained virtually unchanged throughout the course of the study, the levels of plaque varied considerably between individuals over the period of investigation. Thus it is concluded that the use of plaque scores in clinical practice may not adequately reflect the true relevance of dental plaque and its role in the initiation and progression of gingival inflammation in individuals. Furthermore, pooling of data from clinical trials masks the wide variations and changes in plaque scores in individual subjects which may adversely affect the conclusions drawn from the statistical analysis of the data.

Radiographic evidence of bone regeneration using oxidized cellulose mesh as a bioabsorbable membrane: some case studies.

Guided tissue regeneration has been described as a technique to enhance the regrowth of the periodontal tissues after surgical therapy. Originally, nondegradable materials were used for this purpose, but more recently, degradable materials have been advocated for this purpose. Utilizing an adapted technique in which the material was used as an infill material and barrier membrane, this small study in human subjects has demonstrated radiographically that the defects are filled with a bone-like material over a protracted period. Regeneration of tissues, with bone deposition in infrabony defects, may not be complete as long as 12 months after surgery.

Observations on the recurrence of destructive periodontal disease during a period of four years after treatment.

The upper and lower extreme percentiles of change in clinical variables were analyzed for a period of four years after completion of periodontal therapy in order to assess the patterns of disease recurrence after treatment. This analysis has demonstrated periods of healing and relapse of sites within individuals, among different individuals, and among different clinical assessment variables utilized. As not all of the sites within different individuals heal or relapse at the same rate, the random asynchronous burst model of pathogenesis seems appropriate to incorporate the different clinical assessment parameters and different sites in different individuals simultaneously. Long-term recession and pocketing, however, may demonstrate opposite trends, giving the erroneous interpretation that attachment levels remain constant with time, whereas, in fact, an active "dynamic equilibrium" of tissue remodeling is established. A statistical model based on the dynamic equilibrium concept would enable account to be taken of the multifactorial interactions that incorporate site and subject interrelationships between different clinical assessment parameters. The dynamic equilibrium model may be suitable therefore as the basis on which statistical analysis of the progression of periodontal disease may be considered. However, as the value of this or other models of the periodontal disease process have not been established, the analysis of data to derive meaningful conclusions from complex statistical techniques may be premature.

A technique for treatment of extensive periodontal defects: a case study.

This case study describes the use of oxidized cellulose mesh to improve healing of periodontal defects of poor regenerative capacity. Circumferential defects with horizontal bone loss were treated by surgical exposure of the root surface followed by scaling and root planing. Prior to flap replacement, oxidized cellulose mesh was positioned in incremental layers over the defects so as to replace the lost alveolar bone. It was to act also as a barrier to the ingress of epithelial cells and gingival fibroblasts into the healing wound using the principles vof guided tissue regeneration. Healing was good, with minimal post-operative recession. Whether regeneration of alveolar bone and periodontal ligament occurred as a result of using this technique could not be determined in this clinical case study.

Recurrence of destructive periodontal disease after treatment. A long term study.

This study demonstrates the difficulties which arise in statistical analysis derived from data of observations in post-treatment healing and recurrence of periodontal disease. Ten individuals received an initial phase of treatment followed by surgical pocket elimination utilizing replaced flap surgery. Clinical measurements of recession and pocketing were taken pre-operatively and 6 monthly thereafter for a period of four years after treatment. The results have shown that surgical treatment is least benefit in cases of mild pocketing, and of most benefit in cases of severe pocketing. A tendency for reduction in recession levels after two years was observed. Pocketing and attachment levels showed a tendency toward relapse as early as 6 months postoperatively. However, this simple observation masks a complex pattern of tissue remodeling in which some sites remain stable, others improve, while others relapse with time. Improvement may occur concurrently in different sites. Continued improvement in the clinical parameters of pocketing and attachment levels was observable in some sites for up to 2 years after surgery, after which the tendency for recurrent disease became more noticeable. Analyses of changes in attachment levels may be misleading, because they may mask the divergent or convergent trends of recession and pocketing, which may be occurring simultaneously. As bursts of healing as well as bursts of destruction could be observed concurrently over the period of 4 years after treatment, it is suggested that a state of "dynamic equilibrium" is established, in which continued tissue remodeling over a protracted period of time, may give rise to the clinical misconception that little or no changes are occurring in the majority of sites with time.

A 4-year controlled clinical study into the use of a ceramic hydroxylapatite implant material for the treatment of periodontal bone defects.

10 patients with chronic adult periodontitis who had greater than 1 tooth with infra-bony pockets were treated at the test defects by periodontal flap procedures with implantation of hydroxylapatite particles; the control defects were treated by the same surgical procedures but without the implant. A total of 58 test defects and 59 control defects were treated. Each defect had measurements carried out at given sites on the involved tooth surfaces, the sites being considered for subsequent tabulation purposes under the category of shallow (less than 3 mm) moderate (3-6 mm) and deep (greater than 6 mm) initial pocket depths. There were 146 and 152 shallow sites, 216 and 241 moderate sites and 140 and 133 deep sites, at test and control sites, respectively. Measurements of recession, probing pocket depths and probing attachment levels were made at 6 months and 1, 2, 3 and 4 years. At all sites over the period of the study, for the moderate and deep initial pockets there was a significant reduction in probing depths and an increase in the probing attachment levels. At the 4th year of assessment for the initially deep pockets, the reduction in probing depths was significantly greater for the sites treated with the implant material. In view of the difficult clinical problem posed by the treatment of teeth with deeper periodontal bone defects, further research using either this type of implant material or similar material should be considered.

Compliance with maintenance therapy after periodontal treatment.

The aim of this study was to investigate the degree of compliance with a post treatment maintenance programme and to establish whether compliance could be related to the clinical assessment parameters before treatment or at the end of the initial phase of treatment. The study was carried out on 231 individuals who had been referred for periodontal therapy. Initial and post treatment plaque and gingivitis levels and pocket depth measurements were evaluated, in order to establish if postoperative compliance could be related to any of the pretreatment clinical parameters, or the changes which took place in these parameters as a result of treatment. It was found that more females tended to comply with the prescribed maintenance programme. Highly significant differences in the clinical parameters were noted for the compliant and non-compliant groups before treatment and at the end of the initial phase of treatment. 42% of individuals did not comply with the prescribed maintenance treatment. It is concluded that the degree of postoperative compliance with maintenance therapy is unrelated to the clinical parameters evaluated. The clinician must therefore recognise that a large percentage of individuals may not comply with the postoperative maintenance programme, although it is not possible to anticipate which individuals are less likely to be compliant from assessment of the clinical assessment parameters routinely used in clinical practice.

Computerized densitometric analysis of interproximal bone levels in a controlled clinical study into the treatment of periodontal bone defects with ceramic hydroxyapatite implant material.

The aim of this controlled clinical study was to utilize computer-assisted densitometric analysis of radiographs to assess the effectiveness of treating periodontal osseous defects with a sintered hydroxyapatite implant material. It was found that over the 2-year period of the study for the osseous defects treated by the implant material, there was a gain in the height of the hard tissue relative to the cemento-enamel junction; this gain was statistically significant compared with the results for the control sites.