Considerations in the statistical analysis of clinical trials in periodontitis

The Oral Health Statistics Guidelines for Reporting Observational Studies and Clinical Trials in Oral Health Research: Explanation and Elaboration

Adequate and transparent reporting is necessary for critically appraising research. Yet, evidence suggests that the design, conduct, analysis, interpretation, and reporting of oral health research could be greatly improved. Accordingly, the Task Force on Design and Analysis in Oral Health Research-statisticians and trialists from academia and industry-empaneled a group of authors to develop methodological and statistical reporting guidelines identifying the minimum information needed to document and evaluate observational studies and clinical trials in oral health: the Oral Health Statistics Guidelines. Drafts were circulated to the editors of 85 oral health journals and to task force members and sponsors and discussed at a December 2020 workshop attended by 49 researchers. The final version was subsequently approved by the task force in September 2021, submitted for journal review in 2022, and revised in 2023. The checklist consists of 48 guidelines: 5 for introductory information, 17 for methods, 13 for statistical analysis, 6 for results, and 7 for interpretation; 7 are specific to clinical trials. Each of these guidelines identifies relevant information, explains its importance, and often describes best practices. The checklist was published in multiple journals. The article was published simultaneously in JDR Clinical and Translational Research, the Journal of the American Dental Association, and the Journal of Oral and Maxillofacial Surgery. Completed checklists should accompany manuscripts submitted for publication to these and other oral health journals to help authors, journal editors, and reviewers verify that the manuscript provides the information necessary to adequately document and evaluate the research.

The OHStat Guidelines for Reporting Observational Studies and Clinical Trials in Oral Health Research: explanation and elaboration

Adequate and transparent reporting is necessary for critically appraising research. Yet, evidence suggests that the design, conduct, analysis, interpretation, and reporting of oral health research could be greatly improved. Accordingly, the Task Force on Design and Analysis in Oral Health Research-statisticians and trialists from academia and industry-empaneled a group of authors to develop methodological and statistical reporting guidelines identifying the minimum information needed to document and evaluate observational studies and clinical trials in oral health: the OHstat Guidelines. Drafts were circulated to the editors of 85 oral health journals and to Task Force members and sponsors and discussed at a December 2020 workshop attended by 49 researchers. The final version was subsequently approved by the Task Force in September 2021, submitted for journal review in 2022, and revised in 2023. The checklist consists of 48 guidelines: 5 for introductory information, 17 for methods, 13 for statistical analysis, 6 for results, and 7 for interpretation; 7 are specific to clinical trials. Each of these guidelines identifies relevant information, explains its importance, and often describes best practices. The checklist was published in multiple journals. The article was published simultaneously in JDR Clinical and Translational Research, the Journal of the American Dental Association, and the Journal of Oral and Maxillofacial Surgery. Completed checklists should accompany manuscripts submitted for publication to these and other oral health journals to help authors, journal editors, and reviewers verify that the manuscript provides the information necessary to adequately document and evaluate the research.

The OHStat Guidelines for Reporting Observational Studies and Clinical Trials in Oral Health Research: Explanation and Elaboration

Adequate and transparent reporting is necessary for critically appraising research. Yet, evidence suggests that the design, conduct, analysis, interpretation, and reporting of oral health research could be greatly improved. Accordingly, the Task Force on Design and Analysis in Oral Health Research-statisticians and trialists from academia and industry-empaneled a group of authors to develop methodological and statistical reporting guidelines identifying the minimum information needed to document and evaluate observational studies and clinical trials in oral health: the OHstat Guidelines. Drafts were circulated to the editors of 85 oral health journals and to Task Force members and sponsors and discussed at a December 2020 workshop attended by 49 researchers. The final version was subsequently approved by the Task Force in September 2021, submitted for journal review in 2022, and revised in 2023. The checklist consists of 48 guidelines: 5 for introductory information, 17 for methods, 13 for statistical analysis, 6 for results, and 7 for interpretation; 7 are specific to clinical trials. Each of these guidelines identifies relevant information, explains its importance, and often describes best practices. The checklist was published in multiple journals. The article was published simultaneously in JDR Clinical and Translational Research, the Journal of the American Dental Association, and the Journal of Oral and Maxillofacial Surgery. Completed checklists should accompany manuscripts submitted for publication to these and other oral health journals to help authors, journal editors, and reviewers verify that the manuscript provides the information necessary to adequately document and evaluate the research.

Dental therapists compared with general dental practitioners for undertaking check-ups in low-risk patients: pilot RCT with realist evaluation

Background

Many dental ‘check-ups’ in the NHS result in no further treatment. The patient is examined by a dentist and returned to the recall list for a further check-up, commonly in 6 or 12 months’ time. As the oral health of regular dental attenders continues to improve, it is likely that an increasing number of these patients will be low risk and will require only a simple check-up in the future, with no further treatment. This care could be delivered by dental therapists. In 2013, the body responsible for regulating the dental profession, the General Dental Council, ruled that dental therapists could see patients directly and undertake check-ups and routine dental treatments (e.g. fillings). Using dental therapists to undertake check-ups on low-risk patients could help free resources to meet the future challenges for NHS dentistry.

Objectives

The objectives were to determine the most appropriate design for a definitive study, the most appropriate primary outcome measure and recruitment and retention rates, and the non-inferiority margin. We also undertook a realist-informed process evaluation and rehearsed the health economic data collection tool and analysis.

Design

A pilot randomised controlled trial over a 15-month period, with a realist-informed process evaluation. In parallel, we rehearsed the health economic evaluation and explored patients’ preferences to inform a preference elicitation exercise for a definitive study.

Setting

The setting was NHS dental practices in North West England.

Participants

A total of 217 low-risk patients in eight high-street dental practices participated.

Interventions

The current practice of using dentists to provide NHS dental check-ups (treatment as usual; the control arm) was compared with using dental therapists to provide NHS dental check-ups (the intervention arm).

Main outcome measure

The main outcome measure was difference in the proportion of sites with bleeding on probing among low-risk patients. We also recorded the number of ‘cross-over’ referrals between dentists and dental therapists.

Results

No differences were found in the health status of patients over the 15 months of the pilot trial, suggesting that non-inferiority is the most appropriate design. However, bleeding on probing suffered from ‘floor effects’ among low-risk patients, and recruitment rates were moderately low (39.7%), which suggests that an experimental design might not be the most appropriate. The theory areas that emerged from the realist-informed process evaluation were contractual, regulatory, institutional logistics, patients’ experience and logistics. The economic evaluation was rehearsed and estimates of cost-effectiveness made; potential attributes and levels that can form the basis of preference elicitation work in a definitive study were determined.

Limitations

The pilot was conducted over a 15-month period only, and bleeding on probing appeared to have floor effects. The number of participating dental practices was a limitation and the recruitment rate was moderate.

Conclusions

Non-inferiority, floor effects and moderate recruitment rates suggest that a randomised controlled trial might not be the best evaluative design for a definitive study in this population. The process evaluation identified multiple barriers to the use of dental therapists in ‘high-street’ practices and added real value.

Future work

Quasi-experimental designs may offer more promise for a definitive study alongside further realist evaluation.

Trial registration

Current Controlled Trials ISRCTN70032696.

Funding

This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 9, No. 3. See the NIHR Journals Library website for further project information.

Examiner alignment and assessment in clinical periodontal research

Periodontal research typically relies on clinical examiners to assess variables such as gingival inflammation, plaque scores or probing depths as a means of determining treatment outcomes or for performing group comparisons. The quality of the gathered information is dependent, to a large extent, on the skills of the examiner(s) and on the validity of the assessment methods that are used. Attempts have been made to increase the objectivity of periodontal assessments, for example by introducing scoring systems for gingival inflammation, but within these systems there is often considerable scope for variation when interpreting the scoring criteria, leading to subjectivity when assigning scores to individual periodontal sites. This has led to an awareness of the importance of examiner alignment and assessment to improve the data quality by standardizing techniques and improving examiner reliability. Examiner alignment and assessment is used in preference to the term 'examiner calibration' because calibration implies comparison with an accurate or 'gold' standard, which is not available in periodontal research. In this review, we consider the historical perspective that led to the development of clinical scoring systems for periodontal research using gingival inflammation as an example. A clinical protocol for undertaking examiner alignment and assessment is presented, and we review the common sources of error and bias that can lead to difficulties in aligning examiners, and consider how they can be eliminated. It is particularly important that subjects who are recruited to the examiner alignment and assessment study present with a comparable level of disease to the subjects who will ultimately be recruited to the planned clinical trial. Another challenge in examiner alignment and assessment is applying appropriate statistical tests to assess the outcome of the alignment exercise. In the periodontal literature, the statistic kappa is frequently used to confirm an adequate degree of examiner agreement, but kappa is bound to significant restrictions when applied for this purpose. Through the use of case studies, we present different approaches to data analysis from calibration studies, focusing on continuous variables (such as probing depths and attachment levels) or ordinal data (such as gingival or plaque indices), to enable a correct, although frequently conservative, interpretation of data generated during examiner alignment and assessment studies.

Recording and surveillance systems for periodontal diseases

This paper describes tools used to measure periodontal diseases and the integration of these tools into surveillance systems. Tools to measure periodontal diseases at the surveillance level have focussed on current manifestations of disease (e.g. gingival inflammation) or disease sequelae (e.g. periodontal pocket depth or loss of attachment). All tools reviewed in this paper were developed based on the state of the science of the pathophysiology of periodontal disease at the time of their design and the need to provide valid and reliable measurements of the presence and severity of periodontal diseases. Therefore, some of these tools are no longer valid. Others, such as loss of periodontal attachment, are the current de-facto tools but demand many resources to undertake periodical assessment of the periodontal health of populations. Less complex tools such as the Community Periodontal Index, have been used extensively to report periodontal status. Laboratory tests for detecting putative microorganisms or inflammatory agents present in periodontal diseases have been used at the clinical level, and at least one has been tested at the population level. Other approaches, such as self-report measures, are currently under validation. In this paper, we do not review indices designed to measure plaque or residual accumulation around the tooth, indices focussed only on gingival inflammation or radiographic approaches with limited applicability in surveillance systems. Finally, we review current case-definitions proposed for surveillance of periodontal disease severity.

Accuracy of linear intraoral measurements using cone beam CT and multidetector CT: a tale of two CTs

OBJECTIVES

The aim was to compare the accuracy of linear bone measurements of cone beam CT (CBCT) with multidetector CT (MDCT) and validate intraoral soft-tissue measurements in CBCT.

METHODS

Comparable views of CBCT and MDCT were obtained from eight intact cadaveric heads. The anatomical positions of the gingival margin and the buccal alveolar bone ridge were determined. Image measurements (CBCT/MDCT) were performed upon multiplanar reformatted data sets and compared with the anatomical measurements; the number of non-assessable sites (NASs) was evaluated.

RESULTS

Radiological measurements were accurate with a mean difference from anatomical measurements of 0.14 mm (CBCT) and 0.23 mm (MDCT). These differences were statistically not significant, but the limits of agreement for bone measurements were broader in MDCT (-1.35 mm; 1.82 mm) than in CBCT (-0.93 mm; 1.21 mm). The limits of agreement for soft-tissue measurements in CBCT were smaller (-0.77 mm; 1.07 mm), indicating a slightly higher accuracy. More NASs occurred in MDCT (14.5%) than in CBCT (8.3%).

CONCLUSIONS

CBCT is slightly more reliable for linear measurements than MDCT and less affected by metal artefacts. CBCT accuracy of linear intraoral soft-tissue measurements is similar to the accuracy of bone measurements.

Periodontal status and hyperlipidemia: statin users versus non-users

BACKGROUND

The association between serum lipids and periodontal disease has been studied predominantly in patients with chronic periodontitis with limited data available regarding periodontal status of patients with hyperlipidemia. Meanwhile, the impact of statins on the periodontal health of the population also remains largely underexplored. This study aims to assess the periodontal status among patients with hyperlipidemia and users of statins.

METHODS

In this cross-sectional study, 94 patients with hyperlipidemia (50 receiving statins and 44 receiving non-pharmacologic therapy) and 46 control individuals who were normolipidemic underwent periodontal examination (plaque index, gingival index [GI], probing depth [PD], and clinical attachment level [CAL]). Biochemical parameters measured included serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein cholesterol levels.

RESULTS

PD and GI were significantly higher in patients with hyperlipidemia who were non-statin users compared with the normolipidemic individuals (P <0.001 [PD] and P <0.05 [GI]) and the statin group (P = 0.001 [PD] and P <0.05 [GI]). Periodontal parameters between statin users and the normolipidemic group did not differ significantly. After adjusting for confounders, positive and significant correlations were observed between PD and TG, and TC and LDL, whereas CAL shared correlation with TC and LDL. GI was correlated with TG and TC. Regression analyses revealed that whereas TC was associated significantly with PD (P <0.001), LDL showed significant association with CAL (P = 0.013). TG showed significant association with GI (P = 0.020).

CONCLUSIONS

Our findings suggest that relative to the general population, patients with hyperlipidemia are more prone to periodontal disease. Also, within the limits of this study, statins have a positive impact on periodontal health.

Discovering factors influencing examiner agreement for periodontal measures

OBJECTIVES

Calibration studies are routinely performed to establish examiner reliability in clinical periodontal research. In these studies, each periodontal site is assessed in duplicate, enabling point and interval estimation of agreement measures. We show how these data can be used additionally to discover subgroups among the periodontal sites according to degree of agreement with true periodontal status and to identify factors associated with examiner bias.

METHODS

A Bayesian hierarchical model is developed that, for all examiners, links the examiner's recorded measurement with the site's true periodontal status, allowing for site-specific examiner effects on the recorded measurement. These site-specific examiner effects are modeled as arising from a Dirichlet process mixture, which yields a small number (relative to the number of sites) of distinct effects for each examiner. Hence, sites that share the same examiner effect form a subgroup for which that examiner exhibits consistent bias relative to truth. We fit this model to data from a pilot calibration study for probed pocket depth measurements and use the results to explore examiner-specific groupings of sites according to degree of agreement with true pocket depth. The discovered group assignments were then associated with characteristics of the site.

RESULTS

The Bayesian hierarchical modeling revealed that periodontal sites were grouped according to bias into three, two, and two subgroups, respectively, for each of the three study examiners. The magnitude of the bias was associated with tooth position and true depth of the pocket.

CONCLUSIONS

Our Bayesian hierarchical model enhances the utility of data obtained from calibration studies for periodontal pocket depth by facilitating discovery of subgroups of sites according to examiner bias. The results indicate that targeting specific tooth locations and pocket depths during examiner training, uniquely for each examiner, may reduce bias in periodontal pocket depth measurements, thereby enhancing the quality of oral epidemiologic research.

The effect of locally delivered doxycycline as an adjunctive therapy to scaling and root planing in smokers

BACKGROUND

Locally delivered doxycycline is found to be effective in managing periodontitis as an adjunct to scaling and root planing.

AIM

To evaluate the effect of locally delivered doxycycline (10%) with scaling and root planing in the periodontal treatment of smokers and to compare it with scaling and root planing alone.

METHODS

Twelve smokers with chronic periodontitis and a pocket depth (⩾5 mm) on posterior teeth that bleed on probing were selected. Patients were randomly assigned to scaling and root planing (SRP) or scaling and root planing followed by local application of doxycycline (SRP-D). Plaque, bleeding on probing, gingival recession, clinical attachment level (CAL), and probing depth (PD) were recorded at the baseline, 6 and 12 weeks.

RESULTS

Both groups showed a significant reduction in Plaque, Bleeding on Probing and pocket depth at 6th and 12th week from the baseline. A statistically significant gain of attachment was observed in both groups after treatment. Even though the doxycycline group showed slightly higher attachment gain it was not statistically significant compared to the control group.

CONCLUSION

The observations of the study reveal that the additional benefit of topical application of doxycycline as an adjunct to scaling and root planing in smokers is not convincing. However, further clinical studies may be necessary to substantiate the present observations.

Methods for the statistical analysis of binary data in split-mouth designs with baseline measurements

Many split-mouth trials are characterized by the pairing of site-specific outcome and baseline data within each segment of a subject's mouth. However when the response variable of interest is binary, methods of statistical analysis for this design are not well developed. In this paper we present several analytic approaches that may be taken to the resulting data, showing how the efficiency of statistical inferences can be improved by appropriately incorporating the baseline information. The advantages and disadvantages of the different approaches are discussed in the context of an example from the published literature. The results from a limited simulation study are also presented.

Microbiological findings after periodontal therapy using curettes, Er:YAG laser, sonic, and ultrasonic scalers

AIM

To evaluate and compare the microbiological effects of hand instruments, Er:YAG-laser, sonic, and ultrasonic scalers in patients with chronic periodontitis. Patient perception of each treatment was documented.

MATERIAL AND METHODS

From 72 patients, bacterial samples were collected from the deepest pocket in each quadrant (total: 288 sites). A polymerase chain reaction kit estimated the amount of Aggregatibacter (Actinobacillus) actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Tannerella forsythensis (Tf), and Treponema denticola (Td) at baseline as well as 3 and 6 months after therapy. One quadrant in each patient was randomly assigned to curettes (H-group), Er:YAG laser (L-group), sonic device (S-group), or ultrasonic device (U-group).

RESULTS

Three months post-operatively, the amounts of Pg, Pi, Tf, and Td were significantly reduced in all groups. Laser and sonic instrumentation failed to reduce Aa. Six months after therapy, significant differences were still detected for Pg (L- and U-group), for Pi and Tf (S-group), and for Td (L-, S- and U-group). Patients rated ultrasonic treatment as more preferable than hand and laser instrumentation.

CONCLUSION

The various treatment methods resulted in a comparable reduction of the evaluated periodontal pathogens, and bacterial increase was only partially different 6 months post-operatively. Ultrasonic instrumentation caused less discomfort.

A randomized-controlled trial of low-dose doxycycline for periodontitis in smokers

BACKGROUND/AIM

Tobacco use reduces the effect of non-surgical periodontal therapy. Host-modulation with low-dose doxycycline (LDD) might favour repair and promote an improved treatment response. The aim of this study was to investigate the effect of LDD in smokers on non-surgical periodontal therapy.

MATERIAL AND METHODS

This was a parallel arm, randomized, identical placebo-controlled trial with masking of examiner, care-giver, participant and statistician and 6 months of follow-up. Patients received non-surgical therapy and 3 months of test or control drug. Statistical analysis used both conventional methods and multilevel modelling.

RESULTS

Eighteen control and 16 test patients completed the study. The velocity of change was statistically greater for the test group for clinical attachment level -0.19 mm/month (95% CI=-0.34, 0.04; p=0.012) and probing depth 0.30 mm/month (95% CI=-0.42, -0.17; p<0.001). However, no differences were observed for absolute change in clinical or biochemical markers at 6 months.

CONCLUSIONS

This study does not provide evidence of a benefit of using LDD as an adjunct to non-surgical periodontal therapy in smokers.

Study design for calibration of clinical examiners measuring periodontal parameters

BACKGROUND

We present an approach to examiner calibration study design where the number of calibration subjects is based on a specified margin of error (half-width of the 95% confidence interval [CI]) of the percentage of agreement (exact and within 1 mm) for both intra- and interexaminer reliability assessments.

METHODS

An experienced standard examiner (S) trained three dental hygienists (A, B, and C) in correct procedures for obtaining a variety of periodontal measures. Duplicate measurements of probing depth (PD [mm]) and the free gingival margin to the cemento-enamel junction (CEJ-GM [mm]) were obtained in a pilot study to design a formal examiner calibration study, where sample sizes were adjusted for the effects of within-subject clustering of binary indices of agreement.

RESULTS

Within-subject clustering of agreement indices resulted in an approximate four-fold increase in the variance of the estimates of percentage of agreement with the standard. PD and CEJ-GM percentage of exact agreement measurements (95% CI) for each examiner-standard pair, respectively, were as follows: AS=55% (48%, 61%) and 70% (62%, 78%); BS=52% (45%, 59%) and 73% (63%, 82%); and CS=55% (50%, 61%) and 72% (65%, 79%). The corresponding 95% CIs unadjusted for the effects of clustering underestimated the margin of error associated with the estimates of exact agreement by as much as 57% for PD and 68% for CEJ-GM.

CONCLUSION

Failure to account for dependence among site-level agreement indices results in a false sense of precision in the resulting reliability estimates and can lead to faulty inference.

The effect of a dentifrice and mouth rinse combination containing amine fluoride/stannous fluoride on plaque and gingivitis: a 6-month field study

AIM

To examine the effect of amine fluoride/stannous fluoride (AmF/SnF(2))-containing dentifrice and mouth rinse on plaque formation and gingivitis as compared with habitual oral hygiene procedures with a regular sodium fluoride (NaF) dentifrice.

MATERIAL AND METHODS

In total, 22 general practices participated in this research project. The participants (N=281) were randomly assigned into two groups: the test group received an AmF/SnF(2) dentifrice-mouth rinse combination and the control group received a NaF-containing dentifrice. The patients were requested to brush twice daily for approximately 2 min. The subjects of the test group had to rinse additionally in the evening for 30 s with 10 ml of the mouth rinse.

RESULTS

Both groups started with comparable scores of plaque, bleeding and staining. At 6 months, the plaque scores were 0.95 for the AmF/SnF(2) group and 0.99 for the NaF group (decrease of 16% and 10%, respectively). Bleeding scores, although significantly different from baseline, did not show differences between the two regimes. At the end of the experimental period, the overall staining was more pronounced in the AmF/SnF(2) group (41%) than the NaF group (26%). Both plaque reduction and increase in staining seemed to be correlated to the amount of mouth rinse used in the test group.

CONCLUSION

In instruction-resistant patients recruited from dental practices, the combined use of AmF/SnF(2) did not decrease gingivitis at a significant level in comparison with the regular regime of two times daily brushing with an NaF-containing dentifrice. However, the above-mentioned combination resulted in greater plaque reduction than that observed with the use of the conventional dentifrice. When used according to the manufacturer's instructions, this effect on plaque scores was more pronounced.

Efficacy of subgingivally applied minocycline in the treatment of chronic periodontitis

BACKGROUND

The use of adjunctive minocycline with mechanical debridement in treating periodontitis has been widely studied using different methods. However, the results from these studies are equivocal.

OBJECTIVE

The purpose of this study was to clarify the efficacy of the adjunctive use of subgingival minocycline application plus scaling/root planing as compared with the results of one episode of scaling/root planing in the treatment of chronic periodontitis.

METHODS

Fifteen patients were enrolled in this split-mouth clinical trial. Probing depth, clinical attachment loss, gingival index, and bleeding on probing were evaluated at the baseline before scaling/root planing and 6, 10, 14, and 18 weeks later according to a single-blind protocol. The amount of interleukin-1beta (interleukin-1beta pg/site) at each lesion was also simultaneously measured in gingival crevicular fluid in a parallel comparison design. After full-mouth baseline measurements and scaling/root planing, 78 lesions with a residual mean probing depth of 5 mm at anterior teeth were selected and equally distributed in either right or left sites based on a split-mouth symmetrical design and randomly assigned to one of two treatment groups (with or without minocycline administration, n = 39 for each group).

RESULTS

Probing depth significantly decreased from the baseline (week 0) to week 6 after scaling/root planing (p < 0.05) in both groups, but there was no statistically significant difference between the two groups (p > 0.05). However, at weeks 10, 14, and 18, the experimental group showed significantly greater improvement in pocket reduction than the control group (p < 0.05). Similarly, both groups also showed significant decreases in gingival index scores from weeks 0-6 (p < 0.05), but gingival index reductions at weeks 10, 14, and 18 were statistically significant in favor of the experimental group (p < 0.05). The experimental group had more attachment gain than the control group at weeks 14 and 18 (p < 0.05). Values of interleukin-1beta (pg/site) at the experimental sites were significantly reduced at weeks 10, 14, and 18, as compared to values at control sites (p < 0.01). Finally, the incidence of bleeding on probing showed no differences between the two groups for any time interval (p > 0.05).

CONCLUSIONS

In this 18-week clinical trial, the results suggested that scaling/root planing with adjunctive subgingival administration of minocycline ointment has a significantly better and prolonged effect compared to scaling/root planing alone on the reduction of probing depth, clinical attachment loss, gingival index, and interleukin-1beta content, but not on bleeding on probing.

Analysis of multiple 2x2 tables with site-specific periodontal data

Periodontal data typically consist of observations made at multiple sites within each patient. Observations within a patient tend to be positively correlated; hence, standard statistical techniques that assume independence are invalid. Regression techniques for correlated data have been proposed; communicating results from these models, however, is difficult, due to their inherent complexity. Simpler statistical approaches have also been proposed, but many of these methods can be applied only when covariates are specific to the subject, and do not vary from site to site within a subject. In this paper, we present two methods for the analysis of multiple 2x2 tables containing site-specific periodontal data. The methods presented are modifications of the well-known Mantel-Haenszel methods. We illustrate these methods using a subset of data from a clinical trial examining the effects of scaling and root planing on levels of interleukin-1 beta.

Contrast perception in digitized panoramic radiographs compared with their film-based origin

OBJECTIVES

We sought to compare the visual image quality of film-based and digitized panoramic radiographs through use of a hole-containing test wedge.

STUDY DESIGN

An aluminum wedge containing 100 cells, of which 90 were given shallow holes, was exposed in the film-based Orthophos CD panoramic unit. Two radiographs subjectively exhibiting optimum contrast were selected. Films were digitized with a charge-coupled device flatbed scanner at 300 dpi. Films and digitized images were rated cellwise by 2 similar groups of 50 observers each with respect to spot perception.

RESULTS

The mean sensitivity was 0.26 +/- 0.09 for film and 0.20 +/- 0.07 for digitized images (P =.000), with a pronounced decline in the latter in regions of high background density. The average specificity was 0.93 +/- 0.07 for film versus 0.92 +/- 0.08 for digitized images (P = 0.213).

CONCLUSION

Film yielded a significantly higher sensitivity, but this absolute difference was actually small compared with that of the digitized images.

Subgingival microbiota of indigenous Indians of Central America

OBJECTIVE

To define the subgingival microbial profiles of adult subjects from a previously identified rural community of indigenous Indians in Guatemala, Central America.

MATERIALS AND METHODS

A full-mouth periodontal examination was performed in 114 adult subjects from 45 families. Plaque samples were collected from both deep and shallow periodontal pockets and checkerboard DNA-DNA hybridization was employed to identify 17 species previously associated with periodontitis or health.

RESULTS

Plaque deposits and gingivitis were universal and widespread, and periodontal pocketing > or =5 mm was highly prevalent (84% of subjects). Streptococcus sanguis, Actinomyces naeslundii genospecies 2 and Fusobacterium nucleatum were significantly more prevalent in shallow sites. At the subject level, Actinomyces naeslundii and Peptostreptococcus micros were significantly more prevalent in periodontally-healthy subjects. Actinobacillus actinomycetemcomitans was not detected in any sample.

CONCLUSION

There was no association between periodontal disease status and presence of suspected periodontal pathogens. These latter results conflict somewhat with those from treated populations. However, in this population where extensive plaque deposits and gingivitis are universal, the presence of putative pathogens may be more reflective of the local environment.

Statistical issues in analysis of diagnostic imaging experiments with multiple observations per patient

Many diagnostic imaging experiments are characterized by the presence of several observations for each patient studied. Evaluation of metastases with different imaging modalities in patients with cancer or examination of multiple artery segments in patients with heart abnormalities are some examples of such studies. Data obtained from multiple observations per patient are cluster correlated and should not be analyzed by using standard statistical methods because of correlations within a subject. In this article, positron emission tomographic studies are used as a framework to review statistical methods for the analysis of clustered data. Some simple statistical methods that account for correlation within a subject and that can be applied to conventional and well-known statistical methods, such as the chi(2) and t tests, are introduced. One of these methods is illustrated by using a brief analysis of data from a positron emission tomographic study, which demonstrates how resulting conclusions may be incorrect if appropriate techniques are not applied. Alternative methods that can handle multiple observations and dependency within a subject for diagnostic imaging studies are discussed.

Between-subject and within-subject statistical information in dental research

The evaluation of risk factors in dental research frequently uses observations at multiple sites in the same patient. For this reason, statistical methods that accommodate correlated data are generally used to assess the significance of the risk factors (e.g., generalized estimating equations, generalized linear mixed models). In applications of these methods, it is typically assumed (implicitly, if not explicitly) that between-subject and within-subject comparisons will produce the same estimated effect of the risk factor. When between- and within-subject comparisons conflict, the statistical methods can give biased estimates or results that are difficult to interpret. For illustration, we present two examples from periodontal disease studies in which different statistical methods give different estimates and significance levels for a risk factor. Statistical analyses in dental research should assess whether different sources of information give similar conclusions about risk factors or treatments.

Cost-effectiveness of composite resins and amalgam in the replacement of amalgam Class II restorations

OBJECTIVES

The replacement of an old amalgam Class II restoration is a common treatment and will remain so for decades. In addition to effectiveness, possible adverse health effects and esthetics, the costs of the treatment options will play a role in the choice of material. The aim of this study was to yield information on the relative cost-effectiveness of the use of composite resins and amalgam for the rerestoration of amalgam Class II restorations.

METHODS

As part of a larger randomized clinical trial, treatment effectiveness and treatment costs were estimated in 73 composite and amalgam Class II posterior re-restorations. The main treatment outcome was longevity. Secondary outcomes included need of repair and quality of the margin while in situ. Costs were analyzed from the perspective of dentistry, assuming a treatment strategy aimed at offering 'value for money'. From this perspective, differential costs were based on personnel costs as approximated by treatment time.

RESULTS

Replacing an amalgam Class II restoration with amalgam is associated with lower costs than replacing with a composite resin. A sensitivity analysis, considering type of composite, increasing proficiency with the material, and time needed for future removal of material, demonstrated that these differences are fairly robust. The materials performed equally well for the first 5 years after placement with respect to longevity. Differences in secondary outcomes were minor and not all in favor of the same material.

CONCLUSIONS

It is tentatively concluded that amalgams are more cost-effective than composites for replacing existing Class II amalgam restorations.

Reliability of linear alveolar bone loss measurements of mandibular posterior teeth from digitized bitewing radiographs

Observer reliability in performing linear measurements between the cementoenamel junction and alveolar crest was determined for mandibular posterior teeth from digitized clinical bitewing radiographs acquired during recall examinations. 6 measurements (corresponding to traditional probing measurements) were made per tooth by 3 observers. Mesial and distal measurements made to the most coronal aspects of the alveolar crest were the most reliable and least biased. As was anticipated, intra-observer reliability was better than inter-observer reliability although the 3 observers of our study were able to detect a significant mean change (0.1 mm, p<0.0001) in alveolar bone height over a 1-year period for 10 patients. For our most reliable and unbiased measurements (mesial measurements to the alveolar crest), a change of 0.54 mm (90th percentile) would be required to indicate change at a site from one time to the next. Based on the reliability of our digital radiographic measurements, with the alpha error rate set at 0.05 and beta at 0.20, a difference in alveolar bone height of 0.3 mm could be detected with a patient sample size of between 13 (best case) and 54 (worst case).

Is the chemical prevention of gingivitis necessary to prevent severe periodontitis?

Gingival inflammation seldom causes discomfort, social embarrassment or loss of function. As most sites with gingival inflammation do not progress to severe periodontal disease, gingivitis should not be considered a public health problem. Periodontitis is always preceded by gingivitis. But most gingivitis remains stable for years without progressing to periodontitis. The number of gingivitis sites that do convert is small. The levels of oral cleanliness achieved by the majority of populations in industrialized countries are below the threshold for severe destructive periodontal disease of personal and public health concern. Because methods of measuring the progression of periodontal disease are unreliable, definitive answers regarding conversion of gingivitis to severe periodontitis are lacking. Gingival inflammation frequently remains contained; most gingivitis remains stable for years without progressing to periodontitis. Decreasing gingivitis does reduce shallow pocketing, but the effect on severe periodontitis is not clear. Although the underlying justification for the reduction of plaque is to reduce gingival inflammation to prevent or reduce severe periodontitis and tooth loss, the basis for the approach is equivocal. A reasonably high level of plaque appears to be compatible with acceptably low levels of periodontal disease. Reducing nonspecific plaque levels to such levels is therefore a rational goal. The conventional methods of controlling periodontal disease involve mechanical removal of plaque and calculus. A complimentary ecological approach, using chemicals, would be to alter the environment of the pocket to prevent growth of putative pathogens. Any ecological approach should be sensitive to the dangers of disrupting the natural ecology of dental plaque. Some antimicrobial and antimetabolic agents such as fluoride, chlorhexidine and triclosan and zinc citrate can selectively suppress certain organisms or inhibit bacterial proteases implicated in tissue damage. The uncertainties about factors that convert gingival inflammation into periodontitis and periodontitis into severe periodontitis coupled with insufficient data from controlled clinical trials on the effectiveness of chemical reduction of gingivitis to prevent severe periodontitis leads one to conclude that more research is required before the need for the chemical prevention of gingivitis to prevent severe periodontitis can be justified.

Effect evaluation of an oral health education programme in primary schools in Tanzania

This study aimed to assess the clinical oral health outcome effects among schoolchildren participating in a school-based oral health education (OHE) programme. Local social, cultural and environmental conditions were determinants of the school-based OHE programme, which was compiled on the basis of prevailing beliefs and on what teachers and educational authorities considered to be important for the oral health of schoolchildren. Consequently, the practical aspects of oral hygiene and information on the cause and prevention of caries and gingivitis were the components of oral health education. The teachers were prepared to carry out weekly supervised toothbrushing sessions and monthly lessons on aspects of oral health for the school year in grade 4. Eight participating schools were selected for the clinical effect evaluation and four non-participating schools served as the control. In total, 309 children from the participating schools and 122 children from the non-participating schools were available for the evaluation. Their ages varied between 9 and 14 years. The mean plaque score, calculus score and gingival bleeding score at baseline and at follow-up examinations 3, 8, 15 and 36 months later were not significantly different for participating schools and controls. The mean DMFT value at baseline was 0.4 and 3 years later 0.9 in both the participating and control schools. In conclusion, the present study shows that the implemented school-based OHE programme did not result in significant reductions of the clinical parameters measured.

Meta-analysis of the effect of systemic metronidazole as an adjunct to scaling and root planing for adult periodontitis

The purpose of this meta-analysis was to provide a quantitative overview of clinical trials assessing the use of systemic metronidazole (S-MET) as an adjunct to scaling and root planning (S&RP) in the treatment of adult periodontitis. Eight clinical trials were chosen based upon a priori selection criteria, and two outcomes, "reduction in probing pocket depth" (PD) and "gain in clinical attachment level" (CAL), were analyzed. Results for each outcome were stratified by initial PD 1-3 mm, 4-6 mm, or > or = 7 mm and length of follow-up 4-6 wk, 9-13 wk, or 14-26 wk. S-MET in conjunction with S&RP was superior to S&RP alone in reducing PD where initial PD was 4-6 mm and follow-up was 9-13 wk (0.43 mm; 99% CI 0.12, 0.73). No significant advantage was observed for S-MET for reducing PD where initial PD was less than 4 mm or follow-up was longer than 13 wk. S-MET in conjunction with S&RP was superior to S&RP alone in reducing CAL where initial PD was 4-6 mm and follow-up was 4-6 wk (0.29; 99% CI 0.01, 0.58) and where follow-up was 9-13 wk (weighted mean difference 0.32; 99% CI 0.03, 0.61). Significant heterogeneity of effect was not seen for PD or Cal at any level of initial PD or length of follow-up. No significant dose-response relationship was observed. This meta-analysis was limited due to diversity of data presentation and the small number of trials in each stratum. These results suggest that S-MET in conjunction with S&RP may offer a benefit over S&RP alone in the treatment of adult periodontitis patients in managing pockets of 4 mm or greater, but the additional benefit was not evident if initial PD was less than 4 mm or follow-up was beyond 13 wk.

Subject recruitment, retention, and compliance in clinical trials in periodontics

Recruitment of subjects in randomized controlled trials is the process of screening and enrolling a predetermined number of subjects within a planned time. Differences between projected and actual recruitment rates are common and, when large, form a serious threat to the successful completion of the trial. Recruitment can be enhanced by 1) use of different, concurrent recruitment methods; 2) avoiding underestimations of the costs and time intensity of subject recruitment; and 3) regular monitoring of the efficiency of the recruitment effort. The recruitment process can be complicated by legal requirements of proper representation of sex and race characteristics or by stringent entry criteria. Complex designs (e.g., trials with a pre-randomization placebo run-in, split-mouth designs) have not yet shown to be cost-effective and may endanger recruitment success. Enhancing both subject retention and protocol compliance requires careful planning, attention to product design and staff training. The impact on trial findings is discussed.

Overview of clinical trials of periodontal diagnosis methods and devices

Changing views of the pathogenesis and progression of the periodontal diseases and new modalities for treatment have stimulated a plethora of physical, biochemical, microbiologic, and immunologic diagnostic procedures, tests, and devices. Clinical trials address needs for: 1) screening tests and risk assessment for disease susceptibility; 2) identification of active and progressive disease sites; 3) making therapeutic decisions; 4) monitoring therapy; 5) establishing a maintenance schedule; and 6) prognosis assessment. Needs and priorities of general, specialty, and public health practitioners differ. Validation of tests proceeds in a hierarchy of study designs from cross sectional and case control studies to retrospective and prospective longitudinal multi-center trials. For broad-scale application, randomized controlled trials (and eventual meta-analysis) will be required. Design issues are those common to all clinical trials in periodontics plus special considerations depending on type of test and its intended use. For diagnostic tests, recommended surrogate endpoints are attachment and alveolar bone levels-the traditional "gold standards." Validation of diagnostic tests is best accomplished by generation of 2 x 2 contingency tables to calculate sensitivity and specificity, positive and negative predictive values, relative and absolute risks, and odds rations. Each has a place-depending on the clinical situation and needs of the clinician.

The achievement and maintenance of inter-examiner consistency in the assessment of plaque and gingivitis during a multicentre study based in general dental practices

This study set out to demonstrate that it was possible to train general dental practitioners (gdps) to achieve and maintain high levels of inter-examiner consistency in the use of simple periodontal indices over a 12-month period. The gdps were trained by one trainer in the use of the plaque index (PII) and a modified version of the gingival index (mGI) which assessed gingival bleeding only. All the gdps underwent intensive training and employed a technique, when assessing inter-examiner consistency in the use of the PII, such that the 1st examiner did not disturb in situ plaque from 50% of the circumference of a tooth. The problem of variation due to repeat probing, when assessing inter-examiner consistency for mGI, was overcome by one examiner lightly probing gingival margins and both examiners scoring the results. The problems relating to the multicentre nature of the study included: distance between the centres, the need for strict adherence to the study protocol, consistency in the use of forms and instruments, in the application of periodontal indices, and of inclusion and exclusion criteria. Techniques for overcoming these problems included: the planning and application of a coherent study design, which employed simple indices, a detailed protocol, the recruitment of very well-motivated gdps of similar age and experience as examiners, the recruitment of an experienced trainer who trained the gdps thoroughly and monitored their performance throughout the study, and repeat visits to the practices involved to explain the nature of the study to all their staff members. Initially, the gdps achieved inter-examiner kappa scores of 0.78-0.85 (mean 0.81) for PII and of 0.73-0.94 (mean 0.87) for mGI when assessing 168 sites for each variable. During the following 12 months, individual kappa scores, assessed every 3 months at 42 sites, ranged from 0.51-0.90 for PII and from 0.73-1.00 for mGI. Mean kappa for PII scores achieved by the five gdps fell during the study from 0.81 to 0.76, whereas that for mGI rose from 0.87 to 0.92. It is concluded that it is possible to train gdps to achieve high levels of inter-examiner consistency in the use of PII and mGI and for these high levels to be maintained during a 12-month multicentre study.

Design principles and statistical considerations in periodontal clinical trials

Although clinical trials are a small subset of conducted biomedical research, they have become powerful investigational tools for the evaluation and approval of new treatments by clinician groups and regulatory agencies like the US Food and Drug Administration. To impact the delivery of care, trials in general must meet three criteria: clarity, comparability, and generalizability. Accordingly, trials can offer meaningful data if they have procedures which are well defined and subjects who represent a reasonably homogeneous population. The evaluation of periodontitis interventions presents several challenges due to the disease's heterogeneity and its irregular, episodic pattern; nevertheless, the intent of these novel interventions is to prevent, diagnose, inhibit, or reverse periodontal disease progression. Careful consideration of the trial's objectives should dictate clinical endpoints (primary and surrogate), comparison groups (placebo, standard therapy, test therapy), and equivalence versus superiority as the basis for conclusions. Several design elements such as control population specification, randomization, masking, sample size calculation, and standardization of procedures for patient care and assessment can decrease potential bias and variability. In both parallel and paired (split-mouth) design trials, multiplicities of endpoints, treatments, and subgroups require strategies which address the broader scope of chance findings without excessive loss of study power. Also, the longitudinal assessment of multiple periodontal sites within patients produces correlated data structures for which analytic methods need to account for the appropriate sampling unit. With these design and analytic elements, clinical trials can provide important evidence to investigators, patients, and governmental agencies for the introduction of novel interventions in periodontal practice.

Evaluating the merits of option-3 methods in relative attachment level measurement in a healthy population

Attachment loss is the principal clinical indicator for periodontal disease progression. However, the attachment measurement can be inaccurate due to outliers. A remedial scheme, the option-3 scheme, has been suggested in the literature. This scheme involves first measuring the relative attachment twice at any given site. A third measurement is required if there is a large disagreement between the first two probings. When the third measurement is taken, there are several possible ways to make the final assessment of the true attachment level. Among them are the average of the 3 measurements, the average of the closest 2, and the median of the 3. This report evaluates the merits of the option-3 scheme by comparing it with other schemes to reduce measurements variance and outliers. Since true attachment levels are unknown, we chose to check accuracy through measurement consistency between visits in healthy subjects using the fact that such subjects should have little real change in attachment levels. 12 healthy subjects participated in the study. They visited the clinic 4 times in 4 months. Two types of the Florida stent probe were used by 2 calibrated examiners. It was found that option-3 schemes were more accurate than a single probing or duplicate probings in estimating the relative attachment level. The 3 final assessment schemes performed almost equally well from a practical standpoint, but the median was the best among them in a statistical sense.

A study of the reliability of a no disease progression conclusion

Concluding that the clinical attachment level at a periodontal site is stable, while in reality it is progressing at a clinically relevant rate, is an example of a false-negative conclusion. No guidelines are currently available to evaluate the likelihood for false-negative conclusions in periodontal clinical trials that monitor disease progression by means of clinical attachment levels. The goal of this study was to estimate the amount of linear disease progression in clinical attachment levels that cannot reliably be detected, when it is truly present. This rate is called the critical linear rate; rates equal to or below this critical linear rate cannot reliably be detected. An equation for determining the critical linear rates for various clinical situations is presented and may provide a rule-of-thumb guideline for the interpretation of negative conclusions. If the critical linear rate for a study is larger than what is considered a clinically relevant disease progression rate, negative conclusions should be interpreted with caution; clinically relevant disease progression might be present, but the diagnostic tools used were too insensitive to detect it. False-negative conclusions may be important in diagnostic trials where low sensitivity can translate into lack of clinical utility.

Comparison of 3 periodontal local antibiotic therapies in persistent periodontal pockets

The aim of this study was to evaluate the efficacy of 3 commercially available periodontal systems for local delivery of antibiotics as adjuncts to scaling and root planing in treatment of sites with persistent periodontal lesions following a course of scaling and root planing. Fifty-four patients with 4 pockets > or = 5 mm and bleeding on probing and/or suppuration were randomized in 4 treatment groups including: scaling and root planing plus application of 25% tetracycline fiber (S + Tet) (13 patients), scaling and root planing plus application of 2% minocycline gel (S + Min) (14 patients), scaling and root planing plus application of 25% metronidazole gel (S + Met) (14 patients), and scaling and root planing alone (S) (13 patients). Clinical measurements were taken at baseline and 6 weeks after the end of treatment periods. All treatments were applied using the distributors' recommended protocols and resulted in significant improvement in probing depth, attachment level, bleeding on probing and the modified gingival index (MGI) scores. The improvements in clinical parameters were greater in all three adjunctive treatment groups than scaling and root planing alone. The mean probing depth reductions were: S + Tet = 1.35 mm, S + Met = 0.95 mm, S + Min = 0.87 mm and S = 0.60 mm. The probing depth reduction was significantly greater in the scaling plus tetracycline fiber group than the scaling and root planing alone group (P = 0.002). The difference between groups in improvement of attachment level or bleeding on probing was not significant Scaling plus tetracycline fiber treatment resulted in the greatest reduction in the MGI scores which was significantly greater than all other groups. While the frequency of sites with suppuration was markedly reduced following all treatments, it reached zero in the scaling plus tetracycline fiber group. No serious adverse effects were observed or reported for any treatment. While all three locally applied antimicrobial systems seem to offer some benefit over scaling and root planing alone, a treatment regimen of scaling and root planing plus tetracycline fiber replacement gave the greatest advantage in the treatment of persistent periodontal lesions at least during the 6-week period following treatment.

The periodontal health of homosexual men with HIV infection: a controlled study

OBJECTIVE

Identify types, prevalence and severity of periodontal changes associated with HIV infection.

DESIGN

Cross-sectional controlled blinded study.

SETTING

Open access genito-urinary medicine clinic.

PARTICIPANTS

Convenience sample of 794 homosexual men aged 18-65.

OUTCOME MEASURES

Prevalence, extent and severity of probing attachment loss (PAL), pocketing, gingival ulceration, gingivitis, bleeding on probing (BOP), gingival red bands and diffuse and punctate erythema of the attached gingiva (selected a priori).

RESULTS

Prevalences in men with (n = 312) and without HIV (n = 260) were: PAL (> or = 1 site > or = 4mm), 59.6% and 28.5% respectively (P < 0.001, chi 2); pocketing (> or = 1 site > or = 4mm) 51.0% and 31.9% (P < 0.001); BOP, 96.5% and 92.3% (P = 0.038); gingival ulceration, 3.2% and 1.0% (P = 0.031), red banding, 12.2% and 10.0% (P = 0.410); diffuse erythema, 12.5% and 3.1% (P < 0.001) and punctate erythema, 9.6% and 1.1% (P < 0.001). Decreased CD4 lymphocyte counts predicted the presence, extent and severity of PAL (P = 0.023, 0.027 and 0.060) but not pocketing. Oral candidiasis predicted the extent and severity of gingivitis and the presence of diffuse and punctate erythema. (P = 0.037, 0.011, 0.002 and < 0.001).

CONCLUSIONS

Destruction of periodontal attachment is associated with progression of HIV disease whereas pocketing is associated with HIV infection but not disease progression. Gingival ulceration is associated with HIV but gingivitis and erythema of the attached gingiva are most strongly associated with oral candidiasis. Gingival red bands were not associated with HIV infection.

Examiner agreement on periodontal indices during dental surveys of elders

Indices used to evaluate periodontal health have been widely accepted in epidemiological studies, yet their reliability cannot be guaranteed. The aim of this study was to evaluate the reliability of periodontal indices applied on elders. 19 elderly subjects, 73-years-old on average, were examined at a 1st appointment by 2 independent examiners. They were re-examined 2 weeks later during a 2nd session. The examinations were performed in a dental chair with good illumination. Periodontal health was evaluated using the community periodontal index of treatment need, and tooth mobility was evaluated using 2 different indices. Inter and intra-examiner agreements were evaluated using kappa statistics. Taken as an overall measurement, the CPITN was a reliable assessment of periodontal treatment need in elders. Disagreement occurred mainly on the evaluation of bleeding and shallow pockets. The detection of fairly mobile teeth was reliable; however, the performance of the more sensitive scale was deceptive. it seems that, in the case of tooth mobility, a choice has to be made between sensitivity or reproducibility. It can be concluded that examiners should be trained carefully since the reliability of the CPITN and tooth mobility evaluation were good but close to a critical level for which an agreement is classified as poor.

Examiner agreement on caries detection and plaque accumulation during dental surveys of elders

Indices used to evaluate plaque accumulation and coronal caries have been widely accepted in epidemiological studies, yet their reliability cannot be guaranteed. The aim of this study was to evaluate the reliability of clinical criteria used in coronal and root caries diagnosis and oral hygiene evaluation as applied in elders. Nineteen elderly subjects, 73 years old on average, were examined at a first appointment by two independent examiners. They were re-examined two weeks later. Plaque accumulation was evaluated using the Plaque Index (PI) and coronal and root caries were detected according to the WHO criteria and Fejerskov et al. (1991), respectively. Recurrent caries was recorded as recommended by WHO and by probing at the interface tooth-restoration. Inter- and intra-examiner agreement was evaluated using kappa statistics. The PI score showed good reliability except for examiner b, for whom a simplification of the 4-point scale in 3-point scale improved significantly the reliability. The prevalence of coronal caries was very low and intra- and inter-examiner agreement was poor. Most of the root caries lesions were covered by plaque and the kappa values indicated only poor agreement. Recurrent caries were found with good agreement using WHO criteria but the detection with the probe was not reliable. In conclusion, it seems that examiners should be trained carefully to maximise their reliability and that plaque should be removed to obtain reliable diagnoses of caries. Retraining and calibration may be necessary for surveys continuing over a long period.

Caries lesions and dental restorations as predisposing factors in the progression of periodontal diseases in adolescents. A 3-year longitudinal study

The present study used a novel approach to assess the relationship between untreated caries lesions and defective and non-defective dental restorations and the incidence of gingival inflammation and the progression of chronic inflammatory periodontal diseases at the approximal surfaces of posterior teeth and at the adjacent surface of the neighboring tooth in adolescents over a period of 3 years. Two hundred-twenty-seven (227) 13-year-old schoolchildren were examined clinically and radiographically at baseline and annually at three subsequent occasions. At each site the alveolar bone height and presence of gingival bleeding were assessed. Incipient caries lesions, manifest caries, and defective and non-defective restorations were identified at the same site and also at the adjacent approximal tooth surface at all examinations, both clinically and radiographically. The data were analyzed by the multi-level logistic regression and variance components analyses. On average, 32, 8.5, 7, and 10% of the sites, respectively, were diagnosed as having incipient caries, manifest caries, and defective and non-defective restorations. There was a significant association between the presence of untreated manifest caries lesions, non-defective and defective dental restorations, and the progression of periodontal support loss. Also there was an association between presence of defective restorations and manifest caries and the incidence of gingival inflammation. Consistently, factors detected at the involved site and at the adjacent site had significant effects. The present study indicates that untreated cavities and dental restorations are predisposing factors with a significant negative effect on periodontal health in adolescents.(ABSTRACT TRUNCATED AT 250 WORDS)

Site progression of loss of attachment over 5 years in 14- to 19-year-old adolescents

The aims of this study were (1) to monitor the progression and patterns of progression of loss of attachment > or = 1 mm on a site basis over a 5-year period in adolescents, and (2) to relate the presence of oral deposits and inflammation to the subsequent development and progression of loss of attachment on a site basis. 167 subjects were examined at ages 14, 16 and 19 years. Loss of attachment > or = 1 mm, plaque, subgingival calculus, gingival bleeding and gingival colour change were assessed on the mesio-buccal sites of the 1st molars, 1st premolars and central incisors. Each site was treated separately in the analysis to avoid the problem of within-subject site dependence. Sites were classed as progressing, non-progressing or fluctuating according to the probing attachment level measurements at each of the 3 examinations. During the 5 years of this study, a total of 542 sites in 128 subjects progressed; 1136 sites in 162 subjects did not progress; 43 sites in 30 subjects had fluctuating attachment level measurements. Sites which subsequently progressed had significantly more plaque, subgingival calculus and gingival inflammation than non-progressing sites at the baseline examination and throughout the study (p < 0.001). Between 55-57% of the maxillary 1st molars and 46-49% of the mandibular incisors progressed. In contrast, there was no progression of loss of attachment on over 80% of the maxillary central incisors and mandibular 1st premolars.

Outcome measures in split mouth caries trials and their statistical evaluation

The split mouth study design in trials of fissure sealants and restorative materials neatly controls for confounding by many of the variables associated with poor retention of sealants and occurrence of dental caries. Traditionally, the outcome measures used in split mouth trials have been material retention, (per cent) effectiveness and net gain. A survey of the literature revealed that a large proportion of split mouth studies report no statistical evaluation of outcome measures. In those studies in which statistical evaluation had been conducted, McNemar's X2 was the test most frequently used. This statistic is appropriate for comparing differences between "success" and "failure" tooth pairs (or "positives" and "negatives" in split mouth terminology) but it cannot evaluate directly effectiveness and net gain. The distributions of effectiveness and net gain are different and it would be desirable to estimate confidence intervals for them. In this paper, we consider these statistics, suggest methods by which confidence intervals may be calculated, and provide examples of the calculations. We demonstrate the close relationship between effectiveness (as used in split mouth trials) and relative effect and relative risk (as used in general epidemiological analysis) and recommend that relative risk should be the preferred outcome measure for split mouth trials. Whatever outcome measure is chosen in split mouth trials should always be subjected to statistical evaluation, preferably by the calculation of confidence intervals.

Utilization of dental services as a risk factor for periodontitis

The relation between utilization of dental services from community dentists and the extent and severity of alveolar bone loss is reported for a panel of men followed for over 6 years. Oral health data were collected by the Department of Veterans Affairs, Dental Longitudinal Study, which began in 1969 and still continues. Participants have received regular oral examinations approximately every 3 years. A variety of oral health conditions were assessed, including plaque, calculus, gingival inflammation, probing depth, tooth mobility, clinical attachment level, and alveolar bone loss. Utilization data were abstracted from the dental records of dental offices that participants attended from 1979 through 1988. Multivariate modeling as well as comparisons of high utilizers and non-utilizers indicate that utilization of routine diagnostic and preventive services was not predictive of the extent and severity of periodontitis.

Variance component modeling of attachment level measurements

The purpose of this study was to investigate the influence of within subject and within tooth variability of attachment-level measurements on hypothesis testing. Full-mouth attachment-level measurements were obtained at 4 sites per tooth in early onset periodontitis subjects (both localized N = 89 and generalized N = 139) and adult periodontitis subjects (N = 309). Variance component models utilizing iterative generalized least squares were employed to estimate the % of variance distributed at the level of the site, tooth and subject in the 3 subject populations. The data indicate that a significant % of the variance is distributed within the tooth and the subject. Ignoring the variance attributable to teeth or subjects can result in inappropriately low type I error rates for hypothesis testing. Thus, both the subjects and the tooth must be considered in the modeling of attachment level measurements. Also in studies in which a limited number of samples are taken, data analysis would be simplified if these samples were taken from different teeth.

The diagnosis of periodontal conditions associated with HIV infection

Objective, reliable, and valid diagnostic criteria are required for studies of HIV-associated periodontal conditions. A set of diagnostic criteria were devised based on a literature review and the clinical experience of the authors. Validity was assessed by comparison with clinical photographs and the criteria were evaluated and refined for ease of use and objectivity. To assess the reliability of the criteria, 9 experienced examiners were shown 20 clinical photographs accompanied by brief vignettes of clinical information. Each examiner was asked to identify signs evident in a particular area of the photograph and to record a diagnosis. Five examiners were then trained and calibrated in the use of the criteria. Finally, all 9 examiners were shown the original 20 photographs and asked to identify signs and record diagnoses. The examiners showed only fair reliability in the recognition of clinical signs, made diagnoses intuitively, and had only fair agreement on the diagnosis of periodontal diseases. The inter-examiner reliability of examiners trained and calibrated in the use of the criteria increased and was greater than among untrained examiners. Rigid diagnostic criteria are essential in epidemiologic studies. Inter-examiner reliability will be increased if examiners are trained in their use and calibrated in the recognition of clinical signs. Diagnostic criteria should be modified as understanding of the diseases they classify increases. The proposed criteria will enhance the value of studies of HIV-associated periodontal changes and will contribute to that understanding.