Design issues specific to studies of periodontitis

Endpoints of active periodontal therapy

Aim

Position paper on endpoints of active periodontal therapy for designing treatment guidelines. The question was as follows: How are, for an individual patient, commonly applied periodontal probing measures—recorded after active periodontal therapy—related to (a) stability of clinical attachment level, (b) tooth survival, (c) need for re‐treatment or (d) oral health‐related quality of life.

Methods

A literature search was conducted in Ovid MEDLINE(R) and Epub Ahead of Print, In‐Process & Other Non‐Indexed Citations and Daily <1946 to 07 June 2019>.

Results

A total of 94 papers were retrieved. From the literature search, it was found that periodontitis patients with a low proportion of deep residual pockets after active periodontal therapy are more likely to have stability of clinical attachment level over a follow‐up time of ≥1 year. Other supporting literature confirms this finding and additionally reports, at the patient level, that probing pocket depths ≥6 mm and bleeding on probing scores ≥30% are risks for tooth loss. There is lack of evidence that periodontal probing measures after completion of active periodontal treatment are tangible to the patient.

Conclusions

Based on literature and biological plausibility, it is reasonable to state that periodontitis patients with a low proportion of residual periodontal pockets and little inflammation are more likely to have stability of clinical attachment levels and less tooth loss over time. Guidelines for periodontal therapy should take into consideration (a) long‐term tangible patient outcomes, (b) that shallow pockets (≤4 mm) without bleeding on probing in patients with <30% bleeding sites are the best guarantee for the patient for stability of his/her periodontal attachment, (c) patient heterogeneity and patient changes in immune response over time, and (d) that treatment strategies include lifestyle changes of the patient. Long‐term large population‐based and practice‐based studies on the efficacy of periodontal therapies including both clinical and patient‐reported outcomes (PROs) need to be initiated, which include the understanding that periodontitis is a complex disease with variation of inflammatory responses due to environment, (epi)genetics, lifestyle and ageing. Involving people living with periodontitis as co‐researchers in the design of these studies would also help to improve their relevance.

Periodontal maintenance following active specialist treatment: Should patients stay put or return to primary dental care for continuing care? A comparison of outcomes based on the literature

OBJECTIVES

To review the evidence for the efficacy of periodontal maintenance (PM) carried out in primary dental care (PDC) compared to the specialist setting for patients previously treated in a specialist setting for chronic (ChP) or aggressive (AgP) periodontitis.

METHODS

A focused PICO question and search protocol were developed. Online databases including MEDLINE, EMBASE, WEB OF SCIENCE™ and COCHRANE LIBRARY were searched along with specialist journals in the subject area of periodontal research. Selection criteria included studies that investigated delivery of PM in both specialist and PDC settings for patients with ChP or AgP over a minimum 12 months. We looked for studies that reported changes in clinical attachment levels (CAL), tooth loss, pocket probing depths (PPDs) and bleeding on probing (BoP) as outcome measures.

RESULTS

Eight cohort studies were chosen for inclusion. There was considerable heterogeneity found between the eight studies, which did not allow for quantitative (meta) analysis and statistical testing of differences between groups. Clinical attachment levels remained relatively stable in patients who received specialist PM with mean changes of -0.42 mm to +0.2 mm, while for those enrolled in PDC-based PM for periods >12 months, mean CAL losses were between -0.13 mm and -2.80 mm. PPD reduction for those subjects receiving specialist PM was between 0.05 and 1.8 mm for five studies but two cohorts experienced increases of 0.32 and 0.80 mm, respectively. Increases of up to 2.90 mm (range: -0.1 to +2.90) and a higher proportion of deeper pockets were noted among PDC PM cohorts. Higher rates of BoP among those in receipt of PDC PM were reported in half of all studies. There were insufficient long-term data to make any firm conclusions about the effect of the delivery of PM on tooth loss.

CONCLUSION

Within the limitations of the data available, it appears that specialist PM is effective in sustaining periodontal stability following active specialist intervention. There is limited evidence that PDC provides the same level of care; however, the limited comparative data available suggest that outcomes could be slightly worse in PDC.

Vascular endothelial growth factor levels in gingival crevicular fluid before and after periodontal therapy

INTRODUCTION

Of the various cytokines and growth factors regulating angiogenesis, the most potent agent acting on vascular endothelium is vascular endothelial growth factor(VEGF). The present study aims to access VEGF concentration in periodontal diseases and the effect of periodontal therapy on its concentration in gingival crevicular fluid (GCF).

MATERIALS AND METHODS

Ninety five subjects (47 females and 48 males) 25- 47 y of age were divided into healthy (group-1), gingivitis (group-2), and periodontitis (group-3). GCF samples were collected using micro-capillary pipettes & were transferred immediately to plastic vials and stored at -70˚C until the time of the assay. The concentration of VEGF was determined using commercially available ELISA kit.

RESULTS

The mean VEGF concentration was highest in periodontitis patients (Group 3) (88.08±8.04pg/ml), with lowest in healthy patients (Group 1). VEGF levels reduced significantly after therapy in Groups 2 and 3.

CONCLUSION

VEGF levels in GCF had a significant correlation with both periodontal disease progression and healing after therapy.

Control of periodontal infections: a randomized controlled trial I. The primary outcome attachment gain and pocket depth reduction at treated sites

OBJECTIVE

To compare the treatment outcome of scaling and root planing (SRP) in combination with systemic antibiotics, local antibiotic therapy and/or periodontal surgery.

MATERIAL AND METHODS

One hundred and eighty-seven patients were assigned to eight groups treated by SRP plus none, one, two or three adjunctive treatments and monitored for 24 months in a randomized controlled clinical trial using a 2 × 2 × 2 factorial design. Systemic amoxicillin + metronidazole (SMA), local tetracycline delivery (LTC) and periodontal surgery (SURG) were evaluated as adjuncts. Changes in clinical attachment level (CAL) and probing pocket depth (PPD) were statistically evaluated by ancova of main effects.

RESULTS

Effects of adjunctive therapy to SRP were minimal at 3 months. Between 3 and 6 months PPD reduction occurred particularly in patients receiving periodontal surgery. After 6 months, both CAL gain and PPD reduction reached a plateau that was maintained at 24 months in all groups. The 24-month CAL gain was improved by SMA (0.50 mm) while PPD was reduced by SMA (0.51 mm) and SURG (0.36 mm). Smoking reduced CAL gain and PPD reduction.

CONCLUSION

Patients receiving adjunctive therapies generally exhibited improved CAL gain and/or PPD reduction when compared with the outcome of SRP alone. Only additive, not synergistic effects of the various adjunctive therapies were observed.

Change in periodontitis during pregnancy and the risk of pre-term birth and low birthweight

AIM

Determine whether periodontitis progression during pregnancy is associated with adverse birth outcomes.

METHODS

We used clinical data and birth outcomes from the Obstetrics and Periodontal Therapy Study, in which randomly selected women received periodontal treatment before 21 weeks of gestation (N=413) or after delivery (410). Birth outcomes were available for 812 women and follow-up periodontal data for 722, including 75 whose pregnancies ended <37 weeks. Periodontitis progression was defined as >or=3 mm loss of clinical attachment. Birth outcomes were compared between non-progressing and progressing groups using the log rank and t tests, separately in all women and in untreated controls.

RESULTS

The distribution of gestational age at the end of pregnancy (p>0.1) and mean birthweight (3295 versus 3184 g, p=0.11) did not differ significantly between women with and without disease progression. Gestational age and birthweight were not associated with change from baseline in percentage of tooth sites with bleeding on probing or between those who did versus did not progress according to a published definition of disease progression (p>0.05).

CONCLUSIONS

In these women with periodontitis and within this study's limitations, disease progression was not associated with an increased risk for delivering a pre-term or a low birthweight infant.

Case definitions for use in population-based surveillance of periodontitis

Many definitions of periodontitis have been used in the literature for population-based studies, but there is no accepted standard. In early epidemiologic studies, the two major periodontal diseases, gingivitis and periodontitis, were combined and considered to be a continuum. National United States surveys were conducted in 1960 to 1962, 1971 to 1974, 1981, 1985 to 1986, 1988 to 1994, and 1999 to 2000. The case definitions and protocols used in the six national surveys reflect a continuing evolution and improvement over time. Generally, the clinical diagnosis of periodontitis is based on measures of probing depth (PD), clinical attachment level (CAL), the radiographic pattern and extent of alveolar bone loss, gingival inflammation measured as bleeding on probing, or a combination of these measures. Several other patient characteristics are considered, and several factors, such as age, can affect measurements of PD and CAL. Accuracy and reproducibility of measurements of PD and CAL are important because case definitions for periodontitis are based largely on either or both measurements, and relatively small changes in these values can result in large changes in disease prevalence. The classification currently accepted by the American Academy of Periodontology (AAP) was devised by the 1999 International Workshop for a Classification of Periodontal Diseases and Conditions. However, in 2003 the Centers for Disease Control and Prevention and the AAP appointed a working group to develop further standardized clinical case definitions for population-based studies of periodontitis. This classification defines severe periodontitis and moderate periodontitis in terms of PD and CAL to enhance case definitions and further demonstrates the importance of thresholds of PD and CAL and the number of affected sites when determining prevalence.

Quality of trials in a systematic review of powered toothbrushes: suggestions for future clinical trials

BACKGROUND

This study aimed to assess the quality of reports of randomized controlled trials (RCTs) comparing manual and powered toothbrushes and provide advice on how future trials might be improved.

METHODS

Studies were identified in the Cochrane systematic review of RCTs comparing powered versus manual toothbrushes. Reports were assessed against predefined criteria on the design of the studies to determine the effectiveness of the brushes in everyday home use and on their methodological quality.

RESULTS

Only 42 of 297 identified studies satisfied the inclusion criteria and were eligible for inclusion in the review. Many studies were excluded for more than one reason. Fifteen studies employed split-mouth designs that may have changed toothbrushing behavior. Of 42 included RCTs, the generation of randomization sequence was adequate in 15 trials and concealment of allocation was adequate in 16 trials. Intention-to-treat analysis was reported in only five studies. Plaque data were reported using 10 different indices and gingivitis with nine indices. Only 12 trials lasted 3 months or longer, and there were no data on the benefits of powered toothbrushes for periodontal attachment.

CONCLUSIONS

Some designs created an artificial research environment that may have undermined the findings. Authors of toothbrush trials should consider the Consolidated Standards of Reporting Trials statement. Greater standardization of the indices used is required. Trials of longer duration would enhance the evaluation of powered toothbrushes. Data on thresholds for clinically significant differences in plaque and gingivitis levels would help to determine whether oral hygiene aids provide important health benefits.

Cross-sectional evaluation of clinical parameters to select high prevalence populations for periodontal disease: the site comparative severity methodology

Epidemiological studies have shown strong evidence that periodontal disease does not affect all subjects in the same manner. There are subjects and sites with higher risk for disease progression. This study tested parameters to select "a priori" sites and subjects potentially at risk. The data from periodontal clinical examinations of 2273 subjects was used. The clinical loss of attachment was measured in 6 sites per tooth. Using computer software, the patients were distributed into 14 age groups, with intervals of 5 years, from 11 years to greater than 75 years of age. The measure of each site was compared with the average and the median values of the subject age group, with the results indicating site comparative severity (SCS). Three global parameters were calculated: parameter 1 (P1) - percentage of sites with clinical attachment loss > 4 mm; parameter 2 (P2) - percentage of sites with clinical attachment loss > 7 mm; parameter 3 (P3) - percentage of sites with clinical attachment loss surpassing the median value for the age group by 100% or more. There were 1466 (65%) females and 807 (35%) males. Most subjects had P1, P2 and P3 values less than 30%. Parameter 3 allowed a division of the sample similar to that of Parameters 1 and 2, with the advantage of analyzing the subject in relation to his/her age group. It was suggested that the methodology of SCS is useful for selecting a population with a high disease prevalence, and that cut-off lines between 10% and 20% would be appropriate for using Parameter 3.

Clinical versus statistical significance as they relate to the efficacy of periodontal therapy

BACKGROUND

The author discusses the shortcomings of using statistical significance testing as a method to infer that results of periodontal clinical trials are clinically meaningful. To compensate for these deficiencies, he also identifies criteria and periodontal parameters that can be used to reflect clinically significant outcomes.

TYPES OF STUDIES REVIEWED

The author searched the medical and dental literature to identify commentaries that addressed the problems associated with interpreting statistical significance testing, or hypothesis testing, and defining clinical significance.

RESULTS

The limitations of statistical significance testing related to identifying clinically significant changes include failure to indicate if the detected differences between variables in test and control groups are large or important. After reviewing various definitions of the term "clinical significance," the author reviews and proposes a comprehensive working definition of it. Regarding the efficacy of periodontal therapy, he delineates the advantages and limitations of specific criteria (such as absolute values, cut points) that can be used to define clinical significance.

CLINICAL IMPLICATIONS

The author suggests that clinically significant results should be defined before initiating a study and statistical significance testing should be used to validate that findings did not occur by chance. This would help place the importance of clinical data into perspective, and it would enhance clinicians' ability to select the most appropriate therapies for particular sites in periodontal patients.

Repeated metronidazole and amoxicillin treatment of periodontitis. A follow-up study

BACKGROUND

The prevailing concept is that little or no clear benefit is derived from antibiotic therapy in chronic periodontitis. Studies to determine the effect of metronidazole plus amoxicillin (M+A) on adult periodontitis are questionable because standard design for clinical trials was usually not used. In addition, there is no information about the effect of M+A as the sole therapy for periodontitis.

METHODS

A randomized, triple-blind, controlled clinical trial was used to determine the effect of systemic administration of M+A, as the sole therapy, in progressive adult periodontitis. Forty-six subjects with moderate to advanced adult periodontitis who showed > or =2 mm attachment loss in at least 2 sites in the previous 2 months were entered in the study. Subjects were randomly distributed to a group who received 21 tablets of metronidazole 250 mg plus amoxicillin 500 mg, or to a group receiving a placebo (1 tablet every 8 hours for 1 week). Patients were examined every 2 months for 12 months. The M+A or placebo regimen was repeated at 4 and 8 months. No effort was made to change the oral habits of patients and they received no additional therapy. Differences between groups were assessed using the Mann-Whitney U test. The differences at every 2-month interval within each group were assessed using the ANOVA test.

RESULTS

Seven subjects abandoned the study; at 12 months the M+A group had 20 subjects and the placebo group 19. There were no significant differences in the clinical parameters at baseline between the 2 groups. After 2 months and thereafter, the M+A group showed significant clinical improvement while the placebo group showed a progressive deterioration of periodontal status. At 12 months compared to baseline, subjects of the M+A group showed: 1) a significant overall mean attachment gain of 0.43 mm (P = 0.005); 2) a significant decrease of active sites (P< or =0.03); 3) a significant increase of sites gaining attachment level (P< or =0.01); 4) a significant reduction of pocket depth (P< or =0.00006); and 5) a significant decrease in percentage of bleeding on probing sites (BOP) (P< or =0.0005). Significant differences between both groups at all 2-month evaluations were found in overall mean attachment level (P < or =0.000004), in percent of active sites (P< or =0.03), and in percent of BOP sites (P< or =0.02). Sites exhibiting > or =2 mm of attachment loss in 2 successive or alternate evaluations, and periodontal abscess were noticed only in the placebo group.

CONCLUSIONS

A 1-week course of systemic M+A every 4 months, as the only therapy, arrests the progression of adult periodontitis and significantly improves the clinical parameters of the disease.

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.

Design and implementation of clinical trials of antimicrobial drugs and devices used in periodontal disease treatment

The design and implementation of clinical trials (CTs) carried out to evaluate antimicrobial and anti-infective drugs and devices are one of the most difficult challenges in contemporary periodontal research and product development. The overwhelming amount of evidence which has established a microbial etiology for periodontitis is the basis for developing and testing antimicrobial treatments. Well-designed antimicrobial CTs start with a carefully crafted hypothesis and a protocol which explicitly integrates the requirements of the patient, the clinician, the sponsor, and regulatory authorities. Surrogate variables for effectiveness must be clinically relevant, scientifically sound, and statistically valid. Currently, clinical attachment level measurements and alveolar bone assessments are accepted as proof of effectiveness. Indication and claim support of the antimicrobial product guide the design and implementation of the CT. Adverse microbiologic consequences, such as lack of antimicrobial susceptibility, wrong spectrum, incorrect dosage, non-compliance, and drug interference, must be monitored. Successful CTs balance a large group of variables used to screen, randomize, and assign subjects to experimental and control groups to ensure that prognostic and risk factors are properly accounted for.

Overview of periodontal clinical trials utilizing anti-infective or host modulating agents

Issues in periodontal trials designed to evaluate anti-infective or host modulating agents for the prevention and treatment of periodontal diseases are reviewed in this paper. Clinical trial designs, prevention versus treatment, disease activity, utility of new measurement technologies, ethical and safety issues, selection of outcome variables, and clinical significance are discussed. In general, randomized parallel arm, double-blinded, controlled clinical trials are most appropriate for testing anti-infective and host modulating agents. New measurement technologies may offer increased measurement resolution and automated data capture; but, depending on their specific application and level of examiner reproducibility, these technologies may or may not result in lowered thresholds for declaring change. Mechanical therapy for common plaque-associated gingivitis and adult periodontitis is effective, has low risk, and is widely accepted as a minimum standard of care. New agents for treatment of these diseases must carry minimal risk and have equal or greater effectiveness than this standard of care. Outcome variables for gingivitis trials should include a visual index of gingival inflammation and a separate or component index of gingival bleeding. Prevention studies of periodontitis require a longer duration than treatment studies. Maintenance of mean clinical attachment level should be a primary outcome measure for all prevention studies of adult periodontitis. Maintenance of alveolar bone support is an essential additional outcome for agents specifically acting on bone. The design and conduct of clinical trials for anti-infective and host modulating agents depend on the specific hypothesis to be tested and the ethical demands of providing safe and effective care for all study volunteers.

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.

A multicenter clinical trial of PerioGard in distinguishing between diseased and healthy periodontal sites. (I). Study design, methodology and therapeutic outcome

We designed and performed a multicenter clinical trial to determine the relationship between measurements of the level of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid (GCF) to other measures used to detect periodontal disease and monitor outcome of treatment, including pocket depth and gingival inflammation. 32 periodontitis patients were enrolled at the University of Washington, Seattle, 30 at the University of Florida, Gainesville, and 34 at the University of Illinois, Chicago. 10 periodontally normal control subjects were enrolled at each location. 8 diseased and 4 healthy sites were designated for study in each patient and 8 healthy sites designated in each control subject. Measures of disease included pocket depth, severity of gingival inflammation, and GCF volume. AST levels were measured using the PerioGard test kit. Clinical measurements were made and GCF samples harvested and tested 2x before and 2x after therapy consisting of scaling and root planing under local anesthetic. Specific design and other issues are discussed, including selection of patients and control subjects, sample size, selection of experimental test sites, methods for assessment of diseased and therapeutic improvement, harvesting of GCF and selection of appropriate biostatistical methods for data analysis. Demographics of the patient populations at the 3 locations are reported. As expected, therapy induced only negligible changes in the measures of disease at healthy sites in control subjects, and relatively minor improvement in healthy sites in patients. In contrast, statistically significant improvement relative to pretreatment baseline status in all 3 measures of disease was observed for diseased sites at all 3 study locations with all p-values less than 0.0002. The magnitude of improvement was comparable to that reported previously by others. The % of PerioGard-positive sites decreased significantly between the screening baseline and both post-treatment visits for patients at all 3 locations, with p values of 0.0001 to <0.0008.

Proposed guidelines for American Dental Association acceptance of products for professional, non-surgical treatment of adult periodontitis. Task Force on Design and Analysis in Dental and Oral Research

Guidelines are suggested for determining efficacy of products to supplement scaling and root planing in professional, non-surgical treatment of adult periodontitis. They result from an extended process including a conference on clinical trials in gingivitis and periodontitis, a subsequent workshop, and commentary from industrial, academic, professional and governmental members of the periodontal research community on two drafts. Recommendations are made in the broad areas of basic study design, subject and periodontal site selection, clinical management, choice of outcome variables, statistical summarization and analysis, and criteria for acceptance. Prominent dissenting views, with justifications for positions taken here, are also provided. Groundwork is laid for possible future guidelines addressing products for primary prevention or over-the-counter uses, or for determining superiority or equivalence of competing products. However, issues are identified which require further exploration before responsible and widely acceptable recommendations can be made in these areas. The guidelines suggested here are meant to form the basis of an evolving document rather than a static standard. It is suggested that they be reviewed frequently in the light of improvement in the technology available for periodontal research, and the emergence of products representing new approaches to periodontal therapy.