Predicting dental school performance based on prior dental experience and exposure.

PURPOSE: The purpose of this study was to evaluate whether the variables of students with prior dental assisting experience and students with a parent who is a dentist can be used as predictors of students' pre-clinical and clinical course performance in dental school. MATERIALS AND METHODS: The study population consisted of a cohort of 159 students in the Harvard School of Dental Medicine (HSDM) DMD graduation classes of 2001-2005. Data were collected via self-report using students' applications for admission to the HSDM DMD programme on which students provided information regarding whether they had prior dental assisting experience, including the type and duration of the experience and whether one or both of their parents were dentists. Data on the students' undergraduate science grade point average, Dental Admission Test academic average, Perceptual Ability Test (PAT) score, NBDE Part I and HSDM course grades (three pre-clinical and five clinical assessment categories) were collected from the Office of the Registrar. The pre-clinical categories included the first Oral Comprehensive Exam and the first two classes of the pre-clinical portion of the dental school, Treatment of Active Disease (TxAD) and Restorative Treatment (RTx). The clinical categories included the second Oral Comprehensive Exam and the cumulative grades received for the clinical procedures performed during the third and fourth years in the fields of Endodontics, Operative Dentistry, Periodontics and Prosthodontics. Descriptive and bivariate statistical analyses were performed and included in a multiple logistic regression model. RESULTS: The results revealed that for the variable of prior dental-assisting experience, no statistically significant differences were noted in the pre-clinical and clinical assessment categories. However, students who had any amount of assisting experience were 2.2 times more likely to earn a grade of honours in TxAD compared with students who did not have assisting experience (P = 0.05). Students with a parent who was a dentist performed better only in Operative Dentistry clinical assessment compared with students without a dentist parent (P < 0.05). CONCLUSIONS: Information on prior dental-assisting experience and having a parent who is a dentist have minimal merits for use as predictive agents based on these findings. Dental school admissions committees should continue to review a full spectrum of variables and ensure an applicant's true interest and motivation to pursue a career in dentistry.

Differences in clinical grading associated with instructor status.

PURPOSE: The purpose of this study was to determine whether the clinical evaluation of pre-doctoral students is associated with instructor status. The hypothesis was that there would be no association between instructor status and clinical evaluation grades. MATERIALS AND METHODS: Retrospective analysis of pre-doctoral clinical evaluations for class II amalgams, class III composites, and periodontal scaling and root planing was performed. The grade averages were based on a rank scale. Descriptive statistics were computed to summarise the predictor and outcome variables. Bivariate statistics were computed to evaluate any associations between the predictors and outcomes. Multiple linear regression models were computed to evaluate the simultaneous effects of multiple predictors on clinical evaluations. RESULTS: The study sample consisted of 238 class II amalgams, 246 class III composites, and 675 scaling and root planings which occurred between August 2003 and June 2005. The procedure averages for these procedures were 1.8 +/- 0.67, 1.8 +/- 0.66 and 2.1 +/- 0.56 respectively. The management averages were 2.0 +/- 0.63, 1.5 +/- 0.58 and 1.4 +/- 0.54 respectively. In bivariate analyses, faculty status was associated with treatment averages for all three procedures. CONCLUSIONS: Faculty status was associated with treatment score for all three procedures evaluated. Full-time faculty gave the best grades for restorative procedures. For periodontal procedures, part-time faculty gave the best grades. More studies are warranted to elucidate the nature behind these differences.

Do tutor expertise and experience influence student performance in a problem-based curriculum?

The purpose of this study was to evaluate the association between student performance and tutor expertise and experience in the Restorative Treatment course in a problem-based learning (PBL) dental curriculum. This retrospective study evaluated a cohort of 206 third-year dental students at Harvard School of Dental Medicine who were enrolled in the Restorative Treatment course between 2000 and 2005. Tutor expertise in prosthodontics and prior tutoring experience were measured against student performance in five areas: 1) tutorial session, 2) midterm examination, 3) final examination, 4) preclinical laboratory, and 5) overall cumulative course grade. Student performance in each of the five areas measured against combinations of tutor subject matter expertise and tutoring experience level showed no statistically significant difference between the groups in the overall course grade. However, student performance in the expert group showed a significant difference in the final examination compared to the nonexpert group (p<0.05). Also, students in the group consisting of expert tutors with no experience performed better on the final examination compared to those students who had expert tutors with experience (p<0.05). The results indicate that overall student performance in the problem-based Restorative Treatment course is not affected by tutor expertise or prior tutoring experience.

Relationship between crevicular aspartate aminotransferase levels and periodontal disease progression.

BACKGROUND: Aspartate aminotransferase (AST), an enzyme released from necrotic cells, has been identified in gingival crevicular fluid (GCF), and elevated levels are associated with periodontal tissue destruction. The aim of this study was to examine the relationship between elevated GCF levels of AST and periodontal disease progression. METHODS: Over a 12-month period, 8 to 10 interproximal sites in 41 periodontitis subjects (PS) and 15 healthy subjects (HS) were monitored. Clinical measurements included relative attachment level (RAL), probing depth, and bleeding on probing (BOP). Semiquantitative levels of GCF AST (< 800 microIU, > or = 800 microIU, and > or = 1,200 microIU) were determined using a chairside assay. At the 6- and 12-month visits, scaling and root planing and prophylaxis were performed in the PS and HS, respectively. Sensitivity, specificity, positive predictive values (PPV), and negative predictive values (NPV) were calculated for 2 diagnostic criteria (AST > or = 800 microIU, AST > or = 1,200 microIU) utilizing 4 thresholds of disease progression as determined by 2 methods (absolute change in relative attachment level and cumulative sum [CUSUM]). RESULTS: The percentage of sites exhibiting AST > or = 800 microIU, AST > or = 1,200 microIU, and BOP in the PS was significantly (P<0.02) lower at 6 and 12 months compared to baseline. The use of crevicular AST activity to monitor periodontal disease progression was associated with many false-positive results. Overall, low specificities, PPV, and odds ratios were demonstrated by the assay when using 2 diagnostic criteria and 4 thresholds of disease progression. The high NPV suggest that a negative AST test result was indicative of a periodontally stable site. CONCLUSIONS: These results demonstrate that elevated levels of AST were present at sites that did not subsequently exhibit disease progression. The high prevalence of AST-positive sites due to gingival inflammation diminished the test's ability to discriminate between progressive and stable, but inflamed, sites.

Periodontal disease and risk of subsequent cardiovascular disease in U.S. male physicians.

OBJECTIVES: We sought to prospectively assess whether self-reported periodontal disease is associated with subsequent risk of cardiovascular disease in a large population of male physicians. BACKGROUND: Periodontal disease, the result of a complex interplay of bacterial infection and chronic inflammation, has been suggested to be a predictor of cardiovascular disease. METHODS: Physicians' Health Study I was a randomized, double-blind, placebo-controlled trial of aspirin and beta-carotene in 22,071 U.S. male physicians. A total of 22,037 physicians provided self-reports of presence or absence of periodontal disease at study entry and were included in this analysis. RESULTS: A total of 2,653 physicians reported a personal history of periodontal disease at baseline. During an average of 12.3 years of follow-up, there were 797 nonfatal myocardial infarctions, 631 nonfatal strokes and 614 cardiovascular deaths. Thus, for each end point, the study had >90% power to detect a clinically important increased risk of 50%. In Cox proportional hazards regression analysis adjusted for age and treatment assignment, physicians who reported periodontal disease at baseline had slightly elevated, but statistically nonsignificant, relative risks (RR) of nonfatal myocardial infarction, (RR, 1.12; 95% confidence interval [CI], 0.92 to 1.36), nonfatal stroke (RR, 1.10; CI, 0.88 to 1.37) and cardiovascular death (RR, 1.20; CI, 0.97 to 1.49). Relative risk for a combined end point of all important cardiovascular events (first occurrence of nonfatal myocardial infarction, nonfatal stroke or cardiovascular death) was 1.13 (CI, 0.99 to 1.28). After adjustment for other cardiovascular risk factors, RRs were all attenuated and nonsignificant. CONCLUSIONS: These prospective data suggest that self-reported periodontal disease is not an independent predictor of subsequent cardiovascular disease in middle-aged to elderly men.

Effect on bone healing of bone morphogenetic protein placed in combination with endosseous implants: a pilot study in beagle dogs.

Although dental implants have become an effective treatment modality for the replacement of missing teeth, their predictability relies on successful osseointegration during the healing period. The purpose of this pilot study was to evaluate the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on early bone formation within the perforations of dental implants in beagle dogs. Histologic sections were evaluated for the extent of new bone formation within a 1-mm diameter of through-and-through perforations. Data indicated that significantly more bone formation occurred with rhBMP-2-treated sites within the implant perforation (P < 0.01) compared to sites treated with the vehicle alone. This pilot study indicates that rhBMP-2 increases the rate and extent of bone formation in combination with dental implants.

The effect of interleukin-11 on the progression of ligature-induced periodontal disease in the beagle dog.

BACKGROUND: The rate of progression of periodontal disease is dependent on the complex regulatory interactions between bacteria and the immune modulators of the host response. The purpose of this investigation was to determine if recombinant human interleukin-11 (rhIL-11), known to downregulate several inflammatory modulators, has the ability in subcutaneous administration to reduce the rate and/or extent of periodontal attachment loss and radiographic bone loss in a ligature-induced periodontal disease beagle dog model. METHODS: Twenty 18-month-old female beagle dogs were brought to optimal periodontal health over a 2-week period. Periodontal disease was induced by placing 2.0 silk ligatures around the mandibular first molar and premolar teeth. The dogs were divided into 3 treatment groups and one control group. The 3 treatment groups received subcutaneous injections of either 15, 30, or 80 microg/kg of rhIL-11 in saline buffer twice a week. The placebo group received buffer only subcutaneously twice a week. The gingival health of each animal was measured by recording the presence or absence of gingival inflammation, plaque, and bleeding upon probing. Attachment levels and bone height were also measured. Treatment administration and clinical and radiographic evaluations were performed in a masked fashion. RESULTS: At week 8, the placebo group had 3.89 mm of attachment loss and 73.8% radiographic bone remaining. The 15 microg/kg group had 1.99 mm attachment loss and 89.5% bone remaining; the 30 microg/kg group had 0.84 mm attachment loss and 92.5% bone remaining; and the 80 microg/kg group had 1.05 mm attachment loss and 85.5% bone remaining. All 3 treatment groups lost significantly less attachment and retained significantly more bone than did the placebo group. CONCLUSIONS: The study indicates that subcutaneous injections of rhIL-11 were able to slow the progression of attachment and radiographic alveolar bone loss in a ligature-induced beagle dog model.

Periodontitis in the child and adolescent.

Early onset periodontitis (EOP) which affects individuals thirty-five and younger is characterized by a rapid rate of bone loss and disease progression with defects in host response and a specific etiological microbial flora. Within this classification, there are three subsets of the disease: prepubertal periodontitis, juvenile periodontitis, and rapidly progressive periodontitis. The characteristics of each disease are described along with illustrative cases that will help clinicians diagnose EOP in their patients. Currently prescribed treatment modalities and guidelines from the literature are also discussed in this paper. EOP may represent a complex set of diseases that are likely to be reclassified as further advances in microbiological and genetic research are made. Clinicians should be aware of such changes in order to diagnose, treat, and refer their patients for comprehensive care.

The effect of different diagnostic thresholds on incidence of disease progression.

Detection of periodontal disease progression occurs when a predetermined threshold of attachment loss is exceeded during longitudinal monitoring. The incidence of disease progression in a population may be dependent on the method and threshold utilized to identify significant changes in attachment level measurements. The aim of this study was to investigate the effect of utilizing different methods and thresholds on the incidence of disease progression in an untreated periodontitis population. The relationship between baseline clinical parameters and disease progression was also examined. A total of 411 interproximal sites in 46 individuals were monitored monthly over a 6-month period. Disease progression was determined by the cumulative sum (CUSUM) method and by the absolute change in relative attachment level between months 0 and 6 utilizing 3 different thresholds for attachment level change (0.58 mm, 1.16 mm, and 1.74 mm) based upon examiner repeatability using an automated probe. Utilizing the CUSUM method, 49 of 411 sites (11.9%) demonstrated attachment loss over the 6-month observation period. When attachment level changes > or = 0.58 mm, > or = 1.16 mm, and > or = 1.74 mm were used to identify disease progression, the percentage of sites exhibiting deterioration were 19.5%, 8.8%, and 2.9%, respectively. These results demonstrate that the apparent incidence of disease progression was dependent on the method and threshold utilized to detect progressive sites. When utilizing the CUSUM and 0.58 mm thresholds a significant (P < 0.05), but weak relationship (r = -0.26) was observed between baseline relative attachment level measurements and sites exhibiting disease progression. This finding suggests that sites with significant but relatively less attachment loss may be more likely to experience further breakdown compared to sites with a history of greater periodontal destruction.

Enantiospecific inhibition of ligature-induced periodontitis in beagles with topical (S)-ketoprofen.

Systemic and topical administration of non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to reduce periodontal disease progression in both animal models and human subjects. Our present research focuses on single enantiomers of these agents to examine whether enantiospecific therapy will be efficacious in slowing periodontitis. The purpose of this study was to evaluate the inhibitory effects of (S)-ketoprofen on experimentally induced alveolar bone loss in beagle dogs. 16, 18-month-old, female beagles were brought to optimal periodontal health over a 2-week pretreatment period. Experimental periodontitis was then induced by placing silk ligatures around premolar and molar teeth and by instituting a soft, plaque-promoting diet. At baseline, animals were randomized to 1 of 4 groups, consisting of 2x daily administration of (1) placebo dentifrice, (2) 0.3% (S)-ketoprofen dentifrice, (3) 3.0% (S)-ketoprofen dentifrice, or (4) 10.0 mg (S)-ketoprofen capsules (p.o.) over a 60 day treatment period. Standardized, periapical radiographs exposed at days 1 and 60 were analyzed by computer-assisted digital radiography in order to assess the rate of alveolar bone loss. Secondary outcomes included technetium 99m-tin-diphosphonate (99mTc-Sn-MDP) uptake and the gingival index. At baseline, no differences were observed among the groups for linear bone height or 99mTc-Sn-MDP uptake ratios. From days 1 to 60, cohorts differed significantly in terms of bone loss rates (p < 0.001). In particular, beagles treated with systemic or topical (S)-ketoprofen (0.3% or 3.0% dentifrices) exhibited significantly lower mean rates of bone loss compared to placebo treated beagles (p < 0.05). Group differences in mean radiopharmaceutical uptake ratio changes approached significance (ANOVA, p = 0.07), where animals treated with topical 0.3% (S)-ketoprofen demonstrated a reduction and other groups demonstrated elevations over the 60-day dosing period. Treatment cohorts did differ significantly with respect to changes in mean gingival indices (p < 0.05). Animals treated with 0.3% or 3.0% (S)-ketoprofen dentifrice exhibited significantly reduced elevations in gingival index scores as compared to placebo treated animals. These data provide evidence that enantiospecific therapy with (S)-ketoprofen, topically or systemically delivered, may alter the progression of periodontal disease in the beagle dog model.

A feasibility study evaluating rhBMP-2/absorbable collagen sponge device for local alveolar ridge preservation or augmentation.

This two-center human clinical trial evaluated recombinant human bone morphogenetic protein-2 delivered in an absorbable collagen sponge (rhBMP-2/ACS) for either alveolar ridge preservation after tooth extraction or augmentation of localized osseous defects. This 24-month study comprised two parts: a 4-month acute safety and bone induction period (Part I) followed by a 20-month, osseointegration, functional restoration, and long-term safety evaluation (Part II). The primary objective of Part I, discussed in this article, was to evaluate the short-term safety and technical feasibility of the rhBMP-2 device implantation. Twelve patients (six preservation and six augmentation) were enrolled in the investigation. Patient safety was monitored by oral examinations, radiographs, and the collection of blood samples to measure serum chemistries, hematology, and potential antibody formation. Technical feasibility was evaluated by collecting information relating to the handling properties of the rhBMP-2/ACS device. The ability of various evaluative tools to measure the bone-inducing activity of the rhBMP-2/ACS device was also assessed. The clinical results suggested that rhBMP-2/ACS was well tolerated locally and systemically, with no serious adverse events. The device was found to be easily handled and adapted to the ridge and extraction socket. Using direct measurements, all sites demonstrated firmness and fullness to palpation at 4 weeks; however, a loss of volume was noted in some treatment areas between 4 and 8 weeks. Augmentation of the alveolar ridge was not observed in the patients as assessed by the evaluation techniques. This trial indicated that the use of rhBMP-2/ACS to preserve alveolar ridge after tooth extraction or augmentation of localized defects is safe and feasible. Bone fill was observed in all alveolar sockets filled with the rhBMP-2 device.

Comparison of manual and automated probing in an untreated periodontitis population.

Diagnosis of periodontal disease progression involves recording two probing attachment level measurements over an adequate time interval. A diagnostic instrument which exhibits less measurement variability allows for increased sensitivity and earlier disease detection. Traditionally, a manual probe with an occlusal stent of the cementoenamel junction (CEJ) as a reference landmark has been the method of choice. Automated probes that use an occlusal disk as the reference landmark have been developed as an alternative means of measure. The aim of this study was to compare the variability of these two probing methods. Four hundred eleven (411) interproximal sites in 46 untreated periodontitis patients were monitored by a single examiner over a 6-month period. Each site was measured on a monthly basis, first with an automated probe (AP) followed by a manual probe (MP) in combination with a custom-fabricated acrylic stent. Measurement variability of the two probing methods was also compared over a 7-day interval. The AP measurements were significantly more variable than the MP measurements (P < 0.001) when considering the variability between two passes at the same visit. Over the 6-month period, the MP measurements demonstrated significantly more variability than the AP measurements (P < 0.001). It was also noted that MP measurements exhibited more variability at sites with frequent bleeding during the 6 months of the study (P = 0.006). The results of this study demonstrate that AP may have less variability of attachment level measurements over a 6-month period and may be less influenced by local inflammatory changes. However, future comparison studies should include multiple examiners to reduce examiner bias and should alternate the probing method to reduce bias created by local tissue changes from multiple probings.

A phase I/II clinical trial to evaluate a combination of recombinant human platelet-derived growth factor-BB and recombinant human insulin-like growth factor-I in patients with periodontal disease.

The primary objective of this study was to assess the safety of recombinant human (rh) platelet-derived growth factor-BB (PDGF-BB) and (rh) insulin-like growth factor-I (IGF-I) when applied to periodontal osseous defects in humans; a secondary objective was to begin to accrue data on the therapeutic dose of these growth factors (GFs) required to stimulate periodontal regeneration. Thirty-eight human subjects possessing bilateral osseous periodontal lesions were assigned to one of two treatment groups in a split-mouth design. Following full-thickness flap reflection, test sites received local application of the therapeutic drug delivered in coded syringes by a "masked" investigator. Two dose levels were tested, 50 micrograms/ml each of rhPDGF-BB and rhIGF-I in a gel vehicle (LD-PDGF/IGF-I) and 150 micrograms/ml each of rhPDGF-BB and rhIGF-I plus vehicle (HD-PDGF/IGF-I). Control treatment consisted of either conventional periodontal flap surgery or surgery plus vehicle. Safety analyses included physical examination, hematology, serum chemistry, urinalysis, antibody titers, and radiographic evaluation of bony changes. The primary therapeutic assessment was bone fill measured at re-entry 6 to 9 months after treatment. No local or systemic safety issues were found as a result of GF administration. No patients developed antibodies to the rhGF proteins. In subjects treated with LD-PDGF/IGF-I, there were no enhancements in periodontal regeneration compared to controls. However, in patients treated with HD-PDGF/IGF-I, statistically significant increases in alveolar bone formation were noted as measured by surgical re-entry 9 months following drug delivery (P < 0.05). This corresponded to an increase of 2.08 mm of new vertical bone height and 42.3% osseous defect fill in the HD-PDGF/IGF-I subjects versus only 0.75 mm and 18.5% gains in new bone height and osseous fill, respectively, in the controls. Furcation lesions, although limited in number, responded most favorably to treatment, with 2.8 mm horizontal osseous fill. The results from this study suggest that the local application of rhPDGF-BB and rhIGF-I to periodontal lesions is safe at the dose levels studied. LD-PDGF/IGF-I did not elicit increased defect fill compared to the control; however, HD-PDGF/IGF-I resulted in a significant promotion in bone regeneration. Additional studies are warranted to more fully characterize the effects of PDGF/IGF-I on periodontal regeneration in humans.

Polypeptide growth factors for periodontal regeneration.

The regeneration of periodontal attachment apparatus is particularly difficult to achieve, primarily because of the presence of many different kinds of tissue that must be restored to produce a functional unit. Traditional methods aimed at regenerating the periodontium have limited indications, and their results are not predictable. Recently, investigators have begun to understand the cellular processes necessary for repair and regeneration of periodontal tissues. Proteins called growth factors have been identified that coordinate these cellular events. The growth factors that may contribute to periodontal regeneration include platelet-derived growth factor, insulin-like growth factor, transforming growth factor-beta, and bone morphogenetic proteins. In vitro studies have demonstrated the positive effects of these factors on a number of cell types essential for periodontal regeneration. For instance, it has been shown that platelet-derived and insulin-like growth factors promote proliferation of osteoblasts an periodontal ligament cell-derived fibroblasts. Animal models have also been used to verify that growth factors can enhance regeneration in vivo following periodontal disease and as an adjunct to implant placement. In the future, human clinical trials will be required to identify the ideal growth factors, their proper doses, and the most suitable carrier system for them.

Inhibition of peri-implant bone loss with the nonsteroidal anti-inflammatory drug flurbiprofen in beagle dogs. A preliminary study.

There is increasing interest in how pathways of tissue destruction around dental implants are similar as for teeth and how these pathways can be modulated to slow loss of supporting bone. The purposes of this study were to develop a short-term animal model to study the effect of the nonsteroidal anti-inflammatory drug flurbiprofen, on slowing the rate of induced peri-implant bone resorption. A total of 20 cylindrical titanium implants were placed in 2 beagle dogs using a low-trauma surgical technique. During the 3-month healing period without functional loading of the implants, daily oral hygiene was performed to maintain a Gingival Index of 0 to 0.5. At completion of the healing period, a baseline evaluation was performed which included the uptake of the bone-seeking radiopharmaceutical (BSRU) 99mtechnetium-tin-diphosphonate (99mTc-Sn-MDP) in peri-implant bone and standardized radiographs. Peri-implantitis was induced with 4-0 silk ligatures, cessation of oral hygiene and soft diet. One beagle was given 0.02 mg/kg of flurbiprofen by mouth; the other received a placebo. BSRU and radiographic height of bone were remeasured to calculate the rate of bone loss during the 60-day treatment period. The percent rate of bone loss during the study period was calculated from the radiographs using a computer-assisted method. The radiopharmaceutical uptake for the flurbiprofen-treated implants remained unchanged. However, BSRU for placebo-treated implants was significantly increased from baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Blocking periodontal disease progression with anti-inflammatory agents.

Recent advances in the identification of specific immuno-inflammatory pathways of periodontal disease have encouraged investigators to attempt to modulate some of these host responses in an attempt to slow the periodontal disease process. Some of the best known mediators of these immuno-inflammatory pathways are prostaglandins. The action of prostaglandins can be inhibited through the use of non-steroidal anti-inflammatory drugs (NSAIDs). This review examines research over the last two decades during which the effect of several NSAIDs on the progression of gingival inflammation and alveolar bone loss was explored.

New technologies for the diagnosis of periodontal disease.

Historically the initial onset of periodontal disease in an individual was considered slow but continuously progressive over time. It was inferred that an individual would experience progressive destruction of the attachment structures until edentulous. However, several studies in the early 1970s contested the traditional concept of continuous disease progression. These studies suggested that periodontal disease progressed by recurrent acute episodes. In specific individuals, the loss of attachment was faster than the concept of slowly progressing disease. There were also sites in patients that progressed slower (or not at all) than anticipated on the basis of radiographic and clinical history of previous disease progression. These findings clearly indicated the need to explore the nature of periodontal disease progression and to institute a major effort into innovative methods to diagnose periodontal diseases. Dentists and researchers could more effectively prevent and treat periodontal disease and relate pertinent research findings to specific disease initiation and progression.

The effect of a mouthrinse based on nisin, a bacteriocin, on developing plaque and gingivitis in beagle dogs.

The aim of this study was to evaluate the effect of nisin, an antimicrobial peptide, on the development of plaque and gingivitis in beagle dogs when compared with 0.12% chlorhexidine and a placebo. 16 female beagle dogs 1 year of age were brought to optimum gingival health by scaling, root planing and polishing. At the conclusion of the pretreatment phase, the dogs were divided into 4 groups for the application of the test agents and were placed on a plaque promoting diet of Purina Dog Chow softened with water. Test agents included 100 micrograms/ml nisin and 300 micrograms/ml nisin formulated in a vehicle containing 1 mM NaEDTA; negative control comprised of exactly the same formulation but omitting nisin; and 0.12% chlorhexidine as Peridex. Throughout the treatment period, formulations were applied 2x daily to premolar teeth in each quadrant for 1 min using a Monojet syringe. The development of plaque and gingivitis was monitored at 15, 27, 39, 53, 74 and 88 days during the treatment phase using standard measurements of gingival index, plaque index, stain index and bleeding to probing. Throughout the treatment phase, plaque accumulation increased in all groups, but the rate of plaque build-up was less in groups treated with either nisin or chlorhexidine formulations compared with the placebo treated group. The gingival index of dogs in all groups increased throughout the study period. However, from day 27 onward, the groups receiving nisin had lower gingival index scores than did the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)