Reduction in adherence of Actinomyces viscosus after exposure to low-frequency acoustic energy

Optimizing the use of low-frequency ultrasound for bacterial detachment of in vivo biofilms in dental research-a methodological study

OBJECTIVES

Low-frequency, low-intensity ultrasound is commonly utilized in various dental research fields to remove biofilms from surfaces, but no clear recommendation exists in dental studies so far. Therefore, this study aims to optimize the sonication procedure for the dental field to efficiently detach bacteria while preserving viability.

MATERIALS AND METHODS

Initial biofilm was formed in vivo on bovine enamel slabs (n = 6) which were worn by four healthy participants for 4 h and 24 h. The enamel slabs covered with biofilm were then ultrasonicated ex vivo for various time periods (0, 1, 2, 4, 6 min). Colony-forming units were determined for quantification, and bacteria were identified using MALDI-TOF. Scanning electron microscopic images were taken to also examine the efficiency of ultrasonications for different time periods.

RESULTS

Ultrasonication for 1 min resulted in the highest bacterial counts, with at least 4.5-fold number compared to the non-sonicated control (p < 0.05). Most bacteria were detached within the first 2 min of sonication, but there were still bacteria detached afterwards, although significantly fewer (p < 0.0001). The highest bacterial diversity was observed after 1 and 2 min of sonication (p < 0.03). Longer sonication periods negatively affected bacterial counts of anaerobes, Gram-negative bacteria, and bacilli. Scanning electron microscopic images demonstrated the ability of ultrasound to desorb microorganisms, as well as revealing cell damage and remaining bacteria.

CONCLUSIONS

With the use of low-frequency, low-intensity ultrasound, significantly higher bacterial counts and diversity can be reached. A shorter sonication time of 1 min shows the best results overall.

CLINICAL RELEVANCE

This standardization is recommended to study initial oral biofilms aged up to 24 h to maximize the outcome of experiments and lead to better comparability of studies.

Safety and Design Aspects of Powered Toothbrush-A Narrative Review

The powered toothbrush has become a modern dental tool that is available in the supermarket. Indeed, the design of the powered toothbrush, e.g., mechanical and electrical, would affect not only the efficacy but also the safety of the products. This narrative review attempted to view the powered toothbrush from design, safety, and application points with respect to tufts, filaments, handles, mechanics, motions, and materials interactions from various available sources. Different brands and models of powered toothbrushes have their own designs that might affect the clinical outcome. The rotational design was advocated to be clinically more effective than the manual one, some modern models might be designed with vibrational or oscillation (or mixed) tufts head that might be useful in patients with specific needs, such as having xerostomia or for the elderly. To conclude, tuft retention design is important in the powered toothbrush as it contributes significantly to safety as the fallen off tufts, filaments and metal parts might cause injury. Tests revealing the retention force of brush head plates and brush head bristles will be significant references for consumers to determine which design of powered toothbrushes is relatively safer.

Effectiveness of a motionless ultrasonic toothbrush in reducing plaque and gingival inflammation in patients with fixed orthodontic appliances

OBJECTIVE

To compare the effectiveness of a motionless ultrasonic toothbrush to a manual toothbrush in reducing dental plaque, gingival inflammation, and mutans streptococci in patients with fixed orthodontic appliances.

MATERIALS AND METHODS

Twenty-five orthodontic patients were recruited to this crossover study. The patients were randomized into two groups starting with manual or motionless ultrasonic toothbrushes for 30 days. After a 30-day washout period, the patients switched to the other toothbrush type for 30 days. Plaque and gingival indices were evaluated by two calibrated-blinded examiners before and after each 30-day period of brushing. Salivary samples were also collected for quantification of mutans streptococci.

RESULTS

On the bracket side, the motionless ultrasonic toothbrush showed a significantly higher mean plaque index bracket score after 30-day usage than baseline (P = .049), while the manual toothbrush group showed no difference between the before and after brushing periods (P = .10). The changes in plaque index bracket score were significantly more favorable in the manual toothbrush group than in the ultrasonic toothbrush group (P = .04). In contrast, no difference was observed on the nonbracket side. There was no significant difference in the changes of gingival index or the numbers of mutans streptococci between the two groups.

CONCLUSION

Manual toothbrushing performed better than brushing with the motionless ultrasonic toothbrush in plaque removal on the bracket side in orthodontic patients. However, no difference was observed in terms of gingival status and the numbers of mutans streptococci.

Vibratory stimulus reduces in vitro biofilm formation on tracheoesophageal voice prostheses

OBJECTIVES/HYPOTHESIS

Demonstrate that biofilm formation will be reduced on tracheoesophageal prostheses when vibratory stimulus is applied, compared to controls receiving no vibratory stimulus, in a dynamic in vitro model of biofilm accumulation simulating the interface across the tracheoesophageal puncture site.

STUDY DESIGN

Prospective, randomized, controlled, crossover in university laboratory.

METHODS

Ex vivo tracheoesophageal prostheses were obtained from university-affiliated speech language pathologists at Indiana University School of Medicine, Indianapolis. Prostheses demonstrating physical integrity and an absence of gross biofilm accumulation were utilized. Sixteen prostheses were cleansed and sterilized prior to random placement by length in two modified Robbins devices arranged in parallel. Each device was seeded with a polymicrobial oral flora on day 1 and received basal artificial salivary flow continuously with three growth medium meals daily. One device was randomly selected for vibratory stimulus, and 2 minutes of vibration was applied to each prosthesis before and after meals for 5 days. The prostheses were explanted and sonicated, and the biofilm cultured for enumeration. This process was repeated after study arm crossover.

RESULTS

Tracheoesophageal prostheses in the dynamic model receiving vibratory stimulus demonstrated reduced gross biofilm accumulation and a significant biofilm colony forming unit per milliliter reduction of 5.56-fold compared to nonvibratory controls (P < 0.001). Significant reductions were observed within length subgroups.

CONCLUSION

Application of vibratory stimulus around meal times significantly reduces biofilm accumulation on tracheoesophageal prostheses in a dynamic in vitro model. Further research using this vibratory stimulus method in vivo will be required to determine if reduced biofilm accumulation correlates with longer device lifespan.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:2752-2757, 2016.

Efficacy of Ultrasonic, Electric and Manual Toothbrushes in Patients with Fixed Orthodontic Appliances

OBJECTIVE

This crossover study compared the efficacy of an ultrasonic toothbrush for the reduction of plaque, gingival inflammation, and levels of Streptococcus mutans, in relation to an electric and a manual toothbrush.

MATERIALS AND METHODS

Twenty-one patients with orthodontic appliances were divided into three groups. All patients were evaluated by a periodontist and samples of saliva were collected for quantification of S mutans. The patients received their first brushes with appropriate instructions. For each crossover leg, patients used each toothbrush for a period of 30 days. At the end of each washout period, participants received a periodontal evaluation and new samples of saliva were collected. After 15 days of using their own toothbrushes, patients received the next toothbrushes in the experimental sequence.

RESULTS

The ultrasonic brush group presented significant improvement in the reduction of visible plaque on the buccal surfaces (-6.36%, P = .007). The counts of S mutans decreased in the electric (2.04 x 10(5) to 1.36 x 10(5) colony-forming units [CFU]/mL) and ultrasonic (2.98 x 10(5) to 1.84 x 10(5) CFU/mL) groups. There were no statistical differences among the three brushes for the clinical and microbiological parameters evaluated.

CONCLUSIONS

This study did not demonstrate that the ultrasonic toothbrush was better in reducing gingival inflammation in adolescent orthodontic patients, but plaque scores were lowered on buccal surfaces of teeth with orthodontic brackets. In addition, S mutans counts were markedly decreased in the electric and ultrasonic groups, which should be related to a reduced risk of oral disease.

Removal of oral biofilms by bubbles

BACKGROUND

Previous research showed that the collision of bubbles with biofilm could remove biofilm from a surface. However, the effectiveness of biofilm removal by bubbles and sonic waves had not been determined.

METHODS

The authors mounted Streptococcus mutans biofilms in a chamber containing artificial saliva and exposed them to bubbles and sonic waves. They generated sonic waves via an oscillator at the frequencies and acoustic intensities of sonic toothbrushes. They also mounted biofilms at different angles to measure the effect of a bubble's impingement angle.

RESULTS

The presence of sound had no significant effect on the amount of biofilm removed (F = 0.51). There was no statistically significant difference in the amount of biofilm removed with respect to the angle at which bubbles impinged on the biofilm (F = 0.65). The authors performed analysis of variance tests to determine whether the difference in the amount of biofilm removal was significant (F < 0.05) in the presence or absence of sound and at the different angles tested.

CONCLUSIONS

The collision of a bubble at any angle between 5 and 45 degrees was equally effective in removing biofilm. The addition of sound to a bubble stream at the tested intensities had a negligible effect.

CLINICAL IMPLICATIONS

Bubbles produced by dental instruments are effective in removing biofilm from the surface of the teeth, regardless of the angle at which the bubble impinges on the biofilm.

A review of the clinical efficacy of the Oral-B oscillating/rotating power toothbrush and the Philips Sonicare toothbrush in normal subject populations

Plaque removal by a toothbrush results from a physical scrubbing of bristles on the tooth surface that removes adherent plaque bacteria. Because of the frequency of brush head motion, some power toothbrushes generally remove plaque more effectively than a manual brush. One power toothbrush, Philips Sonicare, claims also to remove plaque as a result of dynamic fluid activity. This effect has been shown in laboratory studies but clinical evidence is currently lacking. This review evaluated the data from well-controlled clinical studies carried out in normal subjects from a general population comparing the Sonicare toothbrushes with the Oral-B oscillating/rotating power toothbrush technology. It focuses on plaque removal from approximal surfaces where it is difficult for toothbrush bristles to reach, as it is here that any dynamic fluid effect should be most apparent. Results from the review found no evidence to support a greater efficacy for the Sonicare toothbrushes either generally or at approximal surfaces. Data revealed that the oscillating/rotating toothbrush was more effective than the Sonicare toothbrushes with respect to plaque removal. It is possible that factors associated with the clinical situation such as damping resulting from bristle contact with the tooth surface and the high viscosity of saliva and dentifrice may counteract dynamic fluid activity in vivo. This review indicates that dynamic fluid activity beyond the reach of bristles as demonstrated in the laboratory is yet unproven in the clinical situation.

Effect of brushing with sonic and counterrotational toothbrushes on the bond strength of orthodontic brackets

The purpose of this study was to evaluate the effect of brushing with both a sonic and mechanical counter rotary power toothbrush on the bond strength of orthodontic brackets. Forty-five extracted teeth were divided into three random groups and had orthodontic brackets bonded to them. One group was brushed with a counterrotational toothbrush, the Interplak, one group with a sonic toothbrush, the Sonicare, and a third group was not brushed and was held as a control. After the equivalent of 2 years brushing, the teeth were placed in an Instron machine and the shear force to remove the brackets was recorded. Group 1, the counter rotary power brush, had a mean of 107.5 kg/cm2, the second group, the sonic brush, had a mean of 79.7 kg/cm2, and the control group had a mean of 125. 4 kg/cm2. Single factor analysis of variance followed by the Fisher-Hayter Multiple Comparison Procedure showed a statistically significant difference between the sonic power brush and the control (P <.01), but no significant difference between the counter rotary and the control (P >.05). There was no significant difference between the two power brushes (P >.05).

Sonic and mechanical toothbrushes. An in vitro study showing altered microbial surface structures but lack of effect on viability

The purpose of the present study was to compare the in vitro effects of a mechanical and a sonic toothbrush on the viability of Actinomyces viscosus, the rationale being that induction of irreparable microbial damage resulting from aggressive mechanical action or sonic energy, may inhibit or disrupt the process of successional colonization. Cultures of A. viscosus were grown to a standardized optical density and subdivided into 3 treatment groups of 20 specimens each. Treatment groups consisted of an untreated control and exposure to a mechanical or sonic toothbrush for 15, 30, 45, and 60 s. Subsequent to the prescribed treatment, samples were taken from each specimen dish, subcultured, and the number of CFUs determined. Additional samples were obtained for negative staining and examination by electron microscopy. The mean number of CFUs for each treatment group at each treatment interval were statistically analyzed by ANOVA and multiple pairwise comparisons. Results showed a significant main effect for toothbrushes (p<0.0001) and exposure time (p<0.01), but only marginal significance for the interaction of toothbrush with exposure time (p<0.055). Post-hoc tests showed a significantly greater number of CFUs for the sonic toothbrush compared to both the untreated control and mechanical toothbrush groups. Electron microscopic examination revealed a decrease in aggregation tendency and loss of fimbriae in the sonic toothbrush group. Based on the lack of morphologic evidence that would indicate cell damage and the increase in CFUs over that of the control group, it appeared that neither the mechanical or sonic toothbrushes affected cell viability.

Effect of brushing with sonic and counterrotational toothbrushes on the bond strength of full veneer crowns

STATEMENT OF PROBLEM

Earlier studies on orthodontic brackets have shown a loss of bond strength after a sonic toothbrush was used.

PURPOSE

This in vitro study evaluated the difference in bond strength of single complete veneer crowns after being subjected to the equivalent of 2 years of brushing with sonic and counterrotational toothbrushes.

MATERIAL AND METHODS

Complete gold crowns were fabricated with a conventional indirect technique for 30 extracted, intact, prepared human premolar teeth. Castings were then luted to the teeth with glass ionomer cement. Teeth were randomly divided into 3 groups of 10 teeth each, 1 group to be brushed with Sonicare sonic toothbrush, 1 group to be brushed with Interplak counterrotational mechanical toothbrush, and 1 group as the control. Groups 1 and 2 were then brushed for the equivalent of 2 years per tooth. A uniform force of 50 g for the sonic toothbrush and 120 g for the counterrotational toothbrush was used. Control specimens were not brushed. Brush heads and sample teeth in contact with the toothbrush were kept moist at all times. Tensile dislodgment force was determined with an Instron universal testing machine.

RESULTS

The castings brushed with a sonic toothbrush required a mean of 43.22 kg (+/- 11.16) force to remove the crowns from the teeth, whereas the counterrotational group required a mean of 42.87 kg (+/- 10.42) and the control group a mean of 42.12 kg (+/- 6.61). Analysis of variance on the force data indicated no differences among the 3 groups in the force needed to remove the castings (F[2,24] = 0.031, P = .97).

CONCLUSION

This in vitro study demonstrated no significant differences between groups in the amount of tensile dislodgment force required to remove cemented full veneer crowns from prepared teeth after brushing for the equivalent of 2 years time with a sonic toothbrush or a counterrotational toothbrush.

Modern supragingival plaque control

Supragingival plaque control is essential for the maintenance of oral health. Despite the many chemotherapeutic agents available as mouthrinses and toothpastes, mechanical plaque removal is still the best method to achieve effective plaque control. This is due, in part, to the lack of development of oral antimicrobials with the effectiveness and substantivity of chlorhexidine gluconate but without its adverse effects of dental staining and calculus formation. The use of the numerous mechanical (manual and electric) oral hygiene devices extant and their effectiveness, however, are dependent upon patient dexterity and compliance and concomitant active professional treatment for the monitoring of home care, oral hygiene instruction and patient motivation. This paper evaluates the current methods available to reduce plaque and gingivitis with emphasis on their effectiveness at both supragingival plaque control and disease prevention. In addition, recent studies on the newer oscillating/rotating electric plaque removers and interdental cleaning devices will be discussed as related to their efficacy and compliance.

The effects of an ultrasonic toothbrush on plaque accumulation and gingival inflammation

The purpose of this study was to evaluate the effectiveness of an ultrasonic toothbrush to reduce plaque and gingival inflammation when compared to a manual toothbrush. 62 healthy adult patients with a plaque index of at least 2.0, a 50% bleeding index and at least 16 natural teeth participated in this study. 31 patients were randomly assigned to the manual toothbrush group (group A) and 31 were assigned to an ultrasonic toothbrush group (group B). The Turesky et al. plaque index (PI), Eastman bleeding index, and Loe & Silness gingival index (GI) were performed at baseline, 15, and 30 days at the beginning of each appointment (pre-brushing). Patients then brushed with their assigned toothbrush and a post-brushing plaque index was recorded. Kruskal-Wallis one-way analysis of variance (ANOVA) was performed to determine between group differences on the parameters of all clinical indices. Results of the pre-brushing plaque index in group B were significantly lower at 15 and 30 days compared to group A. The post-brushing plaque index demonstrated no statistically significant between or within group differences. Both groups demonstrated significant within group reductions in GI and BI from baseline to 15 days and from 15 to 30 days, however, no between group differences were noted. The results of this study support the ability of an ultrasonic toothbrush to significantly remove plaque and reduce inflammation as well as a manual toothbrush over a 30 day period.

Efficacy of a sonic toothbrush on inflammation and probing depth in adult periodontitis

This single-blind, 8-week study compared the efficacy of a sonic toothbrush and a manual brush in 40 patients with adult periodontitis. Qualitative clinical indices and quantitative laboratory methods were used to monitor the periodontal status of 3 pockets 5 to 7 mm deep in each subject. Patients were randomly assigned either a sonic or manual toothbrush. The two groups were comparable with respect to age, gender, and anatomical location of the test sites. Data were collected from all sites at baseline and at 2, 4, and 8 weeks. Over the 8-week period, both groups showed significant improvements in the clinical indices used. Descriptive statistics indicated the sonic brush group had greater improvement than the manual group in the clinical parameters (gingival index, bleeding index, probing depth, and clinical attachment level). Gingival crevicular fluid (GCF) flow was significantly lower in the sonic brush group (P = 0.018). Considerable variation was present in the levels detected for both inflammatory cytokines tested, however, concentration of interleukin-1 beta was significantly lower in the GCF of sonic group patients (P = 0.05), while concentration of interleukin-6 was significantly reduced in both groups (P < or = 0.05) (t tests). Under these conditions, there is some evidence to suggest that the sonic toothbrush is more beneficial in resolving inflammation in patients with moderate periodontal disease.

Comparison of a sonic and a manual toothbrush for efficacy in supragingival plaque removal and reduction of gingivitis

A new sonic electric toothbrush (Sonicare) and a traditional manual toothbrush were compared for efficacy in removing supragingival plaque and reducing gingival inflammation in a 12-week, single-blind clinical trial. 60 subjects with a gingival index (GI) of > 1.5 and no probing depths > 5 mm were randomly assigned to use either the manual or sonic brush, instructed in its use, and asked to brush each morning and evening for 2 minutes. Plaque scores were taken at baseline and at 1, 2, 4, and 12 weeks using the Turesky modification of the Quigley-Hein plaque index. Gingival inflammation was assessed by the GI, bleeding tendency score, presence or absence of bleeding on probing, volumetric measurements of gingival crevicular fluid (GCF), and aspartate aminotransferase (AST) levels in GCF. Repeated measures multivariate analyses of variance were used to detect time- and device-dependent differences for all clinical assessments between the 2 groups over the 5 visits. Both types of brush were effective in removing supragingival plaque. The sonic brush was statistically superior, on a percentage reduction basis, in removing supragingival plaque from the dentition taken as a whole (F-statistic; p = 0.012) and was particularly better in hard-to-reach areas such as posterior teeth (F-statistic; p = 0.003) and interproximal sites (F-statistic; p = 0.004). Both devices were equally effective in reducing gingival inflammation. The sonic brush exhibited less tendency to cause gingival abrasion than the manual brush (1 incident with sonic, 5 incidents with manual), confirming the safety of this product as an oral hygiene device.

Comparison of an oscillating/rotating electric toothbrush and a 'sonic' toothbrush in plaque-removing ability. A professional toothbrushing and supervised brushing study

The purpose of the present study was to compare the Braun/Oral-B Plak Control (D7) and Sonicare (S) in their plaque-removing efficacy. For this study, 35 university students (non-dental) were selected. This was a 2-part study. Prior to each appointment, all subjects were asked to abstain from all oral hygiene procedures for at least 24 h. In Part 1, the efficacy of the toothbrush was studied when one of the investigators brushed the teeth of the panellists. In Part 2, the efficacy of toothbrushing was studied after the students had received professional instruction. The available time for the brushing amounted to a total of 2 min per mouth. Dental plaque was evaluated by means of the Silness and Löe plaque index assessed at 6 sites per tooth. Results showed that both in Part 2 and Part 1 the D7 removed significantly more plaque than the S-electric toothbrush. The plaque reduction assessed according to Silness and Löe in Part 1 was for the D7, 1.28 and for the S, 1.12. In Part 2, the reductions were 0.90 and 0.80, respectively. The majority (n = 34) of subjects preferred the D7 over the S. In conclusion, the results of the present study show that the oscillating/rotating toothbrush (Braun/ Oral-B Plak Control) is more effective in plaque removal than the sonic electric toothbrush (Sonicare). In addition, given a choice, the panellists preferred the oscillating/rotating electric toothbrush.

Clinical evaluation of the effect of an ultrasonic toothbrush on plaque, gingivitis, and gingival bleeding: a six-month study

This study evaluated the long-term effect of an ultrasonic toothbrush used as part of a daily oral hygiene regimen on supragingival plaque, gingivitis, and gingival bleeding. Compared with a conventional toothbrush, the ultrasonic toothbrush was significantly more effective in reducing plaque formation (p < 0.05), removing plaque (p < 0.05), and reducing gingivitis (p < 0.05) during the 6-month study period.

Clinical evaluation of the efficacy and safety of a new sonic toothbrush

The efficacy and safety of a new sonic toothbrush were studied in this single-blind study. The sonic toothbrush combines acoustic vibrations and dynamic fluid activity surrounding the bristles with direct mechanical scrubbing of tooth surfaces. Fifty-one subjects were randomly assigned to either the sonic or the manual toothbrush. Plaque scores were assessed before and after a 2-minute brushing at baseline and 1, 2, and 4 weeks. Gingivitis and sulcular bleeding scores were also taken at each evaluation. To assess long-term safety, 29 subjects returned after 6 months of product use. Repeated measures analysis of variance of the total mean plaque score indicated a significant difference between the devices over time (P < 0.01), with the sonic toothbrush demonstrating a greater level of plaque removal on all tooth surfaces. On average, the plaque reduction from the baseline score for the sonic toothbrush was 3 times greater than the manual brush. However, when broken down by dental region, the sonic toothbrush demonstrated an improved level of plaque removal ranging from 1.5 to 11.9 times better than the manual brush, with the greatest improvement in the interproximal and lingual areas. Both the gingivitis and sulcular bleeding scores exhibited a similar, significant reduction (P < 0.005) over time for both devices with an approximate 17% decrease in the gingivitis index and a 33% decrease in sulcular bleeding sites. Safety assessment after 6 months of use indicated no soft tissue abnormalities which could be attributed to the products.(ABSTRACT TRUNCATED AT 250 WORDS)

Fimbria damage and removal of adherent bacteria after exposure to acoustic energy

The physical effects of low-frequency acoustic energy on Actinomyces viscosus were studied with electron microscopy to explore both acoustically induced damage to fimbriae on the surface of these bacteria and acoustic removal of bacteria from saliva-treated hydroxyapatite disks. A bacterial suspension was exposed to acoustic energy from a laboratory acoustic generator (50 kPa, 200 Hz) and from a new electronic toothbrush, the Sonicare. The exposed bacteria were examined with electron microscopy after negative staining. A decrease in both the percentage of bacterial surface covered with fimbriae and the fimbria length was observed after acoustic exposure. To study the acoustic effects on adherent bacteria, A. viscosus bound to hydroxyapatite disks were exposed to acoustic energy and examined with scanning electron microscopy. Quantitative evaluation of the micrographs for the number of bacteria present after exposure revealed that acoustic energy removed both bacteria adherent to the hydroxyapatite surface and adherent to each other. The results support the concept that an electronic toothbrush employing low-frequency acoustic energy may help prevent and control periodontal diseases by altering bacterial adherence.

Safety testing of a new electronic toothbrush

While there have been major advances in understanding the causes and treatments of the inflammatory periodontal diseases in the past decade, there is still high reliance on the patient to prevent progression of disease through daily oral hygiene, primarily toothbrushing and flossing. A new electronic toothbrush, which produces mild fluid cavitation as well as rapid fluid streaming, has been developed and has shown promise in the ease and efficacy with which it removes plaque. In order to determine the safety of frequent and prolonged use of this device, the gingival tissues of 6 mongrel dogs were exposed to excessively long daily exposures to this toothbrush for up to 2 months. Each quadrant of each dog's mouth was randomly assigned a different treatment: no brushing, manual brush 1.0 minute, electronic brush 1.0 minute, or electronic brush 7.5 minutes. The dogs were examined weekly by a periodontist who was blinded to the treatments. Plaque scores and bleeding on probing scores were calculated, and possible gingival irritation was monitored carefully. At the end of the trial gingival biopsies taken from all the test areas. These were processed for conventional histopathologic evaluation and examined by an oral pathologist who was also blinded as to the treatments. The results showed that brushing a single posterior segment of teeth for 7.5 minutes daily for 2 months with the electronic brush did not result in any clinically or histologically evident damage to the gingiva. Rather, the areas so treated showed excellent health as determined by both clinical and histologic criteria.(ABSTRACT TRUNCATED AT 250 WORDS)