659
Influence of Polishing Procedures on Sonic Scaling Root Surface Roughness Knut . Leknes' and
Tryggve Lié*
the efficacy of various polishing caused by sonic scaling. Proximal root surface areas of extracted, formalin-stored teeth were scaled in a bucco-lingual direction by a sonic sealer. The resulting roughness was measured along the direction of scaling and perpendicular to that direction by a profilometer. The specimens were then split into two groups. Group 1 was polished by an air-powder polishing instrument followed by a rotating rubber cup and chalk; Group 2 was polished by pumice followed by chalk. Root roughness (Ra) was recorded for each step in the procedures. The measurements revealed lower Ra values when the stylus of the profilometer was running perpendicular to the scaling direction, and a weak negative correlation was found when scaling time and Ra values were compared. In both groups Ra values were significantly reduced at each step of the polishing procedures and the terminal result was similar for the groups. Pumice and air-powder polishing gave a similar reduction of the sonic scaling roughness. / Periodontol 1991; 62:659-662. The
present in vitro study aimed to evaluate
procedures
in
reducing
root
roughness
Key Words: Polishing/methods; scaling/methods; ultrasonics.
planing are performed with hand instruby machining techniques. The intention is to remove soft and hard deposits from the dento-gingival pocket area to reestablish healthy periodontal conditions. This debridement can be accomplished with or without surgical access. Following primary treatment, repeated scaling and polishing procedures are included in maintenance therapy to preserve healthy gingival conditions and prevent recurrence of disease. The long-term success of this treatment is dependent on the quality of the maintenance phase.17 A high standard of daily oral hygiene in addition to regular professional cleaning is required. Ideally, scaling and root planing procedures should only remove extraneous staining, plaque, calculus, and bacterial Scaling
and root
ments or
components from tooth surfaces with no or minimal sacrifice of tooth substance or production of surface roughness. However, several in vitro studies have demonstrated iatrogenic effects subsequent to professional instmmentation.8"11 These unintended surface lesions and irregularities increase the surface area, promote bacterial colonization and plaque formation and, thereby, compromise daily plaque removal.1217 Hence, it would be desirable to explore rational root polishing procedures. *
Department of Periodontology, School of Dentistry, University of Bergen, Bergen, Norway and Graduate Periodontics, School of Dentistry, Loma Linda University, Loma Linda, CA. Department of Periodontology, School of Dentistry, University of Bergen, Bergen, Norway and Department of Periodontology, School of Dentistry, Oregon Health Sciences University, Portland, OR.
Recently,
a new
generation of scaling and polishing in-
struments has been introduced. The sonic sealer is run by air and can be directly attached to the air pressure outlet on
the dental unit. This oscillatory instrument may represent a good alternative to conventional ultrasonic sealers.10,11 Air-powder polishing instruments operate by ejecting a slurry of fine sodium bicarbonate particles mixed with air and water against the tooth surface. This aid is advocated as an efficient alternative to traditional cleaning and polishing with mbber 24 cup, pumice, and polishing pastes.18 The main purpose of this study was to evaluate the efficacy of various polishing procedures in reducing the root roughness caused by sonic scaling. Influence of scaling time and scaling direction on the measured roughness was also evaluated. MATERIALS AND METHODS Both the sonic sealer* and air-powder polishing instrument were applied with air pressure, water cooling, sodium bicarbonate content, etc., according to manufacturers' recommendations. An accurate pumice and chalk consistency was obtained by standardizing the mixing procedure. All the teeth were polished with the same slow-speed handpiece equipped with new rubber cups.
Experimental Design
Thirty extracted, formalin-stored, mandibular incisors with plaque and calculus were coded and a test area was marked Titan Sonic Sealer, Syntex Dental Products, Inc., Valley Forge, PA. §Air-Flow, EMS, Electro Medical Systems, SA, Le Sentier, Switzerland.
660
J Periodontol November 1991
EFFECT OF POLISHING ON SONIC SCALED ROOTS
of the proximal root surfaces by 2 parallel faciolingual grooves with a 5 mm distance between the marks. All the teeth were first scaled using a sonic sealer by one operator in facio-lingual direction using slight pressure and on one
the lateral side of the insert in contact with the surface. The scaling stopped when the test area seemed smooth and clean by visual inspection. Individual cleaning time for each test area was recorded. Before randomly splitting the incisors into 2 equal groups, the roughness caused by the sonic scaling was measured by a profilometer according to a standardized procedure. The measurements were incomplete for 4 specimens, and these were excluded from the study. Hence, each group consisted of 13 specimens. All specimens in Group 1 were polished by the polishing instrument for 5 seconds, followed by a rotating rubber cup and chalk (1 g chalk mixed with 1 ml of water), also for 5 seconds at 6000 rpm. In Group 2, the scaled specimens were polished for the same period of time, first by pumice (2 g pumice mixed with 1 ml of water) and then by chalk. The incisors were rinsed in running tap water and further cleaned in an ultrasonic bath for 3 minutes before the surface roughness measurements.
A
C Figure 1. Profilometer profile curves from specimen 5 in Group 2. ARecording performed along the direction of scaling upon completion of sonic scaling. B: Same specimen recorded in same direction following pumice polishing. C." Same specimen and recording direction following chalk polishing. MEAN Ra
Measurements Upon completion of the scaling procedure and after each polishing step, the surface roughness, Ra, was measured with a profilometer11 and the values were recorded by a profile recorder.11 Before the experiment, the equipment was calibrated against a standard. The stylus of the profilometer was first run in 5 parallel scans with 0.5 mm intervals and 1.5 mm in length along the direction of scaling. The specimens were then remounted, and 5 additional scans were run perpendicular to the direction of scaling. Hence, each test area was covered by 10 scans and 10 roughness values were recorded. In order to minimize the effect of the curvature of the surfaces, a filtration was applied corresponding to a cut-off value of 0.25 mm.
Roughness
Statistical Evaluation Statistical testing of differences between mean Ra values witliin the groups for each step in the polishing procedures was made by the Wilcoxon-one-sample signed rank test (WTEST) at a significance level of 0.05. The 2 sample /-test was used for pairwise comparisons between the groups. The WTEST was further used to test differences between mean Ra values recorded along or perpendicular to the direction of scaling. The correlation between the sonic scaling time and the corresponding mean surface roughness value for each specimen (N 26) was tested by the Rank correlation coefficient. =
RESULTS The profilometric scanning of the sonic scaled test areas revealed profile curves with a very irregular outline, char'Perthometer, Perthen, Mahr, Germany.
TITAN-S
AIR-FLOW
GROUP 1
CHALK
T1TAN-S
PUMICE
CHALK
GROUP 2
Mean Ra values ( ± SD) for both groups. Significant (P < 0.01) reduction of roughness at each step in the polishing procedures within both groups. No significant differences between the groups.
Figure 2.
by peaks and slopes with high amplitudes (Fig. 1). Following the polishing procedures, the profile curves appeared less irregular. The mean surface roughness values for the specimen profile displayed in Figure 1 and measured along the direction of the sonic-scaling were 2.28 after the initial scaling, 1.64 after polishing with pumice, and 1.40 after polishing with chalk (specimen from Group 2). A significant effect from the polishing procedures upon the sonic sealer produced surface roughness was observed in both experimental groups (Fig. 2). Within both groups acterized
Volume 62 Number 11
LEKNES,
Table 1. Descriptive Statistics for Each Step of the Treatment Procedures Within the 2 Treatment Groups (N = 13) Treatment Group 1
Scaling Air-powder Chalk
Group 2 Scaling Pumice Chalk
Mean
Median
1.686 1.410 1.198
1.640 1.400 1.180
1.549 1.265 1.104
1.580 1.240 1.050
STD
Minimum
Maximum
0.408 0.113 0.329 0.091 0.265 0.074
1.000 0.880 0.750
2.410 2.060 1.670
0.291 0.081 0.196 0.054 0.225 0.062
1.200 0.990 0.740
2.040 1.620 1.490
SEM
the Ra values were significantly (P < 0.01) reduced at each step of the polishing procedures. However, no statistical differences in roughness were disclosed between the groups following the initial sonic scaling, or following the intermediate or final polishing procedures (Fig. 2). In Group 1 the mean surface roughness value after scaling was 1.69 (Table 1). The "air polishing" procedure reduced this mean Ra value to 1.41 and the final Ra value after polishing with chalk was 1.20. In Group 2 the mean surface roughness value was 1.55 after sonic scaling. The Ra values after the pumice and chalk polishing procedures were 1.26 and 1.10 respectively (Table 1). While the sonic scaling procedure was performed in a facio-lingual direction, the profilometric measurements were obtained along the direction of scaling as well as perpendicular to it. The mean Ra value measured along the direction of scaling was 1.73 (median 1.71; minimum, 0.98; maximum, 2.54), while the corresponding value measured perpendicular to this direction was 1.51 (median 1.51; minimum, 0.90; maximum, 2.44). This difference was statis-
tically significant (P < 0.05). According to the experimental criteria, the sonic scaling ceased when the test surface seemed smooth and clean by visual inspection. The time needed to achieve this result ranged from 42 to 100 seconds. The Rank correlation coefficient comparing scaling time and the resulting mean surface roughness value was —0.153. Accordingly, only a minor reduction in roughness could be obtained with increased scaling time. DISCUSSION This study was initiated to provide scientific guidelines for the clinical performance of cleaning and polishing procedures. Thus, the polishing effects of pumice and chalk were compared to air polishing and chalk. A conflict of interest may exist between therapist and patient in selecting the appropriate tools. The operator wants to perform this treatment quickly. The patient, however, is more concerned about the possibility of root abrasion and sensitivity.25 Extensive loss of tooth substance may represent a potential risk for discomfort and even root fracture. In the present study, an in vitro model was employed in order to facilitate the standardization of the experimental conditions. Comparable test areas were provided and ac-
LIE
661
evaluating methods applied.8'26'27 The cleaning was performed under ideal conditions with direct access to the curate
test surfaces. These
aspects have to be considered when clinical consequences of the study are drawn. Not surprisingly, sonic scaled root surfaces exhibited substantial roughness. In studies by Lie and Leknes10 and Jotikasthira et al.,11 the sonic scaling roughness was graded by the Roughness Loss of Tooth Substance Index (RLTSI), giving mean scores of 1.34 and 1.60 respectively. The frequency of vibration of the sonic scaling tip is in the range of 16 to 18 kHz. According to Gankerseer and Walmsley,28 the pattern of oscillation of the tip was found to be elliptical with the long diameter of the ellipse at 60° to the axis of the instrument and with maximum effect in the transverse direction. This oscillation pattern combined with a lower vibration frequency may explain the lower Ra values recorded when the stylus was running perpendicular to the scaling direction. An equal smoothing effect was obtained on sonic-scaled surface roughness after polishing with air flow or with pumice for 5 seconds. Reports concerning the effect of this dental air-polishing device have stated that some loss of tooth substance does occur,18*20'29-30 but the treated root surfaces were shown to be surprisingly smooth.18,21 Our findings confirmed these observations. A substantial smoothing effect was achieved, but no information about loss of tooth substance can be obtained with this evaluation
procedure.
The test areas were exposed to each polishing device for 5 seconds. The mean time to remove stain by an air-powder "abrasive system" was calculated by Berkstein et al.20 to 3.23 seconds per root surface per treatment. Other studies have tried to estimate an appropriate exposure time both for a single treatment29 and for a patient maintained on a 3month recall for 15 years.18 Based on these calculations, an exposure time of 5 seconds seemed reasonable. Chalk mixed with water gives a very fine and low abrasive paste. Its relative hardness on the Mohs scale is much lower than for pumice.31 Eide and Tveit26 reported that coarse and fine pastes resulted in the same degree of surface roughness when polishing amalgam. In the present study, however, polishing with chalk subsequent to polishing with pumice significantly reduced the surface roughness. This may indicate that root surfaces are more susceptible to abrasion than amalgam. Only a weak negative correlation was found when sonic scaling time and mean surface roughness values were compared. By increasing the instrumentation time, a more complete removal of calculus may be achieved, giving a smoother root surface. On the other hand, extensive scaling may cause more iatrogenic related roughness. However, residual subgingival calculus will probably have a more detrimental effect on periodontal health than roughness from instrumentation. This study has demonstrated that polishing can reduce sonic scaling root surface roughness and this effect is ob-
662
J Periodontol November 1991
EFFECT OF POLISHING ON SONIC SCALED ROOTS
J, Hegdahl T. On the measuring of roughness. Acta Odontol Scand 1981; 39:379-384. Waerhaug J. Effect of rough surfaces upon gingival tissue. / Dent Res 1956; 35:323-325. Lie T. Early dental plaque morphogenesis. A scanning electron microscope study using the hydroxyapatite splint model and a low sucrose diet. / Periodont Res 1977; 12:73-89. Lie T. Ultrastructural study of early dental plaque formation. / Periodont Res 1978; 13:391-409. Lie T, Gusberti F. Replica study of plaque formation on human tooth surfaces. Acta Odontol Scand 1979; 37:65-72. Leknes KN, Lie T. Erythrosin staining in clinical disclosure of plaque. Quintessence Int 1988; 19:199-204. Atkinson DR, Cobb CM, Killoy WJ. The effect of an air-powder abrasive system on in vitro root surfaces. /Periodontol 1984; 55:1318. Mishkin DJ, Engler WO, Javeo , Darby TD, Cobb RL, Coffman MA. A clinical comparison of the effect on gingiva of the ProphyJet and the rubber cup and paste technique. J Periodontol 1986; 57:151154. Berkstein S, Reiff RL, McKinney JF, Killoy WJ. Supragingival root surface removal during maintenance procedures utilizing an air-powder abrasive system or hand scaling. An in vitro study. / Periodontol 1987; 58:327-330. Horning GM, Cobb CM, Killoy WJ. Effect of an air-powder abrasive system on root surfaces in periodontal surgery. J Clin Periodontol 1987; 14:213-220. Galloway SE, Pashley DH. Rate of removal of root structure by the use of the Prophy-Jet device. J Periodontol 1987; 58:464-469. Kontturi-Narhi V, Markkanen H. The gingival effects of dental airpolishing as evaluated by scanning electron microscopy. J Periodontol 1989; 60:19-22. Snyder JA, McVay JT, Brown FH, et al. The effect of air abrasive polishing on blood pH and electrolyte concentrations in healthy mongrel dogs. / Periodontol 1990; 61:81-86. Johnson G, Brännström M. The sensitivity of dentin. Changes in relation to conditions at exposed tubule apertures. Acta Odontol Scand 1974; 32:29-38. Eide R, Tveit AB. A comparison of different techniques for finishing and polishing amalgam. Acta Odontol Scand 1987; 45:147-151. Svinnseth PN, Gjerdet NR, Lie T. Abrasivity of toothpastes. An in vitro study of toothpastes marketed in Norway. Acta Odontol Scand 1987; 45:195-202. Gankerseer EJ, Walmsley AD. Preliminary investigation into the performance of a sonic sealer. / Periodontol 1987; 58:780-784. Hovgaard O, Borg . Den abrasionsmaessige effekt af en ny tan-
tainable with different polishing procedures. The profilometer does not have the capacity to distinguish between "positive" and "negative" roughness or to measure loss of tooth substance. Consequently, further studies should be initiated to compare the loss of tooth substance and the effect on residual calculus of such procedures and to evaluate the clinical consequences of roughness in the marginal root surface area.
12. Leitäo
Acknowledgments
17.
The authors are grateful to Dr. N.R. Gjerdet for guiding the profilometric measurements, to Julie Cranfill for secretarial assistance, and to Frigg B. Sellevoll for data
management. REFERENCES 1. Lövdal A, Arno A, Schei O, Waerhaug J. Combined effect of subgingival scaling and controlled oral hygiene on the incidence of gingivitis. Acta Odontol Scand 1961; 19:537-553. 2. Suomi JD, Greene JC, Vermillion JR, Doyle J, Chang JJ, Leather-
3.
4.
5.
6.
7.
8.
9.
10.
11.
wood EC. The effect of controlled oral hygiene procedures on the progression of periodontal disease in adults: Results after third and final yen. J Periodontol 1971; 42:152-160. Ramfjord SP, Knowles JW, Nissle RR, Shick RA, Burgett FG. Longitudinal study of periodontal therapy. J Periodontol 1973; 44:6677. Nyman S, Rosling B, Lindhe J. Effect of professional tooth cleaning on healing after periodontal surgery. / Clin Periodontol 1975; 2:8086. Axelsson P, Lindhe J. Effect of controlled oral hygiene procedures on caries and periodontal disease in adults. J Clin Periodontol 1978; 5:133-151. Axelsson P, Lindhe J. The effect of controlled oral hygiene procedures on caries and periodontal disease in adults. Results after 6 years. / Clin Periodontol 1981; 8:239-248. Axelsson P, Lindhe J. The significance of maintenance care in the treatment of periodontal disease. J Clin Periodontol 1981; 8:281294. Meyer K, Lie T. Root surface roughness in response to periodontal instrumentation studied by combined use of microroughness measurements and scanning electron microscopy. J Clin Periodontol 1977; 4:77-91. Lie T, Meyer K. Calculus removal and loss of tooth substance in response to different periodontal instruments. A scanning electron microscope study. J Clin Periodontol 1977; 4:250-262. Lie T, Leknes KN. Evaluation of the effect on root surfaces of air turbine sealers and ultrasonic instrumentation. / Periodontol 1985; 56:522-531. Jotikasthira NE, Lie T, Leknes KN. Comparative in vitro studies of sonic, ultrasonic and reciprocating scaling instruments. J Clin Periodontol, accepted for publication.
13. 14.
15. 16.
18.
19.
20.
21.
22. 23.
24.
25.
26. 27.
28. 29.
dransningsmetode. Tandlaegebladet 1986; 90:1-6. 30. Kontturi-Narhi V, Markkanen S, Markkanen H. Effects of airpolishing on dental plaque removal and hard tissues as evaluated by scanning electron microscopy. / Periodontol 1990; 61:334-339. 31. Svärdström G. Klinisk puts. Stockholm: Invest-Odontol AB, 1983.
Send reprint requests to Dr. Knut . Leknes, Department of Periodontology, School of Dentistry, Ârstadveien 17, N-5009 Bergen, Norway. Accepted for publication May 31, 1991.
Influence of Polishing Procedures on Sonic Scaling Root Surface Roughness Knut . Leknes' and
Tryggve Lié*
the efficacy of various polishing caused by sonic scaling. Proximal root surface areas of extracted, formalin-stored teeth were scaled in a bucco-lingual direction by a sonic sealer. The resulting roughness was measured along the direction of scaling and perpendicular to that direction by a profilometer. The specimens were then split into two groups. Group 1 was polished by an air-powder polishing instrument followed by a rotating rubber cup and chalk; Group 2 was polished by pumice followed by chalk. Root roughness (Ra) was recorded for each step in the procedures. The measurements revealed lower Ra values when the stylus of the profilometer was running perpendicular to the scaling direction, and a weak negative correlation was found when scaling time and Ra values were compared. In both groups Ra values were significantly reduced at each step of the polishing procedures and the terminal result was similar for the groups. Pumice and air-powder polishing gave a similar reduction of the sonic scaling roughness. / Periodontol 1991; 62:659-662. The
present in vitro study aimed to evaluate
procedures
in
reducing
root
roughness
Key Words: Polishing/methods; scaling/methods; ultrasonics.
planing are performed with hand instruby machining techniques. The intention is to remove soft and hard deposits from the dento-gingival pocket area to reestablish healthy periodontal conditions. This debridement can be accomplished with or without surgical access. Following primary treatment, repeated scaling and polishing procedures are included in maintenance therapy to preserve healthy gingival conditions and prevent recurrence of disease. The long-term success of this treatment is dependent on the quality of the maintenance phase.17 A high standard of daily oral hygiene in addition to regular professional cleaning is required. Ideally, scaling and root planing procedures should only remove extraneous staining, plaque, calculus, and bacterial Scaling
and root
ments or
components from tooth surfaces with no or minimal sacrifice of tooth substance or production of surface roughness. However, several in vitro studies have demonstrated iatrogenic effects subsequent to professional instmmentation.8"11 These unintended surface lesions and irregularities increase the surface area, promote bacterial colonization and plaque formation and, thereby, compromise daily plaque removal.1217 Hence, it would be desirable to explore rational root polishing procedures. *
Department of Periodontology, School of Dentistry, University of Bergen, Bergen, Norway and Graduate Periodontics, School of Dentistry, Loma Linda University, Loma Linda, CA. Department of Periodontology, School of Dentistry, University of Bergen, Bergen, Norway and Department of Periodontology, School of Dentistry, Oregon Health Sciences University, Portland, OR.
Recently,
a new
generation of scaling and polishing in-
struments has been introduced. The sonic sealer is run by air and can be directly attached to the air pressure outlet on
the dental unit. This oscillatory instrument may represent a good alternative to conventional ultrasonic sealers.10,11 Air-powder polishing instruments operate by ejecting a slurry of fine sodium bicarbonate particles mixed with air and water against the tooth surface. This aid is advocated as an efficient alternative to traditional cleaning and polishing with mbber 24 cup, pumice, and polishing pastes.18 The main purpose of this study was to evaluate the efficacy of various polishing procedures in reducing the root roughness caused by sonic scaling. Influence of scaling time and scaling direction on the measured roughness was also evaluated. MATERIALS AND METHODS Both the sonic sealer* and air-powder polishing instrument were applied with air pressure, water cooling, sodium bicarbonate content, etc., according to manufacturers' recommendations. An accurate pumice and chalk consistency was obtained by standardizing the mixing procedure. All the teeth were polished with the same slow-speed handpiece equipped with new rubber cups.
Experimental Design
Thirty extracted, formalin-stored, mandibular incisors with plaque and calculus were coded and a test area was marked Titan Sonic Sealer, Syntex Dental Products, Inc., Valley Forge, PA. §Air-Flow, EMS, Electro Medical Systems, SA, Le Sentier, Switzerland.
660
J Periodontol November 1991
EFFECT OF POLISHING ON SONIC SCALED ROOTS
of the proximal root surfaces by 2 parallel faciolingual grooves with a 5 mm distance between the marks. All the teeth were first scaled using a sonic sealer by one operator in facio-lingual direction using slight pressure and on one
the lateral side of the insert in contact with the surface. The scaling stopped when the test area seemed smooth and clean by visual inspection. Individual cleaning time for each test area was recorded. Before randomly splitting the incisors into 2 equal groups, the roughness caused by the sonic scaling was measured by a profilometer according to a standardized procedure. The measurements were incomplete for 4 specimens, and these were excluded from the study. Hence, each group consisted of 13 specimens. All specimens in Group 1 were polished by the polishing instrument for 5 seconds, followed by a rotating rubber cup and chalk (1 g chalk mixed with 1 ml of water), also for 5 seconds at 6000 rpm. In Group 2, the scaled specimens were polished for the same period of time, first by pumice (2 g pumice mixed with 1 ml of water) and then by chalk. The incisors were rinsed in running tap water and further cleaned in an ultrasonic bath for 3 minutes before the surface roughness measurements.
A
C Figure 1. Profilometer profile curves from specimen 5 in Group 2. ARecording performed along the direction of scaling upon completion of sonic scaling. B: Same specimen recorded in same direction following pumice polishing. C." Same specimen and recording direction following chalk polishing. MEAN Ra
Measurements Upon completion of the scaling procedure and after each polishing step, the surface roughness, Ra, was measured with a profilometer11 and the values were recorded by a profile recorder.11 Before the experiment, the equipment was calibrated against a standard. The stylus of the profilometer was first run in 5 parallel scans with 0.5 mm intervals and 1.5 mm in length along the direction of scaling. The specimens were then remounted, and 5 additional scans were run perpendicular to the direction of scaling. Hence, each test area was covered by 10 scans and 10 roughness values were recorded. In order to minimize the effect of the curvature of the surfaces, a filtration was applied corresponding to a cut-off value of 0.25 mm.
Roughness
Statistical Evaluation Statistical testing of differences between mean Ra values witliin the groups for each step in the polishing procedures was made by the Wilcoxon-one-sample signed rank test (WTEST) at a significance level of 0.05. The 2 sample /-test was used for pairwise comparisons between the groups. The WTEST was further used to test differences between mean Ra values recorded along or perpendicular to the direction of scaling. The correlation between the sonic scaling time and the corresponding mean surface roughness value for each specimen (N 26) was tested by the Rank correlation coefficient. =
RESULTS The profilometric scanning of the sonic scaled test areas revealed profile curves with a very irregular outline, char'Perthometer, Perthen, Mahr, Germany.
TITAN-S
AIR-FLOW
GROUP 1
CHALK
T1TAN-S
PUMICE
CHALK
GROUP 2
Mean Ra values ( ± SD) for both groups. Significant (P < 0.01) reduction of roughness at each step in the polishing procedures within both groups. No significant differences between the groups.
Figure 2.
by peaks and slopes with high amplitudes (Fig. 1). Following the polishing procedures, the profile curves appeared less irregular. The mean surface roughness values for the specimen profile displayed in Figure 1 and measured along the direction of the sonic-scaling were 2.28 after the initial scaling, 1.64 after polishing with pumice, and 1.40 after polishing with chalk (specimen from Group 2). A significant effect from the polishing procedures upon the sonic sealer produced surface roughness was observed in both experimental groups (Fig. 2). Within both groups acterized
Volume 62 Number 11
LEKNES,
Table 1. Descriptive Statistics for Each Step of the Treatment Procedures Within the 2 Treatment Groups (N = 13) Treatment Group 1
Scaling Air-powder Chalk
Group 2 Scaling Pumice Chalk
Mean
Median
1.686 1.410 1.198
1.640 1.400 1.180
1.549 1.265 1.104
1.580 1.240 1.050
STD
Minimum
Maximum
0.408 0.113 0.329 0.091 0.265 0.074
1.000 0.880 0.750
2.410 2.060 1.670
0.291 0.081 0.196 0.054 0.225 0.062
1.200 0.990 0.740
2.040 1.620 1.490
SEM
the Ra values were significantly (P < 0.01) reduced at each step of the polishing procedures. However, no statistical differences in roughness were disclosed between the groups following the initial sonic scaling, or following the intermediate or final polishing procedures (Fig. 2). In Group 1 the mean surface roughness value after scaling was 1.69 (Table 1). The "air polishing" procedure reduced this mean Ra value to 1.41 and the final Ra value after polishing with chalk was 1.20. In Group 2 the mean surface roughness value was 1.55 after sonic scaling. The Ra values after the pumice and chalk polishing procedures were 1.26 and 1.10 respectively (Table 1). While the sonic scaling procedure was performed in a facio-lingual direction, the profilometric measurements were obtained along the direction of scaling as well as perpendicular to it. The mean Ra value measured along the direction of scaling was 1.73 (median 1.71; minimum, 0.98; maximum, 2.54), while the corresponding value measured perpendicular to this direction was 1.51 (median 1.51; minimum, 0.90; maximum, 2.44). This difference was statis-
tically significant (P < 0.05). According to the experimental criteria, the sonic scaling ceased when the test surface seemed smooth and clean by visual inspection. The time needed to achieve this result ranged from 42 to 100 seconds. The Rank correlation coefficient comparing scaling time and the resulting mean surface roughness value was —0.153. Accordingly, only a minor reduction in roughness could be obtained with increased scaling time. DISCUSSION This study was initiated to provide scientific guidelines for the clinical performance of cleaning and polishing procedures. Thus, the polishing effects of pumice and chalk were compared to air polishing and chalk. A conflict of interest may exist between therapist and patient in selecting the appropriate tools. The operator wants to perform this treatment quickly. The patient, however, is more concerned about the possibility of root abrasion and sensitivity.25 Extensive loss of tooth substance may represent a potential risk for discomfort and even root fracture. In the present study, an in vitro model was employed in order to facilitate the standardization of the experimental conditions. Comparable test areas were provided and ac-
LIE
661
evaluating methods applied.8'26'27 The cleaning was performed under ideal conditions with direct access to the curate
test surfaces. These
aspects have to be considered when clinical consequences of the study are drawn. Not surprisingly, sonic scaled root surfaces exhibited substantial roughness. In studies by Lie and Leknes10 and Jotikasthira et al.,11 the sonic scaling roughness was graded by the Roughness Loss of Tooth Substance Index (RLTSI), giving mean scores of 1.34 and 1.60 respectively. The frequency of vibration of the sonic scaling tip is in the range of 16 to 18 kHz. According to Gankerseer and Walmsley,28 the pattern of oscillation of the tip was found to be elliptical with the long diameter of the ellipse at 60° to the axis of the instrument and with maximum effect in the transverse direction. This oscillation pattern combined with a lower vibration frequency may explain the lower Ra values recorded when the stylus was running perpendicular to the scaling direction. An equal smoothing effect was obtained on sonic-scaled surface roughness after polishing with air flow or with pumice for 5 seconds. Reports concerning the effect of this dental air-polishing device have stated that some loss of tooth substance does occur,18*20'29-30 but the treated root surfaces were shown to be surprisingly smooth.18,21 Our findings confirmed these observations. A substantial smoothing effect was achieved, but no information about loss of tooth substance can be obtained with this evaluation
procedure.
The test areas were exposed to each polishing device for 5 seconds. The mean time to remove stain by an air-powder "abrasive system" was calculated by Berkstein et al.20 to 3.23 seconds per root surface per treatment. Other studies have tried to estimate an appropriate exposure time both for a single treatment29 and for a patient maintained on a 3month recall for 15 years.18 Based on these calculations, an exposure time of 5 seconds seemed reasonable. Chalk mixed with water gives a very fine and low abrasive paste. Its relative hardness on the Mohs scale is much lower than for pumice.31 Eide and Tveit26 reported that coarse and fine pastes resulted in the same degree of surface roughness when polishing amalgam. In the present study, however, polishing with chalk subsequent to polishing with pumice significantly reduced the surface roughness. This may indicate that root surfaces are more susceptible to abrasion than amalgam. Only a weak negative correlation was found when sonic scaling time and mean surface roughness values were compared. By increasing the instrumentation time, a more complete removal of calculus may be achieved, giving a smoother root surface. On the other hand, extensive scaling may cause more iatrogenic related roughness. However, residual subgingival calculus will probably have a more detrimental effect on periodontal health than roughness from instrumentation. This study has demonstrated that polishing can reduce sonic scaling root surface roughness and this effect is ob-
662
J Periodontol November 1991
EFFECT OF POLISHING ON SONIC SCALED ROOTS
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tainable with different polishing procedures. The profilometer does not have the capacity to distinguish between "positive" and "negative" roughness or to measure loss of tooth substance. Consequently, further studies should be initiated to compare the loss of tooth substance and the effect on residual calculus of such procedures and to evaluate the clinical consequences of roughness in the marginal root surface area.
12. Leitäo
Acknowledgments
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The authors are grateful to Dr. N.R. Gjerdet for guiding the profilometric measurements, to Julie Cranfill for secretarial assistance, and to Frigg B. Sellevoll for data
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Send reprint requests to Dr. Knut . Leknes, Department of Periodontology, School of Dentistry, Ârstadveien 17, N-5009 Bergen, Norway. Accepted for publication May 31, 1991.
