Elastomeric Ligatures Research Articles

Does the bracket–ligature combination affect the amount of orthodontic space closure over three months? A randomized controlled trial

Objective: To investigate the effect of bracket–ligature combination on the amount of orthodontic space closure over three months.Design: Randomized clinical trial with three parallel groups.Setting: A hospital orthodontic department (Chesterfield Royal Hospital, UK).Participants: Forty-five patients requiring upper first premolar extractions.Methods: Informed consent was obtained and participants were randomly allocated into one of three groups: (1) conventional pre-adjusted edgewise brackets and elastomeric ligatures; (2) conventional pre-adjusted edgewise brackets and Super Slick® low friction elastomeric ligatures; (3) Damon 3MX® passive self-ligating brackets. Space closure was undertaken on 0·019×0·025-inch stainless steel archwires with nickel–titanium coil springs. Participants were recalled at four weekly intervals. Upper alginate impressions were taken at each visit (maximum three). The primary outcome measure was the mean amount of space closure in a 3-month period.Results: A one-way ANOVA was undertaken [dependent variable: mean space closure (mm); independent variable: group allocation]. The amount of space closure was very similar between the three groups (1 mm per 28 days); however, there was a wide variation in the rate of space closure between individuals. The differences in the amount of space closure over three months between the three groups was very small and non-significant (P = 0·718).Conclusion: The hypothesis that reducing friction by modifying the bracket/ligature interface increases the rate of space closure was not supported. The major determinant of orthodontic tooth movement is probably the individual patient response.

Superficial morphology and mechanical properties of in vivo aged orthodontic ligatures

The degradation of elastic ligatures in the oral environment results in the need of periodic replacement to maintain the optimal force during the orthodontic treatment. The purpose of this study was to perform a clinical prospective randomized study of the degradation of orthodontic elastomeric ligatures in the oral environment by scanning electron microscopy (SEM) and tensile strength test. Two hundred elastic ligatures were randomly selected and placed around the brackets of 5 volunteers and removed in groups of 10, at different times (1, 2, 3, and 4 weeks). The control group was performed by another fifty ligatures which were not submitted to the oral degradation. The analyses were done by scanning electron microscopy (SEM) and strength mechanical test. The tensile strength test results showed reduction in the ultimate strength values after four weeks ageing in the oral environment and no statistical difference in the yield strength values (p < 0.05). The orthodontic elastomeric ligatures surface was significantly degraded in the oral cavity after four weeks. The elastomeric degradation began in the first week when the increase in the roughness could be detected just in some areas. Afterwards, the surface became gradually rougher and, after 4 weeks, it was totally rough with some crack areas. The elastic ligatures aged in the oral environment showed higher superficial degradation and lower loss of mechanical properties after the maximum experimental period.

Frictional resistance in monocrystalline ceramic brackets with conventional and nonconventional elastomeric ligatures

BackgroundThe objective of this study was to compare the frictional forces generated by three types of monocrystalline ceramic brackets coupled with conventional elastomeric ligatures (CEL) and nonconventional elastomeric ligatures (NCEL) during the alignment of apically displaced teeth at the maxillary arch.MethodsAll tests (a total of 480 tests) were carried out in a dry state on a universal testing machine with a testing model consisting of three 0.022-in. monocrystalline ceramic preadjusted brackets (from the maxillary right second premolar through the right central incisor). The canine bracket was bonded to a sliding bar that allowed for different vertical positions. The frictional forces generated by a 0.012- and 0.014-in. superelastic nickel titanium wire (SENT) with conventional and nonconventional ligatures at various amounts of canine misalignment (1.5, 3.0, 4.5, and 6.0 mm) were recorded. Comparisons between the different types of bracket-wire-ligature systems were carried out by means of analysis of variance on ranks with Tukey's post hoc test (P < 0.05).ResultsNo significant differences were assessed among the three types of monocrystalline brackets with NCEL when coupled with 0.012-in. SENT. Radiance brackets with NCEL coupled with 0.014-in. SENT showed significantly greater frictional force than Inspire Ice brackets and Pure brackets with NCEL. A significantly greater amount of frictional force was generated with CEL when compared with NCEL for all the tested variables, with the exception of the Pure brackets with 0.012-in. SENT at 1.5 and 3.0 mm of canine misalignment where similar frictional forces were found.ConclusionsNonconventional elastomeric ligatures are able to reduce friction in monocrystalline ceramic brackets.

Effect of elastomeric ligatures on frictional forces between the archwire and orthodontic bracket

Aim: To evaluate the frictional force between the archwire and orthodontic bracket generated by elastomeric ligatures with polymer coating (Super slick, TP Orthodontics) and conventional ligatures (Morelli) using two types of insertion techniques. Methods: Forty elastomeric ligatures, 20 with polymer coating and 20 conventional, were evaluated. Each type of ligature was separated into two groups (n=10), according to the insertion mode: conventional or crossed (from mesial to distal region crossed in front). To analyze friction, 40 5-cm-long segments of stainless steel orthodontic archwire 0.019 x 0.025 (Morelli) and Edgewise brackets (slot 0.022 x 0.028; Morelli) were used. Each set (bracket, wire and elastic) was submitted to frictional testing in a universal test machine (Instron 4411) at a crosshead speed of 5 mm/min. Each bracket was moved 5 mm on the wire, with maximum friction and mean friction being recorded by software. Three readouts were taken for each bracket. Data were submitted to two-way ANOVA and Tukey’s test (p<0.05). Results: It was shown that for maximum and mean friction, the polymer-coated ligature did not differ statistically from the conventional type in a dry environment condition. Ligatures placed in crossed mode promoted significantly greater friction than those placed in conventional mode, irrespective of the type of elastomeric ligature. Conclusions: Friction depended on the insertion mode, but not on the type of elastomeric ligature.

Evaluation of the susceptibility to pigmentation of orthodontic esthetic elastomeric ligatures

The purpose of this laboratory study was to evaluate changes in the pigmentation of esthetic elastomeric ligatures after immersion in a staining solution. Sixty ligatures were selected and divided into 12 groups according to their brand and also considering their condition, i.e., unstretched or stretched. The groups were divided into: Morelli (clear), TP Orthodontics (clear), American Orthodontics (clear), 3M/Unitek (clear), American Orthodontics (pearl color) and 3M/Unitek (pearl color), separated in groups of 5 unstretched and 5 stretched ligatures. Assessment of their color changes was performed by means of digital photograph and computer analysis using Adobe Photoshop. Standardized digital photographs were taken at T₀ (before the staining process, with unstretched ligatures) and at T₁ (following the 5-days staining process). The staining solution was composed of artificial saliva and foods with staining potential. At T₁ the ligatures were either stretched or unstretched. The results of this study showed that esthetic elastomeric ligatures are prone to staining. Among the evaluated brands, TP Orthodontics and American Orthodontics clear ligatures were the most stable. Moreover, 3M/Unitek pearl ligatures demonstrated statistically significant changes in all variables. Esthetic elastomeric ligatures are susceptible to staining and no statistically significant difference was found between unstretched or stretched ligatures, with the sole exception of the TP Orthodontics brand. The 3M/Unitek's pearl color ligatures displayed the greatest staining potential.

TRADITIONAL ELASTIC LIGATURES VERSUS SLIDE LIGATION SYSTEM. A MORPHOLOGICAL EVALUATION

Elastomeric materials play an important role in the orthodontic practice, including the retraction force to move teeth into extraction sites, closing diastemas, selective shifting of the midline and generalized space closure. Frictional resistance and ligating strength of archwire-bracket-ligature complex occurs during utilization of elastomeric and metallic ligatures when orthodontic forces are applicated. The aim of this study was to analyze elastic deformation of three types of elastomeric ligatures, after clinical use. ELASTOMERIC LIGATURES: ring-shape, transparent, latex ligatures (Leone® S.p.A.), ring-shape, grey, polyurethane ligatures (Micerium® S.p.A.) and grey, polyurethane, Slide low-friction ligatures (Leone® S.p.A.). A total of 9 orthodontic patients undergoing fixed orthodontic therapy were selected. Three specimens were applied, one for each types of ligature, inside the oral cavity of each subject. Samples were kept in the oral cavity for 28 days, ligating 0.16 X 0.22 inches stainless steel archwires to stainless steel premolars brackets (Leone® S.p.A., Sesto Fiorentino, FI, Italy) for Bidimensional technique. After the pre-established time, the systems of ligature were removed and washed. Control group consisted of 9 unused specimens of each ligation type. Each elastomeric ligature was observed under the scanning electron microscope (SEM) to determine variations in size. The archwire-bracket-ligature complex was also analyzed. Transparent O-ring ligatures showed significant volumetric and structural changes. The external rounded shape was rather maintained, while the internal shape tended to appear square. Both external and internal diameter significantly increased (p<0.005 and p<0.0001 respectively) while the thickness decreased ( p<0,005) when analyzed with t-test. Polyurethane ring-shape ligatures retained the initial ring design. Both external and internal diameter increased (p<0.0001), while the thickness remained almost unchanged. The internal border was more squared, and showed jagged edges with continuous and irregular extroversions. Grey, polyurethane Slide low-friction ligatures showed a reduced dimensional change. There was a slight increase in two dimensions, length and width, (14-16%) (p<0.05 and p<0.001) while there was a not significant decrease in thickness (10%). From SEM analysis of ligature morphology it emerges that latex and polyurethane O-ring ligatures endure significant volumetric and structural changes, after clinical use, index of a greater degree of friction and early loss in functionality. Grey, polyurethane Slide low-friction ligatures presented limited variation in size after clinical use.

Microbial colonization around orthodontic ligature ties: An in-vivo study

Introduction: Fixed or removable orthodontic appliances impede oral hygiene and result in plaque accumulation. Studies have evaluated the effects of fixed orthodontic appliances on microbial flora and periodontal status, but only a few have evaluated the method of ligation as an additional factor. Aims and Objectives: To determine the amount of microbial colonization with different elastomeric ligation techniques. Material and Methods: Twenty subjects and a total of five ligature systems divided into five groups were chosen for the split mouth study. Group II and III (super slick ties and slide ligatures) were ligated over the premolars on the right side while Group IV and V (quick stick ties - angulated and easy to fit ties) were ligated over the premolars on the left side in both the arches. Group I (control) or stainless steel ties were made over the cuspids in the same manner. Elastomeric ligatures were removed after a period of 21 days and sent for culture. The amount of microbial colonies was then compared using stereomicroscope. Results: The amount of microbial colonization observed was statistically significant ( P Conclusion: Super slick elastomeric ligatures were found to have minimal microbial adhesion similar to that of stainless steel.

In vivo color changes of esthetic orthodontic ligatures

OBJECTIVE: To assess the color changes that occur in four commercial brands of esthetic orthodontic elastomeric ligatures after exposure to the oral environment. METHODS: The four elastomeric ligatures manufacturers mostly mentioned by orthodontists were investigated: Morelli, Uniden, American Orthodontics (AO) and TP. The sample comprised 25 patients. The elastomeric ligatures were randomly distributed and arranged in the four dental quadrants of each patient, r for 30 days. After this period, two units of each brand were photographed in a standardized manner. Subsequently, color changes were visually evaluated and assigned a score (0, 1, 2 or 3) by a panel of four examiners. The mean scores assigned by the examiners were statistically analyzed by ANOVA and Tukey's test (p &lt; 0.05). RESULTS: The mean pigmentation scores assigned to Morelli (1.80 ± 0.78) and Uniden (1.92 ± 0.66) elastomeric ligatures after 30 days in the oral environment were not statistically different. However, these brands were significantly more pigmented after 30 days in the oral environment (p &lt; 0.01) compared to American Orthodontics (0.97 ± 0.6) and TP (0.83 ± 0.79). CONCLUSIONS: Although all four brands exhibited an undesirable pigmentation after 30 days in the oral environment, color change for American Orthodontics and TP Orthodontics ligatures was significantly lower than Morelli and Uniden products.

Assessment of surface friction of self-ligating brackets under conditions of angulated traction

OBJECTIVE: The aim of this study was to assess resistance to sliding of stainless steel passive self-ligating brackets with 0° and 2.5° angulations and to compare them to active self-ligating brackets at zero angulation. The hypothesis to be tested was that passive self-ligating brackets produce lower frictional forces than active self-ligating brackets. METHODS: Twenty five 0.022 x 0.028-in slot maxillary canine brackets were divided into 5 groups of 5 brackets: Damon SL II (Ormco, CA, USA) self-ligating bracket and Gemini (3M/Unitek, CA, USA) conventional bracket with angulation of 0 and 2.5° and a group of Speed 2 (American Orthodontics, WI, USA) active clip self-ligating system with zero angulation. Twenty five segments of stainless steel 0.020-in archwire (TP Orthodontics, IN, USA) were tested and each bracket/wire interface was evaluated at 4 successive points during sliding. Overall, 100 frictional values were analyzed by parametric analysis of variance and Bonferroni tests. RESULTS AND CONCLUSION: Frictional tests were performed with an Emic DL 10000 testing machine (Emic, Brazil) with a load cell of one kilogram. Passive self-ligating brackets produced lower frictional forces than active self-ligating brackets (p &lt; 0.01). Under angulation, brackets with a slide mechanism produced higher friction than the same brackets under zero angulation (p &lt; 0.01). Nevertheless, the slide system under angulation produced smaller friction values than conventional brackets tied with elastomeric ligatures in 0° tests.

Comparative study of frictional forces generated by NiTi archwire deformation in different orthodontic brackets: In vitro evaluation

INTRODUCTION: The purpose of this study was to compare the frictional forces between 0.014-in NiTi wires (Aditek) with 4 mm horizontal deflection and brackets with different archwire ligation systems. METHODS: Four types of self-ligating brackets (Damon MX, Easy Clip, Smart Clip and In-Ovation), a triple bracket (Synergy) and a twin bracket with 8-shaped ligature (Tecnident) were tested. Twin brackets with conventional elastomeric ligatures (Morelli) were used as control group. Tests were repeated 10 times for each bracket/archwire combination. Frictional forces were measured in an Instron universal tensile machine at 3 mm/minute speed and a total displacement of 6 mm. Statistical analysis comprised ANOVA and Dunnett's multiple comparison post hoc test. RESULTS: Deflection-induced frictional (DIF) forces increased in the following order: Synergy, Damon, 8-shaped Ligature, Easy Clip, In-Ovation, Smart-Clip and conventional ligatures. The differences among groups were significant, with the exception of the 8-shaped ligature groups which was equal to the Damon and Easy Clip groups. CONCLUSIONS: Compared to conventional ligatures, all ligation systems tested reduced frictional forces. However, such reduction varied according to the ligation system employed.

Self-ligating brackets in orthodontics: current concepts and techniques (2011)

Self-ligating brackets in orthodontics: current concepts and techniques (2011) Editors: Bjoern Ludwig, Dirk Bister, and Sebastian Baumgaertel Publisher: Thieme Price: ₤163.99 ISBN: 978-3131547019 Self-ligating bracket systems are not a new concept, but they have gained a lot of popularity and are now widely accepted. Self-ligating brackets eliminate the use of steel or elastomeric ligatures. Manufactures claim that this system reduces the friction between the bracket and the wire and consequently provides more efficient tooth movement. However, the efficiency and effectiveness of self-ligating brackets are still controversial. This textbook provides extensive information about current concepts on the clinical use of self-ligating brackets with a series of references. The book contains nine chapters divided into two main …

In vitro study of cytotoxicity of orthodontic elastomeric ligatures

This study investigated the cytotoxicity of crystal-coloured orthodontic elastomeric ligatures of polyurethane. Six ligatures from distinct manufactures were divided into 6 groups of 10 elastics each: Groups P1, P2, P3, P4, P5 and P6 (Polyurethane). The cytotoxicity essay was performed using L-929 line cells, which were submitted to the cell viability test with neutral red (dye-uptake) at time intervals of 1, 2, 3, 7 and 28 days. Analysis of variance (ANOVA) with multiple comparisons and Tukey's test were used (p < .05). There were statistical differences (p < .05) in cell viability between Groups P1, P4, P2 and P3, and Groups P5 and P6 at 1 and 2 days. All elastomeric ligatures were considered suitable for clinical use. The hypothesis was accepted, the P5 and P6 elastomers and the processing route of injection molding for these ligatures showed the lowest cell viability, due the temperature and pressure distinct in the processing of these elastomers.

Comparative study of classic friction among different archwire ligation systems

OBJECTIVE: To describe and compare three alternative methods for controlling classical friction: Self-ligating brackets (SLB), special brackets (SB) and special elastomeric ligatures (SEB). METHODS: The study compared Damon MX, Smart Clip, In-Ovation and Easy Clip self-ligating bracket systems, the special Synergy brackets and Morelli's twin bracket with special 8-shaped elastomeric ligatures. New and used Morelli brackets with new and used elastomeric ligatures were used as control. All brackets had 0.022 x 0.028-in slots. 0.014-in nickel-titanium and stainless steel 0.019 x 0.025-in wires were tied to first premolar steel brackets using each archwire ligation method and pulled by an Instron machine at a speed of 0.5 mm/minute. Prior to the mechanical tests the absence of binding in the device was ruled out. Statistical analysis consisted of the Kruskal-Wallis test and multiple non-parametric analyses at a 1% significance level. RESULTS: When a 0.014-in archwire was employed, all ligation methods exhibited classical friction forces close to zero, except Morelli brackets with new and old elastomeric ligatures, which displayed 64 and 44 centiNewtons, respectively. When a 0.019 x 0.025-in archwire was employed, all ligation methods exhibited values close to zero, except the In-Ovation brackets, which yielded 45 cN, and the Morelli brackets with new and old elastomeric ligatures, which displayed 82 and 49 centiNewtons, respectively. CONCLUSIONS: Damon MX, Easy Clip, Smart Clip, Synergy bracket systems and 8-shaped ligatures proved to be equally effective alternatives for controlling classical friction using 0.014-in nickel-titanium archwires and 0.019 x 0.025-in steel archwires, while the In-Ovation was efficient with 0.014-in archwires but with 0.019 x 0.025-in archwires it exhibited friction that was similar to conventional brackets with used elastomeric ligatures.

Pigment effect on the long term elasticity of elastomeric ligatures

OBJECTIVE: To evaluate the response of elastomeric ligatures in several colors for a 4 mm traction over time. METHODS: Morelli® elastomeric ligatures, were submitted to traction forces using two rods of circular cross section, until a 4 mm distance was reached, matching the approximate diameter of an upper central incisor bracket of the same manufacturer. The ligatures were kept in artificial saliva immersion at 37 ºC. Forces levels were measured immediately (0 h), 2, 4, 6, 8, 10, 12, 24, 48, 72, 96 hours, 1, 2, 3, 4 weeks and results were submitted to two-way repeated-measures ANOVA statistical analysis. RESULTS: The gray samples showed the higher initial values of tensile strength. The lowest values were presented by purple, light pink, green, black and red groups. The greater tensile strength instability was presented by red, black, silver, green and gray groups. The greater tensile strength stability was presented by deep pink, dark blue, blue, purple and light pink groups. CONCLUSION: Elastomeric ligatures do not present stable behavior when suffering traction forces over time and different colors display different behaviors. Deep pink, dark blue, blue, purple and light pink groups, displayed the most stable forces, suggesting that they should be used during the treatment to obtain constant forces.

Clinical efficiency of nonconventional elastomeric ligatures in the canine retraction phase of preadjusted edgewise appliance therapy: An in-vivo study

Various ligation techniques and materials have been shown to affect the frictional resistance and the rate of tooth movement with sliding mechanics for space closure. The aim of this study was to evaluate the clinical efficiency of nonconventional elastomeric ligatures and conventional elastomeric ligatures during the canine retraction phase by comparing the rates of canine retraction. The 20 patients (12 female, 8 male) in our sample had individual canine retraction (in the first premolar extraction space) in each quadrant (2 maxillary, 2 mandibular) with nonconventional elastomeric ligatures and conventional elastomeric ligatures on either side of the arch. The amount of canine retraction in each interval of 1 month was determined. The rate of canine retraction was calculated and subjected to statistical calculations. The rates of canine retraction were higher with the nonconventional elastomeric ligatures. However, no statistically significant difference was observed in relation to the maxillary arch. Clinically, in most instances, canine retraction was completed in the same interval in both groups. No significant difference in the rate of canine retraction was observed between the nonconventional elastomeric ligature and conventional elastomeric ligature groups in the maxillary arch. Clinically, the nonconventional elastomeric ligature group showed no reduction in time required for complete canine retraction in the maxillary and mandibular arches.

Evaluation about Antimicrobical Activity of Silver in Orthoshield Safe-T-Tie® Ligatures Used in Orthodontic Patients

Purpose: to value efficacy of anti microbic propriety of silver ligatures Orthoshield Safe-T-Tie® on periodontal tissues in orthodontic patients. Materials and methods: 50 orthodontic patients between 11 and 20 years old with permanent teeth were selected in this study. We evaluated periodontal health of maxillary and mandibular lateral incisors and canines at TO before the substitution of elastomeric ligatures with Orthoshield Safe-T-Tie® ligatures and at T1 (one month after substitution of ligatures). We used PI (Periodontal Index), GI (Gingival Index) and PRC-real-time to analyze periodontal health. Results: there was an improvement of gingival inflammation and a reduction of periodontal pathogens. Conclusions: Orthoshield Safe-T-Tie® ligatures improve periodontal health in orthodontic patients.

In vitroevaluation of resistance to sliding in self-ligating and conventional bracket systems during dental alignment

ObjectiveTo investigate the resistance to sliding (RS) in self-ligating and conventional ligation bracket systems at 5 different second-order bracket angulations by using low-stiffness alignment wires in a 3-bracket experimental model and to verify the performance of the main RS components in both systems when these wires are used.MethodsInteractive self-ligating brackets with closed and open slides were used for the self-ligating (SL) and conventional ligation (CL) groups, respectively; elastomeric ligatures (1 mm inner diameter) were used in the latter system. The alignment wire used was 0.014 inch heat-activated NiTi (austenitic finish temperature set at 36℃ by the manufacturer). A custom-made testing machine was used to measure frictional resistance. Tests were repeated 5 times at every angulation simulated. All data were analyzed statistically.ResultsThe RS increased significantly with increasing angulation in both SL and CL groups (p < 0.0001). However, the RS values were significantly higher at every angulation (p < 0.0001) in the CL group.ConclusionsDespite the relevance of the binding phenomenon, ligation forces predominantly affect the RS when low-stiffness alignment wires are used.

Frictional Properties of Self-Ligating Brackets and Low-Friction Ligatures

Problem statement: To evaluate the frictional forces generated by five different orthodontic brackets when used in combination with stainless steel and NiTi archwires in dry conditions at physiological temperature. Approach: Five different types of maxillary canine brackets (Damon 3 MX, Step, Quick, Sprint, Mini Mono) with a slot size 0.022 inch were coupled with 0.016” and 0.019”×0.025” stainless steel and with 0.016” and 0.018”×0.025” NiTi archwires. Step, Sprint and Mini Mono were used both with traditional ligatures and with Slide ligatures. A total of 320 archwires and brackets were used; ten tests were carried out for each group of bracket-wire combination at physiological temperature and in dry state. Frictional forces were measured by Instron Universal Testing Machine. The statistical significance level was established at P<0.05. Results: Damon 3 MX and Step brackets with Slide ligatures produced statistically lower friction than Quick and conventional brackets with elastomeric ligature. Frictional force increased proportionally to the wire size; NiTi archwires presented higher frictional resistance than stainless steel archwires. Slide ligatures showed lower fictional values in comparison with elastic ligatures. Conclusion: Stainless steel brackets with new Slide ligature show frictional forces similar to self-ligating brackets with passive clip.

Frictional resistance of orthodontic wires tied with 3 types of elastomeric ligatures

Frictional resistance of orthodontic wires tied with 3 types of elastomeric ligatures

Archwire cleaning after intraoral ageing: the effects on debris, roughness, and friction

Dental material science has paid more attention to mechanical properties of as-received materials than to changes produced after intraoral exposure. Orthodontic archwires when exposed to the intraoral environment have shown a significant increase in the degree of debris, surface roughness (Ra), and frictional force. The purpose of this split-mouth study was to evaluate the effects of two methods of archwire cleaning on these variables after clinical use for 8 weeks. For eight individuals, four sets of three brackets each (n = 32) were bonded from the first molar to the first premolar. A passive segment of 0.019 × 0.025 inch stainless steel (SS) archwire was inserted into the brackets and tied by elastomeric ligature. Debris level [via scanning electron microscopy (SEM)], Ra, and frictional force were evaluated in a paired comparison after 8 weeks of intraoral exposure and after cleaning with a steel wool sponge (SWS) for 1 minute or ultrasound (US) cleaning for 15 minutes. Kruskal-Wallis, Friedman's, and Spearman and Pearson correlation tests were used for statistical analysis. The debris and Ra of SS rectangular wires increased significantly (P < 0.05) during clinical use, causing a significant increase in the frictional force level. These changes can be effectively eliminated by either of the investigated cleaning methods, although a SWS seems to be clinically more practical.