in clinical practice , patients frequently ask their physicians about removable denture care , which is often insufficient and sometimes is absent altogether ) . a questionnaire - based survey was conducted at lithuanian university of health sciences ( luhs ) clinic of orthopedic odontology . the survey showed that patients most frequently used wet toothbrushes for the care of their dentures , with sodium chloride ( table salt ) , sodium hydrogen carbonate ( baking soda ) , or toothpaste  colgate total  applied as cleaning substances . the participants of the survey stated that they usually cleaned their dentures 3 times per day for 12 minutes each time . even though there are various denture care techniques such as disinfecting tablets , disinfection with microwaves or ozone [ 13 ] , or plaque removal with ultrasound , these techniques are not as common as toothbrush use is . patients do not realize that the use of cheap additional substances available in every household may damage their dentures . increasing rough surface area and the number of scratches result in multiple micro - retention zones that accumulate microorganisms and cause formation of dental calculi on the dentures . patients discontinue regular use of their dentures , and eventually they become ill - fitting . the aim of the study was to evaluate the possible damage to the dentures caused by denture care measures , and to develop recommendations concerning the care of removable dentures . plates with all the characteristics of removable denture bases were produced from heat - polymerized acrylic resin meliodent heat cure ( heraeus - kulzer , germany ) used for denture manufacturing ; the plates were produced following the polymerization regimen set by the manufacturer . polishing and buffing of the plates was carried out following the removable denture production standards ; the plates were then cut into 1.55 cm strips , which were numbered . following that , each strip was assigned hard- , medium- , or soft - bristled toothbrushes ( oral - b complete ) with additional cleaning substances . the following groups were formed : a wet medium - bristled toothbrush ; a wet medium - bristled toothbrush with toothpaste  colgate total  ; a wet medium - bristled toothbrush with crystalline sodium hydrogen carbonate ; a wet medium - bristled toothbrush with crystalline sodium chloride ; a wet soft - bristled toothbrush with toothpaste  colgate total  ; a wet hard - bristled toothbrush with toothpaste  colgate total  . reflection measurements of the plates were conducted prior to the testing and after 2 and 6 hours . a device imitating tooth brushing movements was constructed . within 1 minute it performed 100 reciprocal movements with the amplitude of 1.5 cm , and with 2.4 n pressure force of the toothbrush on the plate . the plates were monitored with a usb4000 ( oceanoptics ) spectrometer by measuring surface reflection in 2 wavelengths : 250400 nm  for small scratches , and 600800 nm  for large scratches . during the denture cleaning simulation , a new 0.5 g dose of the abrasive substance and 0.5 ml of water were reapplied on the plates every 10 minutes . the plates were placed in a holder under the spectrometer so that their measured areas would coincide . during each studied exposure , 708 automatic spectrometry measurements were performed at the wavelength of 250400 nm in each plate . every plate was examined prior to the simulation , and after 2 and 6 hours of testing . in total , the monitoring of each studied plate yielded 2124 reflection measurements of different points of the evaluated surface . at the wavelength of 600800 nm , 1075 spectrometry measurements were performed in each plate . in total , 3225 reflection measurements of different points of the evaluated surface were obtained from each studied plate after the simulation sequence . the evaluation of differences in plate surface reflection showed that all abrasive substances altered the reflection . evaluation of the mean values by applying the dispersion analysis , anova , and tukey s method showed no statistically significant difference between the results of the 5 tests ( p>0.05 ) . statistically significant ( p<0.05 ) changes were observed in all studied plates after the tooth brushing simulation ( table 1 ) . medium - bristle toothbrushes inflicted most damage when used with baking soda ( nahco3 )  they reduced the surface reflection by 4.820.1% . table salt inflicted the least damage when applied on a medium - bristle toothbrush  the surface reflection reduction was 3.50.16% ( figure 1 ) . when comparing the effect of toothbrushes with toothpaste (  colgate total  ) applied , the least damage was observed with a soft - bristled toothbrush  the surface reflection decreased by 3.010.12% ( p>0.05 ) . the most damage was inflicted with a hard - bristled toothbrush  the surface reflection reduction was 4.60.05% . when testing medium - bristle toothbrushes , the fewest small scratches were detected with the tested toothpaste  the surface reflection dropped by 2.70.11% . removable denture care has been actively researched for a number of years , yet the number of articles in the literature suitable for this study was scarce . more attention is usually paid to denture attrition , its mass reduction , or measurement of microgrooves left by toothbrushes . the results of our study were based on changes in plate surface reflection , indicating the general wear of the denture surface . other authors found no statistical difference between scratches inflicted by various toothbrushes on the surface of different heat polymerized acrylic resins . in our study , we used heat - polymerized acrylic resin , meliodent heat cure ( heraeus - kulzer , germany ) . this would mean that the results of the study should be irrespective of the manufacturer of the heat -polymerized acrylic resin . acording to some authors the main difference between artificial teeth and denture base materials is the incorporation of tooth - colored pigments rather than pink ones . the vickers hardness number ( vhn ) of both materials is 20 . because there is no difference in the hardness , there were no tests conducted to test the acrylic teeth wear caused by the toothbrush . the technique of this study was based on the questionnaire survey data concerning the most common hygienic denture care techniques used by 110 patients with removable dentures . the study simulated all variants of the additional substances used in the cleaning of dentures , taking into account the most common use of medium - bristle toothbrushes . toothpaste for denture cleaning . to evaluate the effect of toothbrushes with different brush head types on the surface of the acrylic resin , soft - bristled and hard - bristled toothbrushes were used in the test with toothpaste . when constructing the device that imitated tooth brushing , we tried to reproduce the actual movements of the toothbrush in the oral cavity , thus the rotational movement ( which causes grater surface changes ) the toothbrush was pressed against the surface with a force of 2.4 n ; the selection of such force was based of the mean value of the force most frequently applied during tooth brushing . the toothbrush movement speed ( 50 mm / s ) was selected on the basis of in vivo studies , where it ranged between 30 and 150 mm / s . the results of our study confirmed that baking soda has stronger abrasive characteristics compared to table salt , although both substances are of equal hardness according to the mohs scale  2.5 . this is associated with the crystal structure and a better solubility of nacl in water ( 35.89 g/100 g water at 20c ) , compared to nahco3 ( 9.6 g/100 g water at 20c ) . the residual amount of undissolved crystals causes changes in the surface of the acrylic resin . we also noticed that table salt was rather aggressive during the first 2 hours , but later on its abrasiveness dropped due to the dissolution and consequent shrinking of its sharp crystals . in other words , more rounded crystals moved between the bristles of the toothbrush and the surface of the plate , thus reducing the abrasiveness of table salt . in removable denture care , all mechanical cleaning techniques that involve toothbrush use have a negative effect on the denture base surface , yet the use of chemical measures alone is insufficient . when using toothpaste , hard - bristled toothbrushes cause the greatest surface damage . the usage of baking soda is not recommended for removable denture care .
bakcgroundthe aim of this study was to evaluate the effect of substances used for hygienic cleaning of dentures on the surface of the denture base material.material/methodsmeliodent heat cure ( heraeus - kulzer , germany ) heat - polymerized acrylic resin was used to produce plates with all the characteristics of removable denture bases ( subsequently ,  plates  ) . 
 oral - b complete toothbrushes of various brush head types were fixed to a device that imitated tooth brushing movements ; table salt and baking soda ( frequently used by patients to improve tooth brushing results ) , toothpaste (  colgate total  ) , and water were also applied . 
 changes in plate surfaces were monitored by measuring surface reflection alterations on spectrometry . 
 measurements were conducted before the cleaning and at 2 and 6 hours after cleaning.resultsno statistically significant differences were found between the 3 test series . 
 all 3 plates used in the study underwent statistically significant ( p<0.05changed )  the reflection became poorer . 
 the plates were most affected by the medium - bristle toothbrush with baking soda 
 the total reflection reduction was 4.820.1% ; among toothbrushes with toothpaste , the hard - type toothbrush had the greatest reflection - reducing effect 
 4.60.05% , while the toothbrush with table salt inflicted the least damage ( 3.5  0.16% ) due to the presence of rounded crystals between the bristles and the resin surface . 
 toothbrushes with water had a uniform negative effect on the plate surface 
 3.890.07%.conclusionsall substances used by the patients caused surface abrasion of the denture base material , which reduced the reflection ; a hard toothbrush with toothpaste had the greatest abrasive effect , while soft toothbrushes inflicted the least damage .