the oral rehabilitation of patients with implants requires the placement of stable 
 prostheses enabling security , comfort and longevity to treatment .
the beginning of the 
 construction of prosthetic treatment requires the faithful reproduction of the working 
 cast of the situation found in mouth , to reduce the errors inherent to this 
 stage .
numerous studies have tried to find the " perfect " fit between prosthetic 
 components and the implant .
however , the variables found in the steps of the clinical 
 and laboratory procedures involved in the fabrication prostheses become an obstacle in 
 the search for a perfect fit , leading 
 to errors that make it impossible to obtain a dental implant with a perfect framework 
 fit . during the production stages of a cast , some processes may influence the correct 
 analogue position of the working cast , increasing the chances of distortion and misfit 
 of the final prosthesis .
the casting 
 material used , the casting 
 technique and the casting 
 impression conditions are factors that can influence the accurate reproduction of the 
 clinical situation .
another important aspect to be considered is the step of sending the molds to the 
 laboratory .
a study by christensen 
 ( 1997 ) demonstrated that most jobs ready to be poured with gypsum were deficient in some 
 aspect .
the 
 literature , although large 
 and concerned with the techniques and impression materials , is scarce when dealing with 
 the variables of everyday practice .
a small number of studies focused on the influence 
 of factors such as casting of the plaster cast or the technique for casting on dimensional changes of the 
 casts . in an attempt to minimize distortions in the procedures for obtaining a working cast , 

improve the accuracy of implant prostheses and assist dentists , we developed a small , 
 silent and portable vibrator .
we hypothesized that this device would be able to reduce 
 the vibration generated by conventional devices , thus leading to fewer changes in the 
 working cast , better adaptation between the cylinders of implant - supported dentures and 
 their respective analogues .
this would result in a more faithful copy of the situation 
 in the mouth , with minimal bubbles and dimensional change in the working cast .
the purposes of this study were to test the technique of casting plaster using this 
 portable vibrator device , comparing it with conventional methods , and to evaluate the 
 influence of this device on the position of implant analogue working casts .
a master acrylic resin template ( palaton - dencril , pirassununga , sp , brazil ) of a class 
 iv edentulous maxillary arch , with two external hexagonal implants  3.75x11 mm ( master 
 screw ; conexo sistemas de prteses , so paulo , sp , brazil ) positioned in the region of 
 the maxillary right lateral incisor ( a ) and maxillary left lateral incisor ( b ) was 
 manufactured for the study design ( figure 1 ) .
two 
 abutments ( micro - unit ; conexo sistemas de prteses , aruj , sp , brazil ) were installed 
 by manual ratchet key until a torque of 20 n.cm was produced according to the 
 manufacturer 's directions and 30 transfer moldings were made with open trays .
this cast 
 was then randomly divided into three groups , depending on the plaster casting 
 technique : step - by - step fabrication of the portable device designed to casting plaster ( a ) : 
 electric toothbrush ; ( b ) : bristles of the brush removed ; ( c ) : hole on tip of the 
 toothbrush in place of the bristles ; ( d ) : installation of the tip of a brush on 
 the opposite side of the bristles and ( e ) : portable vibrator ready group i ( gi):pouring performed at an outsourced dental laboratory with conventional 
 plaster vibrator ( 10 casts ) ; group ii ( gii):pouring performed at ufsc laboratory with conventional plaster vibrator 
 ( 10 casts ) ; group iii ( giii ) : pouring performed with the portable vibrator fabricated for this study 
 ( 10 casts ) . to make the impressions , standard size ( no .
3 ) perforated plastic trays were used ( jg , 
 jon , so paulo , sp , brazil ) , with an opening at the top of two holes designed for the 
 removal of screws for transferring squares .
the material of choice for the impression 
 was polyvinyl siloxane ( pvs ) ( express xt silicone addition , 3 m espe , usa ) and manipulation was done by the single 
 step double impression technique .
the transfer copings were screwed in 
 their abutments in the master cast and splinted together with a metal rod and acrylic 
 pattern resin ( trim plus red - acrylic pattern ; harry j. bosworth company , skokie , il , 
 usa ) , reducing the distortion 
 of polymerization .
after 10 min of union with transferring acrylic resin , heavy - body pvs 
 was handled according to the manufacturer 's instructions and the tray was loaded with 
 the material , while light - body pvs was injected into the region of the implants and 
 their components . to standardize the molding , heavy - body pvs
was measured in a plastic 
 syringe injector for elastomer ( jon ) filled with slurry by cast .
setting of the dummy 
 tray was held constant with manual pressure until it clicked into a reference point 
 located on the mannequin , then held in position for 10 min to complete polymerization of 
 the material .
all impressions were made in the same temperature - controlled air 
 conditioning between 18c and 22c .
after the mold was ready , the transfer copings were 
 loosened to remove the impression and screwed to the respective analogues of the 
 abutments ( conexo sistemas de prteses ) . for all transfer copings
a torque of 10 n.cm 
 was applied manually with a keyed ratchet ( conexo sistemas de prteses ) , but the 
 placement of analogues was performed with a digital grip , because the torque applied by 
 a 10 n.cm ratchet could cause rotation of the transferor pvs .
adaptation of 
 impressions prior to the tightening grip and digital analogue was again verified by the 
 transferor with explorer no .
when the impressions were ready , with the union of the analogues , they were randomly 
 assigned to groups according to the technique of casting plaster .
the 30 plaster casts 
 used microgranulated special type iv plaster ( durone , dentisply , petrpolis , rj , 
 brazil ) , and pouring was conducted in an area for at least 60 min and at most 3 days 
 after the order was ready . for casting plaster of group iii , we developed a portable vibrator made from an 
 electric toothbrush ( 360 sonic power , colgate palmolive ind .
the bristles of the brush were removed using a carborundum disk - type cutter 
 and maxi - cut , and a hole in the place of the bristles was made for installation of 
 the tip of a brush on the opposite side ( round marta brush tropical 006 , tigre , so 
 paulo , sp , brazil ) , maintaining a slight inclination toward the end to facilitate 
 placement of the plaster inside the impression ( figure 
 1 ) .
ten impressions were sent to the outsourced laboratory , in a routine procedure for 
 work on prosthetic implants . along with the impressions ,
an order tab was included 
 with the request for plaster casting of special type iv , for a minimum 
 standardization with the other groups .
the casts of groups ii and iii were poured with 100 g of powder type iv gypsum , 
 proportioned to 22 ml of water and hand - mixed for 60 s. insertion of 
 the plaster cast was performed according to the technique assigned to each group , 
 with group ii using the leaked vibrator with conventional casting and group iii with 
 the portable vibrator . after a period of at least 1 h of setting time for the 
 plaster , the working casts were removed from the mold .
all casts were stored at room 
 temperature for at least 92 h before assessment of misfit . to standardize the samples , all steps of molding , 
 tooling , and casting of plaster
were made by the researcher in charge , while handling 
 the pvs was done by an assistant operator .
verification of the accuracy of the position of analogues and comparison between 
 groups was performed to develop an infrastructure ( ie ) from two metal cylinders of 
 titanium abutment micro - unit , bolted to the abutment of the master cast ( mc ) and 
 joined together by a titanium bar and laser welding . to calculate the misfit of the casts and make comparisons between groups , we measured 
 the vertical misfit of ie in the mc to verify the reliability of the adaptation and 
 the value of the initial ie misfit .
then , the evaluations also were carried out in testing casts 
 ( tc ) of groups i , ii , and iii , with ie placed on them , whose respective averages were 
 subtracted from the initial value obtained for mc in order to obtain the real misfit 
 value .
the implants of mc and related analogues of the tested casts were recorded as 
 a and b , from left to right , as with the cylinders of ie .
evaluation of misfit was 
 based on the protocol of tightening the screw only to test the passivity of the 
 implant structures , which had the 
 grip of a retainer and evaluation of the contrary retainer ( figure 2 ) .
infrastructure placed on the master cast ( mc ) ( a ) and the test cast ( tc ) ( b ) to 
 test the single screw the misfit was measured at 120x magnification in a measuring microscope accurate to 
 1.0 m ( uhl mm-100-bt , uk ) , equipped with a digital camera ( kc-512nt ; kodo br 
 electronics ltd . , so paulo , sp , brazil ) and analyzer unit ( qc 220-hh quadra - check 
 200 ; metronics inc . , bedford , nh , usa ) . the casts were placed randomly under the 
 microscope so that the blind evaluator did not know to which group they belonged .
all 
 casts were evaluated at identical points and cylinders a and b of ie were marked with 
 a carborundum disk  75x0.2 mm on the handpiece .
the readings were performed by an examiner on two calibrated points on the buccal ( 1 
 and 2 ) and two in the lingual face ( 3 and 4 ) , ordered from left to right .
the 
 sequence of assessment was followed by the tightening of the screw in the implant b 
 with 10 n.cm and measuring the distance in micrometers ( m ) of 1 - 4 points on the 
 interface of the cylinder to the abutment / analogue interface , identifying the 
 considered misfit ( figure 3 ) .
the same 
 procedure was then performed for b. each point was measured three times and the 
 average value used for the analysis .
microscopic image of the misfit generated at the interface of one point means and standard deviations for each plaster casting technique were calculated and 
 analyzed by one - way anova to determine whether there were significant differences 
 between groups , at =0.05 .
after anova , data were subjected to holm - sidak multiple 
 comparison test , which identified the p values .
the software used was sigmastat 3.5 
 ( systat software , inc . , chicago , il , usa ) .
for casting plaster of group iii , we developed a portable vibrator made from an 
 electric toothbrush ( 360 sonic power , colgate palmolive ind .
the bristles of the brush were removed using a carborundum disk - type cutter 
 and maxi - cut , and a hole in the place of the bristles was made for installation of 
 the tip of a brush on the opposite side ( round marta brush tropical 006 , tigre , so 
 paulo , sp , brazil ) , maintaining a slight inclination toward the end to facilitate 
 placement of the plaster inside the impression ( figure 
 1 ) .
ten impressions were sent to the outsourced laboratory , in a routine procedure for 
 work on prosthetic implants . along with the impressions ,
an order tab was included 
 with the request for plaster casting of special type iv , for a minimum 
 standardization with the other groups .
the casts of groups ii and iii were poured with 100 g of powder type iv gypsum , 
 proportioned to 22 ml of water and hand - mixed for 60 s. insertion of 
 the plaster cast was performed according to the technique assigned to each group , 
 with group ii using the leaked vibrator with conventional casting and group iii with 
 the portable vibrator . after a period of at least 1 h of setting time for the 
 plaster , the working casts were removed from the mold .
all casts were stored at room 
 temperature for at least 92 h before assessment of misfit . to standardize the samples , all steps of molding , 
 tooling , and casting of plaster
were made by the researcher in charge , while handling 
 the pvs was done by an assistant operator .
verification of the accuracy of the position of analogues and comparison between 
 groups was performed to develop an infrastructure ( ie ) from two metal cylinders of 
 titanium abutment micro - unit , bolted to the abutment of the master cast ( mc ) and 
 joined together by a titanium bar and laser welding . to calculate the misfit of the casts and make comparisons between groups , we measured 
 the vertical misfit of ie in the mc to verify the reliability of the adaptation and 
 the value of the initial ie misfit .
then , the evaluations also were carried out in testing casts 
 ( tc ) of groups i , ii , and iii , with ie placed on them , whose respective averages were 
 subtracted from the initial value obtained for mc in order to obtain the real misfit 
 value .
the implants of mc and related analogues of the tested casts were recorded as 
 a and b , from left to right , as with the cylinders of ie .
evaluation of misfit was 
 based on the protocol of tightening the screw only to test the passivity of the 
 implant structures , which had the 
 grip of a retainer and evaluation of the contrary retainer ( figure 2 ) .
infrastructure placed on the master cast ( mc ) ( a ) and the test cast ( tc ) ( b ) to 
 test the single screw the misfit was measured at 120x magnification in a measuring microscope accurate to 
 1.0 m ( uhl mm-100-bt , uk ) , equipped with a digital camera ( kc-512nt ; kodo br 
 electronics ltd .
, so paulo , sp , brazil ) and analyzer unit ( qc 220-hh quadra - check 
 200 ; metronics inc . , bedford , nh , usa ) .
the casts were placed randomly under the 
 microscope so that the blind evaluator did not know to which group they belonged .
all 
 casts were evaluated at identical points and cylinders a and b of ie were marked with 
 a carborundum disk  75x0.2 mm on the handpiece .
the readings were performed by an examiner on two calibrated points on the buccal ( 1 
 and 2 ) and two in the lingual face ( 3 and 4 ) , ordered from left to right .
the 
 sequence of assessment was followed by the tightening of the screw in the implant b 
 with 10 n.cm and measuring the distance in micrometers ( m ) of 1 - 4 points on the 
 interface of the cylinder to the abutment / analogue interface , identifying the 
 considered misfit ( figure 3 ) .
the same 
 procedure was then performed for b. each point was measured three times and the 
 average value used for the analysis .
means and standard deviations for each plaster casting technique were calculated and 
 analyzed by one - way anova to determine whether there were significant differences 
 between groups , at =0.05 .
after anova , data were subjected to holm - sidak multiple 
 comparison test , which identified the p values .
the software used was sigmastat 3.5 
 ( systat software , inc . , chicago , il , usa ) .
data analysis revealed a statistically significant difference between group iii as 
 compared to groups i and ii ( p<0.001 ) ( figure 
 4 ) .
this means that the technique of casting the plaster with a portable vibrator 
 produces a smaller misfit between cylinders of implant - supported dentures and their 
 respective analogues in comparison with the conventional techniques for casting 
 plaster . means and standard deviations(sd ) of the misfit ( m ) for the three groups . 

for the construction of a fixed partial denture on implants , several steps must be 
 followed to reduce errors and obtain a clinically acceptable product . according to 
 dental knowledge , the larger the number of pontics and retainers in prosthesis , the 
 greater the chances of mismatch . since the installation of the abutment to the working 
 model
also , the fact that the analogues are screwed to the 
 implant makes them susceptible to displacement , especially during vibration of plaster 
 during pouring . this work aimed to check the effectiveness of a new portable vibrator on the plaster 
 pouring of implant - supported dentures , also to verify if this device reduces the 
 possibility of misfit between cylinders of implant - supported dentures and their 
 respective analogues .
the results of the present work showed that the portable vibrator 
 led to lower misfit values between cylinders of implant - supported dentures and their 
 respective analogues when compared to conventional vibrator .
a minimum misfit was found 
 when using the new vibrator , but the " perfect " adaptation is almost impossible to 
 reach . extrapolating to clinical results of acceptable misfit of an implant - supported 
 prosthesis ,
the literature is unable to show an ideal value of 
 adjustment that will not jeopardize the entire system for prosthetic reconstruction . 

according to tossi ( 2010 ) values of 
 marginal fit between frameworks to multiple - units are clinically acceptable within 150 
 m range .
carr ( 1996 ) in an in vivo 
 study on primates verified that there is no statistically significant difference in bone 
 response around the implants supporting frameworks with 38 m and 345 m 
 misfits . according to literature 

the marginal misfit can be influenced by the technique and by the material used to fabricate the 
 frameworks .
however , this research suggests that the vibration is also an important 
 factor at this point , reminding that it refers to just one of many steps that are 
 required to get a prosthetic piece . during the other steps required to complete 
 prosthesis fabrication , such as firing porcelain several times and finishing done by a laboratory technician , misfit 
 values
will be further enhanced , thus emphasizing the importance of using laboratory 
 techniques and devices that decrease the possibility of distortion in the final 
 piece .
the new portable vibrator not only contributes to decrease the misfit , but also has the 
 advantage of being a small , soundless and low - cost device .
the casting technique using the portable vibrator allowed a smaller misfit between the 
 cylinders of implant - supported dentures and their respective analogues than the 
 conventional plaster vibrator .
mauru 
 antnio arruda nbilo , professors of dentistry at the university of campinas , sp , 
 brazil for his contribution and support to this work .
 objectivethe aim of this study was to test a new portable vibrator for plaster pouring 
 ( developed for this purpose ) , comparing the effect of its use on the accuracy of 
 working cast of implant - supported restorations to the conventional vibrator . 
 material and methodsfrom a master cast with 2 implants , 30 transfer moldings were made randomly and 
 divided into three groups : group i ( gi ) : pouring performed in an outsourced dental 
 laboratory with conventional plaster vibrator ( 10 casts ) , group ii ( gii ) : pouring 
 performed in the laboratory of the federal university of santa catarina ( ufsc ) 
 with conventional plaster vibrator ( 10 casts ) and group iii ( giii ) : pouring 
 performed with the portable vibrator fabricated for this study ( 10 casts ) . 
 the 
 position of the analogue and marginal adaptation of the infrastructure were 
 verified by testing the single screw on the master model and on the working model . 
 
 the measurement of misfit was blindly performed with a precision microscope and 
 analyzing unit , quadra - check 200 . 
 the data were statistically analyzed by analysis 
 of variance ( anova ) and the holm - sidak test ( =0.05).resultsmeansstandard deviations were as follows : gi : 19.194.73 m ; gii : 21.725.41 m ; 
 giii : 13.52.39 m ( p<0.05 ) , with giii significantly lower as compared to the 
 other groups . 
 conclusionwithin the limitations of this study , it was concluded that a greater accuracy of 
 working cast was achieved when a portable vibrator was used for casting molds . 
INTRODUCTION
MATERIAL AND METHODS
Fabricating the portable vibrator
Casting molds for Group I
Casting molds for Groups II and III
Evaluation of discrepancies in the position of casts and analogues
Statistical analysis
RESULTS
DISCUSSION
CONCLUSION
ACKNOWLEDGMENTS