Original article: A Comparative evaluation of shear bond strengths of denture base to cross linked acrylic resin maxillary anterior teeth with and without retentive grooves - An invitro study Dr.D.Sudha Madhuri 1 *, Dr.B.Sreeramulu 2 1Associate Professor & Incharge, Dept.of Prosthodontics,Govt,Dental College & Hospital, Vijayawada Andhra Pradesh, India. 2Associate Professor & Incharge, Dept.of Prosthodontics,Govt,Dental College & Hospital, Afzalgunj, Hyderabad,Telangana, India Corresponding author: Dr.B.Sreeramulu Abstract: In our experimental study, the aim was to measure the shear bond strength exhibited by Denture base to cross linked acrylic resin maxillary anterior teeth with and without retentive grooves on their ridge lap surfaces and to compare the bond strengths of each maxillary anterior tooth type as the adequacy of shear bond strength of each Maxillary anterior resin teeth to the acrylic denture base is questionable. Success rate of approximately 90% was obtained with vertical retentive grooves on canines and central incisors. We believe that this method can be used to improve the bond strength of the teeth with the denture base material and prevent their dislodgement from the denture base 1,2 Key words : Shear bond strength, cross-linked acrylic resin teeth,retentive grooves. --------------------------------------------------------------------------------------------------------------------------------------- Introduction: During the past few decades, several scientific developments were carried in the fields of Dental base like faulty boil out procedures, residual wax on ridge lap surfaces of teeth, careless application of tin foil substitutes and other separating medium materials and Prosthodontics to produce denture like sodium alginate to teeth leading to base materials that exhibited excellent fit, contamination of their ridge lap surfaces. dimensional stability,strength, tissue tolerance, The resistance to fracture of acrylic resin teeth from ease of fabrication,esthetics and are economical. denture base depends on SHEAR BOND Though many types of denture base materials were developed, acrylic polymers remained as the most commonly used ones since their introduction by Harold Veron in 1937.Ever since then, there has been constant evolvement of the material to achieve best results.acrylic resin teeth are preferred as functional portions with acrylic resin denture base material as they became integral part of the denture by their chemical bonding resulting in an overall stronger one unit denture. However there are several factors which resulted in poor bonding of acrylic resin teeth to the denture STRENGTH which gives an indication of material performance under conditions of static loading. 3,4 Attempts to increase the strength of the bond between acrylic resin teeth and heat cured denture base resin include 1. Grinding the glossy ridge lap surface of resin teeth. 2. Painting the ridge lap surfaces of teeth with monomer polymer solution. 3. Cutting retentive groves in the ridge lap surface of teeth. Retentive grooves placed in the ridge laps of www.ijhbr.com ISSN: 19-7072 17
denture teeth, increase the area available for physical and chemical bonding and secure the teeth to the base firmly. 5,6 Considering the developments in heat cure acrylic denture base resins and improvements in crosslinked acrylic resin material teeth, the hypothesis for this study were 1.The shear bond strength of cross-linked acrylic resin teeth with grooves cut on their ridge-lap surface would be higher than those without grooves. 2.The shear bond strengths of all three types of cross linked acrylic resin maxillary anterior teeth used in this study would be similar The Aims of this study were 1.To compare the shear bond strengths of denture base to acrylic resin teeth with and without retentive grooves cut on their ridge lap surface. 2. To determine whether central incisor or lateral incisor or canine acrylic resin teeth used in this study, has higher bond strength to denture base. Materials and methods: The glossy ridge-lap surface of 90 cross-linked acrylic resin maxillary anterior teeth of which, 30 were central incisors,30 were lateral incisors and 30 were canines.the specimens were divided into three similar groups, Group A: No further tooth preparation was carried out. Group B:A mesio-distal groove 2mm deep and 2mm wide was cut into the ridge-lap surface of tooth. Group C:A vertical groove 2mm deep and 2mm wide was cut into the center of the ridge-lap surface of tooth extending half way up the lingual surface. Similar teeth were mounted in numbers of ten on triangular shaped wax molds to produce nine wax mold specimens and then flasked.the wax was removed by flushing away with hot boiling water. After the process of dewaxing, the specimens were allowed to cool. At this stage plastic surfaces of teeth were painted with one coat of separating medium. Six acrylic mold specimens containing 10 acrylic resin teeth each were then prepared by conventional curing method of which three specimens were cured with DPI brand resin material and other three with TREVALON brand resin material. The monomer to polymer ratio was maintained at 1:3 by volume for all the samples. A pipette was used to transfer the required volume of monomer to a clean, dry, air tight porcelain mixing jar. Thepolymer was measured with a measuring cylinder and transferred to the jar containing monomer. Thorough mixing was done with a clean stainless steel spatula and the jar was closed till the mix reached dough stage. The resin was removed from mixing container and rolled into a rope like form and placed into upper half of the mold. The flask was re-assembled and was bench pressed by applying pressure incrementally. Pressure was applied until the major portions of the edges of the flask closely approximate one another. The flask with acrylic resin was allowed to bench cure for min. www.ijhbr.com We are now with IC Value 5.99 www.ijhbr.com ISSN: 19-7072 18
Acrylic Resin Teeth With Horizontal,No And Vertical Retentive Shear Bond Strength Testing: The specimens were subjected to testing on a universal testing machine INSTRON (model 6025). The test was initiated by applying load to the specimen at a specified cross head speed of 5mm/min at an angle of 0 to the long axis of the tooth until fracture occurred. The deflection was measured either by the gauge under the specimen in contact with it in the centre of support pan or by measurement of the motion of loading hose relative to the support. This test was conducted as per ASTM-D790. The site of fracture of tooth from resin model was recorded as through the tooth, through acrylic resin and at the tooth acrylic interface of all the teeth fractured at tooth acrylic interface. Instron Universal Testing Machine www.ijhbr.com ISSN: 19-7072 18 19
Instron Machine 3 Point Bend Test FORCE (Kg / cm 2 ) REQUIRED TO SEPARATE CENTRAL INCISORS FROM CAST Name of the Group Denture A Base Resin No 10 8 19 DPI 28 33 25 Group A 22 26 18 27 TREVALON 33 40 42 39 Group B Horizontal Group C Vertical 19 25 44 22 38 33 27 32 45 38 46 35 37 31 39 29 43 Group B Group C 39 46 29 38 19 42 30 53 48 45 52 51 32 36 40 44 35 52 47 www.ijhbr.com ISSN: 19-7072 18
Statistical analysis: The results were subjected to a statistical analysis using a one way analysis of variance (ANOVA) and were appropriate. Results: Shear bond tests: The results were given in table. Table I: specimens of group A for Central incisor teeth is 42 kg/cm 2 while the minimum is 8 kg/cm 2. (Mean and SD 22.1765 ± 8.5676) specimens of group B is 52kg/cm 2 while the minimum is 19kg/cm 2. (Mean and SD 31.8889 ± 9.3676) specimens of group C is 53kg/cm 2 while the mforce (Kg / cm 2 ) REQUIRED TO SEPARATE CENTRAL INCISORS FROM CAST Table II: specimens of group A for lateral Incisor teeth is kg/cm while the minimum is 6kg/cm 2. (Mean and SD.7059 ± 4.321) specimens of group B is 32kg/cm 2 while the minimum is 9kg/cm 2. (Mean and SD 17.0556 ± 6.8382) specimens of group C is 55kg/cm 2 (Mean and SD 29.5556 ± 11.60) FORCE (Kg / cm 2 ) REQUIRED TO SEPARATE LATERAL INCISORS FROM CAST Name of the Denture Base Resin Group A No Group B Horizontal Group C Vertical 8 7 12 10 12 9 25 27 DPI 11 10 19 6 18 9 11 8 11 12 18 26 Group A Group B Group C 21 www.ijhbr.com ISSN: 19-7072 17
34 29 32 33 42 TREVALON 14 17 37 28 21 31 21 53 14 55 28 46 Table III: specimens of group A for Canine teeth is 51 kg/cm 2 while the minimum is kg/cm 2. (Mean and SD 26.88 ± 11.0277). specimens of group B for Canine teeth is 60kg/cm 2 while the minimum is kg/cm 2. (Mean and SD 33.8333 ±.7595). specimens of group C for Canine teeth is 118kg/cm 2 while the minimum is 21 kg/cm 2. TABLE III FORCE (Kg / cm 2 ) REQUIRED TO SEPARATE CANINE TEETH FROM CAST Name of Group A Group Group the No B C Denture Horizont Vertical Base Resin al 17 35 39 14 ** 26 ** 28 34 DPI 19 33 17 27 21 25 27 ** 26 42 18 19 56 Group A Group B Group C TREVALO 27 55 68 www.ijhbr.com ISSN: 19-7072 22 18
N 31 43 88 29 54 102 38 42 118 40 38 121 51 60 2 39 33 88 37 35 67 ** 41 96 ** Indicate the teeth fractured during deflasking Discussion: Acrylic resin has become almost universal since its introduction in 1937 as a denture base material as well as the component of the resin cross-linked teeth. 7,8 This study was conducted to compare the shear bond strengths exhibited by denture base to maxillary anterior resin teeth with and without retentive grooves made on their ridge-lap surfaces. This study also concentrated on the comparison of shear bond strengths exhibited by cross linked acrylic resin maxillary central incisors, lateral incisors and canines used in this study. The results showed that the mean bond strength exhibited by those specimens without retentive grooves was 21.1Kg/sqcm, for those with horizontal grooves was 27.503Kg/sqcm and for those with vertical retentive grooves was 45.648Kg/sqcm.This indicated that specimens with vertical retentive grooves showed significantly higher bond strength than those with horizontal grooves and without grooves. The mean bond strengths obtained for central incisor was 31.928Kg/sqcm, for lateral incisor was.4kg/sqcm and for canine was 42.990Kg/sqcm, the highest among the three tooth types tested in this study.the Vertical retentive grooves showed a statistically significant superior retention in all tooth types. The vertical groove is closer to the point of application of force. A short lever arm requires greater force to separate the tooth from denture base.canine teeth bonded more securely to denture base resin than central incisors and lateral incisors. Thisfinding may be accounted for the ridgelap of canine presenting a greater surface area for bonding to acrylic resin. Morrow et.al using a tensile force to separate teeth from denture base resin found that from denture base resin found that bond strength of high impact resin to plastic teeth was significantly greater than standard resin.in the present study a combined shear compressive force was applied at an angle of 0degrees to simulate clinical conditions. Non significant stastical interactions was noted between tooth type and the retentive grooves.a significant statistical interaction was found between tooth type and denture base resin. Canine teeth bonded more securely to denture base resin than central and lateral incisors. This finding may be accounted for the ridge lap of canine presenting a greater surface area for bonding to acrylic resin. A significantly greater force was required to separate teeth from TREVALON than from DPI. Morrow et al., using a tensile force to separate teeth from denture base resin, found that bond strength of high impact resin to plastic teeth was significantly greater than standard resin. In the present study, a combined shear compressive force was applied at an angle of 0 to lingual surface of teeth to simulate clinical conditions. A statistically significant interaction was found between denture base resins and tooth type. TREVALON showed a www.ijhbr.com ISSN: 19-7072 18
better bond strength with all the types of teeth and it Acrylic resin has become almost universal since its introduction in 1937 as a denture base material as well as the component of the resin cross-linked teeth. This study was conducted to compare the shear bond strengths exhibited by two brands of conventional heat cure denture base resin materials DPI and TREVALON to cross linked acrylic resin maxillary anterior teeth of PREMADENT brand. This study also concentrated on the comparison of shear bond strengths exhibited by cross linked acrylic resin maxillary central incisors, lateral incisors and canines used in this study. The results showed that the mean bond strength exhibited by DPI heat cure denture base material was 22.580 kg/cm 2 while the same for TREVALON was 40.401 kg/cm 2 which indicated that TREVALON has a better bond strength compared to DPI denture base material. The mean bond strength for each tooth type tested also showed significant difference. The mean bond strength obtained for central incisor was 31.928 kg/cm 2, for lateral incisor was.4 kg./cm 2, while that exhibited by canine tooth was 42.990 kg./cm 2, the highest bond strength among the three types of teeth tested in this study. Conclusions: Within the limitations of the methodology of the study, the main conclusions which can be drawn are as follows. A significantly greater force was required to separate teeth with retentive grooves than without grooves from the denture base.. Canine tooth type with vertical retentive grooves exhibited higher bond strength when compared to other tooth types tested in this study.. No consistent trend was noted in the site of fracture for teeth with horizontal and vertical retentive grooves on application of force, all the teeth without retentive grooves fractured at the tooth acrylic resin interface. An increase in the ridge lap surface area of teeth resulted in an increase in shear bond strength References 1. CUNNINGHAM JL.Bond strength of denture teeth to acrylic bases. J Dent 1993; 21(5): 274-280. 2. Jakahashi Y, Chain J.Bond strength of denture teeth to denture base resins.international journal of prosthodontics. 00;(1): 59-65. 3. Thean HP, Chew CL, Goh KL.Shear bond strength of denture teeth to base, a comparative study. Quintenssence Int. 1996 ;27(6):425-428. 4. John N Anderson.The strength of the joint between plastic and copolymer acrylic teeth and denture base resins. British Dental Journal. 1958; 6: 319-3. 5. GeertsAVM.A comparison of the bond strength of the microwave and water bath cured denture material. JPD.1990;70:406-409. 6. Harrison WM, Stansburg BE. The effects of joint surface contour on the transversal strength of repaired acrylic resins. JPD.1970;:464. 7. Consani S, Stolf WL, Ruhnke LA.Comparative study of bonding of acrylic teeth and resin bases. JPD. 1993;690. www.ijhbr.com ISSN: 19-7072 18
8. Can G, KhasuG.An evaluation of the bond strength of plastic teeth to acrylic denture base material. Ankare Umin Ilekein Jak Derg. 1990;17(1): 97-101. www.ijhbr.com ISSN: 19-7072 18 25