Denture base resins- Dental materials prosthodontics

Dental materials- Denture base materials and its advancements

1. Denture base resins Presented by, Ann Mary Varghese 1 st year MDS

2. Definition DENTURE BASE The part of the denture that rests on the foundation tissues and to which teeth are attached.(GPT 9). DENTURE BASE MATERIALS Denture base material is any substance of which denture base may be made.(GPT 9).

3. HISTORY In old days dental base construction made from natural sources. 700BC (bone & ivory ) In 1500’s Japanese made wooden dentures 1800AD (porcelain bases & teeth ) George Washington and Queen Elizabeth I suffered from tooth loss and unfit dentures

4. Dr. John Greenwood designed denture for George Washington by hippo ivory, gold spring and brass screws Real breakthrough when vulcanized rubber discovered by Charles Goodyear in 1850 contains 32% sulphur and metallic oxides for color . 1890 celluloid was a denture base material (camphor, plasticizer had an unpleasant odour; also didn’t hold shape for long) In 1937 Dr. Walter Wright gave dentistry very useful resin, it was polymethylmethacrylate (PMMA) which proved to be much satisfactory material tested until now .

5. MER or MONOMER Chemical compound that is capable of reacting to form polymer eg : Methyl Methacrylate (MMA ) Synthetic resin commonly used in dentistry

6. POLYMERS Polymer is chemical compound consisting of large organic molecules formed by the union of many repeating smaller monomer units.

7. CLASSIFICATION OF POLYMERS BASED ON ORIGIN Natural (cotton, wool, rubber) Synthetic (Polyethylene, Polyvinylchloride) Semisynthetic (cellulose, cellophane, leather) BASED ON THE CONTENT OF THE MAIN CHAIN Organic: backbone with carbon atoms Inorganic: Non carbon containing backbone

8. BASED ON THE TYPE OF MONOMER HOMOPOLYMER COPOLYMER CROSS-LINKING A) Linear B) Branched A) Linear Random B) Block C) Branched Homopolymer + cross-linking agent = provides a sufficient number of bridges between linear macromolecules to form 3 dimensional network.

9. CROSS LINKING The formation of chemical bonds or bridges between the linear polymer is referred to as CROSS LINKING. It forms 3 dimensional network.

10. APPLICATION OF CROSS LINKING The most recent acrylic resins are cross linked variety. It improves the strength, decreases the solubility and water sorption. Acrylic teeth are highly cross-linked to improve its resistance to solvents , crazing and surface stresses.

11. BASED ON THERMAL RESPONSE Thermoplastic – resins that can be repeatedly softened and molded under heat and pressure. ( ie ., Linear and branched polymers can be made to soften and take up a new shape by application of heat and pressure) ( eg : polystyrene, PMMA, polyethylene ) Thermosetting - resins that can be molded only once. These cannot be softened by reheating . ( ie ., Cross-linked polymers that are resistant to heat and pressure are called thermostat) ( eg : silicone)

12. POLYMERIZATION Chemical reaction in which monomer of a low molecular weight are converted into chains of polymers with a high molecular weight The reaction generates heat and is hence considered to be a exothermic in nature.

13. CHEMISTRY OF POLYMERIZATION POLYMERIZATION ADDITION POLYMERTIZATION CONDENSATION POLYMERIZATION

14. CONDENSATION POLYMERISATION ( step growth polymerization) This polymerization is accompanied by repeated elimination of small molecules. This reaction involves two molecules reacting together to form a third larger molecule accompanied by repeated elimination of by-products such as water, alcohol, halogen ammonia etc. The process repeat itself and form macromolecules.

15. The formation of polymers by step growth is comparatively slow because the reaction proceeds in a stepwise fashion from monomer to dimer to trimer so on… until large polymer molecules containing many mer units are eventually formed.

16. ADDITION POLYMERIZATION Addition Polymerization involves joining together of two molecules to form a larger third molecule. Most common polymerization reaction for denture resin. No change in composition and no by-products are formed.

17. How?? Starting from an active centre, one molecule at a time is added and a chain rapidly builds up, till the supply of building blocks (monomers) is exhausted.

18. For addition Polymerization to occur, monomers must contain an unsaturated bond, which may exist in a double carbon-to- carbon or in a ring structure. Carbon-carbon double bond units are known as vinyl groups and are most often exemplified in dentistry by methacrylate monomers

19. CHEMICAL STAGES OF POLYMERIZATION 4 Stages:- Initiation/ Induction Propagation Chain Transfer Termination

20. INITIATION Two processes control the induction stage: Activation (generation of free radical) Initiation (polymerization) Free radicals is required for a polymerization reaction. ( An atom or group of atoms (R) with an unpaired electron (R˙ )) Induction is the process of activation of these free radicals which initiates polymerization.

21. In heat activation the initiator is benzoyl peroxide , which is activated rapidly between 50 and 100 to release free radicals. In chemical activation , the system consist of at least two reactants, when mixed, it undergo a chemical reaction and liberates free radicals. Eg )Self cure resins In light activation photons from the light source activate the initiator to generate the free radicals. Eg ) composite resin.  

22. When a free radical approaches a monomer with high- electron density double bond, an electron is extracted, and it pairs with the R. electron to form a bond between the radical and the monomer molecule, leaving the other electron of the double bond unpaired.

23. Thus , the original free radical bonds to one side of the monomer molecule and forms a new free radical site at the growing end of the chain.

24. PROPAGATION The resulting free radical-monomer complex then acts as a new free radical centre when it approaches another monomer to form dimer, which also becomes a free radical

25. CHAIN TRANSFER The deactivated chain resulting from this exchange can become an active growing chain by a chain transfer from another free radical.

26. TERMINATION The chain reaction should continue until all the monomer has been converted to polymer chains. The termination step can occur in two ways: 1) Coupling 2) Disproportionation

27. Coupling: Coupling is by direct combination of two free radical chain ends that deactivates the radicals with the formation of a covalent bond.

28. Disproportionation Disproportionation involves the transfer of a hydrogen atom from one growing chain to another. The free radical donates the hydrogen and becomes unsaturated while the other receives the hydrogen and becomes saturated. Therefore, there are always unsaturated functional groups remaining in resin-based composite restorations and denture bases.

29. Inhibition of polymerization Impurities in the monomer often inhibit such reactions. An impurity can react with activated initiator or with an activated growing chain and prevent further growth. Addition of methyl ether of hydroquinone , a common inhibitor, inhibits the spontaneous polymerization of dental resins during storage. (not only during storage but also provides adequate working time in case of self cure.)

30. 2. Oxygen reacts readily with the growing chains and results in a radical of low reactivity that does not attract monomers and thus inhibits chain growth.

31. COPOLYMERIZATION The macromolecules is formed by the polymerization of a single type of structural unit. Polymerization of two or more different monomer at the same time. Methyl-Ethyl-Methacrylate (DIMER) Methyl-Ethyl-Butyl-Methacrylate ( TERPOLYMER)

32. DENTURE BASE RESINS

33. FABRICATION OF DENTURES Since 1940s, the majority of denture bases have been fabricated using poly methyl methacrylate (PMMA) resins. The liquid contains mostly methyl methacrylate, dimethacrylate , or trimethacrylate, cross linking agents and an inhibitor. The powder contains predominately PMMA resin in the form of microsized beads.

34. When the liquid and powder are mixed in the proper proportions, a workable mass is formed Polymerization can activated by chemical, heat and light energy. Microwave energy may also used for polymerization CAD/CAM technologies of milling PMMA and 3D printing using methacrylate based monomers are also used

35. CLASSIFICATION OF DENTURE BASE POLYMERS (ISO-1567 ) Type 1 - Heat polymerizable polymers Class 1- Powder and liquid Class 2- Plastic cake Type 2 - Autopoymerizable polymers Class 1- Powder and liquid Class 2 -Powder and liquid pour type resins Type 3 - Themoplastic blank or powder Type 4 - Light- activated materials Type 5 - Microwave- cured materials

36. PRINCIPLE COMPOSITION OF ACRYLIC DENTURE BASE RESINS Powder The powder consists of (1) prepolymerized spheres of PMMA and a small amount of (2)benzoyl peroxide (Initiator) , which is responsible for starting the polymerization process. (3) Pigments - salts of cadmium/ iron/ organic dyes.

37. LIQUID The liquid is predominantly (1)non polymerized methyl methacrylate monomer with small amount of (2)hydroquinone ( Inhibitor), which prevents undesirable polymerization or setting of the liquid during storage. It also retard curing and increase working time. A Cross linking agent, (3) Glycol dimethacrylate (which is chemically and structurally similar to methyl methacrylate)

38. Glycol dimethacrylate can participate in the polymerization of two separate polymer chain and unite the two polymer chains. These interconnections yield a net-like structure that provides increased resistance to deformation.

39. HEAT ACTIVATED DENTURE BASE RESINS Most widely used resins for the fabrication of complete dentures. Available as:- Powder and liquid Powder may be transparent or tooth coloured or pink coloured ( to stimulate the gum, some even contain red fibers to duplicate blood vessels.) Monomer is supplied in tightly sealed amber coloured bottles ( to prevent premature polymerization by light or ultraviolet radiation on storage)

40. TECHNIQUES Compression Molding Technique Injection Molding Technique

41. Compression Molding Technique [ PREPARATION OF THE MOLD] Prosthetic teeth must be selected and arranged in a manner Completed tooth arrangement is sealed to the master cast The master cast is coated with thin layer of separator to prevent adherence of dental stone

42. The lower portion of a dental flask is filled with freshly mixed dental stone and the master cast is placed into the mixture. The dental stone is contoured to facilitate wax elimination, packing and deflasking procedures Upon reaching initial set, the stone is coated with an appropriate separator. Upper portion of the denture flask is positioned and dental stone is poured.

43. The investing stone is added until all surface of the teeth and denture base are completely covered. Incisal and occlusal surface are minimally exposed to facilitate subsequent deflasking procedure The stone is permitted to set and is coated with separator Additional increment of dental stone is mixed and remainder of the flask is filled , stone is allowed to harden.

44. Wax and record base is removed my immersing flask in boiling water for 4 min The record base and softened wax remain in lower portion of the denture flask while prosthetic teeth remain firmly attached in the investing stone Residual wax is removed from mold cavity using hot water.

45. [APPLICATION OF SEPARATING MEDIUM] To prevent water from the mold entering into the acrylic resin. To prevent monomer penetrating into the mold material. Helps easier retrieval of the denture from the mold . TYPES Tinfoil Cellulose lacquers Solution of alginate Soft soap starches

46. Sodium Alginate Solution Most popular separating medium It is water soluble It react with calcium of the plaster to form a film of insoluble calcium alginate. Composition -2%sodium alginate in water , glycerin , alcohol and sodium phosphate.

47. Polymer- to- Monomer Ratio Polymerization of MMA to PMMA yields 21% decrease in the volume of material , which would difficulties in denture base fabrication and clinical use. To minimize dimensional changes, Resin manufacturers prepolymerize a significant fraction of the denture base resin Prepolymerized fraction is supplied as a powder and is commonly referred to as polymer .

48. The nonpolymerized fraction is supplied as a liquid, and is termed a monomer . When the powder and liquid components are mixed in the proper proportions, dough-like mass results . The accepted polymer to monomer ratio is 3:1 by volume. Using this ratio, the volumetric shrinkage can be limited to approximately 7 %

49. Polymer- Monomer Interaction PHYSICAL CHANGES DURING POLYMERISATION 1) Wet/Sandy stage 2) Stringy/sticky stage 3) Dough stage 4) Rubbery or elastic stage 5) Stiff

50. WET / SANDY STAGE no reaction between molecule polymer bead remain unaltered consistency – “coarse” & “grainy”

51. STRINGY / STICKY STAGE Monomer attacks the surfaces of individual polymer beads and is absorbed into beads. S ome polymer chains are disperse in monomer liquid and these chain is uncoil, thereby increase viscosity of the mix. “Stringiness” or “stickiness” when the material is touched or drawn apart.

52. DOUGH STAGE Monomer diffuses into the polymer, the mass becomes more saturated with polymer in solution. I ncreased number of polymer chain enters the solution. large quantity of swollen, undissolved polymer also remains. D oes not adhere to the surface of the mixing vessel or spatula.

53. The physical &chemical characteristic exhibited during the later phase of the stage are ideal for compression molding .

54. RUBBERY / ELASTIC STAGE Acrylic mass become rubber like substance Dissipation of monomer by, a) evaporation b) further penetration into beads Rebounds when compressed or stretched

55. STIFF Continued evaporation of unreacted monomer and appears very dry. Resistant to mechanical deformation.

56. DOUGH FORMING TIME Time required for the resin mixture to reach a dough like stage. It depends on Degree of polymerization ,particle size , polymer monomer ratio, temperature, plasticizer . ANSI / ADA specification No-12 for denture base resin to attain this consistency – in less than 40 minutes Majority of denture base product reach dough like consistency in less than 10 minutes.

57. WORKING TIME Working time is defined as the time a denture base material remains in the dough-like stage. This period is critical to the compression molding process. ANSI/ADA Specification no 12 requires the dough to remain moldable for at least 5 min.

58. PACKING The placement and adaptation of denture base resin within the mold cavity are termed PACKING . OVER PACKING leads to excessive thickness and mal positioning of prosthetic teeth. UNDER PACKING leads to noticeable denture base porosity After the closure the flasks should remain at room temperature for 30-60 min , it is called BENCH CURING .

59. While in dough like stage the resin is made into rope like form The resin form is placed into the portion of the flask that houses the prosthetic teeth A thin polyethylene separator sheet is placed over the master cast, and the flask is reassembled. The flask is placed into the specially designed press Pressure is applied incrementally

60. CURING CYCLE The following curing cycle have been quite successful Processing in a constant temperature water bath at 74 for 8 hrs or longer with no terminal boil. Processing in a 74 water bath for 8 hrs and then increasing the temperature to 100 for 1hr. Processing resin at 74 for approx. 2hrs and increasing the temperature of to 100 for 1 hr .  

61. Following the completion of curing, the denture flasks should be cooled slowly to room temperature. Rapid cooling may result in warping of denture base because of difference in thermal contraction of resin and investing stone Hence flasks should be removed from water bath and bench cooled for 30 min , then immersed in cool tap water for 15 min

62. INJECTION MOLDING TECHNIQUE

63. Available data and clinical information indicate denture bases fabrication indicate from injection molding result in fewer dimensional inaccuracies and polymerization shrinkage than conventional processing.

64. CHEMICALLY ACTIVATED DENTURE BASE RESINS Also called pour resin . Supplied as powder & liquid Composition same as heat cure resin but it has additional chemical activator in liquid . Chemical activation occurs at room temperature.

65. TECHNIQUE Compression moulding technique Fluid resin technique Sprinkle on technique Dough technique

66. COMPRESSION MOULDING TECHNIQUE Mould preparation & resin packing is same as heat cure resin . Short working period . More than two trial closure is not possible . Prolong initiation period by decreasing temperature of resin mass. Initial hardening in 30 minutes of final flask closure . Flask held under pressure for 3 hours to ensure sufficient polymerization.

67. ADVANTAGES: Less shrinkage . Greater dimensional accuracy . Ease of manipulation . DISADVANTAGES: Incomplete polymerization . Decreased tensile strength . Tissue irritation Poor colour stability

68. FLUID RESIN TECHNIQUE Employs a pourable, chemically activated resin for the fabrication of denture bases Supplied in form of powder& liquid components. When mixed in proper proportions yields a low viscosity resin. This resin is poured into a mold cavity, subjected to increased atmospheric pressure and allowed to polymerize

69. Laboratory procedure

70. ADVANTAGES: Improved adaptation Decreased possibility of damage to prosthetic teeth and denture bases during deflasking Reduced material cost Simplification of flasking , deflasking and finishing procedures. DISADVANTAGES: Air entrapment Poor bonding between the denture base material and acrylic teeth . Technique sensitive procedure.

71. SPRINKLE ON METHOD Separating media is applied first on the cast. Powder is taken in container like salt & pepper dispenser Liquid is loaded in a syringe or dropper Powder is sprinkled on the cast and then wet with monomer .

72. To improve strength the appliance is cured in hot water under pressure for around 20 minutes. Extend this procedure to cover the entire denture base area to a thickness of 2.5mm. ADVANTAGE Minimal wastage DISADVANTAGE difficult to obtain uniform thickness. porosity

73. DOUGH METHOD Mix powder & liquid In dough stage, it is kneaded into ball & placed in the center of flat glass plate . Using another plate, dough is pressed & flattened to a thickness of 2mm.

74. Sheet of material lift from the glass plate & placed over the lubricated cast . Adapt using light finger pressure . Trim the excess material with sharp knife . After the complete polymerization it is removed & trimmed. ADVANTAGES: Takes less time . Chance of less porosity DISADVANTAGES: Less working time . Perfect adaptation is difficult . More wastage of material.

75. LIGHT ACTIVATED DENTURE BASE RESINS This material has been described as a composite having a matrix of urethane dimethacrylate and microfine silica. Light( Blue visible) when irradiated at 400- 500nm is the activator. Camphoroquinone serves as the initiator for polymerization. Supplied in sheet & rope forms & packed in light proof pouches to prevent polymerization.

76. Following polymerization, the denture is removed from the cast, finished and polished in conventional manner.

77. ADVANTAGES: Less porosity Fabrication & final adjustment can be done in mouth due to extended working time Light weight No allergic reaction Non toxic Less polymerized shrinkage DISADVANTAGES: Cannot be packed in flask Time consuming

78. POLYMERIZATION VIA MICROWAVE ENERGY Nishii in 1968 used microwave energy to polymerize denture base resin using 400 watt oven in 2.5min. This technique employs a specially formulated resin and non metallic flask. ( Fiber R einforced P lastic Flask) Less curing time required.

79. CAD/CAM in denture base fabrication In 2012 Goodacre et al. published the first clinical account of CAD/CAM dentures milled from pre polymerized PMMA. Advantages associated with CAD-CAM fabrication of complete dentures include enhanced material properties and dimensional stability of the resultant prosthesis. Milled denture bases exhibit improved adaptation to the underlying ridges upon clinical placement and less susceptible to distortion.

80. RECENT ADVANCES IN DENTURE BASE RESINS New Era in Denture Base Resins: A Review by, Dr. Shikha Nadal , Dr. pankaj , Dr. Himanshu ; Dental Journal of Advance Studies, 2013

81. 1. REINFORCED RESINS A)HIGH IMPACT RESINS RUBBER REINFORCED ( butadiene-styrene polymethyl methacrylate ). Rubber particles grafted to MMA for better bond with PMMA. They are so-called because of greater impact strength & fatigue properties, hence indicated for patients who drop their dentures repeatedly e.g. parkinsonism, senility.

82. Available as powder-liquid system processing is same as heat cure resins. E.g) Lucitone 199, D.P.I Tuff ,

83. B) FIBER REINFORCED RESINS Primary problem with PMMA is low impact strength & low fatigue resistance . A study by Johnston et al shows that 68% dentures fracture within few years of fabrication. Maxillary fractures are mostly caused by a combination of fatigue (under occlusal forces) & impact (when accidentally dropped on hard surface) whereas 80% of mandibular fractures are caused by impact .

84. a) METAL FIBER REINFORCED Metals used are cast gold, aluminium & chromium based alloys . Not widely used because unaesthetic , expensive , poor adhesion between wire & acrylic resin & metal being prone to corrosion . Using full lengths of metal fibers offers the best reinforcement.

85. b) CARBON / GRAPHITE FIBER REINFORCED RESIN Carbon fibers (65-70 mm length, 5 % by weight & treated with silane coupling agent) are placed during packing . Anisotropic ( provide strength in one direction)& provide greatest reinforcement of denture base resins when placed longitudinally ( perpendicular to applied forces ).

86. ADVANTAGES Increases flexural strength , impact strength, prevents fatigue strengthens the resin. DISADVANTAGES Unaesthetic because of black colour but this can be covered by an opaquer . The polishing is difficult & also weakens the finished prosthesis.

87. c) ARAMID FIBER REINFORCED Aramid fiber reinforcement increases the strength but again they are unaesthetic & difficult to polish so limited to locations where aesthetics is not important.

88. d) POLYETHYLENE FIBER REINFORCED Multifibered polyethylene strands cut to 65 mm length & surface treated with epoxy-resin & placed during packing . Advantage - highest impact strength & modulus of elasticity Disadvantage - Placement & finishing is difficult as fibers tends to protrude outside mould

89. HIGHLY DRAWN LINEAR POLYETHYLENE FIBERS (HDLPF) Reinforcement in maxilla is done by horizontally positioned fibers in anterior part because maxillary fracture mostly occurs in midline on polished surface of palatal aspect in region immediately behind central incisor. Reinforcement done with 4 layers of fibers (2 in lateral direction sandwiched between 2 layers at 45 degree from middle ones.)

90. In mandible, maximum stresses appear in labial & lingual second premolar region & fracture occurs in middle region. Thus mandibular bases are reinforced with fibers at right angle to ridge located close to polished & fitting surface

91. e) GLASS FIBRE REINFORCED RESIN Continuous parallel fibers provide high strength & stiffness in one direction (anisotropic) while randomly oriented fibers provide similar properties in all directions (isotropic properties ). Continuous fibers provide superior reinforcement over chopped fibres but placing continuous fibers at weak parts of denture is difficult

92. Advantage: Improvement in flexural properties F atigue resistance B est aesthetics E xcellent polishing characteristics .

93. E-GLASS FIBERS Each strand of this E-glass is computer impregnated with a PMMA (porous polymer) and silane coupler that allows dissolution bonding to acrylic. (e.g. Preat Perma Fiber) ADVANTAGES Available in two forms (mesh & fiber) & are transluscent providing esthetics. Because of glass fiber bonding, they also have more strength

94. 2. HYPOALLERGENIC RESINS Hypoallergenic denture base materials exhibit significantly lower residual monomer content than PMMA, thus act as alternatives to Poly Methyl Methacrylate in allergic patients . Eg ) Diurethane dimethacrylate

95. 3. RESINS WITH MODIFIED CHEMICAL STRUCTURE Addition of hydroxy -apatite fillers increases fracture toughness. 2 % quaternary ammonium compound polymerised with a denture acrylic resin displays antiseptic properties & these dentures may be used for geriatric patients to improve their oral health.

96. Addition of ceramic or sapphire whiskers to improve thermal diffusivity Addition of Al2O3 fillers increases the flexural strength & thermal diffusivity that could lead to more patient satisfaction Addition of Triphenyl Bismuth (Ph3Bi) is a promising new additive to provide radiopacity .

97. 4. THERMOPLASTIC RESINS This new procedure, during which a fully polymerized basic material is softened by heat and injected afterwards. I.) THERMOPLASTIC NYLON II.) THERMOPLASTIC ACETAL III.) THERMOPLASTIC ACRYLIC IV) THERMOPLASTIC POLYCARBONATE

98. THERMOPLASTIC NYLON

99. FLEXIBLE DENTURE Super polyamides, which belong to nylon family, which inherent property of flexibility. INDICATIONS: Bilateral undercuts . Allergy to acrylic resin . Patients who do not want a fixed restoration & metal clasps . Bruxism. Patients with compromised neuro -motor function . Single denture . Obturators

100. THERMOPLASTIC ACETAL

101. THERMOPLASTIC ACRYLIC

102. THERMOPLASTIC POLYCARBONATE

103. 5. ENIGMA GUM TONING Custom shade matching of natural gingival tissue using ‘Enigma’ color tones. Gives extra confidence to patient in appearance of their dentures. Available in Ivory, Light Pink, Natural Pink, Dark Pink & Light Brown. Different colors are mixed to get the desired gum tone

104. JOURNAL REVIEW

105. Determination Of The Effective Time Of Denture Cleanser Tablets On The Removal Of Candida Albicans On Denture Base Resins ; by Yeliz Hayran Cumhuriyet Dental Journal: 2019 The aim of this study was to determinate of the effective time of different denture cleanser tablets on the removal of Candida albicans on various base resins . And concluded that Alkaline peroxide and enzymatic cleanser tablets showed remarkable anticandidal activity for all resins. The patients with risk of C. albicans infection should keep their prostheses in cleanser tablets for at least 20 minutes.

106. In-vitro Comparative Evaluation for the Surface Properties and Impact Strength of CAD/CAM Milled, 3D Printed, and Polyamide Denture Base  Resins; by Mohamed  A.  Helal et al. Journal of International Society of Preventive and Community Dentistry; jan 2022 Study aimed to evaluate the Surface Roughness (SR), Surface Hardness (SH) and Impact Strength (IS) of CAD/CAM milled, 3D-printed, and polyamide flexible Denture base resin materials. CONCLUSION: The CAD/CAM milled denture base resin showed lowest surface roughness when compared with 3D-printed and polyamide flexible denture base resins .

107. 2. The CAD/CAM milled and polyamide flexible denture base resins showed higher IS (Impact stregth ) when compared with 3D-printed denture base resins. 3. The CAD/CAM milled and 3D-printed denture base resin showed higher hardness when evaluated with polyamide-pressed materials

108. Determination of Polyetheretherketone (PEEK) mechanical properties as a denture material; by, Saja A. Muhsin , Paul V. Hatton et al. Saudi Dental journal 2019 Aim of the study to estimate the impact, tensile strength and flexural properties of pressed and milled PEEK. Where appropriate, these properties were compared with those of PMMA the PEEK polymer that was milled or pressed at 200 °C mold temperature demonstrates proper and superior mechanical properties compared to PMMA . These findings indicate the promise offered by PEEK as an alternative denture material. However, further studies are required to determine how best to bond PEEK to artificial teeth

109. REFERENCES Philips’ Science of dental materials- 2 nd South Asia Edition Materials used in dentistry 2 nd edition- S. Mahalaxmi New Era in Denture Base Resins: A Review; by , Dr. Shikha Nadal , Dr. pankaj , Dr. Himanshu;Dental Journal of Advance Studies, 2013 Determination Of The Effective Time Of Denture Cleanser Tablets On The Removal Of Candida Albicans On Denture Base Resins ; by Yeliz Hayran ; Cumhuriyet Dental Journal: 2019 In-vitro Comparative Evaluation for the Surface Properties and Impact Strength of CAD/CAM Milled, 3D Printed, and Polyamide Denture Base Resins; by Mohamed A.  Helal et al. Journal of International Society of Preventive and Community Dentistry; jan 2022 Determination of Polyetheretherketone ( PEEK) mechanical properties as a denture material; by , Saja A. Muhsin,Paul V. Hatton et al. Saudi Dental journal 2019

110. THANK YOU!