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    DM Lec#5 By Muna Swwan

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    DM Lec#5 By Muna Swwan

    Post by Sura on 4/11/2011, 11:31 pm



    Last edited by Sura on 9/11/2011, 8:34 pm; edited 2 times in total
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    Sura

    عدد المساهمات : 484
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    Re: DM Lec#5 By Muna Swwan

    Post by Shadi Jarrar on 5/11/2011, 2:19 pm

    Dental materials
    Lec. #4
    Dr. Rabab3a
    By:Muna Sawwan J
    adhesive surface phenomena
    simple revision J :1) we use bonding agent in order to bond composite to the tooth and we have to make a proper isolation to prevent saliva contamination ,, bcoz contamination with water will prevent good bonding,,,,
    2)stress-strain curve (erj3o ll H.O ) :
    x material is tougher than y ,,, tough : material property= area under the curve.
    Note: u cant describe x as a strong material bcoz strength depends on the conditions while u r testing the material.
    X has the highest modulus of elasticity.
    Y will not go under plastic deformation bcoz its brittle ( so r7 tkser).
    Z is a resilient material ( 3ks X elle kant tough or stiff " o a7sn ennk t7ke stiff material bdl tough" ) .
    3) compsite compsed of filler and resin
    Hll2 e7na hdfna enno n3ml proper bonding ll substrate elle mmkn ykon:
    Enamel,Dentine,Metal,Ceramic or any other surface.
    Lam n3raf sho m3na Adhesion !!! ,,,
    Adhesion = bonding between 2 different surfaces, so we need an adhesive material to stick them together. ( tzrko " howat jam3 el6awabe3 !!! o hll2 ba66al 7d yejm3ha,, blab la bla " ).
    Hll2 ahm she mtl ma ento shayfeen ( in H.O) ykoon fe 3nna ( stable joining of the force) ,, o behemna tkoon hay el joint reliable and durable,,
    Sho elfr8 elr2eese ben reliable and durable ???? dr. answer enno : SHO bye3mel el load o cycling o fatigue?? Fe 7ada saken b sha22a a3la 6abe2?? Sho beseer bl d-han?? BEFASHE ,,,!! Had mnsmmeh : BOND DEGREDATION ,,, o e7na hdfna enno nmn3 had elshe b 2enno n3ml durable and reliable bonding .
    " im sorry 3l kelmat elmota8a6e3a ,, bs had elle 3nde bl record !! " anyway nrj3 ll mo7adara:
    Note: fe no. lazm t7fooh >> 20 mega Pascal
    هاد اللي منحصل عنده reliable bond
    Most of the materials that we use in dentistry with composite give us more than 20 mega Pascal ,,, bs el main problem is from el durability >>> beseer 3enna ( bond degradation).
    الدكتور بحكي : هاد علم كبير بس لازم يكون في شوية معرفة يعني انو والله لما يكون عنا wet conditions the bond ability decrease ,,, lamma ykooon very dry condition el bond ability decrease .
    Hll2 we talked a little about surface tension and contact angle ,,, and in order to decrease surface tension so that the surface energy will increase and that means water absorption ability ,, there is certain properties for the surface we talked about in second year J !! ,,,
    انا اسفة اذا الشيت بتشتت بس الدكتور من موضوع لموضوع يعني بسال سؤال وقبل ما يجاوبه بكون صار سائل 3 بعده ،،بس اعتقد انو واضحة الامور تقريبا J
    Now,, in order to achieve adhesion what should we have?? Intimate contact as possible .
    Always el bond is the weakest ,,, and enamel ( hardest ) and composite harder ,, so failure occur in bonding ( adhesion rather than cohesion ).
    Remember in second year 7kena 3nenno high contact angle gives less wetting ,,, less wetting mean less ability to bond ,,,, and remember these names "bowen and ?!! ) "sorry ma fhemt elesm and dwwrt o ma l2eet she !!"
    Hll2 what they did enhom in first generation of composite ,,3mlo treatment for smear layer by using phosphoric acid ,,, ( u know enno inorganic acids are stronger than the organic ,, and the strongest among inorganic is H2SO4 ,,,that we use it to itch teeth ,,, so drs. Always said that we have to use rubber dam in order to keep it away from gingival and oral mucosa bcoz it may burn it .
    Hll2 by using this acid in high conc. We increase surface energy 100 times .
    Marra tanyeh : we talked in second year about chemival bonding and mechanical bonding….and in composite btkoon micromechanical retension .
    نرجع شوي للتعاريف لانها بتهمنا بالمحاضرات الجاي وخلينا نحكي شوي عن ال hybridization
    Wen btkoon el hybrid layer?? In dentine ,,,, why not in enamel ?? what is the main component in enamel ???? menirals ( calcium hydroxyapatite) …
    Main component in dentine is also calcium hydroxyapatite ,,, DON’T SAY dentinl tubule bcoz it’s a histological structure,,,,, ,,
    Calcium hydroxyapatite in enamel 96% and 70% in dentine,,, bs dr. said enno kol elar8an elle 7ketoha ll dentine 3'l6 l2enno it depends eza kan fe caries ,, bla bla bla ,,,,kl had b5telef bs be5llek b range mo3ayyan ,,
    SOOO why we need hybrid in dentine much more than what is needed in enamel ?? ( u know that composite is a hydrophobic material while in dentinal tubule its hydrophilic so we need an intermediate molecule to bond resin to collagen around dentinal tubule and that what is called Hybrid layer.)
    MARRA TANYEH ,,,, we said that after doing acid itch( to improve surface property) we need adhesive material that is ( bonding agent) ,,,,,,,,BUT ,,,,, what is a primer???????
    >>>> we said that resin is a hydrophobic ,,,but in the slide mktoob hydrophilic !!! keeeeeef ??? l2enno we need enno yemsek m3 eldentine ,, so primer is used to bond with dentine,,,,,,,, Y3NE ,, primer is a bifunctional molecule ,,,,,one side is hydrophilic to bind dentine.
    We will talk about two technique in bonding,,, one is Direct bonding, in which we have interphase ( enamel or dentine), adhesive , and then direct restorative material ( mainly compsite ,,, o fe aw2at btkoon m3 el amalgam aw in orthodontic treatment )….
    The other one is the indirect bonding >>> we still use enamel and dentine as one surface ,, we have also the adhesive material ,,and ceramic ( in general ) or metal for crown and bridges.
    Dr. start talking 3n el figures in the slides,,,,
    >>> this is a badly destructed tooth and the second pic. Is the tooth after using composite.
    Hll2 lw konna bdna n3ml crown for that tooth ,, we have first to do ( endo>>> post>>> core >>> preparation >>> crown.
    We can use venners either composite or ceramic ,,,, you learned in lab ( crown and bridge ) how to make proper preparation to achieve retention if you are using a passive cement,, BUT in the slide ,,, palatal surface haven’t been touched ,,
    رح تضلكم تسمعوا انوا ال amalgam احسن شي وانو فش بعدها ،، بس اصلا بعد فترة حتبطلوا تسمعوا باشي اسمو amalgam.
    و رح تفكروا 100 مرة قبل ما تشتغلوا ل pregnant أو إنو تعملولهم amalgam
    ** في طالبة سألت : مش احسن انو نستعمل amalgam for posterior teeth ? لأنو بحس انها بتتحمل اكتر من ال composite
    Dr. : do you remember sth called ( evidence based dentistry ) ???
    " in CONTROLLED clinical situation,,,,,,, more than one trial to test which materil is better" so we can't say enno ana ( b7es) enno amalgam is better,,,,,,, but unfortunately this is still a new science in dentistry,, we don’t have enough randomized controlled trials.
    يعني ازا اجاكم حدا بدو يحكيلكم عن منتج معين في مجال الاسنان اسالوه عن شغلتين:
    Randomized controlled clinical trials ( RCT ,,,, bs mo rct el endo !!)
    And systematic reviews ,,, don’t forget them !!!!! very important .
    ( fe 7ada jawab >> systemic review,,, so dr. asked what is the difference between systemic and systematic??? ,,,
    ( systematic >> well written,,, or thought ,,, system by system ).
    This example illustrates the randomized clinical trials !! :
    You know that bisGMA is the basic monomer in composite, now this bisGMA has viscosity mtl ( el 3asal ),,, and you cant put honey in the cavity in a good way,, so they improved its properties by adding molecules like > uridine based monomers,,, and another one that dr. asked 3nno bs ma 7akah ,,,,,,,,,,,,,,
    Back to our example >>> one of the biggest problems in bisGMA is SHRINKAGE,," we can add cros linking agent" but now they invented what is called " LOW SHRINKAGE RESIN " like >> Silorane ,,,
    NOW in order to prove that Silorane is better than bisGMA I will do the following :
    20 patients with class 2 on lower right molar,, and another 20 patients with class 2 on lower right molar ( same size t2reebn) >>>> and use bisGMA containing composite for first group ,, and Silorane containing composite for the other group ,,,
    بس بشرط انو انا ( المسؤول عن الدراسة ) ما اعرف اي مجموعة اللي استعمنالها النوع الاول واي مجموعة اللي استعملنالها النوع التاني ،،،،،،،،،،،،،،، و وحدة من اهم التجارب اللي من هذا النوع ومستخدمة بالطب لل placebo drugs انهم بجيبوا ناس راسهم بوجعهم وبيعطوا قسم منهم دواء مثلا بنادول والقسم التاني حبة بتشبه البنادول بس ما فيها المادة وبشوفوا تأثير الدواء ،،،
    ( one of the bonds that we use,,,,,,, is BIOLOGICAL BONDING IN IMPLANTS ,,, that adhere to the bone by cells)
    We talked also about the condition of the surface,, and here it should be non-greasy surface
    ) طبعا مهم هاد الحكي لانوا متل ما بتتذكروا بلاب الكيميا العضوية كنا نحط فازلين عالانابيب عشان تفصل عن بعض وما يصير بينهم bonding )
    So we have to remove any surface debris like smear layer.
    ضلكم حاطين ببالكم انو ال generation that we yse for bonding متشابهين بكل شي الا بطريقة تعاملهم مع ال smear layer يعني في نوع بقيمها بالمرة،، في نوع بخففها ،،،،،
    في أي مادة منستعملها لازم يكون في selective itchable component at the surface ليش ؟؟؟
    يعني انو لازم يكون في مناطق بصيرلها itching اكتر من غيرها !! ليش؟؟؟ عشان يصير عنا micromechanical retention,,,
    We need a low surface tension ,,, why??? Bcoz:
    Surface tension means another force against your bonding,, plus that any polymerization process bt3ml shrinkage that will disturb your bonding and adherence to tooth structure,,,,,, y3ne FAILURE ,,,,
    Soooo again ,,, there is certain criteria that we should have to achieve a proper bonding:
    -clear adherent >>> no smear layer,,,we remove it by acid ithch or sth similar ( like in glass ionomer what should we do before using acid itch?? Conditioning ( using weak acid)
    -we should have a good wetting,,, material should flow ,,,, btshoofo enno el bonding bekoon droplets 3ks el composite,,,
    - physical bonding > covalent bonding and van der waal forces.
    - chemical bonding > interaction between large molecular weight components.
    - remember that you can do acid itching using strong acid or ucing conditioner ( with glass ionomer) ,,,
    You may do >> sandblasting ,, mainly with metal.
    Or use silica coating >> with ceramics,,,
    And tribochemical treatment ,,,, r7 n7ke 3nno in next lecture,,,
    Always remember that primers are bifunctional molecule ,,,, mmkn ykoono water based, acetone based, ethanol based,,,,
    متل ما رح تقرؤوا بال article اللي حنعطيكم اياه ان شالله على خير لانو جاي منو بالامتحان J
    والامتحان بالنسبة لاسئلتي رح يكون كتابي ما رح يكون MCQ !!!! J انبسطوا J
    -
    - Sialine coupling agents>> for ceramics.
    -
    - If you remember in dental histology>> which part is affected more in acid itching???? Prismatic or aprismatic enamel ????
    In dentine we don’t want resin tag anymore,, because most of bonding happens around collagen fibers,, and its not important for us enno resin goes down the dentinal tubules 5 microns,,, because we are talking about the hybrid layer ( 2 micron only). So we only consider the interactions at this level.
    When acid itch the tooth you have to wash then to dry,,, for how long you dry the tooth ?!!!!!!!
    This is the question for next lecture !!!!
    FINALLY ,,,,,, im sorry enno elsheet hek !!! bs wallah 7awalt ajmme3 7ake el dr. 3la 2d ma 2dert,,, bs you know mn mwdoo3 l mwdoooo3,,, sorry again and good luck J ,,
    and plz elle 3ndo el recorder ma ydllo y7ke,,,,,,
    correction are welcomeeeeeeeeeeeeeeeeeeeeeeed J
    Lec. #4
    By: muna sawwan J
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    Shadi Jarrar
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    تاريخ التسجيل : 2009-08-28
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