Maret 04, 2017
welcome to the university of michigan dentistrypodcast series promoting oral health care worldwide. so what do we want to look at today are designconsiderations for the various types of partial dentures so we run through the class i, theclass ii, class iii and class iv partials. so when we look at class i partials generally,okay, we may have, whether we look at premolar abutments they will be in either arch, wemay have canine abutments in either arch. sometimes we might have a premolar uh a canineor a lateral incisor, very rarely to have a lateral incisor as an abutment. so if youlook at different types of fulcrum lines again in your text page 96 talks about differentfulcrum lines and rather than bore you and
go over all that what you want to look atis thereãs going to be a fulcrum line axisã³or a fulcrum line axis for tissue directed forcesmeaning when people bite down on hard foods. and if we have free-end distal extension partial,we expect the distal extension portion of the partial to be compressed toward the tissuea little bit. again the tissue is more compressible than the teeth are intrudable. so if you thinkof biting down on a tooth on a tooth socket that's got a periodontal ligament, suspendingit so you bite down on the tooth, it literally intrudes in its socket a tiny little bit.so if you have a class i partial that has a bilateral distal extension and youãve gotbicuspid abutments when you bite on the partial, the bicuspid abutments intrude a little. andthe soft tissue that supports the distal extension
basis of the partial also squashes down sothe compressability of the tissue is several factors many magnitudes more than the intrudabilityof the teeth into their socket which results in a distal pipping a little bit of the partial.so thatãs your fulcrum line or your primary axis on tissue-ward directed toward forces.thereãs also another fulcrum line thatãs the retentive fulcrum line meaning if youeat sticky foods when youãre opening your mouth and thereãs something sticking to thedistal extension aspect of the partial trying to pull the partial denture away from thetissue. thereãs also a fulcrum line for that and that fulcrum line is typically going topass through the retentive tips of the clasps. so if you have a clasp on either side of thearch and the object or that part of the partial
denture that is going to resist movement thatwould try to lift it out of the mouth are the clasps. and where is the retentive aspectof the clasps? itãs at the terminal third, where they are most retentive and they gointo the undercut so a line passing through the terminal third of the clasp tips wouldbe the fulcrum line on a force going away from the tissue. so youãve got a couple differentfulcrum lines not just the one going toward the tissue but another fulcrum line for forcestrying to take the partial away from the tissue. this has been gone over extremely thoroughlyon the chart on page 96. indirect retention, what happens with indirect retention is whenyou have a partial denture framework the finished partial denture thatãs trying to be takenaway from the tissue youãve got your primary
fulcrum line for retention and then the indirectretainer helps brace the base. now the biggest purpose for a third point of reference orindirect retention on distal extension partials comes into play when we are doing relinesof the partials. so if you have a patient in for a periodic recall. how many peoplehave had a patient in for just a check-up, youãre doing a prophy on them, and you'regonna go ahead and check them up and they've either got a combination case thatãs dentureversus a partial denture or theyãve got a partial denture in one or both arches. sohow many people have had a patient like in, just to do a follow-up? three of you? maybea third of you? so the point is what do you look at? when we say evaluate their partial.so, how do you evaluate partial? i donãt
know. [scattered chuckling] howãs it doing?okay good. did you evaluate the partial? yup. how did you do that? i asked mrs. mcgillacutyif it was doing okay. what did she say? she said it was fine. did you do anything else?ehhne. and so one of the things that one would do in a distal extension partial is how wouldyou determine whether or not a distal extension partial might benefit from a re-line. oneof the things was pip a simpler way is if we know when the framework was constructed,letãs say for the sake of argument, that the lower partial denture was done so thatthe teeth we had for this lower partial that youãre imagining is we had first bicuspidthrough first bicuspid left in the patient. so we made a lower partial denture frameworkand we made a lingual plate on it. so we had
an occlusal rest and a clasp on each of thefirst bicuspids and we had a lingual plate that went around the lingual aspect of therest of the front teeth. so if i would say how do you know if the partial denture needsa reline or not just try to make it go tetter-totter across the primary fulculm line. can you seeif you take one finger--gloved hand of course--and hold the lingual plate against the teeth andput another finger on the first molar area of the partial and see if you can tetter-totterit front to back everybody with me now? and if you can see the lingual plate area thatãson the lingual of the anterior of the teeth noticeably lift up off the teeth so when youpush down on the first molar area you can see that the back end of the partial tiltsdown and then that part of the partial framework
that fit against the lingual aspect of thelower anterior teeth lifts up in the air and comes up away from the teeth, can you seethe only thing that can cause that is if the gum tissue on the underside of the distalextension base has remodeled, has reabsorbed and reshaped itself? so the gums under thedistal extension base donãt fit up under the partial as good as they did when it wasfirst made. so when a brand new partial was put in and you look at it to see if it willtetter-totter front to back if itãs bilateral distal extension you don't expect to see alot of this tipping back and forth on a new partial. over time a year, two, three, four,whatãs going to happen is the soft tissue is going to remodel a little bit so when yougo to do that same pushing back and forth
the tissue isnãt supporting the back endof the partial, it goes down and your indirect retainer is your point of reference becauseif that lifts up off the teeth itãs telling you that you got tetter-tottering. question? [question inaudible] professor: uh-huh. tetter-totters a lot. uh-huh. [question continues] professor: the question was if you have aclass iii partial thatãs hypothetically tooth supported at all four corners so there isno distal extension and at least according to the record as much as we can believe therecord, the provider at the time said things
fit well and everything was okay at the timeit was delivered. you are now the poor sucker whoãs doing the recall a year later and youãrecleaning their teeth or youãre doing whatever and you try this class iii partial denturein and it seems like it rocks quite a bit. it doesnãt fit on the teeth very well. weãllgo over class iiis in a little bit here but basically if your partial denture is toothsupported all the way around, would any change in the soft tissue okay, if the gumãs reshapeda little bit would that in theory have an effect on the fit of a class iii partial? nothing to do with it because itãs toothsupported all the way around. now typically if a patient is being compliant. iãll saythat again. if ã± underline three times ã±
if a patient is being compliant and wearingtheir partial on a regular basis would you expect that the partial denture frameworkfitting on the teeth will help stabilize the teeth in that position? when the partial isdelivered? if in fact things fit well which they said it did in the record? is that areasonable assumption? so if the patient fits like socks on a rosteror something really bad okay when you eliminate the impossible everything left however improbableis probably the cause. so the patient was either non-compliant and didnãt wear it whichallowed the teeth to shift. itãs sort of like i donãt know how many of you have undergoneorthodontics and for those of you who did orthodontics did you wear retainers for someperiod of time? and if you got lazy because
youãre just a human being and you went severaldays or a couple weeks without wearing your retainer when you put your retainer back in,it felt like it didnãt fit so good. it fit pretty bad in fact. and just after a day ortwo things seem to settle in and the teeth readjusted themselves to fit your retainer.same thing happens with a partial denture. so if i have a situation like you have i eitherassume one of two things. the patient was non-compliant and didnãt wear their partialfor some period of time, it's been in the dresser drawer for some period of time andput it in when they came in to see you so now itãs your fault because it doesnãt fitor they dropped it or the dog got a hold of it because patients lie. you know, itãs allmy fault. youãre stopped by the cops so you
see the gum machine come up in your rear viewmirror, right? so whatãs the first words out of his mouth? do you know how fast youwere going maãam? you know? [in higher toned voice] no officer i didn't have any idea.iãm the virgin mary here. what happened? you know so it's sort of like people are notthe best at saying: i was doing 20 over, iãm in a hurry, itãs my fault. put the cuffson me. itãs all my fault. probably if you said that you could blow the officer overwith a feather and theyãd let you off with a warning just ã«cause theyãd be so blownaway that someone was just upright honest with them. so to answer your question my greatestsuspicion in that circumstance is they were either non-compliant when wearing the partialand teeth shifted or they dropped it and it
got bent. go ahead. did the tooth in question that had this sortof miniscule resi on one tooth, did it have any lingual or buccal bracing on the toothor that was theã±? okay so the point is you can somewhat of a miniscule resi. but if thereis some sort of retentive arm or bracing arm or clasp arm on the buccal or lingual of thetooth itãs unlikely that itãs gonna shift that much if itãs being worn on a moderatelyregular basis. uh-uh. again if the tooth ã± if the partialis being worn on a fairly regular basis. if they are not wearing it absolutely itãs probablygoing to keep tilting over mesially. but if the partial is in place it runs slam intothe proximal plate on the partial so even
if the occlusal rest were to break off youmight get a little tissue irritation around that tooth because in that area the partialwould be freely--you see what iãm saying? slide up and down around the tooth but becauseof the proximal plate on the partial the tooth would have a heck of a time tilting more mesially.if the partial was being worn. so again when i see those kinds of things especially withan all-tooth supported partial, the first--and with students because again they push youall over the place i canãt tell you how many years itãs been--thatãs one of the advantagesin dentistry of getting gray hair. okay, i canãt tell you how many times over the yearsi come into the cubicle and i tell the patient verbatim exactly what you just told them sixminutes before i got there and theyãre going,
ã¬yes, doctor, okay doctor, uh-huh, okay doctor,ã®and then they leave. and then you come up to me after clinic and you go i want to sendthat person to the moon because i said exactly the same thing you did and they said are yousure? i donãt agree with you dudda-this dudda-that so when you get more gray hair they just sortof tend to and you say the same thing they just donãt fight back as much or push backas much. but many times also if you, itãs sort of like the [clears throat] dna on thedress, you sort of deny, deny, deny right? right up until thereãs incontrovertible proofto the contrary right? and so if you ask the person were you wearing this? oh yes! yes.of course. and we donãt have the dna on the dress so to speak, to sort of make peoplechange their story. but thatãs another matter.
so if we look at a class i partial here basically.whatãs a fairly common circumstance of a class i partial? youãve got a bilateral distalextension. youãve got primary retainers, in this case, bicuspids. this happens to bea lingual bar not a lingual plate so we have an indirect retainer here. again if we imagineour primary fulcrum line here. we imagine sticky foods a milk dud or a juju bee, a gummybear stick in here and try and lift this away from the tissue, the fulcrum line is goingto be through the clasp tips and by fact of this touching the indirect retainer or ifi have a lingual plate and the plate touches the lingual of the anterior teeth thatãsgoing to resist the back end of this thing tipping up in the air. but adds are more importantthan that because really if anyone eats gummy
bears with these theyãre coming out in theirlap anyway. they wonãt stay in that tight. the biggest reason and the biggest advantageof having indirect retainers is an indexing position for the partial to determine whetherit needs a realign and then if you choose, and say gee, it does need a realign. how arewe going to do the realign on a partial? unlike a complete denture, unlike a complete denture.for a partial denture what you are not going to do, what you're not going to do is loadup the underside of these bases with a little bit of pvs, seat it in the mouth and justtell the patient to bite together. youãre not going to do that. how come? can you see that over time the partial denturebase settle down a little bit because it lost
tissue support? itãs very possible that theopposing teeth if they were natural teeth extruded a little bit? so if you just letthem bit down theyãll just tilt it to the same orientation it had. so if you go aheadand put your pvs in the underside of the bases, seat the partial denture framework in andcarefully hold firmly the partial denture framework so that the primary occlusal restsare down and the indirect retainers down. if itãs a lingual plate you hold it so thatyouãre sure that that lingual plate holds down and tight against the teeth. so youãreholding the framework in its proper orientation to the teeth which is essentially suspendingthe free end of the partial in space over the top of the gums and your impression materialis making up the difference retreading a tire.
people get that okay? you send it off to thelab, the lab realigns it so now it comes back itãs got new plastic under it. you fit itin the patientãs mouth, you ask them to bite down, what do you expect to see concerningthe occlusion? itãs too high in the back. so then you just adjust the occlusion on thepartial as necessary to get it so now the partial doesnãt rock front to back, the biteãseven. but we have adjusted the occlusion on the partial a little bit because if in factthe distal aspect of the partial sank down because of loss of support where the tissuechanged, itãs reasonable to assume that the occlusion of the opposing arch followed itdown which is why you donãt just have the patient quote ã¬bite togetherã® when youãrerealigning a partial. you orient the framework
correctly to the teeth and thatãs where theindirect retainers come in as a really good third point of reference for situating theframework on the teeth and knowing itãs well seated. itãs also a great, as i said, it'sa great device for telling whether the partial denture is rocking. has it lost base support?easiest way to tell is to seat it as a tetter-totter. so you look at, hereãs an upper case. nowyou donãt see that much tissue change over time with maxillary partials. theyãve gota lot more real estate to cover. thereãs a lot more square millimeters of gums to supportthem. this whole area across the center of the palate, okay, is pretty good support soi donãt see the need to realign maxillary partials anywhere near the rate at which weneed to realign free-end mandibular partials.
because weãve got a lot more tissue supportfor upper partials. and here just shows one in the mouth. so youbasically got your indirect retainer, youãve got your lingual bar, and youãve got yourclasps. so you check things out and you see: do things rock? here is a lower, weãve got canine abutments.now in this particular case can you see looking straight down on the top of the canines thatweãve built, weãve done crowns on them both and weãve created raised cingula on the twocrowns because again on the lingual of a cuspid as it normally exists, itãs just that slopethat goes all the way down to the gum is just not a good vertical resting spot. so if thetooth does not otherwise need a crown, you
can build that lingual aspect up with compositeto create a ledge on the lingual of it and composite. you could also go to the thickestportion of the canine, the very thickest portion, down on the cingulum, take a parallel-sidedflat ended bur and cut a small ledge, a fairly narrow ledge, or you can build it up withcomposite. any of the three. my main goal isnãt to leap immediately to doing crownson teeth if they donãt otherwise need a crown other than for creating a resting spot. youcan do that other ways. sometimes when canines are rotated weãll actually put a small, littlenotch on the incisal edge of the canine so that this framework fits on that little notch.canines are rotated a bit that does not wind up being aesthetically unpleasing. now manytimes we would not use incisal hooks if we
thought this was going to show very much.rather than use this my own prejudice would be if i could, to try and use a little bitof a ledge down on the cingulum at the lingual. when we look at canine abutments in the maxilla,as much as i possibly can, what i try to do in the maxillary arch is avoid this if i can.because again one of the biggest complaints patients are going to have about partial denturesin general, removable partial dentures, it's actually two things. one they come in andout. can you give me anything thatãs fixed thatdoesnãt come in and out? well depending on the number and distribution of teeth you maynot have that choice. so one big complaint: gee, they come in and out. second biggestcomplaint is theyãre ugly. i donãt like
that big clasp showing on my tooth. whichis why anytime, and i mean anytime, you get a maxillary partial denture in which youãregoing to have a canine as an abutment try to survey it in such a wayã³if this is thecanine and this is the front of the mouth here ã± try to work things in such a way thatyou see if you can come down with a infrabulge clasp arcing toward the distal. so this isthe greatest convexity of the tooth if you look at this from the incisal edge. cuspidteeth or canine teeth when you look at them from the incisal have two faces. thereãssort of a distal face and a mesial face and it sort of comes around like this and if thisis the front of the mouth anything you can get from here back tends to hide. so the cheekis hiding it a little bit. if you can create
an infrabulge clasp with a modified tear andeye at the distal, labial aspect of the tooth as close to the gums as you can get it. againwhen youãre surveying these casts the whole idea about trying to reshape the labial aspectof the tooth to get the height of contour as low as you can towards the gums. iãd likemy 10,000th of an inch of undercut to happen ideally about .5 millimeters from the gumsbecause you can see the closer you get your clasp to the gums two things happen. one isitãs better mechanically because youãre grabbing closer to where the tooth comes outof the bone but secondarily itãs just nicer looking aesthetically because on an uppercase if the clasp is way up toward the gum depending on where the patient smiles theirlip doesnãt come up above the clasp so you
donãt see it and if youãre hiding it aroundthe distal labial of the tooth you donãt see it. so over the years i just see lotsand lots of partials on maxillary cases where thereãs a canine involved and as far as iãmconcerned are just butt ugly. because somebody didnãt take the time to take a study modeland survey the darn thing and say where is the height of contour? can i come up withthe survey that will give me the height of contour that tries to be at the distal labial?then i try to get a good enough impression so i hope i donãt have a lot of undercutof soft tissues to content with up deeper in the vestibule from where i want to comedown on that tooth. because if iãve got real severe undercut up in the soft tissue in thatarea then itãs difficult to do an infrabulge
clasp but on maxillary partials whenever thereãsa cuspid involved, i really like to do an infrabulge clasp if i can at all and thatãswhatãs drawn on here. the thing i would change on the drawing is i would not take it to themid-labial. i would take it to the distal-labial sneaking it around this back corner. now ifi do that, one of the other principles iãve got to do is that iãve got to grab aroundthat tooth more than 180 degrees so that the tooth doesnãt move over time away from thepartial denture framework. so that means i need to get some aspect of my framework asfar up around that mesial-lingual as far up there as i possibly can so if my claspingis at the distal labial i need to get my indirect retention or my occlusal restore-somethingas far around the corner around the mesial
lingual as i can so i get more than 180 degreesof encirclement of the tooth so it doesnãt move over time. and so here are some other cases where weãlldo these this is starting to get to the right idea but it's sort of is like if we carriedit right over to the mesial labial corner and then went back, right idea but itãs sortof like hmmm screwed that one up a little bit. because if we were doing this anywaywhy didnãt we just come down, arc up a little further and have the anterior most aspectof that t-bar be just about mid-labial on the cuspid or little bit distal to the mid-labial?so my clasp engaging was right here because this when the patient smiles jumps right outat you. itãs like this chrome hub cap looking
at you when they drive by. pretty, who didthat for you? dr. shotwell. well iãll be sure to tell all my friends. not bad. thatãsgreat. and if you have a modification space samething here. youãve got your class i because itãs bilateral distal extension happens tohave an anterior modification space. class iis. okay, what weãve got? class ii is aunilateral free-end upper or lower. so what have weãve got here. basically youãve gotyour primary occlusal rest, your primary occlusal rest, indirect retainer. your fulcrum lineruns through the occlusal rest if weãre talking about the fulcrum line that is concerned withtissue-ward movement. if you bite down on food in this area and you try to push thisdown your fulcrum line runs across these occlusal
rests. your retentive fulcrum line is stickyfoods that are trying to lift the partial away from the tissue is gonna go through theretentive tips of this clasp and this clasp. so this is your fulcrum line if it is forocclusal-ward forces. if itãs for sticky forces trying to remove the partial in theretentive fulcrum line goes from the tip of the cuspã³or iãm sorryã³the tip of the claspto the tip of the clasp. so that would be the removal fulcrum line. class ii upper. same kind of a thing. youãvegot a unilateral distal extension. okay we basically have up here our primary retainer,our primary retainer, indirect retainer third point of reference. here again they happento put a t-bar clasp on this what i would
do a lot of times if i could take a high speedhandpiece or a carbide disk. if i had a reasonable retentive contour at this distal labial aspectiãd try to recontour this and cut this part off. again the curvature of this infrabulgeaspect if i can get that to come down a little bit distal to the point of greatest convexity,iãd hide the whole thing better. now with a lot of these patients when youãre assessingthe patient and youãre thinking about what you might be doing for clasp design on anyof these patients male or female when theyãre in and you take your preliminary impressionsone of the things to do with the patients is to get them so they moisten their lips.lips are nice and relaxed. you ask them to smile. then you ask them to put a really fakeysmile on thatãs so hard itãs going to break
their face and see how high they can reallyfakey smile and you may get some people that even on the fakey smile their lip doesnãtget up far enough so that itãs an issue but thatãs useful information. thatãs usefulinformation because if a person has a really high smile line then you want to do anythingyou can to try to hide or diminish how obvious the clasp is. and to that end itãs goingto work out better if you survey these things and be looking real hard for retention atthe distal labial aspect of the tooth. hope that you do not see a frenum attachment comingin there or a big soft tissue undercut. soft tissue undercuts bother me more than frenumattachments. if aesthetics is a big deal, the patient canãt afford a precision attachmentof some sort and i got a frenum in there what
do you suppose iãm going to do? iãm going to call up my friendly neighborhoodperiodontist or if you do it yourself, iãm going to do a frenectomy. iãm just goingto cut it out of the way. so i can put my clasp where will it be aesthetically the mostpleasing and iãll just lose the frenum at that point. if thereãs a huge soft tissueundercut thatãs a little more difficult to deal with. but if itãs a frenum thatãs inthe way you can consider doing a frenectomy to maximize the asethics of your clasp. okaya ii, class ii weãve got a modification space either a front or a back modification spaceso hereãs your class ii unilateral distal extension and thereãs another spot that'sdential so here itãs bounded by teeth so
we have a distal abutment here. so this wouldbe a class ii-p. okay so here basically is the framework of that which shows you theposterior modification space, thereãs the posterior modification space when weãre readyto get a bite on it. same kind of thing in the mouth. okay hereãs our class ii posteriormodification space with the molar. primary occlusal unit our primary uh, primary retentiveunit. another one over here primary retainer. thatãs the word iãm grasping for is ã«retainerãwhich consists of an occlusal rest, a retentive arm, and a reciprocal component. thatãs eithergonna be a lingual reciprocal arm or itãs going to be a lingual plate that goes acrossthe lingual of the tooth so we have occlusal rest, clasp component and reciprocation component,okay? so you can also have a class ii. here's
your distal extension, free end and weãvegot both an anterior and a posterior modification space on this. so again itãs still a classii. it happens to have two modification spaces. and so here is that case in the mouth. combinationcase. youãve got an upper denture, you've got a lower partial, youãve got your freeinside with the clasp okay? weãve got some modification spaces then on over the otherside. thereãs the same thing in a maxillary case.again here weãve tried to make moreã³these were done several years ago when we took thesepictures and over time what weãve tried to do with these i-bars isã³i tend to like amodifed t-bar rather than an i-bar and the reason i like a modified t-bar rather thanan i-bar is it just hasã–
it has a bigger footprint. it touches moretooth than this. and again if i can try to hide this around the back corner of the tooth,i donãt think iãd pay an aesthetic price for that. but it used to be one of our formerfaculty loved doing these and he would try to make these things like jewelry so theyreally got so they were really fine, barely showed up at all. what do you suppose thedown side of that was? that they didnãt necessarily break they justcame out of retention real quick. so you didnãt have a big enough foot print and this armthat came down just wasnãt stiff enough that they were back all the time getting it adjustedwhich over time led to what one individual said is a break. so if iãve got just a slightlymore robust arm here and it doesnãt have
to be a truck bumper okay on a kenworth semigoing down the road. it doesnãt have to be that big but i find that the little foot goingtoward the distal just gives me more square millimeters of contact with the tooth thanthat little area of the i-bar will. but again i try not to have this thing come down mid-labialon the tooth i want it to come down toward the distal labial aspect. because itãs goingto give me a more aesthetic partial and depending on the patientãs smile line, they just donãtshow up that much it works out really well. class iiis. which pertain to one of the questionsasked earlier. if iãve got a class iii hypothetically i shouldnãt have to deal very much with theresorption of the dentureless ridges. so if iãve got an area in here or an area in herewhen you get to the mouth both of these areas
where itãs dentureless are bounded by teeth.so when this person bites down really hard on their partial, theyãre not squashing thegums. because the partial is tooth-supported all the way around. so if this was deliveredlast year and you wind up getting the patient 11 or 12 months after this was delivered andtheyãre telling you it doesnãt fit worth the tankerãs darn again all you can go byis whatãs written down on the form six. so if the form six says everything fit just peachyat the time it was delivered and the occlusion was good and it doesnãt fit so good now myfirst supposition is the patient either has not been compliant about wearing it or itgot dropped. it got dropped. and in either case whatãs going to happen is if the frameworkgets sprung you can try to fiddle and fix
it but itãs not going to work well. if thepartial is not being worn as was asked before this distal molar and this distal molar itãsvery likely that they may in fact be pounded a little more mesially so that distance fromthe mesial marginal ridge to this tooth to the distal proximal of this tooth will havedecreased a little bit. and if you try to seep the partial down in itãll seem really,really, really tight because whatãs happening is your partial denture is now acting likean orthodontic appliance. and youãre trying to see if you can get those distal teeth pushedupright again so depending on long the patient was non-compliant about wearing it you mayor may not be able to get that much movement. you may or may not. so hereãs another one.now many times people will ask if iãve got
a class iii partial thatãs completely toothsupported itãs very common that i will tend to use a metal base with bead retention. becauseagain if iãve got a completely tooth supported partial i donãt plan on having to realignthe underside of that partial. because i donãt expect the gums are going to change much becauseiãm not putting much pressure on them. not putting any pressure on them. so when iãmdoing a completely tooth supported partial pretty common in the dentureless areas. iãmjust going to put a cast metal base with bead retention. occasionally weãve done this ifiãve got tooth in this area. so hereãs a tooth thatãs, a partial thatãs entirelytooth supported but weãre laying right over the top of this tooth and you may or may notbe able to see very well sometimes what happened
with these teeth is the tooth basically iscut off pretty much at the gum line and occasionally these will have a post and coping put on them.now can anyone imagine a reason why i might have my partial denture just go over the topof that tooth? any thoughts? sometimes if you take study models and mountthese cases the tooth in this area sits way up above the plane of occlusion. itãs almostin contact with the upper gums. and when you look at it itãs real obvious from the frontthat this tooth in the back because it was unopposed for some period of time extruded.so if you were going to leave that tooth at the height it showed up at the plane of occlusionon that side in the patient would be going way the heck up in the air where upon youãvegot no room to work on the upper arch. so
one of the things you want to do with studymodels is evaluate the orientation of your plane of occlusion and in other areas wheredo you suppose you learn, where you do learn how to evaluate the orientation of the planeof occlusion? where do you learn that? with your denture patients. yeah? so whatãs areasonable plane of occlusion? even with the anterior teeth to the center of the retromolarpad that you do with the denture. so what happens to students all the time when theyget these bigger cases if thereãs teeth there, no matter how screwed up or crooked the teethare with the anatomic landmarks somehow you people think the teeth came down off mountsinai with moses or something. oh theyãre sacrosanct. oh my god they canãtbe touched! oh we got ã± how can we possibly
work with it dr. shotwell eheheh well, whereare your anatomic landmarks? so maybe on a tooth like this in some cases maybe it wasalready endodontically treated and iãm not even thinking about putting a crown on itiãm going to hose that puppy right off at the gum line. and many times how many of youhave had it, you get a tooth thatãs the terminal tooth in the lower arch. very last tooth inthe lower arch. what do you often see concerning the gums at the distal marginal ridge of thelast tooth in the lower arch? the gums are right up even with the marginal ridge of thetooth. anybody had one of those? theyãre fun to do crowns on, arenãt they? becauseitãs real easy to get that axial wall on the distal. you people are freaking out andyou know i say give me the anesthetic but
theyãre really profoundly numb dr. shotwell,i gave them an infraorbital. i know they are. now was i speaking klingon or what? give methe anesthetic. and then i go and infiltrate the daylights out of this tissue right here.till it turns about as white as my lab coat. ã«cause what am i about to do? rotary gingitage. okay? weãre going to vaporizeit. because iãve got to get a hold of that tooth. there are many times depending on wherethis has extruded to, itãs way above where a reasonable plane of occlusion ought to be.so iãm smoking that puppy down until itãs at a reasonable plane of--- just like youwould if you were going to adjust the wax rim on a denture. so the denture stuff reallydoes come back to help you even when youãve
got teeth there. look at your landmarks. andso the reason one might consider making a partial like this is this side of the mouthis extruded. the tooth perhaps was already endodontically treated so they cut this puppyright down even below the height of the gums at the distal marginal ridge. we smoke thattoo. and then put a bevel around this whole thing and all i do is haul out the whole pulpchamber so when i get this coping back, this post and coping, it sort of looks like a mushroom?this mushroom stem coming down that sort of goes down where the pulp chamber was, peoplefollowing me okay? and the occlusal is just a flat occlusal that doesnãt try to go muchhigher than the gums. it just covers the occlusal of the tooth and it goes down to the bevelthat i created on it. so now i got this thing
about the right height or a little below theheight of an ideal plane of occlusion. then i can take my partial and rest it right overthe top of it. iãll have no intention of putting a tooth on top of this. my teeth aregoing to be up here but my plane of occlusion will now be even and level. and it wonãtbe going way the heck uphill on the side where the tooth was extruding so look at some ofthose things when youãre thinking about these. so here is a class iii all tooth supportedwith an anterior modification space. hereãs another class iii in a maxillary case so youbasically got teeth over here okay? you can see it just come across the palate sometimesyou affectionately refer to these things as a closed-palate or a toilet seat for obviousreasons and so you can go ahead and not cover
too much of the palate but the thing hereis if you look at this and say well why wouldnãt i just choose to do that longer span? youãdhave three pontics. can anyone give me some reasons why i *might* not chose to do thatas a fixed partial denture? why wouldnãt i do it as a bridge? do peoplefeel comfortable about that length of a span? itãs getting pretty long. now youãre goingahead and putting a crown on it, crusting it, putting a crown on a molar. again thething you do is you remember way back in the depths and the recesses of your brain, indr. mayãs lecture something called anteãs law. does anyone vaguely remember what anteãslaw talked about? okay, number of square millimeters of rootsurface in contact with bone. iãm not talking
about anatomical root surface, iãm talkingabout clinical root surface. so if a person has lost some attachment and theyãve lostsome bone height, can you see they still got the same anatomical root surface but theydonãt have the same clinical root surface? people follow the difference between thosetwo? so suddenly if you lose bone your clinical crown gets taller and your clinical root getsshorter. so now you start looking at how many square millimeters of tooth root do i havehere and how many millimeters of tooth root do i have here in bone? and is that equalto or greater than? preferably greater than the square millimeters of tooth root of allthe teeth that are being replaced, all the pontic teeth. now the other thing that happenswhen you have a longer span bridge in the
upper or the lower jaw, what do you supposeone of the forces happens on the fixed partial denture here is that just really beats theperiodontium up a lot? itãs not straight down vertical forces itãs buccal lingualforces. forces that try to rack this thing buccal lingually. and can you see that ifyou do this with a partial denture this is what weãre talking about when we talk aboutcross arch stabilization? so the fact that the partial comes over here and gets a goodgrip on this tooth on the other side of the arch can you see this is now like a three-leggedmilk stool? itãs pretty stable so if any forces try to take this side and wiggle itbuccal lingually it gets braced off this. so longer span from front to back is not alwaysideally treated as a fixed partial denture.
if you can put implants in there not a problembut long span with a fixed partial denture can spell heartache especially if you everget a long span in this anterior tooth and i see it over and over again is a cuspid thathas been endodontically treated and has a post-end core in it. so i canãt tell youover the years how many of these long span fixed partial dentures iãve seen in whichthe anterior abutment is a cuspid that was endodontically treated that had a nice castgold post and core and a really nice fitting pfm crown. what do you suppose i see happento these teeth three to 10 years down the road? vertical root fracture. now we are inthe vernacular scra-hood because now i no longer have a cuspid to hang onto, iãm upto a lateral incisor. lot of support there,
isnãt there? thatãs a real peach. so nowletãs a longer span bridge using a lateral as our primary abutment. duh. well becausethe lateral is not too good letãs just pull the lateral and let's splint the two centralstogether. now youãre just getting insane. just donãt even come to me with that okay?now youãre thinking really hard about implants. youãre thinking really hard about some sortof a partial. so longer spans are not always the best treatment with fixed partial denturesbecause of the buccal lingual force that will go on those long span bridges and the partialcan give us cross arch stabilization. so it really helps mitigate the buccal lingual forceson those teeth. so basically here is just another example of a class iii. tooth supportedall the way around. again we try to keep getting
these things iãm much happier if theyãretucked around the distal, labial, or the distal buccal corner. then we get to the class ivs. class ivs arealways tough because your replacement teeth are always in front. and sometimes these tendto be tippy and itãs really hard to get all the tippiness out of these. so over your practicinglines what you may want to consider is a lot of these class iv partial denture cases canreally be treated successfully if you can find one spot somewhere under this anteriorarea to put a single implant. and the advantage of doing it with a partial denture is thelocation of the implant doesnãt have to line up exactly with the tooth. now if youãrein practice for very long what youãre going
to see is some genius with no planning putssome implants in the anterior area and the location of the implant is exactly in theinterproximal embrasure area of where the tooth ought to be. so now how do you get thatso it looks pretty when youãre trying to put fixed work on it? does it go: it takesrestorative ingenuity itãs sort of like yeah right itãs called paint porcelain to tryto cover up your screw-up, okay? so on these when youãre doing it with a partial dentureyou can just put a single implant anywhere across here put a zest locator on it and itãsgoing to work really well. very seldomã³to show you this oneã³it doesnãt happen oftenif you have one of these people that's got class iii lower arch. it seems like all theteeth sort of tow in lingually. when you survey
it you canãt feel anything on the lingualof the teeth, not very often, but occasionally we will do a labial bar. so all the teethare leaning so far lingually we canãt fit anything down lingually so the partial goesout here and as luck would have it in most of these cases the lip conceals that prettywell. most of the time now would you choose to do that as an implant? absolutely you wouldchoose to do it as an implant. on these big cases the more teeth youãre replacing uphere the more difficult it is to not have that anterior tipping phenomena. and in yourpracticing lives, unlike mine, one of the things i try to tell anyone with this situationis try to get a: an implant up here somewhere to brace the anterior aspect of this. manya time with class ivs when they come back
for recalls this is what you see because ofthat tippiness. you can beat yourself up about this but you canãt always get rid of this.try as you might. try as you might. you have been listening to a presentationfrom the university of michigan's school of dentistry which is dedicated to supportingopen learning and open educational resources. this recording is licensed under the creativecomments. it may be reused and redistributed for nonprofit use. please attribute materialsto the university of michigan's school of dentistry and redistribute under this samelicense. for more information on how this and other university of michigan school ofdentistry recordings may be used visit www.dent.umich.edu/license.
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