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A Quickie Breakdown of Partial DenturesAdam Kirkpatrick & Ulf Temnitzer

Making partials can be pretty overwhelming at first, but it is actually pretty easyonce you get the basics down. In light of that, I have made this “quickie breakdown” so

that you have an idea of what’s going on before you have to start memori ing the nittygritty details. !lso, this is a good refresher for those of us who have gone through theclass and have forgotten things. "artial dentures are made for people who are missingsome teeth and have some stable teeth left. #epending on the conformation of theteeth that remain, there are some different ways to make a partial more stable. $hereare % different classifications of the stability of the teeth, and they are &ennedy 'lass I,II, III and I(.



$here are all these classifications, but you really only have to worry about whether it is tooth)borne or mucosa)borne, and if it’s a &ennedy 'lass I(, you might doa rotational path partial. $his dictates what type of clasps you can use. If you have apatient that has more than one of these classifications, you go with the lowest number,and other missing areas are added as modifications. !lso, there are “modifications” foreach classification. *ave a look at the picture to figure them out. +et’s not get ahead ofourselves, though. +et’s have a look at the different parts of a partial.

'omponents of a "artial

$he main components of a partial are-. 'lasps

. /ests0. Ma1or 'onnectors%. Minor 'onnectors2. !crylic retention meshwork3. "ro4imal plates5. Indirect retainers

'lasps+et’s talk about these first. $here are only 0 types of clasps mainly used here at

"acific, and they are-. !kers

. /"I0. /"'

6asically, you always use an !kers clasp when you have a tooth)borne situation,and you use stress releasing clasps 7either an /"I or /"'8 when you have a tooth)mucosa)borne situation 7distal e4tensions8. If you have to use an /"I or /"', you

would want to use the /"I if the situation qualifies. $hat is the basics of clasps 9 youcan learn more about them from the book.



'lasps 9 More Info 7some nitty gritty8

• Akers . :se this for tooth borne area. It has a rest, pro4imal plate, retentionarm and bracing arm. $he pro4imal plate is on the same side of the rest and

sort of “waterfalls” off of it. $he two arms come off of the pro4imal plate 9 theretention arm is usually on the buccal and the bracing arm is usually on thelingual. $he retention arm is the one that actually engages the undercut ofthe tooth and the bracing arm basically 1ust makes sure that the tooth ishugged and doesn’t become mobile. ;ust as a side note, you can have two!kers clasps back to back on two ad1acent teeth.

• RPI . :se this for tooth)mucosa borne areas 7i.e. distal e4tensions8. In fact,

this is the preferred one for that. It has a mesial /est, "ro4imal plate and Ibar 7the “I” in /"I8. $he rest is always on the mesial, the I bar goes on thefacial and engages the undercut 7and stays below the survey line8, and thepro4imal plate is always on the distal. $he pro4imal plate e4tends from - mmabove the survey line down to the gingiva. <ou can’t use an /"I if anythinggets in the way of the I bar 7super inclined teeth, undercut in the gums lessthan 0mm away from the tooth8.

=.=-=”undercut

Mesia

l /est

"ro4imal"late

I 6ar

/est

"ro4imal"late



• RPC . :se this for tooth)mucosa borne areas 7i.e. distal e4tensions8. $his is what you use if you can’t use an /"I 7if the tooth is inclined too much or if thesoft tissue undercut is less than 0 mm away from the tooth8. It has a /est,"ro4imal plate and 'lasp 7the “'” in /"'8. ;ust like the /"I, the rest isalways on the mesial and the pro4imal plate is always on the distal. $he

pro4imal plate still e4tends from - mm above the survey line down to thegingiva. Instead of the I bar, however, this has a clasp. $he clasp comes offof the pro4imal plate and engages an undercut on the facial.

>n both of the stress releasing clasps 7/"I and /"'8, the pro4imal platedisengages the guide plane on the tooth when the denture has force e4erted on it.#uring chewing, the denture sinks into the tissue a little and basically rotates thepro4imal plate out of contact into the undercut area of the abutment tooth.

/ests$here are only a few types of rests that we mainly use here at "acific and they

are-. >cclusal

. ?4tended >cclusal

0. 'ingulum%. 6all

<eah, rests are pretty simple. <ou can put them either on the mesial or distal ofteeth depending on the situation. More details below and in the book.

Mesial /est

=.=-=”undercut

"ro4imal"late

'lasp



/ests 7nitty gritty8-. >cclusal 9 use on posterior teeth for most situations

o @eed to be a minimum of -.2 mm thick at the marginal ridgeo “Apoon shaped”o -B0 facio)lingual width of the tooth 7or C the distance between cusp tips,

same thing8

. ?4tended >cclusal 9 use on posterior teeth if tooth is tipped to direct the forcealong the long a4is

0. 'ingulum 9 use on anterior teetho “(” or “:” shaped in cross sectiono Atraight or inverted “:” shaped from the lingual



%. 6all 9 use on anterior teetho /ounded outline formo >n mesial or distal half of tooth at 1unction of gingival and middle -B0 rds

o May need to be filled with amalgam if penetrates into the dentin

Ma1or 'onnector$his is the bulk that holds the partial together and provides stability. 6asically,

you want to get away with covering as little gingiva as possible while still maintaining thestrength because having a bulky partial sucks for patients. $hese are the differentma1or connectors that we mainly use at "acific

• Ma4illao Dull "alatal "lateo Modified "alatal "lateo Midpalatal Atrapo !nterior "alatal Atrap 7*orseshoe8o !)" Atrap

• Mandibleo +ingual baro +ingual plate



$here are different reasons for using all of these different ones, and you’ll needto learn about those in the book. $he ma4illary ma1or connectors need to be a minimumof E mm wide. >n the mandible, you would use a lingual bar when you have 5 mm ormore from the gingival margin to the base of the lingual vestibule 70 mm of spacebetween the gingival margin and metal F % mm minimum width of lingual bar8. If you

don’t have 5 mm or more, you would use a lingual plate.

Minor 'onnector

@ot too much to say here. It is 1ust the part that connects the rests and stuff tothe ma1or connector. $hey are easy. $he only thing you need to keep in mind is howfar away the metal framework has to be from the gingival margin. If it is too close, you

will cause plaque retention and tissue irritation. >n the ma4illa, you need to have aminimum of 3 mm from any metal 7ma1or or minor connectors8 to the closest gingivalmargin. >n the mandible, you need to have a minimum of 0 mm from any metal 7ma1oror minor connectors8 to the closest gingival margin. !lso, you need to make sure thatthe minor connectors are at least 2 mm away from any of the other vertical features.

!crylic Meshwork

!nterior "alatal Atrap Dull "alatal"late

Modified "alatal "late !)" "alatalAtrap

MidpalatalAtrap

+ingual6ar +ingual

6ar +ingual"late



!gain, easy pee y. ;ust the metal “meshwork” that holds on the acrylic. <ou want about one hole in the metal for each tooth you are replacing. *ave a look at thema1or connector pictures if you want to see what it looks like.

"ro4imal "lates

$his goes along a “guide plane” that you prepare on the teeth with a bur. $hereare several guide planes made on the teeth, and they guide the partial to seat in theright place. ;ust like with a crown, they need to draw with each other, which I hear ispretty tough to do. $he pro4imal plates are the metal parts of the partial that sit againstthe guide planes. >n abutment teeth with stress releasing clasps 7/"I or /"'8, thepro4imal plate reaches only - mm above the survey line.

@ow a word about the guide planes. $hey are on the occlusal -B0 of abutmentteeth that are ad1acent to an edentulous area 7basically anywhere that the partial willslide against8. $hey are meant to be parallel to the path of insertion of the partial so it isguided into place.

Indirect /etainers

<ou only need these with a distal e4tension partial. >n these partials, there is a“fulcrum line” that e4ists if you draw a line between the two distal most rests. 6asically,if you eat a sticky food and it tries to pull off the distal e4tension, the partial will fulcrumand push down in the front. $he more room it has to push down in the front, the more it

will lift off in the back. Make senseG In order to stabili e this, you can 1ust put a braceanterior to the fulcrum line so that the partial doesn’t have anywhere to push down inthe front. $hat keeps it from lifting off in the back. $his brace is called an indirectretainer and it is basically 1ust a rest connected to the partial with a minor connector thatkeeps the distal e4tension of the partial seated during eating and talking.

Dulcrum line

Indirect retainerresisting “lift off”

"art of denturethat “lifts off”



*ow to !naly e, Aurvey and #esign a "artial>nce you know the stuff we 1ust discussed, this part isn’t that hard. Hranted,

there are a million different scenarios that change what will be e4actly done but if youget the basics it isn’t that tough. !naly ing is the process of figuring out where theundercuts are. Aurveying is the process of drawing on the cast to show where those

undercuts are. #esigning is the process of figuring out what e4actly the partial is goingto look like. $here is an order you do things that makes this process easier, and it is

• !naly ing and Aurveyingo Pat of insertion !tilt"# :se the analy ing rod to find the most ideal path

of insertion 7must be pretty close to parallel with the floor8o $ark Teet # :se led in the surveyersurveyor to mark the heights of

contour on teeth that you are thinking about clasping so that the undercutsare visible.

o Mark $issue . :se led in the surveyersurveyor to mark the soft tissue where you think an undercut may be.

o Tripod # Blue . +ock everything in position on the surveyersurveyor andscratch 0 little hori ontal lines on the cast. <ou want these lines to be outof the way of the rest of your design if possible and as far away from eachother as possible. $his will allow you to put the cast and table back intothe same position if you move it. >nce you scratch the lines in, you markit with a little “F” in blue and circle it.

o A%utment Clasp Undercut ocations !#'(')"# Blue# <ou use anundercut marker to mark an =.-=” undercut in the strategic areas whereyou will engage that undercut with a clasp.

• $ooth Modificationo Rests# 'arve out the rests to their final dimension.o *uide Planes# Drom line angle to line angle and all parallel to each other.

$hey should follow the contour of the teeth.o +ei, t of Contour# If you need to, you can modify the teeth so the clasps

fit in a better location or to optimi e the position of the =.-=” undercut.• #esign

o Rests# Red# >utline the rests on the appropriate teeth.o *uide Planes# Blue# >utline the guide planes that you carved into the

teeth.o Pro-imal Plate# Red# Dor an !kers clasp, this will 1ust come right off the

occlusal rest straight down to the gingiva and e4tend away from the tooth

mm. Dor an /"I or /"', this will e4tend from halfway up the guide planedown to the gingiva and e4tend away from the tooth mm.o $inor connector# Red# $his must be at least mm wide and will e4tend

down the tooth and away from the gingiva at least 3mm on the ma4illa and0mm on the mandible.

o $a.or Connector# Red# >utline the most appropriate ma1or connectorfor that patient. >n the ma4illa, keep in mind it needs to be at least Emm

wide and at least 3mm away from the gingiva. >n the mandible, a lingual



bar needs to be %mm wide in the anterior and at least 0mm away from thegingiva.

o Acr/lic Retention $es work# Red# $here needs to be - hole for eachtooth and the metal needs to be mm wide.

o Plastic !acr/lic"# Blue# It should e4tend into the vestibule when it is

needed for retention 7mucosa borne8 and should only e4tend a little waypast the metal for tooth borne situations.o Clasps# Red# !kers, /"I or /"'. Aee above for e4act specifications.

!gain, here is the order of things, and you’ll learn more about it as you go. <ou willhave to have an idea about your final design while you’re doing the analy ing andsurveying to know what you are looking for.

/otational "ath "artial #enture

'ertain partials can be designed so that one portion seats first and the rest is

rotated into place. ! straight path of insertion is not possible since the minor connectorsin the edentulous area e4tend into the undercut. $he retention mechanism is rigid andcontains a rest and a minor connector.



$here are three possibilities of rotation.• !nteroposterior 7!"8 !nterior segment is seated first and the posterior segment

is rotated into place• "osteroanterior 7"!8 "osterior segment is seated first and the anterior segment

is rotated into place• +ateral >ne side is seated first and the other side is rotated into place

$he rest off of the retentive minor connector 7the one without a clasp8 must be -.2 tomm in thickness, almost parallel walled, and should be prepped perpendicular to the

long a4is of the tooth 7see the picture above8. $he rest should e4tend more than half themesiodistal dimension of the abutment tooth.

!dvantages and #isadvantages of /otational "ath "artial #enture

! rotational path partial denture minimi es the plaque accumulation by having

less tooth coverage 7clasps8. Aince anterior clasps often can be eliminated, the endproduct may be much more esthetic. *owever, the rotational path technique showsless tolerance for errors, the ad1ustments of the retentive components is difficult, andrequires well prepared rest seats or even restorations to develop such a rest seat.

Aurveying and #esigning /otational "ath "artials

Dirst, the model is placed in a = degree position where it is surveyed forundercuts and heights of contour. $he model is tripodi ed by drawing two vertical redlines on each side of the model. $hen, the undercut for the retentive minor connector7the one without a clasp8 is determined to =.= =” all other clasps should be designed

with a =.=-=” undercut as usual.$ilt the model so that the survey rod is parallel to the undercutting surface of theabutment teeth 7the ones that you will put the retentive minor connectors on8. Mark twoblue lines an each side of the model in order to tripodi e the initial path of insertion.!fter you have done this, move the table back to the original position and survey anddesign the cast as usual.

*ave fun in /emovable, it’s your last lab classJ

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