I94 Australian Dental Journal, June, 1985

Volume 30, No. 3.

A longitudinal survey of removable partial dentures. II. Clinical evaluation of dentures

Sybille K. Lechner

Senior Tuior, Depariment of Prosihodoniics, The Universiiy of Sydney

(Received for publication April 1984.)

Introduction

To investigate the effectiveness of the removable partial denture programme at The University of Sydney Dental School, a two-year survey was undertaken on one hundred and sixty-seven patients treated by final-year students. Part 1 of this survey dealt with patient response and patient assessment of their dentures.* This paper discusses the clinical performance of the dentures themselves.

Materials and method

Only dentures of those patients still participating in the survey after the two-year period (109 patients) were assessed for clinical performance. These comprised 150 dentures ( 5 5 maxillary and 95 mandibular) consisting of the following components.

Saddle type Distal extension, 212; tooth-bounded, 129.

Clasps Dentures with cast clasps, 119 (409 clasps); Dentures

with wrought clasps, 31 (76 clasps). Of the 150 dentures, 62 had ‘3 + ’ clasps and 88 had ‘2 only’ clasps.

Artificial ieeih Acrylic, 393; porcelain, 432.

Connectors Acrylic, 17; metal, 133.

Dentures were checked by the clinician at issue and at six-monthly intervals. The following points were noted.

Framework

Fit and retention Fit was considered poor if the tip of a No. 6 probe could

gain purchase between the framework and tooth structure. Retention was measured subjectively by the clinician. Retention was considered good when the denture was difficult to remove, fair when i t was easy to remove, and poor when movement of the denture occurred without the clinician trying to remove it.

Clasps and occlusal rests 1. Number. 2. Material. 3 . Breakages. 4. Adjustments.

Clasps and occlusal rests were only adjusted when requested by the patient.

Major connectors I . Material. 2. Breakages. 3 . Adjustments

Teeth I . Number 2. Material. 3 . Breakages

Saddles

Type Saddles were classified a5 tooth-bounded or distal

extension.

Australian Dental Journal, June, 1985

: 60.;sa 0 U

“ 5 0 -

40

30..

I95

...... example, ulceration. Adjustments were categorized as: ... 1. Simple adjustment; s j ’ ’ . .

64

\ .... ................ . 2. Reline. 54 54 . 47 Differences in percentage were tested using the Student

(p 50.05) .

“ . . . I test, and the level of significance taken at 5 per cent . - - - 3 _ 5 - - - ? ? ‘ 27,

..

- 3 or more clasps [cast & wrought) Results A very high proportion (92 per cent) of denture

frameworks fitted at issue, with a slight gradual decrease

........ 2 clasps (wrought) - 2 clasps (cast) - _

TAHI t 1 Clasp adjustments

Upper Lower Total

No. Total NO. Total No. Total

(‘a\t 40’) 1 196 (3 t ) 25 213 ( 1 1 ) 32 409 (X) Wrought 76 I 42 ( 2 ) 6 34 (18) 7 76 (9)

‘I’otal 485 8 238 (3) 31 241 (I 2) 9 4x5 (8)

I’ercenlagc i n parenlhesi\.

0‘0

’ O i l 90

RO 1

Retention the denture saddle as dewribed by Lechner.’ A measurement of 0.2 mm or less was scored as + . At thi\ measurement there was no clinical sign of movement under Dressure on distal extension saddles.

Adjustments

Time little difference in ‘fit’ scores between upper and lower dentures, except in that two lower dentures showed improvement in their fit. l i g . I .--Decrease in good denture retention with three types

oT retainers over two years.

Positiori - unterior or posterior

Occlustrl contuc1.s

Of the 119 dentures with cast clasps, more with ‘3 + ’ clasps showed good retention (66 per cent) than those with ‘2 only’ clasps (42 per cent).

O f the 31 dentures with wrought clasps, three were classified ‘ 3 + ’ (figures too small to be of value). A

Occlusal contacts were determined by placing a sheet of articulating papert on the occlusal table, asking the patient to bite hard and attempting to withdraw the paper.

I f the paper was torn the occlusion was designated + .

comparison of ‘3 + ’ wrought and cast clasp retention could therefore not be made. Comparison of ‘2 only’ cast and wrought clasps shows a trend towards a larger proportion of good retention for wrought clasps (60 per

Where the paper could be withdrawn without tearing, the cent) than for cast clasps (42 per cent). occlusion was designated - . Note was also taken as to whether the denture occluded with an opposing dentition or with an opposing denture, and whether or not the dentition had a natural stop.

Fit

measuring device using ScutanS and a locating mark on

The number of dentures with good retention decreased over the two-year period for both cast and wrought clasps and in both ‘ 3 + ’ and ‘2 only’ categories; the biggest decrease occurred in the first six months (Fig. I ) .

There was no significant difference in the number of adjustments necessary for cast or wrought clasps, or in

Fit was measured with a Hildebrand-lwanson the number of breakages. Overall the percentage of clasps broken was small (2 per cent). Clasps on lower dentures

tBnuxh Articulaling Pnper: extra thin (0.04 mm). fEipe. We\! Germany

’ Lechner Syhille K . The f i t of partial dentures. A i w Soc f’rmthet Bull 1917;1:1-9.

I96 Australian Dental Journal , June, I985

Fig. ?.--Cross section of acrylic lingual plate incor- porating rigid metal har on inferior border 10 prevent t h i n g and po\aihle hrcakage.

Fig. 3.-Wroughr clasps tacked lo cast frdmeu~ork with either soldzr or resin.

needed more adjustments than on upper dentures (12 per cent:3 per cent) (Table I ) .

Acrylic major connectors covered more tissue and tended to need more adjustment than metal major connectors and no fracture o l a metal major connector occurred. One acrylic denture broke four times and h a s eventually transferred for a remake in metal and some acrylic connector\ \ho\ced small cracks. Eight acrylic teeth (2 per cent), but n o porcelain teeth. tractured.

The greate\t lo\s in occlusal contac t \ occurred where acrylic teeth were in contact with a dentition (57 per cent). There M a \ a diflercnce between acrylic teeth contacting ii dentition (57 per cent losc o f contact) and those contacting an opposing denture ( 3 1 per cent loss of contact). Porcelain teeth lost contact w i t h the opposing occIu\ io~i in 21 per cent ol cx\e\ , there heing little difference ;I\ to uhc the r the oppcxing occltisiori was a deriturc o r the dentit ion.

Lli\tal extension saddles needed more adjustments (29 per cent) and most were carried 0111 i t i the fir\[ six months.

Kelining was carried out mainly on di\ tal extension \addles (10 per cent); and of thew, only I per cent at i \me and 2 per cent after 6 month\. Two tooth-hounded saddles ( I per cent) \ \ere al\o irelined hecauw food particle5 collected under rhern.

Saddle f i t at is5ue was similar for both tooth-hounded and distal extension \addle\ (84 per cent); thereafter. the fit of distal extension \addle\ declined and after tw’o year\ only 7 5 pel- cent fitted. A surprising result w a s the apparent improvement in fit of some tooth-bounded saddles.

Discussion I h e problem\ tound u i t l i iici \ lic major connector\

could lie in incorrect dcnture design. The physical properties of acrylic re\in d o not compare with those o f

Australian Dental Journal, June, 1985

chromium cobalt alloys and the acrylic partial denture should, therefore, not be planned merely as a bulky or overlarge metal denture. Maxillary acrylic dentures must be provided with palatal relief over the median suture to prevent rocking and eventual breakage. Mandibular major connectors should incorporate a rigid metal insert on the inferior border to prevent flexing of the necessarily thin lingual plate (Fig. 2).

The gradual loss of direct retention in the first twelve months as reported by others* was observed.

An assessment of clasp materials shows that wrought clasps tend to provide better retention with less likelihood of fracture than those which are cast. The most successful removable partial denture would, therefore, have a cast framework and wrought clasps (Fig. 3). The greater number of clasp adjustments carried out on mandibular dentures could correlate to the greater number of mandibular distal extension saddles which were more troublesome in all respects. (See Part I ) .

While distal extension saddles in general tended to show a slight decrease in f i t over the two-year period, an interesting result was the apparent increase in fit of some tooth-bounded saddles. This may be due to slight movement of abutment teeth to accommodate small discrepancies of framework fit, or to movement of the mucosa towards the denture as i t attempts to close a 'dead space' under the immobile saddle. Most saddles showed a reading of 0.2 mm betwjeen denture and tissues. I t was not until 0.5 mm of space was recorded that a reline was mandatory because of patients' complaints of discomfort. Adjustments carried out by grinding the tissue surface of the denture to eliminate sore spots in these cases only seemed to aggravate the problem. Relining and occlusal equilibration were more rational approaches and far more successful.

I97

2 Anderson JN, Bates JF. Cobalt-chromium partial dentures. A clinical survey. Br Denr J 1959;107:57-62. ' Tomlin HR. Oaborne J . Cobal t -chromium partial dentures; a clinical survey. Br Dent J 1961;l 10:307-10.

The fracture of acrylic teeth cannot really be related to the non-fracture of porclain teeth in this survey, since only acrylic teeth were used in difficult situations such as isolated teeth or lack of space. A metal backing for such teeth, where aesthetics allows, will eliminate such problems.

Notwithstanding the better performance of porcelain teeth for maintaining occlusal contacts, acrylic teeth should not be entirely discarded as the material of choice opposing natural teeth. Where extensive grinding of occlusal surfaces is necessary, unglazed porcelain often causes marked abrasion of the opposing dentition. I f such abrasion has occurred in the past, or is likely, replacement of acrylic teeth from time to time may be preferable to the risk of permanent damage to the dentition.

The small percentage of relines necessary for distal extension saddles within the first six months indicates that impression techniques using alginate in custom trays or modified stock trays are adequate for distal extension saddles and that the more complex techniques striving for tissue compression may not always be warranted. However, the steady decrease in f i t of distal extension saddles over the two-year period necessitates periodic assessment for later relines. The first six months are of obvious importance regarding changes in the various aspects of partial dentures which were investigated, and highlights the necessity of recalling patients and reassessing denture f i t and function within this period particularly.

Conclusions

A comparison of materials indicates that a combination of cast framework and wrought clasps should be used in the construction of removable partial dentures. Recom- mendations regarding artificial tooth materials could not be established within the parameters of this survey.

Periodic recalls for reassessment of fit and function are indicated.

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