I12 Australian Dental Journal, April, 1985

Volume 30, No. 2

A longitudinal survey of removable partial dentures. 1. Patient assessment of dentures

Sybille K. Lechner

Senior Lecturer, Department of Prosthetic Dentistry, The University of Sydney

ABSTRACT-A system was developed for the assessment of the function and use of partial dentures for 176 patients treated by final-year students in the University of Sydney Dental School. These patients were observed at intervals of six months, and the assessment was made by the author and by the patients.

(Received for publication October 1984.)

Introduction The pathological potential of removable partial

dentures has been widely recognized. Increased plaque accumulation,’.’ caries,’.‘ poor oral hygiene and gingival inflammation,’ and increased mobility of abutment teeth6 have all been attributed to the wearing of partial dentures.

Two s t u d i e ~ ’ ~ ~ have indicated that where dentures are made in accordance with specific design principles, are carefully maintained with importance placed on oral hygiene in highly-motivated patients, then little damage

’ Brill N, Tryde G, Stoltze K, El Ghamrawy EA. Ecologic changes in the oral cavity caused by removable partial dentures. J Prosthet Dent 1977;38:138-48.

Addy M, Bates JF. The effect of partial dentures and chlorhexidine gluconate gel on plaque accumulation in the absence of oral hygiene. J Clin Periodontol 1977;4:41-7.

Tomlin HR, Osborne J. Cobalt chromium partial dentures. A clinical survey. Br Dent J 1%1;110:307-10.

‘ Carlsson GE, HedegPrd B, Koivumaa KK. Studies in partial denture prostheses. Acta Odontol Scand 1962;20:95-119.

’ Seemann. Sybille K. A study of the relationship between perio- dontal disease and the wearing of partial dentures. Aust Dent J 1963;8:206-8. (*Author’s maiden name.)

Koivumaa KK. Changes in periodontal tissues and supporting structures connected with partial dentures. D Abs 1951;2:468-9.

’ Derry A, Bertram V. A clinical survey of removable partial dentures after two years usage. Acta Odontol Scand 1970;28:581-98.

* Bergman B, Hugoson A, Olsson CO. Periodontal and prosthetic conditions in patients treated with removable partial dentures and artificial crowns. A longitudinal two-year study. Acta Odontol Scand 1971;29:621-38.

can be detected after two years usage. To investigate the effectiveness of the removable partial denture programme at Sydney University Dental School, a two-year survey was undertaken on one hundred and seventy-six patients treated by final-year students.

Principles of partial denture treatment The procedure for removable partial denture design and

construction at the Sydney Dental School follows certain basic principles.

History-taking and clinical examination are completed, and preliminary impressions are taken with alginate hydrocolloid in a stock metal tray modified where necessary with impression compound. Casts from these impressions are surveyed and mounted on an adjustable articulator, using a face bow transfer and centric relation records. At this stage a treatment plan is devised by the student and staff based on the need for pre-prosthetic treatment, denture design, and abutment preparation. Pre-prosthetic treatment may involve surgery, orthodontics, periodontal therapy or restorative procedures in relation to anticipated prosthetic requirements. Oral hygiene instruction is also given.

Partial denture design

guidelines. The dentures are designed according to the following

1. Support All dentures are bilateral. Where possible, saddles are

tooth supported by means of occlusal, cingulum or incisal

Australian Dental Journal, April, 1985

rests to provide maximum axial loading. Rests are placed mesially on the abutment tooth of distal extension saddles to improve load distribution. Where tissue support is also required, saddles are made as large as possible. Actual loading is reduced by providing a limited occlusal table and, where applicable, balanced occlusion of denture teeth. Stress-breaking procedures are limited.

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Maxillo-mandibular relationship

Casts are mounted using a face bow transfer and centric relation records, the technique depending on the number and distribution of teeth present. Where sufficient natural teeth remain, the occlusion is recorded using a wax wafer. Tooth bounded saddles necessitate the use of well- supported occlusal rims and wax records. For distal extension saddles, a free-flowing material such as zinc oxide-eugenol paste or plaster is used on rims to record centric relation. Protrusive relationships are also recorded.

2. Retention Retention is gained by means of cast or wrought

extracoronal retainers which may be coronally or gingivally placed depending on hard and soft tissue undercuts, the degree of lateral support required, and aesthetic considerations. All retentive arms are reciprocated.

The importance of indirect retention gained by means of strategically placed rests or denture base extensions is emphasized.

3. Conneclors All major connectors are designed to be rigid and while

some may be constructed in acrylic resin, most are fabricated in cobalt-chromium alloy. Gingival margins are left free by three millimetres wherever possible. Lingual or sublingual bars are used only when they can be placed clear of the lingual gingival margins. Palatal bars may be anterior, middle or posterior, depending on saddle distribution, vault shape and tissue consistency.

Mouth preparation

Mouth preparation depends on the occlusion, aesthetic considerations and design of the denture.

Occlusion is adjusted to correct premature contacts in centric and eccentric positions. Consideration is also given to the integrity of the occlusal plane regarding overerupted or undererupted teeth, to problems of intermaxillary space and to impingement of teeth on soft tissues. Aesthetics may be improved by judicious disking of overerupted or tilted anterior teeth.

Abutment preparation was mainly limited to enameloplasty in the patients surveyed. Occlusal rest preparations are spoon-shaped and as shallow as is consistent with occlusal requirements and masticatory stress. lncisal rest preparations are also shallow and rounded. Proximal, buccal, and lingual surfaces may be disked to alter survey lines. All cut surfaces are smoothed, polished and treated with stannous fluoride prophylactic paste.

Impressions

Final impressions are taken using alginate hydrocolloid in either a modified stock tray, or in a custom tray. Occasionally agar hydrocolloid or rubber base impression materials may be used. Distal extension saddles may be recorded using a corrected cast technique or may be relined at insertion, if necessary.

Insertion lnsertion of the denture is split into primary and

secondary stages, approximately one week apart. At the primary stage, the dentures are fitted using disclosing wax,* and the occlusion is adjusted. The patient is instructed on the removal, insertion, and care of the denture, and is advised not to wear the denture at night and to leave it clean and wet when not in use.

At the secondary stage, one week later, any necessary adjustments are made and adjustment to the occlusion is refined.

Method

Patients used in the survey were randomly selected from those having removable partial dentures fitted by final- year students at Sydney University.

The patients were first examined after mouth preparation had been completed but before the dentures were issued. At this time they were told that a later denture assessment would be carried out and that they would be recalled every six months for a check-up. Some patients, for various reasons, were not interested in returning. These were eliminated from the survey.

All of the remaining patients were assessed for tissue conditiont and then recalled as soon as possible after issue of the denture (1-2 weeks). At this time the patient’s assessment of the denture was recorded and a clinical evaluation of the denture performed. Note was taken of the patient’s age, sex, and previous denture history.

Patients were recalled for re-examination at 6, 12, 18, and 24 months,$ when the patient’s assessment was again noted, a clinical evaluation made, and tissue condition in relation to the dentures recorded. All examinations were conducted by the same operator.

In recalling patients, the following points were noted. I . How many times a patient failed to attend. 2. How many times a patient had made contact as

being unable to attend and a new appointment made.

*Kerr Disclosing Wax mixed with petroleum jelly. p e e Part 111. $Patients received a recall letter o r telephone request to attend the clinic for a check-up. Where the patient failed to respond. two or more contacts were made by letter or telephone before the patlent was declared ‘lost’.

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3. When patients did attend, whether or not their attendance was due to dissatisfaction with their dental state, for example, sore spot, broken tooth, or cavity.

At each recall patients were also asked their own assessment of the denture, as follows.

1. Aesthetics: Do you think the denture makes a difference to your looks? (Better, worse, or no difference.)

2. Mastication: Do you find eating easier or more difficult with the denture? Would you rather have it in or out for meals, or is there no difference?

3. Comfort: Apart from meals, is the denture comfortable or does it hurt or irritate you.

4. Retention: Do the dentures stay in or are they too loose?

Assessments were recorded as +, 0, or - . Patients were considered satisfied with their denture

if three of the four criteria were either + or 0, with a minimum of two being + . Note was also taken of how many hours the denture was worn each day.

To check the significance of various aspects of patients satisfaction with their denture, the following points were noted.

I . Whether patient assessment of improved aesthetics was limited to anterior saddles.

2. Whether the time per day the denture was worn was related to the patient’s feeling that the denture improved their looks.

3. Whether patients felt that their improved ability to chew was related to saddle position, to actual occlusal contact of denture saddles, or both.

4. Whether comfort was related to the type of saddle, fi t of the saddle,’ and occlusal contacts of the dentition.

5 . Whether agreement existed between patient and dentist assessment of retention, and the changes noted in retention over the survey period.

6. Whether patient satisfaction changed over the two- year period.

7. Whether patient satisfaction was related to previous denture experience.

Actual masticatory efficiency was not measured. It was thought that since many people are able to achieve good nutritional status in the completely edentulous state, the criterion of masticatory efficiency in the clinical sense should be a particular patient’s ability to cope, that is, their own assessment of their chewing ability.

Results were based on 55 maxillary and 95 mandibular dentures worn by the 109 patients remaining in the survey after the two-year period.

Differences in percentage were tested using the Student’s t test, and the level of significance taken at 5 per cent @<0.05).

Australian Dental Journal, April, 1985

Lechner Sybille K. The fit of partial dentures. Aust SOC Prosthodont Bull 1977;7:7-9.

Results Recall response

Most of the patients who attended for the survey did so at the first appointment made, and because they were recalled rather than because they had trouble with their dentures.

One hundred and seventy-six (176) patients attended at the time of issue of their partial denture. One hundred and nine (62 per cent) returned at 24 months.

Period worn per day Most dentures (69 per cent) were worn at least 12 hours

per day but a significant proportion of lower dentures (23 per cent) were virtually not worn at all (0.5 hr/day).

I t is interesting to note that even though patients were told not to wear dentures at night, 14 per cent of dentures were worn 19-24 hours per day.

Most patients (53 per cent) did not change the hours the dentures were worn daily, although 23 per cent showed a decrease in the hours worn over the two-year period. A surprising number (13 per cent) varied in hours worn at each visit.

Aesthetics Even where a denture had no anterior saddles, 66 per

cent of patients felt they looked better with the denture than without. In the 0-5 hr/day category (that is, virtually unworn), the ratio of ‘look better’ to ‘no difference’ was very low (13:12 per cent). In all other categories the ratio was much higher, 9:3 per cent (6-1 I hr/day); 37:16 per cent (12-18 hrlday); 7:3 per cent (12-24 hr/day).

Patients whose dentures had anterior saddles felt they looked better in 92 per cent of cases. The high ratio of ‘better’ to ‘no different’ is reflected in all categories of hours worn (approximately 7:l).

Mastication More patients whose artificial teeth did not have

occlusal contact with the opposing denture or dentition felt that their masticatory abilities were improved by the denture than those who did have such occlusal contact (78:67 per cent). While these figures show a trend only, it is nevertheless surprising that the proportion is not reversed. An overall gradual improvement in masticatory satisfaction was evident over the two-year period.

Comfort Tooth bounded saddles were more comfortable than

distal extension saddles (88:77 per cent). The significance of whether a saddle fitted or not

seemed less important as regards comfort for tooth bounded saddles (89:SO per cent) than for distal extension saddles (81 5 2 per cent). Comfort tended to increase over the two-year period for both types of saddles which fitted. Of those saddles which did not fit, comfort increased only

Australian Dental Journal, April, 1985

with tooth bounded saddles. Distal extension saddles which did not fit showed erratic scores for comfort. The greatest increase in comfort occurred at six months. Some saddles could not be scored for fit because of the wearing away of fit marks by relines, adjustments, or excess cleaning.

Patients were significantly more comfortable when their natural teeth were in occlusal contact with the opposing denture or dentition (92 per cent) than when there was no such contact possible (42 per cent). Occlusal adjustments were carried out on the dentures of ‘uncom- fortable’ patients to bring their dentitions into occlusal contact, thus increasing the number of ‘comfortable’ patients. Altogether 28 patients had such occlusal adjustment, 12 at the issue stage.

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Retention Patients overall were happier with retention (88 per

cent) than the actual retention warranted (57 per cent) although there was a slight falling off in the first six months. Patient and dentist agreed on retention in only 64 per cent of cases, the largest category being where both dentist and patient felt the retention was good (54 per cent). The next largest category was where the patient felt the retention was good and the dentist felt it to be poor (33 per cent). The dentist thought retention was better than did the patient in 2 per cent of cases; these related to instability with occlusal imbalance.

A few patients felt retention increased over the two- year period (6 per cent). In one case the dentist thought that retention had improved. Patients tended to feel that retention decreased in less cases (14 per cent) than the dentist did (25 per cent).

Overall satisfaction Overall satisfaction with dentures was high (>80 per

cent). Patients who had previously worn a denture and been satisfied with it had a higher satisfaction rate (>90 per cent) than others. Patients who had been dissatisfied with a previous denture or who had no previous denture had similar satisfaction rates (>75 per cent). A comparable satisfaction rate of 85 per cent was scored for all patients (176) examined at issue.

Discussion It was obvious from the patterns of wear and comments

of the patients that most felt that their dentures served a very necessary function. Patients tended to wear their dentures because they could relate to the obvious benefits of appearance and ease of eating. Upper dentures with their greater potential for aesthetic improvement tended to be worn for more hours daily than lower dentures, although even lower posterior saddles were considered by many patients to improve aesthetics by ‘filling out my face’ or ‘supporting my cheeks’. Some patients felt incomplete when not wearing dentures and they liked to

wear them 24 hours daily despite warnings of possible tissue damage. The obvious rewards of improved aesthetics or mastication far outweigh consideration of long-term tissue reactions to the partial denture in the patients’ eyes.

Whether patients found their dentures comfortable or not depended on several factors, the most important being a lack of interference on the part of the denture with natural tooth contacts in centric occlusion. Patients who could not get their own teeth together tended to complain of bulkiness, pain, inability to chew or general discomfort. This general feeling of discomfort seems to lie principally in the lack of stimulation of the periodontal fibres of the remaining teeth, and patients tend to search for this stimulation either by clenching in an attempt to ‘push’ the denture out of the way or by posturing into protrusive or protruso-lateral positions to find natural tooth contacts.

Occlusal contact between saddle areas appears to be of far less importance for both comfort and masticatory efficiency, patients with no denture occlusal contacts tending to fare better in their assessment of masticatory efficiency than those with such contacts. This result could be a ramification of the patients’ need to achieve occlusal contacts with the dentition since denture occlusal contacts precluded dentition contacts in many cases. However, a small number of patients complained about the lack of denture occlusal contacts expressed as ‘teeth feel blunt’, ‘can’t get enough bite’, and ‘empty feeling between the dentures’.

Ideally, dentition occlusal contacts should be provided as a first priority with simultaneous denture occlusal contacts on a restricted occlusal table. Such a restricted table can be achieved by using narrower teeth or fewer occlusal contacts (Fig. I).

Leaving denture teeth out of contact altogether could be considered for small anterior saddles or where tooth bounded saddles oppose each other. Posterior support provided by occlusal contacts on distal extension saddles is certainly desirable for neuromuscular integrity, but may only be necessary for the second bicuspid region. Also dentures must often provide occlusal stops for an opposing dentition to counteract overreuption of unopposed teeth.

Whether the tissue surface of a denture conformed to the tissues or not (fit) seemed to affect comfort more with distal extension saddles than with tooth bounded ones. This is to be expected since distal extension saddles, particularly large ones, gain their support mainly from the tissues and are therefore more dependent on tissue adaptation than tooth bounded saddles.

Distal extension saddles generally caused more problems than tooth bounded ones, which supports the concept that partial denture design should include saddle design, particularly for large distal saddles. These should be treated as nearly as possible as complete denture sections and particularly attention must be given to

116 Australian Dental Journal, April, 1985

Fig. I.-a, Methods of decreasing occlusal table. Centric contact of artificial molars may not be necessary if retention

of complete upper denture is good.

\ &\ M- -

/’ I

b (iii)

Fig. I .-b. Maxillary molar has exaggerated buccal tilt. (i) To gain maximum intercuspation mandibular artificial molar (M) would need to be placed buccal to denture-bearing area (B) causing instability of mandibular denture. Such maximum intercuspation is contra- indicated. (ii) Narrowing width of artificial tooth and placing it in correct bucco-lingual position may provide unstable point contact on lingual incline of lingual cusp of maxillary molar (L). thus allowing further bucally inclined eruption. (iii) Minimal mouth preparation. flattening maxillary lingual cusp tip and providing flat plane contact

prevents overeruption and provides centric occlusal stop (S).

Australian Dental Journal, April, 1985

peripheral extensions, both in length and width, to buccolingual tooth placement, and to polished surface contours.

The importance of achieving passive stability by correct denture placement and occlusal integrity is also borne out by patients’ assessment of retention where actual retention is found to be comparatively of little importance to the patient compared with the other factors mentioned.

Patients tended not to have a realistic conception of retention, equating ‘tightness’ to stability rather than to actual direct retention. Direct retention can usually be very light if maximum stability has been attained. One denture which had excess direct retention but which had inadequate occlusal equilibration and slight peripheral overextension was described by the patient to ‘bounce around’ and ‘feel loose’. Dentures which were relined were often described as feeling ‘tighter’ even where no clasp adjustment had been performed. Narrowing the distolingual flanges of lower distal extension saddles to provide greater tongue space was also found to make dentures feel more retentive in many cases. It is therefore important for the dentist to be able to interpret patients’ complaints regarding inadequate retention of partial dentures. Mechanical ‘tightening’ of clasps may only give temporary improvement. The denture must be reassessed in all its various components.

The difference in satisfaction rates between patients who had successfully worn dentures before and those who

I17

had not highlights the importance of patient adaptation and attitude in the successful wearing of dentures as opposed to fixed restorative procedures where technical excellence may be the only criterion of success.

Overall a high proportion of patients were satisfied with their dentures and this satisfaction tended to increase over the whole two-year period, but particularly in the first six months as regards comfort and improved mastication.

Conclusions A recall response of 62 per cent of patients was

achieved, and a major proportion were satisfied with their dentures. Patients tended not to have a realistic concept of retention, often equating retention with stability. Dentures should therefore be provided with adequate support and should not interfere with muscle function.

The most significant factor relating to patient comfort was the provision of centric occlusal contacts for the remaining dentition with the opposing denture or teeth.

Provision of occlusal contact for the artificial teeth was of lesser importance, both for comfort and for masticatory efficiency.

91 Bay Street, Beauty Point, N.S.W., 2088.