Large edentulous ridges—Are they better for dentures than small ridges?

Large edentulous ridges-Are dentures than small ridges? W. L. Harvey, D.D.S., MA.,* D. Rouland, D.D.S.**** Univcrsitv of Colorado. School of

W. Hoffman,

D.D.S.,**

D

AND

METHODS

Over an l&month period, casts of edentulous ridges were collected from denture patients in the dental clinics of the University of Cotorado School of Dentist-

“Pr~~fessor

and Chairman.

Division * *:Iw~iatr

of Removable ProCess~w,

l

Department

**.Assistant Clinical Profesor, tivs. and Staff Prosthodon~i~t. L1edic.d (:emer.

“*‘:\sz~~ram duntic<. rmn

THE

and

Iclrdicsl

JOURNAL

Clmiul Chief,

of Restorative

Prwhodonws. L)~\l\ion of Removable Divisicm Denver

Dentistry,

and

Prosthndont~rs.

01 Removable ProsthodonVeterans Administration

Profrssor. Dwision of Removable ProsthoDental Scr\ice. Denvrr Veterans Administra-

Crntcl

OF PROSTHETIC

DENTISTRY

R. Hochstetter,

D.D.S.,***

and

Denver, Cola.

Dentistry.

entists have the commonsense notion that patients who have large edentulous ridges have a better chance for denture success than those who have small ridges.’ If this is true, then: (1) randomly selected dentists should be able to visually classify randomly selected groups of edentulous casts into small, medium, and large categories and (2) larger ridges are better than smaller ones because larger basal seats will contain larger bearing areas, such as the buccal shelf; larger stabilizing areas, such as lingual surfaces of the edentulous ridges; and larger shared areas. We found that (1) most randomly selected dentists could, in fact, classify randomly selected edentulous casts into small, medium, and large categories with good consistency, (2) there was high correlation between ridge size and the stabilizing surfaces, and (3) there was no correlation between either the size of the bearing area and the size of the basal seat or the size of the ridge and the size of the shared surfaces. Larger ridges or larger basal seats may be better for dentures than smaller ones, but the size of the stabilizing area, which consists mainly of the lingual flange area, prohably plays a larger role than the bearing area. MATERIAL

they better for

ry and from the dental service of the Denver Veterans Administration Medical Center. Each cast was assigned a number, and 150 casts were randomly selectedwith a book of random numbers. The basesof the castswere trimmed parallel to the mean foundation plane of the ridge crest and included the retromolar pads,external oblique ridges.The bases were trimmed uniformly to 2 mm outside the facial sulcus of the casts. The casts were duplicated in reversible hydrocolloid and poured in vacuum-mixed gypsum stone. Ten faculty members who were teaching in the multidisciplinary student clinic were selectedto participate in the planning stagesof the prqject. They were individually handed one cast at a time and asked to categorize the residual alveolar ridge of each edentulous cast into either a large (L), medium (M), or small (S) category and to tell the criteria on which they based their decisions.The data were recorded. Finally, basedon the faculty members‘preliminary sorting of the 150 edentulous casts, WC assigned a number to each cast in each group and randomly selecteda smaller, more managabte, group of casts. The final three categoriescontained 10 S, 20 M, and 10 L casts.The reasonwhy a larger number of castsin the medium classification was chosenwill be discussed later. In addition to faculty members, 100 randomly selected dental practitioners agreed to assistin the study. Each dentist was allowed to examine only one castat a time and was then asked (1) to classify the edentulous ridge of each cast into S, M> or L and [2) to indicate one of the most representative criteria used in the determination. The criteria included (1:I the height of the edentulous ridge, (2) the width of the edentulous ridge, and (3) a combination of height and width of the edentulous ridge. The examination concluded when each had classifiedall 40 casts. Most dentists chosea combination of height and width of the edentulous ridges.

595

HARVEY

ET AL

Table I. The casts, their categorization by size, and the components of the basal seat Area

Size of

edentulous ridge

w

Bearing

area

Tracings of large, medium, and small ridges. Top, Small ridge. Large bearing areabut small stabilizing area. No shared surfaces.Middle, Medium knifeedge ridge. Large stabilizing area but small bearing area. No shared surfaces. Bottom, Ideal large ridge. Large bearing, stabilizing, and shared areas. Fig.

1.

The basal seatsof each of the 40 randomly selected castswere outlined in pencil by one investigator. The bearing area was defined as that part of the basal seat that lies within f 45 degreesof the plane formed by the ridge crestsand mainly would support a denture base against vertical forces (Fig. 1). The stabilizing area of each cast was defined asthat part of the basal seat that lies within *45 degreesof the vertical plane, is perpendicular to the plane of the ridge crests, and would mainly support the denture against displacement by horizontal forces. Both the bearing and stabilizing areaswere outlined separately on the casts. The shared area was defined as those surfacesthat lie within both the bearing and stabilizing areas.

596

S S S S S S S S S

M M M M M M M M M M M M M M M M M M M M M M M L L L L L L L L

Basal seat

Bearing

(sq in)

Stabilizing

Shared 0 0 0 0 0 0 0

3.26 3.32 3.79

1.76

1.5

2.44 2.59

1.88 1.2

3.81 3.81

2.22 1.53

1.59 2.28

3.83 3.87

1.84 1.26

1.99 2.61

3.96 3.98 4.02

1.69 2.68 1.96

2.74 2.52 2.63

0.47 1.22 0.57

4.04 4.11

1.88 2.46

2.66 2.08

0.5 0.54

4.15 4.19

2.53 1.96

1.62 3.05

4.19 4.22 4.26

1.78 2.87 2.32

3.22 2.74 1.94

4.31

1.86

4.35 4.38

1.73 2.16 1.79 1.95

3.21 3.47

4.45 4.52 4.56

0 0.82 0.82

1.39 0 0.76 0.85 0.38

2.6

0.9

2.18

3.56 3.57 3.44

2.67 2.69

2.87 2.79

0.98 0.9

4.6 4.64

2.2 2.28 2.04

2.39 2.32 3.45

0.85

4.73 4.81

2.94 2.67

2.82 3.55

1.03 1.41

4.83 4.96

2.55 1.4

3.56 3.52

0.46

5.01 5.02

3.04 2.93

2.78 3.4

5.15 5.53

2.61 2.53

3.9 3.38

5.66 5.66 6.15

2.26 2.78

4.41 4.06

2.99 2.77

4.47 5.06

4.56 4.58 4.59

6.52

1 1.06

0 0

1.28 0.81 1.31 1.36 0.92

1.01 1.18 1.31 1.31

Thin, semitransparentgreen sheetwax was adapted at room temperature to each cast, and the wax was trimmed to the outline of the basal seat. The lines circumscribing the bearing area, stabilizing area, and shared areas could be seenthrough the wax. A sharp lead pencil was used to superimposea line of indentations onto the sheet wax that lay over .the lines drawn on the cast. The sheetwax, pliable at room temperature, was then flattened on graph paper (100 sq in). Each area that had been outlined by indentations was then punched through the sheetwax to the graph paper

JUNE

1982

VOLUME

47

NUMBER

6

EDENTIJLOUS

Table

RIDGE

SIZE

AND

II. A definition

DENTURES

of small, medium,

Size (sq in) Small Medium Large --___

(0 to 3.9) (3.91 to 5) (5.01 and larger)

and large edentulous

N

X (sq in)

11 20 9

3.73 4.42 5.59

deviation

Standard error of mean

0.23 2.71 0.54

.-

Table III. Correlations of categories component parts of the basal seats* Area

Bearing areas

RESULTS The casts that had been classified as “small” by the majority of the randomly selected dentists had the following definition. The basal seat area ranged from 3.26 to 3.87 sq in (Table II). The bearing area of the small ridges ranged from 1.26 to 2.68 sq in. There was no correlation between the size of the basal seat and that of the bearing area (Table III). The stabilizing area of the small ridges ranged from 1.2 to 2.74 sq in. There was moderate correlation between ridge size and the size of the stabilizing area. The shared area of the small ridges ranged from 0 to 1.22 sq in. There was no correlation between the area of the basal seat and that of the shared area. The casts that had been classified as “medium” in size by the practicing dentists had the following definition. The basal seat area ranged from 3.96 to 4.83 sq in. The bearing area of the medium ridges ranged from 1.4 to 2.94 sq in. There was no correlation between the basal seat area and the bearing area. The stabilizing area of the medium ridges ranged from 1.62 to 3.57 sq in. There was moderate correlation (r = +0.51) between the area of the basal seat and the stabilizing area. The shared area of the medium ridges ranged from 0.05 to 1.41 sq in. There was no correlation between the area of the basal seat and that of the shared area. Finally, the ridges called “large” by the 100 practicing dentists ranged from 5.01 to 6.52 sq in. The range of the bearing area of the large category of ridges was 2.26 to 3.04 sq in. There was moderate correlation (r = +0.36) between the area of the basal seat and the bearing area. The stabilizing area of the large ridges ranged from 2.78 to 5.06 sq in. There was high positive correlation (r = +0.87) between the area of the basal seat and the stabilizing area. The shared area of the

JOURNAL

Standard

-_

with a sharp pencil. By connecting all the dots on the graph paper, the basal seat and the component areas of the basal seat were circumscribed. By counting the squares included in each area, the sizes of the basal seat, bearing area, stabilizing area, and shared areas, if any, were recorded in square inches (Table I).

THE

ridges

OF PROSTHETIC

DENTISTRY

Stabilizq areas

Shared areas

Sums of all like areas

Correl&iun

F.07 O.SQ 0 19 . ..- - ~~-.~-..

and r

Small basal seats to small bearing areas Medium basal seats to medium bearing areas Large basal seats to large bearing areas

-0.69

Small basal seats to small stabilizing areas Medium basal seats to meditum stabilizing areas Large basal seats to large stabilizing areas

i-0.54?

Small basal seats to small shared areas Medium basal seats to medium shared areas Large basal seats to large shared areas

to.32

All basai seats to all hearing areas All basal seats to all stabilizing areas All basal seats to all shared

+0.28

-0.76 -0.36

+0.51? +0.87+

to.37 +0.33

t0.7st +O.h2f

areas

large ridge ranged from 0.81 to 1.36 sq in. There was no correlation between the area of the hasal seat and that of the shared area. Finally, the sum of all the basal seats of the 40 casts was compared to the sum of all of the bearing areas, and there was no significance (p > .05); all basal seats to all stabilizing areas (high correlation), and all basal seats to all shared areas (moderate correlation). The tally sheets were analyzed by the Department of Biometrics at the University of Colorado Health Sciences Center. The probability of a dentist choosing each category for a given bearing area was computed

597

HARVEY

Table IV. Ranges for small, medium, and large edentulous ridges (in square inches) Edentulous ridges

Small

Medium Large

Range of basal seat areas

clto 3.9 3.91 to 5 5.01and larger

by using a multinomial logistic function.2 It was found that the majority of dentistsin our study could sort the casts into small, medium, and large categorieswith a high level of interparticipant agreement. DISCUSSION Perhaps the biggest surprise of the project was the lack of correlation between the size of the edentulous ridge and the bearing area. Dentists have long known the importance of extending the basesto spread the masticatory forces and to provide a sealagainst atmospheric pressure. If there were somerelationship between ridge size and success,then, there would most likely be a direct positive relationship betweenridge size and the bearing area, because the bearing area is the surface that supports a denture during the powerful closing or vertical forces. However, it was the stabilizing areas that had high positive correlation to ridge size. It was clear from the beginning of our study that more castswould be needed in the medium category becauselarge and small edentulouscastsare distinctive in someway and, if there was any doubt, the faculty member defined a cast a “medium” by default. Therefore, 20 medium casts were selected to be further examined by the 100 practicing dentists and classified by them as small, medium, and large. The wax method of measuring the ridges was adopted from engineering tests and is used for determining the area of irregularly shaped objects. The method has been used by others in dentistry.3 For usability, the range of ridge sizeswas adjusted: the basal seatsof small ridges should range from 0 to 3.9 sq in; medium from 3.91 to 5 sq in; and large edentulous ridges from 5.01 and larger areas (Table IV).

area is not always directly proportional to the size of the basal seat. The stabilizing area that includes the lingual flange area may play a larger role in success than we once believed. Others have noted the importance of the lingual flange and suggestedtechniquesfor This project has provided a definiits development.4-20 tion of small, medium, and large edentulous ridges based on the area of the basal seat. The method describedshouldprovide a way to measurethk bearing, stabilizing, and shared areasof a patient’s mandibular edentulous ridge. SUMMARY A method was describedfor measuring not only the area of the basalseatof an edentulousridge but alsothe bearing area, stabilizing area, and the areasshared. A definition for small, medium, and large edentulous ridges was provided. Correlations between the basal seat, stabilizing area, and the shared areas were computed. A high positive correlation was found between the area of the basal seat and that of the stabilizing areas. Contrary to what was expected, no correlation was found between the area of the basal seat and that of the bearing areasof the small to large categories. We wish to thank Dr. Richard at the University of Colorado assistance.

598

H. Jones, Professor of Biometrics Health Sciences Center, for his

REFERENCES 1. 2. 3. 4.

Swenson, M. G.: Complete Dentures, ed 4. St. Louis, 1959, The C. V. Mosby Co., p 33. Jones, R. H.: Probability estimations using a multinominal logistic function. J Stat Comp Simulation 3~315, 1975. Luthra, S. P.: Measurement of the area of the maxillary basal seat for dentures. J PROSTHET DENT 30~25, 1973. Levin, B.: Current concepts of lingual flange design. J PROS. THET

5. 6. 7.

DENT

45~242,

1981.

Roberts, B. J.: Mylohyoid ridge reductions as an aid to success in complete lower dentures. J PROSTHET DENT 37:486, 1977. Prieskel, H. W.: The posterior lingual extension of complete lower dentures. J PROSTHET DENT 19:452, 1968. Lott, F., and Levin, B.: Flange technique: An anatomic and physiologic approach to increase retention, function, comfort, and appearance of dentures. J PROSTHET DENT 16~394, 1966.

8. 9.

CONCLUSION The commonsensenotion of basing an edentulous patient’s prognosissolely on the size of the basalseatof their mandibular ridge may be correct. However, the size of that portion of the basal seatcalled the bearing

ET AL

IO. 11.

Tilton, 1952. Fournet, principle stability 23~1028, Tenth, 21:1005, Krol, A. J 34~18,

G. E.: Denture

periphery.

J PROSTHET

DENT

2~290,

S. C., and Tuller, C. S.: A revolutionary mechanical utilized to produce full lower dentures surpassing in the best modern upper dentures. J Am Dent Assoc 1936. R. W.: Impressions for dentures. J Am Dent Assoc 1934. J.: Hydraulic container in complete dentures. Ill Dent 1965.

JUNE

1982

VOLUME

47

NUMBER

6

EDENTULOUS

17.

IS

Edwards, relation 1942. Martone, anatomy tics. Part

RIDGE

StZE

AND

DENTURES

L. F., and Boucher, C. 0.: Anatomy of the mouth in to c,omplete dentures. J Am Dent Assoc !29:331,

17. 18.

A. I,.: Clinical applications of concepts of functional and speech science to complete denture prosthodonVII: Recording phases. J PROSTHET DENT 13~4,

lo. 20.

1963.

14.

15. 16.

Briel, N.. Tryde, G., and Cantor, R.: The dvn,nnic nature of the lower denture space. J PROSTHE.~ DEN.I, tk401, 1905 Fish. E. W.: Principles of Full Denture Pr ,sthcsis cd 6 London. 1964, Staples Press. pp 36-37. Bocage, M., and Lehrhaupt, J.: Lingual Ilange tlesi~n in complete dentures. J PROSTHET DEwI. 37:4(Y), !977. Landesman. II. M.. A technique for the delivesy of complete dentures. J PROS~HET DENT 43~348, 1980

Barrett. S. (i., and Haines, R. W.: The structure of the mouth in the mandibular molar region and its relation to the denture. J PRUSTHET DENT 12835, 1962. Shanahan. 7‘. E. J.: Stabilizing lower dentures on unfavorable ridges. ,I PROSTHET DENT 1!2:420, 1962. Lawson, W. .1.: Influence of the sublingual fold on retention of complete lrnwr dentures. ,J PROWHET DENT 11:1038, 1961.

ARTICLES

Keprlnl

rryilr,/?

Ill-

DR. WAYNE L. HARVEY UNIVLRSITY

OF C:OLORAIX~

SCHOLL OF DF.NTISWL, DEN~EK, CC) 80262

TO APPEAR IN FUTURE

ISSUES

The stressed pulp condition:

An endodontic-restorative

Marwan

Ph.D.

hbou-Rass,

D.D.S., M.D.S.,

Edentulous vestibufoplasty

diagnostic concept

using the palatal graft technique

James Amphlett,

D.D.S., and William

Prosthodontic

rehabilitation

Mohamed A. Aramany, D.M.D., Aslan, D.M.D.

C-284

Colwell,

D.D.S.

for gloseectomy patients

MS., J ane A. Downs, D.M.D.,

@inter

Beery, Ph.D., and Yavw

Retention of dowels using a composite resin as a cementing medium David Assif, D.M.D.,

and Arie Ferber, D.M.D.

Clinical significance

of polymerization

shrinkage

of composite resins

J. Robert Bausch, Kees de Lange, Care1 L. Davidson, Ph.D., August Peters, and Anton J. de Gee, Ph.D.

The tilted posterior tooth. Part II: Biomechanical

therapy

Adrian

and Noah Stern,

Becker, B.D.S., L.D.S., D.D.O.,

Maya Zalkind,

D.M.D.,

D.M.D.,

M.S.D

The nickel problem Luis Blanco-Dalmau,

D.D.S.

Osteoporosis: Some aspects of pathophysio&ogy Charles H. Chesnut III, M.D.,

Effect of 0.4% stannous fluoride abutments Gary D. Derkson, D.M.D.,

Removable

and Michael

gel on the gingival M. MacEntke,

JOURNAL

A.

he&h

of overdenture

L.D.S. (I), F.R.C.D.(C)

partial denture design for the mandibular

David N. Firtell, D.D.S., M.A., and Thomas

THE

and therapy

and Patricia J. Kribbs, D.D.S.

section patient

Curtis, D.D.S.

Laboratory procedures for the maintenance overdenture

of a removable

James A. Fowler, Jr., D.D.S., MS.,

D.D.S., M.S., and Jesus J. Escobedo

OF PROSTHETIC

DENTISTRY

William

A. Kuebker,

partial