Reliability and validation of a Brazilian version of the Oral

Health Impact Profile for assessing edentulous subjects

R. F. SOUZA*, L. PATROCINIO†, A. C. PERO†, J . MARRA† & M. A. COMPAGNONI†

*Department of Dental Materials and Prosthodontics, Ribeirao Preto Dental School, University of Sao Paulo, Ribeirao Preto and †Department of

Dental Materials and Prosthodontics, Araraquara Dental School, Sao Paulo State University, Araraquara, Sao Paulo, Brazil

SUMMARY The aims of this study were to evaluate

the reliability and to validate a Brazilian version of

Oral Health Impact Profile for assessing edentulous

subjects (OHIP-EDENT), an inventory for measuring

oral health-related quality of life of edentulous

subjects. The sample comprised 65 complete den-

ture wearers (23 men, mean age of 69Æ1 � 10Æ3 years).

The translated OHIP-EDENT was applied on two

occasions with a washout period of 3 months. Reli-

ability was assessed by an internal consistency

analysis and a test-retest approach. A preliminary

validation process was conducted by a qualitative

approach ⁄ interview. Results of internal consistency

showed a Cronbach’s a of 0Æ86 or 0Æ90 for the first or

second appointment respectively. Through the test-

retest analysis, an intra-class correlation coefficient

of 0Æ57 was found, and individual answers reflected a

broad range of agreement. Interviewed volunteers

(n = 6) comprehended most questions well. In con-

clusion, the Brazilian version of OHIP-EDENT is

adequate for assessing the oral health-related qual-

ity of life for edentulous subjects.

KEYWORDS: complete denture, edentulous mouth,

patient satisfaction, quality of life, questionnaires

Accepted for publication 25 February 2007

Introduction

Dramatic decrease in tooth loss by adults has been

reported in industrialized countries (1). Nevertheless, a

high prevalence of edentulism persists in Brazil (2),

which remains a public health problem. Loss of natural

teeth often can be rectified by prosthetic treatment.

However, the outcome is variable and relies on

attitudes towards edentulousness and dentures (3).

Thus, acceptance of complete dentures requires

functional and psycho-social adaptation (4) and

this process is highly influenced by patients’

expectations (5).

Now-a-days, interest in assessing diseases affecting

the quality of life has increased. Such diseases can be

evaluated by means of specific inventories, i.e., Oral

Health Impact Profile (OHIP), specifically designed for

oral conditions (6). This inventory provides an estimate

of the impact of oral conditions on edentulous subjects

(7).

Oral Health Impact Profile is composed of 49 ques-

tions covering several conceptual domains affected by

pathological processes. Thus, it provides a thorough

analysis on how oral health affects the quality of life.

However, OHIP is a wide-ranging instrument and some

studies have explored the possibility of reducing it

without adverse changes. Among those smaller ver-

sions, OHIP-EDENT is best because it is a specific

inventory for edentulous subjects. This instrument is

able to detect oral health-related quality of life changes

in denture wearers, before and after receiving new

prostheses (8).

The characteristics of OHIP-EDENT suggest that a

Portuguese-language version would be valuable. How-

ever, a thorough translation of OHIP-EDENT into

Portuguese would not necessarily ensure applicability

among the Brazilian population because of cultural

diversity. Reproducibility and validity testing of the

translated version within the new cultural environment

is recommended (9). The purpose of the present study

ª 2007 The Authors. Journal compilation ª 2007 Blackwell Publishing Ltd doi: 10.1111/j.1365-2842.2007.01749.x

Journal of Oral Rehabilitation 2007 34; 821–826

was to assess the reliability of a Brazilian version of

OHIP-EDENT. A preliminary validation analysis of this

version was also carried out.

Materials and methods

A total of 65 conventional complete denture wearers

(23 men and 42 women) participated in this study.

Inclusion criteria comprised participants who had

passed the functional adaptation and adjustment per-

iod. Volunteers had been wearing the same pair of

dentures for 1 month or longer (10). After inclusion

and following the first assessment, application of the

translated OHIP-EDENT was carried out after an inter-

val of 3 months for a washout period. This period was

respected as long as the volunteers should not remem-

ber the first application of the inventory at the second

assessment. Furthermore, subjects were asked to

answer each question of the OHIP-EDENT using this

period as a reference (6). The mean age of the

volunteers was 69Æ1 � 10Æ3 years, and the mean time

of edentulism was 26Æ2 � 14Æ1 years. They had been

wearing complete dentures for 24Æ1 � 14Æ3 years.

Thirty-two volunteers were retired, twenty two were

unemployed and 11 were employed or autonomous

workers (three were house servants). According to their

educational level, the following situation was reported:

illiterate: 7; incomplete primary school: 39; primary

school graduate: 15; incomplete high school: 1; high

school graduate: 2; university education graduate: 1.

Thirty-four participants were married, seven were

single, seven were divorced and 17 widowed.

One of the authors translated the OHIP-EDENT into

Portuguese. This version was re-translated into English

and each question was assessed for conceptual changes.

After this procedure, the inventory (Table 1) was applied

on the sample. It is composed of a list of questions that is

grouped according to seven subscales, or domains (6): (a)

functional limitation; (b) physical pain; (c) psychological

discomfort; (d) physical disability; (f) psychological

Table 1. Brazilian version of OHIP-EDENT evaluated by the present study. Possible answers for each question were: A) nunca (never); B)

as vezes (sometimes); or C) quase sempre (almost always)

Functional limitation

1. Voce sentiu dificuldade para mastigar algum alimento devido a problemas com seus dentes, boca ou dentaduras?

2. Voce percebeu que seus dentes ou dentaduras retinham alimento?

3. Voce sentiu que suas dentaduras nao estavam corretamente assentadas?

Physical pain

4. Voce sentiu sua boca dolorida?

5. Voce sentiu desconforto ao comer devido a problemas com seus dentes, boca ou dentaduras?

6. Voce teve pontos doloridos na boca?

7. Suas dentaduras estavam desconfortaveis?

Psychological discomfort

8. Voce se sentiu preocupado(a) devido a problemas dentarios?

9. Voce se sentiu constrangido por causa de seus dentes, boca ou dentaduras?

Physical disability

10. Voce teve que evitar comer alguma coisa devido a problemas com seus dentes, boca ou dentaduras?

11. Voce se sentiu impossibilitado(a) de comer com suas dentaduras devido a problemas com elas?

12. Voce teve que interromper suas refeicoes devido a problemas com seus dentes, boca ou dentaduras?

Psychological disability

13. Voce se sentiu perturbado(a) com problemas com seus dentes, boca ou dentaduras?

14. Voce esteve em alguma situacao embaracosa devido a problemas com seus dentes, boca ou dentaduras?

Social disability

15. Voce evitou sair de casa devido a problemas com seus dentes, boca ou dentaduras?

16. Voce foi menos tolerante com seu conjuge ou famılia devido a problemas com seus dentes, boca ou dentaduras?

17. Voce esteve um pouco irritado(a) com outras pessoas devido a problemas com seus dentes, boca ou dentaduras?

Handicap

18. Voce foi incapaz de aproveitar totalmente a companhia de outras pessoas devido a problemas com seus dentes, boca ou dentaduras?

19. Voce sentiu que a vida em geral foi menos satisfatoria devido a problemas com seus dentes, boca ou dentaduras?

R . F . S O U Z A et al.822

ª 2007 The Authors. Journal compilation ª 2007 Blackwell Publishing Ltd

disability; (g) social disability and (h) handicap. Three

possible answers with respective scores were present for

the translated version, as opposed to five in the English

version. They are as follows: (0) never; (1) sometimes; or

(2) almost always. The smaller number of answers was

proposed so that volunteers would better understand

them. Subjects were asked to answer the inventory

according to experiences over the previous 3 months.

Illiterate volunteers answered questions by means of an

interview.

In this study, reliability was assessed through tests of

internal consistency and reproducibility. This consisted

of a test-retest approach, with an interval of 3 months

before the second application. Following the reliability

analysis, the proposed validation method was adminis-

tered.

Reliability

Internal consistency was assessed by Cronbach’s coef-

ficient a (11). Cronbach’s a is a summary statistic,

which captures the extent of agreement between all

possible subsets of questions. It was determined for the

overall results as well as for each domain. Results of this

analysis range from 0Æ0 to 1Æ0. A value similar to or >0Æ7is considered acceptable (9).

The reproducibility analysis included a test of agree-

ment between the two proposed applications of OHIP-

EDENT. This was done after applying the inventory

3 months later on the same volunteers. The stability of

results was evaluated for each question by means of the

weighted kappa coefficient (j). The summary scores for

the translated OHIP-EDENT were analysed for repro-

ducibility using the intra-class correlation coefficient.

Validation

A qualitative approach was used for validating the

translated OHIP-EDENT. An interview was conducted

with the 10 volunteers that had the greatest overall

scores for the second application of the inventory. Each

question marked with ‘almost always’ was represented in

an open format. Care was taken about reasons reported

by the volunteers for their previous answers. The OHIP-

EDENT was developed specifically for edentulous

patients with regard to prosthetic therapy (8). Thus,

expected reasons would comprise the functional limita-

tions of denture treatment (12–14). However, individual

feelings regarding the oral status are variable and include

psycho-social components (15). According to these

reports and to the authors’ experience, denture wearing

can be evaluated very differently by each volunteer with

respect to the oral health-related quality of life.

Results

Table 2 presents the frequency of valid answers for each

question and a descriptive analysis and Cronbach’s a for

the seven subscales. An overall a of 0Æ86 was found for

the first application of the inventory. The second

application attained a Cronbach’s a of 0Æ90. Results

for the second appointment are also shown in Table 2,

whereby 58 volunteers had returned. The association

between the initial and the final results was assessed by

the intra-class correlation coefficient. A coefficient of

0Æ57 (P < 0Æ001) was obtained.

Six volunteers attended the interview. The results of

this stage found good coherence between the contents of

OHIP-EDENT and answers. Complaints about denture

fitting and stability were frequent following questions #1

and #3, such as ‘dentures were a bit loose’ or ‘the lower

one was very unsteady’. One volunteer reported that

difficulty in chewing was due to pain over the edentulous

ridge. When the sample was asked about question #2,

there were references to food retention under denture

base and on external surface. Problems regarding the

‘physical pain’ domain were attributed to soreness over

the ridge (‘…some points were scrapping my gums and

were hurting me’) and cheeks (‘I was biting my cheeks’).

Comfort seemed to be closely related to denture base

fitting as evidenced by several reports. This can be

exemplified by the following commentary: ‘My dentures

were loose. Because I trimmed them with a penknife,

they bothered even more.’ In reply to the ‘physical

disability’ questions subjects generally indicated that it

was the result of impaired chewing ability (‘I have

avoided hard foods because I was not able to chew them’)

and ⁄ or denture looseness (‘Lower denture was falling

out when I was eating’). A report of cheek biting was

found for question #10.

Volunteers reported psychological discomfort and

disability associated with different reasons. Worries

and self consciousness were related to the edentu-

lism ⁄ denture wearer status (‘I do not like wearing a

prosthesis’). Complaints about phonetics (‘I was afraid

to lose my denture while speaking’) and pain (‘Only

when I was feeling pain’) were frequent as a response

to those domains. Poor understanding was reflected in

B R A Z I L I A N V E R S I O N O F T H E O H I P - E D E N T 823

ª 2007 The Authors. Journal compilation ª 2007 Blackwell Publishing Ltd

reports of two participants to question # 8 (‘My teeth

were in pain and then they ‘fell out’). In reply to

question #13, subjects generally indicated problems

with speech, feeding (‘Sometimes the denture annoyed

me during eating and speaking’) and denture wearing

itself (‘Dentures were annoying me and it was difficult

to get used to denture wearing’).

A small number of people felt problems related to

social domains. However, a response to question #16

shows that poor satisfaction with complete dentures

can affect social relationships (‘Because I felt myself

angered with my denture’).

Discussion

An assessment of oral health-related quality of life

proved that complete denture wearers form a hetero-

geneous group. Oral conditions did not exert significant

physical, psychological or social impact on a portion of

the sample. This can be explained by an adequate

adaptation to their prostheses (1). Thus, it can be stated

that oral rehabilitation provided satisfactory health

conditions, at least from the subjective perception.

Another subgroup presented high OHIP-EDENT scores.

In other words, a substantial number suffered from

their oral condition. As long as dentures among the

sample group were constructed according to similar

clinical parameters, a fair amount of variation on scores

can be explained by differently perceived needs (5, 7, 8,

16, 17). The present results stress that clinical decision-

making for edentulous subjects must respect the criteria

of the patient, aside from normative principles.

It was found necessary to change the response

format to a 0–2 scale during a pilot testing of the

Table 2. Application results of OHIP-EDENT. Frequency of answers for each question, results for the seven subscales (n = 65), and

weighted ‘j’ for the questions (n = 58)

Questions

Answers‡ Reproducibility

Results for the subscales, first

examination

Never Sometimes Almost always j CI P Min 1st Q. Med 3rd Q. Max

1. Difficulty chewing 31 (47Æ7) 24 (36Æ9) 10 (15Æ4) 0Æ61 0Æ09 0Æ00* I- Functional limitation (a = 0Æ50

and 0Æ66)†

2. Food catching 25 (38Æ5) 18 (27Æ7) 22 (33Æ8) 0Æ63 0Æ08 0Æ00* 0 1 2 3 6

3. Dentures not fitting 37 (56Æ9) 20 (30Æ8) 8 (12Æ3) 0Æ42 0Æ09 0Æ00*

4. Painful aching 40 (61Æ5) 21 (32Æ3) 4 (6Æ2) 0Æ38 0Æ10 0Æ00*

5. Uncomfortable to eat 36 (55Æ4) 20 (30Æ8) 9 (13Æ8) 0Æ48 0Æ09 0Æ00* II- Physical pain (a = 0Æ75 and 0Æ85)†

6. Sore spots 49 (75Æ4) 11 (16Æ9) 5 (7Æ7) 0Æ20 0Æ10 0Æ03* 0 0 1 4 8

7. Uncomfortable dentures 36 (55Æ4) 20 (30Æ8) 9 (13Æ8) 0Æ50 0Æ10 0Æ00*

8. Worried 47 (72Æ3) 11 (16Æ9) 7 (10Æ8) 0Æ37 0Æ11 0Æ00* III- Psychological discomfort

(a = 0Æ20 and 0Æ54)†

9. Self-conscious 54 (83Æ1) 8 (12Æ3) 3 (4Æ6) 0Æ81 0Æ10 0Æ00* 0 0 0 1 3

10. Avoids eating 39 (60Æ0) 19 (29Æ2) 7 (10Æ8) 0Æ54 0Æ10 0Æ00* IV- Physical disability (a = 0Æ83 and

0Æ80)†

11. Interrupts meals 47 (72Æ3) 13 (20Æ0) 5 (7Æ7) 0Æ25 0Æ11 0Æ01* 0 0 0 2 5

12. Unable to eat 52 (80Æ0) 13 (20Æ0) 0 (0Æ0) 0Æ54 0Æ13 0Æ00*

13. Upset 48 (73Æ8) 15 (23Æ1) 2 (3Æ1) 0Æ51 0Æ12 0Æ00* V- Psychological disability (a = 0Æ56

and 0Æ62)†

14. Has been embarrassed 47 (72Æ3) 17 (26Æ2) 1 (1Æ5) 0Æ73 0Æ09 0Æ00* 0 0 0 1 3

15. Avoids going out 64 (98Æ5) 1 (1Æ5) 0 (0Æ0) )0Æ03 0Æ02 0Æ81ns VI- Social disability (a = 0Æ50 and

0Æ78)†

16. Less tolerant of others 58 (89Æ2) 7 (10Æ8) 0 (0Æ0) 0Æ31 0Æ20 0Æ00* 0 0 0 0 2

17. Irritable with others 62 (95Æ4) 3 (4Æ6) 0 (0Æ0) )0Æ05 0Æ02 0Æ70ns

18. Unable to enjoy company 63 (96Æ9) 2 (3Æ1) 0 (0Æ0) 0Æ55 0Æ23 0Æ00* VII- Handicap (a = 0Æ52 and 0Æ51)†

19. Life unsatisfying 62 (95Æ4) 1 (1Æ5) 2 (3Æ1) 0Æ53 0Æ18 0Æ00* 0 0 0 0 3

nsNon-significant; P > 0Æ05; *Significant; P < 0Æ05; †First and second application respectively; ‡Values in parentheses are expressed as

percentage.

CI = confidence interval (a = 0Æ05); Min, minimum; 1st Q, first quartile; Med, median; 3rd Q, third quartile; Max, maximum; OHIP-

EDENT, Oral Health Impact Profile for assessing edentulous subjects.

R . F . S O U Z A et al.824

ª 2007 The Authors. Journal compilation ª 2007 Blackwell Publishing Ltd

translated OHIP-EDENT. Several volunteers did not

understand the 0–4 scale, as presented in the original

inventory (8). Some statements about the interna-

tional comparability of the Brazilian OHIP-EDENT

should be carried out. Regardless of modifications on

the response format, linking summary scores obtained

from inventories administered in different languages is

a difficult challenge. Specific statistical and psycho-

metric methods can be used to adjust scores obtained

on different versions so that they are comparable (18).

Further efforts are needed for linking Brazilian OHIP-

EDENT scores to those obtained by the original

instrument.

The inventory reported a high prevalence of com-

plaints related to functional limitations. More than 75%

of the sample marked the answers ‘sometimes’ and

‘almost always’ in this subscale in one or more

instances. This is most likely a consequence of the

intrinsic limitations of complete denture treatment

(12), such as low masticatory performance (13) and

retention ⁄ stability features (14). In general, the fre-

quency of these answers is moderate for physical and

psychological subscales. It was rare, however, for the

two social subscales, i.e., social disability and handicap.

Distribution of responses is in agreement with previous

studies (6, 12) which reported a hierarchic relation

between the subscales as follows: limitation, discomfort,

disability and handicap – the last being the greatest

level of impact.

In general, the translated OHIP-EDENT showed good

internal consistency, indicating that the version is able

to measure a unique theoretical construct. Thus, the

inventory can be considered a good indicator of oral

health-related quality of life for edentulous subjects.

However, the low prevalence of acceptable consistency

levels for subscales can be explained by the low number

of questions for each domain. If we consider a Cron-

bach’s a value of 0Æ5 as a cut-off point, only ‘psycho-

logical discomfort’ questions are classified as

inconsistent. A low consistency for subscales was also

found for a Brazilian version of the 14-question OHIP

(19). Thus, the use of the seven subscales for the

present version of the OHIP-EDENT is not supported by

this study.

Reproducibility for each question of the Brazilian-

version OHIP-EDENT presented a wide variation. Some

questions resulted in a high degree of agreement, but

the majority showed acceptable or regular levels. Two

scenarios within the ‘social disability subscale’ showed

weak results. This can be explained by the great

number of volunteers that pointed out no impact, and

small disagreements between examinations have had a

greater effect. Moreover, this is one of the most

complex domains and is influenced by diverse social

conditions as well as oral health. An important limita-

tion was the low educational level of the sample, which

could have resulted in lower reproducibility. Better

reproduction was found from a German version of

OHIP (20), stressing that different groups and distinct

cultural environments can influence response. A poss-

ible source of bias for reproducibility was the time span

after denture insertion. Improved self-perception

occurs at the same time as functional adaptation to

complete dentures. This is intense during the first

month of use (21). Regarding the long-term use of

prostheses, there is no information about oral health

impact behaviour.

Preliminary validation analysis showed good under-

standing of the question content. In general, justifica-

tions for an ‘almost always’ answer corresponded to the

issue at hand. It can be stated that subjects made

reflexive responses according to perceived oral health

conditions at the present time. An exception was the

eighth question. Some of the volunteers reported

problems which occurred before tooth loss. The

strength of this qualitative process is the depth of

analysis, as long as it complements a quantitative

approach. This improves the validity of measured

outcomes (22). In a general manner, expectations

described for the validation procedure were met.

A wide range of reasons was reported varying from den-

ture fitting to problems on emotional adjustment.

The translated version of OHIP-EDENT showed sat-

isfactory reliability and agreement with reported com-

plaints. The employment of this version as an outcome

measurement for clinical research is feasible, as long as

the limitations are known. Future studies are needed

for validation according to the statistical criteria and for

the assessment of possible factors associated with oral

health-related quality of life in edentulous subjects.

However, the development of inventories specifically

based on complaints of Brazilian patients should be

encouraged.

Acknowledgment

This research was supported by FAPESP (grant no. 04-

13 253-5).

B R A Z I L I A N V E R S I O N O F T H E O H I P - E D E N T 825

ª 2007 The Authors. Journal compilation ª 2007 Blackwell Publishing Ltd

References

1. Allen PF, McMillan AS. A review of the functional and

psychosocial outcomes of edentulousness treated with com-

plete replacement dentures. J Can Dent Assoc. 2003;69:

662.

2. Brasil Ministerio da Saude – Divisao Nacional de Saude Bucal.

Projeto SB Brasil: Condicoes de Saude Bucal da Populacao

Brasileira 2002-2003 – Resultados Principais. Brasılıa:

Ministerio da Saude; 2004.

3. Zarb GA, Bolender CL, Eckert SE. Prosthodontic treatment for

edentulous patients: complete dentures and implant-suppor-

ted prostheses. 12th ed. St Louis: Mosby; 2004.

4. Cibirka RM, Razzoog M, Lang BR. Critical evaluation of

patient responses to dental implant therapy. J Prosthet Dent.

1997;78:574–81.

5. Allen PF, McMillan AS, Walshaw D. A patient-based assess-

ment of implant-stabilized and conventional complete den-

tures. J Prosthet Dent. 2001;85:141–7.

6. Slade GD, Spencer AJ. Development and evaluation of the Oral

Health Impact Profile. Community Dent Health. 1994;11:3–11.

7. Allen PF, McMillan AS. A longitudinal study of quality of life

outcomes in older adults requesting implant prostheses and

complete removable dentures. Clin Oral Implants Res.

2003;14:173–9.

8. Allen F, Locker D. A modified short version of the Oral Health

Impact Profile for assessing health-related quality of life in

edentulous adults. Int J Prosthodont. 2002;15:446–50.

9. Hulley SB, Cummings SR, Browner WS, Grady D, Hearst N,

Newman TB. Delineando a pesquisa clınica: uma abordagem

epidemiologica. 2nd ed. Porto Alegre: Artmed; 2003.

10. Leles CR, Compagnoni MA, Souza RF, Barbosa DB. Kinesio-

graphic study of mandibular movements during functional

adaptation to complete dentures. J Appl Oral Sci. 2003;11:

311–8.

11. Cronbach LJ. Coefficient alpha and the internal structure of

tests. Psychometrika. 1951;16:297–334.

12. Heydecke G, Tedesco LA, Kowalski C, Inglehart MR. Complete

dentures and oral health-related quality of life – do coping styles

matter? Community Dent Oral Epidemiol. 2004;32:297–306.

13. Fontijn-Tekamp FA, Slagter AP, Van der Bilt A, Van’t Hof MA,

Kalk W, Jansen JA. Swallowing thresholds of mandibular

implant-retained overdentures with variable portion sizes.

Clin Oral Implants Res. 2004;15:375–80.

14. Fujimori T, Hirano S, Hayakawa I. Effects of a denture

adhesive on masticatory functions for complete denture

wearers – consideration for the condition of denture-bearing

tissues. J Med Dent Sci. 2002;49:151–6.

15. Strassburger C, Kerschbaum T, Heydecke G. Influence of

implant and conventional prostheses on satisfaction and

quality of life: a literature review. Part 2: Qualitative analysis

and evaluation of the studies. Int J Prosthodont. 2006;19:339–

48.

16. Allen PF, McMillan AS, Locker D. An assessment of sensitivity

to change of the Oral Health Impact Profile in a clinical trial.

Community Dent Oral Epidemiol. 2001;29:175–82.

17. Awad MA, Locker D, Korner-Bitensky N, Feine JS. Measuring

the effect of intra-oral implant rehabilitation on health-related

quality of life in a randomized controlled clinical trial. J Dent

Res. 2000;79:1659–63.

18. Dorans NJ. Linking scores from multiple health outcome

instruments. Qual Life Res. 2007 (in press).

19. Oliveira BH, Nadanovsky P. Psychometric properties of the

Brazilian version of the Oral Health Impact Profile-short form.

Community Dent Oral Epidemiol. 2005;33:307–14.

20. John MT, Patrick DL, Slade GD. The German version of the

Oral Health Impact Profile–translation and psychometric

properties. Eur J Oral Sci. 2002;110:425–33.

21. John MT, Slade GD, Szentpetery A, Setz JM. Oral health-

related quality of life in patients treated with fixed, remov-

able, and complete dentures 1 month and 6 to 12 months

after treatment. Int J Prosthodont. 2004;17:503–11.

22. Greenhalgh T, Taylor R. Papers that go beyond numbers

(qualitative research). Brit Med J. 1997;315:740–3.

Correspondence: Dr Raphael Freitas de Souza, Department of Dental

Materials and Prosthodontics, Ribeirao Preto Dental School,

University of Sao Paulo, Av. do Cafe s ⁄ n, 14040-904 Ribeirao Preto,

Sao Paulo, Brazil.

E-mail: raphael@forp.usp.br

R . F . S O U Z A et al.826

ª 2007 The Authors. Journal compilation ª 2007 Blackwell Publishing Ltd