- Email: [email protected]
A randomized clinical trial comparing anatomic, lingualized, and zero-degree posterior occlusal forms for complete dentures
A randomized clinical trial comparing anatomic, lingualized, and zero-degree posterior occlusal forms for complete dentures A. F. Sutton, BDS, MSc, PhD,a and J. F. McCord, BDS, DDSb University Dental Hospital of Manchester, Manchester, UK; Glasgow Dental Hospital and School, Glasgow, UK Statement of problem. There is a lack of evidence to recommend a particular type of posterior occlusal form for conventional complete dentures.
Purpose. The purpose of this study was to compare subject satisfaction with 3 types of posterior occlusal forms for complete dentures in a randomized cross-over controlled trial.
Material and methods. For each participant (n=45), 3 sets of complete dentures were fabricated, each of which had a different posterior occlusal form (0-degree, anatomic, and lingualized). Each set was worn for 8 weeks in a randomized order. Subjective data were collected using the Oral Health Impact Profile 20-EDENT (OHIP-EDENT). The Wilcoxon statistical test was used to compare differences between the groups (a=.05). Results. Lingualized posterior occlusal forms were perceived to be significantly superior in terms of painful aching in the mouth (P=.01), sore spots (P,.001), eating ability (P=.02), and meal interruptions (P=.008), compared with 0-degree posterior occlusal forms. Subjects with anatomic posterior occlusal forms had significantly fewer problems eating (P=.05) compared with 0-degree posterior occlusal forms. There was no significant difference found between the lingualized and anatomic posterior occlusal forms. Conclusions. Participants provided with complete dentures having lingualized or anatomic posterior occlusal forms exhibited significantly higher levels of self-perceived satisfaction compared to those with 0-degree posterior occlusal forms. (J Prosthet Dent 2007;97:292-8.)
CLINICAL IMPLICATIONS In conventional complete denture fabrication, it may be advisable to use lingualized or anatomic posterior occlusal forms instead of 0-degree posterior occlusal forms.
A
high level of patient satisfaction, when fabricating complete dentures, should be the primary goal in the treatment of edentulous subjects. Jacobsen and Krol1-3 stated that there are 3 key principal factors (retention, stability, and support) in the prescription and provision of successful complete dentures. Fish4 stated that complete dentures are made up of 3 surfaces; the impression or intaglio surface, the polished surface, and the occlusal surface. The retention, stability, and support of the dentures are governed by the design of these 3 surfaces.1-3 When the maxillary and mandibular denture teeth come into contact, unfavorable displacing forces may overwhelm the retention and stability of the dentures, resulting in discomfort from trauma to the supporting mucosa.5 If the intaglio and polished surfaces are ideal, it is assumed that the form of the occlusal surfaces and the nature of their
Presented before the Annual Meeting of the British Society for the Study of Prosthetic Dentistry, Cardiff, UK, March 2005. a Consultant in Restorative Dentistry, Department of Restorative Dentistry, University Dental Hospital of Manchester. b Professor of Restorative Dentistry, Glasgow Dental Hospital and School.
292 THE JOURNAL OF PROSTHETIC DENTISTRY
contacts become critical for successful complete denture function.6 There are many philosophies concerning the most appropriate posterior occlusal forms for conventional complete maxillary and mandibular dentures. Studies comparing various types of complete denture teeth have been conducted for years and have explored outcomes such as masticatory efficiency, occlusal force, and patient preference.7-16 To overcome bias resulting from individual variation between subjects, most studies have compared different types of teeth in the same patient in a cross-over fashion.8-16 The methods used in these studies can be divided into 2 groups. First, where subjects received duplicate complete dentures, which had differing occlusal forms, or secondly, where the subjects were provided with complete dentures, which allowed for experimental modification of the posterior teeth by grinding, adding, or interchanging. In a randomized trial, Clough et al8 fabricated 2 sets of dentures, 1 with lingualized occlusion and the other with monoplane occlusion, for 30 subjects. The dentures were worn for 3 weeks and then swapped. Twenty subjects preferred lingualized occlusion, 5 preferred 0-degree, and 5 expressed no preference. Brewer et al,9 VOLUME 97 NUMBER 5
SUTTON AND MCCORD
in a nonrandomized trial, compared the use of 0-degree teeth and anatomic teeth for 25 men. Ten expressed no preference, 8 preferred 0-degree teeth, and 2 preferred anatomic teeth. Shetty10 compared complete dentures having anatomic posterior teeth with 0-degree teeth in a nonrandomized cross-over study using 40 subjects. The majority of subjects preferred anatomic posterior occlusal schemes. Thompson, in 1937,11 was the first investigator to produce complete dentures with interchangeable teeth. Anatomic posterior teeth were judged to be the most efficient for mastication compared with 20-degree posterior teeth, inverted cusp teeth (nonanatomic posterior denture teeth with circular indentations where cusps would normally be located) and channel teeth (posterior denture teeth with anterior-posterior channels placed in the occlusal surfaces). Trappozzano and Lazzari12 used a modified version of Thompson’s method and found no difference in masticatory efficiency with 3 different posterior occlusal forms; namely, 20-degree posterior teeth, 0-degree posterior teeth, and inverted cusp teeth. Hickey et al13 performed an electromyographic study comparing complete dentures with interchangeable posterior teeth comprised of anatomic teeth, 0-degree teeth, and semi-anatomic teeth. The authors found that complete dentures with anatomic posterior teeth required less muscle activity during mastication for the 9 subjects tested. Complete dentures with interchangeable posterior teeth were evaluated by Kydd14 (5 subjects using 33-degree, 20-degree, and 0-degree teeth) and Koyama et al15 (3 subjects using 33-degree teeth, lingualized occlusion, and canine protected articulation) for masticatory efficiency, with no differences found. Yurkstas16 evaluated 20 subjects with 4 cuspless geometric occlusal patterns in acrylic resin posterior teeth and compared these with raised metal inserts in a study spanning 15 months. Results revealed no statistical differences in masticatory effectiveness between the patterns tested. Prior to conducting the current study, a Cochrane Systematic Review database was reviewed to determine if there had been previous randomized controlled trials comparing the efficacy of different occlusal schemes for complete dentures.7 The objective of the systematic review was to identify a superior occlusal scheme for complete dentures. One thousand and seventy six titles, abstracts, and papers were appraised, and only 1 trial was found to satisfy the inclusion criteria (Clough et al8). In that study, subjects preferred prosthetic teeth with cusps as opposed to cuspless teeth (0-degree) in terms of improved masticatory performance. However, that study was judged to be at high risk of bias owing to insufficient information provided regarding the method of randomization and allocation concealment. In addition, the method for assessing the participant satisfaction was unclear. The results of the review highlighted the need for further well conducted, randomized, controlled trials in MAY 2007
THE JOURNAL OF PROSTHETIC DENTISTRY
the area of complete denture occlusion. Randomized cross-over trials have, however, been used successfully in evaluating subject preferences for different types of implant-supported prostheses.17-20 The purpose of this study was to conduct a randomized controlled trial to test the null hypothesis that there is no variation in the level of patient satisfaction for 3 different types of posterior occlusal forms, namely 0-degree, anatomic, and lingualized, for conventional complete dentures.
MATERIAL AND METHODS The Manchester Local Research Ethics Committee granted ethical approval for this study. Edentulous subjects taken from the waiting list of the University Dental Hospital of Manchester and requiring replacement complete dentures were selected for the study. Subjects were excluded if their medical history revealed 1 or more of the following; neuromuscular dysfunction, psychiatric disorder, and/or the presence of oral pathology. Fifty subjects were assessed for eligibility. Five subjects were excluded from enrollment because they refused to participate. Forty-five subjects provided informed consent. Forty-five participants were assigned 3 sets of complete dentures with different types of posterior occlusal forms in a randomized order. The posterior occlusal surfaces of the 3 dentures consisted of anatomic teeth, lingualized occlusion, and 0-degree teeth. Anatomic teeth are defined as artificial teeth with cuspal inclinations greater than 0 degrees that tend to replicate natural tooth anatomy.21 Lingualized occlusion is defined as a form of denture occlusion where the maxillary lingual cusps articulate with the mandibular occlusal surfaces in centric working and nonworking mandibular positions.21 Zero-degree teeth are defined as posterior denture teeth having 0-degree cuspal angles in relation to the plane established by the horizontal occlusal surface of the tooth.21 The dentures were fabricated according to the British Society for the Study of Prosthetic Dentistry Guidelines in Prosthetic and Implant Dentistry.22 The clinical procedures were performed by 1 experienced prosthodontist (AFS), and 1 senior dental technician performed the laboratory procedures. The process consisted of making preliminary impressions (Kemco Tracing Sticks; Associated Dental Products, Purton, UK), making definitive impressions in irreversible hydrocolloid (Xantalgin Select; Heraeus Kulzer, Hanau, Germany) for the maxilla, and zinc oxide eugenol (SS White Manufacturing Ltd, Gloucester, UK) for the mandible, recording the maxillo-mandibular relationship with a central bearing tracing device (PTC UK Ltd, Bolton, UK), and making a face-bow transfer (Denar Slidematic Facebow; Waterpik Technologies Inc, Newport Beach, Calif). The final casts were mounted in a semi-adjustable articulator (Denar Mark II; Waterpik Technologies Inc). The anatomic posterior teeth used 293
THE JOURNAL OF PROSTHETIC DENTISTRY
SUTTON AND MCCORD
Fig. 1. Posterior view of complete dentures with anatomic posterior teeth.
Fig. 2. Sagittal view of complete dentures with anatomic posterior occlusal surfaces.
Fig. 3. Posterior view of complete dentures with lingualized posterior teeth.
Fig. 4. Sagittal view of complete dentures with lingualized posterior occlusal surfaces.
were 33-degree prosthetic teeth (Basic 8, B range; Heraeus Kulzer), arranged and adjusted to balanced articulation with cross-arch and cross-tooth balance (Figs. 1 and 2). The lingualized posterior teeth were modified 33-degree prosthetic teeth (Basic 8, B range; Heraeus Kulzer), arranged and adjusted to balanced articulation with cross-arch balance (Figs. 3 and 4). The modification consisted of tilting the maxillary posterior teeth to avoid all contact of the buccal cusps and selective grinding of the mandibular posterior teeth, creating a concavity in the occlusal surface. The 0-degree posterior teeth were 0-degree prosthetic teeth (Basic 8, G range; Heraeus Kulzer) set on a flat plane and arranged to balance in centric occlusion, with working-side contact only in left and right excursive movements (Figs. 5 and 6). The dentures were evaluated intraorally during subsequent trial insertion appointments. The dentures were processed by conventional compression molding, remounted in the semiadjustable articulator (Denar Mark II; Waterpik Technologies Inc) and the occlusion was adjusted as necessary.5 Even bilateral intraoral tooth contacts were
ensured by means of a remount procedure. Duplication of the dentures was performed once the first set of dentures was deemed to be comfortable by the subject, producing 2 more sets of dentures with different types of posterior occlusal schemes. The dentures had their intaglio surfaces, polished surfaces, and maxillary anterior tooth arrangement replicated as accurately as possible using the following method. The definitive casts were duplicated using reversible hydrocolloid (Polyflex; Dentsply, York, Pa) and mounted in the same relationship as the original final casts. A type IV stone index (Vel Mix; Kerr Corp, Orange, Calif) recorded the position of the maxillary teeth of the original denture and attached to the mandibular member of the articulator (Denar Mark II; Waterpik Technologies Inc). The original set of dentures was used to produce matrices in vinyl polysiloxane (Sherasil; Werkstoff-Technologie GmbH & Co KG, Lemforde, Germany). These matrices were used to fabricate maxillary and mandidubular autopolymerizing acrylic resin bases (Vertex; Vertex Dental BV, Zeist, The Netherlands) with wax teeth (Kemdent Anutex;
294
VOLUME 97 NUMBER 5
SUTTON AND MCCORD
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 5. Posterior view of complete dentures with 0-degree posterior teeth.
Fig. 6. Sagittal view of complete dentures with 0-degree posterior occlusal surfaces.
Associated Dental Products). The maxillary anterior wax teeth were replaced with identical prosthetic teeth using the stone index as a guide for tooth position. Once the maxillary anterior teeth were correctly positioned, the stone index was removed from the articulator and replaced with the mandibular final cast. The mandibular autopolymerizing acrylic resin base with wax teeth was located on the mandibular final cast. The mandibular anterior wax teeth were replaced with identical mandibular anterior prosthetic teeth. Prosthetic posterior teeth with the allocated occlusal form replaced the wax posterior teeth and were arranged and adjusted as described above. The duplicate dentures were processed by conventional compression molding.5 The participants received treatment for any necessary adjustments to the dentures until no further problems were reported. The 3 sets of dentures were worn for 8 weeks, after which the participants completed the Oral Health Impact Profile-20 EDENT (OHIP-EDENT).23,24 The participants were not informed of the type of occlusal form provided or the sequence in which they were allocated. Direct comparisons, by each patient, with the 2 other test sets of dentures were prevented by withholding them during the 8-week trial period. The Oral Health Impact Profile is an oral healthrelated quality of life index and is regarded as a comprehensive and sophisticated oral health-specific measure consisting of 49 items.23 A short version consisting of 20 items specifically designed and statistically validated for the assessment of complete denture wearers was used.24 This modified shortened version has been shown to have measurement properties comparable with the full 49-item version.24 The quality of outcome data were enhanced by using a room in the Prosthodontics Department away from the clinical and waiting area, with the administration of the OHIP-EDENT by a person blind to the trial. The subjects were randomized without restriction into 6 groups that allocated the sequence in which the
3 sets of dentures were provided. A medical statistician blind to the study performed the randomization using a computer program that generated a sequence of random numbers between 1 and 6. The randomized numbers were placed in unmarked, nontransparent envelopes. As a subject entered the trial the next envelope was opened, revealing the randomized occlusal form sequence. The prosthodontist was unaware of the sequence of intervention allocation until treatment commenced. The OHIP-EDENT index uses a 0-5 scale where 0 is never and 5 is always. Therefore, the items, or variables, were ordinal. In order to compare the pairs of groups, as each patient had each denture type, the data were paired. The Wilcoxon test was used to compare differences between pairs of groups, as this is the standard statistical test for ordinal paired data. This method tested the null hypothesis that the medians of the 2 groups were equal, against the research hypothesis that there would be a difference. An alpha level of .05 was accepted for significance in all tests. Data were analyzed using statistical software (SPSS version 12.01; SPSS Inc, Chicago, Ill). Based on preliminary data, 37 participants were required to have 90% power to detect a difference of 10% between groups at the 5% level. However, to compensate for potential dropouts during the study, the number of subjects included was increased to 45.
MAY 2007
RESULTS Figure 7 shows the flow of participants through each stage of the randomized controlled trial, namely enrollment, intervention allocation, follow up, and analysis. Forty-five subjects were randomly assigned to 1 of 6 intervention groups. The 6 intervention groups were the 6 possible orders in which the occlusal forms were allocated. Four subjects were lost to follow up, 2 because they refused to participate further and 2 because they were unable to attend due to poor health. 295
THE JOURNAL OF PROSTHETIC DENTISTRY
SUTTON AND MCCORD
Fig. 7. Flow diagram of phases of randomized trial. A = Anatomic posterior teeth; L = Lingualized posterior teeth; Z = 0-degree posterior teeth.
A total of 41 subjects were used in the data analysis. Table I shows the frequency distribution of denture allocation and group characteristics of the subjects included in the data analysis (after 4 were lost to follow up). Table II shows the median values of the OHIPEDENT responses for the subjects and indicates the direction in which they scored. Table III shows the P values of the comparisons between the 3 occlusal forms. The P values were derived from the Wilcoxon signed rank test for the OHIP-EDENT responses of the subjects for each experimental occlusal form. There were significantly lower numbers of problems recorded for ‘‘painful aching in the mouth’’ (P=.01), ‘‘sore spots in the mouth’’ (P,.001), problems eating (‘‘unable to eat’’) (P=.02), and ‘‘interrupted meals’’ (P=.02) with lingualized compared to 0-degree interventions. Subjects reported being ‘‘unable to eat’’ significantly more frequently with the 0-degree posterior teeth 296
Table I. Frequency distribution of demographics and clinical characteristics for each group at data analysis Order dentures provided
ALZ AZL LAZ LZA ZAL ZLA Total
Frequency
Percent
6 8 6 8 7 6 41
14.6 19.5 14.6 19.5 17.1 14.6 100.0
Mean age (years) (standard deviation)
55.3 66.1 70.1 66.9 72.7 62.1 65.2
(19.4) (9.1) (7.5) (7.6) (3.8) (5.9) (12.8)
Gender male/female
2:4 2:6 2:4 2:6 3:4 2:4 13:28
A = Anatomic posterior teeth; L = Lingualized posterior teeth; Z = 0-degree posterior teeth.
compared to anatomic (P=.05) and lingualized (P=.02) posterior occlusal schemes. When the lingualized and anatomic posterior occlusal forms were compared, no significant difference was found. VOLUME 97 NUMBER 5
SUTTON AND MCCORD
THE JOURNAL OF PROSTHETIC DENTISTRY
Table II. Median values of OHIP-EDENT responses for experimental occlusal forms
Table III. P values from Wilcoxon signed rank test of OHIPEDENT responses for experimental occlusal forms
Functional characteristic
Functional characteristic
Masticatory problems Food catching Fitting properly Painful aching in mouth Uncomfortable eating any foods Sore spots in mouth Ever had uncomfortable dentures Worried about dental problems Self-conscious because of dentures Unclear speech Avoid certain foods Unable to eat Interrupt meals Upset with dentures Embarrassed with dentures Avoid going out Less tolerant with spouse Irritable with other people Avoid other peoples’ company Life is less satisfying
Anatomic
Lingualized
0-degree
3 2 2 2 2 2 2 1 1 2 2 2 2 1 1 1 1 1 1 1
3 2 2 2 2 2 2 2 1 2 2 1 2 2 2 1 1 1 1 1
3 3 3 3 3 3 2 2 1 2 3 3 3 2 1 1 1 1 1 1
1 = Never; 2 = Hardly ever; 3 = Occasionally; 4 = Fairly often; 5 = Very often.
Masticatory problems Food catching Fitting properly Painful aching in mouth Uncomfortable eating any foods Sore spots in mouth Ever had uncomfortable dentures Worried about dental problems Self-conscious because of dentures Unclear speech Avoid certain foods Unable to eat Interrupt meals Upset with dentures Embarrassed with dentures Avoid going out Less tolerant with spouse Irritable with other people Avoid other peoples’ company Life is less satisfying
A vs. L
A vs. Z
L vs. Z
.37 .97 .77 .52 .59 .51 .52 .94 .10 .23 .98 .82 .16 .93 .11 .28 .48 .21 .89 .75
.78 .64 .07 .30 .35 .59 .14 .34 .19 .64 .48 .05y .12 .94 .10 .16 .95 .89 .96 .11
.25 .23 .10 .01y .08 ,.001y .29 .18 .51 .13 .06 .02y .02y .87 .90 .79 .34 .36 .89 .14
y
P value significant for P , .5. A = Anatomic posterior teeth. L = Lingualized posterior teeth. Z = 0-degree posterior teeth.
DISCUSSION The null hypothesis that there is no variation in the level of patient satisfaction for 3 types of posterior occlusal forms, namely 0-degree, anatomic, and lingualized, for conventional complete dentures, was rejected. A simple and accurate method was devised for duplicating the first set of complete dentures fabricated for the participants. Duplication was only performed if the subjects were comfortable with their initial set of dentures. The silicone indices of the first set of dentures ensured the polished surfaces were duplicated accurately. All of the clinical stages were performed by 1 prosthodontist, and 1 senior dental technician fabricated all of the dentures. This ensured that consistency of the complete denture fabrication was maintained. The randomization of the inserted dentures minimized the small differences owing to the duplication procedure. The subject groups were not stratified for age, gender, degree of alveolar reduction, denture experience, or previous type of denture occlusal scheme, and this may be considered a weakness of the investigation. The duration of the trial period was 8 weeks, which, ideally, could have been longer. However, increasing the test period would have severely limited the practicality of this trial owing to participant recall difficulty and possible changes to the denture-bearing tissues of the subjects. A trial period of 8 weeks has been shown to be effective in determining patient preferences between various types of implant-supported prostheses,19 and it was thought to be an appropriate duration of follow MAY 2007
up for this study. It was not possible for the prosthodontist to be blinded to the occlusal scheme provided, and this was, therefore, an uncontrolled bias potential. The findings of this research are in general agreement with the findings of other studies.8,10,11,13 There was a statistically significant difference in favor of the lingualized dentures in the 1 randomized trial8 included in the Cochrane Systematic Review (McNemar chi-square test; P=.041), which is in agreement with the results of this study.7 When using lingualized occlusal surfaces, the subjects reported significantly less painful aching (P=.01) and sore spots in the mouth (P,.001) compared with the 0-degree dentures. The reasons for this may only be speculated; however, it has been shown that reduced forces during mastication are transmitted to the denture-bearing areas with lingualized posterior teeth when compared to 0-degree teeth,14 and may, therefore, result in reduced pain. When subjects rated ‘‘ability to eat’’, the complete dentures provided with lingualized and anatomic posterior occlusal forms were significantly preferred over 0-degree posterior occlusal forms (P=.02 and P=.05, respectively). It has been shown that less force is required to masticate through a food bolus with teeth having cusps compared to 0-degree teeth.13,14 Teeth with cusps by their very nature have a reduced surface area of contact compared with 0-degree teeth and require a reduced masticatory force to penetrate food.13 The 297
THE JOURNAL OF PROSTHETIC DENTISTRY
subjects reported significantly fewer interruptions to their meals with the lingualized occlusal surfaces compared with the 0-degree occlusal surfaces (P=.02). This may be related to the superior masticatory ability with the lingualized posterior occlusal surfaces. Suggestions for future research include comparison of the levels of patient satisfaction between complete dentures fabricated with or without the use of a face-bow transfer or the use of central bearing apparatuses compared to conventional wax occlusal rims.
CONCLUSIONS Lingualized posterior occlusal forms were significantly superior in terms of reduced pain in the mouth, reduced incidence of sore spots, ability to eat, and meal interruptions, compared with 0-degree posterior occlusal forms. Anatomic posterior occlusal forms were significantly better in terms of masticatory function compared with 0-degree posterior occlusal forms. There were no significant differences when lingualized posterior occlusal forms were compared with anatomic posterior occlusal forms. REFERENCES 1. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete denture retention, stability, and support. Part I: retention. J Prosthet Dent 1983;49:5-15. 2. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete dentures. Part II: stability. J Prosthet Dent 1983;49:165-72. 3. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete dentures. Part III: support. J Prosthet Dent 1983;49:306-13. 4. Fish EW. An analysis of the stabilising factors in full denture construction. Br Dent J 1931;52:559-70. 5. Zarb GA, Bolender CL, Carlsson GE. Boucher’s prosthodontic treatment for edentulous patients. 11th ed. St. Louis: Elsevier Health Sciences; 1997. p. 37, 337-43. 6. McCord JF, Grant AA. Registration: stage III–selection of teeth. Br Dent J 2000;24(188):660-6. 7. Sutton AF, Glenny AM, McCord JF. Interventions for replacing missing teeth: denture chewing surface designs in edentulous people. Cochrane Database Syst Rev 2005:CD004941. 8. Clough HE, Knodle JM, Leeper SH, Pudwill ML, Taylor DT. A comparison of lingualized occlusion and monoplane occlusion in complete dentures. J Prosthet Dent 1983;50:176-9. 9. Brewer AA, Reibel PR, Nassif NJ. Comparison of zero degree teeth and anatomic teeth on complete dentures. J Prosthet Dent 1967;17:28-35. 10. Shetty NS. Comparative observations of the use of cusp and zero-degree posterior teeth. J Prosthet Dent 1984;51:459-60.
298
SUTTON AND MCCORD
11. Thompson MJ. Masticatory efficiency as related to cusp form in denture prosthesis. J Am Dent Assoc 1937;24:207-19. 12. Trappozzano VR, Lazzari JB. An experimental study of the testing of occlusal patterns on the same denture bases. J Prosthet Dent 1952;2:440-57. 13. Hickey JC, Woelfel JB, Allison ML, Boucher CO. Influence of occlusal schemes on the muscular activity of edentulous patients. J Prosthet Dent 1963;13:444-51. 14. Kydd WL. The comminuting efficiency of varied occlusal tooth form and the associated deformation of the complete denture base. J Am Dent Assoc 1960;61:465-71. 15. Koyama M, Inaba S, Yokoyama K. Quest for ideal occlusal patterns for complete dentures. J Prosthet Dent 1976;35:620-3. 16. Yurkstas AA. The influence of geometric occlusal carvings on the masticatory effectiveness of complete dentures. J Prosthet Dent 1963;13: 452-61. 17. Feine JS, Maskawi K, de Grandmont P, Donohue WB, Tanguay R, Lund JP. Within-subject comparisons of implant-supported mandibular prostheses: evaluation of masticatory function. J Dent Res 1994;73:1646-56. 18. de Albuquerque Junior RF, Lund JP, Tang L, Larivee J, de Grandmont P, Gauthier G, et al. Within-subject comparison of maxillary long-bar implant-retained prostheses with and without palatal coverage: patientbased outcomes. Clin Oral Implants Res 2000;11:555-65. 19. de Grandmont P, Feine JS, Tache R, Boudrias P, Donohue WB, Tanguay R, et al. Within-subject comparisons of implant-supported mandibular prostheses: psychometric evaluation. J Dent Res 1994;73:1096-104. 20. Khamis MM, Zaki HS, Rudy TE. A comparison of the effect of different occlusal forms in mandibular implant overdentures. J Prosthet Dent 1998; 79:422-9. 21. The glossary of prosthodontic terms. J Prosthet Dent 2005;94:13,49,81. 22. Ogden A. British Society for the Study of Prosthetic Dentistry. Guidelines in prosthetic and implant dentistry. London: Quintessence Publishing Co; 1996. p. 6-10. 23. Allen PF. Assessment of oral health related quality of life. Health Qual Life Outcomes 2003;1:40. 24. 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. Reprint requests to: DR A. F. SUTTON DEPARTMENT OF RESTORATIVE DENTISTRY UNIVERSITY DENTAL HOSPITAL OF MANCHESTER HIGHER CAMBRIDGE STREET MANCHESTER, M15 6FH UNITED KINGDOM FAX: 044-0-161 275 6805 E-MAIL: [email protected] 0022-3913/$32.00 Copyright Ó 2007 by The Editorial Council of The Journal of Prosthetic Dentistry.
doi:10.1016/j.prosdent.2007.03.003
VOLUME 97 NUMBER 5
Purpose. The purpose of this study was to compare subject satisfaction with 3 types of posterior occlusal forms for complete dentures in a randomized cross-over controlled trial.
Material and methods. For each participant (n=45), 3 sets of complete dentures were fabricated, each of which had a different posterior occlusal form (0-degree, anatomic, and lingualized). Each set was worn for 8 weeks in a randomized order. Subjective data were collected using the Oral Health Impact Profile 20-EDENT (OHIP-EDENT). The Wilcoxon statistical test was used to compare differences between the groups (a=.05). Results. Lingualized posterior occlusal forms were perceived to be significantly superior in terms of painful aching in the mouth (P=.01), sore spots (P,.001), eating ability (P=.02), and meal interruptions (P=.008), compared with 0-degree posterior occlusal forms. Subjects with anatomic posterior occlusal forms had significantly fewer problems eating (P=.05) compared with 0-degree posterior occlusal forms. There was no significant difference found between the lingualized and anatomic posterior occlusal forms. Conclusions. Participants provided with complete dentures having lingualized or anatomic posterior occlusal forms exhibited significantly higher levels of self-perceived satisfaction compared to those with 0-degree posterior occlusal forms. (J Prosthet Dent 2007;97:292-8.)
CLINICAL IMPLICATIONS In conventional complete denture fabrication, it may be advisable to use lingualized or anatomic posterior occlusal forms instead of 0-degree posterior occlusal forms.
A
high level of patient satisfaction, when fabricating complete dentures, should be the primary goal in the treatment of edentulous subjects. Jacobsen and Krol1-3 stated that there are 3 key principal factors (retention, stability, and support) in the prescription and provision of successful complete dentures. Fish4 stated that complete dentures are made up of 3 surfaces; the impression or intaglio surface, the polished surface, and the occlusal surface. The retention, stability, and support of the dentures are governed by the design of these 3 surfaces.1-3 When the maxillary and mandibular denture teeth come into contact, unfavorable displacing forces may overwhelm the retention and stability of the dentures, resulting in discomfort from trauma to the supporting mucosa.5 If the intaglio and polished surfaces are ideal, it is assumed that the form of the occlusal surfaces and the nature of their
Presented before the Annual Meeting of the British Society for the Study of Prosthetic Dentistry, Cardiff, UK, March 2005. a Consultant in Restorative Dentistry, Department of Restorative Dentistry, University Dental Hospital of Manchester. b Professor of Restorative Dentistry, Glasgow Dental Hospital and School.
292 THE JOURNAL OF PROSTHETIC DENTISTRY
contacts become critical for successful complete denture function.6 There are many philosophies concerning the most appropriate posterior occlusal forms for conventional complete maxillary and mandibular dentures. Studies comparing various types of complete denture teeth have been conducted for years and have explored outcomes such as masticatory efficiency, occlusal force, and patient preference.7-16 To overcome bias resulting from individual variation between subjects, most studies have compared different types of teeth in the same patient in a cross-over fashion.8-16 The methods used in these studies can be divided into 2 groups. First, where subjects received duplicate complete dentures, which had differing occlusal forms, or secondly, where the subjects were provided with complete dentures, which allowed for experimental modification of the posterior teeth by grinding, adding, or interchanging. In a randomized trial, Clough et al8 fabricated 2 sets of dentures, 1 with lingualized occlusion and the other with monoplane occlusion, for 30 subjects. The dentures were worn for 3 weeks and then swapped. Twenty subjects preferred lingualized occlusion, 5 preferred 0-degree, and 5 expressed no preference. Brewer et al,9 VOLUME 97 NUMBER 5
SUTTON AND MCCORD
in a nonrandomized trial, compared the use of 0-degree teeth and anatomic teeth for 25 men. Ten expressed no preference, 8 preferred 0-degree teeth, and 2 preferred anatomic teeth. Shetty10 compared complete dentures having anatomic posterior teeth with 0-degree teeth in a nonrandomized cross-over study using 40 subjects. The majority of subjects preferred anatomic posterior occlusal schemes. Thompson, in 1937,11 was the first investigator to produce complete dentures with interchangeable teeth. Anatomic posterior teeth were judged to be the most efficient for mastication compared with 20-degree posterior teeth, inverted cusp teeth (nonanatomic posterior denture teeth with circular indentations where cusps would normally be located) and channel teeth (posterior denture teeth with anterior-posterior channels placed in the occlusal surfaces). Trappozzano and Lazzari12 used a modified version of Thompson’s method and found no difference in masticatory efficiency with 3 different posterior occlusal forms; namely, 20-degree posterior teeth, 0-degree posterior teeth, and inverted cusp teeth. Hickey et al13 performed an electromyographic study comparing complete dentures with interchangeable posterior teeth comprised of anatomic teeth, 0-degree teeth, and semi-anatomic teeth. The authors found that complete dentures with anatomic posterior teeth required less muscle activity during mastication for the 9 subjects tested. Complete dentures with interchangeable posterior teeth were evaluated by Kydd14 (5 subjects using 33-degree, 20-degree, and 0-degree teeth) and Koyama et al15 (3 subjects using 33-degree teeth, lingualized occlusion, and canine protected articulation) for masticatory efficiency, with no differences found. Yurkstas16 evaluated 20 subjects with 4 cuspless geometric occlusal patterns in acrylic resin posterior teeth and compared these with raised metal inserts in a study spanning 15 months. Results revealed no statistical differences in masticatory effectiveness between the patterns tested. Prior to conducting the current study, a Cochrane Systematic Review database was reviewed to determine if there had been previous randomized controlled trials comparing the efficacy of different occlusal schemes for complete dentures.7 The objective of the systematic review was to identify a superior occlusal scheme for complete dentures. One thousand and seventy six titles, abstracts, and papers were appraised, and only 1 trial was found to satisfy the inclusion criteria (Clough et al8). In that study, subjects preferred prosthetic teeth with cusps as opposed to cuspless teeth (0-degree) in terms of improved masticatory performance. However, that study was judged to be at high risk of bias owing to insufficient information provided regarding the method of randomization and allocation concealment. In addition, the method for assessing the participant satisfaction was unclear. The results of the review highlighted the need for further well conducted, randomized, controlled trials in MAY 2007
THE JOURNAL OF PROSTHETIC DENTISTRY
the area of complete denture occlusion. Randomized cross-over trials have, however, been used successfully in evaluating subject preferences for different types of implant-supported prostheses.17-20 The purpose of this study was to conduct a randomized controlled trial to test the null hypothesis that there is no variation in the level of patient satisfaction for 3 different types of posterior occlusal forms, namely 0-degree, anatomic, and lingualized, for conventional complete dentures.
MATERIAL AND METHODS The Manchester Local Research Ethics Committee granted ethical approval for this study. Edentulous subjects taken from the waiting list of the University Dental Hospital of Manchester and requiring replacement complete dentures were selected for the study. Subjects were excluded if their medical history revealed 1 or more of the following; neuromuscular dysfunction, psychiatric disorder, and/or the presence of oral pathology. Fifty subjects were assessed for eligibility. Five subjects were excluded from enrollment because they refused to participate. Forty-five subjects provided informed consent. Forty-five participants were assigned 3 sets of complete dentures with different types of posterior occlusal forms in a randomized order. The posterior occlusal surfaces of the 3 dentures consisted of anatomic teeth, lingualized occlusion, and 0-degree teeth. Anatomic teeth are defined as artificial teeth with cuspal inclinations greater than 0 degrees that tend to replicate natural tooth anatomy.21 Lingualized occlusion is defined as a form of denture occlusion where the maxillary lingual cusps articulate with the mandibular occlusal surfaces in centric working and nonworking mandibular positions.21 Zero-degree teeth are defined as posterior denture teeth having 0-degree cuspal angles in relation to the plane established by the horizontal occlusal surface of the tooth.21 The dentures were fabricated according to the British Society for the Study of Prosthetic Dentistry Guidelines in Prosthetic and Implant Dentistry.22 The clinical procedures were performed by 1 experienced prosthodontist (AFS), and 1 senior dental technician performed the laboratory procedures. The process consisted of making preliminary impressions (Kemco Tracing Sticks; Associated Dental Products, Purton, UK), making definitive impressions in irreversible hydrocolloid (Xantalgin Select; Heraeus Kulzer, Hanau, Germany) for the maxilla, and zinc oxide eugenol (SS White Manufacturing Ltd, Gloucester, UK) for the mandible, recording the maxillo-mandibular relationship with a central bearing tracing device (PTC UK Ltd, Bolton, UK), and making a face-bow transfer (Denar Slidematic Facebow; Waterpik Technologies Inc, Newport Beach, Calif). The final casts were mounted in a semi-adjustable articulator (Denar Mark II; Waterpik Technologies Inc). The anatomic posterior teeth used 293
THE JOURNAL OF PROSTHETIC DENTISTRY
SUTTON AND MCCORD
Fig. 1. Posterior view of complete dentures with anatomic posterior teeth.
Fig. 2. Sagittal view of complete dentures with anatomic posterior occlusal surfaces.
Fig. 3. Posterior view of complete dentures with lingualized posterior teeth.
Fig. 4. Sagittal view of complete dentures with lingualized posterior occlusal surfaces.
were 33-degree prosthetic teeth (Basic 8, B range; Heraeus Kulzer), arranged and adjusted to balanced articulation with cross-arch and cross-tooth balance (Figs. 1 and 2). The lingualized posterior teeth were modified 33-degree prosthetic teeth (Basic 8, B range; Heraeus Kulzer), arranged and adjusted to balanced articulation with cross-arch balance (Figs. 3 and 4). The modification consisted of tilting the maxillary posterior teeth to avoid all contact of the buccal cusps and selective grinding of the mandibular posterior teeth, creating a concavity in the occlusal surface. The 0-degree posterior teeth were 0-degree prosthetic teeth (Basic 8, G range; Heraeus Kulzer) set on a flat plane and arranged to balance in centric occlusion, with working-side contact only in left and right excursive movements (Figs. 5 and 6). The dentures were evaluated intraorally during subsequent trial insertion appointments. The dentures were processed by conventional compression molding, remounted in the semiadjustable articulator (Denar Mark II; Waterpik Technologies Inc) and the occlusion was adjusted as necessary.5 Even bilateral intraoral tooth contacts were
ensured by means of a remount procedure. Duplication of the dentures was performed once the first set of dentures was deemed to be comfortable by the subject, producing 2 more sets of dentures with different types of posterior occlusal schemes. The dentures had their intaglio surfaces, polished surfaces, and maxillary anterior tooth arrangement replicated as accurately as possible using the following method. The definitive casts were duplicated using reversible hydrocolloid (Polyflex; Dentsply, York, Pa) and mounted in the same relationship as the original final casts. A type IV stone index (Vel Mix; Kerr Corp, Orange, Calif) recorded the position of the maxillary teeth of the original denture and attached to the mandibular member of the articulator (Denar Mark II; Waterpik Technologies Inc). The original set of dentures was used to produce matrices in vinyl polysiloxane (Sherasil; Werkstoff-Technologie GmbH & Co KG, Lemforde, Germany). These matrices were used to fabricate maxillary and mandidubular autopolymerizing acrylic resin bases (Vertex; Vertex Dental BV, Zeist, The Netherlands) with wax teeth (Kemdent Anutex;
294
VOLUME 97 NUMBER 5
SUTTON AND MCCORD
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 5. Posterior view of complete dentures with 0-degree posterior teeth.
Fig. 6. Sagittal view of complete dentures with 0-degree posterior occlusal surfaces.
Associated Dental Products). The maxillary anterior wax teeth were replaced with identical prosthetic teeth using the stone index as a guide for tooth position. Once the maxillary anterior teeth were correctly positioned, the stone index was removed from the articulator and replaced with the mandibular final cast. The mandibular autopolymerizing acrylic resin base with wax teeth was located on the mandibular final cast. The mandibular anterior wax teeth were replaced with identical mandibular anterior prosthetic teeth. Prosthetic posterior teeth with the allocated occlusal form replaced the wax posterior teeth and were arranged and adjusted as described above. The duplicate dentures were processed by conventional compression molding.5 The participants received treatment for any necessary adjustments to the dentures until no further problems were reported. The 3 sets of dentures were worn for 8 weeks, after which the participants completed the Oral Health Impact Profile-20 EDENT (OHIP-EDENT).23,24 The participants were not informed of the type of occlusal form provided or the sequence in which they were allocated. Direct comparisons, by each patient, with the 2 other test sets of dentures were prevented by withholding them during the 8-week trial period. The Oral Health Impact Profile is an oral healthrelated quality of life index and is regarded as a comprehensive and sophisticated oral health-specific measure consisting of 49 items.23 A short version consisting of 20 items specifically designed and statistically validated for the assessment of complete denture wearers was used.24 This modified shortened version has been shown to have measurement properties comparable with the full 49-item version.24 The quality of outcome data were enhanced by using a room in the Prosthodontics Department away from the clinical and waiting area, with the administration of the OHIP-EDENT by a person blind to the trial. The subjects were randomized without restriction into 6 groups that allocated the sequence in which the
3 sets of dentures were provided. A medical statistician blind to the study performed the randomization using a computer program that generated a sequence of random numbers between 1 and 6. The randomized numbers were placed in unmarked, nontransparent envelopes. As a subject entered the trial the next envelope was opened, revealing the randomized occlusal form sequence. The prosthodontist was unaware of the sequence of intervention allocation until treatment commenced. The OHIP-EDENT index uses a 0-5 scale where 0 is never and 5 is always. Therefore, the items, or variables, were ordinal. In order to compare the pairs of groups, as each patient had each denture type, the data were paired. The Wilcoxon test was used to compare differences between pairs of groups, as this is the standard statistical test for ordinal paired data. This method tested the null hypothesis that the medians of the 2 groups were equal, against the research hypothesis that there would be a difference. An alpha level of .05 was accepted for significance in all tests. Data were analyzed using statistical software (SPSS version 12.01; SPSS Inc, Chicago, Ill). Based on preliminary data, 37 participants were required to have 90% power to detect a difference of 10% between groups at the 5% level. However, to compensate for potential dropouts during the study, the number of subjects included was increased to 45.
MAY 2007
RESULTS Figure 7 shows the flow of participants through each stage of the randomized controlled trial, namely enrollment, intervention allocation, follow up, and analysis. Forty-five subjects were randomly assigned to 1 of 6 intervention groups. The 6 intervention groups were the 6 possible orders in which the occlusal forms were allocated. Four subjects were lost to follow up, 2 because they refused to participate further and 2 because they were unable to attend due to poor health. 295
THE JOURNAL OF PROSTHETIC DENTISTRY
SUTTON AND MCCORD
Fig. 7. Flow diagram of phases of randomized trial. A = Anatomic posterior teeth; L = Lingualized posterior teeth; Z = 0-degree posterior teeth.
A total of 41 subjects were used in the data analysis. Table I shows the frequency distribution of denture allocation and group characteristics of the subjects included in the data analysis (after 4 were lost to follow up). Table II shows the median values of the OHIPEDENT responses for the subjects and indicates the direction in which they scored. Table III shows the P values of the comparisons between the 3 occlusal forms. The P values were derived from the Wilcoxon signed rank test for the OHIP-EDENT responses of the subjects for each experimental occlusal form. There were significantly lower numbers of problems recorded for ‘‘painful aching in the mouth’’ (P=.01), ‘‘sore spots in the mouth’’ (P,.001), problems eating (‘‘unable to eat’’) (P=.02), and ‘‘interrupted meals’’ (P=.02) with lingualized compared to 0-degree interventions. Subjects reported being ‘‘unable to eat’’ significantly more frequently with the 0-degree posterior teeth 296
Table I. Frequency distribution of demographics and clinical characteristics for each group at data analysis Order dentures provided
ALZ AZL LAZ LZA ZAL ZLA Total
Frequency
Percent
6 8 6 8 7 6 41
14.6 19.5 14.6 19.5 17.1 14.6 100.0
Mean age (years) (standard deviation)
55.3 66.1 70.1 66.9 72.7 62.1 65.2
(19.4) (9.1) (7.5) (7.6) (3.8) (5.9) (12.8)
Gender male/female
2:4 2:6 2:4 2:6 3:4 2:4 13:28
A = Anatomic posterior teeth; L = Lingualized posterior teeth; Z = 0-degree posterior teeth.
compared to anatomic (P=.05) and lingualized (P=.02) posterior occlusal schemes. When the lingualized and anatomic posterior occlusal forms were compared, no significant difference was found. VOLUME 97 NUMBER 5
SUTTON AND MCCORD
THE JOURNAL OF PROSTHETIC DENTISTRY
Table II. Median values of OHIP-EDENT responses for experimental occlusal forms
Table III. P values from Wilcoxon signed rank test of OHIPEDENT responses for experimental occlusal forms
Functional characteristic
Functional characteristic
Masticatory problems Food catching Fitting properly Painful aching in mouth Uncomfortable eating any foods Sore spots in mouth Ever had uncomfortable dentures Worried about dental problems Self-conscious because of dentures Unclear speech Avoid certain foods Unable to eat Interrupt meals Upset with dentures Embarrassed with dentures Avoid going out Less tolerant with spouse Irritable with other people Avoid other peoples’ company Life is less satisfying
Anatomic
Lingualized
0-degree
3 2 2 2 2 2 2 1 1 2 2 2 2 1 1 1 1 1 1 1
3 2 2 2 2 2 2 2 1 2 2 1 2 2 2 1 1 1 1 1
3 3 3 3 3 3 2 2 1 2 3 3 3 2 1 1 1 1 1 1
1 = Never; 2 = Hardly ever; 3 = Occasionally; 4 = Fairly often; 5 = Very often.
Masticatory problems Food catching Fitting properly Painful aching in mouth Uncomfortable eating any foods Sore spots in mouth Ever had uncomfortable dentures Worried about dental problems Self-conscious because of dentures Unclear speech Avoid certain foods Unable to eat Interrupt meals Upset with dentures Embarrassed with dentures Avoid going out Less tolerant with spouse Irritable with other people Avoid other peoples’ company Life is less satisfying
A vs. L
A vs. Z
L vs. Z
.37 .97 .77 .52 .59 .51 .52 .94 .10 .23 .98 .82 .16 .93 .11 .28 .48 .21 .89 .75
.78 .64 .07 .30 .35 .59 .14 .34 .19 .64 .48 .05y .12 .94 .10 .16 .95 .89 .96 .11
.25 .23 .10 .01y .08 ,.001y .29 .18 .51 .13 .06 .02y .02y .87 .90 .79 .34 .36 .89 .14
y
P value significant for P , .5. A = Anatomic posterior teeth. L = Lingualized posterior teeth. Z = 0-degree posterior teeth.
DISCUSSION The null hypothesis that there is no variation in the level of patient satisfaction for 3 types of posterior occlusal forms, namely 0-degree, anatomic, and lingualized, for conventional complete dentures, was rejected. A simple and accurate method was devised for duplicating the first set of complete dentures fabricated for the participants. Duplication was only performed if the subjects were comfortable with their initial set of dentures. The silicone indices of the first set of dentures ensured the polished surfaces were duplicated accurately. All of the clinical stages were performed by 1 prosthodontist, and 1 senior dental technician fabricated all of the dentures. This ensured that consistency of the complete denture fabrication was maintained. The randomization of the inserted dentures minimized the small differences owing to the duplication procedure. The subject groups were not stratified for age, gender, degree of alveolar reduction, denture experience, or previous type of denture occlusal scheme, and this may be considered a weakness of the investigation. The duration of the trial period was 8 weeks, which, ideally, could have been longer. However, increasing the test period would have severely limited the practicality of this trial owing to participant recall difficulty and possible changes to the denture-bearing tissues of the subjects. A trial period of 8 weeks has been shown to be effective in determining patient preferences between various types of implant-supported prostheses,19 and it was thought to be an appropriate duration of follow MAY 2007
up for this study. It was not possible for the prosthodontist to be blinded to the occlusal scheme provided, and this was, therefore, an uncontrolled bias potential. The findings of this research are in general agreement with the findings of other studies.8,10,11,13 There was a statistically significant difference in favor of the lingualized dentures in the 1 randomized trial8 included in the Cochrane Systematic Review (McNemar chi-square test; P=.041), which is in agreement with the results of this study.7 When using lingualized occlusal surfaces, the subjects reported significantly less painful aching (P=.01) and sore spots in the mouth (P,.001) compared with the 0-degree dentures. The reasons for this may only be speculated; however, it has been shown that reduced forces during mastication are transmitted to the denture-bearing areas with lingualized posterior teeth when compared to 0-degree teeth,14 and may, therefore, result in reduced pain. When subjects rated ‘‘ability to eat’’, the complete dentures provided with lingualized and anatomic posterior occlusal forms were significantly preferred over 0-degree posterior occlusal forms (P=.02 and P=.05, respectively). It has been shown that less force is required to masticate through a food bolus with teeth having cusps compared to 0-degree teeth.13,14 Teeth with cusps by their very nature have a reduced surface area of contact compared with 0-degree teeth and require a reduced masticatory force to penetrate food.13 The 297
THE JOURNAL OF PROSTHETIC DENTISTRY
subjects reported significantly fewer interruptions to their meals with the lingualized occlusal surfaces compared with the 0-degree occlusal surfaces (P=.02). This may be related to the superior masticatory ability with the lingualized posterior occlusal surfaces. Suggestions for future research include comparison of the levels of patient satisfaction between complete dentures fabricated with or without the use of a face-bow transfer or the use of central bearing apparatuses compared to conventional wax occlusal rims.
CONCLUSIONS Lingualized posterior occlusal forms were significantly superior in terms of reduced pain in the mouth, reduced incidence of sore spots, ability to eat, and meal interruptions, compared with 0-degree posterior occlusal forms. Anatomic posterior occlusal forms were significantly better in terms of masticatory function compared with 0-degree posterior occlusal forms. There were no significant differences when lingualized posterior occlusal forms were compared with anatomic posterior occlusal forms. REFERENCES 1. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete denture retention, stability, and support. Part I: retention. J Prosthet Dent 1983;49:5-15. 2. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete dentures. Part II: stability. J Prosthet Dent 1983;49:165-72. 3. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete dentures. Part III: support. J Prosthet Dent 1983;49:306-13. 4. Fish EW. An analysis of the stabilising factors in full denture construction. Br Dent J 1931;52:559-70. 5. Zarb GA, Bolender CL, Carlsson GE. Boucher’s prosthodontic treatment for edentulous patients. 11th ed. St. Louis: Elsevier Health Sciences; 1997. p. 37, 337-43. 6. McCord JF, Grant AA. Registration: stage III–selection of teeth. Br Dent J 2000;24(188):660-6. 7. Sutton AF, Glenny AM, McCord JF. Interventions for replacing missing teeth: denture chewing surface designs in edentulous people. Cochrane Database Syst Rev 2005:CD004941. 8. Clough HE, Knodle JM, Leeper SH, Pudwill ML, Taylor DT. A comparison of lingualized occlusion and monoplane occlusion in complete dentures. J Prosthet Dent 1983;50:176-9. 9. Brewer AA, Reibel PR, Nassif NJ. Comparison of zero degree teeth and anatomic teeth on complete dentures. J Prosthet Dent 1967;17:28-35. 10. Shetty NS. Comparative observations of the use of cusp and zero-degree posterior teeth. J Prosthet Dent 1984;51:459-60.
298
SUTTON AND MCCORD
11. Thompson MJ. Masticatory efficiency as related to cusp form in denture prosthesis. J Am Dent Assoc 1937;24:207-19. 12. Trappozzano VR, Lazzari JB. An experimental study of the testing of occlusal patterns on the same denture bases. J Prosthet Dent 1952;2:440-57. 13. Hickey JC, Woelfel JB, Allison ML, Boucher CO. Influence of occlusal schemes on the muscular activity of edentulous patients. J Prosthet Dent 1963;13:444-51. 14. Kydd WL. The comminuting efficiency of varied occlusal tooth form and the associated deformation of the complete denture base. J Am Dent Assoc 1960;61:465-71. 15. Koyama M, Inaba S, Yokoyama K. Quest for ideal occlusal patterns for complete dentures. J Prosthet Dent 1976;35:620-3. 16. Yurkstas AA. The influence of geometric occlusal carvings on the masticatory effectiveness of complete dentures. J Prosthet Dent 1963;13: 452-61. 17. Feine JS, Maskawi K, de Grandmont P, Donohue WB, Tanguay R, Lund JP. Within-subject comparisons of implant-supported mandibular prostheses: evaluation of masticatory function. J Dent Res 1994;73:1646-56. 18. de Albuquerque Junior RF, Lund JP, Tang L, Larivee J, de Grandmont P, Gauthier G, et al. Within-subject comparison of maxillary long-bar implant-retained prostheses with and without palatal coverage: patientbased outcomes. Clin Oral Implants Res 2000;11:555-65. 19. de Grandmont P, Feine JS, Tache R, Boudrias P, Donohue WB, Tanguay R, et al. Within-subject comparisons of implant-supported mandibular prostheses: psychometric evaluation. J Dent Res 1994;73:1096-104. 20. Khamis MM, Zaki HS, Rudy TE. A comparison of the effect of different occlusal forms in mandibular implant overdentures. J Prosthet Dent 1998; 79:422-9. 21. The glossary of prosthodontic terms. J Prosthet Dent 2005;94:13,49,81. 22. Ogden A. British Society for the Study of Prosthetic Dentistry. Guidelines in prosthetic and implant dentistry. London: Quintessence Publishing Co; 1996. p. 6-10. 23. Allen PF. Assessment of oral health related quality of life. Health Qual Life Outcomes 2003;1:40. 24. 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. Reprint requests to: DR A. F. SUTTON DEPARTMENT OF RESTORATIVE DENTISTRY UNIVERSITY DENTAL HOSPITAL OF MANCHESTER HIGHER CAMBRIDGE STREET MANCHESTER, M15 6FH UNITED KINGDOM FAX: 044-0-161 275 6805 E-MAIL: [email protected] 0022-3913/$32.00 Copyright Ó 2007 by The Editorial Council of The Journal of Prosthetic Dentistry.
doi:10.1016/j.prosdent.2007.03.003
VOLUME 97 NUMBER 5