A comparison of denture base retention and adaptation

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A comparison of denture base retention and adaptation between CAD-CAM and

conventional fabrication techniques

Mahmoud Amin Faty*

B.D.S, (2009), M.D.S (2016) Ain Shams University

Assistant lecturer, Oral and Maxillofacial Prosthodontics department, Faculty of Dentistry, Ain Shams

University, Cairo, Egypt.

Prof. Dr. Marwa Ezzat Sabet

B.D.S, (1994), M.D.S (1999), P.H.D (2002)

Chairman of Oral and Maxillofacial Prosthodontics Department, Faculty of Dentistry, Ain Shams


Dr. Yasmine Galaleldin Thabet

B.D.S, (2002), M.D.S (2009), P.H.D (2013)

Associate Professor, Oral and Maxillofacial Prosthodontics department, Faculty of Dentistry, Ain Shams


Corresponding author: Mahmoud Amin Faty

Address : 130 El Tawfik city, Nasr city, Cairo, Egypt.

Telephone : (+20) 1221402018

(+20) 22629419

Email address : [email protected]

This peer-reviewed, accepted manuscript will undergo final editing and production prior to publication in IJP.

© 2021 by Quintessence Publishing Co, Inc. Printing of this document is restricted to personal use only. No part may be reproduced or transmitted in any form without written permission from the publisher.

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Submitted June 7, 2020; accepted February 16, 2021

Purpose: To assess the retention and adaptation of milled and printed denture bases and to compare

them to conventional ones. Materials and Methods: A total of 24 completely edentulous patients were

selected. For each patient, three maxillary denture bases were constructed. Three groups were defined

according to fabrication technique: group I = denture bases were constructed by a conventional

technique; group II = denture bases were milled from prepolymerized blocks of polymethyl

methacrylate; and group III = denture bases were fabricated by a 3D printing technique. A digital force

gauge was used for measuring the retention of the denture bases intraorally, while Geomagic Control X

64 software was used to evaluate the adaptation of the denture bases with their corresponding master

casts. Analysis of variance for repeated measures was used for comparison among the groups, followed

by pairwise comparison with Bonferroni correction as a post hoc test. The significance level was set at α

= .05. Results: Statistical analysis showed significant differences among the three groups regarding

retention and adaptation. The highest values of retention and adaptation of denture bases were found in

group II (milling group). Conclusion: Within the limitations of this study, the following could be

concuded: milled denture bases demonstrated better retention and adaptation than the conventional heat-

polymerized and the printed denture bases; and printed denture bases showed better adaptation but

similar retention to conventional heat-polymerized denture bases. Int J Prosthodont 2021. doi:

10.11607/ijp.7193

Introduction

Well adapted denture bases are a prerequisite for attaining adequate retention and stability of

complete dentures. Several techniques have been introduced for the construction of complete denture

bases. The ultimate goal of each technique is to find balance between biocompatibility, esthetics,

minimal distortion and adaptation. (1, 2)



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The conventional protocol for the construction of complete dentures involves several processing

techniques that have been introduced and efficiently used since 1936.(3) However, it involves a sequence

of multiple clinical and laboratory steps that are time consuming. The polymerization shrinkage of poly-

methyl methacrylate (PMMA) and the difficulty to create a duplicate denture are considered as

drawbacks of this protocol. (3)

A recent protocol for the construction of complete dentures has been proposed utilizing

CAD/CAM (computer-aided design and computer-aided manufacturing) technology. CAD/CAM implies

the use of computers to aid in designing, and manufacturing of products. It includes additive and

subtractive manufacturing techniques. (4) In additive manufacturing, 3-dimensional (3D) printing, images

from a digital file are used to create an object by laying down successive layers of a liquid or powder

material which are then solidified upon exposure to UV light (photopolymerization) or LASER (selective

LASER sintering or selective LASER melting). On the other hand, in subtractive manufacturing, images

from the file are used to create an object by milling to physically remove material from a pre-fabricated

block to achieve the desired geometry. (4)

CAD/CAM technology has been widely used in the field of Prosthodontics. However, few

studies have reported its use for fabrication of complete dentures.(5-8)This can be attributed to themultiple

steps required for the construction of complete dentures. In addition to the difficulty in acquiring digital

impressions due to the flexibility of the oral mucosa. The saliva on the smooth soft tissues and the

dynamic movements of the vestibules may also influence the quality of digital impressions.(9, 10)

Moreover, digitalization of the maxillo-mandibular relationship record is still not reliable due to the

unavoidable movement of the record bases which adversely affects the results. (11)

Construction of complete dentures using CAD/CAM is characterized by ease of fabrication with

reduced laboratory procedures. It also leads to higher dimensional accuracy and standardized fabrication.

(9, 12-14)



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Digital design ensures consistent thickness of denture bases which can be adjusted and kept

minimal for patient comfort. In addition, the presence of digital data enables future fabrication of

dentures in case of lost or damaged ones. (15)

Goodacre et al (17)compared the accuracy and reproducibility of milled denture bases with

conventionally fabricated bases where the milled denture bases attained better results. While Hwang et al

(16) evaluated the trueness and adaptation of milled, printed and conventional denture bases and reported

that the printed bases attained the best results. Yet further clinical research is required to evaluate the

different qualities of CAD/CAM dentures. The purpose of this study was to assess the retention and

adaptation of milled and printed denture bases and to compare them with conventional heat polymerized

denture bases. The first null hypothesis was that no difference would be found in the retention of the

denture bases fabricated by the three techniques. The second null hypothesis was that no difference

would be found among the three fabrication techniques in the tissue surface adaptation of the denture

bases to the edentulous maxillary casts.

Materials and methods

Participants:

Twenty four male patients with an age range from 55 to 65 years were selected from the outpatient clinic

of the Removable Prosthodontics Department, Faculty of Dentistry, Ain Shams University to participate

in this study. Detailed information about the study was given to all participants who signed a written

consent for approval.

Patients were selected to have the following inclusion criteria: completely edentulous maxillary and

mandibular well-formed ridges with a firm and healthy covering muco-periostium. Patients were selected

with minimal bony or soft tissue undercuts, adequate salivary flow with moderate consistency and Angle

class I maxillo-mandibular relationship



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Patients having the following criteria were excluded: severely resorbed maxillary ridge, torus palatinus

and V shaped palatal vault. Also, patients with neuromuscular and Tempromandibular joint disorders,

limited mouth opening and allergy to acrylic resin were excluded.

The protocol of the research was approved by the ethical committee of the Faculty of Dentistry, Ain

Shams university on 20/9/2017 (no. of approval: FDASU – REC D 091722). There were no conflicts of

interest in thisstudy.

For each patient three maxillary denture bases were constructed. Thus three groups were defined

according to the technique of construction of the denture base. Group I: Denture bases were constructed

by the conventional (compression molding) technique using heat polymerizing resin. Group II: Denture

bases were digitally designed and milled from prepolymerized blocks of PMMA. Group III: Denture

bases were digitally designed and fabricated by rapid prototyping (3D printing) technique. Denture bases

in group II and III were constructed using the scanned data of the definitive casts.

Designing and printing of denture bases were performed in the Digital center of the Removable

Prosthodontics department, Faculty of Dentistry, Ain Shams University, Egypt.

Construction of the denture bases:

Primary impressions were taken in properly selected and modified stock trays using alginate impression

material(Cavex alginate, Cavex, Holland) and then poured in dental stone to obtain diagnostic casts.

Custom trays were fabricated over the diagnostic casts using autopolymerizing acrylic resin (Acrostone

cold cure denture base material, Acrostone, Egypt). The borders of the tray were trimmed 2-3 mm shorter

than the depth of the vestibule.

Border moulding was done using putty consistency addition silicone impression material (Elite HD+

Putty Soft – Zhermack) and the final wash impression was made using medium consistency

polyether impression material (Impregum Soft Medium Body – 3M ESPE, United States) (Fig. 1).



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Definitive impressions were boxed then poured to obtain definitive casts (Gypsano Lab Dental Stone

(Type 3), Gypsano, UAE).

The geometrical center of the maxillary arch was determined on the cast before the beginning of the

scanning and designing processes. The midline of the maxillary cast was drawn from the center of the

incisive papilla to a point in the middle of a line drawn between the two hamular notches. Then a

midpoint was marked on the midline to represent the center of the arch.(18, 19) Arbitrary scrapping of the

posterior palatal seal area was done on the definitive cast extending through both hamular notches and

across the palate between the anterior and posterior vibrating lines prior to construction of denture bases.

The borders of the denture bases were then drawn on the casts following the depth of the vestibule. (Fig.

2).

In group I, a 2mm layer base plate wax (Cavex Set Up Regular, Modelling wax, Cavex, Holland) was

adapted and trimmed on the definitive cast. A sphere of wax was added to the outer surface of the waxed

up denture base in the position of the center of the arch which is marked on the cast and visible through

the wax (Fig. 3).

The denture base was then processed following the long curing cycle (74°C for 8 hours). Then the

polished surface of the denture base was finished using fine sandpaper fixed to mandrill and polished

using brushes and pumice (excessive heat generation was avoided) (Fig 4).

The 3Shape D850 desktop scanner (D850, 3Shape, Copenhagen, Denmark) and 3Shape dental system

software (3shape dental designer, 3Shape A/S, Copenhagen, Denmark) were used to scan the casts and

design the denture bases for groups II and III . The scanning and designing steps were followed

according to the protocol of the software. The borders of the denture bases were traced following the

depth of the vestibule of the virtual casts guided by the borders previously drawn on the definitive casts.

The denture bases were set to be 2 mm in thickness and with no relief space with their corresponding

virtual casts. A pin attachment was placed on the outer surface of the maxillary denture base to mark the

geometrical center of the arch (fig. 5).



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In group II, pink pre-polymerized polymethyl methacrylate of 98 mm diameter and 25 mm height

(Glorious dental materials, Shandong, China) were used to fabricate the milled denture bases using a 5-

axis milling machine (ARUM 5X-200, Doowon, Daejeon, Korea). The denture bases were retrieved from

the block by cutting the supporting arms using carbide discs, and then the outer surface was finished and

polished as outlined in group I (Fig. 6).

In group III, the STL file of the denture base was imported to the Netfab software to create the

supporting arms generating a new STL file of the denture base with its supporting arms (Fig. 7). The 3d

printing machine (MOGASSAM Dent2 3D Printer, Mogassam, Egypt) was loaded with pink denture

base printing resin (NextDent Base, NextDent, Soesterberg, Netherlands) to fabricate the printed denture

bases. After the printing process was completed, the denture bases were separated from the platform of

the machine and rinsed twice in a 96% ethanol solution in an ultrasonic bath. A first rinse of 3 minutes

was followed by a second rinse in clean 96% ethanol solution for approximately 2 minutes. Finally the

denture bases were dried, then placed in an ultraviolet light box (MOGASSAM Dentcure, Mogassam,

Egypt) for 20 minutes for additional polymerization. The light box delivers a wavelength of blue UV-A

315 to 400 nm and an output of 43.2 kJ. The outer surface of the denture base was finished and polished

in the same manner as group I and II.

All denture bases were immersed in water for 24 hours before the evaluation of retention and

adaptation.(20)

Evaluation of the retention of the denture bases:

A metallic ring was attached to the outer surface of the denture bases at the position of the geometric

center by autopolymerizing acrylic resin (Acrostone cold cure denture base material, Acrostone, Egypt)

(Fig. 8). A digital force gauge (HF-100 Digital Force Gauge, Jinan Hensgrand Instrumentation Co., Ltd.,

Jinan, China) was used to record the retention of the denture bases. The device has a capacity of 100N,

Min unit is 0.1 N and its accuracy is 0.5%. The display before each measurement was adjusted to zero

via the zero button.



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The denture base was inserted in the patient’s mouth and allowed to remain for 5 minutes to ensure its

adaptation before the metallic ring was engaged and dislodging load was applied. )19(

The patient was seated in an upright position in the dental chair with the mouth half opened and lips

relaxed. The patient was instructed to tilt the head backward till the palate and the maxillary ridge were

at nearly 45 degrees to the floor so the applied dislodging force wasnearlyperpendicular to the denture

base. The metallic ring was engaged by the force gauge and a dislodging force was applied to the

denture base until it was forced out of its position (Fig. 9). Retention force was considered as the

maximum force needed to dislodge the denture. The measurement procedures were repeated 5 times at 5

minutes intervals for each denture base and the average value was recorded. All measurements were

performed by the same operator. (19)

Evaluation of adaptation of the denture bases:

All denture bases were lightly coated with antiglare spray (Okklu-Exact, Germany) before their fitting

surfaces were scanned using a 3shape desktop scanner, outputting an STL file which was imported to the

(Meshmixer software) to flip the fitting surface of the denture base (Fig. 10). The STL file of the fitting

surface of the denture base was superimposed on the STL file of the corresponding definitive cast by

using surface matching software (Geomagic Control X 64 software) using the best fit alignment option.

The 3D compare option was used to evaluate the adaptation of the measured data.

The adaptation of the denture base to the cast was presented in the form of a color scale where yellow to

red colors indicated impingement of denture base on the cast. The blue color indicated space between the

denture base and the cast and the green color indicated contact between the denture base and the cast.

It was also presented in the form of numerical values. The negative values indicated gap areas, while the

positive values indicated pressure areas between the denture base and the cast. In addition the average

value of the overall deviation of the denture base from the cast was provided (Fig. 11).

The mean values and standard deviation of the measured data were statistically analyzed by statistical

software (IBM® SPSS® Statistics Version 25). ANOVA for repeated measures was used for comparison



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between the groups followed by pairwise comparison with Bonferroni correction as a post hoc test. The

significance level was set at α =0.05.

Results

A - Retention of the denture bases

Statistical analysis using ANOVA for repeated measures showed a statistically significant difference

between the three groups (Pp= 0.018), where the highest retentive value was found in group II and the

least retentive value was found in group I. However by using Bonferroni test, it showed that there is a

statistically significant difference only between group II and group I (p= 0.035) as shown in tables I and

II.

B - Adaptation of the denture bases

i- Negative average values (gap areas)

Statistical analysis showed significant difference between the three groups (p <0.001) , where the greatest

gap distance was found in group III then group I and the smallest gap distance was found with group II

as shown in table III. The post hoc test showed a statistically significant difference (p <0.001) between

all groups as shown in table IV.

ii- Positive average values (pressure areas)

.StatisticalanalysisdemonstratedthatthelargestpressurewasfoundingroupIII,followedbygroupI,

whilethesmallestpressurewasfoundingroupII(P=0.004)(TableV).

However the post hoc test showed that there is a statistically significant difference only between group

III and group II (p=0.004) (Table VI).

iii- Average values

( p<0.001).

Statistical analysis demonstrated the best adaptation was found in group II, followed by group III, while

the least adaptation was found in group I (p<0.001) (Table VII).



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Discussion

The results of this study suggested that the milled denture bases had significantly higher

retentive force values than conventional denture bases. Hence, the first null hypothesis was rejected.

Moreover, statistically significant differences were found in the adaptation of the denture bases

fabricated by the three techniques, thus the second null hypothesis was also rejected.

Adaptation of the denture bases to the denture bearing tissues is essential for adequate retention,

stability and support of complete dentures. Minimal distortion in processing is mandatory for attaining

adequate mucosal adaptation. Distortion of denture bases during processing is affected by the thickness

and the material of the denture base as well as the processing technique. (2, 21)

In this study the selected patients had healthy and firm muco-periosteum without any signs of

inflammation or flabby tissues which could affect denture base stability and consequently result in false

records during testing the retentive quality of the denture bases. (18) The geometrical center of the arch

was selected to measure the retention of the denture bases as it has been reported as the most reliable

region for measuring the retention of maxillary complete dentures. (18, 19)

The exact geometrical center of the denture base could be accurately determined during the

designing process; however, it was difficult to transfer this position to the conventional denture base.

Consequently, the center of the arch was determined on the definitive cast manually before scanning and

was later transferred to the denture bases for standardization.

In group II, milling was processed by subtraction of an industrially pre-polymerized PMMA

block that has a final dimension. Consequently, dimensional deformation resulting from the

polymerization process was avoided. (20) A five axis dry milling machine was used due to its ability to

produce very complex geometries and smooth external surfaces. Dry milling was used for the purpose of

simplifying the process as it is quicker and has reduced cutting forces, increased tool life and potentially

better surface quality. (22)



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In group III, the Netfab software was used to design and create the supporting system of the

denture bases. The denture bases were oriented in a position directing the contact with the supporting

arms at the polished surface to preserve the accuracy of the fitting surface and to avoid affecting the

results of the adaptation of the denture bases. The location and the number of the supporting arms were

automatically designed by the software.

Denture bases were immersed in water for 24 hours before making the measurements so as to

represent the ultimate base fit obtained after a patient wears a denture and it becomes completely

hydrated.(2, 23, 24) All bases have been tested on the same patients and the same casts, so potential variables

were eliminated.

Previous studies that evaluated the adaptation of denture bases relied on physical measurements

(25-28). In this study, surface matching and best-fit algorithms were used to adapt the denture bases and the

casts as closely as possible then digital measurements were recorded.

The Geomagic software was used to assess the adaptation of the denture bases and it created

color maps that revealed the varying degrees of adaptation produced by the three processing techniques.

While no processing technique produced a color map that was entirely green (which indicates intimate

contact between the denture base and the cast), it was evident that group II had the most uniform

adaptation of the denture base to the cast, and statistical analysis of the digital measurements confirmed

this finding. Since denture base retention depends on multiple factors including adaptation, dimensional

changes and accuracy of construction technique, thus group II attained the highest values.

Manufacturing the denture bases from pre-polymerized PMMA blocks avoids dimensional

changes and porosities caused by packing of the material as well as the polymerization process.(21, 29)

Thus, theoretically there was no dimensional deformation of the denture bases, which can explain the

high values of retention and adaptation attained by group II.

In the 3D printing technique, unpolymerized resins were utilized for manufacturing the denture

bases, and once processed; it required an additional final light-polymerization step to complete the

process. During the 3D printing workflow, polymerization shrinkage is theoretically possible, as the



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denture bases are not completely polymerized before the final light-polymerization procedure. The

deformation can also occur while demounting the partially polymerized denture base from the building

platform. (29)

Despite the higher values of adaptation attained in group II than group III found in the present

study, the milling technique has several disadvantages. Milling units are expensive and mainly suitable

for commercial manufacturing centers. They may not be practical for individual practices or smaller

dental laboratories. Furthermore, these units consume a considerable amount of energy during the

manufacturing process and lead to a considerable amount of material wastage.(29)

In the conventional heat polymerized fabrication technique, factors such as the complexity of

manipulation, time-consuming procedures of waxing up, investing, and wax elimination as well as the

deformation of heat polymerized PMMA might diminish the degree of base adaptation.(2, 21, 30)

Evaluation of the retention of the denture bases was entirely based on the values obtained by the

digital force gauge.

The results of this study support previous studies(13, 19) that showed the superior retentive values

of milled denture bases, which is most likely because of the lack of polymerization shrinkage associated

with the milled denture bases resulting in an improved fit, thereby improved retention. However, further

research is required to assess the different qualities of complete dentures fabricated by CAD/CAM

techniques to verify the superiority of one of them.

Conclusion

Based on the findings of this study the following could be concluded:

• Milled denture bases demonstrated better retention and adaptation than the conventional heat

polymerized and the printed denture bases.

• Printed denture bases showed better adaptation but similar retention to conventional heat

polymerized denture bases.



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References

1. Takamata T, Setcos JC. Resin denture bases: review of accuracy and methods of polymerization. Int

J Prosthodont 1989;2(6):555-62.

2. Sykora O, Sutow EJ. Posterior palatal seal adaptation: influence of processing technique, palate

shape and immersion. J Oral Rehabil 1993;20(1):19-31.

3. Christensen GJ. Removable prosthodontics: a forgotten part of dentistry. The Alpha Omegan.

2006;99(1):26-8.

4. Saponaro PC, Yilmaz B, Heshmati RH, McGlumphy EA. Clinical performance of CAD-CAM-

fabricated complete dentures: a cross-sectional study. J Prosthet Dent 2016;116(3):431-5.

5. Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: current

status and future perspectives from 20 years of experience. Dent Mater J 2009;28(1):44-56.

6. Maeda Y, Minoura M, Tsutsumi S, Okada M, Nokubi T. A CAD/CAM system for removable

denture. Part I: Fabrication of complete dentures. Int J Prosthodont 1994;7(1):17-21.

7. Busch M, Kordass B. Concept and development of a computerized positioning of prosthetic teeth for

complete dentures. Int J Comput Dent 2006;9(2):113-20.

8. Sun Y, Lü P, Wang Y. Study on CAD&RP for removable complete denture . Comput Meth Prog Bio

2009;93(3):266-72.

9. Goodacre CJ, Garbacea A, Naylor WP, Daher T, Marchack CB, Lowry J. CAD/CAM fabricated

complete dentures: concepts and clinical methods of obtaining required morphological data. J Prosthet

Dent 2012;107(1):34-46.

10. Patzelt SB, Vonau S, Stampf S, Att W. Assessing the feasibility and accuracy of digitizing

edentulous jaws. J Am Dent Assoc 2013;144(8):914-20.



14

11. Alghazzawi TF. Advancements in CAD/CAM technology: options for practical implementation. J

Prosthodont Res 2016;60(2):72-84.

12. Infante L, Yilmaz B, McGlumphy E, Finger I. Fabricating complete dentures with CAD/CAM

technology. J Prosthet Dent 2014;111(5):351-5.

13. Kattadiyil MT, Jekki R, Goodacre CJ, Baba NZ. Comparison of treatment outcomes in digital

and conventional complete removable dental prosthesis fabrications in a predoctoral setting. J Prosthet

Dent 2015;114(6):818-25.

14. Kattadiyil M, Goodacre C, Baba N. CAD/CAM complete dentures: a review of two commercial

fabrication systems. J Calif Dent Assoc 2013;41(6):407-16.

15. Lozada JL, Garbacea A, Goodacre CJ, Kattadiyil MT. Use of a digitally planned and fabricated

mandibular complete denture for easy conversion to an immediately loaded provisional fixed complete

denture. Part 1. Planning and surgical phase. Int J Prosthodont 2014;27(5):417-21.

16. Hwang HJ, Lee SJ, Park EJ, Yoon HI. Assessment of the trueness and tissue surface adaptation of

CAD-CAM maxillary denture bases manufactured using digital light processing. J Prosthet Dent

2019;121(1):110-7.

17. Goodacre BJ, Goodacre CJ, Baba NZ, Kattadiyil MT. Comparison of denture base adaptation

between CAD-CAM and conventional fabrication techniques. J Prosthet Dent 2016;116(2):249-56.

18. Nawar NH, Eid HI, Sabet ME. A study on the effect of border molding on retentive efficiency of

maxillary complete denture. Cairo Dent J 2005;21(2):135-40.

19. AlHelal A, AlRumaih HS, Kattadiyil MT, Baba NZ, Goodacre CJ. Comparison of retention

between maxillary milled and conventional denture bases: a clinical study. J Prosthet Dent

2017;117(2):233-8.



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20. Lee S, Hong S-J, Paek J, Pae A, Kwon K-R, Noh K. Comparing accuracy of denture bases

fabricated by injection molding, CAD/CAM milling, and rapid prototyping method. J Adv Prosthodont

2019;11(1):55-64.

21 Artopoulos A, Juszczyk AS, Rodriguez JM, Clark RK, Radford DR. Three-dimensional

processing deformation of three denture base materials. J Prosthet Dent 2013;110(6):481-7.

22. Kanazawa M, Inokoshi M, Minakuchi S, Ohbayashi N. Trial of a CAD/CAM system for

fabricating complete dentures. Dent Mater J 2011;30(1):93-6.

23. Woelfel JB, Paffenbarger GC, Sweeney WT. Changes in dentures during storage in water and in

service. J Am Dent Assoc 1961;62(6):643-57.

24. Komiyama O, Kawara M. Stress relaxation of heat-activated acrylic denture base resin in the mold

after processing. J Prosthet Dent 1998;79(2):175-81.

25. Consani RLX, Mesquita MF, de Arruda Nobilo MA, Henriques GE. Influence of simulated

microwave disinfection on complete denture base adaptation using different flask closure methods. J

Prosthet Dent 2007;97(3):173-8.

26. Ganzarolli S, Rached R, Garcia R, Del Bel Cury AA. Effect of cooling procedure on final denture

base adaptation. J Oral Rehabil 2002;29(8):787-90.

27. Lee CJ, Bok SB, Bae JY, Lee HH. Comparative adaptation accuracy of acrylic denture bases

evaluated by two different methods. Dent Mater J 2010;29(4):411-7.

28. Sartori EA, Schmidt CB, Walber LF, Shinkai RS. Effect of microwave disinfection on denture

base adaptation and resin surface roughness. Braz Dent J 2006;17(3):195-200.

29. Kalberer N, Mehl A, Schimmel M, Müller F, Srinivasan M. CAD-CAM milled versus rapidly

prototyped (3D-printed) complete dentures: An in vitro evaluation of trueness. J Prosthet Dent

2019;121(4):637-43.



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30. Yeung K, Chow T, Clark RK. Temperature and dimensional changes in the two-stage processing

technique for complete dentures. J Dent 1995;23(4):245-53.



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Figures

Figure 1 Maxillary secondary impression.

Figure 2 The geometric center marked on the definitive cast.



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Figure 3 Sphere of wax added to the geometric center of the waxed up denture base.

Figure 4 Heat polymerized denture base after processing.



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Figure 5 Placement of the attachment at the center of the arch.

Figure 6 Denture base after milling.



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Figure 7 STL file of the denture base with the supporting arms.

Figure 8 Metallic ring attached to the geometrical center of the denture base.



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Figure 9 Evaluation of the retention of the denture bases.

Figure 10 STL file of the flipped fitting surface of the denture base.



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Figure 11 Geomagic control report.



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Table1Mean,standarddeviationandpvalueofANOVAforrepeatedmeasurestestoftheretentivevaluesofthe

threegroups.

Group I Group II

Group III

Minimum 41.4 47.8 42.8

Maximum 67.8 73.4 68.8

Mean 54.2208 60.9063 58.9475

+/-S.D. 8.84045 8.17038 9.18263

P value 0.018

Table2Pairwisecomparisonbetweentheretentivevaluesofthethreegroups.

(I) factor1

Mean Difference

(I-J) Std. Error Sig.b

95% Confidence Interval for Difference

Lower Bound

Upper Bound

Group IGroup II -6.685* 2.444 0.035 -12.995 -0.376

Group III -4.727 2.100 0.103 -10.149 0.696

Group II Group I 6.685* 2.444 0.035 0.376 12.995

Group III 1.959 2.404 1.000 -4.249 8.166

Group IIIGroup I 4.727 2.100 0.103 -0.696 10.149

Group II -1.959 2.404 1.000 -8.166 4.249



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Table3Mean,standarddeviationandpvalueofANOVAforrepeatedmeasurestestofthenegativeaveragevalues

oftheadaptation(gapareas)ofthethreegroups.

Group I Group II

Group III

Minimum 0.05 0.03 0.08

Maximum 0.11 0.07 0.16

Mean .0804 .0542 .1161

+/-S.D. .01437 .00941 .02141

P value <0.001

Table4Pairwisecomparisonbetweenthenegativeaveragevaluesoftheadaptation(gapareas)ofthethree

groups.

(I) factor1

Mean Difference



Lower Bound

Upper Bound

Group IGroup II .026* 0.004 0.000 0.017 0.036

Group III -.036* 0.005 0.000 -0.050 -0.022

Group II Group I -.026* 0.004 0.000 -0.036 -0.017

Group III -.062* 0.005 0.000 -0.075 -0.049

Group IIIGroup I .036* 0.005 0.000 0.022 0.050

Group II .062* 0.005 0.000 0.049 0.075



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Table5Mean,standarddeviationandpvalueofANOVAforrepeatedmeasurestestofthepositiveaveragevalues

oftheadaptation(pressureareas)ofthethreegroups.

Group I Group II

Group III

Minimum 0.07 0.08 0.11

Maximum 0.18 0.16 0.23

Mean .1348ab .1259b .1505a

+/-S.D. .02639 .02484 .02571

P value 0.004

Table6Pairwisecomparisonbetweenthepositiveaveragevaluesoftheadaptation(pressureareas)ofthethree

groups.

(I) factor1

Mean Difference



Lower Bound

Upper Bound

Group IGroup II 0.009 0.007 0.719 -0.010 0.028

Group III -0.016 0.007 0.107 -0.034 0.002

Group II Group I -0.009 0.007 0.719 -0.028 0.010

Group III -.025* 0.007 0.004 -0.042 -0.007

Group IIIGroup I 0.016 0.007 0.107 -0.002 0.034

Group II .025* 0.007 0.004 0.007 0.042



26

Table7Mean,standarddeviationandpvalueofANOVAforrepeatedmeasurestestoftheaveragevaluesofthe

adaptationofthethreegroups.

Group I Group II

Group III

Minimum 0.03 0.00 0.03

Maximum 0.06 0.01 0.05

Mean .0443 .0039 .0393

+/-S.D. .00784 .00071 .00773

P value <0.001

Table8Pairwisecomparisonbetweentheaveragevaluesoftheadaptation(3Dcomparison)ofthethreegroups.

(I) factor1

Mean Difference



Lower Bound

Upper Bound

Group IGroup II .040* 0.002 0.000 0.036 0.044

Group III .005* 0.002 0.029 0.000 0.010

Group II Group I -.040* 0.002 0.000 -0.044 -0.036

Group III -.035* 0.002 0.000 -0.039 -0.031

Group IIIGroup I -.005* 0.002 0.029 -0.010 0.000

Group II .035* 0.002 0.000 0.031 0.039



Documents

A comparison of denture base retention and adaptation