Stress Distribution by Improved Designs of Obturator Frameworks

Using Photo-elastic Resin Models. In Vitro Study

LAITH MAHMOUD ABDULHADI AL-SAMAWI

Department of Prosthetic Dentistry

MAHSA University

Jalan SP 2, Bandar Saujana Putra, Selangor

MALAYSIA

AMRO DABOUL

Department of Prosthodontics, Gerodontology and Biomaterials

University Medicine Greifswald

GERMANY

Abstract: - Obturator is a prosthetic appliance that is used to restore irreparable maxillary defects. The frames

were supposed to form the infrastructure of the obturator that intends to close the maxillary arch defects. Five

main types of maxillary defects according to Aramany classification were selected for this study. 15 different

design frameworks were fabricated using Co-Cr dental alloy. The defects were simulated using premade

maxillary arch models that were reproduced in photo-elastic resin. The fabricated metal frames were seated on

the photo-elastic resin models and then were exposed to standardized stress at 3 different locations on the

frames using a global testing machine. A custom made plane polariscope was arranged to provide polarized

illumination for the light emission and analysis through the models. The photo-elastic resin models were

photographed during loading under the testing machine to display the supporting areas deformation

in frontal plane. The results showed that the proposed metallic designs variably distributed the stresses around

the abutments and the remaining hard tissues on the photo-elastic models.

Key-Words: - Maxillofacial replacement, obturator design, palatal defect, photo-elastic analysis, maxillary

defect.

Received: April 9, 2022. Revised: December 7, 2022. Accepted: January 4, 2023. Published: February 13, 2023.

1 Introduction

The massive structure or tissue

loss of maxillary arch due to any reason results in a

mutilation of the supporting oral and dental

components plus impaired vital oral functions. A

prosthetic appliance called obturator is used to

replace the missing oral and dental structures in

order to restore functions as well as aesthetics for

the patient. The support, retention, and stability of

the replacing prosthesis depend on the amount,

quality and distribution of residual hard and soft

tissues. Since functional and parafunctional forces

are transmitted to abutment teeth through rests,

guiding planes, and retainers, the obturator

framework design should be configured in

accordance with the movements of the obturator

during function. The main objective of the

framework design should be primarily

oriented toward preservation of the remaining oral

structures. Despite the framework design will vary

according to the size of the defect, the design

objectives remain the same; to distribute or control

the functional and parafunctional forces so that each

supporting or retaining element can be used to its

maximum effectiveness without being stressed

beyond its physiological limits and to offer the best

biologically and mechanically compatible design.

Photo-elastic stress analysis test allows an

experimental design limiting both patient and

operator variables. Although photo-elastic analysis

has some limitations with respect to its capacity to

reproduce the non homogeneous and an-isotropic

features of teeth, bone, and periodontal ligament, the

technique has been extensively and successfully

used in dentistry to study the interaction of tissues

(teeth and bone) response under simulating oral load

that is induced by prosthetic restorations.

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2 Causes of Defects

Acquired maxillary defects can be caused by

surgical intervention or massive trauma. Surgically

created defects result due to removal of part or all of

the maxilla due to tumor or pathology involving the

maxillary sinus or the palate [1]. Defects from

trauma may be the result of an automobile accident,

industrial accident or a gunshot wound [1], [2].

Congenital maxillary defects like cleft lip and palate

can be treated by different types of obturator

prosthesis. However, the treatment of patients with

acquired maxillary defects differs from that of

patients with congenital defects because of the

abrupt alteration in the physiologic processes

involving each condition. [3].

3 Objectives of the study

- To analyze the forces transmitted to the supporting

structures around abutment teeth in 5 classes of

Aramany classification using photo-elastic models

with different framework designs commonly used to

restore each defect [4].

-To suggest the most suitable design for each defect

that produced the least and most even stress on the

remaining teeth and supporting structures.

4 Analysis of Stress Transmission

Photo-elastic stress analysis is based on the property

of some transparent materials to exhibit colorful

patterns when viewed with polarized light. These

patterns occur as the result of alteration of the

polarized light by the internal stresses into two

waves that travel at different velocities [5].

Photo-elastic stress analysis consists of replicating a

test object in a photo-elastic epoxy resin and then

applying a load to the photo-elastic test object and

viewing the resultant stress patterns by using special

polarizing filters in a polariscope [6].

A plane polariscope consists of a light source and

polarizing filters. Two types of fringes are revealed

by using the plane polariscope. The array of colored

patterns is called isochromatic fringes. These fringes

are related to stress intensity and their number

increases in respond to applied loads. The other

fringes are the isoclinics. These fringes superimpose

on the isochromatic fringes and are related to the

stress direction [5].

The photo-elastic stress analysis technique has been

extensively and successfully used in dentistry to

study the interaction of tissue response and physical

characteristics of implants and prosthetic

restorations. In addition, it has been used in studying

loads transferred to implants [7], [8], [9], removable

partial dentures [10], fixed prosthodontics [11],

endodontics [12], [13], [14], and bio-materials

properties [15].

5 Principles in photo-elasticity

Light is an electromagnetic vibration similar to

radio waves. An incandescent source emits radiant

energy which propagates in all directions and

contains a whole spectrum of vibrations of different

frequencies or wavelengths. Those vibrations are

perpendicular to the direction of propagation. A

light source emits a train of waves containing

vibrations in all perpendicular planes. When a

polariscope is used, the introduction of a polarizing

filter will allow only one component of these

vibrations to be transmitted, which is parallel to the

privileges axis of the filter. Such an organized beam

is called polarized light. The polariscope

arrangement in Fig.1 consists of a light source and

two plates of material that polarize light (the

polarizer and the analyzer), in which the object

being tested is placed between these two plates. The

two plates are set with their axes of transmission at

90º, therefore no light is transmitted by the analyzer.

[16], [17].

Fig.1 Plane polariscope

Light propagates in a vacuum or in air at a speed

(C). In other transparent bodies, the speed (V) is

lower and the ratio C⁄V is called the index of

refraction. In homogeneous body, this index is

constant regardless of the direction of propagation

or plane of vibration. Certain materials behave

isotropically when unstressed but become optically

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anisotropic when stressed. The change in index of

refraction is a function of the resulting strain. When

a ray of polarized light passes through a photo-

elastic material, it gets resolved along the two

principal stress directions and each of these

components experiences different refractive indices.

The difference in the refractive indices leads to a

relative phase retardation between the two

component waves. The two waves are then brought

together in a polariscope. The phenomena of optical

interference takes place and a fringe pattern is

created, which depends on relative retardation.

Thus, studying the fringe pattern can determine the

state of stress at various points in the material.

6 Photo-elastic Observations

The photo-elastic technique will provide a visual

display of the stresses in a model which are revealed

in a polariscope. For most prosthetic appliances, the

main information required is the location,

distribution and intensity of stress concentrations.

Interpretation of the fringes produced in a loaded

model follows two main principles: The more the

number of fringes produced, the higher the stress

intensity, and the closer the fringes are to each

other, the higher the stress concentration [5]. A

simple interpretation of fringes into stress values is

presented in (Fig.2). More than two fringes (> +2)

correspond to high stress, from one fringe to two

fringes (> +1 to +2) correspond to moderate stress,

and less than 1 fringe (< +1) correspond to low

stress.

Fig.2 Fringe orders

7 Study Design

Five main types of maxillary defects (Table. 3) were

selected. Different framework designs were

allocated to each defect type to highlight the most

suitable design (Table 1). The designs were tested

individually by applying a load of 10 lb. (45 N) to

selected loading points on each framework. The

models were compared by means of photo-elastic

stress analysis to determine the most appropriate

design in terms of amount and stress distribution

around the abutment teeth.

Table. 1 Frames and defect types used in the study

7.1 Method

7.1.1 Primary casts preparation

A mold of premade maxillary model (Trimunt.

Japan) Fig.3, was prepared using duplication

silicone (Wirosil® Bego, Germany). Five custom

made blocks were made from auto-polymerizing

acrylic resin (Bego. Germany) and were placed

inside the initial silicone mold respectively to

simulate the defects in each Aramany class. Each

acrylic block was designed to simulate an ideal

Aramany maxillectomy defect (Fig.3, Fig.4).

Working casts with the simulated defects were

produced using the modified silicone mold with the

acrylic blocks (Fig.3,Fig.4). The resultant casts

represented the following defects:

Class I defect: The resection is performed along the

midline of the maxilla and teeth are maintained on

one side of the arch.

Class II defect: Unilateral maxillary defect that

retains the anterior teeth on the contralateral side.

The anterior teeth from central to canine are present.

Class IV defect: A defect crosses the midline and

involves both sides of the maxilla.

Class V defect: The anterior teeth are preserved and

the posterior teeth, hard palate and portions of the

soft palate are resected.

Class VI defect: Posterior teeth preserved with the

palate, the defect involves the premaxilla.

Classes

Class I

Class II

Class IV

Class V

Class VI

Frames

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Fig. 3 Premade model used to make defect cast

Later, each primary cast underwent modifications

according to the defect type and size using a wax

knife and a stone carver to simulate an ideal

resection. A mold of each primary cast was made

using duplication silicone (Wirosil® Bego.

Germany). The models were then relieved

approximately 1.5 mm using a graded 3 wheels bur.

Light body impression silicone (Wirosil® Bego.

Germany) was painted on the relieved casts. The

casts were fitted back on the molds before the

impression silicone was set to ensure that the

impression silicone forms a layer of 1.5 mm

thickness simulating the fibromucosa of the palate.

A second mold of each primary cast was made with

duplicating silicone (Wirosil® duplicating silicone,

Bego, Germany) to be used later for producing the

photo-elastic models.

Fig. 4 Example of the fabricated defect stone model

7.1.2 Preparing the testing models

Casting wax sheets (Bego. Germany) of 0.2 mm

thickness were used to cover individual teeth roots,

stone molds were made for the coated roots. The

molds were washed with hot water to eliminate the

wax around the teeth and to provide an approximate

space of 0.2 mm for silicone mass to be placed to

simulate the periodontal ligament Fig.5 [18].

Plastic artificial teeth (B3-305. Trimunt, Japan)

were coated with light polyvinyl siloxane

impression material (Bego. Germany) in a layer of

0.2 mm to simulate the periodontal ligament, Tray

adhesive (Bego. germany) was applied evenly over

the roots of the teeth to help fix the siloxane

material to the teeth roots. Digital caliper (Mitutoyo

Mfg. Japan) Fig.5, was used to check the thickness

of the silicone layer. Coated teeth were arranged in

the secondary molds, as following:

Class I defect molds: Teeth from central incisor to

2nd molar on the non defect side were preserved.

Class II defect molds: Teeth from the canine on the

defect side to 2nd molar on the non defect side were

preserved.

Class IV defect molds: 1st and 2nd premolars, 1st

and 2nd molars on one side were preserved.

Class V defect molds: Frontal teeth, from 1st

premolar to the 1st premolar on the opposing side

were preserved.

Class VI defect molds: 2nd premolar, 1st and 2nd

molars on both sides were preserved.

Fig.5 fabrication of silicone periodontal ligament

Fig.6 Final photo-elastic model with simulated

fibromucosa

7.1.3 Photo-elastic casting

The molds were preheated to 55º C for 30 minutes

in a hot air oven ( Memmert Gmbh. Germany) to

ease the flow of the PL-2 photo-elastic material and

reduce the amount of air bubbles. The photo-elastic

material was poured into the molds according to the

manufacturer’s instructions to produce the final

photo-elastic testing model

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7.1.4 Obturator framework designs

Obturator frameworks were fabricated using Cobalt

Chromium (Co – Cr) alloy metal (Bego. Germany)

with standardized laboratory methods. The

framework designs were made following the general

principles:

Occlusal rest seats were prepared with round

diamond bur (No.6) with 2.5 mm width, 2.5 mm

length and 1.5 mm depth.

The guiding planes on the anterior abutment in

occluso gingival height are 2 mm to limit torque on

the abutment tooth.

An extension base was fabricated extending into the

defect area at the same level of the remaining palate

to transmit occlusal forces to the cast in all

frameworks.

A bracing component is opposing each retainer.

The following Co-Cr removable partial denture

designs were fabricated to replace each defect of the

Aramany classification:

Fig. 7- Fig. 21, (B: Bracing arm, R: Retention arm,

G: Guiding plane.)

Fig 7 Class I Design 1

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

-Class I , Design 1; Double embrasure clasp on

the molars (distal rest on the 1st molar and

mesial rest on the 2nd molar with buccal

circumferential cast retainers on the 1st and 2nd

molars). Another double embrasure clasp is on

the 2nd premolar and 1st premolar. Buccal

circumferential cast retainers on the 1st and 2nd

premolars Fig.7 [4].

Fig. 8 Class I Design 2

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

-Class I, Design 2; Embrasure clasp is on the 1st and

2nd premolars with mesial occlusal rest on the 2nd

premolar and distal occlusal rest on the 1st

premolar. Palatal circumferential cast retainers are

on the 1st and 2nd molars with mesial occlusal rest

on the 2nd molar and distal occlusal rest on the 1st

molar Fig.8 [4].

Fig. 9 Class I Design 3

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

-Class I, Design 3; Buccal circumferential cast

retainers are placed on the 1st and 2nd molars with

mesial rests on the 2nd molar and distal rests on the 1st

molar. Rest seats on the mesial of the 2nd premolar

and distal of the 1st premolar with no retentive or

bracing arms. I-bar retainer and cingulum rest are on

the central incisor Fig.9 [19].

Fig. 10 Class II Design 1

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

-Class II, Design 1; Buccal circumferential cast

retainers are placed on the 1st and 2nd molars with

mesial rest on the 2nd molar and distal rest on the

1st molar. A cingulum rest with a buccal cast

circumferential retainer is placed on the canine

opposing the defect side and on the canine nearest to

the defect Fig.10 [19].

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Fig. 11 Class II D

A,B,C; stress application points, B; bracing,R;

retentive arm

-Class II, Design 2; Buccal circumferential cast

retainers are placed on the 1st and 2nd molars with

mesial is located on the 2nd molar and distal rest are

placed on the 1st molar. A rest seat is placed on the

canine cingulum and a mesial rest on the 1st

premolar. I-bar retainer and cingulum rest seat are

located on the canine Fig.11.

Fig. 12 Class II Design 3

A,B,C; stress application points, B; bracing,R;

retentive arm

- Class II, Design 3; A buccal circumferential cast

retainer and a distal rest are placed on the 2nd

molar, buccal circumferential cast retainers are on

the 1st premolar and the canine with rests on the

canine cingulum and the mesial of the 1st premolar,

a buccal circumferential cast retainer with a rest are

placed on the canine nearest the defect Fig.12.

Fig. 13 Class IV Design 1

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

- Class IV, Design 1; A buccal circumferential cast

retainer and a mesial rest are placed on the 2nd

molar. A buccal circumferential retainer and distal

rest are placed on the 1st molar. Occlusal rest rested

on mesial of 2nd premolar and distal 1st premolar

with buccal circumferential cast retainers located at

1st and 2nd premolars Fig. 13 [19].

Fig. 14 Class IV Design 2

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

- Class IV, Design 2; Buccal circumferential cast

retainers are put on the 1st and 2nd premolars with

mesial rest on the 2nd premolar and distal rest on

the 1st premolar. Palatal circumferential cast

retainers are placed on the 1st and 2nd molar, mesial

rest on the 2nd molar and distal rest on the 1st molar

Fig. 14.

Fig. 15 Class IV Design 3

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

- Class IV, Design 3; A buccal circumferential

retainer, mesial and distal rests placed on 2nd molar,

buccal circumferential retainer, mesial and distal

rests located on the 1st molar. Mesial and distal rests

are on 1st and 2nd premolars with I-bar retainer on

the 1st premolar Fig.15.

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Fig. 16 Class IV Design 4

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

- Class IV, Design 4; Distal rest with a buccal

circumferential cast retainer are placed on the 2nd

molar, mesial rest with a buccal circumferential cast

retainer are located on 1st molar. Distal rest with

buccal circumferential cast retainer are on 2nd

premolar, Mesial rest with buccal circumferential

cast retainer on 1st premolar (Fig.16). [20].

Fig. 17 Class V Design 1

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

- Class V, Design 1; Cingulum rest placed on both

central incisors and both canines, mesial rests with

I-bar retainers on both 1st premolars Fig. 17, [4].

Fig. 18 Class V Design 2

A,B,C; stress application points, B; bracing,R;

retentive arm,G; guiding plane

-Class V, Design 2; Cingulum rests are placed on

both central incisors, canines and mesial side on the

1st premolars. Buccal circumferential cast retainers

are located on the canines and 1st premolars Fig.18.

Fig. 19 Class VI Design 1

A,B,C; stress application points, B; bracing,R;

retentive arm

-Class VI, Design 1; Buccal circumferential

retainers are placed on 1st and 2nd molars with

mesial rest is located on 2nd molar and distal rest is

on the 1st molar. Mesial rest seats are placed on 1st

molar, distal rest with I-bar retainer are located on

the 2nd premolar Fig .19

Fig.20 VI Design 2

A,B,C; stress application points, B; bracing,R;

retentive arm

- Class VI, Design 2; Mesial rest seats with buccal

circumferential cast retainers are located on the 2nd

molars with mesial and distal rest seats on the 1st

molars, distal rest seats and buccal circumferential

cast retainer on the 2nd premolars Fig. 20 [4].

Fig. 21 Class VI Design 3

A,B,C; stress application points, B; bracing,R;

retentive arm

- Class VI, Design 3; Distal rest with I-bar cast

retainers on the 2nd premolars. Mesial and distal

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rest seats on the 1st molars, mesial rest and

embrasure on 2nd molar Fig. 21.

7.2 Testing

7.2.1 Application of loads

A load of 10 pounds (45 N) was applied vertically to

each loading point respectively by the universal

testing machine (Shimadzu co, Japan) Fig. 22. The

loads were selected within the realistic functional

load levels and also provided a satisfactory optical

response in the photo-elastic model [21].

All frameworks shared a similar location of the

loading points within the same defect. The loading

points for each defect differed according to the size

of the defect

Fig. 22 Universal testing machine

7.2.2 Load application on the obturators

Three points were selected to be the load application

on each Obturator used in the study named A, B, C.

Fig. 7-Fig. 21. Therefore, the total application

number was 3 x15 times.

The photo-elastic model, with its framework, was

seated on a custom made base on the lower plate of

the universal testing machine (Shimadzu co, Japan.

precision was 1/1000 ± 5%). The base was custom

made and marked to keep the position of the model

during the different load applications Fig.23.

Fig. 23 Custom made base for standardization of

model placement

A camera (Olympus E330 EVOLT 8 MP Auto ISO.

14-45 mm / 3.5-5.6 zuiko lens, Japan) was fixed on

a tripod stand that offers two fixed reference

locations. This permitted taking images of different

views of the model while the framework was

subjected to loads.

The photo-elastic models showed zero record of

stress prior to loading Fig. 24. Each model showed

stress fringes when loads were applied and exhibited

no stress when the loads were lifted off. Each

loading and observation sequence was tested by 2

examiners to ensure reproducibility of the results

Table.2. The resultant stresses in all areas of the

supporting structure were monitored and recorded

photographically in the field of a plane polariscope

environment. The polariscope in Fig.25 consists of

two polarizing filters and a light source. The light

source was a 300 watt tungsten filament with fiber

optic extensions.

Fig.24 Testing the model without loading

Fig. 25 The arrangement of experiment components

(LS; light source; photo-elastic model, P; polarizing

filter, C; camera)

7.2.3 Testing and reliability of examiners records

The records of photo-elastic deformation were

checked by two examiners instantaneously and a

reliability test was carried on to reduce the possible

bias between observers using Kappa test,Table. 2.

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Table.2 inter-examiner reliability

The stress patterns developed by the different

designs were compared at the three different loading

points using the color chart presented in Fig.2.

7.3 Analysis of fringe records for each frame

The fringes records at different application load

points (A, B, C) for each design were added and the

total score was compared to other designs. The least

stress records by any design were considered the

best to be used in treating similar maxillary defect

on patients. Since the fringe grading system is

qualitative in nature, therefore a qualitative

statistical test was used to see the difference among

frames of the same Class.

8 Results

8.1 Stress recorded in Class I using 3

different frameworks

Cl I

1Pm

2Pm

Total

Table. 3 Stress records around teeth in Class I, 3

designs (Cl; Class,CI; central incisor, LI; lateral

incisor,C;canine,1Pm;1stpremolar,2Pm;

2ndpremolar,1M;1st molar,2M; 2nd molar).

Results of the statistical analysis for the Class I

design using one-Way ANOVA revealed no

difference among stresses transmission by the 3

designs (DF=2, F statistic=.571, P-value=.575).

However, the locations of stresses are variables. We

concluded that design 1 may be biologically better

than the rest due to that stresses were mainly

supported by posterior teeth,Table.3.

8.2 Stress recorded in Class II using 3

different frameworks

CI II

1Pm

Total

D 1

D 2

D 3

Table.4 Stress records in Class II in 2 different

designs (Cl; Class, C; canine, 1Pm;1st premolar,

1M;1st molar, 2M; 2nd molar)

The analysis showed absence of mean stress

difference among the 3 different designs of

frameworks (DF=2, F-statistic =.223, P-value

=.804), Table.4. Yet, design 2 and 3 showed

reduced stress around teeth in general compared to

design 1.

8.3 Stress recorded in Class IV using 4

different frameworks

Table.5 Stress analysis in Class IV for different

designs (1Pm;1st premolar,2Pm; 2nd premolar,1M;1st

molar,2M; 2nd molar)

No statistical difference was found among the 4

designs of Class IV (Cl; Class, DF= 3, F statistic=

.651, P- value= .597). However, in design 1, the

stress concentration areas were reduced around 1st

premolar and 1st molar compared to other designs.

8.4 Stress recorded in Class V using 2

different frameworks

Cl V

1Pm

Total

Table.6 Stress analysis in Class IV for different

designs (Cl; Class, CI; central incisor, C; canine,

1Pm; 1st premolar).

In this Class only 2 loading points were used

because of the limited area of the remaining arch.

Statistical analysis cannot be done for this class due

to the limited data. The stress around remaining

teeth nearly similar occurrence all teeth nearly

affected because of small number, Table.6.

Observer

Yes

Total

Kappa=

0.934

at 95%

confidence

interval

118

122

118

122

Cl IV

1 Pm

2 Pm

1 M

2ndM

Total

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8.5 Stress recorded in Class VI using 4

different frameworks

Cl VI

2Pm

Total

Table. 7 The stress records around teeth using 3

designs in Class VI (Cl; Class,D; design, 2Pm; 2nd

premolar, 1M; first molar, 2M; second molar)

The photo-elastic model showed little stress in

design 3 due to its configuration that splints the

residual teeth altogether, Table 7.

9 Discussions

9.1 photo-elastic of stress analysis

In our practice, this method is commonly used to

explore the minimum stress generated by any

prosthetic appliance. However, the results are

always limited due to the absence of a huge number

of oral parameters normally found in the oral cavity

like salivary flow, viscoelastic features of mucosa

and periodontal ligament, force intensity, direction

and neuromuscular reflexes during functional and

parafunctional activities. These parameters tend to

make the stress resultant unpredictable in reality.

Another fact is that the stress amount as represented

by a simple scale never reveals the actual intensity

of the reaction inside the supporting tissues. Despite

all of that this method still offers a good way to

reveal the stresses when compared to simulation

models.

9.2 Limitations in the fabrication of photo-

elastic models

Making an ideal photo-elastic model of the oral

cavity with variable components of anatomy and

physiology is non-trivial and requires excellent

experience to bring it close to actual biological

features. However, the results still provide a good

vision about what happens around the supporting

structures of the obturator during function.

9.3 Analysis

Due to the limited number of the sample in some

classes, the statistical analysis gave uncertainty.

Therefore, descriptive logic analysis was used to

reveal the best design in some classes.

10 Conclusion

The designs that promoted splinting configuration of

the remaining supporting teeth showed more even

distribution of stresses around the abutments and

reduction of concentration to lower number of teeth

thus offering more biologically acceptable

infrastructure of the obturator. As a conclusion for

the best design of obturator infrastructure; in Cl I,

D2 and D3 were the best in distributing the stresses

around the supporting teeth (posterior teeth). In Cl

II, D3 showed reduced stresses around teeth due to

the splinting configuration of the abutments. In Cl

IV, D1 revealed reduced loads in comparison with

other designs. In Cl V, no design preference was

obvious and the two models can be used equally. In

Cl VI, D3 seems the best due to its splinting

capability of the supporting teeth. As a general rule,

splinting teeth using any type as a fixed prosthesis

or designing the frame to hold the remaining teeth

as one unit enhances the stability and retention

while directing the functional forces towards the

most resistant area of the remaining arch and

avoiding high stresses on the alveolar or defect area.

The results of this study should proceed with future

enhanced frame designs and simulated clinical trials

with reconstruction of the defect area to distribute

the loads and ameliorate the remaining abutments

longevity inside the oral cavity.

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WSEAS TRANSACTIONS on BIOLOGY and BIOMEDICINE

DOI: 10.37394/23208.2023.20.1

Laith Mahmoud Abdulhadi Al-Samawi, Amro Daboul

E-ISSN: 2224-2902

Volume 20, 2023

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

Abdulhadi LM, carried out the authoring, designing

of the experiment, supervision, mathematical

analysis, and writing of the article.

Daboul A, has implemented all of technical work

and application of the instructions.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

This work is funded by a grant from University

of Malaya.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

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WSEAS TRANSACTIONS on BIOLOGY and BIOMEDICINE

DOI: 10.37394/23208.2023.20.1

Laith Mahmoud Abdulhadi Al-Samawi, Amro Daboul

E-ISSN: 2224-2902

Volume 20, 2023

Conflict of Interest

The authors have no conflicts of interest to declare

that are relevant to the content of this article.