In-Vivo Comparison of Different Impression Methods in Complete Edentulous Upper Jaw
Phase: NA
Conditions: Edentulous Jaw
Sponsor: Hacettepe University

Date: 09.05.2022  Vers/on: 1.1 
RESEARCH PROTOCOL 
 
1) Title of the Project: "In-Vivo Comparison of DiJerent Impression Methods in Complete 
Edentulous Upper Jaw" 
2 )Importance of the Project:  
Complete edentulism is a dental problem that involves the loss of all natural teeth 
due to iatrogenic, therapeutic or traumatic causes followed by alveolar bone resorption. 
The quality of life of edentulous patients is negatively aJected due to functional disorders 
such as phonation and mastication, and their social life is negatively aJected due to 
aesthetic deﬁciency (1). Today, when the socio-economic status of edentulous patients 
and their tolerance to treatment are evaluated, complete dentures are frequently preferred 
(2, 3). The large supportive tissue area in the upper jaw and the ability to provide more 
retention allow the problem-free use of upper complete dentures. Due to the lack of 
retention and mobility in lower complete dentures, patients have diJiculty in using lower 
complete dentures, especially while eating. Recent studies have shown that mandibular 
two implant-supported complete dentures may be the ﬁrst treatment alternative to 
conventional complete dentures, but implant support is generally not required for upper 
complete dentures (4). Complete dentures are often produced with the traditional method 
starting with conventional impression taking, but in recent years, digital workﬂow has been 
used following impressions taken with intraoral scanners.  
The borders of the complete prosthesis and the tissues supporting the prosthesis 
can be recorded with diJerent impression methods. The technique and material used 
during impression determines the contact of the prosthesis with the supporting tissue 
during rest and function, and thus the retention of the prosthesis. In dental schools, 
impressions of edentulous arches are usually taken using the two-stage impression 
method, which involves more complex clinical and laboratory steps, with the assumption 
of providing a better treatment (5). In this method, the initial impression is taken with metal 
'stock' trays and irreversible hydrocolloid (alginate) impression material.  An individual tray 
is produced from the plaster model obtained from the initial impression. The ﬁnal 
impression is taken using zinc-oxide eugenol or elastomeric impression materials after 
border moulding with impression compound using the individual tray (6). As an alternative 
to the traditional two-stage impression method, a one-stage impression method with fewer 
clinical and laboratory steps has emerged. The one-step method uses metal-stock trays 
and irreversible hydrocolloid impression material. This method has been shown to produce 
clinically acceptable complete dentures at a lower cost (7). Among the many techniques 

Date: 09.05.2022  Vers/on: 1.1 
and materials, physicians choose the most appropriate, comfortable and cost-eJective 
alternative for the patient's clinical situation, taking into account the case situation, 
impression making stages and material properties.  
In a randomized controlled trial comparing single and two-stage impression 
methods, it was shown that patients' satisfaction with prostheses produced with the two-
stage method was higher (8). In addition, when diJerent studies comparing single and two-
stage impression methods were examined in the literature, there was no conclusive 
evidence of the superiority of the two-stage impression method, which is accepted as the 
gold standard in dental textbooks (7, 9, 10). 
Computer-aided design / Computer-aided manufacturing (CAD/CAM) techniques 
have emerged with advances in technology. With current approaches, the tissues 
supporting the prosthesis can be recorded with digital methods and more compatible 
dental prostheses can be produced with CAD/CAM techniques (11).  For this purpose, the 
indirect digital impression method, in which the measurements taken with the 
conventional method or the models obtained are scanned with a laboratory scanner and 
digitized, is frequently used. However, the distortion that conventional impression 
materials undergo when they are removed from the patient's mouth and the dimensional 
change they undergo during the time until they are digitized can negatively aJect the 
accuracy of the impression.(12) At the same time, inadequacies in patient comfort, the 
necessity of renewing the entire procedure in case of an inaccurate impression, and cost 
have played a role in the emergence of direct digital impressions. In the direct digital 
impression method, the supporting tissues are recorded simultaneously with the intraoral 
scanner. Initially, direct digitalization was limited to the digital impression of teeth and the 
production of tooth-supported prostheses. However, today, digital impressions of implants 
and complete edentulous arches can be taken (13, 14). However, intraoral scanners have 
diJiculty in matching the soft tissue image in edentulous areas due to the lack of reference 
points and there is insuJicient data in the literature regarding the success of direct digital 
impressions of edentulous arches. 
 
There are few clinical studies in the literature comparing conventional and digital 
impression methods of edentulous arches. Lo Russo et al. compared conventional and 
digital impressions of edentulous jaws in a clinical study. Digital impressions were ﬁrst 
taken from the patients with an intraoral scanner. The impression was transferred to a 
design program in "STL" format and a individual tray was prepared based on the model 
obtained from this impression. A conventional impression was taken with the individual 
tray and polysulﬁde impression material and then the impression was scanned with the 
same intraoral scanner. The impressions taken from the patients were compared and no 

Date: 09.05.2022  Vers/on: 1.1 
statistical diJerence was found. It has been shown that edentulous jaws can be recorded 
with direct digital impressions similar to conventional impression methods and that these 
impressions can be used clinically in the production of tissue-supported removable 
prostheses (15). 
Chebib et al. compared the accuracy of diJerent impression techniques in patients 
with maxillary complete edentulism in a clinical study. Twelve patients participated in the 
study and a total of ﬁve impressions were taken from each patient. In the ALG group, 
impressions were taken with a stock-tray and irreversible hydrocolloid impression material. 
In the ZOE group, individual tray borders were shaped with impression compound and 
impressions were taken with ZOE material. This group was also considered as the control 
group. In the PVS group, individual tray and medium-viscosity polyvinylsiloxane impression 
material were used. In the PVSM group, the inner surface of the impression taken in the PVS 
group was modiﬁed with ZOE impression material. All analog measurements were digitized 
with the same laboratory scanner. In the TRI group, scanning was performed with an 
intraoral scanner after the reference points created with composite on the maxillary soft 
tissue. Then, with the help of a software, the scan data were matched in a best-ﬁt manner. 
As a result of the study, PVS, PVSM and TRI groups showed similar deviations and were 
found clinically acceptable. Irreversible hydrocolloid impression material was shown to be 
contraindicated for the ﬁnal impression of the complete edentulous maxilla (16). 
There is limited information on the comparison of the direct digitalization method 
used in the impression of edentulous arches with traditional impression methods and 
there is a need for improvement. Given this situation, the aim of this study was to expand 
the existing knowledge for direct digitalization in the edentulous maxilla by comparing six 
diJerent edentulous arch impressions. 
3)Materials and Methods: 
 
In this study, it was planned to compare a total of six diJerent permanent 
impressions obtained from patients with complete edentulous maxilla using three diJerent 
conventional impression methods and three diJerent digital impression techniques. 
Patient grouping was not planned in the study, and it was decided to take impressions from 
each patient who met the inclusion criteria under conventional and digital groups.  
Physical Record (fK)= 
 
- fK-I (ALG) (Metal stock tray and irreversible hydrocolloid impression material ("simpliﬁed 
tech.") (7) 
- fK-II (ZOE) (Individual tray, border-moulding and zinc-oxide ojenol impression material) 
- fK-III (E) (Individual tray, border-moulding and elastomeric impression material) 
 

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Direct Digitalization (dD) =  
- dD-I (AI-OFF) (Direct impression with intraoral scanner and A.I oJ)  
- dD-II (AI-ON) (Direct impression with intraoral scanner and A.I on) 
- dD-III (MOD) (Intraoral scanner and scanning with OR (17) and A.I oJ) 
 
All measurements will be completed in two sessions and will be performed by a 
single operator. The ﬁrst session will last 40 minutes and the fK-I (ALG), dD-I (AI-OFF) and 
dD-II (AI-ON) group impressions will be completed. First, the lip and cheek will be excluded 
with an intraoral retractor (OptiView™ Standard Kit) and the dD-I (AI-OFF) impression will be 
completed by direct scanning with the intraoral scanner (TRIOS4; 3Shape A/S, 
Kopenhagen, Denmark) with the A.I closed. Then, with the same intraoral scanner, the A.I. 
will be turned on and the impression will be taken again and the dD-II (AI-ON) impression 
will be completed. Direct scan data will be exported in "STL" format.  For fK-I (ALG), the 
most suitable metal stock tray will be selected and irreversible impression material 
(TROPICALGIN; Zhermack SpA Badia Polesine (RO), Italy) will be used. Within 10 minutes of 
impression taking, the impression will be scanned with the same intraoral scanner. A 
negative of the scan data will be obtained and exported in "STL" format. The individual tray 
will be designed using a design program (Exocad DentalCAD 2.4 Plovdiv; Emerald Dental 
Works, Hamilton) and produced with a 3D printer (Photon Mono; Anycubic Tsim SHA TSUI, 
Kowloon) 
The second session will last 60 minutes, and the fK-II (ZOE), fK-III (E) and dD-III 
(MOD) group impressions will be completed. For fK-II (ZOE), the individual tray will be 
checked in the mouth and necessary adjustments will be made. Border moulding will be 
done using impression compound (Kemco Tracing Sticks; Kemdent, Purton, UK) to ensure 
peripheral closure. The impression will be completed with zinc-oxide ojenol impression 
material (Impression Paste; SS White Lakewood, New Jersey). The impression will be 
digitized with an intraoral scanner within one hour after completion. For fK-III (E), the 
individual tray will be checked in the mouth and necessary adjustments will be made. 
Border moulding will be done with impression compound. The impression will be 
completed with elastomeric impression material. In the same way, it will be digitized with 
an intraoral scanner. dD-III (MOD), the base and wax template prepared for the patient will 
be arranged in accordance with the patient's occlusal vertical dimension, horizontal and 
vertical relationship between the jaws and aesthetic parameters. The base and wax 
template will be ﬁxed in the mouth with a prosthetic adhesive. A tooth will then be selected 
on the upper jaw to allow for pre-scaning. The upper jaw will be scanned together with the 
base and wax template. The opposing jaw will then be scanned and the bite recorded. For 
the main scan of the upper jaw wax template from the pre-scan will be cut manually and 
the whole jaw scan will be completed, starting from the palate (17). 
After all measurements are completed, the data obtained will be transferred to a 
computer software (Geomagic design X version 2016.1.0, 3D Systems Inc. Rock Hill, SC) 
and the comparison of diJerent impression methods used for the edentulous upper jaw 
will be performed with this program. When the literature is examined, studies comparing 

Date: 09.05.2022  Vers/on: 1.1 
diJerent impression methods taken from the upper edentulous jaw were evaluated with a 
similar method (15, 16). 
Within the scope of this study, individuals who have completed upper jaw complete 
denture treatment at Hacettepe University Faculty of Dentistry, Department of 
Prosthodontics, have completed the controls, have been using the delivered prosthesis for 
3 months and have healthy tissues supporting the prosthesis will be included in the study. 
 
Inclusion Criteria; 
1) Accepting voluntary participation in the study after reading the informed and voluntary 
consent form 
2) Individuals with no risk factors in terms of general health status 
3) Individuals whose complete upper jaw prosthesis has been made and delivered with 
known methods, whose controls have been completed, who have been using the delivered 
prosthesis for 3 months and whose tissues supporting the prosthesis are healthy 
 
 Exclusion Criteria; 
1) Not accepting to participate in the study voluntarily after reading the voluntary consent 
form 
2) Individuals with allergic reactions to the measurement materials planned to be used 
3) People with systemic disorders or excessive weight loss that may occur for diJerent 
reasons or dimensional changes that may occur in the tissues supporting the prosthesis 
due to other reasons 
 
Sample Size and Power Analysis 
PS Version 3.0 package program was used in this study. D=0.50, α=0.05, power of the test 
1-b=0.80, correlation between repetitions r=0.20 were assumed and the minimum sample 
size was accepted as 15. However, since working with a larger sample reduces the level of 
bias, it is desirable to work with as many patients as possible.      
 
Randomization 
The study was planned as a clinical study. The six diJerent impressions planned for the 
edentulous upper jaw will be completed in two sessions, and the groups of impressions 
taken in the ﬁrst and second sessions will not change. Three diJerent groups of 
impressions to be taken in each session will not be subjected to randomization. 

Date: 09.05.2022  Vers/on: 1.1 
 
Blinding 
Double blinding will be applied in the study.  
1. Blinding of the evaluating researcher: The researcher will not learn which group the 
obtained data belongs to until the end of the evaluations. 
2. Blinding of the researcher performing statistical analysis: The researcher will not learn 
which group the obtained data belong to until the end of the evaluations. 
 
Data Collection (Primary Data - Secondary Data) 
Primary Data: 
Primary data will be collected for each case in the form of "STL" format obtained by 
exporting all maxillary complete edentulous jaw impressions of that case. These data will 
be overlaid with the help of a computer software (Geomagic design X version 2016.1.0, 3D 
Systems Inc. Rock Hill,SC), the fK and dD groups will be compared with each other and the 
diJerences between the groups will be recorded quantitatively. 
Secondary Data: 
Secondary data will be determined by an evaluation scale asked to the patient to assess 
patient comfort, taste, nausea, burning sensation after the completion of each 
measurement. By analyzing the questionnaires and evaluation scales, the opinions of the 
patients about diJerent measurement methods will be compared. 
 
Statistical Evaluation 
In the study, SPSS 20 package program will be used for data analysis.  In the analysis of the 
study, ﬁrst of all, Kolmogorov Smirnov adaptation test and Shapiro-Wilk test will be used to 
check whether the data have normal distribution. Afterwards, parametric or non-
parametric statistical methods will be used to evaluate whether there is a diJerence (it is 
foreseen that independent and dependent group tests, chi-square test, Anova test, and 
graphs will be given if appropriate). When evaluating the results of the tests, the 
signiﬁcance level will be taken as α=0.05 and the results will be interpreted according to 
this critical value.    
 
 

Date: 09.05.2022  Vers/on: 1.1 
 

Date: 09.05.2022  Vers/on: 1.1 
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