This authors have contributed equally to this work Department of Fixed Prosthodontics, Faculty of Dental Medicine, University of Monastir, Monastir, TunisiaTunisia
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Periodontal destruction observed in restored teeth is strongly caused by marginal discrepancy of the restoration, which is closely influenced by the tooth preparation, the technique of retraction and impression. Materials and Methods A hundred practitioners were selected to constitute the study’s sample. A self-administered questionnaire survey was carried out. The questionnaire was filled in the practitioner's office, completed in the absence of the investigator. However, it has been completed for some clarifications by an interview. A digital form made through the Google Forms application provided free by the Google search engine. The questionnaire included two sections: The identification of the practitioner: this is general information about the practitioner. The conduct of prosthetic treatment. The causes of marginal discrepancy: This section concerns the major factors responsible for a good marginal fit. The collected data was introduced and processed by the microcomputer using the statistical software XLSTAT 2015 for Windows. A simple statistical analysis made it possible to calculate the percentage of the different variables, from their frequency. Results There is a significant correlation between marginal discrepancy and the respect of the finish line geometry (p=0.001). The technique of retraction which provided the best marginal fit was the use of expasyl paste (p=0.18). There was a significant association between marginal discrepancy and the material of impression, marginal adaptation is found in 76% for impressions made by alginate, 45% for impressions made by silicone, and 100% for impressions made by polysulphides (p=0.01). Conclusion Within limitations of this study, it can be concluded that the respect of guidelines of preparation especially the finish line and the good choice of the retraction technique and the material of impression are the major keys to have a good marginal fit.
Keywords: Dental marginal adaptation; Dental impression materials; Tooth preparation; Gingival retraction techniques
A hundred practitioners were selected to constitute the study’s sample. A self-administered questionnaire survey was carried out. The questionnaire was filled in the practitioner's office, completed in the absence of the investigator. However, it has been completed for some clarifications by an interview. A digital form made through the Google Forms application provided free by the Google search engine. The questionnaire included two sections: The identification of the practitioner: this is general information about the practitioner. The conduct of prosthetic treatment. The causes of marginal discrepancy: This section concerns the major factors responsible for a good marginal fit. The collected data was introduced and processed by the microcomputer using the statistical software XLSTAT 2015 for Windows. A simple statistical analysis made it possible to calculate the percentage of the different variables, from their frequency.
There is a significant correlation between marginal discrepancy and the respect of the finish line geometry (p=0.001). The technique of retraction which provided the best marginal fit was the use of expasyl paste (p=0.18). There was a significant association between marginal discrepancy and the material of impression, marginal adaptation is found in 76% for impressions made by alginate, 45% for impressions made by silicone, and 100% for impressions made by polysulphides (p=0.01).
Within limitations of this study, it can be concluded that the respect of guidelines of preparation especially the finish line and the good choice of the retraction technique and the material of impression are the major keys to have a good marginal fit.
Dental marginal adaptation; Dental impression materials; Tooth preparation; Gingival retraction techniques.
ood fitting crown is the most important technical factors for the long-term success of dental restorations.
G
Marginal discrepancy can lead to plaque and bacterial deposition, which can generate many complications as periodontal cc Copyright 2019 by Cherif M. This is an open-access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0), which allows damage, microleakage1 and it may affect the retentive aspect of the restoration.
Several authors explained the marginal discrepancy by the lack of rigor in the completion of the clinical sequence (preparation design, technical and impression materials, decontamination of impressions and sealing) or the laboratory sequence (realization
of the working cast, preparation, and treatment of positive unit models).2 This study aims to identify the factors that lead to good fitting crowns.
This is a cross-sectional study. It lasted for a period of two months, from January 2017 to February 2017.
The example that was the subject of our study is made up of qualified dentists practicing in Tunisia in the private sector, without distinction of sex. It has been established according to the following selection criteria:
- To be a dentist - Be registered on the council of the order - Practice in Tunisia - Practice in the private sector
- Students - Non-registered practitioners on the council of the order - Dentists who specialize in a specialty other than the fixed prosthodontics.
According to these criteria, 100 practitioners were selected to constitute the study’s sample.
We carried out a self-administered questionnaire survey. The questionnaire was filled in the practitioner's office, completed in the absence of the investigator. However, it has been
The questionnaire
1- Seniority of practice < 5 years Between 5 and 10 years Between 10 and 20 years More than 20 years
2- Specialized in fixed prosthesis? Yes No 3- How do you judge the practice of the fixed prosthesis?
4- On an average, how much fixed prosthesis do you Between 1 and 5 prosthesis Between 5 and 10 prosthe- More than 10 prosrealize per month per month
1- What are the steps in the elaboration of the fixed prosthesis that you judge unnecessary? The treatment plan The preliminary impression The provisional restoration
The preparation The global impression Inter occlusal records
Trimming Fitting
Do you respect the choice of the type of the finishing line geometry according to the type of crown that the tooth will receive?
completed for some clarifications by an interview. A digital form made through the Google Forms application provided free by the Google search engine.
The questionnaire included two sections:
- The identification of the practitioner: this is general information about the practitioner.
- The conduct of prosthetic treatment.
- The causes of marginal discrepancy: this section concerns the major factors responsible for a good marginal fit.
The collected data was entered and processed by the microcomputer using the statistical software XLSTAT 2015 for Windows. A simple statistical analysis made it possible to calculate the percentage of the different variables, from their frequency.
Note: No Institutional Review Board (IRB) or any other board’s permissions were required for this study.
The purpose of this study is to identify the causes of marginal discrepancy and the major factors that allow dentists to perform prosthesis with a good marginal fit.
A dear colleague let us express our thanks in response to your cooperation on which the success of this work depends.
It is divided into 3 sections: 1. The general information’s section that contains information about the practitioner; 2. The conduct of prosthetic treatment; 3. Major difficulties faced while fitting.
Easy Affordable Difficult
sis per month thesis per month
Cementation
Always Never Sometimes Often
Do you entrust certain steps of the preparation to the laboratory Always Never technician?
If you do, please specify ………………………………….………………………………….………………………………….………………………
Do you do a temporary prosthesis? Always Never If not, why? ………………………………….………………………………….………………………………….………………………
What is the material you use to Reversible take the global impression? hydrocolloid Others : Please specify ………………………………….……………………………………………….…………………………………………… Do you consider the type of periodontal tissue to choose the global Yes No impression technique?
What are the gingival retraction Retraction techniques that you use? cord Expasyl Others : Please specify ………………………………….……………………………………………….……………………………………………
In your practice, is marginal discrepancy one of the frequent Yes No problems you faced while fitting?
If no, please specify the frequent problem you faced while fitting Cementation
Our study showed that 35 practitioners always adapted the geometry of finish line to the crown’s type, 41 dentists often respected finish line’s geometry adapted to the type of restoration, 16 practitioners sometimes suited the geometry of finish line and seven dentists never did it (Figure 1).
Figure 1. The Respect of the Finish Line’s Geometry Adapted to the Type of Restoration Regarding the materials used for impression, 71 practi- tioners used silicones, 25 dentists preferred alginate, 2 others used polysulphides and no one used the reversible hydrocolloids (Figure 2).
For gingival retraction, 52 practitioners use the retraction cord, 18 favor the use of the temporary prosthesis, 17 dentists use rotary curettage, five practitioners use expasyl, four practitioners favor electro-surgery and four practitioners use other methods (Figure 3).
Sometimes Often
Sometimes Often
Irreversible hydrocolloid Silicone Polysulfures
Temporary prosthesis Electro-surgery Rotary curettage
………………………………….……………………………………
Figure 2. Materials Used for Impression
Table 1. Relationship Between Marginal Discrepancy and the Respect the Finish Line Geometry
Always 77(27) 23 (8) 100 (35) Often 49(20) 51 (21) 100 (41) Sometimes 19(3) 81 (13) 100 (16) Never 50 (4) 50 (4) 100 (8) Total 45 (54) 46 (46) 100 (100) * 2 *Chi2 test:p=0.001; Fisher's exact test:p=0.001
There was nosignificant correlation between marginal discrepancy and the technique of retraction according to the fisher’s test (p=0.19). In fact, the best marginal adaptation was founded using expasyl (80%), second rotary curettage (71%), third, temporary prosthesis (67%), then the electro-surgery (50%) and finally the retraction cord with a success rate of 42% (Table 2).
Table 2. Relationship Between Marginal Discrepancy and the Retraction Technique
Retractioncord 42 (22) 58 (30) 100 (52) Temporaryprosthesis 67 (12) 33 (6) 100 (18) Expasyl 80 (4) 20 (1) 100 (5) Electro-surgery 50 (2) 50 (2) 100 (4) Rotary curettage 71 (12) 29 (5) 100 (17) Others 50 (2) 50 (2) 100 (4) Total 54 (54) 46 (46) 100 (100) * 2 Chi test:p=0.19 Fisher's exact test:p=0.18
There was a significant association between marginal discrepancy and the material of impression. In fact, marginal adaptation is found in 76% for impressions made by alginate, 45% for impressions made by silicone, 100% for impressions made by polyethers. (p=0.01) (Table 3).
Table 3. Relationship Between Marginal Discrepancy and the Material of Impression
Silicones 45 (32) 55 (39) 100 (71) Alginate 76 (19) 24 (6) 100 (25) polyethers 100 (2) 0 (0) 100 (2) Hydrocolloids reversible 0 (0) 0 (0) 0 (0) Others 50 (1) 50 (1) 100 (2) Total 54 (54) 46 (46) 100 (100) * *Chi² test:p=0.031; Fisher's exact test:p=0.01
The data obtained in this study showed that the respect of the finish line geometry had a significant effect on the marginal fit of the resulting restorations.
Percent Total These results are consistent with those found by Ates and Yesil Duymus3 and with those founded by Bottino et al, which reported that the best cervical adaptation of metal crowns was achieved with the chamfer type of finish line.
The study of Raul et al also showed that the marginal misfit measured in zirconium crowns with around shoulder finish line is significantly lower than the measured misfit in chamfer finish line restoration.
Our study reported that the best marginal adaptation was founded using expasyl. Comparing these results with those of the in vitro study of Wottsmann et al, we find almost the same results concerning the comparison between electro-surgery and the retraction cord where there is not a significant difference between these two methods.5
However, these results differ from those found in the comparative study of Shrivastava et al where he compared three gingival spacing methods, which are:
- Magic foam cord - Expasyl paste - Retraction cord impregnated with 15% aluminum chloride
Shrivastava et al reported that all the three displacement systems produced highly significant horizontal gingival displacement. Retraction cord soaked in 15% aluminum chloride produced maximum displacement (0.74 mm), followed by expasyl paste (0.48 mm) whereas magic foam cord produced the least displacement (0.41 mm).6
The results of our study also showed that the marginal adaptation is found in 76% for impressions made by alginate, 45% for impressions made by silicone, 100% for impressions made by polyethers.
These results are consistent with those found by Samet et al where they reported a positive correlation between the impression material and the reproduction of the finish line.7
However, the digital impression provided better marginal fit than the conventional impression.8
According to the study of Mello et al, the conventional method (321 μm) showed greater marginal discrepancy when compared with the computer-aided design (CAD)/computer-aided manufacturing (CAM) system (89 μm) (p<.001).
The marginal adaptation of fixed dental prostheses is influenced not only by the manufacturing technique,10 but also by the restorative material.
In fact, the systematic review of Papadiochou and Pissiotis showed that most of the heat-pressed lithium disilicate
crowns had less marginal discrepancy (MD) values than those produced using a CAD-CAM system. Slip-casting crowns exhibited similar or better marginal accuracy than those fabricated with CAD-CAM. Compared with copy milling, the majority of zirconia restorations produced by CAD-CAM milling elicited better marginal adaptation.11
Within the limitations of this study, it can be concluded that the respect of guidelines of preparation especially the finish line and the good choice of the retraction technique and the material of impression, are the major keys to have a good marginal fit.
The authors declare that they have no conflicts of interest.