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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 7  |  Issue : 1  |  Page : 21-26

Comparative evaluation of the accuracy and efficiency of silicone-based bite-registration record using handheld conventional versus recently introduced powered mixing gun – An in vitro study


Department of Prosthetic Dental Sciences, College of Dentistry, Jazan University, Jazan, Saudi Arabia

Date of Submission05-Nov-2021
Date of Acceptance18-Jan-2022
Date of Web Publication27-Jul-2022

Correspondence Address:
Dr. Mohammed E Sayed
Department of Prosthetic Dental Sciences, College of Dentistry, Jazan University, Jazan
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/KKUJHS.KKUJHS_52_21

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  Abstract 

Purpose: An accurate and functional interocclusal record is very important in restorative dentistry, and any inaccuracies may lead to extensive intraoral adjustments, which can compromise the esthetics and/or mechanical strength of the restorations. The current literature lacks a direct comparison of dimensional accuracy and time efficiency between conventional and powered mixing techniques. The present study compared the accuracy and efficiency of recently introduced powered mixing gun with the conventional handheld gun that was used to mix two silicone-based bite-registration materials. Materials and Methods: A total of 100 bite registrations were recorded on maxillary and mandibular typodont models mounted on a semi-adjustable articulator. Of these, 50 bite registrations were recorded using a handheld conventional mixing gun technique and the other 50 using a handheld powered mixing gun technique. Both types of bite registrations were performed using fast and superfast set bite-registration materials. The dimensional accuracy and time efficiency of both techniques were analyzed and compared. Results: The accuracy and time efficiency of the handheld powered gun mixing technique were significant (P < 0.05) than the conventional mixing technique for fast set bite registration material in vertical distances A1A2 (P = 0.01), B1B2 (P = 0.015), and C1C2 (P = 0.001). However, for horizontal distances AB (P = 0.008) and AC (P = 0.001), accuracy was more significant (P < 0.05) for the superfast set bite registration material compared to the fast set material using the powered mixer. Conclusion: The powered mixing gun technique was more accurate and efficient than the conventional mixing gun technique for recording the bite registration using fast and superfast set materials.

Keywords: Bite registration, fast set and superfast set, inter-occlusal record


How to cite this article:
Sayed ME, Ahmad M, Abdul HN, Ageeli OA, AlShafie T, Alrefaei AM. Comparative evaluation of the accuracy and efficiency of silicone-based bite-registration record using handheld conventional versus recently introduced powered mixing gun – An in vitro study. King Khalid Univ J Health Sci 2022;7:21-6

How to cite this URL:
Sayed ME, Ahmad M, Abdul HN, Ageeli OA, AlShafie T, Alrefaei AM. Comparative evaluation of the accuracy and efficiency of silicone-based bite-registration record using handheld conventional versus recently introduced powered mixing gun – An in vitro study. King Khalid Univ J Health Sci [serial online] 2022 [cited 2022 Oct 2];7:21-6. Available from: https://www.kkujhs.org/text.asp?2022/7/1/21/352524


  Introduction Top


The accurate registration of interocclusal records is a critical clinical step, and any error may lead to extensive intraoral adjustments, which can compromise the esthetics and/or mechanical strength of the restorations.[1],[2],[3],[4] A common problem encountered by technicians in fixed prosthodontics is poor interocclusal records, which may translate to occlusal discrepancies in the final restorations.[5] Such errors are magnified when several teeth are prepared or missing and when the terminal tooth is prepared in a unilateral fixed partial denture due to the lack of 3 point contact and absence of horizontal stability leading to inaccurate mounting of the opposing casts in the articulator.[6]

An interocclusal record should be an accurate and a dimensionally stable representation of the interocclusal space that is subsequently transferred to an articulator.[7] Dental plaster, wax, zinc oxide-eugenol paste, auto-polymerizing acrylic resin, polyether, and polyvinylsiloxane are clinically used for the bite registration procedure.[8] Nonuniform mixing and/or improper handling of the records may lead to the discrepancies in the bite registration record, and ultimately, in the prosthesis.[9] A previous survey that evaluated the communication methods and production techniques used by dentists and dental technicians for the fabrication of fixed prosthesis reported that only 11% of the occlusal records received by dental laboratories were accurate and usable.[10] The accuracy of an interocclusal record is influenced not only by the inherent material properties but also by the recording technique, and mandibular position, which is governed by occlusal contacts, muscular forces, and/or tissue changes in the joints.[11] Apart from the clinical experience and technique followed by the operator, the chosen material can critically affect the accuracy of the interocclusal record.[12]

The current literature lacks a direct comparison of dimensional accuracy between two available bite-registration mixing techniques using two silicone-based bite-registration materials, based on their setting time and ease of fabrication. Therefore, the aim of this in-vitro study was to compare the linear dimensional accuracy and time efficiency of the powered bite registration mixing gun technique with the conventional mixing gun technique with two different silicone based bite-registration materials, selected on the basis of setting time. The null hypothesis was that there would be no differences in vertical or horizontal dimensions and time efficiency between the two bite-registration materials while recording the maxillo-mandibular relationship using the conventional and powered bite registration mixing techniques.


  Materials and Methods Top


Two commercially available addition silicone-based bite registration materials, fast set (Defend, Mydent International, USA, setting time 60 s) and superfast set (Defend, Mydent International, USA, setting time 35 s) bite-registration materials, were evaluated and compared for their dimensional accuracy using a conventional impression mixer (GC dispensing gun, USA) and the recently introduced cordless and powered impression mixer (BFC3 Powered impression gun, Practicon, USA). A total of 100 specimens, 25 specimens for each group (total 4 groups), were fabricated.

Model preparation

Maxillary and mandibular dentulous typodont models (Frasaco, Germany) were mounted at the determined vertical dimension of occlusion on a semi-adjustable articulator (Whipmix Model 2240, USA) to simulate the clinical condition. The maxillary typodont model was mounted using the facebow transfer (Whipmix, Quickmount USA) such that the occlusal plane had a slightly cranial orientation in the posterior region. The mandibular typodont model was mounted in the maximum intercuspation position with the incisal pin touching the incisal guide table at zero inclination. One-millimeter deep indentations were prepared in the mesio-palatal cusps of the maxillary right and left first molars and mid-incisal surface of the left maxillary central incisor [Figure 1] corresponding to the indexing marks A, B, and C. The indentations were made using the 1 mm diameter head round diamond burs. Thus, all the 3 indentations A, B, and C, were standardized. The mounted base of the prepared maxillary and mandibular models was further engraved and fixed with metal double-dowel die pins (BK-Medent, Namgu, Korea) corresponding to three landmarks on the left, right, and anterior sides corresponding to A1, B1, and C1 positions in the maxillary arch and A2, B2, and C2 in the mandibular counterpart [Figure 2]. The anterior die pins were fixed between the central incisors, while the posterior die pins were fixed between the first and second molars on the left and right sides in both arches.
Figure 1: Prepared landmark on maxillary first molars and left central incisor

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Figure 2: Mounted maxillary and mandibular typodont models with dowel pins corresponding to A1, A2, B1, B2, C1, C2 landmarks

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Preparation of the specimens

The two types of bite registration material cartridges were loaded alternatively on handheld conventional and powered impression mixing guns. The plastic cap was removed from the cartridge and a small amount was dispensed to ensure an even presence of the product in the barrel and absence of plugging. A mixing tip was attached and fixed to the cartridges with 90° rotation as recommended. The interocclusal records were obtained using the fast set (Defend, Mydent International, USA) and superfast set (Defend, Mydent International, USA) bite-registration materials. The mixing tips used in the study were from the same manufacturer as recommended for mixing silicone-based bite registration material. When the trigger of the conventional dispensing gun was squeezed, the material in the cartridge mixed and flowed through the mixer. The mixing tip of the cartridge was kept in direct contact with the tray. The bite-registration material was applied on the occlusal surface of the mandibular arch followed by the maxillary arch of the full-arch bite-registration disposable triple tray (House Band, USA). During the registration of the interocclusal record, the articulator was closed, and a standard weight of 39.2 N (approximately 4 kg) was placed on its upper arm to simulate the application of masticatory load on the occlusal surface in clinical settings. This force was applied for the registration of all interocclusal records. The registration was completed in the working time of 30 s for the fast set and 25 s for the superfast set material, according to the manufacturer's guidelines. The setting time for the fast set material was 1 minute, while it was 35 s for the superfast set material. The time intervals from loading both sides of the bite trays to positioning and pin closure were recorded using a stopwatch by a blinded investigator. When the material was completely set, the bite record was removed in an axial direction without any rocking motion. The mixing tip was retained in place on the cartridge to provide a seal for the remaining material in the cartridge. Before recording the next registration, the old mixing tip was removed and discarded, and a new mixing tip was attached. The same procedure was followed for each registration with the handheld conventional and powered impression mixing guns. The records were trimmed with the B.P. blade in such that the excess material extending from the maxillary teeth was cut, and only the imprints of the cusp tips were retained. Similarly, the facial part of the mandibular buccal cusp tips was cut all the way to the posterior part of the tray and was discarded. For standardization, the specimens were labeled and stored at room temperature for 24 h to simulate the time between the clinical and laboratory phases.

Testing of specimens

Before recording the bite registration, the linear vertical distances between the reference points, A1A2, B1B2, and C1C2 (center of the metal dowel pins), were measured on the typodont models mounted on a semi-adjustable articulator using a Vernier caliper (Ati Digital 8/20, Korea) by a calibrated and blinded investigator [Figure 3]. After 24 h, each bite record, fabricated with fast set and superfast set bite registration materials using handheld conventional and powered mixing techniques, were placed on the mounted typodont models, and the distances A1A2, B1B2, and C1C2 were measured again and tabulated [Figure 4]. To measure the horizontal linear dimensional changes, the distances between the engraved reference points in the maxillary typodont models, AB, BC, and AC, were measured under a stereomicroscope with a connected USB CCD camera (Amscope, Irvine, California, USA) following calibration. After obtaining the bite records in all four groups, the distances between AB, BC, and AC were measured under the same stereomicroscope following calibration and data were tabulated. Each bite record was placed on the platform of the stereomicroscope using a reference putty index [Figure 5]. The reference putty index was used to place the bite trays in the same position on the platform of the stereomicroscope. The images were obtained and analyzed using specific software by measuring the metric distance between the engraved landmarks on the bite records.
Figure 3: Vertical measurement without bite record

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Figure 4: Vertical measurement with the bite record after 24 h

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Figure 5: Image of the bite record inserted with calibrated putty index under the stereomicroscope for measuring horizontal distance AB, BC, and AC

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Data analysis

The vertical distances between the points A1A2, B1B2, and C1C2 and horizontal distances between points AB, BC, and AC were entered into a Microsoft Excel Spreadsheet (Microsoft Inc., Redmond, WA). Student's t-test (unpaired) was used to analyze the vertical distances between the points A1A2, B1B2, and C1C2 and the horizontal distances between points AB, BC, and AC to compare variations between standard measurements and study groups, and between study groups themselves. All data were analyzed using SPSS 20 Statistics Software, and α was set at a 5% level of significance.


  Results Top


The statistical evaluations for the dimensional accuracy of bite registrations recorded using the two selected addition silicone bite-registration materials with two different mixing techniques are shown in [Table 1], [Table 2], [Table 3] and plotted in [Graph 1], [Graph 2], [Graph 3]. Descriptive data included the mean and standard deviation values of all variables for both groups. The findings of the study showed that for the fast set bite registration material, the vertical distances A1A2 (P = 0.01), B1B2 (P = 0.015), and C1C2 (P = 0.001) were significant (P < 0.05) for the handheld conventional and powered mixing gun techniques [Table 1]. However, the vertical distance was significant (P < 0.05) only in distance C1C2 (P = 0.014) for the superfast set bite registration material using the conventional handheld and powered mixing gun techniques. The differences from the standard measurements for the fast set and superfast set material using both mixing techniques for vertical distances A1A2, B1B2, and C1C2 are depicted in [Graph 1].
Table 1: Comparison of linear vertical distances A1A2, B1B2, and C1C2 for handheld conventional mixing technique (H) and powered gun mixing technique (P) for fast set and superfast set bite registration materials

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Table 2: Comparison of linear horizontal distances AB, BC, and AC for handheld conventional mixing technique (H) and powered gun mixing technique (P) for fast set and superfast set bite registration materials

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Table 3: Mean time for handheld conventional mixing technique (H) and powered gun mixing technique (P) for fast set and superfast set bite registration materials

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The second part of the study aimed to verify the accuracy of recording the horizontal distances AB, BC, and AC. For the fast set bite registration material using the handheld conventional and powered mixing gun techniques, the horizontal distance AC was significant (P = 0.002) [Table 2]. For the superfast set bite material, distances AB (P = 0.008) and AC (P = 0.001) were significant (P < 0.05) for both mixing techniques, as shown in [Table 2]. The differences from the standard measurements for fast set and superfast set materials using the conventional and powered techniques for horizontal distances AB, BC, and AC are depicted in [Graph 2].

This study also compared the time required for recording bite registrations using the handheld conventional and powered mixing gun techniques. The results showed that the mean time interval required for loading both sides of the bite trays to positioning and pin closure by both techniques were highly significant (P < 0.05). The mean time for the powered gun technique was 26.57 s for fast set and 24.17 s for superfast set bite registration materials. However, the mean time was 46.09 seconds for fast set and 37.57 seconds for superfast set material using the conventional gun technique [Table 3] and [Graph 3].


  Discussion Top


In this study, the accuracy of two additional silicone-based bite registration materials was assessed because they are easy to manipulate and offer little or no resistance to closure. In addition, after polymerization, they can be trimmed easily without distortion and can accurately reproduce the anatomical details. A recent study reported that the setting properties, including the final hardness, may affect the clinical performance of the interocclusal recording materials.[13] The present in vitro study compared the two different fast set and superfast set silicone-based bite registration materials. Unlike regular impression silicone, these materials show greater stiffness and hardness (32–45 Shore D). It exhibits a faster setting time, which is important to reduce the errors caused by the movement of the mandible and to reduce patient discomfort. It does not deflect the mandible from the intercuspal position due to its greater stiffness and hardness.

The discrepancies caused by interocclusal records can occur both in vertical and horizontal directions, which have not been measured in any previous study for fast set and superfast set bite registration materials using two bite registration mixing gun techniques. The findings of the study showed that for the fast set bite registration material, the vertical distances A1A2 (P = 0.01), B1B2 (P = 0.015), and C1C2 (P = 0.001) were significant (P < 0.05) for the handheld conventional and powered mixing gun techniques [Table 1]. However, it was significant (P < 0.05) only for the distance C1C2 (P = 0.014) for the superfast set bite registration material.

The second part of the study verified the accuracy of horizontal distances AB, BC, and AC for fast set and superfast set bite registration materials using the two mixing techniques. For the fast set bite registration material using both mixing gun techniques, the horizontal distance AC was significant [Table 2], and for the superfast set bite registration material, distances AB and AC were significant for the conventional and powered mixing gun techniques, as tabulated in [Table 2]. The negative difference from the standard values showed that the readings observed were below acceptable standards. This could be explained by the inherent characteristic of polymerization shrinkage in the material. The number of specimens was equal to that in previous studies. The null hypothesis was partially rejected because there was a significant discrepancy from the standard horizontal measurement (AC distance) between both bite registration materials. However, measuring the distances between AB and BC revealed no significant differences from the standard distances between both bite registration materials.

All study procedures were conducted at room temperature of approximately 23°C to simulate the fabrication procedures of dental prostheses in the dental laboratory. The interocclusal records were not disinfected to reduce the steps in the experiment, which may have influenced the results. However, it has been reported that the effects of immersion disinfection procedures on the dimensional stability and surface hardness of elastomeric materials are not clinically relevant.[14],[15] Nonetheless, the dimensional stability of the record after storage seems to be of clinical interest because casts cannot be mounted immediately after recording maxillo-mandibular relationships. While comparing the time intervals of recording the interocclusal relationship by the conventional and powered mixing gun techniques, the results showed that the mean time required for the powered gun technique was highly significant [P < 0.05; [Table 3] and [Graph 3]]. The mean times required for the fast set and superfast set bite registration materials by the powered gun technique were 26.5 s and 24.1 s, respectively, which are well within the manufacturer's guidelines. However, for the conventional bite-registration technique, the mean time required to handle the fast set bite registration material was 46 s and the superfast set material was 37.5 s [Graph 3], which are beyond the guidelines recommended by the manufacturer. This delay in handling of the bite registration material by the conventional mixing gun technique as well as polymerization shrinkage of the material may lead to dimensional inaccuracies. The results of this study indicated that powered mixing is superior to conventional mixing in terms of accuracy and time efficiency. Although previous studies have not evaluated powered mixing in terms of dimensional accuracy, however, a common consensus of higher preference and better surface characteristics were seen in powered mixing when compared to traditional mixing methods.[16],[17] Higher preference and willingness to recommend powered technique to colleagues might be explained by higher satisfaction among users as a result of convenience and lesser operator's hand fatigue when compared to conventional mixing technique.

The motorized powered gun is convenient, portable, ergonomic, and rechargeable. Recording a bite registration is easier and faster than the conventional handheld impression gun. No repetitive trigger presses are required similar to the conventional handheld mixer, which could strain the hands while squeezing the material and loading into the tray. Another advantage is that powered guns have auto-reverse anti-drip and auto-stop with overload protection controls when the cartridge is empty. Among the operator-related factors, one should mention the mixing technique at the chair side, the loading of the material into the tray, as well as its injection around the teeth. In the present study, the impact of the mixing procedure on the resulting dimensional accuracy has been addressed, confirming that the powered mixing technique leads to a more accurate bite registration. One of the possible limitations of this study could be the measurement of the three-dimensional accuracy of the different bite registration materials using the coordinate measuring technology.


  Conclusion Top


The choice of the interocclusal bite-registration material and technique of recording bite registration should be based on dimensional accuracy, clinical performance, convenience, patient comfort, and speed. The powered gun mixing technique for recording bite registration is more accurate and time efficient than the conventional mixing technique for recording the bite registration using fast and superfast set materials.

Financial support and sponsorship

This study was funded by Jazan University under the “Seventh Future Scientist Research Program.”

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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