|Year : 2013 | Volume
| Issue : 6 | Page : 730-735
|Comparative study to evaluate the accuracy of polyether occlusal bite registration material and occlusal registration wax as a guide for occlusal reduction during tooth preparation
Niranjan Joshi1, Sridhar N Shetty2, Krishna D Prasad1
1 Departments of Prosthodontics, A.B. Shetty Memorial Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Deralakatte, India
2 Departments of Prosthodontics, A.B. Shetty Memorial Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Deralakatte; Department of Prosthodontics and Center for Advanced Dentofacial and Stomatognathic System, A.B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India
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|Date of Submission||07-Jan-2011|
|Date of Decision||16-May-2013|
|Date of Acceptance||25-Jun-2013|
|Date of Web Publication||20-Feb-2014|
| Abstract|| |
Introduction: The use of different materials and techniques has been studied to decide the safest quantum of reduction of the occlusal surfaces. However, these methods provide limited information as to the actual amount of reduction with limitations in accuracy, accessibility and complexity.
Objective: The objective of this study was to compare and evaluate the reliability of the most commonly used occlusal registration wax that with polyether bite registration material as a guide for occlusal reduction required during tooth preparations.
Materials and Methods: For the purpose of this study, 25 abutment teeth requiring tooth preparation for fixed prosthesis were selected and tooth preparations carried out. Modeling wax strips of specific dimensions were placed onto the cast of prepared tooth, which was mounted on maximum intercuspation on the articulator and the articulator was closed. The thickness of the wax registration was measured at three zones namely two functional cusps and central fossa. Similar measurements were made using the polyether bite registration material and prosthesis at the same zones. The data was tabulated and was subjected to statistical analysis using anova test and Tukey honestly significant difference test.
Results: The differences in thickness between wax record and prosthesis by 0.1346 mm, whereas the difference between polyether and prosthesis was 0.02 mm with a P value of 0.042, which is statistically significant. This means that the wax record was 8.25% larger than the prosthesis while polyether was just 1.27% larger than the prosthesis.
Conclusion: The clinical significance of the above analysis is that Ramitec polyether bite registration material is most suitable material when compared with commonly used modeling wax during the tooth preparation.
Keywords: Occlusal reduction, occlusal registration material, occlusal registration wax, polyether bite registration material
|How to cite this article:|
Joshi N, Shetty SN, Prasad KD. Comparative study to evaluate the accuracy of polyether occlusal bite registration material and occlusal registration wax as a guide for occlusal reduction during tooth preparation. Indian J Dent Res 2013;24:730-5
Occlusal reduction of abutment teeth is an essential step in tooth preparation. One of the principles of tooth preparations is to conserve tooth material without compromising the occlusal morphology. The restored teeth have to articulate with opposing teeth to function harmoniously.
|How to cite this URL:|
Joshi N, Shetty SN, Prasad KD. Comparative study to evaluate the accuracy of polyether occlusal bite registration material and occlusal registration wax as a guide for occlusal reduction during tooth preparation. Indian J Dent Res [serial online] 2013 [cited 2019 Nov 20];24:730-5. Available from: http://www.ijdr.in/text.asp?2013/24/6/730/127622
When preparing teeth for fixed restorations, it is crucial to have the proper amount of occlusal reduction to ensure the long-term success of restorations.  Insufficient occlusal reduction of a tooth may result in failure due to lack of adequate thickness of the restoration.  Excessive tooth reduction may compromise the retention of the restoration or vitality of the pulp. 
To estimate and guide during occlusal reduction, a clinical procedure are being carried out by using a material in plastic form, which sets and hardens quickly. This facilitates to estimate as well as a guide for the quantum of tooth reduction.
The use of many materials and techniques has been studied to guide and decide the safest quantum of reduction of the occlusal surfaces. Use of materials such as folded blotting paper,  color coded flexible clearance tabs with premeasured thickness,  soft ribbon wax  and occlusal registration silicone  has been documented for the same. The use of caliper to measure the thickness of the occluded wax record, base plate wax of premeasured thickness with an articulating paper have also been used. 
| Objective|| |
To compare and to evaluate the reliability of the most commonly used occlusal registration wax that with polyether bite registration material as a guide for occlusal reduction required during tooth preparations.
| Materials and Methods|| |
Source of data
Subjects in this study were selected and consented for treatment with fixed prosthesis. It involved 11 patients with 2 posterior abutments and one patient with three posterior abutments so as to reach a total number of 25 posterior abutments.
Criteria for inclusion
- Patients requiring posterior full coverage fixed partial dentures
- Patients in whom the abutment teeth display good anatomical contours
- Patients with unrestored opposing natural teeth against the teeth to be prepared
- Patients where maximum intercuspation position can be reliably and repeatedly reproduced.
Criteria for exclusion
- Patients with poor neuromuscular control
- Patients with severe attrition
- Patients with severe misaligned teeth
- Patients having supraerupted opposing teeth
- Patients with terminal abutments involved in the prosthesis design.
- Modeling wax (Hindustan modeling wax)
- Ramitec™ (Polyether Bite Registration Material, 3M ESPE)
- Final prosthesis.
- Mounted and articulated casts of the prepared teeth on a Hanau Wide Vue articulator
- Rubber bowl
- Mixing pad
- Mixing spatula
- Lacrons' carver
- Wax gauge (Essago SBC German stainless)
- Metal gauge (Essago SBC German stainless).
Collection of data
Basic principles of tooth preparations were followed in all tooth reductions.
Impressions were made using polyvinyl siloxane impression material and casts poured in type IV dental stone following manufacturers' instructions.
The maxillary cast was secured on a semi-adjustable articulator after recording sagittal relation and transferring it on the articulator. The mandibular cast was mounted in maximum intercuspation position with the central pin touching the incisal guide plane at zero.
Modeling wax (type II) of thickness 1.5 mm was made into strips of 30 × 10 mm. Two such strips are kept over each other. Wax strips were softened uniformly in a water bath at a temperature of 45°C and were placed onto the cast of the prepared tooth mounted on the articulator. The upper member of the articulator is closed completely so that the center pin of the articulator is in touch with the incisal guide table [Figure 1].
Once the wax is hardened to the room temperature, the articulator was opened and the wax record was removed.
The thickness of the wax registration was measured at three zones namely at the two functional cusps (mesial and distal) and at the central fossa, with the watx measuring gauge (Essago SBC German stainless . Such three measurements were carried out for standardization [Figure 2].
|Figure 2: Thickness measured with a round ended wax caliper (Essago SBC German stainless)|
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Same experiments were repeated by using the polyether occlusal registration material.
Occlcusal registration material (Ramitec, 3MESPE) was mixed according to manufacturer's instructions, loaded into a syringe and injected over the prepared teeth mounted on articulator and the articulator was closed [Figure 3]. After the material was set, it was removed and the thickness of the material at three different already selected zones were measured [Figure 4].
|Figure 4: Thickness measured with a round ended wax caliper (Essago SBC German stainless)|
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Conventional protocol is followed in laboratory procedures and prosthesis is obtained for cementation.
The prosthesis was then seated on the cast, mounted on the articulator and the intercuspation is adjusted and checked by the central pin contact to the incisal guide table.
The thickness of the prosthesis was then measured in the above mentioned three selected zones and such measurements were repeated 3 times for standardization [Figure 5].
|Figure 5: Thickness of the prosthesis measured with a sharp ended metal gauge (Essago SBC German stainless)|
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Data thus collected were tabulated and analyzed. The statistical analysis was carried out using SPSS version 15.0 and Microsoft Excel software IBM corporation. A value of P < 0.05 was considered statistically significant.
| Results|| |
- In Zone I, the difference in thicknesses between wax record and prosthesis by 0.140 mm (P = 0.311), whereas the difference between Ramitec and prosthesis was 0.024 mm (P = 0.966), which was statistically not significant (P > 0.05)
- In Zone II, the difference in thicknesses between wax record and prosthesis by 0.108 mm (P = 0.566), whereas the difference between Ramitec and prosthesis was 0.02 mm (P = 0.988), which was statistically not significant (P > 0.05)
- In Zone III, the difference in thicknesses between wax record and prosthesis by 0.156 mm (P = 0.237), whereas the difference between Ramitec and prosthesis was 0.016 mm (P = 0.985), which was statistically not significant (P > 0.05)
- The mean difference for collective thicknesses (n = 75) between wax record and prosthesis was 0.1346 mm (P = 0.05) whereas the difference between Ramitec and prosthesis was 0.02 mm (P = 0.935) with the earlier being statistically significant (P < 0.05).
| Discussion|| |
Establishing a functional occlusion is a primary goal in restorative dentistry for all Prosthodontists. Premature contacts, interferences of cusps, over or under reduction in tooth preparations are the few reasons of failure of restorations. One of the objectives in all restorations is to provide sufficient material thickness. It is necessary for every operator to estimate and establish, during tooth preparation, the thickness of the selected material used for restoration.
Conservation of tooth structure is a vital part of restorative dentistry. It is often required in prosthodontics that teeth be reduced for creating space for the restoration. This reduction is usually accomplished by means of abrasive instruments rotating at a very high speed like rotary diamonds. Since tooth structure removal with these instruments is very rapid, extreme care has to be taken to prevent over reduction and injury to the pulp. Different materials are used for fabricating these restorations such as metal, porcelain fused to metal or all porcelain. These materials require minimum thickness to fulfill the mechanical requirements. If the thickness of these materials is inadequate there is an increased likelihood of prosthesis failure by attrition and fracture under the mechanical stress. Structural durability is stated to be an important principle of tooth preparation. A restoration must also contain a bulk of material that is adequate to withstand the forces of occlusion. This bulk must be confined to the space created by the tooth preparation. Only in this way can the occlusion on the restoration be harmonious and the axial contours normal, preventing periodontal problems around the restoration. 
The clearance required for different materials is different. For metal crowns, there should be a clearance of 1.5 mm on the functional cusps and 1.0 mm on the non-functional cusps. For metal ceramic crowns, a clearance of 1.5-2.0 mm on the functional cusps and 1.0-1.5 mm on the non-functional cusps is deemed necessary. For all ceramic crowns, the clearance required is 2.0 mm. 
The basic inclined plane pattern of the occlusal surface should be duplicated to produce adequate clearance without over shortening the preparation. A flat occlusal surface may over shorten a preparation whose length is already minimal to provide adequate retention. Inadequate clearance makes the restoration weaker. In addition, inadequate reduction under the anatomic grooves of the occlusal surface will not provide adequate space to allow good functional morphology. The restoration will also be readily perforated by finishing procedures or by wear in the mouth. 
The tooth reduction and occlusal clearance being very critical, different materials and techniques have been clinically tried to take guidance to establish adequate space for the restorative material and for establishing harmonious functional occlusion.
Waxes expand when subjected to a rise in temperature and contract as the temperature is decreased. This fundamental property may be altered slightly when various waxes are blended, but the response to thermal changes cannot be reduced to negligible values. The expansion and contraction of dental waxes with changes in temperature are pronounced. In general, dental waxes and their components have the largest coefficient of thermal expansion of any material used in restorative dentistry. 
Addition silicones and polyethers have been formulated for use as bite registration materials. They are also noted for their high stiffness, indicated by the low percent strain in compression and for their low flow and dimensional change even after 7 days. 
This study was undertaken with the objective of comparing the accuracy between the most commonly used material modeling wax and polyether bite registration material to be used as a guide for determining the occlusal clearance during the tooth preparation.
Thickness of the wax record and polyether material were compared with the thickness of the prosthesis in two functional cusp zones and central fossa region.
The results show that wax record mean value was 0.156 mm (10.5%) thicker in central fossa zone, 0.014 mm (8.49%) thicker in mesial functional cusp zone and 0.108 mm (6.73%) thicker in distal functional cusp zone; whereas Ramitec polyether registration material mean value was only 0.016 mm (1.08%) thicker in central fossa zone, 0.024 mm (1.45%) thicker in mesial functional cusp zone and 0.020 mm (1.24%) thicker in distal functional cusp zone than the finished prosthesis [Table 1] and [Table 2] and Graph 1].
|Table 1: Mean and standard deviation of thickness of the various zones with respect to materials namely wax record, polyether bite registration material (Ramitec) and prosthesis and their statistical analysis with ANOVA test |
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|Table 2: Mean difference within the three variables in Zone I, Zone II and Zone III and their statistical analysis using Tukey HSD test |
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From this inference can be drawn that use of Ramitec polyether registration material has better accuracy than wax registration material. However on statistical analysis, this difference in thickness between wax registration and Ramitec in individual three zones was statistically not significant.
When we are discussing about the requirement of thickness of the restorative material to the range of 1.0-2.0 mm, the above percentage of discrepancy between wax and Ramitec can be very critical though the statistical test reveal they are not significant.
Hence, further analysis was carried out by combining the values of all the three zones resulting in 75 samples to verify whether these discrepancies have any significance.
On combining the three zones and analyzing the results, the wax registration has shown to be mean 0.1347 mm (8.25%) thicker than the prosthesis whereas Ramitec polyether registration material was mean 0.020 mm (1.27%) thicker than the finished prosthesis [Table 3] and [Table 4] and Graphs 2 and 3].
|Table 3: Mean and standard deviation of the cumulative thickness of wax record, Ramitec and prosthesis in all zones combined, the minimum and maximum thicknesses of each and their statistical analysis using ANOVA test |
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|Table 4: Mean difference between the cumulative thicknesses of wax record, Ramitec and prosthesis and their statistical analysis with Tukey HSD test |
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On statistical analysis of this data using anova test, a P value of 0.042 was obtained, which indicates that the difference is statistically significant (P < 0.05).
When subjected to Tukey honestly significant difference test it showed that the difference of the mean value of 0.1347 mm (8.25%) between wax record and prosthesis had a P value of 0.05, which is statistically significant (P < 0.05).
Moreover, the mean difference of 0.020 mm (1.27%) between Ramitec polyether registration material and prosthesis had a P value of 0.935, which is statistically not significant (P > 0.05).
The Ramitec polyether bite registration material is more reliable material to be used than modeling wax to evaluate clearance requirement during the tooth preparation.
Since a similar study of this kind has not been documented, future investigation is suggested on a larger sample size in order to obtain data with the use of other materials available for bite registration. Furthermore, this study was conducted on articulated casts using a semi-adjustable articulator and in centric record only. Further studies can be performed in vivo and using eccentric records as well.
| Conclusion|| |
On combination of all the three zones it has shown a statistically significant difference between the thickness of the wax record and the prosthesis while the difference between the thickness of Ramitec polyether bite registration material and prosthesis was not statistically significant. Hence, an inference can be drawn that Ramitec polyether bite registration material is most suitable material when compared with commonly used modeling wax during the tooth preparation.
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Departments of Prosthodontics, A.B. Shetty Memorial Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Deralakatte
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]
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