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ORIGINAL ARTICLE
Year : 2021  |  Volume : 12  |  Issue : 4  |  Page : 204-209

Digital occlusal analysis of bite force distribution in partially edentulous patients before and after prosthetic rehabilitation: An in vivo study


Department of Prosthodontics, Crown and Bridge and Implantology, D.A.P.M.R.V Dental College and Hospital, Bengaluru, Karnataka, India

Date of Submission14-Sep-2021
Date of Decision29-Nov-2021
Date of Acceptance01-Dec-2021
Date of Web Publication20-Dec-2021

Correspondence Address:
Dr. Liza Rahman
D.A.P.M.R.V Dental College and Hospital, CA-37, 24th Main, JP Nagar, ITI Layout, 1st Phase, Bengaluru – 560 078, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/srmjrds.srmjrds_99_20

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  Abstract 


Background: The measurement of bite force can provide useful data for the evaluation of jaw muscle function and activity. Technological advances in signal detection and processing have improved the quality of the information extracted from bite force measurements. Aim: The current study aimed to evaluate the percentage of bite force distribution before rehabilitating in partially edentulous patients rehabilitated with removable partial dentures (RPDs) and fixed partial dentures (FPDs) and change in the force after equilibration. Materials and Methods: 15 patients with partially edentulous ridges (Kennedy class III) along with missing mandibular first molars who met the inclusion and exclusion criteria were selected. Bite force distribution was evaluated with an intraoral sensor and Tek-scan equipment preoperatively, postoperatively after the fabrication of removable prosthesis, after the fabrication of fixed prosthesis and after equilibration. The results were tabulated and statistically analyzed using student paired t-test and ANOVA. Results: The net bite force distribution in the edentulous sextant preoperatively was 36.32 ± 5.98, postreplacement of the tooth with a removable replacement as 42.56 ± 3.37 and fixed replacement was 46.96 ± 2.86. On the contralateral sextant, the bite force distribution measured preoperatively was 63.68 ± 5.98, after a removable prosthesis was 57.44 ± 3.37, after FPD was 53.04 ± 2.86, and post equilibration was 51.15 ± 1.73. Conclusion: The bite force distribution produced by a FPD was more evenly distributed than the force produced by a RPD. The findings of the current study prove the fact that the equalization of bite force distributions is better in case of fixed prosthesis replacement.

Keywords: Bite force, equalization, fixed partial denture, removable partial denture, t scan


How to cite this article:
Rahman L, Kumar P R, Kalavathy N, Shetty M, Sanketh AK, Roopa M. Digital occlusal analysis of bite force distribution in partially edentulous patients before and after prosthetic rehabilitation: An in vivo study. SRM J Res Dent Sci 2021;12:204-9

How to cite this URL:
Rahman L, Kumar P R, Kalavathy N, Shetty M, Sanketh AK, Roopa M. Digital occlusal analysis of bite force distribution in partially edentulous patients before and after prosthetic rehabilitation: An in vivo study. SRM J Res Dent Sci [serial online] 2021 [cited 2022 May 17];12:204-9. Available from: https://www.srmjrds.in/text.asp?2021/12/4/204/332899




  Introduction Top


Replacement of missing teeth is an art that has its foundation laid on the prosthodontics principles of restoring the form, function, and esthetics in an individual. The primary goal of prosthetic therapy is not only to replace lost teeth but also to rehabilitate the patient's occlusion. Replacement of missing teeth contributes to providing adequate masticatory efficiency, improving phonetic and esthetic function, which in turn improves the quality of life of our patients.[1] However, prosthetic rehabilitation can often be complicated and challenging to accomplish with so many factors into consideration in replacement of missing teeth from the extent of the edentulous space, health of the abutment, and remaining teeth to the patient's oral hygiene maintenance. Among the considerations, key feature is the existing occlusion of the patient.[2]

When it comes to replacing missing teeth, prosthetic options are numerous and there can be multiple approaches. On a generic classification, edentulous spaces can be restored with removable and fixed options.[3] Each of these different restorative protocols are governed by the key factor of occlusion. Every situation demands a complete occlusal analysis and determination of the factors that need to be taken care of while rehabilitation of patients.[4]

To assess the masticatory efficiency, bite force values act as a valuable indicator in studying the functional state of the masticatory system. Masticatory efficiency is a combination of bite force and occlusal contact area and studies suggest that, higher the bite force and the larger the occlusal areas, the more efficient is the mastication. The devices available to evaluate bite force include conventional portable hydraulic pressure gauges, bite forks, force sensing resistors, strain gauge transducers, pressurized rubber tube to the recent advancements with the advent of computers and digitization including foil transducers, pressure-sensitive sheets and the gnathodynamometers, examine occlusal contacts and muscle function.[5]

The most recent advent in helping and easing the work of a dentist to assess occlusion and masticatory performance is the Tek-scan (T-scan). T-Scan quantifies the amount of relative occlusal force, which enables us to predictably identify and to locate traumatic occlusal contacts. The T-Scan III Computerized Occlusal Analysis System offers precision technology that analyses occlusal contact force and time sequences in 0.003-s increments and graphically displays them in movie form.[6] The system simplifies occlusal adjustments at prosthesis insertion, as it quickly isolates excessive force concentrations and time-premature contacts, so their eradication is predictable and effective. This study is an effort to evaluate the percentage of bite force distribution before rehabilitating in partially edentulous patients rehabilitated with removable partial dentures (RPDs) and fixed partial dentures (FPDs) is and change in the force after equilibration.


  Materials and Methods Top


The subjects selected for the study were the patients who visited the outpatient Department of Prosthodontics, D. A. Pandu Memorial R. V. Dental College. The study was approved by the institutional ethics committee (ethical clearance no-256/vol-2/2017). All the participants provided written informed consent for the participation in the study. All procedures performed in the study were conducted in accordance with the ethical standards given in 1964 Declaration of Helsinki, as revised in 2013. The inclusion into the study comprised of the following criteria: patients between 22 and 55 years of age, partially edentulous Kennedy class III specifically missing only the mandibular first molar, angle's class 1 molar relation while replacing mandibular tooth, mutually protected occlusion scheme, optimum clearance, and optimum crown root ratio and complying with the study protocol. Subjects were excluded if abutments were periodontally compromised, attrited or tilted abutments, inadequate crown root ratio and bone loss around abutment teeth, parafunctional habits and diminished neuromuscular control, presence of any prosthetic replacements on posterior teeth, and loss of vertical dimension. 15 patients met the inclusion criteria and were informed about the treatment protocol.

Measurement of force distribution

All preprosthetic treatments were completed before exposure to the occlusal scan. The T scan III (Tekscan Inc., South Boston, MA, USA) was used to evaluate the percentage of bite force distribution in the patients. The recording sensor, which comes with the system, consists of two layers of conductive grid encased into highly pressure-sensitive plastic foil. It is U-shaped as one of its parts goes into a scanning handlebar and the other one, dental arch-shaped, registers the occlusal and articulation relations [Figure 1]. The bite force distribution was evaluated at four levels as shown in the [Figure 2]. The recording procedure is performed in strict conformity with the manufacturer's instructions of using the device to register occlusal contacts. The recorded data were tabulated for future comparison.
Figure 1: Image depicting the recording sensor of T scan III

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Figure 2: Flowchart depicting the evaluation of bite force distribution

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Removable partial denture fabrication

An alginate impression of both dental arches in stock metal trays was made and a dental stone cast was poured. The RPD was fabricated with angle's class 1 molar occlusion with heat cure acrylic denture base material denture base resin based on standardized protocol. After 1 week, the patient was subjected to the occlusal scan using the T scan using the same protocol mentioned in the previous section. Bite forces distribution was recorded and tabulated for future comparison.

Fixed partial denture fabrication

Tooth preparation will be based on principles of the tooth preparation by Shillingburg et al.[7] The FPD (porcelain fused to metal crowns) was fabricated with metal copings made from Ni-Cr alloy (Bellabond plus, Bego, Germany) and layering of Porcelain (VITAVMK Master, Vita Zahnfabrik, Bad Sackingen). The fabricated crowns were checked for occlusal interferences on the articulator and necessary corrections was made [Figure 3]. Before the cementation, the occlusal interferences was checked and corrected in the oral cavity as well. Again after 1 week of cementation, the patient was then again subjected to the T scan to evaluate occlusal force using the same procedure mentioned in the previous section. Percentage of bite force distribution were recorded and compared with the both the side, i.e., dentulous and edentulous side. Moreover, if any un even distribution of forces were noticed, it was corrected to achieve equilibrium of forces.
Figure 3: (a)Preoperativeimage(b)Postoperativeimageafterthefabricationofremovableprosthesis(c)Postoperativeimageafterthefabricationoffixedprosthesis

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Statistical analysis

Student paired t-test was used to compare the mean bite force between before and after prosthetic treatment and ANOVA test was used to compare between different prosthetic treatments. The level of significance will be set at P < 0.05.


  Results Top


Total number of subjects included in the study was 15. The mean age of the study subjects was 38.53 ± 11.92. Among the 15 subjects, 5 (33.3%) and 10 (66.7%) were males and females, respectively. The rehabilitation was carried out in 7 (46.7%) and 8 (53.3%) study subjects on the right and left edentulous side, respectively.

[Table 1] shows the percentage change in the variables between the edentulous/corrected side and dentulous side. All the measured variables among the study subjects had a percentage increase when the edentulous and dentulous sides were compared. The highest % increase was seen for the preoperative force (56.44%), followed by force with RPD (52.04%), force with FPD (50.15%), and force with corrected occlusion (62.68%).
Table 1: Comparison between the variables on the dentulous and edentulous side (per quadrant)

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[Table 2] shows the percentage change in the variables between the edentulous and dentulous side (arch section). The highest % increase was seen for the preoperative force (61.31), followed by force with RPD (56.3%), force with FPD (51.52%), and force with corrected occlusal (52.14%). [Table 3] shows the percentage change in the variables between prosthesis.
Table 2: Percentagechangeinthevariablesbetweentheedentulous and dentulous side (arch section)

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Table 3: Percentagechangeinthevariablesbetweenprosthesis

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  Discussion Top


Loss of teeth is a painful process not only during exodontia procedures but also the aftermath that comes out of it. Drifting of teeth, loss of masticatory efficiency, depletion of muscle tone, and bone around the missing tooth are a few to be named. Bortoluzzi MC et al.[8] reported that the efficacy of chewing, mastication and the overall quality of life was impacted by the loss of teeth. The authors stated that chewing disability produces a significant and negative impact over oral health-related quality of life and chewing disability is related with the decrease of the number of natural teeth.

Replacement of missing teeth comes with an array of options ranging from removable dentures to fixed bridges and implant-retained prostheses. The current trend in replacement of missing teeth is shifting toward fixed options taking into consideration of quality of life of the patient.[9] Fixed restorations are being preferred more due to its comfort and ease in maintenance. Furthermore, masticatory comfort and chewing efficiency have proven to be better subjectively with fixed prostheses. However, the amount of bite force that produced by a removable prosthesis and a fixed prosthesis has always been a un answered question. The current study was undertaken to determine the changes in force distribution that occurs in the oral cavity due to a missing tooth and the effect of different prosthesis in restoring a harmonious occlusal force.

Despite the evolution of computer technology and the era of modern dental materials, we still come across a routine use of traditional methods in cases of occlusion analysis. Although most dentists stress the importance of occlusion, the highest percentage of occlusal contacts evaluation is still based on articulation paper, wax, and silicone tables.[10],[11],[12] The T-Scan III Computerized Occlusal Analysis System (Tekscan Inc., South Boston, MA USA) exceeds the limitations of using articulation paper.[13] It provides analysis of relative occlusal forces that are recorded using the intraoral pressure sensor and displays occlusal forces to minimize the possibility of repeating mistakes when occlusion is examined by articulation paper and it depends on the subjective feelings of the patient.

The T-Scan III system enables static and dynamic digital analysis of occlusion in unit time and recording of the distribution of occlusal forces in dental arches in different clinical situations. T-Scan III analyses the occlusal contacts simultaneously, from the moment of the first occlusal contact until the maximum intercuspidation, giving us a view of initial occlusal contacts, the order in which they appear and the amount of relative occlusal forces, which allows us to identify and locate any traumatic occlusal contacts. The T-ScanIII helps us to measurably adjust and create a balanced force distribution between the left and right arch halves and the anterior and posterior quadrants. “Force mapping” is a T-ScanIII system attribute that makes it possible for a clinician to redistribute the unbalanced occlusal force into an occlusal condition where the occlusal forces are no longer disproportionate.[14]

The mean force distribution that was elicited preoperatively on the edentulous side was 36.32 ± 5.98 and the dentulous side was 63.68 ± 5.98. This depicts the reduction of force that is caused due to extraction of teeth and the importance of replacement. It was found that the net force distribution in the edentulous site preoperatively was high for fixed replacement. In a study performed by Amrita Patnaik et al.,[15] higher bite forces were elicited in patients rehabilitated with FPDs and implants and was considered as the most effective mode of rehabilitation with maximum bite force in comparison with removable rehabilitation methods.

On the contralateral site or sextant, the bite force distribution measured preoperatively was 57.44 ± 3.37, after a removable prosthesis was 53.04 ± 2.86, after FPD was 51.15 ± 1.73, and post equilibration was 63.68 ± 5.98. This effect was seen as a balancing act after replacement of the missing tooth.

Following replacement of the missing tooth with a removable prosthesis yielded a force distribution of 57.30 ± 4.23 on the dentulous side and 43.04 ± 4.14 in the edentulous side. This can be attributed to the contact created by the artificial tooth of the RPD while in occlusion. However, the resilience of the underlying mucosa could lead to compression of the denture during occlusion. Thus, the forces distribution may have not been evenly distributed between the replaced and dentulous side.

After replacement of the tooth with a FPD, the bite force distribution was measured to a mean of 52.52 ± 1.89 on the dentulous side and 46.82 ± 2.49 in the edentulous side. The reason for the improvement of bite force distribution in the restored side and balancing of forces between the natural and restored side indicates the efficiency of the FPD to harmonize occlusion by replacing the missing dentition.

The results of this study also substantiate the findings of Diernberger et al.[16] who conducted a study to analyze the preferable chewing side in different types of restorations, removable and fixed. The authors reported that patients with fixed restorations did not have a preferred chewing side while the ones with unilateral removable prostheses had a preferred to chew on the dentulous side. This indicates that the bite force distribution is better in a fixed dental prosthesis over a removable dental prosthesis.

A similar study was undertaken by Reddy Chaithanya et al.[17] to evaluate the changes in occlusal force dynamics after conventional fixed prosthetic rehabilitation subsequent to rehabilitation with a FPD and efficacy of articulating paper perception by conformation with t scan. The authors concluded that T-scan was better to equilibrate the occlusion and articulating paper did not prove to be a reliable indicator of the occlusal equilibration. The results of the current study, however, differ from the findings of Reddy Chaithanya et al. that equilibration following fixed restoration cementation with T scan proved to be an efficient technique.

Although the role of occlusal disturbances as one of the etiological factors in the multifactorial TMDs is controversial, correction of the occlusal disturbance in various cases has been shown to reverse the condition and provide relief to the myalgia. It has been shown that lower surface electromyography activity is associated with higher number of contacts and the maximum level of bite force distribution during centric maximal voluntary clenching. The T-Scan system presents a superior alternative to conventional occlusal registration methods due to its ability to record dynamic tooth contact relationships.[18]

This study has been an effort to understand the amount of percentage of bite force distribution produced by removable and fixed prostheses and the bite force distribution that occurs due to the type of replacement. The reason for reduced percentage bite force distribution in removable prostheses could be attributed to the resiliency of the underlying soft tissue. The findings of the current study prove the fact that, bite force distributions are better in case of fixed prosthesis replacement.

T-scan proved to be a vital tool in quantifying the bite force distribution which otherwise cannot be done using an articulating paper. However, the current software program of the T-scan which had been used in this study does only give the force values in terms of sextants and quadrants and not around a particular tooth. This can be a limitation of the T-scan.


  Conclusion Top


The bite force distribution produced by a FPD is more even either side of the arch when compared with the RPD. However, RPD procedure better force distribution than partial edentulous situation. T-scan serves as a good clinical tool in comparison with articulating paper in determining occlusal interferences and its correction. After the occlusal interferences were corrected in fixed prosthesis with occlusal equilibration, bite force distribution was more even on both the arches.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

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

  [Table 1], [Table 2], [Table 3]



 

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