ORIGINAL RESEARCH |
https://doi.org/10.5005/jp-journals-10015-2257 |
Assessment of Occlusal Contacts Following Bi-jaw Orthognathic Surgery Using T-scan: A Prospective Clinical Study
1Department of Craniofacial Surgery, Nitte Meenakshi Institute of Craniofacial Surgery, KS Hegde Hospital, Nitte (Deemed to be University), Mangaluru, Karnataka, India
2,3Department of Oral and Maxillofacial Surgery, AB Shetty Memorial Institute of Dental Sciences (ABSMIDS), Nitte (Deemed to be University), Mangaluru, Karnataka, India
4Department of Prosthodontics and Crown & Bridge, AB Shetty Memorial Institute of Dental Sciences (ABSMIDS), Nitte (Deemed to be University), Mangaluru, Karnataka, India
Corresponding Author: Tripthi P Shetty, Department of Oral and Maxillofacial Surgery, AB Shetty Memorial Institute of Dental Sciences (ABSMIDS), Nitte (Deemed to be University), Mangaluru, Karnataka, India, Phone: +91 9972351512, e-mails:
drtripthips@nitte.edu.in; tripthi12@gmail.com
Received on: 03 June 2023; Accepted on: 04 July 2023; Published on: 31 August 2023
ABSTRACT
Aim: The aim of the study was to assess occlusion in patients undergoing bi-jaw orthognathic surgeries (OGS).
Materials and methods: A prospective study was done on 20 patients between the age-group of 18 and 32 years having skeletal malocclusions requiring bi-jaw OGS. The occlusal contacts of patients undergoing bi-jaw OGS were assessed in two phases using a T-scan device—(1) immediately prior to surgery and (2) after 3 months of orthognathic surgery. Patients were made to sit in a natural position with Frankfort horizontal plane parallel to the ground, occlusal contacts were recorded using specialized wafers, and information was recorded digitally using a T-scan device.
Results: The study included 20 patients (7 males and 13 females) with a mean age of 22.7 years. The mean number of teeth in contact increased from 2.7 to 3.3 on the left side and 3.3 to 3.7 on the right side when assessed 3 months postoperatively indicating a significant improvement in postoperative occlusal contacts.
Conclusion: The significant increase in the occlusal contacts over the left and right side postoperatively implies a better stomatognathic system and improved masticatory efficiency postorthognathic surgery.
Clinical significance: Orthognathic surgery has been routinely performed to enhance the patient’s facial esthetics, thus the concept of functional occlusion is sometimes forgotten. This study helps in assessing the functional aspect of orthognathic surgery in terms of occlusal contacts which is a keystone in a successful orthognathic surgery.
How to cite this article: Shetty V, Das S, Shetty TP, et al. Assessment of Occlusal Contacts Following Bi-jaw Orthognathic Surgery Using T-scan: A Prospective Clinical Study. World J Dent 2023;14(7):625–628.
Source of support: Nil
Conflict of interest: None
Keywords: Bite force, Masticatory efficiency, Occlusion, Orthognathic surgery
INTRODUCTION
Occlusion can be defined as the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogs.1 The occlusion of an individual is dependent on the position, shape, and size of the tooth which are determined by the developmental processes during its pre and postnatal phase. Whenever there is any anomaly in any stage of the developmental process maxillary or mandibular deformities can occur.2
The masticatory system comprises the masticatory muscles, teeth, and temporomandibular joint (TMJ), which aids in achieving a healthy occlusal system, which in turn allows individuals to chew without any pain or interference.3,4 Distorted occlusion between the upper and lower arches results in improper position and alignment of teeth resulting in various forms of skeletal malocclusions.5
Maxillofacial surgeons routinely perform orthognathic surgeries (OGS) involving Le Fort I osteotomy and bilateral sagittal split osteotomies (BSSO), to correct skeletal malocclusions.6 Balanced occlusion and an enhanced esthetic profile are the two key components for a successful OGS. Teeth at maximum intercuspation (MI) is a fundamental aspect of functional occlusion.7 Although patients remain satisfied with improved esthetics post-OGS, the relevance of functional occlusion is often neglected.
Plaster cast models have regularly been used as a gold standard for recording the occlusion8 while articulating paper and occlusal foils in recording occlusal discrepancies.9 However recent advances in digital dentistry like T-scan have allowed dental surgeons to study even other minute components of the occlusion. T-scan also called as Tekscan occlusal system helps record more dynamic measurements like the center of force, symmetry in the distribution of occlusal load, premature contacts, areas of MI in centric occlusion, and relative and maximum bite forces.10-12
As patients are mostly satisfied with the esthetic enhancement postorthognathic surgery, the concept of occlusion in orthognathic surgery is overlooked.
This study was thus designed to conduct a functional analysis of occlusion, in terms of occlusal contacts in patients who underwent bi-jaw OGS using a T-scan device.
MATERIALS AND METHODS
This prospective study was conducted on 20 patients irrespective of gender reporting to the Department of Oral and Maxillofacial Surgery, AB Shetty Memorial Institute of Dental Sciences (ABSMIDS), Nitte (Deemed to be University), Mangaluru, Karnataka, India, between June 2021 and September 2022. The study included patients with skeletal malocclusions requiring Le Fort I osteotomy with BSSO. Informed consent was obtained from all patients in accordance with the Declaration of Helsinki, and the study was approved by the institutional ethics committee. Patients with previous surgical history in the maxillofacial region or patients with temporomandibular disorders, deleterious habits (tongue thrusting, bruxism), and other syndromic cases were excluded from the study.
Preoperative Evaluation
Patients planned for bi-jaw OGS underwent routine investigations and preanesthetic evaluation prior to surgeries. Preoperative lateral and posteroanterior view cephalogram radiographs were recorded for each patient.
Occlusal contacts were recorded immediately prior to surgery using T-scan III (Tekscan, Inc. Boston, MA, United States).
The patient was asked to be seated in a natural position and in a forward gaze with the Frankfurt horizontal plane [which is determined by the imaginary line joining the highest point on the upper margin of the external auditory canal (porion) and the lowest point on the lower margin of the left orbit (orbitale)] approximately parallel to the floor. T-scan is connected to a Windows-based laptop/computer via a Universal Serial Bus port. The recording handle with the sensor and arch support was placed between upper and lower arches with a center of the sheet between the central incisors and started by pressing the button. The patient was instructed to bite on the sensor until full intercuspation was achieved. In their maximal intercuspation position, the patients were asked to open their mouth and the occlusion was recorded digitally. The arch model was produced on screen when the button on the handle was released. The patient was asked to repeat the bite four times to measure the reproducibility of the device.
The accompanying Windows-based software system received real-time force information from the sensor. This data was presented as a continuous force “movie” of the full-observed occlusal contact event in two and three dimensions. The data came in the form of bars with different color and height of each bar indicating the intensity per contact
Data were collected from the digital T-scan recordings and analyzed statistically.
Surgical Procedure
All patients were subjected to bi-jaw orthognathic surgery: Le Fort I and BSSO with or without genioplasty. Le Fort I osteotomy was done via vestibular incision extending from molar to molar bilaterally. Following disjunction, the maxilla was fractured, mobilized, and secured with an intermediate occlusal splint. The maxillary segment was stabilized using two six-hole titanium mini plates bilaterally. Following Le Fort I osteotomy, all patients underwent BSSO cuts. The vestibular incision was placed extending from the premolar to the ascending ramus of the mandible. Osteotomy was done using the Obwegeser technique with Hunsuck and Epker modification where the horizontal buccal cut was located between the union of the ascending ramus and the body of the mandible in the tooth-bearing zone. The mandibular segment underwent repositioned fixed done with four-hole titanium mini plates and bicortical screw bilaterally. Patients underwent intermaxillary fixation using intraoral elastics for two weeks postoperatively to maintain occlusion. Patients were subjected to genioplasty if required as per treatment objectives.
Postoperative Evaluation
The postoperative stay was uneventful for all patients and was discharged within 5–7 postoperative days. Occlusal readings were taken 3 months postoperatively using a T-scan in a similar way as was recorded preoperatively.
Two investigators with a minimum of 5 years of clinical experience and training in handling T-scan participated in recording the data for all patients.
Statistical Analysis
The occlusal data recorded from the T-scan device were analyzed statistically using Statistical Package for the Social Sciences (SPSS) software (IBM, SPSS Inc). Inferential and descriptive statistics were calculated using paired t-tests. Co-relation between intergroup variables was found using Pearson correlation.
RESULTS
The study includes 20 patients (7 males and 13 females) with a mean age of 22.7 years (range 18–32 years).
On the left side, the mean number of teeth in contact at the pre-treatment level and at 3rd month postoperative was 3.30. The intragroup comparison between pretreatment level and 3rd month done using Pearson correlation with a significance level of 0.05 and r-value of 0.734 showed a positive correlation (Table 1 and Fig. 1).
Variable | Mean | Standard deviation | r-value | p-value | Significant |
---|---|---|---|---|---|
Tooth at maximum intercuspation pre-op | 2.750 | 1.618 | 0.734 | 0.001* | Significant |
Tooth at maximum intercuspation post-op | 3.300 | 1.174 |
*Level of significance at p < 0.05
Fig. 1: Comparison of a tooth at maximum intercuspation preoperative vs 3rd month postoperative on the left side
On the right side, the mean number of teeth in contact at the pretreatment level was 3.30 which increased at the end of 3rd month postoperatively to 3.75. Pearson correlation on the right side revealed significant results as well (Table 2 and Fig. 2).
Mean | Standard deviation | r-value | p-value | Significant | |
---|---|---|---|---|---|
Tooth at maximum intercuspation pre-op | 3.350 | 1.663 | 0.737 | 0.001* | Significant |
Tooth at maximum intercuspation post-op | 3.750 | 1.019 |
*Level of significance at p < 0.05
Fig. 2: Comparison of a tooth at maximum intercuspation preoperative vs 3rd month postoperative on the right side
Patients were assessed for the satisfaction of postoperative occlusion 3 months following surgery in terms of ability to chew hard food, sticky food, and normal dietary intake. 85% of patients were satisfied with their outcomes. Two complained about the inability to chew sticky food and one patient complained of pain postoperatively, and were managed accordingly.
It was seen that the occlusal contacts increased significantly within 3 months after undergoing orthognathic surgery, suggesting the improvement in functional occlusion postorthognathic surgery.
DISCUSSION
Patients with malocclusions were seen to have decreased masticatory performance and bite force efficiency.13-16 As the position of the teeth in the jaws changes, the entire stomatognathic system changes and if the occlusion is improper it results in various disorders such as attrition, muscle pain, temporomandibular disorders, gastric disturbance, and ulcers which in turn hampers the quality of life.17
T-scan has come as a major advancement in the diagnostic front of assessing functional occlusion. It has an edge over articulating paper to assess occlusion as the entire arch can be recorded and visualized in a single time.9 Improper occlusion like premature contacts, and uneven load distribution, could be assessed using a T-scan, thereby implying its importance in assessment postsurgery and the need for further occlusal corrections.18
The occlusal information of the patient like the number of teeth in contact and trajectory of force is analyzed using T-scan. Two or three-dimensional graphical representation or a dynamic movie is made from the occlusal data obtained from the T-scan, and it is analyzed step-wise.2
In the present study, the mean number of teeth contributing to maximum bite force preoperatively on the left side was 2.7, which improved to 3.3 during 3 months of postoperative follow-up. Similarly, on the right side, the mean number of teeth contributing to maximum bite force improved from 3.35 to 3.75 postoperatively. Hence tooth contributing to occlusion improved significantly postoperatively after patients underwent OGS.
Studies conducted by Roldán et al.15 and Hejne19 also established that patients with malocclusion had fewer teeth in contact. In a similar study by Agbaje et al.,2 occlusion was assessed using T-scan in patients both preoperatively and postoperatively after 1 year, and found that the number of teeth contributing to occlusion improved significantly after postsurgery. The good functioning of the TMJ is dependent on the number, size, and location of contacts. Brennan et al.20 and Henrikson et al.21 reported that the number of teeth in occlusion directly affects the masticatory ability and subsequently is responsible for a better quality of life. As the occlusal contacts between the upper and lower teeth increased, the biomechanics of the masticatory muscles improved.
Bakke et al.22 in their study to assess bite force and occlusion found that as the number of teeth in occlusion increases the between bite force generated also increases. Their study was conducted using a transducer kept between the occlusal surfaces of the teeth and absolute bite force was measured.
Shinogaya et al.23 came to a similar conclusion with their study on bite force and occlusal load in healthy young adults using a dental prescale system in 17 students. As the occlusal contacts between the upper and lower teeth increased, the biomechanics of the masticatory muscles improved.
There were certain limitations in the study. One being long-term follow-up needs to be carried out, to assess the improvement in occlusal contacts as the soft tissue and hard tissue changes postsurgery were not static and were progressive in due course of time. The presence of orthodontic bands and brackets both pre and postoperatively reduced patient compliance while recording the T-scan.
Therefore a larger sample size and long-term follow-up ranging from preorthodontic treatment through bi-jaw orthognathic surgery to completion of orthodontic treatment holds the key to future prospects of this study.
CONCLUSION
T-scan helps in dynamic assessment of occlusion and thus aids in diagnosis and designing a treatment framework for the patient. T-scan can also be used as a tool for operative assessment of patients in every follow-up visit.
This study revealed that the number of teeth in occlusion increased following orthognathic surgery signifying improvement of the stomatognathic system postoperatively.
ORCID
Vikram Shetty https://orcid.org/0000-0003-0685-1669
Subhajit Das https://orcid.org/0009-0007-8397-7050
Tripthi P Shetty https://orcid.org/0000-0002-3614-5709
Ganaraj Shetty https://orcid.org/0000-0001-8627-8633
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