Dental Occlusion Interpretation between Patient and Clinician in Eccentric Mandibular Positions

INTRODUCTION

Clinically, the dental occlusion is routinely evaluated by both clinical examination and patient’s perception.¹ Patient’s interpretation or perception comes from sensory afferent outputs from proprioceptors.²-⁴ Several investigators found that both vital teeth and pulpless teeth have a similar sensory response because they have the same periodontal mechanoreceptors (PMRs), not the sensory receptor from the pulp. This information indicated that PMRs which are essential in the perception of dental occlusion exist in both vital and non-vital teeth.²,^4-6 They are located in the periodontal ligament (PDL) area and signal afferent outflow in response to the occlusal force when PDL is stretched.⁷-⁹

Occlusal indicators are conventionally used to examine occlusal contacts of opposing dentition. They are based on the coated ink marks of articulating papers on the tooth surface, removal force of shimstock foil, and perforation of occlusal indicator wax.¹ These conventional techniques are straightforward but the outcomes vary due to the limited ability of waxes and color-coated paper to detect occlusal contact, clinician’s experience, and the patient factors. To control these variations, computerized occlusal contact identifiers such as T-Scan have been advocated.

T-Scan III (Tekscan®, Boston, MA, USA) is an example of the digital occlusal indicator.¹⁰,¹¹ It can display dental occlusion as quantitative data in static and dynamic features.¹⁰-¹² With the advantages of the quantitative information, T-Scan III is used in various fields in dentistry that require high accuracy.¹³,¹⁴ Although T-Scan III shows superior accuracy than the conventional techniques (i.e., using articulating paper or waxes), it is not routinely used in a clinical setting because of the high operating cost. Thus, the combined interpretation of dental occlusion achieved from patients and clinicians is still the key factor.

A previous study reported the association between T-Scan III and the correlation of bite force interpretation from patients and clinicians in maximal intercuspal position (MIP). Results showed that the bite force interpretation from the clinician is more clinically reliable than the patient’s interpretation.¹⁵ Currently, a study of dental occlusion in eccentric mandibular positions has not been investigated. Therefore, this study aimed to compare the interpretation of dental occlusion between patients and a clinician in eccentric mandibular positions when T-Scan III was served as a standard device.

MATERIALS AND METHODS

Naresuan University Ethical Committee approved the study protocol with an IRB No. 0995/60 before data gathering. The undergraduate dental students at Naresuan University (Phitsanulok, Thailand) participated in this study because they have clinical experience, understand tooth contact patterns (i.e., mandibular posture), and no communication problem during data collection.

Sample size justification was calculated using GPower 3.1®. The total sample would be 100 for three independent variables (patient’s perception, clinician examination, and T-Scan III analysis). To compensate for the sample loss (approximately 10–20%), the total sample size would be 110 to 120. The dental occlusion of each participant was required to be examined by all three independent variables. Therefore, the sample size of the current study was set to have at least 40 samples (n = 40). Finally, 43 participants took part in this study following the inclusion and exclusion criteria as follows:

RESULTS

Forty-three participants consisted of 29 females and 14 males. Their age ranged from 19 to 23 years old. The tooth contact agreement between the patient’s perception in eccentric movement and T-Scan III were 65.12% (right excursion), 72.09% (left excursion), and 79.07% (protrusion) (Table 2). The tooth contact agreement between clinician interpretation in eccentric movement and T-Scan III were 72.09% (left and right excursion) and 86.05% (protrusion) (Table 3).

Weighted kappa analysis revealed that the protrusion had the best agreement (highest kappa score) with T-Scan III among three eccentric movements in both patient and clinician interpretation (substantial agreement; κ_ω = 0.661 for the patient and κ_ω = 0.772 for the clinician).

The moderate agreement with T-Scan III of patient and clinician interpretation was observed for lateral excursions. Kappa scores of the right excursion were 0.430 for patient interpretation and 0.545 for clinician interpretation. Kappa scores of the left excursion were 0.569 for both groups (Table 4 and Fig. 2). Intra-examiner clinician reliability (JP) was moderate to an almost perfect agreement (Table 5).

DISCUSSION

Although the digital occlusal indicators offer superiority over the traditional occlusal indicators, the high cost of the equipment is the main reason why they are not widely used. Currently, patients and clinicians are still the keys to detect dental occlusion. A previous study showed that the bite force interpretation in MIP from clinicians is more clinically reliable than patients.¹⁵ No study has ever assessed the interpretation of the dental occlusion in an eccentric position.

This is the first study to have evaluated the dental occlusion interpretation between patients and a clinician in eccentric mandibular positions. The results showed that the highest agreement (substantial agreement) with T-Scan III was protrusion for both patient recognition and clinician interpretation/examination, followed by moderate agreement on the left and right excursions, respectively. Even though both patient recognition and clinician interpretation had the same agreement with T-Scan III, clinician interpretation showed a higher percent of subject agreement than patient’s perception. This finding is possibly due to the inability of patients to discriminate the light contact between the opposing teeth. Siirilä and Laine found that humans can discriminate approximately 8–10 μm of foreign bodies.¹⁷ Their results suggested that humans cannot detect tooth contacts that are %3C;8–10 μm. On the other hand, if the interocclusal space between the occluding teeth is %3E;8–10 μm, humans can pinpoint the contacting pairs of teeth or identify which side of jaws contacts heavier.

In protrusion, incisors guided the protrusive movement as the incisal edges of mandibular incisors moved along the lingually inclined planes of maxillary incisors.¹⁸ The contacting teeth in protrusion are often located on anterior teeth. Anterior teeth have highly sensitive PMRs to force magnitudes than the posterior teeth have.⁵,^8,19 Additionally, studies reported that the most sensitive area to bite force perception is at incisor, canine, and premolar regions, respectively.²⁰,²¹ Johnsen et al. compared the periodontal afferents from the different areas of the dental arch by peanut holding. They found that the more distal part of the dental arch, the more bite force generated. Their finding supported the high sensitivity of PMRs in the anterior teeth, rather than the posterior teeth.²⁰ Therefore, in the current study, the highest agreement with T-Scan III in protrusion compared to other movements can be explained by the highly sensitive PMRs in the anterior region resulting in an increased ability of participants to identify tooth contacts in the anterior teeth than the posterior teeth.

In lateral excursion, the mandible was guided to move away from MIP along the palatal inclined plane of maxillary canine and/or palatal inclined planes of buccal cusps of maxillary posterior teeth.²²,²³ Several investigators reported that the most common lateral excursive pattern in young adults is a group function occlusion.²⁴-²⁷ In this study, posterior teeth (not the canine) which had poorer PMRs than the anterior teeth²⁰ were mainly guided the mandible during the lateral excursion. Therefore, the similar correlation between left and right excursion (moderate agreement), and the lower correlation to T-Scan III than protrusion (a substantial agreement, guided by anterior teeth) may be explained by the poorer PMRs in the posterior segment of the jaw. Moreover, locating the contacting teeth in the posterior segment of the jaw is more difficult than the anterior region (i.e., in protrusion) because they are on the side of the jaw which is not easily seen with the patient’s eyes, and contacting teeth are usually obscured by the surrounding tissue (i.e., cheek).

For the standard device, the T-Scan III system was used in this study because this system can report quantitative data, whereas traditional occlusal indicators cannot. Additionally, the HD sensor of T-Scan III can be used up to 20 times, and data from the first 20 repeated bites were consistent and reliable.²⁸ More importantly, the main advantage of T-Scan III is the elimination of several variabilities such as material properties and clinician’s experience.²⁹,³⁰

Even though studies endorsed the benefits of T-Scan III in terms of high accuracy and reliability,¹⁰,^28,31 the 100-μm thick of the HD sensor was approximately 4–12 fold greater than the physiologic axial tooth movement.³² Consequently, it may affect patient’s bite and cause bite deviation. To minimize these problems, dental students who can practically be trained to bite at MIP and perform jaw movement at different positions were recruited for the study. They were trained to bite on the desired position before data collection. Moreover, the U-shaped HD sensor had a uniform thickness. Therefore, all occluding teeth can simultaneously contact on both sides and the errors resulting from the thickness of the HD sensor were minimized.¹¹ Additionally, the data collection was done three times and reported in consensus.

Even if clinical examination using traditional occlusal indicators may be the most convenient method to examine dental occlusion, no previous research assured the validity of clinician interpretation of dental occlusion in eccentric mandibular positions. Kerstein and Radke investigated the validity of dental occlusion examination evaluated by the clinician using articulating paper marks in relation to T-Scan III analysis. They found that dentists cannot determine the relative bite force effectively.³³ In this study, clinician reliability testing (kappa score) revealed moderate to an almost perfect agreement even with traditional occlusal indicators. This finding maybe because of the restricted properties of the traditional occlusal indicators¹ and the clinical experience of the examiner.

CONCLUSION

This is the first study to have evaluated the reliability of patient and clinician interpretation in an examination of dental occlusion in eccentric positions compared to the digital occlusal analyzer known as T-Scan III. The highest agreement with T-Scan III was protrusion followed by left and right excursion, respectively. The patient’s perception was less reliable (less consistent with T-Scan III analysis) than clinician interpretation in protrusion and right excursion. However, both patients and clinicians equally perceived dental occlusion during the left excursion.

The limitation of this study was that there was only one dentist who evaluated dental occlusion and all participants were dental students who might not represent the patients in the other groups. Therefore, future studies should have a wide variety of dentists and patients. Moreover, a comparison of the combined patient and clinician interpretations with T-Scan III analysis may be beneficial.

ACKNOWLEDGMENTS

The authors thank Dr Pornsuda Norchai for statistical analysis. This study was supported by the Graduate Students Research Funds, Faculty of Dentistry, Naresuan University.

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