A new method for evaluating the threshold of periodontal ligament mechanoreceptor by slow speed mechanical stimulation

Somatosensory evoked magnetic fields of periodontal mechanoreceptors

To evaluate the localization of responses to stimulation of the periodontal mechanoreceptors in the primary somatosensory cortex, somatosensory evoked fields (SEFs) were measured for stimulation of the left mandibular canine and first molar using magnetoencephalography in 25 healthy subjects. Tactile stimulation used a handmade stimulus device which recorded the trigger at the moment of touching the teeth.SEFs for the canine and first molar were detected in 20 and 19 subjects, respectively. Both responses were detected in the bilateral hemispheres. The latency for the canine was 62.1 ± 12.9 ms in the ipsilateral hemisphere and 65.9 ± 14.8 ms in the contralateral hemisphere. The latency for the first molar was 47.4 ± 6.6 ms in the ipsilateral hemisphere and 47.8 ± 9.1 ms in the contralateral hemisphere. The latency for the first molar was significantly shorter than that for the canine. The equivalent current dipoles were estimated in the central sulcus and localized anteroinferiorly compared to the locations for the SEFs for the median nerve. No significant differences in three-dimensional coordinates were found between the canine and first molar. These findings demonstrate the precise location of the teeth within the orofacial representation area in the primary somatosensory cortex.

Passive Periodontal Sensation Threshold of Upper Molars in Patients with Myofascial Pain

Background and Objective:

The relationship between periodontal sensation and Myofascial Pain (MP) is not yet fully clarified. The aim of this study was to test the null hypothesis that there is no difference in the periodontal sensation threshold between subjects with MP and subjects with no Temporomandibular Disorders (TMD).

Methods:

Participants have clinically assessed in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders version 1.0 guidelines and assigned to the MP group (mean age 54.8 ± 14.8 years; 1 male and 11 females) or the control group (mean age: 63.9 ± 13.2 years; 1 male and 15 females). The Passive Periodontal Sensation Threshold (PPST) was evaluated using impulsive mechanical stimulation on the occlusal surface parallel to the tooth axis of the maxillary first molar, if present. The difference in the mean PPST between the MP group and the control group was evaluated using the Student t-test after checking for homoscedasticity.

Results:

The mean PPST value was 1050.1 ± 480.3 mN in the MP group and 712.3 ± 288.5 mN in the control group. A significant difference was observed between these mean PPST values (p = 0.045).

Conclusion:

There was a significant difference in PPST between the MP group and the control group. Although the etiology of the change of PPST is still unknown, the higher PPST value observed in MP patients suggests that future study on occlusal dysesthesia or occlusal sensation-related pathosis is warranted.

Effect of difference in occlusal contact area of mandibular free-end edentulous area implants on periodontal mechanosensitive threshold of adjacent premolars

Implant treatment is believed to cause minimal invasion of remaining teeth. However, few studies have examined teeth adjacent to an implant region. Therefore, this study investigated the effect of occlusal contact size of implants on the periodontal mechanosensitive threshold of adjacent premolars. A cross-sectional study design was adopted. The Department of Oral Implantology, Osaka Dental University, was the setting where patients underwent implant treatment in the mandibular free-end edentulous area. The study population comprised of 87 patients (109 teeth) who underwent follow-up observation for at least 3 years following implant superstructure placement. As variables, age, sex, duration following superstructure placement, presence or absence of dental pulp, occlusal contact area, and periodontal mechanosensitive threshold were considered. The occlusal contact area was measured using Blue Silicone^®and Bite Eye BE-I^®. Periodontal mechanosensitive threshold were measured using von Frey hair. As quantitative variables for periodontal mechanosensitive threshold, we divided subjects into two groups: normal (≤5 g) and high (≥5.1 g). For statistical analysis, we compared the two groups for the sensation thresholds using the Chi square test for categorical data and the Mann–Whitney U test for continuous volume data. For variables in which a significant difference was noted, we calculated the odds ratio (95 % confidence interval) and the effective dose. There were 93 teeth in the normal group and 16 teeth in the high group based on periodontal mechanosensitive threshold. Comparison of the two groups indicated no significant differences associated with age, sex, duration following superstructure placement, or presence or absence of dental pulp. A significant difference was noted with regard to occlusal contact area, with several high group subjects belonging to the small contact group (odds ratio: 4.75 [1.42–15.87]; effective dose: 0.29). The results of this study suggest an association between implant occlusal contact area and the periodontal mechanosensitive threshold of adjacent premolars. Smaller occlusal contact application resulted in an increased threshold. It appears that prosthodontic treatment should aim not only to improve occlusal function but also to maintain oromandibular function with regard to the preservation of remaining teeth.

The relationship between bite force and oral sensation during biting in molars

BACKGROUND

In prosthodontic treatment, the occlusal form should be designed such that bite force is applied at the position that has higher load-bearing capacity and is comfortable for the patient. The purpose of this study was to clarify the differences in bite force and occlusal sensation with different loading positions on the occlusal surface.

METHODS

Twelve healthy subjects were recruited for this study. Bite force and occlusal sensation were measured at five loading points on the upper and lower left first molars. Occlusal sensation was evaluated using a Visual Analogue Scale (VAS).

RESULTS

Bite forces on the lingual side of the upper first molar and the buccal side of the lower first molar were significantly higher and VAS scores were significantly lower, i.e. the subjects felt less discomfort during biting on the buccal side of the upper first molar and the lingual side of the lower first molar compared to the other side of each molar.

CONCLUSIONS

Loading on the occlusal surfaces of the functional cusps of the upper and lower first molars produces more load-bearing capacity and is more comfortable than loading on the non-functional cusps.

The effect of bruxism on periodontal sensation in the molar region: A pilot study

STATEMENT OF PROBLEM

Periodontal sensation in individuals with bruxism may differ from that in nonbruxers, as excessive amounts of occlusal force may be applied to the teeth during the night. However, this concept is not adequately addressed in the literature.

PURPOSE

The purpose of this study was to investigate the effects of bruxism on periodontal sensation in the molar region.

MATERIAL AND METHODS

Fourteen dental school faculty and students lacking objective or subjective abnormalities of stomatognathic function were divided into 2 groups representing nonbruxers (n=7) and bruxers (n=7). Bruxism was confirmed based on the nocturnal electromyography activities of the masseter muscle. Periodontal sensation was assessed based on interocclusal tactile threshold, which refers to the minimal thickness that can be detected between the occlusal surfaces of the teeth. Interocclusal tactile threshold was measured in the first molar region each for the left and right sides by placing variable thicknesses of metal foil and recording the threshold twice daily (morning and afternoon) on 3 separate days. Multivariate ANOVA was performed for bruxism (with or without) as a between-subjects effect, and time of day (morning and afternoon) and side (left and right) as within-subjects effects (alpha=.05)

RESULTS

Multivariate ANOVA revealed no significant differences in interocclusal tactile threshold between morning and afternoon or between the left and right sides in either group. The mean (SD) interocclusal tactile threshold for the bruxers was 17.1 (3.9) microm, while that for the nonbruxers was significantly greater at 29.9(5.6) microm (P<.001).

CONCLUSIONS

The periodontal sensation in bruxers was increased compared to nonbruxers.