Somatosensory Profiling Of Patients With Plaque-induced Gingivitis:A Case-control Study

Gingivitis is characterized by inflammation in the attached gingiva with redness and swelling but without breakdown of the periodontal ligament and loss of clinical attachment level.The most common form of periodontal disease overall,is in response to bacterial biofilms that is attached to tooth surfaces,termed plaque-induced gingivitis.The bacterial biofilm will initiate the body's host response and inflammatory reaction.There is still debate to what extent and in which individuals the plaque-induced gingivitis may progress to a breakdown of the periodontal tissues with loss of attachment level.Nevertheless,plaque-induced gingivitis is an inflammatory response in the oral mucosa and may have consequences for oral health and well-being.Typically,plaque-induced gingivitis is reported to be asymptomatic but somatosensory function in the oral cavity mediated through the maxillary and mandibular branches of the trigeminal nerve could,indeed,be affected by the presence of a low-grade inflammatory response.The free nerve endings in the gingiva may be sensitized by the inflammatory response leading to alterations in responsiveness to mechanical,thermal,and chemical stimuli.Longer-lasting inflammatory responses could also lead to degenerative changes in the afferent nerve populations.As spontaneous pain is often not a clinical finding in cases with plaque-induced gingivitis,the afferent changes in nerve fiber function due to the inflammatory response may be sub-threshold but could be revealed by a systematic and standardized test of different stimulus modalities,including the mechanical stimulation to the periodontal ligament.Quantitative sensory testing(QST)is a reliable psychophysical technique which can provide somatosensory profiles.It has become a valuable assessment tool for various painful disorders.The German Research Network on Neuropathic Pain has developed a standardized QST battery that consists of seven tests measuring 13 parameters in 2006.To evaluate the myelinated larger fiber(A?-fibers),small(A?-fibers)and unmyelinated fiber(C-fibers)lesions a quantitative method has been developed for use in the orofacial region.It allows the investigation of the sensory symptoms and is a reproducible,non-invasive and painless method.QST has been applied to various oral soft tissues such as the tongue,gingiva,lip,palate as well as to the masticatory muscles and temporomandibular joint with good reliability and stability.So far QST has not been attempted to characterize patients with plaque-induced gingivitis.A further development of the QST protocol has shown that pressure pain thresholds(PPT)also can be applied directly to the teeth to measure periodontal sensitivity.The somatosensory properties of periodontal ligament have been shown to innervate by mechanoreceptors.When the pressure was applied to the teeth,the mechanical nociceptors are likely to be activated in the periodontal ligament.Ran Liu et al first applied PPTs to the teeth,and the result showed excellent intra-and inter-examiner agreement in healthy participants.This method may be proposed as an easy and reliable technique to assess mechanical allodynia and hyperalgesia in the periodontal ligament associated with endodontic or periodontal conditions and further clinical studies are warranted.Gingival inflammation may also have potential effect of the somatosensory function of surrounding tissues.The primary aim of the current study was to investigate the thermal and mechanical sensory thresholds at the gingiva and pressure pain thresholds at the teeth in patients with plaque-induced gingivitis compared with healthy controls.The hypothesis was that there would be significant differences both in the gingiva and in the periodontal ligament due to the inflammatory response in patients with plaque-induced gingivitis.Quantitative sensory testing(QST)was used in 22 patients(Men 10,Women 12,age 20-30 yrs)with plaque-induced gingivitis at the lower lateral incisors and in 22 age-and gender-matched healthy volunteers as a control group.One lower lateral incisor(32 or 42)was randomly identified for each included subject.Cold detection threshold(CDT),warm detection threshold(WDT),cold pain threshold(CPT)and heat pain threshold(HPT)of the attached gingiva at the identified lower lateral incisors were assessed in both groups.Pressure pain threshold(PPT)at the teeth was also tested from vertical and lateral directions and analyzed.One-way ANOVA was used to compare the mean values of the identified lower lateral incisors between the two groups.The results showed that the CDT(P=0.027),WDT(P=0.021)and HPT(P=0.005)at the gingiva and PPT(P<0.001)at the identified lower lateral incisors from the vertical direction were significantly less sensitivity,whereas the PPT(P=0.016)at the gingiva of the identified lateral incisors were significantly more sensitivity in the gingivitis group compared to the control group.Plaque-induced gingivitis and the inflammatory response appears to be associated with significant changes in somatosensory sensitivity at the gingiva and periodontal tissue in a bidirectional mode,i.e.,both increased and decreased sensitivity to different types of stimuli.Inflammatory reactions in the gingiva seem to be associated with demonstrable changes in somatosensory function including both hypo-and hyperesthesia.These findings may have significance for general oral health and well-being in patients with even plaque-induced gingivitis.