Combination Therapy with EGFR Tyrosine Kinase Inhibitors and TEAD Inhibitor Increases Tumor Suppression Effects in EGFR Mutation-positive Lung Cancer

EGFR-tyrosine kinase inhibitors (TKI) are the first-line therapies for EGFR mutation-positive lung cancer. EGFR-TKIs have favorable therapeutic effects. However, a large proportion of patients with EGFR mutation-positive lung cancer subsequently relapse. Some cancer cells survive the initial treatment with EGFR-TKIs, and this initial survival may be associated with subsequent recurrence. Therefore, we aimed to overcome the initial survival against EGFR-TKIs. We hypothesized that yes-associated protein 1 (YAP1) is involved in the initial survival against EGFR-TKIs, and we confirmed the combined effect of EGFR-TKIs and a YAP1-TEAD pathway inhibitor. The KTOR27 (EGFR kinase domain duplication) lung cancer cell lines established from a patient with EGFR mutation-positive lung cancer and commercially available PC-9 and HCC827 (EGFR exon 19 deletions) lung cancer cell lines were used. These cells were used to evaluate the in vitro and in vivo effects of VT104, a TEAD inhibitor. In addition, YAP1 involvement was investigated in pathologic specimens. YAP1 was activated by short-term EGFR-TKI treatment in EGFR mutation-positive lung cancer cells. In addition, inhibiting YAP1 function using siRNA increased the sensitivity to EGFR-TKIs. Combination therapy with VT104 and EGFR-TKIs showed better tumor-suppressive effects than EGFR-TKIs alone, in vitro and in vivo. Moreover, the combined effect of VT104 and EGFR-TKIs was observed regardless of the localization status of YAP1 before EGFR-TKI exposure. These results suggest that combination therapy with the TEAD inhibitor and EGFR-TKIs may improve the prognosis of patients with EGFR mutation-positive lung cancer.

CD47 polymorphism for predicting nivolumab benefit in patients with advanced non‑small‑cell lung cancer

Immune checkpoint inhibitors (ICIs), such as nivolumab, play an essential role in non-small-cell lung cancer (NSCLC) treatment. Programmed death ligand-1 has been used as a predictive biomarker for the efficacy of ICI treatment in patients with NSCLC; however, its predictive value is considered insufficient. Therefore, there is an urgent need for better predictive biomarkers. The present study focused on the CD47 molecule, which is associated with macrophages and tumor immunity. The study aimed to investigate the association between CD47 single nucleotide polymorphism (SNP) and the therapeutic effect of nivolumab in patients with NSCLC. The CD47 SNP genotypes and clinical outcomes were retrospectively analyzed in 164 patients with NSCLC treated with nivolumab at Kyoto University Hospital (Kyoto, Japan). Patients with the G/G genotype of the CD47 SNP rs3804639 had significantly longer progression-free survival than those with the G/T or T/T genotypes [2.6 months vs. 2.1 months, hazard ratio (HR), 0.70; P=0.026]. Moreover, the G/G genotype of the CD47 SNP rs3804639 was associated with a significantly longer median overall survival than the G/T or T/T genotypes of the CD47 SNP rs3804639 (24.8 months vs. 12.0 months, HR, 0.64; P=0.021). In conclusion, CD47 polymorphism may be a novel predictive biomarker of nivolumab efficacy in patients with advanced NSCLC.

Yes-associated protein 1 mediates initial cell survival during lorlatinib treatment through AKT signaling in ROS1-rearranged lung cancer

Tyrosine kinase inhibitors (TKIs) that target the ROS proto-oncogene 1, receptor tyrosine kinase (ROS1) gene have shown dramatic therapeutic effects in patients with ROS1-rearranged non-small-cell lung cancer (NSCLC). Nevertheless, advanced ROS1-rearranged NSCLC is rarely cured as a portion of the tumor cells can survive the initial stages of ROS1-TKI treatment, even after maximum tumor shrinkage. Therefore, understanding the mechanisms underlying initial cell survival during ROS1-TKI treatment is necessary to prevent cell survival and achieve a cure for ROS1-rearranged NSCLC. In this study, we clarified the initial survival mechanisms during treatment with lorlatinib, a ROS1 TKI. First, we established a patient-derived ezrin gene-ROS1-rearranged NSCLC cell line (KTOR71). Then, following proteomic analysis, we focused on yes-associated protein 1 (YAP1), which is a major mediator of the Hippo pathway, as a candidate factor involved in cell survival during early lorlatinib treatment. Yes-associated protein 1 was activated by short-term lorlatinib treatment both in vitro and in vivo. Genetic inhibition of YAP1 using siRNA, or pharmacological inhibition of YAP1 function by the YAP1-inhibitor verteporfin, enhanced the sensitivity of KTOR71 cells to lorlatinib. In addition, the prosurvival effect of YAP1 was exerted through the reactivation of AKT. Finally, combined therapy with verteporfin and lorlatinib was found to achieve significantly sustained tumor remission compared with lorlatinib monotherapy in vivo. These results suggest that YAP1 could mediate initial cell resistance to lorlatinib in KTOR71 cells. Thus, combined therapy targeting both YAP1 and ROS1 could potentially improve the outcome of ROS1-rearranged NSCLC.

Sarcomatoid malignant pleural mesothelioma treated with nivolumab: A case series

Immune checkpoint therapy (ICT) with nivolumab has been widely used to treat malignant pleural mesothelioma (MPM) since clinical trials confirmed its efficacy. However, only a few clinical trials have been conducted for the treatment of sarcomatoid MPM, which is a rare histological type of MPM. Additionally, clinical reports of sarcomatoid MPM are scarce. Therefore, the benefits and risks of nivolumab treatment for sarcomatoid MPM remain unclear. The present report describes the treatment of 3 cases of sarcomatoid MPM (all 3 were men) with nivolumab monotherapy. In all three cases, nivolumab was effective despite variations in the duration of treatment, although side effects were observed in 2 patients. Programmed death ligand 1 (PD-L1) expression was positive in all 3 cases. In particular, the patient with the highest PD-L1 expression had the most rapid response of the 3 patients, and the effect lasted as long as those of the other 2, despite receiving the smallest number of doses of nivolumab. It has been reported that sarcomatoid MPM tends to respond poorly to chemotherapy and express higher levels of PD-L1 than epithelial MPM; thus, ICT may be necessary in these cases. This case series suggests that ICT with nivolumab is a promising treatment option for sarcomatoid MPM.

Abstract 5335: Elucidation of initial resistance mechanisms in EGFR mutation-positive lung cancer focusing on YAP1 and cancer stem cells

Background: EGFR mutation-positive lung cancer has high response rates to EGFR-tyrosine kinase inhibitors (TKIs), but eventually acquires resistance to EGFR-TKIs. Acquired resistance mechanisms are diverse because of tumor heterogeneity, which makes it difficult to overcome acquired resistance. Initial resistance is the resistance mechanism of tumor cells that survive the initial treatment. If we could overcome the initial resistance, we could prevent cancer cells from developing various types of acquired resistance. We are now focusing on YAP1 and cancer stem cells, which have been also reported as acquired resistance mechanisms in various types of cancers.

Methods: PC-9 cells and HCC827 cells which were EGFR mutation-positive lung cancer cell lines were mainly utilized in our experiments; they were purchased from ECACC and ATCC, respectively. We mainly utilized osimertinib as an EGFR-TKI and verteporfin as a YAP1 inhibitor. The nuclear translocation of YAP1 was confirmed by fluorescence immunostaining. siRNA was utilized to knock down YAP1. Cell viability assays were performed using CellTiter-Glo reagent. qRT-PCR was performed to confirm the gene expression of cancer stem cells.

Results: YAP1 is activated by nuclear translocation. In PC-9 cells, YAP1 was localized in the nucleus after osimertinib exposure. In contrast, YAP1 was localized in the nucleus of HCC827 cells before osimertinib exposure and remained in the nucleus even after osimertinib exposure. These data suggest that YAP1 activation is correlated with initial resistance. Cell viability assay showed that both PC-9 cells and HCC827 cells became more sensitive to osimertinib with the knocking down of YAP1. In addition, cell viability assays using PC-9 cells with verteporfin and osimertinib showed increased sensitivity to osimertinib. The gene expression of ALDH1A1 and SOX2 which are involved in cancer stem cells were increased in PC-9 cells after osimertinib exposure. On the other hand, the gene expression of ALDH1A1 was up-regulated but SOX2 was down-regulated in HCC827 cells after osimertinib exposure. We hypothesized that increased gene expression of cancer stem cells occurred downstream of YAP1 followed by initial resistance, thus we are currently confirming the gene alteration of cancer stem cells associated with osimertinib exposure with the knocking down YAP1. We are also considering the investigation of combination therapy of EGFR-TKIs and YAP1 inhibitors in vivo studies.

Conclusions: YAP1 and cancer stem cells may be involved in initial resistance mechanisms to EGFR-TKIs in EGFR mutation-positive lung cancer. Our results suggest that especially YAP1 can be a potential therapeutic target, thus we will continue additional studies of combination therapy of EGFR-TKIs and YAP1 inhibitors. In addition, we will continue to investigate whether the gene for cancer stem cells acts downstream of YAP1.

Citation Format: Tatsuya Ogimoto, Hiroaki Ozasa, Kentaro Hashimoto, Hiroshi Yoshida, Kazutaka Hosoya, Masatoshi Yamazoe, Hitomi Ajimizu, Tomoko Funazo, Takahiro Tsuji, Hironori Yoshida, Ryo Itotani, Yuichi Sakamori, Toyohiro Hirai. Elucidation of initial resistance mechanisms in EGFR mutation-positive lung cancer focusing on YAP1 and cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5335.

Abstract 1601: CD47 related to intratumor heterogeneity in alectinib-resistant ALK-rearranged lung cancer cell lines

Overcoming the treatment resistance of cancer is a problem to be solved in improving the prognosis of cancer patients. Recently, genome analysis has revealed that multiple clusters exist in one tumor, and it has been reported that intratumor heterogeneity causes treatment resistance even in lung cancer. However, the mechanism of intratumor heterogeneity has not yet been clarified. Previous studies of intratumor heterogeneity have mainly focused on analyzing cancer cells from patients, classifying clusters of different properties, and identifying factors that define their characteristics. Multiple clusters are present in the tumor tissue of a single patient, and analysis of multiple patients classifies them into even more clusters, but it is difficult to research all of them. To solve this problem, an early model of intratumor heterogeneity in which homogeneous cells become heterogeneous is needed.We hypothesized that intratumor heterogeneity cell model could be found in resistant strains.Alectinib was exposed in vitro to an ALK-positive lung cancer cell line (H2228) to create an alectinib-resistant cell line (H2228-AR1S). H2228-AR1S has two subpopulations that look different. Of the two subpopulations, the smaller cells have high CD47 expression (CD47 high subpopulation), and the scattered spindle-shaped cells have low CD47 expression (CD47 low subpopulation). Using flow cytometry, each subpopulation was isolated, and its properties were investigated. There was no difference in sensitivity to alectinib between the CD47 high subpopulation and the CD47 low subpopulation. In the low subpopulation of CD47, epithelial markers were decreased, and mesenchymal markers were increased using immunoblotting. It suggests that CD47 low subpopulation has undergone epithelial-mesenchymal transition (EMT). The CD47 high subpopulation had high sphere formation ability in vitro, and high tumorigenicity using Xenograft model. CD47 gene inhibition using siRNA reduced the sphere formation ability of the CD47 high subpopulation. This suggests that CD47 is involved in sphere formation.There have been no reports of CD47 being involved in the characteristics of intratumor heterogeneity. Furthermore, using intratumor heterogeneity cell model, we are exploring the mechanism that regulate division into two subpopulations.

Citation Format: Tomoko Y. Funazo, Hiroaki Ozasa, Kentaro Hashimoto, Hiroshi Yoshida, Tatsuya Ogimoto, Kazutaka Hosoya, Hitomi Ajimizu, Takahiro Tsuji, Hironori Yoshida, Ryo Itotani, Yuichi Sakamori, Toyohiro Hirai. CD47 related to intratumor heterogeneity in alectinib-resistant ALK-rearranged lung cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1601.

Relapsing polychondritis after treatment with PD-1 blockade

Nivolumab, a programmed death 1 blockade drug, is used in various types of cancers and can cause a unique immune-related adverse event (irAE). Relapsing polychondritis (RP) is a rare autoimmune disease that mainly involves inflammation of the auricle, nose and airway cartilage. A 72-year-old man with mandibular cancer received nivolumab after surgery for the primary lesion and radiation therapy for lung metastases. He then developed radiation pneumonitis, and prednisolone (PSL) was started. During the tapering of PSL, he developed exertional dyspnea and cough. The condition of mandibular cancer and radiation pneumonitis had not deteriorated. Fluorodeoxyglucose (FDG)-PET/CT showed a thickening of and abnormal FDG uptake in the tracheobronchial and nasal septum cartilage. These characteristic findings were not observed before nivolumab was initiated; thus, we clinically diagnosed the patient as having RP induced by nivolumab. Since the symptoms were mild, the patient's condition was carefully managed with inhaled corticosteroids, and the RP has not progressed thus far. Physicians should be aware that RP can occur as an irAE because RP may progress to serious respiratory symptoms.

Pneumonia Caused by Severe Acute Respiratory Syndrome Coronavirus 2 and Influenza Virus: A Multicenter Comparative Study

Background

Detailed differences in clinical information between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia (CP), which is the main phenotype of SARS-CoV-2 disease, and influenza pneumonia (IP) are still unclear.

Methods

A prospective, multicenter cohort study was conducted by including patients with CP who were hospitalized between January and June 2020 and a retrospective cohort of patients with IP hospitalized from 2009 to 2020. We compared the clinical presentations and studied the prognostic factors of CP and IP.

Results

Compared with the IP group (n = 66), in the multivariate analysis, the CP group (n = 362) had a lower percentage of patients with underlying asthma or chronic obstructive pulmonary disease (P < .01), lower neutrophil-to-lymphocyte ratio (P < .01), lower systolic blood pressure (P < .01), higher diastolic blood pressure (P < .01), lower aspartate aminotransferase level (P < .05), higher serum sodium level (P < .05), and more frequent multilobar infiltrates (P < .05). The diagnostic scoring system based on these findings showed excellent differentiation between CP and IP (area under the receiver operating characteristic curve, 0.889). Moreover, the prognostic predictors were different between CP and IP.

Conclusions

Comprehensive differences between CP and IP were revealed, highlighting the need for early differentiation between these 2 pneumonias in clinical settings.

PD-L1 polymorphisms predict survival outcomes in advanced non-small-cell lung cancer patients treated with PD-1 blockade

BACKGROUND

We previously reported that PD-L1 polymorphisms are associated with the efficacy and immune-related adverse events of PD-1 blockade with nivolumab. However, the association between PD-L1 polymorphisms and survival outcomes under PD-1/PD-L1 blockade is still uncertain. Here, we aimed to investigate whether PD-L1 polymorphisms are associated with survival outcomes in advanced non-small-cell lung cancer (NSCLC) patients treated with nivolumab.

METHODS

PD-1/PD-L1 polymorphisms and survival outcomes were retrospectively analysed in two independent cohorts (133 patients treated with nivolumab and 96 patients with no treatment history of an immune checkpoint inhibitor (ICI) (the non-ICI cohort)) with advanced NSCLC.

RESULTS

Among the 7 studied single-nucleotide polymorphisms, PD-L1 rs822339 and rs1411262 were associated with overall survival (OS) in patients treated with nivolumab. Patients with the A/A genotype of rs822339 had a significantly longer OS than those with A/G or G/G genotypes (not reached versus 12.0 months; hazard ratio (HR), 0.35; 95% confidence interval (CI), 0.18-0.64; p = 0.0008). A similar survival benefit with the A/A genotype was observed regardless of driver mutation status. In multivariate analysis, performance status (PS) and PD-L1 rs822339 genotype were independent prognostic factors for OS. In the non-ICI cohort, the PD-L1 rs822339 genotype did not correlate with OS (HR, 0.77; 95% CI, 0.31-1.70; p = 0.55). The T/T genotype of rs1411262 also showed a significant prolongation of OS compared to that with the C/T or C/C genotypes in patients treated with nivolumab.

CONCLUSIONS

PD-L1 polymorphisms are associated with favourable OS in nivolumab-treated NSCLC patients and may be useful predictive biomarkers, regardless of driver mutation status.

Pembrolizumab-associated bronchiolitis in an elderly lung cancer patient required the treatment with an inhaled corticosteroid, erythromycin and bronchodilators

Immune checkpoint inhibitors (ICIs) have been used to treat lung cancer. Several types of ICI-related interstitial lung diseases have been reported, including organizing pneumonia, non-specific interstitial pneumonia, and diffuse alveolar damage. However, pembrolizumab-associated bronchiolitis requiring treatment for persistent cough has not yet been reported. Here, we describe a patient who developed dry cough while being treated with pembrolizumab for lung adenocarcinoma. Radiography and lung biopsy findings indicated bronchiolitis. His cough improved after the discontinuation of pembrolizumab and treatment with erythromycin, an inhaled corticosteroid, a long-acting muscarinic antagonist, and a long-acting β₂ agonist.

Denture wearing and strong bite force reduce pressure pain threshold of edentulous oral mucosa

Pain in denture supporting tissue is one of the most common and critical problems affecting function and treatment outcomes in complete denture prosthetics. The objective of this study was to investigate the effects of denture wearing and bite force on the pressure pain threshold (PPT) of edentulous oral mucosa. PPT was measured in denture and non-denture-wearing patients by using an electronic-controlled pressure algometer. Bite force was measured in denture-wearing patients by using a pressure-detecting sheet. The mid palate showed 200-300% higher PPT than the buccal alveolar mucosa (two-way anova, P < 0.0001). Denture-wearing patients exhibited 40% lower palatal PPT than non-denture-wearing patients. In denture-wearing patients, PPT in the selected areas of the oral mucosa was negatively correlated with bite force. Denture wearing may reduce PPT in selected areas of the edentulous oral mucosa, and the PPT reduction may be associated with mechanical stress on the mucosa generated by bite force.

Pressure-pain threshold of oral mucosa and its region-specific modulation by pre-loading

Once subjected to denture wearing, oral mucosa has to withstand mechanical loads of various levels and durations. However, how this load affects oral mucosal sensitivity is unknown. This study investigated the pressure-pain threshold (PPT) of oral mucosa with or without pre-loading. An electric pressure algometer was developed specifically for measuring the PPT of oral mucosa. Measurements of 10 dentulous maxillae showed that the baseline PPT (BPPT) of the palatal site was 4.9- and 3.7-fold greater than that of the labial or buccal sites, respectively. The PPT of the labial site decreased significantly compared with its BPPT after 2 s-100% BPPT and 5 s-100% BPPT pre-loading. The PPT of the palatal site increased after 5 s-50% BPPT and 5 s-80% BPPT and 0.2 s-100% BPPT and 2 s-100% BPPT pre-loading. The PPT of the buccal site did not change after all levels and durations of pre-loadings tested. These results indicated the disproportionate modulation of oral mucosal PPT following various loads, suggesting that oral mucosa possesses region-specific psychophysical tolerance to mechanical stimuli.

Mapping, profiling and clustering of pressure pain threshold (PPT) in edentulous oral mucosa

OBJECTIVES

Edentulous oral mucosa involves different tissue types, various innervation and wound healing process. We hypothesized that pressure pain threshold (PPT) of edentulous oral mucosa varies significantly among different regions. The objective of this study is to examine regional differences and correlations of PPT in edentulous oral mucosa.

METHODS

Pain threshold (PPT) was measured at 112 sites in 15 edentulous patients using an electric-controlled pressure algometer. PPT mapping was created by the level of PPT, and PPT clustering was undertaken based on the inter-site correlation of PPT.

RESULTS

PPT increased from the anterior to posterior alveolus in both maxilla and mandible, but decreased from the anterior palate to the posterior palate. PPT decreased from the ridge crest to the buccal vestibule. The inter-site difference was four fold within the maxilla and 2.4 fold within the mandible. Principal component analysis applied on PPT inter-site correlation matrix revealed that the maxilla and mandible could be differentiated statistically. The maxilla and mandible were divided into three and four clusters, respectively.

CONCLUSION

These results demonstrate that different areas of edentulous oral mucosa have different PPT and that the PPT varies proportionally in selected areas, providing useful diagnostic and therapeutic information in removable prosthodontics and a new opportunity for understanding pain underneath the denture.

Pressure-pain threshold determination in the oral mucosa: validity and reliability

Fundamental knowledge of pain in the oral mucosa is lacking. We determined the validity and reliability of the pressure-pain threshold (PPT) measurement in the oral mucosa using a newly developed hand-held pressure algometer. Ten dentulous subjects were recruited, and the PPT was measured at the bilateral buccal (on the attached gingiva apical to the midline of the upper first premolars, 3 mm from the mucogingival junction) and the palatal sites (mid-point between the bilateral upper first molars). The PPT linearly increased with an increase in load-rate (P < 0.0001). The PPT yielded a high intra-individual stability both for the same-day consecutive trials and weekly sessions. The palatal site revealed a 4- to 4.65-fold greater PPT than the buccal sites (Bonferroni, P < 0.0001), whereas no difference was found between the bilateral buccal sites (P=0.663). Despite a great interindividual variation in the PPT, significant intra-individual correlations were found among the measurement sites. This suggested differences in individual sensitivity to pain in the oral mucosa, which may determine overall pain sensation specific to an individual. A pressure algometer described herein reliably assessed the PPT in the oral mucosa and sensitively discriminated PPT differences at different sites and at different load-rates, suggesting the reliability and validity of PPT measurements in the oral mucosa for clinical and research investigations.

The relationship between non-working-side occlusal contacts and mandibular position

No clear description can be found regarding the lateral position when examining non-working-side occlusal contacts. The objective of this study was to test the hypothesis that the non-working-side contact pattern varies with the mandibular position. The characteristics of the non-working-side contact pattern were also determined relative to the working-side contact pattern. Occlusal contacts of 86 young adults were examined using shim stock in standardized lateral positions: 0.5, 1, 2 and 3 mm from the maximum intercuspation (MI), where the 0.5, 1 and 2 mm positions were defined as lateral positions close to the MI and the 3 mm position as an edge-to-edge position. The frequency of non-working-side occlusal contacts decreased gradually from 0.5 to 3 mm position. The frequency of non-working-side contacts was significantly greater in the 0.5 and 1 mm positions than in the 3 mm position. Non-working-side occlusal contacts occurred in nearly half of the 0.5 mm positions. Non-working-side contacts were significantly less frequent with canine protection than with group function for the 0.5 and 1 mm positions. There were no significant differences between the two occlusal schemes for the 2 and 3 mm positions. In conclusions, the non-working-side contact pattern varied with the mandibular position. These results suggest that clinical examination should include contact patterns both in a position close to the MI and in an edge-to-edge position, i.e. in functional and parafunctional ranges. Likewise, data from occlusal contact research should include a standardized definition of mandibular position.

Validity of the examination method of occlusal contact pattern relating to mandibular position

OBJECTIVE

This study was based on the hypothesis that conflicting findings and inconclusive consensus regarding the role of occlusal factors in the masticatory system are due to the variations in the definitions and methods used to describe and examine the occlusal factors. The object of this study was to determine whether contact patterns during lateral movement vary with mandibular positions and whether the contact pattern in lateral positions close to the maximum intercuspation has characteristics distinct from those in an edge-to-edge position.

METHODS

Occlusal contacts of 86 young adults were examined using shim stock in regulated lateral positions: 0.5, 1, 2 and 3 mm from the maximum intercuspation, where the 0.5, 1 and 2 mm positions were defined as lateral positions close to the maximum intercuspation and the 3 mm position as an edge-to-edge position.

RESULTS

The occlusal contact pattern in the 0.5 mm position showed a marked prevalence of posterior tooth contacts on the working and the non-working sides, compared with the 1, 2 and 3 mm positions. The occlusal contact pattern in the 3 mm position predicted the presence or absence of the occlusal contact in the 1 and 2 mm positions (sensitivity > 0.7) but not in the 0.5 mm position (sensitivity < 0.6).

CONCLUSION

The occlusal contact patterns during lateral movement varied greatly with mandibular positions. The examination method of the occlusal contact pattern in one unregulated position will be invalid. It is necessary to distinguish the occlusal contact patterns between a position close to the maximum intercuspation and an edge-to-edge position when investigating its role in the masticatory system and in oral disease.

Pattern of occlusal contacts in lateral positions: canine protection and group function validity in classifying guidance patterns

STATEMENT OF PROBLEM

The concept of canine protection and group function lack consistency in the definitions and examining methods, and a valid system for evaluating and classifying occlusal contact patterns has not been established.

PURPOSE

This study assessed the use of canine protection and group function in classifying occlusal guidance in the natural dentition.

MATERIAL AND METHODS

Occlusal contacts of 86 young adults were examined with shim stock in regulated lateral positions, 0.5,1,2 and 3 mm from the maximum intercuspation. The patterns of occlusal contacts varying with the lateral position were described.

RESULTS

Focusing on the working-side contact only, most contact patterns belonged to group function, and a few to canine protection. Focusing on both the working and nonworking side contacts, nearly half the contact patterns were those other than canine protection and group function and were classified into balanced occlusion.

CONCLUSION

The validity of the classification system using canine protection and group function is questionable. A new classification system of occlusal guidance is desirable.