Polymorphism in epigenetic regulating genes in relation to periodontitis, number of teeth, and levels of high-sensitivity C-reactive protein and glycated hemoglobin: The Tromsø Study 2015-2016.

BACKGROUND: The aim of this study was to investigate the association between periodontitis and four single nucleotide polymorphisms (SNPs) in genes involved in epigenetic regulation of DNA, and between these same SNPs and tooth loss, high-sensitivity C-reactive protein (hs-CRP), and glycated hemoglobin (HbA1c) levels. METHODS: We included participants with periodontal examination (n = 3633, aged: 40-93 years) from the Tromsø Study seventh survey (2015-2016), Norway. Periodontitis was defined according to the 2017 AAP/EFP classification system as no periodontitis, grades A, B, or C. Salivary DNA was extracted and genotyping was performed to investigate four SNPs (rs2288349, rs35474715, rs34023346, and rs10010325) in the sequence of the genes DNMT1, IDH2, TET1, and TET2. Association between SNPs and periodontitis was analyzed by logistic regression adjusted for age, sex, and smoking. Subgroup analyses on participants aged 40-49 years were performed. RESULTS: In participants aged 40-49 years, homozygous carriage of minor A-allele of rs2288349 (DNMT1) was associated with decreased susceptibility to periodontitis (grade A: odds ratio [OR] 0.55; p = 0.014: grade B/C OR 0.48; p = 0.004). The minor A-allele of rs10010325 (TET2) was associated with increased susceptibility to periodontitis (grade A OR 1.69; p = 0.035: grade B/C OR 1.90; p = 0.014). In the entire sample, homozygous carriage of the G-allele of rs35474715 (IDH2) was associated with having ≤24 teeth (OR 1.31; p = 0.018). Homozygous carriage of the A-allele of TET2 was associated with hs-CRP≥3 mg/L (OR 1.37; p = 0.025) and HbA1c≥6.5% (OR 1.62; p = 0.028). CONCLUSIONS: In this Norwegian population, there were associations between polymorphism in genes related to DNA methylation and periodontitis, tooth loss, low-grade inflammation, and hyperglycemia.

Genetic contribution to cancer risk in patients with tooth loss: a genetic association study.

Early-stage cancer diagnosis is critical for higher survival rates. Because early cancers can be difficult to detect, our focus is on the identification of cancer risk markers such as pleiotropic genes involved in the etiology of both craniofacial conditions and cancers. In this study we aimed to test if our previously detected association between ERN1 rs196929 marker and oral health outcomes would be detected in individuals diagnosed with cancer as well as in a subpopulation of individuals who also had one or more teeth missing due to dental caries, periodontal disease, or periapical lesions. We genotyped a total of 1,671 subjects and selected a subset of 1,421 subjects for stratified analysis of cancer types; three hundred and twelve self-reported a diagnosis of various cancer types and 1,109 reported never receiving a diagnosis of cancer. Our results showed a statistically significant association between the rs196929 in ERN1, and cancer overall in both the additive and dominant models (OR = 1.37, 95% C.I. 1.06-1.79, p = 0.014). When we stratified the analysis for each cancer type, our results show that the rs196929 ERN1 variant is associated with skin cancer (OR = 2.07, 95% C.I. 1.27-3.37, p = 0.003) and breast cancer (OR = 1.83, 95% C.I. 1.13-2.99, p = 0.013) in the subset of patients that had tooth loss. An additional nominal association between the rs196929 in ERN1 and male's reproductive system cancers (OR = 1.96, 95% C.I. 1.07-3.59, p = 0.028) was identified. We hope that our study helps guide future genetic studies on these cancers and this specific genetic variant as well as drive attention to the potential for oral health outcomes to serve as indicators for cancer risk. The early identification of genetic markers and/or oral conditions that indicate increased cancer risk could positively impact cancer outcomes and survival rates with timely implementation of preventive and diagnostic measures. In conclusion, our results suggest that the genetic variant in ERN1 (rs196929) is associated with increased risk of skin and breast cancers.

Using national register data to estimate the heritability of periodontitis.

AIM: To identify whether periodontal traits derived from electronic dental records are biologically informative and heritable. MATERIALS AND METHODS: The study included 11,974 adult twins (aged 30-92 years) in the Swedish Twin Registry. Periodontal records from dental examinations were retrieved from a national register and used to derive continuous measures of periodontal health. A latent class approach was used to derive categorial measures of periodontal status. The correlation patterns in these traits were contrasted in monozygotic and dizygotic twin pairs using quantitative genetic models to estimate the heritability of the traits. RESULTS: For continuous traits, heritability estimates ranged between 41.5% and 48.3% with the highest estimates for number of missing tooth surfaces and rate of change in number of deep periodontal pockets (≥6 mm). For categorial traits, the latent class approach identified three classes (good periodontal health, mild periodontitis signs and severe signs of periodontitis) and there was a clear difference in the hazard for subsequent tooth loss between these three classes. Despite this, the class allocations were only slightly more heritable than a conventional dichotomous disease definition (45.2% vs. 42.6%). CONCLUSIONS: Periodontitis is a moderately heritable disease. Quantitative periodontal traits derived from electronic records are an attractive target for future genetic association studies.

Tooth loss and adiposity: possible role of carnitine transporter (OCTN1/2) polymorphisms in women but not in men.

OBJECTIVE: SLC22A4/5 single nucleotide polymorphisms (SNPs) have been reported to affect inflammatory diseases. We report the relationship of these polymorphisms with adiposity and tooth loss as elucidated in a 10-year follow-up study. METHODS: Participants of the Study of Health in Pomerania (SHIP, N = 4105) were genotyped for the polymorphisms c.1507C > T in SLC22A4 (rs1050152) and -207C > G in SLC22A5 (rs2631367) using allele-specific real-time PCR assays. A total of 1817 subjects, 934 female and 883 male aged 30-80 years, underwent follow-up 10 years later (SHIP-2) and were assessed for adiposity and tooth loss. RESULTS: The frequencies of the rarer SLC22A4 TT and SLC22A5 CC alleles were 16.7% and 20.3%, respectively. In women, tooth loss was associated with genotype TT vs. CC with incidence rate ratio IRR = 0.74 (95%C.I. 0.60-0.92) and CC vs. GG IRR = 0.79 (0.65-0.96) for SLC22A4 and SLC22A5 SNPs, respectively. In men, no such associations were observed. In the follow-up examination, the relationship between tooth loss and these SNPs was in parallel with measures of body shape such as BMI, body weight, waist circumference, or body fat accumulation. The association between muscle strength and body fat mass was modified by the genotypes studied. CONCLUSIONS: SLC22A4 c.150C > T and SLC22A5 -207C > G polymorphisms are associated with tooth loss and markers of body shape in women but not in men. CLINICAL RELEVANCE: Tooth loss may be related to obesity beyond inflammatory mechanisms, conceivably with a genetic background.

Facilitation of Bone Healing Processes Based on the Developmental Function of Meox2 in Tooth Loss Lesion.

In the present study, we examined the bone healing capacity of Meox2, a homeobox gene that plays essential roles in the differentiation of a range of developing tissues, and identified its putative function in palatogenesis. We applied the knocking down of Meox2 in human periodontal ligament fibroblasts to examine the osteogenic potential of Meox2. Additionally, we applied in vivo periodontitis induced experiment to reveal the possible application of Meox2 knockdown for 1 and 2 weeks in bone healing processes. We examined the detailed histomorphological changes using Masson's trichrome staining and micro-computed tomography evaluation. Moreover, we observed the localization patterns of various signaling molecules, including α-SMA, CK14, IL-1ß, and MPO to examine the altered bone healing processes. Furthermore, we investigated the process of bone formation using immunohistochemistry of Osteocalcin and Runx2. On the basis of the results, we suggest that the knocking down of Meox2 via the activation of osteoblast and modulation of inflammation would be a plausible answer for bone regeneration as a gene therapy. Additionally, we propose that the purpose-dependent selection and application of developmental regulation genes are important for the functional regeneration of specific tissues and organs, where the pathological condition of tooth loss lesion would be.

Age-Associated Tooth Loss and Oral Microbial Dysbiosis in a Mouse Genetic Model of Chronic Nicotine Exposure.

Nicotine acts as a potent modulator of normal cellular responses through the nicotinic acetylcholine receptor subtype alpha7. In a mouse genetic model of alpha7 receptor dysfunction, alpha7E260A:G, 85 percent of 18 month-old mice exhibit an age-associated spontaneous loosening or complete loss of 3rd molars that was not present in the control mice. The adjacent soft tissues appeared largely unaffected. Further analysis including micro-CT revealed evidence of bone loss surrounding the 3rd molars with areas of cavitation and/or sponge-like (cancellous) bone remodeling in the mandible. The mandible microbiome was examined using 16S-rRNA sequencing. The results show the alpha7E260A:G oral microbiome included increased landscape complexity indicative of dysbiosis, and a significant increase of some bacteria, particularly Staphylococcus. These results suggest that normal alpha7 function plays a relevant role in maintaining normal gene expression and oral microbiome stasis. Consequently, this mouse model suggests there are consequences to ongoing alpha7 receptor dysfunction and oral health, as can occur from chronic exposure to nicotine as expected from electronic nicotine delivery systems (ENDS or "vaping"), that may not be seen until older age.

A novel nonsense variant in SLC24A4 causing a rare form of amelogenesis imperfecta in a Pakistani family.

BACKGROUND: Amelogenesis imperfecta (AI) is a highly heterogeneous group of hereditary developmental abnormalities which mainly affects the dental enamel during tooth development in terms of its thickness, structure, and composition. It appears both in syndromic as well as non-syndromic forms. In the affected individuals, the enamel is usually thin, soft, rough, brittle, pitted, chipped, and abraded, having reduced functional ability and aesthetics. It leads to severe complications in the patient, like early tooth loss, severe discomfort, pain, dental caries, chewing difficulties, and discoloration of teeth from yellow to yellowish-brown or creamy type. The study aimed to identify the disease-causing variant in a consanguineous family. METHODS: We recruited a consanguineous Pashtun family of Pakistani origin. Exome sequencing analysis was followed by Sanger sequencing to identify the pathogenic variant in this family. RESULTS: Clinical analysis revealed hypomaturation AI having generalized yellow-brown or creamy type of discoloration in affected members. We identified a novel nonsense sequence variant c.1192C > T (p.Gln398*) in exon-12 of SLC24A4 by using exome sequencing. Later, its co-segregation within the family was confirmed by Sanger sequencing. The human gene mutation database (HGMD, 2019) has a record of five pathogenic variants in SLC24A4, causing AI phenotype. CONCLUSION: This nonsense sequence variant c.1192C > T (p.Gln398*) is the sixth disease-causing variant in SLC24A4, which extends its mutation spectrum and confirms the role of this gene in the morphogenesis of human tooth enamel. The identified variant highlights the critical role of SLC24A4 in causing a rare AI type in humans.

Phenome-Wide Scan Finds Potential Orofacial Risk Markers for Cancer.

Cancer is a disease caused by a process that drives the transformation of normal cells into malignant cells. The late diagnosis of cancer has a negative impact on the health care system due to high treatment cost and decreased chances of favorable prognosis. Here, we aimed to identify orofacial conditions that can serve as potential risk markers for cancers by performing a phenome-wide scan (PheWAS). From a pool of 6,100 individuals, both genetic and epidemiological data of 1,671 individuals were selected: 350 because they were previously diagnosed with cancer and 1,321 to match to those individuals that had cancer, based on age, sex, and ethnicity serving as a comparison group. Results of this study showed that when analyzing the individuals affected by cancer separately, tooth loss/edentulism is associated with SNPs in AXIN2 (rs11867417 p = 0.02 and rs2240308 p = 0.02), and leukoplakia of oral mucosa is associated with both AXIN2 (rs2240308 p = 0.03) and RHEB (rs2374261 p = 0.03). These phenotypes did not show the same trends in patients that were not diagnosed with cancer, allowing for the conclusion that these phenotypes are unique to cases with higher cancer risk.

Tooth Regeneration: Insights from Tooth Development and Spatial-Temporal Control of Bioactive Drug Release.

Tooth defect and tooth loss are common clinical diseases in stomatology. Compared with the traditional oral restoration treatment, tooth regeneration has unique advantages and is currently the focus of oral biomedical research. It is known that dozens of cytokines/growth factors and other bioactive factors are expressed in a spatial-temporal pattern during tooth development. On the other hand, the technology for spatial-temporal control of drug release has been intensively studied and well developed recently, making control release of these bioactive factors mimicking spatial-temporal pattern more feasible than ever for the purpose of tooth regeneration. This article reviews the research progress on the tooth development and discusses the future of tooth regeneration in the context of spatial-temporal release of developmental factors.

The concept of exposure when selecting comparison groups for determining individual susceptibility to addiction to cigarette smoking.

Smoking is a leading cause of preventable death. The effect of tobacco is even more contundent in people with mental illness and, in general, cigarette smoking addiction is influenced by genetic factors. The opioid system is involved in the mesolimbic reward system, which is of great importance in addictive behaviors, such as smoking and is influenced by genes such as the OPRM1. The aim of this study was to evaluate if selecting a comparison group that include light smokers versus people that never smoked impacts the results of genetic association studies. In addition, to evaluate the genetic association in different groups of smokers by analyzing independent covariates such as mental illness and clinical dental data. All subjects were participants of the Dental Registry and DNA Repository project. Genotyping was carried out using TaqMan chemistry for two markers in OPRM1 (rs553202 and rs7755635). Logistic regression analyses were performed as implemented in PLINK. The established value for alpha was 5%, and the Hardy-Weinberg equilibrium was evaluated by the chi-square test with one degree of freedom for each marker. 1,897 patients were included, which were allocated to eight distinct groups, according to the frequency and quantity of cigarettes smoked and mental illness status. There was no significant association between the two markers in OPRM1 and smoking. When mental illness and dental clinical data (tooth loss, dental caries, and periodontitis) were used as covariates, there were associations between heavy smoking and OPRM1, when non-smokers were used as comparison. We did not have diet or microbiome data to consider for these dental analyses and suggest that these kinds of data should be always incorporated in the future. Significant results were found only when the covariables mental illness and oral clinical data were added to the analysis.

GWAS for Interleukin-1ß levels in gingival crevicular fluid identifies IL37 variants in periodontal inflammation.

There is no agnostic GWAS evidence for the genetic control of IL-1ß expression in periodontal disease. Here we report a GWAS for "high" gingival crevicular fluid IL-1ß expression among 4910 European-American adults and identify association signals in the IL37 locus. rs3811046 at this locus (p = 3.3 × 10-22) is associated with severe chronic periodontitis (OR = 1.50; 95% CI = 1.12-2.00), 10-year incident tooth loss (≥3 teeth: RR = 1.33; 95% CI = 1.09-1.62) and aggressive periodontitis (OR = 1.12; 95% CI = 1.01-1.26) in an independent sample of 4927 German/Dutch adults. The minor allele at rs3811046 is associated with increased expression of IL-1ß in periodontal tissue. In RAW macrophages, PBMCs and transgenic mice, the IL37 variant increases expression of IL-1ß and IL-6, inducing more severe periodontal disease, while IL-37 protein production is impaired and shows reduced cleavage by caspase-1. A second variant in the IL37 locus (rs2708943, p = 4.2 × 10-7) associates with attenuated IL37 mRNA expression. Overall, we demonstrate that IL37 variants modulate the inflammatory cascade in periodontal disease.

Oral manifestations, dental management, and a rare homozygous mutation of the PRDM12 gene in a boy with hereditary sensory and autonomic neuropathy type VIII: a case report and review of the literature.

BACKGROUND: Hereditary sensory and autonomic neuropathy type VIII is a rare autosomal recessive inherited disorder. Chen et al. recently identified the causative gene and characterized biallelic mutations in the PR domain-containing protein 12 gene, which plays a role in the development of pain-sensing nerve cells. Our patient's family was included in Chen and colleagues' study. We performed a literature review of the PubMed library (January 1985 to December 2016) on hereditary sensory and autonomic neuropathy type I to VIII genetic disorders and their orofacial manifestations. This case report is the first to describe the oral manifestations, and their treatment, of the recently discovered hereditary sensory and autonomic neuropathy type VIII in the medical and dental literature. CASE PRESENTATION: We report on the oral manifestations and dental management of an 8-month-old white boy with hereditary sensory and autonomic neuropathy-VIII over a period of 16 years. Our patient was homozygous for a mutation of PR domain-containing protein 12 gene and was characterized by insensitivity to pain and thermal stimuli, self-mutilation behavior, reduced sweat and tear production, absence of corneal reflexes, and multiple skin and bone infections. Oral manifestations included premature loss of teeth, associated with dental traumata and self-mutilation, severe soft tissue injuries, dental caries and submucosal abscesses, hypomineralization of primary teeth, and mandibular osteomyelitis. CONCLUSIONS: The lack of scientific knowledge on hereditary sensory and autonomic neuropathy due to the rarity of the disease often results in a delay in diagnosis, which is of substantial importance for the prevention of many complications and symptoms. Interdisciplinary work of specialized medical and dental teams and development of a standardized treatment protocols are essential for the management of the disease. There are many knowledge gaps concerning the management of patients with hereditary sensory and autonomic neuropathy-VIII, therefore more research on an international basis is needed.

Heritability of the Number of Teeth in Middle-Aged and Older Danish Twins.

Tooth loss is a common health concern in older adults. We aimed to estimate the relative contributions of genetic and environmental factors to the variation in the number of teeth in middle-aged and older populations using a population-based cohort of Danish twins. The study included 5,269 Danish middle-aged or older twins who provided data on the number of teeth at baseline by structured interviews. The data were analyzed using univariate liability threshold modeling, stratified by sex and age, to estimate familial risk of tooth loss as well as estimates of heritability. In the whole cohorts, 23% of participants were edentate and 53% had retained 20 or more teeth. A statistical model including additive genetic factors and environmental factors partly shared by co-twins and partly unique to each individual twin gave the best statistical fit for the number of teeth in both age categories as well as in men and women. Overall, additive genetic factors explained 36% (95% confidence interval [CI]: 23% to 49%), common environmental factors 20% (95% CI: 9% to 31%), and unique environmental factors 44% (95% CI: 40% to 48%) of the total variation of the number of teeth. This study indicates that a substantial part of the variation in tooth loss is explained by genetic as well as environmental factors shared by co-twins. Our results implied that family background importantly affects tooth loss in both the middle-aged and the older populations. Family history is thus an important factor to take into account in dental health care.

Effects of Tooth Loss and the Apolipoprotein E ɛ4 Allele on Mild Memory Impairment in the Fujiwara-kyo Study of Japan: A Nested Case-Control Study.

BACKGROUND: Several studies have suggested that periodontal disease can exacerbate the pro-inflammatory status of the brain. Tooth loss is one of the alternative evaluation indices of periodontal disease. There are few data on the relationship between tooth loss and memory impairment, depending on the apolipoprotein E (APOE) ɛ4 genotype. OBJECTIVE: To determine if tooth loss is associated with mild memory impairment (MMI) and if this association is modified by the presence of the APOEɛ4 allele. METHODS: A nested case-control study was conducted from 2007 to 2012 in Japan. Five hundred and thirty-seven Japanese subjects aged 65 years and over who were cognitively intact at baseline were analyzed. MMI at follow-up was evaluated. RESULTS: The median number of teeth at baseline was significantly lower in MMI participants (n = 179) than in controls (n = 358) (MMI: median 21.0, interquartile range 10.0-25.0 versus controls: 24.0, 14.0-27.0). After adjustment for demographics, vascular risk factors, and APOEɛ4 allele, the multivariate adjusted odds ratio (OR) of ≤8 teeth was 1.97 (95% confidence interval [CI], 1.13-3.44) compared to 25-32 teeth. Participants with both the presence of at least 1 APOEɛ4 allele and ≤8 teeth had a higher risk of MMI compared with those with neither (OR, 2.82; 95% CI, 1.15-6.91). Those with either risk factor alone did not have a higher risk of MMI. CONCLUSIONS: A lower number of teeth is related to risk of MMI. This may be primarily true for those individuals with an APOEɛ4 allele.

[The relationship of molecular genetic markers with clinical signs and risk factors of periodontitis]. / Vzaimosvyaz' molekulyarno-geneticheskikh markerov s klinicheskimi priznakami i faktorami riska razvitiya parodontita.

The study revealed positive correlation between bleeding on probing and teeth loss risk with periodontal hypercolonization by Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. Pathological tooth mobility was associated with hypercolonization by P. intermedia and Tannerella forsythensis. Expression of IL8, TNF-α, MMP8 and MMP9 genes was also assessed in patient groups divided according to the depth of periodontal pockets and-the severity of chronic periodontitis revealing IL8 as positive diagnostic marker.

Unusual cutaneous features associated with a heterozygous gain-of-function mutation in IFIH1: overlap between Aicardi-Goutières and Singleton-Merten syndromes.

Cutaneous lesions described as chilblain lupus occur in the context of familial chilblain lupus or Aicardi-Goutières syndrome. To date, seven genes related to Aicardi-Goutières syndrome have been described. The most recently described encodes the cytosolic double-stranded RNA receptor IFIH1 (also known as MDA5), a key component of the antiviral type I interferon-mediated innate immune response. Enhanced type I interferon signalling secondary to gain-of-function mutations in IFIH1 can result in a range of neuroinflammatory phenotypes including classical Aicardi-Goutières syndrome. It is of note that none of the patients with a neurological phenotype so far described with mutations in this gene was reported to demonstrate cutaneous involvement. We present a family segregating a heterozygous pathogenic mutation in IFIH1 showing dermatological involvement as a prominent feature, variably associated with neurological disturbance and premature tooth loss. All three affected individuals exhibited increased expression of interferon-stimulated genes in whole blood, and the mutant protein resulted in enhanced interferon signalling in vitro, both in the basal state and following ligand stimulation. Our results further extend the phenotypic spectrum associated with mutations in IFIH1, indicating that the disease can be confined predominantly to the skin, while also highlighting phenotypic overlap with both Aicardi-Goutières syndrome and Singleton-Merten syndrome.

Effects of IL6 C-634G polymorphism on tooth loss and their interaction with smoking habits.

OBJECTIVE: To examine the association between an IL6 (Interleukin-6) polymorphism (C-634G or rs1800796) and tooth loss, and an interaction between the polymorphism and smoking habits for the loss. MATERIAL AND METHODS: Our subjects were 4917 check-up examinees ages 35-69. They reported tooth loss and lifestyle in a questionnaire. We regressed the number of teeth on the IL6 genotype, gender, age, smoking, drinking, diabetes, hypertension, physical activity, energy intake, education, and brushing. We further estimated multivariate-adjusted odds ratios (ORs) for having <20 teeth. RESULTS: Participants with a GG genotype tended to have less teeth than those with CC; ß = -0.798 (95% confidence interval [CI] = -1.501--0.096). Subjects with a GG genotype were more likely to have <20 teeth than those with CC; OR was 1.56 (95% CI = 1.08-2.25). Association between current smoking and tooth loss was stronger among those with GG than among those with CC. In a multiple regression analysis, a significant interaction was found between GG genotype and current smoking in the prediction of tooth loss (P = 0.018). CONCLUSION: The IL6 C-634G polymorphism was significantly associated with tooth loss. Our results suggest greater effects of smoking on tooth loss in GG genotype individuals.

Long-term change of disease behavior in Papillon-Lefèvre syndrome: seven years follow-up.

Papillon-Lefèvre syndrome (PLS) is an autosomal recessive disease, characterized by severe periodontitis and palmoplantar hyperkeratosis. Mutations in the cathepsin C (CTSC) gene are the causative genetic factor. PLS starts at very early age, however, the age associated change of PLS has never been characterized. In this report, four PLS patients with CTSC mutations were followed up for seven years, periodontal condition and serum immunoglobulins (Igs) were recorded. Results showed that periodontal inflammation of PLS peaked at teenage years, but declined with time. At the same time the serum IgE change was consistent with the change, suggesting the possibility of using IgE as a monitoring index for PLS inflammation level, or to develop new target for therapy.

Tooth loss induces memory impairment and neuronal cell loss in APP transgenic mice.

Tooth loss is a known risk factor of Alzheimer's disease (AD). However, the association of tooth loss with the molecular pathogenesis of AD is still unknown. The hypothesis that the molecular pathogenesis of AD is enhanced by molar tooth loss was tested. Seventeen female transgenic mice (J20) were divided into the experimental (EX, n=10) and control (C, n=7) groups. In the EX group, maxillary bilateral molar teeth were extracted at the age of 6 months. In the C group, however, these teeth remained intact. Passive avoidance test was performed to evaluate learning and memory abilities right after tooth extraction (6 months old) and 4 months later (10 months old). After the test at 10 months, amyloid beta (Aß) deposition and changes of neuronal cell number and area in the hippocampus were investigated using half of the brains. The other half was homogenized and used to determine Aß40 and Aß42 levels by ELISA. At the 10 months of age, learning and memory abilities were significantly impaired in the EX group compared to the C group (P<0.05). The neuronal cell number in the CA1 and CA3 regions was significantly lower in the EX group than in the C group (P<0.05). Total Aß, Aß40, and Aß42 levels showed no significant intergroup difference. Molar tooth loss may cause neuronal cell loss in the hippocampus, leading to memory impairment; this process may be independent of the amyloid cascade.