Relationship Between Dental Erosion And Gastro-esophageal Reflux Disease And Impact Of Refluxed Gastrointestinal Contents On Dentin

Dental erosion (DE) is an acid-induced loss of dental hard tissue without the involvement of bacteria. The etiological factors of dental erosion are often categorised into two groups:intrinsic and extrinsic factors. Intrinsic factor mainly refers to regurgitated gastric acid. The regurgitated acid has a pH of approximately 1-2 which is much lower than the critical pH 5.5 of enamel dissolution.Gastro-esophageal reflux disease (GERD) is a condition which develops when the reflux of gastrointestinal contents causes troublesome symptoms and/or complications. GERD has become one of the most common diseases in modern civilization. Its symptoms are subclassified into esophageal and extra-esophageal symptoms. GERD can result into esophageal symptoms such as regurgitation and heartburn. It can also be associated with many extra-esophageal symptoms, including oral cavity, ear, nose, throat, trachea, bronchus and pulmonary manifestations. Among these extra-esophageal symptoms, dental erosion, chronic cough, asthma and laryngitis were proved to have significant correlations with reflux by the Global Evidence-based Consensus in 2006.GERD is a common disease in western countries and the prevalence is about 10%～30%. The average prevalence of GERD in China is 3.1% showing an upward trend. Although the prevalence of GERD in China is lower than that in western countries, the number of GERD patients in China is surprising because of the huge population of our country. If number of GERD patients with dental erosion is calculated by average prevalence (24%), there are at least 10 million people appearing dental erosion in China. So dental erosion is becoming a common disease in China, and doctors and patients should pay more attention on it. Till now, there is no clinical data about dental erosion of GERD patients of our country and influencing factors are not clear. So we did this clinical investigation to describe the prevalence of dental erosion and associated factors in GERD patients of China.GERD may cause extra-esophageal symptoms by two possible mechanisms:direct injury to extra-esophageal tissues by refluxed gastric contents (reflux mechanism), and vagally mediated reflex from distal esophageal acid exposure (reflex mechanism).The severity of dental erosion appeared to be correlated with proximal reflux. Chronic cough, asthma, laryngitis are respiratory symptoms of GERD which can be caused by reflux mechanism or reflex mechanism, or both of them. The reflux mechanism has been consistently demonstrated in both human and animal studies. Since both dental erosion and respiratory symptoms are related to proximal reflux in GERD patients, there might be some correlationship between them. The laryngeal pharynx is a critical position which serves as a passageway for food and air, and is connected with esophagus, trachea, oral cavity and nasal cavity. When the reflux reaches this position, it gets a chance to go down to trachea and lungs by micro-aspiration to cause asthma, cough and relevant respiratory symptoms, or go higher into the oral cavity potentially to cause dental erosion. It has been previously shown that GERD patients with airway symptoms have more reflux to proximal esophagus and laryngeal pharynx. Thus, GERD patients with airway symptoms may be at higher risk to develop dental erosion. However, little attention has been focused on the relationship between them from the aspect of reflux mechanism. Therefore, the aim of this study was to investigate the association between dental erosion and respiratory symptoms in patients with GERD.The prevalence of dental erosion in GERD patients is higher than that in normal people and other susceptible people. Besides enamel erosion, some GERD patients show dentin erosion, even lost entire shape of occlusal surface in some serious cases. Other common pathogenic factors can cause dentin erosion but not so worse. The strong erosion potential of refluxed gastrointestinal contents may be responsible for the serious dentin erosion in GERD patients. The refluxed gastrointestinal content is a mixture including food, gastric acid, inorganic ions and digestive enzymes et al. These substances may act together and produce multiple effects on dentin.Previous researches about erosion had mainly focused on enamel, while study about dentin erosion was little. There was less research has been done on the effect of refluxed gastrointestinal contents on dentin. Pathogenetic progresss and mechanism of dentin are still unclear. So we did these vitro experiments to investigate the impact of refluxed gastrointestinal contents (gastric acid, pepsin, trypsin and chymotrypsin) on the dentin.Objective:To describe the prevalence of dental erosion and associated factors in GERD patients, to determine whether dental erosion was correlated with respiratory symptoms in GERD patients, to investigate the impact of refluxed gastrointestinal contents (gastric acid, pepsin, trypsin and chymotrypsin) on the dentin in vitro.Methods:The study consisted of two parts:Part 1:Relationship between dental erosion and gastro-esophageal reflux disease.Chapter 1:Prevalence and influencing factors of dental erosion in GERD patients. 105 GERD patients and 36 healthy controls were recruited. All subjects underwent questionnaire answering and dental examination. Dental erosions were measured by modified method of Smith and Knight Tooth Wear Index (TWI). Analyse prevalence and risk factors of dental erosion in GERD patients.Chapter 2:Relationship between dental erosion and respiratory symptoms in GERD patients.88 GERD patients were recruited and assigned into three groups mainly according to the frequency of respiratory symptoms:GroupⅠ:never; GroupⅡ: occasional (1-2 days a week or less); GroupⅢ:frequent (3-5 days a week or more). All patients underwent medical evaluations, including medical history, questionnaire answering and alimentary tract examinations. Dental examinations were carried out on these patients. Dental erosions were measured by modified method of Smith and Knight Tooth Wear Index (TWI). Location and severity of dental erosion were recorded.Part 2:Impact of refluxed gastrointestinal contents on dentin.Chapter 3:Effect of gastric acid on dentin in vitro. Dentin specimens were eroded by pH 2.0, pH 3.6, pH 5.2 HCl for short-term (0-30 min) or long-term (10 days). Chemical compositions, surface microhardness and surface appearance of dentin specimens were measured by different detection methods.Chapter 4:Impact of gastrointestinal proteolytic enzymes on dentin in vitro. Dentin specimens were eroded by proteolytic enzymes of gastrointestinal tract (pepsin, trypsin and chymotrypsin) either alone or in combination for 10 days. Chemical compositions, collagen degradation, surface microhardness and surface appearance of dentin specimens were measured by different detection methods.Results:Part 1:Relationship between dental erosion and gastro-esophageal reflux disease.Chapter 1:The prevalence of dental erosion in GERD patients was 47.6% which was higher than that in healthy controls (13.89%). The proportion of dental erosion with score 1～4 was 54.0%,26.0%,12% and 8%, respectively. Erosion was found both on anterior and posterior areas in patients, but more on anterior than posterior areas. The course of GERD, existence of extra-esophageal symptoms, esophagus condition under endoscopy, height of reflux were risk factors of dental erosion in GERD patients.Chapter 2:The prevalence of dental erosion in groupⅢ(64.52%) was higher (p<0.05) than that in groupⅠ(36.67%) andⅡ(44.44%). Though proportion of dental erosion with score 2 (7/20) in groupⅢwas higher than that in groupⅠ(2/11) and groupⅡ(3/12), there was no statistical significance in the proportions of erosion scores among three patient groups. Correlation coefficient between airway symptoms and scores of dental erosion was 0.231 (p<0.05). Palatal erosion of upper incisor was seen in 8 persons (72.7%) in groupⅠ,9 persons (75%) in groupⅡand 16 persons (80%) in groupⅢ(p>0.05). Labial erosion of upper incisors was found in 1 person in groupⅠandⅡrespectively and 4 persons in groupⅢ. All patients with labial erosion on upper incisors had palatal erosion, except 1 patient in GroupⅢ.Part 2:Impact of refluxed gastrointestinal contents on dentin.Chapter 3:Gastric acid could cause dissolution of hydroxyapatite of dentin. Dentin erosion started at the peritubular areas, which was followed by intertubular demineralization. Gastric acid could not degradation collagen of dentin. The erosion potential of gastric acid on dentin was related to pH. Gastric acid with pH 3.6 and pH 5.2 resulted in linear dissolution of Ca2+ and PO43-, linear decline of surface microhardness, and partly dissolution of peritubular and intertubular areas. Gastric acid with pH 2.0 caused dissolution of large amounts of Ca2+ and PO43-, dramatically decline of surface microhardness, and large dissolution of peritubular and intertubular areas. The change was obvious at the beginning, and then became slow. Gastric acid with pH 2.0 could cause serious damage on dentin in a short time. The effect of gastric acid with pH 3.6 was weaker than pH 2.0. Gastric acid with pH 5.2 had little impact on dentin.Chapter 4:Impact of gastrointestinal proteolytic enzymes on dentin in vitro. Proteolytic enzymes of gastrointestinal tract (pepsin, trypsin and chymotrypsin) could degradation collagen of dentin. Proteolytic enzymes resulted more dissolution of Ca2+ and PO43- of dentin. Proteolytic enzymes caused tissue lost and accelerated erosion process. Erosion effect of pepsin was the strongest and chymotrypsin was the weakest among groups with each enzyme alone. The effect of proteolytic enzymes in combination was stronger than the effect of enyzme alone.Conclusion:Part 1:The prevalence of dental erosion in GERD patients was high. The course of GERD, existence of extra-esophageal symptoms, esophagus condition under endoscopy, height of reflux are risk factors of dental erosion in GERD patients. In GERD patients, dental erosions are more prevalent in patients with frequent respiratory symptoms than those in patients with occasional and without respiratory symptoms.Part 2:Refluxed gastrointestinal contents have strong erosion potential on dentin. Gastric acid can cause dissolution of hydroxyapatite of dentin. The erosion potential of gastric acid on dentin is related to pH. Gastric acid with pH 2.0 can cause serious damage on dentin in a short time. The effect of gastric acid with pH 3.6 is weaker than pH 2.0. Gastric acid with pH 5.2 has little impact on dentin. Proteolytic enzymes of gastrointestinal tract (pepsin, trypsin and chymotrypsin) can degradation collagen of dentin. The effect of proteolytic enzymes in combination is stronger than the effect of anyzme alone.These results alert people that GERD patients have a high risk of developing dental erosion, refluxed gastrointestinal contents have strong erosion potential on dentin and increasingly preventive measures should be taken with these patients.