BACKGROUND. The Dahl Concept refers to the relative axial tooth movement that is observed when a localized restorations are placed in supra-occlusion in dental hard tissue worn anterior area and posterior full arch occlusal contacts re-establishes over a period of time irrespective of age and gender. The literature reports that the objectives of the Dahl concept are achieved in the majority of cases (94%-100%). Some minor and transient adverse events, such as initial difficulty with mastication could develop. If dental arch is crowded and some of the teeth are pushed away, they tends to be pushed more even they were visually aligned by a heavy preparation under the ceramic restorations such as crowns and veneers. To avoid these costly and teeth-harmful treatment options for patients with anterior crowding and who wants straighter and beautiful looking teeth, we use a conservative approach of Align+Bleach+Bonding technique. MATEREALS AND METHOD. For tooth alignment we used Inman Aligner, Clear Aligner and Clear Smile Braces (fixed ceramic braces with super elastic Ni-Ti wires) or their combination. After short orthodontics a Dahl concept was applied to improve patients’ functional occlusion and anterior guidance. A “free-hand” and “no-any-drill” composite restoration technique was used to restore worn anterior teeth. For proper orthodontic diagnosis, assessment and treatment planning Spacewise analysis and Digital Caliper measurement were performed using models, their digital scans and intra/extraoral photos. We use Inman Orthodontic Lab in Florida for Inman Aligner fabrication and IAS Laboratory in London for Clear smile braces set up. Clear aligners (Scheu Dental, Germany) are planned and fabricated at the Digital Dental Office’s Clear Aligner certified laboratory. All treatments are start only after thorough diagnostic analysis, case discussion and acceptance from technical experts and orthodontists from UK, USA and Germany and acceptance of planned results from the patients. A course of home bleaching was then performed followed by resin bonding of anterior teeth edges to stabilize anterior guidance. RESULTS. More than 200 cases of upper and lower anterior crowding have been treated in comparably short period of time. From those we are introducing 3 different cases which were treated using above mentioned three appliances as an example. Average orthodontic treatment lasted 8-16 weeks depending on degree of crowding and type of appliances used. The arch crowding were less than 4 mm in all of them. No any teeth were extracted. After orthodontic treatment patients had double retentions (fixed+clear retainers). Dahl concept was performed in patients with anterior attrition and few patients experienced minor difficulty with chewing for their first week only. To control results of molar extrusion we measured space between occlusal surfaces of opposing molars in the SAM 3 articulator positioned in the centric relation. CONCLUSION. In order to get a long term proper stability of dento-facial function with a bonus of beautiful smile the concept of keeping own teeth and its structure became essential in cosmetic and restorative dentistry. The good thing of Dahl technique is its simplicity if it is done properly and its cost effectiveness. And as it was described the edge bonding itself could be a permanent retainer which prevents a future relapse in ortho-aligned teeth. Moreover patients were highly satisfied due to fast alignment, opportunity of keeping their teeth untouched and getting aesthetically pleasant result with a stable function.

65 Non-bacterial originated tooth wear is a normal process which occurs throughout lif. If the rate of loss is likely to prejudice the survival of the teeth, or is a source of concern to the patient, then it may be considered ‘pathological’. Robb reported that the prevalence of pathological loss of tooth tissue in patients less than 26 years of age was greater than in many older age groups. Tooth surface loss was classified into 4 groups: attrition, erosion, abfraction and abrasion. To find the prevalence of four different types of tooth wear among patients visited Digital Dental Office, Ulaanbaatar, Mongolia and investigate their dental attrition severity. Methods: From total of patients visited Digital Dental Office clinic between September 2016 and September 2017 adults aged 16-62 who was found with any type of tooth wear were explored by 4 types. Those patients with attrition were chosen and severity was determined by Bardsley’s simplified tooth wear index (TWI). There were total of 5432 patients examined and treated during this period of time. From them total of 1002 patients aged 16-62 presented some degree of tooth hard tissue wear/dental attrition. Most of the patients were with combination of 4 types of tooth wear: attrition, abrasion, abfraction and erosion. Attrition (At) was found in 68 patients which was only 6.7%, Abrasion (Ab) in14 people-1.3%, Abfraction (Abf) in 4-0.3%, Erosion (Er) in 2 -0.1% alone. The combination of these types of tooth hard tissue was dominant. At+ab+abf+er in 59 patients of total 1002 (5.8%). At+ab+er in 58 (5.7%). Ab+abf in 29 (2.8%). At+er in 25 patients (2.4%). Er+ab in 27 (2,6%). At+abf+er in 264 people (26.3%). At+abf in 452 (45.1%), which was the most prevalent combination. Dental attrition severity in these 1002 patients were shown as following: -0-0- No loss of contour. -1-229 people (22.8%) - Loos of enamel surface characteristics. Minimal loss of contour. -2- 505 people (50.3 %) - Loss of enamel exposing dentine for less than one third of surface.Loss of enamel just exposing dentine. Defect less than 1 mm deep. -3- 211 people (21 %) - Loss of enamel exposing dentine for more than one third of surface.Loss of enamel and substantial loss of dentine. Defect less than 1-2 mm deep. -4-57 people (5.6%) - Complete enamel loss - pulp exposure - secondary dentin exposure.Pulp exposure or exposure of secondary dentine. Defect more than 2mm deep - pulp exposure - secondary dentine exposure. In this descriptive study showed patients with some degree of tooth wear were around 19% from total patients visited during 1 year of period. Four types of tooth hard tissue wear shown as a different combination, very low percentage was in these types alone. Most of the attrition patients were with mild to moderate degree of enamel loss. This kind of study should be continued to explore harmful dentofacial change