Variations between Visually Estimated and Actual Convergence Angles of Tooth Preparations

Missing teeth and lost or defective tooth structures can be restored by various types of fixed prostheses, the retention of which can be achieved by many ways. The most important retention technique is minimizing the convergence angle (CA) to an optimal taper that allows proper seating and retention of the dental prosthesis. The CA, measured in degrees, is defined as the taper of a crown preparation or the angle formed between opposing axial walls when teeth are prepared for crowns or fixed dental prostheses. 

This term is best described as the total occlusal convergence . CA values ranging from 4 to 38 degrees have been measured in the literature by various methods, including using a tool-maker microscope, geniometer, three-dimensional (3D)laser scanner, white-light 3D scanner, digitizer, AutoCAD photographs, Lava design, 3D-inspection software, and a protractor to measure a traced silhouette from a photo of the projection of dies. Only one study mentioned using visual estimation to measure CA.

Actual Convergence Angles


Materials and Methods:
In this observational study, tooth preparation characteristics and data were collected from typodonts on which dental students had prepared teeth for their annual practical exams. Among 126 preparations, 65 maxillary premolars that had been prepared for metal-ceramic veneer restorations were randomly selected for evaluation. Direct vision and interference from proctors, instructors, or evaluators were not allowed during the exam. Read more.......

Comments

Post a Comment

Popular posts from this blog

Harvesting Free Palatal Masticatory Mucosal Graft Using 3a Mucotome

Image
The technique of free autogenous gingival grafting (FGG) has undergone little modification since its introduction by Bjorn in Scandinavia in 1963 and by King and Pennel inthe United States in 1964. The technique is widely used to treat a variety of mucogingival problems such as insufficient or lack of attached gingiva, the presence of high frenum attachments, shallow fornix and denuded roots following gingival recession.  FGG can be procured from donor site using scalpels, gingivectomy knife or palatal shaving knife (Paquette knife). The donor site is frequently the palate, although the use of edentulous ridge areas, tuberosity and attached gingiva has also been described. Scalpel is most commonly used and conventional method for procuring gingival auto grafts. Gingivectomy knife, although not commonly used, also works on similar principle. Since the scalpel blade is straight and stiff and the palate is curved, repeated incisions to release the graft from underlying connecti
Read more

Dental Ailments may be risky for Cardiac Patients

Image
Patients that are suffering from cardiac t=disorders are susceptible to physical and mental stress. Dental ailments add to the stress further as these patients are unable to cope with the pain due to cardiac disorders. These patients may encounter medical emergencies in case of dental disorders and they may demand multi disciplinary approach to achieve the success. Additionally, the results of cardiac surgery may suffer if the oral cavity is not maintained well since there is always a fear of infection affecting the heart from the oral cavity. Hence, the cardiac surgeon has to refer surgical patients to a dentist for oral prophylaxis and to treat any oral infections before cardiac surgery to prevent infective endocarditis. PDF LINK
Read more

Non-Instrumented Silver Point Retreatment Using the GentleWave Procedure

Image
Apicoectomies are required for endodontically treated teeth instead of the preferred non-surgical endodontic therapy when biological or technical factors necessitate this therapy. These biological or technical factors may include, but are not limited to, non-healing periapical lesions, persistent clinical symptoms, separated instruments or silver points and the presence of long posts. Success rates for apicoectomies have been reported up to 78% with as many as 4% of endodontically treated teeth requiring this type of surgery. Although success rates are relatively high, once the tooth is no longer a candidate for non-surgical endodontic treatment, the alternatives in lieu of apicoectomy are limited to extraction with no replacement or replacement with a fixed prosthesis, removable prosthesis or implant. Read More>>>>>>>
Read more