Conical Dental Prosthesis Screw for Off-Axis Access
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Solution Overview
Problem
Existing dental prosthesis screws face challenges in securing prostheses at off-axis angles due to the need for off-axis access channels, particularly for aesthetic reasons, which conventional screws cannot efficiently accommodate.
Innovation Solution
A screw design featuring a conical clamping surface with a 25-35 degree angle, a larger head diameter, anti-rotation grooves, and a cylindrical portion, allowing off-axis access and improved clamping without excessive force on the implant material, suitable for both temporary and permanent prostheses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional screw with a cylindrical clamping surface is used, then the screw can be securely tightened, but the access channel must be aligned axially with the threaded bore, which compromises aesthetic appearance
Solution Approach 1:
The patent changes the geometric parameter of the clamping surface from cylindrical to conical, with the cone angle α between 25-35 degrees. This parameter change allows the access channel to be positioned at an angle relative to the threaded bore, enabling aesthetic placement on the rear/lingual surface while maintaining secure tightening capability
Solution Approach 2:
The conical clamping surface introduces an angular dimension to the clamping action. By forming the clamping surface as a cone rather than a cylinder, the screw can accommodate off-axis access channels, adding rotational flexibility to the fastening mechanism and enabling aesthetic positioning independent of the thread orientation
2Shape
If the head diameter is increased to accommodate off-axis access, then aesthetic positioning is improved, but the risk of tool fracture during milling increases
Solution Approach 1:
The patent optimizes the head diameter within a specific range (2.1-3.0 mm) and controls the diameter difference between the head and threaded portion (at least 1.0 mm). This parameter optimization provides sufficient head size for off-axis access while maintaining structural integrity and reducing tool fracture risk during milling operations
Solution Approach 2:
The conical clamping surface with angle α of 25-35 degrees creates a curved, tapered geometry that distributes milling forces more evenly. This curved surface geometry reduces stress concentrations compared to sharp edges, thereby reducing tool fracture risk while enabling the larger head diameter needed for aesthetic positioning
3Strength
If the conical angle is increased to improve clamping effectiveness, then mechanical strength is improved, but excessive force is applied to the implant material
Solution Approach 1:
The patent specifies the conical angle α between 25-35 degrees, with 30 degrees±5% being particularly preferred. This angular parameter optimization balances clamping effectiveness with force distribution, providing sufficient mechanical strength to secure the prosthesis while limiting excessive forces that could damage the implant material or surrounding structures
Data Source
AI summary
A screw (10) for securing a dental prosthesis directly to a dental abutment includes a threaded portion (12) lying within a virtual cylinder (14) of a first diameter D1, and a head portion (16) having a shaped recess (18) for receiving a driver. The head portion (16) has a second diameter D2 greater than first diameter D1. A conical clamping surface (20) lies between threaded portion (12) and head portion (16) and forms a conical angle α to a central axis (22) of the virtual cylinder, where α is between 25 and 35 degrees, and preferably around 30 degrees. The conical clamping surface may be provided with a number of anti-rotation grooves (26).