Machinable Dental Preforms for Chair-Side Shaping Without Further Sintering
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Solution Overview
Problem
Existing methods for creating dental restorations from ceramic materials require separate milling and sintering steps, which are time-consuming and limit the ability to produce chair-side restorations.
Innovation Solution
A machinable preform is developed that can be shaped into a dental restoration with sufficient strength for anterior or posterior applications without the need for further processing, featuring a sintered preform with a unique size and shape, and a stem for a unique tool path and machining strategy, allowing direct shaping into a final restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If separate milling and sintering steps are used to create dental restorations, then high strength restorations can be achieved, but the process time is excessive and chair-side production is limited
Solution Approach 1:
The invention pre-sinters the ceramic blank before milling, creating a green state preform that has sufficient structural integrity for machining. This preliminary sintering action allows the material to be machined at room temperature without requiring post-milling sintering, thereby reducing overall process time while maintaining restoration strength
Solution Approach 2:
The invention changes the density parameter of the ceramic material by performing partial sintering to create a green state with 50-90% theoretical density. This intermediate density state allows the material to be both strong enough for machining and capable of achieving final strength after the single sintering cycle
2Ease of manufacture
If traditional mill blanks with single size and shape are used, then manufacturing is simple, but material waste increases
Solution Approach 1:
The invention creates preforms with geometry that locally matches the final restoration shape, particularly with the cylindrical body and stem configuration that corresponds to crown anatomy. This local geometric quality matching reduces material waste while keeping the manufacturing process simple through injection molding
Solution Approach 2:
The invention designs a universal preform geometry with a cylindrical body and stem that can accommodate multiple restoration types and sizes. The standardized preform shape serves multiple functions: it facilitates injection molding manufacturing, enables consistent machining operations, and reduces material waste across different restoration applications
3Manufacturing precision
If porous ceramic materials are milled with enlargement factor, then final density can be achieved after sintering, but the process complexity increases and chair-side production is precluded
Solution Approach 1:
The invention performs preliminary sintering to create a green state preform with controlled porosity (50-90% theoretical density). This pre-sintering action establishes the green strength needed for machining while eliminating the need for post-milling sintering, thereby simplifying the overall process and enabling chair-side production
Solution Approach 2:
The invention extracts the sintering step from the post-milling sequence and performs it before milling. By taking out the sintering operation and repositioning it in the process sequence, the invention eliminates the need for enlargement factors and complex post-processing, simplifying the manufacturing workflow
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the time required to create custom dental restorations by enabling chair-side shaping without additional sintering, while minimizing material waste and ensuring high strength and aesthetic quality.
Implementation Method 1
sintering the shaped form to full density to form the sintered preform
Data Source
AI summary
A machinable preform for shaping into dental restorations is described that comprises material having suitable strength for use in dental applications without requiring further processing after shaping to strengthen the material (such as sintering). In one embodiment, a preform is comprised of a machinable dental material having a Vickers hardness value in the range of 4 HV GPa to 20 HV GPa, and comprises a body and a stem that extends from the outer surface of the body that supports the body during shaping. A method for making the machinable preform, and a kit comprising a machinable preform and a grinding tool, are also described.