Description:Field of the invention – Forensic odontology
Background of the invention -
Computer-aided design and computer-aided manufacturing (CAD/CAM) milled dental crowns have enabled dental professionals to carve and spot the smallest markings on tooth crown prostheses. Additionally, the micro Quick Response (QR) code differs from the regular QR code as it is much smaller and can store fewer characters within it. Micro QR codes are of four types namely M1 to M4. QR codes are measured in modules. M2 micro QR code has a length and breadth of 13 and 13 modules, respectively. They can be embedded in a surface as small as 3mm in length and breadth.
This invention is a method of converting a two-dimensional micro QR code into a three-dimensional micro QR code embedded in one of the surfaces of a CAD/CAM milled dental crown. The process is done by careful planning, designing, creating surface fissures during the milling of the dental crown and staining the created fissure with liquid dark ceramic.
The CAD/CAM milled crowns are strong and cannot be destroyed easily by mechanical forces. They can withstand temperatures exceeding 2400°C without shrinking or deforming and exhibit good water resistance. A dental crown is unique and custom-made for a specific patient; therefore, the invention has an application in forensic odontology as it can provide a decent tool for victim identification in unforeseen situations.
Detailed description -
Identification is a major landmark in the subject of forensic odontology. Embedding all the necessary patient’s detail on the crown of artificial tooth is very challenging. This innovation is a complex mechanism and at the same time simple for the user to identify the whereabouts of the person or the victim who is wearing the artificial tooth crown fabricated.
This innovation has three components:
1. Creating and filling necessary information in the micro QR code and parent website.
2. Embedding a micro QR code in one of the surfaces of the CAD/CAM milled dental crown.
3. Using the internet and parent website to translate codes into patient’s information.
Component 1
A micro QR code is generated using a Python script.[Figure 2] The dimension of the micro QR code is 13*13 modules. It can incorporate 10 numerical or 6 alphanumeric characters. Thus, before generating the QR code, a number is assigned to the patient between 1 and 9999999999. The size of one module is 0.21 mm so that it can be printed and scanned with standard resolution smartphone camera. Thus, the size of the micro QR code is 2.73*2.73 mm. [Figure 3(a)]
For generating Micro QR code (13*13), segno library inside the python tool is used.
For example, if the number is “12345” we use the following code:
# import segno
# data = '12345'
#qr = segno.make_micro(data, version=1, error='L')
#print(f"Version: M{qr.version}")
#print(f"Symbol size: {qr.symbol_size()} modules") qr.save('micro_m1.png', scale=10)
#qr.save('micro_qr.png', scale=10)
As the PNG image is generated, we send the PNG to the CAD/CAM milling device to embed that PNG into all ceramic crowns. (component 2)
In our website https://forensictoothcrownidentification.com, we assign a dedicated webpage to the generated code, which can be easily accessed using search tool in the homepage. The page contains the following information about the patient such as:
Name:
Address:
Mobile No.:
Emergency contact no.:
Type of crown:
Date of fabrication of crown:
Warranty of the crown:

Component 2
Step 1: Tooth preparation
The dentist begins by preparing the tooth that requires the crown. This involves shaping the tooth to accommodate the crown. In case of implant, abutment should be adequately trimmed to provide the required occlusal clearance.
Step 2: Taking impression
Once the tooth/implant abutment is prepared, the dentist either takes a conventional silicone putty impression or uses a digital scanner to take a three-dimensional impression of the tooth. The scanner, extra-oral or intra-oral captures the shape, size, and position of the tooth, as well as the surrounding teeth and gum tissue.
Step 3: Crown Design
The digital impression is uploaded to the CAD/CAM software, which creates a virtual model of the tooth. The dentist or the lab technician uses the software to design the crown, specifying the shape, size, and color of the restoration. The software also takes into account the patient’s bite and the alignment of the surrounding teeth.
Step 4: Embedding micro QR code in the design
During the process of designing micro QR code (component 1) is digitally transferred to the desired surface of the tooth. During the design, a depth of 0.25 mm is programmed for each black module of the QR code, whereas the white module is not altered.
Step 5: Milling
Once the design is complete, the CAD/CAM system sends the instructions to a milling machine, which carves the crown from a block of ceramic. The milling process is precise and accurate, ensuring that the crown fits perfectly on the tooth and matches the patient’s natural teeth. [Figure 5]
Step 6: Staining and finishing
Once the crown is milled, it is removed from the block and checked for accuracy and fit. A dark color glaze is applied in the grooves of milled modules of the micro QR code to increase the depth and give contrast to the QR code. Other surfaces of prosthesis are also glazed according to aesthetic needs and polishing is done. [Figure 6]
Step 7: Checking the quality of the milled QR code
Before sending the crown for insertion, the micro QR code is scanned for the accuracy of the print. If data is replicated in the scan, then the crown is sent to the dentist for placement in the patient’s oral cavity.
As aesthetics is the prime concern for the patients with dental crown, the surface chosen for incorporating QR code is the distal surface of the crown in case of posterior teeth or the palatal/lingual surface in case of anterior teeth. The minimum size to embrace a micro QR code in crown is 13*13 modules, which requires a minimum size of 3*3 mm.
If the surface area is not enough for embedding micro QR code, then the following area is utilized in the mentioned sequence: distal surface, lingual/palatal surface, and mesial surface.
During the designing process of the crown, the generated QR code is transferred to the crown, for each module of the micro QR a depth of 0.25 mm depth is programmed and milling is done. [Figure 3(b)]
Component 3
We have developed a website with URL https://forensictoothcrownidentification.com. All the necessary information about the patient such as name, address, mobile no., emergency contact no., type of crown, date of insertion of crown and warranty of crown is filled and saved with unique code allotted to the patient.
When the CAD/CAM tooth crown is retrieved, the micro QR code is scanned and the numerical code of the patient is recovered.[Figure 7] The code is searched in our website https://forensictoothcrownidentification.com, and the information about the patient appears. Therefore, identifying the patient as well as the emergency contact information of the patient. [Figure 8, Figure 9]
, C , Claims:We claim
1. The method described for embedding a micro QR code of the mentioned dimension and size in the invention.
2. The method described for embedding a micro QR code of any other dimensions and size in the invention.
3. Altering the milling by creating a negative micro QR code instead of the original as described in the invention.
4. Embedding a regular QR code instead of a micro QR code on the surface of the CAD/CAM crown.
5. All the above claims in any other CAD/CAM milling in any other material, such as CAD/CAM metal ceramic crowns.