Executive Summary

This report summarizes the progress made on the preliminary

design by the Orthodontic Measurement Jig team. The goal of this

project is to design, fabricate and test a device that measures the

orthodontic forces that are placed on an average sized human arch

when braces are applied. The requirement for this device arose

because of the uncertainty in the current applications in orthodontics.

Though the exact forces are not known, orthodontists have a rough

estimate of the mechanics involved. This device will help make the

orthodontic process more efficient and result in a faster procedure.

When there is too much force applied to a tooth, the result is damaged

bone, soft tissue and tooth structures which prolongs the process. If

the force is too small, then it is ineffective in adjusting the tooth.

The team utilized the methods of the Engineering

DesignPlannerTM to effectively design the orthodontic jig. The first

five facets in this method of designing have been completed. In the

first chapter of this process, Recognize and Quantify the Need, we

discuss the goals and perform background research. The second

chapter, or facet, we brainstormed to develop three initial concepts.

In the following chapter we assess the feasibility of these three

concepts and eventually select one of these concepts. For the fourth

chapter we discuss the objectives and specifications that are required

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for the project. The fifth facet involves the analysis of any possible

problems that may occur with the orthodontic jig. The final chapter of

this report is a summary of the current status of the project and

discuses the plan for the completion of the prototype that will be

performed next quarter in the spring.

The appearance of the jig has gone through many changes

throughout the design process. The final design consists of twelve

sets of mounted teeth that are arranged in an array to form an arch.

Each set of mounted teeth includes a post that is tapped and screwed

into a tooth, a boot that is set-screwed into the post, and a u-bolt that

is set-screwed into the bolt. In order to measure the forces, a rosettes

strain gauge is connected to each of the twelve posts and will detect

all of the forces needed. All of the strain gauges will be placed into

quarter bridge architecture and their outputs are to be amplified and

fed into an analog to digital converter. The resulting digital

measurements will then be fed via universal serial bus into a host

computer for manipulation and storage.

The final design of the project is shown in the drawings that are

included in the technical data package. The final design package

includes both parts drawings and assembly drawings of the

mechanical components, and schematics of the electrical components.

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Table of ContentsExecutive Summary............................................................................1Table of Contents................................................................................31.0 Recognize and Quantify the Need.........................................4

1.1 Project Mission Statement.................................................4 1.2 Product Description.............................................................4 1.3 Scope Limitations.................................................................5 1.4 Stake Holders........................................................................5 1.5 Key Business Goals..............................................................6 1.6 Financial Analysis................................................................6 1.7 Primary Market....................................................................6 1.8 Order Qualifiers....................................................................7 1.9 Order Winners......................................................................7 1.10 Innovation Opportunities...................................................7

2.0 Concept Development.............................................................9 2.1 Strain Gauge Rosettes.........................................................9 2.2 Set Screw Repositioning System......................................10 2.3 Slender Rod Mounting......................................................11

3.0 Feasibility Assessment..........................................................13 3.1 Posts Mounted to Strain Gauges.....................................13 3.2 Saddles and Posts...............................................................13 3.3 Raytracing...........................................................................14 3.4 Feasibility Conclusion.......................................................15

4.0 Performance Objectives and Specifications.......................16 4.1 Design Objectives...............................................................16 4.2 Performance Specifications..............................................16 4.3 Safety Issues.......................................................................18

5.0 Analysis of Problem & Synthesis of Design.......................31 5.1 Baseplate Design................................................................19 5.2 Saddle Design.....................................................................21 5.3 Strain Gauge Design..........................................................24 5.4 Electrical Systems Design.................................................25

6.0 Future Plans...........................................................................27 6.1 Experimentation.................................................................28 6.2 Setup....................................................................................28 6.3 Schedule..............................................................................28 6.4 Budget..................................................................................29

7.0 Conclusion..............................................................................31Appendix.............................................................................................33

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1.0 Recognize and Quantify the Need

1.1 Project Mission Statement

The Orthodontic Measurement Jig Senior Design Team is to

design and fabricate a working prototype at the Rochester Institute of

Technology. This prototype will be used to analyze the forces and

moments on each simulated tooth created by a set of braces.

1.2 Product Description

Orthodontists are challenged with custom fabrication of force

systems that maintain biological compatibility that will accomplish the

desired goals. Specifically, if forces are too high they are detrimental

to bone, soft tissue, and tooth structures due to chemicals released by

the body in response to the insult. Much research has been done to

show optimal force/moment levels for movement of a single tooth (or a

few teeth). However, the force systems created by the orthodontist

are too complicated to analyze by analytical beam mechanics, as the

systems are indeterminate. The system consists of brackets (braces)

and beams (wires). The rectangular wires fit into a rectangular

bracket to generate a 3 dimensional force/moment system on each

tooth.

One of the most challenging problems with constructing a

simulated model of the human mouth is that no one mouth is identical

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to the other. Since every mouth is different, an adjustable jig fixture

would be used to simulate the infinite possible tooth orientations.

In order to determine all the forces and moments applied to each

tooth, strain gages are mounted to the jig fixture. Each strain gage is

then connected to a computer via a USB port. The strain gage/USB

setup allows the user to instantly analyze the given tooth

arrangement.

This project has several potential applications. This fixture will

allow orthodontists to establish the maximum allowable force/moment

that can be safely applied to teeth without causing damage to the

bone, soft tissue, or the tooth. Once the maximum allowable

forces/moments are determined, these forces can be applied to the

teeth, which ultimately may reduce the length of time the braces must

be on for.

1.3 Scope Limitations

By the end of RIT’s fall quarter, 20031, the Brace Jig Fixture shall

be completely designed and completely fabricated and assembled by

the end of the spring quarter. At the end of the winter quarter, the

senior design team will hold a Preliminary Design Review. At this

review the team will present:

1) Detailed CAD Drawings

2) The Budget

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At the end of Spring Quarter, 20033, the senior design team will

present the working prototype. At this presentation the team will

present:

1) A Working Prototype

2) Test Performed Using The Prototype

3) Final Report / Binder

1.4 Stake Holders

The three main stakeholders involved with the design and

fabrication of the Brace Jig Fixture are Dr. Comella, the students

working on the team, and the faculty associated with the project.

1.5 Key Business Goals

The key business goals are to fabricate a jig in the form of a

typical dental arch with simulated teeth with brackets affixed to them.

The jig must accurately represent and produce data using strain

gauges to determine the forces and moments on each simulated tooth.

1.6 Financial Analysis

A budget of $1000 has been proposed for the development of the

Brace Jig Fixture. Materials to be included in this budget are:

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• Strain Gages

• Amplifiers

• Electronic Hardware

• Sample Teeth

• Steel Rods & Plate

• Welding Supplies

1.7 Primary Market

The primary market of the Brace Jig Fixture is orthodontists who

are concerned about applying the necessary forces \ moments to

teeth. This prototype will also impact orthodontists’ clients who wear

braces by providing them with a more effective and efficient

treatment.

1.8 Order Qualifiers

The Brace Jig Fixture Team shall design and fabricate a prototype

that will produce numerical and graphical data of forces and moments

created on individual teeth. Once the team has successfully

assembled the prototype, fixture will undergo a series of experiments

to verify that the apparatus is operating appropriately.

1.9 Order Winners

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The following are goals of the Brace Jig Fixture:

•Produce numerical and graphical data of forces and

moments created on individual teeth.

•Be reliable.

•The prototype is easy to use and reuse.

•Have a user friendly interface with a computer.

•Aesthetically pleasing to the eye

•Light weight / Portable

1.10 Innovation Opportunities

Potentially the Brace Jig Fixture will allow orthodontists to

establish the maximum allowable force/moment that can be safely

applied to teeth without causing damage to the bone, soft tissue, or

the tooth. Once the maximum allowable forces/moments are

determined, these forces can be applied to the teeth, which ultimately

may reduce the length of time the braces must be on for. This would

also permit an orthodontist to simulate a patient’s mouth/brace

system and allow them to better understand the impact of the brace’s

design.

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2.0 Concept Development

After an initial meeting with the project sponsor, during which

the initial specifications and goals for the project were established,

the Orthodontic Jig project group met to develop a list of initial design

possibilities. Both overall design concepts and small, sub-assembly

components were conceived by the group to solve the project’s unique

problems. Eighteen potential ideas and solutions were considered,

with the group using a consensus voting technique to narrow the list

to the three top-priority design possibilities. The group determined

that the following solutions would be pursued to attain the project’s

goals: strain gauge rosettes mounted on a slender rod connected to

each tooth, a thumbscrew/setscrew tooth repositioning system, and

mounting slender rods through the bottoms of the upper arch of teeth.

Once the three most promising ideas were decided upon, each

group member took to drawing out early, concept sketches of each

proposal. Each drawing was subsequently shown to the entire group

and added to and modified according to the input gained from the

perspective of the group as a whole. The enhanced drawings aided in

solidifying the ideas behind each concept and were used as the basis

for all of the analysis and design synthesis that has been completed

since the group’s formation. Each of the three most promising

concepts is expanded upon in greater detail in the following sections.

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2.1 Strain Gauge Rosettes

The group determined that in order to measure the force on

each tooth accurately and with a technique that was both attainable

and cost effective, strain gauge rosettes would be used to measure the

strain induced on a slender rod by the force of the brace bracket on

each tooth. The slender rod would be attached to each tooth in such a

manner that the force on each tooth would be able to be resolved

through analyzing the output of each directional element of the three-

element strain gauge rosette, along with the geometric considerations

of the system when it is at static equilibrium. A strain gauge rosette

with direction elements at -45°, 90° and +45° will produce an output

voltage that can be scaled, by using transformations stemming from

Mohr’s Circle analysis, to produce the forces and moments necessary

for a thorough analysis of the system at static equilibrium. Such

analysis will produce the moments and forces about the X, Y and Z

axes, which will help to attain the goals set for the project.

It is essential that the slender rods, which will be circular in

cross-section, produce an appropriate amount of strain under the

given load conditions. Therefore, an analysis of the slender rod will

be performed in ANSYS to determine the material properties that will

be needed to produce a measurable amount of strain. Particularly,

the Young’s Modulus must be determined and set within a range that

is both commercial available in common engineering materials and

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that provides an ample degree of workability. Common loading

conditions will be provided through literature and conversations with

the project sponsor and will be used as the basis for most of the

project’s theoretical analysis.

2.2 Setscrew Repositioning System

In order to adequately simulate the upper arch of teeth, which

must be able to be off-set in order to simulate a degree of disorder

among the teeth that will need to be corrected via bracing, a setscrew

repositioning system was devised by the group. As mentioned above,

each tooth will be connected to a slender rod upon which a strain

gauge rosette will be mounted. Those slender rods, in turn, will be

connected to a saddle that will be the basis for the setscrew system.

A saddle will be fashioned for each tooth to be input into the

system. The saddle and the accompanying setscrews will provide the

range of motion and degrees of freedom necessary to constrain the

system and provide the amount of off-set needed to accurately

simulate an arch of teeth. Each tooth needs to be able to be adjusted

in the following manner (the X-axis extends along the arch of the

teeth, the Y-axis up through the root of each tooth, and the Z-axis out

from the face of each tooth):

1. Angular displacement about the X and Y axes.

2. Translation in the Y axis.

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Translation in the X axis and rotation about the Z axis will be

constrained for each tooth as they do not accurately represent the

movement of real teeth.

In order to accomplish such displacements, each saddle will slid

onto a bar extending across the X axis to provide the necessary X axis

rotation. Y axis rotation will be accomplished by embedding the

slender rod into a hole drilled into the top of the saddle. Y axis

translation will be provided by allowing the bars that extend across

the X axis, and subsequently support the entire saddle and tooth

arrangement, to be raised or lowered. All of these movements will be

accomplished by drilling and tapping holes into which setscrews will

be placed. The setscrews will provide the metal-to-metal friction

necessary to hold each tooth in its final position, which will allow the

unconstrained slender rods to bend under the loads applied to each

tooth.

2.3 Slender Rod Mounting

Mounting the slender rods to each tooth proves to be a

challenge when the geometry of the arch are considered. The points

of each tooth’s root converge on a point located some distance above

the hard palette. In essence, each tooth is angled toward the center

of the head. Considering this, it was decided that the slender rods

needed to be mounted to the bottom of the teeth from the top arch. In

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this manner, the teeth could be angled in the proper way while still

providing the functionality necessary for completely the project’s

goals.

A model of a typical arch was provided by the project’s sponsor

and said model was used to determine the proper angular orientation

of each tooth. The angles determined will be used to construct the

overall shape of the jig, and will also be used to determine the size of

the saddles, due in part to the fact that the convergent roots produce

divergent angles at the location of the saddle and will provide the

extra space needed to allow for human manipulation and adjustment

of each tooth’s orientation in space.

In order to physically attach each tooth to the slender rods, the

aluminum teeth being used will be drilled into, in the case of the

large, flatter teeth, or ground down to a flat surface and drilled into,

in the case of the smaller, more pointed teeth. Into those drilled

holes, small, extremely stiff rods will be adhered using commercial

epoxies. Those stiff rods will in turn be adhered to the slender rods

via drilled holes. The stiffness of each of the small rods will be such

that, under the given loading conditions, the slender rods will

experience the majority of the bending induced by the forces applied

to the teeth. This will introduce a small amount of error into the

overall system, however, it is a necessity and will be accounted for

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when calculating and discussing the final results of the system at

static equilibrium.

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3.0 Feasibility Assessment

Out of the myriad of concepts that were developed in the

brainstorming session, three finalists were chosen with a weighted

voting method. Using the twelve question guide from the design

planner package, a feasibility assessment was conducted to determine

the most desirable design candidate.

3.1 Posts Mounted to Strain Gauges

A rigid track system was devised to hold twelve posts and their

associated rosettes in an effort to ascertain involved forces and

moments. The track system has the advantage of being the most

sturdy method of mounting the strain gauges, and thus, introducing

the smallest amount of error into the measurements. Each post would

be affixed to the forward face of the tooth and would extend up into a

boot that slides along the main track. Posts would be secured and

able to be repositioned with a set of thumbscrews.

From a fabrication standpoint, the most challenging part of this

design would be the machining of the track holes in each post. This

presents a special challenge, as depending on the curvature of the

track, each track hole might have to be designed with built-in

curvature. Moreover, the associated thumbscrew design would need

to then involve at least three thumbscrews to obtain an adequate level

of tightness to the track. That would not only require extremely

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precision machining, but it would also compromise the structural

integrity of each post. As a result this design was ruled as not being

suitable for the project.

3.2 Saddles and Posts

In an effort to obtain further flexibility, the posts will be

rounded at one end, and allowed to sit inside a movable boot on

individual saddles. This additional degree of freedom will allow

further flexibility in placement without significant consequences to

force calculation. Moreover, the addition of individual saddles for

each post to be placed on will eliminate the track curvature problem

that existed in the track/post design. Each saddle will be individually

mounted to a baseplate that will be configured in an anatomically

compatible manor. For the above improvements and simplicity of the

design, this design is the overall best candidate.

3.3 Raytracing

A novel way of determining tooth position and geometry at a

given instant is to adopt “raytracing” techniques that have often been

employed in precision mapping and electron microscropy. This would

involve using a laser and an array of photosensors to sweep over all

tooth surfaces. The resulting reflections would indicate a distance to

each point. When combined in aggregate, this would provide a highly

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accurate picture of the exact position of all teeth. Finally, when this

process is completed at periodic time intervals (eg. Days or weeks), it

will illustrate the resulting movement and give an idea of the relative

forces present.

There are several problems with this approach, first off the

engineering group present is more conducive to a mechanical

solution. Next, the estimated cost and precision of the system

required would be immense, especially to undertake such a

miniaturization of the system would vastly outstep resources. Finally,

the system still does not directly measure the forces present, it simply

detects the movement of the teeth and given knowledge of some

variables would allow for back-calculation of the forces present.

3.4 Feasibility Conclusion

The Saddles and Posts design candidate is clearly the best out of

the three options considered. It comes out on top in issues of cost and

complexity over the raytracing solution. It also does not have the

structural and imprecision problems associated with the original

post/track solution.

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4.0 Performance Objectives and Specifications

In order to meet the standards and expectations of the sponsor,

our team decided to agree on certain objectives and specifications of

our design. These objectives and specifications that we used as a

guideline are briefly discussed in this chapter.

4.1 Design Objectives

There are certain design objectives that serve as a starting point

for the project. These objectives outline the physical characteristics

of the project and are a requisite from the sponsor. These objectives

are as follows:

1. The base of our design is that the final configuration’s volume

must not be any larger than one cubic foot. The purpose of this

objective is that the design is intended to be portable and used

for demonstration purposes.

2. Another objective that relates to the last topic is that the final

design must be moderately light weight in the respect that it

will not be uncomfortable for the average human to carry by

hand. This objectives purpose is to make the final design

portable, which is the same purpose of the last objective.

3. In order to make the final design suitable for demonstration

purposes, it must have a presentable appearance. This means

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that the final design shall be clean-looking and have a

professional appearance.

4.2 Performance Specifications

The team decided that in order to meet the standards that were

given to us by our sponsor, we must first compile a list of

specifications. These specifications are the minimal requirements of

our orthodontic fixture design that must be met in order to obtain the

correct data. Consequently, our completed product shall meet these

specifications so that the sole purpose of the project may be fulfilled.

These specifications are listed below:

A) THE DEVICE SHALL RECORD FORCE ON THE TEETH IN

THE Y AXIS AND THE MOMENTS ABOUT THE X AND Y AXES

This is the main purpose of the project and is what our team has

had to use as a foundation. This is the data that the sponsor is looking

for and because of this it is what we build from.

B) EACH TOOTH WILL HAVE A FIXED FREEDOM OF MOTION

IN THE Y AXIS AND TWIST ABOUT THE X AND Y AXIS

In order to fulfill the main purpose of the project, as listed

above, the teeth need to be adjusted so there can be a force applied to

each individual tooth. Because there is a vast amount of variations in

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misalignment of the teeth, each tooth requires this amount of freedom

in movement.

C) THE DEVICE SHALL HAVE A SIMPLE COMPUTER

INTERFACE

This is a requirement that was made so a person with a small

amount of computer software knowledge, mainly Microsoft Office

based, would be able to use the device. This would make the device

very easy to use and allows the user to analyze the data in a more

efficient manner.

4.3 Safety Issues

There are few safety issues that are involved with the use of the

jig. Due to the nature of the electrical components involved in the

data collection device, the component should be kept dry to reduce

shock hazards. The forces and moments on the system are very small,

meaning that any failure of the components will more than likely not

result in any injury.

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5.0 Analysis of Problem & Synthesis of Design

The analysis of the problem facing the team was done mainly on

the geometric aspects of the mechanical design, with the remaining

aspects focused on providing the necessary electrical systems to

accomplish the desired goals. Due to the relatively low amount of

forces imposed on the system, the design team concluded that finite

element analysis of the system would not have produced any

meaningful results. Being composed almost entirely of steel and

aluminum, and with forces no greater than 2.0 N and moments no

greater than 1 Kg/m imposed on each tooth, finite element analysis on

the system would have been meaningless. It was therefore the

decision of the team to focus on generating accurate tooth geometry

and providing the best functionality possible from the system.

5.1 Baseplate Design

The design of the baseplate is the most critical aspect of the

overall design in that it provides the geometric constraints, along with

the saddles, that will allow the system to be analyzed with strain

gauging. In order to accurately recreate the upper arch of teeth, a

model upper arch, provided by the project’s sponsor, was

dimensioned using calipers and protractors. While this method may

seem crude, it is the only way to accurately obtain dimensional

information on the upper arch as there is no anatomical information

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available that would have been useful. Each individual’s upper arch is

different, therefore the team operated under the assumption that the

arch provided to them was, dimensionally, average.

By drilling holes into the model arch and inserting posts, dimensional

information was obtained for each of 12 teeth in the model system.

Due to the three dimensional nature of the system, angular position

was considered in all three spatial dimensions. Human teeth are

angled both radially out from a central point, and are pitched forward

from a vertical datum. And, more importantly, these angles are

different for each tooth in the arch. Therefore, in order to create a

system that has the appearance of an actual arch, holes must be

drilled into the baseplate to receive fixtures that will constrain and

define the teeth in free space. By appearance alone, these holes will

not resemble the shape of the actual arch. Rather, they will be spaced

out somewhat erratically. When the angular orientation of each tooth

is considered and input into the system, however, the end result will

produce an arch of teeth very similar to an actual human arch. The

figures below demonstrate how the angles for each tooth were

measured:

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Figure A – Arch Geometry & Tooth Dimensions

Figure B – Tooth Angular Geometry From Common Point

Figure A was used to determine the spatial requirements of each

saddle system and thus the placement of the saddle’s positioning

holes in the baseplate. Figure B was used to orient the holes for the

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saddle system at the proper angle so that the completed system will

resemble a common dental arch.

5.2 Saddle Design

While the baseplate design provides the location for mounting

further components, the saddle design provides the constraints and

allows for repositioning the teeth so that the braces affixed to the

teeth will produce forces and moments. Under the direction of the

project’s sponsor, the teeth will be allowed to translate and rotate

only in the directions that accurately mimic the motions of actual

human teeth. The figure below was obtained from the project’s

sponsor and defines the axial system of translation and rotation that

each tooth in the system should support:

Figure C – Tooth Degrees of Freedom

From the direction of the project’s sponsor, motion in the X-direction

and rotation about the Z-axis were considered to be zero, as they do

not accurately represent the motions of actual teeth. Only translation

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in the Y- and Z-axes and rotation about the Y- and X-axes were

considered for this project.

In order to obtain such motions, a saddle and setscrew

repositioning system were devised to support each tooth. Each tooth

with be supported by a system outlined as such: the baseplate will

receive a system of rods, which will support a saddle; each saddle will

be allowed to rotate about the rods, producing rotation about the X-

axis; into the saddles will slide slender posts; each of these posts will

translate and rotate about the Y-axis while being constrained from

translating in the X-axis; into each post will be fit a tooth, upon which

forces and moments will be applied via the bracing system. As Figure

D below further illustrates, the saddles will allow for the angulation of

each tooth about the X-axis, the translation of each tooth in the Y-axis,

and the angulation of each tooth about the Y-axis.

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Y

Provides translation and rotation in the Y-axis

Figure D – Setscrew Repositioning System Characteristics

The translation in the Y-axis is accomplished not only by allowing the

post connected to each tooth to translate in the saddle. The entire

assembly supporting each tooth in the baseplate can be positioned in

the Y-axis. This system was devised in order to allow the teeth to be

angulated correctly. Without it, rotating the teeth about the X-axis

would produce more translation in the Z-axis that it would rotation

about the X-axis and would not accurately resemble an actual human

arch.

Setscrews will allow the system to be statically constrained and

remain in the desired position throughout the analysis. Tightening of

the setscrews in the lower portion of the saddle will provide friction

that will hinder the rotation of the saddles about the rods in the

baseplate. The two setscrews in the upper portion of the saddle will

provide the friction that will hinder the translation and rotation of the

slender post inside the saddle once the post’s proper position has

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X

Z

Provides rotation about

Provides translation in the

been determined. In order to accomplish an adequate amount of

friction, the surfaces of the rods will be roughed in order to increase

the coefficient of friction between the rod and the footprint of the

setscrew. Since the system experiences relatively low forces, the

setscrews will be able to adequately hold the components in place via

hand tightening.

5.3 Strain Gauge Design

The system devised is ultimately designed to output force and

moment information for each tooth in the system. In order to

accomplish this, a three element (+45,90,-45) strain gauge rosette

will be attached to each of the slender rods. The slender rods will

experience the stress and strain caused by the forces and moments

imposed on the teeth by the brace system and will flex, twist and bend

accordingly. The strain gauges will record the strain of each of the

slender rods, which can, via a system of electronic devices, be made

to produce an output for the forces and moments on each tooth

through stress and strain translations based on the overall system

geometry. That overall system geometry, however, is unknown since

each tooth will be arbitrarily repositioned in order to produce a

measurable output from the strain gauges. Also, the strain gauges

themselves contain mathematical factors in their measurements that

cannot be determined at this time. Pursuant with those statement,

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generalized equations will be derived once the system has been

assembled and will be presented in greater detail at the project’s

completion.

The system of electronic devices consists of amplifiers, analog-

to-digital converters, voltage regulations, an analog multiplexer, and

an USB interface device that will allow for connectivity to a PC. The

electrical system is needed in order to amplify and condition the

extremely low voltage output of the strain gauges, typically able of

outputting only on the micro-volt scale. Due to the extremely low

voltage nature of the electrical system, filters and conditions will be

used to eliminate electrical noise that could degrade the quality of the

electrical signal received by the PC and could be detrimental to the

analysis of the system.

5.4 Electrical Systems Design

Each strain gauge can be conceptualized as a variable resistor

that is initially set at 120 ohms. When combined into a quarter bridge

circuit and fed with a known voltage as shown in Figure E, the

differential change in the applied strain results in a measurement

signal proportional to the strain and voltage applied. This resultant

signal is impedance matched and fed into a low noise amplifier.

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Figure E – Quarter Bridge Circuit

A series of multiplexers are time-switched to measure each

channel at a low rate. A Texas Instruments analog-to-digital converter

then quantizes the resultant data from each channel into a sixteen-bit

word. Words are fed via serial connection into the Cypress FX2

enhanced 8051/ USB controller. Attendant software and firmware

components are utilized to cache data until it can be transmitted via

USB into a host personal computer.

Software on the PC applies stress/strain calculation formulas and

provides the resultant forces present on each tooth. The data is then

available for export to other programs such as Microsoft Excel.

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6.0 Future Plans

At the time of compilation of this report, the initial design work

of the project has been completed. Over the course of the Winter co-

op period the team will remain vigilant for any additional ideas that

might be incorporated into the design. Background research and

analysis on items such as software and firmware development will

also be undertaken in the winter.

Prototyping materials ordered in the Winter by the faculty will

arrive by the beginning of the Spring Quarter. Fabrication will begin

immediately, with the completion of the prototype projected at the

end of April 2004. At that point, the team will commence a

troubleshooting and testing period for the rest of the quarter.

Constructive input will be obtained from the project sponsor and

integrated into the computation of the forces in software. Along the

way, critical design documentation will be generated and compiled for

the final critical design review. Prototype delivery to the customer is

projected to occour on or about 14 May 2004.

The testing and fabrication phase of the project will also include

the need to properly calibrate the force sensors. The current plan is

to take initial measurements of voltage output from the rosettes when

no force is present, then apply this calibration information to

software.

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One of the overall goals of the project was to obtain a realistic

view of the forces and moments present in modern orthodontic

treatment. Provided the results obtained from the project are

assumed to mirror the actual forces of a human arch, a better model

for orthodontic treatment could be an eventual goal.

6.1 Experimentation

There are two main areas of experimentation that are to be

pursued: These include the initial calibration of the orthodontic

model, and the analysis of the force results obtained after all

calibration is complete.

Calibration of the design will take place in software. The

method will consist of taking and recording initial voltage

measurements of rosettes that are not subjected to any forces. The

initial data obtained will then be used to calibrate the rosettes when

they are finally affixed to the jig. This is a flexible method and allows

for recalibration in the event that a rosette is damaged or replaced.

The final experimental task will revolve around collection and

modeling of the forces found to be present in the arch. Provided that

the calibration is accurate, it should be possible to obtain all forces

and moments required by the customer.

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6.2 Setup

The experimental setup will simply consist of the completed

force measurement jig, a computer running the appropriate software,

and the electrical signal processing equipment. After all calibration

testing is complete, the testing phase should be comparatively simple.

All data will be logged to Excel or another technical software data

package.

6.3 Schedule

A Gantt chart has been created that projects each task required

and the requisite time for the entire academic year. Start and

completion dates, as well as task causality requirements are all

annotated on the chart, which can be found in the appendix. As of the

time of this writing the entire team was on schedule to meet all

milestone dates reported on the chart.

6.4 Budget

The following illustration, Figure F, shows the team’s

preliminary budget that will be submitted for purchasing. The team’s

initial budget for this project was $1,000 and the calculated

preliminary budget for the project is $798.84. This amount though

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does not include shipping and taxation on the goods ordered, but does

have room within the original budgeted plan to allow for these

additional charges.

Senior Design Preliminary Budget Total = $ 798.94

Item Vendor Vendor Part Number Quantity Price Per

Unit Items Per Unit

Mechanical Components2-56, 3/32", Cup Point Set Screw McMaster-Carr 92311A073 1 $ 11.11 100

     

45°/90°/45° 3-Element Strain Gauge Rosette

Texas Measurements,

Inc.FRA-1-11 2 $ 165.00 10

     6', 1/4" D, 304 Stainless Steel Round Bar Stock McMaster-Carr 89535K21 1 $ 6.18 -

     6', 1/2", 304 Stainless Steel Square Bar Stock McMaster-Carr 89415K25 1 $ 41.24 -

     8" x 8", 1.5" Thick, 6061 Aluminum Plate McMaster-Carr 9246K81 1 $ 50.03 -

     6', 1/8" Thick, Grade S 6AL-4V Titanium Round Bar Stock

McMaster-Carr 89055K31 1 $ 41.40 -

     

8-32, 1", Plastic Knurled Head Thumb Screws McMaster-Carr 91185A4444 1 $ 12.03 25

Electrical ComponentsResistor Network DigiKey 767-163-R120-ND 6 $ 0.66 -     USB/Micro FX2 DigiKey 428-1332-ND 1 $ 16.00 -     Inst. Amplifier Arrow AMP04EP 1 $ 13.55 -     3.3v Voltage Reg DigiKey 296-13424-1-ND 1 $ 0.56 -     USB "B" Female DigiKey WM17109-ND 1 $ 1.94 -     

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USB Cable A-B DigiKey WM17103-ND 1 $ 4.55 -     24 MHz Crystal DigiKey XC527CT-ND 1 $ 2.03 -     64K I2C EEPROM DigiKey 24LC64-I/SN-ND 1 $ 1.01 -     22k 0805 Resistor DigiKey - - - -     0.1uF 0805 Cap DigiKey - - - -     22pF 0805 Cap DigiKey - - - -     16bit serial ADC DigiKey 296-12500-5-ND 1 $ 10.30 -     16 Ch Analog Mux DigiKey 296-9225-5-ND 3 $ 0.48 -     Terminal Block - - - - -     5v Voltage Reg DigiKey ZR78L05GCT-ND 1 $ 1.61 -     100 0805 Resistor DigiKey - 1 - -

Miscellaneous ComponentsPCB Fabrication (1 Turn) - - 1 $ 250.00 -

Free Components From SponsorComplete 2 Arch Set Of Aluminum Teeth - - - - -

Complete Set Of Brace Brackets - - - - -

Model Upper Arch - - - - -Uniaxial Strain Gauges - - 3 - -

Figure F – Preliminary Budget

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7.0 Conclusion

This senior design team for the orthodontic jig has completed

the first six facets of the design process during this quarter. These

facets include the recognizing the needs, concept development,

feasibility assessment, design objectives and performance

specifications, analysis of problems and synthesis of the design and

future plans of the project.

The orthodontic measuring jig is a unique device whose

requirement is caused by current lack of knowledge of the exact

mechanics involved in orthodontics. The goal of this project is to

design, fabricate and test a working prototype that would record the

forces applied to the teeth when a set of braces is applied.

After meeting with the customer to determine the needs and

requirements, the team started the project by brainstorming ideas for

a design and selected three concepts from this brainstorming session.

These three concepts included rosettes on each tooth connected by a

straight rod, welded brackets on a metal test mouth, and an elaborate

thumbscrew repositioning system. The feasibility of each of these

concepts was reviewed and compared in order to further determine a

preliminary design. Due to the feasibility analysis, the team decided

to mount the rosettes gauges on each tooth, which will be connected

by a straight rod.

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In order to assure the design’s functioning ability, the team

needed to analyze any of the problems that may arise. Due to the

relatively small forces that are involved in the application, there will

be no fatigue or significant stress involved in the members. The true

problem involved in the design is the recreation of the exact shape of

the arch. In order to make the data as accurate as possible, the arch

must hold true in its original form to that of an average human’s

structure.

By the end of the spring quarter, the team will have fabricated a

working model of the orthodontic jig. The team will conduct

experiments to test the reliability of both the mechanical and

electrical components.

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