CHAPTER 3 MANDIBULAR ADVANCEMENT DEVICE
3.2 Products
The U.S. Food and Drug Administration (FDA) is responsible for protecting the public health by assuring the safety, efficacy, and security of human and veterinary drugs, biological products, medical devices, food supply, cosmetics, and products that emit radiation in the United States [49]. The mission of Center for Devices and Radiological Health (CDRH), one department of FDA, is to assure that new medical devices are safe and effective before they are on market. The FDA has classified all the medical devices into three classes. Each of those devices is assigned to one of three classes based on the level of control necessary to assure safety and effectiveness of the device. Everyone who wants to market Class I, II, and some III devices intended for human use in the U.S. must submit a premarket notification, 510(k), to FDA at least 90 days before marketing unless the device is exempt from 510(k) requirements.
The oral appliances are assigned to the Class II devices [50] that must receive a 510(k) from FDA for the treatment of snoring or OSA. Therefore, all the OAs for snoring and/or OSA can be searched within which devices have received the 510(k) clearance and are available in the CDRH 510(k) database.
For the purpose of searching for all related products of the snoring or OSA treatment, the more effective method is to search by category rather than by other terms. Each category is referring to an individual product code. The intraoral devices for snoring and/or OSA are referring to the following product codes: “LRK”, Anti-Snoring Device; “LQZ”, Jaw Repositioning Device. There are totally 72 products in these two categories including all kinds of oral appliances. Depending on sifting all the products carefully, there are at least 16 products which are the adjustable two-pieces mandibular advancement devices. These devices with their specification are collected and listed in Table 3.2-1 and Table 3.2-2.
Table 3.2-1 List of adjustable MAD products
Model Applicant Approval Date
Klearway® Dr. Alan A. Lowe, Inc. 05/25/1995 Silencer® Silent Knights Ventures, Inc. 10/30/1995 Adjustable PM Positioner® Jonathan A. Parker, D.D.S. 02/08/1996
Herbst Appliance® Univ. Dental Assoc. Dept. of
Orthodontics 03/20/1996
TAP® Airway Management Inc. 01/24/1997
Silent Nite® Glidewell Laboratories 09/18/1997
EMA® Frantz Design, Inc. 09/29/1997
Adjustable TheraSnore® DISTAR, Inc. 11/12/1997
Snoring Control Device® Kenneth Hilsen 01/09/1998
Snore-Aid plus® Dental Imagineers, LLC 07/22/1999
NORAD® Dennis R. Bailey, DDS 05/28/2002
SUAD® Strong Dental Inc. 07/08/2003
OASYS Oral/Nasal Airway System® Mark Abramson, D.D.S., Inc. 08/26/2003 MDSA TM RJ & VK Bird Pty Ltd. 10/27/2004
SomnoMed MAS ® Somnomed Ltd 07/12/2005
TAP-T® Airway Management Inc. 07/12/2006
SomnoGuard AP/AP Pro® Tomed Dr. Toussaint GmbH 09/08/2006
Table 3.2-2 Comparison of adjustable MAD products
Model
Klearway® Silencer®
Photo
Company Dr. Alan A. Lowe, Inc. Silent Knights Ventures, Inc.
Inventor Alan A. Lowe (Canada) Leonard W. Halstrom (Canada)
Approval Date 05/25/1995 10/30/1995
FDA
510(k) Reg. No. K950763 K954530
Treat Snoring Yes Yes
Treat OSA Yes Yes
Connector Wire Screw/Post
Adjustor (P-R) Dual-thread screw Series of aperture
Adjustor (E-D) N/A N/A
Lateral movement Slot Slot
Patents US 5409017 US 5365945, US 5868138
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model
Adjustable PM Positioner® Herbst Appliance®
Photo
Company Jonathan A. Parker, D.D.S. Univ. Dental Assoc. Dept. of Orthodontics
Inventor Jonathan A. Parker (U.S.) (No data)
Approval Date 02/08/1996 03/20/1996
FDA
510(k) Reg. No. K955503 K955822
Treat Snoring Yes Yes
Treat OSA Yes Yes
Connector Wire Linkage
Adjustor (P-R) Dual-thread screw Screw
Adjustor (E-D) N/A Elastic band
Lateral movement Linkage Linkage
Patents US 5816799 (No data)
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model
TAP® Silent Nite®
Photo
Company SCHEU-DENTAL GmbH Glidewell Laboratories
Inventor W. Keith Thornton (U.S.) (No data)
Approval Date 01/24/1997 09/18/1997
FDA
510(k) Reg. No. K964516 K972424
Treat Snoring Yes Post (Hook)
Treat OSA Yes Screw
Connector Post (Hook) Slot
Adjustor (P-R) Screw N/A
Adjustor (E-D) Slot US 6305376
Lateral movement Surface contact Elastic band
Patents US 6305376 (No data)
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model
EMA® Adjustable TheraSnore®
Photo
Company Frantz Design, Inc. DISTAR, Inc.
Inventor Don E. Frantz (U.S.) Thomas E. Meade (U.S.)
Approval Date 09/29/1997 11/12/1997
FDA
510(k) Reg. No. K971794 K973038
Treat Snoring Yes Yes
Treat OSA Yes Yes
Connector Elastic band Elastic band
Adjustor (P-R) Replace component Replace component
Adjustor (E-D) Replace component Replace component
Lateral movement Elastic band Elastic band
Patents US 5947724, US 6109265 US 5947724, US 6109265 (All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model
Snoring Control Device® Snore-Aid plus®
Photo
Company Ridgewood Dental Associates Dental Imagineers, LLC Inventor Kenneth L. Hilsen (U.S.) William A. Belfer (U.S.)
Approval Date 01/09/1998 07/22/1999
FDA
510(k) Reg. No. K963591 K991449
Treat Snoring Yes Yes
Treat OSA No Yes
Connector Interlocking member Post +Surface contact
Adjustor (P-R) Interlocking member Elastic band (Bind posts)
Adjustor (E-D) N/A Surface contact
Lateral movement Surface contact Surface contact
Patents US 5611355 US 20030234022
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Inc. Strong Dental Inc.
Inventor Charles D. Kownacki (U.S.) Patrick J. Strong (Canada)
Approval Date 05/28/2002 07/08/2003
FDA
510(k) Reg. No. K020893 K023836
Treat Snoring Yes Yes
Treat OSA Yes Yes
Connector Elastic band Linkage
Adjustor (P-R) Series of aperture Elastic band
Adjustor (E-D) N/A Elastic band
Lateral movement Surface contact Elastic band/Linkage
Patents US 20040177853 US 6418933, US 6526982
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model
OASYS® MDSA®
Photo
Company Mark Abramson, D.D.S., Inc. RJ & VK Bird Pty Ltd.
Inventor (No data) John Gaskell (Australia)
Approval Date 08/26/2003 10/27/2004
FDA
510(k) Reg. No. K030440 K042161
Treat Snoring Yes Yes
Treat OSA Yes Yes
Connector Wire Post (Hook)
Adjustor (P-R) Screw/Slot (Telescope) Screw
Adjustor (E-D) Surface contact N/A
Lateral movement Surface contact Surface contact
Patents (No data) US 6845774
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model
SomnoMed MAS® TAP-T®
Photo
Company Somnomed Ltd SCHEU-DENTAL GmbH
Inventor
Richard George Palmisano
(Australia) W. Keith Thornton (U.S.)
Approval Date 07/12/2005 07/12/2006
FDA
510(k) Reg. No. K050592 K061732
Treat Snoring Yes Yes
Treat OSA Yes Yes
Connector Surface contact Post (Hook)
Adjustor (P-R) Dual-thread screw Screw
Adjustor (E-D) Replace component N/A
Lateral movement N/A Slot
Patents US 6604527 US 7174895
(All rights of the pictures belong to individual incorporation respectively)
Table 3.2-2 Comparison of adjustable MAD products (cond.)
Model SomnoGuard AP/AP Pro®
Photo
Company Tomed Dr. Toussaint GmbH
Inventor
Toussaint Winfried Dr (Germany)
Approval Date 09/08/2006
FDA
Lateral movement Surface contact
Patents DE 20018772, EP 1203570
(All rights of the pictures belong to individual incorporation respectively)
CHAPTER 4
QFD AND REQUIREMENTS
4.1 Introduction
The quality function deployment (QFD) method was developed in Japan in the 1970s and introduced to the United States in the 1980s. It is one of the best and currently the most popular technique used to generate engineering specifications from customers’ requirements [51]. The advantage of the QFD method is that it develops the required information systematically for understanding the problem during product development. Some objectives which can be achieved by using the QFD method are showing as follows:
z To understand specifications or goals for the product.
z To understand how the competition meets the goal.
z To understand what is important from the customers’ viewpoints.
z To set the numerical targets to work toward.
Furthermore, QFD is a quality control method. It supplies a process for product design to ensure the result will meet the customers’ requirements. The process can be divided into four stages [52] as follows:
z Product Planning Stage (Customers’ Requirements Æ Engineering Specifications) z Product Deployment Stage (Engineering Specifications Æ Product Specifications) z Process Planning Stage (Product Specifications Æ Manufacturing Requirements) z Production Planning Stage (Manufacturing Requirements Æ Operating Instructions) Among the four stages, the first stage is the most important one because its outcome will be
the input information of next stage. Besides, the engineering specifications are generated to be the criteria during product design process in this stage.
Apply the QFD steps to build the house of quality shown in Fig. 4.1-1. Each room of the house contains valuable information which needs to be filled by designers. The numbers in the diagram refer to the steps that are detailed in next section.
Fig. 4.1-1 The house of quality, also known as the QFD diagram
4.2 QFD for MAD
In this section, the QFD for MAD will be established step-by-step and the engineering targets for the design of MAD will be generated in the end, as shown in Fig. 4.2-1.
z Step 1: Identify the customers (Who)
The customers are widely defined as all personnel relating to this product, including consumers, manufacturing personnel, sales staff, service personnel, and so forth. In this case, doctors, patients, and sales staff are considered as the customers of MAD.
z Step 2: Determine the customers’ requirements (What)
After the customers have been identified, the next step is to determine what is to be designed and what the customers want. Many requirements can be observed from customers who are using the existing products. Furthermore, surveys are usually used to gather information. For example, the literatures, the questionnaires, the face-to-face interviews, or any other ways can gather the opinions from people. All of the requirements can be classified into several types, such as functional performances, human factors, manufacturing, life-cycle concerns, and etc. In the design of MAD, the requirements are developed by the above mentioned ways and the results are shown in Table 4.2-1.
z Step 3: Determine relative importance of the requirements (Who vs. What)
The third step of the QFD method is to evaluate the relative importance of each customers’ requirement. The elimination of the least important requirements is proceeded by customers before ranking all items. Referring to the results listed in Fig. 4.2-1, the smaller number represents the more important requirement. The results can be used to generate a weighting factor for each requirement.
Table 4.2-1 List of customers’ requirements for MAD
Distribute force caused by bruxism
Easy to adjust
Easy to wear into mouth Easy to remove from mouth
Avoid exaggeration of opening of jaw Use for a long time
Comfortable to use
Period of Using Manufacturing
Low cost
Structure of parts are simple Parts are easy to be manufactured Product is easy to be manufactured Others
Close mouth completely
Simple operational steps to wear Opening mouth is allowed Breathing through mouth
No Impingement of tongue space Not irritate oral tissues
Easy to clean
Difficult to disengage from dentition Without side effects
Long life Tiny size
Difficult to break
Good-looking appearance z Step 4: Identify and evaluate the competition (Now)
The goal in this step is to determine the competition’s ability of existing products for each of the requirements. The results can bring out what already exists and that is something can be improved on what already exists. For each customer’s requirement, the existing design can be rate on a scale of 1 to 5 as follows:
1 ＝ The product does not meet the requirement at all.
2 ＝ The product meets the requirement slightly.
3 ＝ The product meets the requirement somewhat.
5 ＝ The product satisfies the requirement completely.
In this study, the most popular products in the market, TAP-T, is selected as the competition benchmark, as shown in Fig. 4.2-1.
z Step 5: Generate engineering specifications (How)
In this step, the customers’ requirements will be translated into a set of measurable engineering specifications which are the parameters for design, as shown in Fig. 4.2-1. A set of units is associated with each of the measures. Furthermore, the direction of improvement, more is better (↑) or less is better (↓), is also developed here.
z Step 6: Relate customers’ requirements to engineering specifications (What vs.
How)
The center portion of the house of quality represents the relationships between engineering specifications and customers’ requirements. Each cell of the portion will be mentioned according to the strength of relationship. Different numbers are filled in cells to refer to different strength as follows:
9 ＝ strong relationship 3 ＝ medium relationship 1 ＝ weak relationship
Blank ＝ no relationship at all
The results in this step are presented in Fig. 4.2-1.
z Step 7: Identify relationships between engineering requirements (How vs. How) Engineering specifications may be dependent on each other. Realize the dependency during design process can help us to know the work for meet one specification may cause positive or negative effects on others. The results are presented in Fig. 4.2-1 by referring to several typically used symbols as follows:
＃ ＝ Negative
¯ ＝ Strong Negative
＝ Strong Positive { ＝ Positive
z Step 8: Set engineering target (How much)
The final step in the QFD is to determine a target value for each engineering specification. Comparing to the specifications of competition products can establish the target for the new product. All the target values for the design of MAD are given in Fig.
4.2-1.
After the QFD house has been established, the design problem is fully understanding, and the product specifications are also determined. In the following of the product design process, conceptual designs can be obtained.
CHAPTER 5
CONCEPTUAL DESIGN
5.1 Design Method
Based on the results generated from QFD, the conceptual design phase is proceeding to innovate and create concepts for new designs. A general conceptual design process can be described as follows:
z Problem formulation: make sure the problem required to be solved.
z Overall function: generate the main function of the product.
z Functional decomposition: divide the overall function into several sub-functions.
z Concept generation: generate concepts to achieve each sub-function respectively.
z Concept combination: combine the concepts from sub-functions to form various complete conceptual designs for the new product.
There are still some problems existing in the commercial products. The most significant one is the failure of the MAD during using. The failure of the MAD will lead to the ineffective treatment and the extraneous expenses for repairing the device. Therefore, the problem here is to design a new MAD which will not break easily during the using time. The main function of the MAD is to make the jaw move forward to achieve the purpose of treating snoring and OSA. Thus the overall function in designing the MAD can be defined as:
maintain the jaw position advancement. In according to the overall function, the functional decomposition proceeded to identify all the sub-functions, and the result is shown in Fig.
5.1-1.
The overall function is divided into several sub-functions by the consideration of the functions which should be included. The functional decomposition leads to a better understanding of the design problem. In the MAD, six primary sub-functions promote the effective work on treating snoring and OSA, which are the fixation of the MAD, the connection between both fixers, the adjustability of jaw advancement, the lateral movement of the jaw, the prevention of the device from breaking, and the force directions acting on the jaw.
After all sub-functions have been developed, the next goal is to generate as many concepts as possible for each sub-function. A popular method, brainstorming, is selected to generate concepts because of its advantage of gathering ideas from each group member in their own viewpoint. The group of idea sources is formed by the members in my laboratory.
As the brainstorming method proceeding, all of the members should follow the four rules below [51]:
z Record all the ideas generated.
z Generate as many ideas as possible, and then verbalize these ideas.
z Think wild. Silly or impossible ideas sometimes lead to useful ideas.
z Do not allow evaluation of these ideas, just the generation of them.
The result of concept generation is a list of concepts generated for each function. The next step is to combine the individual concepts into complete conceptual designs by using the method that is to select one concept for each function and combine those selected into single design. Finally, various conceptual designs will be generated by accomplishing the conceptual design process.
5.2 Concepts
There are many combinations can be generated by combining individual concepts of each sub-function which described in the above section. However, some of them are impossible to be assembled together. Among the useful combinations, the relation between each individual concept should be good for arranging in pairs and without incompatible. In addition, some combinations are similar or almost the same with existent design or commercial products. At last, four complete concepts are selected and going to be described individually bellow.
5.2.1 Concept 1
Fig. 5.2-1 shows the conventional assembly of the MAD which includes an upper tray, a lower tray, and a mechanism to maintain the jaw advancement. The upper and lower tray are made by the acrylic resin, one kind of thermoplastic material, which can provide a good fit with dentition to make the well-fixed MAD. All of the concepts are going to use this method to perform the function of fixation. The mechanism of concept 1 is composed of an upper plate, a bottom plate, a sliding plate, and two screws, as shown in Fig. 5.2-2.
Fig. 5.2-2 Structure of mechanism in concept 1
The upper plate is fixed on the upper tray. Within the upper plate, the space provides a moveable region for sliding plate to allow the lateral movement of the lower jaw. The “S”
shape is designed to form the side wall of the upper plate. When the biting force applies on the bottom surface of the upper plate, the “S” shape makes less torque and tensile force applying to the fixed portion to avoid the failure of the MAD. The bottom plate fixes on the lower tray and assembles two screws together. These screws connect to the sliding plate with nuts to adjust its position and against the bottom plate moving backward.
This concept is workable for moving the lower jaw forward with an adjustable amount.
Furthermore, the proper height of the mechanism makes the lower jaw opening and downward slightly that causes the advancement more smooth to prevent TMJ from soreness.
However, adjustor is composed of two screws. It means that each adjustment process has to make twice efforts.
5.2.2 Concept 2
This concept includes the disengagement function to prevent the device from failure. Fig.
5.2-3 shows the whole assembly of concept 2. In this concept, the mechanism is composed of an upper plate, a bottom plate, and a screw, as shown in Fig. 5.2-4. The grooves on the upper and bottom plates are used to fix them more secure to the tray respectively. The upper plate provides a nut to connect with one end of the screw. On the other end, the root of the notch head tracks within a slot which is provided by the bottom plate.
The screw between the upper and bottom plate can adjust the amount of the jaw advancement and limit the moveable region of the lower jaw in the lateral direction. As the lower jaw move more widely to keep in touch with the side wall of the slot, the notch head receives the force applied from the border of the slot and starts to deform and shrink until the notch head disengages from the slot. The amount of the force for disengagement should less than the force which can make the device failure. However, the only method about how to adjust the disengagement force is the replacement of different materials. Maybe this is difficult to achieve and become a disadvantage of this concept.
Fig. 5.2-3 Assembly view of concept 2
Fig. 5.2-4 Structure of mechanism in concept 2
5.2.3 Concept 3
This concept includes the disengagement function to prevent the device from failure. A concept of the adj-slider integrated the adjustment function. Therefore, lateral movement is provided and combined in this concept. The adj-slider is installed in the upper tray opposite to the disengagement mechanism which is installed in the lower tray, as shown in Fig. 5.2-5. The adj-slider is composed of a sliding base, a sliding post, a screw set, a telescopic tube, and an upper plate, as shown in Fig. 5.2-6. The upper plate and the two ends of the sliding base are fixed to the upper tray to form a triangle. The sliding post slides along the slot of the sliding base at one end, and connects with the telescopic tube at another end. Then, the telescopic tube pivot to the upper plate to form a telescopic sliding mechanism in the triangle. The screw set is installed coaxial to the sliding post to receive the retractive force from the lower jaw and
This concept includes the disengagement function to prevent the device from failure. A concept of the adj-slider integrated the adjustment function. Therefore, lateral movement is provided and combined in this concept. The adj-slider is installed in the upper tray opposite to the disengagement mechanism which is installed in the lower tray, as shown in Fig. 5.2-5. The adj-slider is composed of a sliding base, a sliding post, a screw set, a telescopic tube, and an upper plate, as shown in Fig. 5.2-6. The upper plate and the two ends of the sliding base are fixed to the upper tray to form a triangle. The sliding post slides along the slot of the sliding base at one end, and connects with the telescopic tube at another end. Then, the telescopic tube pivot to the upper plate to form a telescopic sliding mechanism in the triangle. The screw set is installed coaxial to the sliding post to receive the retractive force from the lower jaw and