Abstract:
A universal impression tray can be reshaped shortened or lengthened allowing a clinician the ability to use one tray in any clinical situation. The tray itself can be used with patients requiring complete removable dentures, root supported and implant-supported overdentures and in some selected dentate cases. The tray can be infinitely modified allowing total control by the clinician. Trays in accordance with features of the present invention are made of a material composition including thermoplastic resin and thermochromic pigment. The material composition softens and changes color in warm water but tends to hold its shape until manipulated by the dentist. The thermoplastic resin portion of the tray can include polycaprolactone resin, styrene resin and dental modeling compound and can vary for specific uses to roughly 50% polycaprolactone /styrene resin and 50% dental modeling compound. Thermochromic pigment can represent up to 5% of the overall material composition of a tray.

Description:
PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This patent application is being filed as a Continuation-in-part and claims priority to U.S. Non-provisional patent application Ser. No. 11/256,519, filed Oct. 20, 2005, and which further claims priority under 35 U.S.C. § 119(e) to provisional patent application Ser. No. 60/621,026 filed Oct. 20, 2004, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is generally related to impression making trays. More particularly, the present invention is related to a universal impression tray that enables a clinician to use only one maxillary and or one mandibular impression tray in any clinical situation where impressions are required. 
       BACKGROUND 
       [0003]    Many dental procedures require the dentist to form an impression of patients&#39; teeth, either alone or in conjunction with the gums and vestibular anatomy. This impression typically is either used directly by the dentist to analyze the patient&#39;s mouth structure or is used to form a plaster replica of the patient&#39;s teeth, gums, and vestibule. Such impressions are typically used to produce dental replacement components and dental assemblies such as crowns, teeth, bridgework, dentures and other oral prostheses. 
         [0004]    Dental impression trays for obtaining an impression of a patient&#39;s dentition are well known. Such trays generally include tray portions anatomically contoured to fit at least a part of a patient&#39;s upper and/or lower oral anatomy, of which an impression is to be obtained. An appropriate impression material is placed in the tray and inserted in the mouth. After the impression material sets, it is used as a mold, into which plaster or dental stone can be poured which upon setting forms a model of the patient&#39;s oral anatomy. In addition, the set impression material may also be used directly as a mold for other purposes such as the fabrication of temporary restorations, the process of teeth whitening etc. 
         [0005]    Dentists use trays to carry impression material to the mouth and to support the moldable material intra-orally until it cures. The design of the tray depends on the size and shape of the area to be recorded. Tray sets typically include variably-sized upper and lower troughs, each filled with impression material such as a settable material. The upper impression corresponds to an impression section of maxilla, the lower impression corresponds to a complimentary section of mandible, and the two complimentary impressions jointly provide an impression of the bite relationship of mandible to maxilla. 
         [0006]    Metal trays are typically used for the above-mentioned procedures. Metal trays are expensive. They require cleaning and sterilization before reuse, which is inconvenient. In the process of obtaining any impression, called the modeling process, dental trays to contain the impression materials are used, and such dental impression trays are generally classified into ready-made (stock) trays and customized trays. In order to obtain more exact impression, customized trays fitted on an individual are manufactured from the model made by using the ready-made trays. So, ready-made trays could be regarded as one of the most basic apparatus for manufacturing an exact restoration. The arch has the shape of a horse hoof formed by person&#39;s teeth and alveolar bones, and its size and shape differs from person to person. A set of ready-made dental impression trays usually comprises at least 4 maxillary trays (small, medium, large and extra large) and at least 3 mandibular trays (small, medium and large). However, these conventional ready-made trays are so complex that even an expert has some difficulty in selecting and classifying them, and furthermore, there are some cases that none of such ready-made trays fits an individual. It is, therefore, difficult to obtain an exact impression through conventional ready-made trays. 
         [0007]    Current disposable trays are inexpensive, which gives them the convenience of disposability. However, their flexibility and plastic memory can cause intra-oral distortions in the impression. The lack of complete rigidity in a plastic tray can create a “springback” distortion transfer from the tray to the impression material on release of pressure to the tray sides, which is inadvertently applied by hard- and soft-tissue interferences at some point during the impression-making process. For example, pressure can be generated by the tongue, by occlusal forces pushing material against the tray wall, by the cheeks, or by tray impingement of gingival tissues, alveolar ridge, retromolar pad, tuberosity and teeth. This pressure flexes the tray while the impression material sets, causing inaccuracies in the impression when the distorted tray attempts to return to its original shape upon removal from the mouth. An impression in a flexible frame can also be distorted by forces applied to remove the tray from the patient&#39;s mouth or during routine laboratory handling. These inaccuracies are then transferred to the master cast when it is made in the dental laboratory. 
         [0008]    The use of thermoplastics in the field of dentistry is known. Conventionally, hardened or semi-hardened thermoplastics are used in the making of dental impressions, for example. Thermoplastics are also used as material to build up regions of castings that serve as the basis for making dentures. In order to melt or soften thermoplastics in the conventional dental office or laboratory, a dedicated water bath, which may be a so-called crock pot, such as found in the domestic kitchens, has been used to soften the thermoplastic. Alternatively, it has been known to heat up a cup of water in a microwave oven to a temperature of 150.degree. F. or more, and then carry the hot cup of water into the room where the dentist or technician is working the thermoplastic material. Currently in the dental field thermoplastic is typically used in the form of pre-formed wafers, such as so-called TEMP-TABS™, which are heated in use. There is also known thermoplastic which is incorporated in a triple tray or dental impression tray, such as a so-called THERMO-TRAY™. Both the TEMP-TABS™ and the THERMO-TRAY™ must be softened in hot water, as discussed above. This heating in the dental office not only leads to the problems discussed above, but if the thermoplastic is improperly overheated, it may develop undesirable bubbles. Further, the TEMP-TABS™ are very costly and, even if a relatively small quantity of TEMP-TABS™ is required for a procedure, such may be cost prohibitive. 
         [0009]    Unformed thermoplastic is a relatively inexpensive material. Needless to say, such prior art devices and methods of heating and using heated thermoplastic material are impractical, if not unwieldy. 
         [0010]    What is needed is a new tray system that will fit any patient during any clinical situation using any impression making technique that is required. What is also needed is a tray system that is universal and easy to use by clinicians. 
       SUMMARY 
       [0011]    In accordance with features of the present invention, a universal impression tray will now be described that is designed to produce high-quality final impressions in one clinical visit. 
         [0012]    In accordance with features of the present invention, a universal edentulous impression tray is disclosed that is comprised of a thermoplastic resin that softens and changes its color in warm water but tends to hold its shape until manipulated. 
         [0013]    In accordance with another feature of the present invention, the tray includes a main body including a trench, interior wall and exterior wall; and a handle integrated with the front of the main body, wherein the tray can be reshaped shortened or lengthened allowing a clinician the ability to use one tray in any clinical situation. 
         [0014]    In accordance with a method of using the invention, a set of universal trays (one maxillary tray and one mandibular tray) are accessed from clinic stock and are compared with the maxilla or mandible regions of a patient&#39;s mouth. After the comparison the tray is heated to at least 140 degrees Fahrenheit so that excess material can be added or removed to the tray as needed to adapt it to the entire maxilla or mandible region of the patient&#39;s mouth. Tray heating is indicated by a change in tray color, which is enabled by a thermochromic pigment incorporated into the tray material. Surfaces of the tray can then be smoothed out after material is added or removed prior to reinstalling the tray into the patient&#39;s mouth for further adjustment. A clinician can determine if the adjusted tray fits within the patient&#39;s mouth along the maxilla or mandible regions by determining whether the tray requires more or less material; and if the tray requires the addition or removal of material, the tray is reheated and then excess material can be again added/removed and the tray smoothed out until a match is obtained. The tray is then reheated and chilled during manipulation and while the tray is being adapted to the patient&#39;s maxilla or mandible regions. This process is repeated until a satisfactory fit is achieved. Once a fit is achieved, impression material is added to a satisfactory fitting tray, and the tray placed in the patient&#39;s mouth so that an impression of the maxilla or mandible regions can be achieved. 
         [0015]    In accordance with additional features of the present invention a universal maxillary and single mandibular tray can be easily reshaped shortened or lengthened allowing a clinician the ability to use one tray in any clinical situation. The tray itself can be used with patients requiring complete removable dentures, root supported and implant-supported overdentures and in some selected dentate cases. The tray can be infinitely modified allowing total control by the clinician. The tray can be easily adapted in the chair side or in the laboratory and formed in the patient&#39;s mouth. Any impression-making philosophy is supported by this impression tray system. For the first time the dentist is able to adapt a single tray to fit his or her unique impression making technique rather than compromising technique to fit the limitations of inflexible trays that cannot be easily modified. Of course, a tray in accordance with teachings of the present invention can be quickly adapted to patients with maxillofacial defects. 
         [0016]    The present invention accomplishes superior results over the prior dental impression technology in two ways. Trays in accordance with features of the present invention are made of a thermoplastic resin including thermochromic pigment that softens and changes color in warm water but tends to hold its shape until manipulated by the dentist. The resin is comprised of polycaprolactone resin, styrene resin and dental modeling compound. The proportions of thermoplastic resin portion of the tray can vary for specific uses but are ideally 50% polycaprolactone /styrene resin and 50% dental modeling compound. Very little thermochromic pigment is required to indicate temperature change in the tray. Less than 5% of the trays composition can include thermochromic pigment to accomplish a thermochromatic effect during tray heating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]      FIG. 1  illustrates a top view of a maxilla tray in accordance with features of the present invention. 
           [0018]      FIG. 2  illustrates a bottom view of the maxilla tray in  FIG. 1 . 
           [0019]      FIG. 3  illustrates a rear view of the maxilla tray in  FIG. 1 , shown with more detail of the trench as formed by the interior wall and exterior wall. 
           [0020]      FIG. 4  illustrates a cross sectional rear view of the maxilla tray in  FIG. 1 . 
           [0021]      FIG. 5  illustrates a side view of the maxilla tray shown in  FIG. 1 . 
           [0022]      FIG. 6  illustrates a front view of the maxilla tray shown in  FIG. 1 . 
           [0023]      FIG. 7  illustrates a perspective view of the maxilla tray  100  shown in  FIG. 1 . 
           [0024]      FIG. 8  illustrates a top view of a mandible tray in accordance with features of the present invention. 
           [0025]      FIG. 9  illustrates a bottom view of the mandible tray shown in  FIG. 8 . 
           [0026]      FIG. 10  illustrates a rear view of the mandible tray shown in  FIG. 8 , with more detail of a trench as formed by interior and exterior walls. 
           [0027]      FIG. 11  illustrates areas of variable thickness along the trench and wall areas of the mandible tray from  FIG. 8 , which enable tray manipulation. 
           [0028]      FIG. 12  illustrates a side view of the mandible tray shown in  FIG. 8 . 
           [0029]      FIG. 13  illustrates a front view of the mandible tray shown in  FIG. 8 . 
           [0030]      FIG. 14  illustrates a perspective view of the mandible tray shown in  FIG. 8 . 
           [0031]      FIG. 15  illustrates a flow diagram of a process of using a tray in accordance with features of the present invention. 
           [0032]      FIG. 16  illustrates a flow diagram of a process of using a tray in accordance with features of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]    In accordance with features of the present invention, a single set of trays can be used for maxilla or mandible impression making procedures. The preformed, universal trays of present invention accomplish superior results over the prior dental impression technology in two ways. Maxilla and mandible trays in accordance with features of the present invention are made of a thermoplastic resin that softens in warm water but tends to hold its shape until manipulated by the dentist. 
         [0034]    Referring to  FIG. 1 , a top view of a maxilla tray  100  in accordance with features of the present invention is shown. The tray  100  is shown with a handle  110  and a main body  120  that is formed as an arch or as the shape of a horse hoof. The main body  120  is further formed by person&#39;s teeth and alveolar bones during use when they are received within the trench  130  also formed along the main body in the form of an arch, but including interior and exterior walls, labeled  140  and  150  respectively. 
         [0035]    The material composition of the tray  100  includes a uniform thermoplastic resin-based material and a thermochromic pigment. The thermoplastic resin can include polycaprolactone resin, styrene resin and dental modeling compound. The thermoplastic material proportion of the tray is the dominant material in the tray and can vary for specific uses, but can be roughly 50% polycaprolactone/styrene resin and 50% dental modeling compound. The thermochromic pigment material is the less dominant material and can comprise up to 5% of the overall material composition of the tray. 
         [0036]    By incorporating a thermochromic pigment, the tray can change color when warmed and allows the practitioner to selectively modify the tray in the patient&#39;s mouth and create a custom tray prior to making a final impression. In actual test, tray material incorporating thermochromic pigment changes color from blue to tan when heated in warm water, which then indicates that the tray material is heated and is therefore pliable an can be easily shaped to the contours of the patient&#39;s edentulous ridge. The new contours can then be retained in the tray when cooled and permits the making of an accurate final impression of the edentulous ridge. 
         [0037]    Referring to  FIG. 2 , a bottom view of the maxilla tray  100  is shown. Also shown in  FIG. 2  is the outer surface detail of the trench wherein a ridgeline  135  generally follows the shape of a horseshoe along the bottom surface, opposite the trench  130  shown in  FIG. 1 . 
         [0038]    Referring to  FIG. 3 , a back view of the maxilla tray  100  is shown with more detail of the trench  130  as formed by the interior wall  140  and exterior wall  150 . The handle  110  is also shown in  FIG. 3  in lowered relation to the main body  120 . 
         [0039]    Referring to  FIG. 4 , a cross sectional back view of the maxilla tray  100  is shown with lines to illustrate various thick and thin regions along the trench and wall area of the tray. Thin areas enable easy manipulation of the tray, while thicker areas help maintain the trays integrity. The cross sectional view best illustrates the various thicknesses embodied within the tray&#39;s main body  120 . The thick regions  170  enable technicians/dentists to maintain the trays integrity, including its basic horseshoe shape. The thinner regions  160  are located in areas along the tray that traditionally cause most problems during use, including patient discomfort, difficulty achieving a snug fit of the tray with the patients teeth, gums and mouth. 
         [0040]    Referring to  FIG. 5 , a side view of the maxilla tray  100  is shown. The main body  110  and handle  120  are shown. The side view of the main body  110  also shows the exterior wall  140 . 
         [0041]    Referring to  FIG. 6 , a front view of the maxilla tray  100  is shown. The main body  110  and handle  120  are also shown in the back view of  FIG. 6 . 
         [0042]    Referring to  FIG. 7 , a perspective view of the maxilla tray  100  is shown. 
         [0043]    Referring to  FIG. 8 , a bottom view of a mandible tray  200  in accordance with features of the present invention is shown. The tray  200  is shown with a handle  210  and a main body  220  that is formed as an arch or as the shape of a horse hoof. The main body  220  is further formed by person&#39;s teeth and alveolar bones during use when they are received within the trench  230 , which includes interior and exterior walls, labeled  240  and  250  respectively. The tray  200  is made of a single, uniform thermoplastic resin-based material. The resin is comprised of polycaprolactone resin, styrene resin and dental modeling compound. The proportions can vary for specific uses but are roughly 50% polycaprolactone/styrene resin and  50 % dental modeling compound. 
         [0044]    Referring to  FIG. 9 , a top view of the mandible tray  200 . The handle  210  is also shown in  FIG. 9 . Also shown in  FIG. 9  is the outer surface detail of the trench wherein a ridgeline  235  generally follows the shape of a horseshoe along the bottom surface, opposite the trench  230  shown in  FIG. 8 . 
         [0045]    Referring to  FIG. 10 , a back view of the mandible tray  200  is shown with more detail of the trench  230  as formed by the interior wall  240  and exterior wall  250 . The handle  210  is also shown in  FIG. 10  in raised relation to the main body  220 . 
         [0046]    Referring to  FIG. 11 , thick and thin walled areas of the mandible tray  200  are shown.  FIG. 11  illustrates the various thicknesses embodied within the tray&#39;s main body  220  that enable ease of tray manipulation (thin areas  260 ) while overall tray integrity can be maintained (thick areas  270 ). The thick regions  270  enable technicians/dentists to maintain the trays integrity, including its basic horseshoe shape. The thinner regions  260  are located in areas along the tray that traditionally cause problems during use, including patient discomfort, difficulty achieving a snug fit of the tray with the patients teeth, gums and mouth. 
         [0047]    Referring to  FIG. 12 , a side view of the mandible tray  200  is shown. The main body  210  and handle  220  are shown. The side view of the main body  210  also shows the interior wall  230  and exterior wall  240 . 
         [0048]    Referring to  FIG. 13 , a front view of the mandible tray  200  is shown. The main body  210  and handle  220  are also shown. 
         [0049]    Referring to  FIG. 14 , a perspective view of the mandible tray  200  is shown. 
         [0050]    Both the maxillary and mandible trays are stiff and inflexible at body temperature. The resin becomes pliable after placing the tray in at least 140 degrees F. water for 30 to 45 seconds. Over heating the trays, however, can cause the integrity of the tray to breakdown. Therefore, the ideal range for heating trays is from 140 degrees to 160 degrees Fahrenheit, with a target temperature of 150 degrees Fahrenheit. Overheating can also be prevented by removing the tray from the water before the entire tray softens and it is controlled by the second design element. The trays are manufactured with varying cross-sections. Thinner areas soften first and thicker areas soften last. Areas that should be soft and flexible during the impression tray making process such as the flanges of the tray are thinner than the core of the tray that must stay rigid and intact. However, even the thin areas of the tray vary in their thickness. This allows the trays to soften in sections allowing even more control of the impression making process. The clinician has a great deal of control of the tray&#39;s flexibility—the part of the tray one desires to manipulate is simply heated and becomes soft while the other parts of the tray will remain rigid. 
         [0051]    During the basic process of developing a patient&#39;s impression, a warmed tray is first placed in the patient&#39;s mouth. The tray is adapted to the unique anatomy of the patient&#39;s mouth and the tray is removed. After cooling in cold water, the tray is modified by adding or removing material as needed. The tray is then warmed again and border molded. The tray is once again removed and cooled. The final impression is then made using any impression material chosen by the clinician. 
         [0052]    Heating and cooling is a basic technique required to use the trays effectively. This accomplishes two things—cooling the tray sets the position of the tray material and two—cooling the tray prevents the tray core from softening and distorting the trays shape. Since the tray is mostly made of a single, uniform thermoplastic material, care must be taken to heat and soften only the areas that are to be manipulated. This is accomplished by selective heating the tray. Heated regions of the tray are visually indicated by change in color of thermochromic pigment when used with the tray&#39;s thermoplastic material. The tray is partially submerged into 150 degree F. (or 140 to 160 F.) water for 30 to 45 seconds. This softens the tray flanges without softening the rest of the tray. If the tray is softened for less time or cooled off with water, the material will become less pliable. If the tray is heated longer or in hotter water, the material will become softer. Of course overheating will cause the tray to break down and become unwieldy. This can be reversed by placing the tray in cold water. Cooling the tray causes the tray to quickly harden. Room temperature water will do but chilled or ice water works faster. 
         [0053]    Material can be added to trays to extend the flanges, add a posterior palatal seal, fill the palate, if necessary, or create the foundation for an obturators bulb. The technique is simple. Warm a room temperature or cold tray for a few seconds in at least 140 degree F. water in order to create a soft skin on the surface. Squeeze the molten excess material onto the tray with some pressure. This effectively bonds the added material to the tray. You can&#39;t bond softened material to a cold tray. Although this may occasionally be used to your advantage, it usually causes problems somewhere down the line. 
         [0054]    There are only a few tools required to use the trays effectively—the first being the trays themselves. Each tray can be added to using extra tray material to enlarge or modify the tray as needed. The tray and material are placed in hot water of about 150 degrees F. Once the tray and material become soft, the extra material is placed as needed along the tray. The tray is then placed into chilled or ice water, which will cool the tray quicker. A sharp blade (e.g., such as a bard parker blade) is used to trim excess material. A tray can also be reduced. Large sections of tray can effectively be removed with cutters or nippers. Once modifications are made to the tray, a rotating nylon wheel can be used to thin the tray flanges. Since these cuts can be irritating to the patients&#39; oral mucosa, it&#39;s usually a good idea to smooth these cut surfaces by heating the tray for a few moments in warm water and then polishing the surface with a gloved finger. 
         [0055]    The resin can be perforated without compromising the structural integrity of the tray. The insertion of perforations or holes within the trays is helpful for open tray techniques for implant impression making. 
         [0056]    Mistakes to the trays can be corrected. The tray can be shaped by simply recontouring the warm material with a gloved finger or fingers. After recontouring, the repaired tray can be chilled in cold water. 
         [0057]    The thickness of the tray flanges can be important. A nylon brush can be used to thin cold flange material where necessary and to recontour other areas of the tray if desired. The surfaces roughened by the wheel can be polished by warming the tray surface and polishing the roughed edges with a gloved hand. 
         [0058]    Most impression making techniques required some tray relief to allow for the passive placement of tray material. The simplest way to create relief is to recontour the warmed tray material with gloved fingers. This allows for placing relief in the intended places. Using a second technique, relief can be created using wax. Wax can be placed in the tray in areas that relief is planned. The waxed tray is first placed in the mouth and manipulated. The wax is then removed after the tray is cooled in chilled water. The resultant space will be filled during the final impression making procedure. 
         [0059]    The completed tray should be placed in the patient&#39;s mouth prior to making the final impression. Any shrinkage of the material can be adjusted by heating the tray for a few seconds and finessing the shape in the patients&#39; mouth. The final impression can be made using any tradition impression-making medium. Vent holes can also be placed in the tray if desired. 
         [0060]    Referring to  FIG. 15 , a flow diagram  300  of the general process of using the universal tray described herein is shown. Referring to Block  310 , a universal tray is accessed from clinic stock and is compared with the maxilla or mandible regions of a patient&#39;s mouth. After the comparison, and as shown in Block  320 , the tray is heated at about 150 degrees Fahrenheit so that excess material can be added or removed to the tray as needed to adapt it to the entire maxilla or mandible region of the patient&#39;s mouth. As shown in block  330 , surfaces of the tray are smoothed out after material is added or removed prior to reinstalling the tray into the patient&#39;s mouth for further adjustment. As shown at block  340 , the clinician will determine if the adjusted tray fits within the patient&#39;s mouth along the maxilla or mandible regions. As shown in decision block  350 , the clinician decides whether the tray requires more or less material. If the tray requires the addition or removal of material, the process returns to block  320  where the steps for blocks  320  through  350  are repeated. If no further material alterations are required, the clinician move on to block  360  wherein the tray is reheated and chilled during manipulation and while the tray is being adapted to the patients maxilla or mandible regions. The process is repeated until a satisfactory fit is achieved. At block  370 , impression material is added to a satisfactory fitting tray, and the tray placed in the patient&#39;s mouth so that an impression of the maxilla or mandible regions can be achieved. 
         [0061]    Referring to  FIG. 16 , another flow diagram  400  of a process of using a universal tray including thermochromic material is shown. The method of use is as follows: at least one of two different edentulous trays can be provided and are compared by a dental professional with the maxilla or mandible regions of a patient&#39;s mouth, as shown in block  410 . The tray is heated by partially immersing the tray body into 140 to 160 degree Fahrenheit water as shown in block  420 . The immersed material changes color (typically from a blue to tan color) indicating which areas of the tray will soften and become flexible and which areas will remain rigid, as shown in block  430 . This selective heating of the tray body will allow the tray body to retain its shape during the impression making process. After the tray is warmed, it is place on the patient&#39;s edentulous arch and manually molded to the edentulous contour by massaging the patient&#39;s face, as shown in block  440 . This process adapts the softened material to the ridge and begins to customize the tray. Then as shown in block  450 , the tray is removed from the mouth and cooled in cold water. The warm material returns to its original color (i.e., blue) indicating a return to a rigid state. The tray is evaluated by the dental practitioner and further modified if needed, which is shown in block  460 . Modifications could include shortening the tray&#39;s contours with a knife or scissor, adding extra material to the original tray form, smoothing sharp edges, or removing excess material with a bur. All these modifications require heating or cooling the material and is facilitated the color changing ability of the tray material; therefore, the steps shown in blocks  420  through  460  can be repeated as necessary, which is shown in decision block  460 . The tray is again warmed in water and placed in the patient&#39;s mouth. This step confirms the fit of the tray, as shown in block  470 . The tray is then removed from the mouth and cooled if necessary. As shown in block  480 , an accurate final impression material is placed in the tray and the tray is reinserted in the patient&#39;s mouth. The tray and cured impression material is removed from the mouth and evaluated for accuracy and detail as shown in block  490 . The impression making process is then completed as shown in block  495 .