Toothbrush and electric toothbrush

Various embodiments of novel toothbrush bodies are provided. In one embodiment, a first toothbrush body has a handle, while two other toothbrush bodies are attached are attached to the first toothbrush body by curved stainless steel arm pins disposed on opposite sides of the first toothbrush body. Removable nuts are provided to allow the other two toothbrush bodies to be replaced. In another embodiment, three toothbrush bodies have fitting grooves in their outer surfaces, and stainless steel joints having a channel shape are fitted in the grooves. In another embodiment, three toothbrush bodies are integrally joined to each other by a curved stainless steel enclosing plate that is fastened to the bodies by screws. A hard sponge cushion, rather than a bristle assembly, is attached to the lower surface of the toothbrush bodies.

&lsqb;Description of reference numerals&rsqb; 1 Al, A3 toothbrush 1 grip handle 10 engaging body 2 crown cap 20 engaging hole 21 vertical wing 22 horizontal wing 24 guide hole 25 adjustment screw 3, 3a bristle assembly 30 brush base A2 electric toothbrush la handle 5 grip base 51 motor Fourth through seventh inventions will be described in detailed below based on embodiments shown in the drawings. FIG. 6 is a perspective view of a toothbrush according to an embodiment of the present invention. FIG. 7 is a view illustrative of the structure of bristle assemblies and the manner which the bristle assemblies abut against tooth surface. FIG. 8 is an enlarged view of tip ends of bristles. toothbrush A 1 which is manually operable in use comprises a grip handle 1 and a crown cap 2 . The grip handle 1 is in the form of a rod of plastic and the crown cap 2 is fixed to a distal end of the grip handle 1 . The crown cap 2 is molded of plastic and has a molar tooth fitting portion 21 having a substantially heart-shaped cross section and a front tooth fitting portion 22 having a substantially V-shaped cross section. The front tooth fitting portion 22 is of a curved shape such that its central region is slightly narrow as viewed in plan. The crown cap 2 has a round outer profile for protecting the inside of a mouth when in use. A bristle assembly 3 is planted on the inner surface of the molar tooth fitting portion 21 substantially in its entirety such that the bristle assembly 3 are inclined at an angle of substantially 45° to surfaces of molar teeth to be fitted in the molar tooth fitting portion 21 . Furthermore, a bristle assembly 3 a is planted on the inner surface of the front tooth fitting portion 22 substantially in its entirety such that the bristle assembly 3 a are inclined at an angle of substantially 45° to surfaces of front teeth to be fitted in the front tooth fitting portion 22 . As shown in FIG. 8 , the bristle assemblies 3 , 3 a have bristles 30 whose tip ends are bent toward the bent corner of the crown cap 2 and are rounded. The bristles 30 thus shaped are sufficiently effective to remove plague off teeth without damaging the gum when they brush the teeth. A process of using the toothbrush according to this embodiment and operation thereof will be described below with reference to FIGS. 6 through 8 . (1) The molar tooth fitting portion 21 is fitted over a molar tooth Tl and the bristle assembly 3 are directed substantially at 45° with respect to surfaces of the molar tooth Tl. Then, the grip handle 1 is manually angularly moved back and forth around its own axis or in the direction of the tooth axis or the direction normal thereto for thereby brushing the molar tooth Tl. Though the bristle assemblies 3 , 3 a are angularly moved back and forth at this time, since the bristle assemblies 3 , 3 a are inclined to the tooth surfaces, the fric-tional force is stronger upon movement toward the tip end of the tooth, and weaker upon movement in the opposite direction. Therefore, plague, tartar, and calculus deposited on the occlusal tooth area, the tooth sides, and the tooth neck of the molar tooth Tl are gathered toward the center of the molar tooth fitting portion 21 . For the same reason, the gum is not peeled off the tooth neck, and plaque, tartar, and calculus deposited on the tooth neck are removed without being pushed between the tooth and the gum. (2) When the brushing of the molar tooth Tl is finished, the front tooth fitting portion 22 is fitted over a front tooth T 2 . Upon brushing the front tooth T 2 in the same manner as with the molar tooth Tl, plaque, tartar, and calculus are gathered toward the center of the front tooth fitting portion 22 , and removed without being pushed between the tooth and the gum. FIG. 9 is a perspective view of an electric toothbrush according to the present invention. An electric toothbrush A 2 has a grip base 5 including a handle la on its distal end. The handle la can be actuated by a motor 51 housed as an electric actuator means in the grip base 5 , to angularly move back and forth about its own axis (as indicated by the arrows “a”) and in the direction of the tooth axis (as indicated by arrows “b ”) through a converter mechanism 53 . The converter mechanism 53 is of a known structure, and will not be described in detail. In this embodiment, it is possible for the handle la to switch in its movement between the direction around its own axis, the direction of the tooth axis, and the direction normal thereto with a selector switch (not shown). A battery 52 is also housed in the grip base 5 and a switch 54 is mounted on the grip base 5 . The structures of a crown cap 2 and bristle assemblies 3 , 3 a fixed to the distal end of the handle la are the same as those of the toothbrush A 1 described above, and will not be described in detail. Those parts of the electric toothbrush A 2 which are identical or equivalent to those of the toothbrush A 1 are denoted by identical reference numerals. A method of using the electric toothbrush A 2 and operation thereof are substantially the same as those of the toothbrush A 1 except that the bristle assemblies 3 , 3 a are angularly moved back and forth by electric energy for higher efficiency. FIGS. 10 and 11 are front elevational views showing other structures of crown caps. A crown cap 2 a shown in FIG. 10 is of a structure having a molar tooth fitting portion 21 and bristle assembly 3 only, and is used solely for brushing molar teeth. A crown cap 2 b shown in FIG. 11 is of a structure having a front tooth fitting portion 22 and bristle assembly 3 a only, and is used solely for brushing front teeth. Those parts of the crown caps 2 a, 2 b shown in FIGS. 10 and 11 which are identical or equivalent to those of the crown cap 2 are indicated by identical reference numerals. While the crown caps 2 a, 2 b operate substantially in the same manner as the crown cap 2 according to the above embodiment, the crown caps 2 a, 2 b are simpler in structure and smaller in size, and hence can be moved easily in the mouth. 
 &lsqb;Brief description of the drawings&rsqb; &lsqb; FIG. 6 &rsqb; is a perspective view of a toothbrush according to an embodiment of the present invention; &lsqb; FIG. 7 &rsqb; is a view illustrative of the structure of bristle assemblies and the manner in which the bristle assemblies abut against tooth surfaces; &lsqb; FIG. 8 &rsqb; is an enlarged view of tip ends of bristles; &lsqb; FIG. 9 &rsqb; is a perspective view of an electric toothbrush according to the present invention; &lsqb; FIG. 10 &rsqb; is a front elevational view of the structure of another crown cap; and &lsqb; FIG. 11 &rsqb; is a front elevational view of the structure of still another crown cap. 
 &lsqb;Description of reference numerals&rsqb; 2 Al toothbrush 1 grip handle 2. 2a, 2b crown cap 3. 3a bristle assembly A2 electric toothbrush la handle 5 grip base 51 motor Eighteenth and nineteenth inventions will be described in detail below based on embodiments shown in the drawings. FIG. 12 is an exploded perspective view of a toothbrush according to an embodiment of the present invention. FIG. 13 is a view illustrative of the structure of bristle assemblies and the manner in which the bristle assemblies abut against tooth surfaces. FIG. 14 is an enlarged view of tip ends of bristles. A toothbrush A 1 which is manually operable in use comprises a grip handle 1 and three toothbrush bodies 2 a, 2 b, 2 c. The grip handle I is in the form of a rod of plastic and the toothbrush bodies 2 a, 2 b, 2 c are detachably mounted on a distal end of the grip handle 1 . Each of the toothbrush bodies 2 a, 2 b, 2 c has a handle 20 with bristle assemblies 21 mounted on its distal end portion which as a round profile for protecting the inside the mouth from damage during use. The structure by which the toothbrush bodies 2 a, 2 b, 2 c are attached to the grip handle 1 will be described below. The distal end of the grip handle 1 has three fixing holes lla, lib, lie defined therein and three threaded holes also defined therein between the fixing holes lla, lib, lie and an outer surface of the grip handle 1 . Fastening screws 12 are threaded in the respective threaded holes. When the fastening screws 12 are tightened, the respective ends of the handles 20 of the toothbrush bodies 2 a, 2 b, 2 c that are received in the fixing holes lla, lib, lie are secured therein. The fixing holes lla, lib, lie have a substantially elliptical cross section similar to that of the handles 20 , so that when the handles are inserted into the respective fixing holes lla, lib, lie, the angles of the toothbrush bodies 2 a, 2 b, 2 c about their own axes are automatically set. The angles to which the toothbrush bodies 2 a, 2 b, 2 c are set will be described below with reference to FIG. 13 . The toothbrush body 2 a corresponds to the occlusal tooth area of a tooth, and its bristle assemblies 21 abut against the occlusal tooth area substantially perpendicularly thereto. The toothbrush bodies 2 b, 2 c correspond respectively to the opposite sides of the tooth. The bristle assemblies 21 of the toothbrush bodies 2 b, 2 c are inclined at an angle of substantially 45° to the tooth sides toward the tip end of the tooth which is to be fitted in a region surrounded by these bristle assemblies 21 . As shown in FIG. 14 , the bristle assemblies 21 have bristle fibers 210 whose tip ends are bent toward the tip end of a tooth and are rounded. The bristle fibers 210 thus shaped are sufficiently effective to remove plague off teeth without damaging the gum when they brush the teeth. A process of using the toothbrush according to this embodiment and operation thereof will be described below with reference to FIG. 12 through 14 . A tooth T is fitted into the space surrounded by the bristle assemblies 21 , and the bristle assemblies 21 corresponding to tooth sides Tl are directed substantially at 45° with respect to the tooth sides Tl. Then, the grip handle 1 is manually vibrated around its own axis or in the direction of the tooth axis or the direction normal thereto for thereby brushing the tooth. Though the bristle assemblies 21 are vibrated at this time, since the bristle assemblies 21 are inclined to the tooth sides Tl, the frictional force is stronger upon movement toward the tip end of the tooth, and weaker upon movement toward the roots of the tooth. Therefore, plague, tartar, and calculus deposited on the occlusal tooth area, the tooth sides, and the tooth neck of the tooth are gathered toward the center of the tip end of the tooth. For the same reason, even when rubbed by the bristle assemblies 21 , the gum is not peeled off the tooth neck, and plaque, tartar, and calculus deposited on the tooth neck are removed without being pushed between the tooth and the gum. FIG. 15 is a perspective view of an electric toothbrush according to the present invention. An electric toothbrush A 2 has a grip base 5 including an attachment 51 on its distal end. To the attachment 51 , there are attached three toothbrush bodies 2 a, 2 b, 2 c as with the toothbrush A 1 . The attachment 51 can be actuated by a motor 51 housed as an electric actuator means in the grip base 5 , to angularly move back and forth about its own axis (as indicated by the arrows “a”) and in the direction of the tooth axis (as indicated by arrows “b”) through a converter mechanism 53 . The converter mechanism 53 is of a known structure, and will not be described in detail. In this embodiment, it is possible for the attachment 51 (handle 20 ) to switch in its movement between the direction around its own axis and the direction of the tooth axis with a selector switch 54 . In addition, the attachment 51 may be vibrated in the direction normal too the direction of the tooth axis ( i. e., vibrated in the direction in which the attachment 51 moves into and out of the mouth). A battery 55 is housed in the grip base 5 . Those parts of the electric toothbrush A 2 which are identical or equivalent to those of the toothbrush A 1 are denoted by identical reference numerals. A method of using the electric toothbrush A 2 and operation thereof are substantially the same as those of the toothbrush A 1 except that the toothbrush bodies 2 a, 2 b, Ic (the bristle assemblies 21 ) are vibrated by electric energy for higher efficiency. FIG. 16 is an exploded perspective view of an electric toothbrush according to another embodiment of the present invention. An electric toothbrush A 3 has three handles 56 a, 56 b, 56 c mounted on an attachment 51 a. The handles 56 a, 56 b, 56 c can be vibrated about their own axes independently by a converter mechanism 53 . The handles 56 a, 56 b, 56 c have respective fitting portions 57 of square-shaped cross section on their distal ends. Toothbrush bodies 2 al, 2 bl, 2 cl are detachably mounted on the respective fitting portions 57 . The toothbrush bodies 2 al, 2 bl, 2 cl include respective handles 20 which have in their proximal ends respective fitting holes 201 that receive the respective fitting portions 57 fitted therein. The fitting portions 57 can detachably be fitted in the fitting holes 201 by known means in one operation. The angles at which the toothbrush bodies 2 al, 2 bl, 2 cl are attached around the axis of the toothbrush are set in the same manner as with the above embodiments. Those parts of the electric toothbrush A 3 which are identical or equivalent to those of the electric toothbrush A 2 are indicated by identical reference numerals. A method of using the electric toothbrush A 3 and operation thereof are essentially the same as with the electric toothbrush A 2 except that the toothbrush bodies 2 al, 2 bl, 2 cl can be detached and attached with ease and the toothbrush bodies 2 al, 2 bl, 2 cl (the bristle assemblies 21 ) can be vibrated about their respective axes by electric energy. FIG. 17 is a fragmentary perspective view of toothbrush bodies according to a second embodiment of the present invention. In this embodiment, only a toothbrush body 2 a 2 has a handle 20 , and toothbrush bodies 2 b 2 , 2 c 2 which are of substantially the same extent as bristle assemblies are attached to the toothbrush body 2 a 2 by curved arm pins 28 of stainless steel that are disposed on opposite sides of the toothbrush body 2 a 2 . The arm pins 28 are secured in position by nuts N that are tightened. When loosened, the nuts N allow only the toothbrush bodies 2 b 2 , 2 c 2 to be replaced. The angles at which the toothbrush bodies 2 a 2 , 2 b 2 , 2 c 2 are attached around the axis of the toothbrush are set in the same manner as with the above embodiments. FIG. 18 is a fragmentary perspective view of toothbrush bodies according to a third embodiment of the present invention, and FIG. 19 is a cross-sectional view of one of the toothbrush bodies according to the third embodiment. In this embodiment, toothbrush bodies 2 b 3 , 2 c 3 are attached to a toothbrush body 2 a 3 by arm pins 29 extending from the neck of a handle 20 of the toothbrush body 2 a 3 . As shown in FIG. 19 , an adjustment screw 30 is undetachably rotatably mounted on an upper surface of the handle 20 near its distal end. The adjustment screw 30 has a threaded hole 31 defined in its lower portion. The handle 20 has a recess 202 defined in a lower portion thereof near its distal end and housing a vertically movable body 203 . A screw 204 is vertically fixed to an upper surface of the vertically movable body 203 , and threaded in the threaded hole 204 . A bristle assembly 21 a is mounted on a lower surface of the vertically movable body 203 . When the adjustment screw 30 is turned, the vertically movable body 203 is vertically moved to adjust the height of the bristle assemblies 21 of the toothbrush bodies 2 b 3 , 2 c 3 for use. The angles at which the toothbrush bodies 2 a 3 , 2 b 3 , 2 c 3 are attached around the axis of the toothbrush are set in the same manner as with the above embodiments. FIG. 20 is a fragmentary perspective view of toothbrush bodies according to a fourth embodiment of the present invention. In this embodiment, toothbrush bodies 2 a 4 , 2 b 4 , 2 c 4 have fitting grooves 205 defined in their respective outer surfaces, and joints 33 of stainless steel having a channel shape in front elevation are fitted in the fitting grooves 205 . The joints 33 are secured in position to the toothbrush bodies 2 a 4 , 2 b 4 , 2 c 4 , thus integrally joining the toothbrush bodies 2 a 4 , 2 b 4 , 2 c 4 to each other. The angles at which the toothbrush bodies 2 a 4 , 2 b 4 , 2 c 4 are attached around the axis of the toothbrush are set in the same manner as with the above embodiments. FIG. 21 is a fragmentary perspective view of toothbrush bodies according to a fifth embodiment of the present invention. In this embodiment, toothbrush bodies 2 a 5 , 2 b 5 , 2 c 5 are integrally joined to each other by a curved enclosing plate 35 of stainless steel which is fastened to them by screws 36 . A cushion 21 b made of hard sponge, rather than bristle assembly, is attached to a lower surface of the toothbrush body 2 a 5 . Those parts of the toothbrushes shown in FIGS. 17 through 21 which are identical or equivalent to those of the aforesaid embodiments are indicated by identical reference numerals. 
 &lsqb;Brief description of the drawings&rsqb; &lsqb; FIG. 12 &rsqb; is an exploded perspective view of a toothbrush according to an embodiment of the present invention; &lsqb; FIG. 13 &rsqb; is a view illustrative of the structure of bristle assemblies and the manner in which the bristle assemblies abut against tooth surfaces; &lsqb; FIG. 14 &rsqb; is an enlarged view of tip ends of bristies; &lsqb; FIG. 15 &rsqb; is a perspective view of an electric toothbrush according to the present invention; &lsqb; FIG. 16 &rsqb; is an exploded perspective view of an electric toothbrush according to another embodiment of the present invention; &lsqb; FIG. 17 &rsqb; is a fragmentary perspective view of toothbrush bodies according to a second embodiment of the present invention; &lsqb; FIG. 18 &rsqb; is a fragmentary perspective view of toothbrush bodies according to a third embodiment of the present invention; &lsqb; FIG. 19 &rsqb; is a cross-sectional view of one of the toothbrush bodies according to the third embodiment of the present invention; &lsqb; FIG. 20 &rsqb; is a fragmentary perspective view of toothbrush bodies according to a fourth embodiment of the present invention; and &lsqb; FIG. 21 &rsqb; is a fragmentary perspective view of toothbrush bodies according to a fifth embodiment of the present invention. 
 &lsqb;Description of reference numerals&rsqb; 3 Al toothbrush 1 grip handle 2a, 2b, 2c toothbrush body 20 handle 21 bristle assemblies lla, lib, lie fixing hole 12 fastening screw A2 Electric toothbrush 55 battery 5 grip base 51 attachment 52 motor 53 converter mechanism Preferred embodiments of tenth through sixteenth inventions will be described below. FIGS. 22, 23 , and 24 show an electric toothbrush 10 according to an embodiment of the present invention. As shown in FIGS. 22, 23 , and 24 , the electric toothbrush 10 has a casing 14 with a handle 12 projecting from one end therof. The casing 14 houses a bristle assembly 16 reciprocally angularly movable to swing upwardly along teeth sides while being held against the teeth sides or neighboring regions, and a reciprocally rocking mechanism 18 for reciprocally angularly moving the bristle assembly 16 . As shown in FIGS. 22 and 23 , the casing 14 comprises a vertical case 20 on one side and a horizontal case 22 on another side, the cases 20 , 22 being joined in an inverted L shape as viewed in end elevation. The horizontal case 22 is joined to the vertical case 20 so as to project from an upper end of the vertical case 20 . The vertical case 20 and the horizontal case 22 are made of a hard synthetic resin or the like. The vertical case 20 has a hole 24 defined in an inner side wall thereof for placing the bristle assembly 16 therein, and a drain hole 25 defined in a bottom wall thereof for draining water out of the casing 14 . As shown in FIGS. 23 and 24 , the reciprocally rocking mechanism 18 has a rotatable shaft 26 journaled in an upper position in the vertical case 20 , and a pair of swing shafts 28 disposed vertically in the vertical case 20 at respective positions near the ends of the vertical case 20 . The rotatable shaft 26 is rotatably supported by a pair of bearings 30 disposed in the upper position in the vertical case 20 . A pair of plate cams 32 is fixedly mounted on the rotatable shaft 26 near its opposite ends and held in sliding contact with the respective upper ends of the swing shafts 28 . The swing shafts 28 are journaled in shaft holes that are defined in two upper bearing plates 34 horizontally disposed in the upper position in the vertical case 20 , and shaft holes that are defined in a lower bearing plate 36 horizontally disposed in a lower position in the vertical case 20 . Coil springs 38 are mounted on the swing shafts 28 , respectively, between the upper bearing plates 34 for normally urging the swing shafts 28 to move upwardly. Pivot supports 40 by which the bristle assembly 16 are pivotally supported are fixedly mounted in upper and lower regions on the swing shafts 28 between the upper and lower bearing plates 34 , 36 . When the rotatable shaft 26 of the reciprocally rocking mechanism 18 is rotated, the swing shafts 28 are lowered against the bias of the coil springs 38 each time cam lobes of the plate cams 32 make one revolution, and hence are reciprocally moved in the vertical direction. The reciprocally rocking mechanism 18 is not limited to the rotating plate cams 32 , but crank mechanisms or the like may be combined with the rotatable shaft 26 for vertically moving the swing shafts 28 in interlinked relation thereto. As shown in FIGS. 24, 25 , and 26 , the bristle assembly 16 have two or three bristle bases 42 positioned in upper and lower positions between the swing shafts 28 of the reciprocally rocking mechanism 18 and extending obliquely upwardly toward the hole 24 defined in the inner side wall of the vertical case 20 . Each of the bristle bases 42 is of a flat shape elongate in the horizontal direction and has a support shaft 44 extending longitudinally through and fixed to a lower end thereof. Bristles 46 are planted on an upper end of each of the bristle bases 42 . The bristle bases 42 are pivotally supported by opposite ends of the support shafts 44 on the pivot supports 40 that are fitted over the swing shafts 28 in their upper and lower regions. Resilient members 48 such as coil springs are connected between the opposite ends of the bristle bases 42 and the swing shafts 28 . The bristle bases 42 project obliquely upwardly from within the vertical case 20 toward the hole 24 in the inner side wall thereof. As shown in FIGS. 25 and 26 , each of the bristle bases 42 is inclined upwardly at an angle of about 45° from its pivots on the swing shafts 28 . Upper and lower stoppers 50 , 52 are horizontally mounted on the pivot supports 40 on the swing shafts 28 such that the bristle base 42 can swing vertically in an upward angle of about 15° from the inclined position and in a downward angle of about 15° from the inclined position. When the bristles 46 on the bristle bases 42 abut against a tooth side and the swing shafts 28 are lowered, the bristle bases 42 are turned upwardly and hence closed until they are engaged by the upper stoppers 50 while being lowered. When the swing shaft 28 are lifted, the bristle bases 42 are spread and received by the lower stoppers 52 while being elevated. On their way upward, the bristle bases 42 are closed under the bias of the resilient members 48 and return to their original position. At this time, the tip ends of the bristles 46 are reciprocally angularly moved upwardly in coaction with the swing shafts 28 along paths as shown in FIG. 27, i .e., a path a-b where the ends of the bristles 46 are lowered and substantially held against a tooth neck, a path b-c where the ends of the bristles 46 abut against the tooth neck and the bristles 46 are spread, a path c-d where the ends of the bristles 46 brush a tooth side upwardly in a scraping manner and move upwardly while being spread, and a path d-a where the ends of the bristles 46 are closed). Since the bristles 46 are closed as they are lowered, they do not peel off the end of the gum. When the bristles 46 are elevated, they can scrape plaque deposited on the tooth neck and tooth side. In the embodiment shown in FIGS. 23 and 24 , the bristle bases 42 are disposed in upper, middle, and lower positions. The bristles 46 on the bristle bases 42 are longer, shorter, and medium successively from the lower position through the middle position to the upper position. With this arrangement, the bristles 46 of the bristle assembly 16 can be brought into abutment against a curved tooth surface extending from the tooth side along the tooth neck for scraping off deposited plaque. The bristle bases 42 may be located in upper and lower positions. In this case, the bristles 46 on the bristle base 42 in the lower position should preferably be longer than the bristles 46 on the bristle base 42 in the upper position for abutment against the curved tooth surface extending from the tooth side along the tooth neck for scraping off deposited plaque. The bristles 46 may be planted through a coupling on the bristle bases 42 so that the bristles 46 can be replaced. As shown in FIGS. 22 and 24 , a temporary positioning member 54 for temporarily positioning the bristles 46 of the bristle assembly 16 for engagement with the tooth side and the tooth neck is mounted on the horizontal case 22 of the casing 14 . The temporary positioning member 54 has a base plate 58 fitted in a recess 22 that is defined in a lower surface of the horizontal case 22 , and bristles 46 planted on a lower surface of the base plate 58 . Instead of the bristles 46 , a resilient member such as of sponge may be fixed in place to the base plate 58 . An adjustment screw 62 threaded through a threaded hole 60 defined in the horizontal case 22 has a lower end loosely engaging the base plate 58 that is fitted in the recess 56 . When the adjustment screw 62 is turned in one direction or the other, the base plate 58 is vertically slid in the recess 56 for thereby adjusting the height of the bristles 46 . When the bristles 46 of the temporary positioning member 54 is held in abutment against the occlusal area of the crown of a tooth, the bristles 46 of the bristle assembly 16 that project from the inner side wall of the vertical case 20 are accurately brought into abutment against the tooth side and the tooth neck, allowing the bristle assembly 16 to brush the tooth upon reciprocating angular movement. As shown in FIGS. 22 and 23 , the casing 14 has joint sleeves 64 extending from upper portions of its opposite ends for detachably joining 12 handle 12 . In the joint sleeves 64 , there are disposed respective gears 66 fixed to respective opposite ends of the rotatable shaft 26 of the reciprocally rocking mechanism 18 which project into the joint sleeves 64 . The handle 12 comprises a cylindrical body 70 detachably joined to one of the joint sleeves 64 and housing an actuator 68 , and a grip cylinder 74 detachably joined to the cylindrical body 70 and housing a battery 72 or a booster or the like for converting AC electric energy into DC electric energy. The actuator 68 comprises a small motor 76 having a rotatable shaft to which a gear 78 is fixed, and a gear 66 fixed to the rotatable shaft 26 in the joint sleeve 64 is held in mesh with the gear 78 . When a switch 80 mounted on an upper surface of the cylindrical body 70 is turned on, the small motor 76 is energized to actuate the reciprocally rocking mechanism 18 in the casing 14 . The joined ends of the joint sleeve 64 and the cylindrical body 70 should preferably be reinforced by a reinforcing band 82 mounted thereon. The electric toothbrush 10 according to the present invention is used as follows. While the user is gripping the handle 12 , the user holds the temporary positioning member 54 against the occlusal area of the crown of a tooth T for thereby positioning the tip ends of the bristles 46 of the bristle assembly 16 in abutment against the tooth side to the tooth neck of the tooth T, as shown in FIG. 24 . Then, the user turns on the switch 80 on the handle 12 to cause the small motor 76 of the actuator 68 to rotate the rotatable shaft 26 in the casing 14 . The swing shafts 28 of the reciprocally rocking mechanism 18 are moved vertically, causing the bristle bases 42 of the bristle assembly 16 coupled to the swing shafts 28 to angularly move reciprocally. The tip ends of the bristles 46 are angularly moved reciprocally in a manner to turn upwardly to scrape off plaque deposited on the tooth side and the tooth neck without pushing the plaque into a gum groove. The bristles 46 are also effective to massage the gum. The temporary positioning member 54 of the casing 14 is moved along the occlusal areas of upper and lower teeth in abutment thereagainst for thereby removing plaque deposited on the tooth side and the tooth neck of each tooth T. When the electric toothbrush 10 is to be used on the back of teeth T or the opposite side of the teeth, the cylindrical member 70 of the handle 12 is fitted over the joint sleeve 64 on the other end of the casing 14 . When the electric toothbrush 10 according to the present invention is used, therefore, the gum is prevented from being peeled off the tooth necks, and hence can be maintained in a healthy condition for protection against peri-odontites and dental caries. As shown in FIG. 28 , the lower end of each brush base 42 may be pivotally coupled to the swing shafts 28 in the vertical case 20 and the sides of each brush base 42 may be pivotally mounted in a lateral hole 84 defined in the inner side wall of the vertical case 20 . When the swing shafts 28 are moved vertically, the brush base 42 is angularly moved to cause the bristles 46 on the end of the brush base 42 to remove plaque and tartar deposited on the tooth side and the tooth neck of each tooth T. With the electric toothbrush 10 according to the present invention, the casing 14 may not necessarily be limited to an inverted L shape, but may be of a shape spreading at an obtuse angle. Furthermore, only the vertical case 20 may serve as a casing with the bristle assembly 16 housed therein. Such an arrangement is easier to use. 
 &lsqb;Brief description of the drawings&rsqb; &lsqb; FIG. 22 &rsqb; is a perspective view of an electric toothbrush according to an embodiment of the present invention; &lsqb; FIG. 23 &rsqb; is a cross-sectional view taken along line A-A of FIG. 22 ; &lsqb; FIG. 24 &rsqb; is a cross-sectional view taken along line A-A of FIG. 23 ; &lsqb; FIG. 25 &rsqb; is an enlarged fragmentary vertical cross-sectional view of a bristle assembly; &lsqb; FIG. 26 &rsqb; is an enlarged fragmentary front elevational view of the bristle assembly; &lsqb; FIG. 27 &rsqb; is a diagram showing paths followed by the tip ends of bristles when the bristle assembly is angularly moved reciprocally; &lsqb; FIG. 28 &rsqb; is a fragmentary vertical cross-sectional view of a brush assembly according to another embodiment; and &lsqb; FIG. 29 &rsqb; is a view illustrative of the structure of a tooth. 
 &lsqb;Description of reference numerals&rsqb; 4 10 electric toothbrush 14 casing 16 bristle assembly 18 reciprocally rocking mechanism; 46 bristle 54 temporarily positioning member 68 actuator &lsqb;Advantages of the invention&rsqb; The present invention with the above arrangement offers the following advantages: (a) The bristle assemblies of a toothbrush are inclined at a certain angle with respect to the sides of teeth toward the tip ends of the teeth that are fitted between the bristle assemblies. Therefore, when the teeth are fitted in the tooth fitting portion to bring the tip ends of the bristle assemblies into abutment against the teeth surfaces, and the bristle assemblies are angularly moved reciprocally, the frictional force applied by the bristle assemblies is stronger upon angular movement toward the tip ends of the teeth, and weaker upon angular movement in the opposite direction. Therefore, plaque, tartar, and calculus deposited on the occlusal tooth areas, the tooth sides, and the tooth necks are gathered toward the center of the tooth fitting portion by the bristle assemblies, and efficiently removed. (b) As described above, when the bristle assemblies are angularly moved reciprocally, the frictional force applied by the bristle assemblies is stronger upon angular movement toward the tip ends of the teeth, and weaker upon angular movement in the opposite direction. Therefore, even when the tooth necks are brushed, the gum is not peeled off the tooth necks, and plaque, tartar, and calculus deposited on the tooth necks are not pushed between the teeth and the gum, and do not cause periodontites. (c) The electric toothbrush can brush teeth more efficiently than the manually operable toothbrush because the bristle assemblies can be angularly moved reciprocally at higher speeds. (d) With the toothbrush including the adjusting means, the projection of the bristle assembly can be adjusted by the adjusting means such that the bristle assembly adjustable by the adjusting means will abut against the occlusal tooth areas of teeth and the other bristle assemblies will abut reliably against the boundaries (the tooth necks) between the tooth sides and the gum. The toothbrush can thus accommodate various lengths, which differ from individual to individual, of teeth projecting from the gum, and is capable of brushing teeth effectively in a manner to suit the user. (e) The electric toothbrushes according to the tenth through sixteenth inventions have a bristle assembly reciprocally angularly movable to swing upwardly along teeth sides while being held against the teeth sides or neighboring regions, a reciprocally rocking mechanism for reciprocally angularly moving the bristle assembly, and an actuator coupled to the reciprocally rocking mechanism. When the bristle assembly held against the tooth sides and the tooth necks are repeatedly turned upwardly, the gum is prevented from being peeled off the tooth necks, and hence can be maintained in a healthy condition. The bristle assembly can efficiently scrape plaque off upwardly along the tooth sides and the tooth necks for protection against periodontites and dental caries.