Adjustable guide system for positioning dental implants

Abstract

The invention discloses an adjustable guide system (1) for positioning dental implants that comprises: a tool (2) having a head (21); a drill bit (3) configured to be attached to the head (21); a set of bushings (4) configured to be attached to the head (21); and a splint (5) having an anatomical shape configured to abut against the maxillary bone of the patient, wherein the splint (5) comprises at least one guide hole (51) for the bushings (4). Furthermore, the attachment between the actuation head (21) and the bushing (4) is configured to give the bushing (4) at least two working positions separated from one another in a longitudinal direction. This attachment is preferably implemented by means of a bayonet connection or a special threaded connection.

Description

[0001] DESCRIPTION

[0002] Adjustable guidance system for the placement of dental implants

[0003] OBJECT OF THE INVENTION

[0004] The present invention belongs to the field of dentistry, and more particularly to the sector of dental implantology.

[0005] A first object of the present invention is a novel guidance system for the placement of implants with the possibility of length adjustment.

[0006] A second object of the present invention is a guidance system provided with an adapter with a new design.

[0007] BACKGROUND OF THE INVENTION

[0008] Dental implants are a solution for replacing or substituting lost or damaged teeth. A dental implant is an implant inserted into the jawbone, onto which a crown or prosthesis is subsequently placed to replace the missing or damaged tooth in appearance and function.

[0009] Typically, surgery to place dental implants in a patient's mouth is a manual process, where the precision and trajectory of the final position of the dental implant are closely linked to the dentist's skill and experience. To do this, the path of the hole in the jawbone to which the implant will be attached is initially studied. The desired hole is then drilled, and finally, the dental implant is inserted into the drilled hole.

[0010] The hole in the jawbone is created using a drill bit attached to a motorized tool, operated by the dentist's expert hand. However, a manual process can be imprecise and dangerous in the event of a human error. Therefore, and to reduce the risk associated with manual surgery, there are aid systems on the market for guiding tools during surgery and the placement of dental implants. The best-known guidance systems use 3D radiological images of the patient's teeth and jaws. Using an intraoral scanner of the tooth surface, the treatment and the ideal implant placement are virtually planned and calculated. From the virtual planning, a guide splint is generated with holes in the predefined directions in which the dental implant must enter.The guide splint is used to guide the drilling process in the appropriate direction, as well as to prepare the bone bed that will house the implant and insert the implant.

[0011] Application EP23382107, filed in the name of the applicant of the present application, describes a guidance system of this type. Fig. 1 , belonging to this document, shows the splint (F) manufactured from 3D data of the patient's anatomy, such that it fits perfectly in the area of ​​the mouth where the implant is to be placed. The splint (F) has at least one hole (A), specifically two cylindrical holes (A) in the example shown in Fig. 1 , whose position precisely coincides with that of the hole to be made in the patient's jaw. In guidance systems prior to application EP23382107, the holes (A) served directly as a guide for the drill (FR) which ultimately makes the hole in the patient's jaw.

[0012] However, the guidance system of application EP23382107 also comprises a set of bushings (C) of different lengths configured to be fixed to the head (CB) of the tool (H) that drives the milling cutter (FR). These bushings (C), normally cylindrical, have a proximal end (Cp) and a distal end (Cd), and their diameter essentially coincides with the internal diameter of the holes (A) of the ferrule (F). The proximal end (Cp) of the bushing (C) is fixed to the head (CB) of the tool (H), for example, by means of a thread. When a bushing (C) is fixed to the tool (H), the milling cutter (FR) longitudinally passes through the cylindrical internal cavity of said bushing (C) and protrudes through its distal end (Cd). Depending on the length of the bushing (C), the length of the section of the milling cutter (FR) that protrudes through the distal end (Cd) of said bushing (C) varies.

[0013] Thus, once a bushing (C) is fixed to the tool (H), it is possible to introduce it through the hole (A) of the splint (F), such that the bushing (C), and therefore the drill bit (FR) that passes through it, are guided by said hole (A) to ensure a desired drilling path. This system also makes it possible to set the drilling depth by selecting a bushing (C) with a desired length. In effect, the depth of the drill bit made will coincide with the length of the section of drill bit (FR) that protrudes from the distal end (Cd) of the bushing (C). Although this system adequately solves the problem of how to provide guidance both in trajectory and depth for the holes necessary for the placement of dental implants, it has the disadvantage of reduced versatility with regard to selecting the desired depth.In effect, the number of depth options directly corresponds to the number of available sockets, which is naturally limited by space reasons.

[0014] In view of this, there is still a need in this field for more flexible guidance systems with regard to the depth of the hole to be drilled.

[0015] Furthermore, the guidance system of application EP23382107 also describes an adapter designed to allow the use of the aforementioned bushings when using a tool that is not specifically designed for that purpose and which, therefore, does not have means for securing the bushings in the head. As can be seen in Fig. 2, belonging to said document, in that case an adapter (AD) is used configured for fixing to the head (CB) of the tool (H). The adapter (AD) is in the form of an essentially cylindrical sleeve with an open angular section, and has longitudinal slots to improve its elasticity. This adapter (AD) is arranged around the head (CB), and is fixed to it by means of a hook (G) configured to rotate and embrace a neck (CU) of the tool (H) just adjacent to the head (CB).

[0016] While this adapter solves the problem at hand, allowing the use of sockets when using generic tools not designed for this purpose, there is still room for improvement.

[0017] DESCRIPTION OF THE INVENTION

[0018] In this document, the term "working position" refers to a position in which the attachment between the bushing and the head is sufficiently rigid to allow the drilling process to be carried out safely. In this regard, it is important to note that, although prior art bushings can be coupled to the head in two different positions simply by not screwing the bushing into the stop, in that case these would not be two working positions. Indeed, in that case, there would be play between the male and female threads which, given the mechanical stresses to which the assembly is subjected during a drilling operation, would prevent the planned path from being accurately followed. For this reason, in a conventional threaded connection such as that featured by prior art bushings, it is essential to screw the bushing into the stop to carry out the drilling operation, and therefore there is only one working position.That is, in that case any hypothetical second position other than the one in which the bushing is fully threaded would not be a working position.

[0019] In this document, the terms "proximal" and "distal" have the meanings they commonly have in the medical field. Specifically, the term "proximal" refers to the element or portion of an element that is closest to the medical professional performing the drilling operation, while the term "distal" refers to the element or portion of an element that is farthest from the medical professional performing the drilling operation.

[0020] In this document, the term “longitudinal direction” refers, unless the context clearly indicates otherwise, to the direction containing the axis of rotation of the tool head motor, the axis of the cutter when fixed to the head, and the axis of the bushings when fixed to the head.

[0021] First aspect: adjustable guidance system

[0022] The present invention solves the first of the aforementioned problems by means of a novel adjustable guidance system for the placement of dental implants, wherein the attachment of the sleeves to the head is designed such that each sleeve can adopt at least two longitudinally separated working positions. That is, the sleeve can be firmly fixed in a first working position and in a second working position, where the longitudinal distance between the distal end of the sleeve and the head in the first position is different from that in the second position.

[0023] This configuration is advantageous because it reduces the number of bushings required to perform a drilling operation, as each bushing effectively performs the function of two bushings in the conventional system. In other words, the system operates as if each bushing could have two slightly different lengths depending on whether it is engaged in the first or second working position.

[0024] The first aspect of the invention is therefore directed to an adjustable guidance system for implant placement. This adjustable guidance system mainly comprises the following elements: a) A tool comprising a drive head. This tool is essentially similar to those known in the prior art except for the means for securing it to the bushing, as will be seen in detail later in this document. b) A drill configured to be secured to the drive head of said tool along a longitudinal direction. The drill is essentially a conventional drill of the prior art. c) A set of bushings configured to be secured to the drive head of the tool in the longitudinal direction. Thus, when the drill is secured to said drive head, said drill passes through an inner cavity of the bushings.The operation of the sleeves is, with the exception of the design of the means for attaching them to the head, essentially similar to that of the sleeves of the prior art. d) A splint having an anatomical shape configured to rest on the patient's jaw, the splint comprising at least one guide hole for the sleeves. This splint is essentially similar to the splints used in the prior art.

[0025] So far, the described system is essentially the same as a guidance system according to the prior art, for example, the guidance system described in application EP23382107.

[0026] However, the adjustable guidance system of this first aspect of the present invention differs from that in that the attachment between the drive head and the bushing is configured to provide at least two longitudinally spaced working positions of the bushing. That is, the longitudinal distance between the tool head and the distal end of the bushing in the first working position is different from the longitudinal distance between the tool head and the distal end of the bushing in the second working position. As mentioned above, this allows, in the adjustable guidance system of the invention, each bushing to, in practice, perform the function of two conventional bushings of different lengths.In principle, the fastening system between the drive head and the bushing can be implemented in any manner, provided that it allows for sufficiently firm and stable fastening in two longitudinally separated working positions. While the adjustable system of the invention is intended to be protected for any manner in which this fastening is designed, this document explicitly describes two possibilities for implementing this connection: bayonet connection and connection using a special thread.

[0027] Each of these two configurations is described in greater detail below. a) Bayonet connection

[0028] In this first preferred embodiment of the invention, the adjustable fixing between the drive head and the bushing comprises a bayonet connection with at least two positions longitudinally separated from each other.

[0029] A bayonet connection is a connection in which two parts are connected by two elements that cooperate with each other through a relative displacement of one of said elements relative to the other. Specifically, one element is an elongated slot defined by two normally parallel main edges, where one of its edges has a gap near one end of the slot. The other element is a stud or projection whose dimensions are configured to enter the aforementioned slot through the gap. Once inside, a relative displacement between the part with the slot and the part with the stud, for example, a linear displacement or a rotation, causes the stud to move along the slot until it is housed at the end opposite the recess. The end of the slot in which the stud is housed is configured to retain the stud, for example by means of a small projection or some similar element.This is a well-known connection; a detailed description of how it works can be found on the following Wikipedia pages: https: / / es.wikipedia.org / wiki / Bayoneta (conexi%C3%B3n) (Spanish) (English).

[0030] A conventional bayonet connection, as described in the previous paragraph, normally has a single position. In this case, however, a bayonet connection with two positions is used, with the particularity that these two positions are designed so that there is a gap in the longitudinal direction between the first and second positions. This can be achieved in various ways, although two preferred configurations are described here: a bayonet with a longitudinal step and a bayonet with an inclined slot.

[0031] Bayonet with longitudinal step

[0032] In a particularly preferred embodiment of the invention, a slot is used in which a longitudinal step is implemented, i.e., a step in the longitudinal direction. More specifically, this bayonet connection comprises a slot and a pin specifically configured as follows:

[0033] - Slot

[0034] This is a slot arranged between the drive head and the socket. In other words, the slot could be in the drive head, in which case the pin would be in the socket. Alternatively, the slot could be in the socket, in which case the pin would be in the drive head.

[0035] This slot is limited by a leading edge and a supporting edge opposite said leading edge, where the leading edge has a gap located in a central section of said leading edge. That is, when the stud enters through the gap in the leading edge, it can selectively move in one direction or the other along the direction of the slot. The slot is essentially parallel to a plane perpendicular to the longitudinal direction, but with the particularity that the supporting edge has a longitudinal step separating a first slot section from a second slot section. Thus, there is a distance in the longitudinal direction between the first slot section and the second slot section.

[0036] - Teton

[0037] The pin is arranged on the other side of the drive head and the bushing. That is, as mentioned above, the pin could be on the drive head, in which case the slot would be in the bushing, or alternatively, the pin could be on the bushing, in which case the slot would be in the drive head. In either case, the pin is configured to enter the slot through the gap and, by means of relative rotation between the slot and pin, selectively engage one end of the first slot section or an opposite end of the second slot section.Thus, when it is housed in the end of the slot located in the first section, there is a first distance in the longitudinal direction between the distal end of the bushing and the tool head, while when it is housed in the end of the slot located in the second section, there is a second distance in the longitudinal direction between the distal end of the bushing and the tool head.

[0038] Bayonet with inclined slot

[0039] In an alternative preferred embodiment of the invention, a slot is used that is inclined relative to the longitudinal direction. More specifically, this bayonet connection comprises a slot and a pin configured as follows:

[0040] - Slot

[0041] As in the previous case, it is a slot arranged between the drive head and the bushing. The slot is also limited by a leading edge and a bearing edge opposite said leading edge, and the leading edge comprises a recess located in a central section of said leading edge. However, instead of having a step, in this case the slot is essentially parallel to an inclined plane, for example, with an inclination at an angle of between 1 e and 10 e , in relation to the longitudinal direction.

[0042] - Teton

[0043] The pin is arranged on the other side of the drive head and the bushing. The pin is configured to enter the slot through the gap and, by means of relative rotation between the slot and said pin, selectively accommodate one end of the slot or an opposite end of the slot. Since the slot is inclined relative to the longitudinal direction, there is a distance in the longitudinal direction between the position corresponding to the pin accommodated at one end and the position corresponding to the pin accommodated at the opposite end. Again, it should be noted that these two configurations are merely examples; there are other ways of designing a bayonet connection with two positions separated in the longitudinal direction, or even with more than two positions separated in the longitudinal direction. b) Special threaded connection

[0044] In this second preferred embodiment, an alternative to using a bayonet connection, a special threaded connection is specifically designed to ensure a sufficiently firm and stable connection in the two or more working positions. This is achieved by using the shorter thread length and a difference in pitch between the male and female threads.

[0045] Indeed, the purpose of a threaded joint is to ensure that the different parts joined by the threads and / or the screw / nut assemblies behave mechanically as a single unit. A conventional threaded joint is designed with a specific manufacturing clearance, a parameter known in this field that includes both longitudinal and radial clearance. In the case of longitudinal clearance, it is a measure of the difference in size in the longitudinal direction between the threads of the male thread and the female threads into which the former must fit. That is, taking a longitudinal direction that traverses the thread turns, the clearance is the difference along that line between the width of the female turn and the width of the male turn.Since, for the male coil to fit into the female coil, the width of the female coil is always greater than that of the male coil, the longitudinal clearance is always a positive number whose maximum value can be a few tenths of a millimetre at most.

[0046] In a conventional thread, where the male and female threads have the same pitch, the relative position in the longitudinal direction of the male turns and the corresponding female turns in which they are received is always the same. That is, let's consider that each male turn has a first side and a second side in the longitudinal direction, and that each female turn is limited in the longitudinal direction by a first side and a second side opposite the first. In that case, the first side of each male turn is separated by a first distance from the first side of the female turn in which it is received, and the second side of each male turn is separated by a second distance from the second side of the female turn in which it is received. In a conventional thread, the first distance and the second distance would take the same value for all turns. The clearance would be the sum of both distances.This will become clearer from the description of the figures shown later in this document.

[0047] This conventional configuration allows for easy assembly and disassembly, since in all thread turns, both sides of the male turn are separated from the walls of the female turn by the same distances as the first and second. However, this separation also implies a play between both parts, such that, if there is no pretension, that is, if both parts are not tightened, they do not behave as a single unit. When the two parts are tightened, each male turn is displaced to one end of each female turn in which it is housed, with one side of each male turn contacting the corresponding wall of each female turn. That is, for all thread turns, one of the two distances assumes a zero value, and the other distance adopts the value of the longitudinal clearance. This ensures a firm, play-free fixation.

[0048] In the context of this document, loose play in the threaded joint when not properly tightened would be fatal to the guiding precision of the tool and the drill, compromising the entire guiding system. It would imply the loss of the connection between the position planned in the 3D software and the position achieved by the drill in the patient's bone. For this reason, as previously mentioned, in a conventional thread, there is only one working position that can be defined as such.

[0049] Thus, in this preferred embodiment of the invention, the attachment between the drive head and the bushing comprises a special threaded connection between a first thread arranged at the distal end of the drive head and a second thread arranged at the proximal end of the bushing. One of said threads is a male thread and the other is a female thread. In addition, one of the first thread and the second thread has a substantially greater overall length than the other. This allows relative longitudinal movement between the drive head and the bushing to alternate between the first working position and the second working position. In this context, it is irrelevant which of the two threads is the male thread and which is the female thread, as well as which of the male and female threads is the shorter thread. It should also be noted that the width and shape of all the male and female turns are constant.The threaded connection is configured such that, once the shorter thread has been fully inserted into the longer thread, a first side of the first coil of said short thread is constantly in contact with a first side of the corresponding coil of the long thread, and a second side of the last coil of the short thread is constantly in contact with a second side of the corresponding coil of the long thread, the first side of the first coil of the short thread being opposite the second side of the last coil of the short thread. That is, the first and last coils of the short thread rest against longitudinally opposite sides of the corresponding coils of the long thread, so that there is no play between the two parts. In this situation, the intermediate coils of the short thread do not touch the corresponding coils of the long thread.This relative position between the threads of both parts is maintained regardless of whether the part with the short thread moves along the long thread of the other part. Therefore, each and every possible position that the part with the short thread can assume along the long thread constitutes a working position.

[0050] This configuration is achieved by choosing a suitable combination of the length of the short thread and the difference in pitch between the short thread and the long thread. More preferably, the product of the number of turns minus one of the short thread and the difference in pitch between the short thread and the long thread should be similar to the longitudinal clearance. As described above, the longitudinal clearance is the difference in a longitudinal direction between the width of the female turns and the width of the male turns. In this context, the term "similar" implies, for example, a difference of less than about 20%, more preferably less than 15%, even more preferably less than 10%, and still more preferably less than 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%.

[0051] In mathematical terms, the relationship described would be as follows:

[0052] (Nec - 1)- (Pr1 - Pr2) « H where:

[0053] Nec is the number of turns of the short thread

[0054] Pr1 is the pitch of the first thread Pr2 is the pitch of the second thread H is the longitudinal clearance

[0055] Furthermore, since only the first and last turns of the short thread contact the corresponding turns of the long thread, according to another preferred embodiment of the invention, the short thread lacks turns along an intermediate section of its length. That is, the short thread would only comprise a first turn zone and a last turn zone, with the workpiece in question being a smooth cylinder in the intermediate space between the two. Each of the end turn zones could have only one to two turns.

[0056] Thanks to this configuration, once the entire short thread is threaded into the long thread, sufficient fixation is achieved thanks to the contact between the first and last turns of said short thread and the corresponding turns of the long thread. In other words, the short thread is "engaged" in the long thread because the first and last turns contact the walls of the corresponding complementary turns on opposite longitudinal sides. This "engaged" fixation remains unchanged as the short thread continues to be inserted into the long thread, since the first and last turns of the short thread are in contact at all times. This configuration, therefore, not only allows alternating between two specific working positions, but also provides a continuum of possible positions between both positions.

[0057] The conventional sleeves described in application EP23382107 are cylindrical in shape, so they are designed so that their proximal end passes through the splint hole until it abuts against the patient's jawbone. In a particularly preferred embodiment of the invention, however, each sleeve also comprises a proximal portion having a first diameter and a distal portion having a second diameter smaller than the first diameter. In this way, a step is formed between both portions, configured to rest against the edges of the splint hole. This creates a second abutment element which, depending on the geometry of each case, can be used as an alternative to, or in combination with, the abutment of the distal end against the patient's jawbone.Furthermore, resting the step of the sleeve on the edges of the splint hole is advantageous over resting its distal end on the patient's jawbone because it can help reduce discomfort and possible damage to the gum. In another preferred embodiment of the invention, each sleeve also comprises at least one window that allows viewing the interior cavity through which the drill passes during the drilling process. In general, this window can be located at any point in the sleeve, typically in a middle area or close to its distal end. For example, when the sleeve is formed by two portions of different diameters, two windows can be implemented, one in the wall of each of said portions.The provision of one or more windows of this type is advantageous because it allows the medical professional to check at all times where the drill is located, so that he or she can more easily use depth markings or indications placed on the drill itself.

[0058] On the other hand, regardless of their configuration, guidance systems have the disadvantage that the splint does not allow the progress of the drill to be observed as it drills the hole in the patient's jaw. To solve this problem, in another preferred embodiment of the invention, a side wall of the splint hole comprises a gap to allow viewing of the drill's progress during the drilling process. In a preferred embodiment, this gap extends longitudinally, being open at its upper and lower ends. In another preferred embodiment, the gap is window-shaped, bounded by the side wall of the splint along its entire perimeter.

[0059] Second aspect: guidance system with adapter

[0060] The present invention solves the second of the aforementioned problems by means of a new adapter design that is improved over the prior art adapter described above. Specifically, the adapter attaches to the tool head in a simpler manner, providing greater strength and security to the connection.

[0061] This second aspect of the invention is directed to a guidance system for implant placement, which mainly comprises the following elements: a) A tool comprising a drive head. This tool is essentially similar to those known in the prior art except for the means for attaching it to the bushing, as will be seen in detail later in this document. b) A drill configured to be attached to the drive head of said tool along a longitudinal direction. The drill is essentially a conventional drill of the prior art. c) A set of bushings configured to be indirectly coupled to the drive head of the tool in the longitudinal direction. Thus, when the drill is indirectly coupled to said drive head, said drill passes through an inner cavity of the bushings.The operation of the sleeves is, except for the design of the means for indirect coupling to the head, essentially similar to that of the sleeves of the prior art. d) A splint having an anatomical shape configured to rest on the patient's jaw, the splint comprising at least one guide hole for the sleeves. Again, this splint is essentially similar to the splints used in the prior art. e) An adapter configured to couple to the drive head of the tool. The adapter comprises a body and a connecting element for securing the body to the head. The body is in the form of an essentially cylindrical sleeve with an open angular section that fits over the drive head. In addition, a distal end of the body comprises means for securing the sleeves.

[0062] So far, the described system is essentially the same as a guidance system according to the prior art, for example, the guidance system described in application EP23382107.

[0063] However, the guidance system according to this second aspect of the invention is characterized by the novel design of the connecting element. Specifically, the connecting element comprises a threaded ring configured for attachment to a thread located at the proximal end of the body. Thus, when the body is fitted onto the drive head, the attachment of the threaded ring to the proximal end of the body, which is located next to a proximal end of the drive head, secures the body to the drive head. More preferably, the body is configured to fit onto the drive head of the tool by sliding around said head longitudinally in a distal-proximal direction.

[0064] Furthermore, it is important to note that in this new guidance system, the bushings can be attached to the distal end of the adapter in any manner that ensures sufficient rigidity. This includes both conventional connection systems, such as a conventional threaded connection of the proximal end of the bushing to the distal end of the adapter, and any of the longitudinally adjustable connection systems described in this document (e.g., bayonet connection or connection using a special thread).

[0065] BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Fig. 1 shows a view of a first configuration of the guidance system described in application EP23382107 according to the prior art.

[0067] Fig. 2 shows a view of a second configuration of the guidance system described in application EP23382107 according to the prior art.

[0068] Fig. 3 shows a view of a first embodiment of an adjustable guiding system with bayonet connection according to the present invention.

[0069] Fig. 4 shows a schematic view illustrating the shape of the groove of a joint in a first bayonet joint design according to the present invention.

[0070] Fig. 5 shows a schematic view illustrating the shape of a joint slot in a second bayonet joint design according to the present invention.

[0071] Figs. 6a-6c show detailed views of the bayonet connection implemented in the adjustable guidance system shown in Fig. 3.

[0072] Fig. 7 shows perspective views of the bayonet-adjustable guidance system of Fig. 3 in its two possible working positions.

[0073] Figs. 8A-8C show detailed views of an adjustable guidance system with a threaded joint according to the present invention.

[0074] Fig. 9 shows a schematic sectional view of a portion of a conventional thread showing the different parameters described in this document.

[0075] Figs. 10A-10D show longitudinal sections of some threaded joints, where the joint of Fig. 10A is conventional, the joints of Figs. 10B-10C show a combination of correction of erroneous pitch and short thread length that causes interference between the threads, and the joint of Fig. 10D corresponds to a preferred embodiment of the present invention.

[0076] Fig. 11 shows a detail of a special thread according to the invention similar to that shown in Fig. 10D.

[0077] Fig. 12 shows perspective views of the adjustable guidance system of Fig. 3 with threaded connection in its two possible working positions, as well as disconnected.

[0078] Fig. 13 shows a first embodiment of a splint where the gap that allows observing the advancement of the splint is open at both ends.

[0079] Fig. 14 shows a second embodiment of a splint where the gap that allows observing the advancement of the splint is shaped like a window.

[0080] Fig. 15 shows another example of a guiding system equipped with an adapter to allow its use with tools not specifically designed for fixing the bushings.

[0081] Fig. 16 shows a detailed view of the adapter already attached to the tool head.

[0082] PREFERRED EMBODIMENT OF THE INVENTION

[0083] An example of an adjustable guidance system (1) for the installation of dental implants according to the present invention is described below with reference to the attached figures 3-12.

[0084] Fig. 3 is a view of the adjustable guidance system (1 ) for placing dental implants, showing the main elements comprising it. The system (1 ) comprises a tool (2) provided with a head (21 ) whose distal end is configured for attaching a drill bit (3). Inside the head (21 ) there is also a small electric motor that rotates a shaft oriented in the longitudinal direction (DL). In this way, when the drill bit (3) is coupled to the distal end of the head (21 ), its base is fixed to the shaft, such that the drill bit (3) rotates when the motor is activated. The shape and internal structure of the tool (2) as a whole is similar to that of a conventional tool of this type, except for the attachment of the bushings (4), as will be described later.

[0085] A distal end of the tool (2) is configured for fixing a proximal end of a bushing (4). The bushing (4) is formed by two portions (41, 42), specifically a first portion (41), or proximal portion, and a second portion (42), or distal portion. The diameter of the first portion (41) is greater than the diameter of the second portion (42) in the area where both are joined, such that a radial step (E) is formed at that point. Depending on the geometry of the bushing (4) and ferrule (5), this step (E) can rest on the edges of the holes (A) of the ferrule (5) to limit the depth of the hole made by the cutter (3). That is, the stop exerted by the sleeve (4) during the drilling process can take place when the distal end of the second portion (42) hits the patient's jaw, or when the step (E) hits the edges of the hole (A) of the splint (5).This configuration of the sleeve (4) thus provides greater flexibility in how to achieve the stop effect on the depth of the hole made by the drill (3), and also prevents the stop from occurring against the patient's jaw, which can sometimes be inconvenient.

[0086] An internal longitudinal cylindrical channel runs through both portions (41, 42), such that the milling cutter (3) passes through it when both elements, milling cutter (3) and bushing (4), are coupled to the head (21). Naturally, the milling cutter (3) is longer than the bushing (4), such that the distal end of the milling cutter (3) protrudes a certain length beyond the distal end of the bushing (4). In a conventional system such as those shown in Figs. 1 and 2, by choosing a certain bushing (4) from a set of bushings (4) of different lengths, the difference in length between the milling cutter (3) and bushing (4) can be adjusted. This makes it possible to select the depth of the hole made by the milling cutter (3).

[0087] The particularity of the adjustable guiding system (1) of the present invention lies in the fact that the fixing system that allows the bushing (4) to be fixed to the head (21) is of the adjustable type, that is, it allows the bushing (4) to be fixed in two separate working positions in the longitudinal direction.

[0088] Again, it should be emphasized that a "working position" is one that presents sufficient stability and rigidity to properly carry out the drilling operation. In prior art guidance systems, such as the one shown in Fig. 1 , the bushing (C) is fixed to the head (CB) using a conventional thread. In a conventional thread, both the male and female threads have the same pitch. Therefore, to ensure a sufficiently firm fixation, it is essential that the bushing (C) be fully threaded into the head (CB). Insufficiently threading the bushing (C) into the head (CB) would result in play that would prevent the drilling of a maxillary hole along the desired path.Therefore, fixing a bushing (C) to a head (CB) of a conventional tool (H) by threading it insufficiently, even if it involves a longitudinal separation in relation to a position in which the bushing (C) is threaded to the stop, does not constitute a “working position”.

[0089] The present invention describes two ways of carrying out this fixation that provide at least two longitudinally separated working positions: bayonet connection and special threaded connection.

[0090] Bayonet union

[0091] A first configuration of the bayonet connection is shown in the aforementioned Fig. 3. Fig. 4 shows a detailed view of this connection in much greater detail.

[0092] As can be seen, the bayonet connection comprises a slot (6), located in a rim of the proximal end of the bushing (4), and a stud (7), which projects radially from the edge of the distal end of the head (21). The proximal end of the bushing (4) has a larger diameter than the distal end of the head (21), so that to fix the bushing (4) it is possible to fit the distal end of the head (21) inside the proximal end of the bushing (4).

[0093] The slot (6) is essentially parallel to a plane perpendicular to the longitudinal direction (DL) and is essentially delimited by two edges: a leading edge (61 ) and a supporting edge (62). The leading edge (61 ) is located on the proximal side of the slot (6) and has a gap (61 h) located in a central section. This is the gap (61 h) through which the stud (7) will be introduced. The supporting edge (62) is located on the distal side of the slot (6). The supporting edge, along which the stud (7) moves when fixing is carried out using this joining system, has two areas parallel to a plane perpendicular to the longitudinal direction (DL) connected to each other by a longitudinal step (62e). In this way, the slot (6) is divided into two pieces or portions separated from each other in the longitudinal direction: a first section (T1 ) and a second section (T2).

[0094] Thus, when the distal end of the head (21 ) is introduced into the proximal end of the bushing (4), it is possible to pass the pin (7) through the gap (61 h) of the leading edge (61 ) of the slot (6). Once inside, in the position shown in Fig. 4, the side to which the bushing (4) is rotated can be chosen. If it is rotated in a first direction, the pin (7) will travel along the first section (T1 ) of the slot.

[0095] (6) until it reaches one of its ends. If it is rotated in a second direction, the pin

[0096] (7) will travel the second section (T2) of the slot (6) until it reaches the opposite end. Depending on which way it is turned, the distance between the distal end of the bushing (6) and the distal end of the head (21) will vary a distance equivalent to the height of the step (61 h).

[0097] Figs. 6A-6C show this process in greater detail. In Fig. 6A, the bushing (4) is about to be fixed to the head (21 ). In Fig. 6B, the bushing (4) has already moved sufficiently longitudinally to cause the pin (7) to enter through the gap (61 h) and has then been rotated in a certain direction. The result is that the pin (7) is housed at the end of the first section (T1 ) of the slot (6), and the bushing (4) is thus fixed to the head (21 ) in a first working position. Similarly, in Fig. 6C, the pin (7) has been introduced through the gap (6h) and the bushing (4) has been rotated in the opposite direction to the previous one. In this case, the pin (7) is housed at the end of the second section (T2) of the slot (6), thus being fixed to the head (21 ) in the second working position. It can be seen how in the first working position (Fig.6B), the end of the cutter (3) protrudes further than in the second working position (Fig. 6C).

[0098] Fig. 7 shows a guiding system (1 ) as described in the previous lines with the bushing (4) fixed respectively in the second and first working positions. This figure also shows the patient's jaw with a splint (5) arranged thereon. As previously described in this document, the splint (5) of the system (1 ) of the invention is essentially the same as the known splints of the prior art shown in any of Figs. 1 and 2. Specifically, in the example shown in Fig. 7, the splint (5) has three holes (51 ) intended to guide the drilling process thanks to the distal portion of the bushings (4) fitting tightly inside it. On the other hand, Fig. 5 shows a second bayonet connection configuration alternative to that described in Fig. 4.In this case, as can be seen, the groove (6) is not essentially contained in, or essentially parallel to, a plane perpendicular to the longitudinal direction (DL). On the contrary, the groove (6) is parallel to a plane inclined relative to the longitudinal direction (DL). This inclination may be, for example, a few degrees, for example, between 1. 2 and 10 e , or even up to 20 e . In this way, when the pin (7) moves along the groove (6) during the coupling process between the bushing (4) and the head (21), a displacement in the longitudinal direction occurs at the same time. The consequence is that there is a difference in the longitudinal direction between a first working position corresponding to the pin (7) housed at one end of the groove (6) and a second working position corresponding to the pin (7) housed at the opposite end of the groove (6).

[0099] Special threaded union

[0100] This configuration is described here taking as an example a short male thread and a long female thread although, as mentioned earlier in this document, it is irrelevant which of the threads is male or female, as well as which of them is implemented in the bushing and which in the drive head.

[0101] Fig. 9 shows a detailed view of a thread, where the various parameters are represented. Specifically, it shows:

[0102] Pr 1: the pitch of the male thread (which will be the first thread, i.e. the head thread)

[0103] Pr2: the pitch of the female thread (which will be the second thread, i.e., the bushing thread). d1: the first distance (which is the distance between the top side of the male coil and the top side of the female coil in which it is housed). d2: the second distance (which is the distance between the bottom side of the male coil and the bottom side of the female coil in which it is housed).

[0104] The clearance (H) will be the sum of the first distance (d1) and the second distance (d2). In mathematical terms: H = d1 + d2

[0105] Fig. 10A shows a conventional threaded joint. The turns of both threads are trapezoidal in shape. The male thread is 4 mm long, while the female thread is substantially longer, and, as is conventional, both male and female threads have the same pitch of 0.35 mm. Since the pitch is the same, the first distances (d1) and the second distances (d2) are the same for all turns. This allows for a play that facilitates the movement of the bushing with the female thread relative to the head with the female thread, simply by screwing and unscrewing naturally. However, to achieve a firm fixation, it is necessary to screw the head with the male thread up to the stop located at the top end of the figure and tighten. Any other position does not provide a firm joint due to the aforementioned play.

[0106] Fig. 10B shows a threaded joint where the female thread still has a pitch of 0.35 mm and the male thread has a pitch of 0.37 mm. The length of the male thread remains at 4 mm. As a result, the first and second distances are different for each of the turns, the turns being increasingly compressed as the male thread is inserted into the female thread, until the last turns of the male thread interfere with the adjacent turns of the female thread. This difference in pitch would therefore not be feasible, since threading both parts is impossible.

[0107] In Fig. 10C, the clearances of 0.35 and 0.37 for the female and male threads, respectively, are maintained, but the length of the male thread is reduced to 2.5 mm. In this case, interference still appears at least in the last two turns of the male thread, so this combination is not feasible.

[0108] Fig. 10D, finally, shows a combination where the female thread pitch is 0.35, the male thread pitch is 0.364, and the length of the male thread (the shortest thread) is 2.50 mm. Fig. 11 shows a detail of the area in Fig. 10D where the male thread coils are located. In these figures, it can be seen that, in the last coil of the male thread, the one located lowest in the figure, the second distance is zero. That is, the lower side of the last male coil is in contact with the lower side of the female coil in which it is housed. Similarly, in the first coil of the male thread, the one located highest in the figure, the first distance is also zero. That is, the upper side of the first male coil is in contact with the upper side of the female coil in which it is housed. In other words, the first and last turns of the male thread are “fitted” against opposite sides of the respective turns of the female thread.These two support points ensure a sufficiently stable connection for precise guidance and, at the same time, allow the sleeve to be threaded with the female thread along the male thread of the head over an arbitrarily long distance. Therefore, once the male thread is fully inserted into the female thread, any relative position between the two can be selected as the working position.

[0109] It can be verified that the relationship mentioned above in this document is fulfilled, that is, the following relationship:

[0110] (Nec - 1 ) ■ (Pr1 - Pr2) = H

[0111] Indeed, the parameters involved take the following values:

[0112] Nec (number of turns of the male thread) = 7

[0113] Pr1 (male thread pitch) = 0.364

[0114] Pr2 (female thread pitch) = 0.35

[0115] H (clearance) = d1 + d2 = 0.09 mm

[0116] Therefore:

[0117] (Nec - 1 ) ■ (Pr1 - Pr2): (7 - 1 ) ■ (0.364 - 0.35) = 6- 0.014 = 0.084 H = 0.09

[0118] It is found that 0.0847 ~ 0.09, since they differ by only 7%. This formula allows us to select those configurations that result in male and female thread combinations that can be screwed together and where the "fitting" effect of the first and last turns of the short thread into the long thread occurs. If this ratio is not met, it will either be impossible to insert one thread into the other, or there will be no "fitting" effect.

[0119] Note that since contact occurs essentially only on the first and last turns of the male thread, i.e., the short thread, it would potentially be possible to eliminate the intermediate turns of the short thread. This means the head could have only two turns separated by a smooth cylindrical space.

[0120] Fig. 12 shows a perspective view of a system (1) provided with a special thread as described where the bushing (4) has been fixed to the head (21) of the tool (2) in two longitudinally separated positions.

[0121] Figs. 13 and 14 show two preferred embodiments of splints (5) according to the present invention, each in plan and elevation views respectively. In this specific case, both splints (5) have only one guide hole (51).

[0122] In Fig. 13, the splint (5) has a gap (52a) that completely interrupts the wall of one of the sides of the hole (51 ) adjacent to the patient's jaw. That is, the gap (52a) is a slot that runs through the wall of said side of the hole (51 ) from top to bottom, or in a direction parallel to the longitudinal direction (DL). Therefore, when the distal end of the drill (3) and the distal end of the sleeve (4) are introduced into the hole (51 ) to carry out the drilling process, it is possible to visually follow the advance of the drill (3) and the distal end of the sleeve (4) along the hole (51 ).

[0123] In Fig. 14, on the contrary, the gap (52b) does not completely interrupt the lateral wall of the hole (51) adjacent to the patient's jaw, but is constituted only by a window delimited on all four sides.

[0124] Finally, an example of a guidance system (1) for installing dental implants with a modified adapter according to the present invention is described with reference to the attached figures 15-16.

[0125] In this case, the adapter (10) that allows the use of the bushing system (4) with a conventional tool (2) has a modified configuration that offers advantages in relation to the prior art. In particular, as can be seen in Fig. 15, the adapter (10) is formed by two physically distinct elements: body (11) and connecting element (12).

[0126] The body (1 1 ) is relatively similar to that of the prior art shown in Fig. 2, since it has the shape of an ellipsoidal / cylindrical sleeve with an open angular section (11 1 ). However, instead of having slots for flexibility, the body (11 ) in the present invention is mostly continuous and, in addition, is made of metal. This body (1 1 ) is designed to fit over the head (21 ) of the conventional tool (1 ) by moving it from bottom to top according to the position of the figures, so that it is not necessary for it to have flexibility. Once positioned, as shown in Fig. 16, the body (11 ) almost completely surrounds the head (21 ), except mainly for the area where the junction between the handle of the tool (2) and the head itself (21 ) is located.

[0127] The connecting element (12) is in the form of a threaded ring and its function is to firmly fix the body (11) in its position in which it embraces the head (21) of the tool (2). To do this, the connecting element (12) is screwed into a thread provided at the proximal end of the body (11). The connecting element (12) may also have an inward radial flange such that once it is screwed fully into the distal end of the body (11) it completely immobilizes the latter.

[0128] Finally, the body (11) has a distal end, which may optionally comprise a completely closed annular area, i.e., up to where the open angular section does not reach. This distal end has a thread to which the bushings (4) can be fixed. Alternatively, although not explicitly shown in Figs. 15-16, the means of fixing the bushings (4) could be any of those previously described in this document to allow two or more longitudinally separated working positions, such as the bayonet connection or the connection with a special thread.

Claims

CLAIMS 1. Adjustable guidance system (1) for the placement of dental implants, comprising: - a tool (2) comprising a drive head (21); - a cutter (3) configured for fixing to the drive head (21) of said tool (2) along a longitudinal direction (DL); - a set of bushings (4) configured for fixing to the drive head (21) of the tool (2) in the longitudinal direction (DL) such that, when the cutter (3) is fixed to said drive head (21), said cutter (3) passes through an inner cavity of the bushings (4); and - a splint (5) having an anatomical shape configured to rest on the patient's jaw, the splint (5) comprising at least one guide hole (51) for the bushings (4), characterized in that the fixing between the drive head (21) and the bushing (4) is configured to provide at least two working positions of the bushing (4) longitudinally separated from each other.

2. Adjustable guidance system (1) according to claim 1, wherein the fixing between the drive head (21) and the bushing (4) comprises a bayonet connection with at least two positions longitudinally separated from each other.

3. Adjustable guidance system (1) according to claim 2, wherein the bayonet connection comprises: - a slot (6) arranged in one of the drive head (21) and the bushing (4), said slot (6) being limited by a leading edge (61) and a bearing edge (62) opposite said leading edge (61), the leading edge (61) being provided with a recess (61 h) located in a central section of said leading edge (61), said slot (6) being essentially parallel to a plane perpendicular to the longitudinal direction (DL) and the bearing edge (62) having a longitudinal step (62e) separating a first slot section (T1) from a second slot section (T2); and - a stud (7) arranged on the other side of the drive head (21) and the bushing (4), the stud (7) being configured to enter the slot (6) through the gap (61 h) and, by means of a relative rotation between the slot (6) and said stud (7), selectively lodge at one end of the first section (T1) of the slot (6) or at an opposite end of the second section (T2) of the slot (6).

4. Adjustable guidance system (1) according to claim 2, wherein the bayonet connection comprises: - a slot (6) arranged in one of the drive head (21) and the bushing (4), said slot (6) being limited by a leading edge (61) and a bearing edge (62) opposite said leading edge (61), the leading edge (61) being provided with a recess (61 h) located in a central section of said leading edge (61), said slot (6) being essentially parallel to a plane inclined with respect to the longitudinal direction (DL); and - a stud (7) arranged on the other side of the drive head (21) and the bushing (4), the stud (7) being configured to enter the slot (6) through the gap (61 h) and, by means of a relative rotation between the slot (6) and said stud (7), selectively be housed at one end of the slot (6) or at an opposite end of the slot (6).

5. Adjustable guidance system (1) according to claim 1, wherein the fixing between the drive head (21) and the bushing (4) comprises a threaded connection between a first thread arranged at the distal end of the drive head (21) and a second thread arranged at the proximal end of the bushing (4), one of them being a male thread and the other a female thread, where one of the first thread and the second thread has a total length substantially greater than the other to allow relative longitudinal movement between the first working position and the second working position, and where said threaded connection is configured such that, once the short thread has been completely inserted into the long thread, a first side of the first coil of said short thread is constantly in contact with a first side of the corresponding coil of the long thread,and a second side of the last turn of the short thread is constantly in contact with a second side of the corresponding turn of the long thread, the first side of the first turn being opposite the second side of the last turn.

6. Adjustable guidance system (1) according to claim 5, wherein the product of the number of turns minus one of the short thread by the difference in pitch between the short thread and the long thread must be similar to the longitudinal clearance, where the longitudinal clearance is the difference in a longitudinal direction between the width of the female turns and the width of the male turns.

7. Adjustable guidance system (1) according to any of claims 5-6, wherein the short thread lacks turns in an intermediate section of its length.

8. Adjustable guidance system (1) according to any of the preceding claims, wherein each bushing (4) comprises a proximal portion (41) having a first diameter and a distal portion (42) having a second diameter smaller than the first diameter, forming a step (E) between both portions (41, 42) configured to rest on the edges of the hole (A) of the splint (5).

9. Adjustable guiding system (1) according to any of the preceding claims, wherein each bushing (4) further comprises at least one window (41 v, 42 v) that allows viewing the interior cavity through which the cutter (3) passes during the drilling process.

10. Adjustable guiding system (1) according to any of the preceding claims, wherein a side wall of the hole (51) of the ferrule (5) comprises a gap (52a, 52b) to allow viewing of the advance of the cutter (3) during the drilling process.

11. Adjustable guidance system (1) according to claim 10, wherein the gap (52a) extends in the longitudinal direction, being open at its upper and lower ends.

12. Adjustable guidance system (1) according to claim 10, wherein the gap (52b) is window-shaped limited by the side wall of the splint (5) along its entire perimeter.

13. Guidance system (1) for implant placement, comprising: - a tool (2) comprising a drive head (21); - a cutter (3) configured for fixing to the drive head (21) of said tool (2) along a longitudinal direction (DL); - a set of bushings (4) configured to be indirectly coupled to the drive head (21) of the tool (2) in the longitudinal direction (DL) such that, when the cutter (3) is indirectly coupled to said drive head (21), said cutter (3) passes through an inner cavity of the bushings (4); - a splint (5) having an anatomical shape configured to rest on the patient's jaw, the splint (5) comprising at least one guide hole (51) for the bushings (4), and - an adapter (10) configured to be coupled to the drive head (21) of the tool (2), the adapter comprising a body (11) and a connecting element (12) for fixing the body (11) to the head (21), the body (11) having an essentially sheath-shaped shape.

14. Guidance system (1 ) for placing implants according to claim 1 , wherein the connecting element (12) comprises a threaded ring configured for fixing to a thread located at a proximal end of the body (11 ) such that, when the body (11) is fitted onto the drive head (21), fixing the threaded ring (12) to the proximal end of the body (11) located next to a proximal end of the drive head (21) fixes the body (11) to the drive head (21). 13, where the body (11) is configured to fit into the drive head (21) by sliding around said head (21) longitudinally in a distal-proximal direction.

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