DENTAL PROSTHESIS

Abstract: This invention is a dental prosthesis (10) and method for using, installing, and fabricating the same. The prosthesis (10) includes an implant (20) and an abutment (40) defining an implant abutment joint (IAJ) (72) therebetween. The implant (20) and abutment (40) are configured such that a crown (60) secured to the abutment (40) extends distally past the IAJ (72) to cover the IAJ, and prevent any bacterial colonization or other deterioration in the IAJ.

Description: DENTAL PROSTHESIS Field of the Invention The present invention relates to the field of dental prostheses and, in particular, to an apparatus and method for a dental prosthesis which includes a crown having a prosthetic margin extending past the joint between an abutment to which the crown is attached and an implant to which the abutment is attached. Bjiπkground of the Invention Dental prostheses are a common approach to address extensive damage to teeth caused by injury or disease. A typical dental prosthesis includes an implant, an abutment and a crown. The implant is generally a metallic component which is implanted into the bony structure of a patient's mouth after suitably removing the damaged tooth or teeth and perhaps one or more adjacent teeth. The implant is commonly installed by preparing a hole in the bony structure and screwing threads on a shaft of the distal end of the implant into the hole. The bone normally recovers and grows around the implant to result in bone integration. The implant may be smooth, etched or may be coated with biocompatible coatings such as hydroxylapatite which enhance bone integration around the implant. The usual procedure is to install the implant, and then allow integration of the implant. The proximal end of the implant includes a means for attachment of the abutment such as cement, male or female threads, tapers or other geometries. The abutment component extends from the implant to beyond the gum line, and includes at its distal end an attachment means which mates with the attachment means of the proximal end of the implant. If the implant was installed with the proximal end below the gumline - or submerged - then the installation of the abutment to the implant requires a second surgical procedure for the purpose of accessing the implant. If installed nonsub erge , then only a single surgical procedure is required. The shaft of the abutment extending proximally is adapted to receive the crown. Crowns are fabricated and installed in accordance with well-established procedures which include taking a transfer impression of the abutment to establish precisely the configuration and orientation of the abutment to which the crown will attach. Abutments to which crowns are attached may be natural in the form of prepared teeth, or artificial in the form of the abutments described above. The completed crown is cemented or screwed to the abutment to complete the prosthesis. The joining of the implant, abutment and crown results in several distinct joints. An important joint for consideration in the long-term viability of the prosthesis is the joint between the implant and the abutment which is referred to as the implant abutment joint or "IAJ." Recent research suggest that the IAJ plays a key role in bone loss around the neck of the implant. Such "bone loss" has not been well studied or well documented, but is believed by the dental profession to be a common occurrence. Over time, bone loss can compromise the implant or even cause it to fail by breaking loose from the bony structure in which it is implanted. Aside from the obvious inconvenience and discomfort this causes the patient, it is of serious medical concern because the resulting bone loss or mutilation may render the installation of a replacement implant difficult or impossible. It has been stated that bone loss at the neck of the dental implant is a normal occurrence and eventually reaches a steady state; Adell R, Lekholm U, Rockier B, Brane ark P-I, Lindhe J. Eriksson B, Sbordone L. Marginal tissue reactions at osseointegrated titanium fixtures: a three-year longitudinal prospective study. Int J Oral Maxillofac Surg 1986;1:39-52; Cox JF, Zarb GA. The longitudinal clinical efficiency of osseointegrated dental implants: a three-year report. Int J Oral Maxillofac Implants 1987;2:91-100; Quirynen M, Naert I, Van Steenberghe D, Nys L. A study of 589 consecutive implants supporting complete fixed prostheses, part I: periodontal aspects. J Prosthet Dent 1992;68:655-663. Another view suggest that surgical trauma either during placement of the implant or at the time of second-stage surgery may play a role in inducing coronal bone loss; Adell R, Lekholm U, Rockier B, Branemark P-I, Lindhe J. Eriksson B, Sbordone L. Marginal tissue reactions at osseointegrated titanium fixtures: a three-year longitudinal prospective study. Int J Oral Maxillofac Surg 1986;1:39-52; Apse P. Allen PP, Overall CM, Zarb GA. Microbiota and crevicular fluid collagenase activity in the osseointegrated dental implant sulcus: a comparison of sites in edentulous and partially edentulous patients. J Periodont Res 1989;24:96-105; Haraldson T. A photoelastic study of some biomechanical factors affecting the anchorage of osseointegrated implants in the jaw. Scand J Plast Reconstr Surg 1980;14: 209-214; Plank H Jr, Haider R. Velikogne W. Lill W. Watzek G. The effects of drilling on endosseous implant fixation. Fourth World Biomaterials Congress 1992 ; Berlin, Germany. Occlusal trauma also has been cited as a causative factor; Misch CE. Progressive Bone Loading. In: Misch CE, ed. Contemporary implant dentistry. St. Louis, Mo.:C.V. Mosby; 1993: 623-650; Bidez MW, Misch CE. Force transfer in implant dentistry: basic concepts and principles. J Oral Implant 1992;18:264-274. A compelling chain of evidence furthermore indicates that the role of bacterial invasion may be significant; Zablotsky MH, Diedrich DL, Meffert RM. Detoxification of endotoxin-contaminated titanium and hydroxyapatite-coated surfaces utilizing various che otherapeutic and mechanical modalities. Implant Dent 1992; 154-158; Zablotsky MH, Diedrich DL, Meffert RM, Witting E. The ability of various chemotherapeutic agents to detoxify the endotoxin-infected HA-coated implant surface. Int J Oral Implant 1991;8:45-51; Dennison DK, Huerzeler MB, Quinones C, Caffesse RG. Contaminated implant surfaces: an in vitro comparison of implant surface coating and treatment modalities for decontamination. J Periodontal 1994;65:942-948; Nakou M, Mikx FHM, Oosterwool PJM, Kruijsen JCWM. Early microbial colonization of permucosal implants in edentulous patients. J Dent Res 1987;11:1654-1657; Zablotsky MH, Wittrig EE, Diedrich DL, Layman DL, Meffert RM. Fibroblastic growth and attachment on hydroxyapatite-coated titanium surfaces following the use of various detoxification modalities, part II: contaminated hydroxyapatite. Implant Dent 1992;1:195-202; Newman MG, Flemming TF implants and implant-assoc 1988;52:737-744. Periodontal considerations of implants and implant- associated microbiota. J Dent Ed 1988; 52:737-744; Mombelli A, Lang NP. Microbial aspects of implant dentistry. Periodontology 2000 1994;4:74-80; Mombelli A, Van Oosten MAC, Schuerch EJ, Lang NP. The microbiota associated with the successful or failing osseointegrated titanium implants. Oral Microbial Immunol 1987;2:145-151; Brandes R. Bea er B. Holt SC. Clinical-microscopic observation of ligature induced "peri-implantitis" around osseointegrated implants. J Dent Res 1988;67 (special issue) :287 (abstr 1397); Ong ESM, Newman HN, Wilson M, Bul an JS. The occurrence of periodontitis-related microorganisms in relation to titanium implants. J Periodontal 1992;63:200-205; Gruder U. Hunzeler MB, Schupbach P. Strub JR. Treatment of ligature-induced perio-implantitis using guided tissue regeneration. A clinical and histological study in the beagle dog. Int J Oral Maxillofac Implants 1993;8:282-293; Schou S. Holmstrup P. Kornman KS. Non-human primates used in studies of periodontal disease pathogenesis. A review of the literature. J Periodontal 1993;64: 497-508; Schou S. Holmstrup P. Reibel J. Juhl M. Hjorting-Hansen E, Kornman KS. Ligature-induced marginal inflammation around osseointegrated implants and ankylosed teeth. Serologic and histologic observations in cyno olgus monkeys (Macaca fascicularis) . J Periodontal 1993;64:529-537. Dental plaque irritates tissue and leads to gingivitis and periodontitis ; Zablotsky MH, Wittrig EE, Diedrich DL, Layman DL, Meffert RM. Fibroblastic growth and attachment on hydroxyapatite-coated titanium surfaces following the use of various detoxification modalities, part II: contaminated hydroxyapatite. Implant Dent 1992;1:195-202; Newman MG, Flemming TF implants and implant-assoc 1988;52:737-744. Periodontal considerations of implants and implant-associated microbiota. J Dent Ed 1988; 52:737-744; Mombelli A, Van Oosten MAC, Schuerch EJ, Lang NP. The microbiota associated with the successful or failing osseointegrated titanium implants. Oral Microbial Immunol 1987;2:145-151; Brandes R. Beamer B. Holt SC. Clinical-microscopic observation of ligature induced "peri-implantitis" around osseointegrated implants. J Dent Res 1988; 67 (special issue) : 287 (abstr 1397); Ong ESM, Newman HN, Wilson M, Bulman JS. The occurrence of periodontitis-related microorganisms in relation to titanium implants. J Periodontal 1992;63:200-205. A limited number of studies have suggested some differences in the way bacteria adheres to and plaque forms on artificial surfaces such as titanium; Zablotsky MH, Wittrig EE, Diedrich DL, Layman DL, Meffert RM. Fibroblastic growth and attachment on hydroxyapatite-coated titanium surfaces following the use of various detoxification modalities, part II: contaminated hydroxyapatite. Implant Dent 1992;1:195-202; Newman MG, Flemming TF implants and implant-assoc 1988;52:737-744. Periodontal considerations of implants and implant- associated microbiota. J Dent Ed 1988; 52:737-744; Mombelli A, Van oosten MAC, Schuerch EJ, Lang NP. The microbiota associated with the successful or failing osseointegrated titanium implants. Oral Microbial Immunol 1987;2:145-151; Brandes R. Beamer B. Holt SC. Clinical-microscopic observation of ligature induced "peri-implantitis" around osseointegrated implants. J Dent Res 1988;67 (special issue) :287 (abstr 1397); Ong ESM, Newman HN, Wilson M, Bulman JS. The occurrence of periodontitis-related microorganisms in relation to titanium implants. J Periodontal 1992;63:200-205; Nakazato G. Tsuchiya H. Sato M, Yamauchi M. In vitro plaque formation on implant materials. Int J Maxillofac Impl 1986;4:321-325; compared to natural oral hard tissues; Gould T. Brunette D. Ultrastructural study of the attachment of human gingiva to titanium in vitro. J Prosthet Dent 1984;52:418-420. Regardless of the precise mechanism for bacterial attachment, however, evidence is ample that supragingival and subgingival bacterial colonization can occur after dental implants have been inserted; Fryioka-Hirai Y. Akagawa Y. Minagi S. Tsuru H. Miyake Y. Suginaka H. Adherence of streptococcus mutans to implants. J. Periodontal 1992; 63:200-205. Moreover, both clinical and microbial findings indicate that the bacterial flora around failing implants are the same as or very similar to those implicated as pathogens in periodontal disease; Adell R. Lekholm 0, Rockier B. Branemark P-I, Lindhe J. Eriksson B. Sbordone L. Marginal tissue reactions at osseointegrated titanium fixtures: a three-year longitudinal prospective study. Int J Oral Maxillofac Surg 1986; 1 : 29-52 ; Apse P. Allen PP, Overall CM, Zarb GA. Microbiota and crevicular fluid collagenase activity in the osseointegrated dental implant sulcus: a comparison of sites in edentulous and partially edentulous patients. J Periodont Res 1989 ; 24:96-105. Mombelli A, Van Oosten MAC, Schuerch EJ, Lang NP. The microbiota associated with the successful or failing osseointegrated titanium implants. Oral Microbial Immunol 1987;2:145-151; Brandes R. Beamer B. Holt SC. Clinical-microscopic observation of ligature induced "peri-implantitis" around osseointegrated implants. J Dent Res 1988;67 (special issue) :287 (abstr 1397); Ong ESM, Newman HN, Wilson M, Bulman JS. The occurrence of periodontitis-related microorganisms in relation to titanium implants. J Periodontal 1992; 63:200- 205. Mombelli A, Van Oosten MAC, Schuerch E, Lang NP. The microbiotia associated with successful or failing osseointegrated titanium implants. Oral Microbial Immunol 1987;2:145-151. Rams TE, Link CC. Microbiology of failing dental implants in humans: electron microscope observations. Oral Implantal 1983;11:93-110; Joshi RI, Eley A. The in vitro effect of a titanium implant on oral microflora: comparison with other metallic compounds. J Med Mlcrobiol 1988;27:105-107; Lekholm U. Eriksson I, Adell R. Slots J. The condition of the soft tissues at tooth and fixture abutments supporting fixed bridges. A microbiological and histological study. J Clin Periodontal 1986; 13:558-562; Mombelli A, Buser D, Lang NP. Colonization of osseointegrated titanium implants in edentulous patients: early results. Oral Microbial Immunol 1988;3:113-120; Rams TE, Roberts H. Tatum H. Keyes PH. The subgingival microbial flora associated with human dental implants. J Prosth Dent 1984; 51:529-534; Mombelli A, Merieske-Stern R. Microbiological features of stable osseointegrated implants used as abutments for overdentures. Clin Oral Implant Res 1990;1:1-7; George K, Zafiropoulos GGK, Murat Y. Hubertus S. Nisengard RJ. Clinical and microbiological status of osseointegrated implants. J Periodontal 1994;65:766-770. Both periodontitis and peri-implantitis exhibit virtually identical signs: bleeding upon gentle probing, suppuration, pocket formation, and bone loss. A number of studies have demonstrated the existence of hemides osomal attachment to titanium; Gould T. Brunette D, Westbury L. The attachment mechanisms of epithelial cells to titanium in vitro. J Periodont Res 1981; 10:68-79; James RA, Schultz RL. Hemidesmosomes and the adhesion of junctional epithelial cells to metal implants: a preliminary report. J Oral Implant 1973;4:294-302; Listgarten MA, Lai CH. Ultrastructure of the intact interface between an endosseous epoxy resin dental implant and the host tissue. J Biol Buccale 1975;3:13-28; McKinney R. Steflik DE, Koth DL. Evidence for a junctional epithelial attachment to ceramic dental implants. J Periodontal 1985;56:579-591; Buser D, Weber HP, Lang NP. Tissue integration of nonsubmerged implants. Clin Oral Implants Res 1990;1:33-40; ten Bruggenkate CM, Muller K, Oosterbeek HS. Clinical evaluation of the ITI (F-type) hollow cylinder implant. Oral Surg Oral Med oral Pathol 1990;70:693-697; Gotfredsen K, Rostrup E, Hjoerting-Hansen E, Stoltze K, Budtz-Jorgensen E. Histological and histomophometrical evaluation of tissue reactions adjacent to endosteal implants in monkeys. Clin Oral Implants Res 1991;2:30-37; Buser D, Weber HP, Bragger U. Balsiger C. Tissue integration of one-stage ITI implants: three-year results of a longitudinal study with hollow-cylinder and hollow-screw implants. Int J Oral Maxillofac Implants 1991;6:405-412; Alberektsson T. Branemark P-I, Hansson H-A, Lindstrom J. Osseointegrated titanium implants. Requirements for ensuring a long-lasting direct bone-to-implant anchorage in man. Acta Orthop Scand 1981;52:155-170. Due to the delicate epithelial-implant interface; Gould T. Brunette D. Ultrastructural study of the attachment of human gingiva to titanium in vitro. J Prosthet Dent 1984;52:418-420, plaque control is needed to maintain this attachment and preserve the peri-implant soft tissue health; Wolinsky EL, de Camargo PM, Erard JC, Newman MG. A study of in vitro attachment of streptococcus sanguis and actinomyces viscosus to salvia-treated titanium. Int J Oral Maxillofac Impl 1989 ;4: 27-31; Thornson-Neal D, Evans G. Meffert RM, Davenport WD. A SEM evaluation to various prophylactic modalities on different implants. Int J Perio Rest Dent 1989;9:301-311; Rapley JW, Swan RH, Hallmon WW, Mills MP. The surface characteristics produced by various oral hygiene instruments and materials on titanium implant abutments, int J Oral Maxillofac Implants 1990;5:47-51; Meffert RM. The importance of periodontal maintenance for the dental implant. Pract Periodont Aesth Dent 1990;2: 19-22. Modern oral implant systems provide easy access to the exposed surfaces on which bacterial colonization may occur. Removal Of bacterial aggregates from these surfaces by means of local mechanical or anti-microbial intervention offers the possibility of some control over bacterial colonization; Wolinsky EL, de Camargo PM, Erard JC, Newman MG. A study of in vitro attachment of streptococcus sanguis and actinomyces viscosus to salvia-treated titanium. Int J Oral Maxillofac Impl 1989; 4: 27-31; Thomson-Neal D, Evans G. Meffert RM, Davenport WD. A SEM evaluation to various prophylactic modalities on different implants. Int J Perio Rest Dent 1989;9:301-311; Rapley JW, Swan RH, Hallmon WW, Mills MP. The surface characteristics produced by various oral hygiene instruments and materials on titanium implant abutments. Int J Oral Maxillofac Implants 1990;5:47-51; Meffert RM. The importance of periodontal maintenance for the dental implant. Pract Periodont Aesth Dent 1990;2: 19-22. It is the clinician's responsibility to educate the dental implant patient about proper oral hygiene procedures, including methods for removing existing bacterial plaque thoroughly and preventing new plaque formation. Once informed, the patient bears the responsibility for performing the necessary maintenance. This responsibility is a critical one. Numerous studies have demonstrated a link between poor oral hygiene procedures and the occurrence of peri-implantitis; Zablotsky MH, Wittrig EE, Diedrich DL, Layman DL, Meffert RM. Fibroblastic growth and attachment on hydroxyapatite-coated titanium surfaces following the use of various detoxification modalities, part II: contaminated hydroxyapatite. Implant Dent 1992;1:195-202; Newman MG, Flemming TF implants and implant-assoc 1988;52:737-744. Periodontal considerations of implants and implant- associated microbiota. J Dent Ed 1988; 52:737-744; Mombelli A, Lang NP. Microbial aspects of implant dentistry* Periodontology 2000 1994;4:74-80; Mombelli A, Van Oosten MAC, Schuerch EJ, Lang NP. The microbiota associated with the successful or failing osseointegrated titanium implants. Oral Microbial Immunol 1987;2:145-151; Brandes R. Beamer B. Holt SC. Clinical-microscopic observation of ligature induced "peri-implantitis" around osseointegrated implants. J Dent Res 1988;67 (special issue): 287 (abstr 1397); Ong ESM, Newman HN, Wilson M, Bulman JS. The occurrence of periodontitis-related microorganisms in relation to titanium implants. J Periodontal 1992;63:200-205; Gruder U. Hunzeler MB, Schupbach P. Strub JR. Treatment of ligature-induced perio-implantitis using guided tissue regeneration. A clinical and histological study in the beagle dog. Int J Oral Maxillofac Implants 1993;8:282-293; Schou S. Holmstrup P. Kornman KS. Non-human primates used in studies of periodontal disease pathogenesis. A review of the literature. J Periodontal 1993; 64: 497-508; Schou S. Holmstrup P. Reibel J. Juhl M. Hjorting-Hansen E, Kornman KS. Ligature-induced marginal inflammation around osseointegrated implants and ankylosed teeth. Serologic and histologic observations in cynomolgus monkeys (Macaca fascicularis) . J Periodontal 1993;64:529-537. Other studies of implantitis patients whose problems have been corrected indicate that instituting good oral hygiene can prevent a reoccurrence of infection; Zablotsky MH, Diedrich DL, Meffert RM. Detoxification of endotoxin-contaminated titanium and hydroxyapatite-coated surfaces utilizing various chemotherapeutic and mechanical modalities. Implant Dent 1992; 154-158; Zablotsky MH, Diedrich DL, Meffert RM, Witting E. The ability of various chemotherapeutic agents to detoxify the endotoxin-infected HA-coated implant surface. Int J Oral Implant 1991;8:45-51; Dennison DK, Huerzeler MB, Quinones C, Caffesse RG. Contaminated implant surfaces: an in vitro comparison of implant surface coating and treatment modalities for decontamination. J Periodontal 1994;65:942-948; Nakou M, Mikx FHM, Oosterwool PJM, Kruijsen JCWM. Early microbial colonization of permucosal implants in edentulous patients. J Dent Res 1987;11:1654-1657. At the same time, however, patients may have the ability, knowledge, and willingness to maintain the implant prosthesis and yet still develop problems. In such cases, the design and/or placement protocol of the implant system may be preventing the patient and clinician from achieving adequate maintenance at the IAJ. SuTrmarv of the Invention The present invention is designed to lessen bone loss around the neck of a dental prosthesis implant by covering the IAJ with the crown or suitable prosthesis. In a preferred embodiment, the prosthesis includes an implant having a conventional implant body for implantation into the bony structure of the oral cavity or other body areas. The neck of the implant includes a first portion distal to the prosthetic margin of the crown and a second portion proximal to the prosthetic margin. The IAJ which defines the surface boundary between the implant and the abutment is located proximal to the prosthetic margin. Thus, the IAJ is covered by the crown. The covering of the IAJ with the crown, achieved by extending the margin distaliy from the IAJ along the implant, isolates the IAJ and any microgap at the IAJ from bacterial invasion, plaque, contamination and other deteriorations effects. This results in a number of benefits to the implant manufacturer, the dentist and the patient. Bone loss is lessened or eliminated at the implant neck because disease is unable to thrive in and around the IAJ. A second major benefit is the antirotation of this type of connection of the prosthesis to the implant. The installation procedure is straightforward using techniques already familiar to the dental profession. Moreover, the responsibility for ensuring a close fit of the implant joint is shifted from the implant manufacturer which produces the implant and abutment joined at the IAJ, to the dentist or laboratory technician who produces the crown for fitting onto the implant system being utilized. The fabrication and fitting of the crown onto the abutment with the crown margin extending onto the implant is similar to the fabrication and fitting of ordinary crowns onto natural teeth, a procedure with which most dentists are familiar. Several implant configurations are taught in the detailed description below, including a slightly tapered neck in the portion proximal to the prosthetic margin; a tapered neck with a curved boundary at the prosthetic margin; a tapered neck with an abrupt squared-off boundary of the prosthetic margin; and a highly tapered neck in the portion proximal to the prosthetic margin. The implant may be of any conventional material, coated or uncoated, with a configuration and dimensions suitable for routine surgical implant placement. Brief Description of the Drawings FIG. 1 is an exploded perspective view of a prosthesis in accordance with the present invention, including a crown, abutment and implant. FIG. 2 is a perspective view of an assembled prosthesis. FIG. 3 is a side sectional view of an assembled prosthesis. FIG. 4 is a side sectional view of a portion of a prosthesis in accordance with the present invention. FIG. 5 is a side sectional view of a portion of an alternative embodiment. FIG. 6 is a side sectional view of a portion of another alternative embodiment . FIG. 7 is a side sectional view of a portion of another alternative embodiment. FIG. 8 is a side sectional view of a portion of another alternative embodiment. FIG. 9 is a side sectional view of a portion of another alternative embodiment. Detailed Description of the Invention An exploded perspective view, and an assembled perspective view, of a prosthesis 10 are shown in FIGs. 1 and 2 respectively. The principal components of the prosthesis 10 are an implant 20, an abutment 40 and a crown 60. The implant 20 in a first preferred embodiment includes an implant body 22 and an implant neck 24 which meet at a neck junction 26. The implant body 22 is of any conventional design, typically including threads 28 and terminating in a distal end 30 of any design. The implant body 22 may be uncoated or may be coated with hydroxylapatite or other suitable biocompatible material to assist in integration, and may be unetched or etched with a suitable acid or other solution. The abutment 40 may be very simple in design as shown in FIG. 1, consisting in the preferred embodiment of a shaft 41 and a truncated cone 43. The abutment is generally metalic and is received by the inner area 32 of the implant 20. The attachment of the abutment to the implant 20 may be by a suitable adhesive, or may be accomplished in a mechanical fashion by hex joints, threads or other attachment means well known in the art, some of which are depicted in the alternative embodiments described below. The crown 60 is of a conventional inert biocompatible material such as ceramic or metal or both, and is configured in the desired exterior surface configuration in the manner known in the art. The sectional views of FIGs. 3 and 4 show the interrelation among the implant 20, abutment 40 and crown- 60 of the present invention. The abutment distal end 42 is received by the inner area 32 of the implant 20, and abutment proximal end 44 is received by the crown 60. Suitable adhesive is used to attach the crown 60 to the abutment 40, and suitable adhesive or mechanical means or both are used to attach the abutment 40 to the implant 20. The implant neck 24 includes a tapered portion 36 and a nontapered portion 34 which meet at the prosthetic margin 70. The tapered portion 36 is in the shape of a truncated one, and the non-tapered portion 34 is substantially cylindrical. The crown 60 includes a blind hole 62 in the distal end 64 to receive the abutment 40, and a larger chamfered hole 66 leading to the blind hole 62 to receive the tapered portion 36 of the implant 20. The tapered portion 36 of the implant 20 and the conical portion 43 of the abutment 40 thus are snugly received by the crown 60. The provision of a tapered portion 36 of the implant 20 and a chamfered hole 66 in the crown 60 ensures that the IAJ 72 defining the boundary between the implant 20 and abutment 40 is completely covered by the prosthesis 60. The prosthetic margin 68 is distal to the IAJ 72. The IAJ is therefore completely isolated from the deteriorous effects of bacterial invasion, plaque and disease. Other embodiments of the invention are depicted in the views of FIGs. 5-9. In FIG. 5, the. implant 120 includes a neck 124 having a substantially cylindrical portion 134 similar to the substantially cylindrical portion 34 of the embodiment of FIG. 4, and a narrowed portion 136. The substantially cylindrical portion 134 and the narrowed portion 136 are joined by a transition portion 137 having a curved surface as viewed in two dimensions, or a cone-like surface when viewed in three dimensions. The embodiment of FIG. 5, like that of FIGs. 1-4, serves to cover completely the IAJ 172 with the prosthesis 160, since the prosthetic margin 168 is well distal to the IAJ 172. Further, the embodiment of FIG. 5 avoids any knife-edge at the prosthetic margin 168 which could be susceptible to breakage or other damage in the case of a ceramic crown. A knife-edge is acceptable in the case of crowns having a prosthetic margin of gold or other mallable material, as shown in other embodiments herein. The embodiment of FIG. 6 is similar to the embodiment of FIG. 5, except that the transition portion 237 between the substantially cylindrical portion 234 and the narrowed portion 236 of the implant 220, is abrupt or squared off rather than rounded. The result is still that the IAJ 272 between the implant 220 and the abutment 240 is completely covered by the prosthesis 260, because the prosthetic margin 268 extends sufficiently distal of the IAJ 272. As in the embodiment of FIG. 5, the embodiment of FIG. 6 avoids any vulnerable knife-edge at the prosthetic margin 268. Yet another embodiment is shown in FIG. 7. The embodiment of FIG. 7 again includes a substantially cylindrical portion 334 of the neck 324 of the implant 320. The remainder of the neck 324, however, is a substantially tapered portion 336. Thus the IAJ 372 defined by the boundary between the abutment 340 and implant 320 is covered by the prosthesis 360 due to the location of the prosthetic margin 368 distal to the IAJ 372. Another embodiment is shown in FIG. 8. The embodiment of FIG. 8 is similar to that of FIGS. 1-4 except that the abutment shaft 42 is threaded 441 in order to be threadably received by the implant 420. A recess 443 is provided in the top of the abutment 440, having a wrench pattern to rotate the abutment 440 in order to thread it into the implant 420. The crown 460 covers the IAJ 472 as the prosthetic margin 468 is located distaliy thereto. A final embodiment is depicted in FIG. 9. The abutment 540 includes a shaft 553 and an abutment 551 extending around the upper portion of the shaft 553. The lower portion of the shaft 553 is threaded 541 and is threadably received by the implant 520. The upper portion of the shaft 553 includes a recess 543 to receive a wrench or other tool for threading the shaft 553 into the implant 520. An advantage to this two-piece design for the abutment 540 is that the abutment 551 can be chosen from a variety of configurations depending on use parameters. As in the other embodiments, the prosthetic margin 568 is distal to the IAJ 572 to ensure that the IAJ is covered by the crown 560.

Claims: CLAIMS What is claimed is: 1. A dental prosthesis for use with a patient, comprising: an implant adapted for implantation in a bony structure of an oral cavity or other areas of the body of the patient, the implant having an implant distal end for implantation in said bony structure and an implant proximal end opposite the implant distal end, an abutment having an abutment distal end secured to the implant proximal end to define an implant abutment joint where an exterior surface of the abutment meets an exterior surface of the implant, and an abutment proximal end opposite the abutment distal end; and a crown, the crown having a crown distal end 5 secured to the abutment proximal end and a crown proximal end opposite the crown distal end, the crown distal end having a peripheral prosthetic margin positioned distaliy from the implant abutment joint such that the crown covers the entire implant abutment joint. o 2. The prosthesis of claim l, wherein the implant includes a body and a neck in a proximal direction in relation to the body, the neck having a first portion with a first width and a second portion in a proximal direction in relation to the body having a second width, the 5 second width being less than the first width whereby the crown extends over the second width and not over the first width. 3. The prosthesis of claim 2, wherein the second portion is tapered. 0 4. The prosthesis of claim 3, wherein the second portion is substantially conical. The prosthesis of claim 1, wherein the first portion and second portion are joined by a curved portion. 5. The prosthesis of claim 4, wherein the 5 abutment distal end includes a shaft attached to the implant and the abutment proximal end includes a head attached to the crown. 6. The prosthesis of claim 5, wherein the abutment head narrows in the proximal direction. 7. The prosthesis of claim 6 , wherein the abutment head is substantially conical. 8. The prosthesis of claim 7, wherein the abutment head is substantially a truncated cone. 9. The prosthesis of claim 8, wherein the abutment head and implant second portion form a substantially truncated cone. 10. The prosthesis of claim 1, wherein the second portion is substantially cylindrical. 11. The prosthesis of claim 1, wherein the abutment is threadably attached to the implant by threads on an abutment shaft on the abutment distal end. 12. The prosthesis of claim 11, wherein the abutment proximal end includes means for engaging a tool to rotate the abutment to thread the abutment shaft into the implant. 13. The prosthesis of claim 12 , wherein the abutment includes a collar separate from and positionable on the shaft, the collar having a width greater than a width of the shaft. 14. A method of fabricating and installing a dental prosthesis in a patient, comprising: drilling a hole into a bony structure of the patient's oral cavity or other bony structures; threading an implant into said hole, the implant having an implant distal end with a set of threads to engage the hole and an implant proximal end opposite the implant distal end; attaching an abutment to the implant to define an implant abutment joint therebetween, the abutment having an abutment distal end for attachment to the implant proximal end and an abutment proximal end opposite the abutment distal end; making a transfer cast of the attached abutment and implant; fabricating a crown from the transfer cast, the crown having a distal end for attachment to the abutment and a proximal end opposite the distal end; and - attaching the crown to the abutment whereby the crown substantially completely covers the implant abutment joint. 15. The method of claim 14, wherein the abutment includes a threaded shaft or cemented shaft and wherein said step of attaching the abutment to the implant includes threading the abutment shaft into the implant.

Inventors: CALLAN DONALD P, CALLAN, DONALD, P.
Applicants: CALLAN DONALD P, CALLAN, DONALD, P.
Application year: 1997
Main classification: A61C8
IPC codes: A61C8