Izchak Barzilay, DDS, MSHead of the Division of ProsthodonticsMount Sinai HospitalAssociate in DentistryUniversity of TorontoToronto, Ontario, Canada

Immediate Implants:Their Current Status

Immediate implants are implants placed into a preparedextraction socket following tooth removal. Short-term animaland human studies have shown these implants to becomparable to implants placed into healed bone. Theadvantages of the procedure include fewer surgical sessions,elimination of the waiting period for socket healing,shortened edentulous time period, reduced overall cost, aswell as preservation of bone height and width. Althoughimmediate implantation is more demanding both surgicallyand prosthetically compared to the conventional placementtechnique, the advantages make it very appealing to patientswho are in need of both extractions and implant therapy.Int J Prosthodont 1993;6:169-175.

W ith the introduction of "osseointegrationtechnology" to North America at the 1982

Toronto Conference, prosthodontic treatment ofpatients was to change significantly. It became pos-sible to anchor prostheses firmly to osseointe-grated implants and significantly improve comfortfor those who for so many years were "sentenced"to wearing removable prostheses. Original studiesreported high success rates related to implantsplaced in the anterior symphysis of the mandible ofedentulous patients.1,2 It is based on tryese successrates that the implant procedure became morecommon in restoration of the maxillae and thenused for the partially edentulous patient and incraniofacial reconstruction. With experience, de-mands of placing restorations for the partially eden-tulous patient in less than ideal locations promptedthe development of newer surgical devices andtechniques. (sinus and ridge grafting, local bonegrafting at individual implant sites) to assist in im-

plant placement. New prosthetic components thatwould allow for prosthetic correction of angulationand esthetic difficulties were developed.

In situations where teeth required extraction,original protocol suggested a 6- to 12-month waitfor healing of the site before implant placemenP-sto allow the complete ossification of the extractionsocket.6 Placement of an implant directly into aprepared extraction socket at the time of extractionhas several advantages that have the potential toimprove patient acceptance of the procedure:

1. Elimination of the waiting period for socketossification

2. Fewer surgical sessions required3. Shortened edentulous time period4. Reduced overall cost5. Preservation of alveolar bone height and width

allowing for optimal placement in relation toimplant length, width, and angulation

Literature Review

Reprint requests: Dr Izchak Barzilay, 2300 range Street, Suite 905,

Box 2334, Toronto, Ontario, Canada M4P 1£4.Several investigators reported placing implants

directly into extraction sockets before the NorthAmerican osseointegration era.7-12 These studiesgenerally reported poor success rates with soft tis-sue noted at the interface.

Presented at the University of Toronto Implant Symposium, "TheImpadofOsseointegration on the Treatment of the Prosthodon-tic Patient," November 12-13,1992.

169Volume 6, Number 2,1993 The International journal of Prosthodontics

bone healing have suggested their usefulness inthe immediate implantation procedure.40-42 Thesematerials have been used with and without barri-ers. More research is needed before these materi-als can be used routinely in clinical practice.

While a review of the literature indicates a greatinterest in and promise for immediate implant treat-ment, much of the published information is basedon short-term data. One must still consider this typeof treatment new and not conclusively supported bylong-term controlled clinical studies. If the proce-dure is to be undertaken, it can only be done withpatient acknowledgment that placing an implantinto an extraction socket at the time of extraction is asurgical"art" and not implant science.

Clinical Requirementsfor Immediate Implantation

As with all implant treatment, good initial diagno-sis and treatment planning is essential. For theimmediate implant patient this includes the stand-ard procedures for conventional implant place-ment with special attention being given to:

1. The tooth that is to be extracted and surround-ing structures

2. Surgical difficulties3. Possible prosthodontic complications

The ideal scenario for an immediate implant in-volves an atraumatic extraction, stabilization of theimplant within the confines of the prepared extrac-tion socket so that it has maximal contact withfreshly prepared bone and is in proper angulation,primary closure of the surgical flap, uneventfulhealing, and final restoration of the implant with afunctioning prosthesis.

Evaluation of the Tooth and Surrounding Structures

In planning for an immediate implant procedure,it is vital that one considers the tooth that is to beextracted for its general dental health, root anat-omy, and root orientation. The published animalstudies generally evaluated extracted teeth free ofsigns of inflammation. Clinically, this may presentas an unrestorable tooth with little or no activeperiodontal disease. It is important to consider thatonce the tooth is extracted, the implant site mustbe free of pathosis. This is best achieved by properpatient selection and waiting for the extractionsocket to heal if disease is present in the area. Teethwith periapical pathosis or active periodontal dis-ease are not prime candidates for immediate im-

Aluminum oxide intraosseous implants have beenplaced into extraction sockets of rhesus monkeysand baboons showing low "survival rates" ofsmooth and horizontal fin implants, respectively.13.14Human studies have shown poor success rates at 5years (57%)15 and at 8 years (23%).16 The TObingenimplant has been placed into extraction sites as wellas healed bone of human subjects with a high de-gree of success.17-20 long-term controlled animaland human studies using occlusally loaded TO-bingen implants (placed into fresh extraction sock-ets) have yet to be reported.

Research showing that hydroxyapatite (HA) pro-duces bony ankylosis attachment when placed intoextraction sockets21 has led to its evaluation in im-mediate implantation. Hydroxyapatite implants,designed to be loaded with a crown, were placedinto extraction sockets and showed immobile fixa-tion; how.ever, failure occurred because of poorstrength of the material, implant fractures,22 as wellas cement breakdown between the titanium postand the HA.23 Immediate implantation of HAplasma-sprayed implants have been shown to inte-grate with a great degree of success.24-27

Earlier research using animal models to evaluateunloaded titanium implants in extraction socketsshowed high degrees of bone at the implant inter-face.s.28 Barzilay et al29.30 compared pure titaniumimplants placed into extraction sockets of monkeyswith implants placed into healed bone. After a load-ing period of 7 months, clinical, radiographic, andhistologic data indicated no significant differencebetween immediate and conventional implants.

Although not evaluating implants placed into ex-traction sockets, investigators have reported highsuccess rates with titanium implants placed at thetime of extraction following radical alveolectomiesor alveoplasty.31.32

There have been many recent reports of immedi-ate implants with the techniques of guided tissueregeneration. The technique appears useful in situ-ations of dehiscence and fenestration as well aswhen gaps are present between prepared bone andthe implant. Recent research evaluating tissue re-generative procedures using membranes aroundtitanium implants has shown enhanced bone for-mation at extraction sites when dehiscences werepresent.33 Other studies have shown improvedbone fill around titanium implants when mem-branes were used versus when they were notused.34.3s Clinical reports have documented thistechnique to be useful in the healing of immediate

implants.36-39Recent research into the use of bone augmenta-

tion materials and enhancing agents to increase

The International Journal of Prosthodontics R Volume 6, Number 2, 1993

Fig 1 Classification of the implant-bone interface.

Fig 2 Radiograph of a maxillary rightcentral incisor immediate implant at thetime of insertion. Note the gap betweenthe implant and the prepared bone site atthe coronal end of the implant.

shapes and sizes of roots there is a greater likeli-hood that when dealing with immediate implants aspace will be present between the implant and theprepared socket. In the type II situation a space ispresent at the coronal aspect of the implant, whilethe apical portion of the implant is secured infreshly prepared bone (Fig 2). A type III situationexists when a space is present along tl1e lateralborder of the implant. This may be the reason thatthe immediate implantation procedure was slow todevelop, since this gap may have initially con-cerned researchers as a possible mode for failure.

plants. Whereas the presence of caries in itself isnot a contraindication, its presence may make ex-traction of the tooth more difficult and therebynecessitate bone removal during extraction. Thisloss of bone would lead to an overall reduction ofinitial support for the implant.

An assessment of the root orientation must bemade, since this has a direct bearing on the angula-tion of the implant. Maxillary incisors and caninesare curvilinear in shape and as such the long axis ofthe root and the long axis of the crown are notparallel. Placement of the implant along the longaxis of the extraction socket (long axis of the root)in these situations may result in buccally angulatedimplants. An assessment of the root's shape(round, ribbon-shaped, etc) must be made, since ithas a direct bearing on both the type of implant-bone interface that can be expected once the im-plant is placQd as well as the angulation of the

implant.Since there are a limited number of implant

diameters available (most sizes being 3.75 and 4.0mm) it is reasonable to assume that spaces existbetween the implant and the prepared bone sitebecause of the shape of the extraction socket. Theimplant-bone interface can be classified as type I,

II,orlll(Fig1).Type I Interface. Ideally, one would prefer to see

an implant with freshly prepared bone along itscomplete periphery (type I). This can be accom-plished when the root is smaller than the implantand is often seen when small teeth are extracted orwhen the teeth that are extracted have had peri-odontal disease and the remaining socket size isminimal. The type I interface can be created byplacing the implant deep into the socket so as toengage only the apical portion of the socket and theprepared bone beyond the apex. In these situa-tions, once the site is prepared the implant will bein contact with freshly prepared bone along itscomplete periphery. The type I interface can alsobe created when an alveolectomy is performed,thereby allowing the implant to be placed into basalrather than alveolar bone. Unfortunately, if theimplant is forced into a deeper position, it mayencroach on other structures (nerves, major bloodvessels), be esthetically compromised, or have in-creased cantilever potential. The alveolectomy alsoreduces the potential implant length and thereforeit may be preferable to have immediate implantsstabilized within the confines of the socket at amore ideal occlusal height and then use guidedtissue regenerative procedures to fill the bone-implant void.

Type II and III Interfaces. Because of the different

Volume 6, Number 2, 1993 Fl The International Journal of Prosthodontics

Immediate Implant Status Barzilay

Fig 3 Cross section of an immediate implant placed into thepalatal root socket of a maxillary molar of M fascicularis. Densebone of the palatal cortex is supporting the palatal side (right) ofthe implant, while the buccal side (left) has only a thin layer ofdense lammelar bone at the interface with minimal physicalsupport. An implant extending from buccal to palatal cortexwould be supported by more cortical bone for overall better

physical support.

Fig 4 Histologic section of the immediate maxillary molar in Fig3. Thick, dense lamellar bone is present on the palatal aspect(right), while only a very thin rim of lamellar bone is present onthe buccal aspect (left). The buccal-side interface is supportedby bone marrow. (Modified Masson-Goldner trichrome stain,original magnification x 25)

Fig Sa Pure titanium screw-shaped implant has been posi-tioned within the prepared root socket of a maxillary first premo-lar. The implant engages bone in the apical region of the socketand along the buccal socket wall but is not in contact with bonealong most of its palatal surface (good example of a type IIIinterface). The site was augmented with freeze-dried decalcifiedbone and a nonresorbable membrane. (Courtesy of Dr M. Arlin,Weston, Ontario.)

Fig 5b At the time of uncovery, bone can be seen filling thevoid that was present at the time of implant placement. (Cour-tesyof Dr M. Arlin, Weston, Ontario.)

Surgical Difficulties Complicated extractions .lessen the amount of alve-olar bone available for implant support. Once thetooth is extracted, the socket must be closely evalu-ated for the most ideal location to secure the im-plant. Ideally, an implant placement guide shouldbe used to orient the implant surgeon as to theproposed placement of the clinical crown. The im-plant should be placed so that its coronal surface isapproximately 3 to 4 mm apical to the cemento-enamel junction of the adjacent teeth, and thescrew access should exit through the cingulum orthe central groove of the final crown. While keep-ing these factors in mind, the implant surgeon mustplace the implant within the confines of the socket

Surgical complications encountered with imme-diate implantation can be associated with severalfactors: .

1. Complicated extractions2. Perforation of the cortical plate3. Socket anatomy that precludes ideal implant

placement4. Close proximity to adjacent teeth, sockets or

implants5. Difficulties associated with barrier techniques6. Problems associated with flap closure

The International journal of Prosthodontics R Volume 6, Number 2,1993

and maximize contact between prepared bone andthe implant. The implant should be placed so that itcontacts cortical plate, wherever possible, to im-prove stability. This is difficult because a superiorcortical plate is unavailable (as a result of extrac-tion). The inferior, buccal, lingual, or palatal cor-tices should be engaged if possible. This is mostimportant in areas of poor bone quality (posteriormaxillae and mandible) (Figs 3 and 4).30 When anideal bone-implant interface (type I) cannot beachieved, it becomes necessary to use guided tis-sue regenerative procedures to augment areas ofthe interface that are not in contact with bone (FigsSa, Sb, and 6). However, using this techniquemakes it difficult to approximate the edges of theflap because of the increased bulk of material un-der the flap. Although it may not always be neces-sary to approximate the edges of the flap, it isdesirable. .

Ideally, the flap should be approximated to allowfor primary healing of the surgical site. When deal-ing with conventionally placed implants this is not aproblem, because intact tissue was originally in-cised to raise the flap. An immediate implant doesnot have the tissue to close as a result of the extrac-tion. The flap edges can be approximated by releas-ing the periosteum, creating a sliding pedicle flap,or interdigitating the papillae to close the surgicalsite. When placing the implant into the extractionsocket, it should be submerged below the level ofthe surrounding bone. In such instances, primaryclosure of the flap may preclude the guided tissue

regenerative procedure.30

Fig 6 Radiograph of maxillary right cen-tral incisor immediate implant shown inFig 2 alter guided tissue regeneration anda 6-month healing period. Radiographicevidence of bone fill can be seen in thecoronal portion of the implant.

Prosthodontic Como/ications

Prosthodontic complications associated with theimmediate implant procedure can be encounteredimmediately after the surgical implant placement.These complications include: Fig 7 Immediate implant placed into a maxillary premolar site

shows severe buccal angulation.

1. Reduced vestibular depth2. Angulation problems3. Deep or shallow implant placement within the

socket tion abutments" that reorient the screw access ofthe crown. Angulation problems can also be man-aged using cementable components.

A surgical tendency to place the implant deepwithin the socket (to engage more bone} can leadto prosthetic difficulties in restoration as well as inpatient maintenance of a prosthesis. Shallow place-ment makes esthetic restoration difficult if a mini-mal amount of gingival tissue is present. Compo-nents bringing the prosthesis to a level close to theimplant body itself help with this type of problem.

By approximating the flap edges, a loss of vestib-ular depth may occur and make reinsertion of thepatient's interim prosthesis difficult. The dentureborder must be adequately reduced, and a softliner is placed to minimize pressure on the dis-placed vestibule.

The most common problem faced by this authoris that of poor implant angulation (Fig 7). Most ofthese problems are easily managed with "angula-

Volume 6, Number 2, 1993 R The Internationallournal of Prosthodontics

Conclusion

Short-term research (animal and human studies)has shown that immediate implants are comparableto implants placed using the conventional tech-nique. The procedure is more demanding bothsurgically and prosthodontically but provides sig-nificant advantages for the patient. long-term stud-ies are needed to conclusively prove the usefulnessof this procedure.

References

1. Adell R, lekholm U, Rockier B, Branemark pol. A 15-yearstudy of osseointegrated implants in the treatment of theedentulous jaw. Int) Oral Surg 1981 ;6:387-416.

2. Adell R, Eriksson B, lekholm U, Branemark pol, )emt T. A

long-term follow-up study of osseointegrated implants in thetreatment of totally edentulous jaws. Int ) Oral MaxillofacImplants 1990;5:347-359.

3. Ohrnell lO, Hirsch )M, Ericsson I, Branemark pol. Singletooth rehabilitation using osseointegration. A modified sur-gical and prosthodontic approach. Quintessence Int 1988;19:871-877.

4. Branemark pol. Personal communication, 1986.5. Anneroth G, Hedstrom KG, Kjellman 0, Kondell PA,

Norderam A. Endosseous titanium implants in extractionsockets-An experimental study in monkeys. Int) Oral Surg

1985;14:50-54.6. Shulman lB. Surgical considerations in implant dentistry. )

Dent Educ 1988;52:712-720.7. Sarnachiaro 0, Gargentini lC. Biological tissue reaction to

immediate post extraction blade implants. Implantol1979;1:44-51.

8. Weiss MB, Rostoker W. Development of a new endosseousdental implant, Part 1: Animal studies. ) Prosthet Dent1981;46:646-651.

9. Hodosh M, Povar M, Shklar G. The porous vitreous carbonpolymethacrylate replica implant. Continuing studies.) Pros-thetDent1979;42:557-565.

10. Karagianes MT, Westerman RE, Hamilton AI, Adams HF, WillsRC. Investigation of long-term performance of porous metaldental implants in nonhuman primates. ) Oral Implantol

1982;10:189-208.11. Stanley HR, Hench l, Going R, Bennett C, Chellemi S), King

C, et al. Implantation of natural tooth form bioglasses inbaboons.) Orallmplantol1976m;1 :34-47.

12. Stanley HR, Hench ll, Bennett CG, Chellemi S), King q,Going RE, et al. The implantation of natural tooth formbioglass in baboons - long-term results. ) Oral Implantol

1981;2:26-31.13. Brose MO, Rieger MR, Driskell TD. Multicrystalline alumi-

num oxide tooth implants in rhesus monkeys. ) Orallmplan-toI1987;13:204.

14. Brose MO, Rieger MR, Downes R), Hassler CR. Eight-yearstudy of alumina tooth implants in baboons. ) Orallmplantol1987;13:409-424.

15. Brose MO, Reiger MR, Avers R), Hassler CR. Eight-year analy-sis of alumina dental root implants in human subjects. ) Oral

ImplantoI1988;14:9-23.16. Brose MO, Avers R), Rieger MR, Duckworth )E. Submerged

alumina dental root implants in humans - Five-year evalua-tion. ) Prosthet Dent 1989;61 :594-601.

17. Schulte W. The intra-osseous AI2O3 (Frialit*) Tuebingen im-

plant. Developmental status after 8 years (I). QuintessenceInt1984;15:9-26.

18. Quayle M, Cawood J, Howell RA, Eldridge DJ, Smith GA.The immediate or delayed replacement of teeth by permuco-sal intra-osseous implants: the TObingen implant system.Part 1. Implant design, rationale for use and pre-operativeassessment. Br Dent J 1989;166:365-370.

19. Quayle M, Cawood J, Smith GA, Eldridge DJ, Howell RA.The immediate or delayed replacement of teeth by permuco-sal intra-osseous implants: The TObingen implant system.Part 2: Surgical and restorative techniques. Br Dent J1989;166:403-410. .

20. Zetterquist L, Anneroth G, Nordenram A: Tissue integrationof Al2O3-ceramic dental implants: An experimental study inmonkeys. Int J Oral Maxillofac Implants 1991 ;6:285-293.

21. Denissen HW, deGroot K. Immediate dental root implantsfrom synthetic dense calcium hydroxylapatite. J ProsthetDent 1979;42:551-556.

22. de Putter C, de Lange GL, de Groot K. Permucosal oralimplants of dense hydroxylapatite: Fixation in alveolar bone.In: van Steenberghe D (ed). Tissue Integration in Oral and'Maxillo-facial Reconstruction [proceedings of an interna-tional congress, May 1985, Brussels]. Amsterdam: ExcerptaMedica, 1986.

23. Denissen HW, Kalk W, Velhduis MH, van den Hooff A.Eleven-year study of hydroxyapatite implants. J Prosthet Dent1989;61:706-712.

24. Block MS, Kent IN. Placement of implants in extraction sites- Four-year experiences. J Dent Res 1991 ;70(special is-

sue):60.25. Block MS, Kent IN. Placement of endosseous implants into

extraction sites. J Oral Maxillofac Surg 1991 ;49:1269-1276.26. Yukna RA. Clinical comparison of hydroxyapatite-coated tita-

nium dental implants placed in fresh extraction sockets andhealed sites. J PeriodontoI1991;62:468-472.

27. Golec TS, Krauser JT. long-term retrospective studies onhydroxyapatite coated endosteal and subperiosteal implants.Dent Clin North Am 1992;36:39-65.

28. Woolfe SN, Kenney EB, Keye G, Taylor D, O'Brien M. Effect ofimplantation of titanium implants into fresh extraction sock-ets. J Dent Res 1989;68(special issue):762.

29. Barzilay I, Graser GN, Iranpour B, Natiella J, Proskin H.Histologic and clinical assessment of impla~ts placed intoextraction sockets. J Dent Res 1990;69(special issue):1452.

30. Barzilay I: Immediate Implantation of Pure Titanium Im-plants Into Fresh Extraction Sockets of M Fascicularis [Mas-ter's thesis]. Rochester, NY: University of Rochester, 1991.

31. Krump JL, Barnett BG. The immediate implant: A treatmentalternative. Int J Oral Maxillofac Implants 1991 ;6:19-23.

32. Tolman DE, Keller EE. Endosseous implant placement imme-diately following dental extraction and alveoloplasty: Prelim-inary report with 6-year follow-up. Int J Oral MaxillofacImplants 1991 ;6:24-28.

33. Becker W, Becker BE, Ochsenbein C, Handelsman M,Albrektsson T, Cellete R. The use of guided tissue regen-eration for implants placed in immediate extraction sockets.In: laney WR, Tolman DE (eds). Tissue Integration in Oral,Orthopedic, and Maxillofacial Reconstruction. Chicago:Quintessence, 1992:200-202.

34. Warrer K, Godtfredsen K, Karring T, Hjorting-Hansen E.Guided bone regeneration around dental implants insertedinto extraction sockets. J Dent Res 1991 ;70(special is-sue):654.

35. Jovanovic SA, Spiekermann H, Richter EJ, Kenney EB. Re-entry measurements after guided tissue regenerationaround titanium dental implants. J Dent Res 1991 ;70(specialissue) :658.

174 I Volume 6, Number 2, 1993The International Journal of Prosthodontics

40. Todescan R, Pilliar RM, Melcher AH. A small animal model forinvestigating endosseous dental implants: Effect of graftmaterials on healing of endosseous, porous-surfaced im-plants placed in a fresh extraction socket. Int J Oral Maxillo-fac Implants 1987;2:217-223.

41. Armstrong R, Chang R, deleon E, Rao P, Kincaid S, Chu G.Osteoinduction in titanium and ceramic implants treatedwith bone extracts. J Dent Res 1989;68(special issue):1327.

42. Jabro M, Sotiriou F, Mcley l, Strates B. Osteogenesis inimplants of bone matrices and bone morphogenetic protein.J Dent Res 1991;70(special issue):650.

36. Lazzara RI. Immediate implant placement into extractionsockets: Surgical and restprative advantages. Int I PeriodontRest Dent 1989;9:333-343.

37. Nyman S, Lange NP, Buser D, Bragger U. Bone regenerationadjacent to titanium dental implants using guided tissueregeneration: A report of two cases. Int I Oral MaxillofacImplants 1990;5:9-14.

38. Ross SE, Strauss T, Crossetti HW, Gargiulo AW. The immedi-ate placement of an endosseous implant into an extractionwound: A clinical case report using the RosTR system. Int IPeriodont Rest Dent 1989;9:35-41.

39. Becker W, Becker BE. Guided tissue regeneration for im-plants placed into extraction sockets and for implant dehis-cences: Surgical techniques and case reports. Int I PeriodontRest Dent 1990;10:377-391.

Literature Abstracts

Marginal Adaptation of Castings Made With Dual-Archand Custom Trays

The dual-arch impression technique, which incorporates the maxillary and mandibular impression anda jaw relation record into one procedure, has gained wide popularity. The purpose of this study was tocompare the marginal fit of castings made with custom acrylic resin trays and castings made with metalor plastic dual-arch impression trays. Standard clinical and laboratory procedures were used to make36 gold castings, 12 castings with each type of tray, for a metal typodont die. Marginal openings of thecastings were determined on the metal die with a measuring microscope at six precisely markedlocations on the die. Mean marginal openings were between 25 and 28 IJ.m in all test groups. Therewere no significant differences in marginal opening based on tray type or location of measurement on themetal die. The results of this study support and strengthen the findings of previous studies which usedlinear measurements to compare the accuracy of the impression techniques. The authors conclude thatthe limitations of the dual-arch impression technique are related to the development of occlusion ratherthan the accuracy of the dies.

Davis R, Schwartz R, Hilton T. Am J Dent 1992;5(5):253-254. References: 11. Reprints: Dr Richard Schwartz,Department of General Practice, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr, SanAntonio, TX 78284-7914. - Richard R. Seals, Jr, DDS, MEd, MS, Department of Prosthodontics, The University of

Texas Health Science Center at San Antonio, San Antonio, Texas

Microleakage Full Crowns and the Dental Pulp

The purpose of this study was to test three crown margin preparations to determine whether marginpreparation affects microleakage. Thirty freshly extracted molar teeth, all noncarious or with smallrestorations, were mounted in acrylic resin blocks and prepared with a full shoulder, a chamfer, or ashoulder and a bevel. All crowns were cen:lented with zinc phosphate cement. All teeth were cycled100 times between 4°C and 60°C water baths containing 0.05% crystal violet dye. Total immersion timewas 100 minutes. The crowned teeth were then embedded in clear autopolymerizing acrylic resin andsectioned buccolingually into three equally thick sections. All crowns leaked regardless of the type ofcrown margin preparation. The leakage pattern was the same and the leakage followed the dentinaltubules directly into the pulp in every case. Since this study demonstrated that there is leakage in everytooth regardless of which crown margin preparation is used, dentists must be aware of the possibility ofsubsequent microbiologic damage to the pulp through the dentinal tubules. The authors conclude thatmicroleakage could be a cause of pulpal inflammation, and even pulpal death, under complete crowns.

Goldman M, Laosonthorn ~ White RR. J Endodon 1992;18(10) :473-475. References: 20. Reprints: Dr Melvin Goldman,Department of Endodontics, Tufts University School of Dental Medicine, 1 Kneeland St, Boston, MA 02111. -Richard R. Seals, Jr, DDS, MEd, MS, Department of Prosthodontics, The University of Texas Health Science Center atSan Antonio, San Antonio, Texas