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Should Implants Be Connected toNatural Teeth? by Dr. GordonChristensen
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by Gordon J. Christensen, DDS, MSD, PhD
Both you and I find occasionswhen patients have clinicalsituations where it seemslogical and feasible to attachimplants to natural teeth.However, you’ve heard fromsome specialists that thisconcept is not successful andshould not be attempted. Whatis the current state of the artabout this procedure? I’ve been placing and restoring root-form dentalimplants for more than 30 years. All practitionerswho place implants find reasons to want toconnect natural teeth to implants, but many arereticent to do so. I’ll begin this discussion withinformation somewhat broader than justconnecting teeth to implants.
Implants have been relatively well proven overmany years of use. However, in the past fewyears, the continued and growing incidence of thepresence of peri-implant mucositis and peri-implantitis around implants has given pause totheir use. Implants that looked perfect whenplaced often show bone loss after a few years,while other implants look good after decades ofuse.
Many have theorized specific reasons for thesedeteriorating conditions, but the reasons appear tobe too many to allow a logical guess on the mostimportant factor. They include occlusion, immuneresponse changes, metal allergies, systemicdiseases, microorganisms, diet, oral hygiene,radiation and drugs taken by the patients. Thedegeneration shown in peri-implant mucositis andperi-implantitis resembles closely the sameconditions that occur with periodontal disease onnatural teeth. The subject needs continuedresearch to understand the problem. So, whatdoes the rising trend of implant deterioration haveto do with the title of this article?
Study of periodontal disease has been ongoing formany decades, and the profession knows how toprevent and treat periodontal disease aroundnatural teeth. The idea that implants are equal toor even better than natural teeth is now underquestion. My strong conclusion after years ofobserving thousands of dental implants in serviceis: There is nothing like a natural tooth. Keepthem if at all possible.
When you can accomplish conventional operativedentistry and fixed and removable prosthodontics,don’t consider these procedures to be a second-tier level of treatment. In many cases, they shouldbe the primary choice, because we know well theproven longevity of these types of treatment.
When should connecting anatural tooth to an implant beconsidered?Financial considerations. Implants areexpensive. The fee for an implant, potentialgrafting, an abutment and a crown amounts tothousands of dollars. Often, patients cannot affordsuch treatment. Minimizing the number ofimplants is an option, but it may requireconnecting the implant to a natural tooth.
Fig. 1 shows a potential need for attachment of anatural tooth to an implant. At the time oftreatment, the patient was retired and somewhatdebilitated, and had dental treatment fail in hismouth. He did not want to have additional,extensive and expensive dental treatment.
Inadequate quantity or quality of bone.Grafting bone is a common procedure, but it’s notdone by many general dentists. Each year, moregeneral dentists are placing implants, and Iencourage them to learn how to do grafting afterextractions on a routine basis. Grafting requirestime for maturation, and is expensive for patientsand dentists. There are times when a simpleconnection of a natural tooth to an implanteliminates the extra procedures and costsexplained above.
Figs. 2 and 3 show a patient who had adequatebone density in the posterior right mandibular areawith less bone density in the first molar area.Rather than place an implant in that area, the twoimplants were connected to a stable, vital tooth.The photo in Fig. 3 was taken 14 years aftertreatment.
Need for more support for a cemented fixedprosthesis. There are times when there is notenough bone for an implant without grafting, asshown in Fig. 4. In this case, we solved thedilemma by connecting the remaining naturaltooth to an implant.
There are many times when there are not enoughnatural teeth to support a fixed prosthesis. Figs. 5and 6 show such a case: This person with a cleftpalate desired to have a fixed prosthesis. She hadtwo conventional-diameter implants placed byanother person, both of which failed rapidly.
I violated two sacred rules of implantology tomake the prosthesis. She rejected having moregrafting to allow conventional-diameter implants.We used small-diameter implants in the healedareas where the conventional-diameter implantshad failed, and we seated a fixed prosthesis overboth teeth and implants. This was a difficult andcontroversial case at a time when both conceptswere considered to be controversial or evencontraindicated. Fig. 6 shows the result after 12years of service.
There also are numerous other legitimate reasonsto connect teeth to implants, including accidentsand mobile but healthy teeth.
Technique for connecting teethto implants Contrary to popular belief, when accomplishedproperly, teeth can be connected to implants. Aftermany years of placing implants, I will fully admitthis is not my preferred technique; however, itsolves commonly occurring treatment planningchallenges, a few of which have been identified inthis article.
What is the proper technique?
Select only strong, healthy teeth. Connectingimplants to mobile teeth is highly questionable.The teeth should be solidly in bone and haveenough remaining tooth structure or build-ups toensure acceptable retention of the abutmentcrown.
Use porcelain-fused-to-metal. I recommendwaiting until zirconia has had a few more years ofclinical use and the restoration strength can betrusted. Too many zirconia crowns are currentlycoming off in service. Unfortunately, there arenumerous formulations of zirconia, some of whichare not strong and have minimal or notransformation toughening to reduce subsequentfailure. Most dentists are not aware of thedifferences in the highly promoted types ofzirconia. Only the original Glidewell BruxZir hashad adequate research to validate it. Others arecurrently in clinical research and they lookpromising.
Tooth preparations and implant abutmentsmust be very retentive. Separate abutments forthe implants can be avoided if the implants areperpendicular to the occlusal plane. A screw alonecan then connect the crown to the implant, as inFig. 4 (page 42). If that’s not possible, make theimplant abutment very parallel to the toothpreparation. If the abutment crown comes loosefrom the tooth, the tooth will intrude into the bonerapidly. I learned this 20 years ago with severalfailed cases.
Scratch and roughen the axial walls of thetooth preparation and the implant abutment,if using a separate abutment. This will providea “luting” effect and interdigitation of the cementinto the tooth prep and the abutment.
Use resin cement. Resin cement such as 3MRelyX Unicem 2, Kerr Maxcem Elite Chroma,Ivoclar Vivadent Multilink Automix and KurarayPanavia offer strength. You need strength!
Avoid use of provisional cements. Theconnection between the implant and the toothmust be rigid, or the tooth will fail by intrusionwhen the cement fails on the tooth abutment.
Adjust occlusion carefully. Traumatic occlusioncan break the cement bond and cause overallfailure.
SummaryThe false assumption that implants should not beattached to natural teeth has permeated theprofession for several years. It is now obviousfrom both clinical observation and controlledresearch that this procedure, done correctly, isviable.
This article includes suggestions for when thisprocedure is desirable, describes an acceptabletechnique, and shows examples of several long-term, successful cases.
Fig. 1
Fig. 2
Fig. 3
Fig. 1: Patient with failed hemisected molar previously grafted in thesecond-molar area. Patient was not interested in extensive andexpensive repair and wanted the most conservative plan. Connectingone implant to the strong premolar was the accepted treatment plan,after explaining the potential challenges of the tooth-to-implanttechnique to the patient. The radiograph on the right is 12 years afterthe prosthesis was placed. The porcelain-fused-to-metal fixedprosthesis on the maxillary arch has now served more than 30 years.Don’t throw conventional dental treatment away yet! Fig. 2: Patientwith adequate bone quality and quantity in the second-molar area, andsomewhat questionable quality in the first-molar area. The decisionwas made to connect the two implants to the vital premolar tooth. Thattreatment was accomplished many years ago. Today, I would not placeabutments on the implants, as in the photo, but rather would connectthe splinted crowns to the implants by screwing through the crownsinto the implants. Fig. 3: The radiograph on the left is at placement ofthe fixed prosthesis in 2004. The radiograph on the right is the samepatient as described in Fig. 2 after 14 years.
Fig. 5
Fig. 6
Fig. 5: A hopeless, discouraged cleft palate patient who had twoconventional-diameter implants fail that were planned for removableprosthesis retention. She wanted a fixed prosthesis. The image on theright shows two small-diameter implants at the day of placement in thehealed bone. There is almost no bone in the anterior area. Fig. 6: Thenine-unit porcelain-fused-to-metal fixed prosthesis has now served for12 years supported and retained by both teeth and implants. She hasbeen a very faithful patient with her oral hygiene and has avoidedchewing hard foods in the anterior portion of her mouth.
Author Bio
Gordon J. Christensen, DDS, MSD, PhD, is apracticing prosthodontist in Provo, Utah, and an
adjunct professor at the School of Dentistry at theUniversity of Utah. He is a diplomate of the AmericanBoard of Prosthodontists, and the CEO of PracticalClinical Courses and the Clinicians Report Foundation.Information: pccdental.com
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