2012;143(9):1011-1012JADA Ben BaleviAnte's law is not evidence based

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Clinical question. In adultpatients who have a fixed dentalprosthesis (FDP) that has healthyperiodontal tissue support, wouldabutments that have severelyreduced periodontal tissue support(that is, those not satisfying Ante’slaw1), compared with abutmentsthat have no or minimally reducedperiodontal tissue support (that is,those satisfying Ante’s law), lead tolower FDP survival rates?Review methods. The re-

viewers searched one electronicdatabase (PubMed) through Sep-tember 2006 and hand searched

seven relevant journals. They con-sidered only prospective and retro-spective cohort studies published inthe English language. They in-cluded in the review only studies ofFDPs with abutment teeth that didnot meet the requirements ofAnte’s law, according to clinical andradiographic data. The primaryoutcomes the reviewers measuredand calculated were the five- and10-year survival rates of theseFDPs. They then compared the out-comes with published survivalrates of FDPs that had abutmentteeth satisfying Ante’s law.

Main results. Six retrospec-tive studies met the inclusion cri-teria. Ameta-analysis incorporatingthe results of only two studies (84participants at baseline [with 17dropouts] and 79 FDPs) yielded anestimated FDP survival rate of 96.4percent (95 percent confidenceinterval [CI], 94.6-97.6 percent)after five years and 92.9 percent (95percent CI, 89.5-95.3 percent) after10 years. These results were com-parable with published survivalrates of FDPs with abutments thatsatisfied Ante’s law.Conclusions. The long-term

prognosis of FDPs with abutmentsthat have severely reduced perio-dontal support depends on propercontrol of periodontal disease,strict adherence to a maintenancecare program and rigid splinting ofmobile abutment teeth.The review described in this critical sum-

mary was funded by the Clinical ResearchFoundation for the Promotion of Oral Health,University of Bern, Switzerland.

Dr. Balevi maintains a private practice in general dentistry in Vancouver, British Columbia, Canada, and has an appointment to the faculty of medicine,University of British Columbia, Vancouver. He also is an evidence reviewer for the American Dental Association. Address reprint requests to Dr. Balevi, Fac-ulty of Medicine, University of British Columbia, No. 306, 805 W. Broadway, Vancouver, British Columbia, Canada V5Z 1K1, e-mail drben@dentalben.com.

Systematic review conclusion. The long-term prognosis of a fixed dental pros-thesis (FDP) with abutments that have severely reduced periodontal supportdepends on the maintenance of a healthy periodontium.Critical summary assessment. Although the results of this review are limitedby the quantity and quality of included articles, there appears to be no scientificevidence requiring that in fixed dental prosthesis (FDP) design, “the total perio-dontal membrane area of the abutment teeth must equal or exceed that of theteeth to be replaced”1 (Ante’s law).Evidence quality rating. Limited.

Ante’s law is not evidence basedA critical summary of Lulic M, Brägger U, Lang NP, Zwahlen M, Salvi GE. Ante’s (1926) lawrevisited: a systematic review on survival rates and complications of fixed dental prostheses(FDPs) on severely reduced periodontal tissue support (published correction appears in ClinOral Implants Res 2008;19[3]:326-328). Clin Oral Implants Res 2007;18(suppl 3):63-72.

Ben Balevi, DDS, MSc

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COMMENTARYImportance and context. Ante’s law statesthat “the total periodontal membrane area of theabutment teeth must equal or exceed that of theteeth to be replaced.”1 For more than 80 years,this law has been taught in standard textbooksof prosthodontics as an important conditioninfluencing FDP design.2,3 If Ante’s law is shownnot to be evidence based, then the option of anFDP supported by abutments with healthy butcompromised periodontal bone support would beviable for patients and clinicians to consider.

Strengths and weaknesses of the system-atic review. The authors of this review soughtto answer a well-focused question and provideda complete description of the criteria used toinclude and exclude articles. However, thereview is limited by the authors’ decision tosearch only one database and to include onlyEnglish-language articles. Also, they conductedno assessment of selection agreement betweentwo independent reviewers (in other words, theyprovided no κ statistic). The findings of the sixretrospective studies included are well summa-rized, but discussion is lacking regarding therisk of bias or of heterogeneity among thestudies. For example, it is unclear whether theauthors were consistent in applying to all theincluded studies the criteria used to determinewhether an FDP satisfied Ante’s law. The lack ofconsistency between studies allowed for only twostudies to be included in the meta-analysis. Also,the authors did not assess the potential risk ofpublication bias to their review.

Strengths and weaknesses of the evi-dence. The six included studies were of thelower-quality retrospective design. Furthermore,the authors could not find a single clinical studyin which the investigators compared the survivalrates between FDPs that did not meet therequirements of Ante’s law and those that did.Hence, this left the authors to make compari-sons between the results of studies of eachrespective FDP design. Nevertheless, the resultsof all reviewed studies appeared to demonstrateconsistently that FDPs placed on severely com-promised periodontally supported abutmentswere serviceable. Only two studies, whichincluded only 79 FDPs and had a high overallparticipant dropout rate (20 percent), were eli-gible for meta-analysis. Nevertheless, the esti-mated five- and 10-year survival rates of 96 and92 percent, respectively, are slightly higher thanthe 10-year survival rate of 89.1 percent (95 per-cent CI, 81-93.8 percent) reported in Tan and

colleagues’4 systematic review of FDPs thatinvolved abutments with generally good perio-dontal support. Lulic and colleagues explainedthe slight difference as possibly being caused byoperator bias because their own review includedFDPs in patients who were treated and whoseFDPs were maintained regularly by clinical spe-cialists, in contrast to those in the review by Tanand colleagues,4 which included FDPs completedby general dentists and dental students. Also,Tan and colleagues’ meta-analysis consisted of2,881 FDPs, compared with only 79 in thisreview. However, investigators in two studiesthat were published after this review and thatmet its inclusion criteria also confirmed theimpressive long-term prognosis of FDPs thatwere supported by periodontally healthy tissuebut that had compromised bone-supportedabutments.5,6

Implications for dental practice. Withwell-maintained, healthy periodontal tissue sup-port, FDPs not satisfying Ante’s law have sur-vival rates comparable with the high rates ofFDPs that do satisfy Ante’s law. Therefore, thedesign of an FDP does not necessarily have tosatisfy Ante’s law. �

Disclosure. Dr. Balevi did not report any disclosures.

Critical Summaries is supported by grant G08 LM008956 from theNational Library of Medicine and the National Institute of Dental andCraniofacial Research, National Institutes of Health, Bethesda, Md.

These summaries, published under the auspices of the AmericanDental Association Center for Evidence-Based Dentistry, are pre-pared by practitioners trained in critical appraisal of published sys-tematic reviews who work under the mentorship of experts. The sum-maries are not intended to, and do not, express, imply or summarizestandards of care, but rather provide a concise reference for dentiststo aid in understanding and applying evidence from the referencedsystematic review in making clinically sound decisions as guided bytheir clinical judgment and by patient needs.

For more information on the evidence quality rating provided aboveand additional critical summaries, please visit http://ebd.ada.org.

1. Ante LH. The fundamental principles of abutments. Mich StateDent Soc Bull 1926;8:14-23.2. Shillingburg HT. Fundamentals of Fixed Prosthodontics. 3rd ed.

Chicago: Quintessence; 1997:92.3. Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed

Prosthodontics. 4th ed. St Louis: Mosby Elsevier; 2006:95.4. Tan K, Pjetursson BE, Lang NP, Chan ES. A systematic review of

the survival and complication rates of fixed partial dentures (FPDs)after an observation period of at least 5 years, III: conventional FPDs.Clin Oral Implants Res 2004;15(6):654-666.5. Cabanilla LL, Neely AL, Hernandez F. The relationship between

periodontal diagnosis and prognosis and the survival of prosthodonticabutments: a retrospective study. Quintessence Int 2009;40(10):821-831.6. Bragger U, Hirt-Steiner S, Schnell N, et al. Complication and

failure rates of fixed dental prostheses in patients treated for perio-dontal disease (published online ahead of print Dec. 16, 2010). Clin OralImplants Res 2011;22(1):70-77. doi:10.1111/j.1600-0501.2010.02095.x.

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