Common Longitudinal Studies Without Control Treatments Are Misleading When Choosing the Correct Type of Tooth Restoration

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SYSTEM Initiative: New findings show that the results of common longitudinal studies without control treatments are misleading when choosing the correct type of tooth restorations in clinical dental practice.

SYSTEM Initiative

Results of common longitudinal studies without control treatments are misleading when choosing tooth restorations

Until present, restorative dentistry is informed by volumes of clinical longitudinal studies that do not include control treatments but only investigate the success and failures of novel tooth restorations over periods of time. In order to establish which dental restoration type performs best, particularly when placed in posterior load bearing teeth, prestigious expert reviews have traditionally offered advice to the dental profession on basis of simply comparing the success rates between different longitudinal studies with each other.

In contrast to clinical longitudinal studies, clinical randomised control trials (RCTs) are considered the gold standard in investigating the merits of clinical interventions. In an effort to appraise the current clinical evidence regarding the merits of placing glass-ionomers as tooth restorations, the SYSTEM Initiative of the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, has conducted a systematic review of RCTs and a meta-epidemiological study.

SYSTEM’s investigation shows that there is very poor agreement between results from RCTs and clinical longitudinal studies. While comparisons within an RCT would show that the number of treatment failures of two treatments is exactly the same, the comparison between different longitudinal studies would erroneously show a 64% higher failure rate of one type of treatment above the other. Accordingly, expert reviews would mistakenly recommend the merit of placing one type of tooth restorations above that of another.

SYSTEM’s systematic review included a literature search in 17 global and regional databases, as well as databases for open access journals and ‘grey’ literature. Besides searching the global databases PubMed/Medline and the Cochrane library, the searched additional regional English databases comprised of the scientific dental literature from Africa, Europe, India and North America, whilst regional non-English databases comprised of the dental literature from China and Latin-speaking American countries.

In total, 38 trials were accepted as evidence, comprising the investigation of more than 10 000 placed tooth restorations. The outcome shows that new generation, high viscous glass-ionomers cannot be regarded as inferior to amalgam, since no overall statistically significant difference was found in the clinical failure rate between load bearing high-viscosity glass-ionomer and amalgam restorations after follow-up periods ranging from one to six years.

The results of SYSTEM’s meta-epidemiological study show that statements concerning glass-ionomer’s inferiority to amalgam and other types of materials are based on incorrect statistical comparison methods. Such methods include the still common naïve-indirect comparison of restoration failure rates from uncontrolled clinical longitudinal studies. Simply put, the traditional argument against the use of glass-ionomers in modern dentistry is based on the wrong assumption that results from unrelated clinical trials with differing clinical settings and patient groups can be directly compared to one another. Instead, statements concerning the merits of clinical interventions should rest on the direct comparison of competing treatment options via randomised control trials.

The new findings suggest that placing high-viscosity glass-ionomer restorations may offer an alternative to placing restorations with silver amalgam in load bearing posterior cavities of permanent teeth.

High-viscosity glass-ionomer restorations do not require provision of macro-retention by high-speed drilling, thus they offer the dental profession a more patient friendly approach for placing tooth restorations. Placing glass-ionomer restorations also reduces the likelihood of a repeated restoration cycle, because repair of failed restorations does not require the removal of remaining filling material from the tooth cavity.

The published full reports of the new findings are available online:

[1] [Mickenautsch S, Yengopal V. Failure rate of high-viscosity GIC based ART compared to that of conventional amalgam restorations - evidence from a systematic review update. S Afr Dent J 2012; 67: 329-31.

[2] http:// Mickenautsch S, Yengopal V. Direct contra naïve-indirect comparison of clinical failure rates between high- viscosity GIC and conventional amalgam restorations. An empirical study. PLOS One 2013; 8: e78397.

[3] Mickenautsch S, SYSTEM Research note on: How should competing clinical interventions be compared in dentistry? – A simulation-based investigation. J Minim Interv Dent 2013; 6: 73-80.

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Dr S Mickenautsch
SYSTEM Initiative, Univ. of the Witwatersrand, Johannesburg
+27 823363214
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