On Violating the Biological Width By Dental Restorations

Update below

A recent case report [1] by Frese et al. (2014) has provided detailed procedures and 1-yr clinical results of and some speculation on biological responses to a direct composite resin restoration of a cavity with its floor adjacent to the proximal alveolar bone. Despite certainly careful application of all operative dentistry measures, the description of how periodontal tissues were treated  was alarming. Authors’ “critical review” and their misconceptions and clueless speculations about the “dogma” of the biological width [2], possible (“re”-)attachment of epithelial cells to the composite resin surface and lack of awareness of, for instance, animal studies [3] which would have answered some of the authors’ most urgent questions about the nature of the epithelial attachment; and finally claims for more clinical studies on “tolerable extent of violation of the biological width, favorable materials in the subgingival area …” are, at best, dubious.

The case report qualifies itself for some educational purposes, though. The restoration was done in one (!) session in a 75-yr-old lady who had lost the filling on tooth #45, apparently some time ago. Authors describe the situation at tooth #45 as follows.


Left: Periapical radiograph indicating that the floor of the cavity distally at tooth #45 is short of the bony crest. Center: The situation immediately after placement of a direct composite resin restoration. Note that the restoration margin seems to be at the bony crest. Right: Situation after 1 year. There is again a distance between the margin of the restoration and the bony crest suggesting about 1 mm bone loss. (Frese et al. 2014. Artwork by authors.)

Intraoral evaluation revealed carious decay on the cervical margin of the cavity reaching beyond the CEJ [cemento-enamel junction]. The proximal margin was partly covered by overgrowing gingival tissue […]. Radiographic examination of tooth #45 revealed that there was no periapical translucency and that the distance between the cavity margin and the alveolar bone crest was between 0.5 mm and 1.0 mm […]. As the proximal cavity margin was already beyond the CEJ invading biological width [sic!], it was assumed that after caries removal it would be located at the level of the alveolar crest. It was explained to the patient that the gold-standard treatment [sic!] would be placement of an indirect partial or full crown [sic!] in combination with surgical or orthodontic pretreatment. Alternatively, it was clarified [sic!] that if the marginal ridge was still intact, a direct restoration with composite resin could be an option. However, it was also explained that the outcome of this procedure would be less predictable than that of an indirect restoration. The patient [sic!] favored a restoration with direct composite resin to avoid surgical or orthodontic interventions.


Upper left: The clinical situation at tooth #45 before treatment. Note that gingival tissue has grown into the lingual part of the cavity. Upper central: Situation after excavation. The gingiva had been removed by electrosurgery (!) although authors claim that the cavity floor was close to the bone crest. Lower left: A retraction cord is placed soaked with an astringent paste to facilitate dryness. Lower right: Situation after proximal box elevation

There’s more than one way to skin a cat, and the most reasonable and, well, least invasive suggestion could have been proper surgical crown lengthening, re-evaluation after sufficient healing, and then placing a direct composite resin restoration. Since the patient had apparently lost the filling long time ago, there is no reason to hurry and do, as it turned out, quite complicated (see below) and in fact risky therapy maneuvers in just one session. Regardless unquestionable operative skills of Dr. Frese, suggesting placing direct composite resin restorations in these cases rather than lege artis routines to general practitioners is certainly misleading [4].

Authors used electrosurgery to remove gingiva which had grown into the lingual part of the cavity. The result can be seen in the upper right picture above. Using electrosurgery for pre-restorative preparation is generally discouraged. In particular in case of deep subgingival cavity margins it cannot be predicted if crestal bone was irreversibly damaged with delayed wound healing and even sequestration. In particular the authors’ note that “it was clear that the proximal cavity margin was close to the alveolar crest, making the application of a partial or circular matrix impossible,” is suspicious. The problem here is not so much whether a matrix band can be applied but whether bone has irreversibly been damaged. Further application of a not-specified “astringent retraction paste” in a cord in close contact with the bone for 2 min must be considered deleterious as well. When afterwards “proximal box elevation” was performed without a matrix band, etching the tooth surface with 37% phosphoric acid must not be regarded as biologically inert. Then, when applying the so-called snowplough technique, overhangs of composite resin are inevitable, and authors are fully aware of that. “[Overhangs] were removed carefully with a rotary diamond instrument […] and a scalpel.” I suppose that tap water spray rather than physiological saline  was used for rinsing, which is, in case of exposed alveolar bone, not recommended.


Upper left: Authors created a tight proximal contact area. Upper right: Clinical result immediately after placement of restoration. Lower left: Result after 1 year indicating some shedding of composite resin in the distal ridge area. Lower right: No pocketing at the distobuccal aspect of tooth #45

After having “elevated the proximal box”, placement of a matrix band was possible and authors spent considerable time to create a tight proximal contact area. The immediate clinical picture as well as control periapical radiograph show in fact an impressive result. The distal margin of the composite filling is actually at the bone level, as the central radiograph above shows. But at 1 year follow-up, there is an about 1 mm distance betwen resin and bone visible (right radiograph above). What the authors have noted, too, was that mother Nature helped herself and created a new proper distance between the composite resin and the bone. When authors speculate about epithelial attachment to resin, a close look at the distolingual aspect of their restoration would most probably have revealed that its margin was not even in a subgingival position any more. Authors admit in one paragraph that, after 12 months, there was “only a minimal loss of alveolar bone […] observed,” but in another (in the Discussion) that “no adverse reactions, such as chronic inflammation of soft and hard tissue, attachment loss, or bone resorption, were observed at the 12-month follow-up.” There was certainly bone loss (evident on radiographs) and attachment loss (not measured; authors provide an unsuitable picture of the buccal aspect of the tooth which was not restored).

Remains the answer to the authors’ question why “The reasons for individual variations in biological response to restorations below the CEJ that are invading biological width are yet unknown.” Well, the biological width is not related to the cemento-enamel junction but to the position of the gingiva. There are different periodontal phenotypes, and paradoxically biological width is easier violated in individuals with a thick periodontal phenotype. While individuals with a thin phenotype likely respond by gingival recession as was observed in the case by Frese et al. (2014), violation of the biological width in patients with a thick phenotype may result in chronic inflammation, pocketing, attachment loss, and bone loss. If, and only if, no gap between tooth substance and restoration material is present, a long junctional epithelium can be expected even on the resin surface. Animal experiments have clearly shown that that is possible,see, for instance, Martins et al. (2007). Gaps or overhangs will inevitably lead to changes in the composition of the microflora, and I want to refer here to the classic paper by Lang et al (1983).

So, while the present, highly complicated and time-consuming, procedure had yielded, unexpectedly, an auspicious result, it cannot be recommended for routine daily practice. In particular, use of electrosurgery with the risk of bone exposure is highly discouraged. A simple surgical crown lengthening procedure, sufficient time for wound healing, and careful restoration of the tooth with direct composite resin (rather than a crown), which is both easier and more predictable than the described procedure, must be considered the least invasive treatment. It is therefore the treatment of choice.


[1] Frese C, Wolff D, Staehle HJ. Proximal box elevation with resin composite and the dogma of biological width: Clinical R2-technique and critical review. Oper Dent 2014; 38: 22-31.

[2] See, for instance, Schmidt JC, Sahrmann P, Weiger R, Schmidlin PR, Walter C. Biologic width dimensions – a systematic review. J Clin Periodontol 2013; 40: 493-504.

[3] As a recent example, Martins TM, Bosco AF, Nobrega FJO, Nagata MJH, Barcia VA, Fucini SE. Periodontal tissue response to coverage of root cavities restored with resin materials: A histomorphometric study in dogs. J Periodontol 2007; 78: 1075-1082.

[4] That Frese et al. do not only want to present an interesting case with an auspicious outcome and some new observations but suggest to practitioners their approach may be derived from a translation and slight modification of the entire article in the German Federal Dental Association’s magazine Zahnärztliche Mitteilungen, see pdf here.

12 March 2014 @ 2:02 pm.

Update 16 March 2014. As I have just learned the present case report is prominently featured on the cover of a new book published by Quintessenz Verlag which apparently deals with controversies in restorative dentistry. I suppose the author, H. J. Staehle, is eagerly inclined to provoke vital discussions about pros and cons of his unconventional approach, so comments to the above are welcome.


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