Miller Classification of Marginal Tissue Recession Revisited After 35 Years

The original article on classification of marginal tissue recession, published more than 30 years ago, described four classes of recession.¹ The common feature of Miller Class I and Class II recession was no loss of interdental bone or soft tissue, and complete root coverage could be predictably achieved. The difference between a Class I and Class II recession was based on whether or not the recession extended to or beyond the mucogingival junction (MGJ).

However, in the original article, the distinction between attached and unattached gingiva was not emphasized. Miller Class III recession pointed out two scenarios in which complete root coverage could not be achieved. One was an extruded tooth with no interdental bone or soft-tissue loss and the other was associated with loss of some interdental bone and soft tissue that limited the amount of root coverage that could be achieved. Newer surgical techniques now allow the clinician to sometimes attain complete root coverage when interdental bone loss exists. In Miller Class lV recession, the interdental recession was described as being severe and the papilla absent, which meant that root coverage was unachievable.

Currently, dentistry also has a more complete understanding of the role of interdental papilla. This article presents a new classification of papilla form that points out the significance of the width and height of the papilla. Also, because there is some confusing periodontal terminology that warrants a revisit, a new classification of these terms-intended to be an updated, more accurate description of the terminology-will be presented (Table 1). The author will use these terms throughout the article.

When the original classification of marginal tissue recession was published, the emphasis in periodontics was on the treatment of disease and not esthetics.¹ Non-disease surgery was referred to as mucogingival surgery.² The concept of periodontal plastic surgery had just been introduced and periodontics was entering a new era.³

The focus of mucogingival surgery was to produce a functional result, while the emphasis of periodontal plastic surgery was to achieve not only a functional result but an esthetic one as well. At that time, the options for treating marginal tissue recession were limited and included the laterally positioned flap (LPF), coronally positioned flap (CPF), and epithelialized palatal graft (EPG).^4-6

While both the LPF and CPF produced a very pleasing esthetic result, the EPG had major drawbacks. Not only did it require a second surgical wound, but also the color variation was apparent and it often resulted in tissue with a keloid appearance.

A significant breakthrough came with the presentation of the subepithelial connective tissue graft (SCTG).^7,8 In this technique, the graft was covered by an overlying flap providing bilaminar circulation and additional blood supply that enhanced graft survival.⁹ The graft was harvested from within the palate, reducing palatal discomfort. Currently, allograft and xenograft materials are being substituted for the patient's tissue, thus avoiding the palatal wound. The status of allograft and xenograft materials is outlined in the report from the 2014 American Academy of Periodontology Regeneration Workshop.¹⁰

With current advances having been made in surgical techniques, there is a need to revisit Miller's original classification. A new classification of the papilla is added.

In Class I and Class II recession, there is no loss of interdental bone or soft tissue, and complete root coverage is expected. The difference between these two classes is the presence or absence of attached gingiva (Figure 1). Class I recession was originally described as recession that does not extend to the MGJ. While this is true, the distinction between attached and unattached gingiva was not emphasized. If gingiva was present on the facial, it was considered a Class I recession. In reality, if the gingiva is unattached, there is "hidden recession," and this is actually a Class II recession (Figure 2).¹¹ Therefore, in sites where gingiva is present on the facial, it is necessary to probe to determine whether the gingiva is attached or unattached.

While complete root coverage is attainable in both Class I and Class II recession, different treatment modalities may be indicated. For example, if adequate keratinized tissue is present in a Class I recession, the simplest root coverage procedure, CPF, may be indicated, whereas in a Class II recession some type of soft-tissue grafting would be required. The CPF often can be done in a Class I recession but not in a Class II. Treatment of a Class II recession requires more complicated grafting procedures. Combining Class I and Class II into a single classification could be detrimental to the understanding of the clinician attempting root coverage. In the author's view, a new classification of recession presented at the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions¹² that combines Class I and Class II did not take this into consideration.

Class III recession was originally described as interdental loss of bone and/or soft tissue or extrusion of the tooth. Only partial root coverage could be attained. By undermining and elevating the papilla using the tunneling technique,^13-15 further root coverage can be gained in certain Class III recessions (Figure 3 and Figure 4).

When the original classification article was written, the emphasis of periodontal treatment was on health and function rather than esthetics. The images in the original article showed only Class III recessions with no attached or unattached gingiva. Often the root exposure was an esthetic problem rather than a functional one, and attempting even partial root coverage was not considered.

In Class IV recession, regardless of severity of recession, root coverage cannot be achieved because there is no papilla (Figure 5).

In 1992, Tarnow et al showed that the height of a normal interdental papilla was 5 mm coronal to the crest of the bone interdentally.¹⁶In 1998, Nordland and Tarnow published a classification of papilla recession as it relates to the cementoenamel junction (CEJ).¹⁷However, it is a 1-dimensional description that does not take into account the width or facial-lingual dimension of the papilla. With the advent of the tunneling technique, the volume of the papilla takes on greater significance, particularly regarding the mesial-distal width of the papilla at the line angle of adjacent teeth. A papilla with adequate size within the facial-lingual area provides a greater blood supply for the graft. This contributes to improved proximal root coverage in Miller Class III sites.

Based on the author's observations and as he has previously presented on various occasions, papillae can be divided into three types: A, B, and C (Table 2). Type A and type B are similar in that there is no interdental bone loss. The papilla extends 5 mm coronally to the crest of the interdental bone.

The difference between the two is the width of the papilla. A type A papilla is ≥3 mm wide at its base (Figure 6) and a type B papilla is <3 mm wide (Figure 7). In type C papilla, there is either interdental bone loss or the tooth is extruded (Figure 8). Whenever there is interdental bone loss, the papilla is always a type C.

Where there is interdental bone loss, the papilla may extend ≥5 mm coronal to the crest of interdental bone. Determining a type C papilla can be challenging because the papilla form may not necessarily follow the bone form. Because there is bone loss in the interdental area and the papilla has not receded, the recognized 5 mm dimension may be greater and there is hidden recession in the interdental area. The distinguishing feature is that there is loss of interdental bone. The width of a type C papilla may be ≤3 mm. Clearly, a wider papilla is more desirable.

Class I and Class II recessions have either a type A or type B papilla. A Class III recession has a type C papilla, and a Class IV recession has no papilla. Type A papillae provide a favorable environment for graft survival, while type B papillae provide a more limited source of blood supply and stability as their width narrows, thereby reducing predictability of complete root coverage.

In the maxillary anterior, unless teeth are malaligned, the width of a type A papilla is ≥3 mm. Conversely, in the mandibular arch the papilla is seldom this wide, especially when the mandibular anterior teeth are crowded. The papilla width, height, and distance from the bone crest impact the amount of root coverage that can be achieved in Class III recession sites. Clinical experience shows that adequate papilla width is necessary for providing sufficient blood supply and tissue volume for placing a suture.

With the advent of the tunneling technique and subsequent modifications allowing coronal positioning of the tunnel and elevation of the papillae, complete root coverage of mild Class III recessions has become possible.^13,18-20 The papilla form becomes an important factor in such sites.  In addition to the features of a type C papilla described above, the papilla needs to have sufficient volume facial-lingually to survive the coronal movement. In an ideal setting, up to 2 mm of vertical papilla gain may be achieved. The advantages of the tunneling technique include complete coverage of the graft, the undermining and elevation of the interdental papilla, and the avoidance of external vertical or horizontal incisions.

P.D. Miller, DDS

Clinical Professor, Medical University of South Carolina, Charleston, South Carolina; Fellow, International Society of Periodontal Plastic Surgeons