Clinical Cases in Periodontics. Группа авторов

gingival inflammation and attachment loss. Restorative margins are most compatible with the periodontium when located either supragingivally or at the level of the gingival margin. Should the restorative margin violate the biologic width, the resulting inflammatory process may lead to gingival recession, bone loss, and exposure of the restorative margin. The restorative contour (e.g. crown contour) should follow the root surface contour rather than accentuating the cervical bulge to support periodontal health. In the case of bridges, the design of the pontic can affect its ability to be cleaned and hence the periodontal health of the teeth (Figure 1.7.14).

      B. A furcation is an anatomic area where the roots of a multirooted tooth start to diverge. Mandibular molars and maxillary first premolars are bifurcated because they each have two roots. Maxillary molars are trifurcated because they each have three roots.

      A furcation consists of two parts: (i) root separation area, where alveolar bone begins to separate the roots, and (ii) fluting area, the part of the root that is directly coronal to the root separation area.

      There are often concavities in the furcal side of the roots. In mandibular molars, all the mesial roots have concavities on the furcal side, with each concavity averaging 0.7 mm in depth [13]. Likewise, 99% of the distal roots of mandibular molars have concavities on the furcal side, with an average depth of 0.5 mm [13]. The root trunk, which is the distance from the CEJ to the level of root separation, is about 4.0 ± 0.7 mm in mandibular first molars [13,14].

      In maxillary molars, 94% of the mesiobuccal roots have concavities on the furcal side, with each concavity averaging 0.3 mm in depth [15]. Roughly one‐third (31%) of the mesiodistal roots and one‐quarter (17%) of the palatal roots have concavities, and each concavity is about 0.1 mm in depth [15]. The lengths of root trunks of maxillary molars are 3.6, 4.2, and 4.8 mm on the mesial, buccal, and distal surfaces, respectively [16,17].

Figure 1.7.14 Overhangs on the mesial and distal of tooth #30 that may eventually lead to bone loss on the mesial and distal of #30.

      All bifurcated maxillary first premolars have a mesial and distal root trunk of about 8 mm. In addition, almost all the buccal roots have “developmental depressions” also known as “buccal furcation groove” present at the 9.4‐mm level on the furcal side [18,19].

      Furcation invasion is defined as a loss of attachment within a furcation. When there is a loss of clinical attachment, the presence of concavities on these roots at furcation will hinder effective plaque control at these areas.

      C. There are a number of different classification systems of furcation invasion. The three most commonly used systems are as follows.

       Glickman Classification

      The Glickman classification [20] describes both the vertical and horizontal components of the furcation invasion.

Grade I	Pocket formation into the fluting area but with intact interradicular bone.
Grade II	Pocket formation into the root separation area with interradicular bone loss that is not completely through to the opposite side of the furcation.
Grade III	Same as grade II but with through‐and‐through interradicular bone loss (the soft tissue still covers part of the entrance of the furcation).
Grade IV	Same as grade III but with gingival recession making furcation clinically visible.

       Hamp Classification

      The Hamp et al. classification [21] describes the horizontal component of the furcation invasion.

Degree I	Horizontal bone loss going into the furcation <3 mm.
Degree II	Horizontal bone loss going into the furcation >3 mm but not to the opposite side.
Degree III	A through‐and‐through horizontal bone loss in the furcation.

       Tarnow and Fletcher Classification

      The Tarnow and Fletcher classification [22] describes the vertical component of the furcation invasion.

Subclass A	Vertical attachment loss 0–3 mm in furcation.
Subclass B	Vertical attachment loss of 4–6 mm in furcation.
Subclass C	Vertical attachment loss of >7 mm.

      D. The most effective way to diagnose a furcation invasion is to use a combination of clinical examination and radiographic evaluation. The clinical examination involves using periodontal and furcation probes to detect the furcation invasion.

Radiographs must be taken with a paralleling technique to minimize distortion of the images. Note that radiographically the palatal root of maxillary molars may leave a grade III furcation invasion undetected due to the overlapping of the palatal root with mesiobuccal and distobuccal roots. In addition, the presence of a furcation arrow (a triangular shadow seen at either the mesial or distal roots in the interproximal area on maxillary molars) may possibly suggest the presence of grade II–III furcation invasion on maxillary molars [23] (Figure 1.7.15). The more extensive a given furcation invasion, the higher the likelihood of observing the furcation arrow. However, it must be noted that the absence of furcation arrow does not necessarily suggest the absence of a furcation invasion.

      Generally, interproximal surfaces of the maxillary molars are more prone to furcation invasion than buccal surfaces [24].

Figure 1.7.15 Furcation arrow (red arrow) is showing furcal involvement on the mesial of #14 radiographically.