Patients will frequently present with both thick and thin periodontium in the same dentition. Canines and mesiobuccal roots of maxillary molars tend to have a thin periodontium due to their position in the dental arch. Central incisors are usually associated with thick periodontium. As a general rule, the prevalence of thick periodontium is more common in males than in females, in younger patients than in older patients, in the maxilla than in the mandible, and in white patients (72% to 88%) than in patients of Asian descent (< 40%). These differences are due to intra- and interindividual variations in conjunction with tooth type, tooth shape, tooth position, and genetic determinants.90,94–99
The thick phenotype is commonly associated with periodontal durability and health. It is characterized by dense fibrotic gingival tissue, a wide band of keratinized tissue, and flat soft tissue with thick underlying bony architecture. The thin phenotype is usually associated with delicate and friable gingiva that is almost translucent in appearance, a narrow band of keratinized tissue, and highly scalloped soft tissue with thin or minimal underlying buccal bony thickness86–93 (see Table 1-1).
Clinical implications of tissue phenotype
The clinician should be able to correctly identify and categorize these two distinct gingival phenotypes. Differences in gingival and osseous architecture have been shown to have a significant impact on treatment outcomes. Accordingly, thin and thick phenotypes behave differently when subjected to inflammation, tooth extraction, and surgical trauma93 (Table 1-2). They also respond differently to restorative, periodontal, implant, and orthodontic therapy.41,60,86,89,90,92,93,97,100–107
Table 1-2 Clinical implications of gingival phenotype*
| Thin phenotype | Thick phenotype | |
|---|---|---|
| Inflammation | ||
| Soft tissue | Gingival recession without pocket formation | Marginal inflammation with pocket formation, bleeding on probing, and edema |
| Hard tissue | Loss of the thin vestibular bone plate | Formation of intrabony defects |
| Surgical procedures | ||
| Osseous surgery | More susceptible to gingival recession | Marginal periodontal tissue shows a tendency to grow in a coronal direction |
| Mucogingival surgeries | Associated with partial root coverage | Associated with complete root coverage |
| Guided tissue regeneration | Greater postoperative recession | Less postoperative recession |
| Orthodontic treatment | Greater risk of developing soft tissue recession | Prevents or minimizes soft tissue recession |
| Implant therapy | More susceptible to marginal bone loss, angular bone defects, and recession | Maintains stable crestal bone and is less prone to recession |
| Restorative procedures | Restoration may be slightly visible through the thin soft tissue | May mask discoloration from metal-ceramic restorations with metal collars and disappearing margins, metal implant abutments, and discolored roots |
| Extractions | Extensive ridge resorption | Minimal ridge resorption |
*Data compiled from multiple studies.41,59,90,92,93,100–107
Gingival recession
A major clinical challenge is gingival recession around ceramic veneers and complete-coverage restorations when the finish line is placed subgingivally. Many etiologic factors have been proposed as the cause for recession. Faulty restorative margins, mechanical and chemical irritants from impression procedures, overcontoured restorations, incomplete removal of excess cement, violation of biologic width, or adverse gingival reactions to alloys used in the oral cavity have all been implicated.92 Patients with thin gingival phenotype are more susceptible to such recession. Gingival grafting should be considered prior to restoration to modify the phenotype to a thicker state.
Gingival inflammation
The thin phenotype reacts to insult by initial gingival inflammation followed by gingival recession, while the thick phenotype responds by tissue proliferation and eventual formation of a periodontal pocket. This is probably due to the fact that a thick periodontium has a greater volume of soft tissue than the thin periodontium, with attachment loss leading to development of a periodontal pocket instead of recession.92
Surgical periodontal therapy
During the healing stages following osseous resective crown lengthening surgery, the marginal periodontal tissue shows a tendency to grow in a coronal direction. This pattern of coronal displacement of the gingival margin is more pronounced in patients with a thick periodontium compared with those with a thin periodontium phenotype.41 In the context of osseous surgery, it is extremely important to make a distinction presurgically between flat and scalloped gingival architecture. Usually, markedly scalloped soft tissue architecture would be more challenging in terms of pocket recurrence than flat architecture in the interproximal area. This is especially true if the gingiva takes on a scalloped architecture while the underlying osseous tissue does not follow the same scalloped pattern, resulting in greater distance between the tip of the papilla and the crest of the bone, leading to the formation of interproximal pocket depth.86
For mucogingival surgery such as the coronally positioned flap, it has been shown that greater initial thickness of gingival tissues (> 0.8 to 1.1 mm) is positively associated with complete root coverage. The probabilities of obtaining better root coverage outcomes are strongly related to the marginal tissue thickness.108,109 Tissue thickness is also an important factor to be considered during regenerative procedures around teeth. Tissue thickness greater than 1 mm led to less postoperative recession at 6 months compared with thin tissue (0.6 vs 2.1 mm).102
Orthodontic therapy
The development of gingival recession during orthodontic treatment is a major concern as well. Alterations of the mucogingival complex are inevitable during orthodontic therapy, but the important factors to consider are the direction of the tooth movement and the thickness of the buccal gingival tissue. Movement of the tooth in the lingual direction will result in increased thickness of the gingival tissue on the facial aspect. It will also result in coronal migration of the free gingival margin. Movement of the tooth in the facial direction will result in reduced tissue thickness and migration of tissue apically, resulting