typically healing in a routine and uneventful manner. The effects of tooth loss in humans can perhaps best be understood when viewed at three related levels, namely: local site effects, effects on the individual, and effects on the population (Figure 5.1). The effects of tooth loss on the site, individual, and population levels have a profound influence on clinical decision‐making and treatment strategies. While the site of the extraction heals in a predictable manner, the impact of the loss of the tooth on the individual can be quite variable. There is considerable evidence relating tooth loss to diminished oral health‐related quality of life at the population level, and in addition a more heterogeneous experience can be found at the individual level [1].
Figure 5.1 Tripartite effect of tooth loss.
5.1.1 Local Site Effects of Tooth Loss
The loss of a tooth or teeth initiates a dynamic sequence of events resulting in marked changes to the surrounding alveolar process of the jaw, largely a tooth‐dependent structure [2], while causing little change to the underlying basal bone. The gradual pattern of bone resorption in the mandible is depicted in Figure 5.2, which shows the contour changes from the dentate state (image on lower left) to advanced alveolar bone loss (image on upper right).
Figure 5.2 Resorption patterns of the mandibular edentulous ridge (note the significant reduction of the alveolar process with lesser change of the underlying basal bone).
Immediately following tooth extraction, the residual socket fills with blood and a clot is formed [3, 4]. The blood clot occupying the volume of the socket is rapidly remodelled within the first week following extraction, with granulation tissue rich in vascular structures, fibroblasts, and inflammatory cells beginning to fill the socket [3, 5]. Connective tissue begins to replace granulation tissue between the first and third weeks post‐extraction [3, 5, 6]. The epithelium then migrates across the underlying connective tissue at this time, soon closing the orifice of the extraction socket. The granulation tissue and connective tissue is gradually replaced by a primary matrix and woven bone at approximately six weeks post‐extraction, with the socket predominantly containing primary matrix and woven bone by weeks 12–24 [3, 5]. While initial tissue modelling in the extraction socket is a relatively rapid process, remodelling of woven bone into lamellar bone requires more time, with little observation of the lamellar bone being present at 12–24 weeks post‐extraction [5]. Figure 5.3 depicts how the healing process of the extraction socket evolves over time.
Figure 5.3 Progressive healing of extraction socket. BC, blood clot; GT, granulation tissue; CT, connective tissue; PM, provisional matrix; WB, woven bone.
This return to tissue homeostasis does not prevent alterations to the local hard and soft tissue contours following healing, as the resulting residual ridge architecture is diminished in both horizontal and, to a lesser degree, vertical dimensions (Figure 5.4). The clinical reduction of alveolar ridge width upon healing was found to be 3.87 mm on average, while the clinical vertical reduction was 1.67 mm [7]. The alteration of the residual ridge width is most pronounced on the buccal aspect [8, 9]. This observed pattern of resorption often results in a narrower and shorter ridge that is relocated to a more palatal or lingual position relative to its pre‐extraction condition [10]. This pattern of bone loss may have a direct influence over the subsequent positioning of any replacement teeth proposed, both for functional and aesthetic purposes.
Figure 5.4 Hard and soft tissue healing of a single tooth extraction. (a) Clinical photograph of UR4 prior to atraumatic extraction and (b) four months following extraction. (c) Radiographic image of UR4 prior to extraction, and (d) four months following extraction.
The alteration of soft tissue dimension following tooth extraction happens more rapidly than that of the hard tissue, with more than 50% of the changes observed in the first two weeks following extraction [11]. In the pre‐extraction condition, no significant correlation has been observed between soft tissue thickness and the buccal bony wall thickness under the tissue [12]. Soft tissue thickness generally tends to increase, sometimes quite substantially, following tooth extraction in subjects with the more common thin buccal bony wall phenotypes [11, 13]. This thickening of the soft tissues may mask an underlying deficient bony ridge. Conversely, subjects exhibiting thicker bony wall phenotypes do not exhibit changes in the facial soft tissue thickness from the pre‐extraction condition [11].
Changes in hard and soft tissues following extraction of a tooth may be further exacerbated by systemic factors such as smoking [14]. Local site‐specific factors include the pre‐existing condition of the tooth and surrounding tissue, the number and proximity of teeth being extracted, the number and proximity of teeth remaining, the condition of the extraction socket after tooth removal, the influence of hard and soft tissue biotype, and the use of an interim prosthesis [15].
5.1.2 Effects of Tooth Loss on the Individual Level
There is variability not only in the way which individuals heal from an extraction of a tooth, but also how the individual responds to the loss of the tooth from a functional, emotional, and quality of life perspective. While initial soft tissue healing occurs consistently during the first few weeks post‐extraction in almost all individuals, there is a greater variability in the period of time during which mineralised bone is formed in the socket [5]. Tooth loss in general can be the cause of functional or aesthetic impairment, creating difficulties in chewing efficiency, phonetics, or aesthetic challenges, depending upon the location and number of teeth lost (Figure 5.5). Notably there is strong evidence that the distribution and location of tooth loss has an impact on the oral health‐related quality of life. Oral health‐related quality of life scores tend to drop sharply when lacking a minimum number of occluding pairs of teeth (10 occluding pairs) or total remaining teeth (20 teeth) [1], consistent with the concept of a shortened dental arch [16]. Studies on the impact of tooth loss on an individual's quality of life consist of pooled data reported at the population level and thus may mask heterogeneous data at the individual level. There appears to be wide variation in the emotional response to tooth loss among individuals that cannot be linked closely to the distribution or number of teeth lost [17].
