Research Progress of Alveolar Bone Characteristics in the Lower Incisor Area with Class III Malocclusion Volume 61- Issue 4

Li Li Xie*

• Head of orthodontic department, Hebei General Hospital, Shijiazhuang, China

Received: April 24, 2025; Published: May 01, 2025

*Corresponding author: Li Li Xie, Head of orthodontic department, Hebei General Hospital, Shijiazhuang, Hebei province 050057, China

DOI: 10.26717/BJSTR.2025.61.009635

Abstract PDF

Class III malocclusion has a serious impact on the appearance of patients and is a difficult type for orthodontic. This article reviews current research on the characteristics of alveolar bone in the lower incisor area with Class III malocclusion, to explore the ways for improving clinical treatment efficiency. The current research mainly uses cephalometric measurement and CBCT to study the thickness and height of alveolar bone, as well as the relationship between incisors and orthodontic treatment. However, there is no unified conclusion on the specific characteristics of alveolar bone in Class III malocclusion, except for narrow alveolar bone morphology and low bone mass in the incisor area. Whether it is orthodontic compensation treatment or orthodontic orthognathic combined treatment, the movement range of the upper and lower incisors in the alveolar bone should be considered. Therefore, studying the alveolar bone characteristics of Class III malocclusion can help develop healthy orthodontic plans and improve orthodontic outcomes.

Keywords: Class III Skeletal Malocclusion; Lower Incisor; Characteristics of Alveolar Bone; Bone Cracking and Fenestration

Class III malocclusion is a common clinical case with a family heredity. 14.98% of patients with skeletal Class III malocclusion in the permanent dentition period in China [1], and the incidence rate of skeletal Class III malocclusion reported abroad is 15.69% -19.9% [2]. Class III malocclusion is characterized by anterior crossbite, mesial molar relationship, mandibular protrusion, midface dificiency, and vertical excess of the lower face. This morphological pattern damages facial aesthetics and may have adverse effects on mental health. In severe cases of malocclusion, the lack of functional anterior bite contact can result in impaired food cutting ability and reduced chewing efficiency due to the excessive reverse overjet of anterior teeth. Therefore, there is an urgent desire for orthodontic in patients with Class III malocclusion. The orthodontic treatment methods and effects of Class III malocclusion are closely related to the range of movement of the lower incisor in the alveolar bone. Exploring the morphological characteristics of the alveolar bone in the lower incisor area can avoid the risk of insufficient alveolar bone mass [3]. There is no unified conclusion on the specific characteristics of alveolar bone in Class III malocclusion, except for narrow alveolar bone morphology and low bone mass in the incisor area. This article provides a review of the alveolar bone characteristics of lower incisors with Class III malocclusion, in order to provide assistance for orthodontic treatment plans.

1. Current research suggests that the alveolar bone mass of lower incisors with Class III malocclusion is narrower than that of Class I malocclusion [4-6], the thickness of the labial bone is thinner than that of the lingual. Skeletal Class III subjects with high mandibular plane angles showed thinner mandibular alveolar bone in most areas compared to normal or low angle subjects. Mandibular plane angle was negatively correlated with buccolingual alveolar bone thickness [5].This developmental feature is believed to be related to the reduced chewing efficiency of anterior malocclusion in Class III malocclusion [2], and as the mandibular plane angle increases, the strength of the chewing muscles further decreases [7], which may lead to insufficient alveolar bone development and compensatory continuous eruption of the mandibular incisors [8,9], the thickness of the alveolar bone at the apical level becomes relatively narrower[10].Research suggests that the reduction in alveolar bone thickness on the labial and lingual sides compensates for vertical abnormalities and achieves relatively normal occlusion [11,12]. However, it should be noted that as facial height increases, the thickness of the alveolar bone of the mandibular anterior teeth decreases [13], and the range of movement of the lower incisors in these patients is smaller [14], making it more difficult to design orthodontic treatment plans. At the same time, we found that the conclusions about the alveolar bone height of lower incisors with Class III malocclusion are inconsistent. Although many scholars [15-18] have found that the vertical bone height in the lower anterior tooth area is reduced in patients with skeletal Class III malocclusion, other studies suggested that the bone height of the lower incisors is not affected [19]. As some scholars have found, the vertical bone loss of the lingual anterior teeth is more severe than that of the labial side [16], while other scholars believe that the height reduction of the alveolar bone on the labial side is more significant [17]. These differences conclusions are likely due to differences in sample selection.

2. The correction of Class III malocclusion is closely related to alveolar bone mass and the inclination of the lower incisors, but the conclusions are also unconsistent. When the mandibular plane angle increases, the inclination of the lower incisors tends to decrease [20], showing compensatory lingual inclination [21], and the root angle of the mandibular anterior crown is significantly larger than that of Class I and II malocclusion [22]. However, how does the inclination of the lower incisors affect the morphology of the alveolar bone? The more parallel the long axis of lower incisors is to mandibular chin axis, the greater thickness of the alveolar bone and cortical bone [23,24]. Jain et al. [25] found that the labial inclination of the lower incisors is positively correlated with the thickness of the lingual alveolar bone in the apical region. Different conclusions suggest that the labial alveolar bone morphology of lower angle Class III malocclusion is positively correlated with the inclination of incisors, and there is no statistical difference on the lingual bone [26]. The thickness of lingual cancellous bone decreased along with increase of the angle of tooth inclination. [27]. At this point, we should fully consider the relationship between teeth and bone [28], and alveolar bone mass may continue to decrease during treatment, especially in the neck of lingual teeth [29]. Therefore, it is currently believed that the more severe the lingual inclination of the lower incisors, the greater risk of root resorption during orthodontic [13]. Although alveolar bone can be reshaped with the movement of teeth [30], optimal remodeling of alveolar bone can only occur when the incisors are within the normal angle range [31], and the speed of bone remodeling is slower than the speed of tooth movement. When designing orthodontic routes for incisors, priority should be given to the positional relationship between the root of the tooth and the alveolar bone [32]. When the alveolar bone is insufficient, the tipping movement of the lower incisors makes it easier for the root apex to come into contact with cortical bone, which is the cause of bone resorption, bone fenestration, and root resorption [9,33,34]. In addition, when the attachment height of the alveolar bone decreases, the resistance center of tooth movement will change, accelerating the approach between the tooth root and cortical bone, leading to tooth root resorption [35], and increasing the tendency of tooth recurrence after orthodontic treatment [36]. The morphology of the alveolar bone in the lower incisor area directly affects the development of orthodontic planning and treatment progress [37]

3. It is because of the recognition of these risks that scholars are paying more attention to the relationship between the characteristics of Class III malocclusion alveolar bone and lower incisors. Yagci, et al. [38] analyzed skeletal Class I, II, and III malocclusions using CBCT and concluded that lower alveolar bone in Class III malocclusions is more prone to defects. Yang Hua [39] has found that bone loss is more common in the 1/2 area of the anterior teeth with Class III malocclusion. The 1/3 neck of the lower anterior tooth root corresponds to the alveolar bone and root apex area, which may be a sensitive area for orthodontic bone window opening and dry fracture [22]. We look forward to evaluating the morphological characteristics of alveolar bone, especially for high angle cases, before developing orthodontic treatment plans for Class III malocclusion, and through pre evaluating the range of motion of the lower anterior teeth, [40] we can ensure that the root of the lower incisors within the safe range of alveolar bone remodeling, thereby reducing the risk of periodontal tissue or root damage [5].

The treatment plan for Class III malocclusion is closely related to the tipping of lower incisors and alveolar bone, thus exploring the movement of the lower incisors and the remodeling rules of the alveolar bone can reduce the risk and improve the effectiveness of orthodontic treatment.

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