Ectopic eruption of the first permanent molar is a common malocclusion in the early stage of mixed dentition. The incidence among children aged 6-10 years is 0.83%-8.7%, with an increasing trend. The main manifestation is mesial impaction of the first permanent molar during eruption, which is accompanied by the loss of root resorption and space loss of the second primary molar. Ectopic eruption of the first permanent molars can lead to underdevelopment of the dental arch and severe crowding of the posterior dentition. Prevention and early intervention are very important. The ectopic eruption of the first permanent molar is related to the disruption of the differential growth and developmental balance among the teeth, alveolar bone and jaw. In clinical practice, the diagnosis can be made according to the patient's medical history and clinical and imaging examinations, and the treatment can be performed by dividing the teeth, dividing the distal slices of the second primary molars, and distally moving the first permanent molars. This paper reviews the incidence, etiology, clinical manifestations, risks of ectopic eruption of the first permanent molar, diagnostic methods, and common treatment options to provide references for clinical treatment.

Traumatic dental injury (TDI) in children and adolescents has become one of the most serious problems in public health. TDI has relatively high prevalence, broad etiology, which may influence esthetic and function of involved teeth, resulting in economic loss and affecting life quality. The prevalence of TDI increases with children’s age. Males suffer from TDI more easily than females. Maxillary central incisors are most commonly affected. Luxation and enamel fracture are common types of TDI. The main causes of TDI include fall, collision, sport, violence and accident. Overjet, lip incompetency and caries may be risk factors of TDI. According to risk factors of TDI, appropriate prevention measures need to be taken, which is the key of preventing TDI.

The pulpal or periapical diseases of immature permanent teeth often lead to incomplete root development. It is a challenge for us to figure out how to ensure the continuous growth of the teeth and the formation of roots. There are many cases about pulp regeneration reported recently. With the regeneration and differentiation ability of stem cells, which exist in residual pulp tissue, periapical and periodontal tissues, the regeneration of new vital pulp tissue was induced under proper conditions, which is highly vascularized and rich in connective tissue, thus prompting continuous root growth and development, increasing root length, thickening root canal walls, and facilitating the coarctation of the apical foramen. Besides, clinical and radiographic examinations shows successful results about the regenerative treatment, which is of milestone significance. The pulp regeneration treatment is designed to replace the pathological dental pulp tissue with new regenerated pulp tissue, based on biological tissue engineering process. This process includes two key parts: one is pulp revascularization, regenerating new vital pulp tissue in the root canal to achieve the continuous root growth and development; the other is tissue engineering, new pulp dentin complex is regenerated by the stem cells under the induction of suitable biological active scaffolds and growth factors. This article reviews about the research progress and clinical characteristics of aforementioned two key parts.