This study focused on isolated congenitally missing permanent canines, a complex condition influenced by polygenic inheritance, as well as environmental and epigenetic factors. The genetic patterns of congenital tooth agenesis may include autosomal dominant, autosomal recessive, or X-linked inheritance [14]. Research [15] indicated that EDARADD (c.308 C > T, p.Ser103Phe) and COL5A1 (c.1588G > A, p.Gly530Ser) were specifically associated with canine agenesis. A study [16] on a family with congenital maxillary canine agenesis identified ITGAV as a potential pathogenic gene. Whilst, some studies suggested that the absence of maxillary canines were associated with WNT10A gene [17,18,19,20].

In this study, the overall prevalence of CMPC was 0.69%. In the younger age group, the prevalence of CMPC was 0.57%, aligning closely with findings of Qiu (0.51%) [10] and Davis (0.45%) [9] in China. A Study [11] has also reported CMPC in the orthodontic population in Israel, with a prevalence of 0.76%. It is speculated that racial factors significantly influence this process. Research findings [21] indicated that racial differences exist in the occurrence of congenitally missing teeth. Genetic processes such as genetic drift, gene flow, and natural selection lead to variations in genomic compositions among different races and populations [22].The variations from other studies may also be attributed to differences in regional populations, sample sizes, and sample selection. Samples from specialist hospitals were more likely to detect missing teeth. Different complaints for dental visits before and after the expected eruption age of permanent canines should be considered. Younger children were less likely to have chief complaint of non-eruption of canines, which could better indicate the true prevalence of CMPC. Research [23] has shown that mandibular canines erupt at approximately 9 years of age, whereas maxillary canines erupt at approximately 10 years of age, with an average of approximately 10.1 years or 121 months. This study categorized participants into two groups based on the age of 121 months. The significantly greater prevalence of CMPC in older children(1.08%), which is twice that of younger children(0.57%), may be attributed to parents observing no eruption of their children’s canines and prompting them to seek medical attention. The result in older age group (1.08%) was similar to those(0.76%) in orthodontic patients reported by Finkelstein [11].

Previous research has indicated a predominance of females in cases of Hypodontia [3]. Whilst, this study demonstrated no gender predominance for CMPC, aligning with earlier findings [10]. Nonetheless, a study suggested that women were more affected by CMPC and that CMPC differed from hypodontia, exhibiting different gender tendencies [6].

No significant difference was found in the prevalence of CMPC between the left and right sides, which is consistent with previous research [10]. CMPC are more frequently found in the maxilla, which is consistent with the findings of previous studies [5,6,7, 9, 11, 12]. Some studies have reported [6, 7] a greater prevalence of congenitally missing left maxillary canines. Cleft lip and alveolar anomalies are more likely to affect the maxilla and may be associated with dental abnormalities [21]. It’s suspected that CMPC were more prevalent in the maxilla, likely for similar reasons. However, right mandibular dominance has been reported in CMPC, which remains unexplained [6]. In this study, of the 4 quadrants, maxillary canines were more commonly affected than mandibular canines, with no other similar site dominance observed.

CMPC typically involved the absence of one or two permanent canines with persistent primary canines, with no cases exceeding the absence of three found in this study. However, previous studies have reported cases in which three to four permanent canines were congenitally missing [6, 10]. This discrepancy may be attributed to the extremely low prevalence of congenitally missing mandibular permanent canines. This study found that 89.42% (93/104) of the missing permanent canines had visible primary canines in patients with CMPC, aligning with Qiu’s research [10]. The absence of permanent successors delayed normal resorption of primary tooth roots, resulting in primary teeth being retained for 40 or 50 years [3].

The presence of associations among various tooth anomalies is significant in clinical practice [24], as the early detection of one anomaly may suggest an increased risk for additional anomalies [25]. A total of 58.33% of patients with CMPC had no other dental abnormalities. There was a suspicion that CMPC demonstrated a tendency toward isolated absence. Among 58 accompanying permanent tooth absence, second premolars (39.66%) were most observed, followed by first premolars (25.86%) and lateral incisors (22.41%). These characteristics were consistent with those observed when these anomalies occur independently. 7 patients with CMPC exhibited microdontia of maxillary lateral incisors. Microdontia and hypodontia exhibit significant and intimate genetic associations [26]. Additionally, a rare combination of abnormal tooth numbers was observed in 3 patients with CMPC, who also presented with supernumerary teeth in the maxilla. Disturbances in the differentiation, migration and proliferation of neural crest cells are associated with interactions between epithelial and mesenchymal cells during odontogenesis initiation and may be responsible for “concomitant hypo-hyperdontia” [27, 28].

In multistage restorative therapy for CMPC, many factors should be considered, such as the early diagnosis of agenesis, malocclusion and the facial skeleton. Ephraim [29] et al. emphasized the impact of the congenital absence of teeth on developing dentition, underscoring the significance of early diagnosis of mixed dentition to prevent malocclusion from evolving. Primary canines, when not replaced by their permanent successors, usually exhibit minimal or no root resorption, which helps preserve the alveolar bone for future prosthetic rehabilitation [30]. Therefore, preservation of primary canines is recommended whenever feasible. However, despite their prolonged retention time, primary canines still face the issues of root resorption and tooth loss. Consulting an orthodontist and restorative dentist is necessary to prevent difficulties caused by space loss and jaw atrophy resulting from premature primary canine loss in the developing dentition. To optimize the restoration process, clinicians should focus on minimizing or consolidating the edentulous space and reducing the required number of implants. For instance, the consideration of guided eruption and orthodontic treatment for premolar substitution in cases where permanent maxillary canines are missing can be beneficial [11, 31, 32]. One study reported the successful replacement of primary canines with implants [33]. Mini-implants can be utilized for the temporary restoration of missing permanent teeth in adolescent patients [32, 34]. This alternative approach facilitates vertical development of the alveolar process and maintains bone density and alveolar morphology, obviating the need for additional surgical procedures for dental implantation and leading to favourable long-term outcomes.

One limitation of this study was that it might not accurately represent the prevalence and distribution of CMPC among the Chinese population; hence, the generalizability of the results is limited. To validate the prevalence observed in this study, multicenter research utilizing electronic health records (EHR) systems or other comprehensive medical databases is recommended. Additionally, long-term follow-up to assess the absence of second permanent molars and other dental anomalies, such as taurodontism is recommended. Further genetic investigations into the pathogenic genes associated with CMPC in affected patients may provide additional insights.