Interventions for promoting the eruption of palatally displaced permanent canine teeth, without the need for surgical exposure, in children aged 9 to 14 years.

BACKGROUND: A permanent upper (maxillary) canine tooth that grows into the roof of the mouth and frequently does not appear (erupt) is called a palatally displaced canine (PDC). The reported prevalence of PDC in the population varies between 1% and 3%. Management of the unerupted PDC can be lengthy, involving surgery to uncover the tooth and prolonged orthodontic (brace) treatment to straighten it; therefore, various procedures have been suggested to encourage a PDC to erupt without the need for surgical intervention. OBJECTIVES: To assess the efficacy, safety and cost-effectiveness of any interceptive procedure to promote the eruption of a PDC compared to no treatment or other interceptive procedures in young people aged 9 to 14 years old. SEARCH METHODS: An information specialist searched four bibliographic databases up to 3 February 2021 and used additional search methods to identify published, unpublished and ongoing studies. SELECTION CRITERIA: We included randomised controlled trials (RCT) involving at least 80% of children aged between 9 and 14 years, who were diagnosed with an upper PDC and undergoing an intervention to enable the successful eruption of the unerupted PDC, which was compared with an untreated control group or another intervention. DATA COLLECTION AND ANALYSIS: Two review authors, independently and in duplicate, examined titles, keywords, abstracts, full articles, extracted data and assessed risk of bias using the Cochrane Risk of Bias 1 tool (RoB1). The primary outcome was summarised with risk ratios (RR) and 95% confidence intervals (CI). We reported an intention-to-treat (ITT) analysis when data were available and a modified intention-to-treat (mITT) analysis if not. We also undertook several sensitivity analyses. We used summary of findings tables to present the main findings and our assessment of the certainty of the evidence. MAIN RESULTS: We included four studies, involving 199 randomised participants (164 analysed), 108 girls and 91 boys, 82 of whom were diagnosed with unilateral PDC and 117 with bilateral PDC. The participants were aged between 8 and 13 years at recruitment. The certainty of the evidence was very low and future research may change our conclusions. One study (randomised 67 participants, 89 teeth) found that extracting the primary canine may increase the proportion of PDCs that successfully erupt into the mouth at 12 months compared with no extraction (RR 2.87, 95% CI 0.90 to 9.23; 45 participants, 45 PDCs analysed; very low-certainty evidence), but the CI included the possibility of no difference; therefore the evidence was uncertain. There was no evidence that extraction of the primary canine reduced the number of young people with a PDC referred for surgery at 12 months (RR 0.61 (95% CI 0.29 to 1.28). Three studies (randomised 132 participants, 227 teeth) found no difference in the proportion of successfully erupted PDCs at 18 months with a double primary tooth extraction compared with extraction of a single primary canine (RR 0.68, 95% CI 0.35 to 1.31; 119 participants analysed, 203 PDCs; mITT; very low-certainty evidence). Two of these studies found no difference in the proportions referred for surgical exposure between the single and the double primary extraction groups data at 48 months (RR 0.31, 95% CI 0.06 to 1.45).  There are some descriptive data suggesting that the more severe the displacement of the PDC towards the midline, the lower the proportion of successfully erupted PDCs with or without intervention. AUTHORS' CONCLUSIONS: The evidence that extraction of the primary canine in a young person aged between 9 and 14 years diagnosed with a PDC may increase the proportion of erupted PDCs, without surgical intervention, is very uncertain. There is no evidence that double extraction of primary teeth increases the proportion of erupted PDC compared with a single primary tooth extraction at 18 months or the proportion referred for surgery by 48 months. Because we have only low to very low certainty in these findings, future research is necessary to help us know for sure the best way to deal with upper permanent teeth that are not erupting as expected.

Open versus closed surgical exposure of canine teeth that are displaced in the roof of the mouth.

BACKGROUND: Palatally displaced canines or PDCs are upper permanent canines, commonly known as 'eye' teeth, that are displaced in the roof of the mouth. This can leave unsightly gaps, cause damage to the surrounding roots (which can be so severe that neighbouring teeth are lost or have to be removed) and, occasionally, result in the development of cysts. PDCs are a frequent dental anomaly, present in 2% to 3% of young people.Management of this problem is both time consuming and expensive. It involves surgical exposure (uncovering) followed by fixed braces for two to three years to bring the canine into alignment within the dental arch. Two techniques for exposing palatal canines are routinely used in the UK: the closed technique and the open technique. The closed technique involves uncovering the canine, attaching an eyelet and gold chain and then suturing the palatal mucosa back over the tooth. The tooth is then moved into position covered by the palatal mucosa. The open technique involves uncovering the canine tooth and removing the overlying palatal tissue to leave it uncovered. The orthodontist can then see the crown of the canine to align it. OBJECTIVES: To assess the effects of using either an open or closed surgical method to expose canines that have become displaced in the roof of the mouth, in terms of success and other clinical and patient-reported outcomes. SEARCH METHODS: Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 24 February 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (in the Cochrane Library, 2017, Issue 1), MEDLINE Ovid (1946 to 24 February 2017), and Embase Ovid (1980 to 24 February 2017). The US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases. SELECTION CRITERIA: We included randomised and quasi-randomised controlled trials assessing young people receiving surgical treatment to correct upper PDCs. There was no restriction on age, presenting malocclusion or type of active orthodontic treatment undertaken. We included unilaterally and bilaterally displaced canines. DATA COLLECTION AND ANALYSIS: Two review authors independently screened the results of the electronic searches, extracted data and assessed the risk of bias in the included studies. We attempted to contact study authors for missing data or clarification where feasible. We followed statistical guidelines from the Cochrane Handbook for Systematic Reviews of Interventions for data synthesis. MAIN RESULTS: We included three studies, involving 146 participants. Two studies were assessed as being at high risk of bias.The main finding of the review was that the two techniques may be equally successful at exposing PDCs (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.93 to 1.06; three studies, 141 participants analysed, low-quality evidence).One surgical failure was due to detachment of the gold chain (closed group). One study reported on complications following surgery and found two in the closed group: a post-operative infection requiring antibiotics and pain during alignment of the canine as the gold chain penetrated through the gum tissue of the palate.We were unable to pool data for dental aesthetics, patient-reported pain and discomfort, periodontal health and treatment time; however, individual studies did not find any differences between the surgical techniques (low- to very low-quality evidence). AUTHORS' CONCLUSIONS: Currently, the evidence suggests that neither the open or closed surgical technique for exposing palatally displaced maxillary canine teeth is superior for any of the outcomes included in this review; however, we considered the evidence to be low quality, with two of the three included studies being at high risk of bias. This suggests the need for more high-quality studies. Three ongoing clinical trials have been identified and it is hoped that these will produce data that can be pooled to increase the degree of certainty in these findings.

Hypodontia--a retrospective review of prevalence and etiology. Part I.

A retrospective literature review was carried out to determine the prevalence of hypodontia and current knowledge of associated etiological factors. Reported studies vary widely in their reports of prevalence. The majority are retrospective radiographic studies, and reported rates vary from 2.6% to 11.3%. Racial differences have been determined: in Caucasian studies the mandibular second premolars and maxillary lateral incisors were the most frequently recorded absent and in Asian studies, the mandibular incisor was the most frequently recorded absent. Prevalence rates are higher in females compared to males (3:2, respectively). The association of hypodontia with other systemic conditions and dental anomalies is widely reported. Hypodontia can be regarded as a multifactorial condition. Recent developments in molecular genetics have established the importance of the muscle specific homeobox genes (Msx1 and Msx2) in dental development. Specific genes that are responsible for the more severe types of hypodontia, including ectodermal dysplasia, have been identified by linkage analysis. However, variable expression of the trait suggests a polygenic mode of inheritence with epistatic genes and environmental factors interacting.