To determine the prevalence and factors associated with hypotonia. Systematic review and meta-analysis. A search strategy was developed along with inclusion criteria and run in MEDLINE and EMBASE (published from 2002 to August 2012) databases to reveal all studies on the prevalence of hypodontia or associated factors. A hand search of reference lists and a Google search aimed to improve the sensitivity of the literature search. All studies on the prevalence of hypodontia or associated factors published from 2002 onwards were included. Abstracts of non-English papers were also analyzed. All potential articles were checked against the inclusion criteria independently, and in duplicate by two investigators. A checklist was used to assess the quality of selected studies. Prevalence of hypodontia, excluding third molars. The overall prevalence of hypodontia was found to be 6.4% (95% CI: 5.7, 7.2). There was a statistically significant difference in the prevalence of hypodontia by continent (Q = 34.18, P<0.001). Prevalence of hypodontia was the highest in Africa: 13.4% (95% CI: 9.7, 18.0), followed by Europe (7% CI: 6.0-8.0%), Asia (6.3% CI: 4.4, 9.1) and Australia (6.3% CI: 5.3, 7.4) with a lower prevalence in North America (5.0% CI: 4.1-5.9) and Latin America and Caribbean (4.4% CI: 3.2-6.1). Females were found to have a higher prevalence than males (combined OR 1.22; 95% CI: 1.14, 1.30). The most commonly affected teeth were mandibular second premolars followed by maxillary lateral incisors and maxillary second premolars. The prevalence of mild, moderate and severe hypodontia was found to be 81.6, 14.3 and 3.1% respectively. There was a high variation in the prevalence of hypodontia between the studies. African populations were found to have a higher risk for tooth agenesis and there was an increased risk for females to have hypodontia than males.

Titanium particles as a product of degradation have been detected in periimplant oral tissues and it has been assumed that implants were the source of these particles. Periimplantitis sites had higher concentrations of particles in comparison to healthy implant sites. Several factors have been identified in the degradation of dental implant surface, such as mechanical wear, contact with chemical agents, and the effects of biofilm adhesion. Titanium particles silently prompt the immune-system activation and generate a pro-inflammatory response in macrophages, T lymphocytes and monocytes. During the activation, inflammatory cytokines are released including, granulocyte–macrophage colony-stimulating factor (GM-CSF), prostaglandin, and TNF-α, IL-1β, IL-6. The nanoparticles depict unique features such as high level of biological reactivity and potentially harmful compared to microparticles since they have a relatively greater surface area to volume ratio. Allergic response to titanium as a cause of implant failure has not been well documented. Evidence demonstrating biological complication due to titanium particles release includes peri-implant tissue inflammation that lead terminally to implant loss. There is a biological probability for a relation between the presence of titanium particles and ions, biological complication, and corrosion, but there is no justifiable evidence for unidirectional series of causative actions.

Dental education involves teaching and assessing the acquisition of verifiable domains that require superior psychomotor, communication, and cognitive skills. Evolving technologies and methods of a...

A multifactorial model based on an underlying continuous distribution of tooth size, with thresholds determining hypodontia and supernumeraries, has been proposed [1]. Our aim is to investigate this model by comparing tooth morphology of affected patients and their first degree relatives with normal controls. An image analysis system [2] was used to measure teeth on study models of controls, patients with hypodontia of varying degrees and location, first-degree relatives of hypodontia index cases, and patients with supernumerary teeth in the maxillary incisor region. Mesio-distal crown size in hypodontia patients was smaller than controls, and this difference was significant for all tooth types. There was a general pattern: the more severe the hypodontia, the smaller the size of the tooth formed. Patients with supernumerary teeth had permanent maxillary central and lateral incisors and canines that were significantly larger in mesio-distal width than controls. The maxillary central incisors also differed in taper in supernumerary patients compared to controls. Hypodontia prevalence was higher in first-degree relatives (22%) of hypodontia index cases than in the general population (4.4%), and unaffected relatives had smaller teeth than controls. Thus, there were generalized and localized effects within the dentition, and these findings are compatible with the statistical expectations of the proposed multifactorial model.

Supernumerary teeth in the premolar region, unlike other supernumeraries, occur more often in the mandible where they are generally of the supplemental type. Occasionally, they are conical or smaller than normal, particularly in the upper premolar regions. They might occur singly or in multiples, be erupted or impacted, but the majority have been found to be unerupted and asymptomatic. The prevalence of supernumerary teeth in the premolar region has been demonstrated to be between 0.01 and 1 percent depending on the population studied. Interestingly, populations from the East or Africa are known to be the most affected. Various theories have been suggested to explain the etiology of supernumerary teeth in general including both genetic and environmental factors. Furthermore, it has been suggested that supernumerary premolar teeth belong to a third (postpermanent) series, developing from extensions of the dental lamina. Several consequences can result from the presence of supernumerary premolars, especially in the mandible, such as cyst formation, transposition, and other clinical scenarios.

The aim of this systematic review was to address the clinical effectiveness of space maintainers and space regainers in the prevention and correction of dental arch decreases in mixed dentition. An electronic search was conducted using five databases: the Cochrane Database for Systematic Reviews, EBSCO Host, ScienceDirect, PubMed, and Scopus (until February 2021) and 6 relevant journals. Inclusion criteria were: Randomized Controlled Clinical Trials (RCTs), Controlled Clinical Trials (CCTs), cohort studies and case-control studies of children in the mixed dentition requiring a space maintainer or a space regainer, children with mild to moderate crowding, and with Class I and mild Class II or Class III skeletal pattern. All articles included in this review were examined independently by three teams of investigators to assess the level of bias using the Cochrane risk of bias tools RoB 2.0 (for RCTs) and ROBINS-I (for non-RCTs). Following the three phases of a systematic search, 11 studies were included for the final analysis, of which nine used space maintainers (a lower lingual arch) and two used space regainers (one lip bumper and one transpalatal arch) with contradicting results. Four of the former and one of the latter devices showed a significant increase in arch length. Out of the 11 articles, one was found to be of critical risk, two of serious risk and eight of moderate risk of bias. There is very low evidence to suggest that space maintainers and regainers are effective in preserving arch length and preventing mild to moderate crowding in children during the mixed dentition stage at the expense of lower incisor proclination. However, considering the low evidence provided by this systematic review, high-quality studies are needed.