Incisor

Molar incisor hypomineralization (MIH) is an enamel condition characterized by lesions ranging in color from white to brown which present rapid caries progression, and mainly affects permanent first molars and incisors. These enamel defects usually occur when there are disturbances during the mineralization or maturation stage of amelogenesis. Both genetic and environmental factors have been suggested to play roles in MIH's development, but no conclusive risk factors have shown the source of the disease. During head and neck development, the interferon regulatory factor 6 (IRF6) gene is involved in the structure formation of the oral and maxillofacial regions, and the transforming growth factor alpha (TGFA) is an essential cell regulator, acting during proliferation, differentiation, migration and apoptosis. In this present study, it was hypothesized that these genes interact and contribute to predisposition of MIH. Environmental factors affecting children that were 3 years of age or older were also hypothesized to play a role in the disease etiology. Those factors included respiratory issues, malnutrition, food intolerance, infection of any sort and medication intake. A total of 1,065 salivary samples from four different cohorts were obtained, and DNA was extracted from each sample and genotyped for nine different single nucleotide polymorphisms. Association tests and logistic regression implemented in PLINK were used for analyses. A potential interaction between TGFA rs930655 with all markers tested in the cohort from Turkey was identified. These interactions were not identified in the remaining cohorts. Associations (p<0.05) between the use of medication after three years of age and MIH were also found, suggesting that conditions acquired at the age children start to socialize might contribute to the development of MIH.

BackgroundUprighting incisors is particularly important with clear aligner therapy as incisor tip determines the mesio-distal space needed in the arch, and consequently the fit of the aligner. The objective of this study was to investigate the accuracy of ClinCheck® software to predict lower incisor tip by comparing digitally prescribed movements with actual clinical outcomes and to determine whether the presence of a vertically orientated rectangular composite attachment influences the efficacy of incisor tip.MethodologyThis retrospective study included 66 lower incisors from 42 non-extraction adult patients treated using the Invisalign® appliance. Twenty-one incisors had vertical attachments, while 45 incisors did not have any attachments. Lower incisor tip was measured at T0 (pre-treatment), T1 (predicted post-treatment) and T2 (achieved post-treatment) on digital models using metrology software. The change in position from T0 to T1 and T0 to T2 was measured from the estimated centre of resistance (CRes) of each tooth. The estimated centre of rotation was plotted relative to the CRes to describe the type of orthodontic tooth movement (OTM) predicted and achieved.ResultsPredicted incisor tip and achieved incisor tip were positively correlated (R2 = 0.55; p ConclusionsThe amount of lower incisor tip achieved was on average substantially less than the ClinCheck® displayed. Vertically orientated rectangular attachments are recommended where large root movement is planned, and their presence slightly improves apex movement.

The tooth movement in the alveolus is possible due to bone remodeling. This process could be the risk factor for the formation of gingival recessions-the most common side effects of orthodontic therapy. Gingival recessions are found 5.8-11.5% more frequently among the orthodontically treated patients. What is more, anterior mandibular teeth are the ones most prone to gingival recession dehiscences and fenestrations. The aim of this narrative review was to evaluate, based on CBCT (Cone beam computed tomography) scans, the changes in the alveolar bone of lower incisors in adolescent and adult patients after orthodontic tooth movements. From the pool of 108 publications, a total of 15 fulfilled the criteria of this review. Both retrospective and prospective longitudinal studies-using CBCT or CT (Computed Topography) and evaluating alveolar bone changes in mandibular incisors during orthodontic treatment performed before and after teeth movement-were included. In the group of growing patients, either proclination or retroclination of mandibular incisors led to increase of the distance from CEJ (cementoenamel junction) to marginal bone crest. The difference in bone loss was greater on the lingual side of the incisors in both types of tooth movement. The results were similar for adults patients. The thickness of the alveolar bone was reduced after proclination (total bone thickness) among growing and non-growing patients and retraction (lingual and buccal) of lower anterior teeth in the group of growing patients. The only improvement was measured for buccal thickness of mandibular incisor in bimaxillary protrusion patients treated with extraction therapy. The control of retraction movement (more root than crown movement) enhanced preservation on bone height and thickness. In order to minimize possible deterioration and place teeth in the center of alveolus, CBCT monitoring and scrupulous clinical evaluation are recommended.

OBJECTIVES: This laboratory study evaluated the effect of deep margin elevation (DME) on the marginal integrity and fracture resistance of anterior teeth with crown-root fractures. MATERIALS AND METHODS: Fifty-two extracted permanent human maxillary central incisors were randomly divided into four groups. All teeth received a standardized simulated crown-root fracture, selective enamel etching followed by universal adhesive application, resin-based composite (RBC) build-up (conventional or bulk-fill), root canal treatment, and glass fiber post placement. Crown preparations were performed either entirely in natural tooth structure with subgingival finish lines (DME absent) or partially on the RBC build-up, yielding supragingival finish lines (DME present). Marginal integrity was assessed microscopically at baseline, after initial thermomechanical loading (TML), and after extended TML. Fracture resistance was determined by load-to-fracture testing. Statistical analyses included Kruskal-Wallis, Dunn’s post hoc, and Fisher’s exact tests (α = 0.05). RESULTS: Median marginal continuity remained 100% across all groups. Fracture resistance (1,305-1,595 N) showed no significant differences between groups. Fractures during TML occurred exclusively in groups without DME. CONCLUSIONS: Within the limitations of this in vitro study, DME did not adversely affect marginal integrity or fracture resistance of restored anterior teeth. In contrast to non-DME groups, specimens with DME did not exhibit failures during TML. CLINICAL RELEVANCE: DME restorations can maintain high marginal integrity and load-bearing capacity in anterior teeth with crown-root fractures. These findings provide preliminary evidence supporting DME as a conservative approach for managing anterior crown-root fractures in select cases, with confirmation needed from clinical studies.