Relevant factors of posterior mandible lingual plate perforation during immediate implant placement: a virtual implant placement study using CBCT.

BACKGROUND: To explore the influence of cross-sectional type and morphological parameters at the mandibular molar sites on lingual plate perforation (LPP) during the immediate implant placement (IIP). METHODS: 181 implants were virtually placed in the mandibular molar sites on the cone beam computed tomography (CBCT). Each cross-section of the implantation site was divided into the Undercut (U)/Parallel (P)/Convex (C) types. Morphologically relevant parameters were measured on the cross-sections, including width of the upper end (Wb), width of the lower end (Wc), vertical height (V), angle between the natural crown axis and the alveolar bone axis (∠ß), LC depth (LCD), LC height, and angle between the horizontal line and the line connecting the most prominent point and the most concave point of lingual plate (∠α). Besides, the distance from the end of the virtual implant and the lingual bone plate of the cross-section (DIL) was calculated. Relationships between all the morphologically relevant parameters and the DIL were further analyzed. RESULTS: A total of 77 (42.5%) cross-sections were classified as U-type, which was the most common one, accounting for 63% of the second molar regions. All LPP cases and most of the nearly LPP (87.9%) cases occurred at the U-type cross-sections, and the relationship between the DIL and the morphological parameters can be expressed by a multivariate linear equation. CONCLUSIONS: The occurrence rate of U-type cross-sections in the second molar region was very high, and the risk of LPP should be considered during IIP. Except for the U-type, significant large LCD, small Wc, and large âˆ ß were the important relevant factors. CBCT and multivariate linear equations could help to assess the LPP risk and provide a reference for implant placement design pre-surgery.

A novel approach to full-mouth rehabilitation of dentinogenesis imperfecta type II: Case series with review of literature.

RATIONALE: Dentinogenesis imperfecta (DI) is an autosomal-dominant disorder. The most common clinical manifestations, including obliterated tooth tissues and severe tooth wear, usually lead to tooth extractions. It remains a great challenge for dentists to preserve the residual tooth tissue and establish the esthetics and occlusion of dentitions. PATIENTS CONCERNS: 25-year-old twin sisters, who had suffered from dentinogenesis imperfecta type II for more than 10 years, presented with continuous tooth wear and discomfort from wearing a removable partial denture for more than 3 years. DIAGNOSIS: Intraoral examination showed extensive tooth wear with enamel exfoliation and typical amber-brown color with an opalescent discoloration. Their panoramic radiographs revealed completely obliterated tooth tissues and severe tooth wear. INTERVENTIONS AND OUTCOMES: The dentitions were restored with post-and-core crowns and pin lays after preparing root post paths and pin holes guided by computer-aided design/computer-aided manufacturing (CAD/CAM) procedures, resulting in a successful repair. LESSONS: Severe tooth wear and tooth tissue obliteration are typical clinical manifestations in DI-affected dentitions, increasing the complexity and difficulty in dental restorations. Early diagnosis and appropriate treatments are essential to achieve a favorable prognosis. CAD/CAM procedures, permitting accurate and effective treatment, possess promising potential in the treatment of DI-affected dentitions.