Estimating the occurrence of labial bone perforation and implantation into the maxillary sinus maxillary premolars based on the morphology of maxillary premolars: A clinical study.

STATEMENT OF PROBLEM: Previous studies have classified the sagittal root position of the maxillary anterior teeth and measured buccal plate thickness to aid treatment planning. A thin labial wall and buccal concavity may cause buccal perforation, dehiscence, or both in maxillary premolars. However, data on the restoration-driven principle to classify the maxillary premolar region are lacking. PURPOSE: The purpose of this clinical study was to investigate the occurrence of labial bone perforation and implantation into the maxillary sinus between various tooth-alveolar classifications with respect to the crown axis in maxillary premolars. MATERIAL AND METHODS: Cone beam computed tomography images of 399 participants (1596 teeth) were analyzed to determine the probability of labial bone perforation and implantation into the maxillary sinus when associated with variables that included tooth position and tooth-alveolar classification. RESULTS: The morphology in the maxillary premolars was classified as straight, oblique, or boot-shaped. The first premolars were 62.3% straight, 37.0% oblique, and 0.8% boot-shaped, and labial bone perforation occurred in 4.2% (21 of 497) of the straight, 54.2% (160 of 295) of the oblique, and 83.3% (5 of 6) of the boot-shaped first premolars when the virtual implant was 3.5×10 mm. When the virtual tapered implant was 4.3×10 mm, labial bone perforation occurred in 8.5% (42 of 497) of the straight, 68.5% (202 of 295) of the oblique, and 83.3% (5 of 6) of the boot-shaped first premolars. The second premolars were 92.4% straight, 7.5% oblique, and 0.1% boot-shaped, and labial bone perforation occurred in 0.5% (4 of 737) of the straight, 33.3% (20 of 60) of the oblique, and 0% (0 of 1) of the boot-shaped, respectively, when the virtual tapered implant was 3.5×10 mm; and labial bone perforation occurred in 1.3% (10/737) of the straight, 53.3% (32/60) of the oblique, and 100% (1/1) of the boot-shaped second premolars when the virtual tapered implant was 4.3×10 mm. CONCLUSIONS: When an implant is placed in the long axis of a maxillary premolar, the tooth position and tooth-alveolar classification should be considered when assessing the risk of labial bone perforation. Attention should be paid to the implant direction, diameter, and length in the oblique and boot-shaped maxillary premolars.

Influence of bone anatomical morphology of mandibular molars on dental implant based on CBCT.

BACKGROUND: To apply CBCT to investigate the anatomical relationship between the mandibular molar and alveolar bone, aimed to provide clinical guidelines for the design of implant restoration. METHODS: 201 CBCT data were reevaluated to measure height of the alveolar process (EF), width of the alveolar process (GH), width of the basal bone (IJ), the angle between the long axis of the first molar and the alveolar bone (∠a) and the angle between the long axis of the alveolar bone and basal bone (∠b). The angle and width were measured to determine the implant-prosthodontic classification of the morphology in the left lower first molar (36) and right lower first molar (46). All measurements were performed on the improved cross-sectional images. RESULTS: EF, GH and IJ were measured as (10.83 ± 1.31) mm, (13.93 ± 2.00) mm and (12.68 ± 1.96) mm for 36, respectively; and (10.87 ± 1.24) mm, (13.86 ± 1.93) mm and (12.60 ± 1.90) mm for 46, respectively. No statistical significance was observed in EF, GH, IJ, ∠a and ∠b between 36 and 46 (all P > 0.05). The morphology was divided into three categories including the straight (68.7-69.2%), oblique (19.9-20.4%) and concave types (11%). Each type was consisted of two subcategories. CONCLUSIONS: The proposed classification could provide evidence for appropriate selection and direction design of the mandibular molar implant in clinical. The concave type was the most difficult to implant with the highest risk of lingual perforation. The implant length, width, direction required more attention.

Cyclic tensile forces enhance the angiogenic properties of HUVECs by promoting the activities of human periodontal ligament cells.

BACKGROUND: This study aimed to investigate whether human periodontal ligament (PDL) cells secrete pro-angiogenic factors that induce the vascularization of surrounding bone tissue under tensile stress. METHODS: Quantitative real-time PCR and Western blotting were used to analyze the mRNA and protein expression levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), Angiopoietin-I (Ang-I), connective tissue growth factor （CTGF）, and macrophage colony-stimulating factor (M-CSF) in PDL cells after tensile force treatments of different durations. Enzyme-linked immunosorbent assay was used to measure the VEGF concentration in the supernatants of cell cultures. Cell viability assay, wound healing assay, and tube formation assay were performed to evaluate the angiogenic behaviors of human umbilical vein endothelial cells (HUVECs). RESULTS: The mRNA expression and protein expression of VEGF, bFGF, Ang-I, and M-CSF was increased in the cells that received 6 to 48 hours of tensile force treatment. And, the VEGF level in the supernatant significantly increased in the human PDL cell cultures stressed for 6 to 48 hours. The abilities of HUVECs to proliferate, migrate, and form tubes were enhanced in media conditioned with tensile-stressed human PDL cells. Hence, tensile force induced human PDL cells to express and release pro-angiogenic factors enhancing the proliferation, migration, and angiogenic capacity of HUVECs. CONCLUSION: Tensile stress induced human PDL cells to express and release pro-angiogenic factors, including VEGF, bFGF, Ang-I, and M-CSF, thereby enhancing the proliferation, migration, and angiogenic capacity of HUVECs.