Evaluation of the efficacy of a prosthodontic stent in determining the position of dental implants

Purpose: To evaluate the efficacy of a dual purpose (diagnostic and surgical) acrylic resin stent with gutta percha marker used in conjunction with 3D imaging in determination of the position and inclination of dental implants. Materials and Methods: This study was performed as a case control study. A total of 41 implants, of which 20 had been placed without the use of stents and 3D imaging (control group) and 21 were placed using stents and 3D imaging (study group), were studied. A diagnostic and surgical stent with radio‐opaque indicator (gutta percha) was fabricated to determine the planned prosthetic position and inclination of the implant. Computed tomography images were obtained and were analyzed using Denta Scan software. The position of the implant was analyzed in mesiodistal and buccolingual dimensions in terms of both position and angulation. SPSS v15.0 was used for statistical analysis (p < 0.05 was considered statistically significant). Results: The study group demonstrated an overall 98.9% efficacy of the test technique being used in the study. On qualitative assessment, the results obtained were within the defined ideal threshold level for four of five parameters (distance from buccal and lingual cortical plate, inter‐implant distance, and buccolingual angulation of the implant relative to underlying alveolar bone). For mesiodistal distance from adjacent teeth, the observation was not above threshold value for only one case. For the control group, the overall efficacy was 66.9%. Conclusion: The technique of combined use of a prosthodontic stent and 3D imaging is an efficacious and better technique in achieving an ideal position of dental implants as compared to conventional techniques using periapical and panoramic radiographs and a cast.     

Fragile X AGG analysis provides new risk predictions for 45–69 repeat alleles

We investigated the effect of AGG interruptions on fragile X repeat instability upon transmission of fragile X intermediate and small premutation alleles with 45–69 CGG repeats. The FMR1 repeat structure was determined for 375 mothers, 48 fathers, and 538 offspring (457 maternal and 81 paternal transmissions) using a novel PCR assay to determine repeat length and AGG interruptions. The number of AGG interruptions and the length of uninterrupted CGG repeats at the 3′ end were correlated with repeat instability on transmission. Maternal alleles with no AGGs conferred the greatest risk for unstable transmissions. All nine full mutation expansions were inherited from maternal alleles with no AGGs. Furthermore, the magnitude of repeat expansion was larger for alleles lacking AGG interruptions. Transmissions from paternal alleles with no AGGs also exhibited greater instability than those with one or more AGGs. Our results demonstrate that characterization of the AGG structure within the FMR1 repeat allows more accurate risk estimates of repeat instability and expansion to full mutations for intermediate and small premutation alleles. © 2013 Wiley Periodicals, Inc.     

CT based evaluation of odontoid morphology in the Indian population

Background:

Anterior fixation using two 3.5 mm screws is typically recommended for type II odontoid fractures. However, it is unsuitable in patients with an odontoid diameter of <9.0 mm. There is no data regarding the morphology of odontoid process in the Indian population. The aim of our study was to: a) Measure the external diameters of odontoid process in the Indian population using CT scan and thus determine the feasibility of two 3.5 mm screw fixation in them. b) Determine if any correlation exists between body height (Ht) and weight (Wt) and external odontoid diameters.

Materials and Methods:

CT images of odontoid process of 100 consecutive patients were analyzed. Antero- posterior (AP) and transverse (TD), outer diameters of the odontoid process were measured from the base and at 1 mm interval upwards on axial CT images.

Results:

The mean AP and mean TD were 11.52 mm and 9.85 mm, respectively. Fifty-five (55%) of the patients had at least one TD <9.0 mm. Five (5%) patients had at least one TD <7.4 mm. None of the patients had any diameter <5.5 mm. Body Ht correlated significantly with mean AP and mean TD of the odontoid process (AP: r = 0.276, P = 0.013; TD: r = 0.359, P = 0.001), whereas body Wt correlated significantly only with mean TD (AP: r = 0.162, P = 0.15; TD: r = 0.297, P = 0.007).

Conclusion:

More than half of the study population (55%) was unsuitable for two 3.5 mm screw fixation for type II odontoid fracture. Two 2.7 mm screws can be safely used in 95% of the population. A 4.5 mm Herbert screw can be safely used in the entire population. We recommend two 2.7 mm screws or a 4.5 mm Herbert screw for fixation of these fractures in the Indian population. Body height showed a significant correlation with external odontoid diameters, whereas weight showed significant correlation only with TD of the odontoid process.