Evaluation of sagittal condylar guidance angles using computerized pantographic tracings, protrusive interocclusal records, and 3D-CBCT imaging techniques for oral rehabilitation.

OBJECTIVE: The goal of registering the condylar guidance is to recreate the patient's occlusion as exactly as possible on the articulator, and is therefore essential for successful prosthodontic rehabilitation. Clinical, radiographic, and pantographic methods are used to determine sagittal condylar guidance angles (SCGAs). These methods generate different angles in the same patients. The present study is the first disquisition to evaluate and correlate SCGAs determined by the use of pantographic tracing (PT), protrusive records (PR), and radiographic (CBCT) techniques. MATERIALS AND METHODS: The condylar guidance was measured using PT, PR, and CBCT imaging techniques in 23 nonpatient participants aged between 18 and 30 years irrespective of sex. PT was recorded using Cadiax® Compact system, a computerized recorder of SCGAs. PR was obtained using polyvinyl siloxane bite registration material, transferred to a semiadjustable articulator (Denar Mark II, Whip Mix Corp., USA) using facebow transfer (Denar Mark II, Whip Mix Corp., USA) and CR records, to determine SCGAs. Images of the mid-facial region were obtained using CBCT scan for 3D reconstruction. The angle formed between Frankfort horizontal plane (FHP) and a line extending from the most supero-anterior point on the glenoid fossa to the most convex point on the apex of articular eminence (AE) was measured to obtain SCGAs. RESULTS: The mean left and right SCGAs were as follows: PT (34.42° and 33.93°, respectively), PR (32.14° and 31.82°), and CBCT (38.96° and 38.12°). The Pearson coefficients for the correlations with PT and PR on the left and right sides were 0.899 and 0.907, respectively, while it was 0.911 and 0.934, and 0.842 and 0.874 from PT and CBCT, and PR and CBCT, respectively. CONCLUSION: Strong correlations were found between SCGAs obtained using PT, PR, and CBCT techniques.

CBCT analysis of schneiderian membrane thickness and its relationship with gingival biotype and arch form.

OBJECTIVE: The purpose of this study was to investigate a relationship between gingival tissue biotypes and arch form with Schneiderian membrane thickness, using limited cone beam computed tomography. MATERIALS AND METHODS: A total of 90 subjects were selected. For each subject three parameters were assessed - gingival biotype - clinically by Probe transparency method as thin or thick and coded as 0 and 1, respectively, gingival thickness and Schneiderian membrane thickness in mm, arch form as square, oval, or tapered (radiographically by cone beam computed tomography images). Central incisors and first molars were assessed for gingival biotype and gingival thickness and Schneiderian membrane thickness was determined at 16. Numerical data were estimated for normal distribution. Analysis of Variance test was followed by Tukey honestly significant difference test and Pearson's correlation coefficient test for analysis. RESULTS: Thin gingival biotype was found associated with the central incisors and thick gingival biotype with molars. Limited cone beam computed tomography scans evaluation revealed highest prevalence of square arch form followed by oval, and tapered. The average thickness of the Schneiderian membrane was 1.18 ± 0.43 mm on left side and 1.09 ± 0.41 mm on right side with a range of 0.50 - 2.00 mm. Mean Schneiderian membrane thickness was more in case of thick gingival biotype and with square arc form both on right and left sides. CONCLUSIONS: The Schneiderian membrane thickness was positively and highly associated with gingival biotype. The gingival biotype and arch form had significant effect on Schneiderian membrane thickness and can provide valuable clinical information on Schneiderian membrane thickness preoperatively for implant placement and sinus lift procedures.

3-D mapping of cortical bone thickness in subjects with different face form and arch form: A CBCT analysis.

OBJECTIVE: To determine the relationship between face form (FF), arch form (AF), and cortical bone thickness in anterior and posterior region of the mandibular jaws, using cone beam computed tomography (CBCT). PATIENTS AND METHODS: Total 90 subjects were selected. For each subject FF (euryprosopic, mesoprosopic, and leptoprosopic) was determined using Prosopic Index. CBCT scans were done for each subject to determine mandibular AF (as tapered, oval, or square in horizontal sections) and cortical bone thickness (at two vertical levels 4 and 7 mm from the alveolar crest in the anterior and posterior region of mandible in sagittal sections). Numerical data so obtained were analyzed using descriptive statistics, analysis of variance followed by Tukey HSD (honestly significant difference) test at a statistical significance level of 5%. RESULTS: Significant difference in thickness of cortical bone was noted between various AF and face. In square AF, mean value of thickness of cortical bone was highest both at 4 and 7 mm vertical level and tapered AF had minimum mean values at 4 mm and oval at 7 mm in anterior region and posterior region on buccal and lingual sides, in all the three-FF. CONCLUSION: Significant effects of FF and AF on cortical bone thickness were seen both on buccal and lingual side and the effect of AF was more compared to FF. The availability of the cortical bone in euryprosopic FF and square AF patients was more; therefore, implants with a shorter length may be used in these clinical cases.

CAD/CAM to fabricate ceramic implant abutments and crowns: a preliminary in vitro study.

BACKGROUND: This study evaluated the feasibility of fabricating implant abutments and crowns from pre-sintered feldspathic porcelain blocks using the chair-side CAD/CAM, CEREC3D((R)) system. METHODS: Thirty-two implant analogues were divided into two groups. In the control group, prefabricated machined anatomical titanium (Ti) abutments were screw-retained to the analogues. In the test group, machined feldspathic porcelain abutments were cemented on prefabricated machined Ti links and screw-retained to the implant analogues. These feldspathic porcelain abutments were fabricated out of pre-sintered feldspathic porcelain blocks as duplicates of the abutments in the control group using the CAD/CAM, CEREC3D system. Thirty-two feldspathic porcelain crowns, also fabricated out of pre-sintered ceramic blocks, were then cemented with resin cement on all the abutments in both groups. All samples were subsequently subjected to fracture strength testing under static load. An unpaired t-test was used to compare fracture load values between the two groups. RESULTS: The test group using feldspathic porcelain abutments and crowns showed statistically significant higher mean fracture strength than the control group with the Ti abutments and feldspathic porcelain crowns. CONCLUSIONS: This preliminary study showed that the chair-side CAD/CAM technology can be utilized to fabricate customized ceramic abutments with their associated ceramic crowns using pre-sintered feldspathic porcelain blocks.