The effect of adhesive resin cement, obturation material and root dentin location on the retention of glass fiber-reinforced composite resin posts.

PURPOSE: To assess the effects of adhesive resin cement, obturation material and dentin location on the retention of glass fiber-reinforced resin composite (FRRC) posts. METHODS: 60 root canals in single rooted teeth were obturated with three different protocols (n= 20), including no obturation material (Control), GuttaFlow and Gutta-percha. Spaces were prepared for glass (FRCR) posts. Subgroups of the roots (n=10) were allocated for receiving posts luted with RelyX Unicem or Calibra resin cements. The specimens were mounted in plastic molds using epoxy resin. They were sectioned transversely to obtain three 1 mm-thick coronal, middle and apical slabs. Post retention was measured using a universal testing machine. The push-out test was performed at a crosshead speed of 0.5 mm/minute until post dislodgement occurred. Dislodged posts were examined microscopically to evaluate the mode of failure. Data were analyzed using univariate tests to reveal the effects of dependent variables and their interactions on post retention. Tukey test was used to determine significant differences for post retention in obturation material and dentin location groups. P-values ≤ 0.05 were considered significant. RESULTS: The adhesive resin cement, obturation material, dentin location and cement obturation materials interaction affected post retention. The mean bond strength was higher for posts cemented with RelyX Unicem than for those cemented with Calibra resin cements. Post retention in coronal locations was significantly superior to middle or apical locations. The failure mode was primarily mixed. CLINICAL SIGNIFICANCE: When using RelyX Unicem cement for luting glass fiber-reinforced root canal posts, complete removal of all obturation materials from the post space significantly improves the retention. Although Calibra cement is less technique sensitive than RelyX Unicem resin cement, it produces notably lower retention of fiber-reinforced glass root canal posts.

Cone beam computed tomography analysis of residual dentin thickness after virtual post placement in the palatal roots of maxillary first molars.

STATEMENT OF PROBLEM: In endodontically treated maxillary first molars, post space preparations in the palatal roots can compromise the residual dentin thickness (RDT) and increase the risk of perforations or root fractures. This can be attributed to the direction of the buccopalatal curvature that cannot be viewed with conventional 2D imaging. PURPOSE: The purpose of this clinical study was to investigate the RDT of palatal roots following the placement of digital post analogs of different diameters positioned at various distances from the radiographic apex by using cone beam computed tomography (CBCT). MATERIAL AND METHODS: A total of 122 deidentified CBCT data sets containing both maxillary permanent first molars were randomly selected from a private radiology practice. Digital parallel-sided post analogs were superimposed onto the CBCT coronal images at distances of 3 mm, 4 mm, and 5 mm from the radiographic apex and at a depth equal to the height of the anatomic crown (1:1 crown/post ratio). Post analogs of 0.9 mm, 1.0 mm, and 1.14 mm in diameter were matched with safety zone analogs representing 1 mm of circumferential RDT. The minimum RDT for each analog was determined and grouped into 3 categories: RDT≤0 mm, 0 mm50.0%) had inadequate or no RDT. The depth of the post (P<.001) had a greater impact on RDT than the post diameter (P>.017). No similarities were found in the RDT between contralateral molars in 86.9% of the images. CONCLUSIONS: The risk of insufficient RDT (<1 mm) after the placement of parallel-sided posts in the palatal roots of maxillary first molars is minimized if the post is inserted to a depth equaling the height of the crown compared with 3, 4, and 5 mm from the radiographic apex. The RDT of the palatal root of a maxillary first molar is not a reliable predictor of the contralateral palatal root RDT in the same patient.

Investigation of inter- and intra-rater reliability using digital dental software for prosthodontics crown preparations.

INTRODUCTION: Since the introduction of the digital dental assessment systems, there has been a shift towards this trend as it appears to provide a more accurate, reliable, time efficient, and reproducible assessment. The Planmeca Emerald scanner coupled with Romexis Compare software allows students and staff to objectively assess individual crown preparations, receive numerical values of key dimensions, and subsequently undergo comparison with ideal crown preparation dimensions. OBJECTIVES: To measure the inter- and intra-rater reliability using the intra-oral scanner and Romexis Compare for prosthodontic crown preparations, and to evaluate the possible implementation of this software as a grading and self-assessment tool in a preclinical setting. METHODS: The Planmeca scanner and Romexis Compare were used to compare the difference between 30 experimental preparations (n = 15 anterior teeth, n = 15 posterior teeth) with their respective unprepared typodont teeth. Three student examiners (W., K., V.) independently scanned the typodont teeth in pre-formed standardized and non-standardized putty jigs. Each preparation was measured from facial, lingual, incisal/occlusal, and margin surfaces. A second trial was completed after 2 weeks to assess intra-rater reliability. The data were tabulated, graphed, and analyzed using SPSS and GraphPad Prism. RESULTS: The results of the study show greater consistencies in inter-operator measurements for anterior teeth. Some variations, however, were found in posterior teeth measurements between the operators. The results of the intra-rater measurements appear to be relatively consistent. CONCLUSION: With some limitations, Romexis Compare can be used as a reliable and repeatable method for objective and consistent evaluation of student prosthodontic preparations in a preclinical setting.

Effect of Multiple Use of Impression Copings and Scanbodies on Implant Cast Accuracy.

PURPOSE: There are currently no clear guidelines on the reuse of metal implant impression copings and scanbodies in implant dentistry. Manufacturers generally recommend single use, which has cost and ecological implications. The objectives of this study were to examine the effect of multiple use of implant impression copings and scanbodies on the accuracy of partially dentate implant casts. MATERIALS AND METHODS: Ten direct polyether impressions were made of a partially dentate mandibular acrylic resin master model fitted with two internal connection implants (Straumann RC bone level) in the positions of right first premolar and molar, to produce 10 dental stone casts. A single set of impression copings was utilized for the 10 impressions. The sample casts and the master model were digitized using a laboratory scanner. Ten digital scans were then performed on an implant stone cast with two bone-level internal connection implant analogs using one set of scanbodies to produce scans 1 to 10. Measurements were made on all the digitized casts using computer software and discrepancies calculated in the x-, y-, and z-axes, and in the overall three-dimensional position (R). Data were statistically analyzed using paired t tests (α = .05), and P values were adjusted using Holm-Bonferroni sequential correction. RESULTS: The outcomes were mixed, in that no significant differences were found between the casts or scans produced by reusing impression copings (P > .05) and scanbodies (P > .005), respectively, in all dimensions, for most repetition cycles; however, significant differences were noted in the y-axis for cast 6, and in 2 relation to R, for casts 2, 4 (P < .05), and 8 (P < .005), and the scanbody reuse elicited significant differences in 3D(R) with scan 2 alone (P < .005). CONCLUSION: Reuse of impression copings and scanbodies up to 10 times did not seem to consistently affect the accuracy of partially dentate multi-implant dental casts and digital models.

Awareness, attitude, and expectations toward dental implants among removable prostheses wearers.

PURPOSE: To assess removable denture patient awareness, expectations, and source of information about dental implants (DIs). MATERIALS AND METHODS: Three hundred patients [150 removable partial denture (RPD) wearers and 150 complete denture wearers (CDWs)] attended the removable prosthodontic clinic at Faculty of Dentistry, Jordan University of Science and Technology. Patients were evaluated using a pilot-tested, 21-question questionnaire. RESULTS: Ninety-six percent of participants were aware of DIs, with no difference between CDWs and RPD wearers (p > 0.05). The participants' friends and relatives were the main source of information (63.4%), followed by dentists (32.4%). Improvement in function was the predominant reason (55.7%) for patients to consider DIs. Fear of unknown side effects was the major factor in preventing patients from choosing DIs (11.7%), followed by high cost (9.7%) and surgical risk (8.7%). Approximately 89% had no information or were poorly informed about DIs. Over two-thirds of patients did not know about the care (78.3%) of DIs, causes of DI failure (69.7%), or DI duration of service (80.7%). Only 24.7% knew that DIs would be anchored to the jawbone; however, 27.3% and 56.7% of CDWs and RPD wearers, respectively, preferred (p < 0.05) to have their teeth replaced with DIs. High costs were considered the major disadvantage of DIs in 45% of participants, followed by fear of surgery (27.3%), and long treatment times (24.7%). CONCLUSIONS: There was a high awareness about DIs among removable denture patients; however, this awareness was associated with a low level of accurate information.

Effect of an occlusal screw-access hole on the fracture resistance of permanently cemented implant crowns: a laboratory study.

This study aimed to evaluate the fracture resistance of cement-retained metal-ceramic implant-supported posterior crowns. Three groups of 10 restorations each were tested: group A (cement-retained using zinc phosphate), group B (cement-retained using zinc oxide-eugenol), and group C (cement-retained using zinc phosphate but with an occlusal screw-access hole). All specimens were thermocycled and vertically loaded in a universal testing machine. Mean values of fracture loads were calculated and analyzed statistically. The cement-retained restorations without an occlusal screw-access hole showed significantly higher mean fracture loads than those having one. The type of cement did not affect the porcelain fracture resistance significantly.

Porcelain fracture resistance of screw-retained, cement-retained, and screw-cement-retained implant-supported metal ceramic posterior crowns.

PURPOSE: The purpose of this in vitro study was to compare the porcelain fracture resistance between screw-retained, cement-retained, and combined screw- and cement-retained metal-ceramic (MC) implant-supported posterior single crowns; and to investigate the effect of offsetting the occlusal screw-access opening on porcelain fracture resistance of screw-retained and cement-retained MC implant-supported posterior single crowns. MATERIALS AND METHODS: Forty standardized MC molar-shaped restorations were fabricated. The 40 restorations were divided into four groups (SRC, SRO, CRP, and CSC) of 10 specimens each. Group SRC: screw-retained, screw-access hole placed in the center of the occlusal surface; Group SRO: screw-retained, screw access hole placed 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group CRP: cement-retained, zinc phosphate cement was used; Group CSC: cement-retained with a screw-access hole in the center of the occlusal surface. The screw-retained restorations and abutments were directly attached to 3i implant fixtures embedded in acrylic resin blocks. Subsequently, all test specimens were thermocycled and vertically loaded in a universal testing machine at a crosshead speed of 2 mm/min until fracture. Mean values of load at fracture (in N) were calculated in each group and compared with a one-way ANOVA and Tukey's Studentized test (alpha= 0.05). RESULTS: Mean values of loads required to fracture the restorations were as follows (N): Group SRC: 1721 +/- 593; Group SRO: 1885 +/- 491; Group CRP: 3707 +/- 1086; Group CSC: 1700 +/- 526. Groups SRC, SRO, and CSC required a significantly lower force to fracture the porcelain than did the CRP group (p < 0.05). CONCLUSION: The cement-retained restorations showed significantly higher mean fracture loads than the restorations having screw-access openings in their occlusal surface. The position of the screw-access hole within the occlusal surface did not significantly affect the porcelain fracture resistance.