Effect of internal hexagonal index on removal torque and tensile removal force of different Morse taper connection abutments.

STATEMENT OF PROBLEM: The maintenance of the mechanical stability of implant-abutment connections is relevant to the clinical success of implant-supported restorations. However, the reduction in the conical area of abutments with an internal hexagonal index may result in a biomechanical disadvantage in Morse taper connections. PURPOSE: The purpose of this in vitro study was to evaluate the influence of an internal hexagonal index on the removal torque and tensile removal force of different Morse taper connection abutments submitted to thermomechanical cycling. MATERIAL AND METHODS: Forty Morse taper implants with their respective abutments were divided into 4 groups (n=10): straight abutment without index (PRNI); straight abutment with index (PRI); angled abutment without index (PANI); and angled abutment with index (PAI). Each abutment received an insertion torque of 15 Ncm, and the removal torque was recorded before and after thermomechanical cycling (106 cycles, 2 Hz, load of 130 N). After cycling, the groups were submitted to tensile testing at 0.5 mm/min under a load of 500 N until displacement of the abutment. A paired t test was performed for the intragroup analysis of removal torque before and after cycling and 2-way ANOVA followed by the Tukey Honestly Significant Difference (HSD) test was used for intergroup comparison (α=.05). RESULTS: Statistical analysis showed significant differences in intragroup removal torque values before compared with after thermomechanical cycling (P<.05). No statistically significant differences were found between the experimental groups in the removal torque of the prosthetic screw after cycling. The index factor (P=.028) was significant for tensile removal force. CONCLUSIONS: The type of abutment did not significantly influence the removal torque or tensile removal force after cycling. However, the presence of the internal hexagonal index significantly reduced the force necessary to dislodge the abutment from the implant.

Crown-root fracture with pulp exposure: a case report with 16-year follow-up.

A 12-year-old boy presented for dental care 35 days after he fell from his bicycle. Clinical and radiographic examinations revealed a longitudinal crown-root fracture with pulp exposure in the maxillary left central incisor. The radiograph also suggested necrosis of the maxillary right central incisor. Urgent treatment of the left central incisor involved gingivectomy followed by autogenous bonding of the tooth fragment with self-curing composite resin. Immediately after bonding, coronal access was prepared, chemical and mechanical preparation was completed, and a calcium hydroxide intracanal dressing was placed. One week after the initial appointment, endodontic treatment was initiated in the right central incisor. The root canal of the maxillary left central incisor was maintained with calcium hydroxide paste (replaced at 45-day intervals) for 1 year and then definitively obturated. At the 16-year follow-up, satisfactory periodontal, esthetic, and clinical conditions were observed, and a radiograph revealed no resorption or periapical changes.

Autogenous bonding of lower incisors: case report and 17-year follow-up.

Among injuries that affect permanent teeth, the most prevalent is an uncomplicated crown fracture. Currently, autogenous bonding of the fragments is still the procedure of choice to restore fractured anterior teeth if the fragments are recovered by the patient and taken to a dental office within a reasonable time in an appropriate storage medium. There is no study or case report in the literature regarding autogenous bonding of lower incisors. This study presents a case with a 17-year follow-up for a 9-year-old patient who underwent uncomplicated crown fractures of the permanent mandibular central incisors and was treated by autogenous bonding of the tooth fragments. After 17 years, clinical and radiographic dental elements present vitality, and the restorations remain without major cosmetic changes. This case shows that autogenous bonding can be considered as a treatment option in the management of fractured lower incisors.

Dimensional accuracy of stone casts obtained with multiple pours into the same mold.

Aim. The aim of the present study was to compare the dimensional accuracy of stone casts obtained with vinyl polysiloxane molds through the double-impression technique with three pours into the same mold. Methods. A stainless steel master model was constructed simulating a three-unit fixed prosthesis. Twelve impressions were taken of this master model with addition silicone, using the double-impression technique. Three pours of type IV gypsum were then made into each mold, thus producing 36 casts. The pours were made 1 hour, 6 hours and 24 hours after the impression procedure. Next, intra- and interabutment measurements were made in a coordinate measuring machine. Results. Comparative analysis of the dimensional accuracy of stone casts resulting from multiple pours was not statistically significant in pours first and second (P > 0.05). These values, however, were statistically significant at third pour in the height in abutment 1 and upper distance interabutment. Conclusion. The wait time (1 hour, and 6 hours) observed before pouring the stone into the same molds did not cause significant dimensional accuracy of the casts.