Is There "A Best" Centric Relation Record? Centric Relation Records, Condyle Positions, and Their Practical Significance.

PURPOSE: To investigate if and how the positions of condyles in centric relation (CR) varied from each other using different CR records. MATERIALS AND METHODS: Condylar positions in CR were repeatedly recorded by four licensed clinicians in 81 stomatognathically healthy, fully dentate subjects with six different types of CR records. The maxillary casts were mounted in articulators after individual facebow transfer, and the mandibular casts were mounted with a central bearing point (CBP) registration on the tip of the Gothic arch. Mean values from three registrations of the centric condylar positions with each of the six methods were calculated, and comparative calculations were made. RESULTS: The median spatial distances of the condylar positions between the CBP and all other CR records was 0.73 ± 0.24 mm (0 to 3.19 mm). The median spatial values between the condylar positions of the different CR records ranged from 0.48 to 0.79 mm. Statistically, the positions of almost all types of registration were slightly different from each other. CONCLUSION: Different CR records reproduce slightly different positions of the mandible, which is especially true for CBP registration, whereas reproducibilities and SDs between registrations are similar. Unrefined wax-wafer registrations using bimanual manipulation have proven particularly successful with regard to precision and time requirements, as has CBP registration with regard to condylar position.

The Effect of Primary Stabilization of the Graft in a Combined Surgical and Prosthodontic Ridge Preservation Protocol: A Prospective Controlled Clinical Pilot Study.

The objective of this study was to evaluate the influence of a modified surgical and prosthodontic ridge preservation protocol with direct insertion of a temporary but fixed reconstruction at the time of extraction. After atraumatic extraction and filling of the socket with an in situ-hardening graft material to fortify the outline position of the marginal rim of the former socket, the change in buccal volume was documented with an analog impression and digital scanning and processing workflow of the data. Changes in the soft tissue profile were calculated as the difference between the digitized surface on the day of extraction and at the 6-month follow-up. The results indicate that in the group with stabilization of the graft material with a fixed temporary appliance, the amount of buccal volume loss was reduced to -1.06 mm (95% confidence interval = -1.8 to -0.29) in comparison to the group without temporary reconstruction for sites in the mandible (-2.09 mm), and for the group in the maxilla without temporary reconstruction (-2.17 mm). The difference was statistically significant (P = .0059). Using a single-stage approach while simultaneously reconstructing the esthetic appearance of the patient with a fixed temporary appliance, the described modification of current ridge preservation techniques is able to reduce buccal volume loss after extraction. This might aid the final esthetic rehabilitation of a visible site after extraction by means of a conventional or implant-based fixed reconstruction.

Minimally Invasive Alveolar Ridge Preservation Utilizing an In Situ Hardening ß-Tricalcium Phosphate Bone Substitute: A Multicenter Case Series.

Ridge preservation measures, which include the filling of extraction sockets with bone substitutes, have been shown to reduce ridge resorption, while methods that do not require primary soft tissue closure minimize patient morbidity and decrease surgical time and cost. In a case series of 10 patients requiring single extraction, in situ hardening beta-tricalcium phosphate (ß-TCP) granules coated with poly(lactic-co-glycolic acid) (PLGA) were utilized as a grafting material that does not necessitate primary wound closure. After 4 months, clinical observations revealed excellent soft tissue healing without loss of attached gingiva in all cases. At reentry for implant placement, bone core biopsies were obtained and primary implant stability was measured by final seating torque and resonance frequency analysis. Histological and histomorphometrical analysis revealed pronounced bone regeneration (24.4 ± 7.9% new bone) in parallel to the resorption of the grafting material (12.9 ± 7.7% graft material) while high levels of primary implant stability were recorded. Within the limits of this case series, the results suggest that ß-TCP coated with polylactide can support new bone formation at postextraction sockets, while the properties of the material improve the handling and produce a stable and porous bone substitute scaffold in situ, facilitating the application of noninvasive surgical techniques.

The effect of screw preload and framework material on the success of cementable fixed partial prostheses: A finite element study.

The rigidity of framework materials and overload of the implant system directly affect the final transferred load of the bone around implants. The aim of the present study has been to analyse the influence of framework materials on the transferred load to the implant system and the surrounding bone. A finite element model of a long-span cementable implant-supported fixed prosthesis was created with two coping layers (gold and hybrid composite) to optimise the fitting of the prosthesis to the abutments. Three framework materials were analysed: titanium, gold alloy, and zirconia. The connection screws were first preloaded with 200 N. The framework was then loaded with 500 N vertically and at 30° to the framework long axis. Two loading conditions were considered: at the mesial and distal boundaries of the framework and at the centre of the framework. The stresses and strains within the framework materials and bone bed around the supporting implants were analysed. The region and angle of load applications showed an obvious effect on the values of the stresses and strains within the framework itself and, consequently, their distribution in the implant system and surrounding bone. A correlation of the framework material and stresses of the coping materials was observed as well. The gold framework showed acceptable values of stress within the cortical bone (92 MPa and 89 MPa with 30° loading at two points and at the centre, respectively) in comparison to titanium (92 MPa and 113 MPa) and zirconia (88 MPa and 115 MPa).