Muscle and joint mechanics during maximum force biting following total temporomandibular joint replacement surgery.

Total temporomandibular joint replacement (TMJR) surgery is the established treatment for severe temporomandibular joint disorders. While TMJR surgery is known to increase mouth-opening capacity, reduce pain and improve quality of life, little is known about post-surgical jaw function during activities of daily living such as biting and chewing. The aim of this study was to use subject-specific 3D bite force measurements to evaluate the magnitude and direction of joint loading in unilateral total TMJR patients and compare these data to those in healthy control subjects. An optoelectronic tracking system was used to measure jaw kinematics while biting a rubber sample for 5 unilateral total TMJR patients and 8 controls. Finite element simulations driven by the measured kinematics were employed to calculate the resultant bite force generated when compressing the rubber between teeth during biting tasks. Subject-specific musculoskeletal models were subsequently used to calculate muscle and TMJ loading. Unilateral total TMJR patients generated a bite force of 249.6 ± 24.4 N and 164.2 ± 62.3 N when biting on the contralateral and ipsilateral molars, respectively. In contrast, controls generated a bite force of 317.1 ± 206.6 N. Unilateral total TMJR patients biting on the contralateral molars had a significantly higher lateral TMJ force direction (median difference: 63.6°, p = 0.028) and a significantly lower ratio of working TMJ force to bite force (median difference: 0.17, p = 0.049) than controls. Results of this study may guide TMJ prosthesis design and evaluation of dental implants.

Effect of prefabricated immediate interim prosthesis design and insertion workflow on seating accuracy on implants placed via static computer-assisted implant surgery: A cross-sectional in vitro study.

BACKGROUND: Immediate implant restoration by prefabricated prosthesis has multiple benefits. However, the design and insertion workflow of the prosthesis may influence the seating. PURPOSE: Evaluation of seating accuracy of prefabricated interim prosthesis of different designs and insertion workflows for immediate restoration of implants placed via static computer-assisted implant surgery (sCAIS). MATERIALS AND METHODS: A maxillary model without incisors was used to plan for two implants at the lateral incisor locations. According to the planned implants, sCAIS surgical template and a four-unit interim prosthesis were designed. Four prostheses were fabricated based on the design and insertion workflow. The first prosthesis involved complete fabrication (CF) of the interim prosthesis, where the interim prosthesis is fabricated for laboratory attachment to abutments. The other three prostheses were produced by partial fabrication (PF), where the interim prosthesis shell was produced with internal spacing between the fitting surface and the abutments. The PF prostheses were cemented on abutments attached to the inserted implants. Three different PF prosthesis designs were included with different levels of internal spacing: 100 µm (PF.1), 200 µm (PF.2), and 300 µm (PF.3). A total of 15 surgical models received implants on which each prosthesis was seated and scanned by a laboratory scanner. The vertical, horizontal, and proximal contact errors were measured. RESULTS: Although all prostheses were seated on every model, the CF prostheses had greater vertical error, followed by PF.1, PF.2, and PF.3 prostheses, respectively. A similar pattern was observed for proximal contact error, where PF.3 was most superior. PF.3 prostheses had the least horizontal error than the other prostheses. CONCLUSIONS: All interim prostheses experienced errors at the vertical, horizontal, and proximal surfaces, which can be attributed to deviations of the inserted implants. The PF of interim prosthesis with increased internal spacing for intraoral insertion appeared to reduce seating errors.

Influence of Implant Adjacent Teeth on the Accuracy of Digital Impression.

OBJECTIVE: The aim of this study was to evaluate the effect of adjacent teeth patterns on the accuracy of digital scans of parallel and divergent implants for three-unit prostheses. MATERIALS AND METHODS: A maxillary typodont model with implants in the locations of the first premolars and first molars was used to develop three clinical scenarios for three-unit prostheses: (S1) Partially edentulous arch with missing first premolars and first molars only; (S2) partially edentulous arch with missing first premolars, second premolars and first molars; and (S3) partially edentulous arch with missing canines, first premolars, second premolars, first molars, and second molars. On one side, the implants were parallel, and for the other side, the implants had a 15-degree buccolingual angle. With the aid of scan bodies, 10 digital impressions were taken for each scenario and for each side. To evaluate the accuracy, a reverse engineering software was used to measure trueness, precision, and interimplant distance. RESULTS: The best trueness for parallel implants was observed for S2 (30.0 µm), followed by S3 (67.3 µm) and S1 (74.8 µm) (p < 0.001). Likewise, S2 had the best precision for parallel implants (31.3 µm) followed by S3 (38.0 µm) and S1 (70.3 µm) (p < 0.001). For the divergent implants, S2 exhibited the best trueness (23.1 µm), followed by S3 (48.2 µm) and S1 (59.4 µm) (p = 0.007). Similarly, the S2 had the best precision (12.3 µm) followed by S3 (62.1 µm) and S1 (66.9 µm) (p < 0.001). The S2 had the least interimplant distance deviation followed by S1 and S3. The difference was significant for parallel implants (p = 0.03), but insignificant for divergent implants (p = 0.15). CONCLUSION: Regardless of the presenting scenario, digital implant impressions for three-unit prostheses appear to be clinically accurate. A clear interimplant area between scan bodies enhanced the accuracy of digital impressions. This observation can be attributed to more accessible axial surface scanning of the scan body.

The Effect of Various Lasers on the Bond Strength Between Orthodontic Brackets and Dental Ceramics: A Systematic Review and Meta-Analysis.

Background/objective: This systematic review and meta-analysis aimed to assess how laser conditioning affected brackets bonded to dental ceramics' shear bond strength (SBS). Materials and methods: The study was conducted by searching Pubmed/Medline, Scopus, Embase, Web of Science, the Cochrane Library, and Google Scholar up to September 14, 2022. In addition, the reference lists of the relevant articles were checked manually. Articles that compared SBS of laser-treated feldspathic, lithium disilicate, or zirconia surfaces with other standard techniques for bonding metal or ceramic orthodontic brackets were considered. Using a random-effects model, data pooling was carried out as the weighted mean difference (WMD). Results: This study initially contained 1717 reports, and following review, 32 articles were deemed suitable for our meta-analysis. The pooling results showed that the treatments with lasers such as "Er:YAG" [WMD = -1.12 MPa; 95% confidence interval (CI): -1.93 to -0.31], "Er:YAG + Silane" (WMD = -3.08 MPa; 95% CI: -4.77 to -1.40), and "Nd: YAG + Silane" (WMD = -2.58 MPa; 95% CI: -3.76 to -1.40) had statistically significant lower adhesion values compared with controls. Contrarily, "Ti:Sapphire femtosecond" demonstrated significantly higher bonding values (WMD = 0.94 MPa; 95% CI: 0.29-1.60). In contrast, other interventions obtained no statistically significant difference in SBS. Conclusions: Most of the laser groups showed results comparable with those of conventional approaches. Although more research is necessary for definitive conclusions, laser treatment may be an effective option for treating the surfaces of ceramic materials.

Effect of pilot-guided implant placement concept on the accuracy of osteotomy preparation and implant placement.

PURPOSE: To evaluate the accuracy of osteotomy preparation and implant placement for 3 pilot-guided (PG) concepts, namely, a surgical template with a metal sleeve (MS), a surgical template with an in-built nonmetal sleeve (NMS), and a surgical template with an in-built nonmetal sleeve for round bur indentation (RB). METHODS: Surgical models with missing maxillary molars were studied. The MS templates were designed to accept metal sleeves, while the NMS and RB templates were designed with in-built nonmetal sleeves. Ten templates were tested per group (n = 10). After each step (pilot drilling, 2nd drilling, 3rd drilling, profiling, and implant placement), the surgical model was scanned and compared against the planning model to determine maximum horizontal deviation (MHD) and maximum angle deviation (MAD). RESULTS: The MS and NMS templates exhibited a similar increase in MHD with successive drilling steps. The MAD for the pilot drilling step was significantly lower for MS than for the other groups. However, the differences among groups for MHD and MAD diminished in later steps. All templates had an MHD of 1.0 mm or less and an MAD less than 8°. CONCLUSION: The investigated PG implant placement concepts resulted in similar deviations in the placed implants.

Kinematics of the jaw following total temporomandibular joint replacement surgery.

Total temporomandibular joint (TMJ) replacement surgery aims to improve mandibular function, reduce pain and enhance quality of life in patients suffering from end-stage TMJ disorders. Traditional post-operative jaw evaluation is carried out using measurement of maximum interincisal opening distance; however, this can correlate poorly to joint function. The present study aimed to evaluate three-dimensional (3D) jaw motion during border movements and chewing in unilateral total TMJ replacement patients and healthy controls. Motion analysis experiments were performed on six unilateral total TMJ replacement patients and ten age-matched healthy controls. Subject-specific motion tracking plates worn by each participant were registered to CT scans of each participant's skull and mandible to enable anatomical mandibular kinematics measurement using an optoelectronic system. Participants performed 15 repetitions of maximal opening, protrusion, lateral excursions, and chewing cycles. Total TMJ replacement patients had significantly smaller incisal displacements at maximum mouth opening relative to the controls (median difference: 7.1 mm, p = 0.002) and decreased anterior translation of the prosthetic condyle (median difference: 10.5 mm, p = 0.002). When TMJ replacement subjects chewed using their contralateral molars, there was a significant increase in inferior condylar translation of the non-working condyle (median difference: 9.7 mm, p = 0.016). This study found that unilateral total TMJ replacement surgery was associated with mouth opening capacity within the range of healthy individuals, but reduced anterior movement of the prosthetic condyle and restricted protrusion and lateral excursions. The results provide future direction for prosthetic TMJ design to enhance postsurgical implant functionality and improve long-term clinical outcomes for prosthesis recipients.

Measuring tooth movement with treatment using the Dahl principle: An observational study.

STATEMENT OF PROBLEM: Research on the quantification of 3-dimensional tooth movements in patients undergoing treatment using the Dahl principle is lacking. PURPOSE: The purpose of this observational clinical study was to measure the magnitude, direction, duration, and rate of tooth movement occurring in patients to reestablish tooth contact and create restorative space. MATERIAL AND METHODS: A total of 104 paired preoperative and postoperative physical and virtual casts from 26 patients were obtained. Commencement and completion dates were recorded to calculate movement duration to reestablish occlusion. Dental casts were digitized, and the 3-dimensional digital casts obtained were superimposed via a surface matching and analysis software program by using the global registration function. Color maps were used to visualize direction, and the annotation feature quantified magnitude of tooth movement in millimeters when specific reference points were selected. Teeth within the arch were categorized as per their location to evaluate their impact on occlusal reestablishment. The average rate of movement was determined by time taken for extrusive and intrusive movements over the treatment duration. Post hoc Tukey tests were applied if a significant difference was present in the magnitude of movement between different tooth categories. RESULTS: All participants showed evidence of tooth movement during treatment. Duration of occlusal reestablishment ranged from 3.9 to 28.2 months, with more posterior tooth extrusive movements (56.9%) than anterior tooth intrusive (43.1%) movements occurring. A comparison of magnitude of extrusive or intrusive movement between categories (molar-anterior, premolar-anterior, and premolar-molar) showed that premolar and molar extrusive movements and anterior intrusive movements were significantly different (P<.001). The amount of buccal and lingual movement for molars and premolars was similar. Anterior teeth demonstrated more buccal than lingual movements. All teeth showed more mesial than distal movements. The extrusive and intrusive movement rate was 0.13 and 0.11 mm/mo, respectively. CONCLUSIONS: Tooth movement occurred in patients regardless of age and sex. The results of this study indicated that tooth movements have a 3-dimensional nature. Occlusal reestablishment mainly occurred via a combination of extrusive and intrusive movements. The study further highlighted the advantages of digital technology such as surface scanners and 3-dimensional software programs that can be used to quantify change in patients undergoing treatment.

Marginal Accuracy of Monolithic and Veneered Zirconia Crowns Fabricated by Conventional and Digital Workflows.

PURPOSE: To compare the marginal accuracy of zirconia crowns fabricated by different workflows (conventional and digital) and designs (monolithic and veneered). MATERIALS AND METHODS: A prepared maxillary first molar was used for the study. Four workflow combinations were evaluated: (1) intraoral scanning and monolithic zirconia (IOS-M), (2) intraoral scanning and veneered zirconia (IOS-V), (3) conventional impression and monolithic zirconia (IMP-M), and (4) conventional impression and veneered zirconia (IMP-V). All of the specimens had similar designs. The veneered groups had a buccal cutback for esthetic veneer application. A total of 10 crowns were produced in each workflow. The vertical and horizontal marginal accuracies were measured with a traveling microscope. Depending on the normality of the data, one-way analysis of variance test or Kruskal-Wallis test were applied to evaluate the differences among the groups (α = 0.05). RESULTS: The most superior vertical marginal accuracy was observed for IOS-V (mean = 22.5 µm; SD = 6.7 µm), followed by IMP-V (mean = 23.9 µm; SD = 7.8 µm), IOS-M (mean = 28.7 µm; SD = 10.3 µm), and IMP-M (mean = 39.8 µm; SD = 22.0 µm), respectively (p < 0.001). The IOS-M had the greatest mean horizontal discrepancies (mean = 23.9 µm; SD = 4.3 µm) followed by IMP-M (mean = 21.3 µm; SD = 5.7 µm), IMP-V (mean = 19.2 µm; SD = 5.3 µm) and IOS-V (mean = 17.6 µm; SD = 5.7 µm) (p < 0.001). CONCLUSIONS: Monolithic zirconia crowns fabricated digitally had superior marginal accuracy than monolithic zirconia crowns fabricated conventionally. Esthetic buccal veneering of predominantly monolithic zirconia copings improved the vertical and horizontal marginal accuracies.

Effect of preparation type on the accuracy of different intraoral scanners: An in vitro study at different levels of accuracy evaluation.

OBJECTIVE: Evaluation of the effect of preparation type (inlay, onlay, and crown) on the accuracy of different intraoral scanning (IOS) systems at the preparation and arch segment levels. MATERIALS AND METHODS: Three molars were prepared for inlay, onlay, and crown. Each preparation was scanned 10 times by CEREC Omnicam, Trios 3 (TS), and Medit i500 scanners. Each image was trimmed twice. The first trimming produced a preparation image (PI), and the second trimming extracted a segment image (SI) that involved the preparation with the adjacent teeth. Trueness and precision were calculated at the PI and SI levels. RESULTS: At the PI level, all IOS systems had similar trueness pattern for all preparations, where the inlay had the best trueness followed by the crown and onlay. At the SI level, the different preparations showed similar trueness. The precision did not show a clear pattern of superiority for any preparation. The TS was significantly more precise than other IOS systems at the PI and SI levels, for every preparation. The proximal areas suffered from the greatest errors, regardless of preparation type. CONCLUSIONS: The preparation type influenced PI trueness, and the IOS system affected PI and SI precisions. CLINICAL SIGNIFICANCE: The smaller and less complex preparations have greater IOS accuracy than larger and more complex preparations. As the proximal areas are more affected regardless of the preparation, a more accessible proximal area for scanning is desirable.

Proximal contact loss between implant prostheses and adjacent natural teeth: A qualitative systematic review of prevalence, influencing factors and implications.

Objectives: To evaluate the prevalence of proximal contact loss (PCL) between implant prostheses and natural teeth, and identify the risk factors and implications associated with PCL. Data/sources: PubMed (MEDLINE), Google Scholar, Cochrane Library Database, Scopus, EMBASE, Open Grey, ScienceDirect, and Web of Science were electronically searched to retrieve clinical studies on PCL around implant prostheses up to September 2021. Study selection: A total of 19 studies were eligible. The short-term studies (less than 2 years) revealed a PCL prevalence of 11-30%, the medium-term studies (2-5 years) indicated a PCL prevalence of 13-65%, and the long-term studies (more than 5 years) showed a PCL prevalence of 29-83.3%. The likely influencing factors were the duration of service and the mesial location of proximal contacts. Other factors, such as occlusion, vitality of adjacent teeth, implant location, patient age and splinting had a less obvious relation to PCL. The reported implications of PCL were food impaction and patient dissatisfaction. Bone loss, peri-implant inflammation, bleeding on probing and pocket depth had a less clear association with PCL. Conclusions: PCL development between implant prostheses and natural teeth is frequent, inevitable and progressive. While the review identified several influencing factors and implications of PCL, future research is needed to outline the influence of prosthesis design on PCL and food impaction. Clinical significance: Patients with implant prostheses should be informed about PCL likelihood and the risk of food impaction around implant prostheses. The proximal contact quality and its implications should be monitored during the review visits.

Current techniques for digital complete denture fabrication.

The integration of modern technologies in removable prosthodontics in terms of complete denture fabrication has revolutionized fabrication procedures, improved outcomes, and led to advancements in denture materials. Numerous publications have described the digital techniques of complete denture fabrication. The steps described in these publications for the proposed digital workflow are diverse. This is suggestive of the flexibility of these modern techniques in terms of their integration with the steps of conventional protocols. Automated technologies have reduced the need for skilled manual work, while particular knowledge and a new skills set are required for both clinicians and dental technicians. Moreover, the effectiveness and efficacy of these modern technologies in complete denture fabrication are yet to be determined. To consolidate the existing literature on digital techniques of complete denture fabrication, this review summarizes the current digital workflows of the clinical and laboratory stages, describes the digital alternatives in each step, and discusses their advantages and limitations.

Clinical and Laboratory Outcomes of Angled Screw Channel Implant Prostheses: A Systematic Review.

The purpose of this systematic review was to evaluate the clinical and laboratory outcomes of angled screw channel (ASC) restorations and to summarize the influencing factors. An electronic search of the English language literature was performed in four databases and enriched by manual searches. Retrieved studies were screened against the predefined exclusion and inclusion criteria. Eight clinical and seven laboratory studies were eligible for the analysis. The risk of bias for included observational studies was performed using the Newcastle-Ottawa quality assessment scale. Laboratory studies quality assessment method was adapted from previous published systematic reviews. Two clinical studies focused on technical outcomes and the rest reported the biological outcomes of the ASC restorations. Out of the seven laboratory studies, two studies investigated the fracture resistance of ASC restorations, four studies evaluated the reverse torque value of the nonaxially tightened screws, and one study evaluated both variables. The present review revealed that while the performance of ASC restorations is promising in short-term clinical studies, the evidence of their long-term reliability is still lacking. The laboratory studies indicated comparable fracture resistance results of the ASC restorations with the straight screw channel restorations. In addition, factors, such as initial torque value, configuration of the screw driver, screw design, abutment system, and the angulation of screw channel, were shown to influence the screw resistance to loosening.

An In Vitro Evaluation of the Effect of 3D Printing Orientation on the Accuracy of Implant Surgical Templates Fabricated By Desktop Printer.

PURPOSE: To evaluate the effect of different 3D printing orientations on internal and seating accuracy of implant surgical templates fabricated by a digital light processing (DLP) printer. MATERIALS AND METHODS: A single maxillary model with a missing central incisor was used to design a surgical template for single implant placement. According to the printing orientation, three surgical template groups were included in the study: horizontal (H), angled (A) and vertical (V) (n = 10). For the H group, the templates were produced parallel to the printing platform, while for the V group, the templates were perpendicular to the platform. The A group templates had a 45° angle orientation to the platform. Each template was scanned at the fitting surface and after seating on the master model. The internal accuracy involved measuring the trueness and precision of the internal surface, while for the seating accuracy, the vertical discrepancy after seating the template was measured. To determine the difference among the groups, ANOVA test was applied followed by Tukey post hoc tests (α = 0.05). RESULTS: The H group had the lowest internal surface inaccuracy (trueness = 100.7 µm; precision = 69.1 µm) followed by A (trueness = 114.0 µm; precision = 77.3 µm) and V (trueness = 120.3 µm; precision = 82.4 µm) groups, respectively (p < 0.001). Similarly, the H group had the most superior seating accuracy (543.8 µm) followed by A group (1006.0 µm) and V group (1278.0 µm), respectively (p < 0.001). CONCLUSIONS: The orientation of 3D printing of implant surgical templates fabricated by the DLP desktop printer influenced the accuracy of the templates. The horizontally printed templates consistently exhibited superior accuracy. To reduce deviation of implant placement, it is recommended to print the surgical templates with their largest dimension parallel to the printing platform.

Effect of Aging on the Load-to-Failure of Molar Implant-Supported Monolithic Zirconia Crowns: A Laboratory Study.

PURPOSE: To evaluate the effect of hydrothermal aging on the load to failure and number of cycles to failure of implant-supported monolithic zirconia molar crowns under cyclic loading. MATERIALS AND METHODS: Twenty identical implant-supported monolithic zirconia crowns with molar morphology were produced. Half of the crowns were aged according to ISO standard 13356 to simulate 5 years in vivo. The non-aged crowns served as a control group. All crowns were subjected to cyclic loading with increasing increments of load until failure. The load to failure, the number of cycles to failure, and the failure pattern were determined for each crown. RESULTS: The load to failure values were 3,630 N (SD: 547.8 N) and 3,640 N (SD: 389.3 N) for the non-aged and aged crowns, respectively. The non-aged crowns failed after 33,480.1 cycles (SD: 23,138.4 cycles), and the aged crowns failed after 28,456.1 cycles (SD: 10,158.7 cycles). There was no significant difference between the two groups for the load to failure or number of cycles to failure. The predominant form of failure was catastrophic crown fracture, which was observed for all the non-aged crowns and 9 of the aged crowns. CONCLUSION: Within the limitations of this study, aging of the implant-supported monolithic zirconia crowns with molar morphology did not affect the load to failure or the number of cycles to failure under cyclic loading. Since all the crowns failed at much higher loads than the expected physiologic loads, clinical application of implant-supported monolithic zirconia crowns to replace missing molars seems reasonable.

Duration, deviation and operator's perception of static computer assisted implant placements by inexperienced clinicians.

INTRODUCTION: This study measured the duration, deviation and operator's perception of implant placement by fully guided (FG), pilot-guided (PG) and freehand (FH) protocols by postgraduate students with minimal implant experience. MATERIALS AND METHODS: Twenty postgraduate students participated in the study. Half of them placed single anterior (S-Ant) and single posterior (S-Post) implants, and the other half placed anterior (B-Ant) and posterior (B-Post) implants in a wide edentulous area. The PG placement involved surgical guides that only controlled pilot drilling, whilst the FG placement controlled all the drilling steps and implant placement. The duration of implant placement and the operator's perception (ease of drilling, ease of implant placement and operator's preference) were measured. The deviations of placed implants were quantified by measuring the trueness and angulation deviations in relation to the planned implants. RESULTS: The PG placement was the quickest for inserting implants, followed by FG and FH placements, respectively (p < .05). The location of the implant had influenced the duration of implant placement only for the PG placement. In relation to ease of drilling, ease of implant placement and operator's preference, there was no significant difference amongst the different placement protocols or implant locations. The FG placement was associated with least deviations, followed by PG and FH placements, respectively (p < .05). CONCLUSIONS: In the hands of postgraduate students with minimal implant experience, FG and PG placements reduced the implant placement duration in comparison with FH placement. The FG placement was consistently more accurate followed by PG placement.

Accuracy of digital impressions versus conventional impressions for 2 implants: an in vitro study evaluating the effect of implant angulation.

BACKGROUND: Accurate implant impression is an essential requirement for the fabrication of implant prosthesis. This in vitro study evaluated the accuracy of digital impressions by intraoral scanner (IOS) systems in comparison to conventional impressions for recording the position of 2 parallel implants and 2 divergent implants. MATERIALS AND METHODS: In vitro 3-unit prosthesis master models with 2 tissue level implants were fabricated; one model had parallel implants, and the other model had one 15° tilted implant. The conventional open-tray impressions were obtained with non-splinted (NSP) and splinted (SP) impression copings. Trios 4 (TS), Medit i500 (MT), and True Definition (TD) were used to make digital impressions with scan bodies. A total of 10 impressions were obtained with every technique. The virtual test images of the conventional and digital impressions were converted to 2 virtual implant images. For each group, trueness, precision, inter-implant distance deviation, and angle deviation were measured. RESULTS: There was a general tendency for digital impressions to provide a more accurate outcome for trueness, precision, and angle deviation. The 2 conventional impressions showed similar accuracy, except for the angle deviation, where the NSP was significantly inferior than SP (p < 0.01) for the divergent implants model. The TD was generally the least accurate among all the IOS systems, especially for the inter-implant distance deviation (p < 0.05). CONCLUSIONS: Within the limitations of the laboratory set-up of the present study and the limited clinical resemblance, the digital impressions appeared to have sufficient accuracy for 2 implants and were least affected by the presence of angle between implants. The most inferior outcome was observed for the NSP technique.

Accuracy of static computer-assisted implant placement in long span edentulous area by novice implant clinicians: A cross-sectional in vitro study comparing fully-guided, pilot-guided, and freehand implant placement protocols.

BACKGROUND: To ensure accurate implant placement, surgical guides are used to control the steps of implant placement surgery. PURPOSE: Evaluation of the accuracy of implant placement in long span edentulous area by novice implant clinicians according to fully-guided (FG), pilot-guided (PG), and freehand (FH) placement protocols. MATERIALS AND METHODS: Maxillary surgical models with four missing teeth from the right first canine to the first molar were produced by 3-dimensional printing. Fourteen clinicians new to implant dentistry participated in the study, and each one of them inserted one canine and one molar implant for every implant placement protocol. All implant placement steps were completed in phantom heads to simulate the clinical situation. To evaluate the accuracy, the implant vertical, horizontal platform, horizontal apex, angle, and interimplant distance deviations from the planned positions were calculated. RESULTS: With the exception of vertical deviation, the FG placement was clearly more accurate than the PG and FH placements for all the variables for canine and molar implants. The PG placement was significantly more accurate than the FH placement for the horizontal platform and apex deviations, and interimplant distance deviation. The FG placement did not show a significant impact of the location of the implant, or the horizontal deviations of the platform or the apex. The PG and FH placements showed increased deviation at the canine implant than the molar implant, and at the apex of the implants than the platform of the implants. CONCLUSIONS: Within the limitations of this in vitro study, novice clinicians achieved a significantly more accurate implant position with FG placement, followed by PG and FH placements respectively. Therefore, a form of guided surgery is beneficial for novice clinicians.

Influence of the application of a pre-sintered surface augmentation on zirconia and lithium disilicate bonding using an adhesive composite resin cement.

OBJECTIVE: The purpose of this laboratory study is to evaluate the application of a pre-sintered surface augmentation to zirconia (Zir) and lithium disilicate (LDS) ceramics on the delamination strength of adhesive resin cement. The applied surface augmentation was the ruling of lines to the pre-sintered surface of the ceramics. METHODS: Ninety milled Zir and sixty pressed LDS specimens (3mm×0.5mm×25mm) were created and divided into five groups (n=30). Group 1: Zir no surface treatment (control Zir-NT); Group 2: Zir airborne particle abraded (Zir-APA) with 30µm CoJet; Group 3: Zir pre-sintered surface augmentation (Zir-SA); Group 4: LDS etched (control LDS-etched) and; Group 5: LDS with pre-sintered surface augmentation and etching (LDS-SA). A resin adhesive cement (3mm×1mm×8mm) was then applied and cured to the ceramic specimens. The delamination strength values of the resin cement from the ceramic were recorded. The delamination strength data were analysed statistically using one-way ANOVA and Turkey post hoc analysis. RESULTS: The mean delamination strength and standard deviation, when comparing only the Zir-SA to the resin cement were statistically different (p<0.001); Zir-SA 63.42±11.85, Zir-NT 26.82±12.07, and Zir-APA 48.11±17.85MPa. Comparison between LDS groups were not significantly different (p=0.193); LDS-etched 33.49±16.07 and LDS-SA 28.83±10.15MPa. The delaminated Weibull modulus was highest for surface augmentation Zir specimens (m=13.56) but decreasing to less than half for Zir-APA (m=6.27) and Zir-NT (m=5.68). The Weibull values for the LDS-SA and LDS-etched specimens was 5.63 and 3.38 respectively. SIGNIFICANCE: Incorporating the pre-sintered surface augmentation to zirconia improved the delamination strength and reliability of Zir to the resin cement but not for LDS.

Seating accuracy of implant immediate provisional prostheses fabricated by digital workflow prior to implant placement by fully guided static computer-assisted implant surgery: An in vitro study.

OBJECTIVES: Evaluation of seating accuracy of implant immediate provisional prostheses fabricated prior to fully guided static computer-assisted implant surgery (sCAIS). MATERIALS AND METHODS: Two maxillary training models were used to plan for single anterior (S-Ant) and single posterior (S-Post) implant prostheses, and a bridge (B) spanning from an anterior implant (B-Ant) to a posterior implant (B-Post). A commercial software was used to plan the implant location, design the surgical guides and design the provisional prostheses. The master models with the provisional prostheses were scanned to generate virtual master models. For each maxillary model, a total of 10 guides and 10 surgical models were produced. Following implant placements in each surgical model, the provisional prostheses were attached to the implants and were scanned to produce virtual surgical models. The virtual master and surgical models were superimposed to measure the vertical error, the proximal contact error and the proximal contact quality. RESULTS: The vertical error was greatest for the S-Post (0.41 mm), followed by B-Post (0.29 mm), B-Ant (0.26 mm) and S-Ant (0.21 mm). There was no significant difference in vertical errors among the prostheses. For the proximal contact, the S-Ant had significantly greater error (0.45 mm - 0.46 mm) than S-Post (0.15 mm) and B (0.09 mm - 0.15 mm). A similar pattern was observed for proximal contact quality. CONCLUSIONS: All prostheses were associated with errors vertically and at the proximal contacts. Therefore, the clinicians who plan to use this workflow should be prepared to adjust the prosthesis after implant insertion.

Accuracy of Intraoral Scanners for Recording the Denture Bearing Areas: A Systematic Review.

PURPOSE: To systematically review clinical and laboratory studies that investigated the accuracy of intraoral scanners in recording denture bearing areas. MATERIALS AND METHODS: Electronic and manual searches were conducted to identify all the available clinical and laboratory studies reporting the accuracy of digital impressions for recording denture related soft tissues. After the application of predetermined inclusion and exclusion criteria, the final list of articles was reviewed to meet the objective of this study. RESULTS: The inclusion criteria were met by 18 studies out of which 8 were clinical and the rest were laboratory investigations. The eligible studies assessed the accuracy of intraoral scanners in recording both the denture supporting structures and the peripheral mobile tissues. The accuracy results were different among the various intraoral scanners. Likewise, the effect of several influencing factors, such as artificial markers, scanner head size, scanning strategy, and the operator's experience, were evaluated. CONCLUSION: While the accuracy of intraoral scanners was comparable to the conventional techniques in recording bony structures with attached mucosa, they were not capable of accurately registering the mobile tissues. In addition, factors such as presence of a marker, larger scanner head size and specific scanning techniques appeared to improve the accuracy of the digital impression.