Statement of problem The angled screw channel (ASC) design has been well accepted for implant prostheses. However, investigation into the behavior of the ASC connection is sparse. Purpose The purpose of this in vitro study was to assess the effect of cyclic loading on the internal connection of an ASC system compared with straight access systems by measuring reverse torque values (RTVs) and using microcomputed tomography (µCT) imaging. Material and methods Thirty dental implants (SLActive; Institut Straumann AG) were embedded in autopolymerizing acrylic resin and divided into 3 groups: Group V0, prefabricated abutment with a straight access channel; Group V25, prefabricated abutment with a 25-degree access channel; and Group C, cemented custom abutment with straight access. All specimens were initially secured with 10 Ncm using a digital torque gauge. A subset of specimens from each group (n=4) were randomly selected and assigned for µCT imaging examination and then reimaged after tightening to 35 Ncm. All specimens were subjected to cyclic loading for 5000 cycles with a loading force of 155 ±5 N at 1.2 Hz frequency in a 37 °C water bath using a fatigue machine. Repeat µCT imaging was done after cyclic loading for the representative specimens. The changes to the internal connection were measured on µCT images using a software program, and the RTV measurement of each specimen after cyclic loading treatment was recorded. The ANOVA test was used to analyze the statistical significance of the RTVs among groups (α=.05). The paired t test was used to conduct within-group comparisons of the measurement data. Results Mean ±standard deviation of RTVs varied from 29.05 ±2.99 Ncm to 29.75 ±2.61 Ncm, with no statistically significant differences among the 3 groups (P=.820). The distances from the base of the screw head to the apex of the screw-abutment-implant (SAI) system and internal air space volume within the groups V0 and V25 decreased significantly (P<.05) between the 10-Ncm and 35-Ncm torque applications. Off-axis loading resulted in rotational movement of the abutment that might have created a tensional force on the implant screw. Conclusions Results for the prefabricated abutment groups (V0, V25) indicated that the RTVs were not affected by the amount of angle correction. A counterclockwise rotational movement of the abutment and screw within the SAI system would be formed during off-axial loading.

Sandblasted with large grits and acid-etched (SLA) surface topography has been a common method of implant surface modification to promote bone-implant integration in titanium-based dental implant manufacturing. However, the acid etching protocols used are various. The aim of this investigation was to validate the effect of different acid-etched treatments of sandblasted titanium surfaces on enhancing osteogenic potential. Five different titanium surface groups were prepared and tested including: i) smooth (Control), ii) sandblasted (SL), iii) sandblasted and acid-etched with H2SO4/HCl mixed solution (SLA/SOCl), iv) sandblasted and acid-etched with H2SO4 solution (SLA/SO), and v) sandblasted and acid-etched with HF solution (SLA/HF). The surface characterization, protein adsorption, and cell behavior were examined to determine the osteogenic potential. Compared with the control group, other surface treated groups showed rougher surface, better wettability, more protein absorption, and cell viability, especially in the SLA/SOCl surface group. The results indicated that SLA surfaces prepared with H2SO4/HCl mixed acid solution provided significant potential to promote osteogenesis.

Implant cantilever beam torque limiting devices suffer from two prominant issues. 1. They do not record the peak torque applied. 2. They suffer from viewing angle parallax. A simple, inexpensive device, placed between the measurement reader arms of th instrument that can resolve these issues is described.

Management of implant abutment screw loosening should go beyond simply retightening the abutment screw. This case report highlights the need to check all components for damage before disinfection and re-tightening if possible. Major concerns include the implant-abutment connection site, screw, and debridement of the internal implant surfaces. Scanning electron microscopy and optical microscopic exam of the debris removed after cleaning demonstrated the presence of titanium metal particles and biological materials. Protocols should be developed to address these issues before reattaching the implant restoration.

PURPOSE:To investigate residual debris within internal features of new 'as received' dental implants. MATERIALS AND METHODS:A total of 15 new dental implants representing various dental implant brands were obtained in sealed containers from the manufacturers. Batch numbers and implant types were documented. In a controlled setting, implants were carefully unpacked, and their internal aspects were visually examined. Further analysis involved light microscopy imaging to document and photograph any foreign material. The internal aspect of the implants were sampled with both an endodontic paper cone and a fine bristle brush swab. These were inserted into the implant, rotated three times, then removed and examined under a microscope at 30× magnification. After sampling, some of the brushes and swabs were washed with alcohol to remove debris that could be further examined under magnification. RESULTS:Inspection of the implants without magnification revealed no visible foreign materials. However, under light microscopy (10× and 30×), all 15 implants exhibited small black particles at various internal sites, including connections, threads, and deep within screw channels. Swabs evaluated at magnification detected what appeared to be metal particles in all 15 implants, ranging from distinct metal shards to smaller particles. CONCLUSIONS:This study suggests that implant manufacturers have not effectively removed all machining debris from within implant bodies, potentially producing prosthetic and clinical complications.

Statement of problem The impact of free gingival graft (FGG) dimensions on the postsurgical shrinkage of keratinized tissue width (KTW) and surface area in posterior implant sites is unclear. Standardized assessments of how graft dimensions influence KTW and surface area shrinkage rates over a 6-month period after FGG are lacking. Purpose The purpose of this prospective parallel cohort study was to examine the impact of the graft dimensions on the postsurgical shrinkage of KTW and surface area over a 6-month follow-up period after FGG in the posterior regions. Material and methods Thirty partially edentulous participants with insufficient buccal KTW in the posterior regions were recruited. Before implant placement, participants received FGG procedures and were categorized into single-tooth and dual-tooth groups according to the range of recipient area. Intraoral scanning was performed before and after FGG and at subsequent follow-ups for 6 months. The KTW and surface area shrinkage rates of the grafted area were calculated and statistically analyzed by using the Student t test and ANOVA, and Bonferroni post hoc tests were performed to compare the shrinkage rate of KTW at various edentulous sites (α=.05). Results The mean ±standard deviation KTW shrinkage rate was 18.84 ±5.11% over 6 months postoperatively, and the mean ±standard deviation SA shrinkage rate was 21.53 ±5.70%. The dual-tooth group had a statistically significantly higher KTW shrinkage rate (28.42 ±2.46%) when the second molar edentulous sites were involved (P<.05). Differences in surface area shrinkage rates between the single-tooth and dual-tooth groups over 6 months were statistically similar (P=.239). However, grafts in the second molar area exhibited significantly higher surface area shrinkage rates compared with those at the premolar and first molar areas (P<.001). Conclusions The dimension of free gingival graft tissues did not significantly affect surface area shrinkage rates, and a mean 25% shrinkage rate occurred in the second molar areas.

STATEMENT OF PROBLEM:An implant cantilever beam torque wrench (ICBTW) must be accurate and precise when delivering torque. Any hinderance to its action may have a detrimental effect. A marker device has been proposed as a means of recording the peak torque value of implant screw assembly when using an ICBTW. However, its impact on the torque delivered to the screwdriver along with friction-induced resistance remains unknown. PURPOSE:The aim of this in vitro study was to evaluate the effect of attaching the marker device on torque delivery by testing various ICBTWs with and without the device and comparing the torque values transmitted to the screwdriver. MATERIAL AND METHODS:Four calibrated ICBTWs from 2 manufacturers (Nobel BioCare and Straumann) were connected to their respective screwdrivers and to a calibrated electronic torque measuring device (Imada HTG2-4). The nonfixed end of each cantilever beam was attached to a force gauge (Shimpo FGV-5XY) with an initial crosshead speed of 50 mm/minute and a jogging action of 5 mm/minute. The applied force was recorded when the torque value reached 35 Ncm. For each torque wrench system, 15 measurements were performed with the polyolefin marker device and 15 without the marker device. Statistical analysis consisted of the paired correlated sample t test (α=.05). RESULTS:All paired measurements remained highly consistent. Mean differences were within the measurement error of the force gauge (±0.01 N), indicated that adding the marker device did not affect the torque wrench performance at 35 Ncm (P>.999). CONCLUSIONS:Adding a marker device to the cantilever beam torque wrench can help record reproducible peak torque values without any loss of accuracy or precision.

A practical and novel technique used both in testing and in practice when tightening dental implant screw systems is described for determining the preload implant screw systems, which differs from traditional tightening procedures that are based solely on the application of a predetermined manufacturer specified torque value. Preload is the critical quantity for a reliable joint: about 90% of tightening torque goes into overcoming friction and the remaining amount, approximately 10%, goes into preload. Because of the heavy dependence of torque on friction, the actual preload achieved is subject to large variability of up ±35%, depending on surface conditions (dry, wet, or contaminated). Current methods of testing for preload require complex equipment such as load cells, strain gauges, or finite element analysis. This practical technique integrates tightening torque with removal torque value measurements and screw geometry to determine preload. This information subtracts out the friction components, thereby accounting for differences in surface conditions and reducing the need for multiple test conditions.

Ingestion or aspiration of dental implant screwdrivers or implant components is potentially life-threatening. There are no reports on the frequency at which dentists drop these devices within the mouth or which components are most problematic. There are few reports on what protective measures clinicians take, where risks exist, and how this problem is managed. A 9-part questionnaire was provided to dentists. Data collected included clinicians’ roles, implant surgeons, restorative clinicians, or both—the frequency of dropping implant screwdrivers or components, items considered most problematic. Patient protection and management were also requested. Finally, questions related to how much of a problem clinicians considered this to be and if further solutions and a standardized management protocol should be developed. One hundred twelve dentists voluntarily completed the survey. Of the dentists, 54% restored, 37% restored and surgically placed, and 9% solely placed implants. Twenty-nine percent claimed never to drop components, with 56% dropping an instrument less than 10% of the time. Less than half would suggest patients seek medical advice if a screwdriver or component was accidentally dropped intraorally and was not recovered. Thirty percent never tied floss tethers to screwdrivers, and a similar percentage reported they only sometimes did so. Throat pack protection was reported 51% of the time. Ninety percent considered dropping components an issue, with screwdrivers most problematic. Aspiration or ingestion of implant screwdrivers and components is problematic, with dentists varying their use of protection devices. There is a need to standardize and implement patient protection procedures and management and develop methods to reduce the risk of these potentially life-threatening issues.

Abstract Background The assessment of hard and soft tissue at edentulous sites is important for subsequent implant treatment design. The aim of the present study was to explore the associations between the keratinized mucosa width (KMW) and the underlying alveolar bone dimensions at partial edentulous molar sites. Methods In this retrospective study, a total of 110 patients with at least one missing molar were selected. The buccal KMW of the edentulous molar sites was evaluated. Cone-beam computed tomography scans were collected, and the height discrepancy between the alveolar crest and the buccal bone plate (HC−B) as well as the alveolar bone height (ABH) were measured. The KMW was compared among the HC−B and ABH groups at both maxillary and mandibular sites. Linear regression and generalized estimation equations (GEEs) were used to explore the associations between the KMW and alveolar bone dimensions at α = 0.05. Results Among the 110 patients, 158 edentulous molar sites were analyzed. The average HC−B and ABH were significantly lower at the maxillary sites (1.26 ± 1.62 mm, 11.62 ± 3.94 mm) than at the mandibular sites (3.67 ± 2.85 mm, 14.91 ± 3.01 mm, p < 0.001). The KMW was significantly lower at sites with HC−B > 2 mm than at sites with HC−B ≤ 2 mm both in the maxilla and mandible (p < 0.001). No significant differences were found between the KMW at sites with ABH < 10 mm and sites with ABH ≥ 10 mm (p > 0.05). Linear regression and GEEs analyses revealed that the HC−B was significantly associated with the KMW (B = -0.339, p < 0.001), while the association between the KMW and the ABH was not statistically significant (B = -0.046, p = 0.352). Conclusions The buccal KMW at edentulous molar sites was significantly associated with the HC−B. Alveolar ridges presenting with a sloped configuration were more prone to possess a narrower band of keratinized mucosa. Both hard and soft tissue augmentation should be considered for implant treatment at these sites. The correlations of dynamic changes between the KMW and alveolar bone dimensions after tooth extraction should be further investigated.

Abutment screw loosening is the most common complication in single implant-supported crowns, typically remedied by simply reattaching the restoration, preferably using a new abutment screw. The internal aspect of the implant along with any other components should be decontaminated before reconnection. This clinical report provides information on the appropriate management of the decontamination process, as well as evidence of the foreign material found within the implant body.

Statement of problem The esthetic assessment of smile lines by laypersons is a subject of ongoing debate. However, smile lines often appear with different types of upper lip curvature, which further complicates the esthetic assessment process, and studies on this combination are lacking. Purpose The purpose of this clinical study was to investigate a layperson’s esthetic perception of smile lines and upper lip combined images. Material and methods Twenty-six smile images resulting from combinations of 3 upper lip types, 4 anterior smile line types, and 3 posterior smile line types were generated by an image editing software program. Eighty-three laypersons (39 men and 44 women; 18 to 35 years of age) completed rating images using a visual analog scale. Unattractive smiles were designated to be those with scores <50 and attractive ones with scores ≥50. Data were analyzed using 1-way analysis of variance and Bonferroni post hoc tests (α=.05). Results High anterior smile line with gingival display >4 mm obtained significantly lower scores of <50 when combined with all upper lip curvatures (upward: 28.29 ±22.79, straight: 38.74 ±23.00, downward: 30.67 ±22.25, P<.01). High anterior smile lines with gingival display ≤4 mm combined with upward and straight upper lip curvature images obtained significantly higher scores, and all were ≥50 (upward: 63.24 ±22.22, straight: 61.40 ±21.58, P<.01). Conclusions From a layperson’s perspective, high anterior smile lines with gingival display >4 mm combined with any lip type were determined to be unattractive. If gingival display was ≤4 mm combined with both upward and straight lip types, the smile was assessed as attractive.

OBJECTIVES:To retrospectively assess the periodontal conditions of teeth adjacent to and contralateral to implants presenting with or without peri-implantitis, following non-surgical periodontal and peri-implant mechanical therapy. MATERIALS AND METHODS:One hundred and one patients with existing dental implants and chronic periodontitis, who underwent non-surgical periodontal and peri-implant mechanical therapy, were included. The periodontal clinical probing depth (PPD), gingival recession (GR), and bleeding on probing (BOP) were recorded at six sites around the adjacent (Adj-) teeth and the contralateral (CL-) teeth relative to the implant. The potential factors influencing the periodontal conditions of 316 teeth were analyzed by multivariate linear regression models with generalized estimating equation methods and α = .05. RESULTS:The PPD of Adj-teeth was significantly different from that of CL-teeth before and after non-surgical therapy when the implant was diagnosed with peri-implantitis (PI) (p < .05). The PPD of teeth was shown to be affected by neighboring implants diagnosed with peri-implantitis (β = .825 mm, p < .001), teeth adjacent to implants (β = .245 mm, p = .004), a molar tooth type (β = .435 mm, p = .019), and non-surgical therapy (β = -.522 mm, p < .001). CONCLUSIONS:Relatively compromised periodontal conditions at Adj-teeth after non-surgical PI therapy were detected. Therefore, clinicians should be aware that non-surgical therapy may be less successful at teeth adjacent to implants with PI.

BACKGROUND:Alveolar ridge preservation (ARP) in molar areas might be effective in minimizing ridge resorption and facilitated implant treatment. The purpose of the systematic review was to evaluate the outcomes of the ARP procedure at molar extraction sites in comparison to spontaneous healing through meta-analysis. MATERIAL AND METHODS:Studies published in PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials, and the System for Information on Grey Literature in Europe were searched. Primary outcomes were changes in alveolar ridge width and height. Secondary outcomes included sinus pneumatization and need for additional augmentation at the time of implant placement. RESULTS:A total of 7 studies composing of 4 randomized controlled trials (RCTs), 2 prospective non-randomized clinical trials, and 1 prospective case control study were included. They involved a total of 237 molar extraction sockets from 236 participants. This review revealed that ARP resulted in statistically significant reductions for horizontal changes {mean difference (MD) = 2.21 mm, 95% confidence interval (CI) [0.02, 4.39]}, vertical mid-buccal changes (MD = 1.34 mm, 95% CI [0.85, 1.83]), and vertical mid-lingual changes (MD = 0.96 mm, 95% CI [0.54, 1.38]) when compared with spontaneous healing. The difference in ridge width changes between the two groups was not statistically significant (MD = 1.94 mm, 95% CI [-1.67, 5.55], P = .29) and with substantial heterogeneity (I2 = 92%, P < .001) when restricted to RCTs. ARP decreased the necessity for additional augmentation during implant placement in comparison to extraction alone (Risk ratio: 0.41; 95% CI: 0.26 to 0.65; P < .001). CONCLUSIONS:ARP is efficacious in reducing socket bone and ridge changes, and minimizing the need for additional augmentation procedures in the molar region. Further well-designed multicenter randomized controlled studies with larger sample size and longer follow-up periods are still needed to further confirm the findings of the current review.

Statement of problem. The output torque delivered by a dental implant toggle-style torque wrench is known to be affected by activation rate. The International Organization for Standardization (ISO) established the ISO 6789-1 standard to provide guidance on activation rates relative to desired output torque in the Nm torque range. Whether the ISO 6789-1 standard applies at the relatively lower dental torque ranges is not known, and little information is available on the activation rates that clinicians use and how this may affect output torque.Purpose. The purpose of this in vitro study was to determine how output torque values vary with the activation rates used by clinicians at dental implant-relevant target torque values.Material and methods. To determine clinically relevant activation rates, a new adjustable dental implant toggle-style torque wrench was activated from 0 to 25 Ncm target torque by 5 prosthodontists by using a custom mandibular and maxillary typodont model containing implants and abutments with screws. This provided a baseline of activation rates (mm/sec). Data were transferred to a computerized numerical control model incorporating a variable speed linear motor, which was used to drive a dental implant toggle-style torque wrench attached to an electronic torque measuring device. Constant speed and a regulated dual-speed-assigned 80/20 rate group, where 80% of target torque value was delivered first, then a pause, and the final 20% at different speeds as suggested by the ISO 6789-1 standard, were evaluated. Fast, medium, and slow rates were categorized and applied with target torque values of 10, 25, and 35 Ncm, respectively, for n=12 activations. The output torque values were recorded for both constant and 80/20 groups and compared with the desired target torque values. Data were statistically analyzed with 1-way ANOVA and the Scheffe post hoc paired t test (a=.05).Results. The clinicians' activation rates from 0 to 25 Ncm on the typodont model converted into linear speeds resulted in fast =24.19 mm/sec, medium =14.5 mm/sec, and slow =7.25 mm/sec. When actioned at a constant rate, the mean output torque values were generally in the order of slow > medium > fast in activation rates. Generally, precision output torque decreased as target torque increased, especially when slow and medium rates, either constant or regulated 80/20 were used. All mean output torque for slow, medium, and their 80/20 variants were greater than target torque. Fast and 80/20 fast produced the lowest mean output torque values for all torque settings, and at the 35 Ncm setting, the dental implant toggle-style torque wrench output torque mean values were lower than target torque. Statistically significant differences (P<.05) were found among groups, most notably in the 80/20 dual-speed groups, especially in comparisons with the 80/20 fast rate group. When the target torque value was 10 Ncm with the 80/20 fast rate, the output torque value deviated from the maximum ISO limit by more than 6%. Conclusions. The rate of actioning a dental implant toggle-style torque wrench influenced the delivered torque value, with fast rate actioning producing lower and less precise output torque values. (J Prosthet Dent 2023;129:763-8)

PURPOSE:The aim of this in vitro study was to assess the effects of using different cements and titanium copings designs on the retention of implant-supported fixed dental prostheses (IFDPs) using a pull-out test. MATERIALS AND METHODS:Fifty zirconia (ZirCAD; Ivoclar Vivadent) and 20 prepolymerized denture acrylic resin (AvaDent) rectangular (36 mm × 12 mm × 8 mm) specimens were milled to mimic the lower left segmental portion of the All-on-Four IFDPs. Cylindrical titanium copings (Variobase; Straumann) (V) were used in 2 prepolymerized denture acrylic resin groups (n = 10) while conical titanium copings (Straumann) (C) were used as a control group for zirconia with 4 groups using cylindrical titanium copings. Before cementation, the outer surfaces of all titanium copings and the intaglio bonding surface of prosthetic specimens were airborne-particle abraded. All specimens were cemented following the manufacturer's recommendations and instructions according to the experimental design. After artificial aging (5000 cycles of 5°C 55°C, dwelling time 20 s; 150 N, 1.5 Hz in a 37°C water bath), all specimens were subjected to retention force testing using a pull-out test using a universal testing machine and a custom fixture with a crosshead speed 5 mm/min. Modes of failure were classified as Type 1, 2, or 3. Retention force values were analyzed by the t-test for the prepolymerized denture acrylic resin specimen groups, and 1-way ANOVA and the Tukey test for the zirconia groups at α = 0.05. RESULTS:Mean and standard deviation retention force values varied from 101.1 ± 67.1 to 509.0 ± 65.2 N for the prepolymerized denture acrylic resin specimen groups. The zirconia groups ranged from 572.8 ± 274.7 to 1416.1 ± 258.0 N. There is no statistically significant difference in retention force values between V and C specimens cementing to zirconia with Panavia SA cement (Kuraray Noritake) (p = 0.587). The retention forces and failure modes were influenced by the cement used (p < 0.05). Modes of failure were predominantly Type 2 (mixed failure) and Type 1 (adhesive fracture from prosthetic materials) except for the quick-set resin group (Type 3, adhesive failure from coping). CONCLUSIONS:When bonding IFDPs onto titanium copings, quick-set resin provided significantly higher retention force for prepolymerized denture acrylic resin prostheses. Conical and cylindrical titanium copings performed similarly when cemented to zirconia with Panavia SA cement under the same protocol. The stability of the bonded interface and retention forces between zirconia prostheses and titanium copings varied from the cement used.

Statement of problem. A novel zirconia-alumina composite (ZAC) particle has yet to be studied for airborne-particle abrasion in a bonding protocol for the zirconia surface.Purpose. The purpose of this in vitro study was to evaluate the shear bond force of resin cement to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) when using spherical ZAC particles to conduct airborne-particle abrasion and modify the topography of Y-TZP. Material and methods. Spherical 30-to 70 -mm ZAC particles were fabricated by using a hybrid gel technique. A total of 160 & empty;6.6x4.0-mm zirconia disks were fabricated from 4 commercially available zirconia blanks, e.max ZirCAD zirconia (EM), NexxZr T zirconia (NE), Lava Plus High Translucency zirconia (LP), and Imagine High Translucency Zirconia (IM), by using computer-aided manufacturing technology. As-sintered specimens without further surface treatment were used as controls (ZR0). Surface treatment groups included sharp-edged alumina airborne-particle abrasion (ABC), 50 mm, 0.2 MPa; airborne-particle abrasion with ZAC particle at 0.2 MPa (2ZA); and airborne-particle abrasion with spherical ZAC particle at 0.4 MPa (4ZA). All surface treatment groups were airborne-particle abraded at the specified pressures for 10 seconds at a standardized distance of 10 mm. The surface roughness (Ra) and area roughness (Sa) of specimens from each group were measured. Following the application of an adhesive (Scotchbond Universal), 06.6x4.0-mm resin cement (RelyX Ultimate) buttons were fabricated for shear bond testing by using a universal testing machine at a 5-mm/min crosshead speed (n=10). The data were analyzed by using a 2-way ANOVA, Tukey HSD test, and regression analysis (a=0.05). Scanning electron microscopy (SEM) was performed to observe changes of the zirconia surface and the failure modes of each group before and after shear bond testing.Results. The mean +/- standard deviation shear bond force values ranged from 272.6 +/- 41.4 N to 686.7 +/- 152.8 N. Statistically significant higher force values than those of the controls (P<.05) were obtained by using airborne-particle abrasion. No significant differences were found among any of the airborne-particle abrasion treatment groups (P>.05). The mean of Ra values ranged from 0.27 mm to 0.74 mm, and the mean of Sa values, from 0.48 mm to 1.48 mm. SEM observation revealed that the zirconia surface was made jagged by abrasion with sharp-edged alumina particles. The spherical ZAC particles create microcraters on the zirconia surface. Fractographic observation disclosed that failures were adhesive-cohesive failure modes with residual resin cement attached on the zirconia surface.Conclusions. The surface treatment of zirconia with sharp-edged alumina or the spherical ZAC abrasives improved the bonding force between the zirconia and resin cement. No statistically significant differences in shear bond force values were found between airborne-particle abrasion surface treatment groups.

Statement of problem. Implant cantilever beam torque-limiting devices are affected by parallax, which may result in measurement read error. The overread or underread of the true target torque value could lead to premature failure of the screw joint of a dental implant. Purpose. The purpose of this in vitro study was to determine the effect of the operator's viewing angle relative to the cantilever beam and measurement reading scale when the torque-limiting device is actioned toward or away from the operator. Material and methods. A beam torque wrench (Nobel Biocare USA) was used with the cantilever beam position fixed by using a wedge to read 32 Ncm on the marker arm. It was suspended in a vertical position relative to a digital single-lens reflex camera set at a fixed distance of 48 cm from the marker reading. The camera was rotated in 10-degree increments clockwise and counterclockwise relative to the cantilever beam reading, starting perpendicular to the marker. Photographs were recorded at each angle. Percentage measurement read error was calculated from dimensions of the cantilever beam torque device, including the beam diameter, distance from the marker arm, and the incremental marks on the measurement scale. Data were analyzed descriptively to determine the differences after comparison with the International Organization for Standardization (ISO) 6789-1:2017 recommendations. Results. Photographs compared beam position relative to the 32-Ncm marker. The beam diameter was recorded as 1.5 mm, corresponding to approximately 5 Ncm. The distance between the marker arm and center of the beam was 0.08 mm. Percentage errors were greatest at lower torque values and increased relative to the viewing angle. Photographs showed that instrument overread was most likely to occur as the beam was moved away from the operator, which would result in potential undertightening unless compensated for. Underread was noted when the beam was pulled toward the operator. Conclusions. To prevent measurement read error when using an implant cantilever beam torque-limiting device, the operator should be positioned as close to a perpendicular viewing angle to the cantilever beam as possible. Viewing from an angle greater than 10 degrees from the perpendicular should be avoided for torque values less than 15 Ncm. For screws tightened between 25 Ncm and 35 Ncm, the viewing angle should be less than 30 degrees so that the applied torque is within the maximum deviation of the target torque value set by the ISO 6789-1:2017 recommendations. (J Prosthet Dent 2023;130:597-601)

Purpose The aim of this in vitro study was to assess the efficacy of fiber reinforcement to enhance flexural strength of the transitional implant-supported fixed dental prosthesis (TISFDP). Materials and methods One hundred and forty denture acrylic resin plates (64 mm x 12 mm x 5 mm) with two 7 mm diameter holes were fabricated using heat-polymerized type (Lucitone 199) and CAD-CAM prepolymerized type (AvaDent) materials to simulate a chair-side reconstruction of the TISFDP. Specimens were divided into 7 groups (n = 10) according to the airborne-particle abrasion of titanium cylinder (Straumann) surface and locations of fiber reinforcement ribbons (Ribbond-ULTRA). No cylinder surface abrasion and no fiber added acrylate specimens were used as the controls. The prosthetic screws were hand-tightened on a custom fixture with analogs. Specimen hole and cylinder were joined using a 50:50 mixture of chemically polymerized resin (QYK-SET; Holmes Dental) and repair resin (Dentsply Sirona). Ten acrylate specimens with no holes were fabricated from each tested material and assigned as positive controls. A modified four-point bending test (ASTM standard-D6272) was conducted using a universal testing machine and a custom fixture with a crosshead speed 1 mm/min. The maximum failure loads were recorded. Data were statistically analyzed using 2-way ANOVA and the Tukey tests at alpha = 0.05. Results The flexural strength values ranged from 55.4 +/- 8.3 to 140.9 +/- 15.4 MPa. The flexural strength decreased significantly when fiber was attached on the titanium cylinder surface (p < 0.05). There were no statistically significant differences in flexural strength values between specimens with and without titanium cylinder surface abrasion (p > 0.05). Statistically significant improvement in flexural strength was observed in specimens with fibers attached around the specimen holes (p < 0.05) buccally and lingually. The obtained values were not statistically significantly different from the positive controls (p > 0.05). Some fixation screw fractures were observed before catastrophic failure of specimens during testing. Conclusions Fiber reinforcement significantly improved the flexural strength of denture acrylic resins only if placed around the specimen holes on the tension side at the site of initiation of crack propagation. Even when the specimens underwent catastrophic failure, the segments remained attached to each other with the attached fibers.

Changes in alveolar bone dimension after tooth extraction may affect placement of the subsequent implant, resulting in ridge deficiency that can adversely impact long-term implant stability or aesthetics. Alveolar ridge preservation (ARP) was effective in reducing the amount of ridge resorption following tooth extraction. There is sparse evidence regarding the benefit of ARP at periodontally compromised molar extraction sockets. This study will be a randomized trial to assess the soft tissue contour, radiographical, and histological changes of ARP at molar extraction sites in order to compare severe periodontitis cases with natural healing results and determine the most beneficial and least traumatic clinical treatment for such patients. This research is designed as a two-group parallel randomized controlled trial. The total number of tooth extraction sites will be 70 after calculation with power analysis. Teeth will be randomly assigned to two groups with the test group conducting ridge preservation and the control group healing naturally. Periodontal examination, cone beam-computed tomography (CBCT) data, and stereolithographic (STL) files obtained by intraoral scanning will be collected through the follow-up period, and bone biopsy samples would be obtained during implant surgery. The primary outcomes are the vertical and horizontal change of alveolar ridge measured on CBCT images, soft tissue contour changes evaluated by superimposing the digital impressions, alterations of mucosa thickness (as measured by superimposing the CBCT data and STL files), histological features of implant sites and periodontal parameter changes. The secondary outcomes are patient-reported post-operative reaction and conditions of simultaneous bone graft or sinus lifting procedures during implantation. This study will provide information about hard and soft tissue dimension changes and histomorphology evaluation following ARP and natural healing in periodontally compromised molar sites, which may contribute to complement the missing information of ARP at periodontally compromised molar extraction sockets. Chinese Clinical Trial Register (ChiCTR) ChiCTR2200056335. Registered on February 4, 2022, Version 1.0.