Impact of physical and mental training on dental students' fine motor skills.

BACKGROUND: Mental training can be beneficial when learning new motor skills. OBJECTIVE: To evaluate whether a combination of physical and mental training can replace physical training. METHODS: Sixty dental students were randomly divided into six groups, which were assigned different regimens of physical and mental training: A. 75% mental 25% physical; B. 50% mental 50% physical; C. 75% physical 25% mental; D. 100% mental; E. 100% physical; F. control, no practice. The physical training comprised eight different tasks performed on the Purdue Pegboard: four tasks with direct vision (PD) and four tasks with indirect vision (PIND). The mental training involved listening to a recording explaining the actions to be performed. The tests were performed twice: T0, before training; and T1, at 24 h after training. The non-parametric Mann-Whitney test was used to detect differences between the groups. Changes between T0 and T1 within a group were analysed by Wilcoxon signed-rank test. RESULTS: There were no significant differences between the groups at T0. At T1, members of Groups A, B, C, and E had improved at five to eight tasks, while Groups D and F had improved at two tasks. Notably, Group D improved in the assembly tasks. Ranking the extent of improvement at T1, indicated that For PD Groups B, E > F, D while for PIND B, C, E > A, F and E > D. CONCLUSION: Substituting some physical training by mental training can provide similar improvements in fine motor skills, although the optimal combination remains to be determined. Mental training may be more effective for cognitive tasks.

Comparing fracture resistance on bovine incisors restored by tooth fragment reattachment versus direct composite restoration techniques.

BACKGROUND/AIM: Anterior teeth are prone to traumatic dental injuries (TDIs). Although a number of techniques ranging from original tooth fragment reattachment (TFR) to direct composite restoration (DCR) can be used to restore uncomplicated crown fractures, there is no consensus on which method is best. The purpose of this study was to investigate the fracture resistance of bovine incisors restored by two different techniques (TFR and DCR) in three different fracture models. MATERIALS AND METHODS: Sixty extracted bovine lower incisors were randomly divided into three groups (n = 20). Angle, oblique, or transverse sections of all the teeth in a group were prepared by using a disk. The cut surfaces were scanned, and the cross-sectional areas (CSA) of the enamel and dentin were measured. Half the teeth in each group were restored by DCR (n = 10) and the other half by TFR (n = 10). The forces required to fracture the restored teeth were then measured using a Universal testing machine, and the fracture modes were analyzed (cohesive, adhesive, or mixed). RESULTS: No statistically significant differences between the TFR and DCR restorations were detected for total and enamel CSAs in any of the restoration shapes (p > .067). The fracture forces required to break DCR angle and transverse restorations were significantly greater than for the corresponding shapes restored with TFR (p < .033). However, the difference in the forces needed to fracture oblique section restorations by DCR or TFR was not statistically significant (p = .239), despite a similar trend (143.4 ± 51 N and 120.9 ± 25 N, respectively). CONCLUSION: This study revealed that a greater force is required to fracture teeth restored by the DCR than by the TFR technique, especially for a transverse section. This demonstrates that restoring a fractured tooth provides a superior outcome compared to reattaching the fractured fragment.

Circumferential root strains generated during lateral compaction with stainless steel vs. nickel-titanium finger spreaders.

The circumferential strains created in the radicular dentin by nickel-titanium (NiTi) and stainless steel (SS) finger spreaders (FSs) during a simulated clinical procedure of lateral compaction were compared after minimal (size 50) and extensive (size 100) canal preparations. Nineteen maxillary central incisors underwent minimal preparation, while 10 underwent an extra phase of extensive preparation. Four miniature strain gauges were bonded circumferentially in the apical third of the root (buccal, lingual, mesial, and distal). Lateral compaction was performed using either NiTi-FSs or SS-FSs. Force and strains were continuously recorded. The maximal strains (with and without normalization according to force) were recorded. The SS-FSs generated higher maximal strains normalized according to force compared with the NiTi-FSs. The maximal normalized strains were higher by 37%-43% for the mesial and distal aspects and by 6%-14% for the buccal and lingual aspects after the minimal preparation and by 24%-28% for the mesial and distal aspects and by 19%-20% for the buccal and lingual aspects after extensive preparation. The maximal normalized strains increased by 30%-70% from minimal to extensive preparations, with two teeth exhibiting vertical root fracture while compaction with SS-FS. The NiTi-FSs induce less strain in root dentin than the SS-FSs and thus may contribute less to the risk of vertical root fracture.

The effect of impact tool geometry and soft material covering on long bone fracture patterns in children.

INTRODUCTION: The effect of impact tool geometry and soft material covering on bone fracture patterns plays a major role in fracture patterns. However, the literature is nearly void of such studies and only general correlations between the fracture pattern and the mechanism underlying the insult were reported. PURPOSE: The aim of this study is to reveal the association between the geometry of the impact tool and the presence of soft material covering on bone fracture patterns. The Dynatup Model POE 2000 (Instron Co.) low energy pendulum impact machine was utilized to apply impact loading on fresh pig femoral bones (n = 50). The bone clamp shaft was adjusted to position the bone for three-point bending with additional bone compression simulating a situation occurring in pedestrian road traffic accidents. Five different tests using varying impact tool sizes with and without soft interface covering were carried out. RESULTS: A significant positive correlation was found between the fracture features and the impact tool's geometry. Only bones that were damaged by a rounded impact body result in a "false" butterfly fragment; in all other cases where the impact body is flat and wide, double trapezoid fragments are observed in the area of impact. The impacted aspect is the most affected. All fracture line features were significantly greater in bones subjected to an impact by tools without soft covering. With an impact with soft covering, the impacted aspect exhibits numerous unique fracture lines and a fragmented pattern. Our study clearly shows that impact tool geometry and soft material covering markedly affect the fracture pattern.

Subacromial corticosteroid injections transiently decrease suture anchor pullout strength: biomechanical studies in rats.

BACKGROUND: Arthroscopic rotator cuff (RC) repair incorporates suture anchors to secure torn RC tendons to the greater tuberosity (GT) bone. RC repair strength depends on the anchor-bone interface and on the quality of the GT. We evaluated the effect of single and multiple corticosteroid injections on the pullout strength of suture anchors. METHODS: Fifty rats were divided into those receiving saline solution injection (control group), a single methylprednisolone acetate (MTA) injection (MTA1 group), or 3 once-weekly MTA injections (MTA3 group). Rats were killed humanely at 1 or 4 weeks after the last injection. A mini-suture anchor was inserted into the humeral head through the GT. Specimens were tested biomechanically. RESULTS: At 1 week after the last injection, the mean maximal pullout strength was significantly reduced in the MTA1 group (63.5%) and MTA3 group (56%) compared with the control group (P < .05 for both). Mean stiffness decreased significantly in both treatment groups compared with controls (P < .05). At 4 weeks after the last injection, there was a significant increase in the mean maximal pullout strength after single and triple MTA injections compared with values recorded at the 1-week time point (P < .05). At 4 weeks, the mean maximal pullout strength after a single MTA injection was 92.8% of the pullout strength measured in the control group. CONCLUSIONS: We showed a significant detrimental effect of corticosteroid exposure on the pullout strength of a suture anchor at 1 week. However, this effect was transient and resolved within a relatively short period. These findings indicate that a waiting period is required between subacromial corticosteroid injection and RC repair surgery that involves the use of suture anchors.

Biomechanical evaluation of two arthroscopic techniques for biceps tenodesis: triple loop suture versus simple suture.

BACKGROUND: Several techniques and procedures have been described to treat long head of the biceps pathology; however, tenodesis and tenotomy are the 2 most common procedures performed. This study evaluated the initial fixation strength of the biceps tenodesis triple loop suture (TLS) technique and compared it with that of the simple suture technique (SST). METHODS: Twenty fresh frozen cadaveric human shoulders (humeral head and neck with attached biceps tendons) were harvested. The biceps tendon was tenotomized proximally before reattachment to the bicipital groove of the matching humerus using suture anchors. Tenodesis was performed using the SST or the TLS technique. Specimens were tested biomechanically for load to failure, stress, and stiffness. The mechanism of failure was evaluated and compared between the 2 suture techniques. RESULTS: Maximal load to failure was significantly greater using the TLS technique (122.2 ± 26.73 N) than the SST (46.12 ± 14.37 N, P < .001). There was no difference in the mean stiffness (SST: 7.33 ± 4.41 N/mm, TLS: 7.46 N/mm ± 2.67, P = .94). The failure mechanism in all SST samples occurred by suture cutout through the longitudinal fibers of the tendon. In all TLS samples, the failure occurred by suture slippage. CONCLUSION: This study demonstrated superior load to failure of the TLS compared with the SST technique for biceps tenodesis. Furthermore, this study provides the first description of the TLS technique as a possible application in biceps tenodesis. Clinical application of the TLS must be carefully considered, because although it achieved a superior biomechanical profile, experience with this stitch is limited.

Effects of a Program for Improving Biomechanical Characteristics During Walking and Running in Children Who Are Obese.

PURPOSE: To investigate the influence of a weight-reduction program with locomotion-emphasis on improving biomechanical characteristics of children who are obese (OW). METHODS: Ten children who are OW participated in a 6-month multidisciplinary childhood obesity management program (GRP1); another 10 children who are OW participated in the same multidisciplinary childhood obesity management program with additional locomotion-emphasis exercises for improving biomechanical characteristics (GRP2); and 10 control children who are OW with no intervention program. Outcomes were anthropometric measurements and temporal and foot pressure parameters. RESULTS: GRP2 had significantly improved foot pressure in the different walking/running speeds compared with GRP1. In the temporal parameters, pretests by speed by group interactions were significantly improved for GRP2 compared with GRP1. CONCLUSIONS: We found evidence to support beneficial effects of combined dietary and physical activity/locomotion-emphasis exercises on the movement characteristics of children who are OW.

Skeletal effect of casein and whey protein intake during catch-up growth in young male Sprague-Dawley rats.

The aim of the present study was to determine whether the type of protein ingested influences the efficiency of catch-up (CU) growth and bone quality in fast-growing male rats. Young male Sprague-Dawley rats were either fed ad libitum (controls) or subjected to 36 d of 40 % food restriction followed by 24 or 40 d of re-feeding with either standard rat chow or iso-energetic, iso-protein diets containing milk proteins - casein or whey. In terms of body weight, CU growth was incomplete in all study groups. Despite their similar food consumption, casein-re-fed rats had a significantly higher body weight and longer humerus than whey-re-fed rats in the long term. The height of the epiphyseal growth plate (EGP) in both casein and whey groups was greater than that of rats re-fed normal chow. Microcomputed tomography yielded significant differences in bone microstructure between the casein and whey groups, with the casein-re-fed animals having greater cortical thickness in both the short and long term in addition to a higher trabecular bone fraction in the short term, although this difference disappeared in the long term. Mechanical testing confirmed the greater bone strength in rats re-fed casein. Bone quality during CU growth significantly depends on the type of protein ingested. The higher EGP in the casein- and whey-re-fed rats suggests a better growth potential with milk-based diets. These results suggest that whey may lead to slower bone growth with reduced weight gain and, as such, may serve to circumvent long-term complications of CU growth.

Effect of Silane Reaction Time on the Repair of a Nanofilled Composite Using Tribochemical Treatment.

PURPOSE: To investigate the influence of silane reaction time on the repair strength of an aged nanofilled composite and to characterize the bonding mechanism. MATERIALS AND METHODS: Nanofilled composite disks (n = 110, Filtek Supreme XT) were aged for 90 days in water. After tribochemical treatment (CoJet-Sand), the specimens were assigned to 5 groups (n = 22), primed with silane (Espe-Sil), and left to react for 1, 2, 3, 4, and 5 min. A thin layer of adhesive (Visio-Bond) was applied and a new composite with the same dimension was placed and cured. Non-aged specimens immediately layered and cured using the incremental technique served as controls. After aging (30 days in water plus 5000 thermal cycles), the interface was subjected to a shearing force until failure. Failure mode was evaluated under a stereomicroscope and scanning electron microscopy (SEM). Additional aged and treated surfaces were evaluated for morphology as well as elemental and molecular composition using SEM/EDX and ATR-FTIR. RESULTS: The mean shear bond strength (SBS) of the repaired specimens was 53.9 ± 8.6 MPa, with no significant difference among the various reaction times, but significantly lower compared to the control (88.1 ± 12.5 MPa). Tribochemical treatment created an irregular surface morphology with particles imbedded in the aged surface. Interfacial SEM/EDX analysis showed a 5-µm non-uniform high atomic number zone rich in Al and Si. CONCLUSION: Tribochemical treatments for repairing composite using a short silane reaction period (1 min) are equally effective as the prolonged reaction periods (2 to 5 min), yielding interfacial shear strength of ~60% of unrepaired material.

Platelet-rich plasma did not improve early healing of medial collateral ligament in rats.

BACKGROUND: The medial collateral ligament (MCL) is the most frequently injured ligament of the knee. Platelet-rich plasma (PRP) is a relatively new treatment option developed to enhance the healing response after injury to different tissue types. This study aimed at investigating whether the addition of PRP to MCL tears in rats would alter healing both biomechanically and histologically. METHODS: Bilateral full-thickness tears of the MCL were surgically induced in the knees of 32 rats. Right ligament was saturated with PRP (n = 32, study group), and the left ligament was saturated with saline (n = 32, control group). The animals were killed 3 weeks later and the surgical sites were evaluated by gross inspection, biomechanically and histologically. RESULTS: There was no gross difference in the mass of granulation tissue, load to failure, stiffness and displacement between the study and control groups. Histological examination by means of maturity score revealed no significant differences between the study and control groups. CONCLUSION: The addition of PRP to a healing MCL did not improve any of the outcome measures in this model.

A single dose of platelet-rich plasma improves the organization and strength of a surgically repaired rotator cuff tendon in rats.

INTRODUCTION: Rotator cuff tear (RCT) is a common cause of pain and disability among adults. Platelet-rich plasma (PRP) is a fraction of whole blood containing concentrated growth factors and proteins important for tissue healing. This study aimed at investigating the effects of local autologous PRP injection on repaired rotator cuff (RC) tendon repair in rats. METHODS: Following experimental RCT and suturing, 44 Wistar rats were randomly allocated into two groups: (1) RC repair only (controls); (2) RC repair + PRP administration-shoulders were treated with intra-articular PRP immediately after the repair. Animals were killed after 3 weeks and tendon, were tested biomechanically in tension (12 rats/group). The remaining tendons (10 rats/group) were stained using hematoxylin and eosin and Picro-sirius Red. Histological analysis evaluated the cellular aspects of the repair tissue. RESULTS: PRP administration following experimental RC tear and suture resulted in a significantly higher maximal load (p < 0.001) and stiffness (p < 0.005) as compared to non-treated animals. Bonar score of PRP-treated tendons was significantly better (p = 0.018) than the control group. Collagen birefringence was significantly higher in PRP shoulders (p = 0.002), indicating improved organization. Vascularity scores were similar in both groups. CONCLUSION: Application of a single dose autologous PRP in adjunct to surgical repair resultes in improved tendon-to-bone healing, assessed by histological and biomechanical testing in a rat model of acute RCT, when tested at 3 weeks compared to controls. Further studies will be essential to determine the role of PRP in clinical practice.

Long- and short-term effects of headgear traction with and without the maxillary second molars.

INTRODUCTION: A quantitative assessment of maxillary first molar distalization with and without the maxillary second molar (M2) was carried out. METHODS: Fifty-six cervical headgear patients undergoing fixed appliance orthodontic treatment were divided into 2 groups: before (G - M2) and after (G + M2) eruption of the maxillary second molars (ages, 11.87 ± 1.20, and 13.05 ± 1.55 years, respectively). The tightness of the dental contact point (TDCP) and the space between the second premolar and the maxillary first molar were measured at 6 levels of headgear force (0-15 N) at 3 intervals 6 months apart (T0, T1, T2). RESULTS: Relationships were found between space and TDCP, time, and presence or absence of the maxillary second molar at T1 and T2 (P <0.001). The TDCP decreased and space increased with increase in initial headgear force. An increase in initial force beyond 6 to 9 N did not significantly increase the initial maxillary first molar distalization. The G - M2 TDCP and space measurements were similar to those of G + M2 at T2 with the eruption of the maxillary second molar. From T0 to T1, maxillary first molar distalization was greater in G - M2. In comparison with our previous headgear-alone study, initial distalization with a fully bonded appliance was reduced by 4-fold. CONCLUSIONS: Headgear therapy is more effective before the eruption of the maxillary second molar. Once it erupts, the distalization pace of the maxillary first molar is reduced, but it can nevertheless be pursued at a slower pace when the maxillary second molar is present.

The effect of one-step vs. two-step impression techniques on long-term accuracy and dimensional stability when the finish line is within the gingival sulcular area.

PURPOSE: To evaluate the effect of two putty-wash impression techniques on the long-term accuracy and dimensional stability of poly(vinyl siloxane) (PVS) in the gingival sulcus area. MATERIALS AND METHODS: Impressions were taken from a master cast to simulate molar crown preparation. A space around the abutment served as the gingival sulcus. Fifteen impressions using the one- and two-step impression techniques were taken using Express Regular, Express Fast, and President impression materials with custom trays. Using a Toolmaker's microscope, the long (LD) and short distances (SD) of the abutment and the planar distance between two parallel lines (PL) at the circumference of the cast were taken at 0.5, 2, 24, 48, 72, 96, 120, and 144 hours after mixing. ANOVA was performed, with the discrepancy between the distances of the impressions and the master cast as the dependent variable. RESULTS: The differences when different materials and impression techniques were used were significant (p < 0.001) for LD, SD, and PL, as was the interaction between the material, time, and technique (p < 0.001). SD discrepancies were higher than those of LD for all materials and times. The two-step impression technique was more accurate, with smaller discrepancies than the one-step impression technique. For all materials, the PL discrepancy was deemed acceptable (less than 0.5%) for all tested times. President had higher discrepancies than the other materials. CONCLUSIONS: When using the two-step putty-wash impression technique, pouring of the impressions may be postponed up to 30 hours; however, when using the one-step impression technique, pouring should be performed within 2 hours.

Locking versus standard screw fixation for acetabular cups: is there a difference?

INTRODUCTION: Total hip replacement has been established as a valid treatment option for displaced subcapital fractures. However, insufficient primary fixation may be the reason for early loosening in these osteoporotic patients. Primary fixation of the cup is usually achieved by press-fit fixation that can be enhanced using screws. Locking the screws into their respective cups may seem to improve the primary fixation of the construct, as locked plates proved superior fixation for osteoporotic fractures. METHODS: The study consisted of three groups: in each group, three cups were fixed into blocks of foam bone using press-fit technique. In the first group, no additional screws were used, in the second group two standard screws were inserted, while in the third group two acetabular screws were cemented into the cup to simulate locked screw fixation. Load was applied onto the rim of the acetabular component to cause shearing between the cup and the block. Cup fixation was examined by a loading machine that acquired load versus displacement. The stiffness (load vs. displacement) was calculated. RESULTS: Screws, either locked or non-locked, enhanced cup fixation by 26 % (p value <0.01). No significant changes were found between the locking and non-locking screws groups. DISCUSSION: These experimental results indicate that acetabular screws enhance primary cup fixation. This may become significant in conditions where the acetabular bone stock is suboptimal, such as when performing total hip arthroplasty after displaced subcapital fractures. However, there is no superiority for locked screws over standard screw fixation.

Ulnar Superficialis Slip Resection Versus Radial Superficialis Slip Resection: A Biomechanical Pilot Study.

BACKGROUND: There are numerous clinical scenarios during which the surgeon contemplates whether the radial or ulnar slip of the flexor digitorum superficialis (FDS) should be sacrificed. To date no study has assessed the point of failure of each one of the FDS slips in each digit, aiding the avid surgeon in deciding which slip to sacrifice. METHODS: A total of 41 digits were assessed, each digit was dissected, and a specimen containing the denuded bone of the middle phalanx with the attachments of the ulnar and radial FDS slips was obtained. An Instron 4502 device was utilized to biomechanically assess the point of failure of each slip of each digit. RESULTS: There was no statistical difference between ulnar and radial slip point of failure when compared across all digits and subjects. There was no statistical difference between male and female subject's specimens. The point of failure was higher in the ulnar slips of the second and third digits, whereas the point of failure was higher in the radial slips of the fourth and fifth digits. CONCLUSIONS: Sacrifice of a FDS slip may cause loss of grip strength. In several clinical scenarios one may be faced with the dilemma which FDS slip to sacrifice. Our findings show this is not an arbitrary choice. Hand surgeons should keep our findings in mind when deciding which slip to sacrifice, in effort to preserve function and strength in the injured hand.

Assessment of the modified O'Connor Tweezer Dexterity and Purdue Pegboard test for use among dental students.

OBJECTIVES: The current study aimed to assess criteria validity and test-retest reliability of the modified O'Connor Tweezer Dexterity (O'Connor) and the Purdue Pegboard test (PPT) for use among dental students. Occupational therapists were asked to assess dentist-related skills due to the high percentage of students who failed the dental school exams that year. The O'Connor and the PPT are suitable for these purposes, they aim to evaluate fine motor skills requirements. The original tests were modified for use under indirect visualization conditions (through a mirror) to mimic the typical dentists' work environment. MATERIALS AND METHODS: A total of 110 dentists were included in the present study (50 dentists for the O'Connor test and 60 for the PPT). Both tests were conducted twice. Initially, the original version of the tests was followed by the modified versions (through a mirror). For the test-retest reliability assessment, 21 participants (10 participants from the O'Connor group and 11 participants from the PPT group) repeated the evaluation within a 1-week interval using the same settings (original followed by modified versions). RESULTS: Both versions of the O'Connor tests were significantly correlated (r = 0.54, p < 0.01), as were the two PPT versions (r = 0.640, p < 0.01). Significantly test-retest reliability was found for both tests. The interclass correlation ranged between 0.883 and 0.997, p < 0.000. CONCLUSION: The results confirmed our hypothesis, demonstrating a criteria validity and test-retest reliability assessment of the modified O'Connor and the modified PPT for assessing dentists.

Effect of Different Etching Times on Pit-and-Fissure Sealant Micro-Shear Bond Strength to the Enamel of Primary Teeth.

Successful clinical use of pit-and-fissure sealants relies on the sufficient etching of the enamel, field isolation and sealant retention. The etching time changes the physical and mechanical surface properties of the etched tooth tissues; therefore, it impacts both etching depth and the bond strength of sealants to the enamel. We examined if reducing the recommended 15 s etching time of primary teeth enamel affects the micro-shear bond strength (µSBS) of pit-and-fissure sealants. The cusps of forty non-carious, extracted human primary molars were separately etched for 8, 15 or 30 s. Then, a pit-and-fissure sealant was placed and light-cured. The µSBS values were evaluated and compared among the three groups. The mean µSBS values ± standard deviations were 34.68 ± 16.93, 34.19 ± 17.35 and 36.56 ± 16.57 MPa in the cusps etched for 8, 15 and 30 s, respectively. No statistically significant differences in µSBS were observed among the three test groups. In this study, we showed for the first time that the recommended etching time of primary teeth enamel may be reduced from 15 to 8 s without compromising the µSBS of the sealant. Further evaluations in a clinical setting are warranted.

Influence of periodontal ligament simulation and splints on strains developing at the cervical area of a tooth crown.

Many in vitro tooth models do not incorporate periodontal ligament (PDL) simulation. This study presents the influence of physiologically loaded occlusal splints on cervical strains in a model incorporating roots and PDL. Four sets (N = 10) of occlusal splints differing in material (hard/soft) and location (upper/lower) were prepared for first maxillary and mandibular anatomic molars. Two strain gauges were bonded to the buccal and lingual aspects of the lower molar. Teeth were embedded in acrylic resin with/without a PDL-simulating material. Force vs. strain data were acquired during loading and the maximal strains at 500 N were analyzed. When PDL was incorporated into the model without splints, buccal compressive strains were significantly decreased. Usage of a soft splint resulted in compressive strains on both tooth aspects. Usage of a hard splint on the lower tooth resulted in higher compressive strains on the lingual side compared with the buccal side, whereas usage of this splint on the upper tooth resulted in tensile strains on the lingual side. Bending towards the buccal side occurred when the splints were located on the upper tooth. Soft splints reduce buccal bending, but do not reduce cervical strains. Periodontal ligament stimulation materials should therefore be incorporated in models involving teeth.

Effects of Aging Torque Controllers on Screw Tightening Force and Bacterial Micro-Leakage on the Implant-Abutment Complex.

AIM: We assess the accuracy of torque controllers after several aging processes and the bacterial leakage on implant-abutment complexes (IAC). METHODS: A total of 12 spring-type and 12 friction-type torque controllers and 48 IAC (24 conical and 24 hexagonal connections) were evaluated. Chemical, mechanical, temperature, and pressure-aging methods were applied individually to replicate clinical use. Torque controller accuracy was analyzed before and after aging using a calibrated gauge. To assess bacterial leakage, the IAC were suspended in a bacterial medium for 24 h. Direct Contact Test (DCT) and Polymerase Chain Reaction Test (RT-PCR) analyzed the infiltration of F. nucleatum and P. gingivalis into the IAC micro-gap. RESULTS: A significant decrease in torque after 10 days of aging was found. The spring-type torque controller was affected the most, regardless of the aging method (P < 0.05). PCR results indicated that all groups exhibited significantly more bacterial leakage, regardless of the method used (P < 0.05). The conical IAC demonstrated more bacterial leakage of P. gingivalis compared with the hexagonal IAC (P = 0.07). DCT found bacterial growth in the IAC only before aging and was not identified after aging. CONCLUSION: Aging affects torque accuracy. A reduction in force was noticed after 10 days. The conical IAC exhibits more bacterial leakage, although this was not statistically significant.

Collagenase Administration into Periodontal Ligament Reduces the Forces Required for Tooth Extraction in an Ex situ Porcine Jaw Model.

Minimally invasive exodontia is among the long-sought-for development aims of safe dental medicine. In this paper, we aim, for the first time, to examine whether the enzymatic disruption of the periodontal ligament fibers reduces the force required for tooth extraction. To this end, recombinantly expressed clostridial collagenase G variant purified from Escherichia coli was injected into the periodontal ligament of mesial and distal roots of the first and second split porcine mandibular premolars. The vehicle solution was injected into the corresponding roots on the contralateral side. Following sixteen hours, the treated mandibles were mounted on a loading machine to measure the extraction force. In addition, the effect of the enzyme on the viability of different cell types was evaluated. An average reduction of 20% in the applied force (albeit with a large variability of 50 to 370 newton) was observed for the enzymatically treated roots, reaching up to 50% reduction in some cases. Importantly, the enzyme showed only a minor and transient effect on cellular viability, without any signs of toxicity. Using an innovative model enabling the analytical measurement of extraction forces, we show, for the first time, that the enzymatic disruption of periodontal ligament fibers substantially reduces the force required for tooth extraction. This novel technique brings us closer to atraumatic exodontia, potentially reducing intra- and post-operative complications and facilitating subsequent implant placement. The development of novel enzymes with enhanced activity may further simplify the tooth extraction process and present additional clinical relevance for the broad range of implications in the oral cavity.