Comparison of laser fluorescence devices for detection of caries in primary teeth

The aim of this in vivo study was to evaluate the performance of fluorescence‐based devices in detecting occlusal caries lesions in primary molars compared with conventional methods. Two examiners assessed 44 occlusal surfaces of first and second primary molars in 20 patients using two fluorescence devices: DIAGNOdent (LF) and DIAGNOdent pen (LFpen). Teeth were also assessed by visual examination and bitewing radiograph. Histological examination served as the gold standard after extraction. By using the McNemar test, the sensitivity, specificity, accuracy, and area under the receiver operating curve were calculated as outer enamel (D1), inner enamel (D2) and dentine caries (D3) lesion thresholds. The intra‐ and inter‐examiner reproducibility were calculated using the Cohen's unweighted kappa statistics. At the D1 threshold, the LFpen sensitivity was statistically higher than LF and radiographic examination (P < 0.001), whereas there was no statistically significant difference among the groups at the D2 and D3 thresholds (P > 0.05). All methods demonstrated the highest sensitivity values at D3. At the D1 and D2 thresholds, there were no significant differences between the LFpen specificity and the other methods. All methods presented similar performance in detecting all lesions considering the area under the receiver operating curve. The LFpen showed better performance than LF. Furthermore, visual examination and the LFpen device seem to be sufficient for detection of occlusal caries in primary molars.     

Comparison between a laser fluorescence device and visual examination in the detection of occlusal caries in children

Occlusal surfaces of molars are especially susceptible to the development of caries due to the features, such as pits and deep fissures, of their anatomical structure.AimTo evaluate the efficiency of DIAGNOdent laser fluorescence measurements in comparison with visual examination for occlusal caries detection for first permanent molars in children.MethodsThe study involved 156 permanent molar teeth in 40 children aged 7–12 years. A relatively new technology, the fluorescence laser DIAGNOdent pen, was used for detecting and diagnosing caries on the occlusal surfaces of molars. The visual examination of fissures was based on the Ekstrand classification system.ResultsThe results showed a strong relationship between examination with the DIAGNOdent and visual inspection. DIAGNOdent’s sensitivity and specificity were 97% and 52%, respectively, indicating that the laser fluorescence DIAGNOdent pen is a reproducible and accurate diagnostic tool that may be very helpful in conjunction with visual examination in the detection of occlusal caries in permanent molars in children.     

A follow-up study of the use of DIAGNOdent for monitoring fissure caries in children

OBJECTIVES: The aim of this study was to evaluate the utility of the laser fluorescence device DIAGNOdent for monitoring occlusal caries longitudinally as part of a routine dental check-up in a public dental clinic. METHODS: Children aged 7-8 and 13-14 years at baseline participated in the study. As part of two consecutive dental check-ups with a mean interval of 1,19, years, 423 permanent molars and 315 primary molars in 81 children were examined visually and using DIAGNOdent by one dentist. In teeth where, as judged by visual examination, caries had emerged or progressed during the follow-up, the DIAGNOdent values had increased significantly from the baseline. RESULTS: In permanent teeth with a change in visual score from sound to enamel or dentin caries, the mean DIAGNOdent value increased from 24 to 37 and in primary teeth from 8 to 40. The increase in DIANGOdent values correlated positively with the increase in visual score. The mean DIAGNOdent value at baseline was significantly higher in teeth that became carious than in those that remained sound during the follow-up. For permanent teeth with a visual reversal from inactive or active enamel caries to a sound surface, the mean DIAGNOdent value decreased from 36 to 24. CONCLUSIONS: These results suggest that DIAGNOdent is useful in monitoring occlusal caries in both permanent and primary molars.     

ICDAS Ⅱ与DIAGNOdent检测乳牙早期龋及相关性研究

目的:采用ICDAS Ⅱ和DIAGNOdent激光荧光龋检测仪检测幼儿乳牙不同牙面早期龋患情况,分析2种方法之间的相关性.方法:选取西安市某幼儿园小班3岁学龄前儿童164名,依次用ICDAS Ⅱ和DIAGNOdent检测代表性牙位54、51、64、74、71、84牙共16个牙面位点的患龋情况.SPSS 19.0软件数据统计分析.结果:ICDAS Ⅱ检查结果显示,所有检查位点中脱矿率(ICDAS=1,2)大于成洞龋(ICDAS=3,4,5,6)(P＜0.05);DIAGNOdent检查结果显示,除乳磨牙咬合面外,其余位点显示了与ICDAS Ⅱ同样的结果.同时,随着ICDAS Ⅱ检查结果数据的增大,所对应的DIAGNOdent读数中位数呈阶梯状增大,且咬合面高于光滑面.乳磨牙咬合面和光滑面ICDAS Ⅱ与激光检查方法之间的秩相关系数分别为r=0.647(P ＜0.01)和r=0.741(P＜0.01).结论:ICDAS Ⅱ与DIAGNOdent均能有效发现乳牙早期龋,两者之间存在一定相关性;3岁学龄前儿童牙齿龋损主要以早期脱矿为主要表现.     

Performance of a new laser fluorescence device for the detection of occlusal caries in vitro

The new device DIAGNOdent pen based on red laser light induced fluorescence was introduced for the detection of approximal and occlusal caries. The aim of this study was to test its performance on occlusal surfaces. The new device comes with two different sapphire fibre tips: a cylindrical tip and a conical tip. The two new sapphire fibre tips were used and compared with the tip currently available with DIAGNOdent (DD). METHODS: The teeth were selected from a pool of extracted permanent human molars, which were stored frozen at -20 degrees C, until use. Prior to being measured the teeth were defrosted and cleaned. One hundred and nineteen teeth were selected and measured with the old tip and with the two new tips of the new device by two independent assessments. The teeth were histologically prepared and assessed for caries extension. RESULTS: Specificity values for D(1), D(2) and D(3) ranged between 0.69 and 0.89, sensitivity between 0.78 and 0.96. There were no statistically significant differences obtained between the two tips of the new and the one tip of the old device (p>0.05). Intra-examiner reliability with kappa values of >0.83 was high. CONCLUSIONS: In this study, the new laser fluorescence device performed on occlusal surfaces as well as the available device.     

Long-term clinical evaluation of direct resin composite restorations in vital vs. endodontically treated posterior teeth — Retrospective study up to 13 years

ObjectivesThis retrospective study evaluated and compared the survival rate of Class II posterior direct resin based composite (RBC) restorations made in vital teeth (VT) and endodontically treated teeth (ETT). The influence of risk factors on the long-term performance of restorations was also investigated.MethodsPatients (n = 245) receiving RBC posterior restorations between 2004 and 2012 were selected. A total of 597 restorations (485 in VT, 112 in ETT) with minimum 2.5–3 mm remaining cusp thickness, made with the same brand of RBC and adhesive, were evaluated using the USPHS criteria. Data were analyzed with Mann–Whitney, Chi-square and Fisher’s Exact Test, Extended Cox-regression and Kaplan–Meier analysis (p < 0.05). Relative risk ratio was estimated for each evaluated parameter.ResultsThe mean observation period was 8.6 ± 2.3 years. An annual failure rate in VT and ETT of 0.08% and 1.78%, respectively, was detected. The reasons of failures included restoration fracture, secondary caries in VT; vertical root fracture, cusp fracture, restoration fracture, secondary caries and loss of adhesion in ETT. Significantly better performance was observed in RBCs of VT for each evaluated parameter. Among the evaluated risk factors only occlusal stress affected negatively the survival of RBC in ETT (Hazard Ratio 37.1; CI_95% 8.4–163.7).SignificanceAlthough, there is significant difference in the success rate of RBCs in VT (98.97%) and ETT (76.8%), the long-term (6–13 years) durability of Class II RBCs with 2.5–3 mm cusp thickness in ETT is also clinically acceptable. The presence of occlusal stress decreases the survival of RBCs in ETT.     

Digital replacement of the distorted dentition acquired by cone beam computed tomography (CBCT): a pilot study

During cone beam computed tomography (CBCT) scanning, intra-oral metallic objects may produce streak artefacts, which impair the occlusal surface of the teeth. This study aimed to determine the accuracy of replacement of the CBCT dentition with a more accurate dentition and to determine the clinical feasibility of the method. Impressions of the teeth of six cadaveric skulls with unrestored dentitions were taken and acrylic base plates constructed incorporating radiopaque registration markers. Each appliance was fitted to the skull and a CBCT performed. Impressions were taken of the dentition with the devices in situ and dental models were produced. These were CBCT-scanned and the images of the skulls and models imported into computer-aided design/computer-aided manufacturing (CAD/CAM) software and aligned on the registration markers. The occlusal surfaces of each dentition were then replaced with the occlusal image of the corresponding model. The absolute mean distance between the registration markers in the skulls and the dental models was 0.09 ± 0.02 mm, and for the dentition was 0.24 ± 0.09 mm. When the method was applied to patients, the distance between markers was 0.12 ± 0.04 mm for the maxilla and 0.16 ± 0.02 mm for the mandible. It is possible to replace the inaccurate dentition on a CBCT scan using this method and to create a composite skull which is clinically acceptable.     

激光龋齿探测仪探测窝沟龋的界值研究

目的研究激光龋齿探测仪(DIAGNOdent,DD)诊断乳、恒牙窝沟龋的界值范围。方法收集离体磨牙、乳磨牙,清洁,用DD探测面可疑点荧光值,沿该点切开,在体视显微镜下阅片,以镜下所得龋损分级结果作为参照,分析DD对应龋损各阶段的荧光值(d值)范围,即DD界值,并评价按这一标准对龋病的诊断与临床磨开后诊断的一致率。结果DD探测磨牙窝沟龋,d值为0时显示无龋损,1～33之间显示龋损局限在釉质1/2或者正常,大于45显示龋损已超过釉质1/2;DD探测乳磨牙窝沟龋:d值为0时同样显示无龋损,大于25显示龋损已超过釉质1/2。且按实验所得乳磨牙龋病的DD界值标准诊断与临床磨开后的诊断一致率较好。结论DD探测龋病时,一个适当的界值标准可以很好地辅助临床诊断龋病。     

Effect of storage in artificial saliva and thermal cycling on Knoop hardness of resin denture teeth

PurposeThis study aimed to evaluate the effect of different storage periods in artificial saliva and thermal cycling on Knoop hardness of 8 commercial brands of resin denture teeth.MethodsEigth different brands of resin denture teeth were evaluated (Artplus group, Biolux group, Biotone IPN group, Myerson group, SR Orthosit group, Trilux group, Trubyte Biotone group, and Vipi Dent Plus group). Twenty-four teeth of each brand had their occlusal surfaces ground flat and were embedded in autopolymerized acrylic resin. After polishing, the teeth were submitted to different conditions: (1) immersion in distilled water at 37 ± 2 °C for 48 ± 2 h (control); (2) storage in artificial saliva at 37 ± 2 °C for 15, 30 and 60 days, and (3) thermal cycling between 5 and 55 °C with 30-s dwell times for 5000 cycles. Knoop hardness test was performed after each condition. Data were analyzed with two-way ANOVA and Tukey's test (α = .05).ResultsIn general, SR Orthosit group presented the highest statistically significant Knoop hardness value while Myerson group exhibited the smallest statistically significant mean (P < .05) in the control period, after thermal cycling, and after all storage periods. The Knoop hardness means obtained before thermal cycling procedure (20.34 ± 4.45 KHN) were statistically higher than those reached after thermal cycling (19.77 ± 4.13 KHN). All brands of resin denture teeth were significantly softened after storage period in artificial saliva.ConclusionStorage in saliva and thermal cycling significantly reduced the Knoop hardness of the resin denture teeth. SR Orthosit denture teeth showed the highest Knoop hardness values regardless the condition tested.     

In vitro quantification of smooth surface caries with DIAGNOdent and the DIAGNOdent pen

OBJECTIVE: A new generation of the laser fluorescence device, DIAGNOdent, for caries detection and quantification has been introduced recently. It is the DIAGNOdent pen. The aim of this study was to compare the validity and reliability of both laser-based devices, DIAGNOdent and the DIAGNOdent pen, in quantifying smooth surface caries. MATERIAL AND METHODS: The material comprised a sample of 52 premolar teeth extracted on orthodontic indication. The teeth were visually sound or had various stages of non-cavitated carious lesions on smooth surfaces. All teeth were photographed and measured with both DIAGNOdent and the DIAGNOdent pen by two examiners independently. The teeth were then sectioned into 300-microm slices and analysed under a microscope for verification of lesion depth. Histopathological analyses were performed by two observers to assess lesion depth, which was classified into five categories ranging from sound to dentinal caries. Reliability and validity of the two devices were evaluated in terms of intra-class coefficients and Spearman rank correlation coefficient, respectively. The relation between measurements performed by DIAGNOdent and the DIAGNOdent pen was analyzed using Pearson's correlation coefficient. RESULTS: Both DIAGNOdent and the DIAGNOdent pen had excellent intra-observer agreement and acceptable inter-observer agreement. The correlation with histology for DIAGNOdent and the DIAGNOdent pen ranged between 0.47 and 0.57, although the correlation between DIAGNOdent and the DIAGNOdent pen was high. CONCLUSIONS: In this in vitro study, the new laser fluorescence device, the DIAGNOdent pen, showed similar reliability and validity at quantification of smooth surface caries compared to the conventional DIAGNOdent device. Agreement between DIAGNOdent and the DIAGNOdent pen was excellent.     

Performance of fluorescence‐based and conventional methods of occlusal caries detection in primary molars – an in vitro study

International Journal of Paediatric Dentistry 2012; 22: 459–466 Aim. This in vitro study aimed to test the performance of fluorescence‐based methods in detecting occlusal caries lesions in primary molars compared to conventional methods. Design. Two examiners assessed 113 sites on 77 occlusal surfaces of primary molars using three fluorescence devices: DIAGNOdent (LF), DIAGNOdent pen (LFpen), and fluorescence camera (VistaProof‐FC). Visual inspection (ICDAS) and radiographic methods were also evaluated. One examiner repeated the evaluations after one month. As reference standard method, the lesion depth was determined after sectioning and evaluation in stereomicroscope. The area under the ROC curve (Az), sensitivity, specificity, and accuracy of the methods were calculated at enamel (D1) and dentine caries (D3) lesions thresholds. The intra and interexaminer reproducibility were calculated using the intraclass correlation coefficient (ICC) and kappa statistics. Results. At D1, visual inspection presented higher sensitivities (0.97–0.99) but lower specificities (0.18–0.25). At D3, all the methods demonstrated similar performance (Az values around 0.90). Visual and radiographic methods showed a slightly higher specificity (values higher than 0.96) than the fluorescence based ones (values around 0.88). In general, all methods presented high reproducibility (ICC higher than 0.79). Conclusions. Although fluorescence‐based and conventional methods present similar performance in detecting occlusal caries lesions in primary teeth, visual inspection alone seems to be sufficient to be used in clinical practice.     

A dual energy micro-CT methodology for visualization and quantification of biofilm formation and dentin demineralization

ObjectiveThe aim of this study was to induce artificial caries in human sound dentin by means of a microcosm model using human saliva as source of bacteria and to apply a novel dual-energy micro-CT technique to quantify biofilm formation and evaluate its demineralization potential.DesignEight sound third molars had the occlusal enamel removed by cutting with a diamond disk and five cylindrical cavities (±2 mm diameter; ±1.5 mm depth) were prepared over the dentin surface in each specimen (n = 40 cavities). After sterilization, each specimen received the bacterial salivary inoculum obtained from individuals without any systemic diseases presenting dentin caries lesions and were incubated in BHI added of with 5% sucrose for 96 h to allow biofilm formation. After that, two consecutive micro-CT scans were acquired from each specimen (40kv and 70kv). Reconstruction of the images was performed using standardized parameters. After alignment, registration, filtering and image calculations, a final stack of images containing the biofilm volume was obtained from each prepared cavity. Dentin demineralization degree was quantified by comparison with sound dentin areas. All data were analyzed using Shapiro-Wilk test and Spearman correlation using α=5%.ResultsDual-energy micro-CT technique disclosed biofilm formation in all cavities. Biofilm volume inside each cavity varied from 0.30 to 1.57 mm³. A positive correlation between cavity volume and volume of formed biofilm was obtained (0.77, p < 0.01). The mineral decrease obtained in dentin was high (± 90%) for all cavities and all demineralized areas showed mineral density values lower than a defined threshold for dentin caries (1.2 g/cm³).ConclusionDual-energy micro-CT technique was successful in the quantification of a microcosm human bacterial biofilm formation and to quantify its demineralization potential in vitro.     

Observations on fluid flow from exposed dentine in primary teeth: An in vitro study

ObjectiveTo investigate fluid flow through dentine in primary teeth in vitro using the replica technique, and to compare the results with those obtained from permanent dentine.DesignThe experiments were carried out on 22 extracted, mandibular, primary, incisor teeth. The incisal edge was removed to 1 mm below the dentino-enamel junction and half the exposed surface etched with phosphoric acid. The exposed dentine was blotted dry and the pressure in the pulp cavity held at 0, 15, 30 or 45 cm H₂O above atmospheric for 30 s. Fluid that accumulated on the dentine surface was recorded with impression material and a replica made with epoxy resin which was examined in a scanning electron microscope.ResultsStructures resembling fluid droplets were present in the replicas of unetched dentine in all 22 teeth, and at all the pulpal pressures tested. The droplets formed at 45 cm H₂O were significantly larger (median diam., 5.14 mm; interquartile range, 3.26 mm; Friedman repeated measures analysis of variance on ranks (RMAVR) and Tukey test) than those formed at other pressures. There was no evidence of droplets in the replicas of etched dentine with any of the pulpal pressures.ConclusionsThese results demonstrate that fluid will tend to flow from dentine in deciduous teeth when it is exposed. They are similar to those obtained in a previous study in this laboratory on permanent teeth. The fact that fluid droplets were absent from etched dentine suggests that, after being blotted, the etched dentine matrix absorbed fluid that tended to flow out through the dentinal tubules.     

Fracture resistance and failure modes of polymer infiltrated ceramic endocrown restorations with variations in margin design and occlusal thickness

Purpose

The purpose of this in vitro study was to assess the effect of varying the margin designs and the occlusal thicknesses on the fracture resistance and mode of failures of endodontically treated teeth restored with polymer infiltrated ceramic endocrown restorations.

Inhibition of enamel mineral loss by fissure sealant: An in situ study

ObjectivesThis study evaluated the effect of fluoride and non-fluoride sealants on hardness decrease (HD) and marginal adaptation (MA) on enamel substrates after cariogenic challenge.MethodsOcclusal enamel blocks, from human third molars, were randomly divided into six groups (n = 12), according to occlusal fissures condition (S – sound; C – caries-like lesion; CF – caries-like lesion + topical fluoride) and sealants (F – FluroShield; H – Helioseal Clear Chroma). Lesion depths were 79.3 ± 33.9 and 61.3 ± 23.9 for C and CF groups, respectively. Sealants were placed on occlusal surface and stored at 100% humidity (37 °C; 24 h/d). HD was measured by cross-sectional microhardness analysis at the sealant margin distances: ?1 (under sealant), 0 (sealant margin), 1, 2 (outer sealant). Sealant MA was observed by polarized light microscopy and scored according to: 0 – failure (no sealant MA or total sealant loss); 1 – success (sealant MA present). MA and HD were analysed by ANOVA-R and mixed model analysis, respectively.ResultsFor HD (ΔS), F values (6900.5 ± 3686.6) were significantly lower than H values (8534.6 ± 5375.3) regardless of enamel substrates and sealant margin distances. Significant differences were observed among sealant margin distances: ?1 (5934.0 ± 3282.6) < 0 (8701.5 ± 6175.7) = 1 (8473.2 ± 4299.4) = 2 (7761.5 ± 4035.1), regardless of sealant and substrate. MA was similar for all groups (p ≥ 0.05).ConclusionMA was not affected by sealant type or substrate condition, whereas enamel HD was favourably impacted by fluoride in the sealant. In addition, sealants were more effective as a physical barrier than as its chemical potency in reducing enamel HD.Clinical significanceSealing with a fluoride material is a recommended procedure to prevent caries of occlusal permanent molars in high-caries-risk patients, even though those exhibiting white spot lesions, since the enamel hardness decrease when fluoride sealant was used in vitro.     

Caries diagnosis using light fluorescence devices in comparison with traditional visual and tactile evaluation: a prospective study in 152 patients

The objective of the study was to evaluate the in vivo effectiveness of two fluorescence techniques (DIAGNOdent and VistaProof) and of visual and tactile evaluation in the diagnosis of occlusal caries in permanent teeth. A total of 302 teeth (molars and premolars) from 152 patients were studied. The occlusal surfaces were cleaned using pumice mixed with water, followed by application of the diagnostic methods according to the instructions of the manufacturer, and of the visual and tactile methods according to the recommendations. The true extent of the lesions was determined by fissurotomy. The sensitivity and specificity of visual diagnosis were 79 and 72 %, respectively, versus 53 and 98 % in the case of tactile diagnosis. Teeth with caries lesions exhibited significantly higher DIAGNOdent and VistaProof scores than those without caries. Using the optimum cutoff point of 23.5 obtained in our study for DIAGNOdent, sensitivity and specificity were found to be 92.4 and 92.7 %, respectively, while values of 88.1 and 95.1 % were obtained with a cutoff point of 28.5. Sensitivity in the case of the VistaProof system varied between 92.9 % (cutoff point 1.05) and 85.3 % (cutoff point 1.3), with respective specificity values of 95.8 and 88.6 %. The areas under the curve were 0.756, 0.759, 0.954 and 0.965 for the visual and tactile methods and for DIAGNOdent and VistaProof, respectively. The fluorescence-based techniques showed greater internal and external validity than the visual and tactile methods in diagnosing occlusal caries in permanent teeth. VistaProof is the best method for diagnosing caries in its early stages.     

Randomized clinical trial on effectiveness of silver diamine fluoride and glass ionomer in arresting dentine caries in preschool children

ObjectiveTo compare the effectiveness of annual topical application of silver diamine fluoride (SDF) solution, semi-annual topical application of SDF solution, and annual application of a flowable high fluoride-releasing glass ionomer in arresting active dentine caries in primary teeth.MethodsA total of 212 children, aged 3–4 years, were randomly allocated to one of three groups for treatment of carious dentine cavities in their primary teeth: Gp1-annual application of SDF, Gp2-semi-annual application of SDF, and Gp3-annual application of glass ionomer. Follow-up examinations were carried out every six months to assess whether the treated caries lesions had become arrested.ResultsAfter 24 months, 181 (85%) children remained in the study. The caries arrest rates were 79%, 91% and 82% for Gp1, Gp2 and Gp3, respectively (p = 0.007). In the logistic regression model using GEE to adjust for clustering effect, higher caries arrest rates were found in lesions treated in Gp2 (OR = 2.98, p = 0.007), those in anterior teeth (OR = 5.55, p < 0.001), and those in buccal/lingual smooth surfaces (OR = 15.6, p = 0.004).ConclusionAnnual application of either SDF solution or high fluoride-releasing glass ionomer can arrest active dentine caries. Increasing the frequency of application to every 6 months can increase the caries arrest rate of SDF application.Clinical significanceArrest of active dentine caries in primary teeth by topical application of SDF solution can be enhanced by increasing the frequency of application from annually to every 6 months, whereas annual paint-on of a flowable glass ionomer can also arrest active dentine caries and may provide a more aesthetic outcome.     

Effect of full crown preparation on pulpal blood flow in man

ObjectiveTo determine if full crown preparation causes an increase in pulpal blood flow (PBF), indicating inflammation, in human subjects.DesignThe experiments were carried out on 35 intact, mandibular posterior teeth in 13 subjects: 32 were abutments for 16 fixed bridges that replaced first molars; the other 3 were first premolars adjacent to abutment teeth that served as un-operated controls. Crown preparations were made using an air-rotor with water-spray under regional block anaesthesia (4% articaine with epinephrine 1:100,000). PBF was recorded with a laser Doppler flow meter (LDF) before and after administering the anaesthetic, with the LDF probe on the buccal enamel. PBF was then recorded from the abutment teeth with the probe on buccal dentine after preparing the buccal surfaces of both teeth, after completing the crown preparations, and after 1 and 7 days. PBF was also recorded from the buccal enamel of the control teeth on each occasion.ResultsThe mean ± S.D. PBF values before and after anaesthesia were 2.63 ± 2.13 and 2.42 ± 2.38P.U. respectively, which were not significantly different (Paired t-test). The mean values for the abutment teeth after buccal preparation, after complete crown preparation, and after 1 and 7 days were 5.20 ± 2.49, 4.53 ± 2.52, 4.92 ± 2.98 and 5.48 ± 2.65P.U. respectively. The 4 values for each tooth were not significantly different (two-way RM ANOVA). In the control group, the values under all six conditions were not significantly different.ConclusionsRegional block anaesthesia produced no change in PBF, nor did full-crown preparation, neither immediately after the procedure nor 1 and 7 days later.     

Differences in the biomechanical behaviors of natural teeth and dental implants

ObjectiveThe lack of a PDL, which acts as an energy absorber, is a contributor to implants’ early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo.MethodsWe designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load–control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants.ResultsBiphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load–time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300 g in a loading rate 3 g/s could dissipate the energy of 7.35 ± 1.18 × 10^?2 mJ, approximately 50 times that of the dental implants (1.47 ± 1.22 × 10^?3) with statistically significant (p < 0.05).SignificanceWe confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.