Computer aided stitching approach for dental restoration models

According to the bio-characteristics of the lower and upper cavity surfaces of dental restoration, a stitching approach is proposed based on a virtual zipper working mechanism and a minimization of the surface total curvature energy, which is used to resolve the stitching problems existing during computer-aided design for dental restorations. First, the two boundaries corresponding to the lower and upper surfaces are triangulated based on the zipper working mechanism to generate the initial stitching surface patch, of which the edges are distributed uniformly between the boundaries. Secondly, the initial stitching surface patch is subdivided and deformed to reconstruct an optimized surface patch according to the bio-characteristics of the teeth. The optimized surface patch is minimally distinguishable from the surrounding mesh in smoothness and density, and it can stitch the upper and lower cavity surfaces naturally. The experimental results show that the dental restorations obtained by the proposed method can satisfy both the shape aesthetic and the fitting accuracy, and meet the requirements of clinical oral medicine.

Urinary levels of nickel and chromium associated with dental restoration by nickel-chromium based alloys

This paper aims to investigate if the dental restoration of nickel-chromium based alloy(Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine.Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination.Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry.Compared to the control group,the urinary level of Ni was significantly higher in the patient group of < 1 month of the restoration duration,among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain.Urinary levels of Cr were significantly higher in the three patient groups of <1,1 to <3 and 3 to <6 months,especially in those with a higher metal crown exposure index.Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups.Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration.Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.

Insightful Understanding of the Role of the Mechanical Properties in Defining the Reliability of All-Ceramic Dental Restorations: A Review

Since the last two decades, restorative dentistry has been witnessing an increased acceptance of the use of the well-known all-ceramic materials for the fabrication of single dental restorations, such as inlays, onlays, crowns, anterior and posterior fixed partial dentures (PFPDs). These restorations certainly offer the potential for better biocompatibility coupled with superior aesthetic qualities, especially when compared with the conventional prostheses made from porcelain that is fused with metal ceramic restorations. However, brittleness and extreme sensitivity of all-ceramic materials to micro-like defects or cracks that are inherently present, or may grow, in their microstructure during different laboratory fabrication steps, during necessary clinical adjustments, or from post-placement chewing activity, remain major shortcomings of these dental restorations. In fact, many researchers are of the opinion that the improved mechanical properties can significantly improve the lifetime of all-ceramic restorations and result in enhanced reliability. Therefore, efforts of researchers, as well as manufacturers, have been directed towards the improvement of the mechanical properties in order to overcome such limitations. This article reviews the characterization of the most important mechanical properties that can delineate the behavior of all-ceramic dental materials upon loading. These include fracture mechanics, the brittle nature of ceramics, the relationship between microstructural features and fracture behavior, sources of cracks and flaws that may initiate a fracture and the effect of different fabrication procedures and/or clinical adjustments on the mechanical behavior of dental ceramics are also reviewed and discussed.

Periodontal Health among Type 2 Diabetes Patients Treated with Different Dental Restorations

Background: Diabetes increases periodontal disease risk and its complications, which are worsened with age or faulty restorations. Aim: Evaluate periodontal health among patients with diabetes treated with different dental restorations. Materials and Methods: This comparative cross-sectional study was conducted at the faculty of dentistry, Najran University, KSA, from March 2018 to February 2020. It included 260 diabetics, treated with different dental restorations, divided into four groups, each comprising 65 patients aged 45 - 60 years: Group 1 (G1), no restorations (control group);Group 2 (G2), Class II amalgam restorations;Group 3 (G3), Class II composite resin restorations;and Group 4 (G4), three-unit posterior metal ceramic prostheses. The Ages of all restorations ranged from 8 to 10 years. All groups were assessed for the Plaque Index (PI) and Gingival Index (GI), Overhangs Rate (OR), Alveolar Bone Loss (ABL) (the latter two using panoramic X-ray). HbA1c and duration of participants were also assessed and compared. Results: The mean HbA1c results of the groups ranged from 8.1% to 9.5%, and their mean diabetes durations ranged from 7.2 to 12 years. All the groups showed worse periodontal scores, ranging from 2.45 - 2.95 for PI and 2.25 - 2.8 for GI. G2 had higher scores than G1 and G3 (p < 0.001). G4 had the highest two recorded scores (p < 0.001). G2 had a higher rate of overhangs than G3 (p < 0.037). The mean ABL was 44% (SD 6.4) for G1, 56.0% (SD 6.7) for G2, 46.5% (SD 5.8) for G3, and 74.5% (SD 6.4) for G4. The lowest values were recorded in G1 and G3 (p = 0.987). The highest value was observed in G4, which was significantly higher than other groups (p < 0.001). Conclusion: The worse periodontal parameters among subjects treated with either three-unit metal ceramic or Class II amalgam restorations indicated severe periodontal destruction. Untreated subjects and subjects treated with Class II composite resin had relatively better periodontal status.

Mechanical and biocompatible properties of polymer-infiltrated-ceramic-network materials for dental restoration

Dental restorative materials with high mechanical properties and biocompatible performances are promising.In this work,polymer-infiltrated-ceramic-network materials(PICNs)were fabricated via infiltrating polymerizable monomers into porous ceramic networks and incorporated with hydroxyapatite nano-powders.Our results revealed that the flexural strength can be enhanced up to 157.32 MPa,and elastic modulus and Vickers hardness can be achieved up to 19.4 and 1.31 GPa,respectively,which are comparable with the commercial computer-aided design and computer-aided manufacturing(CAD/CAM)blocks.Additionally,the adhesion and spreading of rat bone marrow mesenchymal stem cells(r BMSCs)on the surface of such materials can be improved by adding hydroxyapatite,which results in good biocompatibility.Such PICNs are potential applicants for their application in the dental restoration.

Optimized sintering and mechanical properties of Y-TZP ceramics for dental restorations by adding lithium disilicate glass ceramics

The novel dental ceramics can be fabricated at lower temperatures when sol-gel derived lithium disilicate glass ceramics(LDGC)was used as an additive for yttria stabilized tetragonal zirconia polycrystalline(Y-TZP)ceramics.The effect of LDGC on the sintering,mechanical,and translucent properties of Y-TZP ceramics was investigated in the present study.The results showed that the LDGC additive effectively improved the densification of Y-TZP at 1100℃,which was much lower than the sintering temperature for pure Y-TZP.When sintered at 1100℃,the Y-TZP with 1 wt%LDGC reached a relative density of 95.45%,and prossessed a flexural strength of 482.4 MPa and a fracture toughness of 5.94 MPa-m12.Moreover,its translucency was also improved.While,the addition of LDGC could result in an escape of yttrium atoms from the grain lattice of zirconia,which induced the tetragonal-monoclinic transformation of zirconia and abnormal growth of monoclinic grains.The escaped yttrium atoms diffused into the intergranular glass phase.The results indicated that the novel Y-TZP-LDGC ceramics has a great potential to be used for all-ceramic restorations.

A dual-axis chewing simulator for in vitro wear test of dental restoration materials

The wear rate of dental restoration materials on fixed, removable, and implant prostheses is important in the maintenance of cuspate form, masticatory efficiency and occlusal stability. Many permanent restoration materials such as composite, amalgam, gold, or porcelain show enough resistance to wear, but the wear rates of newly developed materials are generally unknown. To evaluate the wear rate of these dental materials, in vivo (clinic) and in vitro methods can be used. Since in vivo investigations are expensive, time consuming, and difficult to standardize, various in vitro methods have been developed. The use of a chewing machine is considered the best method, because a variety of wear mechanisms, temperature changes, and chemical effects of food and drink can be simulated simultaneously. This paper describes a dual axis chewing simulator for in vitro wear test of dental restoration materials. It consists of 8 test chambers, two stepper motors and related mechanism, a hot and cool water circle system, and a control unit. In the chambers, samples and antagonists make chewing movements vertically and Albert Ludwigs University, School of dentistry, Freiburg, Germany (Lü XY, Kern M and Strub JR) horizontally driven by the stepper motors so that the gnashing and slippage of two teeth against each other is simulated. A weighted test object is programmed to collide with a sample under precise operator control. The antagonists strike against the samples at various speeds from a slow nudge to snapping. Sample holders are designed for installation of varying samples, from single teeth to complete dentures. Two baths, six valves, and a group of pipes are used for the thermocycling. The machine can simulate various chewing modes in the mouth, including fully programmable thermal water cycling between 5℃ and 60℃ The control unit consists of a computer system with a built in specific program. Important operations such as “Start”, “Zero point”, and “Stop” are carried out by pressing the function keys on the front board of the unit. During the programming process and the simulation, several test modes and relevant test parameters are shown on the monitor. The control unit is connected via a series of interfaces to different controlled parts of the machine, such as the stepper motors and the pumps of cool and warm water.

Advance in Functional Restoration of Injured Nerve with Low Level Laser and its Utilization in the Dental and Maxillofacial Region

The inferior alveolar nerve and facial nerve are the two most important nerves in the dental and maxillofacial region.The injury to them is one of the major postoperative complications after alveolar surgery and orthognathic surgery.However,recovering the nerve function after injury takes a long time and the recovery effect tends to be unsatisfactory.In recent years,an intensively investigated technique,low level laser which has been applying in assisting the recovery of nerve function,has been gradually proved to be effective in clinically treating postoperative nerve injury.In this article we review in terms of the mechanisms involved in low level laser-assisted functional restoration of nerve injury and its clinical application in the recovery of nerve function in the dental and maxillofacial area as well.

下颌All-on-4种植固定义齿不同咬合接触应力分布的有限元分析

背景:All-on-4种植固定义齿的长期修复效果与生物力学问题密切相关,其中咬合设计影响修复体各部位的应力分布,然而,国内外目前有关All-on-4种植固定义齿的生物力学研究较少且无定论。目的:分析不同咬合接触对下颌All-on-4种植固定义齿应力分布的影响。方法:建立下颌All-on-4种植固定义齿的模型,通过改变加载力的大小、方向和加载部位,设置了10种加载工况,模拟正中咬合、侧方咬合和前伸咬合,通过在不同牙位上加载模拟不同的咬合接触类型,分析比较各组模型不同加载工况中模型各部分的应力分布和最大应力值。结果与结论:①各组模型的应力分布云图基本相似,种植体应力主要集中在种植体颈部,周围骨组织的应力主要集中在种植体颈部周围,并且皮质骨的应力明显高于松质骨;基台的应力主要集中在基台与种植体和基台与上部修复体连接的部位,上部修复体中钛支架的应力主要集中在基台与钛支架连接部位,上部修复体中树脂面的应力主要集中在各加载点上;②模拟正中咬合中,末端悬臂不加载时种植体的最大Von-Mises应力值明显增大,说明下颌All-on-4种植固定义齿在正中咬合时末端悬臂区可有咬合接触;③模拟侧方咬合中,在模拟尖牙保护[牙合]工况中模型各部分的最大Von-Mises应力值明显增大;模拟平衡[牙合]工况中模型各部分的最大Von-Mises应力值较组牙功能[牙合]工况略低,说明下颌All-on-4种植固定修复在完成骨整合永久修复时,为了提高咀嚼效率,可选择组牙功能[牙合],种植术后即刻修复时可选择平衡[牙合];④模拟前伸咬合中,只在前牙区加载时模型各部分的最大Von-Mises应力值明显增大;模拟平衡[牙合]工况中,后牙区加载点在悬臂区和在悬壁区前方时模型各部分的最大Von-Mises应力值较小,说明下颌All-on-4种植固定修复义齿前伸运动的咬合接触可选择前伸平衡[牙合]。

EVALUATION OF ORAL MIDAZOLAM AS CONSCIOUS SEDATION FOR PEDIATRIC PATIENTS IN ORAL RESTORATION

Objective To evaluate the effect of midazolam alone on sedation in young children for dental restorative care. Methods Forty children, aged 5 to 10 years with a mean age of 7.3 years, participated in this study. Twenty-one patients were assigned to intervention group received 0. 5 mg/kg of oral midazolam 20 minutes prior to the beginning of dental treatment, and 19 patients in control group received placebo liquid 20 minutes before treatment. All patients received painless local anesthetic injection and were restrained with children＇s board and bands. Blood pressure （ BP）, heart rate （HR）, oxygen saturation, treatment compliance scores of the Ramsay scale, the Briekopf and Butmer scale, Frankl scale, and the Houpt scale were recorded. Each procedure was taped and all the data were evaluated every 5 minutes by an anesthetist or experienced dentist who was unaware of the drug given to the child. Results HR in intervention group （82. 5 ± 5.1 bpm） was much lower than that in control group （95.2 ± 8.9 bpm; F=31.20, P 〈0. 001 ）. Intervention group had a significantly lower systolic BP level （94.8±5.6 mmHg） than control group （98.5±5.5 mm Hg; F=4. 34, P =0. 04）, but the diastolic BP （63.0 ± 3.5 mm Hg） was not significantly lower than control group （ 65.5 ± 4. 8 mm Hg; F = 3.31, P = 0. 07 ）. Children in intervention group showed more compliance. The patients＇ scores of the Ramsay scale, Briekopf and Buttner scale, Frankl scale, and Houpt scale in intervention group （ 1.37 ± 0. 96, 1.37 ± 0. 83, 1.32 ± 0. 67, and 2. 32 ± 1.49, respectively） were significantly lower than those in control group （3.71 ± 1.23, 2.71 ± 0. 96, 2.71 ± 0. 90, and 4.71 ± 1.19 ; F = 44. 66, 22. 36, 30.39,and 31.88,respectively,all P〈0.001） Conclusions Oral midazolam alone is safe and produces effective sedation for the dental treatment of young children. Oral midazolam application should be generally preferred because it is more easily accepted by pediatric patients.

Restorative Dental Materials

本书系牙科大学生用教科书,也供牙科医生继续教育参用。 作者简介: RobertG,CRAIG MS,PhD:1923年生。美国Michigan大学牙医学院生物学和材料科学系名誉教授。

DIFFERENTIAL CYTOTOXIC SENSITIVITY AMONG MTT,NR AND ALPASE ACTIVITY ASSAYS IN HUMAN PULP CELLS EXPOSED TO DENTAL RESIN MONOMERS

A transformed human dental pulp cell(LSC) was made to assess thecytotoxicity of dental resin monomers with MTT assay,NR assay and ALPase activity assay. L- 929 cells were used as comparative cell line. The sensitivity amongMTT,NR and ALPase activity assays and between two types of cells were investigated. The relationship of ALPase activity to two colorimetric assays was also evaluated. According to IC50 and statistics analysis on cytotoxicity curve,there were significance differences between MTT and NR assay or both cell lines for TECDMAmonomer (P＜0．005). MTT assay showed lower sensitivity than NR assay in twokinds of cell for both monomer,and LSC cells presented less sensitivity than L-929cells for TEGDMA monomer. The ALPase activity assay revealed the highest sensitivity among the three tested assays. There was a positive relationship between thecontent of ALPase activity and cytotoxic response of the other two assays. The results indicated that the sensitive degree of test assay or cell line may differ from thetest chemicals. MTT assay may be more suitable for screening a wide large of unknown tested materials due to its ralative less viariation with cell lines and moderatesensitivity.

Complete oral rehabilitation in a case with severe dental fluorosis

The authors have presented a technique of full occlusal rehabilitation in a case of severe dental fluorosis. In this technique, maxillary and mandibular anterior teeth were simultaneously prepared and restored first. This was followed by simultaneous preparation of maxillary and mandibular posterior teeth that were restored in canine guided occlusion. The technique and sequence followed here is unique and is not available in dental literature. This technique reduces number of appointments while fulfilling all objectives. Periodontal followup over 3 years was satisfactory. A restorative treatment protocol has been devised for fluorosis which will act as a guide for the dental practitioners.

Excellence in education and research Penn dental sumposium

In conjunction with the opening of the Penn Wharton China Center in Beijing,Penn Dental Medicine will present a one-day academic symposium on Sunday,March 8,2015.The symposium will focus on the essence of our teaching philosophy and advances in the dental specialties of restorative dentistry,periodontics and endodontics. The day will also feature scientific research on mesenchymal stem cells as it relates to pulp biology and regeneration. We anticipate the day will be an active exchange of ideas and discussions with professors from Chinese dental schools.

Twelve-month evaluation of the atraumatic restorative treatment approach for class Ⅲ restorations:An interventional study

BACKGROUND Atraumatic restorative treatment(ART)may be appropriate for populations without accessibility and affordability.More data are required regarding the success rate of ART in anterior teeth.AIM To evaluate the clinical performance of restoring class III cavities in anterior teeth of permanent dentition using the ART approach.METHODS A longitudinal interventional field study was carried out at two rural primary health centers,Tumkur district,India.A total of 54 teeth in 39 patients were evaluated for the survival rate of class III restorations in permanent anterior teeth using the ART approach in children and adult populations.Evaluation of ART restoration was carried out using Frencken J criteria,the mean procedure time,patient acceptance and reported pain severity during the ART approach were evaluated using a visual analog scale.Calculation of the cost of ART was also performed.RESULTS The mean time taken to perform the ART procedure was 14.79±5.8 min with the majority of patients reporting only mild pain.At 6 mo follow-up,72.2%remained in a good state,but this reduced to 27%at 12 mo.The cumulative survival rate of the restorations was 94.4%at 6 mo and 80.9%at 12 mo follow-up.Estimation of the direct cost for a single class III restoration was 186.50 INR(2.64 USD).CONCLUSION ART may be a good comprehensive option for basic oral health care for underserved or inaccessible populations,and preventive care for patients.

Prediction of Facial Profile Based on Morphometric Measurements and Profile Characteristics of Permanent Maxillary Central Incisor Teeth

The computation of facial profile from dental morphometrics has been a subject of great interest in forensic odontology.The use of teeth to draw a profile and facial features is valuable in times of mass disasters when body remains are unavailable due to extreme destruction.This study aims to identify and evaluate applicable parameters in the permanent maxillary central incisors and the face of an individual.A correlation of these parameters establishes a mathematical equation that further charts a tooth‑facial profile table.Thirty soft and hard tissue landmarks on the face in the frontal and the lateral profiles(using standardized photographs)and seven landmarks on the facial/labial surface of the clinical crown of the permanent maxillary central incisor(using casts of the maxilla)were identified for the study.Based on these,a set of eight horizontal and seven vertical parameters on the face and four parameters on the tooth were created for the assessment.Internal and external correlations between the two were carried out and statistically analyzed.A logistic regression was made to predict the probability of the parameters most likely to be reproduced in the creation of the facial profile,based on tooth morphometrics.The results indicated a definite correlation between the facial and the tooth parameters.Among the multiple parameters,a definite correlation in the horizontal dimension could be established between the mouth width and the mesiodistal width(MDW)of the tooth.In the vertical dimension,a definite relationship existed between the crown height of the tooth and the width of the midface(zygoma‑mandible).There exist divergences in the correlation of tooth and facial parameters.

无牙颌患者种植固定义齿饰面材料研究及应用进展

目前无牙颌患者种植固定义齿常用饰面材料包括丙烯酸树脂、聚合瓷、陶瓷、氧化锆等,不同材料的理化性质、临床表现各不相同。临床上固定义齿饰面材料的选择与患者口腔修复空间及软硬组织状况、力、生活习惯、口腔副功能、对颌牙材料及患者期望有关。无牙颌患者种植固定义齿相关的常见机械并发症为饰面材料的折裂/崩瓷及磨损,可通过咬合调整、修复体设计加工以及合适的修复材料选择予以规避。本文就常用无牙颌患者种植固定义齿饰面材料的特点、选择与设计要点、临床常见修复体材料相关并发症的病因及处理展开综述,以期为临床无牙颌患者种植固定义齿饰面材料的选择提供参考。

MTA与iRoot BP Plus行直接盖髓术治疗龋源性露髓恒磨牙临床疗效分析

目的:观察成熟恒磨牙去龋未净时露髓使用无机三氧化物聚合体(Mineral trioxide aggregate,MTA)和生物陶瓷类材料(iRoot BP Plus)行直接盖髓术的临床疗效,探讨此类术式的可行性及其影响因素,比较两种盖髓剂疗效的差异。方法:选取2018年4月-2019年10月就诊于笔者科室符合纳入标准的53例患者,共53颗患牙,随机分为M组和B组,分别使用MTA与iRoot BP Plus行直接盖髓术,术后定期复查,比较两组的临床疗效。结果:共计45例患者(45颗患牙)完成2年随访,总体成功率84.4%;M组和B组分别为85.7%、83.3%,两组比较差异无统计学意义(P>0.05)。性别、年龄、露髓孔大小等因素对疗效均无显著影响(P>0.05)。结论:成熟恒磨牙术中露髓时使用MTA或iRoot BP Plus行直接盖髓术均可获得良好疗效;相较于性别、年龄、露髓孔大小等因素,如何简单准确评判牙髓状态及避免龈下微渗漏更加值得关注。

种植修复10分钟及1个月后基台中央螺丝扭矩丧失情况的横断面研究

目的:本横断面研究采用4种不同的种植系统修复单颗前磨牙或磨牙缺失,观察种植修复体戴入,基台中央螺丝初次旋紧后的10 min及1个月,基台中央螺丝扭矩丧失的情况。方法:2021年7月~2023年6月于北京大学深圳医院口腔医学中心种植科完成单颗后牙种植体植入术后3个月,转修复科修复的患者268例,戴入了在二氧化锆全冠中央开孔并与基台口外粘接的改良粘接固位种植修复体。修复体调整至合适后,按照各厂家要求的扭矩旋紧基台中央螺丝。分别观察基台中央螺丝初次旋紧10 min及1个月后,当扭矩扳手再次旋紧基台中央螺丝至厂家要求的扭矩时,扭矩扳手自旋转起点至终点顺时针旋转的角度。旋转的角度越大,说明基台中央螺丝扭矩丧失的情况越严重。结果:基台中央螺丝初次旋紧10 min后再次旋紧时,所有实验组病例扭矩扳手旋转的角度均为0°。基台中央螺丝初次旋紧1个月后再次旋紧时,无论实验组(基台中央螺丝初次旋紧10 min后曾再次旋紧)还是对照组(基台中央螺丝初次旋紧10 min后未再次旋紧),无论前磨牙组还是磨牙组,无论种植体是Ankylos、Straumann、Zimmer或Nobel,所有病例扭矩扳手旋转角度均>0°。其中,共有29例病例(10.82%)扭矩扳手旋转的角度>90°,且这一比例在各组间没有显著差异(P>0.05)。没有病例扭矩扳手旋转的角度达到或超过180°。结论:在部分种植系统中,单颗后牙种植修复后1个月,部分病例基台中央螺丝扭矩丧失的情况较为明显,且比例与是否曾在基台中央螺丝初次旋紧10 min后再次加力,及前磨牙或磨牙位点、采用何种植系统无关。

Ceramage高嵌体修复无髓年轻恒磨牙的临床疗效分析

目的比较Ceramage高嵌体、树脂充填修复大面积牙体缺损的无髓年轻恒磨牙的临床疗效。方法回顾性分析2016年1月至2017年1月收治的大面积牙体缺损的35例40颗无髓年轻恒磨牙,根据修复方法分为Ceramage高嵌体组16例(18颗)、树脂充填组19例(22颗)。Ceramage高嵌体组采用Ceramage聚合瓷高嵌体修复,树脂充填组采用直接树脂充填修复。修复后1、6年按照美国公共健康协会修正标准对修复体进行评价,并比较2组修复体脱落情况。结果修复后1年,2组临床效果比较差异无统计学意义(P>0.05)。修复后6年,Ceramage高嵌体组修复体完整性、无基牙折裂效果优于树脂充填组(P<0.05)。Ceramage高嵌体组修复体脱落率[5.56%(1/18)]低于树脂充填组[40.91%(9/22)],差异有统计学意义(P<0.05)。结论Ceramage高嵌体和树脂充填在修复牙体严重缺损的年轻恒磨牙时短期修复效果差别不明显,长期的修复效果Ceramage高嵌体优于树脂充填。