Age-related changes in tooth enamel as measured by electron microscopy: implications for porcelain laminate veneers

STATEMENT OF PROBLEM: Available information on the dimensions of the enamel and pulp tissues of tooth structure, as well as their correlation with chronologic age, is limited. However, this information is a significant determinate in planning the tooth reduction for a porcelain laminate veneer (PLV) restoration. PURPOSE: This study examined variations in tooth enamel thickness and its correlation with chronologic age as it relates to available tooth substrate for PLV restorations. MATERIAL AND METHODS: Forty human maxillary central incisors extracted from patients within the age range of 30 to 69 years were used to evaluate the thickness of tooth layers. Measurements were made for the following tooth areas using scanning electron microscopy (SEM): facial enamel thickness at 1, 3, and 5 mm above the cemento-enamel junction (CEJ), palatal enamel thickness at 5 mm above the CEJ, facial and palatal enamel thickness at the incisal edge, maximum facial-palatal (MFP) width at incisal edge, physiologic secondary dentin (PSD) height, facial-cervical enamel-pulp (FCEP) distance, and the incisal edge enamel-pulp (IEP) distance. The relationship between thickness and age was evaluated with a regression analysis (alpha=.05). RESULTS: Significant differences (P<.001) were observed in all of the relationships between tooth thicknesses and chronological age. Outcome variables of enamel thickness related to age showed a steady decrease, beginning at approximately age 50. Mean values of facial enamel thickness at 1, 3, and 5 mm above the CEJ were 0.31 +/- 0.01, 0.54 +/- 0.01, and 0.75 +/- 0.02 mm, respectively, for the age range of 30 to 69 years. The thickness of maximum incisal width (R(2) = 0.95), PSD height (R(2) = 0.76), and IEP distance (R(2) = 0.99) indicated that all are subject to an increase in relation to age. CONCLUSION: Facial enamel thickness above the CEJ decreases, while MFP increases in relation to age. The PSD height and IEP distance also increased with age.     

瓷贴面修复牙体不同预备类型比较的研究进展

瓷贴面因其种种优势,在前牙美学修复中占据了重要的地位。目前,牙体预备类型是学者们比较关注的一个方面,直接关系到修复体修复后的强度、颜色和形态等。但是,关于贴面的牙体预备,学者们尚未形成一致的观点,相关研究的结果也不尽相同。本文回顾了当前研究的现状,并就贴面修复牙体预备量、预备类型、相关体外研究和临床研究等方面展开讨论。     

Microleakage in porcelain laminate veneers

The effectiveness of two dentine-enamel bonding agents has been investigated in vitro when used together with an unfilled, low viscosity resin in eliminating the microleakage of porcelain laminate veneers. The restoration margins were located below and above the amelocemental junction of extracted maxillary central incisors. The bonded specimens were thermocycled and investigated for microleakage by employing a standard dye penetration technique. Leakage was scored at the cervical and incisal margins. Tenure was found more effective than Creation 3 in 1 in preventing leakage at both the cervical enamel and dentine/composite lute interfaces. With Tenure dentine bonding agent, the leakage observed at the cervical dentine/composite lute interface was found to be similar to that observed at the cervical enamel/composite lute interface. Sealing of finished veneer margins reduced the leakage at all interfaces.     

An in vitro assessment of the strength of porcelain veneers dependent on tooth preparation

The treatment of teeth using veneer restorations combines aesthetic and functional improvements with a low destructive technique. Different kinds of tooth preparation techniques are described in the literature for this kind of restoration. This in vitro study aimed to examine the influence of the incisal preparation on the loadability of teeth restored with porcelain laminate veneers. Thirty-six selected mandibular incisors were randomly assigned to three groups with 12 teeth per group. In the first group, only the facial surface was prepared. In the second group, the preparation included a rounded incisal edge and a distinct chamfer lingually. The third group served as an unprepared control. Empress(R) veneers were then fabricated and cemented with a low viscous luting composite material. After 120 days storage in Ringer's solution, the specimens were loaded incisally to the point of failure. Statistical analysis of the results showed significant differences between the series (P=0.0103). Group 2 (with preparation of the incisal edge) exhibited the lowest fracture resistance (466+/-99 N) (N, mean forces). When prepared only facially, the teeth restored with Empress veneers reached the strength of unprepared teeth. Compared with the biting force described for incisors in the literature, the in vitro loadability reached in this investigation seems to jusitify the clinical use of both preparation designs tested.     

Tooth preparation techniques for porcelain laminate veneers

OBJECTIVE: The purpose of this study was to determine the effect that two guides to tooth preparation had on an operator's ability to appropriately and consistently prepare teeth for porcelain laminate veneers. STUDY DESIGN: In-vitro study. MATERIALS AND METHODS: Thirty typodont central incisor teeth were randomly allocated into three groups and a general dental practitioner was asked to prepare the teeth for porcelain laminate veneers. Group A were prepared freehand while Groups B and C were prepared with the assistance of a silicone index and depth preparation bur respectively. Images of the prepared teeth were used to calculate the mean labial depth of preparation and incisal reduction of teeth in each group. RESULTS: The mean labial reduction for Groups A, B and C was 0.37 mm (SD 0.13), 0.62 mm (SD 0.17) and 0.61 mm (SD 0.15) and the mean incisal reduction for Groups A, B and C was 1.0 mm (SD 0.28), 1.0 mm (SD 0.38) and 1.03 mm (SD 0.26) respectively. CONCLUSION: It is suggested that consideration be given to the use of a silicone index or depth gauge bur when teeth are prepared for porcelain laminate veneers.     

Visualization before finalization: a predictable procedure for porcelain laminate veneers.

The success and acceptance of anterior aesthetic restorations is based on a shared common vision and understanding between the patient and the clinician. If each has a different perception of how the definitive restorations will appear, this may lead to disappointment and refusal of the final restorations by the patient. This article describes the treatment of six maxillary anterior teeth with porcelain veneers using a practical approach that allows the dentist and the patient to agree on the appearance of the final restorations prior to actual fabrication and fitting of the definitive veneers.     

Long-term survival of porcelain laminate veneers using two preparation designs: a retrospective study

PURPOSE: This study evaluated the long-term survival of anterior porcelain laminate veneers placed with and without incisal porcelain coverage. MATERIALS AND METHODS: Two prosthodontists in a private dental practice placed 110 labial feldspathic porcelain veneers in 50 patients; 46 veneers were provided with incisal porcelain coverage, and 64 were not. The veneers were evaluated retrospectively from case records for up to 7 years (mean 4 years). RESULTS: At 5, 6, and 7 years, the cumulative survival estimates were 95.8% for veneers with incisal porcelain coverage and 85.5% for those without incisal coverage. The difference was not statistically significant. Six of the nine failures occurred from porcelain fracture in the veneers without incisal coverage. CONCLUSION: Although there was a trend for better long-term survival of the veneers with incisal porcelain coverage, this finding was not statistically significant.     

Clinical observations of porcelain veneers: a three-year report.

One hundred and sixty-five Cerinate porcelain veneers were placed by 11 private practice clinicians from diverse locations throughout the USA. The veneers were evaluated over a 3-year service period using Kodachrome photographs and grading of clinical characteristics by evaluators. The following factors were evaluated: (1) esthetics; (2) margin fit; (3) margin discoloration; (4) breakage; (5) gingival irritation; (6) patient acceptance; and (7) caries. Specific characteristics and their evaluations over three years were: (1) Esthetics started out excellent and remained that way; (2) Margin fit was acceptable at the beginning of the study and was actually perceived to improve, perhaps related to cement at the margins wearing and smoothing; (3) Margin discoloration started very low and became slightly worse; (4) Breakage was present during each of the 3 years, and 13 percent of veneers had some breakage after 3 years. Changes in clinical procedures are suggested in this paper to diminish this problem; (5) Gingival irritation was minimal throughout the study; (6) Patient acceptance was excellent at the beginning of the study and improved; and (7) Dental caries involvement was minimal, with only one veneered tooth showing caries involvement. Over the 3-year period, the veneers provided excellent service overall.     

Dynamometric assessment of the mechanical resistance of porcelain veneers related to tooth preparation: a comparison between two techniques

STATEMENT OF PROBLEM: There is little agreement regarding a palatal extension of the preparation for porcelain veneers, as it represents a more invasive technique than a preparation limited to the facial surface of a tooth. PURPOSE: The purpose of this study was to detect the stress in maxillary anterior teeth restored with porcelain veneers and compare the resistance to fracture of porcelain veneers prepared using different preparation designs. MATERIAL AND METHODS: Forty-five maxillary anterior teeth were restored with porcelain veneers and divided into 9 groups as follows: Ca, canines with no preparation; Ca-Ch, canines with palatal chamfer preparation; Ca-W, canines with window preparation; LI, lateral incisors with no preparation; LI-Ch, lateral incisors with palatal chamfer preparation; LI-W, lateral incisors with window preparation; CI, central incisors with no preparation; CI-Ch, central incisors with palatal chamfer preparation; CI-W, central incisors with window preparation. Shear-flexural fracture tests were performed. The fractured specimens were subjected to scanning electron microscope (SEM) analysis. Data were statistically analyzed with univariate analysis of variance and the Tukey post hoc test for multiple comparisons (alpha=.05). RESULTS: The following mean fracture load values (N) were recorded: Ca, 395 +/- 6; Ca-Ch, 310 +/- 8; Ca-W, 322 +/- 8; LI, 309 +/- 8; LI-Ch, 242 +/- 6; LI-W, 225 +/- 8; CI, 298 +/- 8; CI-Ch, 255 +/- 8; CI-W, 221 +/- 6. The SEM analysis showed that both adhesive and cohesive fractures were primarily concentrated at the cervical region. Statistical analysis showed that both the type of tooth and the design of the preparation significantly influenced the resistance to fracture of the restored teeth (P<.001). CONCLUSION: The chamfer preparation is recommended for central incisors, whereas the window preparation showed better results for canines. Both preparations can be adopted in the restoration of lateral incisors.     

Fatigue resistance of monolithic lithium disilicate occlusal veneers: a pilot study

Odontology - The use of thin lithium disilicate (LD) occlusal veneers is an effective method to increase the vertical dimension of occlusion in cases of tooth wear. However, doubt remains regarding...     

From a hippopotamus tooth to a porcelain tooth

The history of dentistry is written as if thousands of years of obscurity were followed by a couple of hundred years of enlightenment. The turning point was the work of the Father of Modern Dentistry Pierre Fauchard (1678-1761). But historically speaking this notion of progress has theoretical and practical disadvantages. In this article a practical example is given, that of porcelain. The production developed completely in the times of obscurity and only a simple pharmacist just saw the possibilities of the result in dentistry.     

下颌切牙Empress 2瓷贴面与全瓷冠牙预备体及全瓷修复复合体的抗折裂研究

目的比较下颌切牙Empress 2瓷贴面和全瓷冠牙预备体及修复体粘接后复合体的抗折强度。方法选择人离体下颌切牙50颗,随机分为5组。A组为瓷贴面牙体预备组,B组为全瓷冠牙体预备组,C组为瓷贴面修复组,D组为全瓷冠修复组,E组为完整下颌切牙（对照组）。采用标准化牙体预备过程,Empress 2铸瓷系统及树脂粘接技术完成瓷贴面-牙体和全瓷冠-牙体复合体。使用Instron万能试验机测试5组牙齿的抗折裂载荷值,采用方差分析进行统计学分析。结果A、B、C、D、E组的抗折裂载荷值分别为：（576.11±91.53）、（204.13±85.88）、（451.50±116.81）、（386.16±117.75）、（566.05±121.37）N。经统计学分析,B组抗折裂载荷值低于其他组（P<0.01）;A、E组间的差异无统计学意义,其值最高,高于其他组（P<0.05）;C、D组间的差异也无统计学意义,其值低于A、E组,但高于B组（P<0.05）。结论下颌切牙瓷贴面预备后,牙体抗折能力无明显降低。下颌切牙Empress 2瓷贴面与全瓷冠粘接后,2种复合体的抗折裂能力无明显区别。     

Minimally invasive porcelain veneers: indications for a conservative esthetic dentistry treatment modality

Patients have many restorative options for changing the appearance of their teeth. The most conservative restorative treatments for changing the appearance of teeth include tooth bleaching, direct composite resin veneers, and porcelain veneers. Patients seeking esthetic treatment should undergo a comprehensive clinical examination that includes an esthetic evaluation. When selecting a conservative treatment modality, the use of minimally invasive or no-preparation porcelain veneers should be considered. As with any treatment decision, the indications and contraindications must be considered before a definitive treatment plan is made. Long-term research has demonstrated a 94% survival rate for minimally invasive porcelain veneers. While conservation of tooth structure is important, so is selecting the right treatment modality for each patient based on clinical findings.     

Clinical evaluation of porcelain laminate veneers: a four-year recall report

The following is a clinical evaluation of custom laboratory processed porcelain laminates for the conservative treatment of the discolored dentition--a four-year recall report.     

PREPassistant: a system for evaluating tooth preparations

Learning the widely differing forms of tooth preparation, especially in restorative dentistry, places high demands on both trainees and instructors with regard to precision, reproducibility, assessment, evaluation and three-dimensional conceptualization. In the past, evaluation of such preparations has been against subjective parameters and their interpretation by the assessor (usually the instructor). The use of CAD systems in teaching seminars and courses allows an objective assessment of tooth preparations and offers the trainee the possibility of measuring him/herself against a standard, of detecting errors, and of achieving perfection in the required tasks. The PREPassistant system described in this article is one such CAD-assisted learning system. It is recommended both for students in dental schools and for the continuing education of established dentists. Its strengths are that it produces a design for a tooth preparation, enables exact comparison with an ideal preparation, detects errors, and promotes improvements and perfection.