A Comparative Micro-topographic Study of the Buccal Enamel of Different Tooth Types

Abstract

The aim of this study was to perform an in vitro examination of the etch pattern achieved on the orthodontic bonding area (OBA) of different tooth types, and to compare the extent and definition of etch achieved. Six examples of each permanent human tooth type were studied. These were collected from adolescents. A standardized etch regime was employed on the OBA and the etch pattern examined under the scanning electron microscope. The degree of definition of etch achieved on every third enamel prism was evaluated. Results showed that the extent of etch achieved decreased toward the distal end of each arch and was significantly less on the first molars (covering <2% OBA) than on the incisors (covering >90% OBA). It was also noted that the degree of definition became poorer towards the distal end of the arches and was worst on the mandibular molars.

It is suggested that the etched enamel morphology of different tooth types could affect composite resin bond strengths. Consequently, this feature could effect the clinical survival of orthodontic brackets and contribute to the higher failure rate of brackets on posterior teeth.     

Investigation of a Hydrophilic Primer for Orthodontic Bonding: an in vitro study

Abstract

A common reason for bond failure is moisture contamination. This study investigates the in vitro bond strength of brackets bonded using a new hydrophilic primer, designed to be insensitive to moisture, and compares it with a conventional primer. Using a standardized technique, the in vitro bond strength of brackets bonded with the hydrophilic primer was compared to identical brackets bonded with a conventional primer. Although designed to be moisture insensitive, the directions for use stipulate drying the teeth before bonding. Therefore, for the purposes of comparison with a conventional primer the experiment was conducted under dry conditions. The results were analysed using the Weibull distribution modelling.

The median bond strength with the hydrophilic primer (6?43 MPa, 95 per cent C.I. 7?69–9?50) was significantly lower (P = 0?0001) than the conventional primer (8?71 MPa, 95 per cent C.I. 5?89–7?59). The Weibull distribution modelling showed that brackets bonded with the hydrophilic primer were 3?96 times more at risk of failure (95 per cent C.I.: 2?39–6?56; P <0?0001). The bond strength at which 5 per cent of the brackets failed was also lower for the hydrophilic primer.

The bond strengths obtained with the hydrophilic primer were significantly lower than with the conventional primer. Although the median bond strength values were promising, the laboratory results for this particular hydrophilic primer were disappointing when using the Weibull analysis, where the whole distribution of bond strength is taken into account.     

An Ex Vivo Assessment of a Resin-modified Glass Ionomer Cement in Relation to Bonding Technique

Abstract

Objective: This study assessed a resin modified glass ionomer bonding system, Fuji ortho L.C.? using different bonding techniques and compared it with a composite control (Transbond?).

Design: Ex vivo study. Twenty extracted premolar teeth in each group were bonded as follows: (i) Group 1 Control (Transbond); (ii) Group 2 Fuji ortho L.C. without an etch procedure/wet enamel surface; (iii) Group 3 Fuji ortho L.C. without an etch procedure/dry enamel surface; (iv) Group 4 Fuji ortho L.C. using a conventional acid etch technique.

Outcome: Shear bond strength, site of bond failure and adhesive remnant index.

Results: Brackets bonded as recommended by the manufacturer (Group 2) have significantly (p < 0?001) lower bond strengths compared with the control (Group 1). Bonding with an etch technique (Group 4) will significantly (p < 0?001) increase the bond strength compared with the other Fuji groups. All the Fuji groups tended to fail at the enamel/resin interface with lower ARI scores compared with the control.

Conclusion: The lower bond strength of Fuji ortho L.C. would limit its use as a routine bonding agent. When bonded with an acid etch technique, the bond strength may be sufficient for low loading situations such as the upper anterior teeth.     

State of the art of self-etch adhesives

This paper reflects on the state of the art of self-etch adhesives anno 2010. After presenting the general characteristics of self-etch adhesives, the major shortcomings of the most simple-to-use one-step (self-etch) adhesives are addressed. Special attention is devoted to the AD-concept and the benefit of chemical interfacial interaction with regard to bond durability. Finally, issues like the potential interference of surface smear and the more challenging bond to enamel for ‘mild’ self-etch adhesives are discussed.     

Survey of clinically used adhesive ceramic bonding methods – follow up after 12 years

ObjectivesThis survey evaluated dentists’ use of adhesive bonding methods of all-ceramic restorations over a period of twelve years. This is a follow-up survey which had been undertaken in 2007, 2011, and in 2015 [1].MethodsA multiple choice questionnaire regarding adhesive bonding methods for all-ceramic restoration was developed and handed out in 2007 and 2019 to dentist participating in a local annual dental meeting in Northern Germany. The questionnaires were evaluated on the basis of evidence-based techniques from the scientific literature.ResultsData from 93 questionnaires (2019) were compared with 90 evaluated questionnaires from 2007. Bonding of oxide ceramic had improved over the years of observation (7% to 62%) whereas evidence-based bonding of silicate ceramic restorations decreased from 66% to 38%; common mistakes were using air abrasion on silicate surface. Females showed better values for correct adhesive cementation than males (f: 39–50%, m: 22%–41%). A correlation between correct cementation and years of professional experience could not be revealed.ConclusionIncorrect bonding of oxide ceramic restorations decreased within the 12 years investigated whereas there was no improvement of evidence-based bonding procedures of silicate ceramics. Still a high number of survey participants need additional training in bonding techniques.     

Effect of Surface Preparation on the Failure Load of a Highly Filled Composite Resin Bonded to a Denture Base Resin

Purpose: The purpose of this study was to evaluate the effect of the surface preparation on the maximum fracture load value of a highly filled gingival shade composite resin bonded to a denture base resin. Materials and Methods: Block specimens were prepared from a heat‐processed denture base resin and divided into five groups. The flat surfaces of the specimens were abraded with 400‐grit silicon carbide paper, then prepared in one of the following ways: (1) without preparation (group 1); (2) application of silane coupling agent (group 2); (3) application of dichloromethane (group 3); (4) application of dichloromethane following the silane coupling agent (group 4); or (5) tribochemical silica coating (group 5). A highly filled gingival shade composite resin was applied (area Ø= 5 mm) and polymerized with a light polymerizing unit. Specimens made entirely of heat‐processed denture base resin were also fabricated as references (group 6). The halves of the specimens of groups 4, 5, and 6 were thermocycled up to 10,000 times in water between 5°C and 55°C with a 1‐minute dwell time at each temperature. Shear testing was performed in a universal testing machine at a crosshead speed of 1 mm/min, and the maximum fracture load values were determined (n = 10). Results: The maximum fracture load values of the highly filled gingival shade composite resin bonded to the denture base resin for all preparation groups were significantly enhanced before thermocycling (p < 0.05). Group 5 exhibited the greatest fracture load value, followed by group 4, compared to the other groups (p < 0.05), however, the fracture load values significantly decreased for these groups after thermocycling (p < 0.05), whereas the fracture load value of group 6 did not decrease (p > 0.05). Conclusions: Tribochemical silica coating and the application of dichloromethane after the silane coupling agent were effective surface preparations for the bonding of a highly filled gingival shade composite resin to a denture base resin, however, the bond durability of these treatments may be insufficient.     

Cervitec处理后牙本质与复合树脂粘结状态的SEM观察

用Ｃｅｒｖｉｔｅｃ涂布新鲜离体牙窝洞后,再行复合树脂充填．在ＳＥＭ下观察牙本质与复合树脂修复体的粘结状态,发现牙体与修复体粘结良好,无明显裂隙,而在常规酸处理并涂粘结剂的对照组则存在裂隙．结果推测Ｃｅｒｖｉｔｅｃ具有粘结作用。     

牙本质表面状态对粘结界面影响的激光扫描共聚焦显微镜研究

目的 :研究不同表面状态下形成的牙本质湿粘结界面的异同。方法 :以RhodamineB为荧光剂 ,用激光扫描共聚焦显微镜 (LSCM)分别观察干燥或湿润粘结时形成的牙本质粘结界面的异同。结果 :湿粘结时 5种粘结系统在牙本质粘结界面都有良好的渗透。以丙酮为溶剂的粘结系统干燥粘结时形成的混合层的厚度有明显的降低 ,牙本质小管中树脂突较细 ,中断现象增多 ,长度缩短。结论 :干燥粘结时 5种粘结剂在牙本质表面的渗透性减弱。     

喷砂处理对脱落托槽再使用的实验研究

目的探讨一种简便、高效的白体脱落托槽再使用的方法。方法将60颗离体双尖牙随机平分成三组，分别粘结经喷砂处理后的脱落托槽、热处理后的脱落托槽和未经使用的新托槽，对各组作剪切粘接破坏力和拉伸粘接破坏力的测试并进行比较。结果脱落托槽喷砂处理组的剪切粘结破坏力和拉伸粘结破坏力比热处理组有显著提高（P〈0．01），与新托槽组粘结强度相接近（P〉0．05）。结论喷砂处理能有效提高脱落托槽的粘结强度，达到较理想的粘结效果。