Effect of groove placement on the retention/resistance of resin-bonded retainers for maxillary and mandibular second molars

STATEMENT OF PROBLEM: Lack of retention/resistance form in the clinical preparation of teeth for resin-bonded retainers may lead to clinical failure. PURPOSE: This study investigated the effect of proximal grooves on the retention/resistance of cast resin-bonded retainers for maxillary and mandibular second molar teeth. MATERIAL AND METHODS: Two ivorine teeth (a maxillary and a mandibular second molar) were prepared for resin-bonded retainers. Twenty metal replicas of the prepared teeth were made (10 for each tooth morphotype). Resin-bonded retainers 0.5 mm thick were made for the 40 replicas and luted with Panavia EX cement. Forces for dislodgment of the retainers were applied along the long axes of the teeth. Forces recorded at the time of dislodgment were analyzed with 2-way analysis of variance and the post hoc Scheffé test. RESULTS: Grooves resulted in substantial increases in debonding forces for maxillary molars (P<.001). The effect of grooves on mandibular second molars was not significant (P=.13). CONCLUSION: Grooves placed in tooth preparations of maxillary molar teeth for resin-bonded retainers had a significant effect on retention/resistance. The effect of grooves on mandibular second molars was less pronounced.     

Effects of resistance form on attachment strength of resin-retained castings

This study evaluated the effects of tooth preparation design on resistance to dislodgment of a resin-bonded fixed partial denture (RBFPD). The variations of tooth preparation tested included axial coverage, retentive grooves, and an occlusal rest. Patterns of the tooth preparation designs were prepared and cast in a base metal alloy. Retainer patterns were waxed to refractory casts of metal dies, cast, finished and then bonded to the dies. The complete assemblies were loaded to failure on an Instron mechanical testing machine, and analysis indicated that retainers with occlusal rests were the most resistant. Grooves provided no statistically significant increase in resistance to failure of the cement. Increased axial coverage did not increase resistance to dislodgment. Successful fixed partial dentures (FPDs) depend on cast retainers to resist displacement of the restoration during function. Introduction of resin-bonded restorations opened the possibility of FPDs with minimal reduction of abutments. Specific questions concerning long term success and tooth preparation designs were prominent concerns. The influence of resistance form on overall stability of a restoration was also of particular interest. Buonocore established the foundation for retention of composite resins to acid-pitted enamel. Rochette used this technology to bond perforated cast metal splints to periodontally compromised teeth. A mechanical interlock was created as composite resin engaged these perforations and sustained the cast splint to acid-etched enamel. Howe adapted this design for replacement of anterior teeth by adding porcelain to a metal ceramic framework and then bonding the framework to abutments without tooth preparations. The advantages of these procedures were their conservative nature, esthetics, and ease of rebonding after dislodgment. Livaditis and Thompson adapted the procedure proposed by Tanaka of corrosion-pitting the bonding surface of a base metal alloy. They increased the surface area to be bonded, eliminated the perforations to improve rigidity of the framework, and described tooth preparation modifications of the abutments. They suggested an occlusal rest, establishment of guide planes through axial reduction, and a proximal extension to the facial surface to resist lingual displacement. Simonson, et al., based their anterior tooth preparation design on the configuration suggested by Livaditis which included a slight chamfer finish line plus reduction of the lingual surface to provide a thicker metal framework. Barrack introduced an inlay type tooth preparation for the occlusal rest plus shallow vertical proximal grooves, and Meiers used grooves as an esthetic alternative to proximal extensions. Clinical studies and surveys have identified specific variables involved with success and failure, while in vitro studies have evaluated framework designs, bonding agents, and methods for pitting the metal surface. This study evaluated resistance of RBFPDs to dislodgment of different tooth preparation designs.     

Cavity convergence angles for direct composite inlays.

Direct composite inlays may sometimes be difficult to remove from the cavity following primary polymerization. The aim of this work was to find the lowest cavity convergence angle (taper) which would allow reliable inlay removal. Cavity finish and cavity size were also taken into account. Standardized mesio-occlusal-distal cavities of 6 degrees taper were cut into 10 teeth of varying mesiodistal width and finished with either 12-bladed tungsten carbide or 25 microns diamond burs. After separating medium had been applied. Coltene Brilliant Dentin composite resin was packed into the cavity and light cured. The force required to remove the inlay was measured with an Instron Universal Testing Machine. The cavities were then refinished with the alternative finish and the experiment repeated. The same sequence was used for cavities of 12 degrees and finally 18 degrees convergence angle which were cut consecutively in the same 10 teeth. Force levels related to cavity convergence angle, cavity finish and tooth size were tested by ANOVA and regression analysis. The forces required to remove some of the inlays from the 6 degrees, and to a lesser extent 12 degrees angled cavities, proved unacceptably high, while an 18 degrees convergence angle resulted in statistically significant lower forces which were unlikely to damage tooth or inlay. Cavity finish and tooth size did not influence inlay withdrawal force.     

In vitro evaluation of resin-retained extracoronal precision attachments

The bond strength of resin-bonded restorations supporting extracoronal precision attachments retaining distal extension removable partial dentures was evaluated. Rigid bars of different lengths were attached to retainers with and without precision attachments. Retainers covering large areas of the teeth and having a generous "wraparound" design were used, but the teeth were not prepared to enhance resistance form. The retainers without attachments resisted forces as large as 200 N. When less circumferential tooth coverage was used, lower bond strength values were recorded. Four attachments of different loading designs were used. The precision attachments frequently became disengaged before the retainers debonded. Some low bond strengths indicated that there is a measure of unpredictability in the technique.     

涡轮机法拔除下颌阻生智齿的临床研究

目的:比较拔除中位和低位阻生智齿时,凿骨劈冠法与涡轮机去骨拔除法的优劣。方法:51例双侧中位或低位阻生齿,双侧随机分组,分别使用涡轮机去骨拔除法和传统的凿骨劈冠拔除法拔牙,对术中反应、手术时间,以及术后疼痛、术后肿胀进行对比观察和统计分析。结果:对中位阻生智齿,涡轮机去骨拔除法的手术时间和术后反应大于凿骨劈冠法(P<0.05),但对于低位阻生齿,涡轮机去骨拔除法手术时间更短、术后反应小(P<0.05)。结论:涡轮机去骨拔除法在拔除低位阻生齿时具有明显的优势,在拔除中位阻生智齿时并不比凿骨劈冠法有明显的优势。     

Dental fracture fragment attachment: fracture model and luting agent comparisons

PURPOSE: The purpose of this study was twofold: 1. To compare two different research models for simulating a traumatic anterior tooth fracture: the blunt trauma method (standard method) and an AL2O3 sectioning method (experimental method). 2. To compare the bond strength of tooth fragments bonded with resin modified glass ionomer vs. a light cured composite resin. METHODS: Two hundred bovine incisors were used in the study and kept in plain tap water throughout. The study consisted of five basic steps: 1. Fracture of the teeth by either blunt trauma (chisel and hammer) or AL2O3 sectioning disc. 2. Luting of the fractured fragments back to the teeth using either a composite resin or resin modified glass ionomer. 3. Thermocycling of the repaired teeth. 4. Dislodging the teeth to determine the strength of repair. 5. Determination of fracture type. RESULTS: One-way ANOVA revealed a statistically significant difference in the forces required to fracture the resin modified glass ionomer and composite resin regardless of whether the teeth were originally fractured with the blunt force method (p=0.030) or the disc sectioning method (p=.001). One-way ANOVA also revealed a statistically significant difference between the forces required for fracture by blunt trauma and the disc fracture techniques with the resin modified glass ionomer group (p=0.000345). However, there was no significant difference when the two techniques were compared for the composite resin (p= 0.2941). CONCLUSIONS: 1. The resin modified glass ionomer was significantly stronger than the composite resin when both the blunt trauma and the disc fracture techniques were employed. 2. The study's results do not support substituting the ease of the AL2O3 disc for the more time-consuming blunt trauma method.     

Root substance removal by scaling and root planing.

The amount of root substance removed by scaling and root planing is largely unknown. The present study evaluated in vitro the root substance loss caused by a defined number of working strokes at known forces. Forty extracted teeth with loss of connective tissue attachment into the middle third of the roots were washed and embedded in plaster, leaving one entire corono-apical tooth aspect exposed. The teeth were reproducibly repositioned in a bench-vise, where a profilometer repeatedly measured root surface levels at the same location. In a standard area of the roots a total of 40 working strokes were applied. Low forces were used in 30 teeth and high forces in 10 teeth. The forces were recorded using a piezo-electric receiver built into the upper shank of the curet. Root substance loss was measured after 5, 10, 20, and 40 working strokes. The results showed that the mean low force used per working stroke across all 40 strokes was 3.04 Newtons for the low forces, and 8.48 Newtons for the high forces. Mean cumulative loss of root substance across 40 strokes was 148.7 microns at low forces, and 343.3 microns at high forces. The mean force per stroke increased slightly across the 40 strokes, while substance removal per stroke decreased. Substance removal per stroke during strokes 1 to 5 was 6.8 microns using low forces and 20.6 microns using high forces. During strokes 21 to 40 mean removal per stroke was 2.3 microns at low forces, and 5.6 microns at high forces. These results suggest that high forces remove more root substance, and loss per stroke becomes less with increasing numbers of strokes.     

Effects of temporary cementation on permanent cement retention to composite resin cores

This in vitro study compared the effects on retention of base metal cylindrical retainers placed on composite resin cores when pretreated with eugenol and noneugenol temporary cements. Sixty composite cores and base metal cylindrical retainers were tested. The cores were pretreated with eugenol and noneugenol temporary cements before eventual cementation with resin and zinc phosphate cements. Cemented core retention was measured by application of a compressive force to the cores in an Instron machine. Differences were found between the two permanent cements. Pretreatment with eugenol cement reduced retainer retention with resin cements, but had no effect with zinc phosphate cement. Pretreatment with noneugenol cement did not reduce retainer retention.     

Stability of the Bonded Lingual Wire Retainer—A Study of the Initial Bond Strength

Bonded lingual retainers (individually adjusted multistranded wires with one bond site per tooth) are used extensively to maintain the orthodontic treatment result. Failure or loss often leads to a relapse.The bond strength of bonded lingual retainers has not yet been studied in respect of the loads that can be withstood by them through deflection of the interdental archwire region. Furthermore, human anterior teeth have never before been used for a study of this kind.Six different wire/composite combinations were studied (wires: Dentaflex co-axial 0.018", Dentaflex multistranded 0.018", and Respond Dead Soft straight, length 0.0175"; composites: Tetric Flow and Heliosit Orthodontic) by bonding 1 cm lengths of wire to the lingual surfaces of 360 extracted lower anterior teeth. Using an Instron 6025 universal testing machine, vertical shear bond strength tests at the bond site as well as vertical shear bond strength tests and horizontal tensile strength tests were performed. The failure characteristics after failure at maximum force were evaluated by light microscopy, scanning electron microscopy, and morphometry. Most failures were observed at the enamel/composite interface. The selected wires displayed no significant differences; Tetric Flow proved to be the most stable resin; and no enamel tear-outs were observed.     

Shock absorbability and hardness of commercially available denture teeth

PURPOSE: Composite resin teeth are more widely used than porcelain or acrylic resin teeth in the fabrication of removable dentures because of their high fracture toughness and high abrasion resistance. The purpose of this study was to evaluate the shock absorbability of commercially available artificial posterior teeth by the free drop-ball test with an accelerometer and to evaluate the Vickers hardness at the surface. MATERIALS AND METHODS: The tested artificial teeth included seven composite resin teeth, one acrylic resin tooth, and one porcelain tooth. Specimens were tested 50 hours after immersion in distilled water at 37 degrees C. The impact value and Vickers hardness were measured. A one-way analysis of variance was used to analyzed the data (P = .05). RESULTS: The composite resin teeth showed an intermediate impact value between that of the acrylic resin tooth and the porcelain tooth. Among the artificial teeth investigated, the porcelain tooth showed the highest impact value. A significant difference in the impact value was observed between the porcelain tooth and the composite resin and acrylic resin teeth. However, no significant difference was observed among the composite resin teeth tested. A significant correlation was found between the impact values and the Vickers hardness of the artificial teeth. CONCLUSION: The present findings suggest that composite resin teeth and acrylic resin teeth have a higher shock absorbability than porcelain teeth.     

An all porcelain lingual bonded retainer: a case study

In recent years, resin bonded metal retainers have been used to replace teeth in a conservative manner. In addition, porcelain laminates or veneers have been used in esthetic dentistry on single teeth in areas that previously dictated reductions of tooth structure. This paper describes a method of replacing a missing lower anterior tooth with an all porcelain bonded retainer.     

An All Porcelain Lingual Bonded Retainer: A Case Study

In recent years, resin bonded metal retainers have been used to replace teeth in a conservative manner. In addition, porcelain laminates or veneers have been used in esthetic dentistry on single teeth in areas that previously dictated reductions of tooth structure. This paper describes a method of replacing a missing lower anterior tooth with an all porcelain bonded retainer.     

Bone regeneration in alveolar bone dehiscences produced by jiggling forces

The aim of this experiment was to achieve support for the hypothesis that bone resorption, induced by jiggling forces, leaves a component within the supracrestal soft tissue with a capacity of reforming bone. The maxillary lateral incisors and first premolars and the mandibular second premolars in two monkeys were used in the study. Using metal pins inserted into the neighboring teeth as retainers, orthodontic elastics were stretched and placed alternately around the buccal and lingual surfaces of each experimental tooth in order to produce jiggling forces. After 5 months of continuous jiggling, when bone dehiscences were produced on the buccal aspect of the teeth, the elastics were removed. After repositioning of the teeth a split thickness flap was raised. On one side of the jaw the soft tissue within the bone dehiscences was removed. At the contralateral teeth a sham operation was performed maintaining the soft tissue within the bone dehiscences. The monkeys were sacrificed 6 months after surgery. Tissue blocks containing test and control specimens were dissected free and prepared for microscopic analysis. The length of the supracrestal connective tissue attachment and the amount of coronal bone regeneration were assessed in the histological sections. It was found that buccal alveolar bone, reduced in height by jiggling forces, regenerated after discontinuation of the forces. When the soft tissue within the buccal bone dehiscences produced by the jiggling forces was surgically removed, the coronal regeneration of the alveolar bone was markedly reduced. These observations suggest that bone resorption, induced by jiggling forces, leaves a soft tissue component with a capacity of forming bone.     

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目的比较分析Hawley保持器和透明压膜保持器的正畸治疗保持效果。方法从2006年1月至2007年6月在湖北省襄阳市口腔医院正畸科采用直弓丝矫治器治疗矫治完成的各种错畸形病例中选择60例,按双盲法随机分成2组,30例应用Hawley保持器,30例应用透明压膜保持器进行保持,保持器均佩戴2年。在模型上测量保持前、后的PAR指数的7项指标(牙齿排列、覆盖、覆、中线、颊舌向关系、近远中关系、垂直向关系),评价复发情况。结果戴用保持器2年前后的指标变化均为透明压膜保持器组小于Hawley保持器组,但只有牙齿排列、覆、颊舌向关系方面差异有统计学意义,其余各项指标变化比较差异无统计学意义。结论在直丝弓矫治器治疗术后戴用保持器2年,透明压膜保持器与Hawley保持器相比在牙齿排列、覆、颊舌向关系方面有更加稳定的保持效果。     

残留牙面粘结剂不同去除方法对牙面的影响

目的：评价不同方法去除残留于牙面的托槽粘结剂对牙釉质表面的影响。方法：收集60颗因正畸拔出的健康前磨牙,按不同去除粘结剂方法随机分为3组,每组20颗,分别使用慢速碳钨车针（A组）、超声波洁治（B组）、矽粒子（c组）进行去粘结剂处理,记录每组去除粘结剂所需时间;用万能工具显微镜测量去除粘结剂前后牙釉质厚度改变以计算釉质损失量;体视显微镜下观察釉质表面的粗糙度改变。对操作时间和釉质损失量作方差分析。结果：去粘结剂后釉质损失量排序为超声龈上洁治组〉矽粒子组〉碳钨车针组,三组存在显著差异性（P〈0．05）;去除粘结剂所需时间排序为碳钨车针组〈超声龈上洁治组〈矽粒子组,三组存在显著差异性∽〈0．05）。去粘结剂后体视显微镜观察显示;碳钨车针组镜下釉质表面均匀规则,有少量细微残留物,见少量的细小划痕;超声洁治组镜下釉质表面明显划痕,深浅不一,并有轻重不同的釉质裂纹,牙面上见粘结剂残留较多;矽粒子组划痕较细而浅,数量明显较少。结论：用碳钨车针去除残留牙面粘结剂方法对牙面的影响较小,时间适合临床操作,是临床值得推荐的一种去粘结方法。     

A nine-year clinical case study of a resin-bonded fixed partial denture seated on the maxillary anterior teeth

PatientThis report describes the longevity of a resin-bonded fixed partial denture (RBFPD). This denture was seated on the maxillary anterior teeth with minimal tooth preparation. The RBFPD was cast from a silver–palladium alloy (Castwell M.C. 12), and the pontic was veneered with an indirect composite material (Estenia). The retainers were primed with a metal conditioner (V-Primer) and seated with a tri-n-butylborane initiated adhesive resin (Super-Bond C&B). After an observation period of eight years, a fracture occurred in the incisal edge of the central incisor abutment. The fractured area was restored with light-polymerizing composite resin and the anterior guidance was re-adjusted.DiscussionRBFPD abutment teeth with deep vertical overlap should be carefully prepared to avoid abutment tooth fracture.ConclusionThe clinical performance of the RBFPD made from a silver–palladium–copper–gold alloy was sufficient when seated with tri-n-butylborane initiated adhesive resin after surface modification using vinyl-thiol primer.Clinical significanceThe use of vinyl-thiol primer and tri-n-butylborane initiated adhesive resin is a clinically reliable bonding system for seating resin-bonded fixed partial denture (RBFPD) made from a silver–palladium–copper–gold alloy. The RBFPD, based on a reliable bonding system, can clinically function for a long time, even if the vertical overlap of the abutment teeth is excessive.     

Resin-bonded prostheses for posterior teeth.

This study evaluated fixed partial dentures bonded with resin to dentin on posterior teeth with minimal tooth preparation. The patients included were missing at least one premolar or first molar. The abutment teeth next to the modification spaces were moderately restored with MOD or class II restorations on most of the teeth. A total of 20 patients with 23 fixed partial dentures were included in the study. After removal of existing restorations, the abutment teeth were prepared to eliminate undercuts on the perimeter of the preparations. Undercut areas within the preparation were not filled but were blocked out later in the laboratory. The fixed partial dentures employed inlays as retainers for a metal ceramic pontic. The metal framework was cast in a high noble gold alloy. The areas of the retainers to be bonded were treated with the Kulzer Silicoater method. Immediately before cementation, enamel was etched and exposed dentin was treated with Gluma. Kerr's resin bonded bridge cement was used for cementation. Patients were recalled after periods of 1 week, 1 month, 6 months, 1 year, 2 years, and 4 years for evaluation. None of the restorations lost retention and no major adverse effects were observed in the 4-year follow-up period.     

Longitudinal study on forces transmitted from denture base to retainers of lower free-end saddle dentures with Aker''s clasps

The aim of this study was to make a longitudinal analysis of the forces transmitted from denture base to retainers of lower free-end saddle dentures with Aker's clasps using a newly developed transducer. The experimental apparatus consisted of two components, a metal framework and a denture base embedded with a force-detecting unit. This device was the transducer, which could detect changes in lateral and vertical forces transmitted from denture base to retainers at the same time. Forces were measured on several separate occasions from the insertion of new dentures to about 4 months afterwards. The result are summarized as follows: (i) the maximal mean value of vertical forces transmitted from denture base to retainers was decreased after 1 week of insertion of new dentures, then increased and reached a constant level (about 10N) 4-6 weeks after the insertion of new dentures; (ii) there were large differences in the maximal mean value of lateral forces between subjects.     

Direct application of fiber-reinforced composites in splinting in a case of periodontitis. II

Attachment loss through advanced periodontitis results in tooth mobility, and then loss of teeth. To prevent progression it is needed to eliminate any exciting agent and correct functional disorders in consequence of disease. Regeneration of periodontium is impossible and mastication is difficult because of tooth mobility. Long-term maintenance of mobile teeth is doubtful. We have to prevent the extraction of these teeth to stabilise them by a splint made of material that is inexpensive, reparable, provides sufficient support for the artificial tooth. Fiber-Reinforced Composite (FRC) fulfills the above requirements. In their case-reports the authors demonstrate the practical application of splinting with FRC materials. In these cases the FRC splints are not only periodontal splints but they act as orthodontic retainers or supports for an artificial tooth.     

Bond Strength of Fiber-Reinforced Composite Resin Restorations

Severe tooth wear is common in older dentate individuals, with one treatment option being composite resin restorations reinforced with a suitable matrix. This study evaluated the use of high modulus polyethylene (Celanese) fibers as a reinforcing matrix for composite resin. Human mandibular incisor teeth were sectioned to simulate severe tooth wear. Sectioned surfaces were measured, the teeth paired and assigned to control or test sample groups, and further assigned to be tested with a labial or lingual shearing force. A phosphorylated dentin bonding adhesive was applied to the abraded dentin surface. Labial and lingual intra-enamel bevel preparations were cut on each specimen. A piece of Celanese fabric was bonded onto the acid-etched labial and lingual bevels of the test specimens using an enamel bonding agent. Class IV composite resin restorations were then placed onto the test and control specimens. Following water storage, the specimens were subjected to shearing forces. Bond strengths for test specimens were significantly greater (p < 0.03) than the controls. Specimens with a labially applied force also had significantly higher bond strengths (p < 0.001). SEM analysis revealed adhesive bond failures over dentin surfaces, with cohesive bond failures within the composite resin. Celanese fibers maintained the restorations on the teeth, although adhesive failures were seen between the fibers and enamel bonding agent.