Prediction, analysis and application of learning curve of tooth preparation for all ceramic crowns of maxillary central incisors / 北京大学学报(医学版)

OBJECTIVE@#To predict the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training based on the modified Wright learning curve model, then to analyze and applicate the learning curve.@*METHODS@#Twelve graduate students participating in standardized dental resident training were selected to prepare the resin maxillary central incisors on phantom head simulators for all ceramic crowns 4 times. The results of preparation were evaluated by 3 prosthetic experts with at least 10 years' experience focusing on the reduction, contour, taper, shoulder, finish line, margin placement, adjacent tooth injury, and preparation time for tooth preparation. The learning rate of tooth preparation was calculated by scores of tooth preparation of 4 times. The learning curve of tooth preparation was predicted based on the modified Wright learning curve model. According to the criteria of standardized training skill examinations for dental residents in Beijing, 80 was taken as the qualified standard score. The minimum training times for tooth preparation to satisfy the qualified standard score (80) was calculated, to analyze the characteristics of learning curve and evaluate the effectiveness of tooth preparation.@*RESULTS@#The scores of 4 tooth preparation were 64.03±7.80, 71.40±6.13, 74.33±5.96, and 75.98±4.52, respectively. The learning rate was (106±4)%, which showed the learning curve an upward trend. There were no significant differences between the qualified standard score and the predicted scores of tooth preparation from the 5th preparation to the 13th preparation (P > 0.05). The predicted score of the 14th preparation was higher than the qualified standard score (P < 0.05).@*CONCLUSION@#The trend of the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training is upward, which predicts the minimum training times higher than the qualified standard score is 14 times.

Reabilitação com coroas metal free em dentes anteriores traumatizados e com rizogênese incompleta: relato de caso / Rehabilitation with metal free crowns in traumatized anterior teeth with incomplete rhizogenesis: case report

Objetivo: rizogênese incompleta refere-se a dentes permanentes em que não houve a formação completa do ápice radicular, ocasionando perda da vitalidade pulpar e, consequentemente, incapacidade da bainha epitelial de Hertwig para induzir a formação completa da raiz. Devido ao traumatismo e escurecimento dental, se faz necessário em certos casos a confecção de coroas em porcelana pura para reabilitar a paciente em estética e função. O presente trabalho tem como objetivo demonstrar um caso de reabilitação estética e funcional em dente com rizogênese incompleta, onde se consideraram as perdas estruturais e alteração de cor, para que seja possível estabelecer o tratamento mais adequado. Relato de caso: paciente de 16 anos, gênero feminino, atendida na Clínica de Odontologia de uma instituição privada, insatisfeita com a estética do seu dente devido ao escurecimento do elemento 21, pois quando tinha 5 anos o dente foi traumatizado juntamente com o elemento 11. O plano de tratamento adotado para ambos os elementos foi a confecção de peças protéticas em porcelana e cimentação. Considerações finais: esse caso demonstrou que a confecção de coroas estéticas em porcelana é considerada uma boa conduta na rotina clínica em casos de escurecimento dental, devolvendo estética e função para o paciente.(AU)

Objective: incomplete rhizogenesis refers to permanent teeth with incomplete formation of the root apex, causing loss of pulp vitality and the consequent inability of the Hertwig epithelial sheath to induce complete root formation. Due to dental trauma and darkening, some cases require the production of pure porcelain crowns to rehabilitate the aesthetics and function of patients. The present study aims to show a case of aesthetic and functional rehabilitation in a tooth with incomplete rhizogenesis, in which structural losses and color change were considered to establish the most appropriate treatment. Case report: a 16-year-old female patient treated at the Dental Clinic of a private institution. The patient was not satisfied with the aesthetics of her tooth due to the darkening of element 21, because at 5 years old the tooth was traumatized along with element 11. The treatment used for both elements was the production of prosthetic porcelain crowns and cementation. Final considerations: this case showed that the production of aesthetic porcelain crowns is considered a good conduct in the clinical routine in cases of tooth darkening, returning aesthetics and function to the patient.(AU)

Consideraciones periodontales y protéticas para el tallado de piezas dentarias / Periodontal and prosthetic considerations for teeth grinding

Las preparaciones dentales para prótesis fija, involucran al tejido duro, además la proximidad que existe con la encía hace necesario la comprensión de su estructura y la función del aparato de protección, para que las restauracionesno invadan el ancho biológico constituido por el epitelio de unión y las fibras gingivales; basándonos en los estudios de Gargiulo en 1961, donde la inserción del tejido conjuntivo mide 1.07 mm y la adherencia epitelial 0.97 mm en promedio, sumados al espacio del surco gingival. El biotipo periodontal es de vital importancia para la elección de la altura de terminación del hombro de la preparación, donde el mismo deberá establecerse, previo sondaje óseo a no menos de 2.5 mm de la cresta según Kois (2008). La utilización de materiales y técnicas para la toma de impresiones definitivas deben ser amigables con los tejidos blandos a fin de no producir alteraciones y que las restauraciones sean predecibles, tanto funcional como estéticamente en el transcurso del tiempo

Dental preparations fixed prosthesis, involving the hard tissue, there is also proximity to the gum is necessary to understand the structure and function of the protection device, to restorations without invading the biologic width consisting of the epithelium junction and the gingival fibers; based on Gargiulo studies in 1961, where the insertion of the connective tissue and epithelial measured 1.07 mm 0.97 mm in average adhesion, coupled with sulcular space. The periodontal biotype is of vital importance for the choice of the termination of the shoulder height of the preparation, where it must be established prior tobone sounding no less than 2.5mm crest according Kois (2008). The use of materials and techniques for making final impressions should be friendly soft so as not to alter tissues and restorations predictable, both functionally and aesthetically over time.

Laminados cerâmicos: técnica não invasiva / Laminate veneer: non-invasive technique

Atualmente, o cuidado com a estética vem sendo valorizado de tal forma que, além de ser um referencial de saúde, ter um sorriso bonito significa também estar em harmonia consigo mesmo e ser uma pessoa bem sucedida. Dentro da Odontologia, a procura por um sorriso harmonioso e bonito vem crescendo a cada dia. Essa busca está diretamente relacionada a fatores sociais, culturais e psicológicos, que se alteram em função do tempo, dos valores de vida e da idade do indivíduo. Uma alternativa para a correção de imperfeições nos dentes é a utilização dos laminados cerâmicos que restabelecem a forma, cor, função e harmonia do sorriso, além de proporcionar longevidade do tratamento e satisfação plena do cliente. Os laminados cerâmicos são indicados para a correção de imperfeições dentárias, fraturas e dentições desgastadas pelas forças mastigatórias, substituindo estruturas defeituosas por um esmalte artificial integrado funcional e biologicamente aos tecidos dentários e periodontais. O estudo da resistência à fratura e à fadiga dos laminados cerâmicos fornece dados relativos ao reforço, estabilidade e a manutenção da estrutura dentária, prevenindo o preparo total da coroa dental. O presente relato apresenta, com base na literatura, uma reabilitação estética do sorriso usando laminados cerâmicos sem realização de preparo ou desgaste dos dentes. A comunicação harmônica entre o cirurgião dentista, TPD e os critérios científicos de planejamento são de fundamental importância para a obtenção resultados estéticos e funcionais com longevidade clínica.

Nowadays, the care with aesthetics aspects has been valued in such a way that, besides being an indicator of health, a beautiful smile is also associated to be in harmony with yourself and being a successful person. In Dentistry, the search for a beautiful and harmonious smile is increasing each day. This search is directly related to social, psychological and cultural factors that change with time, as with life values and age of the person. An alternative to correct dental imperfections is the use of laminate veneers that restore the shape, color, function and harmony of the smile, as well as provide longevity to the treatment and the complete satisfaction of the patient. The laminate veneers are indicated for the correction of dental imperfections, fractures and teeth worn by chewing forces, replacing defective structures by artificial enamel functionally and biologically integrated to the dental and periodontal tissues. The study on fracture and fatigue resistance of the laminate veneer provides data on the reinforcement, stability and maintenance of the dental structure, preventing the total preparation of the dental crown. This report is based on the literature and presents an aesthetical rehabilitation of the smile using laminate veneers without the realization of preparation or wear of the teeth. An effective communication between dentist surgeon, dental technician and the scientific criteria of planning are fundamental for obtaining aesthetic and functional results with clinical longevity.

Assessment of convergence angle of full-coverage porcelain fused to metal crowns in clinical practice.

Background: Full-coverage porcelain fused to metal crowns is commonly recommended for restoration of extensively damaged teeth. Ability of the dentist to adequately prepare teeth is fundamental to success and longevity of these restorations. Aims: This study was designed to compare recommended convergence angle and taper values of tooth preparation with clinically practiced values and to assess the factors such as tooth position, operator experience, vitality, and restorative status on convergence angle of prepared teeth. Setting and Design: It was a descriptive, cross-sectional study design and held at The Aga Khan University Hospital, Dental Section, for a period of 1 year. Materials and Methods: A minimum of 197 crown preparation models of molar and premolar teeth prepared by residents and specialists were collected in order to achieve the objectives of the study on the basis of convenient sampling technique. Statistical Analysis: One sample t-test used to compare the mean practiced convergence angle values with its recommended values. Independent sample t-test and one-way ANOVA was used to see difference in the convergence angle values of the teeth prepared by different operators, tooth type, vitality status, and restorative status of teeth. Results: Mean reported convergence angle and axial wall taper values were 23.7°±8.9° and 11.3°±7.8°, respectively, which is significantly greater (P<0.001) than the recommended values. Convergence angle values were greater for molars as compared to premolars. Conclusion: There was a considerable disparity between the convergent angles values recorded in this study and the recommended guidelines and are affected by tooth type, vitality, and restorative status of tooth.

Palateless custom bar supported overdenture: A treatment modality to treat patient with severe gag reflex.

Objective: To suggest a custom bar supported overdenture treatment modality for prosthodontic management of patients with severe gag reflex. Background: Some patients have a severe gag reflex and cannot tolerate conventional maxillary complete dentures with maximum palatal coverage and extensions of all borders. The condition further gets complicated in patients suffering from respiratory problems along with severe gag reflex. Severe gagging acts as a barrier to treat such patients with accepted clinical procedures and prevent patients from wearing the prosthesis. By saving some of the remaining natural teeth and fabricating, a horse shoe shape palateless simple tooth or bar supported overdenture can be successfully used for treating such patients. Materials and Methods: The remaining maxillary right and left canines were prepared with the tapered round end diamond bur to receive copings of custom bar after intentional root canal treatment of same teeth. Impression was made with light body and putty of the polyvinyl siloxane elastomer with double step putty wash technique. Impression was poured with die stone. Wax pattern of copings with bar was fabricated with inlay wax which was invested and casted. After retrieving the bar, it was finished and its fit was evaluated. The coping-bar assembly was finally cemented with the glass ionomer cement. Palateless overdenture was fabricated by conventional technique used for the fabrication of complete denture. Conclusion: Palateless custom bar supported overdenture procedure can be successfully used for the management of patients with severe gag reflex with improved denture retention, stability, chewing efficiency and comfort of the patient.

A CAD-CAM prosthodontic option and gingival zenith position for a rotated maxillary right central incisor: An evaluation.

Objective: Even with beautifully done restorations, an unattractive gingival zenith position, can negatively affect the smile of a person. In this short communication we describe the treatment of a rotated maxillary right central incisor using a digital photographic approach instead of the conventional approach. Background: The conjecture literature on prosthodontic considerations and gingival zenith position in cases of rotated maxillary central incisors is sparse. The gingival zenith level (GZL) in an apical-coronal direction of lateral incisors, relative to the gingival tangential zenith line joining the adjacent central incisor and canine, is approximately 1 mm under healthy conditions. Materials and Methods: For our patient, the treatment plan was decided by CAD-CAM technique as Zirconia, jacket crown. Clinical procedures included enameloplasty on the left central and right lateral maxillary incisors. Reduction of the rotated and crooked incisor was performed in the normal manner; periodontal plastic surgery was also done. Results: The patient expressed satisfaction with the intermediary (preliminary) two-dimensional photographs that were provided by the CAD-CAM system. The technique distinguished among the different treatment modalities for aesthetics and to relieve the emotional problems which were faced by female patient. The gingival zenith level of the rotated incisor was also improved. Conclusion: Digital imaging provides an immediate treatment option for the patients. Software also provides an interim aid, for the clinician as well as technician, in the form of two-dimensional photographs. CAD-CAM is entirely a helping instrument against the conservative prosthetic options and gingival zenith position for a rotated central incisor. It helps in patient education and in motivation.

Standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in Jordan

OBJECTIVES: To investigate if general dental practitioners (GDPs) in private practice in Jordan follow universal guidelines for preparation of anterior teeth for resin bonded all-ceramic crowns (RBCs). MATERIAL AND METHODS: A sample (n=100) of laboratory models containing 208 tooth preparations for IPS Empress and In Ceram, featuring work from different GDPs, was obtained from 8 commercial dental laboratories. Aspects of preparations were quantified and compared with accepted criteria defined following a review of the literature and recommendations of the manufactures' guidelines. RESULTS: Subgingival margins on the buccal aspect were noticed in 36 percent of the preparations, 54 percent demonstrated overpreparation with a tendency to overprepare the teeth on the mesiodistal plane more than buccolingual plane. Twenty percent of samples presented a shoulder finish line while a chamfer margin design was noticed in 39 percent. Twenty-nine percent and 12 percent of samples had either a feathered or no clear margin design respectively. Incisal underpreparation was observed in 18 percent of dies of each type. Only 17 percent of all preparations were found to follow the recommended anatomical labial preparations while 29 percent of the RBC preparations were found to have the recommended axial convergence angle. In total, 43 percent of preparations were found to have the recommended depth of the finish line. CONCLUSIONS: It was found that relevant guidelines for RBC preparations were not being fully adhered to in private practice in Jordan.

Estudo comparativo entre um novo método de transferência de planos guias no preparo de boca para Próteses Parciais Removíveis e outras duas técnicas / Comparative study between a new method for tranferring guide planes on mouth preparation for Removable Partial Denture and two other techniques

A confecção de uma prótese parcial removível exige a correta determinação do eixode inserção e, consequentemente, o preparo cuidadoso de planos guias parasatisfazer os princípios de retenção e estabilidade. Entretanto, grande parte dosprofissionais negligencia esta etapa, seja por desconhecimento de sua importância,dificuldade técnica, quantidade limitada de opções cientificamente comprovadas deseus resultados, ou pela aparente e ilusória economia de tempo e de trabalho quesua realização possa tomar. Então, em função do número limitado de técnicaseficientes para transferência de planos guias e da necessidade de um método queotimize o tempo dos profissionais de forma prática e didática, o presente estudobuscou introduzir uma nova maneira de transferir os planos guias. A nova técnicaconsiste na utilização de uma placa de vacuum-form (PV), comparando-a compreparos realizados em delineador e com duas outras técnicas pré-existentes: à mãolivre (ML) e coroas-guia (CG), analisando sua eficácia e precisão. Réplicas idênticas(n=44) de um modelo de gesso representativo da arcada inferior foram divididas em11 grupos, com 4 modelos cada. Cada um dos onze estudantes de Odontologiarecebeu 4 modelos - em um deles os planos guias já tinham sido previamentepreparados com delineador, os quais serviram apenas de referência para quefossem empregados os outros métodos. As diferenças angulares dos planos guiasnos 44 modelos, nos sentidos ântero-posterior, látero-Iateral e cruzado forammensuradas por meio de uma máquina de medição por coordenadas. A análise devariância para medidas repetidas e o Teste de Comparações Múltiplas (método deTukey) revelaram que tanto no sentido látero-Iateral, como na avaliação cruzada,houve diferença significativa na média dos preparos feitos no delineador em relaçãoa todas as outras técnicas. No entanto, não foram identificadas diferenças

The confection of a removable partial denture requires accurate determination of thepath of insertion and consequently, the carefuI preparation of guide planes to meetthe principies of retention and stability. However, a great number of professionalsneglect this step because of unconsciousness of its importance, or technical difficulty,ar limited options of techniques or because of apparent and illusory saving of timeand work. Due to the limited number of proven effective techniques for guide planespreparation and the need of an effective method for optimizing time of dentalsurgeons in a clear and practical way, this present study aimed the introduction of anew technique for transferring guide planes. The new technique consists on the useaf a vacuum form splint (VF). To measure its efficiency and accuracy it wascampared with the preparations carried out in a dental surveyor and with two otherpre-existing techniques: freehand (FH) and acrylic resin guide crown (GC). Identicalreplicas (n=44) of a gypsum model representing a dentallower arch were divided into11 groups of four. Each of the eleven dental students received four models - in one ofthe models, the guide planes were previously prepared with the surveyor to be usedas a reference for the application of the three transfer techniques in the other threeremaining models. The angular differences of the the prepared guide planes on the44 models were measured by a coordinate measuring machine in theanteroposterior, laterolateral and crossed views. The Analysis of Variance and Tukeymethod revealed that, for the laterolateral evaluation and crossed evaluation,significant differences were found in the average of the preparations obtained by thesurveyor in relation to ali other techniques. There were no significant differencesamong the three techniques. Anteroposterior evaluation showed significant differencebetween the average of the preparations

Collarless metal ceramic restorations to obscure the umbrella effect.

Esthetics with porcelain fused to metal restoration in the anterior region can be adversely affected due to the inadequate teeth preparations and design of the prosthesis. We presented here a case report where esthetics was compromised due to darkening of the interdental papilla and marginal gingival and overcontoured restorations in relation to porcelain fused to metal restorations. Good esthetic results were obtained by using basic principles of tooth preparation and using collarless metal ceramic restorations.

Influence of ferrule preparation with or without glass fiber post on fracture resistance of endodontically treated teeth

OBJECTIVE: This study evaluated the effect of ferrule preparation (Fp) on the fracture resistance of endodontically treated teeth, restored with composite resin cores with or without glass fiber posts. MATERIAL AND METHODS: Forty-four bovine teeth were sectioned 19 or 17 mm (2 mm ferrule) from the apex, endodontically treated and assigned to four groups (n = 11): Group 1: Fp and post; Group 2: Fp and without post; Group 3: without Fp and with post; Group 4: without Fp and without post. All specimens were restored with composite resin core and metal crown. Specimens were subjected to fracture resistance testing in a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed by two-way ANOVA and Tukey's tests (α=0.05). RESULTS: The mean fracture resistance values were as follows: Group 1: 573.3 N; Group 2: 552.5 N; Group 3: 275.3 N; Group 4: 258.6 N. Significantly higher fracture resistance was found for the groups with Fp (p<0.001). CONCLUSION: There was no statistically significant interaction between the "Fp" and "post" factors (p = 0.954). The ferrule preparation increased the fracture resistance of endodontically treated teeth. However, the use of glass fiber post showed no significant influence on the fracture resistance.

Comparison of the pain levels of computer-controlled and conventional anesthesia techniques in prosthodontic treatment

OBJECTIVE: The objective of this study was to compare the pain levels on opposite sides of the maxilla at needle insertion during delivery of local anesthetic solution and tooth preparation for both conventional and anterior middle superior alveolar (AMSA) technique with the Wand computer-controlled local anesthesia application. MATERIAL AND METHODS: Pain scores of 16 patients were evaluated with a 5-point verbal rating scale (VRS) and data were analyzed nonparametrically. Pain differences at needle insertion, during delivery of local anesthetic, and at tooth preparation, for conventional versus the Wand technique, were analyzed using the Mann-Whitney U test (p=0.01). RESULTS: The Wand technique had a lower pain level compared to conventional injection for needle insertion (p<0.01). In the anesthetic delivery phase, pain level for the Wand technique was lower (p<0.01). However, there was no difference between the Wand and conventional technique for pain level during tooth preparation (p>0.05). CONCLUSIONS: The AMSA technique using the Wand is recommended for prosthodontic treatment because it reduces pain during needle insertion and during delivery of local anaesthetic. However, these two techniques have the same pain levels for tooth preparation.

Correlation between margin fit and microleakage in complete crowns cemented with three luting agents

Microleakage can be related to margin misfit. Also, traditional microleakage techniques are time-consuming. This study evaluated the existence of correlation between in vitro margin fit and a new microleakage technique for complete crowns cemented with 3 different luting agents. Thirty human premolars were prepared for full-coverage crowns with a convergence angle of 6 degrees, chamfer margin of 1.2 mm circumferentially, and occlusal reduction of 1.5 mm. Ni-Cr cast crowns were cemented with either zinc phosphate (ZP) (S.S. White), resin-modified glass-ionomer (RMGI) (Rely X Luting Cement) or a resin-based luting agent (RC) (Enforce). Margin fit (seating discrepancy and margin gap) was evaluated according to criteria in the literature under microscope with 0.001 mm accuracy. After thermal cycling, crowns were longitudinally sectioned and microleakage scores at tooth-cement interface were obtained and recorded at ×100 magnification. Margin fit parameters were compared with the one-way ANOVA test and microleakage scores with Kruskal-Wallis and Dunn's tests (alpha=0.05). Correlation between margin fit and microleakage was analyzed with the Spearman's test (alpha=0.05). Seating discrepancy and marginal gap values ranged from 81.82 µm to 137.22 µm (p=0.117), and from 75.42 µm to 78.49 µm (p=0.940), respectively. Marginal microleakage scores were ZP=3.02, RMGI=0.35 and RC=0.12 (p<0.001), with no differences between RMGI and RC scores. The correlation coefficient values ranged from -0.27 to 0.30 (p>0.05). Conclusion: Margin fit parameters and microleakage showed no strong correlations; cast crowns cemented with RMGI and RC had lower microleakage scores than ZP cement.

Incrustaciones de resina compuesta: consideraciones generales / Composite resin inlays: general considerations

Las incrustaciones de resina compuesta cumplen funciones similares a las incrustaciones metálicas y cerámicas en lo que se refiere a la rehabilitación de piezas dentarias posteriores con gran daño estructural, pero su capacidad de integración a la subsuperficie, buen rendimiento clínico, facilidad de elaboración, menor costo y la familiaridad del odontólogo con el material, hacen de ellas un notable recurso clínico. No obstante, existen factores sumamente sensibles e importantes que deberán ser tenidos en cuenta: la preparación dentaria, el proceso de elaboración de la incrustación y la fijación adhesiva de la misma al diente

Effect of cement types on the tensile strength of metallic crowns submitted to thermocycling

O objetivo deste estudo foi verificar a resistência à tração de coroas metálicas fixadas com diferentes cimentos e submetidas à termociclagem. Setenta e duas coroas foram fundidas com liga de Ni-Cr Verabond II e cimentadas em preparos padronizados com 8º de paredes laterais e acabamento cervical com ombro reto, ombro biseldo 20º e ombro chanfrado 45º. As coroas foram separadas em três grupos de oito elementos de acordo com os cimentos: fosfato de zinco (SS White), ionômero de vidro modificado por resina Vitremer (3M ) e resinoso Rely X (3M), e submetidas a 500 ciclos térmicos em banhos de 5ºC e 55ºC. A retenção foi avaliada de acordo com a carga de tração (kgf) necessária para separar a coroa do preparo, numa máquina Instron com velocidade de 0,5 mm/minuto. Os resultados submetidos à análise de variância e ao teste de Tukey (5 por cento) mostraram que a retenção mais eficiente foi obtida com o cimento resinoso, independentemente do tipo de acabamento cervical.

Nuevos enfoques en la reconstrucción coronaria del diente endodónticamente tratado (DET) / New approaches in the coronal reconstruction of the endodontically treated tooth (ETT)

Los conceptos referidos a la rehabilitación del diente endodónticamente tratado han cambiado sustancialmente. Se acepta como verdadero refuerzo a la misma estructura dentaria, por lo tanto, los procedimientos que la conserven son de elección. Asimismo, se deben diferenciar las situaciones en el sector anterior y posterior de la arcada dentaria, siendo necesaria en el sector anterior una estabilización mecánica con pernos o potes. Será en cambio, más habitual no utilizar dipositivos intrarradiculares en el sector posterior. La integración de superficies que se consigue con los mecanismos adhesivos, permite más ahorro de tejidos. En tanto que las restauraciones (inlays, onlays, coronas y postes no metálicos) elaboradas con materiales más fácilmente integrables (cerámicos y compuestos) cobran mayor importancia en relación con esta filosofía

Consideraçöes morfológicas sobre a preparaçäo de dentes pilares em prótese fixa / Morphology approach to tooth preparation in fixes prosthodontics

O diagnóstico perceptivo realizado pelo odontológo e a qualidade da preparaçäo dentária predeterminam a longevidade da maioria das próteses fixas. Procedimentos em próteses fixas biologicamente toleráveis iniciam-se pela preparaçäo dentária. Os princípios biomecânicos da preparaçäo dentária e sua relaçäo com a morfologia dos dentes são aqui discutidos