Year : 2015 | Volume
: 1 | Issue : 1 | Page : 2--7
Clinical insight into tooth preparation: An update
Manisha Jayna1, Amit Jayna2, Bhupender Yadav1, Nupur Dabas1,
1 Department of Prosthodontics, SGT Dental College and Hospital, Gurgaon, Haryana, India
2 Department of Prosthodontics, ITS Dental College, Greater Noida, Uttar Pradesh, India
Dr. Manisha Jayna
Department of Prosthodontics, C134, Greater Kailash, Part 1, New Delhi - 110 048
Dentistry has witnessed some major discoveries during the past two decades, to the extent that many routine procedures in modern dental practice vary considerably from the way in which they were practiced for over half a century. The purpose of this article is to provide an insight to the latest techniques of crown preparation. A sound tooth preparation is the foundation stone for the longevity of a restoration. This can only be achieved if the dentist has an adequate knowledge and understanding of the various factors, which enable one to achieve this goal.
|How to cite this article:|
Jayna M, Jayna A, Yadav B, Dabas N. Clinical insight into tooth preparation: An update.Saint Int Dent J 2015;1:2-7
|How to cite this URL:|
Jayna M, Jayna A, Yadav B, Dabas N. Clinical insight into tooth preparation: An update. Saint Int Dent J [serial online] 2015 [cited 2020 Jul 12 ];1:2-7
Available from: http://www.sidj.org/text.asp?2015/1/1/2/161793
It takes a genius to create a masterpiece. Creators like Michelangelo are born once in a lifetime. However, every dentist can aim to be like Michelangelo creating perfect restorations, provided one follows the scientific principles, and blend them with art.
Tooth preparations must be based on fundamental principles for a predictable success of prosthodontic treatment. The principles of tooth preparation may be divided into the preservation of tooth structure and periodontium, retention and resistance form, marginal integrity, structural durability, and esthetic considerations. Improvement in one area often adversely affects another area, and striving for one may lead to failure in another. Careful attention to every detail is imperative during tooth preparation. It is important to remember that even though we as clinicians are meticulous in our preparations, impressions, provisionalization, and cementation these are traumatic events for the teeth. Teeth do not possess the regenerative ability found in most other tissues.
The various factors to be considered while tooth preparation depends on the type of restoration, type of luting cement used, optimal aesthetic requirement, retention and resistance form, position of the margins, and tooth alignment. 
In-depth knowledge and an understanding of the various criteria is a prerequisite to the development of optimum tooth preparation. This enables a clinician to find a best combination of compromises among the applicable biological, mechanical, and esthetic considerations.
Preservation of Tooth Structure
Care must be taken to preserve the health of oral tissue. The adjacent teeth, soft tissue, and the pulp of the tooth being prepared can be easily damaged while tooth preparation.
Protection of adjacent teeth
Iatrogenic damage to the adjacent tooth is a common error in dentistry. The technique of tooth preparation must avoid and prevent damage to the adjacent tooth. This can also be achieved by using a matrix band or by using the proximal lip of enamel of the tooth that is being prepared for protection of the adjacent tooth. 
A damaged proximal contact area makes it more susceptible to dental caries in spite of reshaping and polishing, as compared to the intact tooth surface. This could be due to high fluoride concentration in undamaged tooth structure and also because the smooth surface is less prone to plaque retention. 
Protection of pulp
Pulpal degeneration can occur many years after tooth preparation. , Extreme temperature, chemical irritation, and microorganisms can cause irreversible pulpitis, , particularly when they occur on freshly sectioned dentinal tubules.
Minimizing heat production during the preparation
During tooth preparation, energy used in the cutting process is mostly transformed into heat, which primarily depends on type of bur-diamond or carbide, pressure applied, cutting time and rate, cooling technique, and last but not the least the speed and torque of the rotary instrument. , Prevention of pulpal damage necessitates the selection of techniques and materials that reduce the risk of damage.
The handpiece pressure and speed affect the rise of intrapulpal temperature. It was established that doubling the rotating speed of the bur and/or the pressure applied on the handpiece produced a 50% increase in the tooth temperature.  Most dentists, when preparing teeth for fixed restorations with a high-speed handpiece, apply a force  that varies from 50 to 150 g/cm 2. Cutting force of 100 g/cm 2 is considered optimal for medium-grit (bur with blue-band) diamond burs.  The torque of the handpiece has a significant effect on the cutting force. Handpiece with higher torque requires a mean cutting force of 1.44 N compared to a lower torque handpiece, which requires a force of 1.2 N. 
One of the initial concerns about cutting with ultra-high-speed handpiece (200,000-400,000 RPM) is the temperature rise caused by the heat generated due to friction. Temperature rise causes thermal expansion of the dentinal fluid and its outward flow. Cooling during high-speed cutting diminishes the outward fluid flow, whereas cutting dry causes inward fluid flow, which stimulates the A-delta neurons of the pulp, eliciting a sharp pain. , In vivo measurements of tooth temperature rise showed that water-cooled high-speed tooth preparation resulted in a 3-4°C rise in pulpal temperature, whereas dry, air cooled high-speed preparation caused a 14°C rise in temperature. ,
By increasing the water flow from minimal to 45 ml/min and using light pressure, slight or no changes in pulpal temperature have been observed. , The water spray (which is directed at the area of contact between tooth and bur) not only cools the intrapulpal temperature, but also removes debris and prevents desiccation of dentin. Collection of debris causes clogging of the bur, which in turn reduces its cutting efficiency. , The higher coolant flow rates  and handpiece with multiple spray ports help in clearing the cutting debris more efficiently. 
It is essential to reduce pulpal damage for the longevity of treatment. This can be achieved to some extent by having adequate patient chair time, using copious water spray and a feather-light touch while preparation and also by using new burs and avoiding "bur drag". Cutting with carbide burs is most efficient at ultra-high-speed in dentin, with intermittent cutting.  Whereas finishing of the preparation (using bur with red and yellow band) should be done using a slow-speed handpiece with light intermittent pressure.
The chemical action of certain luting cements can cause pulpal damage when used on a freshly cut tooth. Use of cavity varnish and dentin bonding agents form an effective barrier in most cases, but their effect on the retention of cemented crowns is controversial. ,, According to a study conducted in 2013, it was observed that though resin sealer can decrease the retention of the castings when zinc phosphate is used for permanent cementation, it increases the retention when used with glass-ionomer cement.  In 2009, Magne and Nielsen  concluded that air blocking and pumicing the existing resin coatings was necessary to obtain defect-free impressions, regardless of the type of dentin bonding agent used. Certain chemical agents used for cleaning and degreasing can also cause pulpal irritation. 
It is of utmost importance to remove any carious lesion prior to making impressions for a restoration. Presence of any residual traces of infection at the site of restoration affects the success of restoration. , The bacteria which gain access to dentin because of microleakage can cause pulpal damage. The highest anti-bacterial value of luting cement was found for zinc phosphate,  polycarboxylate cement, and glass ionomer cement. ,,, Application of a dentine bonding agent prior to making an impression provides immediate protection against bacterial leakage and sensitivity, improved patient comfort, and helps in tissue conservation. 
Conservation of tooth structure
As a dentist, it is our duty to conserve as much tooth structure as possible while tooth preparation. Thickness of the remaining dentin is inversely proportional to the pulpal response.  As good clinicians we should avoid extending the tooth preparation in close proximity to the pulp, should follow the occlusal anatomy during occlusal reduction and produce minimum taper. Partial veneer crown should be preferred whenever possible, provided patient maintains good oral hygiene.
The placement of finish line plays an important role in the success of the restoration. Margins should ideally be as smooth as possible, should be easily duplicated in the impression and on the die to produce good fit of the restoration and should be placed such that both the dentist and the patient can clean it. Finish lines should be placed in enamel and also supragingivally whenever possible. The dentin-enamel junction has fracture toughness approximately 5-10 times greater than the enamel, but about 75% lower than dentin. , Some studies reported subgingival margins as the major cause of periodontitis. ,,,,,,, Whereas some suggested that margin location is not as crucial when placed by a highly skilled dentist in the mouth of a cooperative patient who understands the importance of oral hygiene.  Mechanical insults to supracrestal gingival attachment are reversible as long as restoration does not invade biological width. If junctional epithelium and gingival fibers are not disturbed, then the level of alveolar crest and gingival margin level remains stable. The intracrevicular margin should not be placed deeper than 0.5-0.7 mm.
The periodontal pocket depth can be tested by inserting a periodontal probe with defined force (0.2-0.3 N) in an apical direction parallel to the tooth axis between gingival and tooth surface.  In posterior teeth, the probing depth is up to 2 mm. In anterior teeth, the probing depth can be up to 1 mm, so it is easy to violate the biological width in anteriors. A buffer zone must exist between the finish line of prepared tooth and bottom of the gingival crevice to prevent apical migration of gingiva. This can be achieved by prepacking gingival sulcus with non-impregnated cords (for not more than 30 min) taking care that does not displace into the connective tissue. Furthermore, dentist should use end cutting burs to relocate the margin subgingivally, to prevent injury to gingival sulcus.
Flemmig et al.  advocated the use of 0.12% chlorhexidine gluconate for 2 weeks prior to tooth preparation. This helps in reducing gingival inflammation around the teeth and provides healthy working environment.
The dentist should advice the use of mouthwash with 0.2% chlorhexidine prior and also after crown preparation. The dentist should try to keep the margins of the preparation supragingival in areas where esthetics are not so much of a concern, for the ease of cleansing by the patient. In the esthetic zone where margins have to be placed subgingivally, patient needs to be motivated for good hygiene.
Mechanical considerations would include factors affecting the integrity and durability of the restoration and would include resistance form, retention form, and deformation.
It is advised to use a flat end tapered fissure bur for preparing a shoulder finish line. The use of torpedo or round-end bur has been suggested for preparing chamfer finish lines. Mansueto  concluded in his study that preparation of a chamfer finish line was statistically better when a round-end bur type was used as compared to torpedo-shaped diamond bur of similar bur-tip size.
A restoration must have adequate bulk of material to withstand the occlusal forces without distortion. Furthermore, this bulk should be within the natural confines of the tooth being prepared to avoid any periodontal insult. Occlusal clearance required for a metal crown is 1.5 mm on the functional cusp and 0.7-1 mm on a nonfunctional cusp. Metal-ceramic crown requires occlusal reduction of 1.5-2 mm on the functional cusp and 1-1.5 mm on a nonfunctional cusp. For an all-ceramic restorations, there should be 2 mm of occlusal clearance. Furthermore, a functional cusp bevel plays an integral part in occlusal reduction. Adequate bulk of metal is needed on the functional cusp, it being an area of heavy occlusal loads. Clinicians should round off all the line angles of the tooth prepared to avoid stress concentration.
Creating resistance and retention form
More recently, resistance to lateral forces and not retention along the path of insertion has been advocated as the determining factor in a crown's resistance to dislodgement. Theoretically, the more parallel the opposing walls of a tooth preparation are, the greater the retention and the more conservative is the tooth preparation. However, it is difficult to achieve parallel walls under all clinical conditions without the risk of incorporating undercuts into the tooth preparation.
Total occlusal convergence
Historically the accepted total occlusal convergence (TOC) is 2-6° taper. However, it has been determined that dental students, general dentists, and prosthodontists are unable to routinely create this minimal taper. Weed et al.  reported that dental students produced a taper of 12.7° on typodonts and 22.8° during clinical preparations. Some studies suggested 16.5° as clinically achievable TOC without affecting the retention of crowns irrespective of the cements used. 
The best way for clinically observing TOC is by visualizing the preparation in a mirror rather than looking occlusally that is by using binocular vision. A tapered diamond bur imparts a taper of 2-3° to a tooth surface it cuts, if the shank of the instrument is held parallel to the intended path of insertion of the preparation. 
Various studies have been conducted to determine TOC. In recent years, recommended optimal taper for tooth preparations for full crowns have ranged from 3° to 5°,  6°,  7-9°,  10-14°,  11.3 ± 7.8°. 
Parker et al.  in his study evaluated the ratio of occluso-cervical (OC)/inciso-cervical dimension to facio-lingual (FL) dimension and its relation to TOC. He proposed a new guideline for preparation of taper. According to which adequate resistance form can be achieved when OC/FL ratio is 0.1 and TOC is 5.6°when OC/FL ratio is 0.2 and TOC is 11.6°, when OC/FL ratio is 0.3 and TOC is 17.6° and when OC/FL ratio is 0.4 and TOC is 23.6°. Maxwell concluded that for a crown with minimal of 3 mm OC dimension, 6° TOC was required to provide adequate resistance for crowns. Based on the results of newer testing methods and resistance data it has been proposed that TOC of 10-20 is acceptable.
Though the crown preparation modifications enhanced the resistance form, however, reduction in cervical TOC proved to be more effective than proximal grooves. According to a study, the crown retention in a tooth with adequate crown height was statistically higher, followed by retention in clinically short crowns with boxes then short crowns with grooves and finally conventional crown preparation for short crown height.  Short clinical crown height can be managed by decreasing TOC, by introducing auxiliary retentive features (like grooves and boxes) and lastly by surgically increasing the crown height. Proussaefs et al.  in 2004 and Roudsari and Satterthwaite  in 2011 advised use of resin cements for cementing crown on a tooth with short clinical height, though they also found that the resistance form plays a more important role in retention than resin cement. O'Kray et al.  in a study done in 2012 concluded that by placing one or two horizontal circumferential grooves into the internal surface of the metal complete crowns increased their retention on an optimal tooth preparation. He also concluded that grooves placed into the crown were as effective as or more effective than grooves placed into the tooth/die.
Thus, one can conclude that in a clinical situation, where crown height is adequate TOC can be >20°. However, in situations where crown height is inadequate TOC <20° should be planned, with some auxiliary retentive features in preparation or on the internal surface of the crown. Use of resin cements can be of some benefit. The best way for clinically observing TOC is by visualizing the preparation in mirror rather than looking occlusally that is by using binocular vision. A tapered diamond bur imparts a taper of 2-3° to a tooth surface.
Luting cements, which bond to tooth and restoration may aid in the retention of restorations, while passive luting cements merely fill the gap between crown and tooth and mechanically lock the restoration.  Zinc phosphate cement has been used successfully for over a century to lute well-fitting metal and metal-ceramic definitive restorations, as it is a very inexpensive, rigid material and with very high early compressive strength. However, because of its high acidic nature and solubility it is no longer used. Polycarboxylate cement has lower compressive strength but high tensile strength and is less injurious to the pulp. Zinc oxide eugenol and zinc oxide noneugenol cements typically have good sealing abilities, but their relatively low compressive and tensile strengths, inherent brittleness, and high solubility limit usage to provisional restorations or implant supported crowns. 
Resin cements are typically formulated for a specific function or metal-free restorations  as they offer strength, aesthetics, flexible working times, and very low solubility though they are technique sensitive, expensive, and often hard to clean-up. Glass ionomer cements offer good strength, optical properties, and potential for fluoride release/recharge, but may have short working times, and are sensitive to moisture or dehydration and take time to fully set. Resin-modified glass ionomer cements are hybrid, dual-phase materials which are manipulated like glass ionomer, but set quicker and are stronger. ,
New Methods of Crown Preparation
Ultrasonic instruments have recently been developed for finishing crown preparations. They are successful in accessing difficult areas on the preparation margin. Ultrasonic diamond coated tips have been created for sulcus penetration and intracrevicular finish line preparation and polishing. The use of ultrasonic instruments to prepare dentin resulted in comparable bond strengths to the use of diamond burs.
Recent study by Ellis et al.  states that the extremely precise margin preparation with ultrasonic instruments improves the quality and accuracy of crown preparations, which may lead to better impressions and closer adaptation of restorations. The margins finished with the ultrasonic instruments exhibited a better-defined axial wall/margin angle and a smoother marginal surface. Rotary instruments produced a sharper and more continuous external line angle. Two-dimensional surface roughness analysis showed that the margins produced with the ultrasonic instruments were approximately half as rough as the margins prepared with the conventional rotary instruments. ,
Erbium: Yttrium-aluminium-garnet (Er: YAG) laser has been investigated for tooth preparation because of its mechanical ablation process by microexplosion. Geraldo-Martins et al.  offered new perspectives for enamel and dentin removal without significant adverse thermal effects. Er: YAG lasers have been introduced that cut dental hard tissues and most recently an Er, Cr 3+ :YSGG laser that cuts soft and hard tissues.
According to a study done by Mollica et al., the use of Er: YAG laser and high-speed handpiece for cavity preparation resulted in similar intrapulpal temperature rise and ultrasound tips generated significantly higher intrapulpal temperature rise. Though this rise in temperature due to ultrasonic tips did not reach the critical value and can be considered safe for use.
Tooth preparation is an art, which is based on fundamental principles for a predictable success of the prosthesis. In-depth knowledge and an understanding of the various criteria is a prerequisite to the development of optimum tooth preparation. It is essential to reduce iatrogenic damage to the pulp and the adjacent tooth for the longevity of treatment. This can be achieved to some extent by having adequate patient chair time, using copious water spray, feather light touch while preparation, and by use of new burs. In a clinical situation, where crown height is adequate TOC can be more than 20°. However, in situations where crown height is inadequate TOC <20° should be planned, with some auxiliary retentive features in preparation or on the internal surface of the crown. Use of resin cements can be of some benefit. It is advised that one must use a mouthwash with 0.2% chlorhexidine prior and also after crown preparation for good gingival health. A dentist while preparing a tooth for a crown should try to keep the margins of the preparation supragingival, in areas where esthetics is not so much of a concern. Whereas in the esthetic zone, margins have to be placed subgingivally, so the patient needs to be motivated for good hygiene. Finishing of the preparation should be done using a slow-speed handpiece with light intermittent pressure.
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Conflicts of interest
There are no conflicts of interest.
|1||Zoellner A, Herzberg S, Gaengler P. Histobacteriology and pulp reactions to long-term dental restorations. J Marmara Univ Dent Fac 1996;2:483-90.|
|2||Rosenstiel SF, Martin F, Land and Junhei Fujimoto. Principle in fixed prosthodontics. Contemporary Fixed Prosthodontics. 3 rd ed. St. Louis, Missouri: Mosby Inc.; 2001. p. 166-201.|
|3||Langeland K, Langeland LK. Pulp reactions to crown preparation, impression, temporary crown fixation, and permanent cementation. J Prosthet Dent 1965;15:129.|
|4||Baldissara P, Catapano S, Scotti R. Clinical and histological evaluation of thermal injury thresholds in human teeth: A preliminary study. J Oral Rehabil 1997;24:791-801.|
|5||Brannstrom M. Dentinal and pulpal response. Application of an air stream to exposed dentine, short observation period: An experimental study. Acta Odontol Scand 1960;18:17.|
|6||Hatton JF, Holtzmann DJ, Ferrillo PJ Jr, Stewart GP. Effect of handpiece pressure and speed on intrapulpal temperature rise. Am J Dent 1994;7:108-10.|
|7||Norling B, Stanford J. Evaluating the performance of dental rotary cutting instruments. The Cutting Edge: Interfacial Dynamics of Cutting and Grinding. Chicago, IL: US Department of Health, Education and Welfare, DHEW Publication No.(NIH) 76-670; 1976. p. 203-20.|
|8||Siegel SC, von Fraunhofer JA. Dental cutting with diamond burs: Heavy-handed or light-touch? J Prosthodont 1999;8:3-9.|
|9||Elias K, Amis AA, Setchell DJ. The magnitude of cutting forces at high speed. J Prosthet Dent 2003;89:286-91.|
|10||Brännstrom M, Lindén LA, Johnson G. Movement of dentinal and pulpal fluid caused by clinical procedures. J Dent Res 1968;47:679-82.|
|11||Ahlquist M, Franzén O. Pulpal ischemia in man: Effects on detection threshold, A-delta neural response and sharp dental pain. Endod Dent Traumatol 1999;15:6-16.|
|12||Rizoiu I, Kohanghadosh F, Kimmel AI, Eversole LR. Pulpal thermal responses to an erbium, chromium: YSGG pulsed laser hydrokinetic system. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86:220-3.|
|13||Evans CD, Wilson PR. The effects of tooth preparation on pressure measured in the pulp chamber: A laboratory study. Int J Prosthodont 1999;12:439-43.|
|14||Cavalcanti BN, Otani C, Rode SM. High-speed cavity preparation techniques with different water flows. J Prosthet Dent 2002;87:158-61.|
|15||Cavalcanti BN, Serairdarian PI, Rode SM. Water flow in high-speed handpieces. Quintessence Int 2005;36:361-4.|
|16||Laforgia PD, Milano V, Morea C, Desiate A. Temperature change in the pulp chamber during complete crown preparation. J Prosthet Dent 1991;65:56-61.|
|17||von Fraunhofer JA, Siegel SC, Feldman S. Handpiece coolant flow rates and dental cutting. Oper Dent 2000;25:544-8.|
|18||Siegel SC, von Fraunhofer JA. The effect of handpiece spray patterns on cutting efficiency. J Am Dent Assoc 2002;133:184-8.|
|19||Ohmoto K, Taira M, Shintani H, Yamaki M. Studies on dental high-speed cutting with carbide burs used on bovine dentin. J Prosthet Dent 1994;71:319-23.|
|20||Mausner IK, Goldstein GR, Georgescu M. Effect of two dentinal desensitizing agents on retention of complete cast coping using four cements. J Prosthet Dent 1996;75:129-34.|
|21||Going RE. Status report on cement bases, cavity liners, varnishes, primers, and cleansers. Council on Dental Materials and Devices. Council on Dental Therapeutics. J Am Dent Assoc 1972;85:654-60.|
|22||Dahl BL. Effect of cleansing procedures on the retentive ability of two luting cements to ground dentin in vitro. Acta Odontol Scand 1978;36:137-42.|
|23||Patel P, Thummar M, Shah D, Pitti V. Comparing the effect of a resin based sealer on crown retention for three types of cements: An in vitro study. J Indian Prosthodont Soc 2013;13:308-14.|
|24||Magne P, Nielsen B. Interactions between impression materials and immediate dentin sealing. J Prosthet Dent 2009;102:298-305.|
|25||Brännström M, Nyborg H. Cavity treatment with a microbicidal fluoride solution: Growth of bacteria and effect on the pulp. J Prosthet Dent 1973;30:303-10.|
|26||Tobias RS, Browne RM, Wilson CA. Antibacterial activity of dental restorative materials. Int Endod J 1985;18:161-71.|
|27||Tobias RS, Rippin JW, Browne RM, Wilson CA. A further study of the antibacterial properties of dental restorative materials. Int Endod J 1988;21:381-92.|
|28||Quarnstrom F, Collier N, McDade E, McLean K, Munk A, Nicholls J. A randomized clinical trial of agents to reduce sensitivity after crown cementation. Gen Dent 1998;46:68-74.|
|29||McComb D, Ericson D. Antimicrobial action of new, proprietary lining cements. J Dent Res 1987;66:1025-8.|
|30||Scherer W, Lippman N, Kaim J. Antimicrobial properties of glass-ionomer cements and other restorative materials. Oper Dent 1989;14:77-81.|
|31||Palenik CJ, Behnen MJ, Setcos JC, Miller CH. Inhibition of microbial adherence and growth by various glass ionomers in vitro. Dent Mater 1992;8:16-20.|
|32||Forss H, Jokinen J, Spets-Happonen S, Seppä L, Luoma H. Fluoride and mutans streptococci in plaque grown on glass ionomer and composite. Caries Res 1991;25:454-8.|
|33||Magne P. Immediate dentin sealing: A fundamental procedure for indirect bonded restorations. J Esthet Restor Dent 2005;17:144-54.|
|34||Sorensen JA. A rationale for comparison of plaque-retaining properties of crown systems. J Prosthet Dent 1989;62:264-9.|
|35||Imbeni V, Kruzic JJ, Marshall GW, Marshall SJ, Ritchie RO. The dentin-enamel junction and the fracture of human teeth. Nat Mater 2005;4:229-32.|
|36||Dong XD, Ruse ND. Fatigue crack propagation path across the dentinoenamel junction complex in human teeth. J Biomed Mater Res A 2003;66:103-9.|
|37||Waerhaug J. Histologic considerations which govern where the margin of restorations should be located in relation to the gingiva. Dent Clin North Am 1960;4:161-76.|
|38||Mörmann W, Regolati B, Renggli HH. Gingival reaction to well-fitted subgingival proximal gold inlays. J Clin Periodontol 1974;1:120-5.|
|39||Janenko C, Smales RJ. Anterior crowns and gingival health. Aust Dent J 1979;24:225-30.|
|40||Romanelli JH. Periodontal considerations in tooth preparation for crowns and bridges. Dent Clin North Am 1980;24:271-84.|
|41||Wilson RD, Maynard G. Intracrevicular restorative dentistry. Int J Periodontics Restorative Dent 1981;1:34-49.|
|42||Silness J. Periodontal conditions in patients treated with dental bridges 3. The relationship between the location of the crown margin and the periodontal condition. J Periodontal Res 1970;5:225-9.|
|43||Larato DC. Effect of cervical margins on gingiva. J Calif Dent Assoc 1969;45:19-22.|
|44||Reeves WG. Restorative margin placement and periodontal health. J Prosthet Dent 1991;66:733-6.|
|45||Koth DL. Full crown restorations and gingival inflammation in a controlled population. J Prosthet Dent 1982;48:681-5.|
|46||Eickholz P. Clinical periodontal diagnosis: Probing pocket depth, vertical attachment level and bleeding on probing. Perio 2004;1:75-80.|
|47||Flemmig TF, Sorensen JA, Newman MG, Nachnani S. Gingival enhancement in fixed prosthodontics. Part II: Microbiologic findings. J Prosthet Dent 1991;65:365-72.|
|48||Mansueto MA, Abdulkarim HA, Thabet WR, Haney SJ. The chamfer finish line: Preclinical student performance using different bur designs. J Dent Educ 2010;74:612-7.|
|49||Weed RM, Suddick RP, Kleffner JH. Taper of clinical and typhodont crowns prepared by dental students. J Dent Res 1984;63:286.|
|50||Mack PJ. A theoretical and clinical investigation into the taper achieved on crown and inlay preparations. J Oral Rehabil 1980;7:255-65.|
|51||Shillingburg HT, Hobo S. Principles of tooth preparation. Fundamentals of Fixed Prosthodontics. 3 rd ed. Carol Stream, IL: Quintessence Publishing; 1997. p. 119-37.|
|52||Dykema RW, Goodacre CJ, Phillips RW. Johnston′s Modern Practice in Crown and Bridge Prosthodontics. 4 th ed. Philadelphia: WB Saunders Co.; 1986. p. 24.|
|53||Shillingburg HT, Hobo S, Fisher DW. Preparation for Cast Gold Restorations. Chicago, IL: Quintessence Publishing; 1974. p. 16.|
|54||Ayad MF, Maghrabi AA, Rosenstiel SF. Assessment of convergence angles of tooth preparations for complete crowns among dental students. J Dent 2005;33:633-8.|
|55||Tylman SD, Malone WF. Biomechanical principles of tooth preparation. Tylman′s Theory and Practice of Fixed Prosthodontics. 8 th ed. Tokyo, St. Louis: Ishiyaku Euro America, Inc., CV Mosby Co.; 1978. p. 113-44.|
|56||Ghafoor R, Siddiqui AA, Rahman M. Assessment of convergence angle of full-coverage porcelain fused to metal crowns in clinical practice. Indian J Dent Res 2012;23:241-6.|
|57||Parker MH, Calverley MJ, Gardner FM, Gunderson RB. New guidelines for preparation taper. J Prosthodont 1993;2:61-6.|
|58||Pai V, Shetty P, Joseph M. Comparative evaluation of effect of auxiliary retentive features on retention of complete cast crowns in teeth with adequate and inadequate crown height. An in vitro study. Indian J Dent Res 1999;10:5-10.|
|59||Proussaefs P, Campagni W, Bernal G, Goodacre C, Kim J. The effectiveness of auxiliary features on a tooth preparation with inadequate resistance form. J Prosthet Dent 2004;91:33-41.|
|60||Roudsari RV, Satterthwaite JD. The influence of auxiliary features on the resistance form of short molars prepared for complete cast crowns. J Prosthet Dent 2011;106:305-9.|
|61||O′Kray H, Marshall TS, Braun TM. Supplementing retention through crown/preparation modification: An in vitro study. J Prosthet Dent 2012;107:186-90.|
|62||Burke FJ. Trends in indirect dentistry: 3. Luting materials. Dent Update 2005;32:251-4, 257-8, 260.|
|63||Sabouhi M, Nosouhian S, Davoudi A, Nourbakhshian F, Badrian H, Nabe FN. The effect of eugenol-free temporary cement′s remnants on retention of full metal crowns: Comparative study. J Contemp Dent Pract 2013;14:473-7.|
|64||Haddad MF, Rocha EP, Assunção WG. Cementation of prosthetic restorations: From conventional cementation to dental bonding concept. J Craniofac Surg 2011;22:952-8.|
|65||Hill EE, Lott J. A clinically focused discussion of luting materials. Aust Dent J 2011;56 Suppl 1:67-76.|
|66||Jayna A, Jayna M, Bhasin S, Goel A. Current trends in luting indirect all ceramic restorations. J Indian Prosthodont Soc 2012;Suppl 2:213-7.|
|67||Ellis R, Bennani V, Purton D, Chandler N, Lowe B. The effect of ultrasonic instruments on the quality of preparation margins and bonding to dentin. J Esthet Restor Dent 2012;24:278-85.|
|68||Horne P, Bennani V, Chandler N, Purton D. Ultrasonic margin preparation for fixed prosthodontics: A pilot study. J Esthet Restor Dent 2012;24:201-9.|
|69||Sous M, Lepetitcorps Y, Lasserre JF, Six N. Ultrasonic sulcus penetration: A new approach for full crown preparations. Int J Periodontics Restorative Dent 2009;29:277-87.|
|70||Geraldo-Martins VR, Tanji EY, Wetter NU, Nogueira RD, Eduardo CP. Intrapulpal temperature during preparation with the Er: YAG laser: An in vitro study. Photomed Laser Surg 2005;23:182-6.|
|71||Mollica FB, Camargo FP, Zamboni SC, Pereira SM, Teixeira SC, Nogueira L Jr. Pulpal temperature increase with high-speed handpiece, Er: YAG laser and ultrasound tips. J Appl Oral Sci 2008;16:209-13.|