Review Article Relationship Between Periodontics and Prosthodontics: The Two-Way Street

Yung-Ting Hsu DDS, MDSc, MS Abstract Visiting clinical assistant professor, The interdisciplinary approach has been a trend for Department of Periodontics and Allied a comprehensive dental treatment. Within modern Dental Program, Indiana University, , periodontics and prosthodontics share Indianapolis, IN, USA an intimate and inseparable relationship in multiple aspects, including treatment plan, procedures execution, outcome achievement and maintenance. By controlling Nan-Chieh Huang DDS, MDSc, MS inflammation and preparing sites for proper prosthetic Resident, Department of prosthodontics, prostheses, periodontists no doubt can provide a solid Indiana University, Indianapolis, IN, USA foundation for successful prosthetic outcomes. On the other hand, prosthodontists could construct proper restorative margin, shapes and contacts that benet the Hom-Lay Wang DDS, MSD, PhD harmony of periodontium and prosthesis. This article Professor and Director of Graduate was aimed at addressing the key relationship between prosthodontics and periodontics. The impacts of Periodontics, Department of Periodontics healthy periodontium on longevity of prostheses were and Oral Medicine, School of Dentistry, addressed. In addition, how the restorative factors such University of Michigan, Ann Arbor, MI, as biologic width violation, retraction techniques and USA. Research Advisor, Eng. A.B. Research defective restorations, inuenced on periodontal/ peri- Chair for Growth Factors and Bone implant tissues were also discussed. This systematic Regeneration, King Saud University Riyadh, review also comprised the association between the Saudi Arabia presence of residual cement and the occurrences of peri-implant diseases. In short, frequent and efficient communications are essential between periodontists and prosthodontists through the entire treatment procedures Corresponding author: to ensure an overall successful treatment since both Hom-Lay Wang, DDS, MSD, Ph D. specialties share a common goal: to create pleasing Professor and Director of Graduate esthetic with a harmonious stomatognathic system. Periodontics Department of Periodontics and Oral Keywords: Periodontics, restorative, prosthodontics, Medicine implant, biologic width, in ammation University of Michigan School of Dentistry 1011 North University Avenue Introduction Ann Arbor, Michigan 48109-1078, USA. omprehensive dental therapy is founded on team Tel: (734) 763-3383 works. Of all disciplines within modern dentistry, Fax: (734) 936-0374 Cperiodontics and prosthodontics have the strongest and E-mail: [email protected] the most intimate connections. For prosthodontics, peri- odontal health plays an important role on the longevity of restorations. On the other hand, defective prostheses may contribute to progression of periodontal diseases. To achieve successful treatment outcomes, periodontists and prosthodontist should cooperate in treatment plan, per-

04 Volume 4, Number 1, 2015 Review Article formance and maintenance. on periodontal/peri-implant inflammation 5-7 This review attempted to address the key remained inconclusive , mucogingival proce- relationship between periodontics and prosth- dures may also benefit esthetic outcomes and odontics. e interaction between periodontal oral health maintenance. health and prosthetic factors were discussed as Regular periodontal maintenance is a key well as the recent hot issues related to dental to reduce the incidence of tooth or implant loss implants. following prosthetic therapy. Due to limitation of routine home cares, regular professional maintenance therapy plays a key role on reduc- The impacts of periodontal/implant tion of periodontal inflammation induced by health on prosthetic therapy plaque accumulation, especially in the subgin- Prior to treatment plan, tooth prognosis gival space. For those patients who had history should be addressed both on individual tooth of periodontitis, regular supportive periodon- and the overall dentition. Several periodontal tal therapy is even more beneficial to prevent prognositication systems have been introduced further disease progression. Previous studies 1 based on either periodontal stability or certain showed that sites with treatment but without 2-4 parameters , such as furcation involvement, maintenance had a 2 times higher tooth loss tooth mobility, the severity of bony destruc- than the sites with regular maintenance after 2,3 tion, etc. rough identifying the etiology and periodontal treatment . A recent study even contributing factors of periodontal diseases, showed a 3 time higher tooth loss in the irregu- these prognositication systems indicate the lar compliers comparing with patients with possibility of tooth sustainability in short term regular maintenance over a 5-year observation and long term. As an integral portion of den- period. Besides, the results also showed that tal practice, determination of individual teeth the majority of these teeth were missing due prognosis allows a virtual approach on interdis- to periodontal origins. In other words, regular ciplinary conversation for treatment strategies. compliance of periodontal maintenance is the Overall prognosis is benecial to communica- key to prevent the recurrence of periodontal tions between lay people and professionals. diseases and to maintain the integrity of treat- 8 Active periodontal/peri-implant diseases ment outcomes . and contributing factors should be eliminated or controlled prior to prosthodontic construc- The impacts of prosthetic factors tions. The signs of active periodontal inflam- on periodontal/ peri-implant health mation include pocket formation, the presence Prostheses should be carefully designed of bleeding on probing or suppuration, and and performed, in harmony with the surround- tissue changes of gingiva. Without control- ing periodontium, to maintain periodontal/ ling the existing periodontal inflammation, a peri-implant health. Defective restorations cascade of adverse events of periodontal de- contribute to disease progression by increasing struction would take place and cause persistent accumulation of dental plaque and retention inammation, bone resorption and eventually of food debris. Invasion of biologic width may tooth loss. In other words, function and lifes- also result in periodontal inammation. pan of the prosthesis will be compromised if periodontal diseases remain uncontrolled aer Biologic width delivery. In addition, periodontal inflamma- The dimension of dentogingival complex, tion results in soft tissue changes in terms of called "biologic width (BW)", is a cuff-like texture, color, size and gingival consistency. It barrier that acts as a protective physiological then leads to impaired esthetic outcomes by seal around natural teeth. It possesses a self- deteriorating the harmony between periodon- restoration capacity and dynamic adaptability. tium and prosthesis. The compositions of BW include junctional In addition to inammation control, perio- epithelium and connective tissue attachment. dontists could offer a hand for soft and hard e mean distance of epithelial and connective tissue management to prepare sites for success- tissue components are 0.97mm and 1.07mm, ful prosthetic treatments. Surgical procedures, respectively. However, the dimension is dy- such as ridge and bone augmentation as well as namic in particular the epithelial attachment, 9 sinus liing, could be performed for future im- varying from individuals . Similar to natural plant sites to correct existing ridge deformities. teeth, a consistent width of peri-implant mu- Although the effects of mucogingival defects cosa was found adhering to the surface of the

Journal of Prosthodontics and Implantology 05 Review Article

19 implant abutment. Histologically, it prevents esthetic demands or sites with bone removal . further supragingival plaque formation via a Hence, communication prior to treatments zone of healthy connective tissue separating between periodontists and prosthodontists the inflammatory cell infiltration and alveolar is essential to determine the treatment time- 10,11 bone crest . frame, feasibility of surgery and the locations The violation of BW has been widely of restorative margins. discussed as a contributing factor which jeop- Most researchers believe that BW is one of 12,13 20,21 ardizes periodontal health . BW invading the causes of early implant bone loss . Dur- could result from several reasons, such as ex- ing the initial phase of implant healing, peri- tensive caries, subgingival restorations, short implant bone remodeling is from the process clinical , and teeth fracture. From hu- of BW reformation to allow a stable so tissue 22 man autopsies, Vacek and coworkers reported barrier . In addition, the locations of micro- greater length of epithelial aachments around gaps and smooth/rough-surface interfaces may 14 restored teeth than non-restored teeth . In be associated with the length of peri-implant 23,24 the group with supracrestal amalgam restora- BW . us, one of the strategies to prevent tions, BW violation would also lead to signi- early implant bone resorption is control of cant increases of gingival recession and crestal biologic width and microgap. In 2006, Laz- 12 bone loss . Resulting from the breach of BW, zara and Porter introduced the concept of histologically, aachment loss will be found to "platform-switching" for inward horizontal reestablish the certain dentogingival junction repositioning of the implant-abutment junc- 25 around restorations and lead to periodontal tion . Via connecting the implant xture with destruction. Clinically, the signs of BW viola- a narrow-diameter abutment, the inammato- tion consist of pain, gingival inammation, lo- ry cell inltration could be limited around the calized gingival hyperplasia, pocket formation, implant neck with platform-switching design, and loss of periodontal apparatus. Therefore, instead of further apical migration. Previous further corrective procedures should be con- studies suggested that platform-switching may sidered prior to restorative treatments if any benet tissue preservation. On the other hand, qualms about BW violation, including orth- limited effects of platform-switching on hard 26-31 odontic extrusion and surgical crown length- tissues have been claimed by some authors . ening procedures. e clinical signicances of eects on marginal Surgical could be per- bone preservation may be questioned. In con- formed via multiple techniques: gingivectomy, clusion, the available data remained contro- apically positioned flap surgery (APF), APF versial and further longitudinal studies are still with osseous reduction. From periodontal needed. point of views, several parameters should be taken into account for the feasibility of this surgery: esthetics, possible exposure of furca- Proximal relationship tion involvement, remaining bony support Embrasure types, referring both horizontal and crown/ root ratio for the future results. and vertical dimensions of the interproximal 15 In spite of individual and sites variations , a spaces, show impacts on the presence of inter- minimum of 3mm distance from bone to the proximal papilla. Loss of interproximal papilla restorative margin has been suggested by most results in impaired esthetics and promotion 13,16 researches . e ferrule eect for the future of food impaction, aggravating periodontal prosthetic design should also be a key factor destruction. As for the distance from contact 17,18 in determination of the surgical plan . Post- point to the alveolar crest, the maximum of the operatively, final prostheses should only be distance should not exceed more than 5mm to delivered once the tissue maturation was com- preserve the interdental papillae in natural den- 32 pleted. A minimum of 6-8 weeks of healing tition . is concept has also been conrmed period is highly recommended following surgi- by a retrospective study examining the vertical cal crown lengthening that without bone re- dimension between single implant restora- 33 section. From a total of 85 teeth of 25 patients, tions and a natural tooth . The demands for Bragger and coworkers found that 12% of teeth implant-support prosthesis are more strict: a sites showed further apically marginal dis- minimum of 3mm of inter-implant distance is placement between 6 weeks to 6 months post- suggested to maintain the alveolar crestal level, 16 operatively . As a result, 6 months of waiting preventing the possible papillary loss; whereas period should be taken in those sites with high papillary loss would be expected if the verti-

06 Volume 4, Number 1, 2015 Review Article cal dimensions between two implants is more ating 100 patients, Jeffcoat and Howell classi- 34,35 than 3mm . ed overhang into 3 sizes: small (<20% of the Contact types between prostheses may interproximal space), medium (20-50%) and also play a role on periodontal health. e rela- large (>50%). A signicant marginal bone loss tionship between open contacts and periodon- aliated to the restoration occupied more than 46 tal destruction has been a controversial issue 20% of interdental space . Vice versa, removal since last century. To verify the impacts of of overhang may also benet the reduction of 47 open contacts on periodontium, Jenberg and pocket depth and clinical aachment gain . colleagues conducted a cross-sectional study To sum up, restorative overhang should be enrolling 104 patients with unilateral open prevented by the proper uses of matrix bands contacts. In addition to greater prevalence of and wedges. Meanwhile, inadequate crown re- food impaction, the sites with open contacts duction for the restorative material should be presented greater pocket depth and clinical avoided to prohibit the overcontoured crown. aachment loss although there was no signi- cant dierence for gingival index, bleeding and The location of restorative margins 36 calculus index between contact types . More- Restorative margin locations should be over, another cross-sectional study reported established based on several factors, including an increase of bone loss (2.4%) in the patients extension of caries, retention/resistance forms, 37 with initiate periodontitis . However, another and esthetics. Using free gingival margin as classic study failed to approve the trend from a the references, the supra- and subgingival res- total of 1040 contacts. On the other hand, the torations have their own pros and cons. With authors suggested the increasing pocket depth respect to periodontal health, the supragingival may be in relation to the presence of food im- restoration is the most favorable design since it 38 48 paction . In spite of an indirect relationship is easy to be cleaned . In spite of beer esthet- between open contact and periodontal inam- ics, subgingival restorations were associated mation, it could be speculated from these stud- with greater periodontal inflammation in the 49 ies that food impaction contributes to increas- sites with keratinized gingiva less than 2mm . ing pocket depth and clinical aachment level. In addition to tissue biotype, subgingival Thus, clinicians should avoid to place open restorative margins may be harmful to peri- contacts between xed prostheses. Meanwhile, odontium/ peri-implant tissues because of the through proximal cleaning should be addressed following reasons. First, the margin has higher to patients. risk of BW invasion, enhancing further peri- odontal destruction. From 59 patients, New- Restoration contours comb investigated a total of 75 anterior Adequate crown contours could provide crowns with subgingival margins. A strong pos- protection of gingival margins, allow cleans- itive correlation was found between gingival ing action of the musculature and facilitate the inammation and the subgingival extension of 39 50 access for . Indeed, overcontour restorative margins . e limited access is an- may have negative inuence on periodontium other possible cause when restorative margins 40,41 since it increases plaque retention . Utilizing are placed subgingivally. In particular amalgam acrylic facings as standard overcontour, Sacke or composite resin fillings, it is difficult for and Gildenhuys compared tissue changes at operative to polish restorations and 42 pairs of experimental and control sites (ad- thereby produce rough surfaces underneath jacent teeth) over a period of 42-49 days. 59% gingiva. Rough surfaces are more prone to ac- of mandibular test sites and 70% of maxillary cumulate dental plaque and, therefore, induce 51 test sites showed signicant gingival inamma- periodontal inflammation . Likewise, over- tion in relation to overcontour. Besides, more hang and improper restorative margins could than 50% of these sites had increasing amount be ascribed to the progression of periodontal of gingival sulcular fluid compared with their destruction due to the inclination of plaque 42 43 controls . accumulation . Even though subgingival ce- Restorative overhang is also considered as mentation margin is a common procedure on a contributing factor of periodontal diseases. the implant in esthetic zone, moreover, it is 43 As a prevalent type of restorative defects , ll- dicult to discover the excess cement residu- ing excess may aggregate the plaque accumula- als around subgingivally placed implants. In- tion which potentiates gingival inflammation vestigating the amounts of undetected cement 44,45 and worsen the periodontal status . Evalu- following cleaning, Linkevicius and coworkers

Journal of Prosthodontics and Implantology 07 Review Article found significantly greater cement remnants ing periodontal destruction as a co-destructive 59,60 were linked to deeper subgingival margin factor along with inflammation . Previous positions. The lack of perpendicular fiber at- studies also demonstrated a signicant role of tachment around dental implants may even tooth mobility on progression of periodontal 61,62 facilitate the apical migration of cement excess diseases . A cross-sectional study examined 52 and worsen the tissue inammation . Further- the signs of TFO and severity of periodontitis more, the ecacy of proper oral hygiene main- from 333 maxillary rst molars of 300 patients. tenances is questioned for extensively subgin- In comparison with teeth without TFO, the gival restorations. The penetration depths of group with TFO had signicantly greater prob- plaque control methods for homecare is within ing depth, greater clinical aachment loss and 53 63 1-3mm subgingivally, such as mouth rinsing , less bone support . In the late stage, chronic 54,55 56 toothbrush , and interproximal cleaning . TFO may cause tooth migration and loss of In regards to subgingival irrigation, American vertical dimension, enhancing impaired esthet- 64,65 Academy of Periodonotology (AAP) posi- ics and the need of oral rehabilitation . tioned paper suggested a 3mm of subgingival Occlusal overloading also causes biome- 57 penetration or 50% of the probing depth . chanical implant complications and marginal 66,67 To prevent periodontal destruction, in bone loss around dental implants . By cre- conclusion, supragingival restorative margins ating supra-, Miyata and coworkers are highly recommended at the sites with less investigated the effect of occlusal overload esthetic concerns. For the site that the sub- on peri-implant tissue in a series of studies. It gingival margin is required, certain principles showed that the excess occlusal force could ini- should be bear in mind including conservative- tiate marginal bone resorption even under the ly subgingival extension of restorative margin, circumstance of healthy peri-implant tissue. In sucient width of keratinized gingiva (at least addition, the disease may not be reversed once 68,69 2mm of keratinized gingiva including 1mm of it progressed . With the persistence of exces- aached gingiva), smooth restorative surfaces sive force, loss of is possible 70 with proper nished margin and the avoidance and end up with implant failure . Other clini- of BW breach. Adequate daily home care needs cal manifestations of biomechanical implant to be addressed to patients and regular profes- complications include fracture of prosthetic sional maintenance is necessary. components and loosening of attachment or 71,72 abutment screw . In addition to implant Trauma from occlusion overloading, several factors may contribute to As a functional unit, the tooth and its sup- biomechanical implant complications, includ- 73 74,75 porting structures bear the brunt of occlusal ing bone quality , implant designs , pros- 76,77 78,79 forces on the crown. In response to occlusal thetic design and parafunction . To deal forces, the attachment apparatus may experi- with mechanical complications, check occlu- ence tissue changes, including injury, repair sion is the rst step to verify the etiologic fac- and adaptive remodeling of the periodontium. tors. All possible contributing factors should Several factors are relative to trauma from oc- also be controlled or eliminated before repair clusion (TFO) including occlusal disharmony, or replacement of loosening/ fractured com- parafunction (i.e. clenching and ), and ponents. Non-surgical or surgical intervention occlusal schemes. Although the role of TFO may be considered in the treatment of mar- plays in periodontal/ peri-implant diseases re- ginal bone loss. Ultimately, the patient is highly mains controversial, clinicians should perform recommended to wear the occlusal splint to prosthetic treatments with caution to avoid prevent the recurrence of biomechanical com- 67 failure following TFO. plications . As a result of excessive force or reduced periodontal supports, teeth under TFO or oc- Gingiva retraction technique: the clusal trauma showed following clinical charac- effects on soft tissue teristics: tooth pain, increasing tooth mobility, An acceptable impression was needed to sensitivity to percussion, fremitus, occlusal avoid improper marginal adaptation that may wear and even tooth fracture. e radiographic cause periodontal tissue inflammation or the changes consist of PDL space widening, dis- risk of recurrent caries. Management of the ruption of the lamina dura, root resorption and gingival tissue is essential for obtaining accept- 58 peri-apical or furcation radiolucency . Some able impression especially for subgingivally lo- 80 researchers believe it may aggravate the exist- cated restorations . Various gingival displace-

08 Volume 4, Number 1, 2015 Review Article ment methods, such as mechanical, chemo- and higher prevalence of peri-implant inflam- 93 mechanical and surgical are available. Ruel and mation . Moreover, modications on implant coworkers reported that gingival displacement abutment and cementation techniques were methods may cause 0.1-0.2 mm gingival re- also introduced to limit the amount of cement cession and the destruction of the junctional extending into the gingival sulcus of implant- 81 94,95 epithelium that took 8 days to heal . Chemical retained crowns . Fortunately, most of agents as well as the mechanical force of retrac- the cement-associated peri-implant diseases tion cords could trigger temporary gingival could be solved following complete removal 82,83 92 recession and gingival inammation . It has of residual cement . Recently, the use of zinc been shown that the dierent time intervals of oxide-eugenol cement is advocated since the the chemical retraction agent placement could subgingival residuals could be dissolved in the 93 cause different degree of tissue inflammation sulcular uid . Further studies are still needed 84 changes in the beginning . Hence, the proper to prevent the peri-implant inflammation in- manipulation dierent gingival retraction tech- duced by residual excessive cement. niques such as materials and time-control are the key factors to avoid permanent tissue dam- Conclusion age while impression-taking process is made. The relationship between prosthodontics Recently, cordless techniques have been and periodontics is intimate and inseparable. introduced as an alternative to displacement Robust supporting periodontal/peri-implant cord methods because of several advantages, tissues provide solid foundations for predict- such as time-saving, ease of application, less able prosthetic therapy. In addition, regaining pressure generation and enhanced patient stable periodontal conditions should rely on 85,86 comfort while being minimally invasive . establishment of proper contact types, occlusal Acar and colleagues evaluated the clinical per- scheme and quality prosthesis. Frequent and formance and impression quality on the cord- ecient communications are essential between less and conventional displacement systems. periodontists and prosthodontists through the e results demonstrated that all methods can entire treatment procedures, including plan, give the comparable and clinically acceptable treatment procedures and maintenance, since impression qualities except for the nonimpreg- both share a common goal: to create 87 nated cord group . Furthermore, a random- pleasing esthetic with a harmonious stomato- ized clinical trial was conducted to assess the gnathic system. clinical and immunological factors related to conventional and cordless techniques. e re- References sults demonstrated the cordless method was 1. Kwok V, Caton JG. Commentary: prognosis revisited: a system less stress for patients and resulted in lower for assigning periodontal prognosis. J Periodontol 2007; 78: post-treatment levels of inflammatory cyto- 2063-71. 88 kines . 2. 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Journal of Prosthodontics and Implantology 09 Review Article

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