Thanks, Shirley. Good afternoon and thanks for joining us. On our call today, I'll provide some highlights from the quarter and then briefly discuss the performance of our two operating segments, clear aligners and oral scanners. John will provide more detail on our financial results and discuss our outlook for the first quarter and how we see 2018 unfolding. Following that, I’ll come back and summarize a few key points and then open up the call to questions. Overall, the fourth quarter was a strong finish to another outstanding year for Align with better than expected revenues, volumes and operating income. Record Q4 revenues were up 43.7% year-over-year, driven by increased Invisalign volumes across all geographies and customer channels as well as by record iTero scanner revenue. Q4 Invisalign volume was up 34.2% year-over-year, reflecting strong international growth from increased utilization and expansion of our customer base, which included over 4000 new customers for the third consecutive quarter. Notwithstanding the strong performance, our Q4 results were impacted by the new US Tax Cut and Jobs Act, which reduced our reported net income and EPS. However, Q4 operating income was a record $109.6 million or 26%. John will discuss this in more detail in his section in a few minutes. For the full year, revenue of 1.5 billion increased 36.4% year-over-year, driven by both record Invisalign revenue, which surpassed the 1 billion mark for the first time ever and record iTero scanner revenues. These results reflect continued progress in execution of our force strategic growth drivers, which focus on driving international expansion, increasing orthodontist’s utilization of Invisalign, especially with teenagers, enabling GP dentists to treat and refer more Invisalign cases and generating consumer demand from millions of people worldwide and connecting them with Invisalign Doctor. Turning to the specifics around our fourth quarter results, let's start with the results of our North American region. For North America, Q4 was a good quarter with Invisalign case volume up 5.1% sequentially and 24.2% year-over-year. Sequential growth primarily reflects the seasonality, a seasonally stronger period for GP dentists as patients’ activities in their offices increased after summer holidays. Ortho customers treated more adult patients following the busy teen season. In addition, Q4 Invisalign utilization increased to 3.3 cases per GP dentist and North American Orthos received a record 14 cases per doctor, reflecting continued confidence and uptake of Invisalign system. On a year-over-year basis, strong growth was driven primarily by increased Ortho utilization and continued expansion of our GP customer base. For the full year, both North America Orthos and GP Dentists achieved record annualized utilization of 47 and 8 cases per doctor respectively. For international doctors, Q4 was another strong quarter with Invisalign case volume up 12.7% sequentially and 52.3% year-over-year. Sequential growth reflects a seasonally stronger quarter for EMEA region following summer holidays for doctors and patients, which offset expected decreases from seasonality in APAC, particularly as the Greater China market observed local holidays. On a year-over-year basis, strong Invisalign volume was driven by growth from both EMEA and the Asia Pacific region. Year-over-year growth for EMEA was up 42.9%, led by Spain, France and the UK. We also saw strong growth across all of our smaller expansion markets, which include Central and Eastern Europe, the Middle East and Africa. And APAC Q4 volumes were up 63% year-over-year, led by China, Japan and Australia with record Invisalign volume in most APAC countries. For the full year, Invisalign volume increased 44.9%, led by growth from China and our core EMEA country markets. In total, international volume represented 38% of worldwide Invisalign case shipments. Now, turning to the teen market, which makes up 75% of total orthodontic case starts each year. In Q4, 63.5 thousand teenagers started treatment with Invisalign clear aligners, an increase of 44.1% year-over-year, driven by continued strong adoption across all major regions and increasingly for younger teens and tweens. For Q4, year-over-year Invisalign teen patient growth for North American Orthos increased 37.8% and international was up 64.7%. Notwithstanding some seasonality during the quarter, given fewer teen case starts, Q4 was a fifth consecutive quarter that Invisalign teenage patient volume grew faster than adults. On a sequential basis, North American ortho teen cases were down as expected as our ortho customers shifted their focus toward adult patient case starts in Q4 following a very busy summer teen season. For the full year, a total of 237,000 teenagers or 26% of our total volume started treatment with Invisalign clear aligners, up 40.4% from 2016. During the year, we continued to drive adoption of teenage patients through sales and marketing programs, including a major new direct-to-consumer campaign, empathizing teens and moms. In addition, at the beginning of 2017, we launched the first clear aligner solution for Class II correction that combines all the benefits of the most advanced clear aligner system in the world with features for moving the lower jaw forward, while simultaneously aligning the teeth. Invisalign teen with mandibular advancement or MATH [ph] as we call it, offers a simpler, more efficient and patient friendly option than functional appliances. MATH was launched in certain country markets in Canada, EMEA and APAC and is ramping up nicely across the board, especially in China. To date, we've shipped over 5000 MATH cases outside the United States, half of which were in Q4 alone and we're very excited about the potential for MATH worldwide. However, we do not expect any material contribution in the US from MATH until the back half of 2018, as we continue to work through the 510k regulatory approval process with the FDA, which includes collecting additional data and analysis. Invisalign brand is one of the most recognized in the dental and orthodontic market. Our integrated consumer marketing programs leverage traditional paying media, search, digital marketing, PR and social media to engage consumers at every point in the consumer purchase journey. These programs continue to drive demand for Invisalign treatment and are key to adoption in both the teen and adult segments. In 2017, we launched a new Made to Move brand platform for Invisalign, which has been really impactful around the world. In North America, we expanded our traditional digital media campaigns, targeting both men and women for the first time and made a significant investment in our marketing to teens and moms. We stepped up our approach to teens by partnering with content developers, teen and mom social media influencers and team brands like AwesomenessTV, which we saw pay off and increases in our consumer website activity and opt-in metrics. We also saw a positive impact from the global Made to Move campaign across EMEA and APAC and may have focused heavily on digital, social and web traffic, which resulted in huge increase in their online smile assessments and other KPIs. APAC markets like Singapore and Australia also saw an increase in KPIs based on their focus on social media and local event and influencer driven marketing. As a result, in total for the year, there were over 15 million unique visitors to the Invisalign websites worldwide, 1.8 million potential patients search for Invisalign provider on Doc locator, up 41% from 2016. 600,000 consumers completed Invisalign smile assessments on our website, of which 445,000 opted in for follow-up in the Invisalign social media community grew over 42% to 745,000 consumers following the Invisalign brand worldwide. You may recall that in January last year, we launched a new smile concierge program in Raleigh, North Carolina with the objective to help more consumers start Invisalign treatment and improve their overall experience by shortening their research cycles and utilizing consumer insights to help our doctors better engage with consumers. Throughout the year, we made great progress from ongoing program improvements in December. We achieved a major milestone with the 6500 Invisalign patients for the smile concierge team. Cumulatively, we schedule over 26,000 Invisalign consultations which equates to connecting hundreds of consumers to Invisalign practices every day. We continue to see incredible potential as our doctors’ offices are implementing changes to better engage with consumers that we send to them every day. We've also started to expand the small concierge service outside the United States with our first teams up and running in Singapore, Brazil and Australia, with each of these countries having a great start to the year helping more consumers become Invisalign patients. Over the course of the year, we’ll update you on our continued progress in leveraging important learnings about consumer behavior and establishing smile concierges team in EMEA and Asia Pacific regions. In 2018, our smile concierge team will be very closely linked to the new Invisalign store pilot that we opened in November, which will utilize our consumer insights to better capture leads coming out of the store experience. The smile concierge team will be utilizing our touch point learnings to reach out to consumers who received a scan but don't schedule an appointment with a doctor. In addition, we’ll use our automated text and email services to remind consumers when and where to pick up their aligners or to see a doctor as scheduled. These are just a few of the exciting new ways that we're helping to educate consumers on the benefits of getting a better smile with Invisalign treatment and connect them with an Invisalign doctor of their choice. The Invisalign store pilot program that launched in November is an extension of our long standing direct-to-consumer marketing programs that connect potential patients directly to doctors for Invisalign treatment. We're looking at other successful brands and how they use a physical location to engage consumers and extend the brand experience. In this case, we are trying to extend and strengthen what we do through digital ad, social media, PR and TV advertising and our customers own in practice patient marketing. Our pilot store model relies on the doctor and the doctor's office for treatment. We are not treating patients in the store. Instead, we are educating consumers on how Invisalign works, showing them a scan driven simulation of how they might look with straighter teeth and offering to connect interested consumers with a doctor of their choice, so that they subsequently decide to pursue treatment. To date, we've learned a lot about creating the right consumer experience with Invisalign system through a store front and are continuing to evolve and make continued progress. In Q1, we will open another pilot store in San Jose, California, near our corporate headquarters. We're planning to open two additional pilot stores on the East Coast sometime in the first half of this year. We look forward to continuing to learn more from these four locations and sharing our progress throughout the year. Q4 was a strong quarter for iTero and better than expected with revenues up 30.8% sequentially and 37% year-over-year on record iTero scanner shipments. Q4 results reflect continued strength in our GP channel following our GP summit in September as well as sales to our major DSO partners and through our iTero distributor, Patterson Dental. The iTero scanner business was also strong in EMEA and has been growing rapidly in Asia Pacific, especially Japan where we see certification for iTero in Q3. Customers are quickly realizing a significant benefit of our iTero scanner platform and we are excited about the opportunity to continue to expand iTero’s footprint worldwide. The iTero scanner is central to our digital approach and overall customer utilization of Invisalign treatment. Use of the iTero scanners for Invisalign case as shipments in place of PBS impressions continues to expand and remains a positive catalyst for Invisalign utilization. For Q4, total Invisalign cases submitted with a digital scanner in North America increased to a record 64.1%, up from 51.3% in Q4 last year. International scans increased to 40.8%, up from 24.9 in Q4 of last year. not only does the iTero scanner provide the best work flow for Invisalign treatment with Invisalign outcomes simulator and progress assessment tool, but it's also seamlessly integrates with downstream restorative workflows, significantly improving their accuracy and precision. iTero is also the only scanner with time lapse technology that makes chair-side consults more productive. By scanning patients at every visit using time lapse and comparing historical scans to a current scan, patients see for themselves the changes in their tooth wear, tooth movement and changes in [indiscernible], encouraging them to accept treatment on the chair-side. In Q4, we cited a distribution agreement with Glidewell Dental for our iTero Element scanner in North America with glidewell.io the in-office solution, a chair-side restorative ecosystem designed to simplify the process of prescribing and delivering laboratory quality dental restorations. In 2017, iTero scanners volumes were up 37.5% year-over-year. To date, over 6.3 million orthodontic scans and 2.4 million restorative scans have started with iTero scanners. Finally, in the doctor-directed at home channel, Align is a third-party supplier to SmileDirectClub and has 19% equity investment in the company. We manufacture a portion of SDC aligners with non-Invisalign clear aligners. For Q4, shipments to SDC were down sequentially as expected as SDC increased their own internal capacity. As an investor and supplier to SDC, Align is focused on two things, expanding the market for orthodontic treatment and providing greater access to simple teeth straightening solutions to millions of more people who prioritize convenience and affordability and creating new opportunities for Invisalign doctors by connecting consumers who aren't candidates for SDC’s limited protocols to an Invisalign practice. With that, I'll now turn the call over to John.